The treatment of water up to potable/drinkable standards is a complex process, with many variables and parameters impacting on each other. In South Africa drinking water delivered to consumers must meet the requirements as recorded in the South African National Standards (SANS). Today, more so than ever, there are a number water sources that can be exploited and treated to provide safe drinking water, namely; surface water (dams and rivers), sea water, ground water and treated wastewater. The focus of this dissertation is on surface water; however, reference is made in the first sections with regards to sea water and ground water. The first step in designing a treatment process begins with analysis of the raw water source. Unfortunately, there is not a one size fits all approach and it is left up to the process engineer to find the correct method of investigation. This can be a daunting task, especially if lacking in experience and available information. The first part of this dissertation focusses on just that. It prescribes the method of sampling and aims to provide the reader with context on when to and what to test for. It goes further to suggest how the results may influence the process design and how certain contaminants can be removed. It also draws the attention to the sampling timeframe required, to obtain representative information, encompassing fluctuations in water quality. The second part of this dissertation describe the methods for designing a conventional water treatment system, comprising; aeration, coagulation, flocculation, dissolved air floatation, sedimentation, filtration and disinfection. It also comments on the water quality that warrants certain process steps to assist the process engineer in choosing the correct configuration. For most steps the design approach of two or more technologies are presented. This allows the process engineer to consider which technology best suits the application at hand. The design procedures are programmed into an, excel based, software model, which permits quick and easy design. A brief description of how the software model can be used is also covered. The results given by the software model is validated through a set of examples, appended to this document. Ultimately it is concluded that although this dissertation provides a guide for designing a treatment process it is not an encompassing tool that considers all the intricacies involved. That is, there are too many factors involved and considerations required, and cannot all be captured in one dissertation such as this. As such, it is finally recommended that any design attempts should be conducted by a suitably qualified and experienced process engineer that may use this dissertation to augment their design development.

This study focuses on assessing the walkability of scholars in the Otjiwarongo Town municipal area in Namibia. The research looks at the overall infrastructure and the conflict between pedestrians and motorists. This study is done to find out the serviceability of walkable paths and their existence for school-going children, how safe they are, and the state of their quality, shelters and visibility. It also reveals the level of conflict scholars tend to encounter on their respective routes every day, and identifies improvements that can be made in order to make it easier for them to walk. Through a literature review from different fields and through an empirical study, this project investigated the concept of walkability by trying to understand the different ways in which the built environment influences walking, e.g. directly influencing the quantity of walking through linking destinations, or enhancing the experience and the quality of walking by determining the condition of roads and sidewalks as a walking environment. It also investigated the different aspects of walking by partitioning walking activities and understanding how they are influenced by different properties of the built environment. By partitioning both the influence of the built environment on walking and the walking activity, the knowledge that this thesis tries to produce is not only on whether or not, but more on how and why the built environment influences walking behaviour. Scholars were used as participants and they were briefed on what was expected of them and the questionnaires were explained to them. The participants came from two different schools and they were randomly selected. Data was analysed using the average or the highest number of respondents from the areas of study on specific criteria. The results of this study are mixed, meaning some areas are worse for walking, while others are much better. The poor area has worse minor streets linking to the main road which is better for walking, and this is in the old suburbs. Newly developed suburbs show good, walkable streets. This is because they were designed according to modern changes in residential area development or beautifications. Orwetoveni suburb has a better walkable rating than Central Town. The municipality needs to improve the walkability of streets rather than paying too much attention to motorists. Pedestrians and cyclists also pay rates too, just as motorists do.

Animals in nature are capable of performing rapid acceleration and braking manoeuvres with ease. However, they have been avoided by researchers due to the complexities of this motion. To investigate and test novel control schemes for such motions, a highly agile mechanical robot is required. The aim of this dissertation was to build a bipedal robot to perform optimal rapid acceleration manoeuvres. This focused on investigating existing robots and using the information therein to design, build and test a new bipedal robot with high agility. The author performed a vigorous investigation into existing actuator schemes and leg topologies that promote agility, balancing the numerous trade-off’s such as mass-specific force and proprioception. This led to the selection of a Quasi-Direct Drive transmission with a scissor linkage leg. Legged robots were generally designed around some known motion [1]. However, selecting suitable mechanical parameters for agile motions with a lack of relevant research was challenging. Trajectory optimisation methods were used to generate unique acceleration motions for bipedal models, aiding in the selection of several physical parameters. With this, a detailed design of Baleka was created, prioritising desirable characteristic for rapid motions. Through several design iterations, the outcome was a fully assembled light weight bipedal robot. All the supporting systems required to operate Baleka were designed and set up, including the Real-time control system, relevant sensors and a boom support to keep it planar. A known metric, vertical agility [2], was used to compare Baleka’s agility to existing robots. Furthermore, a Raibert Controller [3] was also tested on the platform to investigate the robustness of the design. Baleka was found to be the most agile bipedal robot, exceeding the agility of humans. It was able to hop higher than all other robots, verifying it’s suitability for rapid acceleration manoeuvres. However, from the repetitive hopping experiments and high impact forces, slight plastic deformation was witnessed in the gearbox drive shafts.

This dissertation investigates advances in additive manufacturing (AM) technology to determine the feasibility of low-cost 3D printing of horn antennas. Relevant antenna theory and current 3D printing technologies are reviewed and a literature review is conducted looking specifically at microwave and RF devices that have been fabricated using 3D printing technologies. The literature indicates that the fabrication of antennas using AM and metallisation techniques is realisable. One of the objectives of this study has been to design, fabricate and test the performance of lowcost 3D printed antennas to determine their feasibility. To achieve this, a commercial X-band pyramidal horn has been replicated using the microwave simulation package FEKO. The X-band horn has been fabricated using an FDM-based 3D printer and metallised using conductive paint. Ku-band pyramidal and conical horns have also been designed and 3D printed using the same method and have been metallised using both conductive paint and electroplating. The fabricated horns have been measured and tested in an anechoic chamber with the measured results analysed. The fabricated X-band pyramidal horn achieved a gain of 9.2 dBi with an input reflection coefficient of −11.9 dB at a centre frequency of 10 GHz. This is in agreement with the measured gain and reflection coefficient of the X-band commercial horn. The Ku-band pyramidal horns that have been metallised using conductive paint and copper plating achieved gains of 17.5 dBi and 17.7 dBi respectively, measured at a centre frequency of 15 GHz. The input reflection coefficients for the painted Ku-band pyramidal horns are measured as −24.2 dB while the copper plated horns are measured as −23.3 dB. The second set of Ku-band conical horn antennas designed have also been metallised using conductive paint and copper plating. These two antennas achieved gains of 12.0 dBi and 16.6 dBi respectively at a centre frequency of 15 GHz. The input reflection coefficient for the painted Kuband conical horn is −15.2 dB while the plated version has a reflection coefficient of −18.3 dB. The total cost of fabricating and testing each antenna amounted to approximately ZAR 475 per antenna, an order of magnitude lower than the price of a traditional cast or milled antenna. The method of fabrication demonstrated in this report is relatively fast and inexpensive while producing favourable results. As such, this method is highly suited for rapid prototyping and development of more advanced antenna designs.

The national energy development plan for Angola, Angola Energia 2025, identifies the need to balance efforts to expand access to electricity in countries with low levels of industrialisation, across the urban and rural spheres. This need is coupled with the urgency of investing in environmentally sustainable technologies responding to local and international targets addressing the impacts of Climate Change. This dissertation seeks to assess the feasibility of an electricity micro-grid system (a) for uplifting the quality of life and development of two neighboring Angolan coastal villages, and (b) one that (I) depends entirely on domestic renewable sources of electricity generation; (ii)has a sustainable initial generating capacity of not less than 2MW and (iii) is flexible enough to undergo future expansion as needed over time. The design of a proposed Microgrid solution for N'zeto and Tomboco villages located in Angola is developed through a thorough context study used in conjunction with remotely acquired contextual data and a variety of estimation and model techniques. Microgrids are defined as a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity functioning with two modes of operation. The Microgrid design process requires a set of context specific empirical data ranging from load profiles of the site under survey to the availability of endogenous energy resources. The existence of documented public policy, the domestic availability of renewable resources in and around the study area, the present low population density in rural Angola, the low level of Angola's rural electrification , and the existence of financing mechanisms which the country can afford. The load profile and contemplated electrical energy consumption in the study area along with an estimation of the availability, nature, diversity, and extent of the domestic renewable energy sources are developed as key inputs for design decisions related to component sizing. A comparative evaluation of their performance of two proposed candidate solutions, derived from the assessment of the available energy resources is used as a basis to select preferred candidate. The proposed solution is subjected a sensitivity analysis of key design variables. Aspects of the selected design, including concept of operations, reticulation and a discussion on the possible downstream benefits are elaborated in compliance with the technical and policy constraints of the proposed electrification scheme.

Froth flotation is a highly water-intensive process which is under scrutiny due to scarce fresh water supplies and increasingly strict environmental regulations with regards to polluted water discharge. This is driving the mining industry to use recycled water for their operations, which is usually sourced from tailings dams or concentrator thickeners. This means that the recycled water can contain elevated levels of dissolved solids which consist of various ions and other contaminants such as residual reagents. This presents a problem in the flotation circuit as these dissolved solids tend to affect the water quality and can impact the efficiency and performance of flotation operations. The stability of the froth is known to strongly affect flotation performance and thus the grade and recovery of the valuable minerals. Literature shows that both frothers and ions reduce bubble coalescence, and stabilise the bubbles that form, resulting in greater froth stability. Considering that the level of ions in process water is on the rise, and both variables act on the froth in a similar manner, it is becoming increasingly important to understand how frothers behave under conditions of increased ionic strength. If it can be determined how these variables interact, then it may be possible to manage frother dosage in operations that recycle process water with the aim of reducing the quantity and cost of frothers and limiting the need for large amounts of fresh water, while still maintaining flotation performance. Therefore, this study was undertaken to investigate how frother dosage and ionic strength, both individually and simultaneously, affect the froth stability and therefore flotation performance. This study was limited to varying the frother type, frother dosage and ionic strength whilst keeping all other experimental conditions constant. Batch flotation tests were carried out involving the bulk flotation of chalcopyrite and pentlandite. Flotation performance was evaluated by examining the water, solids, copper and nickel recoveries, and the grades of both copper and nickel. The ore used for this study was Kevitsa ore from Finland. Both the individual effects of frother dosage and ionic strength and their simultaneous action were analysed. It was found that increasing the frother dosage stabilised the froth and increased the recovery of water and solids but had no impact on the recovery of copper and only a slightly positive influence on the recovery of nickel. At the same time, the grades of both copper and nickel were found to decrease, likely due to increased gangue recoveries. Increasing the ionic strength also stabilised the froth which increased the recovery of water and solids, but both the recoveries and grades of copper and nickel were not significantly affected. Examining both variables simultaneously revealed that ionic strength was more influential than frother dosage in the recovery of water with the opposite being true for the solids recoveries. This means that a simultaneous increase in ionic strength and decrease in frother dosage by the same amount will increase the water recoveries and decrease the solids recoveries. It will also slightly decrease the nickel recoveries while having no effect on the copper recoveries. The grades of both will either increase or remain the same. Overall, managing the frother dosage under conditions of increased ionic strength, while still maintaining flotation performance, is possible and could result in a decrease in the quantity and cost of frothers required for flotation. It may also allow the mining industry to recycle more of their water without the need for extensive cleaning which in turn will reduce the amount of fresh water required for flotation and reduce environmental discharge. However, because ionic strength and frother dosage have varying levels of influence and therefore must be monitored, the amount by which the ionic strength of the water is allowed to increase, and the amount by which the frother dosage is decreased, need to be tailored to suit the needs of the plant with regards to water recovery and the recoveries and grades of the valuable minerals.

Includes abstract. / Includes bibliographical references. / The Skills Development Act has recently become law in South Africa. The act seeks to develop and enhance the skills of the workforce and proponents argue that it encourages companies to become learning organisations. Under this law, employers are obliged to pay a skills development levy. The levy is essentially a tax, a portion of which can be reclaimed depending on the type of training a company undertakes. The purpose of this project is to explore the implementation of skills development within the new paradigm created by the legislation.

Selective removal of water from the Fischer-Tropsch Synthesis (FTS) during reaction may allow the use of a cobalt catalyst with crystal size <6 nm hence increasing the catalyst activity. Zeolite membranes are a potential route to in-situ water removal due to their chemical and thermal stability under FTS reaction conditions. Zeolite membranes with a low Si/ Al ratio are hydrophilic. It has been hypothesised that reducing the Si/ Al ratio will result in increased water selectivity and permeance. It is also hypothesised that the separation process can be modelled using the MaxwellStefan (MS) formulation. MFI zeolite membranes were synthesised on a-alumina supports, of varying Si/ Al ratio. Two synthesis techniques were used: viz. with and without the assistance of structure directing agents. The membrane physical properties were characterised by SEM and XRD. Membrane quality was evaluated using n-hexane porosimetry. Single gas and mixture separations were carried out. A trans-membrane pressure gradient was applied in single gas measurements. Binary and ternary mixture separations were carried out using a model reaction mixture that approximates FTS conditions. This mixture was fed to a Wicke-Kallenbach cell. The total pressure on both sides of the membrane was equal, with a sweep gas applied to remove the permeate. Single gas permeation measurements on a blank support shows that viscous and knudsen flow are the dominant transport mechanisms in the support. A single gas permeation model for the zeolite membranes show that viscous and knudsen flow still dominate in pure component measurements. This due to the high flux through the zeolite films. During mixture separations viscous and knudsen flow are negligible as there is no pressure gradient. Comparing pure component and binary mixture separations the flux of hydrogen decreases by more than two orders of magnitude for the binary case. In the binary system water adsorption results in blockage of pores hence hydrogen permeance is reduced. Binary H20/H2 separation selectivity increases with decreasing Si/ Al ratio. Increasing temperature results in a decrease in this selectivity. Water adsorption decreases with increasing temperature hence hydrogen can permeate faster. With the addition of n-hexane as a third component, permeance of water and hydrogen decrease, however ternary H20/H2 separation selectivity increases. The Maxwell-Stefan model developed does not predict binary hydrogen permeation well. Permeance is much higher than predicted by the model possibly due to defects. Ternary hydrogen permeance is however more accurately predicted. Water and n-hexane permeances are predicted well by the model.

Includes abstract. / Includes bibliographical references (p. 68-75). / The aim of this study was to do a techno-economic analysis for the use of both energy efficient and renewable energy technologies in supermarkets to determine the best options to implement to reduce grid electricity consumption, and its resulting carbon emissions in a cost-effective way.

Includes bibliographical references (p. [87]-92]. / The development of realistic comminution models is dependent on the accuracy with which ore breakage can be predicted. This hinges on our understanding of the basic concepts of breakage and the different modes in which it manifests in the comminution environment. Three distinctly different modes of breakage were identified and investigated as the elementary processes that govern comminution. Impact breakage was investigated as the first mode of breakage. Drop weight tests were performed to determine the influence of different energy intensities on the product particle size distribution. The drop weight tests were carried out on UG2 platinum and Target gold ore. The particles were broken over a range of six size classes ranging from 13 to l06mm. It was observed that the product size distribution becomes finer with increasing energies and that the sub 400um fraction may contain valuable information for some ore types.