PhD Theses and Dissertations

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Development of a suitable pragmatic and cost effective biomonitoring method for assessing water pollution in tropical African rivers
(NM-AIST, 2015-09) Elias, Julius Daud
The needs of tropical African countries to develop their own biomonitoring indices using local macroinvertebrates as opposed to adoption or relying on non-tropical indices in biomonitoring programmes for assessing freshwater pollution were discussed. The discussion build-up involved: (i) reviewing of existing indices from non-tropical regions and their adoption setbacks in assessing pollution in tropical African rivers; (ii) testing of key review findings in the field at a small scale and then at a wide scope by characterizing macroinvertebrates while examining environmental variables; (iii) assigning pollution sensitivity ratings of macroinvertebrates based on related scoring systems and the help of PRIMER7 software; (iv) determination of macroinvertebrates response towards nutrients loading, and; (v) developing suitable and cost-effective biomonitoring method. The review paper, pilot and detailed studies and toxicity test study were aimed at laying the groundwork needed to develop a simple, quick and advanced tropical biomonitoring tool for initial application on Tanzanian rivers. Collectively, ninety seven macroinvertebrate families belonging to seventeen orders were observed at 85 sampling stations, representing 46 reference and 39 monitoring sites along Tanzanian rivers. All observed orders were subjected to six stepwise criteria to identify the one with a potential of discriminating reference from monitoring sites. The criteria include: numerical truncate test, Mann-Whitney test, inter-quartile overlap levels in Box-and-Whisker plots, Spearman rank correlation (rs) analysis, more diverse order (with > 10 taxa) and validation test. Ephemeroptera (E), Diptera (D), Odonata (O) and Trichoptera (T) orders that comprised the 55% (N = 97) of all Tanzanian families met all test criteria after being found with abundances > 2% upon truncate test, a p-value < 0.05 in a Mann-Whitney U test, a sensitivity score of 3, rs < 75% (with p < 0.005), higher number of taxa (n > 10) and separating reference from monitoring sites and thus, chosen to develop EDOT index. Being developed using only four and most diverse local orders, minimizes data variability, needs for great expertise and time in the field, the credibility that is not hitherto possessed by existing indices.
Impacts of future climate and landuse changes on surface-groundwater balance in Usangu catchment
(NM-AIST, 2019-02) Hyandye, Canute Benedict
This study was undertaken to assess the impacts of future climate and land use/cover changes on surface-subsurface water balance in Usangu catchment, located in the Southern highlands of Tanzania. The objectives of the study were achieved through i) use of stable isotopic compositions of water (18O and 2H), determination of major dissolved ions (K+, Na+, Mg2+, Ca2+, Cl-, CO32-, SO42-) and dissolved silica (SiO2) for rainfall, rivers, springs and wells to assess the origin, flow pathways and hydrological interconnections of water sources, ii) use of Markov Chain and Cellular Automata models to predict land use/cover change of the whole catchment, iii) use of a simple delta change downscaling method to generate 2010-2039 climate scenario from the General Circulation Models (GCMs), iv) use of Soil and Water Assessment Tool (SWAT) to assess future impacts of land use/cover and climate changes on surface and subsurface water balance, taking Ndembera River watershed as case study, and v) evaluate the effectiveness of water and land management practices as the remedies for the adverse impacts of future land use/cover and climate changes on water resources. The isotopes compositions of water for rivers, wells and springs indicated a recharge by recent meteoric water. Usangu catchment has two flow pathways; a short springs-rivers flow system with low concentrations of dissolved ions, and a slow deeper-aquifer flow pathway which is disconnected from rives and springs. The changes in land use/cover affected water resources negatively. At the whole Usangu catchment scale, from 2013 to 2020, the urban and agricultural lands were predicted to increase by 8.2% and 1%, respectively, while forestlands would decrease by 20.6%. For Ndembera River watershed alone, the area under agriculture and evergreen forest would increase by ~10% and 7%, respectively. Also, forestland would decrease by ~12%, and in turn, would decrease the total water yield by ~13%, while the evapotranspiration and overland runoff would increase by ~8% and ~18%, respectively. The period 2010-2039 was shown to be warmer (1.1ᵒC) and wetter (about 2-7% in the wet months) than the baseline period (1980-2009), exacerbating the adverse impacts of land use/cover change. Water stress in the catchment caused by future climate and land use/cover changes could be reduced by management practices such as filter strips, grassed waterways and terracing and contouring.
The impacts of land use and climate change on Simiyu river discharge and the riverine sediment dynamics flowing towards lake Victoria
(NM-AIST, 2024-07) Shinhu, Renatus
This study aimed to trace the dominant sources of riverine sediments and assess climate change's current and future impacts on the river discharge at the critical agroecological region of the Simiyu catchment. Geochemical fingerprinting of the riverbed sediments and potential sediment sources were compared using a Bayesian mixing model (MixSIAR) to attribute the dominant riverine and land-use sources to the Simiyu Mainstem. The mixing model outputs showed that the Simiyu tributary was the dominant sediment source to the Simiyu Mainstem with 63.2%, while the Duma tributary accounted for 36.8%. Cultivated land was shown to be the main land-use source of riverine sediment, accounting for 80 % and 86.4% in the Simiyu and Duma sub-tributaries, respectively, followed by channel banks with 9% in both sub tributaries. The Soil and Water Assessment Tool (SWAT) under RCPs 4.5, 6.0, and 8.5 were also used to project the impacts of climate change on river discharge throughout 2030–2060. The selected three General Circulation Models (GCMs) predicted an increase in the annual average temperature of 1.4°C in 2030 to 2°C in 2060 and an average reduction of 7.8% in rainfall, which causes a decrease in river discharge. The simulated river discharge from the hydrological model under RCPs 4.5, 6.0 and 8.5 revealed a decreasing trend in annual average discharge by 1.6 m3s−1 from 5.66 m3s-1in 2019 to 4.0 m3s-1in 2060. Arbitrary, there will be an increase in frequent flood occurrence in the future (2030–2060) compared to the current period (1990–2019), with extreme discharges of 451.3 m3s−1and 232.8 m3s−1 at exceedance probabilities of 0.01% and 99.99%, respectively. The demonstrated application of sediment source tracing provides an important pathway for quantifying the dominant sediment sources in the rivers flowing towards Lake Victoria. This information is vital for designing catchment wide management plans that should focus on buffering the projected decreases in discharge, reducing soil erosion and sediment delivery from farming areas to the river networks, and ultimately supporting food security and water quality in the Lake Victoria Basin
Influence of rice husk derived nano-silica on performance, emissions, and combustion characteristics of diesel engine fueled with baobab biodiesel
(NM-AIST, 2024-08) Kapile, Fredrick
The increasing number of on-road automobiles as a result of an exponential increase in population and lifestyle places enormous strain on depleted fossil petroleum fuel, energy security, and environmental stability. This situation drives researchers to find an alternative source to replace petroleum diesel. Biodiesel is one of the promising viable substitutes. However, biodiesels may not always fulfill the EN 14214 standard due to differences in fuel properties. This could cause issues with engine operation and emissions. This study therefore aims to use novel nano-silica (SiO2) additives extracted from rice husk to improve its fuel properties. Also focuses on the influence of additives on the operation of the compression ignition (CI) engine. The Adansonia digitata methyl esters (ADME) were made by transesterification process, The physicochemical properties of the fuels with and without additives were measured as per ASTM D6751 and EN 14214 standards methods, and nano silica was analyzed by Thermogravimetry (TGA), Fourier transform infrared spectroscopy (FT-IR), Brunauer Emmett Teller (BET), X-ray diffractometer (XRD. Barret-Joyner Halenda (BJH) pore diameter, specific surface area, and pore volume of SiO2 were observed to be 19.3 nm, 502.24 m2 /g, and 0.761 cm3 /g, respectively. At 400 and 800 ppm dose levels, the oxidation induction period (OIP) increased dramatically, peaking at 10.03 h. The stability of ADME has significantly improved, as evidenced by these results, meeting the >3 h and >8 h standard limits set by ASTM D6751 and EN 14214, respectively. The viscosity of B100 decreased with increasing additive content, from 4.62 mm2 /s for neat B100 to 2.21 mm2 /s for 400 ppm. Cetane number (CN) (60 to 64). All nano-fuel blends used in engine tests were prepared by an ultrasonication process. The results revealed that the brake thermal efficiency (BTE) at maximum brake powers (BP) for B20, B20+SiO2, B100, and B100+SiO2 fuels were 29.9, 28.2, 28.44, and 27.1%, respectively, and brake-specific fuel consumption (BSFC) was reduced as the load increased. The peak heat release rate (HRR) of the B100+SiO2 and B20+SiO2 are slightly higher by 2.9 and 2.6%, respectively, than the neat B100 at medium BP. However, in-cylinder gas pressure (CGP) increased following the order of B20+SiO2
Investigation of uranium derived from phosphate fertilizers on plants uptakes and bacterial diversity in selected agricultural soils of east africa
(NM-AIST, 2024-08) Mwalongo, Dennis
Different types of phosphate fertilizers (PFs) used in agriculture to increase soil fertility contain uranium (U) as an accompanying element. Uranium is both toxic and slightly radioactive. This study investigated the concentrations of U in phosphate rocks (PRs) and PFs used in growing tobacco (Nicotiana tabacum L.) and maize (Zea Mays L) plants from Burundi, Kenya, Rwanda, Tanzania, and Uganda. The results showed that the concentrations of U in phosphates from Burundi, Kenya, Tanzania and Uganda were statistically significant (P ≤ 0.01). The lowest U concentration was 10.7 mg kg−1 found at the Mrima Hill deposit in Kenya and the highest was 631.6 mg kg−1 found at the Matongo deposit in Burundi. Uranium concentrations for local and imported PFs was also statistically significant (P ≤ 0.01). Uranium concentration from PFs ranged from 107.88 ± 9.60 and 281.57 ± 15.82 mg kg−1 . The study also assessed the influence of U from PFs on the radioactivity of agricultural soils and uptake by tobacco plants. The results showed that applications of PFs in agricultural soils increased radioactivity in agricultural soil and tobacco crops. Tobacco smoking and snuffing behaviors resulted in an annual effective dose that was 2.41-6.53 and 1.14-2.45 times greater than annual recommended effective doses for snuffers and smokers. This work also investigated the influence of fertilizer derived U on maize plant uptake and bacterial diversity in soil after application of fertilizers with varying U concentrations. The pilot field experiments showed that application of PFs with different U concentrations influenced bacteria abundance and diversity in maize crops. Applications of Nafaka plus (NP) (3.93 mg kg-1 ) and Minjingu Powder (MP) (3.06 mg kg-1 ) PFs in soil increased bacteria abundance and diversity. Some bacteria were abundant on NP treated soil (high U content) because of their ability to tolerate higher U concentrations. Uptake from soil to crop for maize after applications of PFs of varying U concentrations was investigated by amending soil with Eucalyptus globulus ssp maideii bark and kaolin clay. The soil amendments in reduced U uptake from soil to plant in pot experiments. It is believed that the reduced U uptake is associated with eucalyptus globulus ssp maideni carboxyl groups that can reduce mobile hexa-uranyl ions to immobile tetra uranyl ions that can be absorbed by the kaolin clay. The study recommends further work in understanding the mechanisms of Eucalyptus ssp maidenii bark powder and kaolin U uptake reduction in soil complex matrix.
More than pollutant removal: constructed wetlands and waste stabilization ponds as biodiversity hotspots and community assets in Tanzania
(NM-AIST, 2024-05) Msaki, Gerubin
Waste stabilization ponds (WSPs) and constructed wetlands (CWs) are important ecotechnologies for wastewater treatment. Despite their potential and wastewater management being challenging in urban and peri-urban areas of Tanzania, their adoption and sustainability is not well developed. This study examined (a) social knowledge, attitude, and perceptions (KAPs) on wastewater treatment, technologies involved, and reuse across municipal wastewater treatment plants in four regions of Tanzania; (b) biodiversity of birds, insects, and reptiles in constructed wetlands (CWs) and waste stabilization ponds (WSPs), and (c) bacterial abundance and diversity in different types of CWs. A semi-structured household-level questionnaire (n=327) was used to collect quantitative and qualitative data. The survey involved observations and face-to-face interviews to assess social KAPs on wastewater treatment, technologies, reuse, and potential health risks. Key informants were selected purposively (n=8). The study also employed point counts, direct observations, and camera traps to assess bird diversity in WSPs and CWs. Direct observation and pitfall traps along established transects were used to collect and assess insects and reptiles. Fishnet was used to assess the reptiles living in the WSPs. Additionally, wastewater was collected in four different CWs for bacterial diversity establishment. Community KAPs were analyzed using SPSS, while Jamovi and PAST software were used to analyze the diversity and abundances of birds, insects, and reptiles, whereas bacterial community composition was characterized using Illumina-based sequencing of the V3 and V4 hypervariable region of 16S rRNA. The results show that social KAPs surrounding wastewater treatment and reuse were sufficient based on the KAPs score achieved from the asked questions. However, the general knowledge of treatment technologies, processes and reuse risks was found to be low. Over 90% of respondents were unaware of wastewater treatment technologies and the potential health risks associated with using treated wastewater (59%). Multivariate analysis of variance revealed significant differences (P < 0.05) in KAPs for treated wastewater across different demographic variables examined, i.e., age, sex and education level. Furthermore, results showed that birds exhibit high species abundance (n = 1132), high species richness, Margalef index (D = 4.266), evenness (E = 0.815), Shannon diversity (H = 2.881) and Simpson index (λ =0.903). The abundance and diversity of studied groups differed significantly (P<0.05) between WSPs and CWs. In addition, the results showed that the Proteobacteria were dominant (48.66%) phyla across all CWs. The Gammaproteobacteria class (27.67%), the family Comamonadaceae (35.79), and the genus Flavobacterium (4.35%) were dominant in all examined CWs.
Optimization of incineration process
(NM-AIST, 2019-02) Omari, Arthur Mngoma
Municipal solid waste management has become a challenge in many cities in the developing countries due to the poor methods of waste disposal, which increase the risk of the spread of diseases, leach and increase the demand of land for waste disposal. Characterization study of waste samples from Arusha shows that the combustible fraction is about 87% and biodegradable is 80%. The Thermal gravimetric analyser and Bomb calorimeter show the energy value of about 12.5 MJ/kg and the degradation of about 85%. The study shows that the municipal solid waste disposal method can be thermal, biological or physical. However, thermal method by incineration process is the most preferred and convenient because it destroys pathogens and reduces waste volume in the fastest way. The waste flow analysis of Arusha city shows that the waste has the annual recoverable potential of 128GWh. The case study used an existing incinerator as showed the variation of effluents with operating conditions. The design optimization using computational fluid dynamic techniques to predict the performance of incinerator showed the deviation of input air by 14%, the mass flow rate by 26.5%, the mass fraction of carbon dioxide by 10.4% and slight deviation of nitrogen dioxide and carbon monoxide. The research suggested removing the ash during the incineration process by using a moving grate mechanism to minimize the possibility of formation of NOX. To feed the incinerator by using mechanical means without direct opening the door, it suggested to incorporating moving grate mechanism. The operating conditions of the incinerator designed should have the optimum values for input air one A1-1 as 0.036 39 kg/s, the input air two A2-1 as 0.030 46 kg/s, the input air three A3-1 as 0.034 09 kg/s, the input fuel value as 19.6 kg/h and the maximum capacity of incinerator as 68 kg/h.
Study of crustacean biomass wastes for water defluoridation
(NM-AIST, 2018-09) Wagutu, Agatha W.
High levels of fluoride (F-) in community drinking water supply is recognized as one of the major public health problems. Until now no efficient and affordable F- removal technology exists in many regions. This research explored crustacean biomass waste for development of adsorbent for F- removal. Chitin and calcium carbonate components in crabs and prawns shells were selected for development of three adsorbents: chitosan, calcium phosphate systems (CAPs) and composite of chitosan and CAPs. All the adsorbents were characterized using XRD and FT-IR. Chitosan was obtained by deacetylation of chitin and then modified by cross-linking with glutaraldehyde and protonated using hydrochloric acid. Interaction of F- with the modified chitosan was studied using batch adsorption test and theoretical Density Function Theory (DFT) calculations. Results indicated that computed parameters matched well with experimental results and confirmed that electropositivity of hydrogen atoms influenced F- adsorption by electrostatic attraction. Best performance was achieved in low F- polluted water (≤ 5 mg/l) with adsorption capacity 1.6 mg/g. Calcium recovered from demineralization of shells was precipitated into CAPs using ammonium dihyhrogen phosphate. Crab shell produced dicalcium phosphate dehydrate or brushite (CaHPO4.2H2O) while prawns shell gave hydroxyapatite (Ca5(PO4)6.(OH)2) form of CAPs. Brushite was more effective in F- adsorption with efficiencies above 92% and highest capacity of 13.6 mg/g in field water with fluoride concentration of 5-70 mg/l compared to prawns shell hydroxyapatite with capacity of 8.5 mg/g. FT-IR analysis and kinetic studies predicted defluoridation occurred by ion exchange and ion adsorption mechanisms, described by pseudo 2nd order kinetics. Failure to remove microbes was identified as limitations of the CAPs. Composite of chitosan and brushite was thus developed to address the problem. Analysis with XRD and FT-IR confirmed transformation of brushite phases into hydroxyapatite and formation hybrid composite. Highest F- adsorption efficiency (88%) was achieved for water with F- ≤ 10 mg/l. Microbial count significantly reduced in treated water and final pH was within the acceptable range of 6-9. Adsorbate–absorbent interaction was best described by pseudo 2nd order kinetics.
Surface water – groundwater interactions: A case of a shallow semi-closed lake catchment in northern Tanzania
(NM-AIST, 2023-06) Okwir, Gustavio
Conjunctive use of surface water and groundwater is rapidly growing in many developing countries as an adaptation strategy to climate variability and change. However, the interactions between the groundwater and the surface water systems are not adequately understood, especially among the East African rift valley lakes, where data paucity has limited studies and reporting on the spatial influence of catchment heterogeneity. In its humble contribution to sustainable water development, this study aimed to present a platform for understanding the influence of climatic variation and anthropogenic activities on surface water–groundwater interactions. To be relevant locally, Lake Babati, a freshwater lake in Northern Tanzania that provides the community with fish, freshwater, and a habit for hippopotamus, was studied. The study applied hydrological simulation, grey relational analysis, and stepwise regression analysis to model the hydrological behaviour of the lake. Further, it used hydrogeochemistry and environmental isotopes to identify groundwater fluxes and draw the conceptual understanding of surface water – groundwater interaction and applied topography-based indices to spatially map groundwater potentials within the catchment. The results showed that Lake Babati level is significantly declining (p-value < 0.01) at a rate of 25 mm per annum. The lake level decline could not be explained by climatic variability since the decline occurred when both evaporation and rainfall showed no significant changes either seasonally or annually. Instead, the consistent decline of the lake level in all seasons could be due to the expansion of the spillway, which effectively lowered the lake reservoir level and increased the lake outflow in rainy seasons. The hydro-geochemistry and isotopes data showed that the lake water and groundwater interact and are in hydraulic connections. Further, using Height Above Nearest Drainage based and Topography Wetness Index based methods, the study developed two groundwater potential maps to predict groundwater spatial variability and guide groundwater prospecting efforts and subsequent development. Given that Lake Babati is in a hydraulic connection with the groundwater, its consistent decline will likely impact the groundwater system. Similarly, abstracting groundwater at unsustainable rates could lower the lake levels further. Therefore, integrated water resources management is required for sustainable water resources development and management in the catchment. Mandatory and continuous monitoring of the water resources (groundwater levels, river flows, and lake levels) is recommended to generate quality in situ data for future studies.
Valorisation of solid sisal leaves decortication wastes using black soldier fly (hermetia illucens l.) larvae
(NM-AIST, 2024-08) Konyo, Aziza
The amount of waste generated from sisal industries during sisal fiber production is huge and its management is still challenging and a menace to the environment. These wastes include sisal wastewater and sisal leaf decortication wastes (SLDW) which represent an opportunity for valorization into products. Nevertheless, the sisal leaf decortication wastes is suitable for resource recovery in order to reduce the impacts it causes by just being discarded in the environment without treatment. This study aimed at managing the SLDW using insect-based technology. Specifically, the study characterized the SLDW for its physical and chemical constituents, pretreatment of SLDW to render it suitable for the growth of the insects and optimization of the waste and other blends for production of livestock feed. The use of SLDW for various applications is limited due to its high acidic content and presence of saponin within it. This is the first study of its kind regarding the use the SLDW as a substrate for growth of BSFL. Pre-treatment was a necessary and challenging step done on the waste to meet minimum requirements for rearing of BSF. The resultant waste had Ca, P, K, Mn, Fe, Cu and Zn at varying levels which are all essential for animal growth. The SLDW contained 10 ± 0.01 percent of crude protein, 11 ± 0.02 moisture and energy (1615 kcal/g of Sisal de-corticated waste). The sun dried BSF larvae reared on SLDW contained 53 ± 0.005 percent crude protein, 4 ± 0.01 percent of crude fat, moisture content (10 ± 0.1) %, carbohydrate (43 ± 0.01) % and ash (37 ± 0.08) %. When rearing was done on SLDW, 3000 g of dried pre-treated waste yielded more wet BSF larvae (336 ± 41.3) g compared to 3000 g of fruit waste which yielded (244 ± 4.16) g of wet BSF larvae. Furthermore, the harvested BSFL after optimization process through blending of SLDW, RB and CDW improved growth rate of BSFL (2.2 gram per larvae) and contained sufficient nutritional value to feed poultry and fish, reducing the necessity to de-fatty the larvae as it is being practiced when market waste is being used. The SLDW is a promising feedstock for rearing BSFL because it has good reduction of the waste by 52%. This study eventually creates resource recovery sustainability in sisal industries.

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