Validation of supercritical water oxidation to destroy perfluoroalkyl acids

Abstract

Some of the same unique physical and chemical properties that make per‐ and polyfluoroalkyl substances (PFAS) desirable for a wide range of commercial applications render them recalcitrant to many liquid treatment technologies. As developments in PFAS‐related toxicological studies increasingly suggest potential adverse human health effects, our industry has made great progress in the past several years on concentrating PFAS into small volume waste streams via adsorption and separation mechanisms. Coupled with residual PFAS‐containing commercial products that are being phased out, management of these concentrated waste streams presents an urgent need for the development and validation of destructive treatment technologies. Here, we field‐validate supercritical water oxidation to treat a concentrated waste stream of 12 perfluoroalkyl acids (PFAAs) with liquid and gaseous analysis, adhering to the recent Other Test Method 45 for stack emission sampling from the United States Environmental Protection Agency (USEPA) and USEPA Method 537.1, with quality control and quality assurance protocols from the Department of Defense/Department of Energy Quality Systems Manual 5.3. Results generated suggest greater than 99.999% destruction and removal efficiency of these 12 PFAAs after two ∼120‐min continuous flow trials, with an overall defluorination percentage of approximately 62.6%.

Sonolysis and Super Critical Water Oxidation (SCWO): Development Maturity and Potential for Destroying PFAS

“…Where $$$ {P}_d $$$ is the power density power (kW/L), t is time (h), C i is the initial PFAS concentration (mg/L) and, C f is the final PFAS concentration (mg/L). For SCWO, $$$ {\mathrm{E}}_{\mathrm{E}\mathrm{M}} $$$ (Equation ) is estimated based on the fuel's high heating value (HHV; MJ/kg) which assumes complete combustion of the fuel used to generate super critical conditions, and the density of the fuel (D; kilograms per liter, kg/L) (McDonough et al 2022). $$$$ {\mathrm{E}}_{\mathrm{E}\mathrm{M}}=\frac{HHV\times \mathrm{D}\times 0.28\times {10}^3}{\left({\mathrm{C}}_{\mathrm{i}}‐{\mathrm{C}}_{\mathrm{f}}\right)}\left(\mathrm{kWh}/\mathrm{g}\right) $$$$…”

“…Moreover, the treatment systems being developed and tested in the field treat high PFAS load mixtures like AFFF and AFFF‐impacted water. Therefore, E EM has a strong case when comparing energy consumption among high‐concentration PFAS treatment technologies, including destructive and non‐destructive treatment (Kalra et al 2021; McDonough et al 2022). The energy consumed during the acoustic treatment of AFFF impacted groundwater was measured as 28.01 ± 0.47 kWh or approximately 3.5 kW per hour of treatment, among all conditions tested (Kalra 2021; Kulkarni et al 2022).…”

“…Where P d is the power density power (kW/L), t is time (h), C i is the initial PFAS concentration (mg/L) and, C f is the final PFAS concentration (mg/L). For SCWO, E EM (Equation 3) is estimated based on the fuel's high heating value (HHV; MJ/kg) which assumes complete combustion of the fuel used to generate super critical conditions, and the density of the fuel (D; kilograms per liter, kg/L) (McDonough et al 2022).…”

The dirty side of clean energy: Lithium ion batteries as a source of PFAS in the environment

“…Additionally results suggest that bis-FMeSI will not be effectively treated by routine oxidation approaches, similar to other PFAS. To achieve compound destruction, it will be necessary to evaluate high-energy treatment approaches such as supercritical water oxidation 41 or electrochemical techniques 42 for applicability to bis-FASIs. Lastly, as further described in the supplementary text, these results have implications for routine PFAS analytical approaches that rely on oxidative conversion of PFAS.…”

EPA's detection methods, the drinking water treatability database, and innovative technologies for PFAS remediation

“…In addition to the PFAS Experts Symposium 2, several articles on innovative PFAS treatment technologies were published in Remediation . These technologies include supercritical water oxidation (SCWO) to treat wastewater contaminated with several PFAS (McDonough et al, 2022) and the application of colloidal gas aphrons (CGAs), structures containing water, surfactants, and air, to concentrate PFAS (Kulkarni et al, 2022).…”