Dissertations / Theses on the topic 'Xylene – Biodegradation'

The increased use of alcohols as gasoline additives, and possible substitutes, has prompted the investigation of the fate of gasoline/alcohol mixtures in the environment. In situ bioremediation is one technique that can successfully be applied to remove ground water contaminants particularly in situations where the adsorptive capacity of the soil plays a major role. Frequently, enhanced in situ bioremediation techniques rely on indigenous microorganisms to degrade ground water contaminants; this technique may sometimes include the addition of acclimated bacteria.

In this study, soil microcosms were constructed in order to simulate the conditions found in a saturated aerobic aquifer. The biodegradation potential of methanol, benzene, and m-xylene was investigated. Uncontaminated soil from the surface, 12, 16.5, and 18 foot depths was utilized to observe the differences in microbial responses throughout the soil profile. The biodegradation potential of the indigenous microbiota was determined and compared to that of benzene acclimated bacteria, for all the compounds in the mixture. To observe the impact that chemical and physical soil characteristics may have on microbial responses, soils from each depth were classified on the basis of their particle size, moisture content and pH.

Substantial methanol, benzene, and m-xylene biodegradation by the indigenous microorganisms occurred in all subsurface soils. While methanol was readily biodegradable over concentrations ranging from about 80 mg/L to about 200 mg/L, benzene inhibited methanol biodegradation at about 125 mg/L in all soil depths. The addition of benzene acclimated bacteria considerably increased the biodegradation rates of all compounds in the mixture. Such increases in biodegradation rates may be attributed to the activities of both groups, the indigenous microorganisms and the benzene acclimated bacteria. The results obtained by this study suggest that biodegradation of methanol, benzene, and m-xylene can readily occur in a saturated aerobic subsurface environment. The physical and chemical properties of a ground water aquifer seem to have a marked effect on microbial responses, and consequently on the biodegradation potential of water contaminants.

Master of Science

Microcosm studies were conducted beginning with three xylene isomers: ortho-xylene, meta-xylene and para-xylene; and continued with the four mononitroxylene (MNX) isomers, culminating with testing ten dinitroxylene (DNX) isomers. Soil samples were obtained from a historically contaminated site with high levels of dinitrotoluene (DNT), trinitrotoluene (TNT) and dinitroxylene (DNX) and used as the inoculum for microcosm tests. The microcosm method of different isomers was based on the previous work on biodegradation of nitrotoluene. As it was demonstrated previously that 2,4-DNT degrading bacteria were present at the site, it was hypothesized that these may be capable of transforming or cometabolizing some of DNX isomers. Thus, DNX cometabolism studies were conducted in the presence of 2,4-DNT degrading bacteria. The presence of xylene and 2,4-DNT degrading was confirmed in this thesis. Meanwhile, several MNX and DNX isomers showed degradability in microcosm studies. Cometabolism studies showed that four DNX isomers could be cometabolized by 2,4-DNT enrichment.

Thesis (PhD)--Stellenbosch University, 2003.
ENGLISH ABSTRACT: Plant biomass, the most abundant renewable resource in nature, consists of matrices of mainly lignin, cellulose, hemicellulose as well as inorganic components. Xylan, the major hemicellulose component in plant cell walls, is the most abundant polysaccharide after cellulose. This makes the main constituent sugar of xylan, D-xylose, the second most abundant renewable monosaccharide in nature. Very few hemicelluloses are either homopolymeric or entirely linear. Therefore, the variety of enzymes involved in their hydrolysis is more complex than the enzyme group responsible for the hydrolysis of cellulose. Although the ability to degrade xylan is common among bacteria and filamentous fungi, this trait is relatively rare among yeasts. However, some strains of the yeast Pichia stipitis are, amongst others, able to degrade xylan. As P. stipitis is also one of the best D-xylose fermenting yeasts thus far described, this yeast has the potential of fermenting polymeric xylan directly to ethanol. However, it was shown that the natural xylanolytic ability of this yeast is very weak. In this study, xylanolytic genes were expressed in P. stipitis to test the ability of the yeast to produce heterologous proteins, and to determine the enhancement of xylan utilisation by the recombinant strain. The native xylose reductase gene (XYLl) and transketolase gene (TKL) and the heterologous Saccharomyces cerevisiae phosphoglycerate kinase (PGKl) gene promoter were cloned into P. stipitis transformation vectors and used to express the Trichoderma reesei ~-xylanase encoding gene (xyn2) as reporter gene. It was shown that the XYLl promoter was induced in the presence of D-xylose and that the TKL promoter was constitutively expressed. The PGKl promoter of S. cerevisiae did not function in P. stipitis . When the T reesei xyn2 gene and the Aspergillus kawachii ~-xylanase encoding gene (xynC) were expressed under control of the XYLl promoter, extracellular ~-xylanase activity of up to 136 nkat/ml and 171 nkatlml was observed, respectively. This activity declined over time due to the presence of extracellular proteases, secreted by P. stipitis. Growing the cultures in a fermentor and controlling the pH level to pH 6 did not alleviate the reduction of heterologous l3-xylanase activity. When the Aspergillus niger l3-xylosidase encoding gene (xlnD) was expressed as a fusion gene (designated XL02) with the S. cerevisiae mating factor secretion signal (MFal) under control of the P. stipitis TKL promoter, extracellular l3-xylosidase activity of 0.132 nkatlml was observed. Co-expression of the xyn2 and XL02 genes led to B-xylanase and l3-xylosidase activities of 128 nkatlml and 0.113 nkat/ml, respectively. Co-expression of the xynC and XL02 genes led to l3-xylanase and l3-xylosidase activities of 165 nkat/ml and 0.124 nkatlml, respectively. The expression of the fungal xylanolytic genes in P. stipitis also led to an increased biomass yield when the recombinant strains were cultured on birchwood xylan as sole carbon source. The strain co-expressing the A. kawachii l3-xylanase and A. niger l3-xylosidase encoding genes was the most successful, yielding a 3.2-fold higher biomass level than the control strain. Biomass levels of the recombinant strains were further improved on average by 85% by growing them in a fermentor under conditions of high oxygenation. The strains were also tested for direct conversion of xylan to ethanol and the strain co-expressing the A. kawachii l3-xylanase and A. niger l3-xylosidase encoding genes produced 1.35 giL ethanol, which represents a 3.6-fold increase in ethanol yield over the reference strain. These strains represent a step towards the efficient degradation and utilisation of hemicellulosic materials by ethanol-producing yeasts.
AFRIKAANSE OPSOMMING: Plant biomassa, die volopste hernubare koolstotbron in die natuur, bestaan uit matrikse van lignien, sellulose en hemisellulose. Xilaan, die hoof hemisellulose komponent in plantselwande, is na sellulose die volopste polisakkaried. Gevolglik is die hoof suikerkomponent van xilaan, naamlik D-xilose, die tweede volopste hernubare monosakkaried in die natuur. Baie min hemisellulose molekules is homopolimere of heeltemal linieêr. Daarom is die ensieme betrokke by die atbraak van hemiselluloses meer kompleks as die ensieme betrokke by die atbraak van sellulose. Bakterieë en filamentagtige fungi wat oor die vermoë om xilaan af te breek beskik, kom wydversprei voor maar relatief min giste kan xilaan benut. Sommige rasse van die gisspesie Pichia stipitis het egter beperkte vermoë om xilaan af te breek. P. stipitis is ook een van die beste D-xilose fermenterende giste wat tot dusver beskryf is en het dus die potensiaalom etanol vanafpolimeriese xilaan te produseer. In hierdie studie is gene wat kodeer vir xilaanatbrekende ensieme in P. stipitis uitgedruk om die vermoë van die gis as heteroloë uitdrukking sisteem te evalueer. Verder is die effek van die heteroloë xilaanatbrekende ensieme tydens groei op xilaan as enigste koolstotbron getoets. Die promoters van die xilosereduktasegeen (XYLl), die transketolasegeen (TKL) van P. stipitis en die fosfogliseraatkinasegeen (PGKl) van Saccharomyces cerevisiae is in P. stipitis transformasie vektore gekloneer en gebruik om die Trichoderma reesei ~-xilanasegeen (xyn2) as verklikkergeen uit te druk. Dit het bewys dat die XYLI promotor induseerbaar is in die teenwoordigheid van D-xilose terwyl die TKL geen konstant uitgedruk was. Die PGKI promotor van S. cerevisiae was nie funksioneel in P. stipitis nie. Ekstrasellulêre ~-xilanase aktiwiteit van onderskeidelik 136 nkatlml en 171 nkatlml kon waargeneem word wanneer die T reesei xyn2 geen of die Aspergillus kawachii ~-xilanasegeen (xynC) onder beheer van die XYLI promotor uitgedruk is. Hierdie aktiwiteit het afgeneem na gelang van tyd a.g.v. die teenwoordigheid van ekstrasellulêre proteases wat deur P. stipitis uitgeskei word. Die afname van ekstrasellulêre ~-xilanase aktiwiteit kon nie voorkom word deur die kulture in 'n fermentor te groei en die pH vlak tot pH 6 te beheer nie. Tydens uitdrukking van die Aspergillus niger ~-xilosidase geen (xlnD) as 'n fusiegeen (genoem XL02) met die paringsfaktor sekresiesein (MFal) van S. cerevisiae onder transkripsionele beheer van die P. stipitis TKL promotor, kon ekstrasellulêre ~-xilosidase aktiwiteit van 0.132 nkatlml waargeneem word. Gesamentlike uitdrukking van die xyn2 en XL02 gene het gelei tot ~-xilanase en ~-xilosidase aktiwiteite van 128 nkatlml and 0.113 nkat/ml, onderskeidelik. Gesamentlike uitdrukking van die xynC en XL02 gene het gelei tot ~-xilanase en ~-xilosidase aktiwiteite van 165 nkatlml and 0.124 nkatlml, onderskeidelik. Die uitdrukking van xilaanatbrekende ensieme III P. stipitis het verhoogbe biomassaproduksie teweeg gebring wanneer die rekombinante gisrasse op birchwood xilaan as enigste koolstotbron gegroei het. Die rekombinante ras wat die A. kawachii ~-xilanasegeen en die A. niger ~-xilosidase geen gesamentlik uitdruk, was die mees suksesvolle ras en het 3.2-voudig hoër biomassa as die kontrole ras opgelewer. Die biomassa van die rekombinante rasse tydens groei op xilaan as enigste koolstotbron kon gemiddeld met 85% verhoog word deur die giste onder hoë suurstotkonsentrase in 'n fermentor te kweek. Die rekombinante rasse is verder ook getoets vir hul vermoë om xilaan direk tot etanol om te skakel. Die rekombinante ras wat die A. kawachii ~-xilanasegeen en die A. niger ~-xilosidase geen gesamentlik uitgedruk het, het 'n 3.6- voudige verhoging in etanolproduksie getoon en 1.35 gIL ethanol gelewer. Hierdie rekombinante gisrasse verteenwoordig 'n stap nader aan die doeltreffende atbraak en benutting van hemisellulose deur etanolproduserende giste.

Hidrocarbonetos aromáticos conhecidos como BTEX (benzeno, tolueno, etilbenzeno e xilenos) estão entre os maiores problemas de poluição ambiental. Estes compostos são reconhecidos por sua recalcitrância em ambientes anóxicos, e a remoção destes hidrocarbonetos, de sítios anaeróbios contaminados é dependente da atividade de uma população de microrganismos adaptados capazes de promover a biodegradação destes compostos, nestas condições. Neste sentido, o presente trabalho buscou purificar, caracterizar e utilizar cultura desnitrificante, como inóculo para desenvolvimento de biofilme, em reator anaeróbio de leito fixo preenchido com espumas de poliuretano, além de avaliar o potencial deste biofilme em promover a biodegradação dos compostos de BTEX. Células da cultura apresentaram coloração Gram negativa, com morfologia de cocos (diplococos e cocobacilos). A cultura foi capaz de crescer, sob condições desnitrificantes, utilizando diferentes substratos. A cultura não apresentou capacidade de crescer sob condições sulfetogênicas. Velocidades de crescimento ('mü') de 0,046/h e 0,050/h e tempos de geração (Tg) de 15,1 horas e 13,9 horas foram obtidos para as células crescidas em benzeno e etilbenzeno, respectivamente. A cultura purificada foi utilizada para formar biofilme em RAHLF. Em todas as condições de alimentação as quais os reatores foram submetidos houve remoção da matéria orgânica, nitrato e dos hidrocarbonetos. A menor eficiência de remoção de hidrocarbonetos foi de 89,4%, obtida durante a alimentação dos reatores com benzeno. A matéria orgânica (DQO) foi removida com eficiência média de 87,1%. A eficiência média de remoção de nitrato foi de 94%. O sequenciamento das amostras revelou que o biofilme do RAHLF1 foi formado, principalmente, por espécies de Paracoccus, Pseudomonas e Bacteroides, enquanto que no RAHLF2, alimentado com etilbenzeno, observou-se espécies dos gêneros: Paracoccus, Pseudomonas, Xanthomonas e Variovorax
The monoaromatic hydrocarbons known as BTEX (benzene, toluene, ethylbenzene, and xylene) are among the greatest environmental pollution problems. These compounds are known by their recalcitrance in anoxic environments, and the removal of these toxics from anaerobic contaminated sites depends on the presence of an adapted microbial population capable of to promote the biodegradation of these compounds under such condition. Thus, in the current study a denitrifying culture was purified, characterized and used as inoculum to form a biofilm in a horizontal-flow anaerobic immobilized biomass reactor filled with polyurethane foam, and to assess the potential of this biofilm to promote BTEX compounds biodegradation. Culture cells were Gram negative, with coccus (diplococcus and cocobacilli) morphology. The culture was able to grow, under denitrifying conditions, using different substrates. No growth was seen in sulfate-reducing conditions. Growth velocity('mü') of 0.046/h and 0.050/h, and generation time of 15.1 and 13.9 hours were obtained for cultures isolated in the presence of benzene and ethylbenzene, respectively. The purified culture was used to form a biofilm inside RAHLF. At all feeding conditions the reactors were submitted the organic matter, nitrate and hydrocarbons were removed. The smallest hydrocarbons removal efficiency was 89.4%, obtained during benzene feeding. The organic matter (COD) was removed with mean efficiency of 87.1%. The mean efficiency of nitrate removal was 94.0%. Sequencing of samples showed that the RAHLF1 biofilm was composed specially for Paracoccus, Pseudomonas and Bacteroides species. Biofilm of RAHLF2 reactor, obtained from ethylbenzene feeding, was composed by Paracoccus, Pseudomonas, Xanthomonas and Variovorax species

Lignocellulosic biomass is an abundant renewable resource targeted for biofuel production. Cellulose and hemicellulose from biomass both contain fermentable sugars and other moieties that can be converted to biofuels or other commodity chemicals. Enzymatic hydrolysis of these biopolymers is a critical step in the liberation of sugars for fermentation into desired products. In nature, anaerobic microbes produce protein nanostructures called cellulosomes that efficiently degrade cellulose substrates by combining multiple enzyme activities onto a scaffolding protein. However, current enzyme cocktails used in industry contain secretomes of aerobic microbes and are not efficient enough to be highly economical. Furthermore, most bio-processes focus on cellulose, rendering hemicellulose under-utilized. The three main objectives of this dissertation are to 1) develop multi-functional, self-assembling protein nanostructures for hemicellulose degradation using the architecture provided by cellulosomes, 2) understand the self-assembly mechanism at conditions for consolidated bioprocessing applications, and 3) compare the effectiveness of structured to non-structured hemicellulases in the hydrolysis of biomass. Xylan is a major type of hemicellulose in biomass feedstocks targeted for biofuel production. Six different xylanosomes were designed for hydrolysis of xylan within multiple biomass substrates using the cohesin-dockerin domain systems from Clostridium thermocellum, Clostridium cellulovorans, and Clostridium cellulolyticum. Each two-unit structure contained a xylanase for internal cleavage of the xylan backbone and one side-chain acting enzyme, either a ferulic acid esterase or bi-functional arabinofuranosidase/xylosidase. Expansion to three-unit xylanosomes included a family 10 or 11 xylanase, a bi-functional arabinofuranosidase/xylosidase, and bi-functional ferulic acid esterase/acetylxylan esterase. These multi-functional biocatalysts were used to degrade hemicellulose-rich wheat arabinoxylan and cellulose-containing destarched corn bran. Synergistic release of soluble sugars and ferulic acid was observed with select xylanosomes and in some cases required addition of an endoglucanase and cellobiohydrolase for enhanced hydrolysis. Furthermore, a putative ferulic acid esterase gene from the soil bacterium Cellvibrio japonicus was characterized and its role in xylan hydrolysis investigated. Information for the development of stable and functional cellulosome-like biocatalysts in metabolically-engineered microbes was collected using surface plasmon resonance. The protein-protein interaction of cohesin and dockerin domains for xylanosome self-assembly was examined at various temperatures and in the presence of ethanol to mimic different hydrolysis and fermentation processes and found to retain high affinities at the selected conditions. Moreover, the high-affinity interaction of cohesin and dockerin domains in the presence of non-specific proteins eliminated the need for protein purification for xylanosome construction. In addition to development of the first cellulosome-like biocatalysts targeted for hemicellulose degradation, this dissertation provides insight on possible improvements for the enzymatic hydrolysis of biomass, as well as the applicability of xylanosomes in consolidated bioprocessing.

The rate of removal of benzene, toluene, ethylbenzene and the xylene isomers (BTEX) from contaminated groundwater is needed to design remediation processes. Benzylsuccinic acid (BSA) and methyl-benzylsuccinic acid (methyl BSA) are unambiguous metabolites of anaerobic BTEX biodegradation. An analytical method for quantitative determination of BSA in groundwater samples was developed. Samples containing BSA and methyl BSA were extracted onto 0.5 g of styrene-divinylbenzene, eluted with ethyl acetate, and methylated with diazomethane. Gas chromatography coupled to mass spectrometry with electron impact ionization was used for separation and detection. The recovery from spiked 1 L groundwater samples was 88 to 100 %. The precision of the method, indicated by the relative standard error was ± 4% with a method detection limit of 0.2 μg/L. The method was then used to analyze samples from single-well push-pull tests conducted by injecting deuterated toluene and xylene into BTEX-contaminated wells in order to demonstrate in-situ biodegradation. Unambiguous evidence for deuterated toluene and xylene biodegradation was obtained with the observation of deuterated BSA and methyl BSA coupled with the utilization of nitrate presumably due to denitrification as terminal-electron-accepting process. Minimum first-order degradation rates for deuterated toluene estimated from formation of BSA were 0.0004 to 0.001 day⁻¹. Rates of methyl BSA formation were not calculated because methyl BSA, although detected, was not above the quantitation limit. Removal rates of deuterated toluene and o-xylene were not directly measurable because the rates were too low to measure significant changes in parent compound concentrations. Wells for which the formation of deuterated BSA and methyl BSA were observed had lower relative concentrations of toluene and xylenes relative to total BTEX than wells for which no deuterated BSA and methyl BSA were observed. Retardation factors for injected deuterated toluene and background toluene of 2 and 14, respectively, were obtained from push-pull tests conducted to determine toluene transport properties. Differences in retardation factors for injected and background toluene indicate differences between injected and background solute transport and is a topic that requires further study.
Graduation date: 2002

碩士
明新科技大學
化學工程研究所
95
This study investigated the morphology evolution of the aerobic pure culture Pseudomonas putida (ATCC 11172), by using a culture media. The observation shows that P. putida swelled up in the beginning 9 to 10 hours of the cultivation, this means the microorganism was located in the growth phase. 　　The kinetic study of the substrates, including benzene, toluene, xylene, and phenol (BTXP), was carried out by the usage of the initial rate method. The biomass concentration was measured by UV-Vis Spectrophjotometer in a fixed wavelength, �� = 600 nm. The obtained optical density (OD600) was then used to calculate the corresponding specific growth rate. The results show that, in different soluble concentrations ranges of these four substrates, e.g., ranging from 5 to 1800 mg L-1 for benzene, ranging from 10 to 800 mg L-1 for btoluene, ranging from 10 to 400 mg L-1 for xylene, and ranging from 50 to 1000 mg L-1 for phenol, the substrate concentration effect on the specific growth rate of the biomass, P. putida (ATCC 11172), can be described by Andrews’ model. The kinetic data for each batch experiment was obtained by the aid of the nonlinear regression of the software, SAS. The parameters of Andrews’ model for the respective substrate are as follows: For benzene, �慆B = 1.7976 h-1, KSB = 63.7402 mg L-1 and KIB = 104.8 mg L-1. For toluene, �慆T = 0.9214h-1, KST = 16.3625 mg L-1 and KIT = 344.4 mg L-1. For o-xylene, �慆X = 1.4369 h-1, KSX = 44.218 mg L-1 and KIX = 60.2164 mg L-1. For phenol, �慆P = 0.2532 h-1, KSP = 14.766 mg L-1 and KIP = 3280.8 mg L-1. 　　Next, by analyzing the linear correlations between the apparent yield coefficients and the net specific growth rates, the corresponding true yield coefficients, Y and the endogenous maintenance rates, �徯 of the four different substrates (BTXP) were obtained as follows: YB = 1.339 g g-1 and �徯B = 0.06186 h-1 for benzene; YT = 0.9793 g g-1 and �徯T = 0.1905 h-1 for toluene; YX = 2.7233 g g-1 and �徯X = 0.2879 h-1 for o-xylene; and YP = 2.798 g g-1 and �徯P = 0.1500 h-1 for phenol. 　　And the batch kinetic experiments with more than one substrate were performced at 25 ºC and pH 7.0, and the cross-inhibition between these substrates was carefully investigated as follows: K21 = 18.8 and K12 = 2.5 for the initial concentrations of benzene and toluene: 98 mg L-1 and 80 mg L-1, respectively. K21 = 9.5 and K12 = 3.5 for the initial concentrations of benzene and toluene: 76 mg L-1 and 98 mg L-1, respectively. K21 = 1.5 and K12 = 0.5 for the initial concentrations of benzene and toluene: 1787 mg L-1 and 553 mg L-1, respectively. K21 = 5.2 and K12 = 1.3 for the initial concentrations of benzene and toluene: 388 mg L-1 and 558 mg L-1, respectively. The result shows that the inhibition of toluene on benzene is more obvious. K32 = 0.9 and K23 = 1.3 for the initial concentrations of toluene and o-xylene: 557 mg L-1 and 128 mg L-1, respectively. K32 = 3.3 and K23 = 1.8 for the initial concentrations of toluene and o-xylene: 288 mg L-1 and 128 mg L-1, respectively. The result shows that the inhibition of toluene on o-xylene is more significant. 　　Furthermore, the interation parameters were used for the reactor dynamic analysis. The optimal operating conditions were obtained subsequently. Hence, the effective degradation of the harzadous solvent wastes was validated experimentally by the biological method in a stable steady state mode.

This thesis examined the biological treatment of gas streams containing benzene, toluene, ethylbenzene and o-xylene (BTEX) using solid-liquid two-phase partitioning bioscrubbers (SL-TPPBs). SL-TPPBs consist of a cell containing aqueous phase and a polymeric solid phase that sequesters poorly water soluble and/or toxic substrates, mitigating substrate toxicity in the aqueous phase and improving the gas mass transfer during treatment of VOC contaminated gases. An initial investigation of oxygen transport determined that the polymers in a stirred-tank SL-TPPB enhance gas-liquid mass transfer. In addition, a study on biodegradation kinetics of BTEX by a bacterial consortium identified and quantified substrate interactions such as inhibition, enhancement and cometabolism. The stirred-tank SL-TPPB was then experimentally investigated for treatment of BTEX gas streams during steady-state and dynamic step-change operation to determine performance of the system relative to other biotreatment methods. A mathematical model was developed to predict system performance, which included the microbial kinetic model structure and parameters estimated during kinetic and oxygen mass transfer studies. As a less energy intensive alternative, an airlift SL-TPPB was operated and characterized. The airlift SL-TPPB was compared to an airlift liquid-liquid TPPB (silicone oil as sequestering phase) and a single phase airlift over dynamic step-change loadings, which showed that the airlift SL-TPPB outperformed the single phase airlift by >30% and had similar performance to the liquid-liquid airlift. However, the airlift SL-TPPB performance was lower relative to the stirred-tank SL-TPPB by >15%. Steady-state operation of the airlift SL-TPPB identified a range of operating conditions that provided maximum performance and conditions that were not oxygen limited. This prompted a study of oxygen mass transfer and hydrodynamics in the airlift system, which identified that the addition of polymers to an airlift does not cause physical enhancement of the gas-liquid mass transfer coefficient, but improves aqueous phase mixing and enhances overall oxygen transfer rate. A tanks-in-series mathematical model was formulated to predict performance of the airlift SL-TPPB, wherein the number of tanks-in-series to describe mixing in the airlift was obtained from a residence time distribution analysis of the airlift system completed during the hydrodynamic investigation. This thesis contributes a low-energy solution for the effective treatment of gases contaminated with BTEX.
Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2009-08-18 16:16:22.598