Director - Research & Testing Laboratory
Dr. Schaefer is a chemical engineer with over 25 years of experience in the fate and transport of organic contaminants in soil and bedrock. He currently is the Director of CDM Smith’s Research & Testing Laboratory in Bellevue, WA, overseeing a large number of research projects and treatability studies. Dr. Schaefer’s recent efforts have focused on long-term dechlorination processes impacting chlorinated solvents in low permeability media, and on both the subsurface migration and treatment of emerging contaminants, particularly PFASs.
Electrochemical Oxdiation of Perfluoroalkyl Acid Precursors in AFFF-Impacted Groundwater
While several oxidative technologies have been proposed for treatment of waters impacted by AFFFs, information is lacking regarding the transformation pathways for wide range of chemical precursors to the perfluoroalkyl acids (PFAAs) typically present. This study examined the oxidative electrochemical treatment of PFASs in a series of bench-scale experiments for two AFFF-impacted groundwaters. The transformation and defluorination of a wide range of PFAA precursors were examined, as well as their transient accumulation and defluorination. Results from the first groundwater studied suggested a transformation pathway where sulfonamide-based PFASs oxidatively transformed to perfluorinated sulfonamides and perfluorinated carboxylic acids (PFCAs), with subsequent defluorination. Transient increases in the perfluorinated sulfonamides and PFCAs were observed. For the second groundwater, no transient increases in PFAAs were measured, despite the presence of similarly structured PFAA precursors and substantial defluorination. For both waters, precursors were the primary sources of the generated fluoride, not the PFAAs originally present.