Chemicals which are released into the aquatic environment in very low concentrations as micro-pollutants or “emerging contaminants”, are increasingly attracting attention. Their number, frequency of occurrence and concentration are increasing continuously. Pharmaceuticals and drug residues as well as endocrine disruptors (pseudo-estrogens) are considered especially critical, since they have been reported to cause pharmaceutical or hormonal effects in surface waters. They can be accumulated over the food chain and have been detected in groundwater and even in drinking water. They are chemically diverse and, due to their chemical structure and extremely low concentration, are not eliminated in municipal wastewater treatment plants based on current technology and processes.