Does Waste Water Treatment Plant Upgrading with Powdered Activated Carbon Result in Reduced Water and Sediment Toxicity of the Receiving Stream?

Advanced waste water treatment technologies based on e.g. an additional powdered activated carbon stage are in the focus of today's science and politics. Despite the abundance of detailed information on the efficiency of these new technologies in the literature, little is known about their effects on the connected surface waters. The present study focuses on a large waste water treatment plant in Ravensburg (Southern Germany), which has been equipped with an additional cleaning stage (powdered activated carbon in late autumn 2013. Within the scope of a pre-post study, effluent samples of this WWTP as well as sediment and surface water samples from the connected River Schussen were investigated by chemical analysis and the fish embryo test with the zebrafish (Danio rerio) over a period of 2 years prior and after the WWTP upgrade. Our results clearly show the additional purification step based powdered activated carbon to result not only in a considerable reduction of micropollutants in the wastewater treatment plant effluent and surface water, but also to improve sediment and surface water quality in respect to a significant reduction of embryotoxic effects. Our study thus revealed the ecological and toxicological relevance of the PAC adsorption technology in wastewater treatment.