Professor and Chair
David L. Freedman is a professor and Chair of the Department of Environmental Engineering and Earth Sciences at Clemson University. He received a B.S. degree in Environmental Sciences from the University of Wisconsin-Green Bay, an M.S. in Environmental Engineering from the University of Cincinnati, and a Ph.D. in Environmental Engineering from Cornell University. Dr. Freedman served as a post-doctoral fellow at Cornell University on a project funded by the American College of Toxicology. Throughout his academic career, Dr. Freedman has performed research on anaerobic reductive dechlorination and anaerobic and aerobic oxidation processes for chlorinated aliphatic compounds and other emerging contaminants, including 1,4-dioxane. Dr. Freedman has received research support from SERDP, ESTCP, EPA, US DOE, US Army Construction Engineering Research Laboratory, US Air Force Office of Scientific Research, Westinghouse Savannah River Corporation, Battelle, and numerous consulting firms. He is currently the PI on a SERDP project (ER-2622) to evaluate rates of abiotic and biotic degradation of chlorinated ethenes within fractured rock at three Department of Defense sites. He is co-PI on an ESTCP project (ER-201730) that includes natural attenuation of 1,4-dioxane.
Assessing In Situ Biodegradation of 1,4-Dioxane Using a 14C Assay
Documenting the occurrence of 1,4-dioxane biodegradation in situ is challenging. One of the more significant hurdles is demonstrating that a decrease in concentration with distance is a consequence of contaminant destruction. Under aerobic conditions, the principal products of 1,4-dioxane biodegradation (CO2 and biomass) are difficult to discern from other sources, including naturally occurring organic matter. We have developed an assay utilizing 14C-labeled 1,4-dioxane that quantifies the rate at which degradation products accumulate. It is part of an ESTCP project, ER-201730, which seeks to develop a quantitative framework for evaluating natural attenuation of 1,1,1-trichloroethane, 1,1-dichloroethane, and 1,1-dichloroethene, along with 1,4-dioxane. Groundwater samples from 10 sites have been evaluated. Statistically significant pseudo first order degradation rates were measured for six of the sites, with half-lives ranging from 7.2 to more than 300 years. The assay results correlate reasonably well with other, more traditional lines of evidence for 1,4-dioxane biodegradation.