Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Microorganisms show a tendency to accumulate on surfaces in aqueous environments to form biofilms. Microbial biofilms represent a significant problem in public health microbiology as the development of these microbial communities, especially in water distribution systems, may lead to (i) the enhanced growth of opportunistic pathogens, (ii) the development of organoleptic problems, (iii) the reduction in the flow rate and (iv) the regrowth of microorganisms. In this project, biofilm monitors were installed in a large water distribution system to study biofilm phenomena in drinking water systems, and to deduce the biological stability and quality of the potable water. Measurements of biofilm formation potential showed that biofilms did not reach a steady state after 100 to 150 days. The microbial cells in these biofilms were mostly non-culturable. The contribution of the heterotrophic colony count to active biomass, as determined with cell numbers based on ATP measurements were often < 1%, while the ratio of heterotrophic plate counts and direct acridine orange counts were also <1%. The ratio between cell numbers based on ATP measurements and direct acridine orange counts were often < 100%. Results also showed that under certain conditions, such as those investigated in the present study, 1 pg of ATP may not be equal to approximately 104 active bacteria/cells, as stipulated by previous investigations, and that the average ATP content per active bacterial cell is indeed less than 10-16 - 10-15 g. It was calculated that threshold values for assimilable, and dissolved organic carbon below -5 IJg Gil and -0.5 mg Gil, respectively, should be target values for the control of biofilm formation in this system. It was shown that polyethylene, polyvinylchloride, teflon, plexiglass, copper, zinc-coated steel and aluminium provide favourable attachment surfaces that allowed primary colonisation and subsequent biofilm formation. Significant (p < 0.05) differences in surface colonisation on the materials were observed, indicating that the composition of the material has a direct influence on microbial colonisation. The two grades of stainless steel evaluated in this study were the least favourable materials for biofilm formation. It was further demonstrated that the nature of the surface of these materials, flow conditions and water type all had a direct influence on biofilm formation. While modification of the attachment surface did not result in significant differences (p > 0.05) in disinfection efficiency of two commonly used biocides, the concentration of the biocide, as well as the material to which the biofilm is attached, greatly influenced biocidal efficiency. The results show that biofilm monitoring needs to be implemented at the water treatment plants in addition to common biostability measurements. / AFRIKAANSE OPSOMMING: Mikro-organismes neig om te akkumuleer aan oppervlaktes in akwatiese omgewings om biofilms te vorm. Mikrobiese biofilms verteenwoordig In betekenisvolle probleem in publieke gesondheidsmikrobiologie omdat die ontwikkeling van hierdie mikrobiese gemeenskappe in waterverspreidingsisteme mag lei tot (i) die verhoogde groei van opportunistiese patogene, (ii) ontwikkeling van organoleptiese probleme, (iii) die vermindering in die vloeitempo en (iv) die hergroei van mikro-organismes. In hierdie projek was biofilm monitors geïnstalleer in In groot waterverspreidingsisteem om biofilm fenomene in drinkwatersisteme to bestudeer, en om die biologiese stabiliteit en kwaliteit van drinkwater af te lei. Bepalings van biofilmvormingspotensiaal het aangetoon dat biofilms nie In stabiele stadium na 100 tot 150 dae bereik nie. Die mikrobiese selle in hierdie biofilms was meestal niekweekbaar. Die bydrae van die heterotrofiese kolonie tellings tot aktiewe biomassa, soos bepaal deur seltellings gebaseer op ATP metings was dikwels < 1%, terwyl die verhouding van die heterotrofiese plaatteIIings en direkte akridien oranje tellings ook < 1% was. Die verhouding tussen seltellings, gebaseer op ATP metings en direkte akridien oranje tellings was dikwels < 100%. Resultate het ook aangetoon dat onder sekere omstandighede, soos dié wat ondersoek was in die huidige studie, 1 pg ATP nie gelyk is aan min of meer 104 aktiewe bakterieë/selle soos gestipuleer deur vorige ondersoeke nie, en dat die gemiddelde ATP inhoud per aktiewe bakteriële sel inderdaad minder as 10-16 tot 10-15 g is. Dit was bereken dat die drempelwaardes vir assimileerbare en opgeloste organiese koolstof onder -51-1g C/l en -0.5 mg C/l, onderskeidelik, teikens moet wees vir die beheer van biofilmvorming in hierdie sisteem. Dit was aangetoon dat polyetileen, polyvinielchlroried, teflon, plexiglas, koper, sink-bedekte staal en aluminium gunstige aanhegtings oppervlaktes voorsien wat primêre kolonisering en daaropvolgende biofilmvorming toelaat. Betekinisvolle (p <0.05) verskille in oppervlak kolinisering op die materiale was waargeneem, wat aandui dat die samestelling van die materiaal In direkte invloed op mikrobiese kolonisering het. Die twee tipes vlekvryestaal wat geëvalueer was in hierdie studie, was die minder gunstige materiale vir biofilmvorming. Dit was verder gedemonstreer dat die aard van die oppervlak van hierdie materiale, vloeitoestande, en water tipe almal In direkte invloed het op biofilmvorming. Terwyl die aanpassing van aanhegtingsoppervlak nie die ontsrnettinqsdoeltreffendheid resultaat van die twee algemeen-gebruikte biosiede betekinisvol (p > 0.05) beïnvloed het nie, het die konsentrasie van die biosiede doeltreffendheid grootliks beïnvloed. asook die aanhegtings-materiaal, biosied Die resultate het aangetoon dat biofilm monitering geïmplementeer moet word by waterbehandelingsaanlegte as In alternatief vir algemene biostabiliteit metings.

Chen, Yanmin. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 140-160). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Leung, Tsz Yan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 132-146). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.ii / Table of Contents --- p.vii / List of Figures --- p.xii / List of Plates --- p.xiv / List of Tables --- p.xvii / Abbreviations --- p.xviii / Equations --- p.xxi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Water crisis and water disinfection --- p.1 / Chapter 1.2 --- Common disinfection methods --- p.2 / Chapter 1.2.1 --- Chlorination --- p.2 / Chapter 1.2.2 --- Ozonation --- p.4 / Chapter 1.2.3 --- Ultraviolet-C (UV-C) irradiation --- p.6 / Chapter 1.2.4 --- Solar disinfection (SODIS) --- p.7 / Chapter 1.2.5 --- Mixed disinfectants --- p.9 / Chapter 1.2.6 --- Other disinfection methods --- p.10 / Chapter 1.3 --- Advanced oxidation processes (AOPs) --- p.11 / Chapter 1.4 --- Photocatalytic oxidation (PCO) --- p.13 / Chapter 1.4.1 --- Understanding of PCO process --- p.15 / Chapter 1.4.2 --- Proposed disinfection mechanism of PCO --- p.18 / Chapter 1.4.3 --- Titanium dioxide (Ti02) photocatalyst --- p.21 / Chapter 1.4.4 --- Irradiation sources --- p.22 / Chapter 1.4.5 --- Bacterial species --- p.23 / Chapter 1.4.5.1 --- Escherichia coli K12 --- p.23 / Chapter 1.4.5.2 --- Shigella sonnei --- p.24 / Chapter 1.4.5.3 --- Alteromonas alvinellae --- p.25 / Chapter 1.4.5.4 --- Photobacterium phosphoreum --- p.26 / Chapter 1.4.6 --- Bacterial defense mechanism towards oxidative stress --- p.27 / Chapter 1.4.6.1 --- Superoxide dismutase (SOD) activity --- p.28 / Chapter 1.4.6.2 --- Catalase (CAT) activity --- p.29 / Chapter 1.4.6.3 --- Fatty acid (FA) profile --- p.30 / Chapter 1.4.7 --- Significance of the project --- p.31 / Chapter 2. --- Objectives --- p.34 / Chapter 3. --- Material and Methods --- p.36 / Chapter 3.1 --- Chemicals --- p.36 / Chapter 3.2 --- Screening of freshwater and marine bacterial culture --- p.36 / Chapter 3.3 --- Photocatalytic reaction --- p.39 / Chapter 3.3.1 --- Preparation of reaction mixture --- p.39 / Chapter 3.3.2 --- Preparation of bacterial culture --- p.39 / Chapter 3.3.3 --- Photocatalytic reactor --- p.41 / Chapter 3.3.4 --- PCO disinfection reaction --- p.42 / Chapter 3.3.4.1 --- Effect of initial pH --- p.44 / Chapter 3.3.4.2 --- Effect of reaction temperature --- p.45 / Chapter 3.3.4.3 --- Effect of growth phases --- p.45 / Chapter 3.4 --- Measurement of superoxide dismutase (SOD) activity --- p.47 / Chapter 3.5 --- Measurement of catalase (CAT) activity --- p.49 / Chapter 3.6 --- Fatty acid (FA) profile --- p.50 / Chapter 3.7 --- Bacterial regrowth test --- p.51 / Chapter 3.8 --- Atomic absorption spectrophotometry (AAS) --- p.52 / Chapter 3.9 --- Total organic carbon (TOC) analysis --- p.53 / Chapter 3.10 --- Chlorination --- p.55 / Chapter 3.11 --- UV-C irradiation --- p.56 / Chapter 3.12 --- Transmission electron microscopy (TEM) --- p.56 / Chapter 4. --- Results --- p.60 / Chapter 4.1 --- Screening of UV-A resistant freshwater and marine bacteria --- p.60 / Chapter 4.2 --- Control experiments --- p.62 / Chapter 4.3 --- Treatment experiments --- p.65 / Chapter 4.3.1 --- UV-A irradiation from lamps --- p.65 / Chapter 4.3.2 --- Fluorescent light from fluorescent lamps --- p.65 / Chapter 4.3.3 --- Effect of initial pH --- p.67 / Chapter 4.3.4 --- Effect of reaction temperature --- p.70 / Chapter 4.3.5 --- Effect of growth phases --- p.70 / Chapter 4.4 --- Factors affecting bacterial sensitivity towards PCO --- p.73 / Chapter 4.4.1 --- Superoxide dismutase (SOD) and catalase (CAT) activities --- p.73 / Chapter 4.4.2 --- Superoxide dismutase (SOD) and catalase (CAT) induction --- p.74 / Chapter 4.4.3 --- Fatty acid (FA) profile --- p.75 / Chapter 4.5 --- Bacterial regrowth test --- p.78 / Chapter 4.6 --- Disinfection mechanisms of fluorescent light-driven photocatalysis --- p.79 / Chapter 4.6.1 --- Atomic absorption spectrophotometry (AAS) --- p.79 / Chapter 4.6.2 --- Total organic carbon (TOC) analysis --- p.81 / Chapter 4.6.3 --- Transmission electron microscopy (TEM) --- p.83 / Chapter 4.7 --- Chlorination --- p.89 / Chapter 4.7.1 --- Disinfection efficiency --- p.89 / Chapter 4.7.2 --- Transmission electron microscopy (TEM) --- p.92 / Chapter 4.8 --- UV-C irradiation --- p.96 / Chapter 4.8.1 --- Disinfection efficiency --- p.96 / Chapter 4.8.2 --- Transmission electron microscopy (TEM) --- p.96 / Chapter 5. --- Discussions --- p.103 / Chapter 5.1 --- Screening of UV-A resistant freshwater and marine bacteria --- p.103 / Chapter 5.2 --- Comparison of PCO coupled with UV-A lamps and fluorescent lamps --- p.103 / Chapter 5.3 --- Effect of initial pH --- p.105 / Chapter 5.4 --- Effect of reaction temperature --- p.106 / Chapter 5.5 --- Effect of growth phases --- p.107 / Chapter 5.6 --- Factors affecting bacterial sensitivity towards PCO --- p.108 / Chapter 5.6.1 --- Superoxide dismutase (SOD) and catalase (CAT) activities --- p.108 / Chapter 5.6.2 --- Superoxide dismutase (SOD) and catalase (CAT) induction --- p.110 / Chapter 5.6.3 --- Fatty acid (FA) profile --- p.110 / Chapter 5.6.4 --- Cell wall structure --- p.112 / Chapter 5.6.5 --- Bacterial size --- p.114 / Chapter 5.6.6 --- Other possible factors --- p.114 / Chapter 5.7 --- Bacterial regrowth test --- p.115 / Chapter 5.8 --- Disinfection mechanisms of fluorescent light-driven photocatalysis --- p.116 / Chapter 5.8.1 --- Atomic absorption spectrophotometry (AAS) --- p.116 / Chapter 5.8.2 --- Total organic carbon (TOC) analysis --- p.117 / Chapter 5.8.3 --- Transmission electron microscopy (TEM) --- p.118 / Chapter 5.9 --- Chlorination --- p.122 / Chapter 5.9.1 --- Disinfection efficiency --- p.122 / Chapter 5.9.2 --- Transmission electron microscopy (TEM) --- p.122 / Chapter 5.10 --- UV-C irradiation --- p.123 / Chapter 5.10.1 --- Disinfection efficiency --- p.123 / Chapter 5.10.2 --- Transmission electron microscopy (TEM) --- p.124 / Chapter 5.11 --- Comparisons of three disinfection methods --- p.124 / Chapter 6. --- Conclusions --- p.126 / Chapter 7. --- References --- p.132

So, Wai Man. / Thesis submitted in: October 2007. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 112-124). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract --- p.ii / Table of Contents --- p.vi / List of Figures --- p.x / List of Plates --- p.viii / List of Tables X --- p.v / Abbreviations --- p.xvii / Equations --- p.xix / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Importance of water disinfection --- p.1 / Chapter 1.2 --- Conventional disinfection methods --- p.2 / Chapter 1.2.1 --- Chlorination --- p.2 / Chapter 1.2.2 --- Ozonation --- p.3 / Chapter 1.2.3 --- Ultraviolet-C (UV-C) irradiation --- p.4 / Chapter 1.2.4 --- Sunlight irradiation --- p.5 / Chapter 1.2.5 --- Others --- p.6 / Chapter 1.3 --- Photocatalytic oxidation --- p.7 / Chapter 1.3.1 --- Reactions in PCO --- p.8 / Chapter 1.3.2 --- Disinfection mechanism of PCO --- p.11 / Chapter 1.3.3 --- Photocatalysts --- p.14 / Chapter 1.3.3.1 --- Titanium dioxide (TiO2) --- p.14 / Chapter 1.3.3.2 --- Modification of TiO2 --- p.15 / Chapter 1.3.3.2.1 --- Sulphur cation-doped TiO2 (S-TiO2) --- p.17 / Chapter 1.3.3.2.2 --- Copper(I) oxide-sensitized P-25 (Cu20/P-25) --- p.18 / Chapter 1.3.3.2.3 --- Silicon dioxide-doped TiO2 (SiO2-TiO2) --- p.18 / Chapter 1.3.3.2.4 --- Nitrogen-doped TiO2 (N-TiO2) --- p.19 / Chapter 1.4 --- Bacterial defense systems against oxidative stress --- p.20 / Chapter 1.5 --- Bacterial species --- p.22 / Chapter 1.5.1 --- Salmonella typhimurium --- p.23 / Chapter 1.5.2 --- Klebsiella pneumoniae --- p.24 / Chapter 1.5.3 --- Bacillus thuringiensis --- p.25 / Chapter 1.5.3 --- Bacillus pasteurii --- p.26 / Chapter 2. --- Objectives --- p.27 / Chapter 3. --- Material and Methods --- p.28 / Chapter 3.1 --- Culture media and diluents --- p.28 / Chapter 3.2 --- Screening of target bacteria --- p.28 / Chapter 3.3 --- PCO disinfection reaction --- p.29 / Chapter 3.3.1 --- Photocatalysts --- p.29 / Chapter 3.3.2 --- Bacterial cultures --- p.31 / Chapter 3.3.3 --- PCO reactor --- p.32 / Chapter 3.3.4 --- PCO efficacy test --- p.34 / Chapter 3.3.5 --- Comparison of different photocatalysts --- p.35 / Chapter 3.4 --- Optimization of PCO disinfection conditions --- p.35 / Chapter 3.5 --- Transmission electron microscopy (TEM) --- p.39 / Chapter 3.6 --- Superoxide dismutase (SOD) activity assay --- p.42 / Chapter 3.7 --- Catalase (CAT) activity assay --- p.44 / Chapter 3.8 --- Spore staining --- p.45 / Chapter 3.9 --- Atomic absorption spectrophotometry (AAS) --- p.45 / Chapter 3.10 --- X-ray photoelectron spectrometry (XPS) --- p.46 / Chapter 4. --- Results --- p.47 / Chapter 4.1 --- Screening of wastewater bacteria --- p.47 / Chapter 4.2 --- PCO efficacy test --- p.49 / Chapter 4.3 --- PCO under visible light irradiation --- p.53 / Chapter 4.3.1 --- Fluorescence lamps with UV filter --- p.53 / Chapter 4.3.2 --- Solar lamp with UV filter --- p.61 / Chapter 4.3.3 --- Sunlight with UV filter --- p.67 / Chapter 4.4 --- Optimization of PCO disinfection conditions --- p.75 / Chapter 4.4.1 --- Effect of visible light intensities --- p.75 / Chapter 4.4.2 --- Effect of photocatalyst concentrations --- p.77 / Chapter 4.4.3 --- Optimized conditions --- p.79 / Chapter 4.5 --- Transmission electron microscopy (TEM) --- p.79 / Chapter 4.6 --- Superoxide dismutase (SOD) activity assay --- p.83 / Chapter 4.7 --- Catalase (CAT) activity assay --- p.84 / Chapter 4.8 --- Spore staining --- p.85 / Chapter 4.9 --- Studies on Cu20/P-25 --- p.88 / Chapter 4.9.1 --- Atomic absorption spectrophotometry (AAS) --- p.88 / Chapter 4.9.2 --- X-ray photoelectron spectrometry (XPS) --- p.88 / Chapter 5. --- Discussion --- p.90 / Chapter 5.1 --- Screening of wastewater bacteria --- p.90 / Chapter 5.2 --- PCO efficacy test --- p.90 / Chapter 5.3 --- Comparison between different light sources --- p.90 / Chapter 5.4 --- Comparison between different photocatalysts --- p.93 / Chapter 5.5 --- Optimization of PCO disinfection conditions --- p.95 / Chapter 5.5.1 --- Effect of visible light intensities --- p.95 / Chapter 5.5.2 --- Effect of photocatalyst concentrations --- p.96 / Chapter 5.6 --- Transmission electron microscopy (TEM) --- p.97 / Chapter 5.7 --- Comparison between different bacterial species --- p.99 / Chapter 5.8 --- Possible factors affecting susceptibility of bacteria towards PCO --- p.99 / Chapter 5.8.1 --- Formation of endospores --- p.99 / Chapter 5.8.2 --- Differences in cell wall structure --- p.100 / Chapter 5.8.3 --- SOD and CAT activities --- p.101 / Chapter 5.9 --- Dark control of Cu20/P-25 --- p.103 / Chapter 5.10 --- Studies on Cu20/P-25 --- p.104 / Chapter 6. --- Conclusion --- p.107 / Chapter 7. --- References --- p.112 / Chapter 8. --- Appendix --- p.125 / Chapter 8.1 --- Production of S-Ti02 --- p.125 / Chapter 8.2 --- Production of Si02-Ti02 --- p.125 / Chapter 8.3 --- Production of N-Ti02 --- p.125

An activated unsaturated sand filter (AUSF) is one of only a few of the filtration technologies utilized to treat waters and wastewaters that use unsaturated filter media. AUSF employs sand coated with potassium permanganate and operates with an open chamber allowing free air flow into the column of sand. The AUSF also benefits from operation without the need for a sedimentation unit. Previous studies have demonstrated the efficient removal of iron and manganese using an AUSF, however, to date there are still very limited studies available that use AUSF technology for the removal of metals from waters and wastewaters. Thus, there is an urgent need and opportunity to exploit this technology further. This research was conducted in order to develop and study the characteristics and subsequent operational performance of a novel AUSF media. The study focuses on the removal of copper, manganese, zinc and nickel from a synthetic wastewater and extends current knowledge to a passive aeration process rather than the active aeration used in the previous study by Lee et. al. (2004). The characterisation involved the use of sieving, Brunauer- Fmmett-Teller (BET) analysis, water evaporation studies and scanning electron microscopy (SEM) for structural analysis such as particle size, surface area, porosity and topography. Energy dispersive X-ray analysis (EDX), acid/alkali resistance, isoelectric point determination and acid digestion analysis were used to determine the chemical constituency, chemical stability, electrical charge properties and the binding efficiency of the media. Finally, tracer studies were employed to determine the flow characteristics through the particle media. The manganese coated sand was proven effective for the removal of copper in both agitated tank batch studies and continuous column studies. The batch studies showed that the equilibrium sorption of copper followed a Langmuir isotherm and the sorption rate was best modelled using the pseudo-second-order kinetic model. This suggests that adsorption is taking place as a single homogeneous layer on the surface of the sand particle via the chemisorption method. The Weber-Morris and Bangham models were used to determine the rate-controlling mechanism and this was found to be predominantly intra-particle diffusion. This was confirmed for column studies using the Bohart-Adams model that demonstrated that liquid-film mass transfer was not significant. Several mechanisms of metal removal are proposed and these include precipitation, electrostatic attraction, adsorption, ion exchange and complex ion formation. The column studies demonstrated that dispersion was low under the operating conditions and plug flow performance could be inferred, thus justifying the use of the AUSF model employed. Copper was best removed when operating as an unsaturated particle bed and the removal capacity was increased by approximately 100% when compared to a saturated particle bed. Moreover, the pH increase that occurs on exposure of the process water to the unsaturated column further improves removal capacity. Thus, there is no requirement for an expensive pH adjustment as a pre-treatment process prior to this unit operation. In addition, the removal capacity of the AUSF was demonstrated to increase with lower metal concentrations, lower water flow rates, smaller sand particles, an increase in manganese to sand ratio and an increase in particle bed height. The AUSF performance in removing metals followed the order Cu > Mn > Zn > Ni for individual and mixed component solutions and Cu > Ni > Zn > Mn for a synthetic wastewater typical of the electroplating industries. In conclusion, the novel manganese coated AUSF developed is effective in the removal of metals from solution and offers the potential of a sustainable low cost treatment method for the purification of waters and wastewaters.

Thesis (MTech (Engineering))--Cape Peninsula University of Technology, 2007 / The removal of the colour-eausing natural organic matter (NOM) from natural brown water (NSW) to be used for drinking purposes is of paramount importance. One of the methods available to remove NOM from NSW is the use of pressure-driven membrane separation systems. One of the limitations in efficiently applying membrane filtration in the treatment of NOM-eontaining water is membrane fouling that is caused by foulants, such as NOM, that accumulate on the membrane surface and in the membrane pores. Microfiltration (MF), as a membrane separation system, is susceptible to severe membrane fouling during membrane filtration of NSW. Fouling is characterized by a rapid decline in permeate flux and loss of productivity. Progress in developing more effective control and prevention of fouling is impeded by the absence of suitable fouling measurement and characterization techniques. An in situ method for measuring membrane fouling is necessary for detection of membrane fouling during MF of NSW at the eartiest stages so that the corrective actions can be taken before fouling is permanently adsorbed onto the membrane surface. In this study, an ultrasonic-based method was effectively used to detect and measure the growth of membrane fouling dUring MF of NSW, in situ. Fouling exp~riments results showed the formation of a new peak on the ultrasonic response echo signal due to the presence of a fouling layer on the surface of the membrane. The ultrasonic signals acquired during the in-situ detection of membrane fouling were analysed using wavelet transforms (WTs). Wavelet analysis was applied to differential signals to obtain additional information about fouling. Differential signals were calculated by subtracting the baseline measurement signals from the test signals. The presence of the fouling layer on membranes was verified by atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses of the fouled membranes.

M.Tech. (Chemistry) / This study investigated the functionalization of coke particles and their utilization for the preparation of coke-polymer composite. Looking at the possibility of using it for the removal of lead and chromium ions from their aqueous solutions. Due to various inorganic materials in coke, it was treated with acid to demineralize the ash content. The demineralized coke was further oxidized with hydrogen peroxide to add functional groups on its surface as well as in the bulk of coke particles before coating of the polymers. The composite preparation entails modifying the surface properties of coke with hydrophilic polymers like polyvinyl alcohol (PVA), poly ethylene glycol (PEG) and poly vinyl pyrrolidone (PVP) followed by the crosslinking to improve the interfacial interaction between the polymer and coke to make the synthesized composite stable in water. The structural composition of coke and modified coke was examined by FT-IR spectroscopy, X-ray diffraction, X-ray fluorescence, Raman Spectroscopy, thermal analysis and scanning electron microscopy combined with energy dispersive X-ray analysis. It was also observed that the modified coke samples have enhanced carbon reactivity which indicates that the non-carbon phases were removed by the treatment with acid. The adsorption studies for the removal of Pb (II) and Cr (III) ions from contaminated water was done in batch mode using variables such as pH, contact time and the initial concentration. The synthesized material was found to have better adsorption capacity as compared to raw coke. To understand the adsorption isotherm processes, Freundlich and Langmuir isotherms were applied. The monolayer adsorption capacity for the removal of lead ions was found to be 2.41 mg/g, 2.95 mg/g, 8.32 mg/g, 9.70 mg/g and 9.84 mg/g for raw coke, acid treated coke, PVA coated coke, PEG coated coke and PVP coated coke, respectively. The chromium monolayer adsorption capacity was found to be 9.48 mg/g, 9.94 mg/g, 35.84 mg/g, 32.79 mg/g and 34.13 mg/g for the same order of adsorbents mentioned for lead. Studies were carried out at the optimum pH of 6.0 for both the metal ions. The adsorption kinetic studies showed that both the metal ions followed pseudo second order rate equation and the adsorption equilibrium was attained in 60 minutes and 120 minutes for Pb (II) and Cr (III) ions, respectively.

M.Ing. / The Rietvlei Water Treatment Plant was extended with a granular activated carbon (GAC) filtration system after an exhaustive series of tests, which were started in 1994. Upon commissioning towards the middle of 1999, a year of close monitoring followed to measure the GAC performance at full-scale. After verification that the GAC does indeed ensure a high quality product under all conditions, the emphasis shifted to the optimisation of the GAC handling and regeneration system. Frequently moving the entire GAC inventory from the filters to an off-site regeneration plant and back requires significant operational effort and contributes a major part of the total cost of the GAC system. A number of systematic investigations were carried out in response to a number of practical questions that arose at Rietvlei. The first part of the study was directed towards tracking and quantifying the GAC on and off site. The main findings were that 10.0% of the GAC is lost from the filter during backwashing (0.3%) and removal of GAC from the filter for regeneration (9.7%). The sump traps not all this GAC and 2.3% of the total inventory is lost to the river. Inserting a sieve at the outlet of the sump can eliminate this loss. A further 80.3% of the GAC in a filter is removed for regeneration, of which 18.7% is lost during the regeneration process. The minimising off this loss can only be achieved through the optimisation of the regeneration process, which falls within the domain of the regeneration contractor. The second part of the study was directed at the behaviour of the GAC whilst within the filter bed. The porosity and sphericity was determined by laboratory tests and calculations. The porosity was found to be 0.69 for the 12 x 40 size carbon and 0.66 for the 8 x 30 size carbon and the sphericity was found to be 0.67 for the 12 x 40 size carbon and 0.66 for the 8 x 30 size carbon. By using a calibrated bed expansion model, the bed expansion could be calculated at 9°C and 23°C for the two carbons gradings; the maximum temperature range experienced at Rietvlei. The main finding of this part of the study was that the average available freeboard is 650 mm for the 12 x 40 grading and 430 mm for the 8 x 30 grading, and therefore no GAC should wash over the weir at all during backwashing. The third part of the study measured the physical changes of the GAC found at different points in the GAC cycle. The main findings were that the small fraction of GAC washed out of the bed during backwashing and removal has a finer grading, higher apparent density and lower adsorption capacity than the GAC in the filter bed. There seems to be no marked attrition of the carbon or generation of fines during the removal and transport of the GAC to the regeneration plant. After regeneration, there was a 7% decrease in apparent density and a 30% increase in adsorption capacity. The final part of the study correlated the adsorption capacity of the GAC with its time in use as well as UV254 removal. After regeneration, UV254 removal begins at approximately 20% and declines to 14% after 400 days of operation, and to 10% after 600 days. After regeneration, the iodine number begins at approximately 800, declines to 600 after 400 days of operation, and to 500 after 600 days.

M.Sc. (Chemistry) / Water purification technologies based on membranes are prone to fouling by natural organic matter (NOM) and other biological species in water. This leads to the short lifespan of the membranes and high demand in energy than normal due to high pressure needed to pump water across the fouled membrane. In a quest to address these challenges, polyethersulfone (PES) and polyvinylidene flouride (PVDF) membranes supported on 3 different types of non-woven fabrics NWF1(polyester), NWF2 (polyphenylene sulphide) and NWF3( thicker polyester) were fabricated using the phase inversion method. This enabled the modification the active top layer of PES and PVDF thin film while maintaining the high mechanical strength offered by the NWFs. FTIR spectroscopy, sessile drop contact angle measurements, thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the membranes. The membrane flux and rejection were studied using the cross-flow membrane unit. The contact angle results revealed that the hydrophilicity of PES and PVDF membranes increased as the polyvinyl pyrrolidone (PVP) concentration was increased. TGA revealed that the PES and PVDF membranes were thermally stable up to 580ºC and 530ºC respectively. The cross-sectional SEM revealed that membrane pores become enlarged when PVP has been added. AFM showed that membrane roughness improved when PVP was added. A rejection of 98% humic acid was obtained for PES membranes supported on NWF1, compared to 94 % and 96 % for membranes supported on NWF2 and NWF3 respectively. The highest rejection of humic acid (HA) recorded for PVDF membranes supported on NWF1 was found to be 97 % compared to the 95% for membranes supported on NWF2 and NWF3 fabrics respectively. PES membranes supported on NWF2 exhibited low but best As(III) metal ions rejections whilst PVDF membranes supported on NWF3 exhibited low but best rejections for Cr(III) metal ions.

This thesis investigates the susceptibility of various bacterial species to standard purification process.