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Posted on: July 31, 2019

CFPUA notes second increase this year in 1,4-dioxane levels

pouring a sample from a bottle to tube

CFPUA is consulting with the North Carolina Department of Environmental Quality regarding a recent increase in levels of 1,4-dioxane detected in raw water from the Cape Fear River.

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. Its presence in the Cape Fear River results from upstream discharges.

The Sweeney Water Treatment Plant, which treats water from the Cape Fear River, is one of the few water utilities in North Carolina equipped to significantly reduce 1,4-dioxane in water. This results from past investments in ozone and granular activated carbon filters operated in biological mode, technologies that typically result in average removal rates for 1,4-dioxane of 67 percent.

The latest results, which became available this week, showed concentrations of 1,4-dioxane of 2.2 parts per billion (ppb) in raw (untreated) water on July 1 and 0.54 ppb in finished (treated) water at Sweeney on July 2. The concentration of 1,4-dioxane detected in raw water is the highest detected at Sweeney since 2015.

This is the second time this year that CFPUA has detected a rise in 1,4-dioxane levels in the Cape Fear. In March we reported concentrations 1.8 ppb in raw water on February 13 and 0.54 ppb in finished water treated at Sweeney on February 14.

These results and others are posted on CFPUA’s website. CFPUA has shared these results with its regulatory partners at NCDEQ.

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 parts per billion in drinking water consumed over a lifetime would be expected to cause no more than one additional case of cancer in 1 million people.

It should be noted that these results are insufficient to indicate a trend. Over the last few years, 1,4-dioxane levels in finished water have routinely been below the EPA assessment level.

Importantly, CFPUA and the community it serves is affected by the actions of dischargers upriver: Higher levels of 1,4-dioxane resulting from upriver discharges will affect the levels in finished water.

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