View of a UV Sulfite-Based PFAS Treatment Mobile Unit

The overall objective of this project is to demonstrate a cost-effective and sustainable chemical reductive technology for the on-site destructive treatment of per- and polyfluoroalkyl substances (PFAS) in a concentrated waste stream. The technology can also degrade co-occurring chemicals such as chlorinated volatile organic compounds. The technology is primarily based on hydrated electrons generated in an ultraviolet (UV)/sulfite system. Specific objectives are to:

1. Demonstrate the effectiveness of the technology for destroying concentrated PFAS waste streams under field conditions;
2. Design and construct a mobile, on-site treatment unit that can be used to treat concentrated PFAS waste streams at different locations or multiple sites; and
3. Evaluate the cost-effectiveness of the technology compared to other options such as thermal treatment and disposal at a landfill.

The hydrated electron is one of the most reactive species, with a standard reduction potential of about −2.9 volts. It has demonstrated excellent performance in cleaving carbonfluoride (C−F) bonds and has been shown to be effective in degrading (e.g., defluorinating) PFAS compounds. Hydrated electron in a UV/sulfite system offers unparalleled advantages for PFAS destruction when compared to other technologies, including:

• Deep Defluorination Rate: Near 100% defluorination can be achieved for perfluorinated carboxylic acids (PFCAs), perfluoroalkane sulfonates, and fluorotelomer acids in various chain lengths by UV/sulfite combined with post-treatment with advanced oxidation.
• High Efficiency for Short-Chain PFAS: While the degradation efficiency for short-chain PFAS is challenging for technologies that rely on the aggregation of PFAS at the water-air or water-solid interface, the solution-phase UV/sulfite system has demonstrated excellent defluorination efficiency for both short- and long-chain PFAS.
• Selective Reactivity: Unlike many oxidative technologies, hydrated electrons do not react with hydrocarbon compounds present in PFAS waste streams such as organic surfactants in aqueous film-forming foam, thus preserving their reactivity for PFAS defluorination.
• Low Energy Consumption: The electrical energy per order values for degrading PFCAs by UV/sulfite is orders of magnitude lower than that for competing destruction technologies.
• No Harmful Byproducts: The UV/sulfite system is a reductive process and does not generate toxic byproducts such as perchlorate, chlorate, and bromate.

PFAS represent a liability with growing urgency for the Department of Defense (DoD), as there are more than one thousand military installations that require investigation and remediation. A recent report prepared by the Congressional Budget Office estimated it will cost DoD billions of dollars to address this PFAS liability. This project will demonstrate an innovative destructive technology for PFAS in concentrated waste streams that may be generated from groundwater treatment processes, foam delivery system cleaning, or investigation-derived waste. This technology will offer an on-site treatment technology, thereby reducing or avoiding expensive off-site thermal incineration or disposal at a landfill. The technology can be potentially applied to thousands of DoD installations where PFAS waste streams are generated, achieving significant cost savings for the DoD. (Anticipated Project Completion - 2024)

Yu, X-Y., C. Yang, J. Gao, Z.J. Xiong, X. Siu, L. Zhong, Y. Zhang, and J. Son. 2023. Molecular Detection of Per- and Polyfluoroalkyl Substances in Water Using Time-of-flight Secondary Ion Mass Spectrometry. Frontier in Chemistry, 11:1253685. doi.org/10.3389/fchem.2023.1253685.