In the past, 1,4-dioxane was widely used as a solvent stabilizer, and it is commonly thought of as a groundwater contaminant that co-occurs with chlorinated solvents. While 1,4-dioxane usage in the context of solvent stabilization has been phased out, 1,4-dioxane continues to be used as an industrial solvent (e.g. textile industry, paper industry, production of brominated flame retardants), and it is a by-product of manufacturing processes involving ethylene oxide (e.g. production of surfactants used in laundry detergents and shampoos, production of certain plastics). In a recent EPA study, data for North Carolina showed that all 1,4-dioxane detections occurred in drinking water derived from surface water. In fact, the four highest 1,4-dioxane concentrations shown for NC systems also represent the four highest reported values nationally. The highest 1,4-dioxane concentration was reported in drinking water sampled in Moore County at the East Moore Water District (EMWD) Intertie (9.2 ìg/L). Water at the EMWD intertie represents water purchased from Harnett County Regional Water Treatment Plant (Lillington, NC), which treats Cape Fear River water. Furthermore, data collected in our laboratory show that 1,4-dioxane is present at concentrations of up to about 90 ìg/L in the Haw River, and in drinking water derived from the Haw River at concentrations of up to 80 ìg/L (Pittsboro, NC).
The objectives of the proposed research are to (1) identify 1,4-dioxane sources, (2) establish the spatial and temporal variability in 1,4-dioxane concentrations and mass flows, (3) assess 1,4-dioxane removal by existing point-of-use (POU) treatment devices and identify adsorbent properties that govern 1,4-dioxane removal, and (4) develop fundamental process parameters that describe the oxidative transformation of 1,4-dioxane by O3/H2O2, UV/H2O2, and UV/chlorine advanced oxidation processes in a surface water treatment context. To accomplish the proposed results, stream samples and daily composited samples from drinking water providers will be collected and analyzed by gas chromatography-mass spectrometry (GC-MS). In conjunction with USGS daily stream flow data, the resulting 1,4-dioxane concentration and mass flow results will be used to identify 1,4-dioxane sources, estimate the quantity of 1,4-dioxane released into the environment, and estimate human exposure to 1,4-dioxane via drinking water consumption.
