OZONATION OF TERTIARY TREATED MUNICIPAL WASTEWATER FOR THE REMOVAL OF PERSISTENT ORGANIC POLLUTANTS - RESULTS AND TOXICOLOGICAL EVALUATION

摘要

The case study presented in this paper investigates the removal potential of activated sludge based wastewater treatmentprocesses with different sludge retention times and a subsequent ozonation step at a municipal wastewater treatment plant (4,000,000 p.e). In a first step the removal performance of the former high loaded full scale plant (C removal only) was monitored. Later on, the plant was upgraded to a low loaded nitrogen removal (nitrification & denitrifieation) plant. A new assessment of the removal capacity showed a significant increase of the removal capacity for pollutants such as bisphenol-A, 17α-ethinylestradiol and the antibiotics erythromycin and roxithromycin that were only removed after the upgrade of the WWTP. Nevertheless, a number of organic pollutants were not removed. Thus, a pilot scale ozonation plant (O3 production capacity of 1,000 g/h) was installed for additional treatment of the effluent. The application of 0.6 - 0.9 g O3 g DOC_0~(-1) increased the removal of most of the pollutants, especially for compounds that were not degraded in the previous biological process, as for example carbamazepine and diclofenac. Additionally, standardized ecotoxicity tests were applied to assess the toxicity of the tertiary treated wastewater before and after ozonation for green algae, daphnids, and fish eggs. Endocrine and general health effects on fish were tested using a OECD 21-day fish assay. Enzyme immunoassays considering both unconjugated estrogenic (E-Assay) and androgenic (T-Assay) activity were applied as well as three different standardized mutagenity tests (Salmonella/microsome assay; SCGE - comet assay, Allium cepa micronucleus test).