Julie Robitaille

Water treatment is crucial for removing contaminants to protect human and environmental health. However, not every treatment types are efficient to treat all contaminants. In Northern countries such as Canada, a limiting factor to treatment performance is the cold climate which can limit the efficiency of biological treatment, among others. The study objective was to evaluate the treatment efficiency of water facilities of a municipality in the province of Quebec, Canada, throughout seasons. Samples of influents and effluents were collected at a drinking water treatment plant (DWTP) and two wastewater treatment plants (WWTPs) with aerated ponds in winter, spring and summer of 2021. A total of 90 organic contaminants (e.g. pharmaceuticals, steroids, pesticides, metals) were assessed. In addition, samples’ endocrine disruption potential was assessed using estrogenic and androgenic in vitro bioassays. For the DWTP, the only detected organic contaminant was salicylic acid at 15-120 ng/L (influent) which was removed after treatment (>72% in effluent). For WWTPs, pharmaceuticals, parabens and BPA were detected in influent (12 – 31,000 ng/L) but were generally removed at > 75%, except for BPA and some pharmaceuticals. Estrogenicity in the WWTPs’ influent was high (0.7 – 68.8 ng/L estrogen equivalent (EEQ)) and was affected variably by treatment (10.4 – 47.5 ng/L EEQ). Organic contaminants and endocrine activities were higher in winter, confirming the negative impact of cold weather on biological treatment. Overall, this study indicates the WWTPs equipped with aerated ponds are not adequate to treat organic contaminants especially in winter season, suggesting facilities should be upgraded to reduce environmental risk.