Per‐ and polyfluoroalkyl substances (PFAS) are highly resistant to biotic and abiotic degradation and can withstand very high temperatures before breaking down. The storage of PFAS‐impacted water and sediments in a holding pond or stockpiled investigation or remedial action‐derived waste is occurring on an increasing number of sites. The most common PFAS water treatment options include granular‐activated carbon and resins and the most common soil treatment options have been primarily limited to excavation, offsite incineration, and, in some cases, soil stabilization. An increasing number of states across the United States are establishing part per trillion PFAS guidance levels for drinking water. Removing PFAS from soils removes PFAS source impacts to groundwater. In this study, volatilization of PFAS from soil treated using in situ thermal heating is evaluated as a treatment method to achieve a high degree of PFAS removal from soils. The evaluation of temperatures needed to achieve removal is described. To minimize vapor treatment required for PFAS thermal remediation, a scrubber was incorporated into the treatment train to transfer PFAS to the liquid phase in a concentrated, low‐volume solution. Vapor‐liquid equilibrium behavior and the extent of PFAS volatilization from impacted soil over a range of temperatures were evaluated. Results showed that heating soil to 350°C and 400°C reduces PFAS soil concentrations by 99.91% and 99.998%, respectively. It was also confirmed that sulfonate‐based PFAS generally required higher temperatures for volatilization to occur than carboxylate‐based PFAS.

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.

Electrical resistance heating (ERH) has become a common method of remediation for volatile or-ganic compounds (VOCs) ELECTRICAL RESISTANCE HEATING PROCESSElectrical resistance heating (ERH) passes an electrical current through the soil, rock, and groundwater that requires treatment. The principal current path is the thin layer of water immediately adjacent to the soil or rock grains-relatively little current is carried by the water in the soil pores. The electrical current warms the subsurface and then boils a portion of the in situ moisture into steam. This in situ steam generation occurs in all soil types, regardless of permeability. Sedimentary rocks have significant primary porosity, and the rock grains generally have the thin film of water required for electrical conductivity.The subsurface electrical energy evaporates the target contaminant and provides steam as a carrier gas to sweep volatile organic compounds (VOCs) to the vapor-recovery wells. After the steam is condensed and the extracted air is cooled to ambient conditions, the VOC vapor is treated using conventional methods.The type of contaminant and the desired cleanup goal affect the energy, time, and cost to remediate a site. However, two subsurface parameters are particularly important: the amount of total organic carbon (TOC) and the presence of heavy hydrocarbons such as diesel, oil, or grease. TOC preferentially adsorbs VOCs in comparison to water; VOCs bond to TOC through van der Waals forces. This van der Waals bonding explains why activated carbon is often used for vapor and water treatment.The presence of oil, grease, or other low-volatility hydrocarbons can also slow the evaporation rate of VOCs. Raoult's Law describes this effect. Dalton's Law of Partial PressuresThe boiling point of some VOCs, such as perchloroethene (PCE), is above the boiling point of water (100• C) at sea-level pressure conditions. It should be noted that when a