Testing Activated Carbon Systems for Reduction of PFOA and PFOS
By Rick Andrew
Contamination of drinking water by per- and polyfluoroalkyl substances (PFAS) continues to be a major topic in the news media. On May 6, Environmental Working Group announced an update to their map of known PFAS contamination sites, now reporting 610 such sites in 43 states across the US.(1) These sites include 446 communities with detection of PFAS contamination in their tap-water supplies. My home state of Michigan, with 192 PFAS contamination sites, has the most of any state. The high number of known PFAS sites in Michigan may partially reflect the state’s ongoing comprehensive multi-agency effort to test for PFAS.(2) As other states increase their focus on detection, the number of known sites in those states may increase, as well.
PFAS compounds are synthetic, man-made chemicals that are highly persistent and slow to degrade in the environment. They are considered to be emerging contaminants by US EPA. The two most common of them are perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). These chemicals, historically used in the manufacturing of fluoropolymers, have a unique ability to withstand water and grease, as well as high temperatures, which makes them especially useful for certain applications, including paper and cardboard food packaging, insecticides, electronics, stain repellents, paints, plumbing tape, firefighting foam and non-stick cookware coatings.
Production of PFOA and PFOS was phased out in the early 2000s. By that time, however, large quantities of these chemicals had been released into the environments surrounding their manufacturing locations and locations where they were used for commercial and industrial purposes. US EPA added PFOA and PFOS to their Unregulated Contaminant Monitoring Rule 3 (UCMR3), which was promulgated in 2012.
Standards development response
To address PFAS contamination and address the need to have consensus methods for evaluating effectiveness of POU and POE technologies for treating PFAS contamination of drinking water, the NSF Joint Committee has been developing standards. A year ago, at the May 2018 meeting of the NSF Joint Committee on Drinking Water Treatment Units, the committee unanimously voted to establish requirements in the NSF/ANSI DWTU Standards for reduction of PFOA and PFOS by activated carbon, by anion exchange resin and by POU RO.
Since then, the requirements, including test protocols, for evaluation of activated carbon systems for reduction of PFOA and PFOS have been added to NSF/ANSI 53 and to NSF/ANSI 58. Work continues to develop a test protocol for treatment by anion exchange resin, which will be added to NSF/ANSI 53. The contaminant reduction test protocols for activated carbon and POU RO were based very closely on the protocols previously developed by NSF for NSF P473 Drinking Water Treatment Units – PFOA & PFOS. It is expected that the protocol for anion exchange resin will be based on the protocol for reduction of perchlorate by anion exchange resin that currently exists in NSF/ANSI 53.
Testing activated carbon system reduction of PFOA and PFOS
NSF/ANSI 53 now specifies test methods and reduction criteria for establishing claims of PFOA and PFOS reduction for activated carbon systems. The basic test methodology is the same as other chemical reduction tests under NSF/ANSI 53. The concentration of PFOA and PFOS in the challenge water is specified, as well as the level of treatment that is required. Because the US EPA Health Advisory addresses the total concentration of both PFOS and PFOA, the test includes a mixture of both PFOA and PFOS as the contaminant challenge. This means that there is one test for reduction of both.
The challenge water concentration for PFOS set in NSF/ANSI 53 is based on a review of US EPA occurrence data generated under UCMR3 monitoring samples from 2013 to 2015. The level for PFOS was set at the expected value at which 99 percent of the population will be exposed to waters of lower concentration, which is 1.0 µg/L (or 1.0 ppb) PFOS.
For PFOA, the challenge water concentration was developed from private well and public water supply sampling in Hoosick Falls, NY, one of the sites where contamination by PFAS has been investigated. The level was set at the expected value at which 90 percent of the population will be exposed to waters of lower concentration. The result of this approach based on using Hoosick Falls monitoring sample results was that the challenge concentration is higher than the maximum concentration detected under UCMR3 occurrence data from 2013 to 2015. This influent challenge value is 0.5 µg/L (or 0.5 ppb) PFOA. The result is a total combined challenge of 1.5 µg/L PFOS and PFOA.
Maximum effluent concentration
NSF/ANSI 53 requires a total combined maximum effluent concentration of PFOS and PFOA of 0.07 µg/L, which is 0.07 ppb or 70 ppt. This level is based on the previously mentioned US EPA Health Advisory, which was issued in 2016.(1) To develop this level, US EPA considered a number of toxicological studies and risk assessments. They also incorporated a margin of protection for sensitive populations. See Figure 1 for the reduction requirements for PFOA and PFOS according to NSF/ANSI 53.
Analysis of PFOA and PFOS
PFOA and PFOS are being tested at very low concentrations under NSF/ANSI 53. Because of these low concentrations, they are analyzed under a special method that is specified in Annex L of the standard. In this method, water samples are directly injected and then analyzed by liquid chromatography triple quadrupole mass spectroscopy (LC/MS/MS) in electrospray negative mode, with method sensitivity of 10 ng/L.
The main impact on user instructions requirements in NSF/ANSI 53 resulting from the addition of the PFOA/PFOS reduction claim affects the performance data sheet. Figure 2 describes how the claim is described in the performance data sheet for those treatment systems conforming to NSF/ANSI 53 that meet the requirements for the PFOA / PFOS reduction claim.
Standards that meet the needs of stakeholders
The NSF/ANSI DWTU Standards are continuously updated by the NSF Joint Committee on Drinking Water Treatment Units to meet the evolving needs of stakeholders. PFAS contamination of water has become a major issue over the last several years and the joint committee has responded by adding requirements into NSF/ANSI 53 and NSF/ANSI 58. The addition of these requirements helps manufacturers provide equipment to end users that can be relied upon with confidence to be an excellent solution to a contamination problem that is continuing to be detected in more and more water supplies across the United States and beyond.
- Walker, Bill. “Mapping the PFAS Contamination Crisis: New Data Show 610 Sites in 43 States.” Environmental Working Group. https://www.ewg.org/news-and-analysis/2019/04/mapping-pfas-contamination-crisis-new-data-show-610-sites-43-states
- “PFAS Response: Taking Action to Protect the Public’s Water.” https://www.michigan.gov/pfasresponse/
About the author
Rick Andrew is NSF’s Director of Global Business Development–Water Systems. Previously, he served as General Manager of NSF’s Drinking Water Treatment Units (POU/POE), ERS (Protocols) and Biosafety Cabinetry Programs. Andrew has a Bachelor’s Degree in chemistry and an MBA from the University of Michigan. He can be reached at (800) NSF-MARK or email: Andrew@nsf.org