Screening of organic micropollutants in raw and drinking water in the Yangtze River Delta, China

Abstract

Background: The vast occurrence of organic micropollutants in surface waters has raised concerns about drinking water safety and public health. The Tai Hu Basin region in China, a typical developing and populous area, is facing the challenge of water pollution. To ensure drinking water safety, the knowledge on how treatment techniques and raw water quality affect the quality of finished water must be improved. The aim of the current study was to evaluate drinking water quality with respect to organic micropollutants and how the purity of finished water depends on source water contamination and drinking water treatment strategies. Five drinking water treatment plants (DWTPs), using three different source waters in the Tai Hu River Basin, (i) Yangtze River, (ii) Wetland River Network, and (iii) Lake Tai Hu, were studied by analyzing 291 micropollutants in raw and finished water. Results: Major differences in concentrations and composition profiles of organic micropollutants were observed between the source waters. Among the studied micropollutants, the dominating group was pesticides in the wetland river network and flame retardants in Yangtze. The total concentration of poly- and perfluoroalkyl substances (PFASs) in Tai Hu water was far higher than in other samples. In total, 51 compounds were detected in finished water, with an overall average total concentration of 730 ± 160 ng L-1. The removal efficiency of the detected compounds in the DWTPs averaged 24 ± 150 %, which highlights the major challenge for the DWTPs to remove emerging organic micropollutants through current treatment processes. Conclusions: Our study showed that if the source water contains high levels of PFASs and organophosphorus flame retardants, even advanced treatment procedures are inefficient in removing the micropollutants, and the finished drinking water may contain cumulative levels of organic micropollutants in the mg L-1 range. On the other hand, if pesticides and pharmaceuticals dominate, high overall treatment efficiencies may be obtained if using advanced treatment techniques. DWTPs are advised to use advanced treatment techniques or alternative water sources to guarantee the safety of drinking water. As surface water systems are highly impacted by upstream activities, efforts should also be made in the water sector for improved surface water quality.