Removal of nanoparticles by coagulation.

Conventional water and wastewater treatment methods Nanoparticles (NPs) from anthropogenic sources have applications in several commercial products, including cosmetics, pharmaceuticals, and materials. There is evidence that during their usage and disposal, engineered nanoparticles can andwill be released into wastewater (Gottschalk et al., 2013; Pasricha et al., 2012; Westerhoff et al., 2013; Zheng et al., 2015). If water and wastewater treatment plants are inefficient or incapable of removing NPs fromwater, NPs will be released with the treated effluent, entering drinking water sources and natural aquatic environments, increasing exposure for plants,microorganisms, animals, and humans alike (Farre et al., 2010). Although the large surface area to volume ratio of NPs provides unique materials with altered properties and new applications compared to the corresponding bulk materials, this characteristic, as well as the very small size of NPs, may also result in enhancement of the bioavailability of the material and increase in its toxicity. Consequently, there have been extensive studies with the aim of improving our understanding of the behavior and toxicity of NPs (Kahru and Dubourguier, 2010; Oberdorster et al., 2005; Yin et al., 2015; Zhang et al., 2015b).