A review of the fate of micropollutants in wastewater treatment plants

Municipal wastewaters are contaminated by a wide range of chemicals, from surfactants to heavy metals, including pharmaceutical residues, personal care products, various household chemicals, and biocides/pesticides. Their release into the environment, where they may generate adverse effects on aquatic organisms, depends on their fate in wastewater treatment plants (WWTPs). The sources, the typical concentrations and the fate of more than 160 micropollutants of various classes in conventional WWTPs, were investigated in order to estimate surface water contamination, risks for aquatic organisms, and to propose means to reduce their release into the environment. Relatively hydrophobic pollutants such as heavy metals, persistent organic pollutants (POPs), brominated flame retardants, and several personal care products (PCPs), as well as easily biodegradable pollutants such as surfactants, plastic additives, hormones, several PCPs, some pharmaceuticals, and household chemicals, are usually well removed (>70%) in WWTPs, either by sorption onto sewage sludge or by biodegradation. Good removal efficiencies, however, do not mean that the effluent concentrations will not potentially affect aquatic life, as some of these compounds are toxic at very low concentrations. More hydrophilic and poorly-to-moderately biodegradable pollutants such as several pharmaceuticals, pesticides, and household chemicals (corrosion inhibitors, sweeteners, chelating agents, phosphorus flame retardants) are only poorly removed during treatments. To decrease their discharge into surface waters, source control combined to advanced treatments such as ozonation and adsorption onto activated carbon are necessary.