**4.3. Removal of micropollutants**

studied (lindane pesticides and diazinone), the rates of biosorption of these substances on

It can be assumed that in a system containing a mixture of several pollutants of a similar nature, the biosorption capacity of the individual components of the mixture will be affected by the concentration of the other substances in the mixture. A reduction in biosorbent capacity of tetrachloroethane on the *Rhizopus arrhizus* biomass has been shown to be up to 14% in the presence of the same concentration of trichloroethane [13]. Biosorption is usually an exothermic process, so biosorption capacity usually increases with decreasing temperature. However, the change in temperature does not significantly affect the rate of biosorption [8]. Simjonato et al. [9] studied the process of adsorption of blue remazol and black remazol five dyes with chitin and chitosan, which they performed in the column and an aqueous suspension. The results show that better results were obtained in the column with arthritis than in the chitin-packed column. Comparing the results measured in the column and suspension results in better suspension results. A very good description of Langmuir isothermal experimental values was obtained, with the difference between the measured and calculated adsorption

Biosorption of hazardous pollutants is a suitable technology for removing dyestuffs from municipal and industrial wastewater. Various low-cost biosorbents, such as, for example, biomass of algae, yeast, fungi, vegetable waste, fiber, fruit waste, chitosan, and agricultural

Biosorption and bioaccumulation can also be applied to remedy environments contaminated with heavy metals as complementary methods to currently used physical and chemical methods. It was found that removal of heavy metals from the environment with biotechnological methods should consider a number of physicochemical factors such as temperature, pH, contact time of biomass, and a solution containing metals, concentration and age of biomass, and toxicity when living microorganisms are applied. Improving the efficiency of removal of metals can be performed through physical and chemical modifications and immobilization of biomass. The most frequently applied reactors include stirred tank reactors, fixed-bed, reac-

In the process of biosorption, ions of metals are adsorbed on the surface of a sorbent. Biosorption is a metabolically passive process that uses dead biomass. Biosorption is the first

Environmental pollution of heavy metals is one of the most serious environmental problems. Various biosorbents such as fungi, yeast, bacteria, and algae are used to remove them. These biomaterials are considered to be cost-effective for high-volume and low-heavy wastewater treatment (from 1 to 100 mgl−1). The promising biomaterials for heavy metal removal include *Saccharomyces cerevisiae* fungus. This fungus is commonly used in food and beverage production. Low-cost media is sufficient to cultivate it. It is a by-product/waste from the fermentation

activated sludge were higher for higher concentrations of pollutants.

capacity values being insignificant.

waste were studied [48].

10 Biosorption

**4.2. Removal of heavy metals**

tors and fluidized-bed reactors [49].

step of bioaccumulation [49].

industry.

The large occurrence and presence of micropollutants (MPs) in the aquatic environment is one of the major challenges worldwide. For example, in 2012, some 143,000 compounds were registered on the European market, many of which at some point in their life cycle would end up in the aquatic environment. Most of them are not removed or transformed into conventional wastewater treatment plants (WWTPs), they can persist in the aquatic environment or create new chemicals by reaction with humic substances and sunlight, and they can be bioactive and can bioaccumulate [52–56].

Although present in almost undetectable (ppb; part per bilion) concentrations, their presence in the aquatic environment is associated with various deleterious effects in organisms such as estrogenicity, mutagenicity, and genotoxicity [57].

There is no legal regulation for removing MPs in WWTPs. However, there are some (EU) regulations that set limit values for certain substances that have specific MP properties, pesticides, lindane, nonylphenol, and synthetic hormones [58] in water.

MP can be divided into several categories such as pharmaceuticals personal care products (PPCP), household chemicals and industrial chemicals. A comprehensive list of 242 chemicals is included in the EU 7PP [59] project of which approximately 70% are pharmaceutical and personal care products, and 30% are industrial products, including perfluorinated compounds, pesticides, herbicides, and food additives.

to reducing the volume of aeration tank required and reducing investment costs, this bioreactor configuration is characterized by a high resistance to filamentous sludge bulking. The above mechanisms are also used as part of enhanced biological phosphorus removal processes [14–16]. In a hybrid system, slow and fast biodegradable substances and simultaneous macronutrient removal processes can be carried out by combined activated sludge and immobilized biomass [61]. Higher biomass concentrations and two different solid retention times significantly influence biosorption/bioaccumulation processes and ultimately, their participation in the

Introductory Chapter: Biosorption

13

http://dx.doi.org/10.5772/intechopen.78961

Biosorption and biodegradation also increase the efficiency of anaerobic sludge stabilization. Current research is mainly focused on increasing the efficiency of sludge stabilization. It is also focused on the research of anaerobic decomposition of micro-pollutants. However, there is little information and knowledge about biosorption potential and biosorption mechanisms of these substances. Information on pollutant biosorption on anaerobic sludge is important not only for the removal of pollutants themselves but also for the modeling of biological

Accumulation of dangerous hydrophobic organic pollutants, e.g. in activated sludge biosorption results in their removal from the wastewater stream, but the resulting disposal of contaminated sludge then poses a new environmental problem, especially when pollutants are bound to microbial sludge reversibly [33]. Reduction of sludge mass during stabilization leads to concentration of accumulated compounds, but potentially also to increase of their chemical activity as a result of reduction of sludge sorption capacity in the stabilization processes. This

However, such contamination remains a part of the activated sludge. Its release to the environment is dependent on further treatment with the excess sludge produced, especially if the

One of the current trends in the sludge management and the minimization of the release of priority substances and micro-nutrients through the application of the sludge in agriculture is the research of integrated biological and chemical processes to minimize the production of excess sludge and carry out the simultaneous transformation/degradation of micropollutants

The past decades brought intensive research leading to an understanding of biosorption processes with the aim of their application in water treatment technology t. Numerous papers were published that significantly contributed to a better characterization of complex phenomena involved in biosorption. Information was gathered on the bioprocess mechanisms and the influence of various factors in the removal of inorganic and organic pollutants by biosorption. In spite of targeted research on alternative low-cost sorption materials and extensive knowledge and publication results, it was not possible to apply this process practice in great extent, so far.

may lead to an increased risk related to compounds sorbed to the stabilized sludge.

whole complex of the biological wastewater treatment.

sludge stabilization systems [33].

biosorption of these substances is reversible.

sorbed on activated sludge [62–63].

**5. Conclusions**

The vast majority of MP in municipal wastewater belongs to the class of personal hygiene drugs and products PPCP, the fate and processes for removing these compounds are discussed in detail in this text.

About 70% of the wastewater products come from the household, 20% come from livestock, 5% come from hospital wastewater, and the remaining 5% come from outflows from nonspecified sources [60].

The removal of micropollutants in wastewater treatment plant depends on their solubility, octanol/water partition coefficient, and Henry's constant. For removing micropollutants in wastewater treatment plants significantly contributes their sorption on suspended particles of primary and secondary sludge. Removal of dissolved organic compounds also involves coagulation, flocculation and biodegradation processes. The majority of conventional wastewater treatment plants do not completely remove these substances. Their removal is influenced significantly by the operational conditions, the biochemical environment (aerobic, anaerobic, anoxic, sludge age (SRT), temperature, pH, and redox potential.

### **4.4. Biosorption in municipal wastewater treatment**

Biosorption and bioaccumulation mechanisms continue to play an important role in newly developed processes and technologies for wastewater treatment.

The fate of the priority substances and micropollutants that are transported by wastewater to wastewater treatment plants (WWTPs) depends on their adsorption on suspended particulates, dissolved humic substances, primary and secondary sludge. Adsorption of insoluble matter in primary and secondary treatment units is an important process of MP removal from wastewater. Adsorption may occur as a result of hydrophobic interactions between aliphatic and aromatic groups of lipid fractions in the primary sludge and the lipophilic cell membrane of the microorganisms in secondary sludge. Interactions also occur between positively charged MP groups and negatively charged microorganisms in secondary sludge.

#### *4.4.1. Integrated and hybrid processes*

Both the development of the activated sludge process and the increasing wastewater pollution are also developing biosorption applications. It is, for example, hybrid activated sludge process with activated carbon. Interaction of bio-degradation and adsorption on activated carbon benefits from the higher efficiency and performance of the process due to the concentration of organic matter on activated carbon, consequently higher rates of biological oxidation, as well as better conditions for the degradation of resistant substances, especially for industrial wastewater treatment and groundwater remediation.

In the 1950s of the last century, the activated sludge process with separate sludge regeneration was put into full-scale operation, where the ability to accumulate a substrate was restored. In addition to reducing the volume of aeration tank required and reducing investment costs, this bioreactor configuration is characterized by a high resistance to filamentous sludge bulking. The above mechanisms are also used as part of enhanced biological phosphorus removal processes [14–16].

In a hybrid system, slow and fast biodegradable substances and simultaneous macronutrient removal processes can be carried out by combined activated sludge and immobilized biomass [61]. Higher biomass concentrations and two different solid retention times significantly influence biosorption/bioaccumulation processes and ultimately, their participation in the whole complex of the biological wastewater treatment.

Biosorption and biodegradation also increase the efficiency of anaerobic sludge stabilization. Current research is mainly focused on increasing the efficiency of sludge stabilization. It is also focused on the research of anaerobic decomposition of micro-pollutants. However, there is little information and knowledge about biosorption potential and biosorption mechanisms of these substances. Information on pollutant biosorption on anaerobic sludge is important not only for the removal of pollutants themselves but also for the modeling of biological sludge stabilization systems [33].

Accumulation of dangerous hydrophobic organic pollutants, e.g. in activated sludge biosorption results in their removal from the wastewater stream, but the resulting disposal of contaminated sludge then poses a new environmental problem, especially when pollutants are bound to microbial sludge reversibly [33]. Reduction of sludge mass during stabilization leads to concentration of accumulated compounds, but potentially also to increase of their chemical activity as a result of reduction of sludge sorption capacity in the stabilization processes. This may lead to an increased risk related to compounds sorbed to the stabilized sludge.

However, such contamination remains a part of the activated sludge. Its release to the environment is dependent on further treatment with the excess sludge produced, especially if the biosorption of these substances is reversible.

One of the current trends in the sludge management and the minimization of the release of priority substances and micro-nutrients through the application of the sludge in agriculture is the research of integrated biological and chemical processes to minimize the production of excess sludge and carry out the simultaneous transformation/degradation of micropollutants sorbed on activated sludge [62–63].
