Key findings from 15 years of research on attenuation of trace organic compounds in the River Erpe

Trace organic compounds (TrOCs) in water bodies worldwide are a major concern. In addition to reducing the loads and improving the understanding of the ecotoxicological effects of TrOC cocktails, it is important to gain a better understanding of the pathways and fate of this large group of compounds in the environment. The lowland River Erpe in Berlin/Brandenburg, Germany, which receives treated wastewater from an urban wastewater treatment plant, is an excellent site for such research. The exceptionally high TrOC concentrations in the River Erpe enable reliable process studies with minimal analytical effort, as prior enrichment steps aren’t required. The river system also offers a variety of reaches that differ in terms of hydrology and streambed morphology, enabling different types of investigation. Over the past 15 years, more than 100 researchers have conducted several large-scale and numerous smaller studies on the River Erpe. Topics have included the role of hyporheic zones in the self-purification capacity of streams with respect to TrOCs; seasonal changes in instream processes; interactions between easily degradable organic matter and TrOC attenuation; the importance of identifying flow paths to understand biogeochemical processes; the effects of management actions, such as the removal of macrophytes, on the fate of TrOCs; the effects of losing conditions on TrOC input to aquifers and bank filtration systems; the effects of discharging treated effluents from a large, new industrial site on the composition of the river water; and identifying microbial key players associated with TrOC removal. Current research topics include bioremediation, the impact of migrating bedforms on TrOC fate, as well as the seasonal development of loads. Research highlights and future directions are presented.