Overview

FAQs: Removing Perfluoroalkyl Substances (PFAS) with Ion Exchange Resins

As municipalities discover that levels of PFAS in water systems exceed new Federal Health Advisory levels, many questions arise. This guide can help you find answers to make your drinking water clean and safe.

What are PFAS?
Poly- and perfluoroalkyl substances (PFAS), also known as “forever chemicals,” are a group of man-made chemicals that includes perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), GenX, ADONA, and many other chemicals. PFAS has been manufactured and used in a variety of industries around the globe, including in the United States, since the 1940s. PFOA and PFOS have been the most extensively produced and studied of these chemicals.  Both have been phased out of manufacturing in the US at this time. 

What are the health risks of PFAS?
PFAS are very persistent in the environment and the human body – meaning they don’t break down and they can accumulate in body tissues over time. Exposure to PFAS can lead to adverse health outcomes in humans and are estimated to be in the drinking water of over 110 million people. Studies indicate that PFOA and PFOS can cause reproductive and developmental, liver and kidney, and immunological health effects in laboratory animals. Both chemicals have caused tumors in animal studies. The most consistent findings from human epidemiology studies are increased cholesterol levels among the exposed population as well as low infant birth weights, effects on the immune system, cancer, and thyroid hormone disruption.

How does PFAS get into our water supplies?
Aqueous film-forming foam (AFFF) has been a major source of PFAS contamination since its use in the late 1960s to extinguish petroleum fires at airfields, oil refineries, and military installations. Other important PFAS sources include the manufacture of consumer and industrial products such as Teflon-coated utensils, carpets, pizza boxes, popcorn bags, chrome plating, pesticides, textiles, semiconductors and the manufacture of wires and cables. After decades of disposing of PFAS-containing items in landfills, leachate sent to wastewater treatment plants (WWTP) has resulted in additional contamination of WWTP effluents and biosolids that are subsequently used as fertilizer.

What are the current regulations for PFAS in drinking water?
Health advisory levels vary throughout the world. However, in May 2016, The US EPA issued Health Advisory (HA) levels of 70 parts per trillion (ppt) for PFOS and PFOA combined. To date, the EPA has not issued a Maximum Contaminant Level (MCL) for PFAS in drinking water.  Many US states have issued health guidelines and a few have issued MCLs for several PFAS, inclusive of PFOA, PFOS, PFNA, PFHxS, and PFHpA. The Interstate Technology Regulatory Council (ITRC) maintains an up-to-date listing of proposed and published regulatory changes by individual states – these are lower than the EPA HA levels.  In addition, the EPA provides state-by-state resources. 

What other names are used to refer to PFAS? 
Polyfluoroalkyl substances, perfluorinated chemicals, PFCs, and fluorocarbon chemicals, are additional names used for the category of PFAS or its subsets. A listing of the more commonly found PFAS includes: 

  • Perfluorobutanoic acid (PFBA)
  • Perfluoropentanoic acid (PFPeA)
  • Perfluorohexanoic acid (PFHxA)
  • Perfluoroheptanoic acid (PFHpA)
  • Perfluorooctanoic acid (PFOA)
  • Perfluorononanoic acid (PFNA)
  • Perfluorodecanoic acid (PFDA)
  • Perfluoroundecanoic acid (PFUnA)
  • Perfluorododecanoic acid (PFDoA)
  • Perfluorotridecanoic acid (PFTrDA)
  • Perfluorotetradecanoic acid (PFTA)
  • Perfluorobutanesulfonic acid (PFBS)
  • Perfluorohexanesulfonic acid (PFHxS)
  • Perfluorooctanesulfonic acid (PFOS)
  • Hexafluoropropylene oxide dimre acid (HFPO-DA) (GenX)
  • 4,8-dioxa-3H-perfluorononanoic acid (ADONA)
  • N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA)
  • N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA
  • 9-chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS)
  • 11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS)

What are short- and long-chained PFAS?
The term “long-chain” is used to describe sulfonic-based PFAS with 6 or more carbons in the polymer chain (e.g. PFOS and PFHxS), and carboxylic acid-based PFAS with 8 or more carbons in their polymer chain (e.g. PFOA and PFNA). “Short-chain” PFAS refers to those compounds having fewer carbons than the “long-chain” definitions used above (e.g. PFBS and PFBA).

What are the most popular removal methods for PFAS from water and wastewater?
Granular Activated Carbon (GAC) is currently in widespread use, but the industry is quickly moving to single-use PFAS-selective resins as benefits are realized. PFAS-selective resins can be operated with much shorter empty bed contact times vs GAC, resulting in capital cost that is often a fraction of that for GAC. Equally important, the operating capacity for PFA694E is generally many times higher than that for GAC, resulting in significantly lower operational costs.

Reverse osmosis is another treatment option but creates a large PFAS-laden waste stream. Synthetic media has also been used in limited applications. Foam fractionation or regenerable ion exchange resins have been proven useful when the influent PFAS concentrations are high – for example in the parts per million range.  The effluent water from these latter treatment technologies is often polished for final PFAS removal, using a single-use PFAS-selective resin such as Purofine PFA694. 

What technology is available that can reduce PFAS to less than detectable levels?
Purofine® PFA694E is a single-use PFAS-selective ion exchange resin that can remove fluorocarbon (PFAS) compounds to non-detectable (ND) levels as defined by EPA Method 537.1. 

Can ion exchange resin remove both short- and long-chained PFAS?
Yes. Ion exchange resin removes PFAS by two mechanisms—by ion exchange and by adsorption. GAC predominantly removes PFAS by adsorption. PFAS-selective resin can remove short-chain PFAS compounds (e.g. PFBS and PFBA) to non-detectable (ND) levels.  The operating capacity of the resin and the leakage of PFAS into the treated water varies, depending on the specific PFAS, the background water chemistry, and the empty bed contact time for which the system is designed.

Is Purofine® PFA694E certified for use in drinking water?
Yes, Purofine PFA694E is certified to ANSI/NSF-61 standard for use in drinking water.

Is Purofine® PFA694E an anion resin or adsorbent?
Both ion-exchange and adsorption removal mechanisms are built into this product. PFAS-selective functional groups on the resin target the anionically-charged “head” end of the PFAS molecule, while the hydrophobic tail end of the PFAS molecule is strongly adsorbed onto the hydrophobic surface of the resin. Binding of PFAS compounds is therefore quick, requiring smaller treatment systems with relatively short empty bed contact times.

Does background water chemistry affect operating capacity of Purofine® PFA694E?
Yes, anions typically found in water (e.g. sulfate, nitrate, bicarbonate, and chloride) will have the largest impact on the operating capacity of the resin. In addition, elevated levels of naturally occurring organic matter or total organic carbon (TOC) can negatively impact capacity. Our unique PFAS modeling capability takes all of these factors into consideration in predicting PFAS operating capacity and leakage for its resin.

Are there any pH and anionic excursions upon startup?
PFA694E is supplied in the chloride form.  On start-up, chloride will be released by the resins while other anions like sulfate, nitrate, and bicarbonate will be picked up by the resins. Removal of bicarbonate in the water will result in a temporary reduction in pH of the treated water but it will recover within a few hours of rinsing or being put into service.  Once beyond the start-up phase, the pH of the treated water will not change relative to that in the raw water until the resin is replaced. Concentrations of sulfate and chloride in the treated water will usually after a few hundred bed volumes of water have been treated.

Are there any pH excursions upon startup?
The product is supplied in the chloride form. Upon startup, the pH may be low, but will come to equilibrium (in=out) within several hours of rinsing. The pH will not change after startup. If initial pH changes are not acceptable, Purolite can provide buffered resin with PFA694EBF.  The resin is preconditioned to ensure there will be virtually no reduction in the pH of the treated water.  The buffered resin is designed not to reduce the chloride to sulfate mass ratio of the water.

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