Field Demonstration to Enhance PFAS Degradation and Mass Removal Using Thermally-Enhanced Persulfate Oxidation Followed by Pump-and-Treat

Dr. John Kornuc | NAVFAC EXWC

ER-201729

Objective

Aqueous film-forming foams (AFFF) have been used at hundreds of Air Force and Navy sites and have contaminated vadose zone soils and groundwater with a complex mixture of per- and polyfluoroalkyl substances (PFASs) and other AFFF constituents. PFASs are stable in the environment and as a result, are extremely difficult to treat using any single proven remediation technology. The objective of this project is to demonstrate a cost-effective in situ treatment train approach to destroy and capture PFASs, thereby reducing contaminant mass and the overall duration and cost of remediation. A combination of well-known technologies will be utilized that are field-ready to address PFASs. The field demonstration will be timely, since DoD sites have already completed site characterization for PFASs and are operating interim pump-and-treat systems at several PFAS sites.

ER-201729

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Technology Description

The first stage of treatment consists of in situ chemical oxidation (ISCO) using thermally-enhanced persulfate in a low-pH environment. This technology has been repeatedly demonstrated in the laboratory to fully oxidize perfluorooctanoic acid (PFOA) and other perfluorinated carboxylic acids (PFCAs) as well as anionic, cationic and zwitterionic polyfluorinated substances that are potential precursors of perfluorocarboxylic acids. At sites where only fluorotelomer-based AFFF was used (e.g., crash sites, recent spill sites, any new PFAS sites that arise in the future), this in situ technology could be fully effective for PFAS remediation. However, several common PFASs present in historical 3M AFFF formulations are resistant to chemical oxidation, including perfluorooctane sulfonate (PFOS) and other perfluorinated sulfonic acids (PFSAs). Multiple independent peer-reviewed laboratory studies have indicated that PFOS cannot be degraded using ISCO despite testing various oxidant and reductant formulations and combinations (e.g., peroxide, persulfate, permanganate, Fenton’s reagent). There is no reason to expect that ISCO would be successful in degrading PFOS, based on current theory. Therefore, PFOS and other PFSAs will likely remain in the subsurface throughout ISCO and will require a second stage of treatment consisting of extraction and granular activated carbon (GAC) sorption. This project will demonstrate the effectiveness of thermally-enhanced in situ persulfate oxidation coupled with ex situ GAC sorption at field-scale for complete treatment of PFASs. This two-step process will significantly save both cost and treatment time, compared with the best available technology for PFASs (ex situ GAC sorption).

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Benefits

This non-proprietary technology is aligned with DoD’s preference for in situ remediation and aggressive mass reduction to accelerate site closure. As a public domain technology, it will lead to significant cost savings over proprietary methods. It improves the sustainability of existing pump-and-treat systems, saving decades of system operation and cost. Completely oxidizing PFAS precursors also greatly simplifies the site conceptual model and long-term monitoring program costs. ISCO will convert dozens of PFAS precursors in AFFF with largely unknown fate and transport characteristics into a small suite of compounds with better known characteristics. The project also will provide practitioners with technology design parameters and performance data, a scientific basis for estimating life-cycle costs and treatment timeframes, and overall recommendations for treating PFAS precursors. (Anticipated Project Completion - 2020)

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Points of Contact

Principal Investigator

Dr. John Kornuc

NAVFAC Engineering Service Center

Phone: 805-982-1615

Program Manager

Environmental Restoration

SERDP and ESTCP

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