Browsing by Author "Mulugeta, Eyobel (PhD)"

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    Evaluation of Roof Tops Rainwater Potential for Alternative Water Supply Source a Case of Wachemo University Main Campus
    (Addis Ababa University, 2021-09-25) Abreham, Tamirat; Tesseme, Tamru (PhD); Mulugeta, Eyobel (PhD)
    Roofs top rainwater harvesting has been carried out worldwide to afford an alternative source of water for many people. The aim of the present study was to evaluate of the rooftop rainwater harvesting potential for alternative supply source in Wachemo University. A 20-years rainfall data was analyzed to determine the average monthly and annual rainfall potential in the study area. The possible volume potential that can be harvested from the selected rooftops of the Wachemo University was quantified using rational method. Ripple mass curve method was also applied to determine the storage capacity of the water tank for the harvestable rooftop rainwater in the study area. Google earth and ArcGIS 10.3 tools were used to digitize the buildings rooftops and to locate water sample points. The quality of the rooftop rainwater was examined as per the standard method for the examination of water and wastewater quality. Considering only the four wet season months (March through October), the monthly variation with coefficient of variation ranges between 33% and 69% and yearly variation between 13% and 24 % .The maximum potential of rainwater with annual average rainfall amount 1188 mm and rooftops area 107587 m2 was found to be 102,268 m3 /y which can be harvested from roofs provided that all rain falling on the roofs is collected. This is equivalent to 52.4 % of average water demand of the community in the university. The Ripple mass curve method showed that about 4269.2m3 of storage tank capacity is essential to store the harvestable rooftop rainwater. The water quality examination revealed that of the qualities of the rooftop rainwater were found within the permissible limit of drinking water quality as per the WHO (2017) guideline except the values of the bacteriological parameters. Total cost for installing the rainwater harvesting system in 94 similar buildings inside the Wachemo University main campus evaluated as 6,937,200 Et.Birr (149,187 USD). The study concluded that rooftop rainwater harvesting is a promising alternative solution in Wachemo University to solve water scarcity problem and for ensuring a continual source of non-potable water.
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    Improvement of ‘Injera’ Shelf Life Through the Use of Silver(Ag) and Zinc Oxide (Zno) Nanoparticles
    (Addis Ababa University, 2020-11-11) Legassa, Oli; Zewdu, Ashagrie (PhD); Mulugeta, Eyobel (PhD)
    About two-third of Ethiopian diet consists of Injera, a thin, fermented traditional baked bread, made from the most popular grain of teff(Eragrostis tef (Zucc) Trotter). Even though it is a nutritious food, the shelf life of injera does not usually exceed 3 days due to mould spoilage. This research was conducted with the aim to evaluate the effect of biosynthesized silver Nano particles (AgNPs) and Zinc oxide nanoparticles (ZnONPs) in improving injera shelf life. AgNPs and ZnONPs are synthesized from Eucalyptus globulus and Calpurnia aurea (Ait.) Benth leaf extracts, respectively. Formation of nanoparticle was confirmed by color change and by characterization techniques (UV-vis spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Antimicrobial test on Aspergillus, Pencillinium, and Rhizopus spp. was conducted using disc diffusion method. Then both nano particles were dip-coated on plastic zipper bags at different percentages after disinfection with 70% alcohol and dried in an oven at 600c and used for injera storage. The shelf life was determined as one day before mold growth appearance. Moisture content and pH was determined by oven and pH meter, respectively. Internal temperature of the package during storage was measured by infrared spectroscopy whereas pour plate method was used for mold and yeast count. Finally, migration level was determined by Microwave Plasma - Atomic Emission Spectroscopy (MP-AES). The results from Uvi-vis spectroscopy shows that characteristic peaks observed at 420 and 300 to 400 nm for AgNPs and ZnONPs, respectively. The XRD data also shows that both synthesized nano particles were below 100nm. The SEM image shows that AgNPs was mostly irregular whereas ZnONPs was mostly rod shaped. The result has shown that both of them have significant antimicrobial effect against the studied fungus. ZnONPs has induced greater inhibition zone than AgNPs, which is caused by difference in crystallite sizes (ZnONPs = 64.25nm, AgNPs = 84.07nm).The shelf life of the stored injera samples were increased significantly based on their concentrations. For both Ag and ZnONPs , the optimum concentration was 50% in which injera shelf life increased for 10 days to 15 days, respectively. Both NPs have no significant effect on moisture, pH and internal temperature of the package during storage. The Cfu/g of molds and yeast decreased as the percentage of these nanoparticles coated on plastic bags increased. At 50% concentration the migration was 1.34 and 375mg/Kg for both Ag and ZnONPs, respectively. The migration of both Ag and ZnONPs was relatively high, which was increased with concentration and time of storage. Because, it needs further study and improvements to use these nano particles for injera storage. Thus, it would be advisable if these nano particles will be incorporated as ingredients of plastics to decrease this migration problem.