Preface

During the last 50 years, the world has witnessed strong economic growth and fast urbanization rates, which have lifted millions of people out of poverty. However, this development has been coupled with increasing use of resources and environmental degradation. It is obvious that the increased use of resources is strongly coupled to environmental impacts. Partly this is because of the linear way resources are used. The process leads to environmental impacts all the way and ends with different kinds of waste. Creating decent living conditions for all people while decoupling economic growth from the increasing use of virgin resources and environmental impacts is the major challenge of this millennium. This is also the essence of the United Nations' 2030 Sustainable Development Goals. There are many approaches suggested for solving these problems. One is to change consumption behavior from material products to services. Another option is to find technological solutions to create more closed loops for materials and use fewer virgin resources and energy obtained from clean renewable sources.

Wastewater treatment plants are aimed at decreasing the environmental impacts of discharging untreated wastewater into receiving bodies. Considering the need for long-term ecological sustainability, the objectives of wastewater treatment systems need to include energy and resource savings and waste reduction. Sewage sludge management is a management system that makes sludge recovery a central component of a wastewater treatment plant that strives to integrate it with improving overall sustainability of the plant.

Sludge formation during wastewater treatment is inevitable even with proper management and treatment. However, proper treatment and disposal of sludge is still difficult in terms of cost, the presence of new pollutants, health problems, and public acceptance. Conventional disposal methods (e.g., storage, incineration) have raised concerns about legislative constraints and community perception that encourage the assessment of substitute sludge-management options. Sludge management requires a systematic solution combining environmental effectiveness, social acceptability, and economic affordability. Increased production of sludge (biosolids) worldwide is due to population growth, urban planning, and industrial developments. The sludge needs to be properly treated and environmentally managed to reduce the negative effects of its application or disposal.

The first aim of this book is to investigate the application of biosolids or sewage sludge, together with possible resources for sustainable development. The second aim is to view resource efficiency from a more complex perspective looking at several resources and the causal links between them in order to point out new pathways towards a more sustainable use of resources. The book consists seven

chapters divided into two sections: "Sustainable Sewage Sludge Management" and "Green Economy."

The editor would like to acknowledge and thank the authors for their contributions.

**Dr. Başak Kiliç Taşeli̇** Professor, Department of Environmental Engineering, Giresun University, Turkey

**1**

Section 1

Sustainable Sewage Sludge

Management

## Section 1

## Sustainable Sewage Sludge Management

**3**

**Chapter 1**

**Abstract**

large quantities.

**1. Introduction**

Does Sustainable Management of

Biodegradable Sludge Exist at All?

Due to the modern lifestyle and the formation of large amounts of biodegradable sludge, its processing is becoming a demanding technological and logistical project. Stabilization with pozzolanic ash and its reuse in construction industry represents one of the possible sustainable solutions. Mixing biodegradable sludge with pozzolanic ash triggers a set of physiochemical reactions such as converting heavy metals into insoluble hydroxides, forming heat due to hydration of metal oxides, and forming of a set of pozzolanic structures due to high pH and heat. Studies showed that the produced material is biologically and chemically inert and safe for use under controlled conditions. Comparison of different most widely used technologies, using life cycle analysis, indicated advantages of using material conversion of biodegradable sludge into materials rather than using it for energetic purposes. Based on the calculation of their negative influence on the environment and human health, the analyzed technologies can be categorized from those with less impact to those with higher impact: stabilization with ash < pyrolysis < anaerobic digestion < composting < landfilling. The life cycle assessment (LCA) showed that the decentralized technologies enabling material use of biodegradable sludge are more sustainable than centralized installations for composting biodegradable sludge in

**Keywords:** biodegradable sludge, sustainable, stabilization, pozzolanic ash, LCA

The management of biodegradable sludge (BS) is becoming an important challenge for developers, investors, and managers of wastewater treatment plants (WWTPs) over the world. BS is an unavoidable by-product of advanced techniques of biological purification of wastewater. In general, global population generates between 70 and 90 g BS/person or 1 ton of dry substance/10,000 persons [1]. The management of BS is not only a trivial problem, and investors should be aware about it during the designing of the WWTPs, because studies made in Austria showed that the management of BS (stabilization, drying, pretreatment, and transport) can easily exceed 40 to 53% of all operational costs during the processing of waste waters [2]. Proper and sustainable management with biodegradable waste is the outmost important topic in developed countries, because more expert studies showed that inappropriate approach to management with those waste includes high risks for human health and environment. Legislators all over the world are

A BACOM Project Case

*Marko Likon and Marjan Zemljič*

#### **Chapter 1**

## Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case

*Marko Likon and Marjan Zemljič*

#### **Abstract**

Due to the modern lifestyle and the formation of large amounts of biodegradable sludge, its processing is becoming a demanding technological and logistical project. Stabilization with pozzolanic ash and its reuse in construction industry represents one of the possible sustainable solutions. Mixing biodegradable sludge with pozzolanic ash triggers a set of physiochemical reactions such as converting heavy metals into insoluble hydroxides, forming heat due to hydration of metal oxides, and forming of a set of pozzolanic structures due to high pH and heat. Studies showed that the produced material is biologically and chemically inert and safe for use under controlled conditions. Comparison of different most widely used technologies, using life cycle analysis, indicated advantages of using material conversion of biodegradable sludge into materials rather than using it for energetic purposes. Based on the calculation of their negative influence on the environment and human health, the analyzed technologies can be categorized from those with less impact to those with higher impact: stabilization with ash < pyrolysis < anaerobic digestion < composting < landfilling. The life cycle assessment (LCA) showed that the decentralized technologies enabling material use of biodegradable sludge are more sustainable than centralized installations for composting biodegradable sludge in large quantities.

**Keywords:** biodegradable sludge, sustainable, stabilization, pozzolanic ash, LCA

#### **1. Introduction**

The management of biodegradable sludge (BS) is becoming an important challenge for developers, investors, and managers of wastewater treatment plants (WWTPs) over the world. BS is an unavoidable by-product of advanced techniques of biological purification of wastewater. In general, global population generates between 70 and 90 g BS/person or 1 ton of dry substance/10,000 persons [1]. The management of BS is not only a trivial problem, and investors should be aware about it during the designing of the WWTPs, because studies made in Austria showed that the management of BS (stabilization, drying, pretreatment, and transport) can easily exceed 40 to 53% of all operational costs during the processing of waste waters [2]. Proper and sustainable management with biodegradable waste is the outmost important topic in developed countries, because more expert studies showed that inappropriate approach to management with those waste includes high risks for human health and environment. Legislators all over the world are

promoting methods and techniques allowing decreasing amount of BS on sanitary landfills with the aim of decreasing the greenhouse emission as well as decreasing the quantity of landfill leachate [3–6]. In accordance with Council Directive on the landfill of waste (1999/31/EC), landfilling of BS on sanitary landfills is forbidden within the EU-28 countries from July 2009. The Directive on waste from 2008 (2008/98/EC) even more restrictively implements hierarchy with which the European Commission is trying to promote material and energetical use of waste.

Nevertheless, blindly following the Directives does not necessarily result in the implementation of optimal and sustainable solutions, and we need to think about new approaches. However, because of those new approaches, all decisions need to be supported by different scientific data, and after that all individual solutions need to be evaluated on the same basis.

In order to allow equal treatment and consistent evaluation of different approaches in the management of BS, the EU Joint Research Centre has developed the "life cycle thinking" (LCT) and "life cycle assessment" (LCA) methodologies and has given the interpretation/instructions on how to use these methods, which should facilitate the decision-making and help managers to establish the most effective and sustainable management system for BS treatment [7]. The guidelines were prepared in cooperation with the International Organization for Standardization (ISO) and are registered under the number SIST EN 14040 and 14,044 [standards for LCA and the International Reference Life Cycle Data System (ILCD) Handbook]. A similar approach in the assessment is used in most European countries and almost by all authors of professional publications.

Each year, EU-28 member states produce more than 10 Mt. of communal BS calculated on dry matter [8, 9]. According to the official data, more than 40% of BS is still being disposed on municipal waste landfills [10]; approximately 36% are reused in agriculture or incinerate [8]; however, Eurostat has no data on the remaining 24% BS [7]. Biodegradable sludge is generated during the operation of urban WWTP utility and contains heavy metals, poorly dissoluble organic compounds (residues of detergents, washing agents, personal hygiene preparations, medicines, etc.), and possibly pathogens microorganisms (**Tables 1–4**).

Both unprocessed and processed BS contains heavy metals, residues of phytopharmaceutical products, and surfactants. Their content depends on the origin of the municipal sludge (sludge from the municipal, industrial, or combined treatment plant). In addition to active microorganisms, pathogenic bacteria listed in **Table 3** are also present in unhygienic feces. Because of that, it is difficult to compost them, and the manufactured compost is prohibited for uses in agriculture as fertilizer.

The method for the management of BS is different and depends on their origin, composition, especially contents of hazardous and biodegradable substances, and on available infrastructure and local regulations. BS, which is disposed on landfills, is subject to uncontrolled aerobic and anaerobic processes that cause the release of a large amount of greenhouse and noxious gasses (CH4, CO, CO2, H2S, etc.) and emissions of heavy metals. Currently, the EU and the USA are using incineration, composting, stabilization, and landfilling as recognized methods for bio sludge disposal. All mentioned methods have negative environmental impacts, especially landfilling and incineration. The special problem for the environment presents pathogenic microorganisms of different species that exist inside biodegradable sludge and which must be stabilized or neutralized before further application. One of the most economical and environmentally accepted methods for stabilization of BS is their mixing with wasted alkaline materials as ash, slag, foundry sand, and foundry dust.

According to the available data from the literature and the LCA analyses, the disposal of BS is the worst choice between the possible solutions, even if landfills are equipped with gas capturing systems and devices for its energetic use [12–14].

**5**

the atmosphere.

**Table 2.**

**Table 1.**

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case*

**Constituent Unit Unprocessed BS Processed BS Active BS**

Dry solid % d.s. 2.0–8.0 5.0 6.0–12.0 10.0 0.83–1.16 Volatile sub. % on d.s. 60–80 65 30–60 40 59–88 Fats and oils % on d.s. 6–30 — 5–20 18 5–12 Proteins % on d.s. 20–30 25 15–20 18 32–41 Nitrogen (tot) % on d.s. 1.5–4.0 2.5 1.6–6.0 3.0 2.4–5.0 Phosphorous % on d.s. 0.8–15.0 1.6 1.5–4.0 2.5 2.8–11.0 Ash (K2O) % on d.s. 0–1 0.4 0.0–3.0 1.0 0.5–0.7 Cellulose % on d.s. 8.0–15.0 10.0 8.0–15.0 10 — Iron % on d.s. 2.0–4.0 2.5 3.0–8.0 2.5 — Silicates (SiO2) % on d.s. 15.0–20.0 — 10.0–20.0 — — Alkalis (CaCO3) % on d.s. 500–1500 600 2500–3500 — 580–1100 Organic acids % on d.s. 200–2000 500 100–600 3000 1100–1700 Energetic value TJ/ton 10–12.5 11 4–6 0.2 8–10 pH value 5.0–8.0 6 6.5–7.5 7 6.5–8.0

**Range Avg. Range Avg.**

Disposal of 1 ton of BS with 20% dry substance emits up to 296.9 kg of CO2(eq) into

The incineration of BS which is generated by the operation of WWTPs is therefore becoming a common practice of management with BS. The incineration is primarily used for the reduction of the volume and not for energy production, because ash represents only about 30% of the dry matter volume in BS [15]. However, ash disposal remains a serious problem as it still contains heavy metals. LCA analyses showed that the incineration of BS is meaningful only in cases where the systems of the so-called industrial symbiosis exist, such as the co-incineration of BS [15] with coal [16] but with a presumption that the BS is sufficiently dry and the incineration chamber is specially designed (FBR). The incineration of 1 ton of

*Average composition of heavy metals in sewage sludge in Europe—combined WWTPs [11].*

**Constituent Range Average Unit** Cr 20–60 35 mg/kg of dry solid Cu 200–600 375 mg/kg of dry solid Pb 100–400 175 mg/kg of dry solid Ni 15–50 30 mg/kg of dry solid Sb 1–5 3 mg/kg of dry solid Zn 500–1500 900 mg/kg of dry solid As 5–20 12 mg/kg of dry solid Hg 0.5–3 1.4 mg/kg of dry solid Cd 1–5 2 mg/kg of dry solid Mo 4–20 8 mg/kg of dry solid

*DOI: http://dx.doi.org/10.5772/intechopen.91037*

*Average composition of BS in Europe—combined WWTPs [1].*


*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case DOI: http://dx.doi.org/10.5772/intechopen.91037*

#### **Table 1.**

*Sustainable Sewage Sludge Management and Resource Efficiency*

to be evaluated on the same basis.

promoting methods and techniques allowing decreasing amount of BS on sanitary landfills with the aim of decreasing the greenhouse emission as well as decreasing the quantity of landfill leachate [3–6]. In accordance with Council Directive on the landfill of waste (1999/31/EC), landfilling of BS on sanitary landfills is forbidden within the EU-28 countries from July 2009. The Directive on waste from 2008 (2008/98/EC) even more restrictively implements hierarchy with which the European Commission is trying to promote material and energetical use of waste. Nevertheless, blindly following the Directives does not necessarily result in the implementation of optimal and sustainable solutions, and we need to think about new approaches. However, because of those new approaches, all decisions need to be supported by different scientific data, and after that all individual solutions need

In order to allow equal treatment and consistent evaluation of different approaches in the management of BS, the EU Joint Research Centre has developed the "life cycle thinking" (LCT) and "life cycle assessment" (LCA) methodologies and has given the interpretation/instructions on how to use these methods, which should facilitate the decision-making and help managers to establish the most effective and sustainable management system for BS treatment [7]. The guidelines were prepared in cooperation with the International Organization for Standardization (ISO) and are registered under the number SIST EN 14040 and 14,044 [standards for LCA and the International Reference Life Cycle Data System (ILCD) Handbook]. A similar approach in the assessment is used in most European

Each year, EU-28 member states produce more than 10 Mt. of communal BS calculated on dry matter [8, 9]. According to the official data, more than 40% of BS is still being disposed on municipal waste landfills [10]; approximately 36% are reused in agriculture or incinerate [8]; however, Eurostat has no data on the remaining 24% BS [7]. Biodegradable sludge is generated during the operation of urban WWTP utility and contains heavy metals, poorly dissoluble organic compounds (residues of detergents, washing agents, personal hygiene preparations, medicines,

Both unprocessed and processed BS contains heavy metals, residues of phytopharmaceutical products, and surfactants. Their content depends on the origin of the municipal sludge (sludge from the municipal, industrial, or combined treatment plant). In addition to active microorganisms, pathogenic bacteria listed in **Table 3** are also present in unhygienic feces. Because of that, it is difficult to compost them, and the manufactured compost is prohibited for uses in agriculture as fertilizer. The method for the management of BS is different and depends on their origin, composition, especially contents of hazardous and biodegradable substances, and on available infrastructure and local regulations. BS, which is disposed on landfills, is subject to uncontrolled aerobic and anaerobic processes that cause the release of a large amount of greenhouse and noxious gasses (CH4, CO, CO2, H2S, etc.) and emissions of heavy metals. Currently, the EU and the USA are using incineration, composting, stabilization, and landfilling as recognized methods for bio sludge disposal. All mentioned methods have negative environmental impacts, especially landfilling and incineration. The special problem for the environment presents pathogenic microorganisms of different species that exist inside biodegradable sludge and which must be stabilized or neutralized before further application. One of the most economical and environmentally accepted methods for stabilization of BS is their mixing with wasted alkaline materials as ash, slag, foundry sand, and foundry dust. According to the available data from the literature and the LCA analyses, the disposal of BS is the worst choice between the possible solutions, even if landfills are equipped with gas capturing systems and devices for its energetic use [12–14].

countries and almost by all authors of professional publications.

etc.), and possibly pathogens microorganisms (**Tables 1–4**).

**4**

*Average composition of BS in Europe—combined WWTPs [1].*


**Table 2.**

*Average composition of heavy metals in sewage sludge in Europe—combined WWTPs [11].*

Disposal of 1 ton of BS with 20% dry substance emits up to 296.9 kg of CO2(eq) into the atmosphere.

The incineration of BS which is generated by the operation of WWTPs is therefore becoming a common practice of management with BS. The incineration is primarily used for the reduction of the volume and not for energy production, because ash represents only about 30% of the dry matter volume in BS [15]. However, ash disposal remains a serious problem as it still contains heavy metals. LCA analyses showed that the incineration of BS is meaningful only in cases where the systems of the so-called industrial symbiosis exist, such as the co-incineration of BS [15] with coal [16] but with a presumption that the BS is sufficiently dry and the incineration chamber is specially designed (FBR). The incineration of 1 ton of


#### **Table 3.**

*List of pathogens found in BS originated from combined WWTPs.*


#### **Table 4.**

*List of origin of different pollutants and pathogens in BS.*

BS contributes 232.2 kg of CO2(eq) on climate change, pyrolysis up to 146.1 kg of CO2(eq), while burning of equal quantities of BS and energy-rich RDF can reduce pressure on climate change for 15.4 kg CO2(eq) [17].

The LCA itself is dependent on the environment as well on economic, social, and political conditions where the studied example is positioned. Hospido et al. [18] had studied and conducted a comparative study of agricultural use, incineration, and pyrolysis of BS and came to the conclusion that the ecologically acceptable solution is the co-incineration of BS with a coal, but at the same time, this option is least economically acceptable. It has been established that maximum efficiency and minimal environmental impact is achieved when 10–40% of dry BS are added to coal [15]. Different authors have shown practical examples where environmental impacts are mostly reduced when BS are used as fuel and produced ash used as a binder in cement production [19] and as a binder for roofing production [20].

**7**

composite material.

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case*

Notwithstanding, at the EU level, composting is the most common way of managing with BS, although in the last few years, there has been made a big step towards the implementation of anaerobic degradation and energetic use of pro-

The material use of BS, composting, and anaerobic digestion with energetic use and disposal of compost on sanitary landfills seems to be the most acceptable solution [14], because large plants can be subject of discontent on heavily populated areas due to the emission of stench, bioaerosols, and heavy cargo traffic and the

These problems can be partially resolved with decentralization, namely the construction of smaller local but still economically acceptable systems with produc-

The advantages of the decentralized system are (1) shorter transport routes, which mean reduction of the transport costs, reducing emissions into the atmosphere and reducing noise and freight transport; (2) reducing the amount of storage of BS and consequently the reduction of stench emissions; (3) acquisitions for the local community (e.g., the exploitation of the heat produced in biogas incineration processes, which is impossible to transport on greater distances); and (4) use of smaller plants, which are attached to the environment and are less likely to be noticed. The usability of a decentralized approach by different authors has been confirmed with the introduction of the project named ForBiogas in Bologna [14]. The implementation of technologies for the material processing of BS into value-added products, which are also economically acceptable, is totally complied

This is an example of Eco-Bis technology, developed by a company GreenLife

The technology is based on the stabilization of BS, trough mixing pozzolanic ash, or other waste with alkaline properties. The final product of BACOM technology is a water-impermeable material, which can be used for as a substitute for clay in the construction and closure of different types of landfills, the construction of the beds for sewage systems and roads, the construction of inner filler of anti-flooding barriers and restoring of degraded landscapes, and the closure of degraded areas [25]. This technology is also suitable for natural storage of phosphorous. Additional drying is not necessary because ash reacts with moisture present in BS. Hydration of active metal oxides present in ash enables their conversion into alkalis. Due to the high pH and rising temperature, the heavy metals convert into water-insoluble hydroxides and chelate what prevent their further extraction. Released heat and high pH destroy pathogenic and other microorganisms which make the mixture biologically stable. As we can see, there are different approaches and ideas about managing BS. As part of our study, we chose the typical technologies that are currently being operated and compared them with decentralized technologies that enable the material use of BS.

The BACOM technology base on the stabilization of BS, where the BS is mixed with ash and converted into prepared mixture useful for the construction of the

GmbH from Austria and which enables the production of bio-charcoal from BS. Particularly, this is the process of efficient drying of biodegradable sludge using vacuum filtration and subsequently pyrolysis of BS into bio-charcoal which is further used as a supplement to improve the quality of the soil. Bio-charcoal acts as a retainer for fertilizers, pesticides, and water and, at the same time, acts as fertilizer [24]. This standard is also close to BACOM technology (Biosludge Alkaline

Composite Material), developed by the Slovenian company Insol d.o.o. [25].

*DOI: http://dx.doi.org/10.5772/intechopen.91037*

associated negative impacts on the environment.

with the abovementioned guidelines.

**1.1 BACOM technology: mechanism**

tion capacity of less than 3000 tons per year [14, 23].

duced biogas [21, 22].

#### *Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case DOI: http://dx.doi.org/10.5772/intechopen.91037*

Notwithstanding, at the EU level, composting is the most common way of managing with BS, although in the last few years, there has been made a big step towards the implementation of anaerobic degradation and energetic use of produced biogas [21, 22].

The material use of BS, composting, and anaerobic digestion with energetic use and disposal of compost on sanitary landfills seems to be the most acceptable solution [14], because large plants can be subject of discontent on heavily populated areas due to the emission of stench, bioaerosols, and heavy cargo traffic and the associated negative impacts on the environment.

These problems can be partially resolved with decentralization, namely the construction of smaller local but still economically acceptable systems with production capacity of less than 3000 tons per year [14, 23].

The advantages of the decentralized system are (1) shorter transport routes, which mean reduction of the transport costs, reducing emissions into the atmosphere and reducing noise and freight transport; (2) reducing the amount of storage of BS and consequently the reduction of stench emissions; (3) acquisitions for the local community (e.g., the exploitation of the heat produced in biogas incineration processes, which is impossible to transport on greater distances); and (4) use of smaller plants, which are attached to the environment and are less likely to be noticed. The usability of a decentralized approach by different authors has been confirmed with the introduction of the project named ForBiogas in Bologna [14].

The implementation of technologies for the material processing of BS into value-added products, which are also economically acceptable, is totally complied with the abovementioned guidelines.

This is an example of Eco-Bis technology, developed by a company GreenLife GmbH from Austria and which enables the production of bio-charcoal from BS. Particularly, this is the process of efficient drying of biodegradable sludge using vacuum filtration and subsequently pyrolysis of BS into bio-charcoal which is further used as a supplement to improve the quality of the soil. Bio-charcoal acts as a retainer for fertilizers, pesticides, and water and, at the same time, acts as fertilizer [24]. This standard is also close to BACOM technology (Biosludge Alkaline Composite Material), developed by the Slovenian company Insol d.o.o. [25].

The technology is based on the stabilization of BS, trough mixing pozzolanic ash, or other waste with alkaline properties. The final product of BACOM technology is a water-impermeable material, which can be used for as a substitute for clay in the construction and closure of different types of landfills, the construction of the beds for sewage systems and roads, the construction of inner filler of anti-flooding barriers and restoring of degraded landscapes, and the closure of degraded areas [25]. This technology is also suitable for natural storage of phosphorous. Additional drying is not necessary because ash reacts with moisture present in BS. Hydration of active metal oxides present in ash enables their conversion into alkalis. Due to the high pH and rising temperature, the heavy metals convert into water-insoluble hydroxides and chelate what prevent their further extraction. Released heat and high pH destroy pathogenic and other microorganisms which make the mixture biologically stable.

As we can see, there are different approaches and ideas about managing BS. As part of our study, we chose the typical technologies that are currently being operated and compared them with decentralized technologies that enable the material use of BS.

#### **1.1 BACOM technology: mechanism**

The BACOM technology base on the stabilization of BS, where the BS is mixed with ash and converted into prepared mixture useful for the construction of the composite material.

*Sustainable Sewage Sludge Management and Resource Efficiency*

**Pathogen Disease(s) and/or symptoms** *Salmonella* spp. Salmonellosis, typhoid *Shigella* spp. Bacillary dysentery *Escherichia coli* (enteropathogenic strains) Gastroenteritis

*Yersinia enterocolitica* Acute gastroenteritis

*Mycobacterium* spp. Leprosy, tuberculosis *Leptospira* spp. Leptospirosis *Campylobacter* spp. Gastroenteritis

*Clostridium botulinum* Botulism *Bacillus anthracis* Anthrax *Listeria monocytogenes* Listeriosis *Vibrio cholera* Cholera

*List of pathogens found in BS originated from combined WWTPs.*

*Clostridium perfringens* Gastroenteritis (food poisoning)

BS contributes 232.2 kg of CO2(eq) on climate change, pyrolysis up to 146.1 kg of CO2(eq), while burning of equal quantities of BS and energy-rich RDF can reduce

The LCA itself is dependent on the environment as well on economic, social, and political conditions where the studied example is positioned. Hospido et al. [18] had studied and conducted a comparative study of agricultural use, incineration, and pyrolysis of BS and came to the conclusion that the ecologically acceptable solution is the co-incineration of BS with a coal, but at the same time, this option is least economically acceptable. It has been established that maximum efficiency and minimal environmental impact is achieved when 10–40% of dry BS are added to coal [15]. Different authors have shown practical examples where environmental impacts are mostly reduced when BS are used as fuel and produced ash used as a binder in cement production [19] and as a binder for roofing production [20].

**Pollutant in sewage sludge Domestic use Combined sewage system Industrial discharges** Pathogens Human metabolism Animal faces Meat industry

*Staphylococcus* Impetigo, wound infections, food poisoning *Streptococcus* Sore throat, necrotizing, fasciitis, scarlet fever

*Pseudomonas aeruginosa* Otitis externa, skin infections (opportunistic pathogen)

oil (Pb)

Rain (Pb, Cd, Zn), tires (Cu, Cd), roof corrosion (Zn, Cu),

Oil, pesticides, tar, road deicing, rain, combustion Various

Various

amalgam filling (Hg), thermometers (Hg), pipe corrosion (PB, Cu), batteries (Ni, Cd, Pb)

medicines, wood, treatment, cosmetics, detergents, etc.

pressure on climate change for 15.4 kg CO2(eq) [17].

Heavy metals Paints (Pb),

Persistent organic pollutants Paints, solvents,

*List of origin of different pollutants and pathogens in BS.*

**6**

**Table 4.**

**Table 3.**


#### **Table 5.**

*Average composition of ash [26].*

The process is based on mixing wet biodegradable sludge with ash where the ash is a wasted by-product of energy generation. In general, the rule is that the ash produced from paper, paper sludge, wood chips, and wood biomass (PPLP) contains more live lime (CaO) than ash resulting from the incineration of coal, lignite, and peat (PLS). The boiler dust (KP) and the electric filter ash (EP) are suitable for the hygiene and stabilization of the BS at the CEN-EN 12832, where KP/PPLP is more effective than the EP due to a higher content of free CaO (**Table 5**).

After mixing, chemical hydrolyzation and hydration of active earth metal and metal oxides (CaO, MgO, Fe2O3) present in ash occurs:

$$\text{Me} \text{(H}\_{2}\text{O)}\_{\text{n}} \overset{\text{m}+}{\text{}} \text{H}\_{2}\text{O} \rightleftharpoons \text{Me} \text{(H}\_{2}\text{O)}^{\text{(m-1)}\text{\*}} \text{(OH)}^{\text{(m-1)}\text{\*}} \text{+} \text{H}\_{3}\text{O}^{\text{\*}}\tag{1}$$

$$\text{In } \text{Me}^{\text{m}+} \text{ + } \text{m } \text{OH}^{-} \rightarrow \text{Me}\_{\text{n}} \text{ (OH)}\_{\text{m}} \text{ + } \Delta \text{H}\_{\text{h}} \tag{2}$$

This reaction releases heat, which increases mixture temperature up to 65°C and pH value above 12. Under that conditions heavy metals convert into heavy soluble metal hydroxides Mem(OH)n. However, different heavy metal hydroxides have different solubility depending on pH (see **Figure 1**), and adjustment of pH of the mixture is necessary to get chemically inert product. Due to high pH value of the mixture that can increase up to 12.4, the salts of heavy metals are converted into water-insoluble form which prevents further extraction.

Because of alkaline conditions, proteins in the presence of water undergo hydrolytic decomposition and ammonia is formed. In such conditions all pathogenic microorganisms and their spores are destroyed which ensures biological and biochemical stability of the product. A few minutes after stabilization, no *Salmonella* was detected, and the number of *Escherichia coli* was below legal limits [27].

After that the mixture passes into the phase of solidification. Because of a specific mixture of oxides and the CaO content, ash has a high pozzolanic power comparable to Portland cement. Pozzolans are a mixture of silicate and aluminum oxides which itself do not possess the cement values but, in dusty form and in the presence of water, react with CaO already at room temperature and form cement-like materials. The alkali conditions trigger a set of pozzolanic reactions similar as in crystallization of the cement.

Using X-ray diffraction spectrometry lime, portlandite, calcite, quartz, alumina, muscovite, cellulose, and other different C-H-S structures were detected (see **Figure 2**) [29]:

**9**

**Figure 2.**

**Figure 1.**

*pH (right).*

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case*

3Ca(OH)2+ 2SiO2 → 3(CaO)2(SiO)2\*3(H2O)+ C-S-H structures (4)

After 28 days, ettringite structures Ca6Al2(SO4)3(OH)12 × 26H2O may be devel-

*Solubility of heavy metal in independence of pH (left) and adsorption of heavy metal ions in dependence of* 

*X-ray diffraction pattern of biodegradable sludge (BM), biomass ash (VPPZ1), and the composites after 3, 7, 14, 28, 56, and 90 days (VPK-1 to VPK-6, respectively). Legend: C, calcite; T, talc; P, portlandite; Q, quartz; L, lime; G, gehlenite; CC, clinochlor; D, dolomite; Py, pyrite; CACH1, Ca8Al4O14CO2\*24H2O; CACH2,* 

*Ca4Al2O14CO9\*11H2O; CaCh1H, Ca4Al2O6Cl2 \*10H2O [28].*

CaO+ H2O → Ca(OH)2 + ∆Hh (3)

3Ca(OH)2 +Al2O3+3H2O → 3(CaO)Al2O3\*6(H2O) (5)

*DOI: http://dx.doi.org/10.5772/intechopen.91037*

oped in the presence of sulfates.

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case DOI: http://dx.doi.org/10.5772/intechopen.91037*

$$\text{CaO} + \text{H}\_2\text{O} \rightarrow \text{Ca(OH)}\_2 + \Delta\text{H}\_h \tag{3}$$

$$\text{\textbullet Ca(OH)}\_{2} + 2\text{SiO}\_{2} \rightarrow \text{\textbullet (CaO)}\_{2}\text{(SiO)}\_{2}\text{\textbullet (H}\_{2}\text{O)} + \text{C-S-H structures} \tag{4}$$

$$\text{\\$Ca(OH)}\_{2} + \text{Al}\_{2}\text{O}\_{3} + \text{\textdegree H}\_{2}\text{O} \rightarrow \text{\\$(CaO)Al}\_{2}\text{O}\_{3} \text{\textdegree{\\$(H}\_{2}\text{O})}\tag{5}$$

After 28 days, ettringite structures Ca6Al2(SO4)3(OH)12 × 26H2O may be developed in the presence of sulfates.

**Figure 1.**

*Sustainable Sewage Sludge Management and Resource Efficiency*

The process is based on mixing wet biodegradable sludge with ash where the ash is a wasted by-product of energy generation. In general, the rule is that the ash produced from paper, paper sludge, wood chips, and wood biomass (PPLP) contains more live lime (CaO) than ash resulting from the incineration of coal, lignite, and peat (PLS). The boiler dust (KP) and the electric filter ash (EP) are suitable for the hygiene and stabilization of the BS at the CEN-EN 12832, where KP/PPLP is more

**Parameter Unit KP/PPLP EP/PLS EP/PPLP** SiO2 % wt. 32.92 43.70 19.90 CaO % wt. 49.03 12.14 35.70 MgO % wt. 3.50 1.91 1.64 Al2O3 % wt. 14.13 20.45 10.56 Fe2O3 % wt. 0.82 5.23 2.20 MnO % wt. 0.05 0.10 0.03 K2O % wt. 0.55 2.95 0.40 P2O5 % wt. 0.31 0.46 0.14

After mixing, chemical hydrolyzation and hydration of active earth metal and

This reaction releases heat, which increases mixture temperature up to 65°C and pH value above 12. Under that conditions heavy metals convert into heavy soluble metal hydroxides Mem(OH)n. However, different heavy metal hydroxides have different solubility depending on pH (see **Figure 1**), and adjustment of pH of the mixture is necessary to get chemically inert product. Due to high pH value of the mixture that can increase up to 12.4, the salts of heavy metals are converted into

Because of alkaline conditions, proteins in the presence of water undergo hydro-

After that the mixture passes into the phase of solidification. Because of a specific mixture of oxides and the CaO content, ash has a high pozzolanic power comparable to Portland cement. Pozzolans are a mixture of silicate and aluminum oxides which itself do not possess the cement values but, in dusty form and in the presence of water, react with CaO already at room temperature and form cement-like materials. The alkali conditions trigger a set of pozzolanic reactions similar as in crystallization of the

Using X-ray diffraction spectrometry lime, portlandite, calcite, quartz, alumina,

muscovite, cellulose, and other different C-H-S structures were detected

lytic decomposition and ammonia is formed. In such conditions all pathogenic microorganisms and their spores are destroyed which ensures biological and biochemical stability of the product. A few minutes after stabilization, no *Salmonella* was detected, and the number of *Escherichia coli* was below legal limits [27].

(m−1)+

n Mem+ + m OH<sup>−</sup> → Men (OH)m + ∆Hh (2)

(OH)(m−1)+ + H3 O<sup>+</sup> (1)

effective than the EP due to a higher content of free CaO (**Table 5**).

m+ + H2O ⇄ Me (H2O)

metal oxides (CaO, MgO, Fe2O3) present in ash occurs:

water-insoluble form which prevents further extraction.

Me (H2O)n

*Average composition of ash [26].*

**Table 5.**

**8**

cement.

(see **Figure 2**) [29]:

*Solubility of heavy metal in independence of pH (left) and adsorption of heavy metal ions in dependence of pH (right).*

#### **Figure 2.**

*X-ray diffraction pattern of biodegradable sludge (BM), biomass ash (VPPZ1), and the composites after 3, 7, 14, 28, 56, and 90 days (VPK-1 to VPK-6, respectively). Legend: C, calcite; T, talc; P, portlandite; Q, quartz; L, lime; G, gehlenite; CC, clinochlor; D, dolomite; Py, pyrite; CACH1, Ca8Al4O14CO2\*24H2O; CACH2, Ca4Al2O14CO9\*11H2O; CaCh1H, Ca4Al2O6Cl2 \*10H2O [28].*

#### *Sustainable Sewage Sludge Management and Resource Efficiency*

#### **Figure 3.**

*Schematic explanation of the mechanism of hydration in hydration in the C3S-pozzolan system and the C3A-pozzolan system in the presence of Ca(OH)2 and CaSO4 2H2O [30].*


#### **Table 6.**

*Main characteristics of leachate of final product produced by mixing BS and pozzolanic ash in ration 70/30 [29].*

Crystal structures (see **Figure 3**) capture heavy metal hydroxides, other pollutants, and stabilized organics inside the net and prevent further extraction of pollutants. At the same time, crystal structures give the final material geomechanical characteristics (**Tables 6** and **7**).

#### **1.2 BACOM technology**

BACOM technology is an approved technology for the processing of BS in construction composites. It is based on the idea of the alkalization of biological sludge by mixing with the ash, which expresses pozzolanic activity. The BACOM technology operates in

**11**

that are shown in **Figure 4**:

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case*

**Property Measuring method Result** Humidity ISO/TS 17892-1:2001/AC:2010 23% wt. Max. dry density SIST EN 13286-2:2010/AC:2013 1.2 Mg/m3

Uniaxial compressive strength SIST EN 13286-41:2004 96 kPa Shear strength SIST TS ISO/TS 17892-10:2004/AC:2010 φ = 38.47

SIST EN 13286-2:2010/AC:2013 29.1% wt.

SIST TS ISO/TS 17892-5:2004/AC:2010 8213 kPa

SIST TS ISO/TS 17892-11:2004/AC:2010 2.35 × 10<sup>−</sup><sup>7</sup>

c = 42.6 kPa

8213 kPa 10,704 kPa 15,850 kPa 19,390 kPa 23,693 kPa

accordance with the European CEN-EN 12832 and complies to the conditions for the processing and use of biodegradable, municipal, and similar sludge, including chemical hygienization and inertization of BS and by mixing with live lime and/or ash.

*The main geomechanical characteristics of final product produced by mixing BS and pozzolanic ash in ration* 

• In the first stage, raw biodegradable sludge (1) is mixed with ash (2).

as technological part of the existing biological wastewater treatment plant.

• Thickened material (4) is additionally admixed with composite material (5)

Applying the BACOM technology in the processes of disposal of the biodegradable sludge enables reduction of investment costs in the beginning due to the smaller storage capacities needed for storage biodegradable sludge and alkaline materials. Due to the fast exploitation of the biodegradable sludge, the biological decomposition of the organic components is reduced on the lowest possible level, and because of that, additional reduction of negative impacts on the environment is achieved. The technology can be built as independent facility for the processing of the biodegradable sludge or

• Inside mixing device (3), semisolid mixture (4) is formed.

and the final product (6) is formed.

It enables to mix biodegradable sludge, which contains from 2 to 30% of dry matter with ash (or other alkaline materials) which usually contains up to 80% of earth alkali and/or metal oxides. When the content of dry matter increases up to 60%, the mixture passes to semisolid state and solidify after a short time (in average after 72 hours). The construction and mechanical characteristics can be improved by further admixing different materials such as ash, cement, lime, micro silica, porcelain, slag, foundry sand, natural and artificial fibers, and different kinds of vermiculites. With careful choice of additives, the chemical, mechanical, geotechnical, and hydromechanical characteristics of produced materials can be adjusted and improved before further application. The technological process of BACOM includes three main process operations

*DOI: http://dx.doi.org/10.5772/intechopen.91037*

Optimal humidity on standard

Compressibility module at load rate:

Water impermeability at load rate

Proctor test

• 50 kPa • 100 kPa • 200 kPa • 400 kPa • 800 kPa

200 cm/s

**Table 7.**

*70/30 [29].*

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case DOI: http://dx.doi.org/10.5772/intechopen.91037*


#### **Table 7.**

*Sustainable Sewage Sludge Management and Resource Efficiency*

Crystal structures (see **Figure 3**) capture heavy metal hydroxides, other pollutants, and stabilized organics inside the net and prevent further extraction of pollutants. At the same time, crystal structures give the final material geomechani-

*Main characteristics of leachate of final product produced by mixing BS and pozzolanic ash in ration 70/30 [29].*

*Schematic explanation of the mechanism of hydration in hydration in the C3S-pozzolan system and the* 

**Component Detection method Legal limit in leachate in mg/kg s.s. Result in mg/kg s.s.** As SIST EN ISO 17294-2:2005 0.5 <0.02 Ba SIST EN ISO 17294-2:2005 20 0.94 Cd SIST EN ISO 17294-2:2005 0.04 <0.005 Cr (total) SIST EN ISO 17294-2:2005 0.5 <0.01 Cu SIST EN ISO 17294-2:2005 2 0.94 Hg SIST EN ISO 17294-2:2005 0.01 <0.001 Mo SIST EN ISO 17294-2:2005 0.5 <0.05 Ni SIST EN ISO 17294-2:2005 0.4 0.18 Pb SIST EN ISO 17294-2:2005 0.5 0.15 Sb SIST EN ISO 17294-2:2005 0.06 0.013 Se SIST EN ISO 17294-2:2005 0.1 <0.01 Zn SIST EN ISO 17294-2:2005 4 0.21 Chloride SIST EN ISO 10304-1:2009 800 57.3 Fluoride SIST EN ISO 10304-1:2009 10 1.2 Sulfate SIST EN ISO 10304-1:2009 6000 25.7

*C3A-pozzolan system in the presence of Ca(OH)2 and CaSO4 2H2O [30].*

BACOM technology is an approved technology for the processing of BS in construction composites. It is based on the idea of the alkalization of biological sludge by mixing with the ash, which expresses pozzolanic activity. The BACOM technology operates in

**10**

**Table 6.**

**Figure 3.**

cal characteristics (**Tables 6** and **7**).

**1.2 BACOM technology**

*The main geomechanical characteristics of final product produced by mixing BS and pozzolanic ash in ration 70/30 [29].*

accordance with the European CEN-EN 12832 and complies to the conditions for the processing and use of biodegradable, municipal, and similar sludge, including chemical hygienization and inertization of BS and by mixing with live lime and/or ash.

It enables to mix biodegradable sludge, which contains from 2 to 30% of dry matter with ash (or other alkaline materials) which usually contains up to 80% of earth alkali and/or metal oxides. When the content of dry matter increases up to 60%, the mixture passes to semisolid state and solidify after a short time (in average after 72 hours). The construction and mechanical characteristics can be improved by further admixing different materials such as ash, cement, lime, micro silica, porcelain, slag, foundry sand, natural and artificial fibers, and different kinds of vermiculites. With careful choice of additives, the chemical, mechanical, geotechnical, and hydromechanical characteristics of produced materials can be adjusted and improved before further application.

The technological process of BACOM includes three main process operations that are shown in **Figure 4**:


Applying the BACOM technology in the processes of disposal of the biodegradable sludge enables reduction of investment costs in the beginning due to the smaller storage capacities needed for storage biodegradable sludge and alkaline materials. Due to the fast exploitation of the biodegradable sludge, the biological decomposition of the organic components is reduced on the lowest possible level, and because of that, additional reduction of negative impacts on the environment is achieved. The technology can be built as independent facility for the processing of the biodegradable sludge or as technological part of the existing biological wastewater treatment plant.

#### *Sustainable Sewage Sludge Management and Resource Efficiency*

**Figure 4.** *Schematic explanation of BACOM process.*

Overall, the implementation of BACOM technology into processes of recycling and disposal of BS can decrease investment costs for about 90% comparing to the other mentioned technologies, and overall costs of disposal calculated on dry matter can decrease by 88%. At the same time, the greenhouse effect decreases by 95% compared to incineration. The produced composite can be of further use for cheap replacement for geo-composite material or clay which additionally contributes to decreasing of the greenhouse effect due to reduction of land degradation which is a consequence of the opening of a new mining site.

Up to today the usage of alkaline waste for the stabilization of biodegradable sludge did not get application in big extent due to batch processes of stabilization which demands organization of relatively large storage capacity for biodegradable sludge and large storage capacities for final product. During the uncontrolled storage of the sludge, aerobic and anaerobic degradation processes occur inside the sludge that cause organic decay of organic part and consequently releasing of greenhouse gasses and unpleasant smell into environment. The BACOM technology solved those issues with enabling continuous stabilization of biodegradable sludge with online mixing of the alkaline materials and composite materials into the sludge, and the production of construction composite materials and long storage is not needed. The solution is based on innovative connection of two batch processes inside one efficient continued process, which at the end leads to sustainable production of replacements of geo-composites and clay.

#### **2. Case study**

The example for the determination of sustainability of BACOM technology compared to other available technologies has been placed in Slovenia, which represents a small, closed, and relatively densely populated area. Slovenia has a smaller incinerator in Celje, so the incineration of BS was not taken into account in the performance of the study, but we have therefore studied possible involvement of Eco-Bis technology. The study model is appropriate for smaller, more populated areas with less developed systems for BS management. According to the ARSO (Slovenian Environment Agency) data, in Slovenia 203,059 tons of BS or approximately 100,000 tons of dry matter was produced in 2017. About 70,000 tons of these were exported to Hungary for the preparation of artificial soil; 34,000 tons were driven to incineration; 12,000 tons in landings; 20,000 tons on composting; and the rest wastes were exported to other processing operations. The use in agriculture has

**13**

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case*

been exceptionally small already from 2006. The main transport distance for the

Environmental profiles and comparative studies were made by the LCA methodology standardized according to ISO 14040 and 14,044, which is suitable for comparison and evaluation of different technologies within the prescribed boundaries. Using the SimaPro 7.1 software package and its database, the comparison was made by the IMPACT 2002 + method [31]. The methodology included (1) purpose and definitions, (2) inventory list, (3) determination of effects, and (4) interpretation. The specifics of the methodology, the main hypothesis, the key assumptions,

The aim of the study was to evaluate and compare the different management systems with BS in closed densely populated areas, as well as defining environmental impacts and energy balances. Although in most cases the transport of BS represented a large proportion of emissions, transport was neglected with the reason that the boundaries were determined at the entrance to the processing. The independent evaluation of individual technologies was enabled. In the analysis, due to the continuation of the calculation, the drying process of BS from 2 to 20% of the dry matter is excluded. All calculations were based on the presumption that biodegradable sludge with 20% of dry matter is being processed. The LCA also ignored the construction and dissembling of individual technologies because in this analysis, only the influence of the working activities of individual technologies is of interest. Scenario 1 (landfilling) represents the disposal of BS on sanitary landfills which

have arranged system for capturing biogas and burning of biogas on torches. According to the predictions, about 45% of the generating biogas is captured, and 55% of the generated biogas is emitted into the atmosphere through the different part of the landfill as, for example, drainage system and the boundary slopes. Although such a scenario is undesirable and banned in the EU, it should be considered due to undeveloped and inefficient management systems and because it is used

Scenario 2 (composting) represents composting of BS with 20% of dry substance, with a technique of aerobic digestion in open digs equipped with active aerating systems. According to the experience and literary data, it was presumed that active composting lasts 24 days and further ripening of the compost for another 60 days. The compost with approximately 40% of dry substance is landfilled on sanitary depot. Power consumption for processing 1 ton of BS in compost is 90 kWh; embedding of the compost in the body of the landfill requires additional

Scenario 3 (AD&L) represents anaerobic digestion of BS and use of a manufactured biogas for electricity production. The heat is not used, and the compost is embedded in the sanitary landfill. For anaerobic processing 1 ton of BS with 20% of dry substance in average 34 kWh of electric power and 20 liters of water is used. Processing of BS with 20% of dry matter in biogas and its active use ensures

Scenario 4 (BACOM) represents the solidification/stabilization of the BS with pozzolanic ash in proportions from 30/70 to 70/30 which depends on the final use of the product. The product can be used for replacing clay or bentonite. For the

transport of BS to processing/landings was less than 250 km.

and conclusions will be described through the accompanying text.

*DOI: http://dx.doi.org/10.5772/intechopen.91037*

**3. Methodology**

**3.1 Purpose and definition**

in more than 50% of examples.

use of 0.6 kg of diesel fuel for 1 ton of BS.

production of about 175 kWh surplus of electricity.

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case DOI: http://dx.doi.org/10.5772/intechopen.91037*

been exceptionally small already from 2006. The main transport distance for the transport of BS to processing/landings was less than 250 km.

#### **3. Methodology**

*Sustainable Sewage Sludge Management and Resource Efficiency*

consequence of the opening of a new mining site.

Overall, the implementation of BACOM technology into processes of recycling and disposal of BS can decrease investment costs for about 90% comparing to the other mentioned technologies, and overall costs of disposal calculated on dry matter can decrease by 88%. At the same time, the greenhouse effect decreases by 95% compared to incineration. The produced composite can be of further use for cheap replacement for geo-composite material or clay which additionally contributes to decreasing of the greenhouse effect due to reduction of land degradation which is a

Up to today the usage of alkaline waste for the stabilization of biodegradable sludge

The example for the determination of sustainability of BACOM technology compared to other available technologies has been placed in Slovenia, which represents a small, closed, and relatively densely populated area. Slovenia has a smaller incinerator in Celje, so the incineration of BS was not taken into account in the performance of the study, but we have therefore studied possible involvement of Eco-Bis technology. The study model is appropriate for smaller, more populated areas with less developed systems for BS management. According to the ARSO (Slovenian Environment Agency) data, in Slovenia 203,059 tons of BS or approximately 100,000 tons of dry matter was produced in 2017. About 70,000 tons of these were exported to Hungary for the preparation of artificial soil; 34,000 tons were driven to incineration; 12,000 tons in landings; 20,000 tons on composting; and the rest wastes were exported to other processing operations. The use in agriculture has

did not get application in big extent due to batch processes of stabilization which demands organization of relatively large storage capacity for biodegradable sludge and large storage capacities for final product. During the uncontrolled storage of the sludge, aerobic and anaerobic degradation processes occur inside the sludge that cause organic decay of organic part and consequently releasing of greenhouse gasses and unpleasant smell into environment. The BACOM technology solved those issues with enabling continuous stabilization of biodegradable sludge with online mixing of the alkaline materials and composite materials into the sludge, and the production of construction composite materials and long storage is not needed. The solution is based on innovative connection of two batch processes inside one efficient continued process, which at the end leads to sustainable production of replacements of geo-composites and clay.

**12**

**2. Case study**

**Figure 4.**

*Schematic explanation of BACOM process.*

Environmental profiles and comparative studies were made by the LCA methodology standardized according to ISO 14040 and 14,044, which is suitable for comparison and evaluation of different technologies within the prescribed boundaries. Using the SimaPro 7.1 software package and its database, the comparison was made by the IMPACT 2002 + method [31]. The methodology included (1) purpose and definitions, (2) inventory list, (3) determination of effects, and (4) interpretation. The specifics of the methodology, the main hypothesis, the key assumptions, and conclusions will be described through the accompanying text.

#### **3.1 Purpose and definition**

The aim of the study was to evaluate and compare the different management systems with BS in closed densely populated areas, as well as defining environmental impacts and energy balances. Although in most cases the transport of BS represented a large proportion of emissions, transport was neglected with the reason that the boundaries were determined at the entrance to the processing. The independent evaluation of individual technologies was enabled. In the analysis, due to the continuation of the calculation, the drying process of BS from 2 to 20% of the dry matter is excluded. All calculations were based on the presumption that biodegradable sludge with 20% of dry matter is being processed. The LCA also ignored the construction and dissembling of individual technologies because in this analysis, only the influence of the working activities of individual technologies is of interest.

Scenario 1 (landfilling) represents the disposal of BS on sanitary landfills which have arranged system for capturing biogas and burning of biogas on torches. According to the predictions, about 45% of the generating biogas is captured, and 55% of the generated biogas is emitted into the atmosphere through the different part of the landfill as, for example, drainage system and the boundary slopes. Although such a scenario is undesirable and banned in the EU, it should be considered due to undeveloped and inefficient management systems and because it is used in more than 50% of examples.

Scenario 2 (composting) represents composting of BS with 20% of dry substance, with a technique of aerobic digestion in open digs equipped with active aerating systems. According to the experience and literary data, it was presumed that active composting lasts 24 days and further ripening of the compost for another 60 days. The compost with approximately 40% of dry substance is landfilled on sanitary depot. Power consumption for processing 1 ton of BS in compost is 90 kWh; embedding of the compost in the body of the landfill requires additional use of 0.6 kg of diesel fuel for 1 ton of BS.

Scenario 3 (AD&L) represents anaerobic digestion of BS and use of a manufactured biogas for electricity production. The heat is not used, and the compost is embedded in the sanitary landfill. For anaerobic processing 1 ton of BS with 20% of dry substance in average 34 kWh of electric power and 20 liters of water is used. Processing of BS with 20% of dry matter in biogas and its active use ensures production of about 175 kWh surplus of electricity.

Scenario 4 (BACOM) represents the solidification/stabilization of the BS with pozzolanic ash in proportions from 30/70 to 70/30 which depends on the final use of the product. The product can be used for replacing clay or bentonite. For the

processing of 1 ton of BS with 20% of dry matter, 0.3 kWh of electric power and additional 0.6 kg of diesel fuel for its embedding are used. The emissions into the environment are reduced to 1% compared to uncontrollable landfilling of BS. From 1 ton of BS with 20% dry matter, up to 1.3 tons of clay replacement can be produced.

Scenario 5 (Greenlife Eco-Bis) represents a technology for controlled pyrolyzing of BS into biochar. BS is dried from 20 to 75% dryness with the use of the heat produced with pyrolytic processes. The average use of energy for drying is 192.73 MJ/kg of BS. After that, the dry sludge is pyrolyzed into bio-coal under controlled conditions. The gain of heat using pyrolytic processes is around 243.10 MJ/kg of dry BS, taken into account that the electricity consumption for processes itself is 40 kWh. From 1 ton of BS with 20% of dry substance, the 300 kg of coal can be produced. Produced biochar can efficiently replace artificial and growing fertilizers in agriculture.

#### **3.2 System boundaries**

System boundaries are defined with the input of BS at the entrance into the processing. Due to the equalized assessment, transport and system of drying of the BS are neglected. It is necessary to note that the technology of the BACOM drying the sludge is not necessary because it also works with the sludge where the content of the dry substance is lower than 10%. Greenlife Eco-Bis technology has a builtin effective drying system with the system of vacuum filtration which is exploit surplus heat which is generated within pyrolytic processes. System boundaries are graphically displayed in **Figure 5**.

#### **3.3 Functional unit**

The functional unit is used for the definition of input or output from the system. The purpose of introducing a functional unit is equalizing evaluation of different scenarios. In our case, the functional unit used for evaluation is 1 ton of BS containing 20% of dry substance.

#### **3.4 Inventory analysis**

At this stage, the input materials, energy used, as well as emissions into the atmosphere, water, and soil were evaluated. Data about the BS which is processed by the

**15**

**4. Discussion**

**Table 8.**

**Tables 9** and **10**.

**4.1 Impacts on human health**

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case*

**Scenario 1 2 3 4 5**

CO2 14.23 61.81 61.81 0.1423 0.1020 CO 0.02 0.10 0.10 0.0020 0.0128 CH4 15.14 0.05 — 0.1514 0.0002 VOC 0.02 0.01 0.30 0.0002 — NOX 0.04 — 0.30 0.0004 — Nitrogen 4.63 — — 0.0463 — Oxygen 0.02 — — 0.0002 — H2S 0.02 0.02 — 0.0020 — PM10 — 0.11 — — — NH3 — 0.04 — — — SO2 — 0.01 0.01 — — HCl — 0.01 0.01 — —

**Landfilling Composting Anaerobic BACOM Pyrolysis**

company CeROD d.o.o. and CeROP (for year 2013 and 2015) were obtained from the BS analysis; data on emissions of gasses in the process of degradation of BS were measured and equalized with data obtained from the peer reviewed literature [14, 15, 32] and are shown in **Table 8**. Data about electricity production for Slovenia were obtained from the database BUWAL 250 and data about clay from the ETH-ESU database.

*Partial list of emissions into the atmosphere and water for particular scenarios in kg per ton BS with 20% dry solids.*

Chlorides 0.028 0.028 0.028 0.00028 0.1020 KPK5 0.011 0.011 0.011 0.00011 0.0128 BPK5 0.056 0.056 0.056 0.00056 0.0002 Nitrogen 0.003 0.003 0.003 0.00003 0.0062 Suspended part. 0.002 0.002 0.002 0.00002 0.0146 NH4OH 0.001 0.001 0.001 0.00001 0.0005 P (total) 0.001 0.001 0.001 0.00001 0.0000

Potential effects of five different scenarios (technologies) are listed in

From **Table 10** and **Figure 6**, it is evident that the total impact on human health in the case of landfilling of BS, which is equipped with the system for the active capture and incineration of biogas, is by 16.55 units lesser than the impact on human health caused by composting. Such conclusions come from the fact that the effects in the case of landfilling are limited to fenced and guarded spaces and that there are no emissions of dust, as well as from the fact that the disposal of BS does not require additional

*DOI: http://dx.doi.org/10.5772/intechopen.91037*

Emissions into air

Emissions into water

**Figure 5.** *System boundaries for LCA.*


*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case DOI: http://dx.doi.org/10.5772/intechopen.91037*

#### **Table 8.**

*Sustainable Sewage Sludge Management and Resource Efficiency*

processing of 1 ton of BS with 20% of dry matter, 0.3 kWh of electric power and additional 0.6 kg of diesel fuel for its embedding are used. The emissions into the environment are reduced to 1% compared to uncontrollable landfilling of BS. From 1 ton of BS with 20% dry matter, up to 1.3 tons of clay replacement can be produced. Scenario 5 (Greenlife Eco-Bis) represents a technology for controlled pyrolyzing of BS into biochar. BS is dried from 20 to 75% dryness with the use of the heat produced with pyrolytic processes. The average use of energy for drying is 192.73 MJ/kg of BS. After that, the dry sludge is pyrolyzed into bio-coal under controlled conditions. The gain of heat using pyrolytic processes is around 243.10 MJ/kg of dry BS, taken into account that the electricity consumption for processes itself is 40 kWh. From 1 ton of BS with 20% of dry substance, the 300 kg of coal can be produced. Produced biochar

System boundaries are defined with the input of BS at the entrance into the processing. Due to the equalized assessment, transport and system of drying of the BS are neglected. It is necessary to note that the technology of the BACOM drying the sludge is not necessary because it also works with the sludge where the content of the dry substance is lower than 10%. Greenlife Eco-Bis technology has a builtin effective drying system with the system of vacuum filtration which is exploit surplus heat which is generated within pyrolytic processes. System boundaries are

The functional unit is used for the definition of input or output from the system. The purpose of introducing a functional unit is equalizing evaluation of different scenarios. In our case, the functional unit used for evaluation is 1 ton of BS contain-

At this stage, the input materials, energy used, as well as emissions into the atmosphere, water, and soil were evaluated. Data about the BS which is processed by the

can efficiently replace artificial and growing fertilizers in agriculture.

**3.2 System boundaries**

graphically displayed in **Figure 5**.

**3.3 Functional unit**

ing 20% of dry substance.

**3.4 Inventory analysis**

**14**

**Figure 5.**

*System boundaries for LCA.*

*Partial list of emissions into the atmosphere and water for particular scenarios in kg per ton BS with 20% dry solids.*

company CeROD d.o.o. and CeROP (for year 2013 and 2015) were obtained from the BS analysis; data on emissions of gasses in the process of degradation of BS were measured and equalized with data obtained from the peer reviewed literature [14, 15, 32] and are shown in **Table 8**. Data about electricity production for Slovenia were obtained from the database BUWAL 250 and data about clay from the ETH-ESU database.

#### **4. Discussion**

Potential effects of five different scenarios (technologies) are listed in **Tables 9** and **10**.

#### **4.1 Impacts on human health**

From **Table 10** and **Figure 6**, it is evident that the total impact on human health in the case of landfilling of BS, which is equipped with the system for the active capture and incineration of biogas, is by 16.55 units lesser than the impact on human health caused by composting. Such conclusions come from the fact that the effects in the case of landfilling are limited to fenced and guarded spaces and that there are no emissions of dust, as well as from the fact that the disposal of BS does not require additional


#### **Table 9.**

*List of effects on subgroups IMPACT 2002+.*


**17**

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case*

energy consumption for processing. The reduction of the impact on human health by additional 166.84 units is reflected in the use of Eco-Bis technology instead of landfilling of BS primarily due to the energy utilization and consequentially direct emission reductions as well as additional emissions reductions because of the replacement of artificial fertilizers with environmental friendly bio-coal. The additional reduction in impacts by the 135 units was calculated in case of using the technology of converting BS into replacements for clay and bentonite geo-composites (BACOM). Opening of new clay mines, where energy demanding processes are applied for clay production are not needed anymore in the case of implementation of BACOM technology.

From **Table 10** and **Figure 6**, it is evident that direct landfilling of BS on the waste disposal site has approximately 2.5 times higher negative impact on the ecosystem as a controlled aerobic or anaerobic digestion of BS which also includes disposal of the produced compost on sanitary landfill. This is the result of the reduction of uncontrolled emission of biogas and toxic substances into the environment. A decrease of additional 6.16 units was calculated in the case of the use of Eco-Bis instead of landfilling of BS due to the prevention of its biological decomposing where decreasing impacts on the environment are based primarily on the replacement of the artificial fertilizer with biochar. Further reduction of negative impacts on the ecosystem for 24.45 units can be achieved by using BACOM technology and is the result of prevention of biologic breakdown of BS and of the fact that the manufactured material can

From **Table 10** and **Figure 6**, it is evident that landfilling of BS on the waste disposal site has 344 times more negative impact on climate change than composting and anaerobic processing and the subsequent disposal of compost to the waste disposal site. This is the result of the reduction of uncontrolled emission of greenhouse gasses into the environment. However, additional reduction of 297.76 units was noted when using BACOM technology which is the result of prevention of biologic breakdown of BS and the fact that the manufactured material can be used as a substitute for clay, bentonite, and plastic materials. An additional reduction

be used as a substitute for clay, bentonite, and plastic materials.

*DOI: http://dx.doi.org/10.5772/intechopen.91037*

**4.2 Impacts on ecosystems**

**Figure 6.** *Overall LCA result.*

**4.3 Impacts on climate change**

#### **Table 10.**

*List of effects on groups IMPACT 2002+.*

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case DOI: http://dx.doi.org/10.5772/intechopen.91037*

**Figure 6.** *Overall LCA result.*

*Sustainable Sewage Sludge Management and Resource Efficiency*

Emissions of carcinogenic substances

Emissions of noncarcinogenic substances

Emissions of substances harmful for respiratory system

Emission of substances which destroying ozone

layer

Emission of organic pollutants harmful for respiratory path

Acidification of water environ.

Non-renewable energy sources

Extraction of minerals

> Human health

Climate changes

Natural resources

**Table 10.**

*List of effects on subgroups IMPACT 2002+.*

Ecosystem PDF\*m2

*List of effects on groups IMPACT 2002+.*

**Table 9.**

**Subgroup Unit Landfill Compost AD&L BACOM Eco-Bis**

Ionization DALY 1.66E-07 1.66E-07 0 −0.38479 −0.00135

Aquatic toxicity PDF\*m2\*l 2.68E-05 0.000227 9.92E-05 −0.92158 −1.75714 Soil toxicity PDF\*m2\*l 2.1E-05 0.002301 0.002271 −21.251 −0.24776 Soil acidification PDF\*m2\*l 0.166662 0.454253 0.454224 −3.56515 −3.98712 Land use PDF\*m2\*l 5.86E-07 5.86E-07 0.00 −5.03381 −0.33184

Water eutrophic. — — — — — Climate change kg CO2(eq) 121.444 0.357449 0.35498 −176.323 −203.961

**Effect on: Unit Landfill Compost AD&L BACOM Eco-Bis**

DALY 3.03E-05 0.000613 0.000231 −5.08814 1.75173

DALY 0.024072 0.032287 0.032183 −4.2439 −11.8864

DALY 5.046047 21.85825 21.85621 −291.066 −162.069

DALY 4.73E-07 8.39E-07 1.45E-07 −0.35543 −0.0001

DALY 0.291465 0.018953 0.018951 −0.72645 0.007838

MJ prim. 0.000434 0.005132 0.001863 −162.77 −212.651

MJ prim. 1.52E-08 1.52E-08 0.00 −1.3E-05 −0.0015

DALY 5.361614 21.91011 21.90758 −301.864 −172.197

kg CO2(eq) 121.444 0.357449 0.35498 −176.323 −203.961

MJ prim. 0.000434 0.005132 0.001863 −162.77 −212.652

\*l 0.166711 0.456783 0.456594 −30.7715 −6.32386

— — — — —

**16**

energy consumption for processing. The reduction of the impact on human health by additional 166.84 units is reflected in the use of Eco-Bis technology instead of landfilling of BS primarily due to the energy utilization and consequentially direct emission reductions as well as additional emissions reductions because of the replacement of artificial fertilizers with environmental friendly bio-coal. The additional reduction in impacts by the 135 units was calculated in case of using the technology of converting BS into replacements for clay and bentonite geo-composites (BACOM). Opening of new clay mines, where energy demanding processes are applied for clay production are not needed anymore in the case of implementation of BACOM technology.

#### **4.2 Impacts on ecosystems**

From **Table 10** and **Figure 6**, it is evident that direct landfilling of BS on the waste disposal site has approximately 2.5 times higher negative impact on the ecosystem as a controlled aerobic or anaerobic digestion of BS which also includes disposal of the produced compost on sanitary landfill. This is the result of the reduction of uncontrolled emission of biogas and toxic substances into the environment. A decrease of additional 6.16 units was calculated in the case of the use of Eco-Bis instead of landfilling of BS due to the prevention of its biological decomposing where decreasing impacts on the environment are based primarily on the replacement of the artificial fertilizer with biochar. Further reduction of negative impacts on the ecosystem for 24.45 units can be achieved by using BACOM technology and is the result of prevention of biologic breakdown of BS and of the fact that the manufactured material can be used as a substitute for clay, bentonite, and plastic materials.

#### **4.3 Impacts on climate change**

From **Table 10** and **Figure 6**, it is evident that landfilling of BS on the waste disposal site has 344 times more negative impact on climate change than composting and anaerobic processing and the subsequent disposal of compost to the waste disposal site. This is the result of the reduction of uncontrolled emission of greenhouse gasses into the environment. However, additional reduction of 297.76 units was noted when using BACOM technology which is the result of prevention of biologic breakdown of BS and the fact that the manufactured material can be used as a substitute for clay, bentonite, and plastic materials. An additional reduction

of 27.6 units was calculated in the use of Eco-Bis technology, and it is the result of a completely prevented biological degradation of BS and of the replacement of the artificial fertilizers with biochar.

#### **4.4 Impacts on the use of natural resources**

From **Table 10** and **Figure 6**, it is evident that a landfilling of BS on sanitary landfill, composting, and anaerobic digestion and the subsequent disposal of the compost onto the landfill have no impact on the use of natural resources. Additional reduction of 162 units is enabled with the implementation of the BACOM technology because the manufactured material can be used as a substitute for clay, bentonite, and in some cases as plastic. The additional reduction of 66.9 units is enabled by the usage of Eco-Bis charcoal as the replacement of artificial fertilizers ( **Table 9** and **Figure 6**).

The overall sustainability of using different technologies from the highest to the least efficient is as follows: BACOM > Eco-Bis > AD&L > composting > disposal.

#### **5. Conclusions**

According to expectations, landfilling of BS in sanitary landfills is the least acceptable option, even though modern landfills are equipped with modern biogas capture systems. Composting is an acceptable and widely accepted option because it is cheap and has rather neutral effect on the sustainability of the management of BS. However, considering the investment and operational costs which have no economic effect, it is less desirable option than anaerobic digesting, where the produced biogas can be exploited for energy production.

All abovementioned solutions need centralized organization. Successful operation requires large surfaces, and due to that, the local community must agree with the implementation of such a plant inside local areas. In addition, risk management in centrally organized technologies requires extensive and complex logistic operation and relatively large operating costs to achieve a small economic gain.

Material processing and material use of BS seems to be a much more acceptable and sustainable option than landfilling or incineration, because cheap replacements for materials produced from nonrenewable sources (e.g., artificial fertilizers, clays, bentonite, or even plastics in some cases) can be produced. In many cases these processes reduce negative pressures on the environment and improve life in the local communities.

These installations are usually small and mobile and can be placed directly in the vicinity of the WWTPs. The problems with burdening of the environment and rising costs because of extended logistics are solved or at least minimized in such a case. In addition, material processing and use of manufactured material mean the production of products with an added value, which can be used as raw materials or semifinished products in other industrial sectors, what is in accordance with the principles of industrial eco symbiosis and circular economy. The aforementioned technologies enable the creation of new jobs and the reduction of wastewater treatment costs.

The involvement of material processing technologies is in a consensus with the European Directive on waste (2008/98/EC) as shown in **Figure 2**.

Each technology has its own benefits or deficiencies, but in general the central organizing technologies as, for example, incineration, anaerobic digestion, composting, and landfilling, are more appropriate for processing of BS in a bigger scale (e.g., quantities above 30.000 tons of biosolids per year); meanwhile, smaller and more flexible technologies for material processing are more suitable for processing of BS in quantities below 30,000 tons per year.

**19**

**Author details**

1 Škrlj d.o.o., Slovenia

2 Ekorec d.o.o., Slovenia

\* and Marjan Zemljič2

provided the original work is properly cited.

\*Address all correspondence to: marko.likon@telemach.net

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Marko Likon1

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case*

*DOI: http://dx.doi.org/10.5772/intechopen.91037*

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case DOI: http://dx.doi.org/10.5772/intechopen.91037*

### **Author details**

*Sustainable Sewage Sludge Management and Resource Efficiency*

artificial fertilizers with biochar.

**5. Conclusions**

local communities.

**4.4 Impacts on the use of natural resources**

of 27.6 units was calculated in the use of Eco-Bis technology, and it is the result of a completely prevented biological degradation of BS and of the replacement of the

From **Table 10** and **Figure 6**, it is evident that a landfilling of BS on sanitary landfill, composting, and anaerobic digestion and the subsequent disposal of the compost onto the landfill have no impact on the use of natural resources. Additional reduction of 162 units is enabled with the implementation of the BACOM technology because the manufactured material can be used as a substitute for clay, bentonite, and in some cases as plastic. The additional reduction of 66.9 units is enabled by the usage of Eco-Bis charcoal as the replacement of artificial fertilizers ( **Table 9** and **Figure 6**). The overall sustainability of using different technologies from the highest to the least efficient is as follows: BACOM > Eco-Bis > AD&L > composting > disposal.

According to expectations, landfilling of BS in sanitary landfills is the least acceptable option, even though modern landfills are equipped with modern biogas capture systems. Composting is an acceptable and widely accepted option because it is cheap and has rather neutral effect on the sustainability of the management of BS. However, considering the investment and operational costs which have no economic effect, it is less desirable option than anaerobic digesting, where the

All abovementioned solutions need centralized organization. Successful operation requires large surfaces, and due to that, the local community must agree with the implementation of such a plant inside local areas. In addition, risk management in centrally organized technologies requires extensive and complex logistic opera-

Material processing and material use of BS seems to be a much more acceptable and sustainable option than landfilling or incineration, because cheap replacements for materials produced from nonrenewable sources (e.g., artificial fertilizers, clays, bentonite, or even plastics in some cases) can be produced. In many cases these processes reduce negative pressures on the environment and improve life in the

These installations are usually small and mobile and can be placed directly in the vicinity of the WWTPs. The problems with burdening of the environment and rising costs because of extended logistics are solved or at least minimized in such a case. In addition, material processing and use of manufactured material mean the production of products with an added value, which can be used as raw materials or semifinished products in other industrial sectors, what is in accordance with the principles of industrial eco symbiosis and circular economy. The aforementioned technologies enable the creation of new jobs and the reduction of wastewater treatment costs. The involvement of material processing technologies is in a consensus with the

Each technology has its own benefits or deficiencies, but in general the central organizing technologies as, for example, incineration, anaerobic digestion, composting, and landfilling, are more appropriate for processing of BS in a bigger scale (e.g., quantities above 30.000 tons of biosolids per year); meanwhile, smaller and more flexible technologies for material processing are more suitable for processing

tion and relatively large operating costs to achieve a small economic gain.

European Directive on waste (2008/98/EC) as shown in **Figure 2**.

of BS in quantities below 30,000 tons per year.

produced biogas can be exploited for energy production.

**18**

Marko Likon1 \* and Marjan Zemljič2

1 Škrlj d.o.o., Slovenia

2 Ekorec d.o.o., Slovenia

\*Address all correspondence to: marko.likon@telemach.net

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **References**

[1] Fytili D, Zabaniotou A. Utilization of sewage sludge in EU application of old and new methods—A review. Renewable Sustainable Energy Rewiews. 2006;**12**(1):116-140

[2] Kroiss H. What is the potential for utilizing the resources in sludge. Water Science and Technology. 2004;**49**(10):1-10

[3] Aubain P, Gazzo A, Le Moux J, Mugnier E, Brunet H, Landrea B. Disposal and Recycling Routes for Sewage Sludge. Luxembourg: EC; 2001. p. 38. ISBN: 92-894-1798-6

[4] LeBlanc RJ, Matthews P, Richard RP. Global Atlas of Excreta, Wastewater Sludge, and Biosolids Management: Moving Forward the Sustainable and Welcome Uses of a Global Resource. Nairobi, Kenya: United Nations Human Settlements Programme (UN-HABITAT); 2008. p. 632

[5] EPA. Biosolids Generation, Use, and Disposal in the United States. Washington, DC: EPA; 1999. p. 81

[6] ADB. Promoting Beneficial Sewage Sludge Utilization in the People's Republic of China. Mandaluyong City, Metro Manila, Philippines: DBA; 2012. p. 33

[7] Manfredi S, Pant R. Improving the environmental performance of bio-waste management with life cycle thinking (LCT) and life cycle assessment (LCA). The International Journal of Life Cycle Assessment. 2013;**18**:285-291

[8] Milieu Ltd, WRc, RPA. Environmental, Economic and Social Impacts of the Use of Sewage Sludge on Land. Final Report. Part III. Projects Interim Reports. Belgium: EU; 2010. p. 33

[9] Eurostat. Environmental Statistics and Accounts in Europe. Luxembourg: EC; 2010. p. 346

[10] EC. Communication from the Commission to the Council and the European Parliament on Future Steps in Bio-Waste Management in the European Union. Luxembourg: EC; 2010. p. 235

[11] Arthurson V. Proper sanitization of sewage sludge: A critical issue for a sustainable society. Applied and Environmental Microbiology. 2008;**74**(17):5267-5275

[12] Sonesson U, Björklund A, Carlsson M, Dalemo M. Environmental and economic analysis of management systems for biodegradable waste. Resources, Conservation and Recycling. 2000;**28**:29-53

[13] Peters GM, Rowley HV. Environment comparison of biosolids management systems using life cycle assessment. Environmental Science & Technology. 2009;**43**:2674-2679

[14] Righi S, Olivieto L, Pedrini M, Buscaroli A, Casa CD. Life cycle assessment of management for sewage sludge and food waste: Centralized and decentralized approaches. Journal of Cleaner Production. 2013;**44**:8-17

[15] Liu Q, Jiang P, Zhao J, Zhang B, Bian H, Qian G. Life cycle assessment of an industrial symbiosis based on energy recovery from dried sludge and used oil. Journal of Cleaner Production. 2011;**19**:1700-1708

[16] Nadziakiewicz J, Koziol M. Co-combustion of sludge with coal. Applied Energy. 2003;**75**(3−4):239-248

[17] Wang N, Shih CH, Chiueh PT, Huang YF. Environmental effects of sewage sludge carbonization and other treatment alternatives. Energies. 2013;**1**:871-883

[18] Hospido A, Moriera MT, Martin M, Rigola M, Feijoo G. Environmental

**21**

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case*

soil properties in a fluvisol (calcaric) amended with coal fly ash. Geoderma.

[27] Retelj M. Test Report, num. P749/15-420-1. National Laboratory of Health, Food, Environment and Food, Center for Microbiological Analytics of Food, Water and Other Samples from

[28] Pavšič P, Oštir D, Mladenovič A, Kramar S, Dolenec M, Bukovec P. Sewage-sludge stabilization with biomass ash. Materials Technology.

[29] Mladenovič A, Legat A. Test Report, num. V 0884/13-250-1. Slovenian National Building and Civil Engineering

[30] Ramezanianpour AA. Natural Pozzolans. Cement Replacement Materials: Properties, Durability, Sustainability. Berlin: Springer;

[31] Jolliet O, Margni M, Charles R, Humbert S, Payet J, Rebitzer G, et al. A New Life Cycle impact assessment methodology. International Journal of Life Cycle Assessment. 2003;**8**(6):324-330

[32] Murray A, Horvath A, Nelson KL. Hybrid life-cycle environmental and cost inventory of sewage sludge treatment and end-use scenarios: A case study from China. Environmental Science &

Technology. 2008;**19**:3163-3169

Environment. 2015. p. 4

2013;**47**:349-352

Institute. 2013. p. 5

2014:1-46

2010;**155**:67-74

*DOI: http://dx.doi.org/10.5772/intechopen.91037*

evaluation of different treatment processes for sludge from urban wastewater treatments: Anaerobic digestion versus thermal processes. International Journal of Life Cycle Assessment. 2005;**10**:336-345

[19] Valderrama C, Granados R, Cortina JL, Gasol CM, Guillem M, Josa A. Comparative LCA of sewage sludge valorisation as both fuel and raw material substitute in clinker production. Journal of Cleaner Production. 2013;**51**:205-213

[20] Onaka T. Sewage can make Portland cement: A new technology for ultimate reuse of sewage sludge. Water Science and Technology. 2000;**41**(8):93-98

[21] European Commission. Green Paper on the Management of Bio-Waste in the European Union. Luxembourg: EC;

[22] ORBIT/ECN. Compost production and use in the EU, Final report of ORBIT e.V./European Compost Network ECN to European Commission. Joint

Management Board. Current Anaerobic

Research Centre. 2008. p. 182

[23] California Integrated Waste

Digestion Technologies Used for Treatment of Municipal Organic Solid Waste [Internet]. 2019. Available from: http://www.calrecycle.ca.gov/

[24] Greenlife GmbH. Pyrolisis - Recycling Sewage Sludge to Fertilizer [Internet]. 2019. Available from: www.

[25] Likon M, Černec F, Salobir M, Podobnik E. Procedure and installation for continuous stabilization and conversion of biodegradable sludge into construction composite materials.

SI-Patent No. 22951. 2010. p. 10

[26] Riehl A, Elsass F, Duplay J, Huber F, Trautmann M. Changes in

2008. p. 811

publications/

greenlife.co.at

*Does Sustainable Management of Biodegradable Sludge Exist at All? A BACOM Project Case DOI: http://dx.doi.org/10.5772/intechopen.91037*

evaluation of different treatment processes for sludge from urban wastewater treatments: Anaerobic digestion versus thermal processes. International Journal of Life Cycle Assessment. 2005;**10**:336-345

[19] Valderrama C, Granados R, Cortina JL, Gasol CM, Guillem M, Josa A. Comparative LCA of sewage sludge valorisation as both fuel and raw material substitute in clinker production. Journal of Cleaner Production. 2013;**51**:205-213

[20] Onaka T. Sewage can make Portland cement: A new technology for ultimate reuse of sewage sludge. Water Science and Technology. 2000;**41**(8):93-98

[21] European Commission. Green Paper on the Management of Bio-Waste in the European Union. Luxembourg: EC; 2008. p. 811

[22] ORBIT/ECN. Compost production and use in the EU, Final report of ORBIT e.V./European Compost Network ECN to European Commission. Joint Research Centre. 2008. p. 182

[23] California Integrated Waste Management Board. Current Anaerobic Digestion Technologies Used for Treatment of Municipal Organic Solid Waste [Internet]. 2019. Available from: http://www.calrecycle.ca.gov/ publications/

[24] Greenlife GmbH. Pyrolisis - Recycling Sewage Sludge to Fertilizer [Internet]. 2019. Available from: www. greenlife.co.at

[25] Likon M, Černec F, Salobir M, Podobnik E. Procedure and installation for continuous stabilization and conversion of biodegradable sludge into construction composite materials. SI-Patent No. 22951. 2010. p. 10

[26] Riehl A, Elsass F, Duplay J, Huber F, Trautmann M. Changes in soil properties in a fluvisol (calcaric) amended with coal fly ash. Geoderma. 2010;**155**:67-74

[27] Retelj M. Test Report, num. P749/15-420-1. National Laboratory of Health, Food, Environment and Food, Center for Microbiological Analytics of Food, Water and Other Samples from Environment. 2015. p. 4

[28] Pavšič P, Oštir D, Mladenovič A, Kramar S, Dolenec M, Bukovec P. Sewage-sludge stabilization with biomass ash. Materials Technology. 2013;**47**:349-352

[29] Mladenovič A, Legat A. Test Report, num. V 0884/13-250-1. Slovenian National Building and Civil Engineering Institute. 2013. p. 5

[30] Ramezanianpour AA. Natural Pozzolans. Cement Replacement Materials: Properties, Durability, Sustainability. Berlin: Springer; 2014:1-46

[31] Jolliet O, Margni M, Charles R, Humbert S, Payet J, Rebitzer G, et al. A New Life Cycle impact assessment methodology. International Journal of Life Cycle Assessment. 2003;**8**(6):324-330

[32] Murray A, Horvath A, Nelson KL. Hybrid life-cycle environmental and cost inventory of sewage sludge treatment and end-use scenarios: A case study from China. Environmental Science & Technology. 2008;**19**:3163-3169

**20**

*Sustainable Sewage Sludge Management and Resource Efficiency*

[10] EC. Communication from the Commission to the Council and the European Parliament on Future Steps in Bio-Waste Management in the European Union. Luxembourg: EC; 2010. p. 235

[11] Arthurson V. Proper sanitization of sewage sludge: A critical issue for a sustainable society. Applied and Environmental Microbiology.

Carlsson M, Dalemo M. Environmental and economic analysis of management systems for biodegradable waste. Resources, Conservation and Recycling.

Environment comparison of biosolids management systems using life cycle assessment. Environmental Science & Technology. 2009;**43**:2674-2679

[14] Righi S, Olivieto L, Pedrini M, Buscaroli A, Casa CD. Life cycle assessment of management for sewage sludge and food waste: Centralized and decentralized approaches. Journal of Cleaner Production. 2013;**44**:8-17

[15] Liu Q, Jiang P, Zhao J, Zhang B, Bian H, Qian G. Life cycle assessment of an industrial symbiosis based on energy recovery from dried sludge and used oil. Journal of Cleaner Production.

[16] Nadziakiewicz J, Koziol M. Co-combustion of sludge with coal. Applied Energy. 2003;**75**(3−4):239-248

[17] Wang N, Shih CH, Chiueh PT, Huang YF. Environmental effects of sewage sludge carbonization and other treatment alternatives. Energies.

[18] Hospido A, Moriera MT, Martin M, Rigola M, Feijoo G. Environmental

2011;**19**:1700-1708

2013;**1**:871-883

2008;**74**(17):5267-5275

2000;**28**:29-53

[12] Sonesson U, Björklund A,

[13] Peters GM, Rowley HV.

[1] Fytili D, Zabaniotou A. Utilization of sewage sludge in EU application of old and new methods—A review. Renewable Sustainable Energy Rewiews.

[2] Kroiss H. What is the potential for utilizing the resources in sludge. Water Science and Technology.

[3] Aubain P, Gazzo A, Le Moux J, Mugnier E, Brunet H, Landrea B. Disposal and Recycling Routes for Sewage Sludge. Luxembourg: EC; 2001. p. 38. ISBN:

[4] LeBlanc RJ, Matthews P,

(UN-HABITAT); 2008. p. 632

[5] EPA. Biosolids Generation, Use, and Disposal in the United States. Washington, DC: EPA; 1999. p. 81

[6] ADB. Promoting Beneficial Sewage Sludge Utilization in the People's Republic of China. Mandaluyong City, Metro Manila, Philippines: DBA; 2012. p. 33

[7] Manfredi S, Pant R. Improving the environmental performance of bio-waste management with life cycle thinking (LCT) and life cycle assessment (LCA). The International Journal of Life Cycle Assessment. 2013;**18**:285-291

[8] Milieu Ltd, WRc, RPA. Environmental, Economic and Social Impacts of the Use of Sewage Sludge on Land. Final Report. Part III. Projects Interim Reports.

[9] Eurostat. Environmental Statistics and Accounts in Europe. Luxembourg:

Belgium: EU; 2010. p. 33

EC; 2010. p. 346

Richard RP. Global Atlas of Excreta, Wastewater Sludge, and Biosolids Management: Moving Forward the Sustainable and Welcome Uses of a Global Resource. Nairobi, Kenya: United Nations Human Settlements Programme

2006;**12**(1):116-140

**References**

2004;**49**(10):1-10

92-894-1798-6

**23**

**Chapter 2**

**Abstract**

current status are discussed.

sustainability

generation.

**1. Introduction**

Pre-treatment Technologies to

Enhance Anaerobic Digestion

*Sridhar Pilli, Ashutosh Kumar Pandey, Ankur Katiyar,* 

Sustainable energy production is the major priority in the world due to global warming, climate change, and fossil fuels depletion. Anaerobic digestion (AD) of sludge is the sustainable process producing the energy and minimizing the fossil fuel usage. However, conventional AD of sludge is not sustainable since it takes longer time for digestion which increases the energy input and greenhouse emissions. Therefore, pretreatment technologies have emerged to enhance methane production and thus the energy output from the AD process. In this chapter, pre-treatment technologies adopted mainly physical, chemical, thermal, and other advanced processes to enhance methane production in the last decade are elaborated. In addition, energy balance of the process and the feasibility of the pre-treatment technologies and their

**Keywords:** waste activated sludge, pre-treatment, anaerobic digestion, methane,

The production of inevitable waste activated sludge (WAS) as a by-product during the biological wastewater treatment demands for sustainable treatment options that assist in the proper utilization of sludge before its disposal. The composition of sludge mainly includes microbial cells and organic components such as proteins, carbohydrates, and lipids. Understanding the properties of the sludge may help in processing it to produce beneficial products or as a feedstock for bioenergy

Anaerobic digestion (AD) for sludge stabilization is operated in about 38% of the total treatment plants, whereas only 6% of plants employ aerobic digestion and composting [1]. AD of sludge produces biogas, which mainly contains methane and carbon dioxide. AD of sludge is a sustainable process as it recovers energy from the biogas and replaces fossil fuel usage and minimizes GHG emissions. However, the efficacy of these processes is limited by the presence of complex structural components, extracellular polymeric substances, and rate-limiting cell lysis in WAS [2]. Moreover, the effects of hydrolytic enzymes are reduced in WAS as their penetration inside the bacterial cell is hindered by the cell walls, making the degradation of intracellular organic compounds tedious. Thus, it increases the digestion time and energy required for digestion processes. Hence, to overcome these drawbacks, pre-treatment technologies are adopted to break the cells and to liberate the cell constituents.

*Kritika Pandey and Rajeshwar Dayal Tyagi*

#### **Chapter 2**

## Pre-treatment Technologies to Enhance Anaerobic Digestion

*Sridhar Pilli, Ashutosh Kumar Pandey, Ankur Katiyar, Kritika Pandey and Rajeshwar Dayal Tyagi*

#### **Abstract**

Sustainable energy production is the major priority in the world due to global warming, climate change, and fossil fuels depletion. Anaerobic digestion (AD) of sludge is the sustainable process producing the energy and minimizing the fossil fuel usage. However, conventional AD of sludge is not sustainable since it takes longer time for digestion which increases the energy input and greenhouse emissions. Therefore, pretreatment technologies have emerged to enhance methane production and thus the energy output from the AD process. In this chapter, pre-treatment technologies adopted mainly physical, chemical, thermal, and other advanced processes to enhance methane production in the last decade are elaborated. In addition, energy balance of the process and the feasibility of the pre-treatment technologies and their current status are discussed.

**Keywords:** waste activated sludge, pre-treatment, anaerobic digestion, methane, sustainability

#### **1. Introduction**

The production of inevitable waste activated sludge (WAS) as a by-product during the biological wastewater treatment demands for sustainable treatment options that assist in the proper utilization of sludge before its disposal. The composition of sludge mainly includes microbial cells and organic components such as proteins, carbohydrates, and lipids. Understanding the properties of the sludge may help in processing it to produce beneficial products or as a feedstock for bioenergy generation.

Anaerobic digestion (AD) for sludge stabilization is operated in about 38% of the total treatment plants, whereas only 6% of plants employ aerobic digestion and composting [1]. AD of sludge produces biogas, which mainly contains methane and carbon dioxide. AD of sludge is a sustainable process as it recovers energy from the biogas and replaces fossil fuel usage and minimizes GHG emissions. However, the efficacy of these processes is limited by the presence of complex structural components, extracellular polymeric substances, and rate-limiting cell lysis in WAS [2]. Moreover, the effects of hydrolytic enzymes are reduced in WAS as their penetration inside the bacterial cell is hindered by the cell walls, making the degradation of intracellular organic compounds tedious. Thus, it increases the digestion time and energy required for digestion processes. Hence, to overcome these drawbacks, pre-treatment technologies are adopted to break the cells and to liberate the cell constituents.

Various physical, chemical, and biological pre-treatment methods have been reported in the literature which is used individually or in combination for pre-treatment of WAS. These include treatment by hydrolysis, ultrasound, enzymatic lysis, acidification, alkaline hydrolysis, alkaline-thermal, and thermal-H2O2, microwave alkaline, and others [3]. The use of appropriate pre-treatment strategy can enhance the degradation and disintegration of both extracellular and intracellular substances reducing the retention time needed by biological digestion processes [4].

This chapter presents literature about the different methods of pre-treatment that have been used for enhancing the AD. Moreover, the factors affecting their operational efficiency have also been discussed. Furthermore, a brief account of the large-scale feasibility and economic aspects of the overall pre-treatment processes is discussed.

#### **2. Pretreatment technologies**

The pre-treatment technologies enable the cells constituents easily available for the microorganisms to produce the biogas. Various pre-treatment technologies (mainly mechanical, chemical, biological, and physio-chemical) and their effect on enhancing the AD and methane production presented in the literature during last decade are discussed here.

#### **2.1 Mechanical pre-treatment**

#### *2.1.1 The process involved and mode of action*

Mechanical pre-treatment disintegrates and/or grinds solid particles of the substrates, thus releasing cell compounds and increasing the specific surface area. The increased surface area provides better contact among substrate and anaerobic bacteria, which enhances the AD process [5]. A larger particle radius exhibits lower chemical oxygen demand (COD) degradation and a lower methane production rate [6]. Likewise, the particle size is inversely proportional to the maximum substrate utilization rate of the anaerobic microbes [7]. Therefore, mechanical pre-treatments such as sonication, liquid shear, collision, a high-pressure homogenizer and liquefaction are conducted to reduce the substrate particle size. During sonication the electrical energy from the source is converted to mechanical vibration which then converts to cavitation. The shear forces exerted as a result of cavitation cause WAS floc dispersion and further cell disintegration releasing organic macromolecules that are further degraded into short-chain compounds [8]. The irradiation intensity, time, and temperature-induced, as a result, can impart a cumulative effect enhancing the sludge degradation [9]. The main effect of ultrasonic pre-treatment is particle size reduction at low frequency (20–40 kHz) sound waves [10]. Highfrequency sound waves also cause the formation of radicals such as HO− , H+ , which results in oxidation of solid substances [11]. Besides ultrasonic irradiation, cavitation can also be produced by venturi meter tubes under controlled conditions of liquid flow [12].

High-pressure homogenization (HPH) pre-treatment involves the use of 30 and 150 MPa pressure for 3–30 min to pressurize the heterogeneous sludge components. The homogenization occurs due to shear, that is, when the pressurized sludge is released to impact on a ring [13]. The formed cavitation induces internal energy, which disrupts the cell membranes [14]. Both electroporation and liquefaction pre-treatments cause cellular structure damage, thus the effect on the AD process is similar to maceration [15]. Barjebruch and Kopplow treated surplus sludge with

**25**

*Pre-treatment Technologies to Enhance Anaerobic Digestion*

HPH at 600 bars and showed that the filaments were completely disintegrated [14]. Increased 25% volatile solids reduction was observed in AD for HPH pretreated sewage sludge [16]. This improvement was induced by increased soluble protein,

The advantages of mechanical pre-treatment include no odor generation, an easy implementation; better dewaterability of the final anaerobic residue, and moderate energy consumption. Disadvantages include no significant effect on pathogen removal and the possibility of equipment clogging or scaling [17].

Nanobubbles are spherical liquid structures containing gas which are stable and efficient when possessing typical overall diameters in the nanometer range (less

 nm). The presence of negative charge on nanobubbles is observed when present in pure water over a wide pH range. Nanobubbles stabilized their structures because of the same charge repulsion that occurred between adjacent nanobubbles [18]. However, some reports suggest hydrophobic attraction between negatively charged surfaces of nanobubbles and these contradictory reports could be attributed to the differences in nanobubble generation techniques, surface tension, or varying molecular arrangement at the gas-liquid interface [19]. Nanobubbles with diameters of approximately 13 nm have been well-engineered as spherical water packages with gas for food safety applications whose efficiency is well established based on bubble surface stability and the electrostatic charges present on the bubble surface [20]. Besides possessing high stability, nanobubbles in liquid systems also show a high mass transfer rate and enhanced solubility in gas [21]. Nanobubbles with a varying range of diameters have been engineered by different methods such as constant purging of octafluoropropane gas into an ultrasonicated solution of mixed surfactant which creates bubbles ranging in 400–700 nm mean diameter [22]. Palladium electrode with ultrasonication has been used to form nanobubbles of 300–500 nm diameter [23]. Nanobubbles form reactive free radicals as they collapse due to the presence of ions in groups at the gas-liquid interface [24]. The ability of nanobubbles to form reactive free radicals makes them potent applicants in the field of pre-treatment of wastewater components. In submerged systems, nanobubbles formed by the use of air or nitrogen are known to enhance the activity of aerobic and anaerobic microorganisms that improve the waste degradation efficiency and overall water quality [25]. According to the studies the higher negative charges were observed on sludge components on the addition of nitrogen gas nanobubble water the degradation of carbohydrates and proteins get increased along with methane production, that is,

Cavitation is a process of cavity bubble formation which burst within the liquid to create intense pressure spots and shock waves. These factors create localized energy and turbulence which causes an impact on adjacent particles and also mixing of insoluble substances like oil and water to form emulsion [26]. This mechanism is favorable in cases where AD of sludge is hindered due to the presence of lipidcontaining substances which are insoluble in water. Their insolubility causes

adversity in their interaction with hydrolytic bacteria which decreases the efficiency of the overall hydrolysis process. Applying localized energy supplies insignificant amounts to small elements of the liquid volume resulting in an increase of internal energy of the liquid elements to that point which causes phase change from liquid to gas and the formation of bubbles filled with vapor and gases. Following, when

*DOI: http://dx.doi.org/10.5772/intechopen.93236*

lipid, and carbohydrate concentration.

29% more than that of control [25].

*2.1.3 Hydrodynamic cavitation*

*2.1.2 Nanobubbles*

than 103

HPH at 600 bars and showed that the filaments were completely disintegrated [14]. Increased 25% volatile solids reduction was observed in AD for HPH pretreated sewage sludge [16]. This improvement was induced by increased soluble protein, lipid, and carbohydrate concentration.

The advantages of mechanical pre-treatment include no odor generation, an easy implementation; better dewaterability of the final anaerobic residue, and moderate energy consumption. Disadvantages include no significant effect on pathogen removal and the possibility of equipment clogging or scaling [17].

#### *2.1.2 Nanobubbles*

*Sustainable Sewage Sludge Management and Resource Efficiency*

the retention time needed by biological digestion processes [4].

Various physical, chemical, and biological pre-treatment methods have been reported in the literature which is used individually or in combination for pre-treatment of WAS. These include treatment by hydrolysis, ultrasound, enzymatic lysis, acidification, alkaline hydrolysis, alkaline-thermal, and thermal-H2O2, microwave alkaline, and others [3]. The use of appropriate pre-treatment strategy can enhance the degradation and disintegration of both extracellular and intracellular substances reducing

This chapter presents literature about the different methods of pre-treatment that have been used for enhancing the AD. Moreover, the factors affecting their operational efficiency have also been discussed. Furthermore, a brief account of the large-scale feasibility and economic aspects of the overall pre-treatment processes is

The pre-treatment technologies enable the cells constituents easily available for the microorganisms to produce the biogas. Various pre-treatment technologies (mainly mechanical, chemical, biological, and physio-chemical) and their effect on enhancing the AD and methane production presented in the literature during last

Mechanical pre-treatment disintegrates and/or grinds solid particles of the substrates, thus releasing cell compounds and increasing the specific surface area. The increased surface area provides better contact among substrate and anaerobic bacteria, which enhances the AD process [5]. A larger particle radius exhibits lower chemical oxygen demand (COD) degradation and a lower methane production rate [6]. Likewise, the particle size is inversely proportional to the maximum substrate utilization rate of the anaerobic microbes [7]. Therefore, mechanical pre-treatments such as sonication, liquid shear, collision, a high-pressure homogenizer and liquefaction are conducted to reduce the substrate particle size. During sonication the electrical energy from the source is converted to mechanical vibration which then converts to cavitation. The shear forces exerted as a result of cavitation cause WAS floc dispersion and further cell disintegration releasing organic macromolecules that are further degraded into short-chain compounds [8]. The irradiation intensity, time, and temperature-induced, as a result, can impart a cumulative effect enhancing the sludge degradation [9]. The main effect of ultrasonic pre-treatment is particle size reduction at low frequency (20–40 kHz) sound waves [10]. High-

frequency sound waves also cause the formation of radicals such as HO−

results in oxidation of solid substances [11]. Besides ultrasonic irradiation, cavitation can also be produced by venturi meter tubes under controlled conditions of

High-pressure homogenization (HPH) pre-treatment involves the use of 30 and 150 MPa pressure for 3–30 min to pressurize the heterogeneous sludge components. The homogenization occurs due to shear, that is, when the pressurized sludge is released to impact on a ring [13]. The formed cavitation induces internal energy, which disrupts the cell membranes [14]. Both electroporation and liquefaction pre-treatments cause cellular structure damage, thus the effect on the AD process is similar to maceration [15]. Barjebruch and Kopplow treated surplus sludge with

, H+

, which

**24**

liquid flow [12].

discussed.

**2. Pretreatment technologies**

decade are discussed here.

**2.1 Mechanical pre-treatment**

*2.1.1 The process involved and mode of action*

Nanobubbles are spherical liquid structures containing gas which are stable and efficient when possessing typical overall diameters in the nanometer range (less than 103 nm). The presence of negative charge on nanobubbles is observed when present in pure water over a wide pH range. Nanobubbles stabilized their structures because of the same charge repulsion that occurred between adjacent nanobubbles [18]. However, some reports suggest hydrophobic attraction between negatively charged surfaces of nanobubbles and these contradictory reports could be attributed to the differences in nanobubble generation techniques, surface tension, or varying molecular arrangement at the gas-liquid interface [19]. Nanobubbles with diameters of approximately 13 nm have been well-engineered as spherical water packages with gas for food safety applications whose efficiency is well established based on bubble surface stability and the electrostatic charges present on the bubble surface [20]. Besides possessing high stability, nanobubbles in liquid systems also show a high mass transfer rate and enhanced solubility in gas [21]. Nanobubbles with a varying range of diameters have been engineered by different methods such as constant purging of octafluoropropane gas into an ultrasonicated solution of mixed surfactant which creates bubbles ranging in 400–700 nm mean diameter [22]. Palladium electrode with ultrasonication has been used to form nanobubbles of 300–500 nm diameter [23]. Nanobubbles form reactive free radicals as they collapse due to the presence of ions in groups at the gas-liquid interface [24]. The ability of nanobubbles to form reactive free radicals makes them potent applicants in the field of pre-treatment of wastewater components. In submerged systems, nanobubbles formed by the use of air or nitrogen are known to enhance the activity of aerobic and anaerobic microorganisms that improve the waste degradation efficiency and overall water quality [25]. According to the studies the higher negative charges were observed on sludge components on the addition of nitrogen gas nanobubble water the degradation of carbohydrates and proteins get increased along with methane production, that is, 29% more than that of control [25].

#### *2.1.3 Hydrodynamic cavitation*

Cavitation is a process of cavity bubble formation which burst within the liquid to create intense pressure spots and shock waves. These factors create localized energy and turbulence which causes an impact on adjacent particles and also mixing of insoluble substances like oil and water to form emulsion [26]. This mechanism is favorable in cases where AD of sludge is hindered due to the presence of lipidcontaining substances which are insoluble in water. Their insolubility causes adversity in their interaction with hydrolytic bacteria which decreases the efficiency of the overall hydrolysis process. Applying localized energy supplies insignificant amounts to small elements of the liquid volume resulting in an increase of internal energy of the liquid elements to that point which causes phase change from liquid to gas and the formation of bubbles filled with vapor and gases. Following, when

the bubbles leave the high energy zones, they violently implode and disappear. The localized energy could be provided by a laser beam or a stream of heavy elementary particles such as protons by molecular or optical cavitation process based on the source of applied energy [27]. Hydrodynamic cavitation was frequently been proved as a more energy-efficient method compared to other cavitation techniques [28]. Hydrodynamic cavitation for pre-treatment of sludge where cavitation was generated by using a venturi cavitation system in which bubbles are created in venturi throat (constriction) has been used. The system achieved better energy efficiency than high-speed homogenizer in terms of soluble COD/kJ WAS and also the authors observed linear relationship between total solid concentration and the increased insoluble COD for WAS indicating towards better cavitation formation at high concentration of total solids [29]. In another study, the degradation of WAS was analyzed using a novel rotation generator of hydrodynamic cavitation at pilot scale [30]. Cavitation (as a pre-treatment) of WAS resulting in an increment in soluble COD from 45 to 602 mg/L along with a 12.7% increase in biogas production due to improved AD of the pretreated WAS [30].

#### **2.2 Thermal pre-treatment**

Thermal pre-treatment of WAS has been classified as low-temperature pretreatment (<100°C) and high-temperature thermal pre-treatment at 100–210°C [31]. High-temperature pre-treatment cause disintegration of solids in sludge, removal of pathogens at low sludge retention time and leads to biogas production but it also has been reported that exposure to high temperature causes the formation of new chemical bonds which results in agglomeration of substances present in the sludge [32]. Both the thermal pre-treatment approaches have been reported to degrade volatile solids and produce biogas, however, the efficiency of high-temperature thermal pre-treatment for solids reduction and biogas formation has been known to be comparatively higher [11]. In thermal pre-treatment strategies, temperature and time of application are the main operational parameters which decide the success of the treatment process. When effectively applied, this pre-treatment can cause the disintegration of cell membranes accompanied by the solubilization of organic compounds [33]. During WAS pre-treatment, cell wall disruption and hydrolysis due to temperature generally occur when the temperature is in the range of 160–180°C at a pressure ranging from 600 to 2500 kPa for about an hour [32].

Microwaves generate heat by causing the movement of dipoles in polar molecules, realigning them, and producing thermal effects [34]. They cause both thermal and non-thermal effects (degradation of polymeric structure) on sludge, improving biogas production and reducing volatile solids. However, microwave generation requires higher energy consumption when compared to conventional thermal pre-treatment. The increase in temperature is associated with an increase in biodegradability while a higher concentration of solids present in WAS inversely affects the degree of penetration of microwaves to the sample [35].

#### *2.2.1 High-temperature treatment*

High-temperature thermal pre-treatment is performed at temperature >100°C. The heat exchangers or direct steam injection are used to supply the steam at the desired temperature [36]. The pressure is developed as a result of steam and high temperature which is abruptly released causing a sudden pressure drop. This sudden drop in pressure along with application time and temperature comprises the major parameters necessary for efficient solubilization and subsequent methane production in AD [37]. In many cases, it has been observed that when the temperature is raised

**27**

*Pre-treatment Technologies to Enhance Anaerobic Digestion*

and extracellular polymer substance (EPS) release [42].

*2.2.2 Low-temperature treatment*

low biodegradability [48].

**2.3 Chemical pre-treatment**

*2.3.1 Procedure and mode of action*

above 190°C, recalcitrant and inhibitory compounds, that is, ammonia is released which adversely affect the process [38]. Moreover, at a temperature above 180°C carbohydrates can react with protein amino terminals resulting in pyrolysis of sludge organic matter and formation non-biodegradable compounds [39]. In the case of sludge pre-treatment by high temperature, a range of 150–180°C at 600–2500 kPa @ 30 min to an hour is optimal because when the temperature is further increased, methane production is reduced due to formation of inhibitory products due to Maillard reaction. [38]. If the temperature is not in the required range, certain biomolecules are partially or incompletely degraded, e.g. proteins solubilize during sludge pre-treatment at 175°C but are not completely degraded to ammonia [40]. Some of the advantages of high-temperature thermal pre-treatment include the reduction in viscosity of sludge which in turn eases handling and transport costs [41]. Besides the reduction in viscosity, high-temperature pre-treatment at 134°C causes an increase in specific charge on sludge components as a result of colloids

Low-temperature thermal pre-treatment of WAS deals with the application of <100°C temperature for a few minutes to several hours [31]. At temperatures ranging from 60 to 70°C, particle size reduction and solubilization of organic components occur [43]. Low-temperature thermal hydrolysis of sludge causes solubilization of organic matter and increase in activity of thermophilic bacteria activating the release of hydrolytic enzymes in sludge [44]. Also, rheological properties of sludge and concentration of methane in biogas during AD are positively influenced by thermal pre-treatment of sludge at low temperature [45]. The relation between pre-treatment temperature and the time of application is a very crucial factor that affects the WAS biodegradation rate [46]. It has been reported that deflocculating or reduction in the size of particles is observed when the temperature is applied in the range of 50–95°C resulting in an increased surface area which in turn increases the rate of hydrolysis in WAS [47]. The type of sludge being pretreated by thermal exposure also affects the efficiency of temperature treatment. At 70°C, the total percentage of volatile suspended solids removed from WAS was reported to be 17% which for primary non-stabilized raw sludge was only 28% indicating towards its

In chemical pre-treatment methods alkali, acid or advanced oxidation methods are used to disintegrate the organic sludge components and disrupt microbial cells (**Table 1**). AD generally requires an adjustment of the pH by increasing alkalinity, thus alkali pre-treatment is the preferred chemical method [87]. The increase in pH of WAS due to alkali pre-treatment causes many effects on sludge components which include saponification of lipid bilayer and protein denaturation in the cell membrane, solubilizing EPS by ionization of its carboxyl and amino groups and hydrolysis of sludge organic substances [99]. In the literature it was stated that excessive reagent doses can inhibit the anaerobic microbes and AD, which makes it important to control the amount and type of reagent used along with the pH desired [100]. Besides treatment with alkali and acids, oxidation processes like ozonation are also employed to increase sludge hydrolysis and biogas production rate. An advanced oxidation process like ozonation depends upon the oxidation

*DOI: http://dx.doi.org/10.5772/intechopen.93236*

#### *Pre-treatment Technologies to Enhance Anaerobic Digestion DOI: http://dx.doi.org/10.5772/intechopen.93236*

*Sustainable Sewage Sludge Management and Resource Efficiency*

due to improved AD of the pretreated WAS [30].

**2.2 Thermal pre-treatment**

the bubbles leave the high energy zones, they violently implode and disappear. The localized energy could be provided by a laser beam or a stream of heavy elementary particles such as protons by molecular or optical cavitation process based on the source of applied energy [27]. Hydrodynamic cavitation was frequently been proved as a more energy-efficient method compared to other cavitation techniques [28]. Hydrodynamic cavitation for pre-treatment of sludge where cavitation was generated by using a venturi cavitation system in which bubbles are created in venturi throat (constriction) has been used. The system achieved better energy efficiency than high-speed homogenizer in terms of soluble COD/kJ WAS and also the authors observed linear relationship between total solid concentration and the increased insoluble COD for WAS indicating towards better cavitation formation at high concentration of total solids [29]. In another study, the degradation of WAS was analyzed using a novel rotation generator of hydrodynamic cavitation at pilot scale [30]. Cavitation (as a pre-treatment) of WAS resulting in an increment in soluble COD from 45 to 602 mg/L along with a 12.7% increase in biogas production

Thermal pre-treatment of WAS has been classified as low-temperature pretreatment (<100°C) and high-temperature thermal pre-treatment at 100–210°C [31]. High-temperature pre-treatment cause disintegration of solids in sludge, removal of pathogens at low sludge retention time and leads to biogas production but it also has been reported that exposure to high temperature causes the formation of new chemical bonds which results in agglomeration of substances present in the sludge [32]. Both the thermal pre-treatment approaches have been reported to degrade volatile solids and produce biogas, however, the efficiency of high-temperature thermal pre-treatment for solids reduction and biogas formation has been known to be comparatively higher [11]. In thermal pre-treatment strategies, temperature and time of application are the main operational parameters which decide the success of the treatment process. When effectively applied, this pre-treatment can cause the disintegration of cell membranes accompanied by the solubilization of organic compounds [33]. During WAS pre-treatment, cell wall disruption and hydrolysis due to temperature generally occur when the temperature is in the range of 160–180°C at

Microwaves generate heat by causing the movement of dipoles in polar molecules, realigning them, and producing thermal effects [34]. They cause both thermal and non-thermal effects (degradation of polymeric structure) on sludge, improving biogas production and reducing volatile solids. However, microwave generation requires higher energy consumption when compared to conventional thermal pre-treatment. The increase in temperature is associated with an increase in biodegradability while a higher concentration of solids present in WAS inversely affects the degree of pen-

High-temperature thermal pre-treatment is performed at temperature >100°C. The heat exchangers or direct steam injection are used to supply the steam at the desired temperature [36]. The pressure is developed as a result of steam and high temperature which is abruptly released causing a sudden pressure drop. This sudden drop in pressure along with application time and temperature comprises the major parameters necessary for efficient solubilization and subsequent methane production in AD [37]. In many cases, it has been observed that when the temperature is raised

a pressure ranging from 600 to 2500 kPa for about an hour [32].

etration of microwaves to the sample [35].

*2.2.1 High-temperature treatment*

**26**

above 190°C, recalcitrant and inhibitory compounds, that is, ammonia is released which adversely affect the process [38]. Moreover, at a temperature above 180°C carbohydrates can react with protein amino terminals resulting in pyrolysis of sludge organic matter and formation non-biodegradable compounds [39]. In the case of sludge pre-treatment by high temperature, a range of 150–180°C at 600–2500 kPa @ 30 min to an hour is optimal because when the temperature is further increased, methane production is reduced due to formation of inhibitory products due to Maillard reaction. [38]. If the temperature is not in the required range, certain biomolecules are partially or incompletely degraded, e.g. proteins solubilize during sludge pre-treatment at 175°C but are not completely degraded to ammonia [40]. Some of the advantages of high-temperature thermal pre-treatment include the reduction in viscosity of sludge which in turn eases handling and transport costs [41]. Besides the reduction in viscosity, high-temperature pre-treatment at 134°C causes an increase in specific charge on sludge components as a result of colloids and extracellular polymer substance (EPS) release [42].

#### *2.2.2 Low-temperature treatment*

Low-temperature thermal pre-treatment of WAS deals with the application of <100°C temperature for a few minutes to several hours [31]. At temperatures ranging from 60 to 70°C, particle size reduction and solubilization of organic components occur [43]. Low-temperature thermal hydrolysis of sludge causes solubilization of organic matter and increase in activity of thermophilic bacteria activating the release of hydrolytic enzymes in sludge [44]. Also, rheological properties of sludge and concentration of methane in biogas during AD are positively influenced by thermal pre-treatment of sludge at low temperature [45]. The relation between pre-treatment temperature and the time of application is a very crucial factor that affects the WAS biodegradation rate [46]. It has been reported that deflocculating or reduction in the size of particles is observed when the temperature is applied in the range of 50–95°C resulting in an increased surface area which in turn increases the rate of hydrolysis in WAS [47]. The type of sludge being pretreated by thermal exposure also affects the efficiency of temperature treatment. At 70°C, the total percentage of volatile suspended solids removed from WAS was reported to be 17% which for primary non-stabilized raw sludge was only 28% indicating towards its low biodegradability [48].

#### **2.3 Chemical pre-treatment**

#### *2.3.1 Procedure and mode of action*

In chemical pre-treatment methods alkali, acid or advanced oxidation methods are used to disintegrate the organic sludge components and disrupt microbial cells (**Table 1**). AD generally requires an adjustment of the pH by increasing alkalinity, thus alkali pre-treatment is the preferred chemical method [87]. The increase in pH of WAS due to alkali pre-treatment causes many effects on sludge components which include saponification of lipid bilayer and protein denaturation in the cell membrane, solubilizing EPS by ionization of its carboxyl and amino groups and hydrolysis of sludge organic substances [99]. In the literature it was stated that excessive reagent doses can inhibit the anaerobic microbes and AD, which makes it important to control the amount and type of reagent used along with the pH desired [100]. Besides treatment with alkali and acids, oxidation processes like ozonation are also employed to increase sludge hydrolysis and biogas production rate. An advanced oxidation process like ozonation depends upon the oxidation


**29**

**Type of sludge**

**Pre-treatment method**

**Method**

MW

WAS (14.2±0.7 g TS/kg)

Meat processing Wastewater sludge

Excess sewage sludge

Ultrasonic-Fenton

Ultrasonic density = 720 W/L Duration = 20 min Fe2 + dosage = 0.4 g/L H

O2 2

dosage = 0.50 g/L

Duration = 20 min

Thickened sludge

Ultrasonication

Power = 100 W

Increase of SCOD: 1741%

AD, semi-continuous,

+27% biogas production

[59]

37°C, HRT 20 d, 67 d

Duration = 8 min

Energy = 96 kJ/kg TS

Frequency = 2.45 GHz

Increase of SCOD: 117%

AD, Semi-continuous,

+ 20%biogas production

[59]

37°C, HRT 20 d, 67 d

Power = 800 W

Duration = 1 min

Energy=96kJ/kg TS

Energy = 33 kWh/m3

Accumulation of acetate

AD, MEC, anode

+2.4-fold current density (~3.1 A/m2

)

[60]

potential: −0.3 V vs Ag/

AgCl

increased by 2.6-fold

(43.6 g TS/kg)

Thickened sludge

MW

(43.6 g TS/kg)

Primary sludge

Activated sludge

WAS

Visiblephotocatalysis

NR

Increase COD degradation up to 61.1%

Electro kinetic

Energy = ~34kWh/m3

Increase of SCOD: 220%

AD, CSTRs, 37 ± 1°C,

+33% methane production, +18% TCOD

[61]

removal, –40% digester size

Up to 7866.7 mmol H2/L-sludge of hydrogen production was achieved

[62]

SRT 20 d

AD

disintegration

Electro kinetic

disintegration

Alkaline-MW

Temp = 140°C Duration = 30min, pH = 13

Sludge disintegrate on the degree increased up to 54.9.VS solubilization increased up to 42.5%

Soluble COD increased up

NR

NR

to 2.1 fold

**Condition** Energy = 14,000 kJ/

kg TS

Increase of SCOD/TCOD from 2 to 21%

Aerobic digestion, Batch, 35°C, 35 d

Anaerobic digestion

Increase in biogas production = 44.5%

[57]

**Outcome**

**Biological coupling**

**Method**

**Outcome** +570.7% biogas production

[56]

**Ref.**

*Pre-treatment Technologies to Enhance Anaerobic Digestion*

[58]

*DOI: http://dx.doi.org/10.5772/intechopen.93236*

*Sustainable Sewage Sludge Management and Resource Efficiency*

#### *Pre-treatment Technologies to Enhance Anaerobic Digestion DOI: http://dx.doi.org/10.5772/intechopen.93236*

*Sustainable Sewage Sludge Management and Resource Efficiency*

**28**

**Type of sludge**

**Pre-treatment method**

**Method**

Physical approach

Activated sludge

MW

Power = 800 W

Increase of SCOD: 214%

AD, semi-continuous,

+50% biogas production, +66.6% DS

[49]

37°C, SRT 20 d, 42 d

removal

Duration = 3.5 min

Energy = 336 kJ/kg TS

Frequency = 24 kHz

DDcod: 9%

AD, semi-continuous,

+35% methane yield, 0.86 energy ratio

[50]

37°C, HRT 20 d, 80 d

Power = 300 W

Energy = ~5000 kJ/

kg TS

(40.8 g TS/kg)

Activated sludge

Ultrasonication

(23 g TS/L)

WAS WAS WAS Mix primary and

Ultrasound

secondary sludge

Activated sludge

Thickened sludge

MW

Power = 1250 W

Frequency = 2450 MHz

Intensity = 100%

Electro kinetic

Power = 19 kV

Frequency = 110 Hz

Duration = 1.5 s

disintegration

MW-Alkali

MW

Power = 600 W

Temp = 85°C

Duration = 2 min

Power = 600W

COD solubilization

Aerobic digestion

Soluble COD reduction = 93% VSS

[52]

reduction = 63%

VSS removal efficiency = 55%

[53]

RT = 3 d

increased up to 46%

Dissolution of chemical

Thermophilic aerobic

digestion

oxygen demand up to

44.4%

Increase of SCOD/TCOD:

AD, Batch, 35°C, 20–30 d

+2.5 times higher biogas production

[54]

4.5 times, increase of

exocellular polymers: 6.5

times

Increase of SCOD/TCOD

AD, Semi-continuous

+106% biogas production, the maximum

[55]

VS removal: 53.1%

TPAD

from 0.06 to 0.2

Duration = 2 min

Power = 480 W

Duration = 30 min

High-pressure

Temp = 150°C

36% of active, Heterotrophs

Aerobic digestion

Increase in total mass = 21%

[51]

converted to readily

biodegradable COD and

64%

COD solubilization up to

NR\*

NR

[52]

8.5%

Pressure = 3 bars

Duration = 30 min

thermal hydrolysis

**Condition**

**Outcome**

**Biological coupling**

**Method**

**Outcome**

**Ref.**



**31**

**Type of sludge**

**Pre-treatment method**

**Method**

MW

Dairy activated sludge (11.66 g TS/L WAS (35.5 ± 0.7 g TS/L)

Mixed sludge

WAS WAS WAS WAS Sewage sludge

Thermal

Temp = 120°C

Pressure = 2 atm

Duration = 15 min

Electro kinetic

disintegration

Ultrasonic-acid

Ultrasonic density=

Sludge disintegration

NR

NR

[73]

increased up to 40%

10W/mL

Duration = 10 min

pH = 2.0

Energy = 10kWh/m3

Increase of SCOD/TCOD

AD, batch, 25–30 d

+100% methane production

[74]

to 10%, increase of SCOD

from 20 to & \$2gt;1000

mg/L

Soluble carbon

AD

Increase in methane production = 29%

[75]

concentration, nitrogen,

and phosphorus increased

by 165, 16, and 24%,

Mechanical

Mixing = 5000 rpm

Duration = 10 min

1.5 %

Sludge disintegration the rate was increased up to

NR

NR

[45]

Low thermal

Temp = 70 and 90°C

Duration = 180 min

Sludge disintegration the rate was increased up to 25%

Electro kinetic disintegration

NR

Increase of SCOD: 160%, increase of DOC: 120%

Ultrasonication

**Condition** Frequency = 2450 MHz

Power = 900W Power = 12 min Energy = 1814 kJ/L

Energy = 3380 kJ/kg TS

DDcod: 21%

AD TPAD-BMP assay (55°C→35°C) AD, full-scale WWTP

Anaerobic batch digestion

Increase in methane production = 21%

[45]

+40% biogas production, biosolids requiring disposal reduced by 30%

+42% methane production, +13% VS removal

Increase of SCOD: 19%

AD, semi-continuous, 37°C, SRT 15 d, 170 d

+57% biogas production, +64% VS removal

[70]

**Outcome**

**Biological coupling**

**Method**

**Outcome**

**Ref.**

*Pre-treatment Technologies to Enhance Anaerobic Digestion*

[72]

*DOI: http://dx.doi.org/10.5772/intechopen.93236*

[71]

#### *Pre-treatment Technologies to Enhance Anaerobic Digestion DOI: http://dx.doi.org/10.5772/intechopen.93236*

*Sustainable Sewage Sludge Management and Resource Efficiency*

[65]

**30**

**Type of sludge**

**Pre-treatment method**

**Method**

Mix waste

UV Photocatalysis

Catalyst = TiO2

Duration = 4 h

Temperature = 35°C

UV intensity = 0.7 mW/

cm2

activated and

digested sludge

Mixed sludge (132

Ultrasonication

Power = 150 W

Increase of TOC: 81.5%,

AD, Batch, 35°C, OLR 0.9

+95% methane yield

+2–5 times in VFAs yield, +4–6 times in

VFA production rate

[64]

± 0.1 kg VS/m3 d

AD, semi-continuous,

42 and 55°C, HRT 1–6 d,

142 d

NR

NR

[66]

increase of TN: 50.0%

SS removal: 20–30%,

increase of SCOD/TCOD

from 0.04 to 0.4

The floc structures

disruption, increased from

1.48 to 6.96%

Duration = 45 min

Full-scale CAMBI™

Temperature = 160°C

Pressure = 6 bar

± 1 g TS/kg)

Dewatered sludge

Thermal hydrolysis

(15–20% TS)

Textile dying

Ultrasonic-Fenton

Ultrasonic density=

0.14W/ml

pH < 3.0

Pressure = 150 bar,

NR

AD, full-scale, 36–38°C

reduction

+30% biogas production, +23% sludge

[67]

Flow rate = 2.7 m3/h

sludge

Concentrated

High-pressure

homogenization

(HPH)

sludge (40 g/L)

Dewatered

Thermal hydrolysis

Pilot-scale CAMBI™

Increase of VS removal

AD, pilot-scale, treated

+2.3 times increase in SLR,

[68]

+30–40%biogas production, improved

sludge: primary sludge

(80%:20%),3°C, SRT 20d

AD, batch, 35°C, HRT

+40.2% methane production, +12.6% VS

[69]

removal, +6.8% digestated reduction

30 d

dewaterability

from 26% to 42% (+62%)

Temperature = 65°C

Pressure = 6 bar

Duration = 20 min

activated sludge

(16%TS)

Secondary sludge

Thermal hydrolysis

Temperature =

NR

134–140°C

Pressure = 3.4 bar

Duration = 30

min

Secondary sludge

Ultrasonication

Frequency = 20 kHz

Increase of SCOD/TCOD

AD, batch, 35°C, 30 d

+16.9% VS removal, +7.89 × 10−6 kWh/g

[69]

energy output, 1.0 energy ratio

from 0.02 to 0.10

Power = 750 W

Energy = 5742 kJ/kg TS

(31.4 g TS/L)

(30.00 g TS/L)

**Condition**

**Outcome** Soluble COD concentration

AD

increased from 1087.2

to 1451.6 mg/L for 8 h

pre-treatment

**Biological coupling**

**Method**

**Outcome**

Methane production=1266.7 mL/L

[63]

sludge, VS reduction = 67.4%, total COD

reduction= 60.5%

**Ref.**



**33**

**Type of sludge**

**Pre-treatment method**

**Method**

Chemical approach

Maize canning sludge

WAS Activated sludge (5%TS) Activated sludge

Sewage sludge Pulp and paper

Alkaline treatment

8 g NaOH/100 g TS

Increase of SCOD:83%,

AD, batch, 37°C, 42 d

1040 mg acetate/L, +83% methane yield

[88]

(0.32 m3CH4/kg S removed); sodium

toxicity at 16 g NaOH/100 g TS

Increase of methane production from

[89]

430 to 496 m3 CH4/Mg VS degraded, +3.1

time increased net energy, reduced GHG

emissions (0.128 Mg CO2/Mg of TDS)

Increase in methane production = 34%

[90]

56–192% higher Sv

sludge

Secondary waste

Peroxide/oxidation

60 g H

Fe2+/g H

pH = 3

O2 2

O2

2/kg TS, 0.07 g

Reduction of SS:21%,

AD, lab-scale, 35°C, 30 d

reduction of VSS:25%,

increase of SCOD from 0.82

to 7.8 g/ L

Pre-treatments reduced the

AD

viscosity of the sludge

water sludge

WAS

Alkali

NaOH dosage = 157 g/

kg TS

Alkaline treatment

0.1 mol NaOH/L

Ozonation

Ozone intensity = 0.09g O3/g MLSS, pH = 11

COD solubilization: 40%, TS reduction: 30%

Increase of DDcod from

22.3 to 26.9%

AD, lab-scale AS-MBR, 120 d

Solids degradation: 37%

[86]

AD, batch (BMP), 21 d

+26.4% organic removal, +1.5% biogas

[87]

yield; delay of AD start up due to residual

NaOH

Acidic treatment

8.75 mLHCl/kg wet sludge pH = 2

Four and Six times increase of soluble carbohydrate sand proteins, respectively

AD, semi-continuous, 35°C, HRT 12 d

+14.3% methane yield, –40% polymer dose for dewatering

[85]

Ozonation

Ozone intensity = 10 mg O3/g TSS

DDcod:18%, VSS reduction:18%

AD, batch, F/I0.8, 35°C, 20 d

+800% specific biogas production, +1.6 folds VSS reduction

20 cycles Duration = 30 s/cycle

Ozonation

Ozone intensity = ~0.18 g O3/g D

Increase of BOD5/COD from 26 to 93% (+2.58 times)

AD, batch,30°C, 30 d

Increase of biogas production from 1.037 to 9.52 cm3/g COD d(+8.2 times)

[83]

**Condition**

**Outcome**

**Biological coupling**

**Method**

**Outcome**

**Ref.**

*Pre-treatment Technologies to Enhance Anaerobic Digestion*

*DOI: http://dx.doi.org/10.5772/intechopen.93236*

[84]


#### *Pre-treatment Technologies to Enhance Anaerobic Digestion DOI: http://dx.doi.org/10.5772/intechopen.93236*

*Sustainable Sewage Sludge Management and Resource Efficiency*

[78]

**32**

**Type of sludge**

**Pre-treatment method**

**Method** MW—Alkali

(NaOH)

WAS Mixed sludge

WAS Dewatered sludge

Thermal hydrolysis

Temperature =

140–160°C

Duration = 60– 90 min

times)

Increase in disintegration

AD

of flocs and extracellular

polymeric substances

(16.7 ± 0.5% TS

Primary sludge

MW- Ultrasound

Power = 800 W

Frequency = 2450 MHz,

Duration = 3min

US density = 0.4 W/ml

US intensity = 150 W

Duration = 6 min

Mix aerobic

NaOH Ultrasonic

g/kg

Duration = 30 min

Ultrasonic energy =

7500 kJ\Kg

Pressure = 50MPa

SCOD: 2167 mg/L, DDcod:

AD, batch, 35°C, 7 d

+115% biogas production, +41.17% VS

[82]

removal, +61.89% TCOD removal

7.7%

Cycles = 2

NaOH dosage = 100

Soluble COD increased

Aerobic digestion

50.7%

Increase in organic matter degradation =

[81]

from 275 to 6797 mg/L

thicken sewage

sludge

Sewage sludge (23

High-pressure

homogenization

(HPH)

g TS/L)

Free nitrous acidheat pre-treatment

Temp = 70°C

Nitrous acid = 0.52–1.11 mg N/L

sCOD increased and found

AD

between 0.16 and 0.28 mg

sCOD/mg VS

Increase of DDcod from

AD, batch, 37°C,28d

+~16.5% biogas production, reduction of

[79]

SRT from 18–20 d to 12–14 d

Methane production = 11.9 ml/g tCOD

[80]

4.5 to 34.7–42.5% (+6.7–8.4

High-pressure

Pressure = 12,000 psi

SCOD/TCOD: & 2 gt; 4.0

AD, 2TPAD, SRT 14 d,

OLR 1.24±0.05 g VS/L d

Catalyst = 0.009 g

NaOH/g TS

homogenization

**Condition** Power = 900 W

Temp = 95˚C

pH = 12

**Outcome** Sludge solubilization

increased from 0.5 (raw)

to 52.5%

**Biological coupling**

**Method** Mesophilic aerobic

digestion

**Outcome**

COD degradation =81.1%

[76]

VSS degradation =72.4% VSS RT = 20 d

0.61–1.32 L CH4/L d methane production,

[77]

43–64% VS removal, pathogen removal,

net energy output

Methane production increased by =

17–26%

**Ref.**


**35**

**Type of sludge**

**Pre-treatment method**

**Method** Peroxide/oxidation

50 mg H

O2 Fe/g T Sin sludge

pH = 2.0

Duration = 30 min

2/g TS, 7 mg

Increase of SCOD from 8 ±

1 in control to 103 ± 7 mg/g

TS (+11.9 times)

Activated sludge (13.9 ± 0.2 g TS/L) Biological approach

WAS

Bacterial

Strains = *Bacillus jerish*

Extracellular polymeric

AD

Suspended solids

reduction = 48.5% COD

solubilization = 47.3%

substance decrease to 40

mg/L

EDTA dosage = 0.2

g/g SS

enzymaticpretreatment

Thicken sewage

Bioleaching-Fenton

H

O2

2 dosage= 0.12

mol/L Fe2+ dosage =

0.036 mol/L

s2/g.

Increased dewater ability

by 4%

Duration = 60 min

*NR, not reported; AD, anaerobic digestion; RT, retention time; MW, microwave; WAS, waste activated sludge.*

Bioleaching = 2 days

Volatile solids reduction up

NR

NR

[98]

to 36.93%. Sludge resistance

to filtration was 3.43 × 108

sludge

*\**

**Table 1.**

*Methods for activated sludge treatment.*

**Condition**

**Outcome**

**Biological coupling**

**Method** AD, BMP, 37 ± 1°C, 23 d

+10% methane production, +13%

[78]

methane potential but no significant effect

on hydrolysis rate

**Outcome**

**Ref.**

*Pre-treatment Technologies to Enhance Anaerobic Digestion*

*DOI: http://dx.doi.org/10.5772/intechopen.93236*

[97]


*Pre-treatment Technologies to Enhance Anaerobic Digestion DOI: http://dx.doi.org/10.5772/intechopen.93236*

*Sustainable Sewage Sludge Management and Resource Efficiency*

**34**

**Type of sludge**

**Pre-treatment method**

**Method**

Activated sludge

Peroxide/oxidation

H

O2 2/kg TS

pH = 3

1 h

4 g Fe3+/°/kg TS, 40 g

DDcod:23.6%, (Fe2+),

DDcod:16.7% (Fe°)

(10.2 mg TS/L)

WAS

Fenton

Catalyst iron dosage = 4

Sludge disintegration

AD

increased up to 23.6%

g/kg TS

H

O2 kgTS

pH = 3

Duration = 60 min

Activated sludge

Alkaline treatment

pH = 9–11(4 mol/L

NR

AD, batch,37.0 ± 0.1°C,

+10.7–13.1% TSS removal, +6.5– 12.8%

[92]

VSS removal, +7.2–15.4% biogas yield,

improved dewaterability

+2–2.5 times VSS removal, +14–21%

[93]

methane production, 22–23% better

dewaterability

+36.4% COD removal, +33% TS removal,

[94]

+74% biogas production

Methane production increased by =

[78]

17–26%

25 d

NaOH)

Duration = 24 h

(10.6 ± 0.1 g

TS/L)

Anaerobically

Acidic treatment

Temperature = 170°C

NR

AD, continuous, 35°C,

HRT 20 d

pH = 5–6 (H2SO4)

Duration = 1 h

digested sludge

Activated sludge

WAS Sewage sludge Activated sludge

Alkaline treatment

8 g NaOH/m3 wet

sludge (pH 8)

(11.7 ± 2.3 g TS/L)

Ozonation

Free nitrous acidheat pre-treatment

Nitrous acid = 0.52–1.11 mg N/L

Temperature = 70 °C

Ozone intensity = 0.1 g

O3/g COD

Alkaline treatment

Temperature = 130°C

DDcod: around 60%

sCOD increased and found

AD

between 0.16 and 0.28 mg

sCOD/mg VS

Oxidization of organics:

AD, batch, 33°C, 30 d

+1.8 times methane yield, +2.2 times

[95]

production rate, decreased dewaterability

+9.7% TS removal, +11.5% VS removal,

[96]

+18.1% COD removal, 84.22–78.24 mL/d

for biogas (–7.1%)

38%, solubilization of

organics: 29

SCOD/TCOD: 1.99%

AD, CSTR, 55°C, HRT

21 d

AD, continuous, 35°C,

HRT 20 d

pH = 10 (KOH)

2 dosage = 40 g/

**Condition**

**Outcome**

**Biological coupling**

**Method** AD, BMP, 35°C, 60 d

+30.2%biogas and +38.0% methane

[91]

production for Fe2+, +24.4% biogas and

+26.8% methane production for FeO

Total methane production increased =

[73]

26.9%

**Outcome**

**Ref.**

 *NR, not reported; AD, anaerobic digestion; RT, retention time; MW, microwave; WAS, waste activated sludge.*

**Table 1.**

*\**

*Methods for activated sludge treatment.*

**Type of sludge**

**Pre-treatment method**

**Method** Peroxide/oxidation

Activated sludge (13.9 ± 0.2 g TS/L) Biological approach

WAS

Bacterial

enzymaticpretreatment

Thicken sewage

Bioleaching-Fenton

sludge

reaction of hydroxyl radicals with organic compounds present in WAS. Hydroxyl radicals are highly reactive species and may cause complete mineralization of WAS after oxidation [101]. Ozone forms free radicals on reacting with water and causes hydrolysis of organic matter in WAS enhancing its biodegradability [102]. Chemical pre-treatment is not suitable for easily biodegradable substances containing high amounts of carbohydrates, due to their accelerated degradation and subsequent accumulation of volatile fatty acids, which leads to failure of the methanogenesis [103].

#### *2.3.2 Acid pre-treatment*

Acid pre-treatment is done to disintegrate the polymeric structures and cells in WAS which is achieved by the use of reagents such as HCl, H2SO4, H3PO4, and HNO2. The pH during the acid pre-treatment ranges from 1 to 5.5. During acid pre-treatment, flocculation is observed near isoelectric point as the lowering of pH causes reaction between hydrogen ions and the ionized carboxyl groups rendering them in unionized forms resulting in the formation of aggregates [104]. Strong acidic pre-treatment may result in the production of inhibitory by-products, such as furfural and hydroxyl-methylfurfural [105]. Hence, strong acidic pre-treatment is avoided and pre-treatment with dilute acids is coupled with thermal methods. Other disadvantages associated with acid pre-treatment include the loss of fermentable sugar due to the increased degradation of complex substrates, a high cost of acids, and the additional cost for neutralizing the acidic conditions before the AD process [106].

#### *2.3.3 Alkali pre-treatment*

Alkali treatment is relatively effective in sludge solubilization, within the order of efficacy being highest for NaOH followed by KOH, Mg(OH)2 and Ca(OH)2 [107]. However, too high concentrations of Na<sup>+</sup> or K+ may cause subsequent inhibition of AD [107]. The increase in pH of WAS due to alkali pre-treatment causes many effects on sludge components which include saponification of lipid bilayer and protein denaturation in the cell membrane, solubilizing EPS by the ionization of its carboxyl and amino groups and hydrolysis of sludge organic substances [99].

An alkali pre-treatment study demonstrated that the best-performing alkali for WAS is NaOH. The results of this study indicated an increase by 39.8, 36.6, 15.3, and 10.8% of the soluble COD (mg/L) for WAS by using NaOH, KOH, Ca(OH)2, and Mg(OH)2, respectively [108]. Using 8% of NaOH, an increase in the methane yield by 81% was observed for pulp and paper sludge [88]. Moreover, these pre-treatment methods were further studied with the pH range between 4 and 11 [109]. The results indicated that acidic pre-treatment was less effective than the alkali pre-treatment method for soluble COD in short-chain fatty acids from excess sludge. The main disadvantage of this pre-treatment includes additional pH adjustment need of this pre-treatment for AD which increases operational cost and also increases environmental concerns due to additional chemical agents.

#### *2.3.4 Oxidation*

The COD removal during AD was enhanced through oxidation at 90°C with 2 gH2O2/g VSS (volatile suspended solids) but not by the oxidation at 37°C [110]. Moreover, post-treatment on the recirculation loop, treating 20% of the sludge stream, was more efficient than a configuration with pre-treatment. However, the process consisting of one anaerobic digester, high-temperature oxidation and a

**37**

*Pre-treatment Technologies to Enhance Anaerobic Digestion*

use with increasing dewaterability of sludge [112].

poor dewaterability is observed in the acidogenic effluent.

**3. Other different pre-treatment methods**

**3.1 Thermochemical pre-treatment**

*2.3.6 Temperature phased AD (TPAD)*

second digester led to the highest removal of fecal coliforms [110]. Fenton reaction involves the decomposition of hydrogen peroxide in the presence of ferrous ions as the catalyst to form hydroxyl radicals [111]. The hydroxyl radicals thus formed are highly reactive free radical species that oxidize organic matter in sludge further enhancing WAS biodegradability and dewatering [112]. Besides catalyst and hydrogen peroxide, pH during the reaction is also a very crucial parameter to be maintained during Fenton oxidation as the catalytic activity of ferrous ions is lost at pH > 4 [113]. Hence, an effective Fenton oxidation involves adjustment to acidic pH values, oxidation, neutralization, and separation of by-products [114]. Use of Fenton catalyzed oxidation (0.067 g Fe(II)/g H2O2, and 60 g H2O2/kg TS) decreased sludge resistance to dewatering in terms of capillary suction time, but did not have a positive effect on sludge dewatering performance on a belt press simulation [115].

Ozonation depends upon the oxidation reaction of hydroxyl radicals with organic compounds present in WAS. Ozone forms free radicals on reacting with water and causes hydrolysis of organic matter in WAS enhancing its biodegradability [102]. The pH of the system is reduced after ozonation because ozone degrades higher molecular weight organic compounds into simpler acidic compounds like carboxylic acid [11]. Ozone is a strong oxidant, which disintegrates itself into radicals and reacts with organic substrates [116] in two ways; the direct reaction depends on the structure of the reactant, whereas the indirect reaction is based on the hydroxyl radicals. As a result, the recalcitrant compounds become more biodegradable and accessible to the anaerobic bacteria [117]. Prior to ozone treatment, the methane production was observed to be 440.3 ml CH4/g VS and after applying ozone doses of 0.034 g O3/g TS, 0.068 g O3/g TS, 0.101 g O3/g TS, and 0.202 g O3/g TS increased by 35.2, 46.4, 32.9, and 22.2%, respectively [118]. Several ozonation pre-treatment systems are commercially available in the market. They include the Aspal SLUDGE™ and Praxair® Lyso™. The former offers high dewaterability and low energy consumption, and the latter achieves 80% sludge reduction and 75% reduction in ozone

Temperature phased AD (TPAD) occurs in two phases. In the primary hydrolytic/

Integration of pre-treatment methods has also been studied for sludge stabilization to further improve AD and biogas production. A combination of thermal and chemical pre-treatment methods is known to improve the degradation of volatile

acidogenic phase, 45–70°C temperatures for 2–6 d is applied whereas the second phase is the methanogenic or acetogenic phase for which temperature favorable to thermophilic microorganisms is provided for 14–30 d. The effects of Maillard reaction have not been reported during TPAD which may be due to increased activity of hydrolytic enzymes or defense created by microorganisms through enzymes suppressing the effects of Maillard reaction products [119]. An additional acidification step decreases the amount of polyelectrolyte required to dewater the digestate since

*DOI: http://dx.doi.org/10.5772/intechopen.93236*

*2.3.5 Ozonation*

*Pre-treatment Technologies to Enhance Anaerobic Digestion DOI: http://dx.doi.org/10.5772/intechopen.93236*

second digester led to the highest removal of fecal coliforms [110]. Fenton reaction involves the decomposition of hydrogen peroxide in the presence of ferrous ions as the catalyst to form hydroxyl radicals [111]. The hydroxyl radicals thus formed are highly reactive free radical species that oxidize organic matter in sludge further enhancing WAS biodegradability and dewatering [112]. Besides catalyst and hydrogen peroxide, pH during the reaction is also a very crucial parameter to be maintained during Fenton oxidation as the catalytic activity of ferrous ions is lost at pH > 4 [113]. Hence, an effective Fenton oxidation involves adjustment to acidic pH values, oxidation, neutralization, and separation of by-products [114]. Use of Fenton catalyzed oxidation (0.067 g Fe(II)/g H2O2, and 60 g H2O2/kg TS) decreased sludge resistance to dewatering in terms of capillary suction time, but did not have a positive effect on sludge dewatering performance on a belt press simulation [115].

#### *2.3.5 Ozonation*

*Sustainable Sewage Sludge Management and Resource Efficiency*

methanogenesis [103].

*2.3.2 Acid pre-treatment*

conditions before the AD process [106].

However, too high concentrations of Na<sup>+</sup>

mental concerns due to additional chemical agents.

*2.3.3 Alkali pre-treatment*

reaction of hydroxyl radicals with organic compounds present in WAS. Hydroxyl radicals are highly reactive species and may cause complete mineralization of WAS after oxidation [101]. Ozone forms free radicals on reacting with water and causes hydrolysis of organic matter in WAS enhancing its biodegradability [102]. Chemical pre-treatment is not suitable for easily biodegradable substances containing high amounts of carbohydrates, due to their accelerated degradation and subsequent accumulation of volatile fatty acids, which leads to failure of the

Acid pre-treatment is done to disintegrate the polymeric structures and cells in WAS which is achieved by the use of reagents such as HCl, H2SO4, H3PO4, and HNO2. The pH during the acid pre-treatment ranges from 1 to 5.5. During acid pre-treatment, flocculation is observed near isoelectric point as the lowering of pH causes reaction between hydrogen ions and the ionized carboxyl groups rendering them in unionized forms resulting in the formation of aggregates [104]. Strong acidic pre-treatment may result in the production of inhibitory by-products, such as furfural and hydroxyl-methylfurfural [105]. Hence, strong acidic pre-treatment is avoided and pre-treatment with dilute acids is coupled with thermal methods. Other disadvantages associated with acid pre-treatment include the loss of fermentable sugar due to the increased degradation of complex substrates, a high cost of acids, and the additional cost for neutralizing the acidic

Alkali treatment is relatively effective in sludge solubilization, within the order of efficacy being highest for NaOH followed by KOH, Mg(OH)2 and Ca(OH)2 [107].

or K+

An alkali pre-treatment study demonstrated that the best-performing alkali for WAS is NaOH. The results of this study indicated an increase by 39.8, 36.6, 15.3, and 10.8% of the soluble COD (mg/L) for WAS by using NaOH, KOH, Ca(OH)2, and Mg(OH)2, respectively [108]. Using 8% of NaOH, an increase in the methane yield by 81% was observed for pulp and paper sludge [88]. Moreover, these pre-treatment methods were further studied with the pH range between 4 and 11 [109]. The results indicated that acidic pre-treatment was less effective than the alkali pre-treatment method for soluble COD in short-chain fatty acids from excess sludge. The main disadvantage of this pre-treatment includes additional pH adjustment need of this pre-treatment for AD which increases operational cost and also increases environ-

The COD removal during AD was enhanced through oxidation at 90°C with 2 gH2O2/g VSS (volatile suspended solids) but not by the oxidation at 37°C [110]. Moreover, post-treatment on the recirculation loop, treating 20% of the sludge stream, was more efficient than a configuration with pre-treatment. However, the process consisting of one anaerobic digester, high-temperature oxidation and a

of AD [107]. The increase in pH of WAS due to alkali pre-treatment causes many effects on sludge components which include saponification of lipid bilayer and protein denaturation in the cell membrane, solubilizing EPS by the ionization of its carboxyl and amino groups and hydrolysis of sludge organic substances [99].

may cause subsequent inhibition

**36**

*2.3.4 Oxidation*

Ozonation depends upon the oxidation reaction of hydroxyl radicals with organic compounds present in WAS. Ozone forms free radicals on reacting with water and causes hydrolysis of organic matter in WAS enhancing its biodegradability [102]. The pH of the system is reduced after ozonation because ozone degrades higher molecular weight organic compounds into simpler acidic compounds like carboxylic acid [11]. Ozone is a strong oxidant, which disintegrates itself into radicals and reacts with organic substrates [116] in two ways; the direct reaction depends on the structure of the reactant, whereas the indirect reaction is based on the hydroxyl radicals. As a result, the recalcitrant compounds become more biodegradable and accessible to the anaerobic bacteria [117]. Prior to ozone treatment, the methane production was observed to be 440.3 ml CH4/g VS and after applying ozone doses of 0.034 g O3/g TS, 0.068 g O3/g TS, 0.101 g O3/g TS, and 0.202 g O3/g TS increased by 35.2, 46.4, 32.9, and 22.2%, respectively [118]. Several ozonation pre-treatment systems are commercially available in the market. They include the Aspal SLUDGE™ and Praxair® Lyso™. The former offers high dewaterability and low energy consumption, and the latter achieves 80% sludge reduction and 75% reduction in ozone use with increasing dewaterability of sludge [112].

#### *2.3.6 Temperature phased AD (TPAD)*

Temperature phased AD (TPAD) occurs in two phases. In the primary hydrolytic/ acidogenic phase, 45–70°C temperatures for 2–6 d is applied whereas the second phase is the methanogenic or acetogenic phase for which temperature favorable to thermophilic microorganisms is provided for 14–30 d. The effects of Maillard reaction have not been reported during TPAD which may be due to increased activity of hydrolytic enzymes or defense created by microorganisms through enzymes suppressing the effects of Maillard reaction products [119]. An additional acidification step decreases the amount of polyelectrolyte required to dewater the digestate since poor dewaterability is observed in the acidogenic effluent.

#### **3. Other different pre-treatment methods**

#### **3.1 Thermochemical pre-treatment**

Integration of pre-treatment methods has also been studied for sludge stabilization to further improve AD and biogas production. A combination of thermal and chemical pre-treatment methods is known to improve the degradation of volatile

solids and biogas production [108]. Thermal-alkaline pre-treatment of sludge was reported to cause floc disintegration, cell disruption and reduction in organic sludge components with high increase in sludge pH to 13 [120]. The authors also reported about 100 times increase in SCOD of sludge as compared to raw untreated sludge [120]. The improvement in reduction of volatile solids as a result of thermochemical pre-treatment enhanced two times high reduction in volatile solids than that in control when sodium hydroxide was combined with thermal pre-treatment at 121°C [108]. In a similar study, 72% enhancement in volatile solids removal and biogas production was observed when sludge was pre-treated at 170°C and pH 12 [94]. The improved content of soluble COD after thermochemical pre-treatment plays role in increasing the efficiency of AD with biogas production increased to 52.78% [2]. Chemical pre-treatment of carbohydrates and proteins can increase their hydrolysis into sugars and amino acids, respectively, and these later products react with each other through Maillard reaction at high temperature resulting in high molecular weight polymers like melanoidins. In another study, a high 78% biogas production with 60% methane was obtained after thermochemical pre-treatment at a lower temperature of 70°C [121].

Microwave-alkaline pre-treatment is another integrated technology for sludge pre-treatment which improves the efficiency of AD. Microwave irradiation coupled with alkaline pre-treatment of sludge improved the volatile solids reduction by 35% and methane formation by 53% as compared to control [122].

#### **4. Feasibility of a full-scale application**

With an ever-increasing concern for the environment, different pre-treatment methods can enhance the AD performance. Nevertheless, the high capital cost, high consumption of energy, required chemicals, and sophisticated operating conditions (maintenance, odor control, etc.) are the major factor hindering their full-scale application [123]. There are only a few examples of the thermal hydrolysis process (THP) that have been applied at full-scale such as the Cambi, Porteous, and Zimpro process and thermochemical pre-treatment methods such as Synox, Protox, and Krepro. It should be noted that these methods are all applied for WWTP sludge. Concerning the organic fraction of municipal solid wastes, only a few mechanical pre-treatment methods such as Cambi THP and AD with a pre-hydrolysis stage (two-stage AD) have been applied at a full scale.

#### **4.1 Energy balance**

The required energy depends on the desired pre-treatment temperature. If it is above 100°C, most of the energy is utilized in water vaporization, thus making it less desirable [124]. Microwave heating provides direct heating from the inside and therefore unlike conventional heating strategies, negligible or no heat losses are reported [125]. However, neither microwave nor ultrasound were found to be energy-intensive for pretreating mixed sludge, as the enhanced methane yields were not enough to compensate for the required energy [126]. The total biogas obtained after thermal pre-treatment of sludge is relatively higher than other methods and thus costs could be compensated by utilizing the extra biogas through an efficient heat exchanger [127]. A better energy balance was estimated while treatment of organic fraction of municipal solid waste in two-stage AD systems where the authors observed higher energy potential to be associated with not the first stage hydrogen production but to the higher performance in the methanogenic reactor [128]. The energy efficiency of a two-stage AD reactor for sewage sludge in which excess energy of 2.17 kJ/d was obtained was higher when compared to a single-stage

**39**

**5. Conclusion**

*Pre-treatment Technologies to Enhance Anaerobic Digestion*

18.5% if the two-stage AD process is optimized**.**

0.0162, 0.0187, 0.0264, and 0.0358 US\$/m3

sustainable process for sludge management.

cheaper than ultrasonic and chemical pre-treatments.

system [129]. It was further concluded that the energy balance can be enhanced by

Estimated net profit of various pre-treatments (low-temperature thermal pretreatment not included) to enhance the biogas production of food waste obtained the best result (10–15 euro/ton FW) with less energy-intensive methods (acid and freeze-thaw) [130]. The estimation of the economic feasibility of pre-treatment methods based on a full-scale application has only been reported for WWTP sludge.

sludge per day based on the application of focused-pulsed pre-treatment technology could generate a benefit of 540,000 USD per year [72]. An approximate cost estimate associated with pre-treatment methods was suggested in research which included capital, operational, and maintenance costs between 70 and 150 US \$/ ton sludge [131]. In another cost estimate study, comparative costs for sludge pretreatment methods were calculated to improve the process of AD of sludge where the authors estimated costs associated with microwave pre-treatment, conventional

thermal pre-treatment, ultrasound, and chemical pre-treatment methods as

cost analysis suggested microwave and conventional pre-treatment methods to be

The amount of sludge for pre-treatment is also an important factor to consider when estimating the pre-treatment cost. Pre-treatment strategies such as ultrasound can prove to be energetically acceptable for a large scale application if 6 kWh energy value is considered for each cubic meter of sludge [124]. If higher energy is required, biological pre-treatment such as adding hydrolytic bacteria could be a cheaper option [132]. The extent of net economic benefit also depends upon other factors besides the type of pre-treatment method and quality and quantity of sludge. Other parameters to be considered include treatment capacity, availability of labor, the cost associated with collection and transport, taxes and tariffs, energy prices, price of land selected for setup, costs for additional mixing and pumping requirements, the market value of end product as well as waste and residue disposal [133].

The pre-treatment methods have the potential to solubilize complex sludge components which include the organic matter, EPS, and the microbial cell wall which in turn makes the progression of subsequent biological degradation treatments easier. AD is the sustainable process widely employed for bioenergy generation from the WAS. Further pre-treatment enhances the methane percentage in the biogas thus the process is energy efficient and sustainable. To attain a clear understanding of the mechanism behind each method, the focus should be given to the conversion strategy and structural alterations that occur in complex WAS components upon the application of each pretreatment technology. Many physical, chemical and biological pretreatment methods have been mentioned in the literature that has been used individually but each of them owns certain disadvantages. These limitations range from high energy requirement of microwaves to excess degradation and fermentable sugars loss in acid pre-treatment. Using two pre-treatment methods in combination has known to overcome these problems, reaping the efficiency of both methods simultaneously. Thus combing pre-treatment process and AD will lead to

) treating 380 m3

, respectively [125]. The comparative

The operational and maintenance cost of a full-scale AD (3300 m3

*DOI: http://dx.doi.org/10.5772/intechopen.93236*

**4.2 Economic feasibility**

system [129]. It was further concluded that the energy balance can be enhanced by 18.5% if the two-stage AD process is optimized**.**

#### **4.2 Economic feasibility**

*Sustainable Sewage Sludge Management and Resource Efficiency*

and methane formation by 53% as compared to control [122].

With an ever-increasing concern for the environment, different pre-treatment methods can enhance the AD performance. Nevertheless, the high capital cost, high consumption of energy, required chemicals, and sophisticated operating conditions (maintenance, odor control, etc.) are the major factor hindering their full-scale application [123]. There are only a few examples of the thermal hydrolysis process (THP) that have been applied at full-scale such as the Cambi, Porteous, and Zimpro process and thermochemical pre-treatment methods such as Synox, Protox, and Krepro. It should be noted that these methods are all applied for WWTP sludge. Concerning the organic fraction of municipal solid wastes, only a few mechanical pre-treatment methods such as Cambi THP and AD with a pre-hydrolysis stage

The required energy depends on the desired pre-treatment temperature. If it is above 100°C, most of the energy is utilized in water vaporization, thus making it less desirable [124]. Microwave heating provides direct heating from the inside and therefore unlike conventional heating strategies, negligible or no heat losses are reported [125]. However, neither microwave nor ultrasound were found to be energy-intensive for pretreating mixed sludge, as the enhanced methane yields were not enough to compensate for the required energy [126]. The total biogas obtained after thermal pre-treatment of sludge is relatively higher than other methods and thus costs could be compensated by utilizing the extra biogas through an efficient heat exchanger [127]. A better energy balance was estimated while treatment of organic fraction of municipal solid waste in two-stage AD systems where the authors observed higher energy potential to be associated with not the first stage hydrogen production but to the higher performance in the methanogenic reactor [128]. The energy efficiency of a two-stage AD reactor for sewage sludge in which excess energy of 2.17 kJ/d was obtained was higher when compared to a single-stage

**4. Feasibility of a full-scale application**

(two-stage AD) have been applied at a full scale.

**4.1 Energy balance**

solids and biogas production [108]. Thermal-alkaline pre-treatment of sludge was reported to cause floc disintegration, cell disruption and reduction in organic sludge components with high increase in sludge pH to 13 [120]. The authors also reported about 100 times increase in SCOD of sludge as compared to raw untreated sludge [120]. The improvement in reduction of volatile solids as a result of thermochemical pre-treatment enhanced two times high reduction in volatile solids than that in control when sodium hydroxide was combined with thermal pre-treatment at 121°C [108]. In a similar study, 72% enhancement in volatile solids removal and biogas production was observed when sludge was pre-treated at 170°C and pH 12 [94]. The improved content of soluble COD after thermochemical pre-treatment plays role in increasing the efficiency of AD with biogas production increased to 52.78% [2]. Chemical pre-treatment of carbohydrates and proteins can increase their hydrolysis into sugars and amino acids, respectively, and these later products react with each other through Maillard reaction at high temperature resulting in high molecular weight polymers like melanoidins. In another study, a high 78% biogas production with 60% methane was obtained after thermochemical pre-treatment at a lower temperature of 70°C [121]. Microwave-alkaline pre-treatment is another integrated technology for sludge pre-treatment which improves the efficiency of AD. Microwave irradiation coupled with alkaline pre-treatment of sludge improved the volatile solids reduction by 35%

**38**

Estimated net profit of various pre-treatments (low-temperature thermal pretreatment not included) to enhance the biogas production of food waste obtained the best result (10–15 euro/ton FW) with less energy-intensive methods (acid and freeze-thaw) [130]. The estimation of the economic feasibility of pre-treatment methods based on a full-scale application has only been reported for WWTP sludge. The operational and maintenance cost of a full-scale AD (3300 m3 ) treating 380 m3 sludge per day based on the application of focused-pulsed pre-treatment technology could generate a benefit of 540,000 USD per year [72]. An approximate cost estimate associated with pre-treatment methods was suggested in research which included capital, operational, and maintenance costs between 70 and 150 US \$/ ton sludge [131]. In another cost estimate study, comparative costs for sludge pretreatment methods were calculated to improve the process of AD of sludge where the authors estimated costs associated with microwave pre-treatment, conventional thermal pre-treatment, ultrasound, and chemical pre-treatment methods as 0.0162, 0.0187, 0.0264, and 0.0358 US\$/m3 , respectively [125]. The comparative cost analysis suggested microwave and conventional pre-treatment methods to be cheaper than ultrasonic and chemical pre-treatments.

The amount of sludge for pre-treatment is also an important factor to consider when estimating the pre-treatment cost. Pre-treatment strategies such as ultrasound can prove to be energetically acceptable for a large scale application if 6 kWh energy value is considered for each cubic meter of sludge [124]. If higher energy is required, biological pre-treatment such as adding hydrolytic bacteria could be a cheaper option [132]. The extent of net economic benefit also depends upon other factors besides the type of pre-treatment method and quality and quantity of sludge. Other parameters to be considered include treatment capacity, availability of labor, the cost associated with collection and transport, taxes and tariffs, energy prices, price of land selected for setup, costs for additional mixing and pumping requirements, the market value of end product as well as waste and residue disposal [133].

#### **5. Conclusion**

The pre-treatment methods have the potential to solubilize complex sludge components which include the organic matter, EPS, and the microbial cell wall which in turn makes the progression of subsequent biological degradation treatments easier. AD is the sustainable process widely employed for bioenergy generation from the WAS. Further pre-treatment enhances the methane percentage in the biogas thus the process is energy efficient and sustainable. To attain a clear understanding of the mechanism behind each method, the focus should be given to the conversion strategy and structural alterations that occur in complex WAS components upon the application of each pretreatment technology. Many physical, chemical and biological pretreatment methods have been mentioned in the literature that has been used individually but each of them owns certain disadvantages. These limitations range from high energy requirement of microwaves to excess degradation and fermentable sugars loss in acid pre-treatment. Using two pre-treatment methods in combination has known to overcome these problems, reaping the efficiency of both methods simultaneously. Thus combing pre-treatment process and AD will lead to sustainable process for sludge management.

### **Author details**

Sridhar Pilli1 \*, Ashutosh Kumar Pandey2 , Ankur Katiyar3 , Kritika Pandey4 and Rajeshwar Dayal Tyagi5

1 Department of Civil Engineering, National Institute of Technology, Warangal, Warangal, India

2 Centre for Energy and Environmental Sustainability, Lucknow, India

3 Department of Biotechnology, S.D. College of Engineering and Technology, Muzaffarnagar, Uttar Pradesh, India

4 Department of Biotechnology, Dr. Ambedkar Institute of Technology for Handicapped, Kanpur, Uttar Pradesh, India

5 Institut National de la Recherche Scientifique, Quebec City, Quebec, Canada

\*Address all correspondence to: srenitw@nitw.ac.in

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**41**

*Pre-treatment Technologies to Enhance Anaerobic Digestion*

food waste digestion. Water Science and Technology. 2000;**41**(3):67-73. DOI:

[8] Khanal SK, Grewell D, Sung S, Van Leeuwen J. Ultrasound applications in wastewater sludge pretreatment: A review. Critical Reviews in Environmental Science and Technology. 2007;**37**(4):277- 313. DOI: 10.1080/10643380600860249

[9] Delmas H, Le NT, Barthe L, Julcour-Lebigue C. Optimization of hydrostatic

conditions–power density, intensity, very low frequency–for isothermal ultrasonic sludge treatment. Ultrasonics

[10] Chu CP, Lee DJ, Chang BV, You CS, Tay JH. 'Weak' ultrasonic pre-treatment on anaerobic digestion of flocculated activated biosolids. Water Research. 2002;**36**(11):2681-2688. DOI: 10.1016/

[11] Bougrier C, Albasi C, Delgenès JP, Carrère H. Effect of ultrasonic, thermal and ozone pre-treatments on waste activated sludge solubilisation and anaerobic biodegradability. Chemical Engineering and Processing Process Intensification. 2006;**45**(8):711-718. DOI: 10.1016/j.cep.2006.02.005

[12] Kumar PS, Pandit AB. Modeling hydrodynamic cavitation. Chemical Engineering and Technology: Industrial

[13] Zhang Y, Zhang P, Ma B, Wu H, Zhang S, Xu X. Sewage sludge disintegration by high-pressure

model. Journal of Environmental Sciences. 2012;**24**(5):814-820. DOI: 10.1016/S1001-0742(11)60834-6

[14] Barjenbruch M, Kopplow O. Enzymatic, mechanical and thermal

homogenization: A sludge disintegration

Chemistry Equipment-Process Engineering. 1999;**22**(12):1017-1027

pressure at varied sonication

Sonochemistry. 2015;**25**:51-59

S0043-1354(01)00515-2

10.2166/wst.2000.0057

*DOI: http://dx.doi.org/10.5772/intechopen.93236*

[1] Liu G et al. Scenarios for sewage sludge reduction and reuse in clinker production towards regional ecoindustrial development: A comparative emergy-based assessment. Journal of Cleaner Production. 2015;**103**:371-383. DOI: 10.1016/j.jclepro.2014.09.003

[2] Xu J, Yuan H, Lin J, Yuan W.

alkaline and electrochemical pretreatments on sludge to enhance anaerobic biogas production. Journal of the Taiwan Institute of Chemical Engineers. 2014;**45**(5):2531-2536. DOI:

10.1016/j.jtice.2014.05.029

jhazmat.2019.121847

3012x13347678384602

[3] Xu Y, Lu Y, Zheng L, Wang Z, Dai X. Perspective on enhancing the anaerobic digestion of waste activated sludge. Journal of Hazardous Materials. 2020;**389**:121847. DOI: 10.1016/j.

[4] Hanjie Z. Sludge treatment to increase biogas production. Trita-LWR Degree Project 10-20. In: Skolan för Arkitektur Och Samhällsbyggnad. Kungliga Tekniska Högskolan. Stockholm,

Sweden: Department of Land and Water Resources Engineering: Royal Institute of Technology (KTH) SE-100 44; 2010

[5] Elliott A, Mahmood T. Comparison of mechanical pretreatment methods for the enhancement of anaerobic digestion of pulp and paper waste activated sludge. Water Environment Research. 2012;**84**(6):497-505. DOI: 10.2175/10614

[6] Esposito G, Frunzo L, Panico A, Pirozzi F. Modelling the effect of the OLR and OFMSW particle size on the performances of an anaerobic co-digestion reactor. Process

Biochemistry. 2011;**46**(2):557-565. DOI:

10.1016/j.procbio.2010.10.010

[7] Kim IS, Kim DH, Hyun SH. Effect of particle size and sodium ion concentration on anaerobic thermophilic

Evaluation of thermal, thermal-alkaline,

**References**

*Pre-treatment Technologies to Enhance Anaerobic Digestion DOI: http://dx.doi.org/10.5772/intechopen.93236*

#### **References**

*Sustainable Sewage Sludge Management and Resource Efficiency*

\*, Ashutosh Kumar Pandey2

, Ankur Katiyar3

1 Department of Civil Engineering, National Institute of Technology, Warangal,

3 Department of Biotechnology, S.D. College of Engineering and Technology,

4 Department of Biotechnology, Dr. Ambedkar Institute of Technology for

5 Institut National de la Recherche Scientifique, Quebec City, Quebec, Canada

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

2 Centre for Energy and Environmental Sustainability, Lucknow, India

, Kritika Pandey4

**40**

**Author details**

Warangal, India

and Rajeshwar Dayal Tyagi5

Muzaffarnagar, Uttar Pradesh, India

Handicapped, Kanpur, Uttar Pradesh, India

provided the original work is properly cited.

\*Address all correspondence to: srenitw@nitw.ac.in

Sridhar Pilli1

[1] Liu G et al. Scenarios for sewage sludge reduction and reuse in clinker production towards regional ecoindustrial development: A comparative emergy-based assessment. Journal of Cleaner Production. 2015;**103**:371-383. DOI: 10.1016/j.jclepro.2014.09.003

[2] Xu J, Yuan H, Lin J, Yuan W. Evaluation of thermal, thermal-alkaline, alkaline and electrochemical pretreatments on sludge to enhance anaerobic biogas production. Journal of the Taiwan Institute of Chemical Engineers. 2014;**45**(5):2531-2536. DOI: 10.1016/j.jtice.2014.05.029

[3] Xu Y, Lu Y, Zheng L, Wang Z, Dai X. Perspective on enhancing the anaerobic digestion of waste activated sludge. Journal of Hazardous Materials. 2020;**389**:121847. DOI: 10.1016/j. jhazmat.2019.121847

[4] Hanjie Z. Sludge treatment to increase biogas production. Trita-LWR Degree Project 10-20. In: Skolan för Arkitektur Och Samhällsbyggnad. Kungliga Tekniska Högskolan. Stockholm, Sweden: Department of Land and Water Resources Engineering: Royal Institute of Technology (KTH) SE-100 44; 2010

[5] Elliott A, Mahmood T. Comparison of mechanical pretreatment methods for the enhancement of anaerobic digestion of pulp and paper waste activated sludge. Water Environment Research. 2012;**84**(6):497-505. DOI: 10.2175/10614 3012x13347678384602

[6] Esposito G, Frunzo L, Panico A, Pirozzi F. Modelling the effect of the OLR and OFMSW particle size on the performances of an anaerobic co-digestion reactor. Process Biochemistry. 2011;**46**(2):557-565. DOI: 10.1016/j.procbio.2010.10.010

[7] Kim IS, Kim DH, Hyun SH. Effect of particle size and sodium ion concentration on anaerobic thermophilic food waste digestion. Water Science and Technology. 2000;**41**(3):67-73. DOI: 10.2166/wst.2000.0057

[8] Khanal SK, Grewell D, Sung S, Van Leeuwen J. Ultrasound applications in wastewater sludge pretreatment: A review. Critical Reviews in Environmental Science and Technology. 2007;**37**(4):277- 313. DOI: 10.1080/10643380600860249

[9] Delmas H, Le NT, Barthe L, Julcour-Lebigue C. Optimization of hydrostatic pressure at varied sonication conditions–power density, intensity, very low frequency–for isothermal ultrasonic sludge treatment. Ultrasonics Sonochemistry. 2015;**25**:51-59

[10] Chu CP, Lee DJ, Chang BV, You CS, Tay JH. 'Weak' ultrasonic pre-treatment on anaerobic digestion of flocculated activated biosolids. Water Research. 2002;**36**(11):2681-2688. DOI: 10.1016/ S0043-1354(01)00515-2

[11] Bougrier C, Albasi C, Delgenès JP, Carrère H. Effect of ultrasonic, thermal and ozone pre-treatments on waste activated sludge solubilisation and anaerobic biodegradability. Chemical Engineering and Processing Process Intensification. 2006;**45**(8):711-718. DOI: 10.1016/j.cep.2006.02.005

[12] Kumar PS, Pandit AB. Modeling hydrodynamic cavitation. Chemical Engineering and Technology: Industrial Chemistry Equipment-Process Engineering. 1999;**22**(12):1017-1027

[13] Zhang Y, Zhang P, Ma B, Wu H, Zhang S, Xu X. Sewage sludge disintegration by high-pressure homogenization: A sludge disintegration model. Journal of Environmental Sciences. 2012;**24**(5):814-820. DOI: 10.1016/S1001-0742(11)60834-6

[14] Barjenbruch M, Kopplow O. Enzymatic, mechanical and thermal pre-treatment of surplus sludge. Advances in Environmental Research. 2003;**7**(3):715-720. DOI: 10.1016/ S1093-0191(02)00032-1

[15] Carlsson M, Lagerkvist A, Ecke H, editors. Electroporation for enhanced methane yield from municipal solid waste. In: ORBIT 2008: Moving Organic Waste Recycling Towards Resource Management and Biobased Economy 13/10/2008-15/10/2008. Sweden: University of Technology; 2008

[16] Engelhart M, Krüger M, Kopp J, Dichtl N. Effects of disintegration on anaerobic degradation of sewage excess sludge in downflow stationary fixed film digesters. Water Science and Technology. 2000;**41**(3):171-179. DOI: 10.2166/wst.2000.0069

[17] Toreci I, Kennedy KJ, Droste RL. Evaluation of continuous mesophilic anaerobic sludge digestion after high temperature microwave pretreatment. Water Research. 2009;**43**(5):1273-1284. DOI: 10.1016/j.watres.2008.12.022

[18] Attard P, Moody MP, Tyrrell JWG. Nanobubbles: The big picture. Physica A: Statistical Mechanics and its Applications. 2002;**314**(1-4):696-705

[19] Zhu J et al. Cleaning with bulk nanobubbles. Langmuir. 2016;**32**(43):11203-11211

[20] Vaze N et al. An integrated electrolysis – electrospray – ionization antimicrobial platform using Engineered Water Nanostructures (EWNS) for food safety applications. Food Control. 2018;**85**:151-160. DOI: 10.1016/j.foodcont.2017.09.034

[21] Agarwal A, Ng WJ, Liu Y. Principle and applications of microbubble and nanobubble technology for water treatment. Chemosphere. 2011;**84**(9):1175-1180. DOI: 10.1016/j. chemosphere.2011.05.054

[22] Oeffinger BE, Wheatley MA. Development and characterization of a nano-scale contrast agent. Ultrasonics. 2004;**42**(1-9):343-347. DOI: 10.1016/j. ultras.2003.11.011

[23] Kim JY, Song MG, Kim JD. Zeta potential of nanobubbles generated by ultrasonication in aqueous alkyl polyglycoside solutions. Journal of Colloid and Interface Science. 2000;**223**(2):285- 291. DOI: 10.1006/jcis.1999.6663

[24] Liu S, Oshita S, Kawabata S, Makino Y, Yoshimoto T. Identification of ROS produced by nanobubbles and their positive and negative effects on vegetable seed germination. Langmuir. 2016;**32**(43):11295-11302. DOI: 10.1021/ acs.langmuir.6b01621

[25] Yang X et al. Enhanced hydrolysis of waste activated sludge for methane production via anaerobic digestion under N2-nanobubble water addition. Science of the Total Environment. 2019;**693**:133524. DOI: 10.1016/j.scitotenv.2019.07.330

[26] Brennen CE. Cavitation and Bubble Dynamics. New York, USA: Cambridge University Press; 2014

[27] Ozonek J. Application of Hydrodynamic Cavitation in Environmental Engineering. Boca Raton, FL: CRC Press; 2012

[28] Lee I, Han JI. The effects of wasteactivated sludge pretreatment using hydrodynamic cavitation for methane production. Ultrasonics Sonochemistry. 2013;**20**(6):1450-1455. DOI: 10.1016/j. ultsonch.2013.03.006

[29] Kim HJ, Nguyen DX, Bae JH. The performance of the sludge pretreatment system with venturi tubes. Water Science and Technology. 2008;**57**(1):131- 137. DOI: 10.2166/wst.2008.717

[30] Petkovšek M, Mlakar M, Levstek M, Stražar M, Širok B, Dular M. A novel rotation generator of hydrodynamic

**43**

*Pre-treatment Technologies to Enhance Anaerobic Digestion*

thermal hydrolysis process for sludge pre-treatment. Journal of Environmental Management. 2017;**192**:25-30. DOI: 10.1016/j.jenvman.2017.01.043

[38] Carrère H et al. Pretreatment methods to improve sludge anaerobic degradability: A review. Journal of Hazardous Materials. 2010;**183**(1-3):1- 15. DOI: 10.1016/j.jhazmat.2010.06.129

[39] Wilson CA, Novak JT. Hydrolysis of macromolecular components of primary and secondary wastewater sludge by thermal hydrolytic pretreatment. Water Research. 2009;**43**(18):4489-4498

[40] Graja S, Chauzy J, Fernandes P, Patria L, Cretenot D. Reduction of sludge production from WWTP using thermal pretreatment and enhanced anaerobic methanisation. Water Science and Technology. 2005;**52**(1-2):267-273. DOI:

[41] Dwyer J, Starrenburg D, Tait S, Barr K, Batstone DJ, Lant P. Decreasing activated sludge thermal hydrolysis temperature reduces product colour, without decreasing degradability. Water Research. 2008;**42**(18):4699-4709. DOI:

10.1016/j.watres.2008.08.019

[42] Gianico A, Braguglia CM, Cesarini R, Mininni G. Reduced temperature hydrolysis at 134°C before thermophilic anaerobic digestion of waste activated sludge at increasing organic load. Bioresource Technology. 2013;**143**:96-103. DOI: 10.1016/j.

[43] Liao X, Li H, Zhang Y, Liu C,

10.1016/j.ibiod.2015.10.023

[44] Carvajal A, Peña M, Pérez-Elvira S. Autohydrolysis pretreatment of secondary sludge for anaerobic

Chen Q. Accelerated high-solids anaerobic digestion of sewage sludge using lowtemperature thermal pretreatment. International Biodeterioration and Biodegradation. 2016;**106**:141-149. DOI:

biortech.2013.05.069

10.2166/wst.2005.0527

*DOI: http://dx.doi.org/10.5772/intechopen.93236*

[31] Neumann P, Pesante S, Venegas M, Vidal G. Developments in pre-treatment

Biotechnology. 2016;**15**(2):173-211. DOI:

Fdz-Polanco F. Thermal pretreatment and hydraulic retention time in continuous digesters fed with sewage sludge: Assessment using the ADM1. Bioresource Technology. 2013;**148**:317-324. DOI: 10.1016/j.

[33] Nazari L et al. Low-temperature thermal pre-treatment of municipal wastewater sludge: Process optimization

and effects on solubilization and anaerobic degradation. Water Research.

2017;**113**:111-123. DOI: 10.1016/j.

[34] Vaclavik VA, Christian EW, Christian EW. Essentials of Food Science. Vol. 42. New York: Springer Science+Business Media; 2008

[35] Koupaie EH, Eskicioglu C. Conventional heating vs. microwave sludge pretreatment comparison under identical heating/cooling profiles for thermophilic advanced anaerobic digestion. Waste Management.

[36] Pilli S, Yan S, Tyagi RD,

10.1080/10643389.2013.876527

Surampalli RY. Thermal pretreatment of sewage sludge to enhance anaerobic digestion: A review. Critical Reviews in Environmental Science and

Technology. 2015;**45**(6):669-702. DOI:

[37] Sapkaite I, Barrado E, Fdz-Polanco F, Pérez-Elvira SI. Optimization of a

cavitation for waste-activated sludge disintegration. Ultrasonics Sonochemistry. 2015;**26**:408-414. DOI:

10.1016/j.ultsonch.2015.01.006

methods to improve anaerobic digestion of sewage sludge. Reviews in Environmental Science and

10.1007/s11157-016-9396-8

biortech.2013.08.161

watres.2016.11.055

2016;**53**:182-195

[32] Souza TSO, Ferreira LC, Sapkaite I, Pérez-Elvira SI,

*Pre-treatment Technologies to Enhance Anaerobic Digestion DOI: http://dx.doi.org/10.5772/intechopen.93236*

cavitation for waste-activated sludge disintegration. Ultrasonics Sonochemistry. 2015;**26**:408-414. DOI: 10.1016/j.ultsonch.2015.01.006

*Sustainable Sewage Sludge Management and Resource Efficiency*

[22] Oeffinger BE, Wheatley MA. Development and characterization of a nano-scale contrast agent. Ultrasonics. 2004;**42**(1-9):343-347. DOI: 10.1016/j.

[23] Kim JY, Song MG, Kim JD. Zeta potential of nanobubbles generated by ultrasonication in aqueous alkyl polyglycoside solutions. Journal of Colloid and Interface Science. 2000;**223**(2):285- 291. DOI: 10.1006/jcis.1999.6663

[24] Liu S, Oshita S, Kawabata S, Makino Y, Yoshimoto T. Identification of ROS produced by nanobubbles and their positive and negative effects on vegetable seed germination. Langmuir. 2016;**32**(43):11295-11302. DOI: 10.1021/

[25] Yang X et al. Enhanced hydrolysis of waste activated sludge for methane production via anaerobic digestion under N2-nanobubble water addition. Science of the Total Environment. 2019;**693**:133524. DOI: 10.1016/j.scitotenv.2019.07.330

[26] Brennen CE. Cavitation and Bubble Dynamics. New York, USA: Cambridge

[28] Lee I, Han JI. The effects of wasteactivated sludge pretreatment using hydrodynamic cavitation for methane production. Ultrasonics Sonochemistry. 2013;**20**(6):1450-1455. DOI: 10.1016/j.

[29] Kim HJ, Nguyen DX, Bae JH. The performance of the sludge pretreatment system with venturi tubes. Water Science and Technology. 2008;**57**(1):131-

[30] Petkovšek M, Mlakar M, Levstek M, Stražar M, Širok B, Dular M. A novel rotation generator of hydrodynamic

137. DOI: 10.2166/wst.2008.717

acs.langmuir.6b01621

University Press; 2014

ultsonch.2013.03.006

[27] Ozonek J. Application of Hydrodynamic Cavitation in Environmental Engineering. Boca Raton, FL: CRC Press; 2012

ultras.2003.11.011

pre-treatment of surplus sludge. Advances in Environmental Research. 2003;**7**(3):715-720. DOI: 10.1016/

[15] Carlsson M, Lagerkvist A, Ecke H, editors. Electroporation for enhanced methane yield from municipal solid waste. In: ORBIT 2008: Moving Organic Waste Recycling Towards Resource Management and Biobased Economy 13/10/2008-15/10/2008. Sweden: University of Technology; 2008

[16] Engelhart M, Krüger M, Kopp J, Dichtl N. Effects of disintegration on anaerobic degradation of sewage excess sludge in downflow stationary fixed film digesters. Water Science and Technology. 2000;**41**(3):171-179. DOI:

[17] Toreci I, Kennedy KJ, Droste RL. Evaluation of continuous mesophilic anaerobic sludge digestion after high temperature microwave pretreatment. Water Research. 2009;**43**(5):1273-1284. DOI: 10.1016/j.watres.2008.12.022

[18] Attard P, Moody MP, Tyrrell JWG. Nanobubbles: The big picture. Physica A: Statistical Mechanics and its Applications. 2002;**314**(1-4):696-705

[19] Zhu J et al. Cleaning with bulk nanobubbles. Langmuir. 2016;**32**(43):11203-11211

[20] Vaze N et al. An integrated electrolysis – electrospray – ionization

antimicrobial platform using Engineered Water Nanostructures (EWNS) for food safety applications. Food Control. 2018;**85**:151-160. DOI: 10.1016/j.foodcont.2017.09.034

chemosphere.2011.05.054

[21] Agarwal A, Ng WJ, Liu Y. Principle and applications of microbubble and nanobubble technology for water treatment. Chemosphere. 2011;**84**(9):1175-1180. DOI: 10.1016/j.

10.2166/wst.2000.0069

S1093-0191(02)00032-1

**42**

[31] Neumann P, Pesante S, Venegas M, Vidal G. Developments in pre-treatment methods to improve anaerobic digestion of sewage sludge. Reviews in Environmental Science and Biotechnology. 2016;**15**(2):173-211. DOI: 10.1007/s11157-016-9396-8

[32] Souza TSO, Ferreira LC, Sapkaite I, Pérez-Elvira SI, Fdz-Polanco F. Thermal pretreatment and hydraulic retention time in continuous digesters fed with sewage sludge: Assessment using the ADM1. Bioresource Technology. 2013;**148**:317-324. DOI: 10.1016/j. biortech.2013.08.161

[33] Nazari L et al. Low-temperature thermal pre-treatment of municipal wastewater sludge: Process optimization and effects on solubilization and anaerobic degradation. Water Research. 2017;**113**:111-123. DOI: 10.1016/j. watres.2016.11.055

[34] Vaclavik VA, Christian EW, Christian EW. Essentials of Food Science. Vol. 42. New York: Springer Science+Business Media; 2008

[35] Koupaie EH, Eskicioglu C. Conventional heating vs. microwave sludge pretreatment comparison under identical heating/cooling profiles for thermophilic advanced anaerobic digestion. Waste Management. 2016;**53**:182-195

[36] Pilli S, Yan S, Tyagi RD, Surampalli RY. Thermal pretreatment of sewage sludge to enhance anaerobic digestion: A review. Critical Reviews in Environmental Science and Technology. 2015;**45**(6):669-702. DOI: 10.1080/10643389.2013.876527

[37] Sapkaite I, Barrado E, Fdz-Polanco F, Pérez-Elvira SI. Optimization of a

thermal hydrolysis process for sludge pre-treatment. Journal of Environmental Management. 2017;**192**:25-30. DOI: 10.1016/j.jenvman.2017.01.043

[38] Carrère H et al. Pretreatment methods to improve sludge anaerobic degradability: A review. Journal of Hazardous Materials. 2010;**183**(1-3):1- 15. DOI: 10.1016/j.jhazmat.2010.06.129

[39] Wilson CA, Novak JT. Hydrolysis of macromolecular components of primary and secondary wastewater sludge by thermal hydrolytic pretreatment. Water Research. 2009;**43**(18):4489-4498

[40] Graja S, Chauzy J, Fernandes P, Patria L, Cretenot D. Reduction of sludge production from WWTP using thermal pretreatment and enhanced anaerobic methanisation. Water Science and Technology. 2005;**52**(1-2):267-273. DOI: 10.2166/wst.2005.0527

[41] Dwyer J, Starrenburg D, Tait S, Barr K, Batstone DJ, Lant P. Decreasing activated sludge thermal hydrolysis temperature reduces product colour, without decreasing degradability. Water Research. 2008;**42**(18):4699-4709. DOI: 10.1016/j.watres.2008.08.019

[42] Gianico A, Braguglia CM, Cesarini R, Mininni G. Reduced temperature hydrolysis at 134°C before thermophilic anaerobic digestion of waste activated sludge at increasing organic load. Bioresource Technology. 2013;**143**:96-103. DOI: 10.1016/j. biortech.2013.05.069

[43] Liao X, Li H, Zhang Y, Liu C, Chen Q. Accelerated high-solids anaerobic digestion of sewage sludge using lowtemperature thermal pretreatment. International Biodeterioration and Biodegradation. 2016;**106**:141-149. DOI: 10.1016/j.ibiod.2015.10.023

[44] Carvajal A, Peña M, Pérez-Elvira S. Autohydrolysis pretreatment of secondary sludge for anaerobic

digestion. Biochemical Engineering Journal. 2013;**75**:21-31. DOI: 10.1016/j. bej.2013.03.002

[45] Ruffino B et al. Improvement of anaerobic digestion of sewage sludge in a wastewater treatment plant by means of mechanical and thermal pre-treatments: Performance, energy and economical assessment. Bioresource Technology. 2015;**175**:298-308. DOI: 10.1016/j.biortech.2014.10.071

[46] Hiraoka M, Takeda N, Sakai S, Yasuda A. Highly efficient anaerobic digestion with thermal pretreatment. Water Science and Technology. 1985;**17**(4-5):529-539. DOI: 10.2166/ wst.1985.0157

[47] Prorot A, Julien L, Christophe D, Patrick L. Sludge disintegration during heat treatment at low temperature: A better understanding of involved mechanisms with a multiparametric approach. Biochemical Engineering Journal. 2011;**54**(3):178-184. DOI: 10.1016/j.bej.2011.02.016

[48] Skiadas IV, Gavala HN, Lu J, Ahring BK. Thermal pre-treatment of primary and secondary sludge at 70 C prior to anaerobic digestion. Water Science and Technology. 2005;**52**(1-2):161-166

[49] Appels L, Houtmeyers S, Degrève J, Van Impe J, Dewil R. Influence of microwave pre-treatment on sludge solubilization and pilot scale semicontinuous anaerobic digestion. Bioresource Technology. 2013;**128**:598- 603. DOI: 10.1016/j.biortech.2012.11.007

[50] Braguglia CM, Gianico A, Mininni G. Laboratory-scale ultrasound pre-treated digestion of sludge: heat and energy balance. Bioresource Technology. 2011;**102**(16):7567-7573. DOI: 10.1016/j. biortech.2011.05.025

[51] Burger G, Parker W. Investigation of the impacts of thermal pretreatment on

waste activated sludge and development of a pretreatment model. Water Research. 2013;**47**(14):5245-5256. DOI: 10.1016/j.watres.2013.06.005

[52] Chang CJ, Tyagi VK, Lo SL. Effects of microwave and alkali induced pretreatment on sludge solubilization and subsequent aerobic digestion. Bioresource Technology. 2011;**102**(17):7633-7640. DOI: 10.1016/j. biortech.2011.05.031

[53] Chang TC, You SJ, Damodar RA, Chen YY. Ultrasound pre-treatment step for performance enhancement in an aerobic sludge digestion process. Journal of the Taiwan Institute of Chemical Engineers. 2011;**42**(5):801-808. DOI: 10.1016/j.jtice.2011.01.003

[54] Choi H, Jeong SW, Chung YJ. Enhanced anaerobic gas production of waste activated sludge pretreated by pulse power technique. Bioresource Technology. 2006;**97**(2):198-203. DOI: 10.1016/j.biortech.2005.02.023

[55] Coelho NMG, Droste RL, Kennedy KJ. Evaluation of continuous mesophilic, thermophilic and temperature phased anaerobic digestion of microwaved activated sludge. Water Research. 2011;45(9):2822-2834. DOI: 10.1016/j. watres.2011.02.032

[56] Ebenezer AV, Arulazhagan P, Adish Kumar S, Yeom IT, Rajesh Banu J. Effect of deflocculation on the efficiency of low-energy microwave pretreatment and anaerobic biodegradation of waste activated sludge. Applied Energy. 2015;**145**:104-110. DOI: 10.1016/j. apenergy.2015.01.133

[57] Erden G. Combination of alkaline and microwave pretreatment for disintegration of meat processing wastewater sludge. Environmental Technology (United Kingdom). 2013;**34**(6):711-718. DOI: 10.1080/09593330.2012.715678

**45**

*Pre-treatment Technologies to Enhance Anaerobic Digestion*

Journal of Environmental Management. 2015;**147**:330-337. DOI: 10.1016/j.

Thermal Hydrolysis Plants. Bioresource Technology. 2011;**102**(3):3089-3097. DOI: 10.1016/j.biortech.2010.10.054

[66] Ning XA, Chen H, Wu J, Wang Y, Liu J, Lin M. Effects of ultrasound assisted fenton treatment on textile dyeing sludge structure and dewaterability. Chemical Engineering Journal. 2014;242:102-108. DOI:

[67] Onyeche T. Economic benefits of low pressure sludge homogenization for wastewater treatment plants. In: IWA Specialist Conferences. Moving Forward Wastewater Biosolids Sustainability; Moncton, New Brunswick, Canada;

[68] Oosterhuis M, Ringoot D, Hendriks A, Roeleveld P. Thermal hydrolysis of waste activated sludge at Hengelo wastewater treatment plant. The Netherlands: Water science and

technology. 2014;**70**(1):1-7

[69] Pilli S, Yan S, Tyagi RD,

10.1016/j.jenvman.2015.10.041

[70] Uma Rani R, Adish Kumar S, Kaliappan S, Yeom IT, Rajesh Banu J. Impacts of microwave pretreatments on the semi-continuous anaerobic digestion of dairy waste activated sludge. Waste Management.

2013;**33**(5):1119-1127. DOI: 10.1016/j.

wasman.2013.01.016

Surampalli RY. Anaerobic digestion of ultrasonicated sludge at different solids concentrations—computation of mass-energy balance and greenhouse gas emissions. Journal of Environmental Management. 2016;**166**:374-386. DOI:

10.1016/j.cej.2013.12.064

June 2007

[65] Morgan-Sagastume F, Pratt S, Karlsson A, Cirne D, Lant P, Werker A. Production of Volatile Fatty Acids by Fermentation of Waste Activated Sludge Pre-Treated in Full-Scale

jenvman.2014.09.022

*DOI: http://dx.doi.org/10.5772/intechopen.93236*

[58] Gong C, Jiang J, Li D. Ultrasound coupled with Fenton oxidation pretreatment of sludge to release organic carbon, nitrogen and phosphorus. Science of the Total Environment. 2015;**532**:495-500. DOI: 10.1016/j.

scitotenv.2015.05.131

[59] Houtmeyers S, Degrève J, Willems K, Dewil R, Appels L.

ultrasonic and microwave pretreatments on the solubilisation and semi-continuous anaerobic digestion of waste activated sludge. Bioresource Technology. 2014;**171**:44-49. DOI: 10.1016/j.biortech.2014.08.029

Comparing the influence of low power

[60] Ki D, Parameswaran P, Popat SC, Rittmann BE, Torres CI. Effects of pre-fermentation and pulsed-electricfield treatment of primary sludge in microbial electrochemical cells. Bioresource Technology. 2015;**195**:83-88. DOI: 10.1016/j.biortech.2015.06.128

[61] Lee IS, Rittmann BE. Effect of low solids retention time and focused pulsed pre-treatment on anaerobic digestion of waste activated sludge. Bioresource Technology. 2011;**102**(3):2542-2548. DOI: 10.1016/j.biortech.2010.11.082

[62] Liu C, Lei Z, Yang Y, Zhang Z. Preliminary trial on degradation of waste activated sludge and simultaneous

hydrogen production in a newlydeveloped solar photocatalytic reactor with AgX/TiO2-coated glass tubes. Water Research. 2013;**47**(14):4986-4992

[63] Liu C, Shi W, Li H, Lei Z, He L, Zhang Z. Improvement of methane production from waste activated sludge by on-site photocatalytic pretreatment in a photocatalytic anaerobic fermenter. Bioresource Technology. 2014;**155**:198- 203. DOI: 10.1016/j.biortech.2013.12.041

[64] Martín MÁ, González I, Serrano A, Siles JÁ. Evaluation of the improvement of sonication pre-treatment in the anaerobic digestion of sewage sludge.

*Pre-treatment Technologies to Enhance Anaerobic Digestion DOI: http://dx.doi.org/10.5772/intechopen.93236*

[58] Gong C, Jiang J, Li D. Ultrasound coupled with Fenton oxidation pretreatment of sludge to release organic carbon, nitrogen and phosphorus. Science of the Total Environment. 2015;**532**:495-500. DOI: 10.1016/j. scitotenv.2015.05.131

*Sustainable Sewage Sludge Management and Resource Efficiency*

waste activated sludge and development

of a pretreatment model. Water Research. 2013;**47**(14):5245-5256. DOI:

Lo SL. Effects of microwave and alkali induced pretreatment on sludge solubilization and subsequent aerobic digestion. Bioresource Technology. 2011;**102**(17):7633-7640. DOI: 10.1016/j.

[53] Chang TC, You SJ, Damodar RA, Chen YY. Ultrasound pre-treatment step for performance enhancement in an aerobic sludge digestion process. Journal of the Taiwan Institute of Chemical Engineers. 2011;**42**(5):801-808. DOI:

10.1016/j.watres.2013.06.005

[52] Chang CJ, Tyagi VK,

biortech.2011.05.031

10.1016/j.jtice.2011.01.003

[54] Choi H, Jeong SW, Chung YJ. Enhanced anaerobic gas production of waste activated sludge pretreated by pulse power technique. Bioresource Technology. 2006;**97**(2):198-203. DOI:

10.1016/j.biortech.2005.02.023

[56] Ebenezer AV, Arulazhagan P, Adish Kumar S, Yeom IT, Rajesh Banu J. Effect of deflocculation on the efficiency of low-energy microwave pretreatment and anaerobic biodegradation of waste activated sludge. Applied Energy. 2015;**145**:104-110. DOI: 10.1016/j.

[57] Erden G. Combination of alkaline and microwave pretreatment for disintegration of meat processing wastewater sludge. Environmental Technology (United Kingdom). 2013;**34**(6):711-718. DOI: 10.1080/09593330.2012.715678

watres.2011.02.032

apenergy.2015.01.133

[55] Coelho NMG, Droste RL, Kennedy KJ. Evaluation of continuous mesophilic, thermophilic and temperature phased anaerobic digestion of microwaved activated sludge. Water Research. 2011;45(9):2822-2834. DOI: 10.1016/j.

digestion. Biochemical Engineering Journal. 2013;**75**:21-31. DOI: 10.1016/j.

[45] Ruffino B et al. Improvement of anaerobic digestion of sewage sludge in a wastewater treatment plant by means of mechanical and thermal pre-treatments: Performance, energy and economical assessment. Bioresource Technology. 2015;**175**:298-308. DOI: 10.1016/j.biortech.2014.10.071

[46] Hiraoka M, Takeda N, Sakai S, Yasuda A. Highly efficient anaerobic digestion with thermal pretreatment. Water Science and Technology. 1985;**17**(4-5):529-539. DOI: 10.2166/

[47] Prorot A, Julien L, Christophe D, Patrick L. Sludge disintegration during heat treatment at low temperature: A better understanding of involved mechanisms with a multiparametric approach. Biochemical Engineering Journal. 2011;**54**(3):178-184. DOI:

10.1016/j.bej.2011.02.016

2005;**52**(1-2):161-166

[48] Skiadas IV, Gavala HN, Lu J, Ahring BK. Thermal pre-treatment of primary and secondary sludge at 70 C prior to anaerobic digestion. Water Science and Technology.

[49] Appels L, Houtmeyers S, Degrève J, Van Impe J, Dewil R. Influence of microwave pre-treatment on sludge solubilization and pilot scale semicontinuous anaerobic digestion. Bioresource Technology. 2013;**128**:598- 603. DOI: 10.1016/j.biortech.2012.11.007

Mininni G. Laboratory-scale ultrasound pre-treated digestion of sludge: heat and energy balance. Bioresource Technology. 2011;**102**(16):7567-7573. DOI: 10.1016/j.

[51] Burger G, Parker W. Investigation of the impacts of thermal pretreatment on

[50] Braguglia CM, Gianico A,

biortech.2011.05.025

bej.2013.03.002

wst.1985.0157

**44**

[59] Houtmeyers S, Degrève J, Willems K, Dewil R, Appels L. Comparing the influence of low power ultrasonic and microwave pretreatments on the solubilisation and semi-continuous anaerobic digestion of waste activated sludge. Bioresource Technology. 2014;**171**:44-49. DOI: 10.1016/j.biortech.2014.08.029

[60] Ki D, Parameswaran P, Popat SC, Rittmann BE, Torres CI. Effects of pre-fermentation and pulsed-electricfield treatment of primary sludge in microbial electrochemical cells. Bioresource Technology. 2015;**195**:83-88. DOI: 10.1016/j.biortech.2015.06.128

[61] Lee IS, Rittmann BE. Effect of low solids retention time and focused pulsed pre-treatment on anaerobic digestion of waste activated sludge. Bioresource Technology. 2011;**102**(3):2542-2548. DOI: 10.1016/j.biortech.2010.11.082

[62] Liu C, Lei Z, Yang Y, Zhang Z. Preliminary trial on degradation of waste activated sludge and simultaneous hydrogen production in a newlydeveloped solar photocatalytic reactor with AgX/TiO2-coated glass tubes. Water Research. 2013;**47**(14):4986-4992

[63] Liu C, Shi W, Li H, Lei Z, He L, Zhang Z. Improvement of methane production from waste activated sludge by on-site photocatalytic pretreatment in a photocatalytic anaerobic fermenter. Bioresource Technology. 2014;**155**:198- 203. DOI: 10.1016/j.biortech.2013.12.041

[64] Martín MÁ, González I, Serrano A, Siles JÁ. Evaluation of the improvement of sonication pre-treatment in the anaerobic digestion of sewage sludge.

Journal of Environmental Management. 2015;**147**:330-337. DOI: 10.1016/j. jenvman.2014.09.022

[65] Morgan-Sagastume F, Pratt S, Karlsson A, Cirne D, Lant P, Werker A. Production of Volatile Fatty Acids by Fermentation of Waste Activated Sludge Pre-Treated in Full-Scale Thermal Hydrolysis Plants. Bioresource Technology. 2011;**102**(3):3089-3097. DOI: 10.1016/j.biortech.2010.10.054

[66] Ning XA, Chen H, Wu J, Wang Y, Liu J, Lin M. Effects of ultrasound assisted fenton treatment on textile dyeing sludge structure and dewaterability. Chemical Engineering Journal. 2014;242:102-108. DOI: 10.1016/j.cej.2013.12.064

[67] Onyeche T. Economic benefits of low pressure sludge homogenization for wastewater treatment plants. In: IWA Specialist Conferences. Moving Forward Wastewater Biosolids Sustainability; Moncton, New Brunswick, Canada; June 2007

[68] Oosterhuis M, Ringoot D, Hendriks A, Roeleveld P. Thermal hydrolysis of waste activated sludge at Hengelo wastewater treatment plant. The Netherlands: Water science and technology. 2014;**70**(1):1-7

[69] Pilli S, Yan S, Tyagi RD, Surampalli RY. Anaerobic digestion of ultrasonicated sludge at different solids concentrations—computation of mass-energy balance and greenhouse gas emissions. Journal of Environmental Management. 2016;**166**:374-386. DOI: 10.1016/j.jenvman.2015.10.041

[70] Uma Rani R, Adish Kumar S, Kaliappan S, Yeom IT, Rajesh Banu J. Impacts of microwave pretreatments on the semi-continuous anaerobic digestion of dairy waste activated sludge. Waste Management. 2013;**33**(5):1119-1127. DOI: 10.1016/j. wasman.2013.01.016

[71] Wang Q, Kuninobu M, Kakimoto K, Ogawa HI, Kato Y. Upgrading of anaerobic digestion of waste activated sludge by ultrasonic pretreatment. Bioresource Technology. 1999;**68**(3):309-313. DOI: 10.1016/S0960-8524(98)00155-2

[72] Rittmann BE, Lee HS, Zhang H, Alder J, Banaszak JE, Lopez R. Fullscale application of focused-pulsed pre-treatment for improving biosolids digestion and conversion to methane. Water Science and Technology. 2008;**58**(10):1895-1901. DOI: 10.2166/ wst.2008.547

[73] Sahinkaya S. Disintegration of municipal waste activated sludge by simultaneous combination of acid and ultrasonic pretreatment. Process Safety and Environment Protection. 2015;**93**:201-205. DOI: 10.1016/j. psep.2014.04.002

[74] Salerno MB, Lee H-S, Parameswaran P, Rittmann BE. Using a pulsed electric field as a pretreatment for improved biosolids digestion and methanogenesis. Water Environment Research. 2009;**81**(8):831-839. DOI: 10.2175/106143009x407366

[75] Serrano A, Siles JA, Gutiérrez MC, Martín MÁ. Improvement of the biomethanization of sewage sludge by thermal pre-treatment and co-digestion with strawberry extrudate. Journal of Cleaner Production. 2015;**90**:25-33. DOI: 10.1016/j.jclepro.2014.11.039

[76] Tyagi VK, Lo SL. Enhancement in mesophilic aerobic digestion of waste activated sludge by chemically assisted thermal pretreatment method. Bioresource Technology. 2012;**119**:105- 113. DOI: 10.1016/j.biortech.2012.05.134

[77] Wahidunnabi AK, Eskicioglu C. High pressure homogenization and two-phased anaerobic digestion for enhanced biogas conversion from municipal waste sludge. Water Research. 2014;**66**:430-446. DOI: 10.1016/j. watres.2014.08.045

[78] Wang Q, Jiang G, Ye L, Yuan Z. Enhancing methane production from waste activated sludge using combined free nitrous acid and heat pretreatment. Water Research. 2014;**63**:71- 80. DOI: 10.1016/j.watres.2014.06.010

[79] Xue Y, Liu H, Chen S, Dichtl N, Dai X, Li N. Effects of thermal hydrolysis on organic matter solubilization and anaerobic digestion of high solid sludge. Chemical Engineering Journal. 2015;**264**:174-180. DOI: 10.1016/j.cej.2014.11.005

[80] Mesfin Yeneneh A, Kanti Sen T, Chong S, Ming Ang H, Kayaalp A. Effect of combined microwave-ultrasonic pretreatment on anaerobic biodegradability of primary, excess activated and mixed sludge. Computational Water, Energy, and Environmental Engineering. 2013;**2**:7- 11. DOI: 10.4236/cweee.2013.23b002

[81] Jin Y, Li H, Mahar RB, Wang Z, Nie Y. Combined alkaline and ultrasonic pretreatment of sludge before aerobic digestion. Journal of Environmental Sciences. 2009;**21**(3):279-284. DOI: 10.1016/S1001-0742(08)62264-0

[82] Zhang S, Zhang P, Zhang G, Fan J, Zhang Y. Enhancement of anaerobic sludge digestion by high-pressure homogenization. Bioresource Technology. 2012;**118**:496-501. DOI: 10.1016/j.biortech.2012.05.089

[83] Beszédes S, Kertész S, László Z, Szabo G, Hodur C. Biogas production of ozone and/or microwave-pretreated canned maize production sludge. Ozone Science and Engineering. 2009;**31**(3):257-261

[84] Cheng CJ, Hong PKA. Anaerobic digestion of activated sludge after pressure-assisted ozonation. Bioresource Technology. 2013;**142**:69-76. DOI: 10.1016/j.biortech.2013.04.058

[85] Devlin DC, Esteves SRR, Dinsdale RM, Guwy AJ. The effect of

**47**

*Pre-treatment Technologies to Enhance Anaerobic Digestion*

sludge dewaterability by alkaline pretreatment and its mechanism. Journal of Environmental Sciences (China). 2012;**24**(10):1731-1738. DOI: 10.1016/S1001-0742(11)61031-0

[93] Takashima M, Tanaka Y. Acidic thermal post-treatment for enhancing anaerobic digestion of sewage sludge. Journal of Environmental Chemical Engineering. 2014;**2**(2):773-779. DOI:

[94] Valo A, Carrère H, Delgenès JP. Thermal, chemical and thermochemical pre-treatment of waste

activated sludge for anaerobic digestion. Journal of Chemical Technology and Biotechnology. 2004;**79**(11):1197-1203.

[96] Wonglertarak W, Wichitsathian B.

activated sludge in anaerobic digestion. Journal of Clean Energy Technologies.

10.1016/j.jece.2014.02.018

DOI: 10.1002/jctb.1106

[95] Weemaes M, Grootaerd H, Simoens F, Verstraete W. Anaerobic digestion of ozonized biosolids. Water Research. 2000;**34**(8):2330-2336. DOI: 10.1016/S0043-1354(99)00373-5

Alkaline pretreatment of waste

[97] Kavitha S, Adish Kumar S, Yogalakshmi KN, Kaliappan S, Rajesh Banu J. Effect of enzyme secreting bacterial pretreatment on enhancement of aerobic digestion potential of waste activated sludge interceded through EDTA. Bioresource Technology. 2013;**150**:210-219. DOI: 10.1016/j.

[98] Liu C, Zhang P, Zeng C, Zeng G, Xu G, Huang Y. Feasibility of bioleaching combined with Fenton oxidation to improve sewage sludge dewaterability. Journal of Environmental Sciences (China). 2015;**28**:37-42. DOI: 10.1016/j.

[99] Fang W et al. Effect of alkaline addition on anaerobic sludge digestion

2014;**2**(2):118-121

biortech.2013.10.021

jes.2014.05.039

*DOI: http://dx.doi.org/10.5772/intechopen.93236*

acid pretreatment on the anaerobic digestion and dewatering of waste activated sludge. Bioresource Technology. 2011;**102**(5):4076-4082. DOI: 10.1016/j.biortech.2010.12.043

[86] Kumar MSK, Kumar TK, Arulazhagan P, Kumar SA, Yeom IT, Banu JR. Effect of alkaline and ozone pretreatment on sludge reduction potential of a membrane bioreactor treating high-strength domestic wastewater. Desalination and Water Treatment. 2015;**55**(5):1127-1134. DOI:

10.1080/19443994.2014.923335

[87] Li H, Li C, Liu W, Zou S. Optimized alkaline pretreatment of sludge before anaerobic digestion. Bioresource Technology. 2012;**123**:189-194. DOI: 10.1016/j.biortech.2012.08.017

[88] Lin Y, Wang D, Wu S, Wang C. Alkali pretreatment enhances biogas production in the anaerobic digestion of pulp and paper sludge. Journal of Hazardous Materials. 2009;**170**(1):366- 373. DOI: 10.1016/j.jhazmat.2009.04.086

[89] Pilli S, More TT, Yan S, Tyagi RD, Surampalli RY. Fenton pre-treatment of secondary sludge to enhance

anaerobic digestion: Energy balance and greenhouse gas emissions. Chemical Engineering Journal. 2016;**283**:285-292.

[90] Ruiz-Hernando M et al. Effect of ultrasound, low-temperature thermal and alkali pre-treatments on waste activated sludge rheology, hygienization and methane potential. Water Research.

DOI: 10.1016/j.cej.2015.07.056

2014;**61**:119-129. DOI: 10.1016/j.

[91] Şahinkaya S, Kalipci E, Aras S. Disintegration of waste activated sludge

[92] Shao L, Wang X, Xu H, He P. Enhanced anaerobic digestion and

by different applications of fenton process. Process Safety and Environment Protection. 2015;**93**:274- 281. DOI: 10.1016/j.psep.2014.05.010

watres.2014.05.012

*Pre-treatment Technologies to Enhance Anaerobic Digestion DOI: http://dx.doi.org/10.5772/intechopen.93236*

acid pretreatment on the anaerobic digestion and dewatering of waste activated sludge. Bioresource Technology. 2011;**102**(5):4076-4082. DOI: 10.1016/j.biortech.2010.12.043

*Sustainable Sewage Sludge Management and Resource Efficiency*

[78] Wang Q, Jiang G, Ye L, Yuan Z. Enhancing methane production from waste activated sludge using combined

treatment. Water Research. 2014;**63**:71- 80. DOI: 10.1016/j.watres.2014.06.010

[79] Xue Y, Liu H, Chen S, Dichtl N, Dai X, Li N. Effects of thermal hydrolysis on organic matter

solubilization and anaerobic digestion

Engineering Journal. 2015;**264**:174-180.

[80] Mesfin Yeneneh A, Kanti Sen T, Chong S, Ming Ang H, Kayaalp A. Effect of combined microwave-ultrasonic

[81] Jin Y, Li H, Mahar RB, Wang Z, Nie Y. Combined alkaline and ultrasonic pretreatment of sludge before aerobic digestion. Journal of Environmental Sciences. 2009;**21**(3):279-284. DOI: 10.1016/S1001-0742(08)62264-0

[82] Zhang S, Zhang P, Zhang G, Fan J, Zhang Y. Enhancement of anaerobic sludge digestion by high-pressure homogenization. Bioresource Technology. 2012;**118**:496-501. DOI: 10.1016/j.biortech.2012.05.089

[83] Beszédes S, Kertész S, László Z, Szabo G, Hodur C. Biogas production of ozone and/or microwave-pretreated canned maize production sludge. Ozone Science and Engineering.

[84] Cheng CJ, Hong PKA. Anaerobic

Dinsdale RM, Guwy AJ. The effect of

digestion of activated sludge after pressure-assisted ozonation. Bioresource Technology. 2013;**142**:69-76. DOI: 10.1016/j.biortech.2013.04.058

[85] Devlin DC, Esteves SRR,

2009;**31**(3):257-261

of high solid sludge. Chemical

DOI: 10.1016/j.cej.2014.11.005

pretreatment on anaerobic biodegradability of primary, excess activated and mixed sludge. Computational Water, Energy, and Environmental Engineering. 2013;**2**:7- 11. DOI: 10.4236/cweee.2013.23b002

free nitrous acid and heat pre-

[71] Wang Q, Kuninobu M, Kakimoto K, Ogawa HI, Kato Y. Upgrading of anaerobic digestion of waste activated sludge by ultrasonic pretreatment. Bioresource Technology. 1999;**68**(3):309-313. DOI: 10.1016/S0960-8524(98)00155-2

[72] Rittmann BE, Lee HS, Zhang H, Alder J, Banaszak JE, Lopez R. Fullscale application of focused-pulsed pre-treatment for improving biosolids digestion and conversion to methane. Water Science and Technology. 2008;**58**(10):1895-1901. DOI: 10.2166/

[73] Sahinkaya S. Disintegration of municipal waste activated sludge by simultaneous combination of acid and ultrasonic pretreatment. Process Safety and Environment Protection. 2015;**93**:201-205. DOI: 10.1016/j.

Parameswaran P, Rittmann BE. Using a pulsed electric field as a pretreatment for improved biosolids digestion and methanogenesis. Water Environment Research. 2009;**81**(8):831-839. DOI:

[75] Serrano A, Siles JA, Gutiérrez MC, Martín MÁ. Improvement of the biomethanization of sewage sludge by thermal pre-treatment and co-digestion with strawberry extrudate. Journal of Cleaner Production. 2015;**90**:25-33. DOI: 10.1016/j.jclepro.2014.11.039

[76] Tyagi VK, Lo SL. Enhancement in mesophilic aerobic digestion of waste activated sludge by chemically assisted thermal pretreatment method. Bioresource Technology. 2012;**119**:105- 113. DOI: 10.1016/j.biortech.2012.05.134

[77] Wahidunnabi AK, Eskicioglu C. High pressure homogenization and two-phased anaerobic digestion for enhanced biogas conversion from municipal waste sludge. Water Research.

2014;**66**:430-446. DOI: 10.1016/j.

watres.2014.08.045

wst.2008.547

psep.2014.04.002

[74] Salerno MB, Lee H-S,

10.2175/106143009x407366

**46**

[86] Kumar MSK, Kumar TK, Arulazhagan P, Kumar SA, Yeom IT, Banu JR. Effect of alkaline and ozone pretreatment on sludge reduction potential of a membrane bioreactor treating high-strength domestic wastewater. Desalination and Water Treatment. 2015;**55**(5):1127-1134. DOI: 10.1080/19443994.2014.923335

[87] Li H, Li C, Liu W, Zou S. Optimized alkaline pretreatment of sludge before anaerobic digestion. Bioresource Technology. 2012;**123**:189-194. DOI: 10.1016/j.biortech.2012.08.017

[88] Lin Y, Wang D, Wu S, Wang C. Alkali pretreatment enhances biogas production in the anaerobic digestion of pulp and paper sludge. Journal of Hazardous Materials. 2009;**170**(1):366- 373. DOI: 10.1016/j.jhazmat.2009.04.086

[89] Pilli S, More TT, Yan S, Tyagi RD, Surampalli RY. Fenton pre-treatment of secondary sludge to enhance anaerobic digestion: Energy balance and greenhouse gas emissions. Chemical Engineering Journal. 2016;**283**:285-292. DOI: 10.1016/j.cej.2015.07.056

[90] Ruiz-Hernando M et al. Effect of ultrasound, low-temperature thermal and alkali pre-treatments on waste activated sludge rheology, hygienization and methane potential. Water Research. 2014;**61**:119-129. DOI: 10.1016/j. watres.2014.05.012

[91] Şahinkaya S, Kalipci E, Aras S. Disintegration of waste activated sludge by different applications of fenton process. Process Safety and Environment Protection. 2015;**93**:274- 281. DOI: 10.1016/j.psep.2014.05.010

[92] Shao L, Wang X, Xu H, He P. Enhanced anaerobic digestion and sludge dewaterability by alkaline pretreatment and its mechanism. Journal of Environmental Sciences (China). 2012;**24**(10):1731-1738. DOI: 10.1016/S1001-0742(11)61031-0

[93] Takashima M, Tanaka Y. Acidic thermal post-treatment for enhancing anaerobic digestion of sewage sludge. Journal of Environmental Chemical Engineering. 2014;**2**(2):773-779. DOI: 10.1016/j.jece.2014.02.018

[94] Valo A, Carrère H, Delgenès JP. Thermal, chemical and thermochemical pre-treatment of waste activated sludge for anaerobic digestion. Journal of Chemical Technology and Biotechnology. 2004;**79**(11):1197-1203. DOI: 10.1002/jctb.1106

[95] Weemaes M, Grootaerd H, Simoens F, Verstraete W. Anaerobic digestion of ozonized biosolids. Water Research. 2000;**34**(8):2330-2336. DOI: 10.1016/S0043-1354(99)00373-5

[96] Wonglertarak W, Wichitsathian B. Alkaline pretreatment of waste activated sludge in anaerobic digestion. Journal of Clean Energy Technologies. 2014;**2**(2):118-121

[97] Kavitha S, Adish Kumar S, Yogalakshmi KN, Kaliappan S, Rajesh Banu J. Effect of enzyme secreting bacterial pretreatment on enhancement of aerobic digestion potential of waste activated sludge interceded through EDTA. Bioresource Technology. 2013;**150**:210-219. DOI: 10.1016/j. biortech.2013.10.021

[98] Liu C, Zhang P, Zeng C, Zeng G, Xu G, Huang Y. Feasibility of bioleaching combined with Fenton oxidation to improve sewage sludge dewaterability. Journal of Environmental Sciences (China). 2015;**28**:37-42. DOI: 10.1016/j. jes.2014.05.039

[99] Fang W et al. Effect of alkaline addition on anaerobic sludge digestion with combined pretreatment of alkaline and high pressure homogenization. Bioresource Technology. 2014;**168**:167- 172. DOI: 10.1016/j.biortech.2014.03.050

[100] Li H, Jin Y, Mahar RB, Wang Z, Nie Y. Effects and Model of Alkaline Waste Activated Sludge Treatment. Bioresource Technology. 2008;**99**(11):5140-5144. DOI: 10.1016/j. biortech.2007.09.019

[101] Xu G, Chen S, Shi J, Wang S, Zhu G. Combination treatment of ultrasound and ozone for improving solubilization and anaerobic biodegradability of waste activated sludge. Journal of Hazardous Materials. 2010;**180**(1-3):340-346

[102] Chacana J et al. Effect of ozonation on anaerobic digestion sludge activity and viability. Chemosphere. 2017;**176**:405-411. DOI: 10.1016/j. chemosphere.2017.02.108

[103] Wang L. Different Pretreatments to Enhance Biogas Production: A comparison of thermal, chemical and ultrasonic methods. Sweden: Halmstad University. Master thesis P-51; 2011

[104] Wang LL et al. PH dependence of structure and surface properties of microbial EPS. Environmental Science & Technology. 2012;**46**(2):737-744. DOI: 10.1021/es203540w

[105] Mussoline W, Esposito G, Giordano A, Lens P. The anaerobic digestion of rice straw: A review. Critical Reviews in Environmental Science and Technology. 2013;**43**(9):895-915. DOI: 10.1080/10643389.2011.627018

[106] Modenbach AA, Nokes SE. The use of high-solids loadings in biomass pretreatment—A review. Biotechnology and Bioengineering. 2012;**109**(6):1430- 1442. DOI: 10.1002/bit.24464

[107] Mouneimne AH, Carrère H, Bernet N, Delgenès JP. Effect of

saponification on the anaerobic digestion of solid fatty residues. Bioresource Technology. 2003;**90**(1):89- 94. DOI: 10.1016/ S0960-8524(03)00091-9

[108] Kim J et al. Effects of various pretreatments for enhanced anaerobic digestion with waste activated sludge. Journal of Bioscience and Bioengineering. 2003;**95**(3):271-275. DOI: 10.1263/jbb.95.271

[109] Yuan H, Chen Y, Zhang H, Jiang S, Zhou Q, Gu G. Improved bioproduction of short-chain fatty acids (SCFAs) from excess sludge under alkaline conditions. Environmental Science & Technology. 2006;**40**(6):2025-2029. DOI: 10.1021/ es052252b

[110] Cacho Rivero JA, Madhavan N, Suidan MT, Ginestet P, Audic J-M. Enhancement of anaerobic digestion of excess municipal sludge with thermal and/or oxidative treatment. Journal of Environmental Engineering. 2006;**132**(6):638-644

[111] Kohanski MA, Dwyer DJ, Hayete B, Lawrence CA, Collins JJ. A common mechanism of cellular death induced by bactericidal antibiotics. Cell. 2007;**130**(5):797-810. DOI: 10.1016/j. cell.2007.06.049

[112] Zhen G, Lu X, Kato H, Zhao Y, Li YY. Overview of pretreatment strategies for enhancing sewage sludge disintegration and subsequent anaerobic digestion: Current advances, full-scale application and future perspectives. Renewable and Sustainable Energy Reviews. 2017;**69**:559-577. DOI: 10.1016/j. rser.2016.11.187

[113] Zhang W, Yang P, Yang X, Chen Z, Wang D. Insights into the respective role of acidification and oxidation for enhancing anaerobic digested sludge dewatering performance with Fenton process. Bioresource Technology.

**49**

*Pre-treatment Technologies to Enhance Anaerobic Digestion*

cryptic growth of microorganisms by alkaline treatment of activated sludge. Korean Journal of Chemical Engineering. 2011;**28**(1):164-169. DOI:

10.1007/s11814-010-0334-0

[121] Rafique R, Poulsen TG,

energy.2010.07.011

Nizami AS, Asam Z-u-Z, Murphy JD, Kiely G. Effect of thermal, chemical and thermo-chemical pre-treatments to enhance methane production. Energy. 2010;**35**(12):4556-4561. DOI: 10.1016/j.

[122] Doǧan I, Sanin FD. Alkaline solubilization and microwave irradiation as a combined sludge disintegration and minimization

2009;**43**(8):2139-2148. DOI: 10.1016/j.

[123] Weiland P. Biogas production: Current state and perspectives. Applied Microbiology and Biotechnology. 2010;**85**(4):849-860. DOI: 10.1007/

[124] Pérez-Elvira S, Fdz-Polanco M, Plaza FI, Garralón G, Fdz-Polanco F. Ultrasound pre-treatment for anaerobic digestion improvement. Water Science and Technology. 2009;**60**(6):1525-1532

[125] Bordeleau ÉL, Droste RL.

[126] Mottet A, Steyer JP, Déléris S, Vedrenne F, Chauzy J, Carrère H. Kinetics of thermophilic batch anaerobic digestion of thermal hydrolysed waste activated sludge. Biochemical Engineering Journal. 2009;**46**(2):169-175. DOI: 10.1016/j.

[127] Yang X, Wang X, Wang L.

Transferring of components and energy

Comprehensive review and compilation of pretreatments for mesophilic and thermophilic anaerobic digestion. Water Science and Technology. 2011;**63**(2):291-296. DOI: 10.2166/

method. Water Research.

watres.2009.02.023

s00253-009-2246-7

wst.2011.052

bej.2009.05.003

*DOI: http://dx.doi.org/10.5772/intechopen.93236*

2015;**181**:247-253. DOI: 10.1016/j.

[114] Anjum M, Al-Makishah NH, Barakat MA. Wastewater sludge stabilization using pre-treatment methods. Process Safety and

[115] ErdenKaynak G, Filibelt A. Assessment of Fenton process as a minimization technique for biological

sludge: Effects on anaerobic sludge bioprocessing. Journal of Residuals Science and Technology.

2008;**5**(3):151-160

Environment Protection. 2016;**102**:615- 632. DOI: 10.1016/j.psep.2016.05.022

[116] Kameswari KSB, Kalyanaraman C, Thanasekaran K. Effect of ozonation and ultrasonication pretreatment processes on co-digestion of tannery solid wastes. Clean Technologies and Environmental Policy. 2011;**13**(3):517- 525. DOI: 10.1007/s10098-010-0334-0

[117] Carballa M, Manterola G, Larrea L, Ternes T, Omil F, Lema JM. Influence of ozone pre-treatment on sludge anaerobic digestion: Removal of pharmaceutical and personal care products. Chemosphere.

2007;**67**(7):1444-1452. DOI: 10.1016/j.

chemosphere.2006.10.004

[118] Ariunbaatar J, Panico A, Frunzo L, Esposito G, Lens PNL, Pirozzi F. Enhanced anaerobic digestion of food waste by thermal and ozonation

pretreatment methods. Journal of Environmental Management. 2014;**146**:142-149. DOI: 10.1016/j.

in hyperthermophilic archaea:

272. DOI: 10.1089/rej.2012.1401

[120] Na SH, Shon HK, Kim JH. Minimization of excess sludge and

[119] Szwergold BS. Maillard reactions

Implications for better understanding of non-enzymatic glycation in biology. Rejuvenation Research. 2013;**16**(4):259-

jenvman.2014.07.042

biortech.2015.01.003

*Pre-treatment Technologies to Enhance Anaerobic Digestion DOI: http://dx.doi.org/10.5772/intechopen.93236*

2015;**181**:247-253. DOI: 10.1016/j. biortech.2015.01.003

*Sustainable Sewage Sludge Management and Resource Efficiency*

saponification on the anaerobic digestion of solid fatty residues.

[108] Kim J et al. Effects of various pretreatments for enhanced anaerobic

digestion with waste activated sludge. Journal of Bioscience and Bioengineering. 2003;**95**(3):271-275.

94. DOI: 10.1016/

S0960-8524(03)00091-9

DOI: 10.1263/jbb.95.271

es052252b

2006;**132**(6):638-644

cell.2007.06.049

rser.2016.11.187

[112] Zhen G, Lu X, Kato H, Zhao Y, Li YY. Overview of

Bioresource Technology. 2003;**90**(1):89-

[109] Yuan H, Chen Y, Zhang H, Jiang S, Zhou Q, Gu G. Improved bioproduction of short-chain fatty acids (SCFAs) from excess sludge under alkaline conditions. Environmental Science & Technology. 2006;**40**(6):2025-2029. DOI: 10.1021/

[110] Cacho Rivero JA, Madhavan N, Suidan MT, Ginestet P, Audic J-M. Enhancement of anaerobic digestion of excess municipal sludge with thermal and/or oxidative treatment. Journal of Environmental Engineering.

[111] Kohanski MA, Dwyer DJ, Hayete B, Lawrence CA, Collins JJ. A common mechanism of cellular death induced by bactericidal antibiotics. Cell. 2007;**130**(5):797-810. DOI: 10.1016/j.

pretreatment strategies for enhancing sewage sludge disintegration and subsequent anaerobic digestion:

Current advances, full-scale application and future perspectives. Renewable and Sustainable Energy Reviews. 2017;**69**:559-577. DOI: 10.1016/j.

[113] Zhang W, Yang P, Yang X, Chen Z, Wang D. Insights into the respective role of acidification and oxidation for enhancing anaerobic digested sludge dewatering performance with Fenton process. Bioresource Technology.

with combined pretreatment of alkaline and high pressure homogenization. Bioresource Technology. 2014;**168**:167- 172. DOI: 10.1016/j.biortech.2014.03.050

[100] Li H, Jin Y, Mahar RB, Wang Z, Nie Y. Effects and Model of Alkaline Waste Activated Sludge Treatment. Bioresource Technology. 2008;**99**(11):5140-5144. DOI: 10.1016/j.

[101] Xu G, Chen S, Shi J, Wang S, Zhu G. Combination treatment of ultrasound and ozone for improving

[102] Chacana J et al. Effect of ozonation

[103] Wang L. Different Pretreatments to Enhance Biogas Production: A comparison of thermal, chemical and ultrasonic methods. Sweden: Halmstad University. Master thesis P-51; 2011

[104] Wang LL et al. PH dependence of structure and surface properties of microbial EPS. Environmental Science & Technology. 2012;**46**(2):737-744.

solubilization and anaerobic biodegradability of waste activated sludge. Journal of Hazardous Materials.

on anaerobic digestion sludge activity and viability. Chemosphere. 2017;**176**:405-411. DOI: 10.1016/j.

chemosphere.2017.02.108

DOI: 10.1021/es203540w

[105] Mussoline W, Esposito G, Giordano A, Lens P. The anaerobic digestion of rice straw: A review. Critical Reviews in Environmental Science and Technology. 2013;**43**(9):895-915. DOI:

10.1080/10643389.2011.627018

1442. DOI: 10.1002/bit.24464

[107] Mouneimne AH, Carrère H, Bernet N, Delgenès JP. Effect of

[106] Modenbach AA, Nokes SE. The use of high-solids loadings in biomass pretreatment—A review. Biotechnology and Bioengineering. 2012;**109**(6):1430-

2010;**180**(1-3):340-346

biortech.2007.09.019

**48**

[114] Anjum M, Al-Makishah NH, Barakat MA. Wastewater sludge stabilization using pre-treatment methods. Process Safety and Environment Protection. 2016;**102**:615- 632. DOI: 10.1016/j.psep.2016.05.022

[115] ErdenKaynak G, Filibelt A. Assessment of Fenton process as a minimization technique for biological sludge: Effects on anaerobic sludge bioprocessing. Journal of Residuals Science and Technology. 2008;**5**(3):151-160

[116] Kameswari KSB, Kalyanaraman C, Thanasekaran K. Effect of ozonation and ultrasonication pretreatment processes on co-digestion of tannery solid wastes. Clean Technologies and Environmental Policy. 2011;**13**(3):517- 525. DOI: 10.1007/s10098-010-0334-0

[117] Carballa M, Manterola G, Larrea L, Ternes T, Omil F, Lema JM. Influence of ozone pre-treatment on sludge anaerobic digestion: Removal of pharmaceutical and personal care products. Chemosphere. 2007;**67**(7):1444-1452. DOI: 10.1016/j. chemosphere.2006.10.004

[118] Ariunbaatar J, Panico A, Frunzo L, Esposito G, Lens PNL, Pirozzi F. Enhanced anaerobic digestion of food waste by thermal and ozonation pretreatment methods. Journal of Environmental Management. 2014;**146**:142-149. DOI: 10.1016/j. jenvman.2014.07.042

[119] Szwergold BS. Maillard reactions in hyperthermophilic archaea: Implications for better understanding of non-enzymatic glycation in biology. Rejuvenation Research. 2013;**16**(4):259- 272. DOI: 10.1089/rej.2012.1401

[120] Na SH, Shon HK, Kim JH. Minimization of excess sludge and cryptic growth of microorganisms by alkaline treatment of activated sludge. Korean Journal of Chemical Engineering. 2011;**28**(1):164-169. DOI: 10.1007/s11814-010-0334-0

[121] Rafique R, Poulsen TG, Nizami AS, Asam Z-u-Z, Murphy JD, Kiely G. Effect of thermal, chemical and thermo-chemical pre-treatments to enhance methane production. Energy. 2010;**35**(12):4556-4561. DOI: 10.1016/j. energy.2010.07.011

[122] Doǧan I, Sanin FD. Alkaline solubilization and microwave irradiation as a combined sludge disintegration and minimization method. Water Research. 2009;**43**(8):2139-2148. DOI: 10.1016/j. watres.2009.02.023

[123] Weiland P. Biogas production: Current state and perspectives. Applied Microbiology and Biotechnology. 2010;**85**(4):849-860. DOI: 10.1007/ s00253-009-2246-7

[124] Pérez-Elvira S, Fdz-Polanco M, Plaza FI, Garralón G, Fdz-Polanco F. Ultrasound pre-treatment for anaerobic digestion improvement. Water Science and Technology. 2009;**60**(6):1525-1532

[125] Bordeleau ÉL, Droste RL. Comprehensive review and compilation of pretreatments for mesophilic and thermophilic anaerobic digestion. Water Science and Technology. 2011;**63**(2):291-296. DOI: 10.2166/ wst.2011.052

[126] Mottet A, Steyer JP, Déléris S, Vedrenne F, Chauzy J, Carrère H. Kinetics of thermophilic batch anaerobic digestion of thermal hydrolysed waste activated sludge. Biochemical Engineering Journal. 2009;**46**(2):169-175. DOI: 10.1016/j. bej.2009.05.003

[127] Yang X, Wang X, Wang L. Transferring of components and energy output in industrial sewage sludge disposal by thermal pretreatment and two-phase anaerobic process. Bioresource Technology. 2010;**101**(8):2580-2584. DOI: 10.1016/j. biortech.2009.10.055

[128] Escamilla-Alvarado C, Ríos-Leal E, Ponce-Noyola MT, Poggi-Varaldo HM. Gas biofuels from solid substrate hydrogenogenic-methanogenic fermentation of the organic fraction of municipal solid waste. Process Biochemistry. 2012;**47**(11):1572-1587. DOI: 10.1016/j.procbio.2011.12.006

[129] Lu J, Gavala HN, Skiadas IV, Mladenovska Z, Ahring BK. Improving anaerobic sewage sludge digestion by implementation of a hyperthermophilic prehydrolysis step. Journal of Environmental Management. 2008;**88**(4):881-889. DOI: 10.1016/j. jenvman.2007.04.020

[130] Ma J, Duong TH, Smits M, Verstraete W, Carballa M. Enhanced biomethanation of kitchen waste by different pre-treatments. Bioresource Technology. 2011;**102**(2):592-599

[131] Müller JA. Prospects and problems of sludge pre-treatment processes. Water Science and Technology. 2001;**44**(10):121-128

[132] Park C, Lee C, Kim S, Chen Y, Chase HA. Upgrading of anaerobic digestion by incorporating two different hydrolysis processes. Journal of Bioscience and Bioengineering. 2005;**100**(2):164-167. DOI: 10.1263/ jbb.100.164

[133] Cesaro A, Belgiorno V. Pretreatment methods to improve anaerobic biodegradability of organic municipal solid waste fractions. Chemical Engineering Journal. 2014;**240**:24-37. DOI: 10.1016/j. cej.2013.11.055

**51**

**Chapter 3**

**Abstract**

*Rodrigo de Freitas Bueno*

sludge are usually very large.

dimensioning

**1. Introduction**

Composition, Production,

and Treatment of Sewage Sludge

Sewage treatment ultimately culminates in the concentration of the solid phase. Sludge are separated mainly in primary or secondary decanters. Even in biological treatment, where biological degradation of organic matter actually occurs, there is the separation of excess sludge concentrated in the bottom of the secondary settlers of activated sludge systems or biological filters. In fact, the production of sludge is an important differential in the choice of the treatment system. While purely aerobic systems such as activated sludge or high-rate biological filters can produce 0.6–0.8 kgSS/kgBOD applied, sludge production in an upflow anaerobic sludge blanket (UASB) reactor is only about 0.2 kgSS/kgCOD applied. Even the mixed anaerobic/aerobic system leads to less sludge production than that of an exclusively aerobic system. This advantage is very important nowadays, especially since, besides reducing the treatment needs, the difficulties with the final disposal of the

**Keywords:** sewage sludge, densification, digestion, anaerobic sludge digestors,

At first, the main concern in relation to sewage treatment is to solve the problem of the liquid phase, leaving in the background the solution of the problem of the sludge generated in the treatment of this liquid phase. When there is a sewage treatment in which the generation of sludge is quite significant and the main concern with this sludge, at first, is restricted to its stabilization and dewatering to reach a solid content of the sludge in the range of 15–40%, aiming almost exclusively at its removal from the wastewater treatment plant (WWTP) area by trucks, however, has no clear definition of its final destination. In many cases, it is difficult to find suitable areas and conditions for the disposal of these sludge generated in the WWTPs [1]. Thus, the choice of the solution to be given to the sewage problem must also consider the solution to be given to the sludge generated in the treatment of the liquid phase. In order to study the alternatives for the treatment and disposal of sewage and the sludge generated in the treatment of the liquid phase, it is necessary to first know the possibilities of treating a sewage, in view of the quality of the final effluent to be obtained, as well as the quantities and qualities of the sludge produced in the WWTPs, which constitutes the main objectives of this work. In addition, an estimate of the costs of implementing WWTPs is presented for various types of sewage treatment systems. Currently, a very serious environmental

#### **Chapter 3**

*Sustainable Sewage Sludge Management and Resource Efficiency*

output in industrial sewage sludge disposal by thermal pretreatment

process. Bioresource Technology. 2010;**101**(8):2580-2584. DOI: 10.1016/j.

[129] Lu J, Gavala HN, Skiadas IV, Mladenovska Z, Ahring BK. Improving anaerobic sewage sludge digestion by implementation of a hyperthermophilic prehydrolysis step.

[130] Ma J, Duong TH, Smits M, Verstraete W, Carballa M. Enhanced biomethanation of kitchen waste by different pre-treatments. Bioresource Technology. 2011;**102**(2):592-599

jenvman.2007.04.020

2001;**44**(10):121-128

jbb.100.164

cej.2013.11.055

Journal of Environmental Management. 2008;**88**(4):881-889. DOI: 10.1016/j.

[131] Müller JA. Prospects and problems of sludge pre-treatment processes. Water Science and Technology.

[132] Park C, Lee C, Kim S, Chen Y, Chase HA. Upgrading of anaerobic digestion by incorporating two different hydrolysis processes. Journal of Bioscience and Bioengineering. 2005;**100**(2):164-167. DOI: 10.1263/

[133] Cesaro A, Belgiorno V. Pretreatment methods to improve anaerobic biodegradability of organic municipal solid waste fractions. Chemical Engineering Journal. 2014;**240**:24-37. DOI: 10.1016/j.

[128] Escamilla-Alvarado C, Ríos-Leal E, Ponce-Noyola MT, Poggi-Varaldo HM. Gas biofuels from solid substrate hydrogenogenic-methanogenic fermentation of the organic fraction of municipal solid waste. Process Biochemistry. 2012;**47**(11):1572-1587. DOI: 10.1016/j.procbio.2011.12.006

and two-phase anaerobic

biortech.2009.10.055

**50**

## Composition, Production, and Treatment of Sewage Sludge

*Rodrigo de Freitas Bueno*

#### **Abstract**

Sewage treatment ultimately culminates in the concentration of the solid phase. Sludge are separated mainly in primary or secondary decanters. Even in biological treatment, where biological degradation of organic matter actually occurs, there is the separation of excess sludge concentrated in the bottom of the secondary settlers of activated sludge systems or biological filters. In fact, the production of sludge is an important differential in the choice of the treatment system. While purely aerobic systems such as activated sludge or high-rate biological filters can produce 0.6–0.8 kgSS/kgBOD applied, sludge production in an upflow anaerobic sludge blanket (UASB) reactor is only about 0.2 kgSS/kgCOD applied. Even the mixed anaerobic/aerobic system leads to less sludge production than that of an exclusively aerobic system. This advantage is very important nowadays, especially since, besides reducing the treatment needs, the difficulties with the final disposal of the sludge are usually very large.

**Keywords:** sewage sludge, densification, digestion, anaerobic sludge digestors, dimensioning

#### **1. Introduction**

At first, the main concern in relation to sewage treatment is to solve the problem of the liquid phase, leaving in the background the solution of the problem of the sludge generated in the treatment of this liquid phase. When there is a sewage treatment in which the generation of sludge is quite significant and the main concern with this sludge, at first, is restricted to its stabilization and dewatering to reach a solid content of the sludge in the range of 15–40%, aiming almost exclusively at its removal from the wastewater treatment plant (WWTP) area by trucks, however, has no clear definition of its final destination. In many cases, it is difficult to find suitable areas and conditions for the disposal of these sludge generated in the WWTPs [1]. Thus, the choice of the solution to be given to the sewage problem must also consider the solution to be given to the sludge generated in the treatment of the liquid phase. In order to study the alternatives for the treatment and disposal of sewage and the sludge generated in the treatment of the liquid phase, it is necessary to first know the possibilities of treating a sewage, in view of the quality of the final effluent to be obtained, as well as the quantities and qualities of the sludge produced in the WWTPs, which constitutes the main objectives of this work. In addition, an estimate of the costs of implementing WWTPs is presented for various types of sewage treatment systems. Currently, a very serious environmental

problem, observed in metropolitan regions and medium-sized cities that have implemented sanitary sewage treatment systems, is related to the destination of the sludge produced in their WWTPs [2].

For an adequate solution of this problem, it is necessary initially to know the sludge production according to the used scrubber system. In terms of sludge production, considering only the quantitative aspect of solids produced in a WWTP, this work presents "per capita" values that can be useful to the technicians involved with the problem of the sludge destination considered here. However, the solid content (or moisture) of the sludge is another important parameter for the final disposal of the sludge and depends fundamentally on the type of stabilization used (anaerobic or aerobic biological or chemical) and the type of dewatering equipment used. In principle, the following ranges of solid content values should be considered [1, 3]:

	- Plate press filter—solid content from 30 to 40%
	- Belt press filter—solid content from 16 to 25%
	- Centrifuges—solid content from 25 to 30%
	- Drying beds—solid content from 20 to 30%
	- Plate press filter—solid content from 25 to 35%
	- Belt press filter—solid content from 13 to 18%
	- Centrifuges—solid content from 20 to 25%
	- Drying beds—solid content from 20 to 30%

For the design of the new WWTPs, it is recommended that, in addition to the quality of the effluent to be required depending on the receiving body, the destination to be given to the sludge is also considered, as this aspect may be preponderant for the definition of the sewage treatment system and sludge to be adopted.

#### **2. Sludge treatment steps**

Sludge treatment can be subdivided into three main stages, although depending on the sewage treatment system adopted, some of them can be suppressed. This is the case, for example, with the activated sludge system with prolonged aeration, where the process operates in a range where the digestion of excess sludge can be dispensed with. Sludge discharged from upflow anaerobic sludge blanket (UASB) reactors also requires no densification and complementary digestion. Sludge densification may not be mandatory in activated sludge systems or aerobic biological filters, but, except in small systems, its inclusion is made possible by the benefits brought to later sludge treatment units [1]. When sewage treatment is carried out by pond processes, then the system operates in such a way that the sludge thickens and digests at the bottom of the stabilization or settling ponds, in the

**53**

**2.2 Gravity density**

*Composition, Production, and Treatment of Sewage Sludge*

case of mechanically aerated pond systems. The problem becomes how to produce sludge removal mechanisms for final dehydration before being sent for disposal [2]. Depending on the use to be made of the sludge to be removed from the sewage treatment station, other treatment steps may be necessary, such as its disinfection

The objective of sludge densification is to reduce its moisture content, remove water and thus volume, and increase the solid content. The sludge discharged from "secondary" settlers of activated sludge systems with prolonged aeration has a solid content of less than 1%, and when a densifier raises it to 2%, there is a reduction in the sludge volume of 100% to be dehydrated. In a system of conventional activated sludge or aerobic biological filters, the sludge is mixed, primary and secondary. It is generated with a solid content between 1.0 and 1.5%, and its increase to about 4% allows an even greater reduction in volume, being able to prove the advantage of incorporating it into the system, in view of the much smaller required volume of

The purpose of sludge digestion is to complement its biochemical stabilization, that is, to increase the degree of mineralization. The sludge generated in conventional activated sludge systems and aerobic biological filters has a high volatile suspended solid/total suspended solid (VSS/TSS) ratio (e.g., 0.8) and thus does not allow good conditions for natural or mechanical dehydration. As what prevails in a sludge digestion stage is endogenous metabolism with destruction of VSS, this ratio is reduced (e.g., to 0.4), and the more mineralized sludge has better conditions for final dehydration. The objective of final dehydration is to remove water in order to achieve solid content above 20%, thereby drastically reducing the volume of sludge to be transported and making it compatible with applications such as disposal in

Sludge densification can be done by three main alternative processes. Gravity densification is applicable to both primary settler sludge and secondary settler sludge, that is, excess biological sludge, as well as to mixed primary and secondary sludge. Flotation densification with dissolved air can be an interesting alternative for the densification of excess biological sludge [3, 6, 8]. They result in solid contents higher than that of the gravity-densified sludge, and higher sludge loads per surface area of densifiers can be applied, resulting in the need for smaller areas of densifiers. The structure, however, is much more complex. Part of the final effluent from the WWTP, that is, from the treated sewage, feeds into the pressurization tank

the form of microbubbles. Then, it is mixed with the sludge at the entrance from the bottom of the flotation chamber, with scraping removal of the densified sludge at the top and the sub-liquid to return to the entrance of the WWTP. Recently, machines for the mechanical thickening of sludge have been developed [5, 7]. They are machines designed to provide only a partial dehydration of the sludge, around 4–5%, for later final dehydration that can also be mechanized. Recent research has demonstrated the possibility of obtaining interesting advantages through the chemical conditioning of sludge prior to its densification. In this text, greater

Gravity densifiers are units similar to circular planter decanters, being fed with sludge through the center and at the top, inside a bulkhead that directs it to the

, dissolves in the liquid in

where the air is injected and, at a pressure of 4.0 kgf/cm2

emphasis will be given to gravity densification [2].

*DOI: http://dx.doi.org/10.5772/intechopen.91665*

for application on agricultural soil [4].

anaerobic sludge digesters [1, 5, 6].

landfills or agriculture [4, 6, 7].

**2.1 Sludge densification**

*Sustainable Sewage Sludge Management and Resource Efficiency*

• Anaerobically digested sludge, dehydrated by:

○ Plate press filter—solid content from 30 to 40%

○ Belt press filter—solid content from 16 to 25%

○ Centrifuges—solid content from 25 to 30%

○ Drying beds—solid content from 20 to 30%

○ Plate press filter—solid content from 25 to 35%

○ Belt press filter—solid content from 13 to 18%

○ Centrifuges—solid content from 20 to 25%

○ Drying beds—solid content from 20 to 30%

**2. Sludge treatment steps**

For the design of the new WWTPs, it is recommended that, in addition to the quality of the effluent to be required depending on the receiving body, the destination to be given to the sludge is also considered, as this aspect may be preponderant

Sludge treatment can be subdivided into three main stages, although depending on the sewage treatment system adopted, some of them can be suppressed. This is the case, for example, with the activated sludge system with prolonged aeration, where the process operates in a range where the digestion of excess sludge can be dispensed with. Sludge discharged from upflow anaerobic sludge blanket (UASB) reactors also requires no densification and complementary digestion. Sludge densification may not be mandatory in activated sludge systems or aerobic biological filters, but, except in small systems, its inclusion is made possible by the benefits brought to later sludge treatment units [1]. When sewage treatment is carried out by pond processes, then the system operates in such a way that the sludge thickens and digests at the bottom of the stabilization or settling ponds, in the

for the definition of the sewage treatment system and sludge to be adopted.

• Aerobically digested sludge, dehydrated by:

sludge produced in their WWTPs [2].

be considered [1, 3]:

problem, observed in metropolitan regions and medium-sized cities that have implemented sanitary sewage treatment systems, is related to the destination of the

For an adequate solution of this problem, it is necessary initially to know the sludge production according to the used scrubber system. In terms of sludge production, considering only the quantitative aspect of solids produced in a WWTP, this work presents "per capita" values that can be useful to the technicians involved with the problem of the sludge destination considered here. However, the solid content (or moisture) of the sludge is another important parameter for the final disposal of the sludge and depends fundamentally on the type of stabilization used (anaerobic or aerobic biological or chemical) and the type of dewatering equipment used. In principle, the following ranges of solid content values should

**52**

case of mechanically aerated pond systems. The problem becomes how to produce sludge removal mechanisms for final dehydration before being sent for disposal [2]. Depending on the use to be made of the sludge to be removed from the sewage treatment station, other treatment steps may be necessary, such as its disinfection for application on agricultural soil [4].

The objective of sludge densification is to reduce its moisture content, remove water and thus volume, and increase the solid content. The sludge discharged from "secondary" settlers of activated sludge systems with prolonged aeration has a solid content of less than 1%, and when a densifier raises it to 2%, there is a reduction in the sludge volume of 100% to be dehydrated. In a system of conventional activated sludge or aerobic biological filters, the sludge is mixed, primary and secondary. It is generated with a solid content between 1.0 and 1.5%, and its increase to about 4% allows an even greater reduction in volume, being able to prove the advantage of incorporating it into the system, in view of the much smaller required volume of anaerobic sludge digesters [1, 5, 6].

The purpose of sludge digestion is to complement its biochemical stabilization, that is, to increase the degree of mineralization. The sludge generated in conventional activated sludge systems and aerobic biological filters has a high volatile suspended solid/total suspended solid (VSS/TSS) ratio (e.g., 0.8) and thus does not allow good conditions for natural or mechanical dehydration. As what prevails in a sludge digestion stage is endogenous metabolism with destruction of VSS, this ratio is reduced (e.g., to 0.4), and the more mineralized sludge has better conditions for final dehydration. The objective of final dehydration is to remove water in order to achieve solid content above 20%, thereby drastically reducing the volume of sludge to be transported and making it compatible with applications such as disposal in landfills or agriculture [4, 6, 7].

#### **2.1 Sludge densification**

Sludge densification can be done by three main alternative processes. Gravity densification is applicable to both primary settler sludge and secondary settler sludge, that is, excess biological sludge, as well as to mixed primary and secondary sludge. Flotation densification with dissolved air can be an interesting alternative for the densification of excess biological sludge [3, 6, 8]. They result in solid contents higher than that of the gravity-densified sludge, and higher sludge loads per surface area of densifiers can be applied, resulting in the need for smaller areas of densifiers. The structure, however, is much more complex. Part of the final effluent from the WWTP, that is, from the treated sewage, feeds into the pressurization tank where the air is injected and, at a pressure of 4.0 kgf/cm2 , dissolves in the liquid in the form of microbubbles. Then, it is mixed with the sludge at the entrance from the bottom of the flotation chamber, with scraping removal of the densified sludge at the top and the sub-liquid to return to the entrance of the WWTP. Recently, machines for the mechanical thickening of sludge have been developed [5, 7]. They are machines designed to provide only a partial dehydration of the sludge, around 4–5%, for later final dehydration that can also be mechanized. Recent research has demonstrated the possibility of obtaining interesting advantages through the chemical conditioning of sludge prior to its densification. In this text, greater emphasis will be given to gravity densification [2].

#### **2.2 Gravity density**

Gravity densifiers are units similar to circular planter decanters, being fed with sludge through the center and at the top, inside a bulkhead that directs it to the

bottom, from where it is removed after undergoing densification. Meanwhile, the supernatant liquid flows through the perimeter spillways positioned on the surface of the condenser and can be recirculated at the entrance of the WWTP [1, 3, 9]. **Figure 1** shows a photograph of an empty gravity densifier.

#### *2.2.1 Dimensioning of gravity densifiers*

The main dimensioning factor of gravity densifiers is the rate of application of solids, which is the mass flow of solids applied per unit of surface area of the densifiers. It depends on the type of sludge to be densified. The following ranges of values are proposed (**Table 1**).

The rate of application of solids should be the most restrictive factor in determining the surface area of the densifiers; however, the flow rate, sludge flow applied per unit of the surface area of the densifiers, must be kept within a certain limit, that is, fA = F/SA < 16 m3 /m2 day. Additional recommendations, such as minimum useful depth of densifiers equal to 3.0 m, maximum hydraulic holding time of 24 h, and mandatory mechanized sludge removal when diameters are greater than 3.0 m, are used. The maximum time limit for sludge retention in the compactor is characterized when there is a possibility of anaerobic decomposition and giving off of bad odors. When holding times greater than 24 h result from dimensioning, a portion of the treated sewage, the final effluent from the WWTP, can be recirculated, with a flow calculated to ensure compliance with the limit value.

*Sizing example.* Data:


**55**

*Composition, Production, and Treatment of Sewage Sludge*

*DOI: http://dx.doi.org/10.5772/intechopen.91665*

Solid application rate: 60 kgSS/m2

Adopted useful depth: Hu = 4 m.

Adensifier = 2254 ÷ 60 = 37.6 m<sup>2</sup>

Resulting useful volume: Vu = 4 × 38.5 = 154 m3

Runoff rate: fA = F ÷ SA = 221 ÷ 38.5 = 5.7 m3

Solid content in dense sludge: 4% (estimated). Flow of thick sludge, for specific mass of 1030 kg/m3

FSludge.Densifier = 2254 ÷ (0.04 × 1030) = 54.7 m3

The compactor must have mechanized sludge remover.

Recirculation flow: 221–54.7 = 166.3 m3

the resulting solid application rate will be 2254 ÷ 38.5 = 58.5 kgSS/m<sup>2</sup>

Required density area:

**Table 1.**

**3. Sludge digestion**

**3.1 Anaerobic sludge digestors**

than 1.2 kg/m3

1.2 kg/m3

Anaerobic digestion can be considered as:

day.

day (adopted).

.

/day.

:

/m2 day.

/day.

Depending on the type of sewage treatment and its operational conditions, the sludge from the solid separation units may require complementary biochemical stabilization. For that, aerobic or anaerobic digesters can be used; in both cases the reduction of sludge volatile content via endogenous metabolism is desired. Aerobic digesters are tanks equipped with an aeration system such as those used in activated sludge reactors. In view of the faster growth of these microorganisms in relation to anaerobes, it can be understood that the volumes of reactors are relatively smaller, which may lead to lower implantation costs than others, even though an aeration equipment is required [4]. However, for the aeration of concentrated sludge, the consumption of electric energy is quite high, and the difference between operating costs has led to the widespread use of anaerobic digesters in activated sludge systems and aerobic biological filters [7]. For this reason, a greater emphasis will be placed here on anaerobic sludge digestion.

a.Conventional when the VSS application rate on the digester is equal to or less

b.High rate when the rate of application of VSS on the digester is greater than

day.

day and equal to or less than 4.8 kg/m3

Adopting the diameter D = 7 m, the area of the condenser will be 38.5 m2

*Application rate of solids according to the type of sludge. Source: adapted of Metcalf & Eddy, Inc. [3]*.

Hydraulic retention time: HRT = V ÷ F = 154 ÷ 221 = 0.7 day = 16.7 h.

(diameter D = 6.9 m) (1)

, and

day.


**Table 1.**

*Sustainable Sewage Sludge Management and Resource Efficiency*

**Figure 1** shows a photograph of an empty gravity densifier.

/m2

lated, with a flow calculated to ensure compliance with the limit value.

.

• Sludge type: primary + activated sludge.

• Sludge production: ΔX = 2254 kg SS/day.

• Sludge flow: F = 2254 ÷ (0.01 × 1020) = 221 m3

*Sludge densifier by gravity. WWTP-Sabesp, São Paulo, Brazil (source: the author).*

• Specific sludge mass: 1020 kg/m3

• Sludge solid content: 1%.

*2.2.1 Dimensioning of gravity densifiers*

values are proposed (**Table 1**).

limit, that is, fA = F/SA < 16 m3

*Sizing example.*

Data:

bottom, from where it is removed after undergoing densification. Meanwhile, the supernatant liquid flows through the perimeter spillways positioned on the surface of the condenser and can be recirculated at the entrance of the WWTP [1, 3, 9].

The main dimensioning factor of gravity densifiers is the rate of application of solids, which is the mass flow of solids applied per unit of surface area of the densifiers. It depends on the type of sludge to be densified. The following ranges of

The rate of application of solids should be the most restrictive factor in determining the surface area of the densifiers; however, the flow rate, sludge flow applied per unit of the surface area of the densifiers, must be kept within a certain

mum useful depth of densifiers equal to 3.0 m, maximum hydraulic holding time of 24 h, and mandatory mechanized sludge removal when diameters are greater than 3.0 m, are used. The maximum time limit for sludge retention in the compactor is characterized when there is a possibility of anaerobic decomposition and giving off of bad odors. When holding times greater than 24 h result from dimensioning, a portion of the treated sewage, the final effluent from the WWTP, can be recircu-

day. Additional recommendations, such as mini-

/day.

**54**

**Figure 1.**

*Application rate of solids according to the type of sludge. Source: adapted of Metcalf & Eddy, Inc. [3]*.

Solid application rate: 60 kgSS/m2 day (adopted). Required density area:

$$\mathbf{A}\_{\text{densifier}} = 2254 \div 60 = 37.6 \text{ m}^2 \text{ (diameter D = 6.9 m)}\tag{1}$$

Adopting the diameter D = 7 m, the area of the condenser will be 38.5 m2 , and the resulting solid application rate will be 2254 ÷ 38.5 = 58.5 kgSS/m<sup>2</sup> day. Adopted useful depth: Hu = 4 m. Resulting useful volume: Vu = 4 × 38.5 = 154 m3 . Hydraulic retention time: HRT = V ÷ F = 154 ÷ 221 = 0.7 day = 16.7 h. Runoff rate: fA = F ÷ SA = 221 ÷ 38.5 = 5.7 m3 /m2 day. Solid content in dense sludge: 4% (estimated). Flow of thick sludge, for specific mass of 1030 kg/m3 : FSludge.Densifier = 2254 ÷ (0.04 × 1030) = 54.7 m3 /day.

Recirculation flow: 221–54.7 = 166.3 m3 /day.

The compactor must have mechanized sludge remover.

#### **3. Sludge digestion**

Depending on the type of sewage treatment and its operational conditions, the sludge from the solid separation units may require complementary biochemical stabilization. For that, aerobic or anaerobic digesters can be used; in both cases the reduction of sludge volatile content via endogenous metabolism is desired. Aerobic digesters are tanks equipped with an aeration system such as those used in activated sludge reactors. In view of the faster growth of these microorganisms in relation to anaerobes, it can be understood that the volumes of reactors are relatively smaller, which may lead to lower implantation costs than others, even though an aeration equipment is required [4]. However, for the aeration of concentrated sludge, the consumption of electric energy is quite high, and the difference between operating costs has led to the widespread use of anaerobic digesters in activated sludge systems and aerobic biological filters [7]. For this reason, a greater emphasis will be placed here on anaerobic sludge digestion.

#### **3.1 Anaerobic sludge digestors**

Anaerobic digestion can be considered as:


It is admitted to obtain a typical destruction of up to 50% of VSS and never exceeding 60%, according to the digestion and design conditions.

When selecting the VSS application rate, the influence of the internal temperature of the digester must be considered, and the need for heating of the unit must be verified. Anaerobic digestion should preferably be processed in the temperature range of 30–35°C (mesophilic digestion) or in the range of 50–57°C (thermophilic digestion) [1]. Lower temperatures result in less efficient digestion, to be considered in the project. High-speed primary digesters, with a VSS application rate equal to or greater than 0.5 kg/m3 day, must be homogenized by one of the following devices: turbine mixer, gas homogenization system, and sludge recirculation pumps.

Digestion time should be:

a.For non-homogenized digester, ≥45 days.

b.For homogenized conventional digester, ≥30 days.

c.For high-rate digester, ≥18 days.

Second-stage digesters can be used for sludge storage and supernatant removal. The volume of the second-stage digester is about 1/3 of the volume of the first stage, determined by the criteria presented. **Figure 2** shows a photograph of the set of anaerobic digesters from WWTP.

*Example of sizing a low-rate anaerobic digester.* Data:


VSS application rate: 0.5 kg VSS/m3 day (adopted).

**57**

m2

*Composition, Production, and Treatment of Sewage Sludge*

To meet the minimum detention time of 45 h, we have:

VAnaerobic.digestor = 1757 ÷ 0.5 = 3514 m<sup>3</sup> (2)

VAnaerobic.digestor = 45 × 54.7 = 2461.5 m<sup>3</sup> (3)

per inhabitant [2]. The cost of its structure, the operational

× cycle is recommended. The rates in the region of 10–12 kg SS/

The purpose of sludge dehydration is to raise the solid content generally above 20%, in order to reduce the volume to be transported and to allow its final disposal in landfills, agriculture, etc. It can be done naturally or mechanically. Natural drying can be done in drying beds or mud ponds. Sludge ponds should not be considered as a very suitable final solution. The sludge drying beds should be used more advantageously in small treatment systems. The required bed area is relatively large,

difficulties with the removal of dehydrated sludge, and the excessive presence of rainwater can make its use unfeasible, especially in large treatment systems. Dewatering machines have grown in use in recent years, mainly plate press filters or conveyors, as well as centrifugal decanters. Despite the relatively high cost of these machines, the operational ease has enabled their adoption. For application of the machines, the previous conditioning of the sludge is required. In Brazil, chemical conditioning with ferric chloride and lime is common practice, a progressive

The sludge drying beds are structures composed of bricks, arranged two by two and with joints filled with coarse sand. Under the bricks, layers of coarse sand and gravel of increasing granulometry are placed toward the bottom, an impermeable slab from which the liquid that infiltrates is drained and returned to the entrance of the WWTP. The sludge is disposed on the bricks, drying by infiltration of water in the bed and by evaporation in the sun. The beds are fed on a rotating basis, from channels with gates. A typical drying bed operation cycle, commonly adopted in projects in our region, is 30 days in total, with 20 days reserved for dewatering the sludge and 10 days for removing the dry sludge and rearranging the bed. Solids in the dehydrated sludge above 30% can be expected. For the determination of the necessary drying bed area, an application rate of solids as a criterion which cannot

 × cycle are used in our region (Brazil). Once the total bed area is determined, it is subdivided into a number of beds that should not be too large to reduce opera-

tional difficulties [3]. **Figure 3** shows a view of the sludge drying beds.

practice of substitution of the use of polyelectrolytes [7, 8].

each should be adopted, making a total useful

Required volume of anaerobic digesters:

*DOI: http://dx.doi.org/10.5772/intechopen.91665*

Three digesters of 1200 m3

.

volume of 3600 m3

**4. Sludge dehydration**

on the order of 0.1 m2

**4.1 Sludge drying beds**

exceed 15 kg SS/m<sup>2</sup>

Data:

*Example of sizing sludge drying beds.*

• Sludge production: ΔX = 2254 kg SS/day.

• Volatile fraction: ΔXv = 1757 kg VSS/day.

**Figure 2.** *Anaerobic digester. WWTP-Sabesp, São Paulo, Brazil (source: the author).*

Required volume of anaerobic digesters:

$$\text{V}\_{\text{Anaerobic.digetor}} = \text{1757} \div \text{0.5} = \text{3514 m}^3 \tag{2}$$

To meet the minimum detention time of 45 h, we have:

$$\text{V}\_{\text{Anaeroic.digestor}} = \text{45} \times \text{54.7} = \text{2461.5 m}^3 \tag{3}$$

Three digesters of 1200 m3 each should be adopted, making a total useful volume of 3600 m3 .

#### **4. Sludge dehydration**

*Sustainable Sewage Sludge Management and Resource Efficiency*

tion rate equal to or greater than 0.5 kg/m3

a.For non-homogenized digester, ≥45 days.

*Example of sizing a low-rate anaerobic digester.*

• Sludge production: ΔX = 2254 kg SS/day.

• Volatile fraction: ΔXv = 1757 kg VSS/day.

VSS application rate: 0.5 kg VSS/m3

/day.

*Anaerobic digester. WWTP-Sabesp, São Paulo, Brazil (source: the author).*

c.For high-rate digester, ≥18 days.

anaerobic digesters from WWTP.

• Sludge solid content: 4%.

• Sludge flow: F = 54.7 m3

Data:

b.For homogenized conventional digester, ≥30 days.

recirculation pumps.

Digestion time should be:

exceeding 60%, according to the digestion and design conditions.

It is admitted to obtain a typical destruction of up to 50% of VSS and never

When selecting the VSS application rate, the influence of the internal temperature of the digester must be considered, and the need for heating of the unit must be verified. Anaerobic digestion should preferably be processed in the temperature range of 30–35°C (mesophilic digestion) or in the range of 50–57°C (thermophilic digestion) [1]. Lower temperatures result in less efficient digestion, to be considered in the project. High-speed primary digesters, with a VSS applica-

the following devices: turbine mixer, gas homogenization system, and sludge

Second-stage digesters can be used for sludge storage and supernatant removal. The volume of the second-stage digester is about 1/3 of the volume of the first stage, determined by the criteria presented. **Figure 2** shows a photograph of the set of

day (adopted).

day, must be homogenized by one of

**56**

**Figure 2.**

The purpose of sludge dehydration is to raise the solid content generally above 20%, in order to reduce the volume to be transported and to allow its final disposal in landfills, agriculture, etc. It can be done naturally or mechanically. Natural drying can be done in drying beds or mud ponds. Sludge ponds should not be considered as a very suitable final solution. The sludge drying beds should be used more advantageously in small treatment systems. The required bed area is relatively large, on the order of 0.1 m2 per inhabitant [2]. The cost of its structure, the operational difficulties with the removal of dehydrated sludge, and the excessive presence of rainwater can make its use unfeasible, especially in large treatment systems. Dewatering machines have grown in use in recent years, mainly plate press filters or conveyors, as well as centrifugal decanters. Despite the relatively high cost of these machines, the operational ease has enabled their adoption. For application of the machines, the previous conditioning of the sludge is required. In Brazil, chemical conditioning with ferric chloride and lime is common practice, a progressive practice of substitution of the use of polyelectrolytes [7, 8].

#### **4.1 Sludge drying beds**

The sludge drying beds are structures composed of bricks, arranged two by two and with joints filled with coarse sand. Under the bricks, layers of coarse sand and gravel of increasing granulometry are placed toward the bottom, an impermeable slab from which the liquid that infiltrates is drained and returned to the entrance of the WWTP. The sludge is disposed on the bricks, drying by infiltration of water in the bed and by evaporation in the sun. The beds are fed on a rotating basis, from channels with gates. A typical drying bed operation cycle, commonly adopted in projects in our region, is 30 days in total, with 20 days reserved for dewatering the sludge and 10 days for removing the dry sludge and rearranging the bed. Solids in the dehydrated sludge above 30% can be expected. For the determination of the necessary drying bed area, an application rate of solids as a criterion which cannot exceed 15 kg SS/m<sup>2</sup> × cycle is recommended. The rates in the region of 10–12 kg SS/ m2 × cycle are used in our region (Brazil). Once the total bed area is determined, it is subdivided into a number of beds that should not be too large to reduce operational difficulties [3]. **Figure 3** shows a view of the sludge drying beds.

*Example of sizing sludge drying beds.* Data:


**Figure 3.** *Drying beds. WWTP-Sabesp, São Paulo, Brazil (source: the author).*

Considering that, prior to drying, the sludge will suffer a 55% reduction in volatile solids due to anaerobic digestion, we have:

VXv, RED = 0.55 × 1757 = 966 kg VSS/day. ΔXp/drying = 2254–966 = 1288 kg SS/day. ΔXp/drying = 1288 × 365 = 470,120 kg SS/year. Adopting 12 drying cycles per year, we have: ΔXp/drying = 470,120 ÷ 12 = 39,177 kg SS/cycle.

Adopting the rate of 12.5 kg SS/m2 × cycle, we have the following required area of sludge drying beds:

$$\mathbf{A\_{dry.sludge}} = \mathbf{\color{red}{39,177}} \div \mathbf{12.5} = \mathbf{\color{red}{3134 \text{ m}}^2} \tag{4}$$

**59**

**Figure 5.**

*Plate filter press (source: Andreoli [1]).*

*Composition, Production, and Treatment of Sewage Sludge*

shows the diagram of the operation of a plate filter press.

Using plates (1.5 m × 1.5 m) of 3 cm thick, we have:

Vaccumulated = 1.5 × 1.5 × 0.03 = 0.0675 m<sup>3</sup>

The main types of machines available on the market are plate press filters, continuous belt press filters, vacuum filters, and centrifugal decanters. When plate filter presses are used in activated sludge stations, dosages of ferric chloride, FeCl3, of 7 kg/100 kg SS and hydrated lime, Ca(OH)2, of 15 kg/100 kg SS are required, which makes this stage of the WWTP expensive, increases the volume of sludge, and hinders the agricultural disposal of sludge. When only polyelectrolytes are used, dosages of the order of 0.5–0.6 kg/100 kg SS are normally required [1, 2, 8]. The type of sludge conditioning and the dosages depend fundamentally on the state in which the sludge is generated, mainly its degree of mineralization, with less mineralized sludge being more difficult to dehydrate. **Figures 5** and **6**

where V, volume of the filter press (L); (SS), suspended solids load (kg/day); N, number of presses per day; P, cake solid content (%); ρ, cake specific mass (kg/L).

V = 100 (SS) ÷ N × P × ρ (5)

V = (100 × 6825) ÷ (4 × 30 × 1.06) = 5366 L (6)

Number of plates = 5366 ÷ 67.5 = 80 (8)

= 67.5 L (7)

*DOI: http://dx.doi.org/10.5772/intechopen.91665*

*Example of sizing a plate filter press*

Data:

N = 4. P = 30%. ρ = 1.06.

ΔX = 6825 kg SS/day.

Volume of the filter press:

**4.2 Mechanical sludge dehydration**

Twenty-seven sludge drying beds of 6.0 × 20.0 m in dimensions in each plant are proposed. **Figure 4** shows an example schematic of a sludge drying bed.

**Figure 4.** *Schematic cut of a sludge drying bed (source: the author).*

#### **4.2 Mechanical sludge dehydration**

*Sustainable Sewage Sludge Management and Resource Efficiency*

volatile solids due to anaerobic digestion, we have:

*Drying beds. WWTP-Sabesp, São Paulo, Brazil (source: the author).*

VXv, RED = 0.55 × 1757 = 966 kg VSS/day. ΔXp/drying = 2254–966 = 1288 kg SS/day. ΔXp/drying = 1288 × 365 = 470,120 kg SS/year. Adopting 12 drying cycles per year, we have: ΔXp/drying = 470,120 ÷ 12 = 39,177 kg SS/cycle.

Adopting the rate of 12.5 kg SS/m2

*Schematic cut of a sludge drying bed (source: the author).*

of sludge drying beds:

**Figure 3.**

Considering that, prior to drying, the sludge will suffer a 55% reduction in

× cycle, we have the following required area

Adry.sludge = 39,177 ÷ 12.5 = 3134 m<sup>2</sup> (4)

Twenty-seven sludge drying beds of 6.0 × 20.0 m in dimensions in each plant are

proposed. **Figure 4** shows an example schematic of a sludge drying bed.

**58**

**Figure 4.**

The main types of machines available on the market are plate press filters, continuous belt press filters, vacuum filters, and centrifugal decanters. When plate filter presses are used in activated sludge stations, dosages of ferric chloride, FeCl3, of 7 kg/100 kg SS and hydrated lime, Ca(OH)2, of 15 kg/100 kg SS are required, which makes this stage of the WWTP expensive, increases the volume of sludge, and hinders the agricultural disposal of sludge. When only polyelectrolytes are used, dosages of the order of 0.5–0.6 kg/100 kg SS are normally required [1, 2, 8]. The type of sludge conditioning and the dosages depend fundamentally on the state in which the sludge is generated, mainly its degree of mineralization, with less mineralized sludge being more difficult to dehydrate. **Figures 5** and **6** shows the diagram of the operation of a plate filter press.

*Example of sizing a plate filter press*

$$\mathbf{V} = \mathbf{100} \text{ (SS)} \div \mathbf{N} \times \mathbf{P} \times \boldsymbol{\rho} \tag{5}$$

where V, volume of the filter press (L); (SS), suspended solids load (kg/day); N, number of presses per day; P, cake solid content (%); ρ, cake specific mass (kg/L). Data:

ΔX = 6825 kg SS/day. N = 4. P = 30%. ρ = 1.06.

Volume of the filter press:

$$\mathbf{V} = \begin{pmatrix} 100 \times 6825 \end{pmatrix} \div \begin{pmatrix} 4 \times 30 \times 1.06 \end{pmatrix} = \mathbf{5366 L} \tag{6}$$

Using plates (1.5 m × 1.5 m) of 3 cm thick, we have:

$$\text{V}\_{\text{accumulated}} = \text{1.5} \times \text{1.5} \times \text{0.03} = \text{0.0675 m}^3 = \text{67.5 L} \tag{7}$$

$$\text{Number of plates} = \text{5366} \div \text{67.5} = \text{80} \tag{8}$$

**Figure 5.** *Plate filter press (source: Andreoli [1]).*

#### **Figure 6.**

*Plate filter press in operation. WWTP-Sabesp, São Paulo, Brazil (source: the author).*

Example of sizing a continuous belt filter press. Data:


Using the application rate of 300 kg SS/m × h and two filters with 1 m belt width, we have the following number of daily operating hours:

$$\text{No.of hours} \div \text{day} = \\$212 \div \text{ (300} \div \text{2)} = \text{14.} \tag{9}$$

Polyelectrolyte consumption:

Medium: 6 kg/1000 kg SS. Maximum: 8 kg/1000 kg SS.

Solid content in dehydrated sludge: 30%. Volume of dehydrated sludge, with ρ = 1060 kg/m3 and 90% solid capture.

 Dry sludge = (0.9 × 8212) ÷ (0.3 × 1060) = 23 m<sup>3</sup> /day. (10)

**Figure 7** shows a continuous belt filter press.

#### **4.3 Alternative design of a centrifugal decanter**

Choosing a centrifuge with a feeding capacity of 10 m3 /h, we have the following number of daily operating hours:

$$\text{No. of hours} \div \text{day} = \mathbf{160} \div \mathbf{10} = \mathbf{16} \tag{11}$$

**61**

**Figure 8.**

*Composition, Production, and Treatment of Sewage Sludge*

Considering the dehydrated sludge at 20% solids, ρ = 1060 kg/m3

Dry sludge = (0.9 × 8212) ÷ (0.2 × 1060) = 35 m<sup>3</sup>

Among the processes of sewage disinfection, chlorination and ultraviolet disinfection have been the most considered alternatives, with chlorination currently being the most economically interesting. Despite the potential for the formation of by-products, which can present toxicity, chlorination has been the solution used in almost all WWTPs, without using dechlorination for the time being. Another process used is heat treatment. This treatment effectively reduces pathogenic viruses,

*Photograph of a centrifugal decanter. WWTP-Sabesp, São Paulo, Brazil (source: the author).*

capture, we have the following flow of dehydrated sludge:

*Belt filter press. WWTP-Sabesp, São Paulo, Brazil (source: the author).*

**Figure 8** shows a centrifugal decanter.

**4.4 Disinfection**

**Figure 7.**

, and 90% solid

/day (12)

*DOI: http://dx.doi.org/10.5772/intechopen.91665*

*Composition, Production, and Treatment of Sewage Sludge DOI: http://dx.doi.org/10.5772/intechopen.91665*

**Figure 7.** *Belt filter press. WWTP-Sabesp, São Paulo, Brazil (source: the author).*

Considering the dehydrated sludge at 20% solids, ρ = 1060 kg/m3 , and 90% solid capture, we have the following flow of dehydrated sludge:

$$\text{Drysludge} = (0.9 \times 8212) \div (0.2 \times 1060) = \\$5 \text{ m}^3/\text{day} \tag{12}$$

**Figure 8** shows a centrifugal decanter.

#### **4.4 Disinfection**

*Sustainable Sewage Sludge Management and Resource Efficiency*

Example of sizing a continuous belt filter press.

*Plate filter press in operation. WWTP-Sabesp, São Paulo, Brazil (source: the author).*

• Sludge flow: QSLUDGE = 8212 ÷ (0.05 x 1030) = 160 m3

width, we have the following number of daily operating hours:

Using the application rate of 300 kg SS/m × h and two filters with 1 m belt

/day.

and 90% solid capture.

/day. (10)

/h, we have the following

No. of hours ÷ day = 8212 ÷ (300 ÷ 2) = 14. (9)

No. of hours ÷ day = 160 ÷ 10 = 16 (11)

Data:

**Figure 6.**

• ΔX = 8212 kg SS/day.

.

Polyelectrolyte consumption:

Solid content in dehydrated sludge: 30%.

**Figure 7** shows a continuous belt filter press.

**4.3 Alternative design of a centrifugal decanter**

Volume of dehydrated sludge, with ρ = 1060 kg/m3

Dry sludge = (0.9 × 8212) ÷ (0.3 × 1060) = 23 m<sup>3</sup>

Choosing a centrifuge with a feeding capacity of 10 m3

Medium: 6 kg/1000 kg SS. Maximum: 8 kg/1000 kg SS.

number of daily operating hours:

• ρ = 1030 kg/m3

• Solid content: 5%.

**60**

Among the processes of sewage disinfection, chlorination and ultraviolet disinfection have been the most considered alternatives, with chlorination currently being the most economically interesting. Despite the potential for the formation of by-products, which can present toxicity, chlorination has been the solution used in almost all WWTPs, without using dechlorination for the time being. Another process used is heat treatment. This treatment effectively reduces pathogenic viruses,

**Figure 8.** *Photograph of a centrifugal decanter. WWTP-Sabesp, São Paulo, Brazil (source: the author).*

bacteria, and helminth eggs to levels below those detectable. For the thermal inactivation of 99.9% of viable eggs in digested logos, an exposure time of 35 min at 58°C is required [3, 4].

#### **5. Conclusion**

This chapter covered the classic processes applied to the treatment, digestion, and drying of sewage sludge. Aerobic sewage treatment processes generate much more sludge than anaerobic systems. Of the sewage treatment systems, the stabilization ponds are the ones that generate the lowest amount of sludge, while conventional activated sludge systems have the highest volume of sludge to be treated. This is due to the fact that the sludge produced in the lagoons is retained for several years, undergoing digestion and densification, which induces a reduction in its volume.

Sludge digestion in the conventional activated sludge system is low due to the short sludge residence time in this system. The sludge filtration process leads to a higher concentration of solids than the thickening process. In filtrations with chemical conditions, the concentration of solids can increase in the order of 20–40% depending on the type of sludge and the form of filtration.

In the case of drying beds, it can be observed that in the period of 10–60 days of sludge rest, the concentration of solids increases to approximately 40%.

Aerobic digestion produces sludge with low dehydration capacity due to the destruction of the flake structure during the process of endogenous respiration that occurs in the aerobic digester. Anaerobic digestion can reduce the concentration of volatile solids in the sewage sludge by up to 60%.

The treatment, disposal, and reuse of WWTPs sludge are gaining more and more expression on the world stage, due to the increase in the number of installed sewage treatment plants and the need to meet the environmental requirements and currently the need for resource recovery natural.

#### **Conflict of interest**

The authors declare no conflict of interest.

#### **Appendices and nomenclature**


**63**

**Author details**

Rodrigo de Freitas Bueno

University of ABC, Santo André, SP, Brazil

provided the original work is properly cited.

Central of Engineering, Modelling and Applied Social Sciences of the Federal

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: rodrigo.bueno@ufabc.edu.br

*Composition, Production, and Treatment of Sewage Sludge*

*DOI: http://dx.doi.org/10.5772/intechopen.91665*

*Composition, Production, and Treatment of Sewage Sludge DOI: http://dx.doi.org/10.5772/intechopen.91665*

*Sustainable Sewage Sludge Management and Resource Efficiency*

58°C is required [3, 4].

**5. Conclusion**

bacteria, and helminth eggs to levels below those detectable. For the thermal inactivation of 99.9% of viable eggs in digested logos, an exposure time of 35 min at

This chapter covered the classic processes applied to the treatment, digestion, and drying of sewage sludge. Aerobic sewage treatment processes generate much more sludge than anaerobic systems. Of the sewage treatment systems, the stabilization ponds are the ones that generate the lowest amount of sludge, while conventional activated sludge systems have the highest volume of sludge to be treated. This is due to the fact that the sludge produced in the lagoons is retained for several years, undergoing digestion and densification, which induces a reduction in its volume. Sludge digestion in the conventional activated sludge system is low due to the short sludge residence time in this system. The sludge filtration process leads to a higher concentration of solids than the thickening process. In filtrations with chemical conditions, the concentration of solids can increase in the order of

In the case of drying beds, it can be observed that in the period of 10–60 days of

Aerobic digestion produces sludge with low dehydration capacity due to the destruction of the flake structure during the process of endogenous respiration that occurs in the aerobic digester. Anaerobic digestion can reduce the concentration of

The treatment, disposal, and reuse of WWTPs sludge are gaining more and more expression on the world stage, due to the increase in the number of installed sewage treatment plants and the need to meet the environmental requirements and

20–40% depending on the type of sludge and the form of filtration.

volatile solids in the sewage sludge by up to 60%.

currently the need for resource recovery natural.

The authors declare no conflict of interest.

BOD biochemical oxygen demand COD chemical oxygen demand

UASB upflow anaerobic sludge blanket

SABESP sanitation company of the state of São Paulo, Brazil

**Appendices and nomenclature**

ΔX sludge production

TSS or SS total suspended solids

VSS volatile suspended solids WWTP wastewater treatment plant

**Conflict of interest**

F flow

SA surface area

Xv volatile fraction

sludge rest, the concentration of solids increases to approximately 40%.

**62**

### **Author details**

Rodrigo de Freitas Bueno Central of Engineering, Modelling and Applied Social Sciences of the Federal University of ABC, Santo André, SP, Brazil

\*Address all correspondence to: rodrigo.bueno@ufabc.edu.br

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **References**

[1] Andreoli CV, Von Sperling M, Fernandes F, Ronteltap M. Sludge Treatment and Disposal. IWA Publishing; 2007

[2] Bishop P. Municipal Sewage Sludge: Management, Processing and Disposal. CRC Press; 1995

[3] Metcalf & Eddy, Inc. Wastewater Engineering: Treatment, Disposal, Reuse. 3rd ed. New York: McGraw-Hill International Editions; 1999

[4] de Chernicharo CAL. Post-treatment options for the anaerobic treatment of domestic wastewater. Reviews in Environmental Science and Bio/ Technology. 2006;**5**(1):73-92

[5] Hudson JA, Lowe P. Current technologies for sludge treatment and disposal. Water and Environment Journal. 1996;**10**(6):436-441

[6] Van Haandel AC, Lettinga G. Anaerobic Sewage Treatment. London, England: John Wiley & Sons; 1994

[7] Nowak O. Optimizing the use of sludge treatment facilities at municipal WWTPs. Journal of Environmental Science and Health Part A. 2006;**41**(9): 1807-1817

[8] Dohányos M, Zábranská J, Jenícek P. Enhancement of sludge anaerobic digestion by using of a special thickening centrifuge. Water Science and Technology. 1997;**36**(11):145-153

[9] Shammas NK, Wang LK. Gravity thickening. In: Biosolids Treatment Processes. Humana Press; 2007. pp. 45-69

**65**

**Chapter 4**

**Abstract**

of Bengaluru City.

**1. Introduction**

Bengaluru

*B.P. Naveen and P.V. Sivapullaiah*

Solid Waste Management: Current

Municipal solid waste management (MSWM) has become one of the significant environmental issues, particularly in developing countries. Bengaluru, the state capital of Karnataka, is one of the fastest growing cities in Asia. The Bruhat

of about 10.18 million generates around 5000 metric tons per day of solid waste at an average generation rate of 0.5 kg per capita per day (kg/capita/d). Presently, Bengaluru City is facing significant problems due to existing disposal practices of generated waste, incurring high cost due to lack of proper infrastructural facilities; also, the open dumping in the expanding zone of the city poses severe problems to the structures constructed on these old dumps. In the meantime, groundwater quality deteriorated due to improper leachate management. Intending to assess the possible impacts on the water environment and suggest a better waste management strategy, the present paper discusses the potential for handling the wastes, thereby reducing the amount of waste to be transported to the landfill. If this waste is used for energy and nutrient recovery, decentralization could also become commercially viable and address the technology-wise deficiencies in the existing MSWM system

**Keywords:** collection, disposal, transportation, processing, management, strategy

In ancient times, a harmonious and balanced relationship between humans and nature on this earth is necessary for livelihood. As civilization advanced, humans directly or indirectly interfered with the natural environment. This led to an imbalance in the human-nature relationship, finally leading to environmental problems like soil, air, and water pollution and accumulation of municipal solid waste (MSW). In olden days, MSW disposal did not pose significant problems because the population was very less and the availability of land for the dumping of wastes was large. But these days MSWM is a serious problem everywhere. Due to rapid industrialization and increased population levels, the generation rate of MSW in metropolitan cities accelerates. This has led to the migration of people from villages to cities, which generates thousands of tons of MSW daily with rapid change in the quantity and character of the waste in line with the changing lifestyle of the people and also with the changes in the market technology, building technology, and fuel technology.

and a population

Scenario and Challenges in

Bengaluru Mahanagara Palike (BBMP) with an area of 2190 km2

#### **Chapter 4**

## Solid Waste Management: Current Scenario and Challenges in Bengaluru

*B.P. Naveen and P.V. Sivapullaiah*

#### **Abstract**

Municipal solid waste management (MSWM) has become one of the significant environmental issues, particularly in developing countries. Bengaluru, the state capital of Karnataka, is one of the fastest growing cities in Asia. The Bruhat Bengaluru Mahanagara Palike (BBMP) with an area of 2190 km2 and a population of about 10.18 million generates around 5000 metric tons per day of solid waste at an average generation rate of 0.5 kg per capita per day (kg/capita/d). Presently, Bengaluru City is facing significant problems due to existing disposal practices of generated waste, incurring high cost due to lack of proper infrastructural facilities; also, the open dumping in the expanding zone of the city poses severe problems to the structures constructed on these old dumps. In the meantime, groundwater quality deteriorated due to improper leachate management. Intending to assess the possible impacts on the water environment and suggest a better waste management strategy, the present paper discusses the potential for handling the wastes, thereby reducing the amount of waste to be transported to the landfill. If this waste is used for energy and nutrient recovery, decentralization could also become commercially viable and address the technology-wise deficiencies in the existing MSWM system of Bengaluru City.

**Keywords:** collection, disposal, transportation, processing, management, strategy

#### **1. Introduction**

In ancient times, a harmonious and balanced relationship between humans and nature on this earth is necessary for livelihood. As civilization advanced, humans directly or indirectly interfered with the natural environment. This led to an imbalance in the human-nature relationship, finally leading to environmental problems like soil, air, and water pollution and accumulation of municipal solid waste (MSW).

In olden days, MSW disposal did not pose significant problems because the population was very less and the availability of land for the dumping of wastes was large. But these days MSWM is a serious problem everywhere. Due to rapid industrialization and increased population levels, the generation rate of MSW in metropolitan cities accelerates. This has led to the migration of people from villages to cities, which generates thousands of tons of MSW daily with rapid change in the quantity and character of the waste in line with the changing lifestyle of the people and also with the changes in the market technology, building technology, and fuel technology.

**64**

1807-1817

pp. 45-69

*Sustainable Sewage Sludge Management and Resource Efficiency*

[1] Andreoli CV, Von Sperling M, Fernandes F, Ronteltap M. Sludge Treatment and Disposal. IWA

[2] Bishop P. Municipal Sewage Sludge: Management, Processing and Disposal.

[3] Metcalf & Eddy, Inc. Wastewater Engineering: Treatment, Disposal, Reuse. 3rd ed. New York: McGraw-Hill

[4] de Chernicharo CAL. Post-treatment options for the anaerobic treatment of domestic wastewater. Reviews in Environmental Science and Bio/ Technology. 2006;**5**(1):73-92

International Editions; 1999

[5] Hudson JA, Lowe P. Current technologies for sludge treatment and disposal. Water and Environment Journal. 1996;**10**(6):436-441

[6] Van Haandel AC, Lettinga G. Anaerobic Sewage Treatment. London, England: John Wiley & Sons; 1994

[7] Nowak O. Optimizing the use of sludge treatment facilities at municipal WWTPs. Journal of Environmental Science and Health Part A. 2006;**41**(9):

[8] Dohányos M, Zábranská J, Jenícek P. Enhancement of sludge anaerobic digestion by using of a special thickening centrifuge. Water Science and Technology. 1997;**36**(11):145-153

[9] Shammas NK, Wang LK. Gravity thickening. In: Biosolids Treatment Processes. Humana Press; 2007.

Publishing; 2007

**References**

CRC Press; 1995

The environmental degradation and energy crisis are two significant issues for global sustainable development. Due to rapid urbanization, industrialization and increase of the growth of population have led to severe substantial waste management problems in several developing countries like India, Malaysia, Nepal, and Bangladesh. As the village develops into towns and cities, in developing countries the disposal of solid waste onto access ways, empty lands, and waterways has been witnessed. Presently, more materials are consumed than required to meet their daily needs by a greedy human. Human beings generate domestic, agricultural, industrial, and medical wastes at every level of development. This waste comprises of both solid and semisolid organic wastes, which may be biodegradable and non-biodegradable. Hence, proper collection and subsequent disposal of waste assumed vital importance in community environmental sanitation programs.

MSW has become one of the significant environmental issues, particularly in developing countries. The solid waste generation mainly consists of biodegradable and non-biodegradable waste materials produced due to several societal activities. The improper dumping of solid waste pollutes the air, soil, and water. The BBMP with an area of 2190 km2 and a population of about 10.18 million generates around 5000 metric tons per day of waste at an average generation rate of 0.5 kg per capita per day (kg/capita/d). Presently, Bengaluru is facing significant problems due to existing disposal practices of generated waste incurring high cost due to lack of proper infrastructural facilities; also the open dumping in the expanding zone of the city poses severe problems to the structures constructed on these old dumps. In the meantime, groundwater quality deteriorated due to improper leachate management [1].

In Bengaluru, there are more than 60 illegal dumpsites identified. While BBMP and the Karnataka State Pollution Control Board (KSPCB) close these dumpsites, the new ones emerge elsewhere, posing health risks to residents in their vicinity. The MSW (Management and Handling) Rules, 2000, recommend source-specific waste collection and transportation in addition to appropriate processing and disposal. There is a lack of knowledge of the quantity and characteristics of reliable waste aids in the preparation of a long-term plan for an MSWM system. So, it was deemed necessary by the BBMP to assess the current status of the municipal solid waste management system in Bengaluru [2].

In this context, the present study discusses the potential improvement in handling the wastes and reduces the amount of waste to be transported and dumped in the landfill. If this waste is used for energy and nutrient recovery, decentralization could also become commercially viable. Moreover, it also addresses the wise technology deficiencies in the existing MSWM system of Bengaluru.

#### **2. Bengaluru scenario**

The city of Bengaluru (12.98°N and 77.58°E) in Karnataka is the state capital, and it has a mild and salubrious climate. It is located at an elevation of 900 m. Since the 1980s, Bengaluru has enjoyed the reputation of being one of the fastest developing cities in Asia [3]. The Bengaluru Metropolitan Area covers an area of 1258 sq. km and is the fifth largest city in India. However, with an increased population level, rapid economic growth, and a rise in community living standard, the generation rate of MSW in metropolitan cities accelerates. The local authorities are struggling to provide the proper solid waste management system to a satisfactory level. Recently the authorities have taken initiatives and measures to organize the MSWM sector. This research would help to identify techniques suitable for the current scenario, the loopholes in the adopted methods, and the possible alternatives.

**67**

**Figure 1.**

*BBMP Zonal organization chart.*

*Solid Waste Management: Current Scenario and Challenges in Bengaluru*

The BBMP has a city council that consists of 123 elected members or councilors,

Presently, the Bruhat Bengaluru Mahanagara Palike is the agency vested with responsibility for effective solid waste management system for the Bengaluru City. For a more efficient and effective approach, the Bengaluru City has been divided into different administrative units. There are 294 health wards within the BBMP. Presently, in Bengaluru, there are 198 such administrative or political wards (**Figure 1**). Within the BBMP, there are two departments, namely, the health department and engineering department. The health department is mainly responsible for the collection, transportation, and disposal of solid waste. The engineering department handles the removal of construction and demolition waste, while they also provide technical and infrastructural support to the health department.

each representing a ward. Both the mayor and deputy mayor are chosen from among councilors for a 1-year term. The BBMP has 15,000 employees and is headed by the commissioner. The commissioner is the head of the BBMP, appointed and deputed by the State Government of Karnataka and responsible for performing

*DOI: http://dx.doi.org/10.5772/intechopen.90837*

**3. Municipal organization**

duties and functions.

### **3. Municipal organization**

*Sustainable Sewage Sludge Management and Resource Efficiency*

The environmental degradation and energy crisis are two significant issues for global sustainable development. Due to rapid urbanization, industrialization and increase of the growth of population have led to severe substantial waste management problems in several developing countries like India, Malaysia, Nepal, and Bangladesh. As the village develops into towns and cities, in developing countries the disposal of solid waste onto access ways, empty lands, and waterways has been witnessed. Presently, more materials are consumed than required to meet their daily needs by a greedy human. Human beings generate domestic, agricultural, industrial, and medical wastes at every level of development. This waste comprises of both solid and semisolid organic wastes, which may be biodegradable and non-biodegradable. Hence, proper collection and subsequent disposal of waste assumed vital importance in community environmental sanitation

MSW has become one of the significant environmental issues, particularly in developing countries. The solid waste generation mainly consists of biodegradable and non-biodegradable waste materials produced due to several societal activities. The improper dumping of solid waste pollutes the air, soil, and water. The BBMP

5000 metric tons per day of waste at an average generation rate of 0.5 kg per capita per day (kg/capita/d). Presently, Bengaluru is facing significant problems due to existing disposal practices of generated waste incurring high cost due to lack of proper infrastructural facilities; also the open dumping in the expanding zone of the city poses severe problems to the structures constructed on these old dumps. In the meantime, groundwater quality deteriorated due to improper leachate manage-

In Bengaluru, there are more than 60 illegal dumpsites identified. While BBMP and the Karnataka State Pollution Control Board (KSPCB) close these dumpsites, the new ones emerge elsewhere, posing health risks to residents in their vicinity. The MSW (Management and Handling) Rules, 2000, recommend source-specific waste collection and transportation in addition to appropriate processing and disposal. There is a lack of knowledge of the quantity and characteristics of reliable waste aids in the preparation of a long-term plan for an MSWM system. So, it was deemed necessary by the BBMP to assess the current status of the municipal solid

In this context, the present study discusses the potential improvement in handling the wastes and reduces the amount of waste to be transported and dumped in the landfill. If this waste is used for energy and nutrient recovery, decentralization could also become commercially viable. Moreover, it also addresses the wise tech-

The city of Bengaluru (12.98°N and 77.58°E) in Karnataka is the state capital, and it has a mild and salubrious climate. It is located at an elevation of 900 m. Since the 1980s, Bengaluru has enjoyed the reputation of being one of the fastest developing cities in Asia [3]. The Bengaluru Metropolitan Area covers an area of 1258 sq. km and is the fifth largest city in India. However, with an increased population level, rapid economic growth, and a rise in community living standard, the generation rate of MSW in metropolitan cities accelerates. The local authorities are struggling to provide the proper solid waste management system to a satisfactory level. Recently the authorities have taken initiatives and measures to organize the MSWM sector. This research would help to identify techniques suitable for the current scenario, the loopholes in the adopted methods, and the possible alternatives.

nology deficiencies in the existing MSWM system of Bengaluru.

and a population of about 10.18 million generates around

**66**

programs.

ment [1].

with an area of 2190 km2

**2. Bengaluru scenario**

waste management system in Bengaluru [2].

The BBMP has a city council that consists of 123 elected members or councilors, each representing a ward. Both the mayor and deputy mayor are chosen from among councilors for a 1-year term. The BBMP has 15,000 employees and is headed by the commissioner. The commissioner is the head of the BBMP, appointed and deputed by the State Government of Karnataka and responsible for performing duties and functions.

Presently, the Bruhat Bengaluru Mahanagara Palike is the agency vested with responsibility for effective solid waste management system for the Bengaluru City. For a more efficient and effective approach, the Bengaluru City has been divided into different administrative units. There are 294 health wards within the BBMP. Presently, in Bengaluru, there are 198 such administrative or political wards (**Figure 1**). Within the BBMP, there are two departments, namely, the health department and engineering department. The health department is mainly responsible for the collection, transportation, and disposal of solid waste. The engineering department handles the removal of construction and demolition waste, while they also provide technical and infrastructural support to the health department.

**Figure 1.** *BBMP Zonal organization chart.*

#### **4. Waste generation**

At present, 10% of solid waste is recycled in Bengaluru. Most of the literature reported that the waste generation rate is 0.4–0.6 kg/capita/day. The proposed waste generation rate is about 0.5 kg/capita/day in Bengaluru [4]. Since 1990, the composition of India's urban wastes has changed drastically. At present, the waste generation is about 5000 metric tons, and waste generation is likely to grow over the coming years. Going by the present trend of increase in the quantity of waste, the waste quantity projected for the next 20 years is shown in **Figure 2**.

#### **4.1 Waste composition**

The changes in the composition of MSW should form essential criteria for any waste management system. Hence, the data available on the composition of the waste from different sources over the years have been collected and analyzed. **Figure 3** shows variation in MSW composition from 1999 to 2013 in Bengaluru City. With the increase in urbanization and change in food habits and lifestyle, the amount of MSW has been multiplying, and there is variation in waste composition.

The changes in the composition of MSW should form essential criteria for any waste management system. Hence, the data available on the composition of the waste from different sources over the years has been collected and analyzed. The data presented in **Table 1** was statistically analyzed to get the variations of a different type of waste in rapidly growing cities like Bangalore.

The MSW composition generated in Bengaluru has changed considerably from 1999 to 2013, which is evident in **Table 1**. It was observed that there was an increase in the biodegradable percentage in Bengaluru City from 42% in 1999 to 61% in 2013, indicating increased organic waste generation in the city, which may be primarily due to increasing population, improper solid waste management, or accumulation of green waste. Similarly, there was a 16% decrease in the paper, cardboard, and leather wastes in Bengaluru City, indicating recycling activities of paper and

**69**

**Figure 3.**

**Table 1.**

*Bangalore's urban waste composition.*

**Year Biodegradable Paper/leather/**

*#All components of MSW are expressed in %.*

**cardboard**

*Source: data extracted from Bangalore's Urban Waste Composition [4–7]*

*Variations in MSW composition in Bangalore City from 1999 to 2013.*

*Solid Waste Management: Current Scenario and Challenges in Bengaluru*

cardboard. A considerable increase in plastic wastes was also observed in 2007, which might be due to the urbanization and increased use of plastic carry bags. In 2013, the percentage of plastic waste decreased to 7%, which may be attributable to the effective ban of plastics carry bags below 40microns within city limits in 2012. The glass, metals, and rubber fraction observed a decrease in MSW composition, indicating the decreased use of glass and metal products and effective recycling of

**Rubber/ debris**

 42 16 10 3 7 2 20 45 13 9 6 6 3 18 59 12 5 3 12 1 8 61 9 4 1 7 1 16

**Glass Plastic Metals Others**

The variations in MSW composition shown in **Figure 4** can be utilized in choosing the best method of MSW disposal in Bengaluru City. Biodegradable percentage (61% in 2013), more than 50%, suggests employment of methods, such as windrow composting, community composting process, pyrolysis, and vermicomposting, which assists in manure generation for agricultural practices; also, biomethanation

glass and metal products by segregation at sources itself.

*DOI: http://dx.doi.org/10.5772/intechopen.90837*

**Figure 2.** *Waste quantity expected for the next 20 years.*

#### *Solid Waste Management: Current Scenario and Challenges in Bengaluru DOI: http://dx.doi.org/10.5772/intechopen.90837*

#### **Figure 3.** *Bangalore's urban waste composition.*


*Source: data extracted from Bangalore's Urban Waste Composition [4–7] #All components of MSW are expressed in %.*

#### **Table 1.**

*Sustainable Sewage Sludge Management and Resource Efficiency*

At present, 10% of solid waste is recycled in Bengaluru. Most of the literature reported that the waste generation rate is 0.4–0.6 kg/capita/day. The proposed waste generation rate is about 0.5 kg/capita/day in Bengaluru [4]. Since 1990, the composition of India's urban wastes has changed drastically. At present, the waste generation is about 5000 metric tons, and waste generation is likely to grow over the coming years. Going by the present trend of increase in the quantity of waste, the

The changes in the composition of MSW should form essential criteria for any waste management system. Hence, the data available on the composition of the waste from different sources over the years have been collected and analyzed. **Figure 3** shows variation in MSW composition from 1999 to 2013 in Bengaluru City. With the increase in urbanization and change in food habits and lifestyle, the amount of MSW has been multiplying, and there is variation in waste

The changes in the composition of MSW should form essential criteria for any waste management system. Hence, the data available on the composition of the waste from different sources over the years has been collected and analyzed. The data presented in **Table 1** was statistically analyzed to get the variations of a differ-

The MSW composition generated in Bengaluru has changed considerably from 1999 to 2013, which is evident in **Table 1**. It was observed that there was an increase in the biodegradable percentage in Bengaluru City from 42% in 1999 to 61% in 2013, indicating increased organic waste generation in the city, which may be primarily due to increasing population, improper solid waste management, or accumulation of green waste. Similarly, there was a 16% decrease in the paper, cardboard, and leather wastes in Bengaluru City, indicating recycling activities of paper and

waste quantity projected for the next 20 years is shown in **Figure 2**.

ent type of waste in rapidly growing cities like Bangalore.

**4. Waste generation**

**4.1 Waste composition**

composition.

**68**

**Figure 2.**

*Waste quantity expected for the next 20 years.*

*Variations in MSW composition in Bangalore City from 1999 to 2013.*

cardboard. A considerable increase in plastic wastes was also observed in 2007, which might be due to the urbanization and increased use of plastic carry bags. In 2013, the percentage of plastic waste decreased to 7%, which may be attributable to the effective ban of plastics carry bags below 40microns within city limits in 2012. The glass, metals, and rubber fraction observed a decrease in MSW composition, indicating the decreased use of glass and metal products and effective recycling of glass and metal products by segregation at sources itself.

The variations in MSW composition shown in **Figure 4** can be utilized in choosing the best method of MSW disposal in Bengaluru City. Biodegradable percentage (61% in 2013), more than 50%, suggests employment of methods, such as windrow composting, community composting process, pyrolysis, and vermicomposting, which assists in manure generation for agricultural practices; also, biomethanation

**Figure 4.** *Variations in MSW composition from 1999 to 2013 in Bangalore City.*

can be employed to produce biogas, which can be utilized as a fuel or alternative source for electricity generation. As the significant composition of MSW is organic, waste treatment options like composting were successful in Bangalore, and 3.14% waste reduction was achieved through composting [8].

#### **5. Collection and transportation of waste**

The objective of solid waste management is to remove discarded materials from inhabited places promptly to prevent the spread of disease, to reduce esthetic results arising from purifying organic matter, and, equally important, to dispose of the discarded materials in a manner that is environmentally acceptable [9].

#### **5.1 Collection**

Currently, in Bengaluru, source segregation is still a concern through awareness in picking up slowly. BBMP handles about 30% of solid waste, and the remaining waste activity is outsourced (starting from primary collection to disposal). Solid waste collection is carried out in two phases. The first phase is a primary collection, in which the solid waste is collected on auto tipper and pushcarts. An auto tipper has been provided for every 1000 households and a cart for every 200 homes. About 20,000 pourakarmikas are being utilized (both BBMP and contractors) in the door to door collection, street sweeping, and transportation of MSW. The collected solid waste from houses is brought to a common point, i.e., secondary locations from where the waste is transferred to landfill sites/treatment through tipper lorries and compactors. **Figure 5** indicates a typical scheme of how the collection and transportation are being practiced in most of the wards.

This activity is assigned to self-help groups (SHGs), which are basically below poverty women's groups. BBMP has allocated 3197 pourakarmikas (sweepers) and 18,562 pourakarmikas from a contractor who performs door to door collection and sweeping activities. Annually about 250 crores are spent on solid waste management, i.e., BBMP pourakarmika salary, contract payment, and tipping fees (**Figure 6**).

The survey carried out in Malleswaram by [10] indicated that no norms/guidelines had been followed in setting up waste segregation practices adopted in this ward. There is a lack of awareness among people that leads to confusion. The six

**71**

need to be effected.

*MSW collection process in a typical residential/commercial area.*

**Figure 6.**

**Figure 5.**

*MSW collection system.*

**5.2 Transportation**

*Solid Waste Management: Current Scenario and Challenges in Bengaluru*

categories for segregation mandated by BBMP are overwhelming and are a deterrent to segregation. The waste collectors (pourakarmikas) lack training in proper segregation practices and its importance. Incomplete segregation is the predominant practice currently, and steps to realize a higher level of compliance and efficiency

Transportation of waste from collection centers to the landfill site is another crucial step in waste management. At present, waste transportation is using pushcarts, auto, etc., which bring waste to primary collection centers. From there, trucks collect the municipal solid waste and transport it to waste disposal sites/landfill.

*DOI: http://dx.doi.org/10.5772/intechopen.90837*

*Solid Waste Management: Current Scenario and Challenges in Bengaluru DOI: http://dx.doi.org/10.5772/intechopen.90837*

**Figure 5.** *MSW collection system.*

*Sustainable Sewage Sludge Management and Resource Efficiency*

waste reduction was achieved through composting [8].

*Variations in MSW composition from 1999 to 2013 in Bangalore City.*

**5. Collection and transportation of waste**

tation are being practiced in most of the wards.

can be employed to produce biogas, which can be utilized as a fuel or alternative source for electricity generation. As the significant composition of MSW is organic, waste treatment options like composting were successful in Bangalore, and 3.14%

The objective of solid waste management is to remove discarded materials from inhabited places promptly to prevent the spread of disease, to reduce esthetic results arising from purifying organic matter, and, equally important, to dispose of the

Currently, in Bengaluru, source segregation is still a concern through awareness in picking up slowly. BBMP handles about 30% of solid waste, and the remaining waste activity is outsourced (starting from primary collection to disposal). Solid waste collection is carried out in two phases. The first phase is a primary collection, in which the solid waste is collected on auto tipper and pushcarts. An auto tipper has been provided for every 1000 households and a cart for every 200 homes. About 20,000 pourakarmikas are being utilized (both BBMP and contractors) in the door to door collection, street sweeping, and transportation of MSW. The collected solid waste from houses is brought to a common point, i.e., secondary locations from where the waste is transferred to landfill sites/treatment through tipper lorries and compactors. **Figure 5** indicates a typical scheme of how the collection and transpor-

This activity is assigned to self-help groups (SHGs), which are basically below poverty women's groups. BBMP has allocated 3197 pourakarmikas (sweepers) and 18,562 pourakarmikas from a contractor who performs door to door collection and sweeping activities. Annually about 250 crores are spent on solid waste management, i.e., BBMP pourakarmika salary, contract payment, and tipping fees

The survey carried out in Malleswaram by [10] indicated that no norms/guidelines had been followed in setting up waste segregation practices adopted in this ward. There is a lack of awareness among people that leads to confusion. The six

discarded materials in a manner that is environmentally acceptable [9].

**70**

(**Figure 6**).

**5.1 Collection**

**Figure 4.**

#### **Figure 6.**

*MSW collection process in a typical residential/commercial area.*

categories for segregation mandated by BBMP are overwhelming and are a deterrent to segregation. The waste collectors (pourakarmikas) lack training in proper segregation practices and its importance. Incomplete segregation is the predominant practice currently, and steps to realize a higher level of compliance and efficiency need to be effected.

#### **5.2 Transportation**

Transportation of waste from collection centers to the landfill site is another crucial step in waste management. At present, waste transportation is using pushcarts, auto, etc., which bring waste to primary collection centers. From there, trucks collect the municipal solid waste and transport it to waste disposal sites/landfill.

The issues in transporting waste are mentioned below:


#### **5.3 Effective solid waste management**

Based on the above-presented data and analysis, for effective solid waste management, the following suggestion can be made:


### **6. Waste disposal practices in Bengaluru**

Currently Bengaluru does not have any appropriate scientific treatment techniques for waste generated by municipal and industries around Bengaluru. This has led to the development of various unauthorized dumpsites. The solid waste, generated from hotels, restaurants, Kalyana mandapas, markets, etc., is being directly collected and transported to the treatment/disposal facilities. The treatment facilities have been developed around the city, and their spread over the zone is set out in **Table 2**.

#### **7. Decentralized waste processing plant in Bengaluru**

For making effective solid waste management services, it is essential to select appropriate technology, which can suit and work in the given area successfully.

**73**

are precious.

**Table 2.**

of this way.

**7.1 Dry waste collection center**

returns and creates more jobs.

**7.2 Sanitary landfill site**

*Solid Waste Management: Current Scenario and Challenges in Bengaluru*

6 Mahadevapura Terrafirma 7 Dasarahalli MSGP

8 Raja Rajeshwari Nagar MSGP/Terrafirma

**Sl. No Zone Existing disposal site/facility** South Bingipura, Mavallipura, KCDC East MSGP, Mavallipura, KCDC West Terra firma, Mavallipura, KCDC Yelahanka Mavallipura, Terrafirma Bommanahalli Bingipura, Laxmipura

Simultaneously, proper measures have to be considered for institutional strengthening and internal capacity building. Institutional strengthening can be done by adequately decentralizing the administration, delegating adequate powers at the decentralized level, providing training to the existing staff, and assigning the responsibility for the workforce as well as for supervisory staff. NGO/private sector participation is necessary for making service competitive and efficient. The land is scarce, and public health and environmental resources

In this direction, many decentralized facilities are being established. The decentralization of administration has to be implemented in large cities to make solid waste management service effectively. Decentralization can be divided into three tiers one at the ward level, second at the zone level, and third at the city level. The BBMP established the decentralized processing units for dry waste; details are as follows.

Dry waste materials like batteries, tin cans, plastic-coated milk cartons, nylon, cigarette butts, and leather all take varying lengths of time to degrade: not less than 10 years. Hence, the best way to dispose of these dry waste items is to reuse/ recycle them. Nearly 70% of all the dry waste thrown away can be safely disposed

The aim of Dry Waste Collection Centers (DWCCs) is to keep as much waste out of the landfills/waste dumps as possible and to help make waste useful and profitable. DWCCs run by various agencies in Bengaluru in coordination with the BBMP is decentralized bulk sorting and processing facilities. About 185 DWCCs have been established and functional. DWCCs are set up on municipal/government/private lands and various NGOs, waste pickers, and contractors; self-help groups have been involved for effective functioning. The dry waste generated in the wards is collected and further segregated and sent for recycling from these recycling centers. Receiving in bulk provides these informal sector workers with more significant

Currently, Bengaluru can handle the waste of about 2100 TPD. The existing capacity of waste treatment facility at Mavallipura is 600TPD, Karnataka Composting Development Corporation Ltd. (KCDC) is 300TPD, and Terra Firma is about 1500 TPD as shown in **Figure 7**. For achieving 100% processing of solid

*DOI: http://dx.doi.org/10.5772/intechopen.90837*

*Existing treatment and disposal facilities in BBMP.*

*Solid Waste Management: Current Scenario and Challenges in Bengaluru DOI: http://dx.doi.org/10.5772/intechopen.90837*


**Table 2.**

*Sustainable Sewage Sludge Management and Resource Efficiency*

transport, thereby causing a nuisance.

dangerous to the health of workers.

vehicles.

The issues in transporting waste are mentioned below:

secondary storage system is still dumped on the ground.

to the contractors with the performance in segregation.

decentralized as well as zone-wise processing units.

**7. Decentralized waste processing plant in Bengaluru**

**6. Waste disposal practices in Bengaluru**

tralized processing for dry waste collection center at the source.

and they become out of service for a long time.

**5.3 Effective solid waste management**

going to the landfill sites.

agement, the following suggestion can be made:

• The waste spills from the trucks due to open beds in trucks and tractors, during

system. Problems arise when a transport fleet is modernized because waste at a

• Solid waste loaded manually in a truck without using the protective gears is

• A secondary storage system is not well synchronized with the transport

• The area cannot be appropriately serviced due to an inadequate number of

• Due to inadequate workshop facilities and maintenance procedures, the vehicles are poorly maintained. This problem leads to a breakdown of trucks,

Based on the above-presented data and analysis, for effective solid waste man-

1.Establish the segregation at the source itself, and encourage by giving incentive

2.Establish the wet waste processing units for composting, and encourage decen-

3.Set up the segregation units and zone-wise processing facilities to ensure 100% processing of municipal solid waste, and minimize the solid waste quantity

4.Reduce transportation of municipal solid waste using the above measures of

Currently Bengaluru does not have any appropriate scientific treatment techniques for waste generated by municipal and industries around Bengaluru. This has led to the development of various unauthorized dumpsites. The solid waste, generated from hotels, restaurants, Kalyana mandapas, markets, etc., is being directly collected and transported to the treatment/disposal facilities. The treatment facilities have been developed around the city, and their spread over the zone

For making effective solid waste management services, it is essential to select appropriate technology, which can suit and work in the given area successfully.

**72**

is set out in **Table 2**.

*Existing treatment and disposal facilities in BBMP.*

Simultaneously, proper measures have to be considered for institutional strengthening and internal capacity building. Institutional strengthening can be done by adequately decentralizing the administration, delegating adequate powers at the decentralized level, providing training to the existing staff, and assigning the responsibility for the workforce as well as for supervisory staff. NGO/private sector participation is necessary for making service competitive and efficient. The land is scarce, and public health and environmental resources are precious.

In this direction, many decentralized facilities are being established. The decentralization of administration has to be implemented in large cities to make solid waste management service effectively. Decentralization can be divided into three tiers one at the ward level, second at the zone level, and third at the city level. The BBMP established the decentralized processing units for dry waste; details are as follows.

#### **7.1 Dry waste collection center**

Dry waste materials like batteries, tin cans, plastic-coated milk cartons, nylon, cigarette butts, and leather all take varying lengths of time to degrade: not less than 10 years. Hence, the best way to dispose of these dry waste items is to reuse/ recycle them. Nearly 70% of all the dry waste thrown away can be safely disposed of this way.

The aim of Dry Waste Collection Centers (DWCCs) is to keep as much waste out of the landfills/waste dumps as possible and to help make waste useful and profitable. DWCCs run by various agencies in Bengaluru in coordination with the BBMP is decentralized bulk sorting and processing facilities. About 185 DWCCs have been established and functional. DWCCs are set up on municipal/government/private lands and various NGOs, waste pickers, and contractors; self-help groups have been involved for effective functioning. The dry waste generated in the wards is collected and further segregated and sent for recycling from these recycling centers. Receiving in bulk provides these informal sector workers with more significant returns and creates more jobs.

#### **7.2 Sanitary landfill site**

Currently, Bengaluru can handle the waste of about 2100 TPD. The existing capacity of waste treatment facility at Mavallipura is 600TPD, Karnataka Composting Development Corporation Ltd. (KCDC) is 300TPD, and Terra Firma is about 1500 TPD as shown in **Figure 7**. For achieving 100% processing of solid

**Figure 7.** *Sanitary landfill sites in Bangalore.*

waste, the government has identified new landfill sites. These sites are being set up at the following locations: Kannahalli (500TPD), Seegihalli (200TPD), Doddabidarakallu (200TPD), Lingaderenahalli (200TPD), Subrayanpalya (200TPD), Chikkanagamangala (500TPD), and KCDC (upgradation) (500TPD). Majorly we waste composting plants with a provision to screen compost out of mixed MSW and provision also to store the non-compostable/non-recyclable materials. These materials can be used for co-incineration in cement industries/ power generation [4].

### **8. Emerging technologies for wet waste disposal**

Once the solid waste is collected from the different sectors of the community, the next problem is regarding the safe, economical, and efficient disposal options. Suitable decisions have to be made in this regard to avoid illegal dumping and open dumping of solid wastes that are dangerous and a threat to the environment. Open burning of solid wastes releases smoke containing pollutants harmful to human health and the environment. Therefore, the community has to face severe inconveniences due to illegal dumping practices. Hence, conventional methods employed to safe disposal options of MSW include composting, waste to energy (such as biogas production and incineration), and landfilling. Incineration and composting of MSW are a standard solid waste treatment or processing methods, as they produce secondary waste such as non-biodegradable material rejects from composting and ash from incineration that needs to be disposed of further [11].

#### **8.1 Aerobic composting**

Aerobic composting process involves piling up of waste and requires regular turning, manually or by mechanical devices, and sufficient air, and oxygen has to

**75**

*Solid Waste Management: Current Scenario and Challenges in Bengaluru*

of the compost should have a dark brown color and earthy smell.

doing so adds to the initial costs of the operation [11].

the process, lowering the quality produced.

4.In the rainy season, the process cannot be carried out.

3.Lack of continuous power supply.

**8.3 Community composting**

The following are the challenges in windrow composting:

be provided during the decomposition by bacteria, fungi, and microorganisms like actinomycetes. A mesophilic bacterium is an initial process, which oxidizes the organic matter to carbon dioxide and generates the heat and temperature rise to about 45°C. In the next process, thermophilic bacteria continue the decomposition; in this phase, temperature further rises to about 60°C. Three weeks is required for stabilized compost and fall in temperature of the compost mass. The final product

The waste is dumped in the windrow platform; large items like woods, plastics, clothes, thermocol, etc. are removed; and inoculum will be sprayed on the waste. The inoculum will be prepared using the mixture of bacteria, cow dung, and water. The treated waste is then heaped in windrows with long rows approximately 2 meters in height and 3 meters in width; length will be depending on the size of the landfill site. There are seven rows, each row for each day of the week. Every week these rows are turned for 5 weeks. These rows are turned to remove moisture, improve porosity and oxygen content, and redistribute hotter and colder portions of the pile. As time passes, the sizes of the rows get reduced due to the decomposition of the waste and the resultant volume reduction. Hence, the number of final rows will be decreased than the number of initial rows. Composting will be completed in 25–30 days. This interval is known as maturation in which waste will undergo mechanical process operation. In mechanical processing, sieving occurs in three stages: in the first stage, sieve employs 36 mm mesh, the second stage applies 16 mm mesh, and the third stage has a 4 mm mesh, as shown in **Figure 8**. At each stage of sieving the reject, materials are separated and either reused or disposed of at the landfill. Any leachate or runoff created must be collected and treated. To avoid problems with leachate or runoff, waste piles can be placed under a roof, but

1.Minor mechanical fault leads to a breakdown due to the unavailability of spare

2.The major difficulty is due to the nature of waste. Pulverizers get frequently clogged with pieces of plastic, rubber, leathers, etc., and due to metal and glass pieces, the blades breakdown. If waste is mixed with soil, it causes a problem in

In this process, daily wet waste is collected by the housekeeping staff, directly dumping into the tank. After filling, the tank is covered with a layer of refuse 15–20 cm deep. The materials are allowed to remain in the pit without turning and watering for 3 months. To keep the decomposers working, the aeration aid is needed during the initial pile construction. As long as plenty of air is available, aerobic decomposers work faster and more efficiently, providing you with finished compost on a more rapid time. Charcoal is placed in the tank. Hence, foul smell is avoided. It takes about 3 months to obtain the finished product. Community composting process is shown in **Figure 9**.

*DOI: http://dx.doi.org/10.5772/intechopen.90837*

**8.2 Windrow composting**

parts.

*Solid Waste Management: Current Scenario and Challenges in Bengaluru DOI: http://dx.doi.org/10.5772/intechopen.90837*

be provided during the decomposition by bacteria, fungi, and microorganisms like actinomycetes. A mesophilic bacterium is an initial process, which oxidizes the organic matter to carbon dioxide and generates the heat and temperature rise to about 45°C. In the next process, thermophilic bacteria continue the decomposition; in this phase, temperature further rises to about 60°C. Three weeks is required for stabilized compost and fall in temperature of the compost mass. The final product of the compost should have a dark brown color and earthy smell.

#### **8.2 Windrow composting**

*Sustainable Sewage Sludge Management and Resource Efficiency*

waste, the government has identified new landfill sites. These sites are being set up at the following locations: Kannahalli (500TPD), Seegihalli (200TPD), Doddabidarakallu (200TPD), Lingaderenahalli (200TPD), Subrayanpalya (200TPD), Chikkanagamangala (500TPD), and KCDC (upgradation) (500TPD). Majorly we waste composting plants with a provision to screen compost out of mixed MSW and provision also to store the non-compostable/non-recyclable materials. These materials can be used for co-incineration in cement industries/

Once the solid waste is collected from the different sectors of the community, the next problem is regarding the safe, economical, and efficient disposal options. Suitable decisions have to be made in this regard to avoid illegal dumping and open dumping of solid wastes that are dangerous and a threat to the environment. Open burning of solid wastes releases smoke containing pollutants harmful to human health and the environment. Therefore, the community has to face severe inconveniences due to illegal dumping practices. Hence, conventional methods employed to safe disposal options of MSW include composting, waste to energy (such as biogas production and incineration), and landfilling. Incineration and composting of MSW are a standard solid waste treatment or processing methods, as they produce secondary waste such as non-biodegradable material rejects from composting and

Aerobic composting process involves piling up of waste and requires regular turning, manually or by mechanical devices, and sufficient air, and oxygen has to

**8. Emerging technologies for wet waste disposal**

ash from incineration that needs to be disposed of further [11].

**74**

power generation [4].

*Sanitary landfill sites in Bangalore.*

**Figure 7.**

**8.1 Aerobic composting**

The waste is dumped in the windrow platform; large items like woods, plastics, clothes, thermocol, etc. are removed; and inoculum will be sprayed on the waste. The inoculum will be prepared using the mixture of bacteria, cow dung, and water. The treated waste is then heaped in windrows with long rows approximately 2 meters in height and 3 meters in width; length will be depending on the size of the landfill site. There are seven rows, each row for each day of the week. Every week these rows are turned for 5 weeks. These rows are turned to remove moisture, improve porosity and oxygen content, and redistribute hotter and colder portions of the pile. As time passes, the sizes of the rows get reduced due to the decomposition of the waste and the resultant volume reduction. Hence, the number of final rows will be decreased than the number of initial rows. Composting will be completed in 25–30 days. This interval is known as maturation in which waste will undergo mechanical process operation. In mechanical processing, sieving occurs in three stages: in the first stage, sieve employs 36 mm mesh, the second stage applies 16 mm mesh, and the third stage has a 4 mm mesh, as shown in **Figure 8**. At each stage of sieving the reject, materials are separated and either reused or disposed of at the landfill. Any leachate or runoff created must be collected and treated. To avoid problems with leachate or runoff, waste piles can be placed under a roof, but doing so adds to the initial costs of the operation [11].

The following are the challenges in windrow composting:


#### **8.3 Community composting**

In this process, daily wet waste is collected by the housekeeping staff, directly dumping into the tank. After filling, the tank is covered with a layer of refuse 15–20 cm deep. The materials are allowed to remain in the pit without turning and watering for 3 months. To keep the decomposers working, the aeration aid is needed during the initial pile construction. As long as plenty of air is available, aerobic decomposers work faster and more efficiently, providing you with finished compost on a more rapid time. Charcoal is placed in the tank. Hence, foul smell is avoided. It takes about 3 months to obtain the finished product. Community composting process is shown in **Figure 9**.

**Figure 8.** *Windrow composting process.*

**77**

**Figure 10.**

*Biomechanical process.*

*Solid Waste Management: Current Scenario and Challenges in Bengaluru*

In this process, organic waste such as vegetable and fruit peels and food leftovers, bones, meat, eggshells, household sweeping dry leaves, garden waste, cattle dung, etc. collected from the apartments and other places were identified for segregation for removal of plastic, glass, clothes, paper, leather, etc. for recycling purposes. After segregation of organic waste, it is then fed into the mechanical unit (i.e., organic waste converter) which converts this into a homogenized, crushed, odor-free output (**Figure 10**). The output goes to the curing system for stabilization. Aerobic microbial decomposition controls the entire process; the transition takes place from low pH levels to high pH levels and then stabilizes. This manure is free from weed, foul smell, and pathogen as the process is aerobic. This is environment-friendly operation; this system takes only 15 min to convert the organic waste

More than 50,000 populations of worms can support the moist compost heap of 2.4 m by 1.2 m and 0.6 m high. Organic residues such as straw and other crop residues, animal manure, green weeds, and leaves are filled in the pit and covered loosely with soil and kept moist for a weak. On the top of the heap, well-watered, the worms will be introduced, and air is provided for quick decomposition. *Lumbricus rubellus* (red worm) and *Eisenia foetida* are thermo-tolerant and are particularly useful for vermicomposting. Ideally, the compost pits were left for 2 months, and such pits should be shaded from hot sunshine and kept moistly. 1 kg of worms can produce 10 kg of castings within 2 months. Then the pit will be excavated to the extent of about two-thirds to three-quarters, and worms will be removed by hand (**Figure 11**). The remaining worms will be left in the pit itself for further composting with fresh organic residues. To get a good quality of compost

*DOI: http://dx.doi.org/10.5772/intechopen.90837*

**8.4 Biomechanical composting**

into a homogenized output.

**8.5 Vermicomposting**

**Figure 9.** *Community composting process.*

### **8.4 Biomechanical composting**

*Sustainable Sewage Sludge Management and Resource Efficiency*

**76**

**Figure 9.**

**Figure 8.**

*Windrow composting process.*

*Community composting process.*

In this process, organic waste such as vegetable and fruit peels and food leftovers, bones, meat, eggshells, household sweeping dry leaves, garden waste, cattle dung, etc. collected from the apartments and other places were identified for segregation for removal of plastic, glass, clothes, paper, leather, etc. for recycling purposes. After segregation of organic waste, it is then fed into the mechanical unit (i.e., organic waste converter) which converts this into a homogenized, crushed, odor-free output (**Figure 10**). The output goes to the curing system for stabilization. Aerobic microbial decomposition controls the entire process; the transition takes place from low pH levels to high pH levels and then stabilizes. This manure is free from weed, foul smell, and pathogen as the process is aerobic. This is environment-friendly operation; this system takes only 15 min to convert the organic waste into a homogenized output.

#### **8.5 Vermicomposting**

More than 50,000 populations of worms can support the moist compost heap of 2.4 m by 1.2 m and 0.6 m high. Organic residues such as straw and other crop residues, animal manure, green weeds, and leaves are filled in the pit and covered loosely with soil and kept moist for a weak. On the top of the heap, well-watered, the worms will be introduced, and air is provided for quick decomposition. *Lumbricus rubellus* (red worm) and *Eisenia foetida* are thermo-tolerant and are particularly useful for vermicomposting. Ideally, the compost pits were left for 2 months, and such pits should be shaded from hot sunshine and kept moistly. 1 kg of worms can produce 10 kg of castings within 2 months. Then the pit will be excavated to the extent of about two-thirds to three-quarters, and worms will be removed by hand (**Figure 11**). The remaining worms will be left in the pit itself for further composting with fresh organic residues. To get a good quality of compost

**Figure 10.** *Biomechanical process.*

**Figure 11.** *Vermicomposting process.*

material, sun-drying and sieving have to be carried out. The end product of compost is an ideal constitution and structure. For vermicompost, the unit has to be protected against chicken, other birds, rodents, and heavy rains.

The following are challenges in vermicomposting:


#### **9. Waste-to-energy technology**

Some demonstrated technology approaches are available for waste-to-energy (WTE) projects today which are anaerobic processing/biogas production, refusederived fuel (RDF), and plasma gasification.

#### **9.1 Biogas production/anaerobic processing**

Biomethaization plants are being established for wet solid waste at 16 locations, out of which 8 have been made functional. 400 units are generated per day per plant. The biogas produced from the bio-mechanization of plants is being utilized to light the street lights in that locality.

**79**

**Figure 12.**

*Biomethanation process.*

*Solid Waste Management: Current Scenario and Challenges in Bengaluru*

The following are the disadvantages of anaerobic processing:

2.It is challenging to increase the efficiency of biogas systems.

1.In a large industrial scale, this process is not very economical compared to

3.The gasses come out from biogas as impurities, which are corrosive to the metal

RDF plants are in the initial stage of development in India. In this process, plenty of combustible components of MSW, such as plastic, cardboard, paper, and biodegradable waste, are converted into fuel pellets. It mainly involves drying, separation of combustion from MSW, size reduction, and pelletization after mixing

Biogas is produced in the absence of oxygen or an anaerobic environment, due to the decomposition of organic material through certain bacteria. The whole process is referred as anaerobic digestion because biological decomposition takes place in a reactor, where bacteria produce biogas. This biomass can stay in the reactor for about 2–3 weeks. In the end, the by-product produced in this process is a solid residue that is high-grade manure. Generally, in the biogas plant, biomass like vegetable wastes and animal excreta undergo decomposition in the absence of oxygen and form a mixture of gasses. Biogas consists of about 2/3 methane (CH4), 1/3 carbon dioxide (CO2), a little hydrogen sulfide (H2S), and a low hydrogen (H2). It is created by the decomposition of manure and other forms of organic waste from households or industries in anaerobic tanks where it is heated (**Figure 12**). The biogas is used

*DOI: http://dx.doi.org/10.5772/intechopen.90837*

for cooking and lighting purposes.

parts of internal combustion engines.

4.Not feasible to locate at all the locations.

biofuel.

**9.2 Refuse-derived fuel**

*Solid Waste Management: Current Scenario and Challenges in Bengaluru DOI: http://dx.doi.org/10.5772/intechopen.90837*

Biogas is produced in the absence of oxygen or an anaerobic environment, due to the decomposition of organic material through certain bacteria. The whole process is referred as anaerobic digestion because biological decomposition takes place in a reactor, where bacteria produce biogas. This biomass can stay in the reactor for about 2–3 weeks. In the end, the by-product produced in this process is a solid residue that is high-grade manure. Generally, in the biogas plant, biomass like vegetable wastes and animal excreta undergo decomposition in the absence of oxygen and form a mixture of gasses. Biogas consists of about 2/3 methane (CH4), 1/3 carbon dioxide (CO2), a little hydrogen sulfide (H2S), and a low hydrogen (H2). It is created by the decomposition of manure and other forms of organic waste from households or industries in anaerobic tanks where it is heated (**Figure 12**). The biogas is used for cooking and lighting purposes.

The following are the disadvantages of anaerobic processing:


#### **9.2 Refuse-derived fuel**

*Sustainable Sewage Sludge Management and Resource Efficiency*

material, sun-drying and sieving have to be carried out. The end product of compost is an ideal constitution and structure. For vermicompost, the unit has to be

1.This concept is suitable for only small-scale applications and not an appropriate solution for large-scale application, e.g., 100–300MT/d capacity plants.

2.The exotic species are found to be costing between Rs. 500 and 1000/kg, and

3.The raw waste cannot be fed directly to earthworms, thus necessitating the

4.Earthworms are so sensitive to temperature (ideally between 20 and 28°C);

Some demonstrated technology approaches are available for waste-to-energy (WTE) projects today which are anaerobic processing/biogas production, refuse-

Biomethaization plants are being established for wet solid waste at 16 locations,

out of which 8 have been made functional. 400 units are generated per day per plant. The biogas produced from the bio-mechanization of plants is being utilized

protected against chicken, other birds, rodents, and heavy rains.

indigenous species of earthworms are not found useful.

worms die due to heat built up in the rotting pile or summer.

The following are challenges in vermicomposting:

pre-processing of waste to avoid toxicity.

**9. Waste-to-energy technology**

derived fuel (RDF), and plasma gasification.

**9.1 Biogas production/anaerobic processing**

to light the street lights in that locality.

**78**

**Figure 11.**

*Vermicomposting process.*

RDF plants are in the initial stage of development in India. In this process, plenty of combustible components of MSW, such as plastic, cardboard, paper, and biodegradable waste, are converted into fuel pellets. It mainly involves drying, separation of combustion from MSW, size reduction, and pelletization after mixing

**Figure 12.** *Biomethanation process.*

with binder and additives as required. If MSW contains 35–40% moisture content, then it involves air-drying for 2 days. Then the waste is spread, and manual inspection is carried out to remove large size debris, tires, tree stones, tree trunk, etc. The air-dried MSW is fed uniformly into a rotary drying system, i.e., hot air generation burning oversized wastes. 10–12% moisture content is suitable to be maintained in MSW for densifying into fuel pellets.

After air-drying, MSW is passed through screening equipment (below 8 mm) to separate heavier combustibles and ferrous materials; it may cause harm to process equipment. Fine fraction contains organic matter, and it is already proven to be useful as garden manure.

Air-dried waste is then passed through the density separator; here light combustibles and an air barrier separate dense fractions (e.g., stones, glass, etc.). Parallel MSW is passed over a magnetic separation unit to remove magnetic materials. The binder and additives are mixed with ground solid waste in the mixer before pelletizing. Once pellets are coming out from the pelletizer, they are cooled and stored for dispatch. The RDF pellets are used as a coal substitute at a lower price.

#### **9.3 Plasma gasification**

In plasma gasification, the process converts all types of wastes into a synthesis gas composed of hydrogen, nitrogen, carbon monoxide, and water. This synthesis gas can be used to generate electrical power and useful liquid fuel, such as ethanol.

The following are the advantages of plasma gasification:


**81**

communities.

*Solid Waste Management: Current Scenario and Challenges in Bengaluru*

In this section are some of the options available for waste disposal. However, it should be noted that the option selected for waste disposal must mesh with the

It is a thermal process for burning highly combustible waste like plastics, cardboard, paper, and rubber and combustible wastes like cartoons, wood scrap, floor sweepings, and food wastes at a very high temperature. The method does not apply to Indian conditions due to high dust and ash content of wastes; high capital costs, especially for adequate control of emissions; high operation and maintenance costs; and the need for skilled human resources. However, incineration is also associated with the production and release of carcinogenic and toxic compounds. Therefore, the incineration process is not environmentally friendly and is hence usually not

Pyrolysis is also known as thermal pyrolysis. The combustion process is highly exothermic (releasing heat on burning in the presence of oxygen) in nature, whereas pyrolysis is highly endothermic (consuming flame) in the environment. Hence, the process of pyrolysis is known as destructive distillation. In this method, the solid wastes are heated under anaerobic conditions (i.e., burning without oxygen). The organic components of the solid wastes split up into volatile liquid and gaseous fractions (CO, CO2, CH4, tar, charred carbon). Pyrolysis cannot handle a wide variety of wastes that exists and will only have a small impact on the overall processing of waste.

Transportation is a necessary function for solid waste management activities since municipal solid waste, recyclables, yard waste, and other materials must be collected and transported to be managed. There are various methods for collecting and transporting waste, the choice of which depends on the type of solid waste, the

A vital component of a reliable and well-run solid waste management system is to set up an efficient sanitary landfill and customer-responsive collection and disposal of solid waste. Waste collection services are provided to residents in all cities, either private or self-government agencies. In the meantime, the rapid increase in disposal costs across the city, the cost of collection, and the transfer of wastes continue to raise disposal as a percentage of overall service costs for most

For collection and transfer, waste systems are often complex and challenging to design, because several factors must be considered and a wide range of collection and transfer options are available. The community participation is essential for an efficient MSWM system. However, the municipal authorities have failed to mobilize the community and educate citizens on the principles of handling waste and proper practices of storing it in their bins at the shop, household, etc. Due to the lack of an essential facility of collection of waste from source, citizens are likely to dump

*DOI: http://dx.doi.org/10.5772/intechopen.90837*

**10.1 Incineration**

**10.2 Pyrolysis**

**10. Options available for waste disposal**

existing sociocultural milieu, infrastructure, etc.

recommended as a solid waste disposal technique.

**11. Problems with existing MSW disposal practices**

source of solid waste, and the proper management method used.

The following are the disadvantages of the plasma gasification:


### **10. Options available for waste disposal**

In this section are some of the options available for waste disposal. However, it should be noted that the option selected for waste disposal must mesh with the existing sociocultural milieu, infrastructure, etc.

#### **10.1 Incineration**

*Sustainable Sewage Sludge Management and Resource Efficiency*

MSW for densifying into fuel pellets.

useful as garden manure.

**9.3 Plasma gasification**

2.Waste to energy.

our landscape.

2.Financial risk

3.Technical risk

4.Economics

lower price.

ethanol.

with binder and additives as required. If MSW contains 35–40% moisture content, then it involves air-drying for 2 days. Then the waste is spread, and manual inspection is carried out to remove large size debris, tires, tree stones, tree trunk, etc. The air-dried MSW is fed uniformly into a rotary drying system, i.e., hot air generation burning oversized wastes. 10–12% moisture content is suitable to be maintained in

After air-drying, MSW is passed through screening equipment (below 8 mm) to separate heavier combustibles and ferrous materials; it may cause harm to process equipment. Fine fraction contains organic matter, and it is already proven to be

Air-dried waste is then passed through the density separator; here light combustibles and an air barrier separate dense fractions (e.g., stones, glass, etc.). Parallel MSW is passed over a magnetic separation unit to remove magnetic materials. The binder and additives are mixed with ground solid waste in the mixer before pelletizing. Once pellets are coming out from the pelletizer, they are cooled and stored for dispatch. The RDF pellets are used as a coal substitute at a

In plasma gasification, the process converts all types of wastes into a synthesis gas composed of hydrogen, nitrogen, carbon monoxide, and water. This synthesis gas can be used to generate electrical power and useful liquid fuel, such as

3.A 120 megawatt (MW) facility will require, on average, consuming 3000 tons

4.The plasma system can be retrofit on the existing power-generating plants,

5.Plasma systems can use old landfills, thoroughly cleaning up and beautifying

6.Plasma gasification is an affordable, cost-effective solution compared to other

The following are the disadvantages of the plasma gasification:

The following are the advantages of plasma gasification:

1.No segregation of MSW needed.

of garbage per day (Mt garbage/d).

alternative energy solutions.

1.Lack of regulations needed for permits

reducing time, and greenhouse gas emission.

**80**

It is a thermal process for burning highly combustible waste like plastics, cardboard, paper, and rubber and combustible wastes like cartoons, wood scrap, floor sweepings, and food wastes at a very high temperature. The method does not apply to Indian conditions due to high dust and ash content of wastes; high capital costs, especially for adequate control of emissions; high operation and maintenance costs; and the need for skilled human resources. However, incineration is also associated with the production and release of carcinogenic and toxic compounds. Therefore, the incineration process is not environmentally friendly and is hence usually not recommended as a solid waste disposal technique.

#### **10.2 Pyrolysis**

Pyrolysis is also known as thermal pyrolysis. The combustion process is highly exothermic (releasing heat on burning in the presence of oxygen) in nature, whereas pyrolysis is highly endothermic (consuming flame) in the environment. Hence, the process of pyrolysis is known as destructive distillation. In this method, the solid wastes are heated under anaerobic conditions (i.e., burning without oxygen). The organic components of the solid wastes split up into volatile liquid and gaseous fractions (CO, CO2, CH4, tar, charred carbon). Pyrolysis cannot handle a wide variety of wastes that exists and will only have a small impact on the overall processing of waste.

#### **11. Problems with existing MSW disposal practices**

Transportation is a necessary function for solid waste management activities since municipal solid waste, recyclables, yard waste, and other materials must be collected and transported to be managed. There are various methods for collecting and transporting waste, the choice of which depends on the type of solid waste, the source of solid waste, and the proper management method used.

A vital component of a reliable and well-run solid waste management system is to set up an efficient sanitary landfill and customer-responsive collection and disposal of solid waste. Waste collection services are provided to residents in all cities, either private or self-government agencies. In the meantime, the rapid increase in disposal costs across the city, the cost of collection, and the transfer of wastes continue to raise disposal as a percentage of overall service costs for most communities.

For collection and transfer, waste systems are often complex and challenging to design, because several factors must be considered and a wide range of collection and transfer options are available. The community participation is essential for an efficient MSWM system. However, the municipal authorities have failed to mobilize the community and educate citizens on the principles of handling waste and proper practices of storing it in their bins at the shop, household, etc. Due to the lack of an essential facility of collection of waste from source, citizens are likely to dump

waste on the streets, open spaces, drains, and water bodies in the vicinity, creating insanitary conditions. Later, the pourakarmikas will collect the discharged waste through street sweeping, drain cleaning, etc. Street sweeping has thus become the principal method of primary collection.

The tools used for street sweeping are inefficient and outdated. For instance, the broom with a short handle is still in use, forcing sweepers to bend for hours, resulting in fatigue and loss of productivity.

Transportation of waste from the waste storage depots to the disposal site is done through a variety of vehicles, such as three-wheelers, tractors, and trucks. Most of the transport vehicles are old and open. They are usually loaded manually. Due to inadequate workshop facilities and maintenance procedures, the vehicles are poorly maintained. This leads to the breaking down of vehicles, resulting in failure of services for a long time.

The various technological options available for processing, treatment, and disposal of MSW are composting, vermicomposting, AD, incineration, gasification and pyrolysis, production of RDF, and sanitary landfilling.

The main benefits of composting include improvement in soil texture and augmenting of micronutrient deficiencies. It also increases the moisture-holding capacity of the soil and helps in maintaining soil health. However, it is an age-old concept for recycling nutrients to the soil. It does not require significant capital investment compared to other waste treatment options.

The technology of waste-to-energy projects and its viability and sustainability have been proven worldwide. WTE projects involve higher capital investment and are more complicated than other options of waste disposal. These plants are financially viable in developed countries mainly because of the tipping fees charged by the facility for the service of waste disposal, in addition to its revenue income from power sales. However, at present, in Bangalore, revenue from power sales is the only source of income for WTE plants. Technologically, it is feasible to set up even smaller capacity projects of the 1–5 MW range, corresponding to around 100–500 metric tons per day waste treatment. The significant role in making a WTE facility financially viable is the segregation of waste at the source to avoid the mixing of undesirable waste streams.

#### **12. Impact of solid waste on soil and water bodies**

MSW landfills are essential in modern-day society because the segregation and disposal of solid waste materials into decentralized locations helps to minimize risks to public health and safety. Currently, in Bengaluru, MSW landfills remain open for decades before undergoing closure and post-closure phases, during which steps are taken to minimize the risk of environmental contamination. Although MSW landfills are an essential part of everyday living, they may present long-term threats to surface water and also hydrologically interlinked groundwater bodies. The impact of leachate on groundwater and surface water bodies has attracted much attention because of its enormous environmental significance. In the olden days, landfills were constructed without leachate collection systems and liners. Once leachate enters the groundwater, it will migrate downward through the unsaturated zone until it finally reaches the saturated area. This resulted in creating significant leachate-contaminate groundwater plumes that follow the hydraulic gradient of the groundwater system.

Unscientific management of MSW leachate will lead to contamination of the soil and water bodies. The presence of a contaminant in the soil can change the engineering properties of the soil. The leachate potential to contaminate the soils

**83**

**Figure 13.**

*Solid Waste Management: Current Scenario and Challenges in Bengaluru*

existing MSW practices, which have many drawbacks.

and groundwater and surface water bodies assumes significance in the context of

Considering the importance of the problem discussed, this research mainly focuses on the characteristics of leachate generated from municipal solid waste landfill sites and its effect on surrounding water bodies near the Mavallipura

Many cities, including Bengaluru, are also facing the problems due to old dump yards situated close to the expanding cities. These dump yards need to be reclaimed for the growing needs of the city infrastructure development. This is the case for many cities in India with an alarming rate of the urbanization process. Also, they create a nuisance in the town, and the same needs to be stabilized or reclaimed. The waste sites that were earlier in the periphery of the corporation limits of Bengaluru City are now in the development zone of a more magnificent Bengaluru City, as shown in **Figure 13**. It can be seen from a satellite image that the built-up area has come near and around the earlier dump sites. Thus, it is clear that most of the old dumpsite which is existing around Bengaluru has become potential places for development. These structures built on these dumpsites can undergo distress due to the high settlement and cause failures due to the low strength of the dumped waste. These dumps can also cause groundwater contamination due to leaching of waste by the

Naveen [12] carried out a detailed experimental program to study the variations in geotechnical properties for different wastes with a time of dump yard, i.e., in turn with the age of the waste. The data provided on geotechnical properties of the waste with varying degrees of decomposition helps to plan for the reclamation of

*Location of unauthorized dump sites in and around Bangalore City (Chanakya et al., 2011).*

**13. Reclamation of waste dumps for development in Bengaluru**

*DOI: http://dx.doi.org/10.5772/intechopen.90837*

percolation of rainwater (**Figures 14**–**16**).

waste dumps.

landfill area in Bengaluru.

#### *Solid Waste Management: Current Scenario and Challenges in Bengaluru DOI: http://dx.doi.org/10.5772/intechopen.90837*

*Sustainable Sewage Sludge Management and Resource Efficiency*

principal method of primary collection.

ing in fatigue and loss of productivity.

of services for a long time.

undesirable waste streams.

waste on the streets, open spaces, drains, and water bodies in the vicinity, creating insanitary conditions. Later, the pourakarmikas will collect the discharged waste through street sweeping, drain cleaning, etc. Street sweeping has thus become the

Transportation of waste from the waste storage depots to the disposal site is done through a variety of vehicles, such as three-wheelers, tractors, and trucks. Most of the transport vehicles are old and open. They are usually loaded manually. Due to inadequate workshop facilities and maintenance procedures, the vehicles are poorly maintained. This leads to the breaking down of vehicles, resulting in failure

The various technological options available for processing, treatment, and disposal of MSW are composting, vermicomposting, AD, incineration, gasification

The main benefits of composting include improvement in soil texture and augmenting of micronutrient deficiencies. It also increases the moisture-holding capacity of the soil and helps in maintaining soil health. However, it is an age-old concept for recycling nutrients to the soil. It does not require significant capital

The technology of waste-to-energy projects and its viability and sustainability have been proven worldwide. WTE projects involve higher capital investment and are more complicated than other options of waste disposal. These plants are financially viable in developed countries mainly because of the tipping fees charged by the facility for the service of waste disposal, in addition to its revenue income from power sales. However, at present, in Bangalore, revenue from power sales is the only source of income for WTE plants. Technologically, it is feasible to set up even smaller capacity projects of the 1–5 MW range, corresponding to around 100–500 metric tons per day waste treatment. The significant role in making a WTE facility financially viable is the segregation of waste at the source to avoid the mixing of

MSW landfills are essential in modern-day society because the segregation and disposal of solid waste materials into decentralized locations helps to minimize risks to public health and safety. Currently, in Bengaluru, MSW landfills remain open for decades before undergoing closure and post-closure phases, during which steps are taken to minimize the risk of environmental contamination. Although MSW landfills are an essential part of everyday living, they may present long-term threats to surface water and also hydrologically interlinked groundwater bodies. The impact of leachate on groundwater and surface water bodies has attracted much attention because of its enormous environmental significance. In the olden days, landfills were constructed without leachate collection systems and liners. Once leachate enters the groundwater, it will migrate downward through the unsaturated zone until it finally reaches the saturated area. This resulted in creating significant leachate-contaminate groundwater plumes that follow the hydraulic gradient of the groundwater system. Unscientific management of MSW leachate will lead to contamination of the soil and water bodies. The presence of a contaminant in the soil can change the engineering properties of the soil. The leachate potential to contaminate the soils

and pyrolysis, production of RDF, and sanitary landfilling.

investment compared to other waste treatment options.

**12. Impact of solid waste on soil and water bodies**

The tools used for street sweeping are inefficient and outdated. For instance, the broom with a short handle is still in use, forcing sweepers to bend for hours, result-

**82**

and groundwater and surface water bodies assumes significance in the context of existing MSW practices, which have many drawbacks.

Considering the importance of the problem discussed, this research mainly focuses on the characteristics of leachate generated from municipal solid waste landfill sites and its effect on surrounding water bodies near the Mavallipura landfill area in Bengaluru.

#### **13. Reclamation of waste dumps for development in Bengaluru**

Many cities, including Bengaluru, are also facing the problems due to old dump yards situated close to the expanding cities. These dump yards need to be reclaimed for the growing needs of the city infrastructure development. This is the case for many cities in India with an alarming rate of the urbanization process. Also, they create a nuisance in the town, and the same needs to be stabilized or reclaimed. The waste sites that were earlier in the periphery of the corporation limits of Bengaluru City are now in the development zone of a more magnificent Bengaluru City, as shown in **Figure 13**. It can be seen from a satellite image that the built-up area has come near and around the earlier dump sites. Thus, it is clear that most of the old dumpsite which is existing around Bengaluru has become potential places for development.

These structures built on these dumpsites can undergo distress due to the high settlement and cause failures due to the low strength of the dumped waste. These dumps can also cause groundwater contamination due to leaching of waste by the percolation of rainwater (**Figures 14**–**16**).

Naveen [12] carried out a detailed experimental program to study the variations in geotechnical properties for different wastes with a time of dump yard, i.e., in turn with the age of the waste. The data provided on geotechnical properties of the waste with varying degrees of decomposition helps to plan for the reclamation of waste dumps.

*Unauthorized dumping along with wards in and around Bangalore City.*

**Figure 15.** *Major arterial and sub-arterial road network along with dump sites in and around Bangalore City.*

#### **14. Reclamation of MSW landfill**

The objective of the reclamation is to return the MSW landfill to a condition as close as possible to leave the site in a state compatible with the surrounding ground. MSW landfill reclamation is a new approach used to expand the MSW landfill capacity and minimize the cost of acquiring additional land. The significant factors influencing the success of reclamation include chemical, hydrologic, and physical conditions of the fill materials, climate, availability of suitable plant species, and proper management of reclaimed sites [13].

**85**

project.

**Figure 16.**

waste management system.

**15. Conclusions**

*Solid Waste Management: Current Scenario and Challenges in Bengaluru*

*Satellite image of built-up area along with dump sites in Greater Bangalore.*

The essential benefits may include a reduction in closure costs and reclamation of land for other purposes and recovered materials such as recyclables, soil, and waste, which can be burned as fuel. Some drawbacks exist in MSW landfill reclamation. This technology may release methane and other gasses from decomposing solid wastes. Also, the excavation work process involved in reclamation may cause adjacent landfill areas to collapse/sink. Hence, it is necessary to conduct a site characterization study. The site characterization should assess facility aspects, such as geotechnical and geological features and the stability of the surrounding area and identified groundwater, and determine the fractions of good soil, recyclable waste materials, and hazardous waste at the site [14]. Based on the available information from the site characterization, it provides project planners with a basis for assessing the potential economic benefits of a landfill reclamation

The economic benefits associated with landfill reclamation are indirect; they may include the following: increased disposal capacity; avoided or reduced cost of landfill closure; revenues from recyclable and reusable materials like ferrous metals, aluminum, plastic, and glass; combustion waste sold as fuel; reclaimed soil used as

Geotechnical properties of municipal solid waste presume great importance in their reuse, disposal, as well as reclamation of waste and dump sites. Because of the high demand for land, the abandoned, closed landfills have to reclaim to meet the growing needs of the society. Due to several reasons, the population around the improperly operated landfills is demanding the closure of the landfill. However, just leaving the landfill without proper closure cannot be allowed. Thus any attempt to reclaim land for development should come after the characterization of waste for their physical and chemical composition and geotechnical properties. Therefore, these studies constitute the first step to successfully implementing a comprehensive

Based on the above context, the following conclusions can be drawn:

complicated than the other options of waste disposal.

• For setup, the WTE plants require higher capital investment and are more

cover; and land value of sites reclaimed for other uses.

*DOI: http://dx.doi.org/10.5772/intechopen.90837*

*Solid Waste Management: Current Scenario and Challenges in Bengaluru DOI: http://dx.doi.org/10.5772/intechopen.90837*

*Sustainable Sewage Sludge Management and Resource Efficiency*

*Unauthorized dumping along with wards in and around Bangalore City.*

**84**

**Figure 15.**

**Figure 14.**

**14. Reclamation of MSW landfill**

proper management of reclaimed sites [13].

*Major arterial and sub-arterial road network along with dump sites in and around Bangalore City.*

The objective of the reclamation is to return the MSW landfill to a condition as close as possible to leave the site in a state compatible with the surrounding ground. MSW landfill reclamation is a new approach used to expand the MSW landfill capacity and minimize the cost of acquiring additional land. The significant factors influencing the success of reclamation include chemical, hydrologic, and physical conditions of the fill materials, climate, availability of suitable plant species, and

**Figure 16.** *Satellite image of built-up area along with dump sites in Greater Bangalore.*

The essential benefits may include a reduction in closure costs and reclamation of land for other purposes and recovered materials such as recyclables, soil, and waste, which can be burned as fuel. Some drawbacks exist in MSW landfill reclamation. This technology may release methane and other gasses from decomposing solid wastes. Also, the excavation work process involved in reclamation may cause adjacent landfill areas to collapse/sink. Hence, it is necessary to conduct a site characterization study. The site characterization should assess facility aspects, such as geotechnical and geological features and the stability of the surrounding area and identified groundwater, and determine the fractions of good soil, recyclable waste materials, and hazardous waste at the site [14]. Based on the available information from the site characterization, it provides project planners with a basis for assessing the potential economic benefits of a landfill reclamation project.

The economic benefits associated with landfill reclamation are indirect; they may include the following: increased disposal capacity; avoided or reduced cost of landfill closure; revenues from recyclable and reusable materials like ferrous metals, aluminum, plastic, and glass; combustion waste sold as fuel; reclaimed soil used as cover; and land value of sites reclaimed for other uses.

Geotechnical properties of municipal solid waste presume great importance in their reuse, disposal, as well as reclamation of waste and dump sites. Because of the high demand for land, the abandoned, closed landfills have to reclaim to meet the growing needs of the society. Due to several reasons, the population around the improperly operated landfills is demanding the closure of the landfill. However, just leaving the landfill without proper closure cannot be allowed. Thus any attempt to reclaim land for development should come after the characterization of waste for their physical and chemical composition and geotechnical properties. Therefore, these studies constitute the first step to successfully implementing a comprehensive waste management system.

#### **15. Conclusions**

Based on the above context, the following conclusions can be drawn:

• For setup, the WTE plants require higher capital investment and are more complicated than the other options of waste disposal.

	- Due to the high content of biodegradable waste in Bengaluru, a biological process is needed such as anaerobic digestion and composting to treat the waste, gasification, and pyrolysis.

### **Author details**

#### B.P. Naveen1 \* and P.V. Sivapullaiah<sup>2</sup>


#### \*Address all correspondence to: bp.naveen864@gmail.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**87**

*Solid Waste Management: Current Scenario and Challenges in Bengaluru*

[8] Ramachandra TV, Bachamanda S. Environmental audit of municipal solid waste management. Technical Report: 118. Bangalore: CES, IISc; 2006

[9] Ministry of Environment and Forests (MoEF). Available from: http://www. envfor.nic.in [Accessed: 16 June 2005]

[10] Dhindaw J, Badami K, Sitharam TG, Chanakya HN. Waste Segregation-a Case Study in Malleshwaram,

Bangalore, Technical Report Submitted to CISTUP. Bangalore: IISc; 2014

[11] Sasikumar K, Krishna SG. Solid Waste Management. New Delhi: PHI Learning Private Limited; 2014

geotechnical properties of municipal solid waste and stabilization of waste dumps [master of science thesis]. IISc,

[12] Naveen BP. Evaluation of

[13] Naveen BP, Mahapatra DM, Sitharam TG, Sivapullaiah PV, Ramachandra TV. Physico-chemical and biological characterization of urban municipal landfill leachate. Environmental Pollution. 2017;**220**

[14] Environmental Protection Agency. Guidelines on the Information to be Contained in Environmental Impact Statements. Wexford: EPA; 2002

Bangalore; 2012

(Part A):1-12

*DOI: http://dx.doi.org/10.5772/intechopen.90837*

Sitharam TG. Disposal options for solid waste of Bengaluru city based on its characteristics. International Journal of Environment and Waste Management

[1] Naveen BP, Sivapullaiah PV,

**References**

(IJEWM). 2013;**12**(1):77-88

[2] Naveen BP, Sitharam TG,

Kerala, India; 2014. pp. 11-17

Pollution. 2004;**2**(2):23-30

2013

February 2004]

Delhi; 2000

Technical Report; 2007

[3] Dittrich C. Bengaluru: Divided under the impact of globalization. Asian Journal of Water, Environment and

[4] Evaluation of Technology for processing existing waste at Seven Landfill sites of BBMP, Bangalore. Technical Committee Recommendations on EOI Application Report 3 Jan 2013;

[5] Beukering PV, Sehker M, Gerlagh R, Kumar V. Analysing urban solid waste in developing countries: A perspective on Bangalore. 1999. Collaborative Research in the Economics of Environment and Development (CREED) and Environmental Economics Programme (IIED), Working Paper No. 24, March 1999. p. 24. ISBN: 1357 924X (ISSN). Available on the website: http://www. iied.org/eep/ pubs/creed [Accessed: 20

[6] Central Pollution Control Board (CPCB). Collection, Transportation and Disposal of municipal solid waste in Delhi (India)-a case study, CPCB, New

[7] BBMP. Solid Waste Management in Bruhat Bangalore Mahanagara Palike,

Sivapullaiah PV. Status of solid waste management in Bengaluru and review of solid waste techniques adopted. In: International conference on waste management for sustainable development (21-23 2014); Palakkad,

*Solid Waste Management: Current Scenario and Challenges in Bengaluru DOI: http://dx.doi.org/10.5772/intechopen.90837*

### **References**

*Sustainable Sewage Sludge Management and Resource Efficiency*

tion to its revenue income from power sales.

waste, gasification, and pyrolysis.

gas, and geothermal energies combined.

• WTE plants are suitable in developed countries mainly because of the tipping fees/gate fees charged by the facility for the service of waste disposal, in addi-

○ Due to the high content of biodegradable waste in Bengaluru, a biological process is needed such as anaerobic digestion and composting to treat the

• Plasma gasification technology can reduce the need for landfills; it can create more renewable energy than the projected energy from solar, wind, landfill

• RDF plants are in the initial stage of development in India. It is beneficial in preparing an enriched fuel feed for thermal processes like incineration. The

• The pyrolysis process cannot handle the wide variety of wastes, and the end products of pyrolysis are carbon black oil that can be resent to a refiner and

• Sanitary landfill is the cheapest, simplest, and most cost-effective method for

hydrocarbon gasses that can be used to make electricity or stream.

RDF pellets are used as a coal substitute at a lower price.

**86**

**Author details**

disposing of waste.

\* and P.V. Sivapullaiah<sup>2</sup>

2 CMR University, Bengaluru, India

provided the original work is properly cited.

1 Department of Civil Engineering, Amity University Haryana, India

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: bp.naveen864@gmail.com

B.P. Naveen1

[1] Naveen BP, Sivapullaiah PV, Sitharam TG. Disposal options for solid waste of Bengaluru city based on its characteristics. International Journal of Environment and Waste Management (IJEWM). 2013;**12**(1):77-88

[2] Naveen BP, Sitharam TG, Sivapullaiah PV. Status of solid waste management in Bengaluru and review of solid waste techniques adopted. In: International conference on waste management for sustainable development (21-23 2014); Palakkad, Kerala, India; 2014. pp. 11-17

[3] Dittrich C. Bengaluru: Divided under the impact of globalization. Asian Journal of Water, Environment and Pollution. 2004;**2**(2):23-30

[4] Evaluation of Technology for processing existing waste at Seven Landfill sites of BBMP, Bangalore. Technical Committee Recommendations on EOI Application Report 3 Jan 2013; 2013

[5] Beukering PV, Sehker M, Gerlagh R, Kumar V. Analysing urban solid waste in developing countries: A perspective on Bangalore. 1999. Collaborative Research in the Economics of Environment and Development (CREED) and Environmental Economics Programme (IIED), Working Paper No. 24, March 1999. p. 24. ISBN: 1357 924X (ISSN). Available on the website: http://www. iied.org/eep/ pubs/creed [Accessed: 20 February 2004]

[6] Central Pollution Control Board (CPCB). Collection, Transportation and Disposal of municipal solid waste in Delhi (India)-a case study, CPCB, New Delhi; 2000

[7] BBMP. Solid Waste Management in Bruhat Bangalore Mahanagara Palike, Technical Report; 2007

[8] Ramachandra TV, Bachamanda S. Environmental audit of municipal solid waste management. Technical Report: 118. Bangalore: CES, IISc; 2006

[9] Ministry of Environment and Forests (MoEF). Available from: http://www. envfor.nic.in [Accessed: 16 June 2005]

[10] Dhindaw J, Badami K, Sitharam TG, Chanakya HN. Waste Segregation-a Case Study in Malleshwaram, Bangalore, Technical Report Submitted to CISTUP. Bangalore: IISc; 2014

[11] Sasikumar K, Krishna SG. Solid Waste Management. New Delhi: PHI Learning Private Limited; 2014

[12] Naveen BP. Evaluation of geotechnical properties of municipal solid waste and stabilization of waste dumps [master of science thesis]. IISc, Bangalore; 2012

[13] Naveen BP, Mahapatra DM, Sitharam TG, Sivapullaiah PV, Ramachandra TV. Physico-chemical and biological characterization of urban municipal landfill leachate. Environmental Pollution. 2017;**220** (Part A):1-12

[14] Environmental Protection Agency. Guidelines on the Information to be Contained in Environmental Impact Statements. Wexford: EPA; 2002

**89**

**Chapter 5**

**Abstract**

*Başak Kiliç Taşeli*

potential, and resource consumption.

sustainability, sludge treatment

**1. Introduction**

Comparative Life Cycle

Assessment of Sewage Sludge

(Biosolid) Management Options

Sludge formation during wastewater treatment is inevitable even with proper management and treatment. However, the proper treatment and disposal of sludge are still difficult in terms of cost of treatment, the presence of new pollutants, health problems, and public acceptance. Conventional disposal methods (e.g., storage, incineration) have raised concerns about legislative constraints and community perception that encourage the assessment of substitute sludge management options. Sludge management requires a systematic solution that combines environmental effectiveness, social acceptability, and economic affordability. Life cycle assessment is one of the most important tools to identify and compare the environmental impact of sludge treatment technologies to ensure sustainable sludge management. Increased production of sludge (biosolids) increases worldwide due to population growth, urban planning, and industrial developments. The sludge needs to be properly treated and environmentally managed to reduce the negative effects of its application or disposal. This chapter deals with the application of biosolids or sewage sludge, together with possible resources for sustainable development. In this section, the life cycle assessments of sludge treatment methods were also investigated and found that sludge treatment techniques lead to major environmental impact categories such as global warming potential, human toxicity, acidification

**Keywords:** life cycle assessment, sludge management, biosolid management,

Wastewater treatment plants (WWTP) are aimed to decrease the environmental impacts of discharging untreated wastewater into receiving bodies, but considering the need for long-term ecological sustainability, the objectives of wastewater treatment systems should include energy and resource savings and waste reduction [1]. Sewage sludge management is a management system that makes sludge recovery a central component of a wastewater treatment plant that strives to integrate it with improving the sustainability of wastewater plants. Currently, wastewater sludge production, treatment, and disposal methods vary from country to country, and the continued growth of sludge production is becoming a global problem. The sludge production rate is increasing due to the stricter legislation which is constantly

#### **Chapter 5**

## Comparative Life Cycle Assessment of Sewage Sludge (Biosolid) Management Options

*Başak Kiliç Taşeli*

#### **Abstract**

Sludge formation during wastewater treatment is inevitable even with proper management and treatment. However, the proper treatment and disposal of sludge are still difficult in terms of cost of treatment, the presence of new pollutants, health problems, and public acceptance. Conventional disposal methods (e.g., storage, incineration) have raised concerns about legislative constraints and community perception that encourage the assessment of substitute sludge management options. Sludge management requires a systematic solution that combines environmental effectiveness, social acceptability, and economic affordability. Life cycle assessment is one of the most important tools to identify and compare the environmental impact of sludge treatment technologies to ensure sustainable sludge management. Increased production of sludge (biosolids) increases worldwide due to population growth, urban planning, and industrial developments. The sludge needs to be properly treated and environmentally managed to reduce the negative effects of its application or disposal. This chapter deals with the application of biosolids or sewage sludge, together with possible resources for sustainable development. In this section, the life cycle assessments of sludge treatment methods were also investigated and found that sludge treatment techniques lead to major environmental impact categories such as global warming potential, human toxicity, acidification potential, and resource consumption.

**Keywords:** life cycle assessment, sludge management, biosolid management, sustainability, sludge treatment

#### **1. Introduction**

Wastewater treatment plants (WWTP) are aimed to decrease the environmental impacts of discharging untreated wastewater into receiving bodies, but considering the need for long-term ecological sustainability, the objectives of wastewater treatment systems should include energy and resource savings and waste reduction [1].

Sewage sludge management is a management system that makes sludge recovery a central component of a wastewater treatment plant that strives to integrate it with improving the sustainability of wastewater plants. Currently, wastewater sludge production, treatment, and disposal methods vary from country to country, and the continued growth of sludge production is becoming a global problem. The sludge production rate is increasing due to the stricter legislation which is constantly

solidifying for the sustainable disposal of wastewater. Nowadays, however, due to the increasing environmental awareness of the public and increasing pressure from environmental organizations, sludge management has become necessary with economic and environmentally friendly methods.

Conventional disposal methods (e.g., landfill, incineration, stabilization) have raised concerns about legislative constraints and community perception that encourage the assessment of substitute sludge management options. Sludge management requires a systematic solution combining environmental effectiveness, social acceptability, and economic affordability based on a life cycle approach. Life cycle assessment is one of the most important tools to identify and compare the environmental impact of sludge treatment technologies to ensure sustainable sludge management.

Generally, the terms biosolids and sewage sludge are used interchangeably. Biosolid includes 20% content of fat, 50% carbohydrate content, 30–40% content of organic matter, 3% total nitrogen, 1.5% total phosphorus, 0.7% total potassium content, 10–20% C/N ratio, pH of 6.5–7.0, and a specific gravity of 1.00 as reported by [2]. It is a by-product of treatment plants in large quantities varying in characteristics, containing organic and inorganic chemicals, heavy metals (iron, chromium, manganese, zinc, mercury, lead, nickel, cadmium and copper), and pathogens. It is considered as a resource due to the widespread application in biogas production, soil filling, organic fertilizer, and soil amendment.

Life cycle assessment (LCA) is a standardized and recognized tool to measure the overall environmental impact of providing a product or service. It is increasingly used to support commercial claims of products' environmental performance. It is also used as the basis for European environmental legislation, including Integrated Pollution Prevention and Control (IPPC) and Integrated Product Policy [3].

ORWARE, SimaPro, MARTES, UMBERTO, Ecobilan, LCAiT, SiSOSTAQUA, BioWin\*, STAN\*, GaBi 6, WWEST, BEAM, GEMIS, and Quantis Suite are the best known commercial sludge treatment and management LCA software. Among them SimaPro is the most widely used model. Global warming, acidification, eutrophication, photochemical smog, human toxicity, ecotoxicity, depletion of abiotic resource, and terrestrial ecotoxicity are the fundamental impact categories of sludge management [4–12]. Life cycle assessment methodology is generally implemented for the main sludge management like dewatering, thickening, and anaerobic digestion [12–18].

This chapter deals with the application of biosolids or sewage sludge, together with possible resources for sustainable development. Moreover, the life cycle assessments of sludge treatment methods were also investigated and found that sludge treatment techniques lead to major environmental impact categories such as global warming potential, human toxicity, acidification potential, and resource consumption.

#### **2. Life cycle assessment (LCA)**

Life cycle analysis (LCA) is a method of assessing the environmental impact of products and processes throughout their lives, including raw material procurement, production, use, final disposal, and all transport phases between these stages.

With this analysis, the comprehensive inventory of all energy, water, and substance inputs together with the emitted waste is evaluated together, and the possible environmental effects of the products are calculated. Unlike other narrow-scale environmental impact analyses, the LCA examines environmental issues with its "cradle-to-grave" approach [19].

**91**

*Comparative Life Cycle Assessment of Sewage Sludge (Biosolid) Management Options*

Depending on the stage of the life cycle, LCA studies can be grouped as "cradle to grave," "cradle to door," "cradle to cradle," and "door to door." It is a definition used for studies examining the whole life cycles of a product or process from cradle to grave and includes all the processes to be passed from the raw material produc-

A product or process from the cradle to the door partially covers the processes from the production of the raw material (cradle) to the stage (door) to which it is delivered to the factory. This is a life cycle study which partially covers processes. The recycling of waste during the waste disposal phase is referred to as the

"Door to door" is an approach that deals with the life cycle of a single stage of a

LCA is a rapidly evolving tool designed to help environmental management in sustainable products and services in the longer term, also called "life cycle analysis,"

**First step: aim and scope definition:** At this stage, the objective of LCA study, target groups, basic variables, necessary data, constraints, and assumptions used are defined. Systematic and functional units are the two most important elements defining the scope and knowledge of the study, and while determining the system boundaries, the life cycle of the product is included in the analysis [21]. The functional unit refers to the unit function of the system under consideration and should be expressed clearly and in detail and should reflect the basic function of the

**Second step: life cycle inventory analysis:** At this stage, energy, water, raw material inputs, and released solid waste, wastewater, and air emissions are determined within the boundaries. In the meantime, inventory information about all unit processes in the product's life cycle is compiled through data collection forms, and deficiencies are completed by using literature review and sectoral

All collected data is rearranged according to the functional unit. It is made available for the calculation of environmental impacts. At this stage, data quality and

As a result of the literature research, it was determined that UMBERTO, GEMIS, SimaPro, GLOSSARY BEAM, MARTES, Ecobilan, LCAiT, SiSOSTAQUA, BioWin, STAN, GaBi 6, and WWEST are the most preferred sludge treatment and management LCA software [4–12]. Among them SimaPro is the most widely used model. Global warming, acidification, eutrophication, photochemical smog, human toxicity, ecotoxicity, depletion of abiotic resource, and terrestrial ecotoxicity are the fundamental impact categories of sludge management. Life cycle assessment methodology is generally implemented for main sludge management like dewater-

**Third step: life cycle impact analysis:** At this stage, environmental impact potentials are calculated using inventory data collected and compiled in the previous stage. Mandatory (classification and characterization) and voluntary (normalization and weighting) substages of the impact analysis stage are defined in [23, 24]:

a.At the classification stage, the individual inventory items are assigned according to the relevant environmental impact categories. For example, CO2

emissions are categorized as "global warming." The most commonly used environmental impact categories in LCA studies are acidification, eutrophication, global warming, photochemical ozone formation, ozone depletion, ecotoxicity,

"life cycle approach," "cradle-to-grave analysis," or "ecological balance."

The standard LCA method consists of four main steps:

*DOI: http://dx.doi.org/10.5772/intechopen.91190*

cradle-to-cradle approach.

product or a process [20].

product or system [22].

accuracy are vital at every step.

ing, thickening, and anaerobic digestion [12–18].

and resource consumption (see **Figure 1**).

reports.

tion (cradle) to the disposal of the waste (grave).

#### *Comparative Life Cycle Assessment of Sewage Sludge (Biosolid) Management Options DOI: http://dx.doi.org/10.5772/intechopen.91190*

Depending on the stage of the life cycle, LCA studies can be grouped as "cradle to grave," "cradle to door," "cradle to cradle," and "door to door." It is a definition used for studies examining the whole life cycles of a product or process from cradle to grave and includes all the processes to be passed from the raw material production (cradle) to the disposal of the waste (grave).

A product or process from the cradle to the door partially covers the processes from the production of the raw material (cradle) to the stage (door) to which it is delivered to the factory. This is a life cycle study which partially covers processes.

The recycling of waste during the waste disposal phase is referred to as the cradle-to-cradle approach.

"Door to door" is an approach that deals with the life cycle of a single stage of a product or a process [20].

LCA is a rapidly evolving tool designed to help environmental management in sustainable products and services in the longer term, also called "life cycle analysis," "life cycle approach," "cradle-to-grave analysis," or "ecological balance."

The standard LCA method consists of four main steps:

**First step: aim and scope definition:** At this stage, the objective of LCA study, target groups, basic variables, necessary data, constraints, and assumptions used are defined. Systematic and functional units are the two most important elements defining the scope and knowledge of the study, and while determining the system boundaries, the life cycle of the product is included in the analysis [21]. The functional unit refers to the unit function of the system under consideration and should be expressed clearly and in detail and should reflect the basic function of the product or system [22].

**Second step: life cycle inventory analysis:** At this stage, energy, water, raw material inputs, and released solid waste, wastewater, and air emissions are determined within the boundaries. In the meantime, inventory information about all unit processes in the product's life cycle is compiled through data collection forms, and deficiencies are completed by using literature review and sectoral reports.

All collected data is rearranged according to the functional unit. It is made available for the calculation of environmental impacts. At this stage, data quality and accuracy are vital at every step.

As a result of the literature research, it was determined that UMBERTO, GEMIS, SimaPro, GLOSSARY BEAM, MARTES, Ecobilan, LCAiT, SiSOSTAQUA, BioWin, STAN, GaBi 6, and WWEST are the most preferred sludge treatment and management LCA software [4–12]. Among them SimaPro is the most widely used model. Global warming, acidification, eutrophication, photochemical smog, human toxicity, ecotoxicity, depletion of abiotic resource, and terrestrial ecotoxicity are the fundamental impact categories of sludge management. Life cycle assessment methodology is generally implemented for main sludge management like dewatering, thickening, and anaerobic digestion [12–18].

**Third step: life cycle impact analysis:** At this stage, environmental impact potentials are calculated using inventory data collected and compiled in the previous stage. Mandatory (classification and characterization) and voluntary (normalization and weighting) substages of the impact analysis stage are defined in [23, 24]:

a.At the classification stage, the individual inventory items are assigned according to the relevant environmental impact categories. For example, CO2 emissions are categorized as "global warming." The most commonly used environmental impact categories in LCA studies are acidification, eutrophication, global warming, photochemical ozone formation, ozone depletion, ecotoxicity, and resource consumption (see **Figure 1**).

*Sustainable Sewage Sludge Management and Resource Efficiency*

economic and environmentally friendly methods.

soil filling, organic fertilizer, and soil amendment.

management.

tion [12–18].

consumption.

**2. Life cycle assessment (LCA)**

"cradle-to-grave" approach [19].

solidifying for the sustainable disposal of wastewater. Nowadays, however, due to the increasing environmental awareness of the public and increasing pressure from environmental organizations, sludge management has become necessary with

Conventional disposal methods (e.g., landfill, incineration, stabilization) have raised concerns about legislative constraints and community perception that encourage the assessment of substitute sludge management options. Sludge management requires a systematic solution combining environmental effectiveness, social acceptability, and economic affordability based on a life cycle approach. Life cycle assessment is one of the most important tools to identify and compare the environmental impact of sludge treatment technologies to ensure sustainable sludge

Generally, the terms biosolids and sewage sludge are used interchangeably. Biosolid includes 20% content of fat, 50% carbohydrate content, 30–40% content of organic matter, 3% total nitrogen, 1.5% total phosphorus, 0.7% total potassium content, 10–20% C/N ratio, pH of 6.5–7.0, and a specific gravity of 1.00 as reported by [2]. It is a by-product of treatment plants in large quantities varying in characteristics, containing organic and inorganic chemicals, heavy metals (iron, chromium, manganese, zinc, mercury, lead, nickel, cadmium and copper), and pathogens. It is considered as a resource due to the widespread application in biogas production,

Life cycle assessment (LCA) is a standardized and recognized tool to measure the overall environmental impact of providing a product or service. It is increasingly used to support commercial claims of products' environmental performance. It is also used as the basis for European environmental legislation, including Integrated Pollution Prevention and Control (IPPC) and Integrated Product Policy [3].

ORWARE, SimaPro, MARTES, UMBERTO, Ecobilan, LCAiT, SiSOSTAQUA, BioWin\*, STAN\*, GaBi 6, WWEST, BEAM, GEMIS, and Quantis Suite are the best known commercial sludge treatment and management LCA software. Among them SimaPro is the most widely used model. Global warming, acidification, eutrophication, photochemical smog, human toxicity, ecotoxicity, depletion of abiotic resource, and terrestrial ecotoxicity are the fundamental impact categories of sludge management [4–12]. Life cycle assessment methodology is generally implemented for the main sludge management like dewatering, thickening, and anaerobic diges-

This chapter deals with the application of biosolids or sewage sludge, together

Life cycle analysis (LCA) is a method of assessing the environmental impact of products and processes throughout their lives, including raw material procurement, production, use, final disposal, and all transport phases between these stages. With this analysis, the comprehensive inventory of all energy, water, and substance inputs together with the emitted waste is evaluated together, and the possible environmental effects of the products are calculated. Unlike other narrow-scale environmental impact analyses, the LCA examines environmental issues with its

with possible resources for sustainable development. Moreover, the life cycle assessments of sludge treatment methods were also investigated and found that sludge treatment techniques lead to major environmental impact categories such as global warming potential, human toxicity, acidification potential, and resource

**90**

**Figure 1.** *LCA impact assessment mechanism [19].*


**93**

*Comparative Life Cycle Assessment of Sewage Sludge (Biosolid) Management Options*

dations for the system or product under consideration [23, 24].

The main uses of LCA can be summarized as follows:

a.Analyzing problems related to a specific product

**Fourth step: interpretation of results:** It is the purpose of this stage to interpret the results of the inventory and environmental impact analysis stages according to the purpose and scope of the study and to present important results and recommen-

The carbon footprint is an environmental indicator that measures the global climate change caused by greenhouse gases (GHG) from the life cycle of products and services. Greenhouse gases emitted at each stage are expressed in terms of the total CO2 equivalent units multiplied by the relevant coefficients. Basically carbon footprint calculation is also a life cycle approach; however, unlike LCA, it does not cover all emissions but only inputs that contribute to global warming. Principles and procedures for product carbon footprint calculation and declaration are defined in [24], ISO 14067: 2013. Here, ISO 14040 and ISO 14044 LCA standards are used for footprint calculations, and ISO 14020, ISO 14024, and ISO 14025 standards are

Water footprint calculations are likewise based on life cycle principles, and the basic rules and principles for footprint calculations of products, processes, and institutions are included in the ISO 14046: 2014 standard. With this method, in addition to direct and hence water input-outputs, air and soil emissions affecting

b.Determining the important parameters that affect a study for product

One of the areas where LCA is used in particular is green purchasing applications. Eco-labels (where environmentally friendly products are documented) are preferred by consumers; Blue Angel is used in Germany, but in Scandinavian

a.Compliance of the various packaging alternatives with the European Union's

b.Evaluating the different waste management approaches of the municipalities

c.Comparing different types of biomass for a particular use (e.g., obtaining electricity) to determine environmental advantages and disadvantages

d.Strategic comparison between alternatives in order to make a decision on a public investment, for example, evaluation of transport methods (road, rail,

f. Improving the raw material production stage by switching to sustainable raw

e.Harmonization of the construction sector with the environment

d.Choosing between similar products, processes, and services

*DOI: http://dx.doi.org/10.5772/intechopen.91190*

used for declarations [24].

development

c.New product design

countries Green Swan is used.

packaging directive

materials in production

Below are examples of other uses:

sea) for certain regions or a particular sector

water quality are also addressed [25].

*Comparative Life Cycle Assessment of Sewage Sludge (Biosolid) Management Options DOI: http://dx.doi.org/10.5772/intechopen.91190*

**Fourth step: interpretation of results:** It is the purpose of this stage to interpret the results of the inventory and environmental impact analysis stages according to the purpose and scope of the study and to present important results and recommendations for the system or product under consideration [23, 24].

The carbon footprint is an environmental indicator that measures the global climate change caused by greenhouse gases (GHG) from the life cycle of products and services. Greenhouse gases emitted at each stage are expressed in terms of the total CO2 equivalent units multiplied by the relevant coefficients. Basically carbon footprint calculation is also a life cycle approach; however, unlike LCA, it does not cover all emissions but only inputs that contribute to global warming. Principles and procedures for product carbon footprint calculation and declaration are defined in [24], ISO 14067: 2013. Here, ISO 14040 and ISO 14044 LCA standards are used for footprint calculations, and ISO 14020, ISO 14024, and ISO 14025 standards are used for declarations [24].

Water footprint calculations are likewise based on life cycle principles, and the basic rules and principles for footprint calculations of products, processes, and institutions are included in the ISO 14046: 2014 standard. With this method, in addition to direct and hence water input-outputs, air and soil emissions affecting water quality are also addressed [25].

The main uses of LCA can be summarized as follows:


*Sustainable Sewage Sludge Management and Resource Efficiency*

b.In the characterization stage, inventory items contributing to the same environmental problem are multiplied by the relevant coefficients and expressed over the common unit, and the aggregated impact is calculated for each environmental impact category. For example, CO2, CH4, and N2O emissions leading

c.In the normalization phase, different environmental impact potentials are compared according to the common reference system using accepted normalization methods. Normalization indicates which environmental impact

d.In the weighting phase, the normalization results are multiplied by coefficients using one of the weighted methods that are accepted and based on the reduction targets for each environmental impact category. Weighting reveals which environmental impact potential is more important. LCA has a wide range of applications in the private, public, and academy sector for a wide range of products, services, and systems. LCA develops strategic planning, public policies, and performance indicators; identifies priority products and processes in production; identifies improvement opportunities; provides important inputs in product development or redesign stages, various sustainability declarations, and eco-label programs; and support and compare different production alternatives. Among these, environmental declarations and carbon and water footprint calculations are important in sustainable consumption and production.

to global warming are expressed by an equivalent of kg CO2.

**92**

potential is higher.

*LCA impact assessment mechanism [19].*

**Figure 1.**

d.Choosing between similar products, processes, and services

One of the areas where LCA is used in particular is green purchasing applications. Eco-labels (where environmentally friendly products are documented) are preferred by consumers; Blue Angel is used in Germany, but in Scandinavian countries Green Swan is used.

Below are examples of other uses:


As a summary the LCA study, which covers all stages of the product value chain, evaluates the total environmental impact such as global warming, acidification, eutrophication, photochemical smog, human toxicity, ecotoxicity, depletion of abiotic resource, and terrestrial ecotoxicity which are the fundamental impact categories of sludge management [26].

#### **3. Life cycle assessment of sewage management**

A sludge management that yields the best results requires a systematic solution that combines environmental effectiveness, social acceptability, and economic affordability based on a life cycle approach. For example, it is reported in the literature that total sludge production in China increased by an average of 13% per annum from 2007 to 2013, producing 6.25 million tons of dry solids in 2013 and reaching 39.78 million tons in 2020. In the same study, more than 80% of the sludge was disposed without any process, the organic content of the sludge was around 37%, and because of this low organic matter content, anaerobic digestion was not an efficient method, and therefore storage and incineration after dewatering was the most common method [27]. With the increase in population, the urban settlement areas expanded, and many of the wastewater treatment plants in the rural areas are now located within the settlements, and the gradual improvement in socioeconomic development and living standards has led the residents to pay more attention to the quality of the living environment [1]. In addition, since the environmental awareness of the public has increased, the odors caused by treatment plants have become a new and troublesome social problem. Another study suggests that municipal waste management in China tends to incinerate instead of landfill, but it causes social conflicts as it impedes the construction of treatment plants near public land or habitats [28].

Another study reached a more striking conclusion, stating that the inhabitants of 12 Chinese cities protested the incineration projects due to environmental concerns and only three incineration projects were allowed from 2009 to 2015, while others were canceled and the disposal of sludge into the long-term storage or incineration facilities was increasingly difficult [29].

Since EU member states have to reduce the amount of biodegradable municipal waste to 35% of 1995 by 2016, they have to make the transition from a linear to circular economy where waste can be converted into resources. Therefore, like all biodegradable wastes, wastewater sludge is seen as a source of energy and material production. However, a sewage management should be considered, including the method of processing sludge, where and how the final products (e.g., fertilizer, biogas) are used, the amount of greenhouse gas (GHG) emissions, and the selection of the most sustainable wastewater sludge treatment technology. Composting, anaerobic digestion, incineration, chemical stabilization, and the use of fertilizer in agricultural land are the most commonly used sewage management methods. The change of sludge management methods from country to country was mentioned in

**95**

*Comparative Life Cycle Assessment of Sewage Sludge (Biosolid) Management Options*

the previous chapters. Portugal, Ireland, the United Kingdom, Luxembourg, and Spain use more than 75% of the sludge produced as fertilizer for agricultural land; 86% of the sludge produced in Lithuania, Finland, and Estonia is composted; the Netherlands, Belgium, Germany, Slovenia, Austria, and Switzerland prioritize incineration, while Malta, Romania, Italy, and Bosnia and Herzegovina mostly

In a sludge life cycle assessment study in France, it was noted that the final combination of anaerobic digestion and land application caused the lowest emissions during operation [5]. Many researchers have indicated that, from an economic point of view only, a large-scale incineration plant or anaerobic digester may be the

It was reported that land filling has the greatest impact (296.9 kg CO2 eq./t sludge), followed by mono-incineration (232.2 kg CO2 eq./t sludge) and carbonization (146.1 kg CO2 eq./t sludge) in terms of the emission quantity of greenhouse gases. They also stated that co-incineration with municipal solid waste has the benefit of reducing greenhouse gas emission by −15.4 kg CO2 eq./t sludge [31]. A calculator calculating the greenhouse gas (GHG) emissions (carbon dioxide including bio-based, methane, and nitrous oxide measured as carbon dioxide equivalents) from sewage sludge treatment methods found at the end of the comprehensive study showed that composting, anaerobic digestion, and incineration resulted in the lowest emissions of the GHG gases. If you need to elaborate further, anaerobic digestion generated the least carbon dioxide equivalent emissions among all the treatment methods studied. The second best option was incineration of

In another study a life cycle assessment (LCA) was performed on five common sewage sludge treatment practices, namely, dewatering of mixed sludge, lime stabilization of dewatered sludge, anaerobic digestion of mixed sludge, dewatering of anaerobically digested sludge, and incineration of dewatered anaerobically digested sludge. The sludge residues were applied on agricultural land, and it was found that the incineration of dewatered anaerobically digested sludge scenario performed

Ten impact categories, namely, human toxicity carcinogenic effects, human toxicity non-carcinogenic effects, ecotoxicity, freshwater eutrophication, marine eutrophication, terrestrial eutrophication, terrestrial acidification, particulate matter formation, climate change, and photochemical oxidant formation, were also assessed in this study. It was concluded that in human toxicity and ecotoxicity categories, impacts were dominated by the application of zinc and copper to agricultural soil. For the freshwater eutrophication potential category, the fate of phosphorus was found to be (P) dominated, while the fate of N had a profound effect on all nontoxic impact categories other than freshwater eutrophication [2].

As a result of the literature blended in this section, it is concluded that biosolids have significant disadvantages for their use in agriculture and other applications and, therefore, sludge or biosolids should be sampled, controlled, and monitored regularly for pollutants (pathogens, heavy metals, etc.). However, it is also concluded that biosolids play an important role in energy production, and crop production. The most comprehensive sludge management studies have shown that land application is an important contribution to global warming, eutrophication, and acidification. More scientific research is needed on different aspects of biosolids or sewage sludge to be a more suitable resource for sustainable development. It is

*DOI: http://dx.doi.org/10.5772/intechopen.91190*

report the use of sludge for storage [30].

most effective way to treat sludge [30].

sludge, while the third best was composting [31].

better results [2].

**4. Conclusions**

#### *Comparative Life Cycle Assessment of Sewage Sludge (Biosolid) Management Options DOI: http://dx.doi.org/10.5772/intechopen.91190*

the previous chapters. Portugal, Ireland, the United Kingdom, Luxembourg, and Spain use more than 75% of the sludge produced as fertilizer for agricultural land; 86% of the sludge produced in Lithuania, Finland, and Estonia is composted; the Netherlands, Belgium, Germany, Slovenia, Austria, and Switzerland prioritize incineration, while Malta, Romania, Italy, and Bosnia and Herzegovina mostly report the use of sludge for storage [30].

In a sludge life cycle assessment study in France, it was noted that the final combination of anaerobic digestion and land application caused the lowest emissions during operation [5]. Many researchers have indicated that, from an economic point of view only, a large-scale incineration plant or anaerobic digester may be the most effective way to treat sludge [30].

It was reported that land filling has the greatest impact (296.9 kg CO2 eq./t sludge), followed by mono-incineration (232.2 kg CO2 eq./t sludge) and carbonization (146.1 kg CO2 eq./t sludge) in terms of the emission quantity of greenhouse gases. They also stated that co-incineration with municipal solid waste has the benefit of reducing greenhouse gas emission by −15.4 kg CO2 eq./t sludge [31].

A calculator calculating the greenhouse gas (GHG) emissions (carbon dioxide including bio-based, methane, and nitrous oxide measured as carbon dioxide equivalents) from sewage sludge treatment methods found at the end of the comprehensive study showed that composting, anaerobic digestion, and incineration resulted in the lowest emissions of the GHG gases. If you need to elaborate further, anaerobic digestion generated the least carbon dioxide equivalent emissions among all the treatment methods studied. The second best option was incineration of sludge, while the third best was composting [31].

In another study a life cycle assessment (LCA) was performed on five common sewage sludge treatment practices, namely, dewatering of mixed sludge, lime stabilization of dewatered sludge, anaerobic digestion of mixed sludge, dewatering of anaerobically digested sludge, and incineration of dewatered anaerobically digested sludge. The sludge residues were applied on agricultural land, and it was found that the incineration of dewatered anaerobically digested sludge scenario performed better results [2].

Ten impact categories, namely, human toxicity carcinogenic effects, human toxicity non-carcinogenic effects, ecotoxicity, freshwater eutrophication, marine eutrophication, terrestrial eutrophication, terrestrial acidification, particulate matter formation, climate change, and photochemical oxidant formation, were also assessed in this study. It was concluded that in human toxicity and ecotoxicity categories, impacts were dominated by the application of zinc and copper to agricultural soil. For the freshwater eutrophication potential category, the fate of phosphorus was found to be (P) dominated, while the fate of N had a profound effect on all nontoxic impact categories other than freshwater eutrophication [2].

#### **4. Conclusions**

As a result of the literature blended in this section, it is concluded that biosolids have significant disadvantages for their use in agriculture and other applications and, therefore, sludge or biosolids should be sampled, controlled, and monitored regularly for pollutants (pathogens, heavy metals, etc.). However, it is also concluded that biosolids play an important role in energy production, and crop production. The most comprehensive sludge management studies have shown that land application is an important contribution to global warming, eutrophication, and acidification. More scientific research is needed on different aspects of biosolids or sewage sludge to be a more suitable resource for sustainable development. It is

*Sustainable Sewage Sludge Management and Resource Efficiency*

electronic goods produced through R&D studies

ing changes in product packaging

more recyclable products

categories of sludge management [26].

**3. Life cycle assessment of sewage management**

incineration facilities was increasingly difficult [29].

g.Reducing the carbon footprint by increasing the energy efficiency of the

h.Making product shipments more efficient and reducing air emissions by mak-

i. Reducing the environmental impact of the final disposal phase by designing

As a summary the LCA study, which covers all stages of the product value chain, evaluates the total environmental impact such as global warming, acidification, eutrophication, photochemical smog, human toxicity, ecotoxicity, depletion of abiotic resource, and terrestrial ecotoxicity which are the fundamental impact

A sludge management that yields the best results requires a systematic solution that combines environmental effectiveness, social acceptability, and economic affordability based on a life cycle approach. For example, it is reported in the literature that total sludge production in China increased by an average of 13% per annum from 2007 to 2013, producing 6.25 million tons of dry solids in 2013 and reaching 39.78 million tons in 2020. In the same study, more than 80% of the sludge was disposed without any process, the organic content of the sludge was around 37%, and because of this low organic matter content, anaerobic digestion was not an efficient method, and therefore storage and incineration after dewatering was the most common method [27]. With the increase in population, the urban settlement areas expanded, and many of the wastewater treatment plants in the rural areas are now located within the settlements, and the gradual improvement in socioeconomic development and living standards has led the residents to pay more attention to the quality of the living environment [1]. In addition, since the environmental awareness of the public has increased, the odors caused by treatment plants have become a new and troublesome social problem. Another study suggests that municipal waste management in China tends to incinerate instead of landfill, but it causes social conflicts as it impedes the construction of treatment plants near public

Another study reached a more striking conclusion, stating that the inhabitants of 12 Chinese cities protested the incineration projects due to environmental concerns and only three incineration projects were allowed from 2009 to 2015, while others were canceled and the disposal of sludge into the long-term storage or

Since EU member states have to reduce the amount of biodegradable municipal waste to 35% of 1995 by 2016, they have to make the transition from a linear to circular economy where waste can be converted into resources. Therefore, like all biodegradable wastes, wastewater sludge is seen as a source of energy and material production. However, a sewage management should be considered, including the method of processing sludge, where and how the final products (e.g., fertilizer, biogas) are used, the amount of greenhouse gas (GHG) emissions, and the selection of the most sustainable wastewater sludge treatment technology. Composting, anaerobic digestion, incineration, chemical stabilization, and the use of fertilizer in agricultural land are the most commonly used sewage management methods. The change of sludge management methods from country to country was mentioned in

**94**

land or habitats [28].

#### *Sustainable Sewage Sludge Management and Resource Efficiency*

vital that the most efficient sludge management strategy should focus on economic, technological, and societal constraints.

The LCA study, which covers all stages of the product value chain, evaluates the total environmental impact such as global warming, acidification, eutrophication, photochemical smog, human toxicity, ecotoxicity, depletion of abiotic resource, and terrestrial ecotoxicity which are the fundamental impact categories of sludge management.

A literature blending in GHG showed that composting, anaerobic digestion, and incineration have the lowest emissions. Many researchers have indicated that, from an economic point of view only, a large-scale incineration plant or anaerobic digester may be the most effective way to treat sludge. A sludge management that yields the best results requires a systematic solution that combines environmental effectiveness, social acceptability, and economic affordability based on a life cycle approach.

#### **Author details**

Başak Kiliç Taşeli Environmental Engineering Department, Faculty of Engineering, Giresun University, Giresun, Turkey

\*Address all correspondence to: basak.taseli@giresun.edu.tr

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**97**

3163-3169

*Comparative Life Cycle Assessment of Sewage Sludge (Biosolid) Management Options*

[9] Sablayrolles C, Gabrielle B,

Environmental assessment of anaerobically digested sludge reuse in agriculture: Potential impacts of emerging micropollutants. Water Research. 2010;**44**:3225-3233

[11] Bravo L, Ferrer I. Life cycle assessment of an intensive sewage treatment plant in Barcelona (Spain) with focus on energy aspects. Water Science and Technology.

[12] Linderholm K, Tillman AM, Mattsson JE. Life cycle assessment of phosphorus alternative for Swedish agriculture. Resources, Conservation

and Recycling. 2012;**66**:27-39

[13] Tillman AM, Svngby M,

Lundstrom H. Life cycle assessment of municipal waste water systems. International Journal of Life Cycle Assessment. 1998;**3**:145-157

[14] Bridle T, Skrypski-Mantle S. Assessment of sludge reuse options: A life-cycle approach. Water Science and

Technology. 2000;**41**:131-135

[15] Lundin M, Bengtsson M, Molander S. Life cycle assessment of wastewater systems: Influence of system boundaries and scale on calculated environmental loads.

2000;**34**:180-186

Environmental Science and Technology.

[16] Soda S, Iwai Y, Sei K. Model analysis of energy consumption and greenhouse gas emissions of sewage sludge treatment system with different

2011;**64**(2):440-447

2010;**14**:231-241

Montrejaud VM. Life cycle assessment of biosolids land application and evaluation of the factors impact in human toxicity through plant uptake. Journal of Industrial Ecology.

[10] Hospido A, Carballa M, Moreira M.

*DOI: http://dx.doi.org/10.5772/intechopen.91190*

Liao J. Comparative life cycle assessment of sludge management: A case study of Xiamen. China. Journal of Cleaner

[2] Kumar V, Chopra AK, Kumar A. A review on sewage sludge (biosolids)

agriculture. Archives of Agriculture

[3] Available from: https://www.eiga. eu/index.php?eID=dumpFile&t=f&f= 251&token =6df78a58d 435b481e0c 692d7a2ba67cdbe9deb0b [Accessed: 26

[4] Wiloso EI, Heijungs R, Snoo GR. LCA of second generation bioethanol: A review and some issues to be resolved for good LCA practice. Renewable and Sustainable Energy Reviews.

[5] Suh YJ, Rousseaux P. An LCA of alternative wastewater sludge treatment scenarios. Resources, Conservation and

[6] Gallego A, Hospido A, Moreira MT. Environmental performance of wastewater treatment plants for small populations. Resources, Conservation and Recycling. 2008;**52**:931-940

[7] Murray A, Horvath A, Nelson KL. Hybrid life-cycle environmental and cost inventory of sewage sludge treatment and end-use scenarios: A case study from China. Environmental Science and Technologies. 2008;**42**:

[8] Lederer J, Rechberger H. Comparative

conventional and alternative sewage sludge treatment options. Waste Management. 2010;**30**:1043-1056

goal-oriented assessment of

Recycling. 2002;**35**:191-200

[1] Xiao L, Lin T, Wang Y, Ye Z,

Production. 2018;**192**:354-363

a resource for sustainable

2017;**2**(4):340-347

November 2019]

2012;**16**:5295-5308

and Environmental Science.

**References**

*Comparative Life Cycle Assessment of Sewage Sludge (Biosolid) Management Options DOI: http://dx.doi.org/10.5772/intechopen.91190*

#### **References**

*Sustainable Sewage Sludge Management and Resource Efficiency*

technological, and societal constraints.

management.

approach.

vital that the most efficient sludge management strategy should focus on economic,

A literature blending in GHG showed that composting, anaerobic digestion, and incineration have the lowest emissions. Many researchers have indicated that, from an economic point of view only, a large-scale incineration plant or anaerobic digester may be the most effective way to treat sludge. A sludge management that yields the best results requires a systematic solution that combines environmental effectiveness, social acceptability, and economic affordability based on a life cycle

The LCA study, which covers all stages of the product value chain, evaluates the total environmental impact such as global warming, acidification, eutrophication, photochemical smog, human toxicity, ecotoxicity, depletion of abiotic resource, and terrestrial ecotoxicity which are the fundamental impact categories of sludge

**96**

**Author details**

Başak Kiliç Taşeli

Giresun University, Giresun, Turkey

provided the original work is properly cited.

Environmental Engineering Department, Faculty of Engineering,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: basak.taseli@giresun.edu.tr

[1] Xiao L, Lin T, Wang Y, Ye Z, Liao J. Comparative life cycle assessment of sludge management: A case study of Xiamen. China. Journal of Cleaner Production. 2018;**192**:354-363

[2] Kumar V, Chopra AK, Kumar A. A review on sewage sludge (biosolids) a resource for sustainable agriculture. Archives of Agriculture and Environmental Science. 2017;**2**(4):340-347

[3] Available from: https://www.eiga. eu/index.php?eID=dumpFile&t=f&f= 251&token =6df78a58d 435b481e0c 692d7a2ba67cdbe9deb0b [Accessed: 26 November 2019]

[4] Wiloso EI, Heijungs R, Snoo GR. LCA of second generation bioethanol: A review and some issues to be resolved for good LCA practice. Renewable and Sustainable Energy Reviews. 2012;**16**:5295-5308

[5] Suh YJ, Rousseaux P. An LCA of alternative wastewater sludge treatment scenarios. Resources, Conservation and Recycling. 2002;**35**:191-200

[6] Gallego A, Hospido A, Moreira MT. Environmental performance of wastewater treatment plants for small populations. Resources, Conservation and Recycling. 2008;**52**:931-940

[7] Murray A, Horvath A, Nelson KL. Hybrid life-cycle environmental and cost inventory of sewage sludge treatment and end-use scenarios: A case study from China. Environmental Science and Technologies. 2008;**42**: 3163-3169

[8] Lederer J, Rechberger H. Comparative goal-oriented assessment of conventional and alternative sewage sludge treatment options. Waste Management. 2010;**30**:1043-1056

[9] Sablayrolles C, Gabrielle B, Montrejaud VM. Life cycle assessment of biosolids land application and evaluation of the factors impact in human toxicity through plant uptake. Journal of Industrial Ecology. 2010;**14**:231-241

[10] Hospido A, Carballa M, Moreira M. Environmental assessment of anaerobically digested sludge reuse in agriculture: Potential impacts of emerging micropollutants. Water Research. 2010;**44**:3225-3233

[11] Bravo L, Ferrer I. Life cycle assessment of an intensive sewage treatment plant in Barcelona (Spain) with focus on energy aspects. Water Science and Technology. 2011;**64**(2):440-447

[12] Linderholm K, Tillman AM, Mattsson JE. Life cycle assessment of phosphorus alternative for Swedish agriculture. Resources, Conservation and Recycling. 2012;**66**:27-39

[13] Tillman AM, Svngby M, Lundstrom H. Life cycle assessment of municipal waste water systems. International Journal of Life Cycle Assessment. 1998;**3**:145-157

[14] Bridle T, Skrypski-Mantle S. Assessment of sludge reuse options: A life-cycle approach. Water Science and Technology. 2000;**41**:131-135

[15] Lundin M, Bengtsson M, Molander S. Life cycle assessment of wastewater systems: Influence of system boundaries and scale on calculated environmental loads. Environmental Science and Technology. 2000;**34**:180-186

[16] Soda S, Iwai Y, Sei K. Model analysis of energy consumption and greenhouse gas emissions of sewage sludge treatment system with different processes and scales. Water Science and Technology. 2010;**61**(2):365-373

[17] Brown S, Beecher N, Carpenter A. Calculator tool for determining greenhouse gas emissions for biosolid processing and end use. Environmental Science and Technology. 2010;**44**:9509-9515

[18] Nakakubo T, Tokai A, Ohno K. Comparative assessment of technological systems for recycling sludge and food waste at greenhouse gas emissions reduction and phosphorus recovery. Journal of Cleaner Production. 2012;**32**:157-172

[19] EPA, U.S. Environmental Protection Agency. Life Cycle Assessment: Principles and Practice. Washington, DC. EPA/600/R-06/060; 2006

[20] Jiménez-González C, Kim S, Overcash M. Methodology for developing gate-to-gate life cycle inventory information. The International Journal of Life Cycle Assessment. 2000;**5**:153-159

[21] Tillman AM, Ekvall T, Baumann H, Rydberg T. Choice of system boundaries in life cycle assessment. Journal of Cleaner Production. 1993;**2**:21-29

[22] Wiloso EI, Heijungs R, Snoo GR. LCA of second generation bioethanol: A review and some issues to be resolved for good LCA practice. Renewable and Sustainable Energy Reviews. 2012;**16**:5295-5308

[23] ISO: Environmental management– Life cycle assessment: Principles and framework. ISO 14040:2006, ISO, Geneva, Switzerland; 2006

[24] ISO: Greenhouse gases .Carbon footprint of products: Requirements and guidelines for quantification and communication. ISO/TS 14067:2013, ISO, Geneva, Switzerland; 2013

[25] ISO: Environmental management. Water footprint: Principles, requirements and guidelines. ISO 14046:2014, ISO, Geneva, Switzerland; 2014

[26] Yilmaz O, Anctil A, Karanfil T. LCA as a decision support tool for evaluation of best available techniques (BATs) for cleaner production of iron casting. Journal of Cleaner Production. 2015;**105**:337-347

[27] Yang G, Zhang G, Yang H. Current state of sludge production, management, treatment and disposal in China. Water Research. 2015;**78**:60-73

[28] Xiao LS, Wang R, Chiang PC. Comparative life cycle assessment (LCA) of accelerated carbonation processes using steelmaking slag for CO2 fixation. Aerosol and Air Quality Research. 2014;**14**(3):892-904

[29] Deaton BJ, Hoehn JP. Hedonic analysis of hazardous waste sites in the presence of other urban disamenities. Environmental Science and Policy. 2004;**7**(6):499-508

[30] Piippo S, Lauronen M, Postila H. Greenhouse gas emissions from different sewage sludge treatment methods in north. Journal of Cleaner Production. 2018;**177**:483-492

[31] Wang N-Y, Shih C-H, Chiueh P-T, Huang Y-F. Environmental effects of sewage sludge carbonization and other treatment alternatives. Energies. 2013;**6**:871-883

**99**

Section 2

Green Economy
