CFPUA has asked the North Carolina Department of Environmental Quality for guidance after detecting elevated levels of 1,4-dioxane in raw water from the Cape Fear River for the fourth time this year.
CFPUA periodically tests raw water for 1,4-dioxane, which is used in industrial solvents and for several years has been detected in the Cape Fear and other North Carolina surface waters.
The Sweeney Water Treatment Plant, which treats water from the Cape Fear, is equipped with ozone and biologically active filters. These technologies make Sweeney one of the few water utilities in North Carolina able to significantly reduce 1,4-dioxane in water. Sweeney typically sees removal rates for 1,4-dioxane of about 67 percent.
The latest test results showed concentrations of 1,4-dioxane of 6.3 parts per billion (ppb) in raw (untreated) water on September 9 and 1.3 ppb in finished (treated) water at Sweeney on September 10. Other elevated levels detected this year include:
- 2.2 ppb in raw water on July 1 and 0.54 ppb in finished water on July 2.
- 1.5 ppb in raw water on June 3 and 0.35 ppb in finished water June 4.
- 1.8 ppb in raw water on February 13 and 0.54 ppb in finished water on February 14.
These results and others are posted on CFPUA’s website.
No federal maximum contaminant level has been established for 1,4-dioxane. A risk assessment by the U.S. Environmental Protection Agency has indicated that a concentration of 0.35 ppb in drinking water consumed daily over a lifetime would be expected to cause no more than one additional case of cancer in 1 million people. CFPUA’s monitoring has usually shown 1,4-dioxane concentrations below this level in finished drinking water.
A number of factors may affect concentrations of 1,4-dioxane in the Cape Fear, including river flows. Regardless, the most effective way to address the issue remains controlling discharges at their sources.