Masters Theses and Dissertations

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Contamination assessment and optimization of coagulation-flocculation-sedimentation water treatment process for Kou river in northern Tanzania
(NM-AIST, 2022-06) Gebreyohannes, Netsanet
The Babati Urban Water Supply and Sanitation Authority (BAWASA) in northern Tanzania supplies water from the Kou River to Magugu town for domestic purpose, where its Fe (3.64 mg/L) and turbidity (87 NTU) concentrations were found in excess beyond their acceptable limits. A coagulation-flocculation-sedimentation water treatment plant was planned to be installed for treating the water, where the system’s performance is negatively influenced due to inadequate applications, hence requiring optimization. The quality of sediment and water of the Kou River was examined for physicochemical parameters and 9 metallic elements. The water did not meet the requirements for aquatic, biological life, and irrigation purposes for at least 1 metallic ion. Furthermore, pollution levels of the 9 metals in the river sediments were evaluated using 6 pollution indices and a moderate contamination was found, hardly posing ecological risk. A coagulation-flocculation-sedimentation water treatment system was optimized to respond to coagulant dose, pH, mixing rates, mixing time, and settling time in the removal of Fe and turbidity using jar-test. The optimum dose and conditions were: 30 mg/L alum, an initial mixing rate of 150 rpm for 5 minutes, slow mixing rate of 20 rpm for 30 minutes and settling time for 30 minutes which was validated using scale-up pilot test and resulted in 98.25% turbidity and 97.5% Fe removal. Furthe research on developing enhanced time-saving optimization method and developing a dose indicator technology to assign alum dose requirement based on the fluctuating characteristics of the raw waters (turbidity) is recommended.
Design of an evaporative cooling system integrated with ultraviolet light for preservation of fruits and vegetables at variable tropical weather conditions: a case study of Arusha, Tanzania
(NM-AIST, 2024-07) Gunda, John
Problems with fruits and vegetables spoiling after harvest are particularly acute in tropical regions. This research presents the design, construction, and performance assessment of a solar-powered evaporative cooling storage system incorporating ultraviolet radiation (UV) to preserve foods susceptible to spoilage. Local materials, including sisal, sponge, and bricks, were used to construct the cooling chamber with a UV bulb. We measured the system's efficiency in both sunny and overcast tropical weather conditions by looking at how much air temperature was reduced, how much relative humidity was increased, and how much electricity was used for evaporative cooling. According to research, fruits and vegetables may be kept fresh for much longer after activating the UV light. This method may keep perishable goods for up to 21 days under UV light and 9 days without. An average temperature drop of 5.0℃ and an increase in relative humidity result from active system operation on sunny days. In contrast, the cooling effect is minimal on overcast days, leading to a relative humidity rise of 18% and a temperature drop of around 3.5℃. Based on these results, a solar-powered evaporative cooling system with UV radiation treatment might be a good way to reduce tropical post-harvest losses.
Diversity and quantity of macro-and microplastics in irrigation farms sourcing water from an urban river: a case of Arusha Tanzania
(NM-AIST, 2021-10) Kundu, Mercy
Increased concentration of plastics in urban rivers and agricultural farms causes degradation of river system functionality and reduces the productivity of agricultural soils, respectively. This study assessed the quantity and types of macro-and microplastics found in dependent smallholder irrigation farms downstream of Arusha city in Tanzania. The microplastics' concentration from the sites was visualized using dissecting microscope 40X, enumerated and categorized based on the shape, color, and sizes for soil samples. Then the suspected materials’ spectral were determined using the Attenuated Total Reflectance- Fourier Transform Infrared (ATR-FTIR). Afterwards, the confirmations and identifications of the polymers' types from spectral were confirmed using SiMPle Software. The average microplastic from the water column was 0.57 ± 0.27 items L-1, sediment 0.17± 0.07 items g-1, while in the irrigation farms ranged from 102 to 728 items with a mean of 0.69 ± 0.35 items g-1. However, no international standards have been developed to ascertain the pollution level, but the reported values are unsafe to the environment. Other studies conducted in similar conditions reported mean values within the range of values found in this study and more. Polyethylene was the dominating type of macroplastics evaluated from riverbanks and irrigation farms with a frequency of occurrence 100 %, while polystyrene was abundant in all microplastics samples. Farms adjacent to the irrigation canal had a greater number of microplastics and macroplastics. Thus this study reveals urban rivers as the primary sources of plastics pollution in the irrigation farms situated in flood-prone zones.
Evaluation of recharge areas of Arusha aquifer, northern Tanzania: application of water isotope tracers
(NM-AIST, 2022-01) Lugodisha, Innocent
In Arusha urban, northern Tanzania, groundwater contributes about 80% of the water supply. However, elevated fluoride levels and evidence of anthropogenic pollution have been reported in the groundwater around Mount Meru which is a water source for Arusha urban. This study aims at understanding the recharge areas and flow pathways of groundwater in what has been a poorly monitored area. The study uses the isotopic ratio of oxygen and hydrogen to estimate the groundwater recharge area and flow pathway. The results show the recharge elevation of groundwater is between 1800 and 3500 m above mean sea level on the slopes of Mount Meru. Fluoride showed an increasing trend with elevation while NO3 - decreased with sampling altitude. The high content of NO3 - and Cl in water samples from sources in the lower part of the study area is evidence of anthropogenic contamination. The average fluoride contents in the study area are 5.3 ± 0.4 mg/L greater than the limits of 1.5 mg/L and 4 mg/L set by the World Health Organization (WHO) and Tanzania respectively. The nitrate concentration of 83.9 mg/L at the lower elevation areas (<1400 m above mean sea level) exceeds the 50 mg/L WHO limit. The relationship of F- with δ18O and NO3 - suggests the leaching of fluoride in high altitudes and dilution in lower altitudes. Two flow pathways were identified, that start from the recharge area in the south and south-western slopes of Mount Meru towards the southern part of Arusha urban.
Fluoride and pathogens removal from water using combined electrocoagulation-inline-electrolytic disinfection process
(NM-AIST, 2024-08) Njau, Oscar
The consecutive removal of fluoride (defluoridation) and pathogens (disinfection) in drinking water through combined electrocoagulation-inline-electrolytic disinfection (EC–ECl2) process with aluminum and dimension-stable mixed oxide electrodes was reported in this study. Laboratory trials have been conducted on the effects of flow rate, initial pH, current density, and supporting electrolytes for defluoridation and disinfection processes. The results have shown that with a flow rate of 10 L/h, initial pH of 6, the current density of 9.4 mA/cm2 (EC cell) and 3.1 mA/cm2 (ECl2 cell), supporting electrolyte concentration of 165 mg/L, and electrolysis time of 50 min, a defluoridation rate of 88% (initial concentration of 12.3 mg/L) and complete disinfection (initial fecal coliforms of 19,700 colony-forming units per 100 mL (CFU/100 mL)) can be reached. The final concentration of fluoride and pathogens in treated water was 1.44 mg/L and 0 CFU/100 mL, which are within the acceptable limit of the World Health Organization and the Tanzania Bureau of Standards of 1.5 mg/L and 0 CFU/100 mL, respectively. The EC–ECl2 system is a promising approach for consecutive defluoridation and disinfection of water to save millions from fluorosis and waterborne diseases. However, optimization potential with regard to energy efficiency and system complexity were identified.
Impacts of irrigation water quality, associated soils characteristics and on-farm practices on paddy yields
(NM-AIST, 2022-07) Mpanda, Fridolin
In this study, the impacts of irrigation water quality, soil characteristics and on-farm practices on paddy yields were investigated. Standard spectroscopy and spectrometry methods were used to analyze irrigation water and irrigated soil samples. The irrigation water had sodium adsorption (SAR) values ranging from 0 to 3. The corresponding electrical conductivity (EC) values were between 0.2 and 0.7 dS/m and accounted for 14% of all samples hence posing slight to moderate infiltration problem. Neither sodium nor chloride levels were high enough to cause toxicity problems in the irrigation water. For boron, 54% of the samples was found to have moderate toxicity whereas ~14% of the samples indicated severe boron toxicity in the irrigation water. For bicarbonate, about 86 and 14% of the irrigation water indicated slight-to moderate and severe potential detrimental effect to plant growth, respectively. The trace elements Fe2+, Zn2+, Cu2+, Mn2+, B, As, Cd, Cr2+, Pb2+, Ni2+, and Al3+ in the irrigation water samples were too low to cause any harmful effect. Although soil EC (0.2 to 1.9dS/m), organic carbon (OC) (0.1 to 2.4%) and pH (6.0 to 8.5) indicated favorable levels, there were significant variations in soil Fe (2.6 to 169.5 mg/kg) and Zn (3.9 to 204.1 mg/kg). The mean value of Fe in soils was 19.8 mg/kg. Soils indicated signs of Fe-deficiency. High variabilities were also found in the total N (86 to 2155 mg/kg) content of the studied paddy soils. The levels of phosphorus (Olson P, mean 224.2 ± 149.4 mg/kg) were found to be too high compared to what is reported as normal in similar studies. There might be unsustainable and excessive application of P-containing inputs in the studied area. Furthermore, a low soil K content was observed in the analyzed soil samples. The present study recommends that regular control of irrigation water HCO3-, EC and controlling soil pH levels as well as adoption of standard on-farm practices following of crop calendar, proper application of fertilizers. Availability of extension officers to advice farmers is highly recommended.
Influence of land use change on nitrate sources and pollutant enrichment in surface and groundwater of a growing urban areas
(NM-AIST, 2022-07) Mallya, Clarah L.
In the present study, three-year (1997, 2008 and 2017) satellite images as well as different hydro chemical parameters, nitrogen and oxygen isotopic composition of nitrate were used to examine the impacts of land use and land cover change on surface and groundwater quality. Through isotopic composition, sources of surface and groundwater nitrate contamination was also elucidated. The results showed significant land use transition whereby land use changed from forest and bare land to agricultural land and built-up areas. A slight reduction in the size of areas covered by water bodies was also observed, from 8 km2 in 1997 to 7.4 km2 in 2017. Results indicate differences in nitrate concentration that mirror land use changes. Samples with elevated levels of nitrate above 10 mg/L were located near agricultural fields and areas with intensive livestock keeping activities. In groundwater, ẟ15N-nitrate and ẟ 18O-nitrate ranged from 3.2‰ to 20.1‰ with a mean value of 11.7 ± 1.8‰ and from 2.1‰ to 12.0‰ with mean value of 5.4 ± 1.8‰, respectively indicating nitrate was derived from inorganic fertilizer, manure and sewage. In surface water, ẟ15N-nitrate and ẟ18O-nitrate ranged from 2.4‰ to 19.3‰ with mean value of 4.9 ± 1.4‰ and from 1.5‰ to 21.9‰ with a mean value of 13.5 ± 2.8‰, respectively indicating nitrate from soil N. Isotopic composition data suggest sources of nitrate in groundwater dominated by synthetic and organic fertilizer application and to a lesser extent a natural soil nitrate source.
Optimal design and analysis of a grid- connected hybrid renewable energy system using homer pro: a case study of Tumbatu island, Zanzibar
(NM-AIST, 2024-08) Said, Thani
This study addresses the issue of quality electricity access on Tumbatu Island in Tanzania, with a specific focus on enhancing the high-voltage (HV) transmission line. While many studies concentrate on low-voltage (LV) transmission lines, HV lines play a crucial role and merit more attention. Therefore, the objective of the study is to improve the voltage profile of the HV transmission line through a hybrid energy system comprising solar PV, wind turbines, and batteries. This effort begins with an analysis of the total power demand and consumption, which are essential for designing an effective energy system. The study employs HOMER Pro to simulate various hybrid system configurations. The simulation findings indicate that integrating solar PV, wind turbines, and HV lines leads to a significant enhancement in the voltage profile, raising it from 29.6 kV to 31.23 kV during peak demand. This solution demonstrates the highest economic viability, boasting the lowest Net Present Cost (NPC) of USD 4 003 851 and a relatively short payback period (PB) of 3.79 years. Implementing this hybrid system not only meets the island's energy needs but also contributes to global pollution reduction and minimizes electricity costs for the population of Tumbatu Island. Furthermore, it addresses the demand for clean energy, emphasizing its role in achieving sustainable and accessible electricity in Sub-Saharan Africa and beyond
The potential of water resources contamination around a large-scale gold mine
(NM-AIST, 2022-05) Musiba, Musiba
This study used the hydro-chemical properties and isotopic signatures of water to understand the main sources of deterioration of water quality around the North Mara gold mine in Tarime District, Mara Region. The chemical and isotopic signatures of the surface and groundwater were used in understanding the origin, flow pattern, residence times, and vulnerability to pollution. Most samples that were located downstream, western side of the mine tailings dam were slightly acidic with pH as low as 4.6 and enriched with stable isotopes. Most samples with elevated concentrations of Na+, Cl-, SO42-and NO3-could not be isotopically linked with the local geochemistry, but the observed water chemistry was controlled by evaporation and an thropogenic effects. The Piper trilinear diagram showed Ca and Mg cations dominance, while bicarbonates and sulfates dominated the anions. The heavy metals, Pb and Hg levels (mean 70.29 and 17.95 µg/L, respectively) were all higher than the levels recommended in both the World Health Organization (WHO) and Tanzanian drinking water guidelines. The low pH values and elevated concentrations of cyanides, heavy metals, and metalloids were probably associated with mining activities. The radioactive isotope results indicated the vulnerability of the water to recent contamination that could be attributed to near-surface an thropogenic activities. Moreover, stable isotopic studies indicated the pollutants-carrying water flow pattern was from the eastern to the western side of the study area. Lowland samples had higher tritium activities than the highland ones. Therefore, the present study concludes that groundwater recharge from recent local precipitation may have an impact on the sources studied and the use of shallow dug out wells should be minimized.
Strength and durability properties of concrete blended with pumice and scoria under combined attack of sulphate and chloride
(NM-AIST, 2021-11) Chambua, Safiel
Concrete structures suffer serious deterioration under corrosive environment. Consequently, the safety of these concrete structures is decreased. The influence of natural pumice (NP) and natural scoria (NS) as supplementing cementing materials of concrete exposed to sulphate, chloride and combined effect of sulphate and chloride is studied. Portland cement (PLC) was replaced with NP or NS at a substitution level of 10%. Concrete samples were submerged in portable water for 28 days. Afterwards, the specimens were immersed in 5% sodium sulphate (Na2SO4), 5% sodium chloride (NaCl) and combined sodium sulphate and chloride solutions for 28, 56 and 90 days. The results were compared between concrete mixes with NP or NS and control mix (CT) with PLC. The effects of sulphate, chloride and combined sulphate and chloride were evaluated in terms of change in weight, variation in compressive strength and degree of damage. The compressive strength was not compromised at 10% substitution level. It was observed that, concrete containing NP and NS have compressive strength of 46 MPa (7.7%) and 44 MPa (3.04%) higher than 42.7 MPa of CT submerged in water for 90 days respectively. Concrete samples immersed in 5% Na2SO4 solution, NP and NS has a compressive strength around 45.5 MPa (15.4%) and 44.8 MPa (13.6%) higher than 39.4 MPa of CT mix at 90 days, respectively. However, under 5% NaCl solution the compressive strength of concrete containing NP and NS decreased up to 34.2 MPa (7.5%) and 32.5 MPa (7.2%) for 90 days cured samples. Moreover, under combined effect of 5% Na2SO4 and 5% NaCl concrete containing NP and NS has a compressive strength around 29.8 MPa (8%) and 29.2 MPa (7.3%) higher than 27.4 MPa of control mix at the exposure period of 90 days. It can be concluded that NP and NS have extraordinary potential to be utilized as a cementitious material in concrete.
Water use and crop water productivity in farmer managed irrigation schemes across agro ecological zones of usa river catchment
(NM-AIST, 2021-11) Haymale, Humuri
The Usa River Catchment is the potential area dealing with traditional irrigated agriculture. This study aims to estimate the amount of water abstracted for and yield that reflect water values to enhance crop water productivity. The main objective of this study was to assess water use and crop water productivity in farmer managed irrigation schemes across agro-ecological zones of Usa River Catchment. The specific objectives were: (a) to determine crop water productivity, (b) to determine factors causing the variation of crop water productivity, and (c) conveyance efficiencies in the traditional irrigation schemes in the Catchment. The secondary and primary data were collected and analysed using Statistical Package for Social Science (SPSS) and R-program. Consequently, the average productivity obtained were 2.3 kg/ha, 1.9 kg/ha, and 3.4 kg/ha of maize for downstream, midstream, and upstream zones respectively. Similarly, at twenty (20) furrows, the conveyances efficiency of the water channels was 72%, which reflects the water loss in the conveyances of 28% on average. However, the water abstractions were 3500 L/s more than the permitted amount of 2856.2 L/s, which was against the established water abstraction laws and regulations leading to water shortage in downstream of the catchment. Traditional irrigation infrastructure in this study contributed more water losses and low crop water productivity compared to global average water losses in the conveyance and crop water productivity in irrigation schemes. This study recommends weirs with water control structures intakes to be constructed, canal lining and improve irrigation water management.

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