Fate of bulk organics during bank filtration of wastewater-impacted surface waters

Fate of bulk organics during bank filtration of wastewater-impacted surface waters

More than two years of monitoring data from a bank filtration site in Berlin, Germany, and a long retention soil column system (30 m) were analyzed to study the influence of redox conditions on the degradation of bulk organics. Dissolved organic carbon (DOC), UV-absorption at 254 nm (UVA254) and liquid chromatography with online carbon detection (LC-OCD) was employed to receive qualitative and quantitative information about the fate of different fractions of DOC. It was found that the kinetics of DOC-degradation depend significantly on the dominant redox conditions during infiltration. A faster mineralization of biodegradable DOC was observed during oxic soil passage (~1 month). Anoxic infiltration led to a comparable residual DOC-concentration, but 3-6 months were required for complete removal of biodegradable DOC (BDOC). LC-OCD measurements revealed that the fraction of polysaccharides (PS) is removed very fast during infiltration in the field. Under strictly anoxic conditions the PS were more stable. The fractions of humic substances, building blocks and low molecular weight acids were degraded partially, independently from the redox potential, while the change in aromaticity of the residual DOC was influenced by the dominant redox conditions.