Pollution Control Technologies

Water pollution and air pollution remediation is an important task to avoid their unnecessary impacts on environment and living species. Nowadays, there are several technologies employed to control the water and air pollution. Therefore, the main aim of this book is to provide an overview and future prospect of the pollution control strategies adopted in different sectors including water and air. This book contains 12 chapters and each chapter has its own purpose to discuss the current scenario of control technologies in remediation of various toxic metal ions, pesticides, micropollutants, radioactive pollutants, and dyes. Moreover, this book highlights the pollution control technologies adopted in food processing and desalination as well. Furthermore, it provides valuable informations about particulate matter air pollution and its control techniques. Overall, this book offers an updated literature for researchers and academicians working in field of water and air pollution and their control techniques.

Water pollution is one of the significant environmental issues at present, which primarily originates from the discharge of industrial and agricultural wastewater back into water resources. Persistent organic compounds such as pesticides, dyes, and pharmaceutical wastes are the prominent sources of water pollution. Pesticides are the substances which increase agricultural productivity by destroying pests that are harmful to crops. However, the runoff and leaching of toxic pesticide residues lead to bioaccumulation, xenobiotic and persistence impacts, various health hazards, and severe ecological issues. Also, the industrial effluents containing the recalcitrant pesticide pollute water system by their odor, color, and formation of harmful or oncogenic by-products upon degradation. Due to the complex nature of chemical mixtures present in wastewater, conventional wastewater treatment processes are not always sufficed to remove the entire contaminant load. Therefore, the mineralization of persistent organics by the semiconductor-based photocatalytic process turns out to be a low-cost, environmentally responsive, and sustainable treatment technology which align with the ‘zero’ waste scheme. In this chapter, we discussed and detailed some data on persistent pollutants such as pesticides, their metabolic activities, and environmental impacts. The present perspective on their degradation using (p–n) heterojunction-based semiconductors has also been reviewed.

Pollution causes a significant change in the physico-chemical properties of air, water, and soil that may induce harmful impact and make potential hazards to all living beings. Pollution is one of the severe problems observed throughout the world. Water pollution has ascended due to the nearness of toxic environment, which arisen by human activities such as increased agricultural, industrial, and urban area developments. According to the thriving of the human population, the need for energy is increasing for the development of the world and its economy. Coal, oil, and other nonrenewable fossil are the prime sources of energy which have regularly consumed. Now, the world is facing an unexpected energy emergency. Due to the utilization of radioactive nuclides with the progress in human civilization, the atmosphere is facing cumulative radioactive pollution. Natural and anthropogenic radionuclides and its effect on humans, animals, and all other living beings have become a major environmental problem because of their prevalent occurrence in the atmosphere with concentrations that exceed the World Health Organization (WHO) recommended maximum levels. Operative, suitable, effective, and environmental friendly techniques are essential to mitigate this problem. This chapter describes the development of different conventional techniques and their removal performance of uranium(VI) ions from aqueous solution. Moreover, the chapter also investigates the various adsorbent materials used for the removal of radioactive uranium(VI) ions from water.

Hexavalent chromium is a geochemical element and designated as priority pollutant. It has mutagenic and carcinogenic property and poses a serious threat to both humanity and ecosystem. Despite of toxicity, little dose of chromium acts as micronutrient in the diets of animals and humans and also helps in sugar, protein, and lipid metabolism in mammals. Chromium speciation exists in two states: hexavalent chromium and trivalent chromium, out of which the latter is nontoxic. Health problems associated with high dose of chromium are ulcers, diarrhea, irritation of skin, eye and lung carcinoma, dysfunction of kidney, birth defects, and reduced reproductive health. The lethal dose (LD)₅₀ value for oral toxicity in rats is 50–100 mg kg⁻¹ and 1900–3000 mg kg⁻¹ for Cr (VI) and Cr (III), respectively. Due to high toxicity of Cr (VI) compounds, there is multiplicity of treatment technologies including physico-chemical and biological methods. Physico-chemical methods are high energy demanding, have high operational cost, generate secondary pollutant, and sometimes have lesser efficiency due to high metal concentration and interferences. In contrast to physciochemical method, bioremediation of Cr (VI) reduction is operated at low cost, and less energy is required with high efficiency of reduction, no health and environmental hazards. Microorganisms involved in remediation metabolize the chemicals via enzyme-catalyzed pathway converting into harmless compounds and often use compounds as a source of their growth. Despite of all these methods, some green technologies and modification in these techniques also proved to be effective in chromium reduction. This chapter deals with occurrence and fate of chromium, speciation, various treatment technologies, mechanism of reduction and their advantages-disadvantages, pilot-scale studies, and future perspectives in remediating toxic hexavalent chromium.

Arsenic is a crystalline metalloid present in the earth’s crust in different minerals. Various natural processes and human interventions have mobilized As into the groundwater system over the years. The dissolved As presence in drinking water is now a significant health concern in India and many other countries. As is a proven carcinogen, and long-term ingestion of low concentrations of As can lead to serious health issues. As in drinking water was first regulated by the United States Public Health Service (USPHS), which set a maximum permissible concentration (MPC) of 50 μg/L. Later, based on lung and bladder cancer risk, the United States Environmental Protection Agency (USEPA) promulgated a maximum contaminant level (MCL) of 10 μg/L. Indian standard for drinking water also recommends a total As concentration of 10 μg/L as the acceptable limit. However, some of the developed countries have As standards lower than 10 μg/L as well. The removal of As in drinking water is inevitable, considering its widespread presence in groundwater, potential human toxicity, and stringent regulation in drinking water. Several point-of-use (PoU) and community-based treatment technologies have been developed to provide As-free water to the affected population. The processes adopted in these technologies include coagulation and filtration, sorptive filtration, ion-exchange, electrocoagulation, and membrane filtration. The present chapter reviews these technologies critically and their suitability in the Indian context. The chapter also provides insight into the As occurrence in the environment, its speciation, toxicity, and health effects.

Microplastics (MPs), usually plastic fragments smaller than 5 mm in size, are ubiquitous in the environment and pose an increasing threat to the entire ecosystem as an emerging micropollutant. MPs not only contribute to the accumulation of the plastics in the environment but also get transported into the food chain due to absorption and ingestion by aquatic species. They originate from either the direct environmental discharge of purposefully manufactured microscopic fragments as primary MPs or the fragmentation of large plastic debris by environmental factors as secondary MPs. It is widely speculated that the sewage treatment plants (STPs) are one of the prime conduits for releasing of MPs into the aquatic environment despite some degree of removal in the plants. Therefore, it is imperative to understand the occurrence and fate of MPs in STPs for their effective control. In this context, the current status of the identification, abundance, and removal of MPs in STPs is comprehensively explored. Various protocols for collection, pre-treatment, determination, and characterization of MPs in sewage are outlined and compared. The occurrence of MPs in the STPs in terms of their materialistic composition, shape and sizes, and concentration is summarized. The fate of MPs in various treatment stages in the STPs including entrainment in sewage sludge is also assessed. Further, future prospects on the development of advanced removal techniques are presented for effective MPs control.

Over the last few decades, the effectiveness of the conventional water treatment processes has become limited due to its failure to meet stringent water quality regulations, the emergence of non-conventional contaminants, and space limitations. Membrane technology can serve as a viable option to meet the limitations of the conventional treatment processes due to low chemical use, higher efficiency, easy operation, smaller footprint, and better quality treatment. But its effective usage is hindered due to fouling, shorter life span, and selectivity–permeability trade-off. Thus, there is a need for new-generation membranes that can surpass the limitations of the conventional membrane technologies, with less or no decrement in the efficiency of the treatment. With the advancements in material sciences and membrane fabrication processes, it could be possible to overcome the problems of conventional membrane treatment processes. In this chapter, a brief introduction of the membrane technology, its advantages over conventional treatment processes, commonly used pressure-driven membranes and membrane fabrication processes, the problems of conventional membranes, and some of the promising new-generation membrane materials and membrane systems, and water and wastewater treatment have been discussed.

Fresh, potable water is one of the key elements for the survival of living beings, and with an increasing population, there is water shortage all over the globe. Hence, this situation demands an effective water treatment technology, and one such water treatment method is membrane-based forward osmosis (FO) technology. Wastewater, seawater, and brackish water have great potential to fulfill the water demands, and the FO membrane technology holds the potential to sustainably treat these sources to produce water of good quality. The FO is based on the principle of osmotic pressure difference across the membrane, which provides the gradient for the movement of water molecules from feed solution to draw solution. The advantages offered by the FO-based treatment method are lower fouling propensity and lesser concentration polarization, and, most importantly, it is an energy-efficient process. However, for the enhancement of the treatment process, the FO is used in conjugation with other separation processes, referred to as the FO hybrid system. In this chapter, FO principle, factors affecting the process, membrane fouling, and hybrid FO treatment technology and its application have been discussed.

The quality and quantity of wastewater released from food processing industries vary widely with the products and production processes. These wastewater streams are rich in BOD, suspended solids, and oily substances. Traditionally, biological treatment methods have been utilized in food processing wastewater treatment in meeting the discharge regulations. However, the issues of size of the wastewater treatment systems, their process efficiency, and space availability need to be addressed in the context of stricter standards and sustainability. Moreover, the idea of resource recovery coupled with wastewater treatment is also transforming the traditional wastewater treatment systems, and the focus is increasingly shifting toward recovering nutrients, energy, and water in addition to meeting the discharge standards. This has resulted in the development of novel technologies in the context of food processing wastewater treatment. In this book chapter, the quality and quantity of wastewater generated by major industries are discussed. Subsequently, current wastewater treatment technology that is utilized in key food processing facilities is highlighted. The key challenges to each industry, treatment system in the context of its wastewater are identified and future opportunities are explored. The waste streams and treatment technology have also been identified with respect to their resource recovery potential.

Urban wastewater systems (WWS) comprising of municipal sewage collection, treatment, and disposal play a vital role in alleviating urban water pollution and maintaining overall public health and sanitation. WWS forms one of the most energy-intensive components of the urban water cycle and requires huge financial investment for its construction, operations, and management. The financial burden of WWS operations can be subsided to a significant extent by implementing strategies for energy reduction, optimization as well as energy production and recovery from wastewater. However, developing an energy-neutral or energy-positive WWS is a challenging task, requiring the application of several interdependent energy pathways. In this chapter, comprehensive energy analysis of WWS is carried out, considering the available routes for reducing, optimizing, producing, and recovering energy from wastewater. Alongside this, available approaches for assessing the total energy consumption and energy efficiency of the WWS have also been evaluated. The use of indicators and indices can be particularly effective to both quantify and compare energy efficiency within different components of a WWS or among different WWS. The diagnostic potential of energy efficiency indices (EEIs) proposed specifically for WWS has been comparatively evaluated in this study. Such an index-based energy evaluation can conveniently characterize the energy efficiency of WWS and facilitating energy benchmarking of systems.

Various epidemiological and toxicological studies have shown an association between air pollutants and their risk of respiratory morbidity and mortality. Only a few studies have been conducted in India, which evaluates the impact of seasonal air pollution on data on respiratory morbidity. Machine learning models like random forest regression are employed in the present context to predict the change in number of hospital visits for respiratory morbidity associated with the change in concentration of various air pollutants in the atmosphere and to study the effect of potential confounders like temperature and humidity, and also seasonal effect in Lucknow, India, for period of 2017–18. The results of the model revealed that a decrease of 16 patients daily is predicted if there is a reduction in the ambient concentration of PM_2.5 to National Ambient Air Quality Standards (NAAQS) in the city of Lucknow in one government hospital. SO₂ increases the number of respiratory patients as its ambient air concentration increases. It is observed that with 2 µg/m³ increase from 18 to 20 µg/m³ increased to nearly four patients. The synergistic effect of PM_2.5 and NO₂ is the most harmful for the citizens of Lucknow City. This study provides evidence that respiratory morbidity increases with an increase in the concentration of air pollutants in Lucknow. The post-monsoon season is considered as the most polluted period of the year with a higher number of hospital visits.

In recent years, deterioration of air quality has become a matter of serious concern due to its adverse impacts on human health, local and global climates. These concerns will continue to remain a challenge owing to the inevitable industrial growth to achieve economic progress of the population coupled with inadequate implementation of air pollution control measures. Reducing the emission of pollutants to the atmosphere is indispensable to protect the environment and improve the quality of life. Effective control strategies must be developed to cope up with the existing pollution level and reduce the pollutants emission from various sources. Apart from control strategies such as limiting the emissions at the source and tightening regulations on air pollution, development and deployment of air pollution control devices are necessary to reduce the pollutants before emitting to atmosphere. The aim of this chapter is to review the current available devices used to control particulates in industries and recent development of new emerging technologies to control particulate matter emission.