Short-chain per- and polyfluoroalkyl substances in aquatic systems: Occurrence, impacts and treatment

Per- and polyfluoroalkyl substances (PFAS) are a class of anthropogenic compounds comprised of a perfluoroalkyl backbone and a terminal functional group. As our knowledge on their environmental and health impacts grow, PFAS have drawn increasing regulatory attention and research interest in recent years. While long-chain PFAS have been the center of active research in the past decade or so, and while industrial production and applications of short-china PFAS continue to rise, very few studies have focused on the occurrence, fate, and transformation of short-chain PFAS in the environment. This review aimed to provide an updated overview of the state of the science about the fundamentals, occurrence, impacts and treatment of short-chain PFAS. The key findings from this review include: 1) Short-chain PFAS are more widely detected, more persistent and mobile in aquatic systems, and thus may pose more risks on the human and ecosystem health; 2) conventional adsorption, ion-exchange, and membrane filtration can remove short-chain PFAS, but are less effective than the long-chain homologues, and are challenged with poor material regeneration efficiency and disposal of process waste residual; 3) advanced oxidation such as thermolysis and sonolysis can achieve complete mineralization, but come with a high process cost; and 4) direct photolysis, oxidation/reduction, photocatalysis, and electrochemical reaction may degrade short-chain PFAS following similar degradation pathways as long-chain PFAS, but at a slower rate, and photocatalytic processes appear most promising. Overall, this review reveals an urgent need for developing more cost-effective treatment technologies for short-chain PFAS in drinking water, for advancing our knowledge on the environmental fate, transport and impacts of short-chain PFAS in the environment, and for developing science-based regulations for short-chain PFAS.