Reuse of Treated Water from Municipal Treatment Plants in Mexico

*Ángeles Martínez-Orgániz, Ricardo Herrera-Navarrete, Daniel Pineda-Mora, Viridiana Del Carmen-Niño and Rosa Iris Balbuena-Hernández*

## **Abstract**

Wastewater treatment plants (WWTPs) receive a wide variety of contaminants that cannot be eliminated or completely removed with current conventional methods. In this sense, the development and use of advanced technologies is a challenge in countries where wastewater sanitation is hardly a guarantee. However, the reuse of treated urban wastewater can function as an alternative to mitigate water pressure and, at the same time, guarantees water quality for potential reuse in agriculture, in the irrigation of landscape or urban green areas, but especially for aquifer recharge. Therefore, this chapter is focused on reviewing the current state of WWTPs in Mexico and the potential reuse of treated water.

**Keywords:** water quality, water reuse, aquifer recharge, emerging contaminants, Acapulco

## **1. Introduction**

Water is an indispensable natural resource for promoting economic and social development, as well as being of vital and critical importance for ecosystems [1, 2]. Rapid population growth, high rates of urbanization, and climate change are key factors that put pressure on water resources [3]. Of the approximately 1388 million km3 of water on the planet, only 3% (41.64 million km3 ) is freshwater and less than 1% (13.88 million km3 ) is accessible for human consumption [4], with availability limited by quality. According to Wang et al. [5], millions of people die each year from water pollution-related diseases, and they estimate that by 2050 more than half of the world's population will live in water-scarce regions [6].

In addition to water scarcity, pollution has become a matter of global interest and concern [6], and even more so when considering the appearance of new pollutants called emerging contaminants (ECs), identified mainly in urban wastewater, a consequence of the consumption habits of modern society [7]. In this context, the role of wastewater treatment plants (WWTPs) to face the growing need for larger volumes

of contaminant-free water, whose main objective is to ensure the safety of human health and environmental protection, trying to achieve sustainable urban development of local waters, stands out [8].

Conventional WWTPs consist of four stages for efficient treatment (preliminary, primary, secondary, and tertiary) [9]. However, most of these units fail to remove a wide range of emerging contaminants present in wastewater [10]. Currently, the development of new technologies can be considered as a viable alternative for the efficient processing of treated wastewater and potential reuse in water-demanding activities such as landscape irrigation, industry, agriculture, and even aquifer recharge [11].

Latin America is the region with the highest availability of freshwater; it has 33% of renewable water resources, although only part of it is accessible to the population [12]. In this part of the world, only 8% of the wastewater produced daily is treated. Another part is discharged into surface waters, and yet another part is used for irrigation, covering about 500,000 hectares, mostly with untreated water [13]. Countries such as China, Mexico, and the United States have been identified as those that reuse a large volume of wastewater for agricultural activities, and in some cases no efficient treatment is carried out [14]. In contrast, in other cities such as Windhoek, Namibia, and Orange Country, California, good practices in the reuse of treated wastewater (drinking water supply) have been documented [15].

According to Ghafoori et al. [16], Mexico uses wastewater to irrigate approximately 260,000 hectares of green areas (gardens), which is why this country continues to promote resource management for the construction, rehabilitation, maintenance, and operation of WWTPs [17]. On the other hand, Mexico has a comprehensive and modern regulatory framework that offers the possibility of recharging aquifers with reclaimed water under regulated guidelines, since it has a production potential of 144.7 m3 /s through its 2786 installed WWTPs, among which activated sludge treatment predominates as the most widely used process (69.6%) [15, 18].

Some WWTPs in Mexico operate in optimal conditions according to different studies carried out by the scientific community and governmental institutions in the country [18–20]. Treated wastewater is an underutilized resource despite being considered as a viable alternative in a context of environmental degradation in various bodies of water. Therefore, this study was focused on reviewing the current state of WWTPs in Mexico and the potential reuse of treated water in one of its main municipalities, Acapulco. This port located in the South of Mexico has 18 WWTPs, and its effluents are discharged without any use to the Pacific coast and the city's main river. This chapter aims to strengthen Mexico's commitment to the 2030 Agenda and to cover at the local-level Goal 6 (ensure availability and sustainable management of water and sanitation for all), which includes in its third target "halve the proportion of untreated wastewater and substantially increase recycling and safe reuse." Finally, this study may allow other research to expand on the issues related to reuse of treated wastewater and may serve as a guide for making better decisions on the applications of treated wastewater in areas with greater water stress in Mexico.

### **2. Perspective of wastewater management in Mexico**

#### **2.1 Water pollution**

The problem of water pollution began to be noticed in the early nineteenth century and has become one of the most serious environmental problems of our time,

#### *Reuse of Treated Water from Municipal Treatment Plants in Mexico DOI: http://dx.doi.org/10.5772/intechopen.107204*

generating a global scarcity of clean water, hence the importance of conserving and maintaining the quality of natural water sources to ensure its sustainability and use for future generations [21]. It is of utmost importance to consider adequate wastewater treatment processes that comply with the required parameters for the different types of reuse [15]. Mexico's water resources are facing serious pollution problems due to the fact that water quality is below the permissible limits for human health, both surface water and groundwater are used as receiving bodies for heavy loads of conventional and nonconventional pollutants [22].

In recent decades, impacts to the aquatic environment have been detected by nonconventional pollutants, called emerging contaminants (ECs), and these compounds of different origin and chemical nature are originated by drugs, pesticides, surfactants, surfactants, surfactants, personal care products, and among others and have raised great concern to the scientific community, due to the environmental damage they generate by their physicochemical characteristics when combined with other substances, including water and bioacomulative through the trophic chain [23]. Currently, ECs are not considered in monitoring or regulatory programs, despite the existence of several studies on their occurrence, fate, behavior, and toxicological effects on terrestrial and aquatic ecosystems [24]. The overuse and misuse of antibiotics have become a global problem, as the discharge of antibiotics can not only chemically contaminate water but also induce antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) [10].

Currently, more than 600 active pharmaceutical substances (metabolites and transformation products) have been detected in the aquatic environment belonging to different therapeutic groups worldwide [25, 26]. The widespread use and abuse of active substances have made it possible to be detected in different environmental matrices (e.g. surface water, groundwater, wastewater, and stormwater runoff in urban areas) in various concentrations [27–29]. Therefore, understanding the fate of these pollutants in wastewater treatment can contribute to better management and improve the quality of treated effluents [30]. In Mexico, several studies have been conducted on the presence of ECs in aquatic ecosystems [31–36]. Water quality problems are severe and have a significant lag in their attention compared to those related to quantity and provision of services to the population. Water quality monitoring is a process that must be effective, regulated, and updated. In the same way, water quality assessment is essential to guide efforts to promote water reuse [37].

#### **2.2 Characterization of wastewater**

Rapid population growth and high urbanization rates represent challenges in water management; among them, the increase in wastewater generation [38]. Wastewater (WW) consists of 99% water and 1% suspended, dissolved, and colloidal solids [4]. According to the National Water Law of Mexico, WW is "a varied composition resulting from discharges of urban, domestic, industrial, commercial, service, agricultural, livestock, treatment plants and, in general, from any use, as well as a mixture of them" [39]. Other important sources of pollution to consider are hospitals and clinics, where hazardous waste is disposed into municipal sewers [38].

According to Valdes et al. [2], 135,600 liters per second (L/s) of wastewater were treated in Mexico, which corresponds to 63% of the total water recovered from the country's sewerage systems. An estimated reuse rate of 39,800 L/s was also documented directly from treatment plants and 78,800 L/s indirectly after its first discharge into a water body. However, wastewater discharges cause a high


#### **Table 1.**

*Main conventional contaminants present in wastewater and their treatment [41].*


#### **Table 2.**

*Sites of the water quality monitoring network in Mexico [43].*

degree of stress on aquatic ecosystems [40], due to the presence of various types of contaminants resulting from inadequate treatment. In this sense, **Table 1** shows the behavior of conventional-type contaminants, which is unpredictable during treatment since it can be very effective for some of them and null for others [41].

#### **2.3 Water quality assessment**

Water quality is assessed from physical, chemical, and biological characteristics, evaluated individually or as a group. Physicochemical parameters give extensive information on the nature of the chemical species in the water and their physical properties; these analyses are rapid and can be monitored frequently [42]. In Mexico, the water authority (CONAGUA) has a National Water Quality Measurement Network (**Table 2**).

#### *Reuse of Treated Water from Municipal Treatment Plants in Mexico DOI: http://dx.doi.org/10.5772/intechopen.107204*

The main objectives of the network are (I) to provide the water authority and users with reliable results, which can be transformed into information for decisionmaking, and (II) to obtain water quality results from more than 5000 monitoring sites with the highest quality standards. The criteria for the selection of sites to assess water quality are based mainly on representativeness, standardization, and reliability, considering sources of contamination, reference sites and/or areas (hydrological basins), and among others.

To assess surface water quality, the following indicators are taken as the main reference: Biochemical Oxygen Demand (DBO5), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), *Fecal coliforms* (FC), *Fecal enterococci* (FE), *Escherichia coli* (*E. coli*), and Dissolved Oxygen Saturation (DO), taking the median of the set of data from each study site. Whereas, for acute toxicity, it is calculated as the maximum of the toxicities with Daphnia magna and Vibrio fischeri. As shown in **Figure 1**, water quality results are marked in red or yellow when one or more indicators are not met and marked in green when all water quality indicators are met.

The results presented in **Figure 1** show that of the 4233 study sites only 30% (1266 sites marked in red) did not meet the following parameters: DBO5, COD, toxicity, and/or *fecal Enterococci*. While 29.1% (1228 sites marked in yellow) do not comply with the following parameters: *E. coli*, *fecal coliforms*, TSS, and/or percentage of DO. In addition, only 40.9% (1727 sites marked in green) met all water quality indicators in Mexico [43]. Although the water quality indicators assessed in Mexico can provide a lot of information about the state of water resources, they exhibit at least two important problems: water scarcity and contamination; however, the latter does not

**Figure 1.** *Study sites for the assessment of surface water quality in Mexico [43].*

consider the existence of multiple contaminants that, even in small quantities, can be harmful to health and/or the environment [43].

#### **2.4 Sanitation systems in Mexico**

### *2.4.1 Wastewater treatment plants (WWTPs)*

The technologies commonly employed in WWTPs started globally in the early twentieth century; however, today they work with low levels of efficiency and high levels of energy consumption [44]. This situation requires considerable financial investments to renew and update the infrastructures with a focus on new socioeconomic paradigms such as the circular economy that require better use and reuse of water resources [3].

There are two types of wastewater treatment systems: centralized and decentralized. The centralized system is more common in developed countries where economies of scale favor large facilities, while the decentralized system is more attractive in developing countries, which produces lower energy use and simpler designs, but still represent high operating costs for local governments. For example, Mexico has a large urban and rural area that depends on decentralized systems for wastewater treatment [45].

There are 2786 WWTPs in the country (**Figure 2**), which treat approximately 65.7% of the wastewater produced, 144.71 m3 /s. Wastewater treatment does not exceed 70% of the water collected in the drainage systems. Sewerage coverage represents 97.39% in urban areas and 77.52% in rural areas. Of which, 58.8% (1637 WWTPs) have a treatment flow of <5 l/s, 13% (363 WWTPs) have a flow between

#### **Figure 2.**

*Wastewater treatment plants in Mexico classified by treated flow (l/s) [43].*

5.1 and 10 l/s, 22% (612 WWTPs) have a treatment flow of 10.1–100 l/s, 4.5% (125 WWTPs) have a treatment flow rate of 100.1–500 l/s, 0.8% (23 WWTPs) have a treatment flow rate of 500.1–1000 l/s, and 0.9% (26 WWTPs) have a treatment flow >1000 l/s [43].

The most recent information indicates that, until 2020, the country generated an approximate total volume of municipal wastewater of 8.82 thousand hm3 /year (279.80 m3 /s). Of this generated volume, only 6.79 thousand hm3 /year (215.40 m3 /s) were collected by the sewage systems. This means that 76.98% of the municipal wastewater was collected. In addition, only 4.56 thousand hm3 /year (144.71 m3 /s) were treated, which indicates that 51.7% of the total municipal wastewater generated was treated in that year. Whereas 67.15% of the wastewater that was collected by the sanitation systems was treated [43].

On the other hand, in the same period, sewerage coverage in Mexico reached 95.2%, which means that approximately 119.3 million people, in that year, had access to sewerage services. Therefore, the possibility of reusing municipal wastewater represents a promising alternative source of water supply. However, in the absence of efficient treatment, wastewater can constitute an important source of microbiological risk to human health. Available data on the inventory of WWTPs indicate that from 2004 to 2020 it increased from 394 to 2786 (**Figure 3**). This means that, on average, 85 WWTPs were built each year and the total increase is 316%. This indicates that there is a great effort in the country to increase the number of existing plants and that sanitation plans and policies have had results [43].

## *2.4.2 Types of wastewater treatment*

Wastewater treatment consists of a process to remove contaminants, mainly from domestic wastewater, which includes physical, chemical, and biological processes [46]. WWTPs in Mexico have different types of treatment (**Table 3**). The most used process in WWTPs is activated sludge (39.7%); this type of process can treat wastewater with high organic loads and has the potential to produce biogas, as they

#### *Water Quality – New Perspectives*


#### **Table 3.**

*Main treatment processes and volume of wastewater discharge in Mexico [43].*


#### **Table 4.**

*Stages for wastewater treatment in a WWTP [9, 41, 46, 49].*

are considered simple to construct and have low operating costs compared to modern technologies. Modern technologies include membrane processes (reverse osmosis and nanofiltration), membrane bioreactors, advanced oxidation processes, ozonation, photocatalysis, and radiation, which are becoming attractive approaches for WWTPs despite their high maintenance and operation costs [44].

In this sense, conventional WWTPs also need significant financial investments to improve the facilities and processes in each of their stages, and this situation demands the implementation of new technologies [47]. Nevertheless, current conventional methods are considered a widely used technology, capable of producing a safe effluent to protect ecosystems and human health [48]. According to Hong et al. [9], conventional WWTPs operate with the following treatment stages: preliminary, primary, secondary, and tertiary (**Table 4**).

### *2.4.3 Sanitation system in Acapulco*

The city of Acapulco, Guerrero, is a beach tourist resort located in southeastern Mexico at 16°56′56″ N and 99°55′12″ [50]. Its main urban area is developed around

*Reuse of Treated Water from Municipal Treatment Plants in Mexico DOI: http://dx.doi.org/10.5772/intechopen.107204*

#### **Figure 4.**

*Location of WWTPs in the municipality of Acapulco [6, 34, 50].*

a semicircular bay characterized by a rugged topography (**Figure 4**). The climate is of the Aw1 warm sub-humid type with an average annual temperature of 27.8°C and an average annual rainfall of 561 mm [51]. The accelerated urban development that the city has experienced in recent decades and the deficiencies in public services have caused serious water and soil contamination problems, leading to social and environmental vulnerability [52].

Acapulco Bay and the La Sabana River are exposed to contamination due to wastewater discharges and poor solid waste management [53, 54]. To treat wastewater, the city has 18 WWTPs consisting of conventional treatment (activated sludge), managed by the local water agency. Wastewater is collected and transported through the sewerage network, directing the raw water to the treatment units, which are distributed in different parts of the city, discharging the treated wastewater into the La Sabana River or the Pacific Ocean coast [6]. As a study case, the "Aguas Blancas" WWTP was considered as one of the most representative of the city due to its level of efficiency, treatment capacity, and quality of treated water (**Table 5**).

### **3. Potential reuse of treated wastewater in Mexico**

## **3.1 Reuse of wastewater from environmental, social, economic, political, and technical perspectives**

Currently, wastewater treatment has two main purposes: sanitation and reuse [55], the first is related to human health and environmental protection, and the second to


#### **Table 5.**

*Characteristics of the main WWTP in Acapulco [6].*

mitigate contamination and scarcity problems. The reuse of wastewater is not a new practice; there are indications from ancient civilizations, where it was used for crop irrigation [16]. Among the wide variety of applications of treated wastewater are irrigation, groundwater recharge, domestic use, industrial applications, and even the production of drinking water with high-tech treatments [56].

**Table 6** shows the various reuses of treated wastewater using different degrees of purification, but it is also reused untreated, especially in underdeveloped countries in Latin America, Asia, and Africa, with water scarcity arises the need for high-quality effluents. Therefore, it is necessary to promote conventional and advanced tertiary treatments for wastewater treatment [57].

Globally, the largest demand for water comes from the agricultural sector, which accounts for approximately 70% of all freshwater withdrawals; therefore, the reuse of treated wastewater for this sector has become one of the most reliable and low-cost alternatives [58]. According to Valdes et al. [2] in several studies, the reuse of treated wastewater has been demonstrated; however, this practice reveals some advantages and disadvantages (**Table 7**). Therefore, the level of treatment for reuse depends on the water quality requirements for the intended use [59]. In this sense, it is important to determine the environmental, social, economic, political, and technical aspects involved in the reuse of treated wastewater [60].

#### **3.2 Environmental aspect**

WWTPs aim to protect water resources and human health by reducing nutrients and pathogens discharged to water bodies. However, global problems such as pollution and water scarcity induce toward reuse, an issue of high relevance [44]. The reuse of wastewater can be a viable alternative to solve problems mainly related to scarcity, but it is also important not to lose sight of the issue of ECs; WWTPs have been identified as major sources of this type of pollutants affecting aquatic ecosystems [61].

*Reuse of Treated Water from Municipal Treatment Plants in Mexico DOI: http://dx.doi.org/10.5772/intechopen.107204*


#### **Table 6.**

*Possible reuse of treated wastewater on a global scale [57].*


#### **Table 7.**

*Advantages and disadvantages of reuse of treated wastewater [2].*

#### **3.3 Social aspect**

One of the main challenges in the reuse of treated wastewater is the degree of acceptance, influenced by many factors: education, risk awareness, degree of water scarcity or availability of alternative water sources, calculated costs and benefits, trust and knowledge, issues of choice, environmental attitudes, and participation in decisionmaking, in addition to other cultural, religious, and socioeconomic factors [60].

#### **3.4 Economic aspect**

Water reuse for industrial or irrigation purposes is considered to have a lower environmental impact and cost compared to other alternative water supplies such as: water transfers or desalination; however, these practices are carried out in a limited way due to legal and social issues [62]. On the other hand, considerable investment is required to renovate and upgrade WWTPs to operate more efficiently [3]. The cost of water reclamation (including all costs, investment, operation, and maintenance) from wastewater to the level of drinking water which ranges internationally between 0.70 and 1 USD/m3 [63, 64].

### **3.5 Political aspect**

Decision-making is strongly based on political interests and social pressure. Alignment of common objectives on public health, environmental protection, and agricultural development between local authorities and different sectors is needed to overcome these challenges. On the other hand, they point out that the short terms of the municipal government affect the follow-up of a long-term improvement plan for the supply and sanitation of water, postponing financial resources with state or federal instances [60].

### **3.6 Technical aspect**

Most WWTPs are not designed to handle the excess volumes of heavy rainfall, thus affecting the hydraulic systems and causing wastewater overflows. Another technical aspect refers to the managers of the water systems, since they do not have basic training in issues related to laws and regulations with water resources management or knowledge of urban hydraulic infrastructure [60].

### **3.7 Regulatory framework**

The progress of planned wastewater reclamation and reuse depends not only on technological advances but also on the existence of a robust legal framework that establishes guidelines for reuse that does not entail risks for the beneficiaries. Legislation on wastewater reuse on a global scale is a complicated issue because, while there are countries with legal regulations, others only offer recommendations, each with its own parameters and indicators [65].

In Mexico, water is considered a public resource and is administered by the National Water Commission (CONAGUA) through the National Water Law, which is derived from the Mexican Political Constitution and is embodied in two regulatory articles of great interest, in addition to containing other mandatory regulations (**Table 8**). On the other hand, Mexico is a pioneer in establishing a regulation that describes the requirements for aquifer recharge with treated wastewater [68]. There is a strengthened legal framework; however, the lack of compliance with quality standards in water reuse, mainly in effluents, is noticeable. It is possible that strict legislation could lead to unsafe reuse due to the high costs involved in treatment and monitoring [45].

#### **3.8 Proposal for the reuse of treated water: Acapulco, study case**

According to the studies carried out by Martínez-Orgániz et al. [34] and Martínez-Orgániz et al. [69], the "Aguas Blancas" treatment plant complies with the requirements established according to Mexican Standards. The research proposes a modification in the treatment process to avoid the presence of various types of emerging contaminants, and microorganisms such as *E. coli*. It is important to note that this treatment unit discharges its effluent into the sea. Due to its level of treatment in recent years, it is considered one of the best plants nationwide; however, its efficiency potential can be improved under a design similar to the Orange Country plant (**Figure 5**), which is considered a model plant worldwide [15].

The city of Acapulco is one of the most important beach resorts in the country. The current economic situation of the municipality and of the Municipal Drinking


#### **Table 8.**

*Evolution of the legal framework related to wastewater [18, 66, 67].*

Water and Sewerage Operation Agency (CAPAMA) does not allow for the implementation of treatment systems that involve large-scale restructuring. On the other hand, the Aguas Blancas WWTP is located within the urban area of Acapulco; an area with very few possibilities for expansion which limits the creation of new facilities containing other processes (e.g. Microfiltration, Reverse Osmosis, Granular Activated Carbon).

**Figure 5.** *Outline of the process as a proposal for the Aguas Blancas WWTP (adapted from Orange Country [15]).*

Of the Advanced Oxidation Processes (AOP), Ozonation and Hydrogen Peroxide (H2O2) combined with UV (Orange Country) is the most efficient technology for the generation of hydroxyl radicals (OH**<sup>−</sup>** ).

In addition, hydrogen peroxide is considered a green oxidant, as it decomposes into water and oxygen, and its use in wastewater treatment has increased globally in recent years. Therefore, H2O2/UV is the best AOP in terms of meeting the technical, economic, and environmental constraints for advanced treatment [70]. The proposal is to modify the current treatment process to an Advanced Oxidation Treatment (AOP) using hydrogen peroxide (H2O2). Prior to additional UV treatment, it is suggested to consider lengthening the retention time, which can significantly reduce the discharge of several detected ECs and possible adverse effects to the environment and public health [70]. However, the implementation of this proposal could result in the potential reuse of treated water for agriculture, landscaping, and aquifer recharge, which are of great relevance for the development of the region.

#### *3.8.1 Agriculture*

Agriculture consumes between 50% and 90% of the total water demand; therefore, wastewater reuse for this sector is considered a solution to overcome global water stress [71]. Valdes et al. [2] state that reuse of treated wastewater involves benefits and risks as demonstrated in many studies. However, the limitations are reduced with improved treatment technology, which increases the reliability of treated wastewater production and meet the standards. Consequently, many countries have succeeded in treating wastewater to an acceptable quality for unrestricted reuse in agriculture [72].

#### *3.8.2 Landscape*

The reuse of treated wastewater for landscape irrigation, particularly on a regional scale, is an attractive option, since it can combine essential basic needs such as pollution control, preservation of water quality, and volume for sustainable irrigation of green areas; therefore, the reuse of treated wastewater in this area can be considered a viable alternative for irrigation of parks, sports areas, schoolyards, green areas of residential settlements, and golf courses [45, 59]. Landscape irrigation requires large volumes of freshwater; according to the World Health Organization (WHO), urban green areas are an important element for improving the quality of life [2].

#### *3.8.3 Aquifer recharge*

According to Seguí et al. [15], treated wastewater and rainwater represent a great opportunity for their use in the recharge of aquifers; however, to achieve this strategy, hydraulic infrastructure in optimal conditions is required, since they are mixed in the municipal sewerage systems. On the other hand, several studies assure a low public health risk caused by water contamination in the action that involves the recharge of aquifers with reclaimed water from WWTPs, a concern that leads to consider the application of a regulation in Mexico to guarantee the quality of treated water. In this sense, the recharge of an aquifer with reclaimed water is presented as the best environmental contribution to counteract water scarcity. Other benefits include the increase in groundwater reserves and the preservation of aquatic ecosystems [15].

## **4. Conclusions**

The reuse of treated wastewater should be considered a common practice. It is convenient to establish effective social communication so that users are informed about the environmental benefits that this practice entails in their daily lives, and on the positive impact that its reuse would have on agriculture, a sector that demands large quantities of water. On the other hand, the optimal operational functioning of WWTPs must be a priority for local governments, which implies providing them with technical and financial resources, in addition to guaranteeing that treated wastewater effectively reaches the WWTPs through an effective collection system.

In this sense, the environmental legal framework related to water quality and mainly treated wastewater must be strictly and continuously monitored, as failure to comply not only implies sanctions, but also produces negative consequences for the environment. In order to strengthen current regulations, CEs must be taken into account, since they put public health at risk and cause adverse effects on aquatic ecosystems. Finally, this study proposes an adjustment to a WWTP in the municipality of Acapulco in its water treatment line, which consists of complementing the system with an advanced process (AOP) using hydrogen peroxide (H2O2) before UV disinfection. This improvement eliminates a wide variety of ECs and guarantees water quality for potential reuse in agriculture, in the irrigation of landscape or urban green areas, but especially for aquifer recharge. All these practices are of great relevance mainly for those that demand a greater volume of water.

## **Conflict of interest**

The authors declare no conflict of interest.

*Water Quality – New Perspectives*

## **Author details**

Ángeles Martínez-Orgániz1 , Ricardo Herrera-Navarrete2 \*, Daniel Pineda-Mora<sup>2</sup> , Viridiana Del Carmen-Niño3 and Rosa Iris Balbuena-Hernández4

1 Autonomous University of Guerrero, School of Natural Sciences, Carretera Nacional Chilpancingo-Petaquillas, Chilpancingo, Guerrero, Mexico

2 Autonomous University of Guerrero, Regional Development Science Center, Acapulco, Guerrero, Mexico

3 Autonomous University of Guerrero, School of Sustainable Development, Tecpan de Galeana, Guerrero, Mexico

4 Faculty of Nursing, Autonomous University of Guerrero, Acapulco, Guerrero, Mexico

\*Address all correspondence to: rherrera@uagro.mx

© 2022 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] Mishra B, Kumar P, Saraswat C, Chakraborty S, Gautam A. Water security in a changing environment: Concept, challenges and solutions. Water*.* 2021;**13**:1-21

[2] Valdes A, Aguilera EN, Tobón G, Samaniego L, Díaz L, Carlos S. Potential uses of treated municipal wastewater in a semiarid region of Mexico. Sustainability*.* 2019;**11**:1-24

[3] Romano O, Akhmouch A. Water governance in cities: Current trends and future challenges. Water*.* 2019;**11**:1-9

[4] Abd-Elhamid HF,

Abd-Elmoneem SM, Abdelaal GM, Zelenakova M, Vranayova Z, Abd-Elaty I. Investigating and managing the impact of using untreated wastewater for irrigation on the groundwater quality in arid and semi-arid regions. International Journal of Environmental Research and Public Health. 2021;**18**(14):1-17

[5] Wang D, Hubacek K, Shan Y, Gerbens-Leenes W, Liu J. A review of water stress and water footprint accounting. Water*.* 2021;**13**:1-15

[6] Herrera-Navarrete R, Colin-Cruz A, Arellano-Wences HJ, Sampedro-Rosas ML, Rosas-Acevedo JL, Rodriguez-Herrera AL. Municipal wastewater treatment plants: Gap, challenges, and opportunities in environmental management. Environmental Management. 2022;**69**:75- 88. DOI: 10.1007/s00267-021-01562-y

[7] Vasilachi I, Asiminicesei D, Fertu D, Gavrilescu M. Occurrence and fate of emerging pollutants in water environment and options for their removal. Water*.* 2021;**13**:1-34

[8] Zhang L, Shen Z, Fang W, Gao G. Composition of bacterial communities in municipal wastewater treatment plant. Science Total Environment. 2019;**689**:1181-1191. DOI: 10.1016/j. scitotenv.2019.06.432

[9] Hong E, Yeneneh AM, Sen TK, Ang HM, Kayaalp A. A comprehensive review on rheological studies of sludge from various sections of municipal wastewater treatment plants for enhancement of process performance. Advances in Colloid and Interface Science. 2018;**257**:19-30. DOI: 10.1016/j. cis.2018.06.002

[10] Yang L, Wen Q , Chen Z, Duan R, Yang P. Impacts of advanced treatment processes on elimination of antibiotic resistance genes in a municipal wastewater treatment plant. Frontiers of Environmental Science & Engineering*.* 2019;**13**:1-10. DOI: 10.1007/s11783-019-1116-5

[11] Elizondo LS, Mendoza-Espinosa LG. An analysis of water scarcity in a drought prone city: The case of Ensenada, Baja California, Mexico. Tecnología y ciencias del agua*.* 2020;**11**:1-55. DOI: 10.24850/j-tyca-2020-02-01

[12] Pinos JA, Malo AJ. El derecho humano de acceso al agua: una revisión desde el Foro Mundial del Agua y la gestión de los recursos hídricos en Latinoamérica. INVURNUS*.* 2018;**13**:12-20

[13] Milena A, Ortega Y, Mujica E. Potencial de reutilización del efluente de la planta de tratamiento de agua residuales de Timaná- Huila para riego de pasto estrella (Cynodon Plectostachius). Ingenieria y Región. 2017;**2017**:33-44

[14] Abeledo-Lameiro MJ, Ares-Mazas E, Gomez-Couso H. Use of ultrasound irradiation to inactivate Cryptosporidium parvum oocysts in effluents from municipal wastewater treatment plants. Ultrasonics Sonochemistry. 2018;**48**:118- 126. DOI: 10.1016/j.ultsonch.2018.05.013

[15] Seguí LA, Moeller-Chávez G, De Andrés A. Mexico, the water stress: Challenges and opportunities in wastewater treatment and reuse. Water Policy in Mexico. 2019;**2019**:75-87

[16] Ghafoori S, Hassanpour H, Mohamadvali H, Taherei P. Enhancing the method of decentralized multipurpose reuse of wastewater in urban area. Sustainability*.* 2021;**13**:1-12

[17] De Anda J. Saneamiento descentralizado y reutilización sustentable de las aguas residuales municipales en México. Sociedad y Ambiente*.* 2017;**14**:119-143

[18] CONAGUA. Situación del subsector Agua Potable, Alcantarillado y Saneamiento. Comisión Nacional del Agua. México: Secretaría de Medio Ambiente y Recursos Naturales; 2021

[19] Martínez A, Hernández-Flores G, Toribio-Jiménez J, Becerril JE, Sampedro ML, Mendoza-Ramos JE. Tecnologías para la remoción de antibióticos presentes en agua residual. In Tópicos sobre contaminantes y contaminación del agua, Editorial, C., Ed. México; 2019. pp. 419-440

[20] Suárez A, Lembo C, Ríos JY, Vieitez D, Astesiano G, Corzo JF. Casos de estudio en Asociaciones Público-Privadas en América Latina y el Caribe. In: Planta de tratamiento de aguas residuales Atotonilco. México; 2019

[21] Barceló LD, López MJ. Contaminación y calidad química del agua: el problema de los contaminantes emergentes. Fundación Nueva Cultura del Agua. Panel científico-técnico de seguimiento de la política de aguas. Convenio Universidad de Sevilla-Ministerio de Medio Ambiente; 2008. pp. 1-27

[22] Ding X, Wang S, Jiang G, Huang G. A simulation program on change trend of pollutant concentration under water pollution accidents and its application in Heshangshan drinking water source area. Journal of Cleaner Production*.* 2017;**167**:326-336. DOI: 10.1016/j. jclepro.2017.08.094

[23] Naddeo V, Secondes MFN, Borea L, Hasan SW, Ballesteros F Jr, Belgiorno V. Removal of contaminants of emerging concern from real wastewater by an innovative hybrid membrane process - UltraSound, adsorption, and membrane ultrafiltration (USAMe(R)). Ultrasonics Sonochemistry. 2020;**68**:105237. DOI: 10.1016/j.ultsonch.2020.105237

[24] Adeleye AS, Xue J, Zhao Y, Taylor AA, Zenobio JE, Sun Y, et al. Abundance, fate, and effects of pharmaceuticals and personal care products in aquatic environments. Journal of Hazardous Materials. 2022;**424**:127284. DOI: 10.1016/j. jhazmat.2021.127284

[25] Le-Minh N, Khan SJ, Drewes JE, Stuetz RM. Fate of antibiotics during municipal water recycling treatment processes. Water Research. 2010;**44**:4295-4323. DOI: 10.1016/j. watres.2010.06.020

[26] Watkinson AJ, Murby EJ, Costanzo SD. Removal of antibiotics in conventional and advanced wastewater treatment: Implications for environmental discharge and wastewater recycling. Water Research. 2007;**41**:4164- 4176. DOI: 10.1016/j.watres.2007.04.005

*Reuse of Treated Water from Municipal Treatment Plants in Mexico DOI: http://dx.doi.org/10.5772/intechopen.107204*

[27] Arpin-Pont L, Bueno MJ, Gomez E, Fenet H. Occurrence of PPCPs in the marine environment: A review. Environmental Science and Pollution Research International. 2016;**23**:4978- 4991. DOI: 10.1007/s11356-014-3617-x

[28] Hilton MJ, Thomas KV. Determination of selected human pharmaceutical compounds in effluent and surface water samples by highperformance liquid chromatography– electrospray tandem mass spectrometry. Journal of Chromatography A*.* 2003;**1015**:129-141. DOI: 10.1016/ s0021-9673(03)01213-5

[29] McGrane SJ. Impacts of urbanisation on hydrological and water quality dynamics, and urban water management: A review. Hydrological Sciences Journal*.* 2016;**61**:2295-2311. DOI: 10.1080/02626667.2015.1128084

[30] Wang J, Tian Z, Huo Y, Yang M, Zheng X, Zhang Y. Monitoring of 943 organic micropollutants in wastewater from municipal wastewater treatment plants with secondary and advanced treatment processes. Journal of Environmental Sciences (China). 2018;**67**:309-317. DOI: 10.1016/j. jes.2017.09.014

[31] Estrada-Arriaga EB, Cortes-Munoz JE, Gonzalez-Herrera A, Calderon-Molgora CG, de Lourdes R-HM, Ramirez-Camperos E, et al. Assessment of full-scale biological nutrient removal systems upgraded with physico-chemical processes for the removal of emerging pollutants present in wastewaters from Mexico. Science Total Environment*.* 2016;**571**:1172-1182. DOI: 10.1016/j.scitotenv.2016.07.118

[32] Hernández-Tenorio R, Guzmán-Mar JL, Hinojosa-Reyes L, Ramos-Delgado N, Hernández-Ramírez A. Determination of pharmaceuticals

discharged in wastewater from a public hospital using LC-MS/MS technique. Journal of the Mexican Chemical Society*.* 2021;**65**. DOI: 10.29356/jmcs.v65i1.1439

[33] Lopez-Velazquez K, Guzman-Mar JL, Saldarriaga-Norena HA, Murillo-Tovar MA, Hinojosa-Reyes L, Villanueva-Rodriguez M. Occurrence and seasonal distribution of five selected endocrine-disrupting compounds in wastewater treatment plants of the metropolitan area of Monterrey, Mexico: The role of water quality parameters. Environmental Pollution. 2021;**269**:116223. DOI: 10.1016/j. envpol.2020.116223

[34] Martínez-Orgániz Á, Bravo JE, Llompart M, Dagnac T, Pablo J, Vázquez L, et al. Emerging pollutants and antibiotics removed by conventional activated sludge followed by ultraviolet radiation in a municipal wastewater treatment plant in Mexico. Water Quality Research Journal*.* 2021;**56**:167-179. DOI: 10.2166/wqrj.2021.013

[35] Rivera-Jaimes JA, Postigo C, Melgoza-Aleman RM, Acena J, Barcelo D, Lopez de Alda M. Study of pharmaceuticals in surface and wastewater from Cuernavaca, Morelos, Mexico: Occurrence and environmental risk assessment. Science Total Environment*.* 2018;**613-614**:1263-1274. DOI: 10.1016/j.scitotenv.2017.09.134

[36] Robledo VH, Velázquez MA, Montañez JL, Pimentel JL, Vallejo AA, López MD, et al. HidroquÍmica Y Contaminantes Emergentes En Aguas Residuales Urbano Industriales De Morelia, MichoacÁn MÉxico. Revista Internacional de Contaminación Ambiental*.* 2017;**33**:221-235. DOI: 10.20937/rica.2017.33.02.04

[37] Navarro Frómeta AE, Leyva ZC, Mendoza JC. Tópicos sobre

contaminantes y contaminación del agua. Primera Edición: Editorial CLAVE; 2019

[38] WWAP. The United Nations World Water Development Report 2017. Wastewater: The Untapped Resource. United Nations World Water Assessment Programme (WWAP). Paris: UNESCO; 2017

[39] LAN. Ley de Aguas Nacionales. Cámara de diptutados del H. Congreso de la Unión. Última Reforma del Diario Oficial de la Federación (DOF) 06-01- 2020. México. 2020

[40] Almeida P, Albuquerque T, Antunes M, Ferreira A, Pelletier G. Effects of wastewater treatment Plant's discharges on a freshwater ecosystem—A case study on the Ramalhoso River (Portugal). Water, Air, & Soil Pollution*.* 2021;**232**(5):1-11. DOI: 10.1007/ s11270-021-05131-1

[41] Noyola A, Morgan-Sagastume JM, Guereca LP. Selección de Tecnologías para el Tratamiento de Aguas Residuales Municipales: Guía de apoyo para ciudades pequeñas y medianas. Universidad Nacional Autónoma de México. México: Primera Edición; 2013

[42] Pulido-Madrigal L. Riego con aguas residuales para depuración de contaminantes. H2 O Gestión del agua*.* 2017;**14**:12-17

[43] CONAGUA. Comisión Nacional del Agua - Sistema Nacional de Información del Agua (SINA). [Internet]. 2020. Availabe online: http://sina.conagua.gob. mx/sina/ [Accessed: June 02, 2022]

[44] Tang J, Zhang C, Shi X, Sun J, Cunningham JA. Municipal wastewater treatment plants coupled with electrochemical, biological and bio-electrochemical technologies: Opportunities and challenge toward

energy self-sufficiency. Journal of Environmental Management. 2019;**234**:396-403. DOI: 10.1016/j. jenvman.2018.12.097

[45] Garcia D, Muñoz G, Arteaga A, Ojeda-Revah L, Mladenov N. Greening urban areas with decentralized wastewater treatment and reuse: A case study of Ecoparque in Tijuana, Mexico. Water*.* 2022;**14**:1-18

[46] Demirbas A, Edris G, Alalayah WM. Sludge production from municipal wastewater treatment in sewage treatment plant. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects*.* 2017;**39**:999-1006. DOI: 10.1080/15567036.2017.1283551

[47] Szymanski K, Morawski AW, Mozia S. Effectiveness of treatment of secondary effluent from a municipal wastewater treatment plant in a photocatalytic membrane reactor and hybrid UV/H2O2 – Ultrafiltration system. Chemical Engineering and Processing - Process Intensification*.* 2018;**125**:318-324. DOI: 10.1016/j. cep.2017.11.015

[48] Papa M, Foladori P, Guglielmi L, Bertanza G. How far are we from closing the loop of sewage resource recovery? A real picture of municipal wastewater treatment plants in Italy. Journal of Environmental Management. 2017;**198**:9- 15. DOI: 10.1016/j.jenvman.2017.04.061

[49] Caicedo C, Rosenwinkel KH, Exner M, Verstraete W, Suchenwirth R, Hartemann P, et al. Legionella occurrence in municipal and industrial wastewater treatment plants and risks of reclaimed wastewater reuse: Review. Water Research. 2019;**149**:21-34. DOI: 10.1016/j. watres.2018.10.080

[50] INEGI. Aspectos Geográficos de Guerrero, México. Instituto Nacional *Reuse of Treated Water from Municipal Treatment Plants in Mexico DOI: http://dx.doi.org/10.5772/intechopen.107204*

de Estadística y Geografía. [Internet]. 2018. Availabe online: https://en.www. inegi.org.mx/contenidos/app/ areasgeograficas/resumen/resumen\_12. pdf [Accessed: June 10, 2022]

[51] SMN. Precipitación (mm) por Entidad Federativa y Nacional. Servicio Meteorológico Nacional (SMN). Comisión Nacional del Agua. México: Secretaría de Medio Ambiente y Recursos Naturales; 2022

[52] Rodríguez A, Olivier B, López R, Barragán MC, Cañedo R, Valera MÁ. Contaminación y riesgo sanitario en zonas urbanas de la subcuenca del río de La Sabana, ciudad de Acapulco. México. Gestión y Ambiente*.* 2013;**16**:85-95

[53] IMTA. Estudio de clasificación de la Bahía de Acapulco, Gro. Fondos Sectoriales de Investigación y Desarrollo sobre el Agua Convocatoria 2006- 01 de CONAGUA-CONACYT con número de proyecto 48801. Instituto Mexicano de Tecnología del Agua (IMTA). México: Secretaria de medio Ambiente y Recursos Natruales (SEMARNAT); 2009

[54] Pineda D, Toribio J, Leal MT, Juarez AL, González J, Batista RA. Emerging water quality issues along Rio de la Sabana, Mexico. Journal of Water Resource and Protection*.* 2018;**10**:621-636

[55] Salgot M, Folch M. Wastewater treatment and water reuse. Current Opinion in Environmental Science & Health*.* 2018;**2**:64-74

#### [56] Collivignarelli MC,

Abba A, Miino MC, Caccamo FM, Torretta V, Rada EC, et al. Disinfection of wastewater by UV-based treatment for reuse in a circular economy perspective. Where are we at? International Journal of Environmental Research and Public Health. 2020;**18**:1-24

[57] Prats-Rico D. La reutilización de aguas depuradas regeneradas a escala mundial: análisis y prospectivas. Agua y Territorio*.* 2016;**2016**:10-21. DOI: 10.17561/at.v0i8.3292

[58] AbdelMoula S, Sorour MT, Aly SAA. Cost analysis and health risk assessment of wastewater reuse from secondary and tertiary wastewater treatment plants. Sustainability*.* 2021;**13**(23):1-17

[59] Diogo AF, Resende RA, Oliveira AL. Optimised selection of water supply and irrigation sources—A case study on surface and underground water, desalination, and wastewater reuse in a Sahelian coastal arid region. Sustainability*.* 2021;**13**:1-24

[60] De Anda J, Shear H. Sustainable wastewater management to reduce freshwater contamination and water depletion in Mexico. Water*.* 2021;**13**:1-19

[61] Tran NH, Reinhard M, Gin KY. Occurrence and fate of emerging contaminants in municipal wastewater treatment plants from different geographical regions-a review. Water Research. 2018;**133**:182-207. DOI: 10.1016/j.watres.2017.12.029

[62] Rizzo L, Krätke R, Linders J, Scott M, Vighi M, de Voogt P. Proposed EU minimum quality requirements for water reuse in agricultural irrigation and aquifer recharge: SCHEER scientific advice. Current Opinion in Environmental Science & Health*.* 2018;**2**:7-11. DOI: 10.1016/j. coesh.2017.12.004

[63] Seguí-Amórtegui L, Alfranca-Burriel O, Moeller-Chávez G. Metodología para el análisis técnicoeconómico de los sistemas de regeneración y reutilización de las aguas residuales. Tecnología y ciencias del agua. 2014;**55**:55-70

[64] Tello P, Mijailova P, Chamy R. Uso seguro del agua para el reúso. México: Programa hidrologico Internacional; 2016

[65] Asano T, Cotruvo JA. Groundwater recharge with reclaimed municipal wastewater: Health and regulatory considerations. Water Research. 2004;**38**:1941-1951. DOI: 10.1016/j. watres.2004.01.023

[66] Anglés M, Rovalo M, Tejado M. Manual de derecho ambiental mexicano. Mexico: Universidad Autónoma de México. Instituti de investigaciones juridicas; 2021

[67] Maya JM, Pineda N. Avances, estancamiento y limitaciones de la política de saneamiento en México 1998-2014. Entreciencias: Diálogos en la Sociedad del Conocimiento. 2018;**6**:35-50

[68] Gilabert-Alarcón C, Salgado-Méndez S, Daesslé L, Mendoza-Espinosa L, Villada-Canela M. Regulatory challenges for the use of reclaimed water in Mexico: A case study in Baja California. Water*.* 2018;**10**:1-22

[69] Martínez-Orgániz A, Garza-Ramos U, Sampedro-Rosas ML, González-González J, Nava-Faustino G, Toribio J. Patotipos y resistencia a antibióticos de Escherichia Coli en agua residual. Revista Internacional de Contaminación Ambiental*.* 2020;**36**(4):957-966. DOI: 10.20937/ rica.53711

[70] Chong MN, Sharma AK, Burn S, Saint CP. Feasibility study on the application of advanced oxidation technologies for decentralised wastewater treatment. Journal of Cleaner Production*.* 2012;**35**:230-238. DOI: 10.1016/j.jclepro.2012.06.003

[71] Marinelli E, Radini S, Akyol Ç, Sgroi M, Eusebi AL, Bischetti GB, et al. Water-energy-food-climate Nexus in an integrated peri-urban wastewater treatment and reuse system: From theory to practice. Sustainability*.* 2021;**13**:1-13

[72] Mizyed N, Mays DC. Reuse of treated wastewater: From technical innovation to legitimization. In: World Environmental and Water Resources Congress 2020; Henderson, Nevada. 2020

## **Chapter 3**

## Role of Activated Carbon in Water Treatment

*Muthaian Jaya Rajan and Clastin Indira Anish*

## **Abstract**

Heavy metals, such as lead, mercury, zinc, aluminum, arsenic, nickel, chromium, and cobalt, are the common pollutants present within the environment from various natural and Industrial sources. Synthetic dyes are commonly used for dyeing and printing in a variety of industries. The traditional methods for the removal of heavy metals and dyes from wastewater are chemical precipitation, ion exchange, adsorption, membrane processes, and evaporation which require high capital investment and running costs. Activated carbon prepared from agricultural wastes and its by-products are good alternative sources for adsorption because they are low-cost, renewable sources with high carbon, volatile contents, low ash, and reasonable hardness. The preparation means of activated carbon are physical and chemical methods. The important advantages of chemical activation over physical activation are the process that can be accomplished even at lower temperatures and the yield obtained in chemical activation tends to be greater since burn-off char can be avoided. In this chapter, the removal of heavy metals and dyes, using activated carbon, which was prepared by using agricultural waste, biomass was presented. This helps the researchers to accumulate knowledge.

**Keywords:** activated carbon, biomass, adsorption, activation techniques, hardness

### **1. Introduction**

Disposal of dye effluents from various industries containing heavy metals to water bodies causes water pollution. Due to the scarcity of water recycling, wastewater has become a worldwide concern for the past few decades. It is well known that heavy metals in water are harmful and cause toxic effects to human beings when it is consumed and affects the environment. Dyes are the major cause of water pollutants arising from dye manufacturing and textile industries. The waste chemicals and dyehouse effluents liberated from industries must be treated properly to minimize the effects on the environment. Many traditional methods of separation, such as physical and chemical treatment, including coagulation, adsorption, filtration, precipitation, electrodialysis, oxidation, and membrane separation, have been used for the treatment of dye-containing effluents. The adsorption process is one of the best effective and cheaper methods of removing pollutants from wastewater. Green adsorbents used nowadays are high-cost and rare. Therefore, the adsorption process requires an up-gradation in its limitations. The adsorbent employed in the process should

be inexpensive and readily available. Activated carbon prepared from agricultural biomass is an adaptable adsorbent because of its eminent properties, such as large surface area, pore volume, diverse pore structure, extensive adsorption capacity, and a high degree of surface reactivity. Due to large surface area and pore volume of the activated carbon, it can be employed in the removal of color, odor, and taste from water and wastewater. It can also be applicable for the recovery of natural gas and air purification in inhabited spaces, such as chemical industries, and it can act as catalyst and catalyst support material [1, 2]. Activated carbon can be prepared from various carbonous source materials, such as agricultural waste and textile waste. The adsorptive, chemical, structural, and catalytic properties of activated carbon were not only determined by the fundamental nature of the source, but also depends on the method of preparation and conditions used during the process. The preparation of activated carbon from carbonaceous raw material involves a series of processes that has to be done with almost care.

## **2. Carbonization and activation**

Carbonization and activation are the most crucial steps for activated carbon production because these two processes determine the main surface properties and porous structure of the adsorbent. During carbonization, non-carbon and volatile carbon species are removed. An elementary pore structure with a fixed carbon mass is produced. The carbonized material obtained will be an elementary graphitic crystallite with a disordered and poorly developed porous structure. The process is usually achieved at temperatures below 800°C in a gaseous environment without any existing oxidants. The parameters which determine the quality and yield of the carbonized product are rate of heating, final temperature, processing time at the final temperature, and the nature like physical state of the carbonaceous precursor. The activation process increases the pore volume of the material, also enlarges the width of the pores formed during carbonization, and develops new pores of carbonized materials. Due to this, the property of the adsorbent will be increased after the activation process.

### **2.1 Physical and chemical activation**

Physical and chemical activation are traditional processes to improve the properties of the adsorbents. The physical activation is usually carried out at temperatures between 800 and 1000°C. It takes place in the presence of oxidizing gases like steam, carbon dioxide (CO2), air, or a mixture of these gases [3–6]. Commercially prepared activated carbon uses steam activation due to its cost-efficiency. However, CO2 activation develops a narrow micropore in the early stage of activation, whereas steam activation widened the initial microporosity from the beginning. After the process, activated carbon obtained will have lower micropore volume and larger meso and macropore volumes.

During chemical activation, carbonization and activation are carried out in a single-step process. The raw materials infused with chemical agents during chemical activation are thermally breakdown in between 300 and 800**°C**. The most commonly used reagents for chemical activation are zinc chloride (ZnCl2), phosphoric acid (H3PO4), sulfuric acid (H2SO4), and alkaline salts, such as potassium hydroxide (KOH) and sodium hydroxide (NaOH). These reagents serve as oxidants and dehydrating agents so that carbonization and activation can take place simultaneously.

Activated carbons prepared using KOH (aq) and NaOH (aq) activation obtained a surface area of 2000 m<sup>2</sup> g−1 have been [7–9]. Chemical activation using H3PO4, ZnCl2, or KOH and physical activation using CO2 can also develop activated carbon with very high surface area and pore volume [9–12]. Activated carbon prepared from corncob waste biomass has a pore volume of 1.533 cm3 g−1 and a surface area of 2844 m2 g−1. It was obtained due to chemical activation with KOH at a KOH/char ratio of 4, followed by 30 min CO2 gasification. An important merit of using chemical activation is that it can proceed at a lower temperature and takes less time when compared with physical activation. However, the demerit of chemical activation is further treatment or process required for reusing the leftover chemical reagent.

## **3. Structure of activated carbon**

## **3.1 Porous structure activated carbon**

The higher adsorption capability of activated carbon mainly depends on porous characteristics such as surface area, pore size distribution, and pore volume. Up to 15% of ash content is present in activated carbon in the form of mineral matter. The porous structure of activated carbon forms during the carbonization process and it further develops during the activation process. All activated carbons have different porous structures. The pore system of activated carbon differs from one another, and individual pores may vary in shape and size. Activated carbons possess pores from less than a nanometer to thousand nanometers. Pores are classified according to their average width. The distance between the walls of a slit-shaped pore or the radius of a cylindrical pore is an average width. Conventional classification of pore and width is proposed, and it is officially adopted by the International Union of Pure and Applied Chemistry (IUPAC) [13]. The pore type and its width are shown in **Table 1.**

## **3.2 Crystalline structure of activated carbon**

The microcrystalline structure of activated carbon develops during carbonization. Activated carbon structure is entirely different when compared to graphite. The interlayer spacing is different in graphite than in activated carbon. The interlayer spacing of graphite is 0.335 nm, whereas in activated carbon the interlayer spacing is 0.34 to 0.35 nm. Based on the graphitizing ability of activated carbons, they are classified into two types: graphitizing and non-graphitizing carbons. The graphene layers are oriented parallel to each other in graphitizing carbon. The carbon obtained was delicate due to the weak cross-linking between the neighbor micro crystallites and had a less developed porous structure. The non-graphitizing carbons are hard in nature. Strong cross-linking between crystallites in non-graphitizing carbons shows


**Table 1.** *Classification of pore.*

**Figure 1.** *The structural difference between graphitizing (a) and non-graphitizing (b) carbons [14].*

well-developed micropores structure. The formations of non-graphitizing structures with strong crosslink's are promoted by the presence of associated oxygen or by the insufficiency of hydrogen in the original raw material. The structural differences between graphitizing and non-graphitizing carbons are shown in **Figure 1.**

#### **3.3 Chemical structure of activated carbon**

Activated carbon has a porous and crystalline structure. With this, it also has a chemical structure. The adsorption capacity of activated carbon is determined by its porous structure. But it is strongly influenced by a relatively small amount of chemically bonded heteroatom, mainly oxygen and hydrogen [15]. The variation in the arrangement of electron clouds in the carbon skeleton results in the creation of unpaired electrons and incompletely saturated valences which influence the adsorption properties of active carbons, mainly for polar compounds.

## **4. Synthesis of activated carbon**

Up to date, commercial activated carbon (AC) used in wastewater treatment is produced from coals, woods, coconut shells, and lignite [16, 17]. Activated carbons possess several desirable properties that enable their use in adsorption. Properties, such as large surface area and porosity, together with surface chemistry react with molecules with specific functional groups. The wastewater treatment process is less profitable compared to other industrial sectors; it is always preferable to reduce the cost involved in its treatment process. The potential of low-cost adsorbent prepared from bio-waste has been identified in the last decade, and a great number of studies have been conducted to determine the characteristics and efficiencies of activated carbon produced from different bio-waste in the removal of different pollutants from wastewater. Synthesis of activated carbon from biomass generally starts with pretreatment of the sample, including crushing, drying at ~100°C, and sieving to obtain small particles within a specific size range. After these processes, the sample is carbonized in a dry inert atmosphere at 300−500°C, which promotes the elimination of volatile matters and tars and leads to the formation of biochar. Nowadays, the use

#### *Role of Activated Carbon in Water Treatment DOI: http://dx.doi.org/10.5772/intechopen.108349*

of hydrothermal carbonization is attaining popularity in activated carbon production. In the hydrothermal process, the biomass is mixed along with water or reagent solution before carbonization [18].

The product obtained from hydrothermal carbonization is termed hydro char. Due to the different synthesis methods followed in the preparation of biochar, it is claimed that hydrothermal carbonization is more advantageous than traditional carbonization because the drying step carried out in the preliminary stage is not required. In such a process, a lower temperature of 180−250°C is used. The pressure released from the steam due to its closed system acts as an extra driving force to convert the biomass into hydro char. The formation of subcritical water under such conditions degrades cellulose, hemicelluloses, and lignin in the biomass [19]. The acidic gases, such as carbon dioxide (CO2), nitrogen dioxide (NO2), and sulfur dioxide (SO2). eliminated during the heating will react with water to form an acidic solution. Therefore, the need to treat such gaseous pollutants is not required. The presence of several functional groups, especially oxygenated ones, on the hydro char was also found, which results in a higher adsorption capacity of contaminants [20]. The presence of functional groups improves the adsorption of heavy metals on the hydro char despite lower surface area compared to activated carbon [21]. After the carbonization of biomass, physical or chemical activations are required to activate the carbonized material. Physical activation is normally performed by passing inert gases, such as carbon dioxide (CO2), nitrogen (N2), or steam [22]. The gases are passed into the carbonized material at a high temperature of 700−900°C. Under these conditions, the conversion of carbonized material into CO2 gas through oxidation is limited. Hence the yield of activated carbon is increased when compared to activation using air. Chemical activation proceeds only in the addition of activating reagents usually acid or base to the carbonous material. Former heating at 300−500°C is done, followed by washing the activated carbon to neutralize its pH. Potassium hydroxide (KOH) is one of the common basic reagents used in chemical activation. It inhibits tar formation in carbonized biomass [23]. In addition, KOH reacts with carbon in the precursor to form potassium carbonate (K2CO3), which then reacts further with carbon to form potassium (K), potassium oxide (K2O), carbon monoxide (CO), and carbon dioxide (CO2) [24]. These processes generate porosities in the adsorbents with large micropore volumes and narrower size distribution.

## **4.1 Preparation of activated carbon from agricultural waste biomass**

Activated carbon is prepared from hemp stem [25]. The hemp stem was carbonized at 500°C in nitrogen (N2) atmosphere for 1 hour. The carbonized material was then ground and mixed with potassium Hydroxide (KOH) solution for 24 hours, then it was dried and activated at 800°C in nitrogen (N2) atmosphere. When zinc chloride (ZnCl2) is added, it reacts with the char and governs the pore distribution during the heat treatment [26]. Acidic activating reagents are commonly used. Addition of phosphoric acid (H3PO4) to the carbonous material causes hydrolysis of glycosidic linkage in polysaccharides of hemicellulose and cellulose [27]. When phosphoric acid is used during chemical activation, it is possible to control the reaction of the acid with the carbonized biomass by utilizing the gases used. The resulting activated carbon prepared from hemp biomass will get an application of adsorbent for removing dyestuffs and also in wastewater treatment process.

Activated carbon prepared from spent tea leaves is mixed with phosphoric acid (H3PO4) and heated at 450°C in oxygen and air atmosphere [28]. Phosphoric acid

(H3PO4) reacts with oxygen and air atmosphere to form phosphorus oxides, then phosphorus oxides react with oxygen to form cerium oxide (CeO2) electron pair bonds. Due to the extension of polyaromatic cross-linking, the higher porosity and high surface area could be observed in the formation of activated carbon. Phosphoric acid reacts in the air atmosphere to form phosphorus pentoxide (P2O5), and it sublimes from the activated carbon to increase its porosity development to a further extent. Activated carbon prepared by using steam activation in the atmosphere increases the deposition of carbon and decreases the porosity. When physical activation is compared to chemical activation, it requires a higher cost due to the chemical activating reagent and acid/base utilized for neutralizing pH in activated carbon. Consumption of energy will be lowered due to the lower temperature requirement during chemical activation [29]. Activated carbon prepared from chemical activation will have a higher surface area and well-developed porosity compared to the physical activation process [30]. Therefore, chemical activation is more widely followed in the preparation of activated carbon.

The merits of chemical activation over physical activation can be explained by the microstructure model [31]. This model states that every activated carbon material contains numerous micro domains in spherical shape, where the micropores develop. Mesopores, on the other hand, formed in inter micro domain space. Using physical (steam) and chemical activation (KOH), the phenol resin-based spherical carbon was converted to activated carbon via chemical activation. Activated carbon prepared by potassium hydroxide (chemical activation) exhibits a larger surface area, micropore volume, and average pore width. Whereas activated carbon prepared by physical activation by means of steam activation has less surface area, pore width, and micropore volume even at the same activation temperature. Surface area of the activated carbon material using a chemical process is 2878 m2 /g, at an activation temperature of 900°C, while activated by steam (physical activation) possesses a surface area of 2213 m<sup>2</sup> /g. A lower yield of activated carbon occurs in chemical activation when a loss of carbon mass obtains during homogeneous pore development in the intra-micro domain regions. During physical activation using steam, homogeneous activation was observed, which results in lowering the efficiency of micropore development. Reduction of sizes of particles may also occur. Steam activation produces a lower yield of activated carbon with limited porosity, while chemical activation produces a uniform pore development.

Modifications are attempted in synthesizing activated carbon. The biomass is mixed with activating agents for chemical activation before pyrolysis. The pyrolysis process is carried out at high temperatures of 550−900°C. This method of preparing activated carbon is termed a one-step process. The preparation of activated carbon at a low temperature below 550°C after that activating agent is added for chemical activation. This process is termed as two-step pyrolysis process.

Activated carbon is prepared from corn stalk. One- and two-step processes of activation methods are followed for adsorbing cadmium. After the preparation and treatment of the contaminants, two-step pyrolysis processes increased the microporosity and surface area of the activated carbon. Therefore, the activated carbon prepared using two-step pyrolysis process shows higher adsorption capacity. There is no difference in its electrochemical properties. Activated carbon prepared from corn stalk shows its ability in removing cadmium from wastewater.

Activated carbon is prepared from *Cassia fistula* commonly called golden shower tree. A three-step process was done to synthesize activated carbon. The *C. fistula* was cleaned, dried, and crushed. The crushed sample was carbonized. The hydrochar

## *Role of Activated Carbon in Water Treatment DOI: http://dx.doi.org/10.5772/intechopen.108349*

obtained was further pyrolyzed to form biochar. Finally, it was activated by using potassium carbonate (K2CO3). After the application to adsorption process, the prepared activated carbon shows high performance in cationic dyes. It is evident that three-step preparation processes are more advantageous than using one-step and twostep processes. Morphological studies show that the adsorbent's character strongly depends on its preparation method. Activation process helps the adsorbent to increase its pore volume. Increase in pore volume enhances the adsorbent property to absorb more amounts of dyes. Preparation of Activated carbon using three-step processes reveals that it is a more effective method than other processes. Activated carbon prepared from *C. fistula* is a promising material for removing dyes from wastewater.

Activated carbon is prepared from *Tamarindus indica fruit shell*. It was washed with distilled water to remove its dirt and dried under sunlight to remove its water


#### **Table 2.**

*Preparation of activated carbon from various agricultural waste biomasses, activating agent and its studies [32].*

content. It is chemically activated by using ammonium chloride (NH4Cl). The activated material is filtered and carbonized at 500°C for 2 hours [32]. The Langmuir model shows the formation of the adsorbent's monolayer coverage is at the adsorbent's outer space. While Freundlich model isotherm analysis confirms the monolayer adsorption capacity was high. The maximum dye removal percentage was 24.3 g l − <sup>1</sup> . From this, it is evident that the *T. indica fruit shell* biomass is a promising adsorbent for removing textile dyes and also it can be employed in wastewater treatment process. **Table 2** lists some of the biomass prepared from agricultural waste which can be employed in the water treatment process.

## **5. Applications of activated carbon**

Activated carbons are proven to be effective in the removal of various pollutants from aqueous solutions, including dyes, pharmaceutical personal care products (PPCPs), heavy metals, and organic pollutants.

## **5.1 Removal of dyes from water resources**

Dyes are one of the heavy pollutants which affect water bodies, due to the usage of dyes in paints, clothing, paper products, and plastics. In the textile industry alone, there are more than 3600 types of dyes used (Pure Earth and Green Cross Switzerland, 2017). Around 2−20% of dyes used for coloring in the textile industry are eliminating effluent. Therefore, the textile industry is the root cause of water pollution [33]. Due to the complex structure of dye molecules, the dyes do not degrade in water. Dyes mixed in water bodies, such as ponds, lake, and river, reduce the amount of sunlight reaching water sources, and due to that, photosynthesis gets affected for aquatic plants as well as animals [34]. Polluted water intake by humans also causes mutagenic and carcinogenic effects [35, 36]. Therefore, advanced studies are carried out on removing toxic dyes. For example, methylene blue (MB), a dye used in the textile industry causes complications in eyes, affects brain functions, and also causes skin diseases [37]. **Table 3** lists some of the biomass prepared from agricultural waste involved in removing dyes from water resources.

## **5.2 Removal of heavy metals from water**

Heavy metals and anions present in drinking water become a challenging problem among the public due to their causes. The sources of these heavy metals and ions are paint industry, chemical plants, textile dying, dumping of waste in landfills, etc. Most


**Table 3.**

*Dyes adsorption on adsorbents derived from biomass for water treatment [36, 37].*


**Table 4.**

*Activated carbon from agricultural biomass in active removal of heavy metals from water [38, 39].*

of the ions liberate from industries are toxic and carcinogenic to the environment as well as to humans. Consumption of water, which contains metal ions and anions, usually causes chronic effects instead of acute effects. Long-term disease will be affected by humans due to the usage of this contaminated water. Up to date the effects of heavy metals present in drinking water are identified in human body [38]. Despite the efficiency of adsorption in the removal of contaminants from wastewater, the use of commercially activated carbon is undesirable due to the low affinity towards heavy metals [39]. Therefore, it is vital to develop other adsorbents, especially from biomass waste, to minimize the heavy metal ions from entering the water bodies. **Table 4** lists out some of the biomass prepared from agricultural waste involved in removing heavy metal ions.

### **5.3 Removal of organic pollutants from water bodies**

Palm oil is one of the main ingredients in cooking [40]. Usage of these oils globally, the economic growth raised in some countries like Malaysia and Indonesia, Around 39% of palm oil production is from Malaysia. Despite these huge benefits and economic credits, the removal of oil effluent is a major challenge. Palm oil mill effluent (POME) is a byproduct obtained after processing palm seeds. This effluent contains a high chemical oxygen demand (COD) and biological oxygen demand (BOD). Elimination of palm oil effluent in water sources affects aquatic lives due to the formation of harmful compounds in water. Palm oil mill effluent appears in black or brownish-colored slurry with a foul smell. The traditional method of treating Palm oil mill effluent was dumped in a large pit to degrade. It needs a large land area and long time to degrade [41]. This conventional method of treatment is not effective so the effluent will remain toxic. Therefore, adsorption is one of the best suitable techniques that can be applicable in removing oil effluent. **Table 5** represents some of the adsorbents prepared from agricultural waste biomass that effectively remove toxic compounds from oil effluents.

#### **5.4 Pharmaceutical and personal care products (PPCPs) - pollutant removal**

Due to the increase in diseases all over the world people are practicing or in- taking various kinds of drugs. The commonly used drugs are analgesics, antibiotics, anti-inflammatories, as well as painkillers [42]. Due to the large demand for drugs, production is getting increased, and also pharmaceutical waste is getting increased.


#### **Table 5.**

*Activated carbon from agricultural biomass in active removal of organic pollutants from water bodies [40, 41].*

Pharmaceutical and personal care products (PPCPs) are also the major cause of pollution, due to the disposal of waste in water sources. The toxic compounds liberated in water sources are consumed by wild animals and also human beings and cause various health issues. Biological activity of humans gets affected due to the consumption of drugs even in low concentrations [43]. Carbamazepine, naproxen, diclofenac, and ibuprofen are some of the drugs that are commonly practiced and cause biological effects in humans [44]. The contamination sources of pharmaceutical and personal care products (PPCPs) include hospital effluents, medical waste from factories during production of drugs, and waste due to consuming medicine discharged from the body and disposal of medicinal waste in landfills. **Table 6** represents the activated carbon synthesized from biomass to remove the medicinal waste in water.

## **5.5 Other applications of activated carbon**

## *5.5.1 Removing contaminants in drinking water that add color, odor, and flavor*

The surface of activated carbon helps in effective removal or adsorption of organic compounds. Change in the surface morphology of activated carbon removes flavor, odor, and color from drinking water. The activated carbon is calcinated at high


#### **Table 6.**

*Activated carbon from agricultural biomass in active removal of pollutants in pharmaceutical and personal care products (PPCPs) [43, 44].*

#### *Role of Activated Carbon in Water Treatment DOI: http://dx.doi.org/10.5772/intechopen.108349*

temperatures to increase its surface area. After the carbon preparation, it is activated by steam. Due to this process, the surface area of the activated carbon increases. Adsorption property gets improved after the activation so that the odor and taste of the drinking water will be easily changed. The odor produced by the organic compounds and undesirable substance gets into the pores of the activated carbon. Therefore, the unwanted materials can be removed easily [45].

## *5.5.2 Decaffeination of coffee*

Decaffeination is done to remove the extra content of caffeine present in coffee. Activated carbon is employed in removal of caffeine from coffee. Activated carbon is mixed with a solution of ethyl cellulose to adsorb ethyl cellulose. After this process, the activated carbon-containing ethyl cellulose is allowed to dry. Then, the aqueous coffee extract is added to the activated carbon-containing ethyl cellulose. This mixture will extract the caffeine present in the coffee. Activated carbon employed in decaffeination can be reused in the same application. This improves the cost-effective removal method and also cheaper adsorbent [45].

## *5.5.3 Refining sugar, honey, and candies*

Refining or bleaching of cane sugar and honey is done in food industries. The bleaching process is made in liquid with a certain temperature to reduce its viscosity. Chemically activated carbons prepared from softwoods are best suited for treating darker syrups. The pH of the activated carbon is adjusted to neutral one to do this bleaching process. This refining method is cheaper with high efficiency [45].

## *5.5.4 Discoloration of liquors, juices, and vinegars*

Activated carbon prepared from powdered wood is commonly used. The synthesis of activated carbon from powdered wood increases the size of the pores. An increase in porosity adsorbs the color molecules faster. Powdered wood-activated carbon can be directly added to liquors, juices, and vinegars. On constant stirring, the color will be adsorbed to the activated carbon. The contact time will depend upon the color of the compound. This discoloration method is effective cheaper and easy to process [45].

## *5.5.5 Water treatment in industries*

Activated carbon is commonly used in water treatment industries. By using activated carbon-heavy metals, organic contaminants can be easily removed. Chemical activation will increase the surface and porosity of the activated carbon. Due to this, the adsorption process will occur faster and more effectively. Activated carbon from waste materials like agricultural biomass is used nowadays. This made the treatment process an economic one [45].

#### *5.5.6 Tertiary wastewater treatment*

Activated carbon with the mineral origin is more suitable for the treatment of wastewater. Due to the range of pore formation in activated carbon during the activation process, the adsorption behavior of the material increases. The contaminants

present in the wastewater will be completely eliminated during the treatment process. The odor and color will also be removed [45].

#### *5.5.7 Purification of air and industrial gases*

Toxic gases emitted from industries can be treated by using activated carbon. It adsorbs the toxic material and organic pollutants present in the air. Coconut shell-activated carbon is commonly used because it is a micropore material. Greater granulometry than the coconut shell activated carbon is employed in water treatment process to avoid pressure drop. Chemically activated carbons are used to adsorb organic compounds. Standard activated carbon cannot retain organic compounds and acid gases like aldehydes, ammonia, or mercury vapors [45].

### *5.5.8 Compressed air purification (diving tanks and hospitals)*

To fill oxygen or compressed air in a tank pump is essential. But the pumping equipment will release oils and impurities during pumping. The adsorption filters made using activated carbon are fixed in tanks and pumps to ensure that the air technically remains oil free. This effectively reduces petroleum-derived vapors. The coalescing filters and adsorption filters fixed in the pump will provide compressed air with the highest quality [45].

### *5.5.9 Recovery of gold, silver, and other precious metals*

An activated carbon with a micropore can retain gold, silver, and precious metals. The right size of the adsorbent can give adsorption kinetics in accordance with hydraulics of the process which works better than other processes. The activated carbon should have a certain hardness to withstand acid elution, washing processes at various temperatures, and thermal reactivation [45].

## **6. Conclusion**

Getting clean drinking water and also consuming becomes a major challenge nowadays. Therefore, recycling wastewater effectively fulfills these major problems. The most common problems faced in water treatment process are adsorbents. Adsorbents used in water treatment process are costly and also not available. Due to this, the entire process becomes expensive and non-profitable. Activated carbon prepared from agricultural biowaste can be used as an adsorbent. It has a high potential to replace commercial activated carbon in wastewater treatment processes due to its low cost and high performance. Advancement in adsorption process using biomass is a solution to the challenges of water scarcity. It will certainly lead to large-scale applications of activated carbons from renewable sources in wastewater treatment industry.

## **Acknowledgements**

Dr. M. Jaya Rajan (Associate Professor, Department of Chemistry & Research) and Anish C.I (Research Scholar, Register No: 19113012031017) acknowledge the research

*Role of Activated Carbon in Water Treatment DOI: http://dx.doi.org/10.5772/intechopen.108349*

center Annai Velankanni College, Tholayavattam-629157, Affiliated to Manonmaniam Sundaranar University, Tirunelveli- 627012, Tamil Nadu, India. providing support for this chapter.

## **Author details**

Muthaian Jaya Rajan1 \* and Clastin Indira Anish<sup>2</sup>

1 Department of Chemistry and Research, Annai Velankanni College, Tholayavattam, Tamil Nadu, India

2 Department of Chemistry, Annai Velankanni College, Tholayavattam Affiliated to Manonmaniam Sundaranar University, Tirunelveli, Tamil Nadu, India

\*Address all correspondence to: jayarajanm1983@gmail.com

© 2022 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] Bansal RC, Donnet JB, Stoeckli F. Active Carbon. New York: Dekker; 1988. p. 482

[2] Marsh H, Menendez R. Introduction to Carbon Science. 1st ed. United States: Butterworth-Heinemann; 1989. pp. 1-36. ISBN 9780408038379. DOI: 10.1016/ B978-0-408-03837-9.50006-3

[3] Gonzalez MT, Molina-Sabio M, Rodriguez-Reinoso F. Steam activation of olive stone chars, development of porosity. Carbon. 1994;**32**:1407-1413

[4] Molina-Sabio M, Gonzalez MT, Rodríguez-Reinoso F, Sepulveda-Escribano A. Effect of steam and carbon dioxide activation in the micropore size distribution of activated carbon. Carbon. 1996;**34**:500-509

[5] Gonzalez MT, Rodriguez-Reinoso F, Garcia AN, Marcilla A. CO2 activation of olive stones carbonized under different experimental conditions. Carbon. 1997;**35**:159-165

[6] Yang T, Lua AC. Characteristics of activated carbons prepared from pistachio-nut shells by physical activation. Journal of Colloid Interface Science. 2003;**267**:408-417

[7] Guo Y, Yang S, Yu K, Zhao J, Wang Z, Xu H. The preparation and mechanism studies of Rice husk based porous carbon. Materials Chemistry and Physics. 2002;**74**:320-323

[8] Lillo-Rodenas MA, Cazorla-Amoros D, Linares-Solano A. Understanding chemical reactions between carbons and NaOH and KOH an insight into the chemical activation mechanism. Carbon. 2003;**41**:267-275

[9] Tseng RL, Tseng SK, Wu FC. Preparation of high surface area carbons from corncob with KOH etching plus CO2 gasification for the adsorption of dyes and phenols from water. Colloids and Surfaces. 2006;**279**:69-78

[10] Molina-Sabio M, Rodríguez-Reinoso F, Caturla F, Selles MJ. Development of porosity in combined phosphoric acid-carbon dioxide activation. Carbon. 1996;**34**:457-462

[11] Hu Z, Srinivasan MP. Mesoporous high-surface-area activated carbon. Microporous and Mesoporous Materials. 2001;**43**:267-275

[12] Hu Z, Guo H, Srinivasan MP, Yaming N. A simple method for developing Mesoporosity in activated carbon. Separation and Purification Technology. 2003;**31**:47-52

[13] Lay JJ, Fan KS, Chang JI, Ku CH. Influence of chemical nature of organic wastes on their conversion to hydrogen by heat-shock digested sludge. International Journal of Hydrogen Energy. 2005;**28**:1361-1367

[14] Zhang ML, Fan YT, Xing Y, Pan CM, Zhang GS, Lay JJ. Enhanced bio hydrogen production from cornstalk wastes with acidification pre treatment by mixed anaerobic cultures: Biomass. Bioenergy. 2007;**31**:250-254

[15] Chou CH, Wang CW, Huang CC, Lay JJ. Pilot study of the influence of stirring and pH on anaerobes converting high-solid organic wastes to hydrogen. International Journal of Hydrogen Energy. 2008;**33**:1550-1558

[16] Demirbas A. Agricultural based activated carbons for the removal of dyes from aqueous solutions: A review. Journal of Hazardous Materials. 2009;**167**:1-9

*Role of Activated Carbon in Water Treatment DOI: http://dx.doi.org/10.5772/intechopen.108349*

[17] Li W, Yang KB, Peng JH, Zhang LB, Guo SH, Xia HY. Effects of carbonization temperatures on characteristics of porosity in coconut shell chars and activated carbons derived from carbonized coconut shell chars. Industrial Crops and Products. 2008;**28**(2):190-198

[18] Islam MA, Sabar S, Benhouria A, Khanday WA, Asif M, Hameed BH. Nanoporous activated carbon prepared from karanj (Pongamiapinnata) fruit hulls for methylene blue adsorption. Journal of the Taiwan Institute of Chemical Engineers. 2017;**74**:96-104

[19] Kalderis D, Kotti MS, Mendez A, Gasco G. Characterization of hydrochars produced by hydrothermal carbonization of rice husk. Solid Earth. 2014;**5**(1):477-483

[20] Liu W, Wang X, Zhang M. Preparation of highly mesoporous woodderived activated carbon fiber and the mechanism of its porosity development. Holz Forschung. 2017;**71**(5):363-371

[21] Zhou N, Chen H, Xi J, Yao D, Zhou Z, Tian Y, et al. Biochars with excellent Pb(II) adsorption property produced from fresh and dehydrated banana peels via hydrothermal carbonization. Bio resource Technology. 2017;**232**:204-210

[22] Selvaraju G, Abu Bakar NK. Production of a new industrially viable green activated carbon from Artocarpus integer fruit processing waste and evaluation of its chemical, morphological and adsorption properties. Journal of Cleaner Production. 2017;**141**:989-999

[23] Azmi NB, Bashir MJ, Sethupathi S. Anaerobic stabilized landfill leachate treatment using chemically activated sugarcane bagasse activated carbon kinetic and equilibrium study.

Desalination and Water Treatment. 2016;**57**(9):3916-3927

[24] Basta AH, Fierro V, El-Saied H, Celzard A. 2-steps KOH activation of rice straw an efficient method for preparing high-performance activated carbons. Bio resource Technology. 2009;**100**(17):3941-3947

[25] Zhang B, Ma Z, Yang F, Liu Y, Guo M. Adsorption properties of ion recognition rice straw lignin on PdCl: Equilibrium, kinetics and mechanism. Colloids and Surface. 2017;**514**:260-268

[26] Caturla F, Molinasabio M, Rodriguezreinoso F. Preparation of activated carbon by chemical activation with Zncl2. Carbon. 1991;**29**(7):999-1007

[27] Ahmed TF, Sushil M, Krishna M. Impact of dye industrial effluent on physicochemical characteristics of Kshipra River Ujjain City India. International Research Journal of Environmental Sciences. 2012;**1**(2):41-45

[28] Kan Y, Yue Q , Li D, Wu Y, Gao B. Preparation and characterization of activated carbons from waste tea by H3PO4 activation in different atmospheres for oxytetracycline removal. Journal of the Taiwan Institute of Chemical Engineers. 2017;**71**:494-500

[29] Tang CF, Shu Y, Zhang RQ, Li X, Song JF, Li B, et al. Comparison of the removal and adsorption mechanisms of cadmium and lead from aqueous solution by activated carbons prepared from Typhaangustifolia and Salix matsudana. The Royal Society of Chemistry Advances. 2017;**7**(26):16092-16103

[30] Zubrik A, Matik M, Hredzak S, Lovas M, Dankova Z, Kovacova M, et al. Preparation of chemically activated carbon from waste biomass by single

stage and two-stage pyrolysis. Journal of Cleaner Production. 2017;**143**:643-653

[31] Kim DW, Kil HS, Nakabayashi K, Yoon SH, Miyawaki J. Structural elucidation of physical and chemical activation mechanisms based on the micro domain structure model. Carbon. 2017;**114**:98-105

[32] Abisha BR, Anish C, Beautlin Nisha R, Daniel Sam N, Jaya Rajan M. Adsorption and equilibrium studies of methyl orange on tamarind shell activated carbon and their characterization. Phosphorus, Sulfur, and Silicon and the Related Elements. 2022;**197**(3):225-230

[33] Chequer FMD, de Oliveira GAR, Ferraz ERA, Cardoso JC, Zanoni MVB, de Oliveira DP. Textile dyes: Dyeing process and environmental impact. In: Eco-friendly Textile Dyeing and Finishing. London, United Kingdom: IntechOpen; 2013 [Online]. Available from: https://www.intechopen.com/ chapters/41411 DOI: 10.5772/53659

[34] Regti A, Laamari MR, Stiriba S-E, El Haddad M. Potential use of activated carbon derived from Persea species under alkaline conditions for removing cationic dye from wastewaters. Journal of the Association of Arab Universities for Basic and Applied Sciences. 2017;**24**:10-18

[35] Alizadeh N, Mahjoub M. Removal of crystal violet dye from aqueous solution using surfactant modified NiFe2O4 as nano adsorbent isotherms, thermodynamics and kinetics studies. Journal of Nano Analysis. 2017;**4**(1):8-19

[36] Kalita S, Pathak M, Devi G, Sarma HP, Bhattacharyya KG, Sarma A, et al. Utilization of Euryale ferox Salisbury seed shell for removal of basic fuchsin dye from water equilibrium and kinetics investigation. The Royal Society of Chemistry Advances. 2017;**7**(44):27248-27259

[37] Ardekani PS, Karimi H, Ghaedi M, Asfaram A, Purkait MK. Ultrasonic assisted removal of methylene blue on ultrasonically synthesized zinc hydroxide nanoparticles on activated carbon prepared from wood of cherry tree experimental design methodology and artificial neural network. Journal of Molecular Liquids. 2017;**229**:114-124

[38] Jaishankar M, Tseten T, Anbalagan N, Mathew BB, Beeregowda KN. Toxicity, mechanism and health effects of some heavy metals. Interdisciplinary Toxicology. 2014;**7**(2):60-72

[39] Sigdel A, Jung W, Min B, Lee M, Choi U, Timmes T, et al. Concurrent removal of cadmium and benzene from aqueous solution by powdered activated carbon impregnated alginate beads. Catena. 2017;**148**:101-107

[40] Igwe J, Onyegbado C. A review of palm oil mill effluent (POME) water treatment. Global Journal of Environmental Research. 2007;**1**(2):54-62

[41] Kaman SPD, Tan IAW, Lim LLP. Palm oil mill effluent treatment using coconut shell based activated carbon adsorption equilibrium and isotherm. In: MATEC Web of Conferences. Vol. 2017. 2017. p. 03009. MATEC Web of Conferences 87, 03009 (2017) ENCON 2016

[42] Sun JT, Zhang ZP, Ji J,

Dou ML, Wang F. Removal of Cr6+ from wastewater via adsorption with highspecific-surface-area nitrogen-doped hierarchical porous carbon derived from silkworm cocoon. Applied Surface Science. 2017;**405**:372-379

[43] Ebele AJ. Pharmaceuticals and personal care products (PPCPs) in *Role of Activated Carbon in Water Treatment DOI: http://dx.doi.org/10.5772/intechopen.108349*

the freshwater aquatic environment. Emerging Contaminants. 2017;**3**(1):1-16

[44] Archer E, Petrie B, Kasprzyk-Hordern B, Wolfaardt GM. The fate of pharmaceuticals and personal care products (PPCPs) endocrine disrupting contaminants (EDCs) metabolites and illicit drugs in a waste water treatment works and environmental waters. Chemosphere 2017;**174**:437-446

[45] Carbotecnia [Internet]. 2021. Available from: https://www.carbotecnia. info/learning-center/activatedcarbon-theory/activated-carbonapplications/?lang=en. [Accessed: December 19, 2021]

Section 2
