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Emerging contaminants are chemical and biological agents for which there is growing concern about their potential health and environmental effects. The threat lies in the fact that the sources, fate and toxicology of most of these compounds have not yet been studied. Emerging contaminants, therefore, include a large number of both recently discovered and well-known compounds such as rare earth elements, viruses, bacteria, nanomaterials, microplastics, pharmaceuticals, endocrine disruptors, hormones, personal care products, cosmetics, pesticides, surfactants and industrial chemicals. Emerging contaminants have been found in many daily products, and some of them accumulate in the food chain. Correlations have been observed between aquatic pollution by emerging contaminants and discharges from wastewater treatment plants. Most actual remediation methods are not effective at removing emerging contaminants. This second volume presents comprehensive knowledge on emerging contaminants with a focus on remediation.



Chapter 1. Remediation of Emerging Contaminants

Water pollution by emerging contaminants has become a major source of concern and a priority for society and public authorities. Emerging contaminants are a group of natural and synthetic chemicals and biological agents that are not routinely monitored or regulated in the environment and may have known or suspected adverse effects on the environment and human health. The list of these substances is particularly long and includes pharmaceuticals, personal care products and cosmetics, pesticides, surfactants, industrial products and additives, nanoparticles and nanomaterials, and pathogens. Many emerging contaminants are released continuously into the environment and can cause chronic toxicity even at low concentrations, endocrine disruption in humans and aquatic life, and the development of antibiotic resistant bacteria. It is therefore necessary to mobilize efforts to protect human health and biodiversity.
Two of the main sources of emerging contaminants are wastewater treatment discharges and agricultural practices. However, conventional wastewater treatment plants have not been designed to remove such contaminants. It is therefore important to develop effective treatment methods capable of eliminating the parent emerging molecules and their metabolites. This is a difficult and challenging task because most of emerging contaminants are recalcitrant substances. The methods must also target not only water chemicals but also water microbiols in order to reduce and eliminate the toxicity and impact of the treated wastewater.
During the past two decades, several physical, chemical and biological technologies have been proposed for emerging contaminant removal. Each technology has its own advantages and constraints not only in terms of cost, but also in terms of efficiency, feasibility, and environmental impact. However, among the various treatment processes currently cited for wastewater treatment, only few are commonly employed by the industrial sector for technological and economic reasons. Extensive research on this topic highlights the growing interest of scientists in developing treatment systems that are increasingly effective in removing mixtures of trace pollutants, simple to implement from a technological point of view, economically viable and environmentally friendly, with little or no impact on the environment.
The objective of this chapter is to present the recent state of knowledge on the advanced treatments proposed for the removal of emerging contaminants in wastewater when they are present in trace amounts in wastewater. After general considerations on wastewater treatment plant, the first part is focused on adsorption-oriented processes using conventional (activated carbon, clays) or non-conventional (cyclodextrin polymers, metal-organic frameworks, molecularly imprinted polymers, chitosan, nanocellulose) adsorbents. Biosorbents such as cyclodextrin bead polymers have great potential in environmental applications although they are still at the laboratory study stage. The second part presents examples of biological-based technologies for the degradation and elimination of emerging contaminants. Selected biological approaches include constructed wetlands, biomembrane reactors, strategies based on the use of algae, fungi and bacteria, and enzymatic degradation. The third part briefly presents the membrane filtration strategy that is already used as a tertiary treatment. The final part is focused on advanced oxidation processes that also represent one of the most promising strategies because of their simplicity and efficiency.
Nadia Morin-Crini, Eric Lichtfouse, Marc Fourmentin, Ana Rita Lado Ribeiro, Constantinos Noutsopoulos, Francesca Mapelli, Éva Fenyvesi, Melissa Gurgel Adeodato Vieira, Lorenzo A. Picos-Corrales, Juan Carlos Moreno-Piraján, Liliana Giraldo, Tamás Sohajda, Mohammad Mahmudul Huq, Jafar Soltan, Giangiacomo Torri, Monica Magureanu, Corina Bradu, Grégorio Crini

Chapter 2. Electrochemical Treatments for the Removal of Emerging Contaminants

Emerging contaminants are a diverse group of predominantly anthropogenic pollutants which are present in the environment in the concentrations that can cause known or suspected adverse environmental and health effects. The common denominator of these diverse groups of contaminants is the fact that there is a lack of legislative regulation, as well as lack of monitoring programs or risk assessment studies. For these reasons, their removal from the sources of pollution and from the environment is of key importance. Among possible approaches for the remediation of wastewater as the main source of pollution, electrochemical treatments have recently gained increasing attention as promising, feasible, and environmentally friendly removal techniques.
In this chapter, we have reviewed and critically presented the applications of electrochemical treatments for the removal of selected groups of emerging contaminants from wastewater and similar samples. These contaminants are: bisphenol A, phthalic acid esters, and benzotriazoles, chosen because they are linked to intensive production of plastics, as well as on the basis of a relative lack of review papers. First, we present and compare various available electrochemical treatment approaches, their combinations, and the most frequently applied electrodes. In the main part, the available studies for the chosen contaminants from the last 5 years are reviewed with the emphasis on the effectiveness of the treatment; identification of the transformation products; and elucidation of the degradation mechanisms. We identify the main problems of the reviewed electrochemical treatments: the lack of identification of the transformation products, as well as the general lack of toxicity assessment of the treated samples. Although electrochemical treatments are viable and effective processes for the removal of selected emerging contaminants from wastewater as shown by the high degree of mineralization in several reviewed papers, further studies need to be done with the emphasis on the identified shortcomings.
Borislav N. Malinović, Jernej Markelj, Helena Prosen, Andreja Žgajnar Gotvajn, Irena Kralj Cigić

Chapter 3. Technologies to Remove Selenium from Water and Wastewater

After major pollution by nitrates and pesticides, soils and groundwater in some parts of the world are now facing the emergence of a third major issue of selenium (Se) contamination. Selenium occurrence in ecosystems results naturally from weathering of Se-containing rocks, and is further aggravated by human activities. Selenium is ubiquitous in the environment, and the two main sources of human exposure by Se are food and water. Se, a metalloid, is an important micronutrient due to Se antioxidant, anti-inflammatory and chemo-preventative properties. At normal dietary doses, selenium is an essential diet element that has nutritional properties and is necessary to maintain good health in humans and animals. Nonetheless, exposure to high concentrations of selenium is harmful to living beings. In terms of contamination, selenium as an emerging hazardous substance is receiving particular attention in developing countries, where research is focussing on water treatment. Actual remediation techniques are limited because removing Se from complex mixtures of substances is very challenging. Yet, techniques of water decontamination are developing rapidly. Here, we review selenium occurrence, pollution, properties and remediation. Advanced remediation include technologies based on zero-valent iron, iron-oxy-hydroxides, supported materials, nanofiltration, reverse osmosis, enhanced ultrafiltration, electrodialysis, and activated granular sludge.
Eric Lichtfouse, Nadia Morin-Crini, Corina Bradu, Youssef-Amine Boussouga, Mehran Aliaskari, Andrea Iris Schäfer, Soumya Das, Lee D. Wilson, Michihiko Ike, Daisuke Inoue, Masashi Kuroda, Sébastien Déon, Patrick Fievet, Grégorio Crini

Chapter 4. Advanced Treatments for the Removal of Alkylphenols and Alkylphenol Polyethoxylates from Wastewater

Since the 2000s, among organic contaminants, alkylphenols and alkylphenol polyethoxylates have been listed as hazardous substances by several national, European and international agencies because they are considered endocrine disruptors. Among the molecules classified as priority substances in terms for monitoring and action, nonylphenols and octylphenols and their polyethoxylated derivatives receive particular attention, especially in developing countries. Effluents from treatments plants are considered to be the largest source of alkylphenols in the environment. Although legislation concerning their use has become increasingly strict, these substances are still found in the environment, especially in water resources.
The existing water and wastewater treatment plants have not been designated for these emerging contaminants. Conventional treatments such as biodegradation, sand filtration, carbon adsorption and/or chemical oxidation in place are not effective in their elimination removal. No appropriate methods have been developed to deal them at the urban or industrial scale. Thus, alkylphenols have become a relevant research topic for scientists interested in water engineering issues related to their treatment. However, the challenge is not simple, as it is difficult to remove trace contaminants from complex mixtures of substances in a way that is chemically effective, technologically simple, economically viable, and environmentally friendly.
The main objective of this chapter is to summarize recent trends in proposed advanced treatment methods for the removal of alkylphenols and alkylphenol polyethoxylates from wastewater. After general and brief considerations on these emerging contaminants, this chapter focuses on adsorption-oriented processes, biotechnological methods, and advanced oxidation processes. Among the advanced methods described and discussed are removal of alkylphenols and alkylphenol polyethoxylates by adsorption onto cyclodextrin polymers, clays or molecularly imprinted polymer, biodegradation using microalgae or constructed wetlands or by sequential anaerobic-aerobic digestion processes, treatments based on ozone-carbon coupling, electrochemical degradation, photocatalysis, zero-valent iron-activated persulfate coupling and catalytic ozonation. Among these technologies, advanced oxidation processes, in association with biodegradation and/or adsorption, seem to be the technique of the future, although their costs still prevent their widespread use.
Grégorio Crini, Cesare Cosentino, Corina Bradu, Marc Fourmentin, Giangiacomo Torri, Olim Ruzimuradov, Idil Arslan-Alaton, Maria Concetta Tomei, Ján Derco, Mondher Barhoumi, Helena Prosen, Borislav N. Malinović, Martin Vrabeľ, Mohammad Mahmudul Huq, Jafar Soltan, Eric Lichtfouse, Nadia Morin-Crini


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