A Mobile Supercritical Water Oxidation Reactor for Destruction of PFAS-Impacted Wastes

Per- and polyfluoroalkyl substances (PFAS) have been used extensively for Department of Navy (DON) firefighting applications due to their thermochemical stability and unique properties. PFAS are long-lived in the environment and coming under increased regulatory scrutiny, presenting DON installations with significant environmental compliance and remediation challenges when undertaking construction, dewatering, soil remediation, or wastewater treatment activities. Typically, the removal of PFAS from water during water treatment or wastewater treatment activities involves the use of solid sorbent materials, including granular activated carbon (GAC) or ion exchange resin (IXR). GAC and IXR each have a useful lifespan during which PFAS can be removed to below regulatory thresholds, after which the materials must be disposed of via landfilling or a destruction method. Long-term liability concerns around landfill and incineration are driving stakeholders to seek out alternative destruction technologies for PFAS-laden GAC and IXR. Supercritical water oxidation (SCWO) is a wet waste treatment process which oxidizes all organic pollutants into benign, non-toxic minerals. SCWO relies on the high-density, high-temperature, free radical environment at supercritical water conditions to facilitate extremely fast destruction reactions, capable of completely destroying PFAS, as evidenced by previous studies performed at the University of Washington (UW). In this project, the existing UW SCWO reactor will be retrofit to accommodate the processing of PFAS-impacted solid material, such as spent GAC and spent IXR. Bench studies will be performed to evaluate the effectiveness of the UW SCWO system for the destruction and defluorination of PFAS in the these matrices, and the assess the operational stability of the SCWO system. Overall, a robust demonstration of SCWO for the final disposal of PFAS-impacted solids will be performed.