NEW HANOVER COUNTY — Levels of 1,4-Dioxane in treated Cape Fear Public Utility drinking water tested earlier this month are 3.7 times higher than the federally-recommended lifetime one in a million cancer rate.
1,4-Dioxane does not have a maximum contaminant level and remains mostly unregulated (the state recently required testing, but cannot yet set limits as the Environmental Protection Agency has not set its own).
The compound is used as a solvent in various industrial capacities, is a byproduct of the thermoplastic polymer resin PET, and can be found in a number of household products including shampoos and detergents.
The Environmental Protection Agency (EPA) established a risk assessment level for 1,4-Dioxane of 0.35 parts per billion (ppb) in 2013. This level represents the cancer risk level for one individual out of one million after a lifetime of drinking water containing the compound. The EPA describes 1,4-Dioxane as a likely human carcinogen that does not biodegrade.
In July, Cape Fear Public Utility Authority (CFPUA) shared 1,4-Dioxane was detected in finished drinking water at 0.54 ppb — the highest it has observed since 2015. This month’s results from samples collected on Sept. 9 show finished levels at 1.3 ppb, with raw water detected at a far higher magnitude compared to other readings this summer, at 6.3 ppb.
In July, the Department of Environmental Quality (DEQ) began requiring publicly-owned wastewater treatment facilities in the Cape Fear River basin to perform investigative monitoring of 1,4-Dioxane and total PFAS for three consecutive months. The DEQ has identified wastewater facilities as a potential conduit for releasing high concentrations of 1,4-Dioxane through the wastewater treatment processes. However, these facilities are not believed to be the original source of the compound.
Since 2014, the DEQ has monitored 1,4-Dioxane in the Cape Fear River basin. In May 2015, the DEQ collected sufficient data to establish monitoring stations where 1,4-Dioxane levels were elevated. This included a station located just below the Cape Fear Region’s raw water intake source at Kings Bluff.
Between October 2014 and September 2015, 1,4-Dioxane levels at this station reached as high as 31 times the EPA’s drinking water risk level, at an average of 11 times over the level, at 4 ppb. Over that time frame, the compound was detected at alarming rates upstream, as high as 1,030 ppb in Reidsville. No federally-recommended surface water levels for the compound have been determined.
According to a CFPUA news release Tuesday, the utility’s monitoring “has usually shown” 1,4-Dioxane in concentrations below the EPA’s drinking water risk level.
Though CFPUA approved a $107 million bond package to fund infrastructure upgrades, including adding new Granular Activated Carbon(GAC) filters, this investment won’t immediately result in a reduction of 1,4-Dioxane levels.
1,4-Dioxane is removed by CFPUA due to biofilm, which are microorganisms which clings onto compounds. Biofilm builds up over time on CFPUA’s existing filters and can reduce 1,4-Dioxane concentrations at a 67% removal rate, according to a 2015 N.C. State estimation.
According to Vaughn Hagerty, CFPUA’s spokesperson, it will take time for biofilm to grow on newly-replaced GAC filters.
CFPUA’s release on the Sept. 9 results credit to the utility’s existing technology which makes the Sweeney Water Treatment Plant “one of the few water utilities in North Carolina able to significantly reduce 1,4-dioxane in water.”
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