Issuing federally enforceable limits for PFAS in drinking water was a key action outlined in the U.S. EPA’s 2021-2024 PFAS Strategic Roadmap. In 2023, the agency released its initial proposal. Then, after considering more than 120,000 public comments and a review of the final rule by the Office of Management and Budget (OMB), the final rule was released on April 10, 2024. In this post, we review the different aspects of this rule and its implications for our customers.
Until the rule is published in the Federal Register, you can download the pre-publication rule on the EPA’s website.
The PFAS Limits
While there was a lot of speculation as to whether the final rule would include additional, fewer, or different PFAS, it includes the same six PFAS as the proposed rule, namely PFOA, PFOS, PFHxS, PFNA, HFPO-DA (GenX), and PFBS.
PFOA and PFOS Maximum Contaminant Levels (MCLs) remain at 4 ppt (parts per trillion) with Maximum Contaminant Level Goals (MCLGs) of zero ppt. However, there were several key changes to the MCLs for the four other compounds:
- PFNA, PFHxS, and HFPO-DA now have individual MCLs set at 10 ppt. In the initial proposal, none of these compounds had individual MCLs.
- The Hazard Index remains, but now applies for any mixture containing two or more of the four initial compounds: PFHxS, PFNA, HFPO-DA, and PFBS.
- In the calculation of the Hazard Index, the Health Based Water Concentration (HBWC) value for PFHxS is now 10 ppt instead of 9 ppt as originally proposed.
- The Hazard Index is also set at a unitless value of 1, instead of 1.0. The removal of the decimal place more clearly communicates that the Hazard Index is a ratio and does not indicate a specific unit of measure.
For a refresher on the Hazard Index formula and how to calculate the running annual average, refer to the EPA’s Hazard Index fact sheet.
Final MCLs and MCLGs
Source: EPA Fact Sheet, PFAS National Primary Drinking Water Regulation FAQs for Drinking Water Primacy Agencies
Which Water Systems are Required to Monitor?
The federally enforceable limits apply to a greater number of Public Water Systems (PWS) than previous monitoring rules, such as the EPA’s Fifth Unregulated Contaminant Monitoring Rule (UCMR 5).
The new sampling requirements under the NPDWR cover all community water systems and non-transient, non-community water systems, regardless of the number of customers served. The EPA estimates that this would include 66,000 of the some 149,000 or so water systems in the United States. Presumably, the difference is made up of water systems serving less than 25 people (not considered a community water system) and transient water systems that don’t serve the same people at least six months a year.
The good news for those who were and are required to sample in EPA’s UCMR 5 program is that the data will fulfill some or all the initial monitoring requirements under the new NPDWRs. UCMR 5 requires between 10,000-11,000 of the nation’s largest systems to sample for PFAS between January 2023 and December 2025. In addition, some states have monitoring rules that may also satisfy the requirements if the analysis was conducted using EPA Methods 533 or 537.1.
Initial Sampling Requirements
Initial monitoring requirements are based on the size of the water system and the source water used. Water is monitored at entry points to the distribution system, and combined water samples are not allowed.
- All systems that source their drinking water from surface water are required to monitor quarterly, with samples collected 2-4 months apart.
- Systems serving more than 10,000 customers and use a groundwater source are also required to monitor quarterly for the first 12 months, with samples collected 2-4 months apart.
- If the system serves 10,000 customers or less and uses a groundwater source, it only need to sample twice a year, with samples collected 5-7 months apart.
Once the final rule is published in the Federal Register, water systems have three years to comply with the initial sample requirements and an additional two years to address elevated levels of PFAS. Water systems need not begin notifying customers of elevated PFAS levels until the remediation time period has ended.
The EPA estimates that between 6% and 10% of systems will be out of compliance and be required to take action. In their fact sheet on the Benefits and Costs of Reducing PFAS in Drinking Water, the agency calculates that to be between 4,100 – 6,700 public water systems.
Reduced Monitoring Triggers
In the initial proposal, the triggers for reduced monitoring were set at 1/3 the MCL for each PFAS. The final proposal sets the limit at 1/2 the MCL. Any samples above these levels will trigger quarterly monitoring at that entry point. This could result in a water system having different sampling schedules for different entry points.
If four consecutive quarterly sample results are below the MCLs, primacy agencies have the authority to allow the water system to conduct annual monitoring at that entry point. Three consecutive annual samples below the trigger levels for all regulated PFAS may allow the water system to reduce monitoring to once every three years at the entry point.
Compliance Sampling
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It’s important to understand that an elevated level of PFAS detected in a monitoring sample does not necessarily mean the water system is out of compliance. Instead, the elevated level triggers quarterly monitoring at that entry point. After four quarters of monitoring, the results are averaged, with any results at or below the Practical Quantitation Limit (PQL) reverted to zero.
In its fact sheet, the EPA provides an example of a water system sampling quarterly for PFOA. The results of this sampling at one entry point are 2.0, 3.0, 5.0, and 2.0 ppt. The PQL for PFOA is 4.0; therefore, these results are translated to 0.0, 0.0, 5.0, and 0.0 ppt. Dividing 5 by 4, we get a running average of 1.3 ppt, meaning that the system is in compliance.
Treatment Options
In its fact sheet on Treatment Options for Removing PFAS from Drinking Water, the EPA acknowledges that there is no one-size-fits-all approach. Larger systems are more likely to have the wherewithal to employ Best Available Technologies (BATs), including granular activated carbon (GAC), anion exchange, reverse osmosis, and nanofiltration. Some smaller systems will be able to use these technologies as well. Per the EPA:
- Anion exchange was found to be affordable for systems of all sizes.
- GAC was affordable in most cases for systems serving between 25-500 people.
- Reverse osmosis and nanofiltration was most appropriate for systems serving 3,301 – 10,000 people.
- Changing water sources may also be an appropriate option in some cases.
The EPA says that it will not mandate any specific treatment option. This allows water systems to use the option that best matches their needs for efficacy and affordability. Pace® routinely works with customers to help validate their treatment approach. As an example, see our Florida Keys Aqueduct Authority case study. For systems that opt to change water sources, we can also analyze for contaminants in groundwater and surface water sources to help ensure you’re not replacing one contaminated source with another.
Funding Sources
The EPA estimates that the cost of implementation and compliance will be $1.5B annually and that the quantifiable benefits in terms of human health will also be $1.5B annually. Of course, the health cost savings cannot be used to pay for the cost of implementation and treatment, so water systems will need to find some other way.
As funding options change over time, a good place to learn more is on the EPA website. The EPA’s fact sheet on Benefits and Costs of Reducing PFAS in Drinking Water lays out some of the funding currently available and provides links to more information on how to apply for specific types of funding.
Need a Quote for Service?
Pace® has been providing PFAS testing and analysis of drinking water, non-potable water, and solid matrices for years. We are EPA-approved for UCMR 5, and we maintain laboratory certifications and accreditations in all states that offer them. If you have questions or would like a quote for services, reach out to us. We’re here to help!
