Monday, June 27, 2022

Pilot testing shows Brunswick County’s RO water discharge may exceed state contaminant standards

Brunswick County's $137.8 million water plans, including nearly $100 million low-pressure reverse osmosis technology enhancements, include releasing wastewater back into the Cape Fear River. In order to discharge the wastewater, the county first needs to obtain a state permit.

Plans to discharge wastewater produced by Brunswick County's nearly $100 million reverse osmosis plant include releasing discharge along a nearly 4-mile pipe into the Cape Fear River. (Port City Daily photo/Courtesy North Carolina Department of Environmental Quality)
Plans to discharge wastewater produced by Brunswick County’s nearly $100 million reverse osmosis plant include releasing discharge along a nearly 4-mile pipe into the Cape Fear River. (Port City Daily photo/Courtesy North Carolina Department of Environmental Quality)

BRUNSWICK COUNTY — When unwanted compounds are filtered out of the water, where do they go?

By 2020, in Brunswick County, they could go right back into the river. After extensive considerations, alternative discharge options aren’t feasible, the county’s consultant recently found.

RELATED: Brunswick’s $100-million treatment plant will concentrate contaminants, discharge them back into Cape Fear River

To filter emerging contaminants out of surface water, Brunswick County’s water treatment solution includes discharging wastewater produced by its nearly $100 million planned low-pressure reverse osmosis plant back into the Cape Fear River.

But according to a lengthy — and costly — series of studies produced by Brunswick County’s consultant, its chosen reverse osmosis (RO) treatment plan is the most viable option.

Over a several-month period earlier this year, consultants conducted pilot testing to determine what the planned RO discharge stream might contain. Out of 280 parameters, four were identified as being in excess of state standards or protective values: manganese, aluminum, chloride and dichloracetic acid.

Many chemicals monitored include unregulated compounds. Interpreting the impact of unregulated compounds, even with marked concentrations, is difficult in the absence of extensive research or health guidelines.

Discharge permit

Last month, the county submitted its 142-page discharge permit application to the Department of Environmental Quality.  The nearly $100 million plan hinges on the county’s ability to obtain the permit. If granted, the permit would allow the Northwest Water Treatment Plant the ability to discharge up to four millions of gallons of wastewater a day (MGD) into the Cape Fear River.

Boston-based firm CDM Smith has already received at least $1.3 million from the county to help design and manage the proposed plant. Plans have been designed around a planned 12 MGD expansion, a separate $38.2 million project. Expansion plans would increase the Northwest plant’s capacity from 24 MGD to 36 MGD.

On Monday, Brunswick County Commissioners took the first step toward funding $216 million in debt it anticipates taking on through this project and others. To start, the county initiated a $56,607 water rates study, to re-evaluate its contracts between its 11 wholesale customers.

Related: Brunswick County’s pricey path to RO could spread cost burden across its wholesale customers

Between 0.7 MGD of wastewater, at the lowest operating capacity, and 4 MGD, the maximum capacity, will flow continuously of the proposed outfall stream. The wastewater stream, located 18.3-miles downstream from the region’s raw water source near Lock and Dam No. 1, will be released into “Class C” waters. This type of surface water is protected by the Division of Water Quality to maintain “fishable” and “swimmable” standards.

The Northwest Water Treatment Plant currently holds a filter backwash discharge permit, that releases wastewater next to its facility into Hood Creek, a tributary of the Cape Fear River.

But adding RO discharge to this location at Hood Creek was not considered; instead, the county plans to install a nearly 4-mile long, 16-inch pipe across Mt. Misery Road to reach the Cape Fear River.

Though there are a few dozen residential homeowners right next to the proposed outfall location, a vast majority of the area is comprised of undeveloped wetlands or game lands. Because the rate of dilution at the outfall location is less than 400:1, a state mixing standards threshold, chronic testing will be required.

The waste stream

Upstream, in Riegelwood, Lower Cape Fear Water and Sewer sources the region’s raw water supply. According to Cape Fear Public Utility Authority, the water source was moved upstream decades ago because raw water near Wilmington proved too saline.

According to CDM Smith’s recent findings, the proposed outfall location is comprised of freshwater. The consultant’s report found RO discharge will also be a freshwater solution, too. “The waste stream is not expected to be a brine concentrate…,” the permit application states.

Designs for Brunswick County's proposed $100 million low-pressure reverse osmosis include releasing a wastewater concentrate back into the Cape Fear River. (Port City Daily graphic/Courtesy North Carolina Department of Environmental Quality)
Designs for Brunswick County’s proposed $100 million low-pressure reverse osmosis include releasing a wastewater concentrate back into the Cape Fear River. (Port City Daily graphic/Courtesy North Carolina Department of Environmental Quality)

Aside from contaminants filtered out in the RO process, the wastewater stream could contain polyaluminum chloride, among a host of other contaminants, pilot testing shows. It will also occasionally include a neutralized, spent cleaning solution.

However, according to the consultant’s findings, the wastewater stream at full strength will not exceed state standards. “The quality of the full strength concentrate was below standards and protective values,” the report finds.

Still, pilot testing showed calculated concentrations of manganese, aluminum, chloride, and dichloroacetic acid “slightly above” water quality criteria and protective values. To mitigate this finding, consultants said the wastewater stream’s final solution will be further diluted.

In the state permit application, consultants could not provide any similar case study similar in scope to Brunswick County’s endeavor.  Submitted on Nov. 9, consultants initially planned to apply for the permit this summer, earlier study documents show.

If the permit is granted, and the Local Government Commission issues an opinion that the county is capable of taking on $216 million in debt, the wastewater stream could begin flowing on Oct. 1, 2020.

According to a DEQ records specialist, the application is still under review, with no additional information required of the county. After dilution, CDM Smith predicts the wastewater solution will meet all applicable standards.

“No additional treatment of the waste stream is planned,” the county’s permit states.

Check out the wastewater’s 4-mile path, from Brunswick County’s water treatment plant to the Cape Fear River. 


Send tips and comments to Johanna Ferebee at johanna@localvoicemedia.com

Related Articles