Occurrence and removal of emerging pollutants in urban sewage treatment plants using LC-QToF-MS suspect screening and quantification

Abstract

Urban wastewaters (WW) are a major vector of many emerging pollutants (EPs) to aquatic ecosystems, as urban wastewater treatment plants (WWTPs) are not designed to abate them. New methods are now critically necessary for a more comprehensive analysis of WW samples and for the assessment of the WWTP efficiency in EP removal. To this end, the present study aims to develop a methodology to identify and quantify EPs, especially pharmaceutical residues and pesticides, in the raw and treated wastewater of 10 heterogeneous WWTPs in a highly urbanized territory in France over three sampling campaigns, through the following steps: (1) development and implementation of a suspect screening of EPs in WW samples, based on a solid phase extraction followed by an LC-QToF-MS analysis; (2) confirmation of their identification by reinjection of WW samples spiked with authentic analytical standards; (3) quantification of previously identified compounds by targeted LC-QToF-MS analysis in raw and treated effluents and assessment of their removal efficiency by WWTPs. Forty-one EPs, including 37 pharmaceutical residues (such as anti-depressive, anti-hypertensive, or antipsychotic drugs) and 4 pesticides, were identified by suspect screening. Some of them (e.g. milnacipran) are reported for the first time in urban WWTPs in this study. High variability in detection frequency and concentrations were observed in function of the EP and WWTP. Nevertheless, median removal rates were considered negative or low for more than 50% of the EPs (respectively 4 and 17), leading to a quantification of significant concentrations in treated WW. Their release into receiving streams may thus lead to ecotoxicological risks that should be evaluated in order to prevent any degradation of the exposed ecosystems.