Biodegradation of Methyl Tert-butil Ether Under Different Growth Conditions PDF Download
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Author: Silvia Meléndez González
Publisher:
ISBN:
Category :
Languages : en
Pages : 186
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Author: Silvia Meléndez González
Publisher:
ISBN:
Category :
Languages : en
Pages : 186
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Author: S. M. González
Publisher:
ISBN:
Category :
Languages : en
Pages : 61
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Author: Amy Pruden
Publisher:
ISBN:
Category :
Languages : en
Pages :
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This study investigates the potential for biodegradation of methyl tert-butyl ether (MTBE), a prevalent gasoline additive and groundwater contaminant, under various substrate and oxidation-reduction (redox) conditions. Porous pot reactors designed for biomass retention were operated aerobically under the following conditions: MTBE only, MTBE and ethanol, MTBE and di-isopropyl ether, MTBE and diethyl ether, and MTBE with benzene, toluene, ethylbenzene, and p-xylene (BTEX). In all reactors, optimal performance was achieved when operated without biomass wasting. Mineralization of MTBE and the alternative substrates was observed in all reactors, with an average stable effluent concentration of all compounds being at or below 1 ppb (0.001 mg/l). Anaerobically, MTBE degradation was investigated in porous pot reactors and in batch systems. After a 180 day acclimation period, conversion of MTBE to its intermediate, tert-butyl alcohol (TBA), was observed in both batch and continuous-flow iron-reducing systems, and one instance of degradation was observed in the denitrifying porous pot reactor. No degradation of MTBE under methanogenic or sulfate-reducing conditions was observed after over 1 year of incubation. A molecular tool, denaturing gradient gel electrophoresis (DGGE) was used to monitor and profile the bacterial community structure of all reactors. Members of the Flexibacter-Bacterioides-Cytophaga (F-B-C) group of bacteria were most represented among all aerobic reactors, while delta-Proteobacteria were found to be prevalent in the iron-reducing system. Beta-Proteobacteria with high similarity to the known MTBE degrader, PM1, were detected by DGGE late in operation of the MTBE only and the MTBE and BTEX reactors. Two pure MTBE-degrading cultures with high similarity to PM1 were also isolated from the MTBE only reactor. Studies in pure culture also indicated no significant effect of alternative substrate (BTEX) on MTBE degradation. Results indicate that aerobic degradation of MTBE is reliable under various substrate conditions, and that a porous pot reactor designed for biomass retention is highly effective for attaining low effluent concentrations of MTBE and its intermediates.
Author: Asunción Medrano Gener
Publisher:
ISBN:
Category :
Languages : en
Pages : 63
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Author: Manmohan Sohan Lal
Publisher:
ISBN:
Category : Butyl methyl ether
Languages : en
Pages : 508
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Author: Jeffrey Hodges Scarano
Publisher:
ISBN:
Category :
Languages : en
Pages : 120
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Author: Maria Adriana Martínez-Prado
Publisher:
ISBN:
Category : Butyl methyl ether
Languages : en
Pages : 490
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Mycobacterium vaccae JOB5 and Graphium sp. were studied to evaluate their ability to cometabolize methyl tert-butyl ether (MTBE) and its metabolites after growth on two different alkanes, propane and iso-pentane. Both cultures were capable of cometabolizing MTBE and the metabolites, tert-butyl formate (TBF) and tert-butyl alcohol (TBA). MTBE, TBF, and TBA did not support growth of either microbe. Higher degradation rates were obtained in the bacterial system when the cultures were grown on iso-pentane. Nonlinear least squares regression and direct linear plot methods were used to estimate kinetic coefficients and provided comparable results. The enzymes from Mycobacterium vaccae JOB5 and Graphium sp. that promote the cometabolism of MTBE and its metabolites exhibited similar kinetics and substrate inhibition. The presence of the substrate decreased the degradation rate of MTBE and TBA suggesting competitive inhibition and preference for the substrate. Blockage experiment with acetylene suggested the presence of an alkane monooxygenase for the metabolism of MTBE and TBA, and a hydrolytic enzyme for the degradation of TBF. The presence of a hydrolase enzyme was supported by the fact that TBF was degraded to TBA under either aerobic or anaerobic conditions and was not inhibited by the presence of acetylene, propane, or isopentane. Measured rates of abiotic hydrolysis of TBF were significantly less than biodegradation rates. Acetylene acted as a reversible inhibitor for both cultures when tested in the presence of the growth media and as an inactivator when tested in the presence of a phosphate solution for the bacterial system. Growth-batch reactor experiments were conducted to compare the degradation of iso-pentane and MTBE with the predicted degradation rates based upon kinetic constants determined from single and dual-compound experiments. Experimental data was modeled with Monod kinetics and STELLA® software. Reasonable predictions of reactor performance were achieved when Monod maximum utilization rates were increased compared to single and dual-compound experiments.
Author: Na Wei
Publisher:
ISBN:
Category :
Languages : en
Pages : 80
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Author: Wenhua Ye
Publisher:
ISBN:
Category : Volatile organic compounds
Languages : en
Pages : 190
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Book Description
Gasoline additive Methyl Tertiary-Butyl Ether (MTBE) contaminated ground waters have been a problem nation wide with spills and leaky underground storage tanks. Biodegradation has been implemented under certain favorable environmental conditions. The biodegradation rates have been affected by treatments of nutrients, magnesium peroxide (oxygen), ethanol, temperature, pH and MTBE concentrations. This study was conducted to find the indigenous microorganisms which can degrade MTBE and assess how environmental factors would affect the biodegradation rates. This study compared MTBE biodegradation of the indigenous soil microorganisms with that of pure bacteria Methylobacterium mesophilicum, a well known MTBE degrade. In the pure culture Methylobacterium mesophilicum study, magnesium peroxide was found to enhance the MTBE biodegradation rate. However, ethanol was found to inhibit the biodegradation of MTBE, perhaps because it was degraded more easily and its metabolism decreased oxygen availability. In the soil microorganisms study, both magnesium peroxide and ethanol were found to enhance the MTBE biodegradation rates significantly. Co-metabolism between MTBE and ethanol may be possible in soil microorganisms.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 9
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Book Description
Aquifer microcosms were used to determine how ethanol and methyl-tert-butyl ether (MtBE) affect monoaromatic hydrocarbon degradation under different electron-accepting conditions commonly found in contaminated sites experiencing natural attenuation. Response variability was investigated by using aquifer material from four sites with different exposure history. The lag phase prior to BTEX (benzene, toluene, ethylbenzene, and xylenes) and ethanol degradation was typically shorter in microcosms with previously contaminated aquifer material, although previous exposure did not always result in high degradation activity. Toluene was degraded in all aquifer materials and generally under a broader range of electron-accepting conditions compared to benzene, which was degraded only under aerobic conditions. MtBE was not degraded within 100 days under any condition, and it did not affect BTEX or ethanol degradation patterns. Ethanol was often degraded before BTEX compounds, and had a variable effect on BTEX degradation as a function of electron-accepting conditions and aquifer material source. An occasional enhancement of toluene degradation by ethanol occurred in denitrifying microcosms with unlimited nitrate; this may be attributable to the fortuitous growth of toluene-degrading bacteria during ethanol degradation. Nevertheless, experiments with flow-through aquifer columns showed that this beneficial effect could be eclipsed by an ethanol-driven depletion of electron acceptors, which significantly inhibited BTEX degradation and is probably the most important mechanism by which ethanol could hinder BTEX natural attenuation. A decrease in natural attenuation could increase the likelihood that BTEX compounds reach a receptor as well as the potential duration of exposure.
