Présentations Colloques

    Session 7.02: Urban Hydrogeology
    Burke Victoria
    Column experiments on the attenuation of organic micropollutants during bank filtration- The relevance of the hyporheic zone
    The hyporheic zone, i.e, the interface between surface- and groundwater is considered to be a highly reactive ecotone, and represents the very first part of the flow path of surface water entering the subsurface via bank filtration. Bank filtration typically leads to an improved quality of the infiltrate due to physical filtration, sorption and biodegradation processes that decrease the concentrations of undesirable constituents such as bacteria, viruses or anthropogenically-induced (trace) contaminants. But to what extent does the hyporheic zone contribute to this quality improvement? **In order to estimate its cleaning capacity with regard to the elimination of organic micropollutants, we performed column experiments using undisturbed sediment cores, which originated from a bank filtration site in Germany. The columns were fed with surface water taken from the same field site in order to mimic field conditions as close as possible. As part of a partly closed water cycle, the utilized surface water receives wastewater treatment plant effluents. Thus, the investigated organic micropollutants - a total of 14 frequently applied pharmaceuticals and metabolites - were already present in the water and it was not required to artificially add them. After an adaption phase of several months three depth-dependent sampling events were carried out, considering the hydrochemical conditions along the flow path as well as the fate of the organic micropollutants. **Whereas several of the investigated compounds were more or less unaffected (e.g. carbamazepine, candesartan), other compounds were significantly attenuated along the flow path (e.g. acesulfame, metoprolol). Due to chemical and physical differences regarding the core materials the (degradation) behavior of the investigated compounds clearly indicated site-specific variabilities. Data collected during this study emphasizes the relevance of the hyporheic zone within a partly closed water cycle, as it considerably contributed to the attenuation of surface water constituents.**


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