Distribution, Tansformation, and Fate of Per-and Polyfluoroalkyl Substances in Drinking Water Treatment

Abstract

Per-and polyfluoroalkyl substances (PFASs) are present in surface water, tap water, and even commercial drinking water and pose a threat to human health. In this study, the occurrence and transformation of 14 PFASs were studied in large drinking water treatment plants (DWTPs) with Taihu Lake as the source, and the results showed that a total of 10 PFASs were detected in the water samples, indicating that PFAS were widely distributed in drinking water. The total concentration of PFASs in raw water was 127.4 ng·L-1, with the highest concentration being that of pentadecafluorooctanoic acid (PFOA, 49.8 ng·L-1). Pre-ozone caused a reverse increase in the concentration of PFASs, which may have been due to the presence of precursors or conversion from short to long chains. PFASs were not effectively removed by conventional treatment processes, andozone-biological activated carbon (O3-BAC) had a dominant role in the removal of PFASs (20.74%) from DWTPs. O3-BAC, the main removal process for DWTPs, contained high concentrations of PFASs in the backwash water with similar distribution characteristics to the raw water. Using a pilot plant, five common filter backwash water treatment processes were compared, and the results showed that GAC-ultrafiltration could adsorb and retain a certain amount of PFASs while ensuring a high removal rate of turbidity (99.08%). The 3D-EEM analysis indicated that GAC-ultrafiltration could also remove most of the fluorescent micro-pollutants, and for raw water containing high concentrations of PFASs DWTPs, it is practical to use it as a filter backwash water reuse treatment process.