Abstract
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/m3. 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.
Highlights
Nowadays, water quality and safety has become one of the most concerning environmental issues
As the total mass of pollutants removed is mainly affected by the scale of the Wastewater treatments plants (WWTPs), the removed unit of kg·COD equivalent (CODeq)/m3 was adopted when comparing the technical performance of WWTPs
The biochemical oxygen demand (BOD)/total nitrogen (TN) ratio of seven WWTPs was in the range of 1.92–3.52
Summary
Water quality and safety has become one of the most concerning environmental issues. WWTPs are recognized as important sources of pollutants to aquatic environment [1,2,3,4], and may lead to serious secondary pollution or environmental impacts, such as greenhouse gas emission, eutrophication, and so on [5,6]. WWTPs should maximize the pollutant removal and simultaneously minimize the effluent impact. Due to the worldwide shortage of water resources, the treated effluent from WWTPs are usually reused for agricultural irrigation, road washing, surface water augmentation, or other applications [7]. Water reuse requires a higher quality of the effluent for ensuring water safety, especially for controlling microbial contaminants, heavy metals, and some other pollutants that are pathogenic or toxic [8]. How the operating performance and effluent quality of WWTPs is evaluated so as to guide the operation or upgrading of WWTPs is essential for guaranteeing the safety of water and the environment
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