Biological Toxicity Evaluation of Domestic Wastewater Based on A2/O Treatment Processes Using a Battery of Bioassays

Abstract

In order to accurately evaluate the comprehensive ecotoxicity of domestic wastewater and the toxicity reduction efficiency of different treatment processes, standardized assays focusing on Vibrio fischeri, SOS/umu test and yeast estrogen screen were applied. Simultaneously, male zebrafish was used to address the mode of action of endocrine disrupting effects of wastewater and reclaim water on aquatic life. Results of this study indicated that the influent was severely polluted:highly acute toxicity, genotoxicity and estrogenicity were observed. After the secondary biological treatment, the above toxicities were significantly reduced, making the water quality improved. However, the estrogencity of secondary effluent was detected at 1.89 ng·L-1, which still posed potential risk on the aquatic life in receiving water. In addition, the up-regulation of estrogen receptor (esr 1) and vitellogenin (vtg 1) in the livers of zebrafish was observed after exposure to 2.5 times concentrated wastewaters, which demonstrated that wastewater modulates hormonal activities of aquatic life by disturbing target genes expression. Moreover, the slight down-regulation of esr 1 was observed in the gonads. These observations reflect that the evaluation of biological toxic effect should be analyzed in different tissues or organs, so that more comprehensive information about the adverse effects of wastewaters on aquatic life can be obtained.