Information on how water systems are to monitor for per-and poly-fluoroalkyl (PFAS), how the levels of PFAS within drinking water systems are calculated, actions water systems have to implement to inform the public of PFAS compounds within drinking water, and methods to remove such PFAS from drinking water were outline in a webinar conducted by the Environmental Protection Agency (EPA).

On April 10, 2024, the EPA issued a final rule that sets drinking water standards for five individual PFAS, including PFOA, PFOS, PFNA, PFHxS, and HFPO-DA, and on April 19, 2024, the EPA issued a second final rule designating perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as the “Superfund.”

Implementation of the final rules is expected to reduce exposure to PFAS by 100 million individuals within the U.S., thereby reducing tens of thousands of serious illnesses and preventing thousands of deaths, said Ashley Greene of the EPA’s Office of Water, who provided an overview of the PFAS drinking water regulation over the webinar held April 30, 2024.

Reducing exposure to PFAS requires establishing “non-enforceable public health goals,” that are also known as “maximum containment levels” (MC LGS), as well as legally enforceable standards, said Greene, who added the EPA set the unenforceable MC LGS for PFOA and PFOS at zero because those two substances are carcinogens. “There’s no level of exposure to them without risk of human health impacts,” she said.

The MC LGS for the three other PFAS—PFNA, PFHxS, and HFPO-DA—have each been set at 10 parts per trillion, while the enforceable standards imposed on water systems for those three PFAS is 4.0 parts per trillion, which is based on requirements set under the Safe Drinking Water Act, Greene said.

Furthermore, mixture combinations of four PFAS—specifically, mixtures of PFHxS, PFNA, HFPO-DA, and PFOS— is being regulated by EPA through a “hazard index,” which is being used because research shows those PFAS chemicals can combine into mixtures within the drinking water, Greene said. “Individually,” the chemicals “may not pose a health concern when found at lower levels,” but when “combined in mixtures,” even at lower levels, they “may pose a health concern due to the additive impacts that exceed the hazard levels of the maximum contaminant levels,” she said.

The EPA uses the hazard index in other programs, such as the Superfund program, “to determine the health concerns associated with exposure to chemical mixtures,” Greene said. It is “an equation made up of a sum of fractions or different ratios that compare the exposure or the level of each PFAS measured in water to a level below which health effects are not anticipated,” she said.

“That level is called a ‘health-based water concentration’,” said Greene, who added, “The hazard index is calculated by first dividing the measured concentration of each of the four PFAS by its health-based values, and those health-based values do not change.”

In the final regulation, public water systems, specifically community water systems and non-transmit noncom community water systems, are required to take action, which includes conducting initial and ongoing drinking water monitoring for the regulated PFAS, according to Greene. “If the levels violate the MC LGS, these systems are then required to find solutions to reduce the levels below the enforceable standards, which could include both treatment and non-treatment approaches,” she said.

The final rule also requires water systems to establish monitoring programs, including both initial monitoring and ongoing regular compliance monitoring, and water systems must inform the public of the levels of PFAS in their drinking water, according to Greene, who added that such monitoring would require the collection of at least two outdoor samples at each entry point into the distribution system over a year.

Furthermore, the number of water samples collected depends upon a system’s size and source water type, according to Greene. Because water systems are different in size and scope, EPA was prompted to identify and include as many types of flexibilities as possible in the regulation’s requirements, she added. “In some cases, these flexibilities are geared specifically for small public water systems, including for initial monitoring, the majority of these systems will only be required to collect half as many samples as all the other systems,” Greene said. Ongoing compliance monitoring is scheduled to start in 2027, she added.

In addition, starting in 2029, Green said water systems will be required to issue public notification if regulated PFAS levels violate one or more maximum contaminant levels. Public notification must be provided within 30 days of a violation, and the rule requires annual public notification if any monitoring and testing procedures are violated.

According to Nicolas Dugan, an environmental engineer within EPA's Office of Research and Development, to remove PFAS compounds from drinking water systems, EPA has designated ion exchange resins, granular activated carbon, and memory separation, either by reverse osmosis or filtration, as the best available technologies.

Dugan said the effectiveness and cost of those methods depend on the characteristics of the source water and on the specific characteristics of the design of a water treatment system. He added that PFAS will be found in spent activated carbon and spent ion exchange resin. Spent activated carbon is typically regenerated, while spent exchange resin is typically incinerated or sent to a landfill.

However, Dugan said, there are no commercially available reverse osmosis and filtration concentrate systems that offer full mineralization of PFAS. How well a system works at filtering PFAS depends on the properties of the specific treatment system designed for a specific site and whatever carbon is being used for the PFAS because it will depend on the exact chemical structure of the target PFAS molecule.

Additionally, Dugan said treatment costs vary, especially for systems with flows of less than one million gallons per day.

Watch the webinar.