Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2009. / Includes bibliographical references (p. 75-83).

published_or_final_version / Chemistry / Master / Master of Philosophy

<p>This study has shown that OH˙ radicals can be generated in an Fe/O2 cell from the electrode products via Fenton&rsquo / s reaction and used for water disinfection. The cell system in which the experiments were carried out was open and undivided and contained two electrodes with iron (Fe) as the anode and oxygen (O2) gas diffusion electrode. Typically, 100 ml of Na2SO4.10H2O (0.5M) solution was used as a background electrolyte. OH˙ radicals were produced in-situ in an acidic solution aqueous by oxidation of iron (II), formed by dissolving of the anode, with hydrogen peroxide (H2O2). The H2O2 was electrogenerated by reduction of oxygen using porous reticulated vitreous carbon (RVC) as a catalyst.</p>

Pacific oysters (Crassostrea gigas), Alaska pink salmon (Oncorynchus gorbuscha) roe and chum salmon (Oncorynchus keta) fillets were treated with aqueous ozone in both pilot plant and commercial settings to determine its effect on shelf-life and microbial changes. The microbial quality was analyzed by conducting pyschrotrophic and coliform plate counts on 3M petrifilm. Oxidative rancidity, pH and moisture were measured during the shelf-life study to determine the effects of ozone on quality. Concentrations of 0.5-1.3 ppm of ozone were applied for periods of 30 s, 1, 2 and 4 min at 5°C, 9°C and 15°C to determine an optimum ozone concentration and contact time that would decrease the seafood microbial load and increase shelf-life in the pilot plant studies. Oysters and roe were treated at 15°C and 5°C and fillets were treated at 9°C. There where only minor microbial differences between ozonated and non-ozonated samples. Treatment temperatures rather than treatment types affected the microbial load. The pilot plant experiments at 15°C and 5°C showed 1 log decrease in oysters and roe treated with aqueous ozone at variable concentrations. No increase in shelf-life was observed when salmon fillets were treated with aqueous ozone (1.3 ppm) for 2 min. Bacteria strains were isolated from treated (ozone and water) and control salmon fillet groups at 0, 5 and 10 days of storage and identified using the API20 NE system. The microbial change in the fillet flora did not differ between ozonated and non-ozonated treatment groups. Gram-positive bacteria were predominant in all groups at day 0, Pseudomonas flunrescens and P. putida were the predominant bacterial species found from all groups at days 5 and 10. Aqueous ozone (0.5-1.7 ppm) was applied in a commercial Ikura roe processing facility. A decrease in the microbial load was seen in the pre-processed samples which were ozonated with eggs in the skein. There were no differences in microbial loads from the non-ozonated and ozonated post-processed samples of individual eggs removed from the skein. / Graduation date: 2003

<p>This study has shown that OH˙ radicals can be generated in an Fe/O2 cell from the electrode products via Fenton&rsquo / s reaction and used for water disinfection. The cell system in which the experiments were carried out was open and undivided and contained two electrodes with iron (Fe) as the anode and oxygen (O2) gas diffusion electrode. Typically, 100 ml of Na2SO4.10H2O (0.5M) solution was used as a background electrolyte. OH˙ radicals were produced in-situ in an acidic solution aqueous by oxidation of iron (II), formed by dissolving of the anode, with hydrogen peroxide (H2O2). The H2O2 was electrogenerated by reduction of oxygen using porous reticulated vitreous carbon (RVC) as a catalyst.</p>

Thesis (MSc)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

M.Ing. (Electrical & Electronic Engineering) / Please refer to full text to view abstract

Magister Scientiae - MSc / This study has shown that OHË radicals can be generated in an Fe/O2 cell from the electrode products via Fenton&rsquo;s reaction and used for water disinfection. The cell system in which the experiments were carried out was open and undivided and contained two electrodes with iron (Fe) as the anode and oxygen (O2) gas diffusion electrode. Typically, 100 ml of Na2SO4.10H2O (0.5M) solution was used as a background electrolyte. OHË radicals were produced in-situ in an acidic solution aqueous by oxidation of iron (II), formed by dissolving of the anode, with hydrogen peroxide (H2O2). The H2O2 was electrogenerated by reduction of oxygen using porous reticulated vitreous carbon (RVC) as a catalyst. / South Africa

No description available.

Computational fluid dynamic (CFO) modelling has been applied to examine the operation of the prc-ozonation system at Wiggins Waterworks, operated by Umgeni Water in Durban, South Africa. Ozonation is employed in water treatment process primarily to achieve the oxidation of iron and manganese, the destruction of micro-organisms and the removal of taste and odour causing compounds. It also aids in the reduction of the colour of the final water, enhancement of algae removal and possible reduction of coagulant demand. A hydrodynamic model has been satisfactorily verified by experimental tracer tests. The effect of the gas injection was modelled by increasing the level of turbulence intensity at the ozone contactor inlet. The model prediction of the overall tracer response corresponded closely to the experimental results. The framework of ozone reaction modelling was subsequently established using values of rate constants from the literature. An accurate prediction of the ozone concentration profile requires the application of the correct ozone kinetics involved. In raw waters, the depletion of ozone is influenced by the presence of natural organic matters (NOM). The observed ozone decay was found in good agreement using the pseudo first-order rate law. By measuring the total organic carbon (TOC) as a surrogate for NOM, the experimentally determined rate constants can be calculated to account for the effects of the ozone doses and the water quality. The characterisation study also aimed to provide sufficient information on ozone depletion and to be operated easily, without the lengthy and costly analyses ofa detailed kinetics study. The predicted profile of residual ozone concentration suggests the current operating strategy can be improved to optimise the ozone utilisation. The proposed monitoring point was suggested to be at the end of second companment where most ozone reactions have been completed. By coupling the transport equations of the target compounds with their chemical reaction rates, the concentration profile of these compounds such as ozone can be predicted in order to assist the understanding of an operation and to attain better interpretation of experimental results. / Thesis (Ph.D.)-University of KwaZulu-Natal, 2005.