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  • 1
    Electronic Resource
    Electronic Resource
    Biodegradation of Creosote Compounds: Comparison of Experiments at Different Scales (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water monitoring & remediation 21 (2001), S. 0 
    Details
    ISSN: 1745-6592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: This paper compares the results of biodegradation experiments with creosote compounds performed at different scales. The experiments include field observations, field experiments, large-scale intact laboratory column experiments, model fracture experiments, and batch experiments. Most of the experiments were conducted with till or ground water from the field site at Ringe on the island of Funen. Although the experiments were conducted on different scales, they revealed that some phenomena—e.g., an extensive biodegradation potential of several of the creosote compounds, the inhibitory influence of the pyrroles on the biodegradation of benzene, and the biodegradation of benzothiophene occurs only in the presence of a primary substrate. The experiments show that some biodegradation processes of organic compounds may be common to different microorganisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6592.2001.tb00646.x
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  • 2
    Electronic Resource
    Electronic Resource
    Identification of Heteroaromatic and other Organic Compounds in Ground Water at Creosote-Contaminated Sites in Denmark (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water monitoring & remediation 17 (1997), S. 0 
    Details
    ISSN: 1745-6592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: The occurrence of heteroaromatic compounds (NSO) and their degradation products in ground water at creosote-contaminated sites in Denmark was investigated. NSO are of special interest because of their high polarity, toxicity, and adverse organoleptic properties. In total, the content of about 50 organic tar compounds and the chemical redox parameters of ground water from three creosote-contaminated sites were determined.The organic contamination of ground water varied considerably between sites and wells with concentrations up to mg/L level. The major organic contaminants were NSO, phenols, and monoaromatic hydrocarbons, which are among the most water-soluble creosote compounds. High concentration (several μg/L) of these compounds were observed downgradient of the contamination source. Within a distance of 50 to 80 m from the source, the concentrations of most compounds were reduced significantly, often below detection limits. The NSO constituted from 0.1 percent to 73 percent of all organic compounds determined by gas chromatography (GC) with an increasing dominance downgradient of the source. Among the 17 studied NSO, carbazole, thiophene, benzothiophene, dibenzothiophene, benzofuran, and dibenzofuran were observed most frequently (detection frequency 〉 60 percent). High concentrations (〉100 μ/L) of some NSO such as benzothiophene, carbazole, hydroxyquinolines, and basic N-compounds were observed occasionally. Other recent studies on creosote contamination support the present observations of high ground water concentrations of basic N-compounds and the high detection frequency of the aforementioned NSO. However, unlike the other studies, we did observe thiophene (1-10 μg/L).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6592.1997.tb01283.x
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  • 3
    Electronic Resource
    Electronic Resource
    Laboratory and Numerical Investigations of Air Sparging Using MTBE as a Tracer (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water monitoring & remediation 20 (2000), S. 0 
    Details
    ISSN: 1745-6592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Air sparging experiments were conducted in a laboratory column to investigate air flow and mass transfer behavior in different types of sand at different air injection rates. Methyl tertiary butyl ether (MTBE) was applied as a tracer, and by measuring the volatilization and the mean air content during the experiments, the air flow pattern and its influence on mass transfer were assessed. The experimental results showed large differences among the sand types. In fine sand, the mean air content was high and the volatilization of MTBE was rapid with total recovery after a few hours. In coarse sand, the mean air content was low and the volatilization of MTBE was limited. The results indicate two different air flow distributions. In fine-grained materials, a uniform air distribution can be expected compared to coarse-grained materials where isolated air channels will limit the mass transfer. Afterwards, the experiments were simulated using the numerical multiphase flow code T2VOC, and the results compared to those obtained in the laboratory. The experiments with fine sand were simulated well, while for coarser sand types the volatilization was highly overestimated. The differences between model and laboratory results were mainly attributed to the nonuniformity of the air saturation and the neglection of kinetics in the mass transfer formulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6592.2000.tb00293.x
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  • 4
    Electronic Resource
    Electronic Resource
    DNAPL Transport Through Macroporous, Clayey Till Columns (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 36 (1998), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: This paper provides the first experimental determination of the rates and distribution of transport of a dense, nonaqueous phase liquid (DNAPL) through a naturally bioporous and fractured clayey till deposit. Until now, assessment of DNAPL behavior in this type of deposit has relied on theoretical studies. Predictions of DNAPL transport have proven to be uncertain as a result of difficulties in measuring critical parameters such as DNAPL entry pressure and flow behavior in response to natural fracture/biopore apertures and the degree of interconnection of these structures. In the present investigation, the migration of free product trichloroethylene (TCE) was studied by means of two undisturbed clayey till columns (dimensions: 0.5 m diameter by 0.5 m long) under in situ effective soil stress conditions. The experiments revealed that transport of TCE was restricted to biopores in one column and fractures in another column, bypassing the low-permeability clayey matrix. Effective porosities of the columns, i.e., bio-pores and fractures, were two to three orders of magnitude lower than total porosities (25% and 32%, respectively, for the two columns), i.e., macropores and matrix. Single phase water flow rates through the columns at water-saturated conditions followed a linear relationship with hydraulic gradient. TCE flow could not be predicted from the single-phase calculations because of non-linearity observed between applied TCE injection heads and resulting TCE flow. TCE flow rates were 24 and 10.3 m/day at TCE gradients of 1.18 and 0.91, respectively. The observed flow rates indicate that in cases where vertical biopores or fractures fully penetrate clayey till aquitards, a low-viscosity DNAPL (e.g., TCE) may quickly enter underlying aquifers. The experiments further indicate that 100 liters of a low-viscosity DNAPL are sufficient to contaminate approximately 25 to 100 m3 of till material because of the small effective porosity constituted by the biopores and fractures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1998.tb02840.x
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  • 5
    Electronic Resource
    Electronic Resource
    Ground Water Contamination from Creosote Sites (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water monitoring & remediation 16 (1996), S. 0 
    Details
    ISSN: 1745-6592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Field data from 44 waste sites contaminated with creosote have been compiled in a database. The data from each site included geological and hydrogeological parameters and the concentrations of creosote compounds in the ground water at various distances from the pollution sources. The creosote compounds that were measured included mononuclear aromatic hydrocarbons and polynuclear aromatic hydrocarbons (PAH) and phenols. Already 50 m down-gradient of the creosote waste sites, 90 percent of the concentrations were from three to 50 times lower than at the source, and most of the median concentrations were below detection limit (0.1 to 0.5 μg/L). The maximum concentrations of benzene, toluene, and xylenes (BTX) and phenols were much lower under aerobic than under anaerobic conditions. Among the phenols, the xylenols (dimethylphenols) appear in higher concentrations under aerobic conditions than phenol and the cresols do. The highest concentrations found were of the same order of magnitude as the calculated solubilities found in the literature, except the chrysene and benz(a)pyrene concentrations, which were one to two orders of magnitude higher than the solubilities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6592.1996.tb00578.x
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  • 6
    Electronic Resource
    Electronic Resource
    Modelling the growth of a methanotrophic biofilm: Estimation of parameters and variability (1999)
    Springer
    Biodegradation 10 (1999), S. 177-191 
    Details
    ISSN: 1572-9729
    Keywords: AQUASIM ; biodegradation ; biofilm ; growth ; kinetics ; methane ; modelling ; nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This article discusses the growth of methanotrophic biofilms. Several independent biofilm growths scenarios involving different inocula were examined. Biofilm growth, substrate removal and product formation were monitored throughout the experiments. Based on the oxygen consumption it was concluded that heterotrophs and nitrifiers co-existed with methanotrophs in the biofilm. Heterotrophic biomass grew on soluble polymers formed by the hydrolysis of dead biomass entrapped in the biofilm. Nitrifier populations developed because of the presence of ammonia in the mineral medium. Based on these experimental results, the computer program AQUASIM was used to develop a biological model involving methanotrophs, heterotrophs and nitrifiers. The modelling of six independent growth experiments showed that stoichiometric and kinetic parameters were within the same order of magnitude. Parameter estimation yielded an average maximum growth rate for methanotrophs, μm, of 1.5 ± 0.5 d−1, at 20 °C, a decay rate, bm, of 0.24 ± 0.1 d−1, a half saturation constant, $${\text{K}}_{{\text{S(CH}}_{\text{4}} {\text{)}}} $$ , of 0.06 ± 0.05 mg CH4/L, and a yield coefficient, $$Y_{CH_4 } $$ , of 0.57 ±: 0.04 g X/g CH4. In addition, a sensitivity analysis was performed on this model. It indicated that the most influential parameters were those related to the biofilm (i.e. density; solid-volume fraction; thickness). This suggests that in order to improve the model, further research regarding the biofilm structure and composition is needed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008317906069
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  • 7
    Electronic Resource
    Electronic Resource
    Cometabolic transformation ofo-xylene in a biofilm system under nitrate reducing conditions (1995)
    Springer
    Biodegradation 6 (1995), S. 19-27 
    Details
    ISSN: 1572-9729
    Keywords: o-xylene ; toluene ; biofilm ; denitrification ; cometabolism ; competitive inhibition ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The purpose of this work was to investigate the anaerobic transformation ofo-xylene in a laboratory biofilm system with nitrate as an electron acceptor.o-Xylene was degraded cometabolically with toluene as primary carbon source. A mass balance showed thato-xylene was not mineralized but transformed.o-Methyl-benzalcohol ando-methyl-benzaldehyde were identified as intermediates ofo-xylene transformation which resulted in the formation ofo-methyl-benzoic acid as an end product. A cross inhibition phenomenon was observed between toluene ando-xylene. The presence of toluene was necessary for stimulation ofo-xylene transformation, but above a toluene concentration of 1–3 mg/L theo-xylene removal rate dramatically decreased. In returno-xylene inhibited the toluene degradation at concentrations above 2–3 mg/L.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702295
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  • 8
    Electronic Resource
    Electronic Resource
    Removal of toluene in waste gases using a biological trickling filter (1995)
    Springer
    Biodegradation 6 (1995), S. 109-118 
    Details
    ISSN: 1572-9729
    Keywords: analytical model ; biodegradation ; gas/liquid mass transfer ; kinetics ; surface removal rate ; toluene ; trickling filter ; waste gas treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The removal of toluene from waste gas was studied in a trickling biofilter. A high level of water recirculation (4.7 m h−1) was maintained in order to keep the liquid phase concentration constant and to achieve a high degree of wetting. For loads in the range from 6 to 150 g m−3 h−1 the maximum volumetric removal rate (elimination capacity) was 35±10 g m−3 h−1, corresponding to a zero order removal rate of 0.11±0.03 g m−2 h−1 per unit of nominal surface area. The surface removal was zero order above the liquid phase concentrations of approximately 1.0 g m−3, corresponding to inlet gas concentrations above 0.7–0.8 g m−3. Below this concentration the surface removal was roughly of first order. The magnitude of the first order surface removal rate constant, k1A , was estimated to be 0.08–0.27 m h−1 (k1A a=24–86 h−1). Near-equilibrium conditions existed in the gas effluent, so mass transfer from gas to liquid was obviously relatively fast compared to the biological degradation. An analytical model based on a constant liquid phase concentration through the trickling filter column predicts the effluent gas concentration and the liquid phase concentration for a first and a zero order surface removal. The experimental results were in reasonable agreement with a very simple model valid for conditions with an overall removal governed by the biological degradation and independent of the gas/liquid mass transfer. The overall liquid mass transfer coefficient, KLa, was found to be a factor 6 higher in the system with biofilm compared to the system without. The difference may be explained by: 1. Difference in the wetting of the packing material, 2. Mass transfer occurring directly from the gas phase to the biofilm, and 3. Enlarged contact area between the gas phase and the biofilm due to a rough biofilm surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00695341
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of mineral nutrients on the kinetics of methane utilization by methanotrophs (1993)
    Springer
    Biodegradation 4 (1993), S. 163-170 
    Details
    ISSN: 1572-9729
    Keywords: factorial analysis ; kinetics ; methane ; methanotrophs ; nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of different mineral nutrients on the kinetics of methane biodegradation by a mixed culture of methanotrophic bacteria was studied. The substrate factors examined were ammonia, iron, copper, manganese, phosphate, and sulphide. The presence of iron in the growth medium had a strong effect on the yield coefficient. Yield coefficients up to 0.49 mg protein per mg methane were observed when iron was added at concentrations of 0.10–5.0 mg/l. Iron addition also increased the maximum methane utilization rate. The same effect was observed after addition of ammonium to a medium where nitrate was the only nitrogen source. The observed Monod constant for methane utilization increased with increasing concentration of ammonia. This shows that ammonia is a weak competitive inhibitor as observed by other researchers. Relatively high levels of both ammonia (70 mg/l) and copper (300 µg/l) inhibited the methane degradation, probably due to the toxic effect of copper-amine complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00695118
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  • 10
    Electronic Resource
    Electronic Resource
    Examination of reproducibility in microbiological degradation experiments (1998)
    Springer
    Biodegradation 9 (1998), S. 65-82 
    Details
    ISSN: 1572-9729
    Keywords: model reduction ; Monod model ; nonlinear parameter estimation ; pure culture ; repeated batch experiments ; toluene degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Experimental data indicate that certain microbiological degradation experiments have a limited reproducibility. Nine identical batch experiments were carried out on 3 different days to examine reproducibility. A pure culture, isolated from soil, grew with toluene as the only carbon and energy source. Toluene was degraded under aerobic conditions at a constant temperature of 28 °C. The experiments were modelled by a Monod model – extended to meet the air/liquid system, and the parameter values were estimated using a statistical nonlinear estimation procedure. Model reduction analysis resulted in a simpler model without the biomass decay term. In order to test for model reduction and reproducibility of parameter estimates, a likelihood ratio test was employed. The limited reproducibility for these experiments implied that all 9 batch experiments could not be described by the same set of parameter values. However, experiments carried out the same day (within the same run) were more uniform than experiments carried out on different days (between runs), and a common set of parameter estimates could be accepted for experiments within runs, but not for experiments from different runs. The limited reproducibility may be caused by variability in the preculture, or more precisely, variations in the physiological state of the bacteria in the precultures just before used as inoculum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008215914179
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