Theses and Dissertations (Civil Engineering)
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Browsing Theses and Dissertations (Civil Engineering) by Subject "Dissertations, Academic -- South Africa."
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Item Determining the efficiency of selected vegetated biofilters in reducing nutrients from urban stormwater in the city of Ekurhuleni, South Africa(Vaal University of Technology, 2021-11) Bvumbi, Mulalo Justice; Rwanga, S. S., Dr.; Ochieng, G. M., Prof.Over time, the quality standard of stormwater in the City of Ekurhuleni (CoE) has deteriorated due to industrial, commercial, residential and farming activities. Stormwater quality directly impacts the treatment chain of potable water, and therefore, it should be kept in check at all stages. Innovations in the biofiltration process can provide useful, practical solutions to overcome crucial stormwater pollution problems. In 2013, the CoE developed stormwater design guidelines and standards to be implemented for the design of stormwater management, which include the principles of Water Sensitive Urban Design (WSUD) and Sustainable Urban Drainage Systems (SuDS) in particular. The CoE stormwater design guidelines and standards do not provide details on how the city plans to implement SuDS treatment trains to reduce stormwater pollution experienced by the city. This study aimed to verify the efficiency and effectiveness of vegetated biofilters on the stormwater treatment using CoE – Olifantsfontain's natural stormwater and to determine the most suitable vegetation to be used in the region. The CoE experimental case study was conducted to assess the efficiency of selected vegetated biofilters in lowering the concentration of orthophosphate (PO4-3), ammonium (NH4+), and nitrate (NO3-) from Tembisa/Olifantsfontain stormwater. In the experimental setup, six selected plant species were planted into 30 vegetated biofilter columns, namely: Agapanthus praecox (Dryland plant), Carpobrotus edulis (Dryland plant), Stenotaphrum secundatum (Dryland plant), Zantedeschia aethiopica (Wetland plant), Typha capensis (Wetland plant) and Phragmites australis (Wetland plant). The six species were grouped according to general habitats, i.e. three wetland and three dryland plants. Wetland plants were planted into fifteen vegetated biofilters, and dryland plants were also planted on another fifteen vegetated biofilters. The biofilters contained layers of sandy loam soil, coarse and and gravel sand. Each biofilter had a designated inlet and outlet section fitted with a gate valve to control retention time. The raw stormwater consisting of natural nutrient pollutants was applied to each vegetated biofilter through the inlet section. The samples were collected from the inlet and outlet of the six grouped vegetated biofilters during the month of June. All six plant species reduced outflow concentrations of PO4-3 and NH4+ by an average of 99% and 98%, respectively. The results also show that all plant species excluding Phragmites australis were able to reduce NO3- with outflow concentrations being reduced by an average of 58%. From the results obtained, it may be concluded that all the six plant species may be suitable variants to be applied as biofilter material for the purposes of treating urban stormwater in the CoE. The reason is that the determined removal efficiencies for bio-retention fall within 50% – 60% for PO4-3, and 40% - 50% for NH4+ and NO3- respectively. The results also show that if the plant species were applied for SuDs in the CoE, there could be a great improvement in the urban stormwater quality with the consequent improvement in both surface and groundwater quality of the receiving water bodies in the area. Regardless of the nutrient removal by selected plant species, the inclusion of vegetation in a field setting would slow flow rates and thus encourage infiltration into the soil, improve water quality, and support urban biodiversity. In the CoE, all the selected species could be used in the SuDS treatment trains targeting PO4-3, NH4+ and/or NO3-. The case study results provide a informed records for the CoE in the future/intended application SuDs in the upgrade/rehabilitation of its stormwater system.Item Flash flood risk management in a South African township: a case study of Alexandra(Vaal University of Technology, 2022) Fadupin, Adekunle Oluwatosin; Ndege, M., Prof.; Ochieng, G. M., Prof.Several studies have been carried out on improvement of flood risk assessment and management in South Africa. Despite all these studies, the problem of F lash Flood (FF) persists. This study was designed to determine the most appropriate Flash Flood Inundation Model that could be applied in flash flood risks management in a South Africa Township: a case study of Alexandra. Alexandra Township being a FF prone area was chosen for this study from where a sample of 30 respondents was purposively selected. A survey (Questionnaire) and document search were used to collect relevant quantitative data and qualitatively based secondary information from the sample population respectively. Also, data were collected through in-depth interviews of senior officials in the Disaster Management Services for more well-rounded information. Content analytical method was used to process the qualitative information. The study adopted complementary analytical tools, namely, R-programming and appropriately selected tools from the Statistical Package for Social Sciences (SPSS version 21.0) to analyze the quantitative data and to determine the most appropriate Flash Flood Inundation Model. In search of mitigating the risk of the FF in Alexandra Township, a FF inundation model was determined. People were educated on FF not to build shacks along Juskei River and were trained to prepare for and manage FF. Early Warning messages were sent and community volunteers were trained on managing risks related to FF. The main observed risk factors of FF where building of shacks without abiding by the rules and regulation, blocking of drainage system by illegal dumping of solid waste and growth in population. The major risk factors the respondents agreed to cause FF where annual rainfall intensity (70.0%), poor drainage (56.7%) and human settlement (50.0%). The three Principal Components identified to be contributing to FF in Alexandra Township were terrain, soil texture and poor drainage system. This factors contributed 82.0% of FF risk factors in Alexandra Township. The model revealed that appropriate solid waste disposal, construction of sewers, dredging of Jukskei River, and construction of Gabions along Jukskei River will mitigate flash flood risk and related hazards in Alexandra Township.Item Monitoring and modelling of water quality characteristics along a reticulation system: a case study of modimolle reticulation network(2012-01) Mehlo, Mahlomola; Wanjala, R. Salim, Dr.; Ndambuki, J. M., Prof.Potable water quality can deteriorate immensely from point of treatment to point of usage. This change in quality along a bulk distribution main may be attributed to numerous factors, such as the ingress of storm water. Furthermore, water utilities experience challenges in terms of the microbiological organisms that are not attributed to operational practices. For example, drinking water bulk distribution mains may be a shelter for these microorganisms that are sustained by organic and inorganic nutrients present within the pipe itself. These microorganisms may be active in the water being transported by the pipe, and can cause a significant drop in the water quality. In order to deal with the problem of deteriorating water quality, sufficient information within the bulk main is required, so that the consumer can be protected from ingesting contaminated water or water of poor quality. Hence, the overall objective of this study was to investigate and model water quality characteristics within the Modimolle reticulation network. Water samples were collected from various points throughout the entire system for quality analysis. Different sampling points were established along the main pipeline as well as within the Modimolle distribution system. Water quality software, EPANET, was then used to model the water quality deterioration for both the bulk line and the reticulation network of Modimolle extension 11. Residual chlorine was the main parameter which was monitored. This study presents results of a research on water quality variation within a long distribution mains conveying water up to 87 km. Results show that raw residual chlorine is constantly depleted along the pipeline, and is therefore unable to be maintained at the required level of 0.2 mg/l, as stipulated by the Department of Water Affairs. This means that if any harmful contaminants should enter the water, the residual chlorine in the water will not be able to protect the consumers from the contaminants.