Removal of Persistent Organic Pollutants and Compounds of Emerging Concern in Public-Owned Sewage Treatment Works: A Review

Persistent organic pollutants (POPs) are organic compounds that are resistant to environmental degradation through chemical, biological, and sunlight degradation processes. POPs are known to persist in the environment for long periods due to such properties and can thus be capable of long-range transportation between lands, rivers, and oceans. Such compounds will bioaccumulate in seafood and animal tissues and subsequently become biomagnified in food chains and ultimately impact human health and the environment. Many POPs are pesticides such as DDT, whereas other compounds such as PCBs are used in industrial applications and in the production of a wide range of products. In the past few years, pharmaceutically active compounds (PhACs) and personal care products (PCPs) have been discovered in various environments and water sources. Some of those compounds have been linked to ecological impacts at concentrations of less than 1 ng/L. These PhACs and PCPs were eventually grouped with other emerging contaminants, such as nitrosamines from disinfection by-products (DBPs), metals, and other new additions of compounds, such as endocrine-disrupting compounds (EDCs), and are collectively referred to as compounds of emerging concern (CECs) (Drewes et al. 2006, WERF 2007). It has been reported that certain synthetic compounds, such as detergents and pesticides, and natural compounds, such as sex hormones, can affect the balance of normal hormonal function in animals. These substances are classified as EDCs and have been linked to a variety of adverse effects in humans and wildlife (Snyder et al. 2007). The U.S. Environmental Protection Agency (U.S. EPA) refer to EDCs as exogenous agents that interfere with the “synthesis, secretion, transport, binding, action, or elimination of natural hormones in the body which are responsible for the maintenance of homeostasis, reproduction, development, and/or behavior” (U.S. EPA 1996). In humans, studies have linked the exposure of mothers to phthalates such as diethylhexyl phthalate to adverse impacts in their children, including lowered testosterone levels in boys (U.S. Department of Health and Human Services 2008). EDCs are further classified as thyroidal (compounds with direct or indirect impacts to the thyroid glands), androgenic (compounds that mimic or block natural testosterone), and estrogenic (compounds that mimic or block natural estrogen) (Snyder et al. 2007). Recently, the illegal replacement of palm oil with diethylhexyl phthalate and diisononyl phthalate (plasticizers) by some food-grade manufacturers in Taiwan has caused huge product recalls in numerous food, drink, and medicinal formulations in Taiwan and surrounding trading markets in June of 2011.