Bench Scale Studies of Novel In-situ Aquifer Remediation of Recalcitrant Fluorinated Organic Compounds at Superfund Sites

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Project Summary/Abstract: 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), and 2) the carbon must be changed frequently and 3) treatment (by high temperature regeneration or incineration) is costly. In addition, P&T technology may never achieve EPA Health Advisory concentrations in the aquifer. PFAS are fluorinated anthropogenic pollutants that the USEPA and global health organizations have identified as toxic, persistent, bioaccumulative and highly recalcitrant, being largely resistant to hydrolysis, photolysis, and biodegradation. PFAS were used in many products, including aqueous film- forming foams to combat chemical fires. The use of these foams at military and civilian fire training areas represents a common source of PFAS to the environment. They have been identified in surface waters and they persist in groundwater years after use and are mobile in the subsurface, contaminating and threatening drinking water supplies. As of 2014, the U.S. Department of Defense alone has identified 664 fire/crash/training sites alone 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. Our team will further develop and demonstrate an innovative combined in-situ / ex-situ technology to cost-effectively expedite treatment of PFAS at Superfund sites. The proposed treatment train combines 1) a non-toxic cyclic sugar (CS) to flush sorbed PFAS from the in-situ soil, 2) extraction of the CS-PFAS complex with groundwater and treatment in a high efficiency (99+ % removal) ex-situ reactor that simultaneously degrades, removes, and concentrates (100-1000 times) the PFAS, 3) ultimate on-site destruction by alkaline ozonation (99+% removal), and 4) returns the treated water with low concentration CS amendment to injection wells for continued flushing. The ex-situ treatment reactor can also be used as pre-treatment to existing GAC. Bench scale tests will be used to evaluate those parameters needed to optimize PFAS desorption from soil, destruction of the extracted CS-PFAS complex in the ex-situ reactor, and ultimate destruction of the PFAS concentrate by alkaline ozonation. Batch soil column and small scale multi- staged diffused gas reactor experiments are planned. Test conditions include varying CS and oxidant concentrations, flowrates, pH, residence time, and PFAS removal rates. Design of a site-specific field pilot test for PFAS treatment with estimated costs will be prepared. 1