Current research projects show that the effluent of municipal wastewater treatment plants contain micropollutants harming the environment at concentrations (≤ µg l-1). Actually it is not possible to compile a definitive list of environmentally relevant micropollutants. Nevertheless engineers are seeking wastewater treatment processes and source control methods capable to reduce micropollutant immission. For this purpose different treatment processes (activated sludge, membrane bioreactor and biofilter) shall be compared concerning elimination efficiency of micropollutant and the impact of single operating parameters will be evaluated. Some possible optimization mechanisms are being discussed.