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

Topic Area: 7d. Ex Situ PFAS Water Treatment Technologies

Formatted Title:

Regenerable Resin Five Years Later: What We’ve Learned

Background/Objectives:

Regenerable ion exchange resin for PFAS remediation and containment has been in service in Australia since June of 2017. Currently five full-scale systems are operating continuously at Defence sites. Many pilot demonstrations and much bench-scale work has been performed to optimize both the removal and regeneration processes since this time. This talk will provide data on over 5 years of full-scale performance of regenerable resin, specifically exploring a system servicing the Northern Territory of Australia. In short, the talk will serve as a state-of-the-science for regenerable resin used in PFAS mitigation and regeneration operations. Additionally, a microplastic sampling effort comparing pre- and post treatment using plastic ionic exchange resin will be discussed.

Approach/Activities:

Since system startup in 2019, data have been collected to understand the performance of PFAS treatment in Australia. Optimizing treatment with bench-scale and pilot-scale efforts has led to improvements in system performance. Different strong and weak base anion exchange resins have been investigated. Regeneration recipes (alcohol-brine percentages, bed volumes used during regeneration, etc.) have also resulted in more efficient regeneration cycles. Analytical sampling throughout the treatment process has allowed us to investigate a fluorine, or PFAS, mass balance, i.e., mass removed from the site versus mass recovered during regeneration.

Microplastic sampling was conducted at two different sites. Samples were collected pre- and post-water treatment exploring differences in microplastic concentrations and characteristics seen in the effluent samples.

Results/Lessons Learned:

Since startup, the 200 gpm, full-scale system has removed over 20 kg of PFAS from the subsurface. Resin optimization work has been ongoing since operations commenced. Data showing the regeneration efficiency of the resin will be shared. Since 2019, over 24 regeneration cycles have been performed without buildup of residual PFAS on the resin. Additionally, no physical breakdown of the plastic resin bead has been observed during this timeframe - after repeated exposures to the methanol / brine regeneration solution. Data will be shared to support both observations. From the regeneration perspective, a balance will be performed on “mass PFAS removed” and the “mass PFAS recovered” during regeneration events. This was evaluated through two different mechanisms – one pre-distillation and one post-distillation. Both methods reported numbers within 20% of one another. Data from recent testing with new media will be presented showing capacity 4x greater than the current media employed. If viable, this media would reduce regeneration event frequency, further reducing operational cost of regenerable ion exchange resin systems.

Finally, this talk will provide results from two different microplastic sampling efforts. Samples were collected pre- and post-ion exchange resin vessel and submitted for analysis for the concentration of microplastics and the plastic type, morphology, and size. The objective of the sampling events was to understand if ion exchange resin vessels were contributing a significant mass of microplastics into the environment.

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Paul Newman