The overall objective of this project is to construct a skid-mounted pilot scale demonstration unit to demonstrate the effectiveness of the novel thermal steam plasma technology for direct in-line destruction of chemicals and to measure the efficiency of treatment for destruction of per- and polyfluoroalkyl substances (PFAS), products of incomplete destruction, and co-occurring chemicals in gaseous emissions and/or liquid waste from thermal desorption of PFAS-impacted soils. This will be done through an extensive field trial of the skid-mounted plasma treatment unit to evaluate the robustness and operational reliability of the system under field conditions.

Specific project objectives are: 1) construct a skid-mounted 50 kW steam plasma unit for the treatment of thermal soil desorption exhaust at a rate of 100-1000 standard liters per minute; 2) conduct treatment process modelling and validation with the field operational data; and 3) calculate life cycle costs for the plasma steam treatment unit (standalone versus mobile system) and comparison with the carbon bed treatment process.

Thermal steam plasma is an innovative PFAS treatment technology that can atomize PFAS and other compounds in the vapor waste stream. In a typical plasma treatment process for PFAS waste, the destruction process begins with the vaporization of PFAS-impacted liquid as it is injected into the plasma, and the remaining process occurs in gaseous/plasma states. Therefore, the treatment of PFAS-laden gaseous/vapor stream is an innate ability of this technology. For this effort, the project team will integrate the thermal steam plasma emissions treatment system with an existing thermal desorption process by tapping into its primary exhaust line. Recent ESTCP projects (ER20-5250, ER20-5198) applied thermal conduction heating at two sites to liberate residual PFAS from impacted soil stockpiles and in situ vadose zone soils, respectively. In the system, vapor and liquid wastes from the thermal desorption process will be addressed as follows:

• Liquid waste (from the scrubber and condenser) is injected into the steam plasma plume for instant vaporization and breakdown of PFAS.
• Uncondensed gas is pre-heated and mixed with high temperature steam and directed into the steam plasma torch as the carrier gas, where it is ionized due to joule heating and helps to generate the plasma plume. Any volatile chemicals present in the vapor are broken down into its elemental form thus destroying every and all toxins present.

Thermal Steam Plasma

Synergen Met’s Thermal Steam Plasma process is a well-developed technology for the destruction of PFAS and simultaneous mineralization of fluorine atoms. This technology offers a reliable means of managing volatile PFAS emissions generated from thermal destructive technologies including incineration or soil desorption. Without adequately addressing the vapor, use of thermal processes for soils treatment may be limited in the long-term, despite their potential success for PFAS management. The goal is to ensure these thermal destructive technologies remain options in the remedial toolbox for treatment of PFAS so as to develop cost-effective, field-ready solutions that support defending the homeland, establishing deterrence, and ensuring installations remain mission-capable while safeguarding critical defense infrastructure and the workforce. (Anticipated Project Completion - 2027)