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Supercritical water oxidation as an innovative technology for PFAS destruction
Citation:
Krause, M., E. Thoma, E. Sahle-Demessie, B. Crone, A. Whitehill, E. Shields, AND B. Gullett. Supercritical water oxidation as an innovative technology for PFAS destruction. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 148(2):NA, (2022). https://doi.org/10.1061/(ASCE)EE.1943-7870.0001957
Impact/Purpose:
Per- and polyfluoroalkyl substances (PFAS) are class of persistent pollutants found in many consumer products and fire-fighting foams. Fire-fighting foams, technically called aqueous film-forming foams (AFFF), have the highest concentrations of PFAS of any material and are a potential source of PFAS pollution to the environment and to people. For this reason, states have begun to ban the use of certain PFAS-containing AFFF and stockpiles of the material now need to be disposed of in a manner that is protective of human health and the environment. Supercritical water oxidation (SCWO) is an existing technology that relies on heating and pressurizing water to destroy hazardous chemicals. Three purveyors of SCWO systems were employed to identify if SCWO could be an innovative technology to destroy PFAS. All three systems showed positive results, as indicated by the targeted analysis of influent and effluent streams. Although more comprehensive analyses of SCWO systems are required, these preliminary findings suggest SCWO may be an acceptable alternative to incineration for PFAS-laden wastes. The results of may be of interest to federal and state regulators, municipalities, and the general public.
Description:
At temperatures above 374 °C and pressures above 22.1 MPa, water is considered supercritical, a special state where organic solubility increases and oxidation processes are accelerated. Supercritical water oxidation (SCWO) has been previously shown to destroy hazardous substances such as halogenated compounds. Three separate purveyors of SCWO technology were employed to test the efficacy of SCWO systems to reduce per- and poly-fluoroalkyl substances (PFAS) concentrations from solutions of dilute aqueous film-forming foam (AFFF). The findings of all three experiments showed a greater than 99% reduction of the PFAS compounds identified in a targeted analysis at the bench- and pilot-scales. In one experiment, a mass balance of fluorine and fluoride in the influent and effluent suggested that the targeted analysis accounted for only 27% of the generated fluoride, emphasizing the limitations of targeted analysis alone. As a destructive technology, SCWO may be an alternative to incineration and could be a permanent solution for high-concentration PFAS wastewaters rather than disposal by injection into a deep-well or landfilling. But additional investigation of reaction by-products remains to be conducted for a complete assessment of SCWO’s potential as a safe and effective PFAS treatment technology.
URLs/Downloads:
DOI: Supercritical water oxidation as an innovative technology for PFAS destruction
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