WILMINGTON — A new chemical has been identified in local drinking water, not able to be thoroughly treated by the recently installed granular activated carbon filters.
Cape Fear Public Utility Authority executive director Kenneth Waldroup announced to the board at an Aug. 9 meeting that perfluoropropanoic acid, or PFPrA, continues to be found in its raw and treated water at the Sweeney Water Treatment Plant.
“PFPrA is the first PFAS compound to break through the new GAC filters,” Waldroup said.
The chemical was first detected in a sample Oct. 24, CFPUA spokesperson Vaughn Hagerty said.
“One caveat is that several subsequent PFPrA analyses had contamination problems that invalidated them,” he added. “We only gained high confidence in the PFPrA analyses from our contract lab in April, after they consistently produced reliable results.”
PFPrA is recognized as an ultra-short chain PFAS and is one of the 65 CFPUA is currently monitoring in its bi-monthly water testing.
“It recently received national attention we think warrants a discussion,” Waldroup told the board.
The compound was the subject of a research paper published in April regarding drinking water across the nation. The chemical has been found in drinking water sources around the U.S. Waldroup attributes PFPrA’s presence in Cape Fear from Chemours’ Fayetteville Works facility upstream.
Chemours has been polluting the Cape Fear River with PFAS for more than 40 years. During that time, toxic chemicals were released into the atmosphere, surface water and groundwater — consequences still prevalent today.
The chemical PFPrA is referenced in Chemours’ compliance reports under a 2019 consent order with the company, North Carolina Department of Environmental Quality and nonprofit Cape Fear River Watch. It was also listed in Chemours’ corrective action plan submitted in December 2019 for PFAS that originate from its Fayetteville site.
PFPrA is a commercial byproduct of PFAS manufacturing, produced from longer chain PFAS compounds, according to Waldroup. Like other PFAS, the research on health effects for exposure to PFPrA are limited.
While the levels at Sweeney have not reached the point of alarm, Waldroup said, the chemical does present “unique” treatment challenges.
Ultra-short chains are more difficult to treat, Hagerty explained to PCD, and typically contain three or fewer carbon chains.
The U.S. Environmental Protection Agency developed a “low-confidence reference dose” for PFPrA in July as 0.0005 mg/kg-bw per day. Waldroup explained to the board, this would be equal to roughly 2,100 ppt for a future health advisory level.
A reference dose is an estimate of a daily dose to the human population likely to not cause health impacts over the course of a lifetime. It’s one factor EPA uses to develop health advisories.
By contrast, EPA’s health advisory for GenX is 10 ppt as the maximum contaminant level, 210% lower than the feds’ current advisory for PFPrA.
Waldroup reported CFPUA’s highest level of detection for PFPra was 35 ppt but averages between 15 and 25 ppt in local drinking water.
“At this time, we don’t believe it is appropriate to change the way we treat PFAS, but we are going to be working to experiment with new novel sorbents,” he said, referring to insoluble materials as additional forms of treatment media.
In October 2022, CFPUA announced PFAS-free water flowing through its Sweeney Water Treatment Plant, serving roughly 170,000 customers in the Cape Fear region, after installing the new GAC filters. The new technology holds nearly 3 million pounds of GAC and can treat up to 44 million gallons of water per day.
Waldroup said the technology is “performing extremely well” in removing GenX and other dangerous compounds. It cost CFPUA $43 million to install the filtration system.
Earlier this month, he told the board, based on the new information about emerging compounds, CFPUA plans to change its approach.
The authority will change out filters after approximately 10,000 bed volumes, creating a “dual trigger system.” Based on initial results, CFPUA thought it could wait to swap out filters until about 13,000 bed volumes but as staff evaluates the “ever-changing source water quality,” 10,000 made more sense, CFPUA spokesperson Cammie Bellamy explained to Port City Daily.
A bed volume is measured by the amount of GAC in a single filter, which is equivalent to 76,676 gallons. There are eight filters at Sweeney’s facility that operate with GAC.
“So 10,000 bed volumes would be about 766.8 million gallons,” Hagerty said. “That’s the amount of water treated by a filter that would trigger an exchange of GAC media.”
As an authority policy, CFPUA also switches out the carbon in its filters once PFMOAA — one of the most difficult PFAS to treat, according to CFPUA — reaches 10 ppt.
PFMOAA is an “indicator compound” used to gauge Chemours’ compliance with the Consent Order with the State, according to CFPUA’s release. Effective treatment for PFMOAA indicates successful removal of longer-chain compounds, such as GenX.
“Treating to that level should ensure a very high level of PFAS removal overall,” Bellamy said in April. “We will continuously monitor our PFAS sampling results to evaluate the goal’s efficiency.
Now, the filter change will come either when it reaches 10,000 bed volumes or PFMOAAs are 10 ppt.
Vendors removed GAC from one of the filters at Sweeney for the first time in April; CFPUA anticipated then having to replace the GAC every 300 days or so.
Bellamy told PCD the timing for change out will likely be more frequent now, but it will be dependent on how much water the plant is producing.
“For instance, in high-use summer months, we would reach 10,000 bed volumes faster than in lower-use winter months,” she explained.
CFPUA continues to monitor for several types of PFAS that could break through GAC, Waldroup told the board.
“At least some of this is to be expected as we continue to learn how to use and optimize this new facility,” he said.
The GAC system is flexible in design and able to be modified for new compounds as needed.
CFPUA urges NCDEQ for more studies
Right now, there is no standard method for testing the presence of PFPrA, but CFPUA staff is partnering with the North Carolina Department of Environmental Quality to understand its potential impacts.
“As of July 31, this compound was not on [NCDEQ’s] radar,” Waldroup told the board. “It wasn’t even on the EPA’s strategic roadmap to address.”
The authority sent a letter Thursday to NCDEQ requesting additional studies and for PFPrA to be added to the Secretaries’ Science Advisory Board’s list of priority PFAS.
CFPUA board member and county commissioner Rob Zapple asked why this particular compound is breaking through the granular-activated carbon.
“It’s speculation, but certainly its size seems to indicate one of the first things to break through,” Waldroup replied. “We’re also observing desorption, the process of large chain PFAS knocking loose smaller chains previously bound by the GAC.”
CFPUA also recently switched the laboratory it partners with for testing, from Enthalpy to GEL, the latter being used by NCDEQ as well.
CFPUA engages in experimental methods that are not all EPA-certified. While some PFAS can be tested under EPA-approved methods, they don’t exist for the majority of the compounds.
“In those cases, commercial and academic labs must create their own methods,” Hagerty explained to PCD. “These methods may differ from lab to lab.”
Only six compounds — PFOA, PFOA, PFHxS, GenX, PFNA and PFBS — are proposed for EPA regulation, announced this past March. PFOS and PFOA are proposed at maximum contaminant levels 4 ppt; the other four have a combined limit of 1 ptt.
To determine if the 1 ppt limit has been exceeded, EPA uses an equation, along with the health-based limits for four PFAS: GenX, PFBS, PFNA, and PFHxS, at 10 ppt, 2000 ppt, 10 ppt, 9 ppt, respectively. If the total of those four compounds, based on the formula, is greater than 1 ppt, the proposed EPA Maximum Contaminant Level would be violated.
The federal agency anticipates finalizing the regulations by the end of the year.
The majority of the compounds CFPUA monitors have no benchmarks, such as maximum contaminant levels, health advisories or preliminary health goals.
“We’re at the forefront of the technology for treatment,” Waldroup said to the board.
CFPUA is unlike the more than 5,000 utility companies nationwide, which will have to implement new technology to meet the standards and about 2,400 will have to modify current treatment systems to comply.
CFPUA is partnering with the EPA as an advanced facility to benchmark against, Waldroup told the board, based on its technology to identify, remove and dispose of PFAS.
“Utilities nationwide, professional organizations, the EPA, as of today, are turning toward us to help develop answers that could be applicable nationwide,” Waldroup said. “We’re at the forefront of learning, understanding and dealing with the PFAS issue, by necessity.”
Waldroup will be speaking at 2 p.m. Aug. 31 during a webinar hosted by NCDEQ about CFPUA’s experience planning and constructing projects to address PFAS. The public can listen in here.
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