Theme: 07. Per- and Polyfluorinated Alkyl Substances (PFAS)

Topic Area: 7b. Ex Situ PFAS Treatment Approaches

Formatted Title:

PFAS Destruction Case Study: Pairing Photo-Activated Reductive Defluorination with Foam Fractionation at an Industrial Facility

Background/Objectives:

Destruction of per-and polyfluoroalkyl substances (PFAS) by any method is an energy-intensive endeavor. As a result, energy use is the predominant cost driver for PFAS destruction technologies and drives the economic feasibility of PFAS remediation. Micelle-assisted photo-activated reductive defluorination (PRD) is an emerging technology that received an award from U.S. Environmental Protection Agency and Department of Defense for energy efficiency and cost effectiveness in destroying both long-chain and short-chain PFAS in water. The PRD reaction is facilitated through surfactant addition, which forms a micelle cage that traps PFAS. A non-toxic proprietary chemical is added to the solution which associates with the micelle surface and produces hydrated electrons when stimulated with ultraviolet (UV) light. These highly-reactive hydrated electrons have the energy required to cleave fluorine-carbon bonds resulting in the final PFAS byproducts of fluoride, water, and simple carbon molecules (e.g., acetic acid). This patented PRD reaction was tested and proven extensively for environmental samples in small bench-top studies which led to fabrication of a full-scale PRD unit. The incorporation of UV technology, as a matured treatment approach in water industry, and the ability to operate the full-scale unit at ambient temperatures and pressures allow the PRD process to scale safely and readily to manage a broad range of conditions, concentrations and flows. Like most destruction technologies, PRD is most economical at addressing significant flows when pairing with a concentration technology. This case study illustrates a field-scale pilot test where PFAS-affected water was concentrated ex situ using foam fractionation and the PFAS concentrate was destroyed with PRD.

Approach/Activities:

The pilot test will be completed at a chrome-plating facility in Wyoming, MI, where an inadvertent release of process water resulted in an on-site plume of PFAS-affected groundwater (~4 parts per billion total PFAS). Groundwater extraction will be conducted to prevent off-site migration of the plume, however required extraction rates exceed the capacity of the on-site water treatment plant. The client desired to remove and destroy PFAS from extracted groundwater on site to allow for direct discharge. The pilot study will extract groundwater and be fed directly to the foam fractionation system. The foam fractionation system will involve single and double stage fractionation of both raffinate and foam concentrate to gather field operational data to optimize full-scale design. The foam fractionation unit will produce foam concentrate that will be subsequently introduced into the PFASigator™, Enspired Solutions’ full-scale PRD PFAS destruction reactor, while the raffinate is targeted to meet the plant discharge criteria. Throughout the PFAS destruction stage, fluoride ion concentrations will be recorded with real-time instrumentation as a quantitative indicator of the extent of PFAS mineralization. Real-time fluoride ion concentrations will be supplemented with expedited laboratory analysis of PFAS compounds to confirm system performance.

Results/Lessons Learned:

The pilot test system will operate between November and December 2023 and results are not currently available. The presentation will summarize lessons learned from the case study and identify conditions leading to optimal performance. Data presentation will include field observations, real-time data, and chemistry data from independent laboratory analysis. Anticipated results are that foam fractionation was successful at separating and concentrating PFAS while achieving local discharge targets for treated raffinate. In addition, the pilot is expected to show that PFASigator achieved greater than 99% destruction of regulated PFAS compounds, is relatively simple to operate, and provides adequate real-time information for making automated operational and discharge decisions.

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Suzanne Witt