Brett Hicks

In Situ Remediation with Colloidal Activated Carbon to Reduce PFAS Risk and Liability

Brett Hicks, Central Region Manager, REGENESIS

Background: 

PFAS (per- and polyfluoroalkyl substances) have been released into groundwater at an estimated 57,000 sites in the US alone, including military bases, airports, landfills, and various industries. Recent sampling of public water systems required by the US Environmental Protection Agency (US EPA) already confirms PFAS detections in 89 million people's drinking water, with more sample results pending. The agency's designation of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) as hazardous substances under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) in April 2024 will now force many PFAS-contaminated sites into remediation to prevent future impacts on drinking water wells and other receptors.      

Approach:  

The two remediation approaches currently available to remediate PFAS in groundwater involve groundwater extraction and separation treatment (pump-and-treat) or in situ remediation with colloidal activated carbon (CAC). Despite its use for groundwater remediation for over 40 years, pump-and-treat has proven ineffective in restoring aquifers contaminated with common groundwater pollutants such as trichloroethene (TCE). Using pump-and-treat to flush PFOA and PFOS out of aquifers effectively would be even more problematic as these contaminants sorb to aquifer soils approximately 5 and 25 times more strongly than TCE, respectively, while at the same time, having enforceable maximum contaminant levels (MCLs) that are 1,250 times lower. Therefore, pump-and-treat can only be useful for hydraulic containment to stop advancing PFAS groundwater plumes.  However, this containment method generates a concentrated PFAS waste. This waste material must be managed, transported, and disposed of at a landfill or treated, with each step in the process causing a PFAS exposure risk. Since PFAS do not degrade naturally and bioaccumulate in animals and humans, PFAS-laden wastes present new risks and liabilities, including Strict and Joint & Several Liability under Superfund, not encountered previously with other contaminants.  As such, solutions that avoid generating waste in the first place are desirable.  In situ remediation with CAC occurs below the surface and does not generate waste.  The CAC technology comprises <2 micron-sized activated carbon particles that coat aquifer materials upon application, converting the subsurface into a pollutant filter that effectively removes PFAS from the dissolved phase with no ongoing operation or maintenance required. With PFAS removed, the potential for exposure is also removed, eliminating the risk to receptors downstream.       

Results: 

In situ remediation with CAC has been successfully implemented at over 50 PFAS-contaminated sites globally across four continents. Numerous in-field case studies demonstrate the approach's effectiveness in halting the migration of PFAS in the subsurface, thereby preventing future exposure risk and liability. Additionally, independent, peer-reviewed research and modeling studies predict that typical in situ PFAS plume treatments will be effective for decades or longer. At many sites, the longevity of a CAC permeable barrier can be further increased by treating the upgradient PFAS source area, effectively reducing PFAS risk permanently. Compared to two leading pump-and-treat alternatives, using CAC to remediate PFAS in situ is approximately one-third the cost and has a 98% lower carbon footprint, based on a Life Cycle Assessment completed for a PFAS-contaminated airport site where the in situ approach was used.  The CAC technology is being evaluated as part of numerous US Department of Defense research projects through the Strategic Environmental Research and Development Program (SERDP) and Environmental Security and Technology Certification Program (ESTCP).    

Brett Hicks is the Central Region Manager at REGENESIS, with 15 years of experience in the environmental industry. In his current role at REGENESIS, he leads a team of technical remediation experts across the Great Lakes, Ohio Valley, and Southeastern regions of the United States, delivering solutions for sites contaminated with PFAS, chlorinated solvents, and petroleum hydrocarbons. Brett's team assists environmental engineering and consulting firms, as well as responsible parties, in achieving their site goals using cutting edge colloidal technologies. He has extensive experience in in situ chemical oxidation (ISCO), bioremediation, chemical reduction, and carbon sorption.