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
The Problem: Perfluoroalkyl Compounds are widespread in drinking water supplies.
Poly- and perfluoroalkyl substances (PFAS) are both very toxic and recalcitrant. The U.S. Environmental Protection Agency (EPA) has issued a public health advisory of 70 parts per trillion of total PFASs in drinking water. Also, EPA has recently announced that Maximum Contaminant Levels (MCLs) in drinking water will be promulgated in 2019. Currently, PFAS remedies use groundwater extraction wells followed by media transfer to capture the PFAS and remove it from the extracted groundwater by “pump and treat” requiring decades to clean-up to regulatory closure standards, due to the slow release of adsorbed contaminants such as PFAS from the aquifer material. The currently used media transfer processes require off-site treatment or disposal of residuals presenting a potential liability risk. In-ground or in-situ treatment using chemical oxidation with Enchem’s proprietary OxyZone, has been used to safely destroy many organic contaminants and it has the potential to destroy PFASs as demonstrated in bench scale testing.
Enchem’s Solution: Combined enhanced in-situ extraction with ex-situ treatment.
EnChem Engineering, Inc. (EEI) has developed a process using enhanced PFAS removal from groundwater aquifers by in-situ extraction of PFAS with aboveground (ex-situ) destruction using their proprietary XCT (i.e. extra contact technology) process and OxyZone. XCT removes PFASs and other organic contaminants from both the soil and groundwater in the aquifer using a non-toxic carbohydrate solution. A PFAS-complex is then extracted with the groundwater and treated ex-situ to concentrate and destroy the PFAS on-site. This treatment train approach is safer and more efficient than any in-situ oxidation step alone.
Benefits of their approach:
- XCT desorbs PFASs from the soils in the aquifer and captures dissolved PFASs in the groundwater (in-situ) to accelerate the cleanup process, saving time and reducing cost with no potential by-products.
- In the XCT process, the PFASs in the extracted groundwater are concentrated and destroyed ex-situ to meet the MCLs before treated water discharge or reuse.
- This combined in-situ/ex-situ remedy is expected to use the existing infrastructure (i.e. wells, and/ treated water disposal system) already in place at a site that is typical of an existing pump and treat system, further reducing remediation cost.