By Will Atwater
Allan O’Briant knows that providing clean drinking water to 125,000 customers can be a tall order. As the water treatment plant supervisor for Harnett Regional Water, he’s constantly balancing the need to disinfect the water supply with controlling potentially harmful byproducts.
One of the challenges O’Briant and his colleagues face is controlling trihalomethanes, a chemical liquid byproduct that forms when chlorine, used to kill microorganisms, reacts with natural organic matter in the water.
While chlorine is essential for disinfection, it can also create a tricky balancing act: keeping water safe from microbes while ensuring that trihalomethane levels stay within federally mandated limits. Long-term exposure to trihalomethanes is linked to adverse health effects, including birth defects and bladder and colon cancer.
The stakes are high, and some water systems have struggled to meet the mark.
A recent analysis by the national Environmental Working Group found that nearly 6,000 community water systems in 49 states and Washington, D.C., reported at least one instance of unsafe levels of trihalomethanes between 2019 and 2023. According to the report, these water systems serve approximately 122 million residents.
Among the affected systems, 246 are in North Carolina, and they serve a total of 4.2 million people — about 38 percent of the population. “These systems reported detectable levels of the contaminant at or above the EPA’s legal limit of 80 parts per billion,” said Alex Formuzis, EWG’s vice president of communications and strategic campaigns, in an email.
Harnett Regional, like many other water utilities across North Carolina, switches up its disinfection process once a year to manage this risk. For about three to five weeks, the utility replaces its usual chloramine disinfectant — a combination of chlorine and ammonia — with pure chlorine, flushing the system to clear out buildup and maintain water quality.
“The annual switch helps ensure that microbial growth is kept in check,” O’Briant said.
And so far, it is working to also keep levels of the chemical byproduct down. In 2024, the average level of trihalomethanes in Harnett Regional’s water supply was 40.8 parts per billion — well below the EPA’s limit, O’Briant said.
While water systems like Harnett Regional are finding ways to manage trihalomethane levels by periodically flushing their systems, the broader challenge remains — particularly in areas affected by agricultural runoff.
Pigs and chickens and cows and more
Though manure runoff from agricultural spray fields is a major contributor to trihalomethanes, according to EWG’s report, the issue isn’t limited to rural areas.
“Manure from factory farms is polluting our water supplies, and when utilities try to make that water safe to drink, they unintentionally create another public health hazard,” said Anne Schechinger, the report’s author and EWG’s Midwest director.
Other sources can also spread the contaminant into urban communities.
Schechinger explained that human waste also contains organic matter that can react with chlorine in the drinking water treatment process, producing trihalomethanes.
“Cities use water from streams, lakes, and all that water comes from somewhere — and a lot of times it comes from upstream, near more agriculture,” she added.
Credit: EWG / Environmental Working Group
This means that even urban water systems can experience elevated levels of the trihalomethanes when their water sources are contaminated by agricultural runoff. The report also points to soil erosion, crop plant material and other fertilizers as additional sources of organic matter that can generate byproducts during the disinfection process, further complicating water quality management.
A study published in March 2022 found higher rates of acute gastrointestinal illness among people living near industrial hog operations compared with those living farther away. Another EWG study, released on Dec. 1, 2022, revealed that about 2 percent of North Carolina’s swine and poultry facilities are in or near floodplains, potentially putting some drinking water sources at risk.
To address health concerns, EWG argues that the legal limit for trihalomethanes in drinking water should be .15 ppb, significantly less than the EPA’s current limit of 80 ppb.
“When the EPA sets their maximum contaminant levels, they base their levels on both health as well as treatment cost […],” Schechinger said. But EWG’s suggested contaminant limit is based solely on health, she added. “It’s the level that would only cause one case of cancer out of a million people who drink the water.”
Compliance issues
North Carolina environmentalists have long flagged agricultural runoff as an environmental and public health issue, and they are advocating for stricter regulations to curb the flow of animal manure into the state’s waterways. One source of concern is hog lagoons, which capture waste generated by the hundreds or thousands of animals at swine facilities.
To prevent lagoons from overflowing, a 19-inch buffer (also known as freeboard) must be maintained between the top of the lagoon and the top of the liquid waste. To regulate waste accumulation, farmers will take excess liquid waste from the top of the lagoon and periodically spray it onto agricultural fields to fertilize the soil.
“You see lagoons that have solids that have reached the surface — a lot less space in the lagoon, which means much more frequent spraying,” said Cape Fear Riverkeeper Kemp Burdette.
Burdette said these concentrated facilities must follow rules requiring swine waste to be sprayed only on designated fields, not around rain events or into ditches, tree lines or wetlands — and always under supervision to prevent accidents.
However, Burdette noted that compliance with these regulations is often lacking.
“If all those rules were followed, you would have a system that was still just really maxed out,” he said. “It’s just an enormous amount of waste that we’re talking about here, but [the rules] aren’t followed.”
“I see fields that are soaking wet, standing water on fields and the sprayers are still going,” Burdette added. “I see sprayers that are spraying into ditches or spraying onto roadways.”
He said he’s seen all of this over the years, and he has made referrals to regulators.
“Those referrals have sometimes resulted in notices of violations, and sometimes not,” Burdette said.
Policy and federal challenges
Burdette noted that the state’s poultry industry is even less regulated than swine operations. He pointed to many past and current instances when he’s witnessed piles of poultry litter that were not properly covered or stored.
He also mentioned that sludge derived from human waste is sprayed on agricultural fields.
Lax oversight and rule enforcement “[is] how you get a bunch of organic matter in rivers that later get pulled into drinking water supplies.”
“We are not moving in the right direction,” said state Rep. Pricey Harrison (D-Guilford). In 2023, Harrison co-sponsored House Bill 722, which she described as a study aimed at gathering support for establishing more regulations for the state’s poultry industry. The bill didn’t garner the needed support. In 2025, Harrison co-sponsored House Bill 867, which seeks to establish a permitting program for dry litter poultry operations. The bill has been referred to the Rules, Calendar, and Operations of the House Standing Committee.
“Since the Republicans took over, and I don’t mean to sound partisan, it seems like we have chipped away at a lot of the really important advances we’ve made in environmental protection, particularly regarding water quality,” Harrison stated.
While local efforts to manage contamination are ongoing, federal backup remains uncertain. Schechinger noted that the Inflation Reduction Act, passed during the Biden Administration, allocated resources to help farmers address runoff issues, but the Trump Administration has frozen much of the funding.
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“The Inflation Reduction Act is sending billions of dollars to farmers for things like buffer strips and grass, waterways,” Schechinger noted. “Those practices in farm fields reduce the amount of manure that gets into streams and rivers and then lakes, which are sources of drinking water for much of the country.”
Schechinger noted that without additional support from the federal and state governments, water systems are faced with tackling the problem on their own.
“It is a really hard problem for utilities to fix,” Schechinger said. “It’s likely a lot cheaper and easier to reduce the amount of manure, and the organic matter in the manure that’s getting into water utilities in the first place, rather than trying to have these water utilities fixing the disinfection byproducts.”
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