Nathan Hagelin is a Principal and the Deputy Director of Woods Global Technical Expert Network. He is the remediation technology leader in Wood’s Emerging Contaminants Work Group. He is a Certified Geologist, Licensed Environmental Professional, and Board Certified Environmental Scientist working for 30 years on the remediation of contaminated industrial properties and military installations. He has prior experience as a Hydrologist with the U.S. Geological Survey Water Resource Division.
Optimization of Regenerable Ion-Exchange for PFAS groundwater treatment – Outcomes from two SERDP & ESTCP Projects
INTRODUCTION: Recently, ion exchange resin has developed into a proven groundwater and drinking water remediation technology for PFAS, surpassing granular activated carbon in removal efficiency and cost effectiveness. Full-scale regenerable ion exchange systems are now operational in the US and Australia and performance data are extremely promising. Additional research is ongoing, focused on optimizing the core elements of a treatment train that integrates ion exchange with pre-treatment to improve extraction and treatment efficiency and post-treatment to destroy the concentrated PFAS waste from the regeneration process. A team of researchers from Clarkson University, Texas Tech, Emerging Contaminants Treatment Technology, Wood Environment and Infrastructure Solutions and the US Navy are collaborating on two parallel projects in the SERDP & ESTCP program to optimize and demonstrate the treatment train and provide guidance to future users.
METHODS: Laboratory and field-scale testing is underway. Pre-treatment with several forms of chemical oxidation is evaluated in Texas Tech’s laboratory to transform precursors and improve mobility for efficient capture of PFAS from source zones. Two different regenerable ion exchange resins are tested side by side by Wood/ECT at a former Fire training area. Sixteen different solvent-brine regeneration solutions are tested in ECT’s laboratory. Best performing regeneration solutions are distilled for solvent recovery/reuse and the concentrated PFAS still bottoms are treated at Clarkson in a specialized plasma reactor that destroys PFAS. The results from these trials will be synthesized into an optimized treatment train for a long-term pilot demonstration at the former Pease AFB in New Hampshire.
RESULTS AND DISCUSSION: Results of pre-treatment with chemical oxidation, which at full-scale would be performed in-situ, pre groundwater extraction, have shown higher total PFAS recovery in oxidized samples relative to control. The relative performance of two tested IX resins will be compared, and results to date indicate comparable performance with subtle, compound-specific differences. The regeneration testing reveals that high concentration solvents, greater than 70 percent, and approximately 2 percent salt are required to remove PFAS. One specific blend has resulted in 100 percent PFAS recovery. Early plasma treatment trials indicate 100% destruction of long-chain PFAS from still bottom waste in 120 minutes and overall 76% of total PFAS removal on the basis of TOP analyses. Each of these results will be discussed in detail with additional results available before the EC Summit.
CONCLUSIONS: While successful full-scale application of regenerable ion exchange do exist in the US and Australia, these systems use the same treatment process and media and do not include pre- or post-treatment steps. This research explores opportunities to improve efficiency, optimize the treatment train through comparison of media and regeneration solutions and procedures, and augment with an on-site PFAS destruction module for waste minimization. The outcome of this research will afford easy access to the technology through the users’ manual and knowledge transfer. Regenerable ion exchange coupled with plasma destruction is a valuable technology for PFAS treatment that will gain import as the technology matures and the PFAS challenge evolves into remediation of source zones in a tradition investigation/remediation context.