Risk to Receiving Water Bodies Related to Oestrogenic Activity of Wastewater Treatment Plant Effluents Estimated Through Effect-Based Trigger Values

Wastewater treatment plants (WWTPs) play a crucial role in safeguarding water resources; however, incomplete removal of pollutants such as endocrine-disrupting chemicals (EDCs) may pose ecological risks to receiving waters. Traditional monitoring relies primarily on chemical analyses of selected compounds, while bioassays provide a complementary, effect-based approach for evaluating effluent quality. This study assessed the oestrogenic activity of wastewater from municipal and industrial sources. Influent and effluent samples were collected over four seasonal campaigns from three WWTPs in north-eastern Italy treating mixed municipal and industrial wastewaters. Oestrogenic activity was evaluated using a cell proliferation assay (E-screen) and a reporter-gene assay (MELN cells). The removal efficiency of oestrogenic activity by the WWTPs and the potential ecological risk to receiving surface waters were assessed by comparing measured oestradiol equivalent concentrations (EEQs) with literature-based effect-based trigger values (EBTs). Results confirm the suitability of bioassays for wastewater quality assessment. Although effluents complied with current physico-chemical regulatory standards, EEQs measured by the E-screen (0.8 +/- 0.2 ng/L) and reporter-gene assay (0.6 +/- 0.1 ng/L) exceeded proposed long-term EBTs, suggesting a potential risk to aquatic ecosystems.