Masters Theses and Dissertations

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Assessing adoption and water productivity of the system of rice-intensification under farmer-led irrigation system in northern Tanzania
(NM-AIST, 2021-02) Kavishe, Rosemary
This study was conducted to evaluate farmers‟ appropriation of the system of rice intensification (SRI) in an informal irrigation scheme in northern Tanzania. Understanding the integration and performance of SRI in the local rice farming will assist in short and long-term planning and allocation of available resources. First, a survey was conducted to explore farmers‟ adjustments of SRI principles. Second, yield and water productivity of the integrated system was assessed by setting up experimental plots in the farmers‟ fields. Four treatments representing farmers‟ adaptations of SRI practices were assessed. One treatment (F1) was continuous flooding while the other three treatments (F2, F3 and F4) were under intermittent irrigation. The yield of 4.8, 8.5, 8.2 and 9.2 tons/ha, and water productivity of 0.15, 0.39, 0.35 and 0.51 Kg/m 3 were obtained for F1, F2, F3 and F4, respectively. Water-saving under SRI was 34.3%, 28.9%, and 45.1% for F2, F3 and F4, respectively. The figures are comparable to those reported under full SRI, which is in the range 20% to 60%. The highest yield (9.2 tons/ha), water productivity (0.51 Kg/m 3 ) and water-saving (45.1%) was obtained in F4 involving one seedling 15 days old transplanted at 25 x 25 cm. However, this method is not preferred by many farmers due to lack of supporting infrastructure. Hence, F2 involving two seedlings 21 days old planted at 20 x 20 cm with intermittent irrigation is recommended for this area as it ensures a sufficient number of plants, relatively higher yields and a reduced considerable amount of irrigation water.
Assessment of fluoride bioaccumulation in catfish grown in fluoride rich waters
(NM-AIST, 2021-08) Bejumula, Jophillene
Fluoride bioaccumulation in fish poses a significant impact to their growth performance, survival and consequently to the upper trophic levels. Few studies have reported the impact of high fluoride concentration and their accumulation to catfish in African settings. A 60-days African catfish (Claris gariepinus) cultivation was conducted at Ngarenanyuki ward and at the Nelson Mandela African Institution of Science and Technology (NM-AIST) laboratory in Arusha, Tanzania, to determine fluoride bioaccumulation and its effect on growth and survival of the catfish. The juvenile catfishes were exposed to water containing 36 mg Fˉ/L in a fishpond and synthetic water containing fluoride concentrations (NaF) of 5, 15, 36 and 45 mg/L in the aquaria set at NM-AIST laboratory. Fish growth and survival was determined and the fluoride concentrations in fish tissues were analysed by ion selective electrode. At the end of the experiment, fish survival rate was greater than 90% in fluoride levels of 5, 15, 36 mg/L compared to 65.8% in 45 mg/L aquaria treatment. Also, significant fluoride bioaccumulation was observed in fish bones (222.00 mg/kg, dry weight) followed by gills (177.4 mg/kg), skin (9 mg/kg) and low amount in fillets (1.467 mg/kg). In all these tissues, fluoride bioaccumulation significantly rose with increase in fluoride levels in the water and exposure time (p< 0.001). From this experiment, it is concluded that high fluoride occurrence in surface water led to increased bioaccumulation in the African catfish and correlates with exposure time. Therefore, to grow catfish in water containing more than 45 mg/L requires a deflouridation process to take place.
Assessment of fluoride removal in a batch electro‒coagulation process
(NM-AIST, 2021-06) Mureth, Risala
A presence of excessive amounts of fluoride than the prescribed standards has been reported in sources of domestic water supply around mount Meru slopes and other parts in Tanzania while efforts to remove the excessive fluoride was carried out using various technologies and materials. This study was perfomed to understand the fluoride removal effeciency of the electrocoagulation technique. It has been reported that in the electrocoagulation process, ions removal efficiency depends on the electrolysis time, voltage, pH and initial ions concentration applied. In this electrocoagulation process, experiments were carried out to examine its efficiency on removal of fluoride ions. The fluoride concentration tested ranged from 1.37 to 48 mg/L in both synthetic and natural waters. The voltage applied for the electrocoagulation process ranged from 0 to 50 V while maintaining an optimal pH of 4 to 9. Experimental results showed the removal efficiency of 90% with an optimal time of 30 minutes, at an applied voltage of 20 V and a pH of 6 at initial concentration of 29.5 mg/L at 300 ml. The method showed efficient removal of fluoride in water to achieve the allowable limits by the World Health Organization and Tanzania Bureau of Standards (1.5 mg/L). At this voltage (30 V), the process could be inferred to have the capability of treating the water and hence rendering such water safe for use as reported previously.
Assessment of levels and distribution of progesterone in receiving waters and wastewaters in the vicinity of Arusha city,Tanzania
(NM-AIST, 2020-12) Kasambala, Hildegard
This study aimed at investigating the levels and distribution of progesterone in receiving waters and wastewaters in Arusha, a fast-growing urban area and third largest city in Tanzania. Also, intend to assess the efficiency of waste stabilisation ponds (WSP) and constructed wetland (CW) in removing progesterone. The study was conducted along the Themi River, (WSPs) and CW. Progesterone was detected and quantified by using an Enzyme-Linked Immunosorbent Assay (ELISA) kit. For Themi River samples, the level of progesterone obtained ranged from ‘no detection’ to 439.00 ng/L with a mean value of 120.30 ng/L. The levels detected were significantly higher in the midstream three times and seven times than upstream and downstream, respectively (P ˂ 0.05). Progesterone was spatially distributed much at midstream than upstream and downstream. The elevated values at midstream were attributable to livestock, WSPs and household effluents; agricultural activities; and sewage infiltration. WSPs were observed to release 215 ng/L of progesterone at effluent with zero progesterone detected at the effluent from CW with a removal efficiency of 75% and 100% for WSP and CW, respectively. Although progesterone removal efficiency was high, the amount released was still high enough to cause harm to aquatic organisms. Progesterone levels in the present study, although not extremely high, correspond to those associated with harmful effects in other studies. Therefore, this study suggests that anthropogenic activities conducted nearby the rivers should be strictly avoided to reduce the amount of progesterone to be released to the river.
Assessment of Mpanda groundwater contamination and the effectiveness of the baobab seeds-derived biochar for iron removal from groundwater
(NM-AIST, 2024-08) Mkelemi, Magdalena
Groundwater in Mpanda District, Tanzania, faces excessive iron content, causing a reddish brown colouration due to oxidized iron species. The present study evaluated Mpanda groundwater contamination and the effectiveness of baobab seeds-derived biochar for iron removal from groundwater. First, the physicochemical quality of groundwater was investigated. Nineteen boreholes were randomly selected for assessment, with samples collected in rainy and dry seasons. The study revealed significant variations in groundwater quality both between seasons and among boreholes. Temperature, total dissolved solids, electrical conductivity, lead, iron and manganese exceeding World Health Organization and Tanzania Bureau of Standards limits in some boreholes; necessitating water treatment for human use. Second, the effectiveness of baobab seeds-derived biochar for iron removal from groundwater was assessed. Baobab seeds, were sun-dried, oven dried at 105 ºC, carbonized at 700 ºC, and ground into fine powder. The influence of pH, time, temperature and dose of biochar on the iron removal from groundwater was assessed. Six 1000 mL beakers were filled with groundwater and adsorbent doses of 0.6 g/L, 1.2 g/L, 1.8 g/L, 2.4 g/L, and 3.0 g/L were added into five beakers with the sixth serving as a control. The highest removal efficiency of iron was observed within 5.0-8.0 pH range. Over time, the removal efficiency increased to 87% at 120 minutes and 3.0 g dose, with an initial iron concentration of 5.88 mg/L and residual concentration of 0.76 mg/L. Baobab seeds-derived biochar showed promising efficiency in removing iron ions and is recommended for sustainable iron removal from groundwater.
Assessment of the impacts of groundwater pumpage on the future water supply sustainability in Zanzibar, Tanzania
(NM-AIST, 2020-12) Ali, Zuleikha
In the present study, a 42-year record of rainfall and temperature from Airport and a 43-year rainfall record from Kizimbani meteorological station were analyzed to understand how these climatic variables are affecting groundwater resources on the Island of Zanzibar, Tanzania. Water table fluctuation, abstraction volume and different Physico-chemical parameters such as chlorinity, nitrate, electrical conductivity and total dissolved solids were also studied. The balance between groundwater recharge and water abstraction rates and assess the impact of groundwater pumpage on water quality on the island of Zanzibar was estimated. Through the use of the water table fluctuation (WTF) method, this study estimated the local sustainable yield (SY) and integrated water balance (IWB) in Zanzibar. Rainfall records showed that Zanzibar Island receives a total mean annual rainfall of 1673 mm out of which 7% (equivalent to 1.79 x 10 6 m 3 /y) recharges the groundwater. Temperature variations indicated an incremental trend accompanied by low rainfall. The average estimated local sustainable yield was 0.72% while the integrated water balance showed a deficit of 39%. Furthermore, the total groundwater abstraction rate in the studied area was 2.49 x 10 6 m 3 /y, which is higher than the rate of recharge. This means that the groundwater resources are currently overexploited and if immediate action is not taken, the groundwater aquifers may be subjected to pollution, collapse, and seawater intrusion. The effects of over-pumping are being manifested by the levels of EC, Cl - , TDS, total hardness (TH) and nitrate that have shown an increasing trend with time. Due to the high variation of temperature, a controlled infiltration of harvested rainwater is suggested as a sustainable solution for salt intrusion as well the balance way of recharge and abstraction rate in Zanzibar and other islands.
A column design for groundwater hardness removal using cashew nut shells activated carbon with potential application in low-income communities
(NM-AIST, 2020-02) Mwakobe, Emmanuel C.
Water hardness has been associated with various human health problems. In many developing countries, groundwater is the main source of drinking water. Water hardness has a significant impact on groundwater quality, especially in arid and semi-arid regions, leading to wasted financial investments in borehole drilling and worsening community accessibility to potable water.In this study, relatively cheap and readily available raw materials were used to remove total hardness from groundwater in a laboratory scale column setting. In thisstudy, design parameters for a filter to remove total hardness from groundwater were investigated. The optimal design parameters for the packed column were as follows: area (A) of 265.0 cm2 and diameter (d) of 18.4 cm, at a flowrate (Q) of 75.0 cm3 /min. For the field hard water flowrate of 2.0 mL/min, the optimal empty bed contact time was 70.7 min whereas the breakthrough time was about 430 min. Also, for the field hard water, the results showed that competing ions from other contaminants in groundwater lowered the materials adsorption capacity. Results from this study indicated that Cashew-nut Shell Activated Carbon may be used to adequately remove total hardness from groundwater.Using these results, a pilot filter was designed. The designed water hardness filter may provide the much-needed solution to many potable water problems facing communities in most developing countries. Keywords:Activated carbon; Cashew-nut shells; Column design; Groundwater; Hardness removal;Water filter
Cryptogamic packed biofilter as potential adsorbent for co2, h2s and nh3 impurities from biogas
(NM-AIST, 2020-07) Temba, Norbert Willibrord
The presence of elevated concentrations of carbon dioxide, hydrogen sulfide, ammonia and trace impurities in biogas affect its caloric value as well as causes corrosion and are extremely toxic. There are various methods for removal of these impurities, but most are chemically based, expensive and limited in use. In this work, cryptogams (moss) integrated with soil and biochar packed in a filter have been employed for simultaneous removal of CO2, H2S and NH3, from biogas. Different soil types rich in metallic oxides at a different mass of (100 g, 150 g and 200 g) with a fixed mass of moss and biochar were tested in an on-site experiment to determine the removal efficiency (RE) and sorption capacity (SC). The adsorption dynamics of the filters were investigated at two flow rates, 80 ml/min and 100 ml/min, by determining removal efficiency. For the contribution of each substrate, sorption capacity and breakthrough time were determined by considering 5 g of each substrate that made up the filter. The soils with a high content of extractable cations showed excellent adsorption capacity for H2S by about 20 gS/100 g, which was higher than other adsorbents tested. It was found that integrated biofilter made up of bed arrangement of the soil, biochar and moss plant improved the quality of biogas with SC of 11 g-S and RE of 93% for H2S, 72% for NH3 and 68% for CO2. Keywords: Cryptogams, Biofiltration, Biochar, Removal efficiency, Sorption Capacity.
Effect of industrial dust deposition on photovoltaic module performance: Experimental measurements in tropical region
(NM-AIST, 2020-02) Andrea, Yotham
Dust particles accumulation affects photovoltaic module transmittance of photovoltaic solar cell glazing, and thus leading to substantial reduction of conversion efficiency owing to lower irradiance reaching the surface. In this study, the sensitivity of polycrystalline photovoltaic module towards industrial dust deposition was experimentally investigated under the tropical climatic condition of Arusha Region in Tanzania. Dust involved in the study was collected from fertilizer, gypsum, aggregate crusher and coal mines industries. Particle size analysis was done by sieve analysis technique to get different particle size range 20 μm-45 μm, 45 μm – 90 μm and 90 μm- 180 μm. The dust was uniformly distributed over the module with a baby powder bottle which had 100 g capacity with six holes of 0.1 inch diameter size, the holes was covered with sieve mesh in front of it in order to enhance uniform distribution. The experiment was conducted in an outdoor environment whereby two identical polycrystalline modules of rated power 100 W; were mounted at 15o facing north. Each module was connected to digital voltmeter and ammeter, modules current and voltage were monitored by supplying power to a rheostat, the I-V curves measurements were conducted at three different solar irradiances 720 W/m2 , 800 W/m2 and 900 W/m2 ; characteristic electrical parameters were obtained. Results indicate that dust deposition has more effect on short circuit current and does not affect open circuit voltage. Maximum module efficiency loss on polycrystalline photovoltaic module was determined to be 64%, 42%, 30% and 29% for coal, aggregate, gypsum and organic fertilizer dust, respectively. Therefore the coal dust was observed to have higher photovoltaic efficiency loss (64%) compared to all four tested dust samples. It was also demonstrated that photovoltaic module performance deteriorated with temperature rise owing to heat dissipation caused by dust accumulation. In accordance with literature data this study confirmed that efficiency loss on photovoltaic module also depended on the size of the dust particles accumulated on it; small particles reduced more performance efficiency compared with the larger particles. Keywords: Photovoltaic module, Performance efficiency, Dust, Solar irradiance.
Efficacy of silver nanoparticles in capacitive deionization electrodes as antimicrobial agents
(NM-AIST, 2020-02) Abdallah, Amina
The availability of clean and safe water is still a big challenge in most parts of the world. Drinking water should be free of harmful microorganisms and should contain the required amount of minerals based on the set standards. In this study, silver nanoparticles (Ag-n) embedded in Activated Carbon (AC) electrodes for capacitive deionization (CDI) were evaluated for desalination and also for anti-microbial activities against Escherichia coli and Salmonella enteritidis. The novel AC/Ag-n electrodes were prepared by mixing Activated Carbon powder together with silver nanoparticles. The morphology, surface functional groups, and porosity were characterized by Scanning Electron Microscope (SEM), Fouriertransform infrared (FT-IR), and nitrogen adsorption studies which affirm the formation of disinfecting electrode material. The desalination and disinfection performance of the fabricated electrodes were evaluated by Capacitive Deionization batch mode experiment using natural water collected from the Nganana stream while applying the potential of 2 V for 3h. The AC/Ag-n Capacitive Deionization (CDI) electrodes achieved 100% Escherichia coli and 98% Salmonella enteritidis removal and 45% salt removal efficiency, and electrosorption capacity of 2.56 mg/g and the ions removal efficiency of 89%, 40%, 2.4%, 57.9%, 50%, 8% and 33% for Na+ , K+ , Ca2+ , Mg2+ , PO4 3- , NO3 - and Clrespectively. The microbial disinfection mechanisms were through electrosorption process and physical contacts with the embedded Ag-n. Thus, it is possible to disinfect the water while also removing salt simultaneously using Capacitive Deionization. Therefore, AC/Ag-n are considered as novel electrode material with an excellent antimicrobial agent for the Capacitive Deionization process.
Enhancing the performance of a spray flash evaporation integrated with evacuated tube desalination system
(NM-AIST, 2021-02) Muhunzi, Amour
Numerical analysis for heat exchanger for spray-assisted low-temperature desalination system is presented for an existing low-temperature desalination unit at Arusha Technical College (ATC). The current desalination unit at ATC has two suction fans and a water pump in the condensation unit where significant amount of energy is consumed. So, it will be impractical to implement such a type of desalination system in remote areas where there is limited access to electricity. The study aims to come up with a suitable model for the replacement of the current condensation unit due to high energy consumption. The heat transfer phenomena have been analyzed to understand the effect of mass flow rate, tube length and diameter in a shelland-tube heat exchanger (STHX). A Math CAD model was developed using the Delaware method to obtain the mentioned parameters. The results show that the pressure drop is very low from all STHX configurations, while the heat transfer coefficient seems to be maximum in the smallest diameter within the largest tube length heat exchanger. The maximum possible energy will be extracted by the STHX from the steam while it condenses. According to the results, as long as over-design is considered the proposed system can be implemented with the minimum effect of 5.968 to 10.688 kWh energy consumption. The energy-saving of the proposed system is about 8.856 kWh as the replacement of the STHX from the existing condensation unit. While the current system energy is consumed about 14.824 to 19.544 kWh in a single day of operation. Also, the proposed system will improve the system workability to the remote communities in future implementation.
Experimental investigation of the variation in the potential of selected natural rocks as thermal energy storage materials
(NM-AIST, 2023-08) Kakoko, Lilian
Fossil fuels cause greenhouse gas emissions and are perceived to deplete, hence the use of renewable energy is considered crucial. These renewables include the use of solar thermal energy in concentrated solar power (CSP) generation and solar drying applications. However, solar energy is intermittent, thus solved by incorporating thermal energy storage (TES) to store heat energy for future use. However, the most common weaknesses in TES materials are high cost of investment, environmentally unfriendly and are not locally available. Using natural rocks is recommended as they are readily available, affordable and efficient TES materials for solar drying applications at 40-75 °C and concentrated solar power generation at 500-600°C. Despite its generational use in thermal applications, soapstone rock has not been studied as a TES material. Moreover, site specificity has not been investigated in spite of being stated toaffect the potential of rocks in TES. Therefore, this study investigates the potential of soapstone rock as a TES material, and the influence of the geological-tectonic settings. In the present study, experimental characterization of selected natural rocks namely soapstone and granite, was done to investigate their thermal properties at 20-950°C. Conclusively, soapstone rock from the Craton geo-tectonic setting had the best properties and it had the highest young’s modulus, thermal capacity, thermal conductivity and had a weight loss of only 0.75 % at 900°C. At high temperatures, it did not show visible fracture. Moreover, soapstone and granite from the Craton and Usagaran geo-tectonic settings exhibit significant differences
Fish bladder-based activated porous carbon/co3o4/tio2 composite electrodes for supercapacitors
(NM-AIST, 2020-02) Sirengo, Keith
Supercapacitors as energy storage devices depend on electrode materials, electrolyte and conductive additives. In relation to the above, this master’s dissertation specifically provides a scientific understanding and knowledge to the society on the use of fish bladder derived porous carbon for cobalt oxide/titanium dioxide/activated carbon (Co3O4/TiO2/Ac) composite as electrode materials for supercapacitor applications. Fish bladder was used as a carbon source for the composite after carbonization and chemical activation. Composites of Co3O4/TiO2/Ac, Co3O4/Ac, and TiO2/Ac were later synthesized using simple impregnation method followed by heat treatment and thereafter in-depth investigation on the active material was carried out through material characterization and electrochemical testing. X-ray diffraction and scanning electron microscopy (SEM) revealed that Co3O4 and TiO2 nano phases were well embedded over carbon matrices. Fourier transfer infra-red (FT-IR) measurements showed that the active material had oxygen containing functional groups. Cyclic voltammetry curves demonstrated that specific capacitance of the active material was 946 Fg -1 for Co3O4/TiO2/Ac as compared to Co3O4/Ac, TiO2/Ac, and Ac with specific capacitances of 845 F g-1 , 340 F g -1 , and 308 F g -1 , respectively at a scan rate of 5 mVs -1 . Impedance spectroscopy revealed good capacitive behavior with a series resistance of 0.5 Ω, 0.52 Ω, 0.6 Ω, and 1.1 Ω for Ac, Co3O4/Ac, Co3O4/TiO2/Ac, and TiO2/Ac, respectively. Excellent electrochemical performances observed for the Co3O4/TiO2/Ac electrode was a result of individual contribution of different characteristics of the binary metal oxides such as improved electric conductivity and wettability of the composites associated with porous carbon and TiO2.
Groundwater recharge estimation and quality on the southern slopes of mount Kilimanjaro, Tanzania
(NM-AIST, 2021-07) Lwimbo, Zuberi
This study was undertaken to estimate groundwater recharge rates using three methods (water table fluctuation (WTF), chloride mass balance (CMB) and soil moisture balance (SMB), as well as assessing the impact use of the pesticides and fertilizers on groundwater quality in a Kahe catchment located on the Southern slope of Mt. Kilimanjaro, Tanzania. The estimated recharge rates of the WTF method yielded a higher value of about 248.4 million m 3 /year, whereas that of CMB and SMB methods was 156.0 and 132.1 million m 3 /year, respectively. The concentration of pesticide residues was below the detection limit, while, NO 3 - levels of sampled groundwater were averaged about 18.40 ± 4 and 7.6 ± 1.7 mg/l in the wet and dry season, respectively. An elevated level of nitrate (NO 3 - ), sulfate (SO 4 2- ), phosphate (PO 4 3- ), and ammonium (NH 4 + ) was found nearby the large-scale sugarcane farms. Generally, the groundwater chemistry was dominated by magnesium-sodium-bicarbonate (Mg-Na-HCO 3 ) water type. The cations levels were in the trend of Mg 2+ > Na + > Ca 2+ > K + , whereas anions were HCO 3 - > Cl - > SO 4 2- for both seasons. The heavy metals concentration of Pb, Cd, Fe, Mn, Zn and Cu for both seasons were averaged approximately 0.08 ± 0.03, 0.11 ± 0.03, 0.16 ± 0.02, 0.11 ± 0.01, 0.46 ± 0.05 and 0.55 ± 0.02 mg/l, respectively. Whereas the concentration was higher in shallow groundwater than deep boreholes and most of them were located around the western-eastern zone of the Kahe catchment. The findings from this study provided reliable data information for future monitoring programs of groundwater resources management in Kahe catchment, Tanzania.
Impact of climate change on groundwater recharge in lake Manyara catchment
(2020-08) Omary, Latifa
This study aimed to estimate the groundwater recharge of the Lake Manyara catchment (7920 km2) in two different time intervals, historical 1988-2018 and near-future 2021-2050 climatic condition. This study analyzed the trends, spatio-temporal variability in rainfall and temperature, and the length of the rainy season (LRS) in the Lake Manyara catchment, Tanzania covering a period between 1988 and 2018 using stations and satellite climate product. The Mann-Kendall statistical test, Sen‘s slope estimator and inverse distance weighting interpolation techniques were used to detect the trends, magnitude of trends and spatial distribution of rainfall and temperature. A modified Stern‘s method and water balance concept were used for rainfall onset, cessation and LRS analysis while standardized precipitation index (SPI) was used to investigate the wetness or dryness of the area. Then Coordinated Regional Downscaling Experiment output (CORDEX) Africa data rainfall and temperature projections obtained and lastly used as input data in the WetSpass model for groundwater recharge estimation. The results showed high variability and decreasing trends (4 mm/y) in annual rainfall and non-significant increasing trend for minimum and maximum temperature. The WetSpass results showed historical mean annual recharge of the catchment was 53.9 mm/y with the potential groundwater recharge of 149 Million Cubic Metre (MCM). The results of projected recharge estimated to be 88.5 mm/y with the potential groundwater recharge of 421 MCM. Statistically the contribution of the historical rainfall to the groundwater recharge was 6.7% compared to 8.1% in the projected period. However, the most potential recharge zones in the catchment identified around the northern part (around Ngorongoro), western and southwestern (Buger ward and Mbulu). There is a need, therefore, for adaptation measures such as improving water productivity and irrigation at the farm and catchment level.
Influence of duct configurations on the performance of solar-assisted heat pump dryer for drying tobacco leaves
(NM-AIST, 2023-08) Suleiman, Salum
nadequate storage facilities and preservation techniques lead to a decrease in the quality of agricultural products. Application of modern processing techniques has reduced post-harvest losses of agricultural crops. Drying was done to lower the moisture content for preservation. Tobacco drying requires massive amounts of wood, which has negative effects on the environment such as pollution, deforestation, and desertification. In the present study, a solar- assisted heat pump dryer (SAHPD) has been designed, fabricated and tested its performances as an alternative drying technology for tobacco leaves. The hot air generated from the solar collector and condenser unit of the heat pump was used as a source of heat in the drying chamber. In this study, we investigated thermal performance of three duct configurations of the SAHPD system (open, partially closed and completely closed) to establish the best configuration for drying tobacco leaves where did not conducted before. The average drying temperature was found to be 66, 64 and 60°C; the coefficient of performance of the heat pump was 3.4, 3.2 and 3.0; the heat energy contribution from the condenser was 98.7, 98.5 and 98.3%; and electrical energy consumption was 2.3, 2.8 and 2.6 kWh, for the open, partially and completely closed systems, respectively. Based on these results, the open system demonstrated the best performance. According to the study's findings, SAHPD has been shown to be an energy-efficient method of drying tobacco leaves and environmentally friendly as opposed to the conventional use of wood fuel, which results in environmental pollution, desertification, and deforestation. Future studies should focus on inclusive investigation of the life cycle and techno-economic
Inhibition of aluminium corrosion using carica papaya extracts in acidic media (sulphuric acid and phosphoric acid)
(NM-AIST, 2017-12) Kasuga, Baruku
Corrosion inhibition of aluminium using Carica papaya leaves extracts in 1M H2SO4 and IM H3PO4 was investigated under different temperatures (30, 40 and 500C) and concentrations (from 20-100 v/v %). The inhibitor was found to work by being adsorbed onto the aluminium surface, hence preventing the corrosion of the metal by forming a film that acted like a barrier to the direct contact between the metal and the acids. Gravimetric analysis (Weight loss method) as the main methodology was used throughout the investigation. From the data collected, inhibition efficiency values, adsorption isotherms, kinetic and thermodynamic parameters concerning the adsorption processes were determined; all of these give out important clues on the working ability of the inhibitor. Characterization was also applied using Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FT-IR) spectroscopy. SEM was used to determine the adsorption ability of inhibitor by investigating aluminium coupons through surface profile analysis. The FT-IR machine was used to determine functional groups of the phytochemicals found in C. papaya leaves, inhibitor prepared and those participated in adsorption. Carica papaya leaves extract was found to have a maximum inhibition efficiency of 71.67 % and 56.02 % in H2SO4 and H3PO4 respectively, at the optimal concentration which ranges from 60 to 80 v/v % in both of the media used. Results obtained in this study give hope to corrosion engineers that C. papaya is among of the plants on which its extracts can be used to develop a commercialized natural corrosion inhibitor. This is possible because it has phytochemicals with active functional groups to develop inhibitive properties.
Integration of the energy recovery step in municipal wastewater treatment chain: a case study of Moshi municipality, Tanzania
(NM-AIST, 2020-06) Hance, Vaileth
The energy demand which is expected to increase more worldwide has sparked the interest of researchers to find sustainable and inexpensive sources of energy. This study aims to integrate energy recovering step into municipal wastewater treatment plants (MWWTPS) through anaerobic digestion. The anaerobic digestion of municipal wastewater (MWW) and then co-digestion with sugar cane molasses (SCM) to improve its organic content was conducted at 25 oC and 37 oC. The results showed substrate mixture containing 6% of SCM and total solids (TS) of 7.52% yielded higher amount of biogas (9.73 L/L of modified substrate). However, chemical oxygen demand (COD) of the resulting digestate was high (10.1 g/L) and pH was not stable hence needed careful adjustment using 2M of NaOH solution. This study recommends substrate mixture containing SCM (2%) and TS (4.34%) having biogas production (4.97 L/L of modified substrate) for energy recovering from MWWTPS, since is found to have more stable pH and low COD residue (1.8 g/L) which will not hold back the MWW treatment process. The annual generation of modified substrate (662 973 m3 ) is anticipated to generate about 16 241 m3 of methane which produce up to 1.8 GWh and 8193 GJ per annum. The study concluded that biogas is among of the future fuel if the modern technology on anaerobic digestion is functional. Also the use of combined heat and power (CHP) engine for the conversion of biogas to heat and electrical energy increases the energy value of the wastewater. (Keywords: Anaerobic digestion, Biogas, Municipal wastewater, Sugarcane molasses)
Investigating the potential of producing eco-friendly liquid biofertilizer from domestic wastewater
(NM-AIST, 2023-08) Muga, Elly
Water bodies experience environmental challenges such as eutrophication due to poor management of domestic wastewater in developing countries. Meanwhile, the explosion in population of the world has resulted in a 1.8 percent annual increase in demand for fertilizers that contain important nutrients. Although domestic wastewater contains nutrients (nitrogen, phosphorus, and potassium) that can be used in agriculture, its recovery is still a challenge. Some of the potential methods, such as the use of struvite precipitate in recovering nutrients from wastewater, are not only costly but also introduce a second pollutant into the ecosystem. The ion exchange method can recover phosphorus from wastewater; however, its effectiveness is limited by the presence of competing anions, such as sulfates. Freeze concentration method is one of the potential techniques for recovering nutrients from wastewater. However, its optimal condition such as temperature and time in recovering nutrients from domestic wastewater is not well known by researchers. In this study, method of freeze concentration was studied to establish its optimal condition in recovering nitrate nitrogen and phosphate nutrients from domestic wastewater processed in anaerobic digester. Frozen liquid and unfrozen concentrated liquid are produced. The effect of freezing temperature from -10°C to -80°C, freezing time from 1 hour to 8 hours and energy consumption on the nutrient recovery were investigated. Freezing temperature of -20°C, cooling time of 7 hours and energy consumption of 0.197 kWh/L resulted in the highest nitrate-nitrogen and phosphate nutrient recovery value of 1.114 and 4.667 respectively at the inlet of anaerobic digester 1, 1.325 and 4.975 respectively at the outlet of anaerobic digester 1, 1.099 and 4.859 respectively at the inlet of anaerobic digester 2, 1.132 and 4.755 respectively at the outlet of anaerobic digester 2 and for gravel filter at the outlet the values where 1.111 and 4.861 respectively. This study shows that, when the freeze concentration method is used with the right temperature, time, and energy, a significant amount of nutrients may be recovered from domestic wastewater that can be used as biofertilizer.
Investigation of metallic iron for water defluoridation
(NM-AIST, 2021-12) Lufingo, Mesia
Fluorosis is a significant ailment that affects millions of humans and animals, especially in low income countries. It has been the focus of past and present scientific endeavours to research and develop efficient and deployable technologies, especially in these low-income communities. In this work, metallic Iron (Fe0) is a promising technology, and its filters have successfully addressed both safe drinking water and sanitation and are frugal. The recalled science of Fe0 filters is demonstrated with the lingering design investigations. This study aimed at the critical assessment on defluoridation efficiencies under conventional metallic iron aqueous systems; where at first, Fe0 materials were characterized with 1,10 Phenanthroline (Phen) in aqueous condition, and later batch studies were realized at the laboratory scale for two days under varied experimental conditions of: (a) 0.1 g and 1.0 g of iron mass, (b) Equimolar contamination, 23±2.0 mg/L, of co-solutes, i.e. NO3, PO4, SO4, HCO3, Cl, (c) Initial pH values of 4.5, 7.0 and 9.5, and (d) Disturbed and non-disturbed treatments. Characterization results proved the potential of 1,10-Phenanthroline as a sole Fe0 novel and facile characterization method. Defluoridation results revealed a maximum of 94% and 47% for quantitative (involving co precipitation, adsorption and occasionally size-exclusion remediations) and non-quantitative (associated with adsorption as major remediation means) fluoride removal efficiencies, respectively. Thus, a conventional metallic iron aqueous system requires incorporating suggested nano-scale practices towards enhancing efficiency for affordable defluoridation achievements in future continuous system designs.

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Browsing Masters Theses and Dissertations by Subject "Research Subject Categories::NATURAL SCIENCES"