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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Aerobic biotransformation of chlorinated aliphatic hydrocarbons by a benzyl alcohol grown mixed culture : cometabolism, mechanisms, kinetics and modeling

Tejasen, Sarun 27 June 2003 (has links)
The aerobic transformation of TCE and cis-DCE by a tetrabutoxysilane-grown microorganism (Vancheeswaran et al., 1999) led to the investigation of novel substrates, including benzyl alcohol, for promoting cometabolism. The culture grew on carboxylic compounds and alcohols, but did not grow on formate, methanol, methane, propane, butane, ethylene, benzene, toluene, or p-xylene. Cis-DCE transformation was observed when the culture grew on butyrate, glucose, 1-propanol, 1-butanol, ethanol, benzyl alcohol, and phenol, and effectively transformed TCE, cis-DCE, and vinyl chloride when grown on phenol or benzyl alcohol. Several cycles of growth on benzyl alcohol led to increases in TCE transformation rates and transformation capacities. Products of benzyl alcohol degradation shifted from benzaldehyde to 2-hydroxy benzyl alcohol (2HBA) during the several cycles of growth. In resting cells studies, 2HBA production rates were highly correlated with TCE transformation rates. TCE transformation and 2HBA production rates doubled when the culture was grown on phenol and rates of TCE transformation were correlated with 2HBA production rates. Benzyl alcohol- and phenol-grown cells oxidized toluene to o-cresol, which indicated the similarity between benzyl alcohol ortho-monooxygenase, phenol hydroxylase, and toluene ortho-monooxygenase. 2-Butyne and 1-hexyne (but not acetylene) inhibited benzyl alcohol- and phenol-grown cells similarly, indicating the same ortho-monooxygenase was responsible for TCE cometabolism. Resting cell kinetic studies were performed with cells grown on phenol or benzyl alcohol. Benzyl alcohol degradation followed a Monod kinetics while phenol degradation followed a Haldane kinetics. The maximum transformation rates (k[subscript max]) of TCE, cis-DCE, and VC achieved by phenol-grown cells were about a factor of two higher than achieved with benzyl alcohol-grown cells, while the half-saturation constants (K[subscript s]) were in a similar range. Transformation capacities (Tc) for TCE, cis-DCE, and VC were about a factor of two to four higher with phenol-grown cells. The modeling of TCE, cis-DCE, and VC transformation using independently measured k[subscript max] and K[subscript s] values matched well with observed data from batch tests. Benzyl alcohol was shown to be an effective novel substrate for the aerobic cometabolism of TCE, cis-DCE, and vinyl chloride. Being a non-regulated compound, it might have applications for in-situ bioremediation. / Graduation date: 2004
42

Fate and transport of the surfactant linear alkylbenzenesulfonate in a sewage-contaminated aquifer

Krueger, Carolyn J. 05 December 1997 (has links)
Linear alkylbenzenesulfonate (LAS) is the most widely used anionic surfactant in commercial detergent formulations. The environmental fate of LAS is of interest because of its disposal to wastewater treatment facilities and subsequent occurrence as a micropollutant in surface waters and groundwater. While LAS fate in wastewater treatment systems and surface waters is well-documented, few studies describe LAS fate in groundwater. This work investigates the transport and biodegradation of LAS in sewage-contaminated groundwater using natural-gradient pulsed and continuous field tracer tests and laboratory column experiments. An "in-vial" disk elution technique that couples solid phase extraction disk elution of LAS as tetrabutylammonium ion pairs with injection-port derivatization was developed for the determination of LAS in groundwater. Pulsed tracer tests then were conducted in an aerobic (~9 mg/L dissolved oxygen) uncontaminated zone, and a moderately aerobic (~1 mg/L dissolved oxygen), sewage-contaminated zone. A continuous injection test also was conducted in the sewage-contaminated zone. Chromatographic separation of the surfactant mixture was observed and attributed to the greater retardation of the longer alkyl chain homologs during transport. In the sewage-contaminated groundwater, biodegradation preferentially removed the longer alkyl chain homologs and external isomers resulting in LAS mixtures that were enriched in the more mobile and biologically-resistant components. LAS mass removal coincided with a decrease in dissolved oxygen concentrations, the appearance of LAS metabolites, and an increase in the number of free-living bacteria. The composition of the LAS mixture changed in the continuous field and column experiments and biodegradation rates increased as dissolved oxygen concentration increased. Mass removal rates were generally 2-3 times greater in the column experiments than in the field for similar dissolved oxygen concentrations. Rate constants for the continuous and pulsed tests conducted in the field were comparable indicating that increased exposure time of the aquifer sediments to the LAS did not increase biodegradation rates. / Graduation date: 1998
43

Nitrate and pesticide transport under pear production in clay and sandy soil

Cao, Weidong 06 December 1994 (has links)
Groundwater contamination on irrigated land is of concern in this nation and around the world. In order to reduce the potential of groundwater contamination by agricultural practices such as irrigation, fertilizer and pesticide application, vadose-zone monitoring and sampling are needed. The main objective of this study was to evaluate impacts of current irrigation treatments and soil structures on the migration of pollutants to groundwater. Passive CAPillary wick pan Samplers (PCAPS) and suction cups were installed in two cracking clays and one sandy soil under the pear tree root zone. PCAPS and suction cups were used to collect nitrate-nitrogen and tracer samples. Tracers were applied to track the spatial and temporal patterns of compounds that mimic nitrate-nitrogen and pesticide movement. The observed magnitude of water leaching over 3 months differed between irrigation methods and soil structures and decreased in this order: flooding over 3 months in clay soil (22.8 cm) > micro-sprinkler in clay soil (16.1 cm) > over-head sprinkler in sandy soil (4.1 cm). Leaching patterns were varied spatially; soil structures, irrigation methods, preferential flow, and high water table may have been responsible for the spatial variation of leaching. Mass recovery of all three tracers, including bromide, blue dye, and rhodamine had the same decreasing order: flooding in clay soil > micro-sprinkler in clay soil > over-head sprinkler in sandy soil. Average blue dye and rhodamine concentrations had the following order: flooding in clay soil > micro-sprinkler in clay > over-head sprinkler in sandy soil. Since blue dye and rhodamine have similar properties to some moderately adsorbed pesticides, we may infer that the risk of pesticide movement in three sites should also decrease in this order. Presumably pesticide movement in clay soil would have been more pronounced for flooding than sprinkler irrigation. On the annual/seasonal basis, the total mass of nitrate-nitrogen leaching differed between irrigation methods and soil structures and decreased in the following order: over-head sprinkler in sandy soil > flooding in clay soil > micro-sprinkler in clay soil. The annual average nitrate-nitrogen concentration observed under over-head sprinkler in sandy soil was 15 mg/l over the maximum allowed concentration level (10 mg/l) by the EPA while seasonal nitrate-nitrogen concentration was low in clay soil under current irrigation practices. Strong evidence suggested the occurrence of preferential flow in this study. Preferential flow may contribute to high water leachate, nitrate and pesticide migration. High correlation coefficients between paired PCAPS indicated that PCAPS have similar responses to water and solute leaching. Several improvements in PCAPS are needed to obtain representative samples under severe flooding conditions. Limited data suggested that ultra-low rate irrigation devices could reduce the water leaching and the potential of pollutant migration to the groundwater because ultra-low rate application devices minimize the soil macropore flow. / Graduation date: 1995
44

Use of In Situ Bioremediation to Treat Trichloroethylene-contaminated Groundwater

Chien, Hua-yi 07 February 2010 (has links)
Chlorinated aliphatic hydrocarbons (CAHs) include tetrachloroethene (PCE), trichloroethene (TCE), and others. The industrial solvent TCE is among the most ubiquitous chlorinated compounds found in groundwater pollution. TCE in environment can be removed by physical, chemical and biological procedures. Dehalorespiration is a biological pathway from which bacteria can derive energy from the reductive dechlorination of chlorinated ethenes using hydrogen or organic acids as electron donors and yielding chloride and ethene as degradation products. Dehalorespiration can be used to remediate chlorinated ethene contaminated aquifers if an appropriate aquifer ecosystem exists including populations of dechlorinating bacteria and companion organisms that contribute to the biogeochemical environment conducive to dehalorespiration activity. Enhanced in-situ aerobic or anaerobic bioremediation of chlorinated solvents is a cost-effective, expanding technology for the clean-up of chlorinated solvent-contaminated sites. The objective of this pilot-scale study was to apply an enhanced in situ bioremediation technology to remediate TCE-contaminated groundwater. Both aerobic and anaerobic remedial systems were evaluated at a TCE-spill site located in southern Taiwan. In the aerobic bioremediation zone, the effectiveness of air, nutrient, and sugarcane molasses injection to enhance the aerobic cometabolism on TCE degradation was evaluated. Results show that the decreases in TCE concentration were observed over 204 days operating period. Up to 73¢H-99¢H of TCE removal efficiency was obtained in this treatment system. In the anaerobic test zone, the effectiveness of nutrient and sugarcane molasses injection to enhance the anaerobic dechlorination on TCE degradation was also evaluated. Results show that the decreases in TCE concentration were observed over a 193-day operating period. Up to 53¢H-91¢H of TCE removal efficiency was obtained in this treatment system. Polymerase chain reaction was applied to analyze the gene variation in TCE-microbial degraders during the treatment process. Results from this study indicate that the aerobic TCE-degraders (type¢¹methanotrophs and type ¢º methanotrophs) and the gene of degradation enzymes (toluene monooxygenase, toluene dioxygenase, particulate methane monooxygenase) were detected after the treatment process in the aerobic test zone. In the anaerobic treatment zone, Dehalococcoides (anaerobic TCE-degrader) and the gene of degradation enzyme (vcrA and tceA) were detected and a significant drop of TCE concentration was also observed. Based on 16S rDNA sequence analysis, samples of groundwater from aerobic/anaerobic bioremediation zone are close related to the genera of Dehalococcoides sp. MB, Dehalococcoides ethenogenes 195, Dehalococcoides sp. VS, Acidovorax sp., Alicycliphilus sp., Burkholderiales, Caulobacter sp., Caulobacter tuntrae, Caulobacter vibrioides, Comamonadaceae, Hydrogenophaga sp., Iron-reducing bacterium, Mitsuaria chitosanitabida, Rhodocyclacea, Pseudomonas sp., Rhodoferax ferrireducens, Acinetobater sp., actinomycete, Pseudomonas aeruginosa and Variovorax sp. Results reveal that both the aerobic cometabolism and anaerobic dechlorination are feasible and applicable technologies to clean up TCE contaminated aquifers. Thus, the in situ bioremediation technology has the potential to be developed into an environmentally, economically and naturally acceptable remediation technology.
45

Treatment of Trichlorothylene in the Subsurface Environment Using the Suspension of Nanoscale Palladized Iron and Electrokinetic Remediation Process

Chang, Der-guang 31 August 2005 (has links)
The objective of this research was to evaluate the treatment efficiency of a trichloroethylene (TCE) contaminated soil by combined technologies of the suspension of palladized nanoiron and electrokinetic remediation process. First, nanoiron and palladized nanoiron were prepared using the chemical reduction method. Then they were characterized by various methods. Micrographs of scanning electron microscopy have shown that a majority of these nanoparticles were in the range of 50-80 nm. Specific surface areas were determined to be 76.88 m2/g and 100.61 m2/g for the former and latter, respectively. Results of X-ray diffractometry have shown that both types of nanoiron were poor in crystallinity. Three anionic dispersants were employed for evaluating their performance in stabilizing various nanoiron. Results have demonstrated that an addition of 1 wt% of Dispersant E during nanoiron preparation would result in a good stabilization of nanoiron. If the system pH was adjusted to 2.99, nanoparticles would settle rapidly. Batch tests were carried out to investigate the effects of various operating parameters on degradation of TCE in aqueous solutions. Experimental results have indicated that palladized nanoiron outperformed nanoiron in treatment of TCE in this study. The employment of Dispersant E would enhance the treatment efficiency further. Test results also showed that a linear increase of reaction rate constant was found with an increasing dose of palladium from 0.05 wt% to 1 wt% based on the mass of nanoiron. Further, an exponential increase of reaction rate constant would be obtained with an increasing pH. As for mixing intensity, it was found to be insignificant to the treatment efficiency of TCE in aqueous solutions. The final stage of this study was to evaluate the treatment efficiency of combined technologies of the suspension of palladized nanoiron and electrokinetic remediation process in treating a TCE-contaminated soil. Test conditions used were given as follows: (1) initial TCE concentration: 160-181 mg/kg; (2) electric potential gradient: 1 V/cm; (3) daily addition of 20 mL of suspension of palladized nanoiron (2.5 g/L) to the electrode reservoir; and (4) reaction time: 6 days. Test results have shown that addition of palladized iron suspension to the cathode reservoir yielded the lowest residual TCE concentration in soil. Namely, about 92.5% removal of TCE from soil. On the other hand, addition of palladized iron suspension to the anode reservoir would enhance the degradation of TCE therein. Based on the above findings, the treatment method employed in this work was proven to be a novel and efficient one in treating TCE-contaminated soil.
46

"The Remedial Institution of Soil and Groundwater Pollution¡¨Of The Institutional Evolution Of Analysis

LO, HUI-YI 11 July 2002 (has links)
The social construction and the behavior of organization transform continuously, and the relative prices keep changing. When the relative prices changing will cause the negotiating power of the organization to change and further affects institutional evolution? "The Remedial Institution of Soil and Groundwater Pollution¡¨ had passed through successively institutional evolution during 10 years, how does the pollutant and interest group affect the institutional evolution. Through Douglass C. North¡¦s view of the institutional evolution, I collected many different Taiwanese articles of evolvement policy and rules of soil and groundwater pollution to understand the relationship between the lawmaking of "The remedial institution of soil and groundwater pollution" and the organization of behavior. Besides that, using ¡§The Remedial Fee of Soil and Groundwater Pollution," the subsidiary bill of ¡§The Remedial Institution of Soil and Groundwater Pollution" as a case study. Deeply understand the North¡¦s Theories of institutional evolution in formal rule, informal rule and enforce characteristic and their relationship. According to the analysis of the interaction between institutions and organizations, it explained that the formal rule, The Remedial Institution of Soil and Groundwater Pollution, cause it 10 years for revising. Under such structure of the institutions, the network of the administration, legislative agency and different ideology, had affected the actors who take the action regulate the transaction costs and caused new arrangement of the institution to generate stable and slow changes. It proves that our notion of the behavior of organizations exists transaction cost and has interacted effect on the construction of institutional evolution to be right, and also proves that under North's theory of institutional evolution, provided a good explanation for "The Remedial Institution of Soil and Groundwater Pollution¡¨ can't quickly revise in Taiwan¡¦s current institutions. At the same time, this statement has enhanced the explanation capability of the theories toward the environment policies of Taiwan.
47

Hydrogeology of the Bird's Nest Aquifer, Uintah County, Utah

Phillips, Fred M. (Fred Melville) January 1979 (has links)
No description available.
48

A groundwater flow and solute transport model of sequential biodegradation of multiple chlorinated solvents in the surficial aquifer, Palm Bay, Florida

Burnell, Daniel K. 08 1900 (has links)
No description available.
49

Assessment of permeable reactive barriers alternative media for the remediation of nitrate-contaminated ground-waters.

Zorgani, Abdulmutaleb Esseid. January 2013 (has links)
The increase in the contamination of ground-water (GW) with nitrates in both developing and developed countries mainly results from agricultural activities and improper sanitation systems, and is a recent phenomenon that has become a source of great health concern, particularly in regions where people rely on the ground-water as their primary water source. Due to the advantages of using Permeable Reactive Barriers (PRB) including its cost-effectiveness as well as its capability to remove or mitigate the spread of large spectrum of contaminants (including nitrates), a significant increase has been observed in the use of this subsurface treatment technology compared to other methods. However, identifying more economic and reliable reactive media to be used instead of the costly conventional PRB materials is now of key importance. Two local soils namely Berea Red Sand (BRS) and Umgeni Sand (US) were the main focus of this research. In addition to these soils, Zero Valent Iron (ZVI) was also used in this study. Through the use of batch experiments the feasibility of the nitrate reduction was investigated by five substrates including 100% ZVI, 100% BRS, 100% US, mix of 75% ZVI + 25% BRS, and mix of 50% ZVI + 50% BRS. Five concentrations of nitrate synthetic solution including 10 mg/l, 25 mg/l, 50 mg/l, 100 mg/l, and 500 mg/l were used to simulate nitrate-contaminated ground-water. All the batch experiments were performed under semi-aerobic and uncontrolled pH conditions, and only one solid/liquid ratio of 1:10 was used. The two mixes (mix of 75% ZVI + 25% BRS, and mix of 50% ZVI + 50% BRS) exhibited a nitrate removal efficiency of 100%, with all the different initial concentrations that were used with it; besides these two mixes, none of the other substrates showed this performance. 100% ZVI; however, managed complete nitrate reduction when the 10 mg/l and 25 mg/l concentrations were used. Finally, it was concluded that the benefits of using BRS in combination with other materials such as ZVI in the PRB field are promising. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2013.
50

Evaluating and applying contaminant transport models to groundwater systems /

Purczel, Carl Leslie. January 2001 (has links) (PDF)
Thesis (M.Sc.)--University of Adelaide, Dept. of Applied Mathematics, 2001. / "November 2001." Bibliography: leaves 128-130.

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