Influence of Increasing Concentrations of Organic Pollutants on Biofilm Formation and Flow Parameters in a Sand-aquifer and Its Capillary Fringe.

We followed the development of a Pseudomonas fluorescens biofilm on quartz sand in an instrumented horizontal flow-through stainless steel container (SSC) in lysimeter-scale, to investigate its impact on physical soil parameters within the aquifer and the capillary fringe (CF).Increasingly concentrated biodegradable substances in a liquid medium were pumped through the sand in the SSC creating an artificial aquifer.Biofilm development and its influence on flow parameters and oxygen concentration profiles, as well as temperature or water suction changes with time were determined.After more than 19 weeks of medium flow, at DOC concentrations of finally about 300 mg/L, P. fluorescens formed a strong biofilm and the highest biomass concentrations with up to 2.8 mg volatile solids per g dry sand were found in the transition zone of the CF.The soil temperature, which was slightly increased, or the water suction was significantly influenced during the experiment.The effects were strongest within the first 0.3 m of flow stretch, where the highest biomass values were detected.During the total experimental duration of 54 weeks the average flow velocity was reduced by up to 15 % due to clogging effects and the oxygen profiles were changed drastically.Results may be representative for real polluted aquifers.