Persistent Pollutants in Water and Advanced Treatment Technology

Persistent pollutants are extremely undesirable in the current scenario due to their stubborn, mutagenic, and bio-accumulative nature in the environment and food chain. Their easy exposure, long-distance transport, and mild concentration in the environment are other grave causes of concern. Moreover, the main difficulty with persistent pollutants is that they remain untreated during conventional treatment methods. This book primarily discusses the occurrence and fate of persistent pollutants and their transport in the environment, to understand their harmful impacts on living organisms. The chapters cover many emerging pollutants such as polychlorinated biphenyls (PCBs), per- and polyfluoroalkyl substances (PFASs), pharmaceuticals, phenolic compounds, persistent metals, quinolone, microplastics, and their by-products in water and wastewater medium. In addition, the book also covers the available conventional treatment technologies along with the in-depth discussion and suggestions on the newly developed treatment methods, such as advanced oxidation processes, membrane technologies, microbial techniques, nanotechnologies, and biosorption techniques, for the treatment of persistent pollutants from water and wastewater.

The industrial fabrication of plastics has experienced outstanding growth in recent decades. At the current speed of advancement, this production has been estimated to be doubled and plastic waste spilling into the sea can raise up to threefold in the next twenty years. Presently, plastics are the most persistent components of the oceanic trash and the most accounted materials experienced by marine flora and fauna. Microplastics have been accounted for functioning as vectors by sorbing contaminants and leach various harmful plastic additives. In this way, microplastics can act as a sink and source of these plastic-associated anthropogenic pollutants and likely affecting their fate, bioaccumulation and toxic potency. Oceanic microplastics are readily invaded by aquatic microbes, forming “plastisphere” biofilms. Abundance of antibiotic resistance genes and potential pathogenic bacteria are frequently reported in plastisphere. Interactions between microplastics and their probable first-hand consumers, the lower trophic level microbes, are also topic of interest nowadays, with a particular focus on the effects of microplastics in these microbes. The current book chapter expects to highlight the present status of information on the oceanic microplastics affair, related contaminants microorganisms and effects on marine ecosystems.

Per- and polyfluoroalkyl substances (PFASs) have been used in wide range of industries and daily life and therefore released into the aqueous environment. Due to their unique properties, such as environmental persistence, bioaccumulation, and toxicity, PFASs have drawn increasing concern in recent years. PFASs-contaminated water has adverse effects on water microorganisms and aquatic life as well as human life. So far, tremendous efforts have been made on PFASs pollution and their treatment, yet most of the efforts have been spent on laboratory experiments. Their feasibility, cost-effectiveness, and field applicability are questionable. This review examined studies on existing while updated treatment technologies, with the goal of providing an outlook on these technologies and more importantly, proposing the most likely technique. As such, a constructed wetland-microbial fuel cell (CW-MFC) technology was recommended, which is a newly emerged technology by integrating physical, chemical, and enhanced biological processes plus the wetland plants’ functions with strong eco-friendly features for the comprehensive removal of PFASs. The roles of wetland plants, substrates, and electroactive bacteria (EAB) in the removal of PFASs in the CW-MFC system were discussed with focus on highlighting the different mechanisms. It is expected that the review can strengthen our understanding of PFASs’ research and thus can help select reasonable technical means of aqueous PFASs control.

Plasticizers constitute tens of thousands of synthetic chemical substances added to plastics to increase their elasticity and durability. Plasticizers are commonly found in polyvinyl chloride (PVC) materials, food packaging, medical devices, toys, automobiles, solvents, paints, and adhesives. Phthalates are the most used plasticizers and many have adverse impacts on human health. Plastic monomers include several chemical constituents that act as the building blocks in plastics manufacturing. For example, bisphenol A (BPA) and terephthalic acid (TPA) are monomers of polycarbonate and polyethylene terephthalate-based plastic products. Phthalates and BPA are regulated in consumer products in some countries due to their profound human health impact. Previous studies have reported endocrine-disrupting properties and carcinogenicity of phthalate plasticizers and BPA. Plasticizers and plastic monomers enter the environmental waters and wastewater, mainly through human exposure and leaching from the plastic materials. Plasticizers and plastic monomers are ubiquitously found in all environmental waters and wastewater ranging in concentration from ng/L to µg/L. Most plasticizers and monomers undergo biological or non-biological transformations, and these transformed products are frequently detected in wastewater. Although several analytical pipelines are employed to detect plastic chemical constituents in water, it is always recommended to ensure data quality due to the background interferences from laboratory settings. This chapter provides an overview of plasticizers and plastic monomers’ occurrence, transformations, and fate in environmental waters and wastewater. This chapter also emphasizes the analytical challenges in detecting plastic constituents and provides recommendations to ensure reported data quality.

In recent years, phthalates have attracted attention as an emerging contaminant that adversely affects the environment and human life. Phthalates are found in various kinds of day-to-day products, like personal care products (soaps, shampoos, detergents, etc.), cosmetics, lubricants, medical tubing adhesives, vinyl flooring, etc. Different kinds of phthalate compounds that have been detected in the environment like diethyl phthalate (DEP), dimethyl phthalate (DMP), di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), di-isobutyl phthalate (DIBP), butyl benzyl phthalate (BBP), di-isononyl phthalate (DINP), and dinoctyl phthalate (DNOP). Because of their extensive usage in day-to-day life and their property to leach, phthalates have been detected in groundwater, surface water, wastewater, and even in drinking waters. The primary source of their occurrence in water is the discharge from industries and domestic wastewater. It has become important to treat water contaminated with phthalates before it is discharged into an aqueous environment. Various advanced wastewater treatment methods like adsorption, membrane processes, advanced oxidation processes (e.g. photocatalysis, photo-Fenton, ozonation), and biological treatment processes have been successful to address this problem with wastewater sufficient removal efficiencies ranging from 70 to 90%. This chapter highlights the occurrence of phthalates in the different matrices of the environment and their harmful effects on human life. It also discusses the different treatment methods being used for the removal of phthalate esters. Being a top-priority pollutant, and with its serious harmful impact on human life, there is an urgent requirement to develop proper remediation strategies for phthalate treatment.

The intensification of industrial activities and urbanization have significantly increased the discharge of huge amount of toxic and recalcitrant pollutants into the water bodies. Among these, persistent organic pollutants (POPs) are considered highly toxic to aquatic ecosystem as well as human and animals due to their pervasive and bio-accumulative in behaviour. Moreover, these pollutants are not effectively eliminated by conventional wastewater treatment systems due to their recalcitrant nature; thus, trace concentrations of these persistent pollutants are detected in the effluent of wastewater treatment plants (WWTPs). In this regard, to achieve the safe discharge of POPs laden wastewater into the receiving water bodies, electrochemical technologies, such as electrocoagulation (EC), anodic electrochemical oxidation (AO) and electro-Fenton (EF), have demonstrated the potential to effectively eliminate the POPs from contaminated water. Thus, this chapter aims to annotate the basic principles, advantages, disadvantages, application status of electrode materials, electrocatalysts and latest advancement in the field of electrochemical technologies. Moreover, the factors affecting the performance, bottlenecks, future research directions and status of commercialization of electrochemical technologies also have been articulated in the present chapter for the benefit of the researchers for commercial utilization of these technologies in near future.

Over recent years, industry, agriculture, and other human activities have released a large number of organic or inorganic pollutants into natural water resources. Out of them, water pollution through industrial origin is a great matter of concern since it contributes largely to pollution than other activities. Wastewaters generated from different types of industries like coal processing, pharmaceutical, textile, fertilizers, petrochemical industries, etc., release several types of persistent organic pollutants (POPs) due to their different water handling practices like coke making, dye making, drug and fertilizer manufacturing, etc. Till now there are several treatment technologies that have been applied for the effective elimination of these POPs from water. But most of these technologies have some limitations. Out of them, electrochemical oxidation (ECO) technologies have recognized as highly efficient. This chapter has discussed about the recent progress made in the field of electrochemical oxidation techniques, their modified versions, and future possibilities to get easy and cost-effective wastewater treatment techniques. Authors mainly focused on the working mechanism of the ECO process, different types of electrode materials and their preparation, electrocatalysts, catalytic particle electrodes (CPEs), electrolytes, and their involvement in the reaction. Moreover, authors have also revealed the investment of different operating conditions for the optimization of any electrochemical oxidation technology. Additionally, the preparation of electrodes, their connections (anodes and cathodes) as well as the reactor designs have also been summarized in order to improve the performance of the electrochemical system. Finally, the participation of electrochemical technology specially for the treatment of several persistent organic pollutants generated from different type of wastewaters has been discussed. Lastly, the existing challenges and the limitations in the field of electrochemical oxidation (ECO) technology are also summarized.

Emerging contaminants (ECs) are unregulated chemical substances that on account of their persistent nature and high toxicity can cause inimical impact on the ecosystem. ECs occurred as a mixture of complex compounds where an undesirable synergy between them obviate their proper detection and remediation in the environment. Compounds like pharmaceuticals, personal care products, and poly-fluoroalkyl substances comprised the major category of ECs. The surge in cancer incidence and chemotherapy treatment has enhanced the application of anticancer drugs (ACDs) which contributed to the existing problem of pharmaceutical pollution. ACDs being one of the major emerging contaminants are frequently detected in surface water, municipal wastewater, and pharmaceutical effluent that substantially causes genotoxic and mutagenic effects on the aquatic environment. Several remediation techniques were reported on the removal of pharmaceutical compounds such as anti-inflammatory, analgesic, and endocrine disruptors however very few studies documented the degradation mechanism of anticancer drugs. Hence, this chapter elucidates the occurrence of ACDs and their major route in the environment. In addition to this, the current treatment technology like ozonation, electrochemical treatment, and membrane bioreactor, employed for the removal of ACDs are also discussed.

Quinoline is a nitrogen-containing heterocyclic compound that occurs widely in industrial wastewater originating from pharmaceutical, textile, coking coal and coal gasification industries. Despite its usefulness as a raw material in these industries, quinoline and its derivative compounds cause severe health problems such as damaging central nervous system. Moreover, due to steric hindrance of its bicyclic fused structure, it is difficult to degrade naturally. Various physical and chemical methods such as adsorption, UV catalysis and photocatalytic degradation by metal oxide nanocomposites have been employed for quinoline degradation. These methods typically suffer from poor performance and obstruct regeneration of the process for continuous operation. Apart from these conventional treatment methods, advanced treatment technologies such as catalytic ozonation, advanced oxidation process and hybrid treatment technologies where biological biodegradation is followed by advanced treatment processes are gaining popularity in recent years. These methods have been found to be more effective in terms of a faster rate of degradation, offer complete degradation and are known to produce lesser by products rendering the industrial wastewater for discharge into the environment. This chapter discusses various advanced treatment technologies employed in the past decade for degradation/ treatment of quinoline.

Heavy metals are almost ubiquitous, owing to their persistent nature in the environment. In the past few decades, a significant rise in concentrations of these metals due to anthropogenic activities has been reported in a variety of environmental samples, which has led to an increase in health hazards to both plants and animals including human beings. A variety of strategies have been reported for the remediation of these pollutants; however, bio-sorption remains one of the most prominent due to its good efficiency accompanied by economic feasibility. A wide range of biological materials have been experimented with, and significantly new strategies to improve their adsorption capacity are reported. In the recent past, technological advances have also facilitated the improvisation that has enhanced the selective adsorption capacities of biosorbents. Since selective adsorption paves the path for the economic recovery of these metals, these strategies have emerged as a center of interest for several industries. This book chapter focuses on the strategies that can be used to enhance the sorption capacity and selective nature of the bio-sorbents. A brief review of the processes, approaches, mechanisms, and mathematical models will be presented accompanied by a future course of further research in the field.

Despite extremely low concentrations in the earth’s crust, heavy metals are recognized as one of the biggest causes of water resource contamination. The persistent nature of these metals accompanied by their cytotoxicity leads to their accumulation and gradual increase in chronic toxicity in higher aquatic organisms. Our crucial dependence on these elements in day-to-day life leaves us with no choice but to prevent the entrance of these metal ions into the environment by treatment of anthropogenic discharges. The process of treatment is slow and requires extra capital investments; hence, the pursuit of economical and sustainable methods is always on. In the past few decades, the field of the bioelectrochemical system has flourished and successfully demonstrated that not only does it have the potential to treat a variety of contaminants but also acts as a source of green energy, courtesy to the electrogenic microbes. This book chapter explores the advances in the field of bioelectrochemical systems for the removal of metallic ions from different water media, with special reference to the mechanisms involved in the process. The current, persisting challenges in the field will be reviewed along with possible opportunities and approaches to enhance the treatment efficiencies of the system, making it more economical and sustainable.

Chromium is a pervasive contaminant that is widely used in a number of industries. The two main form of chromium found in nature are Cr(III), or trivalent chromium, and Cr(VI), or hexavalent chromium, in which Cr(VI) is a carcinogen in nature. Human exposure to a chromium contaminant can come from both natural and industrial sources of chromium. Mathematical models are used to understand how biotic and abiotic reactions influence the fate and transport of chromium contamination. Models are created with the understanding that a variety of biochemical processes, including reduction/oxidation, sorption/desorption, precipitation/dissolution, and the formation of complex ions, as well as physical migration processes, like advection, dispersion, and diffusion, can directly or indirectly affect the fate of trace metals. In addition, chromium contamination can take place in air, water, and soil. So mathematical model will be applied for air, water, and soil combined as movement of contaminant in soil and water may be interrelated and also trace metals will follows the principle of fluid dynamic in water and air. A mathematical model consists of a set of differential equations that are known to regulate the pathway of trace metals. The reliability of predictions using the mathematical model depends on how well the model approximates the field situation. To simulate the flow path of the contaminant principally two types of mathematical models are used: the finite difference model and the finite element model. These mathematical models can be used to create a simulator program using C or Python. Several software programs exist such as ModFlow, SWAT Model, RockWorks, which can be used with GIS for a better simulation outcome.

Chromium, mainly in the hexavalent form [Cr(VI)], has become a worldwide menace due to its extensive industrial applications and mining activities. According to the USEPA, it is one of 129 priority pollutants and 25 hazardous compounds, due to its higher toxicity, persistency, carcinogenicity, and mutagenic effects. Cr(VI) is hundred times more toxic than its trivalent form which is principally of geological origin. Cr(III) is generally insoluble and stable in the environment, primarily required for lipid and fat metabolism in human. In an aqueous solution, Cr(VI) is mostly found as the oxyanions HCrO₄⁻ (pH 2), Cr₂O₇²⁻ (pH 2–6), and CrO₄²⁻ (pH > 6), which has very high mobility. Several figures show that Cr(VI) concentrations are significantly higher around the world, despite the fact that the acceptable limit for portable water is 0.05 mg/l and surface water discharge is 0.1 mg/L. Therefore, effective elimination of Cr(VI) from the water source requires long-term water management sustainable technology. Nano-remediation technology has gained a larger insight in the toxic contaminant removal due to its high surface area, non-toxic, vast reduction capacity, and cost-effective nature. It could be a state-of-the-art approach for the safe exclusion of heavy metals (Cr, As, Cd, Pb, and Hg) and organic compounds like pharmaceutical waste, organic solvents, phthalates, hydrocarbons, and persistent organic pollutants (POPs) from the wastewater. Carbon nanostructure, iron-based nanomaterials, metal organic framework, nano-photocatalyst, nanosensors, zeolites, and other methods are available for the reduction of Cr(VI) into Cr(III). Currently, iron-based nanomaterials are being investigated as a promising method for the effective reduction of Cr(VI) into Cr(III) from the aqueous solution, as its negative standard potential (E⁰(Fe²⁺/Fe⁰) = −0.44 V, favors reaction process. Despite all the advantages of iron particles, the pH dependency, agglomeration, and particle passivation limit the procedure. This chapter will discuss the occurrences, environmental cycle, health effects of chromium, as well as current developments in nanomaterial synthesis/modification via physico-chemical methods, probable reaction mechanisms, and the impact of various environmental conditions on Cr(VI) reduction capabilities in aqueous solution.

Compounds like urea and ammonia form one of the major constituents of wastewater. Urea is a principal outcome of protein degradation in mammals and is abundant in sewage wastewater. Urea is also widely used as fertilizer in agriculture. The production of 1300 tons of urea per day results in a wastewater output of 650 tons per day. The discharged wastewater comprises 0.5–2 wt% urea, which contributes to water pollution and algal growth, leading to eutrophication. Ammonia is produced by the hydrolysis of urea, which is very hazardous and toxic to aquatic organisms. Ammonia and urea leach from breeding farms, agricultural runoffs, and many other industrial processes. These can be treated and recovered from wastewater for fertilizer and energy production, reducing the risk of water pollution. There are various technologies for the removal of urea and ammonia, some of which are widely used while others are relatively new. Physicochemical, electrochemical, as well as non-electrochemical methods can be utilized to remove urea and ammonia. Electrochemical and non-electrochemical methods can remove urea. Non-electrochemical treatment methods for urea removal are hydrolysis, enzymatic decomposition, biological degradation, decomposition by strong oxidizing agents, and degradation by catalysts. Electro-oxidation and bio-electro-oxidation are electrochemical methods to remove urea. Urea in urine can be utilized to produce energy through direct urine fuel cells and microbial fuel cells. There are various physicochemical methods for the removal of ammonia. Some of the methods, like air stripping, struvite precipitation, and ion exchange, are very common. Microwave radiation and ozone microbubbles are relatively new and costly. Membrane-based processes like reverse osmosis are gaining interest. The chapter focuses on various wastewater treatment methods for urea and ammonia removal. The chapter also aims to describe methods of using urea-containing urine waste streams for their potential application in space to produce energy.

Membrane technology has grown significantly due to its application in the industrial separation processes, as well as for desalination and wastewater treatment. However, these membrane systems encounter a major challenge of fouling which comprises of biofouling, colloidal fouling, organic fouling, and inorganic fouling. Of these, biofouling can impose a number of negative impacts on the membrane systems because of the undesirable deposition and microbial growth on the surfaces, which can hamper the efficiency of water and wastewater treatment plants. Biofouling can be defined as a complex process of unwanted growth and attachment of microorganisms induced by the release of EPS on surfaces. They have the ability to limit membrane permeability and flux, necessitating the use of high pressure to overcome them, potentially increasing the energy consumption. Biofilms in the water system can also be a reservoir of pathogenic microorganisms, compromising public health and hygiene. As per reports, biofouling in wastewater treatment facilities is to blame for over 80% of bacterial illnesses in humans. Thus, biofouling monitoring and control measures need to be implemented for successful and affordable water and wastewater treatment processes. Therefore, this chapter tries to provide an overview of the several approaches employed to control membrane biofouling, focusing on the physical, chemical, and biological methods. Further, recent advances in the development of biofouling mitigation techniques, to improve treatment performance, are also highlighted.

Rapid growth and industrialization have increased water consumption and enhanced wastewater generation, thereby depleting surface water resources, decreasing groundwater tables, and the scarcity of drinkable water. In the last few years, water-related issues have become highly prominent. Moreover, the availability of freshwater resources is also limited, hence switching to sustainable alternatives such as seawater desalination and wastewater treatment has become essential. Treatment based on membrane separation is crucial for addressing environmental concerns and global water security issues. Due to better efficiency, lower footprint, reduced chemical use, and superior quality treatment, membrane separation becomes a viable solution. However, due to the inherent limitations of the membrane materials, there has been limited advancement in membrane technology for water treatment. With advances in material science and membrane filtration technologies, one can overcome the problems associated with conventional membrane treatment processes. Biomimetic membranes have emerged as a possible solution for membrane-based water purification and removing emerging pollutants in recent years. Bio-inspired technologies can master the challenges associated with existing membranes, including excessive energy consumption, very low selectivity, and limited permeability. Therefore, this chapter aims to briefly introduce different membrane-based separation technologies and compare membrane-deployed water purification and advancements for future development, mainly focusing on biomimetic membranes. Further, the last section deals with the scope of commercializing biomimetic membranes for emerging contaminants (ECs) removal and water purification.

Due to its many advantages over other conventional treatment processes, membrane technology has been successfully used in wastewater treatment and desalination. Smaller footprint, higher efficiency, ease of operation & lower chemical consumption with optimum output are some of the inherent benefits of membrane-based treatment processes. However, some challenges associated with membrane technology, such as selectivity-permeability trade-off, fouling, specificity for uncharged contaminants in pressure-driven membranes, and energy consumption, led the scientific community to look for some improvements in membrane systems. These necessitate a new generation membrane with better selectivity & antifouling capability. Membrane technologies have broad applications in the removal of contaminants from drinking water and wastewater. The ceramic membrane has made rapid progress in industrial/municipal wastewater as well as drinking water treatment owing to its advantageous properties over the conventional polymeric membrane in recent decades. The beneficial characteristics of ceramic membranes include fouling resistance, high permeability, good recoverability, chemical stability, long shelf life, and self-cleaning properties and contaminants degradations which have found applications with the recent innovations in both fabrication methods and nanotechnology. Therefore, ceramic membranes hold great promise for potential applications in water treatment. Porous ceramic membranes have gained a commercial foothold in microfiltration (MF) & ultrafiltration (UF) applications in wastewater treatment. Ceramic-based membranes are promising and will soon become key players in water technology. This chapter mainly highlights the research and progress of fabrication methods to synthesize ceramic membranes. Furthermore, wastewater treatment applications of ceramic membranes, including oily wastewater treatment, heavy metal ion removal, industrial wastewater treatment, bacteria and viruses removal, and removal of emerging contaminants from wastewater are presented. Finally, future scope and challenges for further improving low-cost ceramic membranes are also emphasized in this chapter.

Regulatory authorities are making effluent disposal standards more stringent to minimize the effect of pollution load on natural streams and protect the environment. Industries producing wastewater with a high pollution load and refractory organics are forced to have a near-zero liquid discharge (NZLD) system to meet the effluent standards for disposal. In the NZLD process, solids are separated from wastewater, and recovered water is again used in the process. Thermal methods were used to achieve zero liquid discharge (ZLD), but they are not feasible for diluting wastewater streams due to high energy consumption. At present, membrane processes such as reverse osmosis (RO), forward osmosis (FO), membrane distillation (MD), membrane electrodialysis (MED), and capacitive deionization (CDI) are being used for preconcentration of wastewater before feeding to the thermal units to reduce operational and capital cost. The use of RO and NF reduced energy consumption in conventional ZLD systems by replacing the brine concentrator. RO has high feed TDS limitation and is more prone to fouling due to operation at high pressure. Therefore, FO, MD, or CDI can be used for handling the rejection from 1^st stage RO. CDI and EDR are applicable for relatively lower feed concentrations and can replace 1^st stage RO in the ZLD system. The crystallizer requires a lot of energy and can be replaced with a solar crystallizer or evaporation pond to reduce energy consumption in the NZLD system. This chapter aims to give insight into the application of membrane technology in achieving ZLD and making it economically feasible. The application of recently developed membranes and modifications can improve the efficiency and applicability of membrane-based ZLD systems.