Photoactivated reductive defluorination (PRD) is a chemical reaction that can be implemented in existing ultraviolet (UV) water-remediation equipment and is considered an energetically favorable mechanism for per- and polyfluoroalkyl substance (PFAS) destruction in aqueous solutions. The commercial readiness of the technology has been forwarded by testing it with various environmental samples and conducting preliminary cost comparisons with mainstream PFAS capture methods. This study aims to scale-up PRD from laboratory benchtop testing to field-scale application by combining it with available DoD PFAS concentration techniques for a complete PFAS treatment solution from concentration to full destruction.
The scale-up process is established in stepwise phases comprised of benchtop testing for early optimization of reaction variables (Phase I), commercial design reactor testing to determine full-scale UV system configuration parameters (Phase I), and field pilot-test employing existing commercial equipment (Phase II). The overall objective for Phase I is to obtain site-specific design parameters for a field-scale mobile treatment system to be employed in Phase II. This will include selecting the most appropriate concentration techniques for pairing with PRD, assessing energy efficiency, estimating total cost associated with PRD destruction of concentrated PFAS liquid waste being generated at multiple DoD sites, and developing a cost estimate for construction of a mobile treatment system.
The PRD process is based on a chemical reaction that breaks fluorine-carbon bonds and disassembles PFAS molecules in a linear fashion beginning with the hydrophilic functional groups and proceeds through shorter molecules to complete mineralization. Due to the selective trapping effect of a hydrophobic surfactant micelle and the powerful reactivity of hydrated electrons, the defluorination reaction is accelerated and can be robustly conducted in a wide array of pH and redox conditions to destroy PFAS with varying lengths, resulting in complete mineralization with final products of fluoride, water, and simple carbon molecules (e.g., formic acid and acetic acid). The objectives of this study will be achieved via testing on PFAS liquid waste concentrates produced by ongoing treatment systems, such as AFFF, foam fractionate, nanofiltration concentrate, and resin regenerate. For each test, the success criteria will be grounded in metrics related to the technical effectiveness such as reduced PFAS concentrations and fluoride production, and site-specific economic feasibility of reducing PFAS concentrations in water without creating byproducts that are harmful to human health and the environment.
Given that PRD employs existing UV water treatment equipment, the technology can be applied as a cost-effective PFAS destruction approach at sites with concentrated PFAS liquid waste within 1-3 years. When coupled with appropriate PFAS concentration approaches, the technology can also provide a PFAS destruction solution for high flow rate, low PFAS concentration impacted water streams. The cost analysis produced in this effort will inform best opportunities for economical implementation of PRD as a destruction alternative to minimize long-term liability and mitigate lingering risks of PFAS exposure for human health and the environment. (Anticipated Project Completion - 2023)