Through improved methods of chemical analysis, pharmaceutical and hormone-active substances are increasingly being detected in our water bodies. In most cases, they enter the waste water after being excreted in urine. In the sewage plant, a fraction of the substances is eliminated through sorption and biological degradation. The remaining part enters water bodies with the treated waste water. This article describes possible measures aiming at eliminating the residual substances. These include on the one hand, permanent measures at the source such as an eco label for pharmaceuticals, the pre-treatment of hospital waste waters and the separate treatment of urine. However, on the other hand, as the measures at the source can only be implemented over the long term, it is expedient to also consider technical measures such as raising the sludge age in the activated sludge tanks of sewage treatment plants and, for critical cases, the ozonation of the purified waste water.