Browsing by Author "Kibazohi, Oscar"

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    Estimation of Nitrogen Requirement in Peat and Perlite Biofilters Removing Hexane from Air
    (Springer Netherlands, 2001) Kibazohi, Oscar; Anderson, William A.; Moo-Young, M.
    Biofiltration experiments to remove hexane from air were conducted in column reactors packed with peat, perlite and their mixture. The particle size of the solid medium ranged from 1.70 to 4.75 mm, and the average empty bed superficial velocity was 20 m/h. To achieve and maintain a high rate of hexane removal, addition of nutrient solution was necessary. Adding a nutrient solution of a commercial fertilizer containing 1000 g of nitrogen for the first two weeks, followed by a weekly addition of 280 g of nitrogen per m3 of filter bed was found to be effective in maintaining a high hexane removal rate between 20 and 30 g/m3.h. The hexane removal rate decreased gradually to less than 15 g/m3.h in 50 days due to an accumulation of biomass in the reactors. Pressure drop, which varied depending on the type of packing, also increased drastically to maximum values of 120 Pa/m for 100% perlite and 2930 Pa/m for the mixture. For long-term operation and low energy cost, prevention of biomass accumulation and maintenance of low pressure drop is essential. When the frequency of nutrients addition was reduced excessive biomass growth, and increase in pressure drop with time were controlled. Our observations showed that addition of a nitrogen source of approximately 1 kg of nitrogen per m3 of filter bed for the first and second weeks, and every 30 days (approximately) resulted in an extended life and slightly lower hexane removal. The columns packed with peat and the mixture showed a better hexane removal than the column packed with perlite alone. However, the column packed with perlite had the lowest pressure drop.
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    Nitrification-Denitrification in a Coupled High Rate - Water Hyacinth Ponds
    (Elsevier, 2014) Mayo, Aloyce W.; Hanai, E. E.; Kibazohi, Oscar
    Nitrogen transformation was studied in a coupled high rate and water hyacinth (Eichhornia crassipes) ponds at the University of Dar es Salaam. Samples of wastewater were collected and examined for water quality parameters which were used as input parameters in a mathematical model. A conceptual model was then developed to model various processes in the system using STELLA 6.0.1 software. The studGupta and Sujathay demonstrated the dominant nitrogen transformation process in high rate pond (HRP) was nitrification, but denitrification dominated in water hyacinth pond (WHP). In a HRP denitrification and volatilization accounted for 69.1% and 23.8% of removed nitrogen, respectively. On the other hand, denitrification and net sedimentation were the major nitrogen removal mechanisms in WHP accounting for 81.9% and 13.1% of removed nitrogen, respectively. Model results indicated that 1.22 g N/m2 day and 0.37 g N/m2 day of nitrogen was removed in presence and absence of biofilm, respectively. The decrease in nitrogen removal in absence of biofilm, demonstrates the importance of biofilm attached onto plants. It was concluded that incorporation of HRP improved denitrification in WHP because it enhanced formation of more nitrates in HRP in order to promote denitrification in wetland unit due to anoxic conditions.
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    Removal of Hexane in Biofilters Packed with Perlite and a Peat–Perlite Mixture
    (Kluwer Academic Publishers-Plenum Publishers, 2004-06) Kibazohi, Oscar; Yun, Soon-Il; Anderson, William A.
    Removal of hexane from air–hexane mixtures in biofilters packed with different solid media under nitrogen supplementation was performed for 70 days. Two columns containing Perlite or a mixture of peat and Perlite, were used. The solid media were supplemented with nitrogen source up to 1 kg/m3 per week for high nutrient supplementation and 0.2 kg/m3 per month for low nutrient supplementation. A high rate of hexane removal: 95 g/m3 h was achieved under high nutrient supplementation, high air flow rate and high hexane concentration. However, the percentage of hexane removal decreased with increasing air flow rate and hexane inlet concentration. For high nutrient supplementation the type of solid medium did not significantly affect the biodegradation capacity. With low nutrient supplementation, the highest removal rate was achieved in the column containing the peat–perlite mixture. The column containing perlite had a significantly lower pressure drop (20 Pa/m) than the 2400–2930 Pa/m observed for the column containing the mixture. Perlite offers an opportunity of running a biofiltration process at a lower and stable pressure drop if the nutrient supplementation is managed properly.
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    Vegetable oil production potential from Jatropha curcas, Croton megalocarpus, Aleurites moluccana, Moringa oleifera and Pachira glabra: Assessment of renewable energy resources for bio-energy production in Africa
    (Elsevier, 2011-03) Kibazohi, Oscar; Sangwan, Rajbir S.
    Research on vegetable oil for biofuels in Africa and Asia has focused mainly on Jatropha curcas while other potential oil bearing plants have received little attention. Vegetable oil production potential for five oil bearing plant species namely: Aleurites moluccana, Croton megalocarpus, Jatropha curcas, Moringa oleifera and Pachira glabra were investigated. Nuts and seeds of the plants were collected from the wild and their potential for vegetable oil production assessed in terms of seed/nut acreage yield, seed/nut oil content, harvesting requirement, and upstream processing before vegetable oil recovery. All five varieties were found to contain acceptable but different oil content ranging from 20 to 33% w/w, and seed/nut acreage yield of 3 t ha−1 y−1 to 12.5 t ha−1 y−1. Upstream processing was needed for A. moluccana to break open nuts to release the kernel, and dehulling for both C. megalocarpus and J. curcas to release the seeds, before extracting the vegetable oil, while the seeds of both M. oleifera and P. glabra did not need upstream processing. The Multi-criteria Decision Analysis ranked C. megalocarpus as the plant with the highest vegetable oil production potential of 1.8 t ha−1 y−1 followed by M. oleifera, J. curcas (1 t ha−1 y−1), A. moluccana, and P. glabra. The analysis underlines the need for more studies on C. megalocarpus and M. oleifera for biofuel production in Africa and other regions.