The limnological background of sewage control for relieving water pollution

Summary

This review paper deals with the biotic structure and the community metabolism of biological waste treatment plants, considering these as artificial ecosystems in which high energy compounds are passed through and dissipated by relatively simple food chains. In consequence of the high organic load, stability has to be supported by artificial aeration, but the response to seasonal changes in temperature obviously is characteristic of ecologically stable systems. The hydrodynamical and biochemical conditions promoting dense growths of suspended or attached microorganisms are closely interrelated. Although advanced waste treatment primarily uses physicochemical procedures, biological transformation of N and P compounds is also important.

Modern treatment plants spend vast amounts of electrical energy to dissipate high-grade chemical energy which also could be converted to methane or hydrogen. In view of the shortage of water and the growing demand for energy and fertilizers in many parts of the world, waste treatment no longer can exclusively be practised under the aspect of open systems in which treated effluents are diverted to water bodies serving as recipients. A higher priority has to be given to the development of integrated, ecologically sound waste treatment schemes in which reuse of water and nutrients becomes possible.