Membrane Aging by Chemical Cleaning Drives the Overlooked Release of Per- and Polyfluoroalkyl Substances from Polyvinylidene Fluoride (PVDF) Ultrafiltration Membranes in Drinking Water Treatment

The application of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes in drinking water treatment plants (DWTPs) is increasing rapidly. However, as a class of fluoropolymer materials, PVDF membranes might be a source of per- and polyfluoroalkyl substances (PFAS) in drinking water systems. In this work, we identified the occurrence of PFAS in commercial PVDF UF membranes, with PFOA as the dominant species (82–97% of ∑PFAS). Subsequently, we explored their release behavior during chemical cleaning and membrane aging. NaOH/NaClO solutions induced sustained and enhanced release of C 4 –C 6 and C 8 perfluorocarboxylic acids (PFCAs) (up to 104 ng/L), significantly higher than the leached levels from virgin membranes. Apart from short-term release of leachable PFCA residues, structural degradation of PVDF led to long-term release of PFCAs that were previously nonleachable from virgin membranes. In the chemical-cleaning wastewater from PVDF UF units at a full-scale DWTP, PFAS levels were much higher (up to 371 ng/L) than those observed in laboratory experiments, with similar dominant PFAS species. This study provides evidence that PVDF membrane aging by chemical cleaning induces persistent PFAS release, highlighting these membranes as an overlooked source of PFAS in DWTPs.