Masters Degrees (Microbiology)

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Browsing Masters Degrees (Microbiology) by Author "Belford, Ian"

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    Investigating the removal of Candida and other potential pathogens from wastewater via an experimental rhizofiltration system
    (Stellenbosch : Stellenbosch University, 2013-03) Belford, Ian; Botha, Alfred; Wilsenach, J. A.; Stellenbosch University. Faculty of Science. Dept. of Microbiology.
    ENGLISH ABSTRACT: Water is a requirement of life and its quality, as well as quantity, is very important for sustaining the world‟s economy and human population. However, microbial and chemical pollution of water systems is on the increase, and can mainly be attributed to urban runoff, domestic and industrial discharges, inadequate sanitation, as well as ageing water treatment facilities. Practical solutions for the treatment of runoff are necessary to ensure water systems remain clean and safe for both human use and crop irrigation. Consequently, the ability of a rhizofiltration system to remove chemical and microbial contaminants from urban runoff was evaluated. A rhizofiltration system was constructed at the Stellenbosch Sewage Works, into which settled sewage could be distributed to determine if the presence of reeds improved the removal of chemicals, indicator organisms, pathogens, and potentially pathogenic yeasts. Indications were obtained that settled sewage from the Stellenbosch Sewage Works was microbiologically and chemically comparable to samples collected from the polluted Plankenburg River after a four day settling period in the storage tank constructed for the rhizofiltration system. This showed that the influent of the rhizofiltration system could be considered as urban runoff after four days of settling in the tank. The planted (experimental) and unplanted (control) side of the rhizofiltration system showed similar removal rates with regard to suspended solids, ammonium, Chemical Oxygen Demand, phosphates and sulphates in the influent, which percolated through the system within 45 min. Microbiologically, the experimental side was more effective than the control side in terms of faecal coliform, yeast and Salmonella removal but no difference was found between the two sides with regard to coliphage removal. The majority of yeasts that were isolated belonged to the genus Candida, and the experimental side was more effective than the control side in removing these opportunistic pathogens from wastewater. During the same experiments a number of antibiotic resistant bacteria were isolated which seemed to proliferate within the filter, the majority of which formed part of the Burkholderia cepacia complex. Additionally, the experimental side of the filter was significantly more effective at removing faecal coliforms, potentially pathogenic yeasts and Salmonella trapped within the sand, compared to the control side, six days after the wastewater percolated through the filter. In vitro sand filter experiments revealed that the presence of B. cepacia in the sand may be responsible for trapping some of the Candida species present in wastewater as it percolates through the sand, and thus may prolong the period in which these yeasts are subjected to the antagonistic effect of root exudates or other microbes.