In order to reduce the inputs of trace substances via wastewater treatment plants, many plants are currently being equipped with an additional treatment stage. The range of methods presented serves to demonstrate the efficiency of these measures for the health status of aquatic ecosystems within a short time.

Wastewater treatment plants have been identified as significant point sources for the input of numerous trace substances into aquatic ecosystems. In order to reduce these substance inputs, many plants are currently being equipped with a 4th treatment stage. The presented method repertoire can be used to demonstrate the success of WWTP upgrading for aquatic ecosystems within a few months. The method repertoire is to be understood as a toolbox with which possible and real manifested negative effects in ecosystems in response to the input of wastewater containing trace substances can be presented both in environmental samples and in exposed organisms, such as fish, amphipods or snails, as well as in entire biocoenoses. The reduction of the previously detected effects after the establishment of a 4th treatment stage on a wastewater treatment plant serves here as a measure for the efficiency of the realized measure. Due to the diversity of the range of methods, individual effects can be assigned to possible groups of substances, e.g. genotoxic, phytotoxic or hormonal effects, and, if necessary, causally explained by the presence of substances that can be detected by chemical analysis (e.g. certain PAHs, pesticides or endocrine disruptors). In addition, already manifested or foreseeable ecologically relevant effects in the ecosystem itself can either be detected or at least predicted, since in many cases there are demonstrably plausible links between effects at lower biological levels (molecules, cells) and effects at higher levels (populations, ecosystems).