Theses and Dissertations

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    (2022-10-28) MASIYA, TATENDA MARTHA
    In Namibia, there have been problems of water scarcity, water pollution and water shortages. Despite Swakoppoort reservoir being one of the important sources of surface water in central Namibia, water quality in the reservoir has continued to deteriorate due to urban wastewater pollution. In this research, Klein Windhoek River one of the rivers flowing into the reservoir was studied with the aim of evaluating if a water quality change trend forecast can be a useful tool for water quality management. Water samples were collected from Klein Windhoek River with a focus on industries sited along the river including Ujams Wastewater Treatment Plant, a biological nutrient remover which discharges effluent into Klein Windhoek River. Water quality samples were collected downstream and upstream of Ujams WWTP from Klein Windhoek River to analyse the impact of industrial effluents discharged into the river after treatment at Ujams WWTP. The samples were tested for physical and chemical parameters pH, chemical oxygen demand(COD), dissolved oxygen(DO), total dissolved solids(TDS), conductivity, total phosphate(TP) and chromium. Water quality concentrations in tested samples at times exceeding standards stipulated in Act No.11 of 2013 for COD, DO, TDS, TP and electrical conductivity. WEAP21 modelling software was used to analyse the impact of industrial effluents on Klein Windhoek River by modelling a wastewater treatment plant for four parameters (COD, DO, TDS, TP) for years 2015 to 2021. Results showed unsatisfactory Nash-Sutcliffe efficiency results of below 0.7 with a value of 0.62 for COD, 0.62 for TDS and 0.29 for TP. WEAP21 model showed deficiency in forecasting the ephemeral river’s water quality.
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    Management of water supply and demand remains a major challenge in most developing countries, especially in a semi-arid country like Namibia, where surface water supplies are limited mostly during drought periods. Given the extremities, the Hardap catchment is exposed to, water supply and demand management is a challenge. This results in water resource allocation problems, which threaten the sustainable water resource management in the catchment. A baseline study was conducted to develop and assess a calibrated WEAP model for the Hardap Dam operation and water resource management strategies. Water demand and supply availability were evaluated for three water use sectors, namely, domestic (tourism and livestock included), aquaculture, and irrigation. The WEAP model was structured according to four scenarios with a current account (1999) and reference period (2000-2021). These scenarios are as follows: Scenario 1: 10% demand saving management for Mariental Town and improved irrigation efficiency by changing from the current flood irrigation method to the drip irrigation method. Scenario 2: increased irrigation area for the Hardap Irrigation Scheme. Scenario 3: hydrological seasons for high and low flows which evaluated the change in the hydrological regime; very wet, wet, normal, dry and very dry years. Scenario 4: the discharge of water made from Hardap Dam in 2017 for the downstream demand, Neckartal Dam. The modelling results show that the operation of the Hardap Dam is challenging and the change from 100% to 70% operation rule of full supply capacity has greatly reduced the availability of water supply. The water management strategy results indicate that the 10% demand saving management for Mariental Town has reduced the domestic water demand by 10% hence no impact on the water availability of the Hardap Dam. Improved irrigation efficiency has a positive impact of about 30% reduction in water demand and 13% increase in water availability, with a significant impact of improvements during the drought seasons. Under the increased irrigation area scenario, the irrigation demands are increased by 3.8 Mm3/m for an area of 213 ha and little impact is observed on the storage volumes during dry years. However, the model forecasted a critical and an extreme threshold of 300 and 1000 ha respectively. This has a major impact on demand coverage which was reduced to 90% for the 300 ha. While the 1000 ha has a significant impact on the water supply which depleted the dam levels to below the dead zone. The hydrological seasons were evaluated and the results show that there is a major effect during drought years, due to an increase in storage volumes. The forecasted inflows of 2015 and 2016 were within the observed water year type of dry and very dry. The result of the discharge of 10.7 Mm3 for Neckartal Dam from Hardap Dam in 2017 showed no threat to the water demands and supply as both demands are met.
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    Assessment of Atmospheric Dispersion of Fly Ash within the Vicinity of Van Eck Coal-Fired Power Station, Windhoek, Namibia
    (2020-04) Aushiku, Ndeukumwa
    Increase in population led to the growth of industrialisation which has stimulated the development of alternatives to produce electricity, including the use of coal. Coal-fired power plants produce an abundant amount of electricity, addressing the ever-increasing electricity demand. Power plants produce fly ash as a result of coal combustion for electric power generation. The Van Eck Power Station is the oldest and only coal-fired plant in Namibia that is located at the outskirts of Windhoek. The power plant produces electricity from the combustion of coal. Its refurbishment began in 2013, to improve its efficiency and allow for longer operational period. Van Eck’s rehabilitation included coal feeders which reduce emissions and new grates for boiler units which reduce ash emissions to ensure that the plant is a cleaner coal-fired power plant. Fly ash is produced when coal is pulverised and blown with air into the boiler's combustion chamber where it directly burns and generates heat. Trace elements in coal deposits would not only contaminate the air, soil and underground water but also have an impact on human health. The thesis was aimed at assessing the possible pollutant elements found in fly ash and soil in areas surrounding the Van Eck Power Station. The thesis was also aimed at modelling the distribution and dispersion of those elements at a particular distance in areas around the Van Eck power plant using the Gaussian Plume Model. Soil samples were obtained from sites within the vicinity of Van Eck Power Station, and XRF Analysis was used to determine the concentration of elements in the soil. To obtain samples of fly ash, fall out buckets filled with distilled water were mounted on poles away from the main source of pollution. The deionised water was analysed using the Inductively Coupled Plasma (ICP-OES) Analysis method for the detection of elements. Gravimetric analysis was also applied to measure the weight of dust, which in the report is expressed as fly ash. The study revealed more concentration of sulphur oxides specifically as sulphites and sulphates, as well as Zinc, while the rest of the elements of interest were detected significantly in low amount. Others were below the level of detection in both the fly ash and soil sampling. Also, soil sampled near the power plant was detected with a high amount of SOx and Zinc. Fly ash collected showed that areas near the power plant contain more pollutants than areas further from the power plant. Ash captured through the dust-fallout bucket method within the jurisdiction of the power plant was above the South African dust monitoring criteria. The model illustrated that elements during the day were more absorbed than reflected during the night. Based on the research analysis, it was found that the power plant does not produce an abundant amount of pollution due to off-peak operations. However, comprehensive results may be obtained if this type of research is repeated on a different, specified timeframe. The station may require control efficiency compliance measures for noxious gases and particulate matter (PM) concentrations. These results will be important in the formulation of emission limits, air quality guidelines and control of emission of pollutants. Air quality modelling is essential in baseline reports of projects.