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

• 42 PFAS in raw and treated water in drinking water treatment plants were investigated • The riverbank filtration of raw water was an ineffective pretreatment for PFAS removal • 7 precursors and 3 alternatives were detected in the raw water for the first time in Korea. • GAC demonstrated high removal efficiency during individual processes • Gen-X, a PFOA alternative, poses challenges for effective removal in water treatment 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 also evaluated the removal efficiencies of PFAS by different treatment processes, finding significant variation among PFAS. GAC showed increased removal efficiency with longer carbon chains, ranging from 1.0 ± 19.0% for PFBA to 100 ± 0% for PFDA. In contrast, preozonation and ozonation were generally ineffective, with overall PFAS removal efficiencies of -8.1 ± 43.0% and 6.1 ± 34.7%, respectively. Chlorination also showed limited efficacy, with certain PFAS concentrations, such as PFHxS and PFOS, increasing post-treatment.