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published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

No description available.

A variety of hazardous organic compounds are present in leachate from landfill sites that accept medical and industrial chemical waste. Most of these compounds find their way into nearby streams, rivers and dams, posing a threat to the ecosystem. In the present work two hazardous organic compounds, namely, m-xylene and 2-chloroethanol were chosen to react with ozone gas at different experimental conditions. The ozone initiated oxidation of m-xylene and 2-chloroethanol in solvent free conditions were investigated as a function of time. Gas chromatographic analysis of ozonated m-xylene, showed an increase in the conversion of substrate from about 1 % after 3 hours to about 14 % after 24 hours. Some of the ozonation products identified were formic acid, acetic acid, 3-methylbenzylalcohol, 3-methylbenzaldehyde and 3-methylbenzoic acid. The presence of acetic acid, ethyl acetate or acetone during ozonation significantly improved the percent conversion of m-xylene relative to similar products obtained under solvent free conditions. The presence of activated charcoal during ozonation of m-xylene showed marginal improvement in percent conversion compared to solvent free ozonation. The oxidation of 2-chloroethanol was followed by monitoring the consumption of the halogenated organic substrate which showed an increase in conversion from about 2 % after 3 hours to about 46 % after 12 hours. Ozonated products contained a mixture of acetaldehyde and acetic acid. It was also found that the ozonation of 2-chloroethanol yielded quantitative amounts of chloride ions. The percent conversion of 2-chloroethanol in the presence of acetic acid and ethyl acetate were higher than those under solvent free conditions. The use of activated charcoal during ozonolysis of 2-chloroethanol showed a significant increase in percent conversion of the substrate. Since 2-chloroethanol has a higher solubility in water than m-xylene the effects of solution pH, activated charcoal and hydrogen peroxide on ozone initiated reactions were studied. Solutions of 2-chloroethanol maintained at pH level 4 and 7 showed marginal changes in percent conversion compared to ozonation alone, however percent conversion improved significantly when the pH of the solution was increased to 10. The ozonation of 2-chloroethanol in the presence of 5 % hydrogen peroxide in water at pH levels 4 and 7 showed marginal changes in percent conversion compared to ozonation alone, however, percent conversion and product yields improved significantly, when the pH of the solution was increased to 10. Increasing the strength of the hydrogen peroxide in the reaction mixture from 5 % to 10 % had very little effect in the percent conversion of 2-chloroethanol and product formation. Based on the experimental findings the overall reaction mechanism for the reaction of both m-xylene and 2-chloroethanol with ozone is described. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2010.

Laboratory scale microcosm studies were conducted using site specific groundwater and aquifer solids to assess the feasibility of stimulating indigenous microorganisms in-situ to biologically transform Trichloroethylene (TCE) and its lesser chlorinated daughter products dichloroethylene (DCE) and vinyl chloride (VC). Three different treatments were conducted to determine the best approach for biologically remediating TCE under site specific conditions: anaerobic reductive dechlorination, aerobic cometabolism and sequential anaerobic/aerobic stimulation. Studies were conducted in batch serum bottles containing aquifer solids, groundwater and a gas headspace. Long-term (302 days) TCE anaerobic reductive dechlorination studies compared lactate, benzoate and methanol as potential anaerobic substrates. Site characteristic sulfate concentrations in the microcosms averaged 1,297 mg/L and TCE was added to levels of 2.3 mg/L. Substrates were added at one and a half times the stoichiometric electron equivalent of sulfate. Nutrient addition and bioaugmentation were also studied. Both benzoate and lactate stimulated systems achieved complete sulfate-reduction and prolonged dechlorination of TCE to VC and ethylene. Dechlorination was initiated between 15 to 20 days following lactate utilization and sulfate-reduction in the presence of approximately 300 mg/L sulfate. Benzoate amended microcosms did not initiate dechlorination until 120 to 160 days following the complete removal of available sulfate. After 302 days of incubation lactate and benzoate amended microcosms completely transformed TCE to VC with 7 to 15% converted to ethylene. Re-additions of TCE into both systems resulted in its rapid transformation to VC. The dechlorination of VC to ethylene was very slow and appeared to be dependent on VC concentration. Hydrogen addition at 10����� and 10������ atmospheres had no effect on the transformation of VC. Rapid methanol utilization resulted in its nearly stoichiometric conversion to methane and carbon dioxide without significant sulfate-reduction or dechlorination occurring. Nutrient addition slightly enhanced dehalogenation with lactate but inhibited it with benzoate. Bioaugmentation with a TCE dechlorinating culture from a previous benzoate amended Point Mugu microcosm effectively decreased lag-times and increased overall dechlorination. Aerobic cometabolism studies evaluated methane, phenol and propane as cometabolic growth substrates. Methane and phenol amended microcosms were able to remove only 50 to 60% of the added TCE after four stimulations, while propane utilizers were unable to cometabolize any TCE. Primary substrate utilization lag-times of 4 to 5 days, 0 to 0.5 days and 40 to 45 days were observed for methane, phenol and propane, respectively. Cometabolism of VC was possible in the presence of methane. Complete removal of 210 ��g/L VC was achieved after 2 stimulations with methane under strictly aerobic conditions. Methane utilization and VC oxidation required nitrate addition, indicating that the system was nitrate limited. A sequential anaerobic/aerobic microcosm study failed to achieve methane utilization and VC transformation likely due to oxygen being utilized to re-oxidize reduced sulfate in the system. / Graduation date: 1999

Graduation date: 1995

Graduation date: 1995

Graduation date: 1995

Historical evidence has shown that incidents due to hazardous materials (HazMat) releases during transportation can lead to severe consequences. The public and some agencies such as the Department of Transportation (DOT) show an increasing concern with the hazard associated with HazMat transportation. Many hazards may be identified and controlled or eliminated through use of risk analysis. Transportation Risk Analysis (TRA) is a powerful tool in HazMat transportation decision support system. It is helpful in choosing among alternate routes by providing information on risks associated with each route, and in selecting appropriate risk reduction alternatives by demonstrating the effectiveness of various alternatives. Some methodologies have been developed to assess the transportation risk; however, most of those proposed methodologies are hard to employ directly by decision or policy makers. One major barrier is the lack of the match between available data/database analysis and the numerical methodologies for TRA. In this work methodologies to assess the transportation risk are developed based on the availability of data or databases. The match between the availability of data/databases and numerical TRA methodologies is pursued. Each risk component, including frequency, release scenario, and consequence, is assessed based on the available data/databases. The risk is measured by numerical algorithms step by step in the transportation network. Based on the TRA results, decisions on HazMat transportation could be made appropriately and reasonably. The combination of recent interest in expanding or building new facilities to receive liquefied natural gas (LNG) carriers, along with increased awareness and concern about potential terrorist action, has raised questions about the potential consequences of incidents involving LNG transportation. One of those consequences, rapid phase transition (RPT), is studied in this dissertation. The incidents and experiments of LNG-water RPT and theoretical analysis about RPT mechanism are reviewed. Some other consequences, like pool spread and vapor cloud dispersion, are analyzed by Federal Energy Regulatory Commission (FERC) model.