Identification of persistent mobile chemicals and ultrashort chain perfluoroalkyl substances in full-scale drinking water treatment plants by target and suspect screening analysis

Persistent, mobile, and toxic (PMT) substances are increasingly detected in aquatic environments, posing emerging threats to drinking water safety. However, comprehensive monitoring of these compounds in full-scale drinking water treatment plants (DWTPs) remain limited. This study addresses that gap by analyzing paired raw and treated water samples from 28 DWTPs along two major river basins in Korea. Trifluoroacetic acid (TFA) was detected in 100 % of raw water samples with an average concentration of 3365 ng/L, followed by metformin (DF: 85.7 %; mean: 294 ng/L), acesulfame (64.3 %; 144 ng/L), and melamine (39.3 %; 719 ng/L). Industrial sites exhibited significantly higher raw water contamination (mean: 6237 ng/L) than urban (5409 ng/L) and rural areas (3426 ng/L). In treated water, TFA, metformin, perfluoropropanoic acid (PFPrA), and acesulfame were detected in over 40 % of samples with concentrations ranging from 55.2 to 3629 ng/L, highlighting their persistence through treatment. Notably, PFPrA significantly increased post-treatment (p < 0.01), suggesting precursor degradation. This is the first study to report the occurrence of ultrashort-chain PFASs (US-PFASs) in Korea’s drinking water systems. Additionally, suspect screening tentatively identified seven compounds at confidence levels (CL) 2 – 3, including industrial additives and pharmaceutical intermediates. These findings underscore the widespread occurrence, persistence, and potential health relevance of PMT and very mobile pollutants in DWTPs, emphasizing the need for improved monitoring, treatment strategies, and regulatory oversight.