Recent US Environmental Protection Agency data show that 5 of the 10 highest 1,4-dioxane concentrations in US drinking water occur in communities located in the Cape Fear River watershed of North Carolina. 1,4-Dioxane is a likely human carcinogen, and a one-in-a-million excess cancer risk is associated with the lifetime consumption of drinking water containing 0.35 ug/L. Objectives of this research are to (1) establish the spatial and temporal variability in 1,4-dioxane concentrations and mass flows in the Cape Fear River watershed and (2) assess the effectiveness of water treatment processes for 1,4-dioxane removal. Over 50 sampling points were selected to bracket possible sources, and monthly samples have been taken since October 2014. Samples were analyzed with a new heated purge & trap GC/MS method with which 1,4-dioxane concentrations can be accurately determined in a wide range of water matrices and over a wide range of concentrations. Wastewater discharges from three municipalities are primarily responsible for elevating 1,4-dioxane levels, at times to concentrations exceeding 2,000 ug/L. Plastics and textile industries are possible sources. Apart from monthly stream sampling campaigns, which provide a snapshot in time, daily raw and finished water samples that were composited on an hourly basis were obtained from three drinking water treatment plants. Results for two conventional water treatment plants showed that 1,4-dioxane concentrations were not attenuated. About 65% of the influent 1,4-dioxane was oxidatively transformed in a third utility that employs raw and settled water ozonation. To assess whether point-of-use (POU) treatment devices can help lower 1,4-dioxane exposure, two commercially available pitcher filters and a custom pitcher filter containing a carbonaceous resin were evaluated under both constant and variable 1,4-dioxane concentrations. For the constant 1,4-dioxane concentration scenario, the two commercially available pitcher filters removed 26 and 51% of 1,4-dioxane when a total of 32 gallons of water was processed. In contrast, the custom filter containing the carbonaceous resin removed 78% of 1,4-dioxane under the same conditions. Desorption of 1,4-dioxane occurred when exposing adsorbents in the pitcher filters to low 1,4-dioxane concentrations (~5 ug/L) after a period of treating water with high 1,4-dioxane concentrations (~50 ug/L). Desorption was less pronounced for the carbonaceous resin.

Occurrence of 1,4-dioxane in North Carolina surface water and evaluation of possible treatment options

251st National Meeting (2016)

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