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U.S. EPA Proposes PFAS Drinking Water MCLs

Date: March 17, 2023

On March 14, the U.S. Environmental Protection Agency (EPA) proposed a National Primary Drinking Water Regulation for Per- and Polyfluoroalkyl Substances (PFAS). The proposed rule sets the first-ever legally enforceable Maximum Contamination Levels (MCLs) for six PFAS in drinking water.

WateReuse Association will be engaging a PFAS working group and our Legislative and Regulatory Policy Committee throughout the comment period, and we encourage all members to review the proposed rule and reach out with concerns. If you would like to share your communities’ concerns regarding PFAS and water reuse, please email Aliza Furneaux.

The proposed rule lays out requirements for monitoring, public notification, and appropriate treatment for removal of the six PFAS. The proposed treatments for PFAS removal include processes commonly employed in water reuse systems, including granular activated carbon (GAC), anion exchange resins (AIX), high-pressure membrane technologies, reverse osmosis (RO), and nanofiltration (NF). One key concern for the water reuse community is the lack of proposed guidance for handling or disposal of the spent media, which may be laden with PFAS.

WateReuse also remains concerned about the cost of meeting the MCLs and the financial impact that the treatment and removal of PFAS may have on ratepayers. EPA has estimated that the total cost of compliance for public water systems will range from $769 million to $1.2 billion. While the estimate incorporates monitoring, equipment, capital costs, operations and maintenance, regulatory reporting, and public communications, it falls well below estimated costs from the sector at about $3.8 billion annually.

The rule proposes regulating:

  • PFOA and PFOS with an MCL of 4 parts per trillion (ppt) for each individually
  • PFHxS, PFNA, PFBS, and HFPA-DA (GenX) as a mixture with the MCL at 1.0 (unitless) Hazard Index

The mixture of four PFAS will be assessed using a tool known as a Hazard Index, which evaluates health risks of simultaneous exposure to mixtures of related chemicals. Water systems would monitor and compare the amount of each PFAS in drinking water to its associated Health-Based Water Concentration (HBWC), which is the level at which no health effects are expected for that PFAS. EPA anticipates providing water systems with a web-based form that will automatically calculate the Hazard Index. The rule also sets health-based non-enforceable MCL Goals (MCLGs) at 0 ppt for PFOA and PFOS and 1.0 Hazard Index for PFHxS, PFNA, PFBS, and HFPA-DA individually or as a mixture.

Following publication of the proposed rule in the Federal Register, there will be a 60-day public comment period. The U.S. EPA anticipates finalizing the rule by the end of 2023, and once the rule is final, drinking water systems will have 3 years to comply.

For questions related to public webinars, you can contact PFASNPDWR@epa.gov. Learn more and comment at these upcoming virtual EPA events:

PFAS Regulation Webinar
March 29, 2023
2:00-3:00 pm ET
Register Here
Registration is required to attend. The webinar recordings and presentation materials will be made available following the webinars.

PFAS Regulation Public Hearing
May 4, 2023
11:00 am – 7:00 pm ET
Register Here
At the public hearing, members of the public can register to attend and provide verbal comments to EPA on the rule proposal. Registration is required to attend and the last day to register to speak at the hearing is April 28, 2023. 

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