The use and production of synthetic organic chemicals for use in households and various industries has led to an increase in the occurrence and concentration of chemicals of emerging concern (CEC) in wastewater effluents and consequently the environment. Due to the refractory nature of some CECs, conventional physicochemical and biological treatments are not able to provide adequate elimination of these compounds. It is beneficial that these pollutants are removed by other methods before they are discharged to the environment or before the effluent can be recycled for reuse. The use of low-cost materials for the removal of CECs is an unexploited opportunity in developing countries, as these compounds possess the necessary functionalities to make them an ideal choice for water and water treatment in countries with limited economic and technical resources. This chapter reviews the various treatment processes that has been used for the removal of CECs in literature with a particular emphasis on low-cost materials.
TopIntroduction
A recent study has revealed that at least 4 billion people (66% of global population) around the world, experience water scarcity at some point during the year (Mekonnen and Hoekstra 2016). In its 2018 report, the World Economic Forum ranked water crises (a significant decline in the available quality and quantity of fresh water, resulting in harmful effects on human health and/or economic activity) as one of the top 5 global risks in terms of societal impact (World Economic Forum 2018). It has also been predicted that there will be a 40% gap in the demand and availability of freshwater by 2030 (Addams et al. 2009). The reuse of wastewater effluent holds the key to the efficient utilization of the limited global freshwater resource, by making available an alternative source of water to supplement existing supplies. It has been shown in several research studies that treated wastewater, can be a major component of the water resources strategy to meet the needs of a growing population and wastewater effluent has been used for purposes such as irrigation and groundwater recharge (Miller, G 2006; Levine and Asano 2004). The presence of toxic organic contaminants in the final effluent of wastewater plants is detrimental to organic life in the receiving waters and is a major obstacle to the recycle of the effluent for reuse (Pedersen et al. 2003).
Contaminants of Emerging Concern (CEC) are newly discovered naturally occurring, manufactured or manmade chemicals or materials, suspected to be present in various environmental compartments and whose toxicity or persistence are likely to significantly alter the metabolism of a living being (Sauvé and Desrosiers 2014). They include Pharmaceuticals and Personal care products (PPCPs), Endocrine Disrupting Chemicals (EDCs), steroids, hormones, surfactants and surfactant metabolites, flame retardants, pesticides, industrial additives, nanomaterials and gasoline additives (Stefanakis & Becker, 2016). The use and production of synthetic organic chemicals for use in households and various industries, has led to an increase in the occurrence and concentration of these compounds, in wastewater effluents and consequently the environment. Many studies in recent years have shown that treated wastewater effluent, is the main contributor to water pollution because of the presence of toxic organic pollutants (Ashton et al. 2004; Ternes et al. 2004; Gulkowska et al. 2008; Zhang et al. 2008; Launay et al. 2013).
In recent years, the presence of Endocrine-Disrupting Chemicals (EDC) in the environment has been of particular concern, because of the severe threat they pose to animals and humans. These compounds disturb the endocrine system by mimicking, blocking or disrupting the functions of hormones, affecting the health of humans and animals species (Bolong et al. 2009). For example, hermaphrodite fish has been detected in the lagoons of sewage treatment works, where male fish were found to be producing the female yolk precursor protein vitellogenin (Purdom et al. 1994) and it has been suggested that male and female reproductive system development and function may be susceptible to the effects of EDCs (Fowler et al. 2012; Knez, 2013). Pharmaceuticals and Personal Care Products (PPCPs) are also of particular concern. These substances are natural or man-made chemicals used in prescription medicines and veterinary drugs. The presence of antibiotics in wastewater effluent and aquatic environments, may increase bacterial antibiotic resistance, which can represent a potential threat for human and animal health and create challenges in the control of infections (Stefanakis & Becker, 2016).
Due to the refractory nature of some CECs, conventional physicochemical and biological treatments are not able to provide adequate elimination of these compounds (Luo et al., 2014). The use of low cost materials in the removal of toxic organic compounds from wastewater has gained widespread in recent years, as they offer potentially simple and economic solutions to the challenges imposed by the presence of toxic compounds in the environment. A material can be considered low cost, if it requires minimal pre-treatment and can be found in large quantities in nature (Bailey et al., 1999). The use of low cost materials for the removal of CECs is an unexploited opportunity in developing countries, as these materials possess the necessary functionalities to make them an ideal choice for water and water treatment in countries with limited economic and technical resources. This chapter reviews the various treatment processes that have been used for the removal of CECs in literature, with a particular emphasis on low cost materials.