M. Ing.

M.Ing. (Civil Engineering) / The dissolved air flotation process can be used for different functions in the drinking waterand sewage treatment fields. The focus for this study was on thickening of activated sludge. At first literature was studied to identify all possible parameters. Then five plants were visited periodically and the physical layout and operating parameters were documented. With the examination of the data the different existing models were evaluated, and new relationships were investigated.

M.Sc. / The metallurgical industrial losses of base metals with waste solutions are an environmental threat to water sources, hence these metal ions must be removed prior to discharge into receiving bodies. In this study, Southern African clinoptilolite’s capability as an ion-exchanger with respect to Cu2+ and Co2+ was investigated in order to consider its application in metal cation removal from aqueous solutions. The clinoptilolite was characterised with X-ray powder diffraction (XRD), X-ray fluorescence (XRF), FTIR, thermogravimetric analyser (TGA) and SEM-EDS. The clinoptilolite was found to be a thermally stable alumino-silicate with calcite, dolomite and quartz as the main minerals. Investigations of Co2+ and Cu2+ uptake were first performed on non-mixed solutions of these cations. It was found that Cu2+ was removed faster than Co2+ with removal efficiencies of 79% and 63% respectively. The column method was used in the cation-exchange processes with synthetic solutions of 0.0020 M, 0.0698 M and 0.2000 M of Co2+ and Cu2+ concentrations which were measured using atomic absorption spectroscopy (AAS). The effects of Co2+ and Cu2+ ions on one another’s removal efficiency were investigated on Co/Cu mixed synthetic solutions by varying their concentration ratios in solution. The Cu2+ was generally found to be removed at lower rates than the Co2+. Investigations on added impurities in the form of Si4+ and Fe2+ in the mixed Co/Cu synthetic solutions were carried out to determine their effect on the removal efficiencies of the targeted metals. It was found that both Si4+ and Fe2+ greatly reduced the removal efficiency of Cu2+, especially with increased amounts of Si4+ in the Co/Cu solution.

B.B. Mamba

M.Sc. / The prevalence of toxic contaminants in water remains a huge challenge for water supplying companies and municipalities. Both organic and inorganic contaminants (especially heavy metals) pollutants are often present in water distribution networks. Organic and inorganic pollutants often co-occur in drinking water networks. However, at present there is no water treatment intervention that simultaneously removes organic and inorganic pollutants from water. Additionally, current water treatment technologies fail to remove these contaminants to parts per billion (ppb or µg.L-1) levels. Methods that can simultaneously remove organic and inorganic pollutants to desired levels need to be developed. In our laboratories, both functionalised and unfunctionalised cyclodextrin (CD) polymers have demonstrated the ability to effectively remove organic species from water at low (ppb) concentrations. Cyclodextrins (CDs), which are cyclic oligomers consisting of glucopyranosyl units linked together through α-1,4-glycosidic linkages, behave like molecular hosts. They are capable of interacting with a range of guest molecules within their cylindrical hydrophobic cavities thereby forming the so-called inclusion complexes. Their solubility in water, however, precludes their application in the removal of organic pollutants from water. This limitation is easily dealt with by polymerizing the CDs into water insoluble polymers with suitable bifunctional linkers. On the other hand, ionic liquids (ILs) have been reported to “absorb” heavy metal ions from aqueous media. ILs are low melting point molten salts that are composed of organic cations (e.g. imidazolium and pyridinium ions) and mostly inorganic anions like Cl–, Br–, [PF6]– and [BF4]–. In this study, the two systems were combined by an initial attachment of the imidazolium or pyridinium rings to the cyclodextrin moiety. Polymerisation of the resulting cyclodextrin-ionic liquid (CD-IL) complexes with a suitable linker produced the corresponding water insoluble CD-IL polymers. This dual system has shown excellent capabilities for the removal of model pollutants such as p-nitrophenol (PNP) and 2,4,6-trichlorophenol (TCP) and chromium (Cr6+) from aqueous media. However, the CD-IL polymers showed very little affinity for the absorption of cadmium from water. TGA and DSC studies showed that these polymers are stable over a wide range of temperatures (100-400 C).

M. Ing. / Southern Africa faces an increasingly serious shortage of potable water and will continue to do so for the foreseeable future. Desalination is a process whereby dissolved solids are removed out of a contaminated water source to produce potable water. However, desalination carries an unavoidable energy cost per unit of potable water produced. Minimising this energy cost is an important goal towards making desalination a practical technology for widespread use. A desalination process is proposed by the author which is based on the injection of a brine spray into vacuum conditions. Although a complete desalination process is proposed, only the core components of the desalination process are investigated in the present study. The physical processes taking place in the core components are complex. Computational fluid dynamics is the numerical tool used to investigate the processes taking place in the core components. A commercial computational fluid dynamics code, augmented with user-programming, provides a simulation model for the core components. Due to the complexity of the investigated desalination process not all of its physical aspects are accounted for in the simulation. An analytical as opposed to experimental verification of the simulation is performed. The simulation model is used to perform a number of parametric tests. These tests are used to numerically investigate the effects of a number of process variables on the core components. The results of these parametric tests are presented and discussed

Ph.D. (Chemistry) / The ultrafiltration membranes presented in this study were synthesized using the phase inversion method by casting on a nonwoven fabric. The polymer solutions were mixed with synthetic and bio additives in order to improve the resultant membrane performance. Synthetic additives (polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP)) were compared with a novel and cheap bio additive, lignin. Based on the knowledge that the additives must be soluble in water in order to increase the pore sizes of the membranes, sodium hydroxide was used to elute residual additives that remain in the membrane during coagulation. In order to trace the residual additives remaining, ATR-FTIR was used. Contact-angle analysis and water-absorption experiments were used to elucidate the hydrophilic properties of the prepared membranes. Membranes modified with lignin (Lig) were found to absorb more water (94% water uptake) when compared to the other membranes. In general, the contact angles were found to be low for membranes that were treated with NaOH. Membrane permeability followed the trend, Lig_PSf>PVP_PSf>PEG_PSf which is similar to the trend followed during water uptake. Pore size and pore distribution analysis showed that membranes modified with lignin and PVP had a narrow range (had pore sizes ranging from 10 to 24 nm) compared to that of PEG-PSf membrane (which ranged from 2.5 to 22 nm). A Robeson plot showed that Lig_PSf membranes had high separation factors regardless of the size of the solute being rejected. This study shows the possibility of using cheap and readily available additives to increase the performance of membranes......

M.Sc. / Water that is free from toxic organic pollutants is essential to human health and the environment at large. Organic contaminants may affect the endocrine system of animals and humans, even when present in very low concentrations (i.e. levels ppb). Current technologies fail to remove these organic compounds efficiently from water at ppb levels. So, the development of new technologies that are capable of removing and degrading organic pollutants from water is crucial. Hence, recently in our laboratories cyclodextrin (CD) polymers have demonstrated that they are capable of removing organic pollutants from water at ppb levels. The research has also demonstrated that both functionalized and unfunctionalized CD polymers can remove organic species to as low as parts per billion (ppb) from water. In this project, Si and Ti based compounds which have been reported to degrade organic compounds through photocatalysis in an aqueous media were incorporated. Firstly, attempts were made to attach the silicon (Si) and titanium (Ti) pendent chains onto the CD moiety to form silicon-based cyclodextrin (Si-CD) and titanium based cyclodextrin (Ti-CD) precursors. The Si-CD precursor was synthesized by attaching the 3-(triethoxysilyl)propyl isocyanate onto the native b-CD moiety. The synthesis of the Si-CD precursor was successful and high yields (80%) of the product were obtained. A hydrolysis of this Si-CD precursor in an inert atmosphere led to the formation of silanol. This was followed by curing the silanol in air, after adding TiO2 nanoparticles, and the Ti-CD precursor was formed. The polymerization of Si-CD with suitable bifunctional linkers was a success and water-insoluble polymers were produced. An attempt to polymerize the Ti-CD precursor failed, because the precursor was decomposed. The Si-CD polymers were tested for their capabilities to encapsulate and destroy organic pollutants from water. 1H NMR, FT-IR and EDX spectroscopic techniques were used to prove the formation of the Si-CD and Ti-CD precursors and their corresponding polymers. The Si-CD polymers showed capabilities of being able to remove organic pollutants (33-55%) from water. Unfortunately, the removal is slightly less efficient than the corresponding native CD polymers. However, their efficiency in removing organic pollutants improved when exposed to light. Moreover, the polymers formed display good thermal stabilities, since they decompose at about 300- 400°C. This is observed from the thermograms obtain ed from DSC and TGA. Their morphological studies showed that most of the Si-CD polymers formed were crystalline. This was observed from the SEM images obtained. Based on the information provided by the FT-IR spectroscopy, the synthesis of the Ti-CD precursor was success. However, the challenge was the fact that it decomposed after a while. Hence, it was difficult polymerize it into a water insoluble polymer. The explanation of this phenomenon is not yet established.

M.Sc. / The disinfection of drinking water is an important step in the water treatment process. However, toxic (unwanted) disinfection by-products (DBPs) are often produced during the disinfection of drinking water. One such group of DBPs are the nitrosamines such as N-Nitrosodimethylamine (NDMA). Nitrosamines, particularly NDMA, are highly carcinogenic, mutagenic and teratogenic. The US Environmental Protection Agency (USEPA) placed these compounds into the group B2, which indicates compounds of probable human carcinogens. The USEPA integrated risk information system (IRIS) database lists an estimated 10-6 lifetime cancer risk level for NDMA in drinking water of 0.7 ng/L. The formation of NDMA during drinking water disinfection, particularly chloramination, has been linked to the formation of NDMA through a reaction between monochloramine and organic nitrogen precursors via unsymmetrical dialkylhydrazine intermediates, such as unsymmetrical dimethylhydrazine (UDMH). UDMH is oxidized by dissolved oxygen to form NDMA. Therefore, it is also crucial to remove NDMA precursors (UDMH and dimethylamine (DMA)), before disinfection is carried out. Also, the chlorination of secondary wastewater can result in the formation of NDMA. In this research project, determination of nitrosamines, especially NDMA was done at four different water treatment plants in South Africa. Water samples collected from Midvaal, Sedibeng, Magalies (Vaalkop and Klipdrift) and Rand Water treatment plants were qualitatively analysed for the presence of NDMA. Also, the determination of possible NDMA precursors such as dimethylamine and UDMH was investigated in water samples collected from Sedibeng water treatment plant. The water samples were collected before and after each drinking water treatment process (coagulation, sedimentation, filtration, chlorination and chloramination or ozonation). Solid phase microextraction (SPME) was employed in the extraction of the water samples. Polydimethylsiloxane/divinylbenzene (PDMS/DVB) proved to be the most efficient fibre for the SPME extraction procedure. The water samples vi were then qualitatively analysed using gas chromatography-mass spectrometry (GC-MS). Very small amounts of NDMA were detected in water samples collected from Sedibeng water treatment plant. There was no detectable presence of NDMA or other nitrosamines in water samples collected from the other treatment plants. Water-insoluble cyclodextrin (CD) polyurethanes were then used to ascertain how much of the NDMA they would remove. The CD polymers showed capacity to remove NDMA and dimethylamine (which is a known NDMA precursor) in the water samples with 80% removal efficiency for NDMA (when comparing peak area before and after treatment with CD polymers) and approximately 98% removal rate for DMA.

M.Sc. / Safe drinking water is an essential resource for human survival, health, dignity and development. However, this vital resource has become scarce mainly due to population growth, economic activity, climate change and pollution. Treatment of polluted water is expensive and does not always ensure delivery of safe drinking water to humans. Reports on the detection of pollutants such as organics, bacteria, inorganics and the occurrence of toxic disinfection byproducts in treated water in distribution systems have necessitated further research in improving water treatment methods. Metal impregnated carbon nanotube incorporated into cyclodextrin polyurethanes were synthesised by first functionalising carbon nanotubes and then impregnating them with metal nanoparticles. The resultant product was confirmed using Transmission electron microscopy (TEM). The metal nanoparticles were found to have a diameter range of 6 to 35 nm. The metal impregnated carbon nanotubes were then polymerised to produce cyclodextrin polyurethanes. The polymers were characterised using various techniques such as Scanning electron microscopy (SEM), Emission dispersive X-ray spectrometry (EDX) and Brunauer-Emmet-Teller analysis. The metal nanoparticles were found to be part of the polymers through EDX and the polymers’ surface areas were measured to be 0.78 and 0.3383 m2/g for silver and copper polymers, respectively. The synthesised polymers were tested for their efficacy at destroying pathogenic bacteria from water. The polymers were found to inactivate bacteria by up to 4 logs from spiked water samples. These metal impregnated polymers when compared to native carbon nanotubes and cyclodextrin polymers had an enhanced antibacterial property. In environmental samples, metal impregnated polymers destroyed up to 3 logs of bacteria. There was complete removal of bacteria from filtered environmental water samples. Factors affecting the polymers’ efficacy were turbidity, nature of sample and the ratio of bacterial cells removed per gram of polymer.