Methods and Applications of Life Cycle Material and Energy Flow Analysis in Product/Process Comparisons and Design


Friday, February 11, 2005, 3:30 PM

Room 825 SWM Building

Dr. Rachel A. Brennan, Ph.D.

Assistant Professor of Civil & Environmental Engineering The Pennsylvania State University , University Park , PA

Used for everything from dry-cleaning clothes to degreasing jet engines, the chlorinated solvents tetrachloroethene (PCE) and trichloroethene (TCE) are among the most common groundwater contaminants in the United States. To remove these toxic chemicals from contaminated aquifers, a liquid electron donor (ex., lactate) is traditionally pumped into the contaminated zone to stimulate reductive dechlorination by anaerobic bacteria. Unfortunately, this injection process is labor and cost intensive, often fails to maintain proper reducing conditions, and is typically difficult to achieve in low permeability sediments. As an alternative, a fermentable substrate such as corncobs, woodchips, newspaper, molasses, vegetable oils, or chitin may be placed into boreholes, barrier walls, or hydraulic fractures to provide an inexpensive, long-lasting source of electrons for remediation. Of these fermentable substrates, only chitin contains nitrogen, an essential nutrient for biological growth, which makes it an attractive electron donor for treating contaminated aquifers where nitrogen may be limiting.

This seminar presents the development of chitin-supported bioremediation from bench-scale laboratory column experiments to full-scale field testing. In continuous-flow columns, spatial and temporal correlations were found between the nutrient flux from chitin fermentation, rates of PCE degradation, and the distribution of dechlorinating, fermenting, and methanogenic microbial communities. In field tests at the Distler Brickyard Superfund Site in Kentucky, chitin was delivered into low permeability sediments using hydraulic fracturing. Chitin produced fatty acids similar to laboratory experiments, and created reducing conditions conducive to dechlorination. The talk concludes with a discussion of the longevity of chitin as an electron donor source and its dechlorination performance, both currently being evaluated at the full scale.

 About the presenter:

Rachel Alice Brennan was born in La Jolla, California and grew up in Las Cruces, New Mexico. Rachel earned her B.S. with Honors in Geological Engineering from New Mexico State University in 1997. She obtained her M.S. and Ph.D., both in Environmental Engineering, from the University of Illinois at Urbana-Champaign in 1999 and 2003, respectively. During her graduate studies she was a National Science Foundation Graduate Research Fellow, an Environmental Protection Agency STAR Fellow, and an International Research Fellow at the Technical University of Stuttgart, Germany. In January 2004, Rachel joined The Pennsylvania State University as a tenure-track Assistant Professor in Environmental Engineering. Rachel’s research interests include the bioremediation of soil and groundwater contaminants, molecular microbial community analysis, and the development of alternative nutrient sources for hazardous waste treatment.