Taking a look at the latest PFAS levels in CFPUA drinking water from Sweeney Treatment Plant

This empty stretch of ground at CFPUA's Sweeney Water Treatment Plant is where the utility plans to build nearly $50 million in upgrades. (Port City Daily photo / Benjamin Schachtman)
This empty stretch of ground at CFPUA’s Sweeney Water Treatment Plant is where the utility plans to build $46 million in upgrades. (Port City Daily photo / Benjamin Schachtman)

NEW HANOVER COUNTY — Levels of GenX in the Cape Fear River have decreased by a factor of hundreds – or even a thousand – over the last several years, and current PFAS levels are at the lowest they’ve been in nearly a year of measurement. But according to the Cape Fear Public Utility Authority, these improvements may not be permanent – part of the reason the utility is planning over $200 million in water treatment improvements over the next several decades.

From "Legacy and Emerging Perfluoroalkyl Substances Are Important Drinking Water Contaminants in the Cape Fear River Watershed of North Carolina" published in Environmental Science & Technology Letters on Nov. 10. 2016. (Port City Daily photo / File)
PFPrOPrA – a.k..a. GenX – levels in Wilmington’s water source (Community C). From “Legacy and Emerging Perfluoroalkyl Substances Are Important Drinking Water Contaminants in the Cape Fear River Watershed of North Carolina” published in Environmental Science & Technology Letters on Nov. 10. 2016. (Port City Daily photo / File)

Back in 2013 and 2014, tests conducted by Detlef Knappe and others found GenX concentrations as high as 4,500 parts per trillion (ppt) and at an average level of over 600 ppt in the raw water that feeds CFPUA’s Sweeney Water Treatment Plant. At the end of April 2019, that number was 8.6 ppt. In the finished drinking water from Sweeney the numbers have decreased by similar orders of magnitude – from a maximum of 286 ppt in July of 2017 to just 3 ppt last month.

Other PFAS – which didn’t reach the same concentrations as GenX – have seen similar decreases. In fact, during the most recent finished water tests all PFAS were measured under 3 ppt or were undetectable, except for two – PFO2HxA (6.38 ppt) and PFMOAA (6.5 ptt). The most recent testing showed a total PFAS concentration of 108 ppt in raw water (down from a mean total of 710 ppt in Knappe’s 2013-2014 tests) and 22 ppt in finished water.


Related: Here’s what it will take to get answers about GenX’s health effects

Toxicological information on GenX is scarce and it may be decades before scientists reach a full understanding of the health effects of even one chemical (say, just GenX), let alone all of the PFAS family. It will take even longer to understand what the combined effect of these chemicals – the “chemical cocktail” as it is frequently referred to – is on people. That means it may be a long time before the EPA sets enforceable standards (which, under the Hardison Amendment, means North Carolina’s health and environmental agencies will have their hands tied without direct action by the Governor– although they can continue to enforce both the discharge permits and consent agreement).

For CFPUA, the working theory has been that – given preliminary toxicological tests on GenX – that lower levels of all PFAS are in the public’s best interest. And right now, these chemicals, which CFPUA believes are mainly associated with Chemours’ Fayetteville Works facility, are at all-time lows.

A best-case but impermanent scenario

The latest PFAS levels in raw and filtered water for Sweeney Water Treatment Plant. Note, the missing figure for raw water on April 29 in 108.78 ppt. (Port City Daily photo / CFPUA)
The latest PFAS levels in raw and filtered water for Sweeney Water Treatment Plant. Note, the missing figure for raw water on April 29 in 108.78 ppt. (Port City Daily photo / CFPUA)

The low levels appear to be the result of reduced concentrations in the Cape Fear River and Sweeney’s recently replaced Granulated Activated Carbon (GAC) filter medium, which is working near peak efficiency. But CFPUA warns low levels may fluctuate and likely won’t hold without facility improvements.

“Low levels are great, but it’s important to note that those levels fluctuate, largely depending on levels in the river, which also fluctuate,” according to spokesperson Vaughn Hagerty, who noted that previous totals for PFAS in finished water were 33.6 ppt and the week before 50.6 ppt – a more than twofold difference.

While CFPUA testing shows that the combined PFAS levels have been trending downwards, especially over the last three months, there have been spikes in the past. Some are attributable to spills at Chemours’ facility, others are harder to explain. In any case, CFPUA believes levels could rise again.

CFPUA also noted that while PFAS levels are very low or undetectable right now, it’s a best-case scenario that likely won’t last with Sweeney’s current filter system in place.

“One thing that’s important to note is that what we’re seeing now is likely about the very best we’re going to achieve from this round of GAC replacements. Over time, as the GAC adsorbs PFAS, it will become less effective. So, the amount of PFAS removed from raw water during treatment is likely to diminish. Our models show that, on average over the life of the GAC in these shallow beds, we should achieve about 40 percent removal – more removal at the beginning and far less at the end,” Hagerty said.

Sweeney’s GAC filter media was just replaced, thus the water is seeing maximum filtration.

$215 million in improvements and maintenance

Inside the Sweeney Water Treatment Plant’s filter gallery.

To that end, CFPUA’s board unanimously approved a number of steps to pursue around $46 million in upgrades to Sweeney, namely GAC beds that are three times as deep as the current filters. These upgrades will require GAC filter media to be replaced, at an annual cost of around $2.9 million.

Related: Are CFPUA ratepayers willing to pay $215 million for Sweeney upgrades?

These filters will be able to remove 90 percent of PFAS from the water, according to Hagerty.

CFPUA has continued to meet and work with local organizations, including meetings at the New Hanover County Arboretum and with Residents of Old Wilmington and residents of RiverLights, according to Hagerty. A meeting at the Carolina Bay at Autumn Hall is planned for June. Groups interested in scheduling a similar meeting can contact CFPUA here.


Send comments and tips to Benjamin Schachtman at ben@localvoicemedia.com, @pcdben on Twitter, and (910) 538-2001

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