Effectiveness of advanced treatment technologies in the reduction of ecotoxicity and micropollutants at a German municipal wastewater treatment plant.

Conventional wastewater treatment in industrialized countries effectively removes readily degradable organic matter and nutrients but often fails to sufficiently reduce micropollutants. To overcome this gap and assess the resulting benefits in effluent quality and downstream conditions, advanced processes such as ozonation and powdered activated carbon dosing followed by cloth filtration can be implemented to enhance micropollutant elimination and reduce biological effects in treated effluents. In this case study, a municipal wastewater treatment plant was evaluated following the implementation of a two-step advanced treatment system during summer and fall 2023. To assess changes in effluent quality, effect-based methods were combined with targeted chemical measurements of indicator substances. To investigate potential ecological responses downstream, the benthic invertebrate community in the receiving river was analyzed additionally as an ecologically relevant endpoint shortly after the upgrade. Following implementation, advanced treatment substantially reduced both toxic effects and concentrations of the indicator substances compared with conventional treatment. Nevertheless, residual adverse effects were still observed in the receiving water, as indicated by active biomonitoring with gammarids and gastropods and by patterns in the benthic invertebrate community. In addition, the techniques applied in this study showed that there will be room for further optimization in the upgraded WWTP.