Biodegradation of monoaromatic hydrocarbons by aquifer microorganisms using oxygen, nitrate, or nitrous oxide as the terminal electron acceptor

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 benzene, toluene, ethylbenzene, and xylenes (BTEX) 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. The MtBE was not degraded within 100 d 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.

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“…2). Cometabolism of xylene by toluene degraders appears to be a common substrate interaction under denitrifying conditions [11][12][13][14].…”

Section: Travis Afb Microcosmsmentioning

confidence: 99%

Effect of Ethanol and Methyl-Tert-Butyl Ether on Monoaromatic Hydrocarbon Biodegradation: Response Variability for Different Aquifer Materials Under Various Electron-Accepting Conditions

Ruiz-Aguilar¹,

Fernandez-Sanchez²,

Kane³

et al. 2002

Environ Toxicol Chem

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“…For petroleum hydrocarbons, injection wells are used primarily to stimulate microbial growth and to accelerate degradation of the contaminant, known as the electron donor or primary substrate, by injecting an electron acceptor, such as oxygen. Degradation of key petroleum constituents, benzene, toluene, ethylbenzene, and xylene (BTEX), has been most successful under aerobic conditions with oxygen as the electron acceptor (for reference, see Hutchins [1991]).…”

Section: Objective Function and Constraintsmentioning

confidence: 99%

Risk‐based in situ bioremediation design using a noisy genetic algorithm

Smalley

Minsker²,

Goldberg

2000

Water Resources Research

129

114

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Abstract. Risk-based corrective action (RBCA) is rapidly becoming the method of choice for remediating contaminated groundwater. In this paper, a management model is presented that simultaneously predicts risk and proposes cost-effective options for reducing risk to acceptable levels under conditions of uncertainty. The model combines a noisy genetic algorithm with a numerical fate and transport model and an exposure and risk assessment model. The noisy genetic algorithm uses sampling from parameter distributions to assess the performance of candidate designs. Results from an application to a site from the literature show that the noisy genetic algorithm is capable of identifying highly reliable designs from a small number of samples, a significant advantage for computationally intensive groundwater management models. For the site considered, timedependent costs associated with monitoring and the remedial system were significant, illustrating the potential importance of allowing variable cleanup lengths and a realistic cost function.

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“…In addition, denitri¢cation is important in wastewater treatment as a means of removing ex-cess nitrate and stimulating carbon removal when aeration is di⁄cult. In the latter case, there is increased interest in using nitrate to drive pollutant bioremediation in aquifers [3,4]. In wastewater treatment, removal of nitrogen compounds can be accomplished by a combination of nitri¢cation (oxidation of ammonia to nitrate) and denitri¢cation (nitrate reduction to N 2 or N 2 O) [1,5].…”

Section: Introductionmentioning

confidence: 99%

Molecular characterization of microbial community in nitrate-removing activated sludge

Lee

2002

FEMS Microbiology Ecology

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The microbial community composition and dominant denitrifying populations in high-nitrate-removing (CR-I) and low-nitrateremoving (CR-II) activated sludge from continuous bioreactors were investigated with most probable number (MPN) enumeration, fluorescence in situ hybridization (FISH) and 16S rDNA characterization. MPNs of nitrate-reducing bacteria of sludge CR-I and sludge CR-II were 2.82U10 7 and 2.69U10 4 colony-forming units ml 31 , respectively. Eight denitrifying bacteria and two nitrate-reducing bacteria were isolated from sludge CR-I, and four denitrifying bacteria and three nitrate-reducing bacteria from sludge CR-II. Small subunit rDNA characterization of the isolates showed that the majority belonged to the genus Pseudomonas. By using FISH up to 76% (CR-I) and 52% (CR-II) of total 4,6-diamidino-2-phenylindole cell counts hybridized to the bacterial probe EUB338. Members of L-Proteobacteria were the most abundant proteobacterial group in both sludges, accounting for up to 41.6% and 37.1% of those detected by EUB338, respectively, whereas a higher number of Cytophaga^Flexibacter cluster members were observed in CR-I sludge compared to CR-II sludge. In contrast with culture-based results, the numbers of rRNA group I Pseudomonads accounted for less than 0.01% of those detected by EUB338 in both sludges. Ribosomal DNA clone library analysis showed that the L-Proteobacteria were also dominant in both sludges. In CR-I sludge, they were related to Zooglorea ramigera, Alcaligenes defragrans, denitrifying Fe-oxidizing bacteria and Dechlorimonas sp., whereas in CR-II sludge, they were related to Nitrosomonas sp. and Dechlorimonas agitatus. When this reactor was operated under anaerobic and anoxic conditions, nitrifying bacteria could adapt to the anoxic environment. We inferred that anaerobic ammonium oxidation and nitrite oxidation may occur in low-nitrate-removing sludge CR-II and inhibit denitrification. ß

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Biodegradation of monoaromatic hydrocarbons by aquifer microorganisms using oxygen, nitrate, or nitrous oxide as the terminal electron acceptor

Cited by 111 publications

References 10 publications

Effect of Ethanol and Methyl-Tert-Butyl Ether on Monoaromatic Hydrocarbon Biodegradation: Response Variability for Different Aquifer Materials Under Various Electron-Accepting Conditions

Effect of Ethanol and Methyl-Tert-Butyl Ether on Monoaromatic Hydrocarbon Biodegradation: Response Variability for Different Aquifer Materials Under Various Electron-Accepting Conditions

Risk‐based in situ bioremediation design using a noisy genetic algorithm

Molecular characterization of microbial community in nitrate-removing activated sludge

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