Technical Performance and Environmental Effects of the Treated Effluent of Wastewater Treatment Plants in the Shenzhen Bay Catchment, China

Technical performance and effluent environmental impact of seven wastewater treatment plant (WWTPs) in the Shenzhen Bay Catchment, China were examined. All WWTPs had good performance in the removal of chemical oxygen demand, biochemical oxygen demand, and suspended solids, while total nitrogen and total phosphorus removal should be enhanced to improve the comprehensive pollutants removal loading rate. The effluent eutrophication effect from WWTPs was in the range of 0.0028–0.0092 kg/m3, and nitrate was the major contributor. The effluent greenhouse gas emission of WWTP1–7 was in the range of 3.23 × 10−5–8.70 × 10−5 kg·CO2/m. The effluent eutrophication effects and greenhouse gas emission of WWTPs could be reduced by decreasing the effluent total nitrogen concentration. The ecological risk and healthy risk of heavy metals were low. Among examined heavy metals, lead contributed the most to the ecological risk while arsenic contributed most to the human health risk. The human health risk of microbial pollutants of WWTPs1–7 was in the range of 0.0024–0.0042 DALY (Disability Adjusted Life Years). Finally, an ecosystem-based WWTP framework was proposed to systematically include all environmental effects so as to support the sustainable development of WWTPs.