Acute ecotoxicological effects on daphnids and green algae caused by the ozonation of ibuprofen

Due to its ubiquitous presence in wastewaters, wastewater treatment plant effluents and even surface waters, the removal of the pharmaceutical ibuprofen from water is of special interest. Ozonation is widely applied for the treatment of micropollutants in wastewater treatment plants and is already known to also degrade ibuprofen. However, the formation of a wide range of transformation products during such oxidation steps might affect the aquatic environment. This study focuses on the acute ecotoxicological impact of the ibuprofen ozonation products on the two model organisms Daphnia magna and Desmodesmus subspicatus. For the identification of possibly ecotoxic products, a new workflow combining ecotoxicological testing, analytical methods and toxicity prediction was applied. Examination at different pH conditions with increasing ozone doses can point to respective products for further systematic examination. Seven ozonation products were confirmed in this study, two of them for the first time. Five previously postulated products were rejected. For pH 7 the inhibition of green algae growth was observed for mixtures oxidized with low ozone doses, while at pH 3 the mixtures with higher ozone doses caused toxic effects on the mobility of daphnids. Together with the analytical measurements in combination with ecotoxicity prediction, six products were identified which might have caused the toxic effect on green algae. However, no assignment to the observed toxic effects on daphnids was possible. The gained results indicate that mixture toxicity might play a role in oxidation processes and needs to be considered in ozonation studies concerning the ecotoxicological impact. Furthermore, the different observed toxicity for the two organisms underlines the importance of using multiple test systems for a comprehensive evaluation of the ecotoxicity during ozonation processes.