This project aims to implement a Steed Series hydrothermal alkaline treatment (HALT) system at a centralized waste disposal facility to demonstrate the treatment of per- and polyfluoroalkyl substance (PFAS)-rich liquids using the HALT process. Several parallel projects are expected to generate PFAS-rich liquids, including foam fractionates and sorbent regeneration brines, which will be transported to the project site for destructive treatment testing. During the three-to-six-month deployment, the HALT system will process several hundred gallons of PFAS-rich liquids. The primary goal of the project is to demonstrate that the HALT system can reduce the levels of total PFAS, perfluorooctanesulfonic acid (PFOS), and perfluorooctanoic acid (PFOA) by over 99%. The project will also encompass a comprehensive analysis of energy and chemical consumption, as well as cost estimates for both capital expenditure (CapEx) and operational expenditure (OpEx). Overall, this project will robustly assess the merits of HALT processing for the final disposal of various waste streams.

HALT is a PFAS destruction process that has shown the capability to effectively destroy, mineralize, and defluorinate all known PFAS based on testing conducted to date. HALT leverages high pressures, elevated temperatures, and a high pH under subcritical water conditions (< 374 °C, ~25 MPa) to drive PFAS destruction within a liquid or aqueous phase. Typically, sodium hydroxide is used to increase the pH, converting a PFAS-rich liquid into a high total dissolved solids (TDS) effluent with over a 99% reduction in PFAS levels.

The applications of HALT encompass the treatment of various substances, including foam fractionates, ion exchange still bottoms, aqueous film-forming foam (AFFF) and AFFF solutions, reverse osmosis reject, and other complex liquid wastes.

HALT is particularly effective at directly treating liquid wastes with high TDS, as most salts remain soluble at subcritical water conditions. This process is capable of effectively destroying a wide range of PFAS, including perfluorosulfonic acids (e.g., PFOS, PFBS, PFHxS), perfluorocarboxylic acids (e.g., PFOA, PFHxA, PFBA, TFA), fluorotelomer sulfonates (e.g., 4,2-FTS, 6,2-FTS), and even unique PFAS substances like Gen-X.

HALT will ensure the comprehensive destruction of all present PFAS while remaining resource and energy efficient. This solution creates an accessible process for remediation, ultimately benefitting the warfighter. 

(Anticipated Project Completion - 2027)