Browsing by Author "Selemani, Juma"

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Analysis of spatial and temporal trend of hydro‑climatic parameters in the Kilombero River Catchment, Tanzania
(Springer Nature Limited, 2023-05-15) Sigalla, Onesmo; Valimba, Patrick; Selemani, Juma; Kashaigili, Japhet; Tumbo, Madaka
Inadequate knowledge on actual water availability, have raised social-economic conficts that necessitate proper water management. This requires a better understanding of spatial–temporal trends of hydro-climatic variables as the main contributor to available water for use by sectors of economy. The study has analysed the trend of hydro-climatic variables viz. precipitation, temperature, evapotranspiration and river discharge. One downstream river gauge station was used for discharge data whereas a total of 9 daily observed and 29 grided satellite stations were used for climate data. Climate Hazards Group InfraRed Precipitation was used for precipitation data and Observational Reanalysis Hybrid was used for Temperature data. Mann–Kendall Statistical test, Sen’s slope estimator and ArcMap Inverse Distance Weighted Interpolation functionality were employed for temporal, magnitude and spatial trend analysis respectively. Results confrmed that, spatially, there are three main climatic zones in the study area viz. Udzungwa escarpment, Kilombero valley and Mahenge escarpment. On temporal analysis, with exception of the declining potential evapotranspiration trend, all other variables are on increase. This is with catchment rates of 2.08 mm/year, 0.05 °C/year, 0.02 °C/year, 498.6 m3 /s/year and − 2.27 mm/year for precipitation, Tmax, Tmin, river discharge and PET respectively. Furthermore, rainfalls start late by a month (November) while temperatures picks earlier by September and October for Tmax and Tmin respectively. Water availability matches farming season. However, it is recommended to improve water resources management practices to limit fow impairment as expansions in sectors of economy are expected. Furthermore, landuse change analysis is recommended to ascertain actual trend and hence future water uptake.
Assessment of variation in marginal productivity value of water in paddy farming systems in times of water stress
(MDPI, 2022-10-29) Sigalla, Onesmo; Kadigi, Reuben; Selemani, Juma
Global projections show that increases in agriculture water productivity (AWP) by 30 and 60% in rain-fed and irrigated agriculture, respectively, are required to ensure food security in the period 2000–2025. In sub-Saharan Africa, attempts to understand AWP has seen a lamping of input values which paints an unrealistic picture of AWP. We employed the residual imputation method to isolate the marginal productivity value of water in six paddy farming systems viz. the conventional transplant and flooding system (CTFS), the system of rice intensification (SRI), and the Kilombero Plantation Limited (KPL) mechanized system. Findings showed that AWP for rainfed CTFS is 0.39 kg/m3 or 0.003 US$/m3 , irrigated CTFS (0.30 kg/m3 or 0.002 US$/m3 ), rainfed SRI (0.68 kg/m3 or 0.08 US$/m3 ), irrigated SRI (0.52 kg/m3 or 0.06 US$/m3 ), rainfed KPL (0.33 kg/m3 or 0.05 US$/m3 ), and irrigated KPL (0.68 kg/m3 or 0.11 US$/m3 ). This shows that rainfed systems have good AWP, especially physical ones. We recommend a rollout of rainfed SRI to secure local food security and downstream ecosystem services. In addition, groupings of farmers will assist in optimizing resources, stabilizing markets, and prices for the better economic value of water (US$/m3 ). Adoption of SRI will require intensive demonstration that needs public financing. In addition, revamping the KPL off-taker arrangement with small-holder farmers could also be a good PPP anchor.
Chapter 3 - Nanosensors and diagnostics for disease detection
(Elsevier Inc., 2026) Miraji, Hossein; Ripanda, Asha; Makaye, Angelina; Kilulya, Kessy; Selemani, Juma; Machunda, Revocatus; Sarma, Hemen
Nanosensors and diagnostics, fueled by the frontier of nanotechnology, are redefining disease detection with unprecedented precision. The nanotechnology leverage nanoparticles, such as gold and silver, to bind selectively to biomarkers associated with diseases, enabling molecular at cellular-level detection. Magnetic nanoparticles enhance imaging capabilities in techniques like MRI and MPI. Biosensors, incorporating nanomaterials like nanowires and graphene, immobilize enzymes, antibodies, or aptamers for specific biomolecule capture, enhancing sensitivity. Microfluidics and lab-on-a-chip technologies streamline sample processing and analysis, enabling miniaturization and portability. DNA nanotechnology targets genetic sequences, while plasmonic nanomaterials amplify signals through SERS. Carbon nanotubes, quantum dots, and smart materials further diversify nanosensor capabilities. Machine learning analyzes complex data, and wireless communication facilitates real-time transmission, advancing interconnected and efficient disease detection. In the era of data-driven healthcare, nanosensors offer unparalleled sensitivity, specificity, and adaptability. Therefore, this chapter underscores their role in revolutionizing disease detection, providing a glimpse into a future where early and accurate diagnoses are facilitated by interconnected and portable technologies.
Combatting toxic chemical elements pollution for Sub-Saharan Africa's ecological health
(Elsevier, 2025-02-08) Ripanda, Asha; Hossein, Miraji; Rwiza, Mwemezi; Nyanza, Elias; Selemani, Juma; Nkrumah, Salma; Bakari, Ramadhani; Alfred, Mateso; Machunda, Revocatus; Vuai, Said
With its booming mining, processing industries, agriculture, and increasing urbanization, sub-Saharan Africa experiences an alarming rise in accumulation of toxic chemical elements in all environmental matrices threatening entire ecology. Most toxic chemical elements are mercury, lead, cadmium, chromium, and arsenic. These toxic chemical elements are known human carcinogens, systemic toxicants and can induce multiple organ damage. The occurrences of toxic chemical elements in Sub-Saharan Africa are amplified by anthropogenic activities such as mining, industrial discharges, and agricultural practices. This study examined the extent of exposure to toxic chemical elements in surface and underground waters, sediments, soils, effluents, food crops, vegetables, aquatic organisms, industrial products, humans, and other animals in Sub-Saharan Africa. Results indicate occurrences of toxic chemical elements in surface and underground waters, sediments, soils, effluents, food crops, vegetables, aquatic organisms, industrial products, humans, and other animals above the recommended threshold. These findings highlight the persistent pollution of water, soil, sediments, food crops, aquatic organisms, and even industrial products, emphasizing the potential for bioaccumulation and exposure through the food chain. This requires interdisciplinary approaches, including updating and enforcing stricter regulations tailored to regional industrial and agricultural practices. Advanced remediation technologies, such as phytoremediation, and bioremediation, should be prioritized to remove toxic chemical elements from affected environments. Additionally, promoting sustainable practices, such as waste recycling programs, can help reduce anthropogenic contributions, strengthen environmental monitoring systems, nurture community awareness, and essentially encourage regional and international collaboration to protect ecosystems and safeguard human health in Sub-Saharan Africa.
Design and performance analysis of portable solar powered cooler for vaccine storage
(SCI, 2024-10-31) Marwa, Vicent; Kivevele, Thomas; Kichonge, Baraka; Selemani, Juma
The efficacy of vaccine storage is significantly impacted by temperature fluc- tuations within the cooler, often exacerbated by using phase change materials in existing cooler designs for remote areas. These materials can undergo uneven melting and phase separation, leading to temperature instability and vaccine potency loss. In response to this challenge, the present study intro- duces a novel design of a portable, locally‐made solar‐powered cooler opti- mized for longer storage periods. The cooler's performance in terms of tem- perature distribution, airflow dynamics, and the coefficient of performance (COP) is meticulously examined through computational fluid dynamics (CFD) simulations. The simulated results were validated using experimental data from the open literature, ensuring accuracy and reliability. The findings indicate that the developed cooler achieves significant improvements over traditional models. For instance, the current model reaches a temperature of +12°C in just 84 min, compared to 208 min, as reported in the literature results. Moreover, the current model reaches a temperature of −12°C in 195 min and it has energy efficient with a COP of 4.5. Statistical analysis further confirms the reliability of the simulation results, with root mean square and mean absolute percentage errors of 6.587 and 24.2%, respectively. Additionally, a comparative study of five insulative materials highlights polyurethane (Po) as the top performer, with a heat transfer performance of 14.3%, followed by feather fiber (Fe) (18.7%), fly ash (Fl) (19.8%), fiberglass (Fi) (21.9%), and coconut fiber (Co) (25.9%). Notably, net present value (NPV) of $689.336 and $448.01 was obtained for economic analysis of the current model over the existing model, showing the feasibility of the study. Hence, the cooler's effectiveness in storing vaccines in isolated regions exceeds that of conventional models, providing a hopeful solution to tackle vital challenges in vaccine distribution and preservation.
Distribution and yield of trace metals from the foot of Mount Kilimanjaro to the coastal of Indian Ocean: impacts of natural and anthropogenic factors
(ESS Open Archive, 2022) Selemani, Juma; Zhu, Xunchi; Majjid, Arafa; Zhang, Jing
Cases of water related diseases due to metal pollution are increasing over the global. The condition is serious to most of developing countries as a results of industrialization and population growth. Dissolved and particulate trace elements influence drinking water, aquatic ecosystem health and climate change. Mt. Kilimanjaro is one of the sources of water and icon in Africa but miss studies on dissolved and particulate metals. Therefore, this study was conducted to investigate geochemistry, distribution and yield of dissolved and particulate metals from Mt. Kilimanjaro to Indian Ocean. Surface water was sampled in rainy season and analyzed by high resolution inductively coupled plasma mass spectrometry in State Key Laboratory of Estuaries and Coastal Research. Health assessment revealed that level of Aluminium, iron, vanadium and Manganese in some stations were above recommended level, that can pose health impact to human and aquatic ecosystem. Correlation of Cobalt, Copper, Manganese and Vanadium with dissolved silicate, sulphate, calcium and dissolved organic carbon indicates that these elements were predominantly found in silicate, sulphide, carbonate and organic bounds. Positive relation between magnetic susceptibility with Copper and zinc reflects that magnetic susceptibility can be used as indicator of Copper and Zinc pollution. Rock weathering and anthropogenic activities were main sources of metals whereas redox reactions, pH, temperature and dissolved organic carbon were some of biogeochemical factors influencing level of metals. The basin transported more elements in particulate than dissolved form. Yield from Pangani River to Indian Ocean was lower than most of other rivers in East Africa.
Distribution of organic carbon: possible causes and impacts in the Pangani River Basin ecosystem, Tanzania
(CSIRO PUBLISHING, 2018-06-08) Selemani, Juma; Zhang, Jing; Muzuka, Alfred; Wu, Ying; Njau, Karoli; Zhang, Guosen; Mzuza, Maureen; Maggid, Arafa; Zhang, Miao; Qi, Lijun
There is limited information on organic carbon in African rivers, especially from the eastern side. Here, we report distribution and impacts of total suspended matter (TSM), and dissolved and particulate organic carbon (DOC & POC) in the Pangani River Basin (PRB) ecosystem together with their fluxes to the Indian Ocean. δ13C was also used to trace sources of carbon in the basin. Results showed that the basin is supplied with carbon from allochthonous sources dominated by C3 plants, with higher levels of TSM and DOC in the wet season than in the dry season. Several factors, including altitude, temperature, rainfall, lithology and anthropogenic activities, have a significant influence on the seasonal and spatial distribution of organic carbon in the basin. High discharge in the wet season mobilised terrestrial organic carbon to elevate concentrations of DOC, POC and TSM. Mean concentrations of DOC, dissolved inorganic carbon (DIC), POC and TSM in PRB were in ranges comparable to that in other tropical rivers but their fluxes were lower than in most tropical rivers around the world. Diverting water from the river for irrigation and hydroelectric power production was one of the factors that reduced the flux of carbon. Observed hypoxic conditions in the reservoir indicates that the quality of water for human and aquatic ecosystem health is possibly threatened by a high level of organic carbon; furthermore, the trends of increasing population, deforestation, temperature and rainfall will likely increase the concentration of organic carbon in the future. Better management of waste, afforestation and reforestation are recommended to restore degraded natural forest, so as to reduce uptake of organic carbon from the terrestrial environment.
Dust exposure and its health implications to miners in Mererani artisanal and small-scale mining industry
(Taylor & Francis, 2025-01) Mumba, Edward; Selemani, Juma; Kasambala, Hildegard; Bidu, Jerome; Ripanda, Asha; Rwiza, Mwemezi
This study aimed to identify and quantify the total dust exposure to underground miners in Mererani, Tanzania, and its composition to generate evidence for informed decision- and policy-making. The Analytical Air Monitoring System (AMS) was used for dust collection, and analysis was conducted gravimetrically. The dust composition was analysed using Inductively Coupled Plasma Optical Emission Spectroscopy. The results showed significant variation in dust exposure levels across different mining zones, with miners inhaling up to 1859 mg of dust over an 8-hour period in drilling zones (DZ), 797 mg in loading zones (LZ), and 382 mg in resting zones (RZ). The mean value of dust exposure was significantly different, with a p-value of <0.05. Miners had higher levels of heavy metal and silica than those from unmined sites, with chromium being the most dominant element across all samples. Cumulative exposure to dust over time is linked to long-term respiratory impairment and serious health conditions such as lung cancer. These findings highlight the need for intervention, including education on dust hazards, provision of personal protective equipment (PPE), and enforcement of safety standards to safeguard miners’ health. Addressing these issues is critical to promoting policy reforms and sustainable mining practices in Mererani and similar communities.
Ecological consequences of microplastic pollution in sub-Saharan Africa aquatic ecosystems: An implication to environmental health
(Elsevier Inc., 2023-12-01) Moto, Edward; Hossein, Miraji; Bakari, Ramadhani; Mateso, Alfred; Selemani, Juma; Nkrumah, Salma; Ripanda, Asha; Rwiza, Mwemezi; Nyanza, Elias; Machunda, Revocatus
Microplastic pollution (MPs) emerged as a significant environmental concern due to its persistent nature. These MPs particles endure in waters, soils, and even the atmosphere, posing potential threats to the entire ecosystem. Aquatic organisms are at risk of ingesting MPs, leading to accumulation in tissues, ultimately affecting entire food chain. This study aims to provide an overview of sources of MPs, distribution, and potential environmental impacts. MPs have been documented in various substances such as bottled water, salts, seafood, and even the air. However, the full extent of the health consequences on human exposure remains uncertain. Therefore, it is imperative that we draw public attention to the presence of these pollutants in the environment. To mitigate adverse effects of MPs, reducing plastic consumption, implementing improved waste management practices, and advocating sustainable behaviors are essential for well-being of natural ecosystems and the health human populations.
Enhanced performance of hybrid solar biogas dryer for agricultural products
(Elsevier Ltd., 2025) John, Yawe; Kichonge, Baraka; Machunda, Revocatus; Selemani, Juma; Kivevele, Thomas
Post-harvest losses due to inefficient preservation remain a global challenge to food security and economic development. To address this, a novel hybrid solar-biogas dryer (HSBD) was developed by integrating solar energy with biogas backup to provide consistent drying conditions. This study assessed the HSBD’s performance against open sun drying (OSD) and existing literature using 5 mm thick ripe mango slices. HSBD was operated continuously from 09:30 to 20:00 h, while OSD was limited to 09:30–17:00 h and resumed the following day. Results showed that moisture content decreased from an initial 80.1 % (wet basis) to 3.8 % in HSBD and 16.3 % in OSD within 10 h. The drying behaviour of ripe mango slices in both methods was best described by the Midilli model, with high R2 values of 0.99823 and 0.99942, and RMSE values of 0.0021493 and 0.00047022, compared to OSD’s 4.73 × 10−10 m2/s. While OSD samples retained more vitamin C (6.45 × 102 cfu/g) compared to HSBD (294.46 mg/100 g), the latter exhibited better microbial quality with lower yeast counts (3.95 × 102 cfu/g) than the former (6.45 × 102 cfu/g). The proposed HSBD provides superior drying efficiency, product quality, and microbial safety compared to OSD and existing hybrid solar dryers. This offers a sustainable solution to reduce post-harvest losses under variable ambient conditions.
Enhancements of Heat Islands in the Growing Cities in Developing Countries Due to Land Use Land Cover Changes and Climate Change: A Case of Babati-Tanzania
(Scientific Research Publishing, 2024-12-09) Majula, Atugonza; Machunda, Revocatus; Selemani, Juma
Climate is changing no doubt, with anthropogenic activities considered as the main driver of the change. Flooding, drought and urban heat island (UHI) are some impacts of climate change (CC). Additionally, land use land cover change (LULCC) adds more pressure to the growing cities. Population is increasing with urban cities expected to accommodate the majority of the people while UHI is expected to increase with CC and LULCC. Adaption is the best option to minimize impacts of UHI; however, researchers are required to identify the cause, impacts and ways to cope with the impacts. Therefore, this study investigated how the Land Surface Temperature (LST) of Babati, a fast-growing town in Tanzania, is changing with CC and LULCC. Remote sensing was used with LULC classification, which was performed using a maximum likelihood algorithm, and LST retrieval involved computational formulas using bands R, NIR, and TIR. Results showed a rise in built-up areas, suggesting urbanization at the expense of farmlands and bare land. The LULCC together with global warming from 2002 to 2022 contributed to the increasing average LST by 0.7˚C signifying that more impacts are expected in the future under a business-as-usual scenario. The findings also indicate that higher vegetation density is associated with lower LST and vice versa. This relationship highlights the critical role of vegetation in regulating temperature and suggests that enhancing vegetation cover may be an effective strategy for mitigating urban heat. Improving agricultural practices as population increases and promoting sustainable urbanization in Babati and similar towns are necessary to mitigate UHI effects.
Enhancing agricultural drying efficiency with a novel hybrid solar-biogas dryer: Mathematical modeling and experimental validation
(Elsevier Ltd., 2025-09) John, Yawe; Kichonge, Baraka; Machunda, Revocatus; Selemani, Juma; Kivevele, Thomas
Drying is a crucial post-harvest process for preserving agricultural products. While previous studies have used empirical methods to develop the solar drying backup with biogas, this study introduces a mathematical modeling approach to develop a novel integrated hybrid solar biogas dryer (HSBD). Mathematical modeling involved deriving equations describing the system’s heat transfer mechanisms and energy balance. The model depends on several factors such as solar irradiance, ambient conditions, air velocity and material properties. The mathematical model was implemented in MATLAB R2023b software. The predicted model results were experimentally validated in HSBD using Cavendish bananas with cross-section slices of 5 mm thick. Statistical parameters such as R2, mean absolute error (MAE), and root mean square error (RMSE) were used to evaluate model accuracy. The results showed that Model predictions closely matched experimental data, with an R2 value exceeding 0.98, an MAE of 0.0027, and an RMSE of 0.0157. During experimental validation, the HSBD maintained stable drying temperatures between 58.2 °C and 75.7 °C, reducing dependence on fluctuating solar radiation. Moisture content decreased from 3.07 kg/kg (dry basis) to 0.0849 kg/kg within 14 h, with a drying rate constant of 0.116 h−1. The solar collector achieved a peak thermal efficiency of 27.74 %, outperforming conventional collectors. The mathematical model provides accurate predictions, making it a valuable tool for system optimization recommended for large-scale agricultural and food processing applications.
Enhancing agricultural drying efficiency with a novel hybrid solar-biogas dryer: Mathematical modeling and experimental validation☆
(Elsevier, 2025-09) Yawe, John; Kichonge, Baraka; Machunda, Revocatus; Selemani, Juma; Kivevele, Thomas
Drying is a crucial post-harvest process for preserving agricultural products. While previous studies have used empirical methods to develop the solar drying backup with biogas, this study introduces a mathematical modeling approach to develop a novel integrated hybrid solar biogas dryer (HSBD). Mathematical modeling involved deriving equations describing the system’s heat transfer mechanisms and energy balance. The model depends on several factors such as solar irradiance, ambient conditions, air velocity and material properties. The mathematical model was implemented in MATLAB R2023b software. The predicted model results were experimentally validated in HSBD using Cavendish bananas with cross-section slices of 5 mm thick. Statistical parameters such as R2, mean absolute error (MAE), and root mean square error (RMSE) were used to evaluate model accuracy. The results showed that Model predictions closely matched experimental data, with an R2 value exceeding 0.98, an MAE of 0.0027, and an RMSE of 0.0157. During experimental validation, the HSBD maintained stable drying temperatures between 58.2 °C and 75.7 °C, reducing dependence on fluctuating solar radiation. Moisture content decreased from 3.07 kg/kg (dry basis) to 0.0849 kg/kg within 14 h, with a drying rate constant of 0.116 h−1. The solar collector achieved a peak thermal efficiency of 27.74 %, outperforming conventional collectors. The mathematical model provides accurate predictions, making it a valuable tool for system optimization recommended for large-scale agricultural and food processing applications.
Fluoride contamination a silent global water crisis: A Case of Africa
(Elsevier, 2024-11-20) Hossein, Miraji; Rwiza, Mwemezi; Nyanza, Elias; Bakari, Ramadhani; Ripanda, Asha; Nkrumah, Salma; Selemani, Juma; Machunda, Revocatus
Fluoride contamination in drinking water poses a global health risk, affecting millions worldwide, with Africa bearing a disproportionate burden due to unique geological factors like the East African Rift Valley. High fluoride levels in groundwater in these regions contribute to widespread health problems, notably dental and skeletal fluorosis, which impair quality of life and economic productivity. This study aims to evaluate the scope of fluoride contamination across continents, examining how Africa compares to regions like Asia, North America, and Europe. While some countries have mitigated contamination through advanced water treatment and regulatory measures, Africa still faces significant challenges due to limited infrastructure and resources. Findings highlight that addressing fluoride contamination in Africa requires a targeted approach, involving affordable treatment solutions, regulatory reforms, and community awareness programs. By outlining these strategies and emphasizing international cooperation, this study underscores the urgency of safeguarding health and well-being across affected African communities.
Future Trade-Off for Water Resource Allocation: The Role of Land Cover/Land Use Change
(MDPI, 2024-02-02) Sigalla, Onesmo; Twisa, Sekela; Chilagane, Nyemo; Mwabumba, Mohamed; Selemani, Juma; Valimba, Patrick
Global croplands, pastures, and human settlements Have expanded in recent decades. This is accompanied by large increases in energy, water, and fertilizer consumption, along with considerable losses of biodiversity. In sub-Saharan Africa, policies are implemented without critical consideration; e.g., agricultural expansions impair ecosystem services. We studied land use/cover and the associated rate of change for four time epochs, i.e., 1991, 2001, 2011, and 2021. This employed remote sensing and GIS techniques for analysis, while future projections were modeled using cellular automata and the Markov chain. The kappa coefficient statistics were used to assess the accuracy of the final classified image, while reference images for accuracy assessment were developed based on ground truthing. Overall change between 1991 and 2021 showed that major percentage losses were experienced by water, forest, woodland, and wetland, which decreased by 8222 Ha (44.11%), 426,161 Ha (35.72%), 399,584 Ha (35.01%), and 105,186 Ha (34.82%), respectively. On the other Hand, a percentage increase during the same period was experienced in cultivated land, built-up areas, and grasslands, which increased by 659,346 Ha (205.28%), 11,894 Ha (159.93%), and 33,547 Ha (98.47%), respectively. However, this expansion of thirsty sectors Has not reversed the increasing amount of water discharged out of the Kilombero River catchment. We recommend the promotion of agroforests along with participatory law enforcement and capacity building of local communities’ institutions.
Geochemistry of Potentially Toxic Elements in Soil and Sediments of a Tanzanian Small-Scale Gold Mining Area
(scientific research publishing, 2023-11-17) Karungamye, Johnbosco; Rwiza, Mwemezi; Selemani, Juma; Marwa, Janeth
Small-scale gold mining is linked to significant environmental pollution by potentially toxic elements (PTEs). However, research on the pollution caused by such mining activities remains insufficient especially in developing coun- tries. In the present study, a systematic investigation assessed the pollution and level of ecological risk of PTEs in soil and stream sediments in an active small scale gold mining area of Isanga, in Nzega, Tanzania. Samples amount- ing to 16 soil and 20 sediment were gathered from the study area and ana- lyzed for five PTEs concentrations (As, Cd, Cr, Hg and Pb) using the AAS method. The contamination level and ecological risk were assessed using sev- eral pollution indices. The results suggest that the assessed environmental systems of the Isanga mining area and its vicinities are lowly contaminated by PTEs and have a low potential to pose ecological risks. Hg and Cd with mean concentrations of 0.09 mg/kg and 0.26 mg/kg respectively were found to be the most enriched PTEs in soil, compared to their average continental crust concentrations (0.056 mg/kg and 0.102 mg/kg respectively). The levels of the evaluated PTEs in the study area are susceptible to increase over time if proactive steps are not taken to control mining and waste disposal activities
Hydrogeochemical similarities and groundwater-surface water interactions for the karst hydrological system of northwest Rwanda
(Springer International Publishing, 2023-08) Umutoni, Monique; Selemani, Juma; Rwiza, Mwemezi; Wali, Umaru
The groundwater of karst environments is vulnerable to pollution due to its heterogeneous nature and can be completely depleted due to its strong connection to surface water when predominantly driven by natural and anthropogenic factors. This particular landscape is the main source of drinking water in different parts of the world. Karst Hydrological of Rwanda hosts surface and groundwater resources. Moreover, groundwater is the main source of domestic water use in that area. The surface water is threatened by drying of crater lakes, changes of other lakes, and obstruction of sinkholes swallowing water from streams and runoff. Those problems may have direct and long-term impacts on groundwater recharge. The information on the hydrogeological characteristics of surface and groundwater, groundwater-surface water interaction, was limited. This study investigated the hydrogeochemical characteristics, similarities, and interactions of surface groundwater. To understand long-term impacts of surface water challenges on groundwater when are connected, statistical analyses and Piper diagram were used to achieve the objectives. The results showed a strong correlation among spring waters, reflecting similarity in the water origins. The Piper diagram classified the water as bicarbonate water (HCO−3 , Ca2+, Mg2+). The analysis of variance between surface water and groundwater did not show significant differences at the 0.05 level, which explains a relationship. The results showed a strong similarity and interaction between surface and groundwater. The findings of this study are important for water managers in consideration of future management since current problems on surface water may affect groundwater and community depending on that resource.
Impact of climate change on groundwater recharge in the lake Manyara catchment, Tanzania
(Elsevier, 2021-12-15) Nyemboa, Latifa; Larbi, Isaac; Mwabumbaa, Mohamed; Selemani, Juma; Dotse, Sam-Quarcoo; Limantol, Andrew; Bessah, Enoch
Groundwater account for about 60 to 80% of water supply to the population of Tanzania's semi-arid regions for domestic and agriculture uses. Despite the importance of groundwater resource in semi-arid areas, limited information exists on the recharge amount and potential recharge zones in Tanzania in the context of climate change which could result in unsustainable withdrawals. This study aimed to estimate the potential impact of climate change on groundwater recharge and identify potential recharge zones in the Lake Manyara catchment using Water and Energy Transfer between Soil, Plants and Atmosphere under the quasi-steady State (WetSpass) model. The WetSpass model was setup and calibrated using hydro-meteorological data (rainfall, temperature, wind speed, potential evapotranspiration, and groundwater depth) and biophysical data (soil, land use, topography, and slope). Simulated rainfall, temperature and potential evapotranspiration from an ensemble of four CORDEX-Africa regional climate models for the period 2021–2050 under the Representative Concentration Pathway (RCP 8.5) scenario (hereafter referred as business-as-usual scenario) were used as input in the WetSpass model for the climate change impact assessment. WetSpass model calibration using the water balance equation showed a coefficient of determination (R2) value of 0.9 and Root-Mean-Square Error (RMSE) of 0.49 mm/yr between the simulated and calculated recharge. It was determined that the mean annual recharge of 53.9 mm/year (149 MCM/year) for the period 1989–2018 would increase by 7.9% in the future (2021–2050) under the business-as-usual climate scenario, due to the increase in rainfall. Seasonality and spatial differences in recharge amount were observed, with recharge projected to increase in the dry season and at areas that receive high amount of rainfall. Potential recharge zones in the catchment were found mostly around the northern part near Ngorongoro, the south-western part, and around Mbulu region. Findings from this study would help policymakers, and local stakeholders in planning and management of the groundwater resources for sustainable development.
Improving biological treatment of textile wastewater
(IWA Publishing, 2022-01-01) Laizer, Alpha; Bidu, Jerome; Selemani, Juma; Njau, Karoli
Textile industries are among the primary contributors of water pollution. Treatment of textile wastewater is very important before discharging it to the environment. In the present study, laboratory-scale anaerobic batch reactors were used for co-treatment of a mixture of textile and domestic wastewater at 37 °C. The objective of this work was to investigate optimum conditions for the anaerobic co-digestion of textile wastewater and domestic wastewater. Domestic wastewater as a carbon source to enhance treatment of textile wastewater in color and other pollutants removal was examined. Textile and domestic wastewater were mixed at different proportions to make a total volume of 500 mL. Proportions of domestic wastewater and retention time were two main factors studied in influencing pollutant removal efficiency. Optimum conditions for removal of pollutants were 18 days' residence time at 60 and 40% textile and domestic wastewater respectively. The removal efficiencies were 52.8, 58.3 and 51.6% for Color, BOD and COD, respectively. Phosphorus (PO43−), Ammonium (NH3-N) and Nitrate (NO3-) increased at 78.5, 49 and 87% respectively. However, the concentration levels were above Tanzania Bureau of Standards (TBS) discharge limits. Post treatment is suggested to achieve standard discharge limits.
Integrated constructed wetlands treating industrial wastewater from seed production
(IWA Publishing, 2021) Kiflay, Elizabeth; Selemani, Juma; Njau, Karoli
The performance of an integrated wastewater treatment system composed of horizontal subsurface flow constructed wetland (HSSFCW), floating constructed wetland (FCW), and anaerobic baffled reactor (ABR) was studied for pollutant removal from seed production wastewater. Cyperus alternifolius (Umbrella Papyrus) plants were used in the HSSFCW, and Vetiveria zizanioides (Vetiver grass) in the FCW. The ABR was fed with 25 m3/d wastewater from its equalization tank. The average raw wastewater organic loading rate was 0.208 kg-COD/d. Grab wastewater samples were collected twice weekly for three months from each unit's inlet and outlet. The system's performance in removing biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total suspended solids (TSS), turbidity, nitrate, phosphate, and ammonium was studied. The average removal efficiencies obtained were 95.5% BOD5, 94.6% COD, 86.2% TSS, 76.6% turbidity, 82.4% nitrate, 76% phosphate, and 32.9% ammonium. The results show that integrating ABR, HSSFCW, and FCW improves pollutant removal from seed production wastewater, and the treated water can be used for agricultural purposes.