Browsing by Author "Rubindamayugi, M. S. T."
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Item Effect of Water Hyacinth on Distribution of Sulphate-Reducing Bacteria in Sediments of Lake Victoria(2004) Muyodi, Frederick J; Rubindamayugi, M. S. T.; Semesi, Adelaide K.The effect of the water hyacinth, Eichhornia crassipes (Mart.) Solms-Laub, on the distribution of populations of sulphate-reducing bacteria (SRB) in sediments from various stations on the shores of Lake Victoria around Mwanza Municipality, Tanzania, was studied. Lactate-utilising SRB were observed to be the dominant species in sediments covered by the water hyacinth and at the Mirongo River mouth while acetate-utilising SRB dominated in the offshore open water sediments. Sediments from offshore open waters had the lowest most probable numbers (MPNs) for all the SRB types investigated, more than 100 times less that observed in areas covered by the water hyacinth and the Mirongo River mouth. Lactate-utilising SRB were almost absent in sediments from offshore open waters. A positive correlation between the total populations of SRB and nutrients in sediments was observed. Results showed that sulphate concentration was very high in sediments underneath the water hyacinth at the lakeshore but was minimal in sediments from offshore open waters. It is suggested that water hyacinth decomposition formed lactate, which supported large populations of lactate-utilising SRB.Item Influence of Hydraulic Retention Time on Start-Up and Process Stability of Polyurethane Carrier Reactions(1992) Rubindamayugi, M. S. T.; Op Den Camp, H. J. M.; Lubberding, H. J.; Gijzen, H. J.; Vogels, G. D.Influence of hydraulic retention time (HRT) on start-up of Polyurethane Carrier Reactors treating Volatile Fatty Acids (VFA) based wastewater, at constant organic loading rate (OLR) was investigated. OLR was increased stepwise after start-up to evaluate the influence of HRT on process stability. Four parallel experiements were conducted at HRTs of 48, 24, 18 and 12 hours. Results indicate an influence of HRT on duration of start-up period, and process stability after start-up. The reactor operating at HRT of 24 hours required only a relatively stort start-up period and showed higher process stability under steady-state condition. Analysis of individual VFA degradation indicated that butyrate and propionate consuming acetogenic bacteria increased in sigmoid fashion during start-up. Changes in acetate degradation do not show the true increase of acetoclastic population. Instead they reflect concomitant activity of VFA catabolizing acetogens and aceloclastic methanogens . Immobilized biomass increased exponentially during the first three weeks of start-up. The differences in start-up periods between reactors was probably due to differences in quality and activity of biomass immobilized at different HRTs. The HRT of 24 hours was most optimal to obtain stable reactor performance within a short startup period.Item Performance of a Small Waste Water Stabilisation Pond System in Tropical Climate in Dar es Salaam, Tanzania.(2003) Mbwele, L.; Rubindamayugi, M. S. T.; Kivaisi, A.D. G.Waste stabilisation ponds (WSP) are widely used in Tanzania. Their traditional design focuses on BOD and pathogen removal, but nutrient removal is equally important. WSP performance was evaluated to come up with information that would be used to evaluate pond performance. Samples were analysed twice a month for six months. Results showed total and faecal coliform removal by 4 log units (99.96 and 99.98% respectively). There was partial reduction of COD, BOD, (46% and 27% respectively), conductivity and total dissolved solids (32.6 and 32.4% respectively). Variation for the nutrients like inorganic phosphorus, ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen was not consistent and there was practically no reduction, although there is some nitrification taking place. From this study it may be concluded that BOD and nutrients may not be useful to evaluate pond performance. Instead parameters such as conductivity, total dissolved solids, coliform bacteria, dissolved oxygen, pH and chlorophyll would be suitable for that purpose, due to their consistent variation within cells of the pond system. But BOD and nutrient removal are important and have to be improved to enhance treatment in the WSP.