[en] An analysis of the present situation in water supply, wastewater disposal, and pollution control shows that due to a high population density in many areas environmental quality is endangered. Therefore, nearly all countries face the problem of developing and/or improving control strategies, i.e. building new treatment plants, upgrading overloaded or outdated installations and designing new operating and controlling measures for improved plant performance. In view of limited resources and stringent timing requirements there is a great need for concepts that allow stepwise realisation. (orig./UT)