Formatted Title
Case Studies and Long-Term Strategies for PFAS In Situ Remediation Using Colloidal Activated Carbon
Background/Objectives
Over the past several years, the use of colloidal activated carbon (CAC) has changed from an emerging to a demonstrated technology for in situ remediation of common PFAS of concern such as PFOS, PFHxS, PFOA, and PFNA. While there is some uncertainty in the longevity of a CAC remedy and the extent to which short-chain PFAS will be regulated in the future, there are management strategies and contingency measures available to ensure that CAC will be effective at various PFAS sites. For example, a CAC remedy that is designed to have a longevity of at least 30 to 40 years allows for the deferral of future remedy costs well into the future with little influence on the net present value of the remedial alternative.
Approach/Activities
This study presents a summary of findings from 20 CAC case studies at PFAS sites which include field measurements and/or modeling of long-term performance.
Results/Lessons Learned
Lessons learned include the relative performance for short-chain and long-chain PFAS, pros and cons of source treatment versus plume management, potential effects of competition with chlorinated solvents and petroleum hydrocarbons, and examples of site characterization and long-term monitoring methods. The influence of competitive adsorption on short- and long-chain PFAS adsorption and CAC longevity are demonstrated. Long-term strategies and contingency measures to ensure remedy protectiveness are discussed, as well as the benefit of remedial action objectives that include mass flux and risk reduction.