Ecotoxicological Assessment of Sediment Samples Impacted by Wastewater Treatment Plant Effluents Transporting Contaminants of Emerging Concern

Wastewater treatment plant (WWTP) effluents can be important sources of contaminants of emerging concern (CEC) for riverine ecosystems, with some accumulation in sediments. This study investigated the ecotoxicological effects of sediment samples collected near three WWTPs. Sediment elutriates, simulating resuspension conditions, and whole sediment samples were tested. Results showed that sediments were toxic to some organisms and beneficial to others. Elutriates from one site significantly reduced luminescence in the bacterium <i>Aliivibrio fischeri</i>, though this was not consistently linked to sediment contaminant levels. Significant noxious effects of elutriates were recorded for the macrophyte <i>Lemma minor</i> (yield reductions up to 48%) and the microalgae <i>Raphidocelis subcapitata</i> (yield reductions up to 25%). Exposure to elutriates resulted in increased <i>Daphnia magna</i> reproduction and increased biomass yield of <i>Chironomus riparius</i> exposed to sediments directly. Overall, there were no major toxicity variations in samples collected upstream and downstream of the effluent outfall. Suggesting limited hazardous potential of the effluent and a potential masking effect of background contamination (mostly metals and polycyclic aromatic hydrocarbons). The complexity of effluent-sourced contamination, coupled with the realistic testing approach, renders this work a valuable contribution to understanding the role of WWTP effluents in surface freshwaters contamination and their effects, especially concerning CECs.