Efficiency evaluation of a membrane bioreactor to remove emerging pollutants from a hospital effluent based on the combined use of in vitro and in vivo bioassays and targeted chemicals analyses

Hospital effluents have been identified as an important source of various chemical classes. Because of potential associated risk for humans and wildlife, elimination of such compounds has become an increasing issue of concern. Conventional treatments are often insufficient to eliminate all the active micropollutants. In particular, chemical diversity of endocrine disrupting compounds (EDCs) limits their removal through targeted approaches. Therefore, new processes have emerged, including membrane bioreactor (MBR) to improve removal efficiencies. In the present study, we aimed to evaluate the efficiency of an MBR pilot for the elimination of i) EDCs using a battery of in vitro bioassays (i.e. reporter cell lines) covering a panel of endocrine activities, ii) various pharmaceuticals classes using LC-MS-MS analysis, in hospital effluents. In parallel, standardized ecotoxicological tests were performed to characterize ecotoxic potency of effluent before and after MBR treatment. All these tools were deployed on several sampling campaigns. In the non-treated effluent, estrogenic and androgenic activities were quite similar to those previously reported in other hospital effluents whereas GR-and PXR-like activities were close to those found in industrial effluents. After MBR treatment, an overall reduction of the endocrine activities was noted.Target chemical analyses revealed the occurrence of a broad range of pharmaceutical classes including cytostatic anticancer drugs and antibiotics but also metabolites in the non-treated effluent. Overall, concentrations were similar to those reported in other studies, except for very high amount of the antibiotic ciprofloxacin (up to 1mg/L). MBR treatment allowed either total, partial or no removal of targeted pharmaceuticals classes, depending on chemical. Finally, ecotoxicological tests showed effects at several trophic levels in the non-treated effluents. MBR treatment significantly reduces this ecotoxicity. Altogether, our results confirm the relevance of the combined use of biological and chemical analyses for an hoslitic characterization of hospital effluent contamination by a broad range of active chemicals. We report also that this complex mixture leads to global toxicity for exposed organisms at different trophic level confirming hazard for aquatic ecosystems. One major outcome is the ability of MBR treatment to reduce both endocrine disrupting activity and global toxicity although some persisted after treatment