PFAS (formally known as per- and polyfluoroalkyl substances) are widely used, long lasting chemicals that break down very slowly over time. They break down so slowly that they end up in water, air, fish, and soil all over the world, and trace amounts have even been detected in human blood. Scientific studies have shown that exposure to some PFAS in the environment may be linked to harmful health effects in humans and animals, but we do not know to what extent they may affect us. PFAS possess chemical properties that mean traditional drinking water treatment technologies are not able to remove them. Researchers have been working on a variety of treatment technologies to determine which methods work best to remove PFAS from drinking water. Some of the most successful methods include: activated carbon adsorption, ion exchange resins, and high-pressure membranes. Granular activated carbon (GAC) adsorption: GAC has been shown to effectively remove PFAS from drinking water when it is used in a flow through filter mode after particulates have already been removed. According to EPA researcher Thomas Speth, this method can be extremely effective “depending on the type of carbon used, the depth of the bed of carbon, flow rate of the water, the specific PFAS you need to remove, temperature, and the degree and type of organic matter as well as other contaminants, or constituents, in the water.” Ion exchange resins: Negatively charged ions of PFAS are attracted to positively charged anion resins. Anion exchange resins (AER) have proved to have a high capacity for many PFAS; but this method can be more expensive than GAC. The most promising version of this method is an AER in a single use mode, followed by incineration of the resin. This technology has no contaminant waste stream to treat or dispose due to the lack of need for resin regeneration. High-pressure membranes: Research shows that membranes, such as nanofiltration or reverse osmosis, are typically more than 90 percent effective at removing a wide range of PFAS. However, these methods generate a large volume of high-strength waste stream which can be difficult to treat or dispose of for a water system. This technology may be better suited for a homeowner since it would generate a much smaller volume of waste. PFAS Resources: Drinking Water Treatability Database The Drinking Water Treatability Database (TDB) can be used to identify effective drinking water treatment processes, to plan for future treatment plant upgrades, to provide information to first responders for spills/ emergencies, and to recognize research needs. PFAS Analytic Tools hub This page contains location-specific information related to PFAS manufacture, release, and occurrence in the environment as well as facilities potentially handling PFAS. CWA Analytical Methods for Per- and Polyfluorinated Alkyl Substances (PFAS) This page contains information regarding the EPA’s development of new analytical methods to test for PFAS compounds in wastewater, as well as other environmental media.