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Posted on: August 25, 2023

CFPUA Asks State to Prioritize Study of Difficult-to-treat PFAS Compounds

Bend in Cape Fear River

Cape Fear Public Utility Authority (CFPUA) on Thursday, August 24, asked the State to add perfluoropropanoic acid (PFPrA) to a group of per- and polyfluoroalkyl substances (PFAS) the State has prioritized for study, including assessment of potential health risks. 

The request was made in a letter sent to Sushma Masemore, Assistant Secretary of the N.C. Department of Environmental Quality, and Tom Augspurger, Ph.D., Chairman of the N.C. Secretaries' Science Advisory Board. 

This letter is one of several actions related to PFAS treatment outlined at CFPUA’s August 9 monthly Board meeting.  

Highlights of current and planned actions by CFPUA include: 

  • Adjusting operations at CFPUA’s new Granular Activated Carbon (GAC) filters at the Sweeney Water Treatment Plant to further maximize effective PFAS removal. 
  • Evaluating other, novel treatment media, that potentially could be combined with the GAC to enhance PFAS treatment. 
  • Continuing to seek assistance from the State and academic researchers for up-to-date health and treatment information about the PFAS CFPUA treats. 

About PFPrA: PFPrA is an ultra-short chain compound used in the manufacture of certain products. It also can be created as larger PFAS compounds degrade or as a manufacturing byproduct. CFPUA staff prepared a white paper on PFPrA as part of its August 9 presentation to the Board. 

Connection to Chemours: PFPrA is a known byproduct of the PFAS manufacturing process in the Cape Fear River. It is referenced in compliance reports issued by Chemours under the Consent Order signed on February 26, 2019. PFPrA (also known as PPF Acid) was also included in a table labeled as “Classification of Table 3+ PFAS,” an appendix to a Corrective Action Plan submitted by Chemours on December 31, 2019, for PFAS that originate from the site. Because of the well-documented contamination at the Chemours’ Fayetteville Works site, it is clearly evident the PFPrA contamination in the lower Cape Fear is sourced from Chemours/DuPont manufacturing activities of the last 40 years. 

EPA’s toxicity assessment and low-confidence reference dose: PFPrA was the first PFAS compound detected in treated drinking water at the Sweeney Water Treatment Plant following the October 2022 start of treatment by new Granular Activated Carbon filters. Reliable laboratory analysis for PFPrA is relatively recent, and high confidence in consistent analysis by CFPUA’s contract lab only occurred in April 2023. More information on categories of PFAS test methods may be found here. 

In July, the U.S. Environmental Protection Agency (EPA) released  low-confidence reference dose (RfD) for PFPrA. By itself, an RfD is typically insufficient to provide health guidance, with smaller RfDs considered to have a greater potential for toxicity. An RfD is one factor used to develop guidance such as health advisory levels (HALs). No HAL has been established for PFPrA. EPA has established HALs for some PFAS, including one for GenX of 10 ppt for lifetime consumption of drinking water. The RfD used to derive the GenX HAL is 0.000003 milligrams per kilogram body weight per day (mg/kg bw-day). EPA’s RfD for PFPrA is 0.0005 mg/kg bw-day. CFPUA is seeking analysis on PFPrA from qualified experts at the State and in academia to confirm the implied lower toxicity of PFPrA relative to GenX. 

Adjusting PFAS treatment at the Sweeney Water Treatment Plant: Treatment of drinking water is governed by state and federal regulations, which, among other things, provide enforceable treatment targets for a range of substances. No such regulations exist for any PFAS, although EPA has proposed regulations for six PFAS, including GenX. In the absence of such guidance, CFPUA has selected perfluoro-2-methoxyacetic acid (PFMOAA) as its treatment target: aiming for no more than 10 ppt of PFMOAA in treated drinking water. This is meant to ensure compliance with the proposed EPA regulations for PFAS.  

No HAL has been developed for PFMOAA, although it is on the State’s Priority PFAS study list. PFMOAA is an “indicator compound” used to gauge Chemours’ compliance with the Consent Order with the State. The Consent Order outlines Chemours’ obligations to remediate decades of PFAS contamination at its Fayetteville Works facility. As an ultra-short chain PFAS, PFMOAA is difficult to treat and effective treatment for PFMOAA indicates successful removal of longer-chain compounds such as GenX. 

Achieving the 10 ppt PFMOAA target has required significant coordination by treatment staff, who must schedule GAC media exchanges. These exchanges can take approximately 60 days to complete. Despite this complexity, the GAC filters at Sweeney have been very effective at treating the vast majority of PFAS compounds CFPUA currently monitors, and the GAC filters have consistently met or exceeded National Primary Drinking Water Regulations proposed for six PFAS compounds, including GenX. 

A handful of PFAS compounds have been detected in treated water at Sweeney, most at very low levels. The latest results of CFPUA’s PFAS monitoring for individual sampling events and our current running annual averages for those compounds can be found on the CFPUA website.  

To further maximize PFAS treatment effectiveness, CFPUA is developing a plan that adjusts the GAC exchange schedule consistent with the goal of a dual trigger system: the lower of approximately 10,000 bed-volumes or approximately 10 ppt for PFMOAA in the finished water sampling. This plan will be implemented over the next few months, with results measurable in late fall 2023. 

The road ahead: By next week, CFPUA will add a page to its existing section of the Sweeney Water Treatment Plant to provide information and updates on these and other efforts. We will continue to post results of our ongoing monitoring for PFAS online. In addition to the request for evaluation by NCDEQ, CFPUA is moving to evaluate other treatment media and continues to engage academic researchers to assess the data and provide advice on future actions.

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