In Situ Remediation of 1,4‐Dioxane Using Electrical Resistance Heating

Abstract

Recent regulatory changes need more challenging treatment goals for 1,4-dioxane. However, significant treatment limitations exist in part due to the high solubility and low Henry's law constant of 1,4-dioxane. Two case studies are reported with substantial 1,4-dioxane concentration reductions through in situ thermal remediation via electrical resistance heating (ERH). Concentration reductions greater than 99.8 percent of 1,4-dioxane have been observed in the field using ERH. Concentrations of 1,4-dioxane in air and steam extracted by an ERH vapor recovery system have also been evaluated. Laboratory studies were conducted to further understand the mechanisms that enable ERH remediation of 1,4-dioxane. Vapor liquid equilibrium studies in water and soil were conducted and utilized to develop an ERH treatment cost model for 1,4-dioxane. Existing field data were correlated to the 1,4-dioxane treatment cost model. Field observations and laboratory testing indicate steam stripping that occurs through ERH remediation is an effective treatment method for 1,4-dioxane. c⃝ 2015 Wiley Periodicals, Inc.

Editor's Perspective—Developments in 1,4‐Dioxane Investigation and Remediation Techniques

“…Electrical resistance heating was particularly successful on a pilot‐scale basis (as reported in Remediation previously by Oberle et al. []). An innovative aerobic fixed film biological treatment system is being used to treat groundwater/landfill leachate containing 1,4‐dioxane, tetrahydrofuran, and other constituents (see Cordone et al.). The 1,4‐dioxane appears to be biotransformed through a co‐metabolic pathway in the presence of tetrahydrofuran.…”

1,4‐Dioxane Treatment Technologies

“…However, a DX solution in water has an azeotropic decrease in boiling point to a minimum of 87.7 °C. There is also a 50‐fold increase in Henry's Law Constant between the standard testing temperature of 25 °C and the boiling point of water (Oberle et al., ), which results in substantially higher concentrations in the steam off‐gas than the solution. These characteristics allows for removal of DX from water at elevated temperatures, but less than the boiling point of water.…”

“…Subsequent treatability testing by Oberle et al. () used a high concentration (1,000 mg/L) DX spiked sample of distilled water that was heated slowly and both the water and the released condensate were sampled at regular intervals as the water was brought to a boil. Spiked soil samples were heated until 20 percent, 45 percent, and 80 percent of available moisture was boiled off, and then the treated soil was analyzed using the EPA Method 8260B SIM.…”

“…Based on these testing results, Oberle et al. () estimate that the cost of thermal treatment of DX will range from $150 to $300 per cubic yard.…”

“…The boiling point of DX at 101.320 • C (Smith & Wojciechowski, 1937) is close to but slightly higher than the boiling point of water, which taken at face value suggests all the water would need to be boiled away before the DX would be removed. However, a DX solution in water has an azeotropic decrease in boiling point to a minimum of 87.7 • C. There is also a 50-fold increase in Henry's Law Constant between the standard testing temperature of 25 • C and the boiling point of water (Oberle et al, 2015), which results in substantially higher concentrations in the steam off-gas than the solution. These characteristics allows for removal of DX from water at elevated temperatures, but less than the boiling point of water.…”