Browsing by Author "Kimwaga, Richard"

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    Assessment of nutrient retention by Natete wetland Kampala, Uganda
    (2010-12) Kanyiginya, V.; Kansiime, Frank; Kimwaga, Richard; Mashauri, Damas A.
    Natete wetland which is located in a suburb of Kampala city in Uganda is dominated by Cyperus papyrus and covers an area of approximately 1km2. The wetland receives wastewater and runoff from Natete town which do not have a wastewater treatment facility. The main objective of this study was to assess nutrient retention of Natete wetland and specifically to: determine the wastewater flow patterns in the wetland; estimate the nutrient loads into and out of the wetland; determine the nutrient retention by soil, plants and water column in the wetland; and assess the above and belowground biomass density of the dominant vegetation. Soil, water and plant samples were taken at 50m intervals along two transects cut through the wetland; soil and water samples were taken at 10cm just below the surface. Physico-chemical parameters namely pH, electrical conductivity and temperature were measured in situ. Water samples were analyzed in the laboratory for ammonium-nitrogen, nitrate-nitrogen, total nitrogen, orthophosphate and total phosphorus. Electrical conductivity ranged between 113μS/cm and 530μS/cm and the wastewater flow was concentrated on the eastern side of the wetland. pH varied between 6 and 7, temperature ranged from 19°C to 24°C. NH4-N, NO3-N, and TN concentrations were retained by 21%, 98%, and 35% respectively. Phosphorus concentration was higher at the outlet of the wetland possibly due to release from sediments and leaching. Nutrient loads were higher at the inlet (12,614±394kgN/day and 778±159kgP/day) than the outlet (2368±425kgN/day and 216±56kgP/day) indicating retention by the wetland. Plants stored most nutrients compared to soil and water. The belowground biomass of papyrus vegetation in the wetland was higher (1288.4±8.3gDW/m2) than the aboveground biomass (1019.7±13.8gDW/m2). Plant uptake is one of the important routes of nutrient retention in Natete wetland. It is recommended that harvesting papyrus can be an effective way of nutrient removal especially phosphorus which is not easily lost to the atmosphere like nitrogen. Natete wetland needs to be left in its natural state for better efficiency in nutrient retention. Bio-manipulation of the wetland by spreading the wastewater as it enters the wetland could enhance the interaction between plants and wastewater and subsequent nutrient removal.
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    Characterization of wastewater from an Abattoir in Rwanda and the impact on downstream water quality
    (2010-01) Muhirwa, Déogratias; Nhapi, Innocent; Wali, Umaru G.; Banadda, Noble; Kashaigili, Japhet; Kimwaga, Richard
    This study analyzed processes and products at Nyabugogo Abattoir in Kigali, Rwanda, and investigated how they can be optimized for environmental safety. The average capacity of the abattoir is 566 cattle and 1,512 goats and sheep slaughtered per week. The study assessed the quantity and quality of different raw materials, by-products and wastewater streams and the potential impacts of applying cleaner production principles in abattoir processes. The samples were collected fortnightly, and analyzed using Standard Methods. The analysis emphasized on nutrients, biologically active constituents, and receiving water impacts. The data were processed for trends and variance using SPSS computer package. The wastewater parameters analyzed are temperature, salinity, conductivity, turbidity, dissolved oxygen pH, TSS, TDS, BOD5, COD, fat oils and grease, NO3-N, TKN, total phosphorus, chloride, calcium and total coliforms. The findings showed that the abattoir wastewater streams' total chemical oxygen demand (TCOD) ranged from (7,533±723) for evisceration to (23,778±1,673) mgl-1 from slaughtering step and the discharge into Mpazi River increased its TCOD from (213±29) to (852±94) mgl-1. The TSS varied between 2,452±51 from the slaughter process and 5,252±174 mgl-1 for the effluent from the goat and sheep slaughter section. Results from the bacteriological analysis showed that the average abattoir wastewater discharge count was (560±81)105 cfu/100ml of total coliforms which increased from (2.8±0.58)105 to (8.2±0.86)105 cfu/100 ml. It was concluded that the current effluent quality is not suitable for discharge into watercourses. It was recommended that further treatment of the effluent is required coupled with the application of cleaner production principles.
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    Eco-hydrology of the Pangani River Downstream of Nyumba ya Mungu Reservoir, Tanzania
    (Elsevier, 2008-01) Mwamila, Tulinave B.; Kimwaga, Richard; Mtalo, Felix W.
    Eco-hydro­log­i­cal stud­ies are highly empha­sized world­wide at the moment espe­cially where hydrau­lic struc­tures such as dams are con­cerned, mainly focus­ing on ben­e­fit­ing both humans and exist­ing eco­system for the pres­ent and future gen­er­a­tions. The study at Pan­gan­i basin was aimed at assess­ing the suf­ficiency and the amount of flow reach­ing the down­stream area of the Pan­gan­i River for main­te­nance of eco­sys­tem. Fish spe­cies were con­sid­ered as the indi­ca­tors for eco­sys­tem health. Flow dura­tion curves (FDC) and hy­dro­graphs were devel­oped by using the col­lected his­tor­i­cal daily flow data and used for assess­ing the flow var­i­a­tion before and after Ny­umba ya Mun­gu (NYM) dam con­struction. The results showed that there is no sea­son­al­i­ty and that for most part of the year the flow is within 20–40m3/s. From the com­par­i­son it was found that there is 42.7% decrease in Q5, 2.1% decrease in Q95, 38.9% increase in Q75, 23.4% increase in Q50 and decrease of per­cent­age ex­cee­dence of 50m3/s by 61.5%. Phys­i­cal hab­i­tat sim­u­la­tion model (PHAB­SIM) was used for hydrau­lic sim­u­la­tion incor­po­rat­ing geo­met­ric and flow data col­lected in the field. From the sim­u­la­tions min­i­mum flow for hab­i­tat pro­tec­tion is about 15m3/s and for flood for­ma­tion flows should be greater than 50m3/s. Thus the required res­er­voir out­flow for sus­tain­able water resources man­age­ment at the NYM should fol­low the above spec­i­fi­ca­tions.
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    Effect of Diffusional Mass Transfer on the Performance of Horizontal Subsurface Flow Constructed Wetlands in Tropical Climate Conditions
    (2011) Njau, Karoli N.; Gastory, L; Eshton, Bilha; Katima, Jamidu H. Y.; Minja, Rwaichi J. A.; Kimwaga, Richard; Shaaban, M.
    The effect of mass transfer on the removal rate constants of BOD5, NH3, NO3 and TKN has been investigated in a Horizontal Subsurface Flow Constructed Wetland (HSSFCW) planted with Phragmites mauritianus. The plug flow model was assumed and the inlet and outlet concentrations were used to determine the observed removal rate constants. Mass transfer effects were studied by assessing the influence of interstitial velocity on pollutant removal rates in CW cells of different widths. The flow velocities varied between 3-46 m/d. Results indicate that the observed removal rate constants are highly influenced by the flow velocity. Correlation of dimensionless groups namely Reynolds Number (Re), Sherwood Number (Sh) and Schmidt Number (Sc) were applied and log-log plots of rate constants against velocity yielded straight lines with values β = 0.87 for BOD5, 1.88 for NH3, 1.20 for NO3 and 0.94 for TKN. The correlation matched the expected for packed beds although the constant β was higher than expected for low Reynolds numbers. These results indicate that the design values of rate constants used to size wetlands are influenced by flow velocity. This paper suggests the incorporation of mass transfer into CW design procedures in order to improve the performance of CW systems and reduce land requirements.
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    Heavy Metals Inflow into Lake Muhazi, Rwanda
    (2012-01) Nhapi, Innocent; Wali, Umaru G.; Usanzineza, Denise; Banadda, Noble; Kashaigili, Japhet; Kimwaga, Richard; Gumindoga, Webster; Sendagi, S.
    Most tropical African lakes are facing pollution problems due to the rapid population growth and industrializa-tion in their riparian communities. Lake Muhazi in Rwanda is one of such lakes which has experienced a dramatic decrease in fish production since the eighties, with also reports of low water transparencies and high turbidities. The lakeshores are now being developed for ecotourism and this requires sound environmental management to make the planned activities viable. The purpose of this study was to assess heavy metal pollution in the tributary rivers of Lake Muhazi. The concentration of heavy metals in major tributaries was monitored for the period July to October 2007. The parameters studied are cadmium, chromium, copper, iron, lead, manganese, zinc, pH and temperature. Fourteen sampling stations on the Inflow Rivers and the spillway were monitored fortnightly. The samples collected for heavy metal analysis were preserved and stored in cooler boxes and analyzed in the laboratory using Standard Methods. Temperature and pH were measured in the field using HACH field testing kits. The concentration (mean ± standard deviation) of Zn was found to be 0.040±0.103 mg/L, Cd 0.031±0.007 mg/L, Pb 0.487±0.452 mg/L, Fe 7.53±13.34 mg/L, Mn 1.01±1.31 mg/L, chromium 0 mg/L and copper 0 mg/L. The concentrations of measured parameters deviate much from the recommended ones thus posing serious problems to aquatic life. It has also been shown that the high metal concentration levels in Lake Muhazi are related to landuse activities in the catchment. It is thus recommended that farming practices and erosion be controlled in the catchment to contain pollutant discharges into the lake. Lead is the main anthropogenic pollutant which has been found in the watershed of Lake Muhazi.
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    Meeting the Water and Sanitation MDGs: A Study of Human Resource Development Requirements in Tanzania
    (2013-10) Kimwaga, Richard; Norbert, Joel; Kongo, Victor; Ngwisa, Mpembe
    In the Tanzanian water and sanitation (WatSan) sector, the human resource (HR) requirements for meeting the Millennium Development Goal (MDG) targets have so far been relatively unknown. This study was therefore conducted with a focus on determining HR requirements in the public sector and parastatal institutions, in the private sector (private consultancy companies, individual contractors, etc.), and in non-governmental organizations and community-based organizations active in the broader water, sanitation and hygiene (WASH) sector. The competences assessed were: design and construction of new infrastructure, operation and maintenance (O&M), community mobilization, sanitation, and hygiene promotion. The study found a greater HR shortage in rural areas than in urban areas. The smallest HR need is for social development professionals (estimated at 320 in the urban areas). In the water supply and sanitation sectors, the average number of water supply engineers that will be required to achieve MDGs is estimated at 3,864, compared to the sanitation sector, which will need 637 engineers. In terms of the demand for competences in the water supply sector, the highest need is for O&M professionals (7,589) and the lowest for mobilization professionals (447). The study recommends increasing the HR supply in the WatSan sector through the following measures: increasing support for training institutions offering relevant courses in WatSan; focusing on skills required for asset management and O&M; and giving specific attention to HR capacity development in small towns and rural areas.
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    Menstrual Hygiene Management in Secondary schools in Tanzania
    (2014) Guya, Ezra; Mayo, Aloyce W.; Kimwaga, Richard
    Menstrual hygiene management was studied in 12 secondary schools of Kinondoni and Bagamoyo district in Tanzania. The schools were selected by cluster sampling technique among public and private schools. Data were collected through questionnaire, Focus Group Discussion (FGD), semi-structured interviews and guide checklist for observation. A total of 149 girls participated in the survey and out of them, 84 participated in the FGD. A total of 23 head/deputy head of schools and matrons participated in semi-structured in-depth interview. The information sought included menstrual hygiene management (MHM) facilities, practices and education. The results indicate that all surveyed schools offered some sort of MHM education to girls and 3 schools out of 9 co-education schools involved in the study, provide some education about MHM to boys. A large majority of girls still need more information on MHM and prefer this information be provided at school. Lack of soap, hand wash facilities, privacy in toilet and free pads to attend emergency needs were identified as main problems. A supportive environment for MHM has to be provided in schools and to achieve this; instruction about MHM should be incorporated into compulsory health education in both primary and secondary schools curricula with separate sessions for girls and boys. Moreover, there is an urgent need for girl’s friendly toilet designs and appropriately final disposal facilities for menstrual products in schools. The efforts do not always mean large investments in infrastructure but in many instances, it suffices with just small investment.
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    A review of modeling approaches in activated sludge systems
    (2011-07) Banadda, Noble; Nhapi, Innocent; Kimwaga, Richard
    The feasibility of using models to understand processes, predict and/or simulate, control, monitor and optimize WasteWater Treatment Plants (WWTPs) has been explored by a number of researchers. Mathematical modeling provides a powerful tool for design, operational assistance, forecast future behavior and control. A good model not only elucidates a better understanding of the complicated biological and chemical fundamentals but is also essential for process design, process start-up, dynamics predictions, process control and process optimization. This paper reviews developments and the application of different modeling approaches to wastewater treatment plants, especially activated sludge systems and processes therein in the last decade. In addition, we present an opinion on the wider wastewater treatment related research issues that need to be addressed through modeling.
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    Use of Coupled Dynamic Roughing Filters and Subsurface Horizontal Flow Constructed Wetland System as Appropriate Technologyfor Upgrading Waste Stabilisation Ponds Effluents in Tanzania
    (2004) Kimwaga, Richard; Mashauri, Damas A.; Mbwette, T. S. A.; Katima, Jamidu H. Y.; Jørgensen, S. E.
    As a part of a comprehensive evaluation of post-treatment techniques for upgrading Waste Stabilization Pond (WSP) effluents, coupled Dynamic Roughing Filters (DyRF) and Subsurface Horizontal Flow Constructed Wetland System (HSSFCW) system was evaluated in Tanzania. Coupled DyRF and HSSFCW were considered as cheaper and yet effective and appropriate alternative technology for upgrading WSP effluents in tropical environments like Tanzania. The main objective of the study was to determine the performance treatment of coupled DyRF and HSSFCW for upgrading WSP effluents with respect to organic compounds (TSS and BOD5) and pathogen (FC). A pilot of coupled DyRF and HSSFCW was constructed at the outlet of the Maturation WSP at the University of Dar es Salaam, Tanzania. The study was carried out in a 2.2 m × 0.7 m × 0.7 m deep DyRF as a first stage, using three different fractions of gravel ranging from 8mm to 32mm, from the top to the bottom respectively. In the second stage, a HSSFCW planted with Phragmites Mauritianus with 0.6-m wide, 1.75-m long and 0.6 - m deep was used. The DyRF – HSSFCW system achieved TSS load reduction by 89.35% which is 15.97 gTSS/m2/day, while BOD5 load reduction by 84.47% which is 9.29 gBOD5/m2/day was achieved. The FC mean removal rate of 99.99 % was also achieved. By achieving mean effluent TSS (12.63  4.12 mg/l), BOD5 (14.12  3.84 mg/l), and mean effluent FC concentrations of 790 FC/100ml it was concluded that application of coupled DyRF and HSSFCW in the tropics can be considered technically one of the most appropriate technology for upgrading WSP effluents.