Chloramine is a widely used alternative disinfectant for chlorine in potable distribution water. This alternative was investigated and employed to show its effect for suppressing coliforms, trihalomethanes(THMs), disinfection by-products (DBPs), and corrosivity.Coliform analyses were performed with m-Endo(total coliform) and m-T7 agar(injured coliform) by using a standard Membrane Filtration method. Heterotrophic bacteria were monitored with HPC agar(PCA) and R2A agar (nutrient limited agar). EPA methods 502.2, 524.2, and 504 were used to determine levels of Trihalomethanes(THMs) and Disinfection by-products(DBPs).In our study, we observed no significant differences in coliform counts, that could be attributed to the switch in disinfectant. The most common coliform identified was Enterobacter cloacae. We also noted that m-T7 performed better than m-Endo in the detection of coliforms. We also observed a low level of corrosion (0.4-3.8 mils/year) in the distribution system (DS). Higher counts of heterotrophic bacteria were enumerated on R2A when compared to HPC. DBP values decreased two fold when compared with DBP values for the two previous years during which chlorine was used as the disinfectant. / Department of Biology

Tap water collected according to standard methods was examined for microbial presence. Epifluorescent diagnoses using redox probe 5-cyano-2,3ditolyl tetrazolium chloride (CTC), 4',6-diamidino-2-phenylindole (DAPI), and acridine orange (AO) were employed for direct evidence of microorganisms. Evidence of total (DAPI or AO), respiring (CTC) bacteria, and heterotrophic plate count (HPC) was determined on multiple occasions during the summer, fall, and winter 1996-1997. Pseudomonas aeruginosa, Acinetobacter sp., Bacillus licheniformis, and Methylobacterium rhodinum were isolated and identified by the API and Biolog system using GN and GP procedures. On the basis of comparisons presented in this study between the CTC method and the standard HPC procedure, it appeared that the number of CTC-reducing bacteria in the tap water samples was typically higher than that determined by HPC, indicating that many respiring bacteria detected by the CTC reduction technique fail to produce visible colonieson the agar media used. In the seasonal data obtained by the CTC method, no difference was shown among respiring bacterial counts obtained from June through January. In the examination of P. aeruginosa viability in presence of chlorine, the number of CTC-positive bacteria exceeded the number of CFU by more than 2 logs after exposure to chlorine, suggesting that reliance on HPC overestimate the efficacy of disinfection treatment. In inactivation assays using the Biolog MT plate, no sensitivity to chlorine or chloramine disinfectants was noted even at high concentration levels (5 mg/liter). Following initial drop, bacterial activities increased as contact time increased. Thus, it appears that the MT microplate provides too low a cell concentration, too great a contact time, and/or too low a concentration of tetrazolium dye within the well for successful analysis of disinfectant capability to selected bacterial strains isolated from distribution water. / Department of Biology

Submitted in fulfilment of the academic requirements for the Degree of M.Tech: Chemical Engineering, M. L. Sultan Technikon, 2001. / Historically inorganic coagulants were the coagulants of choice for OAF treatment of potable water. Water treatment practitioners using OAF technology preferred ferric chloride, an inorganic coagulant. Ferric chloride formed light, floatable floes at relatively low flocculation intensities and detention times. The inorganic coagulant was also more forgiving during incidents of overdosing and raw water and pH variability / M

M.Sc. / Drinking water treatment plants in South Africa rely almost entirely on surface water sources, which are often compromised due to high return flows and indirect reuse. The typical treatment plants focus on the removal of physical and microbial contaminants which include turbidity, colour, chemical compounds and micro-organisms. A relatively new alarm to this list is natural organic matter (NOM) which has become a major concern in potable water treatment due to its recent regulation. Conventionally, the drive to remove NOM from potable water would be the desire to remove colour from public water supplies. However, more problems in drinking water treatment associated with NOM have been recently identified. These include taste and odour, its tendency to foul membranes, interference with the removal of other contaminants and its potential to contribute to corrosion and slime growth in distribution systems. Moreover, it causes high demands for coagulants and disinfectants. The NOM is also the main precursor for disinfection by-products (DBPs) formed when it interacts with disinfectants such as chlorine during water disinfection. In this study, different raw water samples, of different NOM composition were collected from selected sources across the country and assessed for the removal of dissolved organic carbon (DOC) and UV absorbance at a wavelength of 254 nm (UV 254) using enhanced coagulation (EC). The efficacy of EC, which can be employed as a practical technology in the removal of both turbidity and NOM, was evaluated in these raw water sources. Jar tests were conducted with ferric chloride as the coagulant, and specific pH values were chosen as target values guiding the different coagulant dosages for the jar tests. The pH of the low-alkalinity (<60 mg/ℓ CaCO3) raw waters were adjusted and raised by the addition of sodium carbonate. Algorithms for finding the optimum coagulant dosage for both turbidity and UV 254 removal were developed and consistently applied to all the results in independent v batch tests, in which residual amounts of UV 254, DOC and turbidity were measured. The raw water parameters and results obtained from these tests were used to develop feed-forward multiplicative models predicting the performance of EC using ferric chloride. The results showed that the raw waters chosen were, indeed, representative of the different water types present in South Africa, and that the general water characteristics were affected by seasonal variations. The EC procedure developed was able to reduce turbidity to levels low enough for removal by subsequent treatment steps in the water treatment train. The residual UV 254 values were in all cases lower than 6 m-1, which theoretically corresponds to about 3.5 mg/ℓ DOC. This was confirmed by the residual DOC values which were found to be lower than 4 mg/ℓ. Generally, the waters of South Africa were found to be amenable to coagulation. In almost all cases, the costs for EC were comparable to those for conventional coagulation, hence EC could be employed as a NOM removal strategy in the South African context.

Titanium dioxide nanoparticles were prepared using the sol-gel process. The effect of temperature and precursor concentration on particle size was investigated. The optimum conditions were then used to prepare carbon and nitrogen doped titanium dioxide (TiO2) nanoparticles. Doping was done to reduce band gap of the nanoparticles in order to utilize visible light in the photocatalytic degradation of organic compounds. A significant shift of the absorption edge to a longer wavelength (lower energy) from 420 nm to 456 nm and 420 nm to 428 nm was observed for the carbon doped and nitrogen doped TiO2 respectively. In this study, the prepared TiO2 photocatalyst was immobilized on carbon nanofibres to allow isolation and reuse of catalyst. The photocatalytic activity of the catalyst was tested using methyl orange as a model pollutant and was based on the decolourization of the dye as it was degraded. The doped TiO2 exhibited higher photocatalytic activity than the undoped TiO2. The materials prepared were characterized by XRD, TEM, SEM, FT-IR, DSC and TGA while the doped TiO2 was characterized by XPS, ESR and Raman Spectroscopy.

M.Sc. / The occurrence of invertebrates in drinking water supplies is a common consumer complaint with studies showing that very few drinking water distribution networks are totally free of organisms. A detailed investigation of different types of metazoan animals in the drinking water supply networks of South Africa has not been undertaken. In limited worldwide studies, invertebrates (mainly Amphipoda, Chironomidae, Cladocera, Copepoda and Ostracoda) have been detected in produced drinking water. In countries that have started monitoring these organisms, the quality of the produced water has improved due to the improved methods of filtering. The occurrence of “worms” (Nematodes and Diptera) and Crustaceans decreases the aesthetic value of the drinking water, and pathogenic organisms, which may also be associated with them, can affect human health. Limited reference works have been compiled during the conducted studies on drinking water distribution networks throughout the world. All fresh water invertebrates have the potential to be passed into the drinking water supply network (Rising mains, pipelines, reservoirs, and consumer taps). There are few complete reference works available for fresh water invertebrates occurring in the fresh water sources and those of Southern Africa. Therefore, there are no reference works regarding fresh water invertebrates that can be used to monitor drinking water supply networks in South Africa. / Prof. J.H.J. van Vuren

Monodisperse titanium dioxide (TiO2) nanoparticles were synthesized by a novel freeze-drying process herein called lyophilization. The process of lyophilization is described in detail. The materials were characterized by scanning electron microscopy SEM) including energy dispersive x-ray spectroscopy (EDXS), high resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), Raman spectroscopy and UV-Vis-IR spectrophotometry. The TiO2 nanoparticles have narrow size distribution, mono-disperse, strained with most of the characteristics showing presence of the four phases of TiO2 thus: anatase, brookite, rutile with each lyophilization process producing its own phase mostly controlled by pH and precursor concentration and anneal/calcining temperatures. With specific reference to HRTEM, Raman spectroscopy results and XRD, it was found that the Scherrer equation, the Williamson-Hall method and others of similar nature were not enough to explain the strain and the grain sizes of these particles. Therefore the Williamson-Hall method was revised to properly explain the new results. The obtained TiO2 nanoparticles were used in three applications: (1) gas sensing (2) degradation of organic water-borne pollutants using methylene blue as an indicator (3) anti-bacterial activity. / Physics / D. Phil. Physics)

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