Occurrence and removal of 42 legacy and emerging per- and polyfluoroalkyl substances (PFAS) in drinking water treatment plants in South Korea

This study investigated 42 Per- and polyfluoroalkyl substances (PFAS) in raw and treated water from drinking water treatment plants in the Nakdong River basin. 22 PFAS were detected in both raw and treated water, especially 6:2 fluorotelomer carboxylic acid (6:2 FTCA), N-methyl perfluorooctanesulfonamidoethanol (N-MeFOSE), hexafluoropropylene oxide dimer acid (Gen-X) were identified for the first time in the raw water in South Korea. In raw water, PFAS concentrations ranged from 13.3 to 189 ng/L, with short-chain PFAS showing higher levels than long-chain PFAS. No significant difference in concentration was observed regardless of riverbank filtration. In treated water, 77.8 % of samples exceeded the MCL for PFOA (4 ng/L, US, EPA). The study assessed PFAS removal across various treatment processes and suggests the potential presence of additional precursors beyond those initially targeted. GAC showed increased removal efficiency with longer carbon chains, ranging from 1.0 ± 19.0 % for PFBA to 100 ± 0 % for PFDA. In contrast, pre-ozonation and ozonation were generally ineffective, with overall PFAS removal efficiencies of -8.1 ± 43.0 % and 6.1 ± 34.7 %, respectively. Chlorination also exhibited low removal efficiency, and in some cases, concentrations of PFHxS and PFOS increased post-treatment, suggesting the latent influence of precursor compounds. These findings highlight the need for further investigation into unidentified precursors and their role in PFAS transformation.