Tungsten doped tantalum oxide films on titanium substrates were investigated for use as anodes in the electrochemical disinfection of wastewater (measured through e. coli inactivation). A sol-gel method for fabricating these films was developed that allowed for control of both the doping concentration (through volumes of tantalum and tungsten ethoxide added to the solutions), and the thickness (through the number of layers applied). The morphology and composition of these films were investigated using SEM and EDX mapping; the morphology was found to be connected to the fabrication heating procedure. Three different doping concentrations (0%, 8% and 14% tungsten by volume of added metals) were investigated for: 1) electrochemical activity; 2) long-term stability; and 3) disinfection capabilities. The 14% samples demonstrated the highest conductivity (0.06μS/cm), good long-term stability (verified using ICPMS, SEM and EDX analysis) and the best electrochemical activity for removal of e. coli (based on wastewater tests).

Tungsten doped tantalum oxide films on titanium substrates were investigated for use as anodes in the electrochemical disinfection of wastewater (measured through e. coli inactivation). A sol-gel method for fabricating these films was developed that allowed for control of both the doping concentration (through volumes of tantalum and tungsten ethoxide added to the solutions), and the thickness (through the number of layers applied). The morphology and composition of these films were investigated using SEM and EDX mapping; the morphology was found to be connected to the fabrication heating procedure. Three different doping concentrations (0%, 8% and 14% tungsten by volume of added metals) were investigated for: 1) electrochemical activity; 2) long-term stability; and 3) disinfection capabilities. The 14% samples demonstrated the highest conductivity (0.06μS/cm), good long-term stability (verified using ICPMS, SEM and EDX analysis) and the best electrochemical activity for removal of e. coli (based on wastewater tests).

Wastewater microbial flocs can protect microorganisms from inactivation by UV light. This effect is detected as tailing at high UV doses in the UV dose response curve. A double-layer structure composed of an inner compact core surrounded by a loose outer layer was proposed by earlier studies to describe UV resistance of microbial flocs. Due to limited oxygen diffusion into the compact cores, the UV inactivation of compact cores and microbial flocs under anaerobic conditions needed to be addressed. The UV disinfection kinetics under anaerobic culturing condition was nearly identical to that of the aerobic study. Moreover, the role of iron concentration on the differences in the UV inactivation kinetics of flocs and cores was assessed. The increase in UV absorbance of floc material due to iron addition could dominate the UV disinfection kinetics of flocs and cores such that they exhibited similar UV disinfection kinetics.

No description available.

Wastewater microbial flocs can protect microorganisms from inactivation by UV light. This effect is detected as tailing at high UV doses in the UV dose response curve. A double-layer structure composed of an inner compact core surrounded by a loose outer layer was proposed by earlier studies to describe UV resistance of microbial flocs. Due to limited oxygen diffusion into the compact cores, the UV inactivation of compact cores and microbial flocs under anaerobic conditions needed to be addressed. The UV disinfection kinetics under anaerobic culturing condition was nearly identical to that of the aerobic study. Moreover, the role of iron concentration on the differences in the UV inactivation kinetics of flocs and cores was assessed. The increase in UV absorbance of floc material due to iron addition could dominate the UV disinfection kinetics of flocs and cores such that they exhibited similar UV disinfection kinetics.

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>A comparative study of electrolysers using different anodic materials for the electrolysis of brine (sodium chloride) for the production of sodium hypochlorite as a source of available chlorine for disinfection of rural water supplies has been undertaken. The electrolyser design used was tubular in form, having two chambers i.e. anode inside and cathode outside, separated by a tubular inorganic ceramic membrane. The anode was made of titanium rod coated with a thin layer of platinum and a further coat of metal oxide. The cathode was made of stainless steel wire. An assessment of these electrolysers was undertaken by studying the effects of some variable parameters i.e.current, voltage and sodium chloride concentration. The cobalt electrolyser has been shown to be superior as compared to the ruthenium dioxide and manganese dioxide electrolysers in terms of hypochlorite generation. Analysis of hydroxyl radicals was undertaken since there were claims that these are produced during brine electrolysis. Hydroxyl radical analysis was not successful, since sodium hypochlorite and hypochlorous acid interfere using the analytical method described in this study.</p>

<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>

Errata sheet has been pasted onto the front end-paper. / Bibliography: leaves 208-217. / x, 217 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Outlines a systematic synthesis and testing of continual sterilization design. Principal aim is to evaluate and develop mathematical models for sterilization, undertake experimental studies for determining thermal inactivation effects on continuous processing of a liquid containing contaminant bacteria and compare the data obtained with those predicted by a selected model. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 2001?

In this thesis, detection of active water-borne bacteria was achieved by combining flow cytometry with vital dyes that characterise the metabolic status of cells. Following optimisation, these techniques were applied to investigate the activity of bacteria exposed to disinfection, both in the laboratory and in real systems. Raw and potable waters from various locations around South Australia were then analysed to investigate relationships between numbers of active bacteria and those detected by traditional culture-based techniques. Flow cytometric cell sorting of active bacteria followed by 16S rRNA gene-directed PCR and denaturing gradient gel electrophoresis (DGGE) was then used to track the survival of bacteria through water treatment and into distribution. In doing so the identification of active bacteria not detected by culture was achieved. Finally, real-time PCR was optimised for detection of ammonia oxidising bacteria. This group of bacteria were responsible for loss of disinfection residual within a chloraminated distribution system. / thesis (PhD)--University of South Australia, 2005.