Untersuchungen zur Verbesserung der Prozeßstabilität bei der Stickstoffelimination in kommunalen Kläranlagen

The on-line determination of nitrogen removal in municipal sewage treatment plants was systematically investigated. The measurements were carried out for three different plants over a period of several months. The results of the investigations into the ammonium removal (nitrification) showed that effluent ammonium peaks were primarily caused by inadequate plant operation: from directing the filtrate from waste sludge dewatering back into the influent of the plant during high loading periods (the filtrate contains up to 15-25% of the total daily ammonium load on the plant); and from allowing the undiluted contents of the primary clarifiers to be flushed directly into the aerated reactors by the high hydraulic during rainfall. In order to keep the effluent ammonium concentration below the required limits it is necessary to keep the amount of influent ammonium below the removal capacity of the system. This can be accomplished by using tanks to store filtrate during sludge dewatering and i nfluent during rainy periods, their contents being fed into the sewage plants during subsequent low loading periods. It was found that removal of nitrate and nitrite (denitrification) was primarily influenced by the relative concentrations between nitrogen compounds and easily degradable carbon sources. Measurements demonstrated that this relationship could vary dramatically and that unfavorable conditions often lead to high effluent N02- and N03-concentrations.