The objective of this proof-of-concept project is to demonstrate a novel synergistic platform for efficient defluorination of per- and polyfluoroalkyl substances (PFAS), mostly perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS), and to explore strategies to optimize the catalytic-biological synergy. The concept begins with a H₂-based membrane precious-metal-film reactor (H₂-MPfR) to reductively defluorinate PFOA and PFOS to less-fluorinated octanoic and octanesulfonic acids. These less-fluorinated compounds are then oxidatively defluorinated and mineralized by microorganisms in a O₂-based membrane biofilm reactor (O₂-MBfR). Although the effort is strongly application-driven, it also will contribute to understanding of the fundamental factors controlling reductive and oxidative defluorination of PFOA and PFOS, processes that occur in groundwater and wastewater treatment settings. In addition, results of this research will provide scientific guidance to research that extends to treating other perfluoralkyl acids (PFAAs).

Bench-scale experiments will be conducted to maximize PFOA and PFOS removal via reductive defluorination in the H₂-MPfR and the cometabolism of partially fluorinated octanoic and octanesulfonic acids via oxidative defluorination and mineralization in the O₂-MBfR. The experiments will focus on strategies to optimize the efficiency and selectivity of PFOA/PFOS defluorination in the H₂-MPfR and to stimulate the growth of PFAA-degrading bacteria. The best strategies will be revealed by exploring changes in the catalyst characteristics in H₂-MPfR and the microbial community structure in the O₂-MBfR. A cost analysis will be conducted to provide data for end users to consider this novel synergistic platform. The experimental and cost data can then be used to guide pilot-scale or field-scale study in a next step.

This synergistic platform is for ex situ treatment, but the principles can be adapted for synergistic in situ treatment of groundwater contaminated by PFAAs, of which the degradation product could be less- or non-fluorinated counterparts. This project also will contribute to understanding of the fundamental factors controlling cometabolic biodegradation of fluoroalkyl compounds, processes that occur during in situ and ex situ groundwater treatment settings.

Long, M., J. Donoso, M. Bhati, W.C. Elias, K.N. Heck, Y.H. Luo, Y.S. Lai, H. Gu, T.P. Senftle, C, Zhou, M.S. Wong, and B.E. Rittmann. 2021. Adsorption and Reductive Defluorination of Perfluorooctanoic Acid over Palladium Nanoparticles. Environ. Sci. Technol, 55(21):14836-14843.

Long, M., W.C. Elias, K.N. Heck, Y.H. Luo, Y.S. Lai, Y. Jin, H. Gu, J. Donoso, T.P. Senftle, C. Zhou, M.S. Wong, and B.E. Rittmann. 2021. Hydrodefluorination of Perfluorooctanoic Acid in the H2-Based Membrane Catalyst-Film Reactor with Platinum Group Metal Nanoparticles: Pathways and Optimal Conditions. Environ. Sci. Technol, 55(24):16699-16707.

Zhou, C., Y. Luo, C. Zheng, M. Long, X. Long, Y. Bi, X. Zheng, D. Zhou, and B.E. Rittmann. 2021. H2-Based Membrane Catalyst-Film Reactor (H2-MCfR) Loaded with Palladium for Removing Oxidized Contaminants in Water. Environ. Sci. Technol, 55(10):7082-7093.