[Current technology of waste water treatment].

For the purification of municipal waste water and industrial waste water predominantly burdened by organic matter, mechanical-biological plants partly based on the method of activation and partly on the trickling filter system are preferably used. Recently overloading of existing plants and tighter water protection requirements imposed the necessity of boosting the performance of conventional biological processes by reducing the sludge burden and the loading per unit volume. This has also resulted in nitrification of the nitrogen compounds and in extensive sludge stabilization. As the oxygen supply to the micro-organisms requires the highest expenditure of energy in the activation process, special attention was given to the development of efficient aeration systems. For waste water containing a high proportion of substances which prove difficult to decompose, or waste water subject to strong fluctuations, multi-stage biological procedures or a combination of various processes are used increasingly. In this context, chemical precipitation for the elimination of phosphorus and biological nitrogen elimination have proven themselves as additional purification methods.