Bioremediation of TCE's
by Mika Pringle Tolson
UC TSR&TP Trainee Kung-Hui Chu
Participating in a research project to assess the environmental damage and the cleanup of the polluted Keelung River in Taiwan gave Kung-Hui Chu her first opportunity to deal with a real environmental issue as a new graduate in environmental engineering. Now she is studying bioremediation techniques for the contaminated subsurface. She attended Cornell University in 1988 and graduated in 1990 with a master of science degree in Agricultural & Biological Engineering. Her advisors at Cornell inspired her interest in bioremediation processes for groundwater. After receiving her master's, Chu took an internship at the Department of Water Pollution Control as a sanitary engineer to identify and regulate the target sources of heavy metals discharging into the south end of San Francisco Bay. However, she did not give up her interest in bioremediation. Since 1993, she has been a doctoral student at UC Berkeley in the Civil & Environmental Engineering program. The goal of her current research project, supported by TSR&TP, is to enhance the biodegradation of trichloroethylene (TCE) by exploiting the nitrogen fixing characteristics of methane oxidizing bacteria. TCE is a liver toxicant as well as a suspected human carcinogen. It is commonly detected in the contaminated subsurface, especially in California where it has been widely used in industry as a degreasing and cleaning agent. Other sources of TCE contamination include agriculture, chemical spills, and wastewater treatment (chlorination). Her previous studies have shown that nitrogen-fixing methane oxidizing cultures were able to degrade TCE as effectively as nitrate- or ammonia-utilizing cultures. Through her research, Chu hopes to understand how different nitrogen sources (nitrate, ammonia, and molecular nitrogen) influence bacterial growth rates and TCE degrading abilities. She is also working to develop an above-ground bioreactor with nitrogen-fixing methane oxidizing bacteria to effectively treat volatile organics. Says Chu, "To implement bioremediation, you have to enrich and maintain the right culture that can break down the contaminants at the bioremediation sites. The nutrient availability to bacteria, especially the nitrogen source, is usually crucial to successful bioremediation." She is currently working on optimizing the operating conditions of the bioreactor in her lab, but she hopes to test the technology in full scale at a field site in the near future. Once she gets her Ph.D., Chu would like to "teach and do research at the same time" as an academic. She hopes to eventually take her knowledge back to her homeland, Taiwan, where, like other developed countries, the focus for the past twenty years has been on economic development and not the environment. Kung-Hui Chu believes that "The results of my research can definitely be applied back to my country."
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