3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Coal fly ash waste management challenges in the South African power generation sector and possible recycling opportunities: a case study of Hendrina and Kendal power stations(2018) Ramagoma, Mbavhalelo JusticeSouth Africa will be dependent on coal for power generation for many decades to come, before a complete transition is achieved where more energy will be generated from non-fossil fuel sources. Through case studies of Hendrina and Kendal Power Stations, this study explored how the management of fly ash (FA) waste in South Africa can be improved to minimise its impact on the environment and human health and examined the potential recycling applications that can benefit local communities. The study drew insights from an environmental justice framework to examine the pollution impacts that FA is exposing to the local community. The environmental justice theory is based on the principle that all people have a right to live in an environment that enhances their wellbeing. Empirical evidence obtained from local community’s in-depth interviews revealed that FA is impacting on the health of communities by exposing them to respiratory and other illnesses and it is also affecting their livelihoods which primarily involves farming. A just transition theory was employed to examine potential socio economic opportunities that can be derived from FA recycling to fulfil redistributive measures that can reduce inequality and eradicate poverty in local communities. Some of Eskom’s power stations like Hendrina are nearing the end of their lifespan since their commissioning in the 1960’s and 1970’s. To aid a just transition, ash recycling was found to have the potential to address the socio economic situation of the power station’s employees and the local communities. The study found that local communities generally lack knowledge about coal ash recycling and need to be empowered and supported to partake in ash recycling ventures. The study argues that a shift in the ash recycling regime is needed in order to benefit local communities and facilitate a just transition to a clean energy production.Item Incipient motion of boulders in open channel flow(2018) Stols, KevinThe use of boulders to create habitat heterogeneity is important for aquatic diversity, and being able to predict the stability of a boulder that is placed in a river will aid in sizing the boulder. Identifying ways to increase the stability could save costs associated with over design or replacement due to the boulder washing away. Existing research on incipient motion centres on determining threshold conditions for bed material or protruding elements within a bed surface with relation to, among others: shape of particle, size of particle, relative depth of particle to flow depth, and impact of channel slope. The existing research is limited to bed material that is of a similar size and there is no research on the conditions for incipient motion elements that are relatively large compared to the bed material it is resting on. An idealised flume study was performed to identify trends that several factors have on boulder stability, as well as to verify the results obtained from a pivoting analysis model prediction for a spherical boulder. An additional study was performed to obtain drag coefficients that were suitable for use on spherical boulders that were either embedded into the bed material or simply resting on top of the bed material. The results of the drag experiments were varied; only the results for the non-embedded were suitable to integrate into the model predictions while drag coefficients for the embedded boulders need to be taken from previously published results. The results of the flume study provided good confirmation of the model predictions with the average absolute experimental error being 4%. The trends identified in the flume study show that the most effective method in improving a boulder’s stability is to embed it into the bed material with this being more effective than increasing the size of the boulder.