Transformation of organic matter and bank filtration from a polluted stream

A case study of the examination of the changes of organic matter in a small, highly polluted stream and the adjacent alluvial aquifer is presented. The investigated stream was actually a collector of effluents from bakerʹs yeast and pharmaceutical industries. The stream was characterized by a COD of several thousands of mg O2 l−1, most of which was biodegradable organic matter. Biodegradation processes took place in the surface water, with consequent oxygen depletion in the stream. The organic matter content of the river sediment was more than 10% of its dry weight. Bank filtration of organic substances was investigated in a number of observation wells at distances of 5–150 m from the river (under different hydrological conditions). The infiltration of organic matter from the polluted stream into the aquifer was found to be significant only at hydrological conditions where the water level exceeds the altitude of the stream bed. The organic matter present in groundwater samples was mainly a humic/fulvic type, and was not degraded during the 64 days of the laboratory biodegradation experiment.