Per- and polyfluoralkyl substances (PFAS) in drinking water system: Target and non-target screening and removal assessment.

The massive use and the persistence of per- and polyfluoroalkyl substances (PFAS) have led to their frequent detection in aquatic environments, which may further threaten drinking water safety. So far, our knowledge about the occurrence of PFAS in drinking water system is still very limited. Here we investigated the occurrence and removal of PFAS in a drinking water system using non-target, suspect and target screening strategies. Sampling was performed in three seasons in the drinking water system including a water source, two drinking water treatment plants, and tap water in five households. The results showed detection of 17 homologous series with 51 homologues in non-target screening and 50 potential PFAS detected in suspect screening. Probable structures were proposed for 15 PFAS with high confidence levels (the first three of the five levels), with seven of them being reported for the first time in drinking water system. Semi-quantification was performed on seven homologous series based on target PFAS, the estimated total concentrations for non-target PFAS ranged between 4.10 and 17.6 ng/L. Nine out of 50 target PFAS were found and precisely quantified (<LOQ-13.4 ng/L) with predominance of perfluorocarboxylic acids (PFCA) and perfluorosulfonic acids (PFSA). All target and non-target PFAS were detected in tap water with similar concentrations in all three seasons. Removal efficiency for the detected PFAS in each processing unit was almost zero, indicating the recalcitrance of these chemicals to the conventional treatment process. The findings from this study clearly show the wide presence of PFAS in the whole drinking water treatment process, and suggest an urgent need for effective removal technology for this group of chemicals.