This presentation will report on recent results from our team by applying hydrothermal alkaline treatment (HALT) to destroy per- and polyfluoroalkyl substances (PFASs) in foam concentrates from foam fractionation (FF) applied to remediate groundwater impacted by the historical use of aqueous film-forming foam (AFFF) and compared their degradation results with previously reported AFFF sample. Results showed that all PFASs identified in foam concentrates, including cationic, anionic, and zwitterionic PFASs, were degraded below analytical detection limits when certain HALT conditions were applied. The foam concentrate matrix, including elevated dissolved organic carbon (DOC), did not significantly affect reaction kinetics for the most recalcitrant PFAS class, perfluoroalkyl sulfonates, compared to other aqueous matrices. In addition, the transformation of DOC during HALT was tracked with proton nuclear magnetic resonance (<sup>1</sup>H-NMR) and high-resolution orbitrap mass spectrometry. The degradable and recalcitrant DOC structures during HALT were characterized. In addition, energy requirements for an integrated process coupling FF with HALT were estimated, and the implication for site remediation was discussed.

Application of hydrothermal alkaline treatment (HALT) for destruction of PFASs in foam fractionation concentrate derived from contaminated groundwater

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