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Your Environment. Your Health.

EnChem Engineering, Inc.

Superfund Research Program

Combined In-Situ/Ex-Situ Remediation of PFAS at Hazardous Waste Sites

Project Leader: Raymond Ball
Grant Number: R44ES028649
Funding Period: Phase II: September 2019 - August 2021

Summary

Poly- and perfluoroalkyl substances (PFAS) in soil and groundwater are currently remediated by extracting the contaminated groundwater for ex-situ treatment via adsorption onto granular activated carbon (GAC) or other sorbents, which only transfers contaminants to another media that still needs to be treated. This is a very long-term and expensive process because (1) it takes decades for the sorbed PFAS on soil to be extracted via groundwater pump and treat (P&T), (2) the carbon must be changed frequently, and (3) treatment (by high temperature regeneration or incineration) is costly. Recently, another research group showed that low molecular weight PFAS break through GAC faster than other compounds. In addition, P&T technology may never achieve U.S. Environmental Protection Agency Health Advisory concentrations in the aquifer.

PFAS are fluorinated anthropogenic pollutants that the EPA and global health organizations have identified as toxic, persistent, bioaccumulative, and highly recalcitrant, resistant to hydrolysis, photolysis, and biodegradation. PFAS were used in many products, including aqueous film-forming foams to combat chemical fires at military and civilian fire training areas, where they are a common source of PFAS to the environment. They have been identified in surface waters, and they persist in groundwater years after use, contaminating and threatening drinking water supplies. As of 2014, the U.S. Department of Defense alone has identified 664 fire/crash/training sites that potentially have PFAS contamination. Thus, there is a critical need for a more cost-effective and in-situ remediation approach for remediating PFAS-contaminated sites that will only increase in the coming years.

The research team is developing and demonstrating an innovative combined in-situ/ex-situ technology to cost effectively expedite treatment of PFAS at Superfund sites. The proprietary treatment train combines (1) a non-toxic cyclic sugar (CS) to flush sorbed PFAS from the in-situ soil and (2) extraction of the CS-PFAS complex with groundwater and treatment in a high efficiency 99+ percent  removal to 70 ppt (parts-per-trillion) ex-situ reactor that removes the PFAS from the extracted groundwater using a process to enhance foam formation that separates and concentrates the PFAS into a separate reactor where it is destroyed in the concentrate to 70 ppt total PFAS. The treated water with a low concentration of CS amendment is re-injected into the subsurface for continued aquifer flushing. In Phase I, it was shown that (1) PFAS can be effectively flushed from highly PFAS-contaminated soils with a relatively small flushing volume and (2) the PFAS can be effectively separated from the extracted groundwater and destroyed in the concentrate. Bench scale tests are being used to evaluate those parameters needed to optimize site-specific PFAS desorption from soil, separation of the extracted CS-PFAS complex, and ultimate destruction of the PFAS concentrate in the ex-situ reactor. A site-specific field pilot test to demonstrate PFAS treatment by the process will be performed in Phase II.

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