BRUNSWICK COUNTY — A new low-pressure reverse osmosis system in Brunswick County could dump millions of gallons of wastewater containing compounds back into the same river it’s designed to filter contaminants out of.
Brunswick County’s $100 million plans to filter out emerging contaminants from the water supply present an inevitable reality: discharge the plant’s wastewater with concentrated levels of GenX and other emerging contaminants, anywhere from 3.6 to 7.2 millions of gallons a day, back into the Cape Fear River.
RELATED: Brunswick County commissioners give go-ahead for $100 million reverse osmosis facility
Compared to other water treatment systems, Brunswick County’s selected technology does not improve the water quality of its water source. At best, the planned reverse osmosis system designed to source water from the Cape Fear River, will keep water conditions in the river the same.
Wastewater discharge permit
The county’s $100 million solution hinges on its ability to obtain a modified discharge permit.
A wastewater discharge permit, issued by the North Carolina Department of Environmental Quality (DEQ), would allow the county to discharge back into its water source. The Northwest Treatment Plant is currently permitted to discharge wastewater treated by conventional means, into Hood Creek, a tributary in the Cape Fear River basin.
If approved for a discharge permit – with expanded capacity treated by reverse osmosis technology – the plant would redirect its discharge force main directly into the Cape Fear River, rather than its tributary.
Based on preliminary plans, it appears the county is behind in its application process. An application was supposed to have been submitted by this summer, according to CDM Smith’s final advanced treatment options report.
Now, according to the Brunswick County Utilities Director, John Nichols, the county intends to submit its discharge permit application in November.
Though the county would spend the time and money to remove emerging contaminants from the river, many compounds will be returned, back to the river.
“GenX and other PFA’s [perflourinated compounds] returned to the river were taken from the river to begin with,” Nichols said. “They are simply being detoured.”
Reverse osmosis technology filters water through a system that results in 10 to 20 percent wastewater discharge, according to Carel Vandermeyden, Cape Fear Public Utility (CFPUA) Authority’s director of engineering.
For example, Brunswick Regional Water and Sewer H2GO’s state-approved discharge permit would allow 1 millon gallons per day (MGD) of discharge for a 4-MGD system and or 2 MGD for an 8-MGD system. H2GO’s permit is not being used, but, that’s another story.
Unlike Brunswick Regional Water and Sewer H2GO’s planned, $36 million reverse osmosis plant, Brunswick County’s must retrieve its raw water from the Cape Fear River. H2GO’s system, if fully built out, would obtain source water from the Lower Peedee and Black Creek aquifers. These groundwater aquifers – both over 300 feet deep – are believed to have no trace of perfluorinated compounds.
CFPUA, New Hanover County’s water supplier, maintains two groundwater systems in addition to its other river-based systems. One in the Ogden area of Wilmington uses a membrane process, similar to reverse osmosis. Wastewater produced by this system produces no environmental strain at all, CFPUA’s director of engineering, Carel Vandermeyden, said.
“That’s groundwater and we don’t have the issue of perfluorinated compounds, so you’re dealing with just traditional, total dissolved solids, things like that,” Vandermeyden said. “Basically the water is crystal clear.”
As for Brunswick County, sourcing raw groundwater to supply 70,000 of its total retail customers isn’t an option. An April CDM Smith report found both the engineering firm and the DEQ confirmed groundwater is inadequate to cover the county’s water demand.
Based on the county’s expansion plans to increase the plant’s current capacity from treating 24 MGD to 36 MGD, introducing a reverse osmosis system could result in daily discharges of millions of gallons of wastewater.
Meanwhile, across the river, CFPUA ruled out reverse osmosis treatment technology using source water from the Cape Fear River. The technology was eliminated in part, because of the “perceived challenges for permitting the waste discharge,” the report states.
“Securing a NPDES [wastewater] permit for discharge of the RO concentrate is a critical element for the project,” CDM Smith’s report states.
Wastewater from Brunswick County’s planned expansion would not be a typical waste stream, Nichols said.
It would meet drinking water standards, he said, composed of treated water with only a high concentration of contaminants not removed by its traditional treatment process.
(Editor’s note: there are currently no federal or state drinking water standards for GenX or other per- or polyfluorinated chemicals, thus their “emerging contaminant status.” North Carolina has issued a “provisional health goal” of 140 nanograms per liter (ng/L) for drinking water, and has found levels of GenX at ten times that level in many surface water tests. A reverse osmosis plant would concentrate these surface-water levels.)
Nichols said the county supports the elimination of source discharges of contaminants, rather than placing a financial burden on customers to remove contaminants near the Brunswick County plant at the Cape Fear River basin.
“Removal of PFAS at these locations is not an effective remediation measure and would put the costs on the water customer rather than the polluter,” he said.
Contaminants produced by Chemours in Fayetteville, a DuPont subsidiary, are being discharged into the water supply through a state discharge permit, similar to what Brunswick County is seeking. Eliminating Chemours’ production is the only practical measure to keep emerging contaminants out of the environment, Nichols said.
“There is significant effort ongoing to ensure that impacts to the river and environment are minimized,” he said. “Chronic toxicity studies and complex hydraulic modeling is being performed to ensure that the water discharged back to the river will not impact aquatic species.”
Granular activated carbon
Compared to New Hanover County, Brunswick County has moved more quickly in its pursuit to filter out emerging, unregulated contaminants. Brunswick County has paid CDM Smith $1.3 million to study and design water treatment options, with a design contract issued in April 2018.
In May, the county voted to approve construction of the $99 million reverse osmosis plant, based on CDM Smith’s recommendation. The motion passed with no discussion by the Board of Commissioners.
Earlier this week, CFPUA voted in favor of pursuing preliminary design services for its $46 million solution, granular activated carbon (GAC).
According to CFPUA’s executive director, Jim Flechtner, a GAC system would not affect its existing discharge permit at Sweeny Water Treatment plant.
As opposed to Brunswick County’s planned reverse osmosis plant, GAC systems can physically remove contaminants from their source, without returning them back.
“[GAC] was just a better fit for our plant,” Vandermeyden said. “That doesn’t mean that [reverse osmosis] isn’t good technology, it was just not a good fit for our plant.”
Both CFPUA’s water treatment study – financed by state funds released by House Bill 56 – and Brunswick County’s study found reverse osmosis to be a costlier water treatment option.
As CFPUA considered water treatment options, it weighed both economic and noneconomic values.
“GAC does not change the chemistry of the water,” Vandermeyden said. Changing a water’s chemistry is inherent in the reverse osmosis process, he said.
“[Reverse osmosis] does change the chemistry of the water and you have additional treatment measures to adjust the chemistry of the water back to where it does not have an impact,” he said. “It’s very doable but we already have a very good erosion control program.”
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