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

Topic Area: 7p. PFAS: Groundwater Treatment Case Studies

Formatted Title:

Steering PFAS Remediation through Technology Evolution and Regulatory Development

Background/Objectives:

Developing regulatory framework along with increasing site investigations leading to discovery of PFAS impacts, has sent responsible parties and practitioners onto a rollercoaster ride. While consensus exists about the need to regulate and remediate, not knowing exactly where the line will be drawn, along with evolving remedial technologies, has made the path to remedial action even more challenging. Lessons learned as we navigate this changing environment around PFAS regulation and treatment will be discussed using examples of independent sites. Treatment of PFAS impacted media remained the overarching goal for all sites discussed here, however each site differed in regulatory requirements and site characteristics. At Site A, the remedial goal was to address overburden and bedrock groundwater impacted with PFAS along with the presence of other contaminants, volatile organic compounds. At Site B, drinking water treatment was needed to decrease PFAS levels, and at Site C, over a hundred of acres of overburden groundwater impacted with PFAS needed treatment.

Approach/Activities:

Desktop evaluation of options was first performed for each site. A combination of overburden hot spot treatment along with ex-situ pump and treat strategy was chosen for Site A, however without a clear regulatory guidance of what level of remediation was needed. It followed laboratory-based testing of a separation/sorption approach. Following desktop evaluation, a pilot test was performed for Site B, where regulatory requirements for drinking water wear clear but the path to vetting the remedy was unclear. Similarly at Site C, a desktop evaluation led to an in-situ groundwater treatment pilot test. While remedial activities at each of these sites were based on application of a separation-based laboratory or field testing, their site-specific application needed through analysis of site characteristics, not limited to lithology, hydrogeology, geochemistry, water quality, PFAS distribution, site constraints, logistics, overall timeline, and definition of success metrics. These considerations for implementation of laboratory or field testing manifested uniquely at each site. The effectiveness of widely established PFAS separation media was not really questioned, but fine-tuning remedial action to make conditions optimal for the separation to work, remained the biggest challenge of these projects.

Results/Lessons Learned:

At Site A, laboratory-based testing of groundwater was used to identify media for treatment of PFAS impacted groundwater. The study showed that presence of other co-contaminants and geochemical characteristics required a robust pre-treatment that could undermine the overall cost-effectiveness of the remedy. At Site B, navigating path to remedy implementation and site constraints was more of a challenge as compared to establishing the efficacy of the media itself. At Site C, low permeability overburden treatment zone proved that reagent distribution was our main challenge. Results of the testing, lesson learned and path forward for each site will be discussed.

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Mathew Wenrick