Micropollutants in the aquatic enviroment

Project No. 10

Study of metabolite formation during the use of ozone in municipal wastewater treatment plants

The use of ozone as an oxidant for the elimination of anthropogenic organic trace pollutants in wastewater treatment is a new approach to reduce the entry of such substances and to improve water quality. The oxidation by use of economically efficient operation conditions normally does not result in complete mineralization of organic substances however more often leads to partially oxidized metabolites. Whether metabolites are formed under certain operating conditions - and if so, which of these substances do have any ecotoxicological or human toxicological effect - has been poorly studied up to now. For the evaluation of ozonation within large-scale wastewater treatment, such knowledge is crucial.

In the context of a joint research project, examination of metabolites formation processes as well as ecotoxicological assessment studies of formed species will be evaluated on three large-scale sewage plants differing in their catchment areas. The ozonation is hereby incorporated in the conventional process of municipal wastewater treatment. The toxicological examinations cover a broad spectrum of in vitro and in vivo batch tests using concentrated samples and online flow systems. The analytical focus covers mass spectrometric methodology for both structural identification and semiquantitative determination of degradation products in toxicological striking fractions. In addition, the formation of toxic by-products from oxidation of unproblematic precursors on the basis of bromate and nitrosamine-forming potential is investigated. Results from these studies will later lead to suitable operating conditions of ozonation in municipal wastewater treatment processes.