The overall objective of this project is to demonstrate the use of an injectable liquid fuel that supports in situ smoldering combustion that causes the destruction and volatilization of per- and polyfluoroalkyl substances (PFAS) and co-occurring chemicals from source areas.
Smoldering is a combustion process that occurs on the surface of a condensed (i.e., solid or liquid‐phase) fuel, converting organic material into primarily heat, carbon dioxide, and water. Commercially available smoldering remediation normally relies on the chemicals themselves to be the fuel that supports the combustion process above and below the water table or in above ground treatment systems. Although PFAS can be present at significant concentrations relative to clean up criteria, they are often still too low to support smoldering. Work conducted under SERDP has shown that adding a surrogate fuel, such as granular activated carbon at low concentrations can support smoldering and generate high temperatures that can decompose PFAS. Other laboratory studies have demonstrated that liquid fuels like emulsified vegetable oils can support smoldering, but do not generate sufficient heat to destroy PFAS. This project will demonstrate that emulsified vegetable oil mixed with low amounts of colloidal or powered activated carbon alone can be successfully distributed through the source zone below the water table, and smoldered to treat PFAS source areas in situ.
In situ smoldering is an innovative in situ technology that can significantly reduce PFAS liability cost-effectively. Application of the technology in PFAS source zones will result in significant mass removal/destruction resulting in reduced source zone mass discharges to plumes and downgradient receptors and has the potential to achieve current soil cleanup guidelines. (Anticipated Project Completion - 2024)