The overall goal of this project is to assess the impact powdered activated carbon (PAC)-based particulate amendments have on the fate and transport of trichloroethene (TCE) in the presence of per- and polyfluoroalkyl substances (PFAS). The specific objectives of this project are as follows:

1. Characterize how the adsorption behavior of PFAS varies as a function of PFAS chain length and functional group to PAC in the presence and absence of TCE.
2. Assess the impact particulate amendments have on the rate and extent of TCE reductive dechlorination in the presence of PFAS under relevant redox conditions.
3. Assess the effectiveness that different particulate delivery injection approaches have on the distribution of PAC, the impact on mass flux, and the transport of PAC in different soil types.
4. Demonstrate the sediment slurry injection technique at field-scale and assess the long-term performance of the particulate amendment injection technique with respect to groundwater quality, chemical mass fluxes, reductive dechlorination, geochemistry, and microbial structure, and PAC-amendment migration.

For the remedial strategy, PAC-based particulate amendments would be injected and mixed with the groundwater plume to decrease both aqueous phase concentrations of chlorinated ethenes and PFAS to levels below the toxicity limit necessary for complete reductive dechlorination to occur. To ensure optimal distribution of particulate amendment, in situ mixing would be done with single-point groundwater recirculation wells downgradient of the source area. Plumes treated in that manner would not only have lower concentrations but also cause high retardation of higher concentrations coming from upstream from the source area.

This project involves the following tasks:

1. The use of sorption batch studies to establish a database on sorption isotherms for PAC-based sorbents for single PFAS in the presence and absence of TCE and for complex PFAS mixtures.
2. The use of microbial batch studies and molecular biological tools to quantify how PFAS chemical interactions will impact the rate and extent of reductive dechlorination and chemical and microbiological interactions.
3. The use of controlled laboratory aquifer model testing to assess different delivery methods for optimal distribution of particulate amendments for the planned field trial.
4. A field-scale demonstration of the amendment strategy developed for Task 3 at a PFAS and chlorinated solvent site, and a long-term performance evaluation using passive flux meters to estimate mass fluxes, compound-specific stable isotope analysis to determine the extent and mechanisms of degradation, a high-throughput quantitative real-time polymerase chain reaction approach to monitor the relevant microbes and genes, and measurement of other standard groundwater parameters. If PAC-based particular amendments were previously applied to a similar site, a performance evaluation would be conducted to serve as a comparison to the field demonstration.

This project will provide the Department of Defense with the information necessary to determine whether PAC-based particulate amendments work as intended in readily sequestering PFAS and chlorinated ethenes, promote biodegradation, determining the optimal method for subsurface distribution, and how this technology performs in situ over the long-term. (Anticipated Project Completion - 2025)