Supercritical Water Oxidation as an Innovative Technology for PFAS Destruction
Publication: Journal of Environmental Engineering
Volume 148, Issue 2
Abstract
Water above 374°C and 22.1 MPa becomes 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 providers of SCWO technology were contracted 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 demonstration studies showed a greater than 99% reduction of the total PFAS identified in a targeted compound analysis, including perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). PFOS was reduced from to , to , and to , from the Aquarden, Battelle, and 374Water demonstrations, respectively. Similarly, PFOA was reduced from 930 to , 883 to , and to nondetect in the three evaluations. Additionally, the chemical oxygen demand of the dilute AFFF was shown to reduce from 4,750 to after treatment, indicating significant organic compound destruction. In one demonstration, a mass balance of the influent and effluent found that the targeted compounds accounted for only 27% of the generated fluoride, suggesting that more PFAS were destroyed than measured and 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 PFAS-laden wastewaters rather than disposal by injection into a deep well or landfilling. Additional investigation of reaction byproducts remains to be conducted for a complete assessment of SCWO’s potential as a safe and effective PFAS treatment technology.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published article.
Acknowledgments
The authors wish to thank Aquarden, Battelle, and 374Water for conducting these experiments at the direction of EPA’s Office of Research & Development PFAS Innovative Treatment Team. The authors thank Matthew Magnuson of EPA for supplying the AFFF used in the Battelle experiments. The authors thank the Naval Research Laboratory for supplying the AFFF used in the 374Water experiment.
Disclaimer
The authors declare no competing financial interest. The views expressed in this article are those of the authors and do not necessarily represent the views or policies of the US EPA. Any mention of trade names, products, or services does not imply an endorsement by the US Government or the US EPA. The EPA does not endorse any commercial products, services, or enterprises.
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Published In
Journal of Environmental Engineering
Volume 148 • Issue 2 • February 2022
Copyright
© 2021 Published by American Society of Civil Engineers.
History
Received: Jul 6, 2021
Accepted: Sep 18, 2021
Published online: Nov 23, 2021
Published in print: Feb 1, 2022
Discussion open until: Apr 23, 2022
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