Remediation of soils and groundwater impacted by per- and polyfluoroalkyl substances (PFAS) is particularly challenging due to the strength of the carbon-fluorine bond and the need to achieve extremely low drinking water levels. Currently, PFAS-impacted groundwaters are often managed using conventional “pump and treat” remediation approaches that rely on extraction and above-ground treatment with granular activated carbon or ion exchange resin. Recently, an alternative in situ approach has been suggested in which particulate amendments, including powdered activated carbon stabilized in a polymer suspension, are introduced into the subsurface to create an in situ reactive zone or barrier that is designed to adsorb and retain PFAS. Proprietary formulations containing injectable particulate amendments are being actively marketed for this purpose. Although injectable particulate amendments hold promise for in situ treatment of PFAS-impacted soils and groundwater, published data are scarce and insufficient to assess adsorption capacity, support remedial design, or evaluate long-term amendment performance under realistic conditions. Thus, the overall objective of this project is to advance the fundamental understanding of the delivery, retention and adsorption performance of particulate amendments in subsurface systems impacted by PFAS.
The technical approach for this project is organized around four complementary tasks: (1) particulate amendment delivery and retention, (2) adsorption performance of particulate amendments, (3) mathematical modeling of particulate amendment delivery, retention, and performance, and (4) research reporting and translation. The research program will couple detailed experimental studies in Tasks 1 and 2 with mathematical model development and validation in Task 3 to advance the fundamental understanding of particulate amendment delivery and sorption performance in the subsurface. Experimental studies will be conducted in batch, column, and aquifer cell systems using both commercially available and in-house particulate amendment formulations. Equilibrium and dynamic measurements of PFAS sorption-desorption by particulate amendments will be obtained under static and dynamic conditions and will include investigations in heterogeneous domains. Data obtained from Tasks 1 and 2 will serve as the basis for the development and validation of mathematical models and modeling tools capable of predicting particulate amendment delivery, retention, and long-term PFAS adsorption performance across a range of scales and complexities. In Task 4, research findings and mathematical modeling tools will be disseminated to environmental remediation practitioners, site managers, state and federal regulators and the broader research community.
The results of this work will provide new information on the delivery and retention of particulate amendments as a function of soil and aquifer material properties, effects of co-occurring chemicals and solution properties on the ability of particulate amendments to adsorb PFAS, and the long-term performance of particulate amendments as barriers for PFAS migration in the subsurface. Key deliverables of this work include mathematical models and modeling tools that can be used to predict the travel distance and retention profile of particulate amendments in porous media, and the subsequent performance of the treated zone to adsorb and retain PFAS over time. The research findings and deliverables generated from this project will benefit site managers, remediation design practitioners, and regulators responsible for the management and remediation of PFAS-impacted soil and groundwater. The project team plans to partner with representatives from professional organizations and government agencies to disseminate the research findings to practitioners, researchers, and public advocacy groups, and will seek to provide technical information to support the potential application of particulate amendments for in situ treatment of PFAS-impacted sites.