A significant improvement of the quality of biologically treated municipal waste water with respect to pathogenic bacteria and viruses and phosphate concentration is possible by a combination of precipitation/ ultrafiltration. But economically feasible is such a process only for an extremely low specific energy consumption and, simultaneously, moderate specific investment costs. Worldwide, there are several groups concerned with the development of such systems. In close cooperation with the Rochem company, Germany, we developed a new ultrafiltration module meeting these requirements. This module has been tested on pilot plant scale (9 m(3)/h permeate) since October 95 with the sand-filtered effluent of the municipal waste water treatment plant Berlin Ruhleben. The major results will be discussed. The second example concerns dumpsite leachate treatment by a combination ＇＇reverse osmosis-nanofiltration-crystallisation-high pressure reverse osmosis＇＇. This combination achieved a water recovery rate of 97% with a very low overall power consumption (similar to 8,3 kWh/m(3) permeate] and far lower investment costs than comparable evaporation processes.