Faculty of Engineering, Design and Technology

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    Household-Level Fluoride Reduction From Drinking Water Using Crushed Fired Clay – Proof of Concept
    (International Formulae Group Journal, 2021) Wozei, E.; Nasasira, B.; Kugonza, B.
    Residents of Bunyangabu District in Uganda have reportedly suffered from cases of dental fluorosis due to consumption of water with high levels of Fluoride from Ntabago Stream. A household-level sand filter incorporating crushed fired clay as an adsorbent was designed for a household to reduce the Fluoride concentration in their drinking water from the natural raw water levels (2-3 mgF/L) to permissible, healthy levels (0.5-1.0 mg/L). Pieces of fired clay bricks were crushed, and particles of 150 μm to 300 μm in size were selectively obtained by sieving. Stream water was filtered through replicate model layered filter columns of the prepared clay, sand (fine sand of 150 μm-2 mm; coarse sand of 2-5 mm), and gravel (6-15 mm). It was found out that fired clay layers of 2.5 and 5 cm thick reduce the concentration of Fluoride in water by up to 74%, to less than 1.0 mg/L. This was deduced by evaluating Fluoride concentration in both the clay and water before and after filtration, using the SPADNS Colorimetric method. Use of crushed fired clay for reduction in Fluoride concentration in drinking water is the focus of this paper. Additional work will optimise filter design to improve overall water quality.
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    Sawdust as a Filtering Media in Sludge Drying Beds
    (International Formulae Group Journal, 2021) Muzoora, David; Ssazipius, Gava Job; Miiro, Maiteki James; Kpange, Sylvia; Babu, Mohammed
    Conventional wastewater treatment is a common method of domestic wastewater treatment in Sub Saharan Africa. Lubigi wastewater treatment plant (LSTP) in Kampala – Uganda is a unique wastewater treatment system combining treatment of on-site faecal sludge and domestic wastewater. High solids content of on-site faecal sludge mean large volumes of the same, thus limited sludge drying space. This means need to optimize sludge drying bed use (improving the sludge drying efficiency) by reducing their drying times. This study investigated use of wood sawdust as a filtering layer in the faecal sludge drying process. Comparison of performance between sand, fine and coarse sawdust as a filtering media was conducted at LSTP. Sludge shrinkage depth (cm) and moisture content (%) were key parameters used to analyze and determine the most ideal media for sludge dewatering. The study was conducted during both wet and dry seasons to determine the impact of seasonal changes. Dry season results showed a drastic decrease in the sludge depth (shrinkage) for all the three media types after a period of 8 days followed by a gradual decrease in sludge depth up to 28 days. This implies that effective dewatering happens for the first 8 days, which goes on for the rest of the remaining days. Overall, the best performing media was fine sawdust, coarse sawdust and lastly sand. Independent two sample t-tests assuming equal variances show that there is a significant difference between the mean sludge depth of sand and fine sawdust t(df) = 56, P<0.05). There was no significant difference in the mean sludge shrinkage depth of fine sawdust and coarse sawdust. Similar results were obtained during the wet season. Comparisons of similar media types during the dry and wet seasons shows that the mean sludge shrinkage for the dry season were significantly lower than that of the wet season (P<0.05). This implies that seasonal changes significantly affect the sludge dewatering. In terms of moisture content (MC), the results for dry season showed that fresh fine and fresh coarse wood sawdust achieved MC of 28% and 31% respectively after 28 days. Sand produced faecal sludge with a higher MC of 49% after 28 days. Similar results of the performance of the three types of media was observed during the wet season. In conclusion, fine sawdust performs better than coarse sawdust and sand media in faecal sludge dewatering. Sludge dewatering is affected by seasonal changes.
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    Assessment of Physical Conditions and Proposed Best Management Practices of Domestic Storage Tanks Supplied by a Water Utility in a Rapidly Growing City
    (International Formulae Group Journal, 2021) Wozei, E.; Makoko, E.W.
    The physical conditions of domestic storage tanks for customers supplied by a water utility were assessed in Kampala, a rapidly growing City in Uganda. A longitudinal assessment of 372 storage tanks in 6 sampled administrative Wards with a minimum of 6 samples collected from each site in both wet (March-May) and dry (June-August) months of 2017 was carried out. A set of guiding questions were used to establish tank conditions with a YES or NO response and a range of low to critical risk rating. It was revealed that there was a statistically significant relationship (p=0.001) between tank physical conditions and quality of stored water. Two of six Wards in the City had high levels of water contamination related to domestic water storage tanks with poor sanitary conditions and contaminated water with E. coli. The study therefore revealed that the physical conditions and management of domestic water storage tanks have an effect on water quality. This is important information for a water utility as it means that it is not enough to supply safe water if the quality may deteriorate upon storage at the consumer premises. A routine inspection checklist and consumer guidelines for domestic storage tank management are proposed.
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    Walking on Sunshine: Pairing Electric Vehicles With Solar Energy for Sustainable Informal Public Transport in Uganda
    (Energy Research and Social Science, 2021-11) Ndibatya, Innocent; Booysen, M.J.; Abraham, C.J.; Rix, A.J.
    Minibus taxi public transport is a seemingly chaotic phenomenon in the developing cities of the Global South with unique mobility and operational characteristics. Eventually this wide-spread effect of minibus taxis will have to transition to electric vehicles. This paper examines the impact of this inevitable evolution on a city-wide scale in Kampala, Uganda. We present a generic simulation environment to assess the grid impact and charging opportunities, given the unique paratransit mobility patterns. We used floating car data to assess the energy requirements of electric minibus taxis, which will have a knock-on effect on the region's already fragile electrical grid. We used spatio-temporal and solar photovoltaic analyses to assess the informal and formal stops that would be needed for the taxis to recharge from solar PV in the region's abundant sunshine. The results showed that the median energy demand across all simulated days of the effect of taxis was 220kWh=d. This ranged to a maximum of 491kWh=d, with a median charging potential (stationary time) across taxis of 8 h=d to 12 h=d. The median potential for charging from solar PV ranged from 0:24kWh=m2 to 0:52kWh=m2 per day, across the taxis. Our simulator and results will allow traffic planners and grid operators to assess and plan for looming electric vehicle roll-outs to the most-used mode of transport in Africa.
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    Ray of Hope for Sub-Saharan Africa’s Paratransit: Solar Charging of Urban Electric Minibus Taxis in South Africa
    (Energy for Sustainable Development, 2021) Ndibatya, Innocent; Booysen, M.J.; Abraham, C.J.
    Minibus taxi public transport is a seemingly chaotic phenomenon in the developing cities of the Global South with unique mobility and operational characteristics. Eventually this ubiquitous fleet of minibus taxis is expected to transition to electric vehicles, which will result in an additional energy burden on Africa's already fragile electrical grids. This paper examines the electrical energy demands of this possible evolution, and presents a generic simulation environment to assess the grid impact and charging opportunities. We used GPS tracking and spatiotemporal data to assess the energy requirements of nine electric minibus taxis as well as the informal and formal stops at which the taxis can recharge. Given the region's abundant sunshine, we modelled a grid-connected solar photovoltaic charging system to determine how effectively PV may be used to offset the additional burden on the electrical grid. The mean energy demand of the taxis was 213kWh/d, resulting in an average efficiency of 0.93kWh/km. The stopping time across taxis, a proxy for charging opportunity, ranged from 7.7 h/d to 10.6 h/d. The energy supplied per surface area of PV to offset the charging load of a taxi while stopping, ranged from 0.38 to 0.90kWh/m2 per day. Our simulator, which is publicly available, and the results will allow traffic planners and grid operators to assess and plan for looming electric vehicle roll-outs.