Environmentally stable per- and polyfluorinated substances (PFAS) have posed significant challenges due to their mobility, persistence, and bioaccumulative nature. Legacy aqueous film-forming foam (AFFF), a major source of PFAS, was extensively used for firefighting throughout the United States. Consequently, many sites are dealing simultaneously with chlorinated solvents, 1,4-dioxane, and PFAS, often commingled in groundwater, and not effectively treated by single methods.

There is an urgent need for treatment technologies (or combinations of technologies and treatment trains) to address mixtures of chemicals of concern, including many that are refractory to conventional treatments. Promising destruction technologies have been demonstrated at the bench- and pilot-scale in the field, but the challenge lies in scaling these technologies for more widespread use. Technologies must strike a balance between mobility and modularity while having the capacity to handle field-scale throughputs. Super critical water oxidation (SCWO) is one of the most scalable and proven destruction technology modules available, as demonstrated by successful pilots and demonstrations to date. However, the capital investment associated with a SCWO unit could limit its widespread deployment. As such, this project aims to evaluate the economic and practical efficiency of deploying SCWO units for on-site treatment of various PFAS-containing wastes at hazardous waste treatment, storage, and disposal facilities (TSDF) in regional centralized treatment “hubs.”

The primary objective of this project is to demonstrate the successful operation of a commercial-scale SCWO system on-site at a centrally located TSDF. Following the review of data from the bench-scale testing and any necessary process adjustments, the SCWO system will be mobilized to the selected TSDF to treat bulk volumes of predetermined test matrices. The technical focus will be on successfully destroying PFAS found in waste concentrates (e.g., membrane reject, foam fractionate concentrate, ion exchange regenerant still bottoms, and AFFF concentrates). Samples of pre-treatment system influent and post-treatment system effluent will be regularly collected to analyze PFAS levels and other analytes of interest. PFAS destruction success will be determined by performing a fluorine mass balance using laboratory analytical data to assess whether complete mineralization of organic fluorine to inorganic fluoride was achieved. Utility and consumable requirements, operating parameters, and associated cost information will be measured to assess the cost effectiveness of the approach.

Dealing with PFAS wastes has become a substantial focal point throughout the United States. SCWO has demonstrated excellent treatment efficacy for a wide variety of waste types and characteristics. This project will assess the economic and practical viability of a regional hub treatment model, which aims to increase the availability of the technology by reducing the barriers to wider use currently associated with the high costs of deploying separate SCWO systems to individual installations. (Anticipated Project Completion - 2025)