The goal of this project is to further examine the effectiveness of the of ex situ thermal desorption (TD) coupled with thermal oxidation (TO) to treat solid investigation derived waste (IDW), including impacted with per- and polyfluoroalkyl substances (PFAS). The overall objective of this project is to refine and scale up the optimal TD/TO operating parameters identified from the pilot-scale for treatment of actual PFAS-impacted soils from a Department of Defense (DoD) site using either a direct fired thermal desorption (DTD) unit coupled with TO or an ITD unit coupled with TO.
This project consists of an on-site full-scale TD/TO demonstration test to treat impacted soils from a release area of aqueous film-forming foam (AFFF) at Joint Base Cape Cod (JBCC), MA. Specific aims include:
- validation of proof-of–concept findings of thermal desorption effectiveness,
- examination of scale-up of optimal operating parameters, and
- assessment of and compliance with air permitting requirements.
Both DTD and ITD will be considered as options for testing, with ultimate selection based on availability of equipment, treatment throughput rates, air permitting considerations, and cost limitations. When used for TD, DTD and ITD are not considered incineration technologies. Rather, they employ physical processes that separate (by desorption) the contaminants from the medium to an off-gas stream, where vapors are treated directly or condensed. Potential options for off-gas treatment include TO, adsorption, condensation, and chemical neutralization. Based on the prior SERDP work, TO is the most viable option for complete PFAS destruction and, therefore, the best available control technology for TD off-gas treatment. Regulatory permitting of the TD unit is governed by standards for efficient, reliable, and safe separation of the contaminants from the soil. In a preliminary review, Massachusetts Department of Environmental Protection permitting requirements for air quality plan approval for this project are not considered onerous, especially considering the proposal to conduct a comprehensive performance demonstration with a stack test. The project team fully expects TO emissions for this short-term demonstration to be lower than regulatory thresholds, qualifying the system as a non-major source. Furthermore, TD/TO was permitted smoothly, at JBCC in 2003-2004 for thermal TD treatment of soils for emerging contaminants.
TD/TO is conveniently mobile, scalable, can be implemented onsite, occupies a small footprint, allows for beneficial reuse of treated media and, depending on volume of soil IDW and other logistical considerations, can be implemented at significantly lower cost than conventional off-site incineration or landfill disposal options. Moreover, TD/TO is a proven treatment technology for traditional organic chemicals co-located with AFFF. TD/TO is viable for treatment of the growing problem of accumulating volumes of soil IDW from remedial investigations as well as soil incidentally encountered during other military deconstruction, construction, and utility-related activities.