PhACs in Wastewater Treatment Plant Effluents & Receiving Surface Waters

Expanding cities are shortening the lapse between the release of treated wastewater into the environment and the uptake by water drinking facilities. Even though wastewater treatment plants usually exceed current discharge standards, the presence of unregulated pollutants in these effluents is of concern (Petrovic et al., 2003). Unregulated contaminants, or emerging pollutants of concern (EPOCs), are defined as substances that were previously undetected or had not been considered as a risk (Daughton, 2001). The main sources of non-regulated contaminants in the environment are wastewater treatment plant effluents (Duaghton and Ternes, 1999), which are not designed to eliminate these compounds. They are present in treated wastewaters at trace levels (μg/l to ηg/l), and include personal care products, pharmaceuticals, surfactants, flame retardants, industrial chemicals, gasoline additives, and disinfection byproducts. These contaminants do not need to be persistent in the environment to cause deleterious effects, since their high transformation and removal rates can be offset by their continuous introduction into the environment (Petrovic et al., 2003). Among the various substances that can be categorized as emerging pollutants, pharmaceutical active compounds (PhACs) are of special concern because of the volumes introduced to the environment, their endocrine disrupting activity, and a potential increase of bacterial resistance. It is estimated that hundreds of tons of PhACs are produced and consumed in developed countries each year (Castiglioni et al., 2005, Kosjek et al., 2005, Daughton & Ternes, 1999, Tauxe et al., 2005). Most of them end up being excreted completely unchanged or only slightly transformed conjugated to polar molecules. These conjugates are often broken during sewage treatment, releasing the original PhAC, so they are constantly introduced into receiving waters (Heberer, 2002a). The following sections will describe the fate of the most characteristic PhACs during and after wastewater treatment.