In addition to expanding its water supply, the town of Pittsboro is also trying to figure out the best way to cleanse it of unregulated, potentially dangerous contaminants.
Last fall, Pittsboro hired engineering and construction firm CDM Smith to complete a public water supply and treatment expansion study. In an October memo, town engineer Elizabeth Goodson wrote that Pittsboro’s current public water demand “is approximately 700,000 gallons per day” but is estimated to grow to approximately 3 million gallons by 2020, 7 million by 2030 and 10 million by 2040.
But in addition to increasing the quantity of drinking water, Pittsboro is also interested in improving the quality of it. While Town Manager Bryan Gruesbeck said the Pittsboro Water Treatment Plant meets state and federal standards, there are high levels of per- and polyfluoroalkyl substances in the Haw River, from where the town’s water comes.
PFAs are not regulated at the state or federal level, but the Pittsboro Board of Commissioners is concerned about their presence in the town’s drinking water and is seeking the best way to dilute the contaminants moving forward.
“I get a very strong feeling from this board that people are interested and concerned about the effects,” Commissioner John Bonitz said in a phone interview. “We’re not interested in just complying with federal law; we’re not interested in just looking like we’re doing the right thing. This board really does want to make sure we are doing the right thing, and that’s a big deal.”
What are PFAs?
According to the North Carolina Department of Health and Human Services, PFAs are “a large group of man-made chemicals that have been used in industry and consumer products worldwide since the 1950s.”
Some PFAs have been phased out, but they are still used in some food-packaging materials, cleaning products and cosmetics. PFAs “can be found near areas where they are manufactured or where products containing PFAs are often used.”
The most common non-worker exposures to PFAs take place through “drinking contaminated water or eating food that contains PFAs,” the DHHS reported.
According to the EPA, PFOA and PFOS are the most commonly occurring and researched PFAs. They’ve been characterized as “very persistent in the environment.”
Once absorbed, PFAs remain in the body for a long time. Human epidemiology studies have linked exposure with increased cholesterol levels, while the EPA says “more limited findings” have associations with: infant birth weights, effects on the immune system, cancer and thyroid hormone disruption.
The study of PFAs in drinking water is still relatively new.
“In fact, we didn’t even know these were in the water until a couple of years ago,” CDM Smith client service leader Reed Barton said during a presentation at a Pittsboro Board of Commissioners meeting on April 22.
How can they be treated?
In its current state, the Pittsboro Water Plant is not capable of treating PFAs, since it was built in 1964 and the presence of PFAs in water supplies has only been recently discovered.
But there are several advanced treatment technologies, which CDM Smith’s Bill Dowbiggin discussed with the board. The most effective option is low pressure reverse osmosis, which received an “excellent” rating from CDM Smith for its ability to treat PFAs and 1,4 Dioxane, another emerging contaminant found in the Haw River.
Barton referred to reverse osmosis as being “kind of like the Cadillac” of treatment options. However, its benefits come at a cost. In terms of capital costs, reverse osmosis is the most expensive at $11 million for treatment at a facility handling 2 million gallons of water per day.
A combination of other technologies, including ion exchange, granular activated carbon and UV-advanced oxidation process, can be used at a similarly effective level at a cheaper cost. But there is a drawback: As shown in a pilot test at Cary and Apex’s water plant in Jordan Lake, the life cycles for granular activated carbon and ion exchange span just three and four months, respectively.
Meanwhile, Dowbiggin said reverse osmosis membranes last for seven years, sometimes longer. That longevity could make reverse osmosis a cheaper option in the long run operationally, but Dowbiggin said a pilot test in the Haw River would be needed to determine total cost.
Beyond price, there are a few additional obstacles involved with reverse osmosis. For one, Pittsboro would need to amend its existing NPDES permit to be able to get rid of additional concentrate.
“I would say there’s probably a year’s worth of work to obtain that permit modification,” Barton said. “It’s done all the time, but it’s not a small effort.”
Additionally, Mayor Cindy Perry expressed concerns about the idea of pulling pollutants out of the town’s drinking water, only to put it back in the river for other communities to deal with.
“That’s what makes it seem so unfair … that we’ve gone to the millions of dollars to remove the chemicals, and now we’re taking the high concentrate and putting it back and saying, ‘Oh, Cary can deal with that,’” Perry said.
A similar sentiment was expressed by Bonitz.
“Do we as a community want to pull the problem out of our drinking water, only to put it back into the river flow for people downstream to have to deal with it again?” he said. “That’s a really big, important question – even if it may be legal and allowed by DEQ. Morally, that’s not something I’m bringing up, this is what I’m hearing from constituents and my fellow elected officials.”
What’s the timeline moving forward?
The information presented to the board by CDM Smith “should be considered draft format and not an accepted statement of formal policy or information,” according to Gruesbeck.
Bonitz said the board has no timeline established for when it will make a decision on treatment options, which will depend on when CDM Smith’s final report is completed. Bonitz said the topic will be discussed at a joint meeting between the Pittsboro and Chatham County boards of commissioners on May 9.
Because PFA levels are lower in Jordan Lake than the Haw River and because the long-term plan calls for Pittsboro using Jordan Lake for its water supply, Bonitz is interested in a collaborative solution between Pittsboro and Chatham County.
“If you’re going to clean pollutants out of water, you’re going to want to have the pollutants as diluted as possible already, and that’s what Jordan Lake has,” Bonitz said. “So to the question of the trial, I think that it makes more sense for us to spend money … if we’re going to do a trial, we should spend money on the water that we would actually be treating in future rather than trying to treat the water that’s in the Haw right now.”
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