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1.
Solano-Serena F Marchal R Huet T Lebeault JM Vandecasteele JP 《Applied microbiology and biotechnology》2000,54(1):121-125
The biodegradability under aerobic conditions of volatile hydrocarbons (4–6 carbons) contained in gasoline and consisting
of n-alkanes, iso-alkanes, cycloalkanes and alkenes, was investigated. Activated sludge was used as the reference microflora. The biodegradation
test involved the degradation of the volatile fraction of gasoline in closed flasks under optimal conditions. The kinetics
of biodegradation was monitored by CO2 production. Final degradation was determined by gas chromatographic analysis of all measurable hydrocarbons (12 compounds)
in the mixture after sampling the headspace of the flasks. The degradation of individual hydrocarbons was also studied with
the same methodology. When incubated individually, all hydrocarbons used as carbon sources, except 2,2-dimethylbutane and
2,3-dimethylbutane, were completely consumed in 30 days or less with different velocities and initial lag periods. When incubated
together as constituents of the light gasoline fraction, all hydrocarbons were metabolised, often with higher velocities than
for individual compounds. Cometabolism was involved in the degradation of dimethyl isoalkanes.
Received: 19 October 1999 / Received revision: 21 January 2000 / Accepted: 23 January 2000 相似文献
2.
Laboratory batch experiments were performed with contaminated aquifer sediments and four soluble aromatic components of jet fuel to assess their biodegradation under anaerobic conditions. The biodegradation of four aromatic compounds, toluene, o-xylene, 1,2,4-trimethylbenzene (TMB), and naphthalene, separately or together, was investigated under strictly anaerobic conditions in the dark for a period of 160 days. Of the aromatic compounds, toluene and o-xylene were degraded both as a single substrate and in a mixture with the other aromatic compounds, while TMB was not biodegraded as a single substrate, but was biodegraded in the presence of the other aromatic hydrocarbons. Substrate interaction is thus significant in the biodegradation of TMB. Biodegradation of naphthalene was not observed, either as a single substrate or in a mixture of other aromatic hydrocarbons. Although redox conditions were dominated by iron reduction, a clear relation between degradation and sulfate reduction was observed. Methanogenesis took place during the later stages of incubation. However, the large background of Fe(II) masked the increase of Fe(II) concentration due to iron reduction. Thus, although microbial reduction of Fe(III) is an important process, the evidence is not conclusive. Our results have shown that a better understanding of the degradation of complex mixtures of hydrocarbons under anaerobic conditions is important in the application of natural attenuation as a remedial method for soil and groundwater contamination. 相似文献
3.
Biodegradation of aromatic compounds under mixed oxygen/denitrifying conditions: a review 总被引:6,自引:0,他引:6
Bioremediation of aromatic hydrocarbons in groundwater and sediments is often limited by dissolved oxygen. Many aromatic
hydrocarbons degrade very slowly or not at all under anaerobic conditions. Nitrate is a good alternative electron acceptor
to oxygen, and denitrifying bacteria are commonly found in the subsurface and in association with contaminated aquifer materials.
Providing both nitrate and microaerophilic levels of oxygen may result in oxidation of the stable benzene rings in aromatic
contaminants and allow for the intermediates of this oxidation to degrade via denitrification. The effects of using mixed
electron acceptors on biodegradation of subsurface contaminants is unclear. Below some critical oxygen threshold, aerobic
biodegradation is inhibited, however high levels of oxygen inhibit denitrification. The mechanisms which regulate electron
transfer to oxygen and nitrate are complex. This review: 1) describes the factors which may affect the utilization of oxygen
and nitrate as dual electron acceptors during biodegradation; 2) summarizes the incidence of dual use of nitrate and oxygen
(aerobic denitrification); and 3) presents evidence of the effectiveness of bioremediation under mixed oxygen/nitrate conditions.
Received 08 November 1995/ Accepted in revised form 09 June 1996 相似文献
4.
Biodegradation of aromatic compounds: current status and opportunities for biomolecular approaches 总被引:1,自引:0,他引:1
Biodegradation can achieve complete and cost-effective elimination of aromatic pollutants through harnessing diverse microbial
metabolic processes. Aromatics biodegradation plays an important role in environmental cleanup and has been extensively studied
since the inception of biodegradation. These studies, however, are diverse and scattered; there is an imperative need to consolidate,
summarize, and review the current status of aromatics biodegradation. The first part of this review briefly discusses the
catabolic mechanisms and describes the current status of aromatics biodegradation. Emphasis is placed on monocyclic, polycyclic,
and chlorinated aromatic hydrocarbons because they are the most prevalent aromatic contaminants in the environment. Among
monocyclic aromatic hydrocarbons, benzene, toluene, ethylbenzene, and xylene; phenylacetic acid; and structurally related
aromatic compounds are highlighted. In addition, biofilms and their applications in biodegradation of aromatic compounds are
briefly discussed. In recent years, various biomolecular approaches have been applied to design and understand microorganisms
for enhanced biodegradation. In the second part of this review, biomolecular approaches, their applications in aromatics biodegradation,
and associated biosafety issues are discussed. Particular attention is given to the applications of metabolic engineering,
protein engineering, and “omics” technologies in aromatics biodegradation. 相似文献
5.
Response of Microorganisms to an Accidental Gasoline Spillage in an Arctic Freshwater Ecosystem 总被引:3,自引:2,他引:1 下载免费PDF全文
The response of microorganisms to an accidental spillage of 55,000 gallons of leaded gasoline into an Arctic freshwater lake was studied. Shifts in microbial populations were detected after the spillage, reflecting the migration pattern of the gasoline, enrichment for hydrocarbon utilizers, and selection for leaded-gasoline-tolerant microorganisms. Ratios of gasoline-tolerant/utilizing heterotrophs to “total” heterotrophs were found to be a sensitive indicator of the degree of hydrocarbon contamination. Respiration rates were elevated in the highly contaminated area, but did not reflect differences between moderately and lightly contaminated areas. Hydrocarbon biodegradation potential experiments showed that indigenous microorganisms could extensively convert hydrocarbons to CO2. In situ measurement of gasoline degradation showed that, if untreated, sediment samples retained significant amounts of gasoline hydrocarbons including “volatile components” at the time the lake froze for the winter. Nutrient addition and bacterial inoculation resulted in enhanced biodegradative losses, significantly reducing the amount of residual hydrocarbons. Enhanced biodegradation, however, resulted in the appearance of compounds not detected in the gasoline. Since the contaminated lake serves as a drinking water supply, treatment to enhance microbial removal of much of the remaining gasoline still may be advisable. 相似文献
6.
Nutrient-limited biodegradation of PAH in various soil strata at a creosote contaminated site 总被引:7,自引:0,他引:7
The effects of nutrient addition on the in situ biodegradation of polycyclic aromatic hydrocarbons in creosote contaminated soil were studied in soil columns taken from various soil strata at a wood preserving plant in Norway. Three samples were used: one from the topsoil (0–0.5 m), one from an organic rich layer (2–2.5 m) and one from the sandy aquifer (4.5–5 m). The addition of inorganic nitrogen and phosphorous stimulated the degradation of polycyclic aromatic hydrocarbons (PAHs) in the top soil and the aquifer sand. These two soils, which differed strongly in contamination levels, responded similarly to nutrient addition with the corresponding degradation of 4-ring PAHs. The ratio between available nitrogen (N) and phosphorous (P) might explain the degree of degradation observed for the 4-ring PAHs. However, the degree of degradation of 3-ring PAHs did not significantly increase after nutrient addition. An increase in the respiration rate, after nutrient addition, could only be observed in the topsoil. In the aquifer sand, 4-ring PAH degradation was not accompanied by an increase in the respiration rate or the number of heterotrophic micro-organisms. PAH degradation in the organic layer did not respond to nutrient addition. This was probably due to the low availability of the contaminants for micro-organisms, as a result of sorption to the soil organic matter. Our data illustrate the need for a better understanding of the role of nutrients in the degradation of high molecular weight hydrocarbons for the successful application of bioremediation at PAH contaminated sites. 相似文献
7.
Biodegradation of gasoline: kinetics, mass balance and fate of individual hydrocarbons 总被引:5,自引:0,他引:5
F. Solano-Serena R. Marchal M. Ropars J. -M. Lebeault J. -P. Vandecasteele 《Journal of applied microbiology》1999,86(6):1008-1016
The degradation of gasoline by a microflora from an urban waste water activated sludge was investigated in detail. Degradation kinetics were studied in liquid cultures at 30 degrees C by determination of overall O2 consumption and CO2 production and by chromatographic analysis of all 83 identifiable compounds. In a first fast phase (2 d) of biodegradation, 74% of gasoline, involving mostly aromatic hydrocarbons, was consumed. A further 20%, involving other hydrocarbons, was consumed in a second slow phase (23 d). Undegraded compounds (6% of gasoline) were essentially some branched alkanes with a quaternary carbon or/and alkyl chains on consecutive carbons but cycloalkanes, alkenes and C10- and C11-alkylated benzenes were degraded. The degradation kinetics of individual hydrocarbons, determined in separate incubations, followed patterns similar to those observed in cultures on gasoline. Carbon balance experiments of gasoline degradation were performed. The carbon of degraded gasoline was mainly (61.7%) mineralized into CO2, the remaining carbon being essentially converted into biomass. 相似文献
8.
This study investigated the potential effect of poultry dung (biostimulation) and stubborn grass (Sporobolus pyramidalis) (phytoremediation) on microbial biodegradation of gasoline and nickel uptake in gasoline-nickel-impacted soil. In addition, the potential stimulatory effects of nickel on hydrocarbon utilization were investigated over a small range of nickel concentrations (2.5–12.5 mg/kg). The results showed that an increase in nickel concentration increased hydrocarbon degraders in soil by a range of 8.4–17.2% and resulted in a relative increase in gasoline biodegradation (57.5–62.4%). Also, under aerobic conditions, total petroleum hydrocarbons’ (TPH) removal was 62.4% in the natural gasoline-nickel microcosm (natural attenuation), and a maximum of 78.5%, 85.7%, and 95.8% TPH removal was obtained in phytoremediation, biostimulation, and a combination of biostimulation- and phytoremediation-treated microcosms, respectively. First-order kinetics described the biodegradation of gasoline and nickel uptake very well. Half-life times obtained were 28.88, 18.24, 14.44, and 8.56 days for gasoline degradation under natural attenuation, phytoremediation, biostimulation, and combined biostimulation and phytoremediation treatment methods, respectively. The results indicate that these remediation methods have promising potential for effective remediation of soils co-contaminated with petroleum hydrocarbons and heavy metals. 相似文献
9.
In this study, we investigated the treatability of co-mingled groundwater contaminated with polycyclic aromatic hydrocarbons
(PAHs), gasoline hydrocarbons, and methyl tert-butyl ether (MtBE) using an ex-situ aerobic biotreatment system. The PAHs of interest were naphthalene, methyl-naphthalene, acenaphthene, acenaphthylene, and
carbazole. The gasoline hydrocarbons included benzene, toluene, ethyl benzene, and p-xylene (BTEX). Two porous pot reactors were operated for a period of 10 months under the same influent contaminant concentrations.
The contaminated groundwater was introduced into the reactors at a flow rate of 4 and 9 l/day, resulting in a hydraulic retention
time (HRT) of 32 and 15 h, respectively. In both reactors, high removal efficiencies were achieved for the PAHs (>99%), BTEX
and MtBE (>99.7%). All the PAHs of interest and the four BTEX compounds were detected at concentrations less than 1 μg/l throughout
the study duration. Effluent MtBE from both reactors was observed at higher levels; nevertheless, its concentration was lower
than the 5 μg/l Drinking Water Advisory for MtBE implemented in California. 相似文献
10.
Bioremediation of soil contaminated by organic compounds can remove the contaminants to a large extent, but residual contamination
levels may remain which are not or only slowly biodegraded. Residual levels often exceed existing clean-up guidelines and
thereby limit the use of bioremediation in site clean-up. A method for estimating the expected residual levels would be a
useful tool in the assessment of the feasability of bioremediation. In this study, three soil types from a creosote-contaminated
field site, which had been subjected to 6 months of bioremediation in laboratory column studies, were used to characterize
the residual contamination levels and assess their availability for biodegradation. The soils covered a wide range of organic
carbon levels and particle size distributions. Results from the biodegradation studies were compared with desorption rate
measurements and selective extractability using butanol. Residual levels of polycyclic aromatic hydrocarbons after bioremediation
were found to be strongly dependent on soil type. The presence of both soil organic matter and asphaltic compounds in the
soil was found to be associated with higher residual levels. Good agreement was found between the biodegradable fraction and
the rapidly desorbable fraction in two of the three soils studied. Butanol extraction was found to be a useful method for
roughly estimating the biodegradable fraction in the soil samples. The results indicate that both desorption and selective
extraction measurements could aid the assessment of the feasability for bioremediation and identifying acceptable end-points.
Received: 15 September 1999 / Received revision: 7 February 2000 / Accepted: 13 February 2000 相似文献
11.
Effect of salt on aerobic biodegradation of petroleum hydrocarbons in contaminated groundwater 总被引:2,自引:0,他引:2
Ulrich AC Guigard SE Foght JM Semple KM Pooley K Armstrong JE Biggar KW 《Biodegradation》2009,20(1):27-38
Hydrocarbon-contaminated soil and groundwater at oil and gas production sites may be additionally impacted by salts due to
release of produced waters. However, little is known about the effect of salt on the in-situ biodegradation of hydrocarbons
by terrestrial microbes, especially at low temperatures. To study this effect, we prepared a groundwater-soil slurry from
two sites in Canada: a former flare pit site contaminated with flare pit residue (Site A), and a natural gas processing facility
contaminated with natural gas condensate (Site B). The slurry with its indigenous microbes was amended with radiolabeled hydrocarbons
dissolved in free product plus nutrients and/or NaCl, and incubated in aerobic biometer flasks with gyrotory shaking at either
25 or 10°C for up to 5 weeks. Cumulative production of 14CO2 was measured and the lag time, rate and extent of mineralization were calculated. For Site A, concentrations of NaCl ≥1%
(w/v) delayed the onset of mineralization of both 14C-hexadecane and 14C-phenanthrene under nutrient-amended conditions, but once biodegradation began the degradation rates were similar over the
range of salt concentrations tested (0–5% NaCl). For Site B, increasing concentrations of NaCl ≥1% (w/v) increased the lag
time and decreased the rate and extent of mineralization of aliphatic and aromatic substrates. Of particular interest is the
observation that low concentrations of salt (≤1% NaCl) slightly stimulated mineralization in some cases. 相似文献
12.
L. Deschênes P. Lafrance J.-P. Villeneuve R. Samson 《Applied microbiology and biotechnology》1996,46(5-6):638-646
The effect of two anionic surfactants was assessed during biodegradation of 13 of the 16 USEPA priority polycyclic aromatic
hydrocarbons (PAH) in a wood-preserving soil contaminated with creosote and pentacholorophenol for a period of at least 20
years. Sodium dodecyl sulfate (SDS) and biosurfactants from Pseudomonas aeruginosa UG2 were utilized at concentrations of 10, 100 and 500 μg/g soil. Because both surfactants are readily biodegradable, the
microcosms received a fresh spike of surfactant every 2 weeks. Biodegradation of aged PAH residues was monitored by GC/MS
for a period of 45 weeks. Results indicated that the biodegradation of the three-ring PAH was rapid and almost complete but
was slowed by the addition of 100 μg/g and 500 μg/g chemical surfactant. Similarly, at the same concentrations, the two surfactants
significantly decreased the biodegradation rate of the four-ring PAH. In this case, the inhibition was more pronounced with
SDS. High-molecular-mass PAH (more than four rings) were not biodegraded under the test conditions. It was suggested that
the preferential utilization of surfactants by PAH degraders was responsible for the inhibition observed in the biodegradation
of the hydrocarbons. The high biodegradability and the inhibitory effect of these two surfactants would have a significant
impact on the development of both above-ground and in situ site reclamation processes.
Received: 22 February 1996 / Received revision: 31 May 1996 / Accepted: 16 June 1996 相似文献
13.
Encapsulated cell bioaugmentation is a novel alternative solution to in situ bioremediation of contaminated aquifers. This study was conducted to evaluate the feasibility of such a remediation strategy based on the performance of encapsulated cells in the biodegradation of gasoline, a major groundwater contaminant. An enriched bacterial consortium, isolated from a gasoline-polluted site, was encapsulated in gellan gum microbeads (16-53 microm diameter). The capacity of the encapsulated cells to degrade gasoline under aerobic conditions was evaluated in comparison with free (non-encapsulated) cells. Encapsulated cells (2.6 mg(cells) x g(-1) bead) degraded over 90% gasoline hydrocarbons (initial concentration 50-600 mg x L(-1)) within 5-10 days at 10 degrees C. Equivalent levels of free cells removed comparable amounts of gasoline (initial concentration 50-400 mg x L(-1)) within the same period but required up to 30 days to degrade the highest level of gasoline tested (600 mg x L(-1)). Free cells exhibited a lag phase in biodegradation, which increased from 1 to 5 days with an increase in gasoline concentration (200-600 x mg L(-1)). Encapsulation provided cells with a protective barrier against toxic hydrocarbons, eliminating the adaptation period required by free cells. The reduction of encapsulated cell mass loading from 2.6 to 1.0 mg(cells) x g(-1) bead caused a substantial decrease in the extent of biodegradation within a 30-day incubation period. Encapsulated cells dispersed within the porous soil matrix of saturated soil microcosms demonstrated a reduced performance in the removal of gasoline (initial concentrations of 400 and 600 mg x L(-1)), removing 30-50% gasoline hydrocarbons compared to 40-60% by free cells within 21 days of incubation. The results of this study suggest that gellan gum-encapsulated bacterial cells have the potential to be used for biodegradation of gasoline hydrocarbons in aqueous systems. 相似文献
14.
Bacterial degradation of pyridine, indole, quinoline, and their derivatives under different redox conditions 总被引:24,自引:0,他引:24
S. Fetzner 《Applied microbiology and biotechnology》1998,49(3):237-250
Bacteria have evolved a diverse potential to transform and even mineralize numerous organic compounds of both natural and
xenobiotic origin. This article describes the occurrence of N-heteroaromatic compounds and presents a review of the bacterial
degradation of pyridine and its derivatives, indole, isoquinoline, and quinoline and its derivatives. The bacterial metabolism
of these compounds under different redox conditions – by aerobic, nitrate-reducing, sulfate-reducing and methanogenic bacteria
– is discussed. However, in natural habitats, various environmental factors, such as sorption phenomena, also influence bacterial
conversion processes. Thus, both laboratory and field studies are necessary to aid our understanding of biodegradation in
natural ecosystems and assist the development of strategies for bioremediation of polluted sites. Occurring predominantly
near (former) wood-treatment facilities, creosote is a frequent contaminant of soil, subsoil, groundwater, and aquifer sediments.
In situ as well as withdrawal-and-treatment techniques have been designed to remediate such sites, which are polluted with
complex mixtures of aromatic and heterocyclic compounds.
Received: 26 September 1997 / Received revision: 23 December 1997 / Accepted: 27 December 1997 相似文献
15.
Biodegradation of xenobiotics by anaerobic bacteria 总被引:2,自引:0,他引:2
Xenobiotic biodegradation under anaerobic conditions such as in groundwater, sediment, landfill, sludge digesters and bioreactors has gained increasing attention over the last two decades. This review gives a broad overview of our current understanding of and recent advances in anaerobic biodegradation of five selected groups of xenobiotic compounds (petroleum hydrocarbons and fuel additives, nitroaromatic compounds and explosives, chlorinated aliphatic and aromatic compounds, pesticides, and surfactants). Significant advances have been made toward the isolation of bacterial cultures, elucidation of biochemical mechanisms, and laboratory and field scale applications for xenobiotic removal. For certain highly chlorinated hydrocarbons (e.g., tetrachlorethylene), anaerobic processes cannot be easily substituted with current aerobic processes. For petroleum hydrocarbons, although aerobic processes are generally used, anaerobic biodegradation is significant under certain circumstances (e.g., O2-depleted aquifers, oil spilled in marshes). For persistent compounds including polychlorinated biphenyls, dioxins, and DDT, anaerobic processes are slow for remedial application, but can be a significant long-term avenue for natural attenuation. In some cases, a sequential anaerobic-aerobic strategy is needed for total destruction of xenobiotic compounds. Several points for future research are also presented in this review. 相似文献
16.
Adaptation to and biodegradation of xenobiotic compounds by microbial communities from a pristine aquifer 总被引:1,自引:0,他引:1
The ability of subsurface microbial communities to adapt to the biodegradation of xenobiotic compounds was examined in aquifer solids samples from a pristine aquifer. An increase in the rates of mineralization of radiolabeled substrates with exposure was used as an indication of adaptation. For some compounds, such as chlorobenzene and 1,2,4-trichlorobenzene, slight mineralization was observed but no adaptation was apparent during incubations of over 8 months. Other compounds demonstrated three patterns of response. For m-cresol, m-aminophenol, and aniline intermediate rates of biodegradation and a linear increase in the percent mineralized with time were observed. Phenol, p-chlorophenol, and ethylene dibromide were rapidly metabolized initially, with a nonlinear increase in the percent mineralized with time, indicating that the community was already adapted to the biodegradation of these compounds. Only p-nitrophenol demonstrated a typical adaptation response. In different samples of soil from the same layer in the aquifer, the adaptation period to p-nitrophenol varied from a few days to as long as 6 weeks. In most cases the concentration of xenobiotic added, over the range from a few nanograms to micrograms per gram, made no difference in the response. Most-probable-number counts demonstrated that adaptation is accompanied by an increase in specific degrader numbers. This study has shown that diverse patterns of response occur in the subsurface microbial community. 相似文献
17.
Adaptation to and biodegradation of xenobiotic compounds by microbial communities from a pristine aquifer. 总被引:9,自引:7,他引:2 下载免费PDF全文
The ability of subsurface microbial communities to adapt to the biodegradation of xenobiotic compounds was examined in aquifer solids samples from a pristine aquifer. An increase in the rates of mineralization of radiolabeled substrates with exposure was used as an indication of adaptation. For some compounds, such as chlorobenzene and 1,2,4-trichlorobenzene, slight mineralization was observed but no adaptation was apparent during incubations of over 8 months. Other compounds demonstrated three patterns of response. For m-cresol, m-aminophenol, and aniline intermediate rates of biodegradation and a linear increase in the percent mineralized with time were observed. Phenol, p-chlorophenol, and ethylene dibromide were rapidly metabolized initially, with a nonlinear increase in the percent mineralized with time, indicating that the community was already adapted to the biodegradation of these compounds. Only p-nitrophenol demonstrated a typical adaptation response. In different samples of soil from the same layer in the aquifer, the adaptation period to p-nitrophenol varied from a few days to as long as 6 weeks. In most cases the concentration of xenobiotic added, over the range from a few nanograms to micrograms per gram, made no difference in the response. Most-probable-number counts demonstrated that adaptation is accompanied by an increase in specific degrader numbers. This study has shown that diverse patterns of response occur in the subsurface microbial community. 相似文献
18.
Although aromatic compounds are most often present in the environment as components of complex mixtures, biodegradation studies
commonly focus on the degradation of individual compounds. The present study was performed to investigate the range of aromatic
substrates utilized by biphenyl- and naphthalene-degrading environmental isolates and to ascertain the effects of co-occurring
substrates during the degradation of mono-aromatic compounds. Bacterial strains were isolated on the basis of their ability
to utilize either biphenyl or naphthalene as a sole source of carbon. Growth and transformation assays were conducted on each
isolate to determine the range of substrates degraded. One isolate, Pseudomonas putida BP18, was tested for the ability to biodegrade benzene, toluene, ethylbenzene and xylene isomers (BTEX) individually and
as components of mixtures. Overall, the results indicate that organisms capable of growth on multi-ring aromatic compounds
may be particularly versatile in terms of aromatic hydrocarbon biodegradation. Furthermore, growth and transformation assays
performed with strain BP18 suggest that the biodegradation of BTEX and biphenyl by this strain is linked to a catabolic pathway
with overlapping specificities. The broad substrate specificity of these environmental isolates has important implications
for bioremediation efforts in the field.
Received: 4 August 1999 / Received revision: 25 October 1999 / Accepted: 5 November 1999 相似文献
19.
Andrew J. Stocking Rula A. Deeb Amparo E. Flores William Stringfellow Jeffrey Talley Richard Brownell Michael C. Kavanaugh 《Biodegradation》2000,11(2-3):187-201
The addition of methyl tert-butyl ether (MTBE) to gasoline has resulted in public uncertainty regarding the continued reliance on biological processes for gasoline remediation. Despite this concern, researchers have shown that MTBE can be effectively degraded in the laboratory under aerobic conditions using pure and mixed cultures with half-lives ranging from 0.04 to 29 days. Ex-situ aerobic fixed-film and aerobic suspended growth bioreactor studies have demonstrated decreases in MTBE concentrations of 83% and 96% with hydraulic residence times of 0.3 hrs and 3 days, respectively. In microcosm and field studies, aerobic biodegradation half-lives range from 2 to 693 days. These half-lives have been shown to decrease with increasing dissolved oxygen concentrations and, in some cases, with the addition of exogenous MTBE-degraders. MTBE concentrations have also been observed to decrease under anaerobic conditions; however, these rates are not as well defined. Several detailed field case studies describing the use of ex-situ reactors, natural attenuation, and bioaugmentation are presented in this paper and demonstrate the potential for successful remediation of MTBE-contaminated aquifers. In conclusion, a substantial amount of literature is available which demonstratesthat the in-situ biodegradation of MTBE is contingent on achieving aerobic conditions in the contaminated aquifer. 相似文献
20.
In this study biodegradation of hydrocarbons in thin oil films was investigated in seawater at low temperatures, 0 and 5 °C.
Heterotrophic (HM) or oil-degrading (ODM) microorganisms enriched at the two temperatures showed 16S rRNA sequence similarities
to several bacteria of Arctic or Antarctic origin. Biodegradation experiments were conducted with a crude mineral oil immobilized
as thin films on hydrophobic Fluortex adsorbents in nutrient-enriched or sterile seawater. Chemical and respirometric analysis
of hydrocarbon depletion showed that naphthalene and other small aromatic hydrocarbons (HCs) were primarily biodegraded after
dissolution to the water phase, while biodegradation of larger polyaromatic hydrocarbons (PAH) and C10–C36 n-alkanes, including n-hexadecane, was associated primarily with the oil films. Biodegradation of PAH and n-alkanes was significant at both 0 and 5°C, but was decreased for several compounds at the lower temperature. n-Hexadecane biodegradation at the two temperatures was comparable at the end of the experiments, but was delayed at 0°C. Investigations
of bacterial communities in seawater and on adsorbents by PCR amplification of 16S rRNA gene fragments and DGGE analysis indicated
that predominant bacteria in the seawater gradually adhered to the oil-coated adsorbents during biodegradation at both temperatures.
Sequence analysis of most DGGE bands aligned to members of the phyla Proteobacteria (Gammaproteobacteria) or Bacteroidetes. Most sequences from experiments at 0°C revealed affiliations to members of Arctic or Antarctic consortia, while no such
homology was detected for sequences from degradation experiment run at 5°C. In conclusion, marine microbial communities from
cold seawater have potentials for oil film HC degradation at temperatures ≤5°C, and psychrotrophic or psychrophilic bacteria
may play an important role during oil HC biodegradation in seawater close to freezing point. 相似文献