Superfund Research Program
Bench Scale Studies of Novel In-situ Aquifer Remediation of Recalcitrant Fluorinated Organic Compounds at Superfund Sites
Project Leader: Raymond Ball
Grant Number: R43ES028649
Funding Period: Phase I: September 2017 - February 2019
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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. In addition, P&T technology may never achieve U.S. Environmental Protection Agency (EPA) 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, and as 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 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.
The EnChem Engineering team is developing and demonstrating an innovative combined in-situ / ex-situ technology to cost-effectively expedite treatment of PFAS at Superfund sites. Their approach 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+ percent removal) ex-situ reactor that simultaneously degrades, removes, and concentrates (100-1000 times) the PFAS, 3) ultimate on-site destruction by alkaline ozonation (99+ percent 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.
The team is using bench scale tests 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. They are also conducing batch soil column and small scale multi- staged diffused gas reactor experiments. Test conditions include varying CS and oxidant concentrations, flowrates, pH, residence time, and PFAS removal rates. The team is also designing a site-specific field pilot test for PFAS treatment and estimating associated costs.