Assessment of the endocrine disruption potential of an advanced tertiary treated sewage effluent using multiple lines of evidence
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In Australia, due to increased uncertainties over security of water supply because of unpredictable drought and flood cycles, alternative water sources are being investigated for commercial, agricultural, industrial and domestic supply, including the option of reusing treated sewage effluents. However, sewage effluent is a known source of estrogenic endocrine disrupting chemicals (EDCs) in the environment. Exposure to sewage effluents containing steroid estrogens and xenoestrogens can cause developmental and behavioural reproductive abnormalities in fish and other aquatic animals. As such, risk of endocrine disruption is one of the water quality issues that needs to be evaluated when assessing the appropriate level of treatment required for reuse applications. The Gerringong-Gerroa sewage treatment plant (GGSTP), currently employs advanced tertiary treatment technology to treat domestic sewage from two small coastal towns (Gerringong and Gerroa), which receive large seasonal influxes of holiday makers. In this study, the efficacy of the treatment at the GGSTP in removing estrogenically active chemicals was assessed using a multi-tiered assessment approach, incorporating chemical analysis, in vitro bioassays and in vivo fish exposure studies. The raw sewage influent was found to contain steroidal estrogens; 17βestradiol (E2), estrone (E1) and estriol (E3) as well as synthetic phenolic xenoestrogens; 4-tertoctylphenol, Bisphenol A and technical nonylphenol at concentrations commonly found in sewage influents. The influent also displayed high levels of activity in the two-hybrid yeast in vitro bioassay. However, the final effluent had no detectable concentrations of steroidal estrogens, no estrogenic activity in the two-hybrid yeast assay and only infrequent occurrence of low concentrations of synthetic phenols. Biodegradation by activated sludge treatment provided significant, but incomplete removal of measured EDCs and estrogenic activity, with the in-line combination of ozone oxidation and biologically activated carbon filtration reducing the remaining estrogenic activity to undetectable levels. EDCs in both the dissolved and particulate phases of the effluent were removed by the treatment process and the efficacy of treatment was not compromised by increases in influent flow during the peak holiday seasons. Treatment of the effluent at the GGSTP was also successful at reducing retinoic acid receptor (RAR) activity and genotoxicity to below detection limits and greatly reducing arylhydrocarbon receptor (AhR) activity. On-site real-time exposure tests using the mosquitofish (Gambusia holbrooki) and rainbowfish (Melanotaenia fluviatilis) demonstrated that the final effluent did not elicit up-regulation of vitellogenin, a well known biomarker of exposure to estrogenic EDCs. Despite the presence of residual concentrations of E1 and the in vitro activity in effluent after being processed through activated sludge treatment, clarification and sandfiltration, vitellogenin up-regulation was not detected in fish exposed to this partially treated effluent. Overall, the results provide evidence that the application of advanced tertiary treatment technology to domestic sewage can produce a final effluent that is unlikely to pose an endocrine disruption risk to the aquatic biota.
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