Formatted Title
Per- and Polyfluoroalkyl Substances Field Pilot Study at Operable Unit 1, Hill Air Force Base, Utah
Background/Objectives
Hill Air Force Base (AFB) is located in northern Utah, approximately 30 miles north of Salt Lake City and 7 miles south of Ogden and has been the site of military activities since 1920, including distribution of military equipment, aircraft rehabilitation and maintenance, and missile assembly. In 1970, the U.S. Air Force (USAF) began using aqueous film forming foam (AFFF), firefighting agents containing per- and polyfluoroalkyl substances (PFAS), to extinguish petroleum fires. Releases of AFFF to the environment routinely occurred during fire training and equipment maintenance, storage, and use. In December 2020, effluent samples were collected at the discharge locations of Operable Unit (OU) 1 and OU 8 and perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) combined concentrations were found to exceed the 70 nanograms per liter (ng/L) limit set by USAF policy at the time. As a result, a field pilot study was performed to evaluate and compare the implementability and feasibility of two PFAS destructive treatment technologies at the groundwater extraction systems at OU 1 and OU 8. The specific objectives of the field pilot study were to identify an implementable, effective, cost-efficient destructive remedial technology for PFAS in effluent at OU 1 that can 1) reduce concentrations of PFAS in the effluent to levels below the United States Environmental Protection Agency (USEPA) regional screening levels (RSLs), 2) continue to meet the requirements stipulated in the publicly owned treatment works (POTW) discharge permit, 3) be implemented in conjunction with the current remedial action, and 4) operate as designed with no adverse impacts on site-specific chemicals of concern (COCs) and effluent water quality.
Approach/Activities
Bench-scale testing first was performed to evaluate the efficacy of each technology to treat the OU 1 water. The field pilot study was then implemented using a reverse osmosis (RO) pre-treatment unit to concentrate PFAS from the OU 1 effluent and decrease necessary volume/flow for treatment by the destructive treatment technologies selected. The clean RO effluent was discharged to the POTW; then the concentrated RO effluent was treated in a side-by-side fashion with two PFAS destructive treatment technologies, super critical water oxidation (SWCO) using Revive’s PFAS Annihilator™ Mobile 2 system and electrical discharge plasma using DMAX Plasma’s Enhanced contact plasma reactors (ECo-PRe™) to evaluate and compare their effectiveness and implementability in the field using the same OU 1 effluent. Analytical and physical data were collected at key locations within the field pilot study treatment system processes during implementation. These data consist of those that are required for (1) ensuring no impacts to existing remedial action operations, (2) evaluation of PFAS treatment/destruction effectiveness and efficiency, and (3) operational parameters to ensure the treatment technologies are operating optimally and as designed.
Results/Lessons Learned
Bench-scale testing of raw OU 1 effluent performed prior to the field pilot study indicated favorable results for both treatment technologies. The results of the pilot study were used to evaluate full-scale implementability and feasibility at OU 1 and OU 8 using baseline water quality and PFAS analytical data collected and site-specific inputs such as average groundwater extraction flow rate, POTW discharge limits, and existing infrastructure. An overview of the two technologies and results from this field campaigns will be discussed in this presentation.