| Abstract: | Evaluation of Long-term Measurements Concerning the Aerobic Degradation Performance of the Subsoil Passage of a Water Catchment at the Lower Rhine The magnitude of the biodegradation of organics during bank filtration was investigated and exemplary quantified at a drinking water catchment in the lower river Rhine area. The catchment is situated at an undercut slope where the Rhine has a steady flow. The observed segment of the quarternary aquifer was free of iron and manganese and showed even under anaerobic conditions no heterotrophic denitrification. This facilitated the assignment and the balance of oxygen consumption and the determination of inorganic carbon due to the metabolic activity of heterotrophic organisms. In particular the progressive curve of the base neutralization capacity up to pH 8.2 of the bank filtered water proved to be a good measure for the biological activity in the river bottom. In the months from summer to autumn there was an increased biological activity. The observed oxygen consumptions could be attributed to the biodegradation of dissolved organic matter by 35 to 45% only. Obviously the particulate organic matter after the rise in temperature during summer takes part in a substantial manner considered little until now. Today the Rhine is regarded as a largely rehabilitated river with respect to oxygen consuming pollutions. The observations demonstrate, that in such flowing waters the particulate organic matter, which should mainly consist of withered organisms, may have a dominant influence on the concentration of oxygen in the bank-filtered water in summertimes. |
