One benefit of this treatment technology is that there is no need for resin regeneration so there is no contaminant waste stream to handle, treat, or dispose. Of the different types of AER resins, perhaps the most promising is an AER in a single use mode followed by incineration of the resin. AER has shown to have a high capacity for many PFAS however, it is typically more expensive than GAC. Negatively charged ions of PFAS are attracted to the positively charged anion resins. Ion exchange resins are like tiny powerful magnets that attract and hold the contaminated materials from passing through the water system. The negatively charged cationic exchange resins (CER) are effective for removing positively-charged contaminants and positively charged anion exchange resins (AER) are effective for removing negatively charged contaminants, like PFAS. There are two broad categories of ion exchange resins: cationic and anionic. The tiny beads that make up the resin are made from hydrocarbons. Ion exchange resins are made up of highly porous, polymeric material that is acid, base, and water insoluble. If used, however, there is an additional problem with what to do with the sludge that contains adsorbed PFAS.”Īnother treatment option is anion exchange treatment, or resins. Speth says, “Even at very high PAC doses with the very best carbon, it is unlikely to remove a high percentage PFAS however, it can be used for modest percent removals. Used in this way, PAC is not as efficient or economical as GAC at removing PFAS. Because of the small particle size, PAC cannot be used in a flow through bed, but can be added directly to the water and then removed with the other natural particulates in the clarification stage (conventional water treatment or low-pressure membranes - microfiltration or ultrafiltration). EPA researcher Thomas Speth says, “GAC can be 100 percent effective for a period of time, 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.”įor example, GAC works well on longer-chain PFAS like PFOA and PFOS, but shorter chain PFAS like Perfluorobutanesulfonic acid (PFBS) and Perfluorobutyrate (PFBA) do not adsorb as well.Īnother type of activated carbon treatment is powdered activated carbon (PAC) which is the same material as GAC, but it is smaller in size, powder like. 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. Activated carbon (GAC) is made from organic materials with high carbon contents such as wood, lignite, and coal and is often used in granular form called granular activated carbon (GAC). Activated carbon is an effective adsorbent because it is a highly porous material and provides a large surface area to which contaminants may adsorb. Adsorption is both the physical and chemical process of accumulating a substance, such as PFAS, at the interface between liquid and solids phases. Activated carbon is commonly used to adsorb natural organic compounds, taste and odor compounds, and synthetic organic chemicals in drinking water treatment systems. These technologies can be used in drinking water treatment facilities, in water systems in hospitals or individual buildings, or even in homes at the point-of-entry, where water enters the home, or the point-of-use, such as in a kitchen sink or a shower.Īctivated carbon treatment is the most studied treatment for PFAS removal. Those technologies include activated carbon adsorption, ion exchange resins, and high-pressure membranes. Therefore, EPA researchers have been studying a variety of technologies at bench-, pilot-, and full-scale levels to determine which methods work best to remove PFAS from drinking water.Ĭertain technologies have been found to remove PFAS from drinking water, especially Perfluorooctanoic acid (PFOA) and Perfluorooctanesulfonic acid (PFOS), which are the most studied of these chemicals. PFAS also dissolve in water, and combined with their chemical properties mean traditional drinking water treatment technologies are not able to remove them. Unfortunately, the characteristics that make them useful are the reason they persist in the environment and can bioaccumulate, or build up, in our bodies and the bodies of animals. They are also found in firefighting foams and are applied in many industrial processes. These chemicals have been used for decades in consumer products to make them non-stick and water resistant. Per- and Polyfluorinated substances (PFAS) are a group of man-made chemicals that persist in the environment.
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