Faecal contamination in water is detected using appropriate microbial models such as total coliforms, faecal coliforms and E. coli. Βeta-D-Galactosidase (β-GAL) and Beta-D-glucuronidase (β-GUD) are two marker enzymes that are used to test for the presence of total coliforms and E. coli in water samples, respectively. Various assay methods have been developed using chromogenic and fluorogenic substrates. In this study, the chromogenic substrates chlorophenol red β-D-galactopyranoside (CPRG) for β-GAL and p-nitrophenyl-β-D-galactopyranoside (PNPG) for β-GUD were used. Potential problems associated with this approach include interference from other organisms present in the environment (e.g. plants, algae and other bacteria), as well as the presence of certain chemicals, such as phenolic compounds in water. Phenolic compounds are present in the aquatic environment due to their extensive industrial applications. The USA Enviromental Protection Agency (EPA) lists 11 Priority Pollutant Phenols (PPP) due to their high level of toxicity. This study investigated the interfering effects of the eleven PPP found in water on the enzyme activities of both the β-GAL and β-GUD enzyme assays. The presence of these PPP in the β-GAL and β-GUD enzyme assays showed that over and underestimation of activity may occur due to inhibition or activation of these enzymes. Three types of inhibition to enzyme activities were identified from double reciprocal Lineweaver-Burk plots. The inhibition constants (Ki) were determined for all inhibitory phenolic compounds from appropriate secondary plots. Furthermore, this study presented a validated reverse phase high performance liquid chromatography (RP-HPLC) method, developed for the simultaneous detection, separation and determination of all eleven phenolic compounds found in the environment. This method demonstrated good linearity, reproducibility, accuracy and sensitivity. Environmental water samples were collected from rivers, streams, industrial sites and wastewater treatment plant effluent. These samples were extracted and concentrated using a solid phase extraction (SPE) procedure prior to analysis employing the newly developed HPLC method in this study. Seasonal variations on the presence of the PPP in the environment were observed at certain collection sites. The concentrations found were between 0.033 μg/ml for 2,4-dinitrophenol in a running stream to 0.890 mg/ml for pentachlorophenol from an tannery industrial site. These concentrations of phenolic compounds found in these environments were able to interfere with the β-GAL and β-GUD enzyme assays.

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.

M.Sc.

M.Ing. (Civil Engineering) / Natural organic matter (NOM) is a complex mixture of organic compounds resulting from the decay of plants and animals. When not properly removed, NOM reacts with disinfectants to form disinfection by-products, of which some are known to be carcinogenic. Regulations have become more and more stringent about the maximum level of NOM in drinking water. Different water treatment processes can be applied to remove NOM. However, because each process targets specific fractions of NOM, this results in the existence of recalcitrant NOM fractions that are not removed, for each treatment process. The main objective of the study was thus to investigate NOM removal by using three advanced water treatment processes alone and in combination. The processes used were enhanced coagulation, granular activated carbon adsorption and ion exchange resin processes. Strong and weak base ion exchange resins were used. Although NOM removal methods have been investigated intensively, little attention is given to a so-called “multi-barrier” approach of NOM removal through enhanced coagulation, granular activated carbon adsorption and ion exchange resin that could be applied in practice. In order to take the seasonal and geographical variability of NOM into account, water samples were collected at eight geographical areas over five to seven seasons from 2010 to 2013. Results showed that different treatment processes remove different NOM fractions with different efficiency. Results also confirmed that EC performs better than the adsorptive treatment processes. But the literature shows that NOM removal by EC is difficult for water with high alkalinity and low SUVA values, which is common with SA waters. The adsorptive processes used for NOM removal revealed that they are not viable options, because even low percentage of NOM removal would require high adsorbent dosages, which removes this approach as a practical option.

D.Phil. (Chemistry) / Elimination of toxic organic compounds from wastewater is currently one of the most important subjects in water-pollution control. Among the many organic pollutants are dyes and emerging pollutants such as natural organic matter (NOM). Dyes such as Eosin Yellow (EY), an anionic xanthene fluorescent dye, can originate from many sources such as textile industrial processes, paper pulp industries and agricultural processes. Most dyes are problematic because they are resistant to conventional chemical or biological water-treatment methods and therefore persist in the environment. NOM consists of a highly variable mixture of products found in water and soils. NOM is formed as a result of the decomposition of plant and animal material and is a precursor to the formation of disinfection by-products (DBP) during water disinfection. These organic compounds cause undesirable colour, taste and odour in water. NOM affects the capacity of other treatment processes to effectively remove organic micro-pollutants or inorganic species that may be present in the water. Its removal also uses up chemicals and energy and so it is expensive to treat. Titanium dioxide (TiO2) has emerged as one of the most fascinating materials in the modern era due to its semiconducting and catalytic properties. TiO2 is a large band-gap semiconductor that exists mainly in the anatase (band gap 3.2 eV) and rutile (band gap 3.0 eV) phases. Its response to UV light has led to increased interest in its application in the photocatalysis research field. It has been investigated extensively for its super hydrophilicity and use in environmental remediation and solar fuel production. In spite of extensive efforts to apply TiO2 for environmental remediation, photocatalytic activity in the visible region has remained quite low hence the ultimate goal of this research was to fabricate highly photoactive catalysts composed of non-metal, platinum-group metal (PGM) co-doped TiO2 and carbon nanotubes (CNTs) and to apply them for water purification using solar radiation...

Ph.D. / This study explored the possible application of a relatively new electrode called exfoliated graphite electrode (EG electrode) in the electroanalysis of organic and inorganic water pollutants. This study also explored the applicability of this electrode in the removal of heavy metal pollutants in water. The EG material was successfully prepared by intercalating bisulphate ions into graphite flakes (>300 μm) followed by thermal shock at 800°C to obtain an exfoliated graphite. After compressing the EG at high pressure, the obtained circular sheets were used to fabricate electrodes. The electrochemical profiles of EG electrode and glassy carbon electrodes (GCE) were recorded and compared using cyclic voltammetryand square wave voltammetry in the presence of various supporting electrolytes and [Fe(CN)6]3-/4-, [Ru(NH3)6]2+/3+, ferrocene redox probes. In the supporting electrolytes (KCl, H2SO4, NaOH, tetrabutylammoniumtetraflouroborate, phosphate buffers), the potential windows of EG were found, in some cases, to be about 300 mV larger than that of GCE. The diffusion coefficients (cm2s-1) of the redox probes were calculated to be 3.638 x 10-6, 1.213 x 10-6 and 4.411 x 10-6 for [Fe(CN)6]3-/4-, [Ru(NH3)6]2+/3+ and ferrocene, respectively. These values are comparable to those obtained from GCE. Furthermore, EG was modified with various nanomaterials such as poly (propylene imine) dendrimer (PPI), gold nanoparticles, silver nanoparticles, dendrimer–gold nanoparticles composite, cobalt oxide and bismuth. The morphologies of the modified electrodes were studied using scanning electron microscopy and their electrochemical reactivities in the three redox probes were investigated. The current and the reversibility of redox probes were enhanced in the presence of modifiers in different degrees with dendrimer and gold nanoparticles having a favourable edge. The electrochemical determination of o-nitrophenol by square wave voltammetry using a nanocomposite of generation 2 poly(propyleneimine) dendrimer and gold nanoparticles modified GCEand EG electrode were compared. A characteristic reduction peak between -600 mV and -700 mV for o-nitrophenol was observed with enhanced current on both GCE and EG modified electrodes.

D.Phil. (Chemistry) / This thesis describes the improvement of sorption capacity and efficiency of synthetic and biological adsorbents towards selected pollutants by introducing functional groups on the sorbents. Functionalization was achieved by chemically modifying the binding sites of the studied adsorbents. The sorbent materials considered were chemical resins (Amberlite XAD 1180) and biomass (maize tassels and seaweed). The adsorbents were modified with ethylenediamine in order to improve their capacity for extraction of heavy metals, namely lead, copper and cadmium from water. For the removal of phenols from water, maize tassels was modified with polydiallyldimethylammonium chloride (polyDADMAC). The main focus of the proposed study was to formulate cheap and sustainable ways of purifying contaminated water by exploiting the pollutants’ affinity towards the adsorbents. Parameters such as contact time, sorbent quantities, analyte concentrations, desorption solution (for stripping adsorbed metals for sorbent reuse) and pH were optimized. Different isotherms were applied on the experimental data to establish sorption mechanisms and energies involved during the sorption process. The Langmuir isotherm was used to test for monolayer sorption while the Freundlich model tested multilayer adsorption on heterogeneous surfaces...

Ph.D. / An investigation was made into the physical, chemical and biological conditions of the Elsburgspruit to establish the extent and quality of pollution over a period of two and a half years from January 1987 June 1989. The results obtained during the investigation can be summarised as follows. Serious faecal pollution as reflected by faecal coliforms, faecal streptococci and coliphage organisms occurs over a large stretch of the river, posing a health risk to the people using the recreational area at' Vosloosrust, downstream from the Elsburgspruit near Kathlehong. The occurrence and large numbers of coliphage organisms occurring at certain sampling localities suggest the possible presence of the pathogenic viruses Salmonella, Pseudomonas and Candida. Effluent and seepage waters from mining areas, discharged into the Elsburgspruit were found to be low in pH and high in concentrations of certain metals such as zinc, manganese and iron. Due to the large volume of this particular effluent, the effects thereof on the water quality and fauna of the streams are felt over a distance of more than seven kilometres. As a result, the recovery of the stream from pollution is severely retarded. A number of species of the numerically dominant aquatic and semi-aquatic macrophytes which occurred within the flood-plain of the Elsburgspruit, were found to be able to absorb and to accumulate substantial concentrations of the various heavy metals, directly from the water, or from adjacent moist soils. It was also found that the Spanish reed, Arundo donax, which covers a large area of the wetland region of the Elsburgspruit in its lower section, absorbed and accumulated substantial quantities of the different heavy metals from the water of the stream. A comparison was made of the extent to which metals are deposited into the sediment under both acidic and alkaline conditions...

No description available.

Two adsorption/microcoulometric methods have been investigated for total organic halogen (TOX) in water. TOX, a proposed water-quality parameter, is a rapid, surrogate method to detect halides microcoulometrically and does not require compound identification before water quality can be judged. An XAD resin is used to concentrate organic halides that are eluted by a two-step, two-solvent procedure, followed by analysis using :chromatography or pyrolysis to convert organic halides to halide. In the granular activated carbon (GAC) method, the entire GAC-organic halide sample is pyrolyzed. TOX measurements of model compounds are comparable by both methods, but GAC was found to be superior to XAD for adsorption of chlorinated humics in drinking water and chlorinated lake water.