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.
Abiotic Dechlorination of Trichloroethene Under Oxic and Anoxic Conditions in Natural Soils (ER-2530)
Bench-scale experiments were performed on soils to assess abiotic TCE dechlorination under both aerobic and anaerobic conditions. In the absence of oxygen, TCE dechlorination proceeded via a reductive pathway generating reduced gases. Reductive dechlorination rate constants up to 3.1 x 10-5 d-1 were measured. In the presence of oxygen, TCE dechlorination proceeded via an oxidative pathway generating volatile fatty acids, and oxidative dechlorination rate constants up to 7.4 x 10-3 d-1 were measured. These rates correspond to half-lives of 60 and 0.25 years for abiotic TCE dechlorination under anaerobic and aerobic conditions, respectively. For both dechlorination pathways, measured first-order rate constants increased with increasing ferrous iron content. Hydroxyl radical formation was measured and increased with increasing oxygen and ferrous iron content. Rate constants associated with TCE oxidation products increased with increasing hydroxyl radical generation rates, and were zero in the presence of a hydroxyl radical scavenger.