Cometabolic degradation of MTBE at low concentration

Liu, Catherine Yuen Yiu
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Methyl tert-butyl ether (MTBE) contamination of groundwater is of concern because it has a strong and unpleasant taste and odor, even at low concentrations. MTBE is a known animal carcinogen at high concentrations. This research was undertaken to determine the feasibility of using aerobic cometabolism to biologically remediate low concentrations of MTBE (100’s µg/L-1 mg/L) contaminated water. Research objectives included identifying a bacterial culture that could cometabolize low concentrations of MTBE, determining MTBE degradation rates of the culture, examining factors that affected MTBE cometabolic degradation by the bacterial culture, and evaluating the effectiveness of using the bacterial culture in a hollow fiber membrane bioreactor (HFMB) system to remediate low-level MTBE contaminated water. v Arthrobacter sp. (ATCC 27778), Nocardia sp. (ENV425), Methylosinus trichosporium OB3b PP358, and Streptomyces griesus were tested for their ability to cometabolize MTBE. Butane-oxidizing Arthrobacter was found to degrade MTBE. Arthrobacter degrading MTBE was determined to have an apparent half saturation concentration (Ks) of 2.14 mg/L and a maximum substrate utilization rate (kc) of 0.43mg/mg TSS/d. Comparison of the MTBE degradation kinetic constants for Arthrobacter and other MTBE degrading bacteria indicated that Arthrobacter would be more effective at treating MTBE at low concentrations, but not at high concentrations. Arthrobacter demonstrated MTBE degradation activity when grown on butane, but not when grown on glucose, butanol, or on Tryptose Phosphate Broth, suggesting that a butane-oxidizing enzyme cometabolized MTBE. Enzyme competition effects were observed for MTBE degradation in the presence of both butane and acetylene, further supporting the theory that MTBE degradation was carried out by a butane-oxidizing enzyme. The feasibility of utilizing cometabolism to treat MTBE-contaminated water was explored by conducting a bioreactor study in a HFMB. The bioreactor study demonstrated that Arthrobacter was able to sustain relatively constant MTBE biodegradation activity for over 200 hours. However, a large portion of the biomass became entrapped within the hollow fiber membrane module (HFMM) section of the bioreactor during the study.