The Martinsville, Virginia Case Study highlights the successful application of Gas Thermal Remediation (GTRTM) to remediate chlorinated volatile organic compounds (VOCs) and BTEX contaminants. The remediation was conducted at a site in Martinsville, targeting a treatment area of 8,796 square feet, extending from the surface to bedrock encountered at different depths within two solvent pits. Specifically, the treatment extended to a depth of 57 feet below ground surface (bgs) in Pit 1 and 30 feet bgs in Pit 2. The subsurface geology primarily consisted of reddish-tan to brown micaceous silty sand and silty clay. Groundwater was encountered at a depth of 80 feet bgs, though it was not part of the treatment scope for this project(Martinsville, Virginia).
The remediation technology used was Thermal Conduction Heating (TCH), which involves the use of heater wells to generate subsurface heat that propagates through soil, groundwater, and contaminant matrices by conduction. A total of 56 heater wells were installed to heat the subsurface soil, with 37 wells in Pit 1 and 19 wells in Pit 2. The target temperature for the site was set to 100°C, and the heating period lasted for 165 days, during which contaminants were volatilized and removed from the treatment area(Martinsville, Virginia).
Remediation Objectives and Approach: The project aimed to reduce the mass of chlorinated VOCs and BTEX in the soil through the use of TCH. The site was equipped with 39 Soil Vapor Extraction (SVE) wells—25 wells in Pit 1 and 14 wells in Pit 2—which were used to remove the vaporized contaminants and steam from the vadose zone. The extracted off-gas was treated using GTR+O burner units, where the pollutant vapors were oxidized to provide supplemental energy for the in-situ heating process. This approach helped utilize waste vapors as a source of energy, thereby increasing the overall efficiency and sustainability of the remediation process. The condensed water and extracted steam were fully treated using cooling systems and granular activated carbon (GAC) to ensure thorough contaminant removal before final disposal(Martinsville, Virginia).
Key Results:
The remediation achieved an average contaminant reduction rate of 96% across the entire site, with each chemical of concern (COC) reduced by more than 80%, thereby meeting the project's remediation goals.
The treatment successfully removed chlorinated VOCs and BTEX from the subsurface, demonstrating the efficacy of using thermal conduction for in-situ remediation of complex contaminants in the vadose zone.
Site Features and Technology:
Heater Wells: A total of 56 TCH wells were used to reach the target depth, ensuring the heat effectively propagated through the contaminants in both pits.
SVE Wells: 39 Soil Vapor Extraction wells were deployed to facilitate the removal of vapor-phase contaminants, contributing to the high removal rate of VOCs.
Supplemental Energy Use: The project utilized GTR+O units to oxidize off-gas, transforming pollutant vapors into supplemental energy that powered the in-situ heating process, thus enhancing energy efficiency.
The Martinsville project serves as a compelling case for the use of thermal conduction heating combined with vapor extraction and oxidization to achieve high rates of contaminant removal. The use of waste vapors as an energy source further highlights the sustainability and innovation embedded in this approach, offering an effective solution for challenging remediation projects involving chlorinated VOCs and BTEX. The success in Martinsville underscores the potential for similar technologies to be applied in other contaminated sites, particularly where energy efficiency and high contaminant reduction are priorities.
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