Browsing by Author "Mashauri, Damas A."

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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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    Constructed Wetland at the University of Dar Es Salaam
    (Elsevier, 2000) Mashauri, Damas A.; Mulungu, Deogratias M. M.; Abdulhussein, B. S.
    Following lack of investment in wastewater treatment, high investment and maintenance cost, conventional treatment systems have not been used in Tanzania. On the other hand, cost effective wastewater treatment methods like the use of septic tanks, soak pits, drainage fields and waste stabilization ponds are widely applied. One of the methods of achieving compliance using conventional treatment systems at low cost, producing treated water pollution free and fostering a community responsibility for wastewater treatment involves the use of natural or constructed wetlands. To date, no wetlands have been used for treating wastewater in Tanzania. Therefore in an attempt to promote the use of constructed wetland for wastewater treatment, a horizontal flow constructed wetland at the University of Dar es Salaam was commissioned for treatment of wastewater effluent from the University waste stabilization ponds (WSP).This paper presents results obtained from a constructed wetland (CW) installed at an outlet of the WSP of the University of Dar es Salaam. The field tests were conducted at low and high filtration rates 0.27 m/h and 2.3 m/h respectively for a period of 4 weeks. Treatment effectiveness was evaluated which indicated high mean removal efficiencies; 80% for SS, 66% for COD, 91% for faecal coliforms (FC) and 90% for total coliforms (TC) achieved at the low filtration rate. Thus, wetlands if properly designed, operated and maintained can provide an efficient and economical means of upgrading the quality of secondary treated wastewater to an acceptable level.
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    Modelling Nitrogen Transformation in Horizontal Subsurface Flow Constructed Wetlands Planted with Phragmites Mauritianus
    (2004) Senzia, M. A.; Mashauri, Damas A.; Mayo, Aloyce W.
    A mathematical model was developed to permit dynamic simulation of nitrogen interaction in a pilot horizontal subsurface flow constructed wetland receiving effluents from primary facultative pond. The system was planted with Phragmites mauritianus, which was provided with root zone depth of 75 cm. The root zone was packed with gravel of 6 to 25 mm diameter in uniform proportions. Stella II software was used to simulate nitrogen transformation processes. The results show that the most influential nitrogen transformation processes were nitrification, denitrification, plant uptake, decomposition and accretion of organic nitrogen. Volatilisation played a negligible role in reducing nitrogen at the typically neutral pH levels found in subsurface wetland systems. Denitrification process, which ensures the permanent removal of nitrogen, accounted for 0.219 g/m2.d, which was only 15.0% of incoming nitrogen load (1.458 gN/m2.d). Harvesting of plants removed 0.195 gN/m2.d (13.4%) from the system. Accretion of organic nitrogen was a major pathway accounting for 0.279 g/m2.d, which is 19.2% of all the influent nitrogen. The accumulation of ammonia nitrogen was found to be high compared to other water phase state variables (organic nitrogen and nitrate nitrogen).
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    Rainwater Harvesting For Domestic Use in Tanzania a Case Study: University of Dar Es Salaam Staff Houses
    (Taylor and Francis, 1991) Mayo, Aloyce W.; Mashauri, Damas A.
    The bacteriological, chemical and physical analyses of water samples from rainwater cistern system at the University of Dar es Salaam in Tanzania were carried out between October 1988 and December 1989. Faecal coliforms, total coliforms and faecal streptococci were enumerated. The results shows that 86% of the samples were free from faecal coliforms. However, faecal streptococci were obtained in 53% of the samples and 45% of the samples tested for total coliforms were positive. The physical quality of water was found to be appealing during the whole study period with turbidity less than 5 NTU and colour less than 5 mg Pt/l. However, about 54% of the consumers raised objections over the taste of water.
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    Resolving and Prevention of Shared Water Resources Conflicts
    (2004-05) Mulungu, Deogratias M. M.; Mashauri, Damas A.
    International shared water resources conflicts can be resolved through negotiation and arbitration. The negotiation and arbitration must be supplied with decision aiding tools and management plans for the shared water resources so as to come up with workable framework that can be used to prevent future water resources conflicts in the riparian countries. Various methodologies in literature have been given for conflict resolution with consideration to hydrological, environmental, economic, legal and political factors. Because of the complex nature of conflicts and cooperation, currently with the development of technology, computer and model applications are used to assist decision-making during conflicts and cooperation. In this paper, potential resolving and preventive alternative methods and/or experiences have been presented so that we can properly formulate and implement suitable policies, strategies and actions to avoid occurrence of water-based conflicts and their adverse consequences in Africa. As an example, conflicts and cooperation on some shared river basins in Africa (Nile river basin and SADC region rivers) have been highlighted. Learning from experiences from other parts of the world, it was recommended to incorporate game theory technique in water resources conflicts and cooperation in the African river basins for equitable and fair utilization and management of shared water.
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    Suitability of Constructed Wetlands and Waste Stabilisation Ponds in Wastewater Treatment: Nitrogen Transformation and Removal
    (2003) Senzia, M. A.; Mashauri, Damas A.; Mayo, Aloyce W.
    It is estimated that 90% of sewage in cities in developing countries are today discharged untreated into water bodies. In Tanzania, pollution of rivers such as Karanga, Njoro and Rao in Moshi; Mirongo in Mwanza and Themi in Arusha is the cause of frequent disease outbreaks in communities downstreams. Solutions to effluent crisis can be found by its proper treatment and disposal. The principal objective of wastewater treatment is to allow effluents to be disposed without danger to human health or unacceptable damage to the ecology of receiving water bodies. Field investigations were made on pilot scale horizontal subsurface flow constructed wetlands (CW) units located downstream of waste stabilisation ponds (WSP). Six units filled with gravel of 6–25 mm diameters in equal proportion, which gave an initial hydraulic conductivity of 86 m/d were used. While four units covering surface area of 40.7 m2 each, were located downstream of primary facultative pond, the other two units with surface area 15.9 m2 each were located downstream of maturation pond. An attempt was made to compare the output of mathematical models for Phragmites and Typha macrophytes located downstream of primary facultative pond. Based on total inflow nitrogen of 1.457 gN/m2 d, while Phragmites has shown a removal of 54%, Typha had a removal of 44.2%. Furthermore, while the system downstream of primary facultative pond has accretion as a major pathway, accounting for 19.1% of inflow nitrogen, the system downstream of maturation pond has denitrification as its major removal mechanism accounting for 20.5%. In this paper, a comparison of land required by CW and WSP based on the amount of water to be treated is made.
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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.