A Thermal Desorption Solution for PFAS in Soils
Solutions to per- and poly fluoroalkyl Substances (PFAS), a group of toxins commonly known as "Forever Chemicals," are widely discussed. Among them, thermal desorption is a leading process that shows promise in its effectiveness to treat contaminated soil.
Scientists at Clean Earth are focusing on research, development, and demonstration (RD&D) projects using current technology called thermal desorption as a viable process to remove PFAS from soils. Thermal desorption is not a new process, but its application to PFAS could be game-changing. The technology relies on understanding the PFAS chemical's boiling points and applying that knowledge to desorb and destroy the toxins in the soil.
In the thermal desorption process, contaminants are separated from soil by heating the material to near or above the contaminant's boiling point. This results in a process air stream containing the desorbed contaminants which have been thermally reduced by a thermal oxidizer.
The thermal treatment process is reproducible and predictable due to its direct dependence on the boiling point of the contaminant. PFAS are good candidates for this approach because their boiling points are generally below 500°F, far lower than many of the recalcitrant contaminants in matrixes, such as coal tar, for example.
This technology has been used effectively and safely by Clean Earth since 1992 to recycle a variety of organic contaminants.
Initial testing to examine the effectiveness of thermal desorption on PFAS happened under the direction of the New York State Department of Environmental Conservation (NYSDEC). Research was performed on approximately 22 tons of contaminated soil at Clean Earth's Fort Edward, New York facility in December 2018 and February 2019.
Based on measurements of specific compounds before and after treatment, the thermal desorption approach successfully eliminated greater than 99% of PFOS and PFOA from the soil when measured by total mass concentration and synthetic precipitation leaching procedure (SPLP) analysis. The other PFAS compounds analyzed for and detected were removed to below detectable limits from the soil samples analyzed.
With the encouraging results of this preliminary thermal desorption treatment of PFAS-contaminated soil, Clean Earth is continuing work with state agencies to establish criteria to demonstrate the process's efficiency and optimize the treatment process.
Clean Earth will continue to work with state agencies to further its knowledge of the technology’s efficiency in treating PFAS contaminated soil.
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