By Rick Andrew
In 2019, NSF/ANSI 53 was updated to include requirements for reduction of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Since then, work has been ongoing to expand the scope of PFAS reduction claims under the standard. As a result, NSF/ANSI 53 has been updated to include requirements for the reduction of total PFAS. This broad claim of reduction of total PFAS has tremendous value because it clarifies for end-users that the treatment will be effective regardless of which PFAS compounds may be present in their drinking water.
PFAS Contamination of Drinking Water
PFAS compounds are synthetic, man-made chemicals that are highly persistent and very slow to degrade in the environment. The U.S. Environmental Protection Agency (EPA) has been working to establish regulations for PFAS compounds in drinking water. The two most common PFAS compounds are PFOA and PFOS.
These chemicals were historically used in the manufacturing of fluoropolymers. They have a unique ability to withstand water and grease, as well as high temperatures, which makes them especially useful for certain applications, including in paper and cardboard food packaging, insecticides, electronics, stain repellants, paints, plumbing tape, firefighting foam, and nonstick cookware coatings.
Production of PFOA and PFOS was phased out in the early 2000s. However, by this time, 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. The EPA added PFOA and PFOS to its third Unregulated Contaminant Monitoring Rule, which was promulgated in 2012.
Standards Development Response
To address PFAS contamination and the need for consensus methods for evaluating the effectiveness of point-of-use (POU) and point-of-entry (POE) technologies for treating PFAS contamination of drinking water, the NSF Joint Committee has been developing standards.
Work was initiated at the May 2018 meeting of the NSF Joint Committee on Drinking Water Treatment Units. There, the committee unanimously voted to establish requirements in the NSF/ANSI Drinking Water Treatment Units (DWTU) Standards for reduction of PFOA and PFOS by activated carbon, anion exchange resin, and POU reverse osmosis.
By 2019, the requirements, including test protocols, for evaluation of activated carbon systems for reduction of PFOA and PFOS were added to NSF/ANSI 53. Since then, a test protocol for treatment by anion exchange resin was developed and added to NSF/ANSI 53, as well.
These contaminant-reduction test protocols for activated carbon were based very closely on the protocols previously developed by NSF for NSF P473 Drinking Water Treatment Units – PFOS & PFOA. The protocol for anion exchange resin is based on the protocol for reduction of perchlorate by anion exchange resin that already existed in NSF/ANSI 53.
Subsequently, work was initiated on a more comprehensive test protocol that could support a broad claim of PFAS reduction. The entire class of PFAS compounds, including chemical structure and properties, was studied and evaluated to establish a mixture of compounds that can be used to assure reduction of any PFAS compounds that might be present in drinking water. This new test protocol and claim were published in the 2022 version of NSF/ANSI 53.
Total PFAS Reduction Claim
There are two approaches in the standard to establish reduction claims for PFAS compounds. The first method is to make a mixture of seven PFAS compounds with the influent concentration of 2,160 parts per trillion (ppt) total PFAS, made up of the compounds and concentrations listed in Figure 1.
The second option is to reduce individual PFAS compounds from their respective influent concentrations to their individual health advisory effluent concentrations. Two PFAS compounds, PFBS (perfluorobutanesulfonic acid) and PFDA (perfluorodecanoic acid), are excluded from the individual contaminant reductions because their occurrence level is less than their health advisory level.
See Figure 2 for the requirements for average influent challenge, maximum effluent concentration, and EPA methods for these PFAS compounds.
Testing Protocol for Activated Carbon Systems
The basic test methodology for PFAS reduction is the same as other organic chemical reduction tests under NSF/ANSI 53. The concentration of PFAS in the challenge water and the level of required treatment are specified in Figure 2.
Testing involves operating the system at the highest achievable flow rate with an initial clean system inlet pressure of 60 pounds per square inch. The flow through the system is cycled on and off using valves, typically using a 10-minute on and 10-minute off cycle known as 50/50 cycling. At the manufacturer’s discretion, a 10/90 cycle can be used, which is typically two minutes of flow followed by 18 minutes without flow.
Two POU or POE systems are tested in parallel, with samples of the influent and effluent collected at start-up, 50 percent, 100 percent, 150 percent, 180 percent, and 200 percent of the manufacturer’s rated treatment capacity. For systems with a performance indication device (filter change indicator), samples are collected at start-up, 25 percent, 50 percent, 75 percent, 100 percent, and 120 percent of the manufacturer’s rated treatment capacity. All samples must meet the requirements per Figure 2 for a passing result.
The main impact on user instructions requirements in NSF/ANSI 53 resulting from the addition of the total PFAS reduction claim affects the performance data sheet. The additional details regarding the PFAS reduction claim including the substance, the influent challenge concentration, and the maximum permissible effluent concentration must be added to the table of contaminant reduction information in the performance data sheet.
Evolving Standards to 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 better part of the last decade, and the committee has responded by adding requirements to NSF/ANSI 53 as those requirements have been developed by the PFAS reduction task group. Their addition helps manufacturers provide end-users with equipment that can reliably address the contamination problem that continues to taint water supplies across the United States and beyond.
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: [email protected]