Organic micropollutant removal during river bank filtration: batch studies

Organic micropollutant (OMP) removal during river bank filtration (RBF) under oxic conditions was simulated in a batch experiment. A cocktail of 16 OMPs, with varying physico-chemical properties, was dosed to try to relate OMP removal behavior to these properties. An indication for the biodegradation potential of the OMPs was obtained by comparing a batch filled with sand and river water to a batch filled with sand, river water and sodium azide (NaN3) as biocide. It is concluded that all charged, both positive and negative compounds, are biodegraded. For neutral compounds there is no clear trend visible for biodegradation potential: metolachlor, diuron, caffeine and lincomycin (Log D ranging from -0.64 to 3.44) are neutral and biodegraded. Atrazine, carbamazepine, phenytoin and sulfadiazine (Log D ranging from -0.14 to 2.63) are also neutral but not biodegraded. Both neutral groups cover the same range in Log D which implies that other factors/physico-chemical properties than hydrophobicity are playing a role in the biodegradation behavior of neutral compounds. Further research is required to determine the origin of biodegradation potential of neutral compounds. The addition of an easily biodegradable carbon source (sodium acetate) at regular time intervals did not have a significant effect on OMP removal after 14 days. Further research should explain whether this was caused by a lack of nutrients or the water:sand ratio and the dosed concentration OMPs. Since OMP removal is similar in the batch filled with river water and sand and the batch filled with demineralized water and sand after 14 days, it can be concluded that OMP removal mainly takes place in the soil phase. This was expected since in the soil more biomass (biofilm) is present and this biomass seems to play an important role in OMP removal