Pittsboro reviews unregulated chemicals in its drinking water

Posted 4/26/19

PITTSBORO — Meeting Monday, the Pittsboro Board of Commissioners reviewed the nature of its water quality with respect to unregulated chemicals and considered treatment options and costs.

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Pittsboro reviews unregulated chemicals in its drinking water

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PITTSBORO — Meeting Monday, the Pittsboro Board of Commissioners reviewed the nature of its water quality with respect to unregulated chemicals and considered treatment options and costs.

The town contracted with CDM Smith, an engineering and construction company which provides solutions in water and other arenas for government and private clients. The company is working with the town on a water supply and treatment plant expansion study, which is still in its draft stage, but commissioners requested the company provide an initial review of the unregulated chemicals in the town’s drinking water and provide an initial review of potential treatment options.

The company used data collected by N.C. State University in 2013 and 2018 as well as data collected by the Haw River Assembly in August 2018 to determine the levels of certain chemicals in the Haw River, which supplies the town’s drinking water. The data sets identified levels of 1,4 Dioxane, a solvent in the manufacture of other chemicals and as a laboratory reagent. The data also identified several perfluorochemicals, a group of chemicals used to make coatings and products that resist heat, oil, stains, grease, and water. None of the identified chemicals are currently regulated by either the state or the federal government with regard to “safe” levels in drinking water.

The data showed that the concentrations of the chemicals are more significant in the Haw River as it comes downstream. The likely cause, according to the CDM Smith, are manufacturing facilities and wastewater treatment discharges from localities upstream in Reidsville and Burlington. The data also showed that when the water reaches Jordan Lake, the concentrations are notably diluted. As a result, Pittsboro’s water treatment plant must deal with far higher concentrations in the removal process than treatment plants that use Jordan Lake for its drinking water supplies.

CDM Smith also noted that this particular combination of chemicals is unique to the Cape Fear River Basin of which the Haw River is part. In discussing potential treatment options, the company noted that because of this combination, the town would likely need to consider a combination of techniques to remove the chemicals. Adding to the challenge, as the chemicals are not regulated, there is no guidance for the town to determine to what degree the chemicals must be removed.

CDM Smith provided four different advanced treatment options during the meeting for removal of the targeted chemicals. Company representatives noted that none of the options were necessarily perfect as the removal of these particular chemicals is still in the early stages of development. Each of the options also carries different capital costs to initialize. In addition, the company was unable to provide any operating costs because they were unsure how long the supplies required for each option to remove the chemicals will last considering the levels of chemicals in the Haw River and how much disposal costs for would be.

CDM Smith noted that a reverse osmosis treatment option would yield the best results, but was also the most expensive — costing between $11-23 million for start-up costs alone. Another consideration for reverse osmosis is the after the chemicals are removed from the drinking water, they are returned back to the river. The “combination” treatment systems can run between $8-21 million for start-up costs. However, other mediums used in the process, such as carbon, would also have to be disposed of either in a landfill or burned.

These treatment options would be the last step in the process. The costs for these systems do not include the additional costs for expanding the plant and upgrading the standard water treatment equipment that also must be in place. Those costs were not provided on Monday night because the study has not yet been complete.

CDM Smith suggested the town perform a pilot comparison at the plant before determining which treatment option might best serve the town. The pilot comparison would at least partially answer several questions such as how well do each of the treatment options perform and how long with the mediums that remove the chemicals last. The company also noted that since there are no guidelines for these chemicals, the town would need to determine a goal for the treatment which could be a base-level of chemicals or a percentage of reduction of chemicals.

Since the discussion was a preliminary one, the board made no decision about how to move forward. Members did ask for certain data sets to be included in the final study for clarity. There was no definitive date given for the completion of the entire water supply and treatment plant expansion study.


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