Abstracts

“Experimental Evaluation and Mathematical Modeling of Particulate Amendment Delivery, Retention and Adsorption Performance in the Subsurface” by Dr. Kurt Pennell (ER21-1129)

Remediation of groundwater impacted by PFAS is challenging due to the strength of the carbon-fluorine bond and the need to achieve nanogram per liter drinking water targets. Previous studies have shown that granular activated carbon (GAC) and ion exchange resin (IXR) can serve as effective sorbents for the removal of PFOA and PFOS in conventional water treatment systems. The goal of this project is to evaluate the efficacy of injectable particulate amendments to create permeable adsorptive barriers (PABs) that can treat PFAS-impacted groundwater in situ. Two injectable materials have been developed in our laboratory, a polymer-stabilized powdered activated carbon (S-PAC) and a polymer-stabilized ion exchange resin (S-IXR). Laboratory and mathematical modeling studies were conducted to assess the delivery and retention of the particulate amendments and to assess their ability to retain individual PFAS and PFAS mixtures. For the multi-solute column experiments, aqueous solutions containing equal concentrations of PFOS, PFOA, PFNA, PFHxS, PFHpA, and PFBS were injected into S-PAC and S-IXR treated columns. Effluent samples were collected continuously to monitor for PFAS breakthrough, and at the conclusion of each experiment, the solid phase was collected to obtain PFAS retention profiles and perform scanning electron microscopy (SEM). Samples were analyzed for PFAS using a Waters ACQUITY ultra high-performance liquid chromatograph coupled with a Waters Xevo triple quadrupole mass spectrometer (UPLC-MS/MS). For S-PAC and S-IXR treated columns, PFAS retention increased by more than three and five orders of magnitude, respectively, compared to untreated control columns. Multi-solute column studies conducted with S-IXR revealed earlier breakthrough of shorter-chain length PFAS, consistent with the mixed PFAS adsorption data. The mathematical model was able to simulate polymer and particulate amendment delivery and retention in one-dimensional and radial flow fields, as well as the subsequent adsorption of PFAS measured in the laboratory studies.

“An Investigation of Factors Affecting In Situ PFAS Immobilization by Activated Carbon” by Mr. Matt Vanderkooy and Dr. Anh Pham (ER21-3959)

Containment of PFAS through activated carbon is an option with benefits and drawbacks. Injecting powdered or colloidal activated carbon (AC) into the subsurface offers an outcome not obtainable with other current remediation technologies: reducing and even potentially eliminating fluxes of PFAS by creating a passive in situ adsorption barrier. This is a potentially powerful technology that can attain orders of magnitude of reduction in PFAS mass flux, but the flux reductions are not necessarily permanent, and they may not be sufficient to meet cleanup criteria which are still in development. Moreover, PFAS are not destroyed by in situ adsorption but are only adsorbed, a process that is reversible. This project evaluates the in situ immobilization of groundwater plumes containing PFAS via AC barriers that are created by injecting powdered AC or colloidal AC into the subsurface. Using bench-scale experiments, this project examines the fundamental processes that govern the adsorption/desorption of PFAS. In addition, a field-scale experiment is underway to assess the retention of PFAS under more complex hydrogeochemical conditions and to support benchmarking reactive transport models. Research outcomes will support informed prediction of the long-term effectiveness of in situ immobilization of PFAS by particulate AC amendments.

Speaker Biographies

Dr. Kurt Pennell is the 250th Anniversary Professor of Engineering in the School of Engineering at Brown University. Previously, Dr. Pennell was chair of the Department of Civil and Environmental Engineering at Tufts University, and the Bernard M. Gordon Senior Faculty Fellow in Environmental Engineering. He also was a professor in civil and environmental engineering at the Georgia Institute of Technology and held an adjunct faculty appointment in the Department of Neurology at the Emory University School of Medicine. His current research focuses on PFAS treatment, environmental exposures, and the use of engineered nanomaterials for subsurface characterization. Dr. Pennell has published over 200 referred journal articles and book chapters and has received numerous research and teaching awards, including the SERDP Project of the Year in Environmental Restoration (2006, 2012), a National institutes of Health Career Award, and the Order of Omega Faculty Member of Year Award. Dr. Pennell received a bachelor’s degree from the University of Maine, a master’s degree from North Carolina State University, and a doctoral degree from the University of Florida.
 
Mr. Matt Vanderkooy is a principal contaminant geoscientist at Geosyntec Consultants. He is an expert on the development of PFAS conceptual site models, as well as PFAS fate, transport and remediation. He currently leads PFAS characterization and remediation programs in surface water, sediment, groundwater, air, stormwater, and soils. He is the principal investigator for SERDP Project ER21-3959 (An Investigation of Factors Affecting In Situ PFAS Immobilization by Activated Carbon). He also manages a large PFAS impacted groundwater project, which recently won the National Groundwater Association’s 2023 Outstanding Groundwater Remediation Project Award. Mr. Vanderkooy received a bachelor’s degree in chemistry from the University of Waterloo and a master’s degree in hydrogeology from the University of Waterloo.

Dr. Anh Pham is an assistant professor in the Department of Civil and Environmental Engineering at the University of Waterloo, where he leads the Environmental Aquatic Chemistry research group. His research group applies aquatic chemistry and geochemistry principles and employs analytical chemistry tools to investigate contaminant fate, transport, and treatment. His current research focuses on PFAS in groundwater, soil, surface water, wastewater, and biosolids. Dr. Pham serves on the editorial board of Critical Reviews in Environmental Science and Technology and is an ad-hoc proposal reviewer for American Association for the Advancement of Science. He received a bachelor’s degree in chemical engineering from Hanoi University of Technology, and master’s and doctoral degrees in civil and environmental engineering from the University of California, Berkeley.