Evaluating contaminants of emerging concern in municipal wastewater effluents

Abstract

Municipal wastewater treatment plant effluent (MWWE) is a complex matrix that acts as a significant source of contaminants to aquatic receiving environments. Contaminants of emerging concern (CECs) are known to affect aquatic organisms downstream of MWWE discharges. Past studies in the Grand River watershed of southern Ontario on the small-bodied, benthic rainbow darter (Etheostoma caeruleum) have shown altered gene expression, sex steroid levels, gonad size and expression of intersex (testis-ova) associated with wastewater outfalls. The Region of Waterloo is upgrading the two major wastewater treatment plants (WWTP) within the Grand River watershed (Waterloo, Kitchener) where biological impacts in the receiving waters have been observed. Although extensive research is currently being performed in the Grand River to determine the biological impacts of WWTP upgrades on exposed fish and benthos, there was no comprehensive work being done on the chemistry of the effluent itself. The objectives of the current study were to determine how process changes and temporal variability altered the concentration of select CECs present in the effluent as well as the total estrogenicity of the discharged effluent. Archived and current effluent samples from 2009 through to 2015 were analyzed for select CECs with LC-MS/MS as well as total estrogenicity with the Yeast Estrogen Screen assay. Concentrations of selected pharmaceuticals, such as ibuprofen and naproxen, are greatly reduced with nitrifying treatment while other contaminants such as carbamazepine and diclofenac remain recalcitrant. The removal of key CECs varies dependent on their physiochemical properties, with readily biotransformed CECs the most effectively removed by the WWTP after a transition to nitrifying treatment. Increased understanding of how major upgrades to treatment plant infrastructure alter the contaminant concentrations in wastewater effluent will greatly improve our ability to inform future watershed regulatory decision-making. These improvements have potential significance for the environment downstream of the WWTPs where endocrine disruption has been documented, including high expression of intersex in fish. This data is a crucial piece of information supporting numerous studies examining the biological consequences of CECs in the aquatic receiving environment.