Wastewater Treatment Plant Upgrade Improves Ecosystems

(Swiss Federal Institute of Aquatic Science and Technology Eawag, June 01, 2017)

A research project launched by Eawag aimed to analyze the effect of a planned upgrade of selected wastewater treatment plants (WWTPs) to reduce micropollutant loads. Micropollutants enter rivers and streams in effluents discharged from WWTPs. Between 2013 and 2014, regular sampling was carried out in reaches upstream and downstream of 24 WWTPs and identified the substances present. The analyses demonstrate that numerous micropollutants enter rivers in treated wastewater. Particularly striking was the increase in medicines and household chemicals. In the case of medicines, concentrations were 30 times higher downstream than upstream of WWTPs. Downstream organisms showed various symptoms of stress exerted by micropollutants. But effects of the introduction of an additional treatment step were seen: algae lost their increased tolerance to micropollutants relatively rapidly, and the induced expression of detoxification genes was likewise lost in brown trout living downstream.