Per-and polyfluoroalkyl substances (PFAS) removal in drinking water with point-of-use water treatment systems

Abstract

Per- and poly-fluoroalkyl substances (PFAS) have gained much attention recently due to their high persistence and potential health risks. PFAS are often used in the fabrication of various consumer products, such as firefighting foam, non-stick utensils, water-repellent clothes, stain-resistant materials, and food packaging products. PFAS are highly stable and persistent due to their strong carbon-fluorine bonds and have been found to be absorbed in humans and animals for significant amount of time. Studies have shown that drinking water may act as a reservoir of trace level PFAS and contribute to the accumulation of PFAS in human bodies, which may lead to adverse health issues in liver, kidney, and reproductive systems. However, limited studies have been done to remove trace level PFAS in point-of-use (POU) water treatment systems, including reverse osmosis (RO) and activated carbon (AC) systems. The objective of this study was to evaluate PFAS removal in POU systems and factors that may impact PFAS removal efficiencies. Mixtures of perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), and perfluorobutane sulfonic acid (PFBS) under two different concentrations (1 μg/l and 10 μg/l) were spiked into tap water and PFAS removal efficiencies in three RO and three AC systems were evaluated. Solid phase extraction coupled with liquid chromatography tandem mass spectrometry (SPE-LC/MS/MS) was used to quantify trace level PFAS concentrations. The results showed that PFAS were effectively removed in both RO and AC systems with average removal efficiencies greater than 90% in all tested POU systems. Among the three evaluated PFAS with different chain-lengths (PFOS: 8 carbons, PFHxS: 6 carbons, PFBS: 4 carbons), higher removal efficiencies were observed in long-chain perfluoroalkyl sulfonic acids (carbon chain-length ≥ 6), while relatively low removal efficiency and high variability was observed in PFBS removal. These results suggest that POU systems are generally effective to remove PFAS, but short-chain PFBS may not be consistently removed, even though they have been frequently used as alternative PFAS to replace conventional long-chain PFAS. The results from this study may improve the understanding of PFAS removal in POU systems and provide useful information for the design, operation, and maintenance of POU systems to minimize health risks of PFAS in drinking water.