Research Repository :: Browsing by Author "Mayo, Aloyce W."

Browsing by Author "Mayo, Aloyce W."

Now showing 1 - 20 of 37

BOD5 Removal in Facultative Ponds: Experience in Tanzania
(1996) Mayo, Aloyce W.
This paper discusses the removal of BOD5 in facultative ponds under tropical conditions. Data was collected from pilot and field ponds at the University of Dar es Salaam and was compared to other ponds in Dar es Salaam. Results showed deviations of performance, in some cases, from assumptions made during the design. The permissible organic loading rate for ponds in Dar es Salaam was 450 kg BOD5/ha/d. To reduce concentration of algae in the final effluent, a sunken outlet structure was suggested.
Challenges and Prospects of Private Sector Participation in Solid Waste Management in Dar Es Salaam City, Tanzania
(Elsevier, 2016) Kirama, Aminatha; Mayo, Aloyce W.
The objective of this research was to evaluate effectiveness of private sector participation in solid waste collection and transportation in Dar es Salaam City. The study covered 20 private service providers in municipalities of Kinondoni, Temeke and Ilala. Information was collected through questionnaires, interview guides, physical observation and field studies. Data were sought from 5 private companies, 15 Community Based Organizations, Dar es Salaam City Council, Waste Departments of Municipal authorities and local governments of ward and streets. The results show that private sector service providers collected and transported 9% of the 29,764 tons of solid wastes generated per week. They have also provided employment opportunities to over 350 people, who are helping to keep the city clean and increase national income through payment of various taxes. It was also observed that private sector operates in difficult conditions because of low cost recovery, the use of inferior wastes collection and transportation equipment, limited scheduling, short contract duration, inefficient system of refuse fee collection, an absence of planned wastes recycling systems, inaccessible roads and weak implementation of relevant municipal policies and by-laws. It was further noted that the success of the system will depend on accountability of municipal authorities by raising the awareness of the communities in order to improve willingness to pay for refuse fees and discourage illegal dumping of waste by individuals, enforcing municipal by-laws, and planning and promotion of environmentally friendly waste management practices.
Challenges of Adoption of Urine-Diversion Dry Toilets Technology as Sanitation Option by Coastal Communities of Mkuranga District in Tanzania
(2015) Mayo, Aloyce W.; Mubarak, Twaha
Mkuranga District council in collaboration with African Medical and Research Foundation (AMREF) introduced ecological sanitation option using urine-diversion dry toilets (UDDT) to the community between 2007 and 2009, which was later declared unsuccessful. This study analyzed factors that hindered the uptake of UDDT by the community by assessing the project implementation strategy. Techniques used for the study were questionnaire, interviews, observation and focus group discussion while respondents were government official and the community at the household level. The study reveals that the literacy level in Mkuranga district is 79.1%, but only 40.6% had some knowledge of ecological sanitation although only 9% proves that. About 52% of the respondents are using conventional pit latrines, but 27.3% have no toilet facilities. There was no evidence of adoption of UDDT technology at household level and only one of the seven UDDTs constructed by the project is operational. There was no sufficient evidence to suggest that Mkuranga District has sufficiently supported the project through supervision, advocacy and addressing community requirements. As a result, the idea came in top-bottom approach which failed because communities were not adequately involved in the project.
Diurnal Cycles of Variation of Physical–Chemical Parameters in Waste Stabilization Ponds
(Elsevier, 2002) Kayombo, S.; Mbwette, T. S. A.; Mayo, Aloyce W.; Katima, Jamidu; Jørgensen, S. E.
Diurnal fluctuations of pH, dissolved oxygen (DO), water, air temperature and sunlight intensity were investigated in the waste stabilization ponds at the University of Dar es Salaam. The variation of these parameters followed the diurnal pattern of light intensity. The rate of oxygen production based on first order linear regression analysis was between 0.02 and 0.36 mg/l per h with high production rate being observed in secondary facultative ponds. The rate of utilization of dissolved oxygen (total respiration) during the night by the microbial population in the pond ranged between 0.016 and 0.435 mg/l per h. The average rate of increase of pH during the day was 0.0006–0.243 units of pH per h, and the rate of decrease was 0.0003–0.101 units of pH per h. The ponds receiving low organic loading showed high diurnal variation of physical–chemical parameters. The relationship between average hourly DO and pH followed a polynomial trend with the coefficient of regression (R2) ranging from 0.76 to 0.82. It may be concluded that the diurnal variation of the parameters in the WSPs is due to hourly and daily variation of light intensity.
Dynamics of Nitrogen Transformation and Removal in a Pilot High Rate Pond
(Scientific Research, 2014) Mayo, Aloyce W.; Hanai, Emmanuel E.
The transformation and removal of nitrogen was studied in a pilot high rate pond with a surface area of 10.2 m2 and water depth of 60 cm. The pilot unit received wastewater from an existing field scale primary facultative pond at the University of Dar es Salaam. Wastewater samples were collected from the influent and effluent of high rate pond and were analyzed for physical-chemical parameters in the laboratory and in situ. An appropriate model complexity was selected, from which a conceptual model was then developed to model various processes in the system using STELLA 6.0.1 software. The study demonstrated that dominant nitrogen transformation processes in HRP were nitrification and denitrification, which transformed 0.95 and 0.87 gN/m2∙d, respectively. These were followed by mineralization (0.37 gN/m2∙d), ammonia uptake by microorganisms (0.34 gN/m2∙d), volatilization (0.30 gN/m2∙d), sedimentation (0.24 gN/m2∙d), and regeneration (0.15 gN/m2∙d). Uptake of nitrate was not observed because of microorganisms preference for ammonia, which was abundant in the pond. The major nitrogen transformation mechanisms in high rate pond were denitrification, net sedimentation and volatilization, which accounted for 69.1%, 7.1% and 23.8% of the total permanent removal mechanisms of nitrogen in High Rate Pond.
Effect of Glucose Loading on the Growth Behavior of Chlorella vulgaris and Heterotrophic Bacteria in Mixed Culture
(Elsevier, 1994) Mayo, Aloyce W.; Noike, Tatsuya
The effect of glucose concentration on the growth of Chlorella vulgaris and heterotrophic bacteria in mixed culture was studied. Granular glucose was fed daily as a source of organic carbon to provide an input concentration ranging from 25–700 mg/l. Growth rates of heterotrophic bacteria and algae increased with glucose loading rate but excessive loading rates were detrimental to the survival of the algae and bacteria. The maximum specific growth rates for the algae and bacteria were 1.58 and 1.70 d−1, respectively. However, the saturation constants were significantly different with values of 27 and 174 mg/l for bacteria and algae, respectively. Under anaerobic conditions, bacterial density and algae growth were significantly affected by accumulation of volatile fatty acids (VFA). Although in low glucose loaded reactors, pH reached as high as 10.6, no significant effect of pH was observed on the survival of Chlorella vulgaris and heterotrophic bacteria. Inorganic carbon production increased with increasing glucose loading rate. When volatile fatty acids accumulated in anaerobic reactors, pH dropped resulting in a shift of equilibrium between H2CO3, HCO3− and CO32− in favor of H2CO3 production, most of which was released as CO2(g) to the atmosphere.
Effect of HRT on Nitrogen Removal in a Coupled HRP and Unplanted Subsurface Flow Gravel Bed Constructed Wetland
(2004) Mayo, Aloyce W.; Mutamba, Jeremiah
This paper discusses the effect of hydraulic retention time (HRT) on nitrogen removal in a coupled high rate pond (HRP) and a gravel bed subsurface constructed wetland (SSCW) wastewater treatment plant. A pilot plant consisting of a high rate pond (HRT) coupled to an unplanted gravel bed subsurface constructed wetland (SSCW) was used to investigate nitrogen removal from domestic wastewater at the University of Dar es Salaam. The influent, which is predominantly of domestic origin, was drawn from the facultative pond unit of the university’s waste stabilisation pond system. The pilot plant’s HRP unit, which was 0.6 m deep, was designed to nitrify the influent while SSCW unit, which was filled to 10 cm above water level with 19-mm diameter aggregates, was predominantly anoxic and promoted denitrification. The study was conducted at two different operational settings. In Phase 1, both the HRP and the SSCW units had a retention time of 5 days. During Phase 2, the hydraulic retention time in HRP was increased to 8 days while the retention time of the SSCW unit was maintained at 5 days. Samples were collected daily for laboratory analysis of influent and effluent wastewater quality. All experiments were conducted in accordance with Standard Methods. The results showed that improved nitrogen removal occurred with increase in hydraulic time of the HRP unit. In Phase 1 an average nitrogen removal of 33% was achieved while removal efficiency improved to 43% in Phase 2. It was also revealed that the HRP can effectively be used to promote nitrification and the unplanted gravel bed subsurface constructed wetland can be used as a denitrifying unit.
Effect of Pond Depth on Bacterial Mortality Rate
(American Society of Civil Engineers, 1989) Mayo, Aloyce W.
The bactericidal action of solar radiation was investigated in pilot scale waste stabilization ponds under the tropical climate of Dar es Salaam, Tanzania. Bacterial reduction was observed to proceed with increasing direct solar intensity and hydraulic detention time. The mortality rate of faecal coliforms used as test micro-organisms was higher in samples incubated near the surface and decreased rapidly when the samples were incubated at greater depths in the pond. The disappearance rate of faecal coliforms for samples incubated at the pond surface and at a depth of 1.0 m was 1.66 d-1 and 0.37 d-1 respectively. Faecal coliforms were also found to be reduced rapidly in shallow ponds. The mortality rate in 1.0 m and 1.5 m deep ponds was respectively 0.43 and 0.32 d-1. The dieoff rate constant was observed to vary significantly with pond depth but was independent of hydraulic detention time.
Effects of Cell Retention Time, Butyrate Loading Rate and Ph on Oxidation of Butyrate in Aerated Lagoons
(1997) Mayo, Aloyce W.
The treatability of butyrate in aerated lagoon was investigated in continuous laboratory-scale aerated reactors at 35°C. The effects of cell retention time, organic loading rate and pH on cellular growth and oxidation rate of butyrate were investigated. The cell retention time was varied in series of bioreactors from 1.5 to 8.0 days and influent pH was varied from 4.0 to 7.0. Butyrate loading rate of up to 3 kg/m3/d as soluble organic carbon was investigated. The analysis showed that the maximum specific growth rate of heterotrophic bacteria was 2.1 d-1, yield coefficient was 0.51, bacterial decay coefficient was 0.133 d-1 and cell maintenance coefficient was 0.262 d-1. The maximum specific substrate utilization rate, half-rate saturation constant and substrate inhibition constant were 1.22 mg SOC/mg POC/d, 7.8 mg SOC/L, and 5900 mg SOC/L, respectively. Butyrate removal rate was influenced by loading rate, but was independent of the mode of variation of butyrate loading rate. No evidence was found to support the view that total butyrate concentration influenced the density of heterotrophic bacteria. However, the concentration of undissociated butyrate was found to significantly affect the density of heterotrophic bacteria. In the alkaline pH range, heterotrophic bacteria increased as butyrate concentration increased. Densities of heterotrophic bacteria as high as 1.1×1010 cfu/mL were observed when effluent pH was 8.4, but decreased to 3×103 cfu/mL when effluent pH decreased to 4.3.
Effects of Temperature and Ph on the Growth of Heterotrophic Bacteria in Waste Stabilization Ponds. Water Research, 30, 447-455
(Elsevier, 1996) Mayo, Aloyce W.; Noike, Tatsuya
This paper presents the effects of temperature and pH on the growth of heterotrophic bacteria in Chlorella vulgaris-heterotrophic bacteria culture. The growth of heterotrophic bacteria was studied at 10, 15, 20 and 30°C, and pH was controlled from 3.0 to 11.5 in a series of fed-batch chemostat reactors supplied with glucose as the sole source of carbon. Samples were analyzed for heterotrophic bacteria by tryptone glucose extract agar in triplicate. The agar pH of 7.0 was the best for enumeration of heterotrophic bacteria. The bacteria grown at pH near neutral were more sensitive to the variation of agar pH than those grown at very alkaline pH. No significant difference in the number of cells capable of forming colonies was noted for incubation temperature of 20 and 35°C, but the lag time for colony formation was longer at 20°C. Samples for enumeration of heterotrophic bacteria collected from algal-bacterial systems such as waste stabilization ponds are recommended to be incubated at 35°C for 72 h. Depending on the pH of the culture, about 86–98% of the cells capable of forming colonies will be visible to the naked eyes after incubation at 35°C for 72 h. At the steady state conditions, heterotrophic bacteria were not sensitive to temperature in the range of 10–20°C. However, at 30°C, a notable competition for glucose between Chlorella vulgaris and heterotrophic bacteria was observed. This competition was responsible for the low bacterial density near neutral pH. No evidence was found to support the view that the discharge of bactericidal substances from Chlorella vulgaris was responsible for reduction of heterotrophic bacteria at high pH.
Effects of Temperature and Ph on the Kinetic Growth of Unialga Chlorella Vulgaris Cultures Containing Bacteria
(1997) Mayo, Aloyce W.
The kinetic growth of unialga Chlorella vulgaris was investigated in mixed-culture fed-batch chemostat reactors, with special reference to temperature and pH. The experiments were carried out at 10 degrees C to 40 degrees C, pH was controlled from 3.0 to 11.5 in a series of reactors, and glucose at a concentration of 75 mg/L was fed as the sole source of organic carbon. The maximum growth rate of 0.50 day(-1) was obtained at pH of about 6.31 to 6.84, and the optimum temperature was 32.4 degrees C. The activation energy of the growth-limiting reaction and the enthalpy change for the enzyme-inactivation reaction were 24.5 and 253.36 kJ/mole, respectively. The saturation constants for hydrogen ion, K-H, and hydroxyl ion, K-OH, were temperature-dependent. At temperatures below optimum, K-H increased when temperature increased, but K-OH decreased. Above the optimum temperature, K-H decreased and K-OH increased with temperature.
Faecal Coliform and BOD Reduction in Facultative Ponds under Tropical Climatic Conditions
(1992) Mayo, Aloyce W.
Fecal Coliform Mortality in Water Hyacinths Ponds
(2000) Mayo, Aloyce W.; Kalibbala, Martin
The effects of various environmental factors, sedimentation and attachment of faecal coliforms on water hyacinths, Eichhornia crassipes, were investigated in a pilot-scale water hyacinths pond. This investigation was conducted to evaluate the role of solar intensity, pH, dissolved oxygen, temperature, sedimentation, and attachment of faecal bacteria on Eichhornia crassipes on disappearance of bacteria in a water hyacinths pond. A mathematical model that used the plug flow philosophy and incorporated aforementioned factors to predict faecal coliform mortality rate was developed. The proposed multifactor model satisfactorily predicted mortality rate of faecal coliforms in a pilot-scale water hyacinths constructed wetland. The environmental factors such as solar intensity and pH were the key factors if the coverage of water hyacinths is minimum, but attachment of bacteria to water hyacinths played a major role in a wetland fully covered with water hyacinths.
Gender Mainstreaming in Integrated Rural Water Supply and Sanitation Project in Mzimba, Malawi
(2014) Mwamsamali, O. K. K.; Mayo, Aloyce W.
Gender mainstreaming in the water sector in Malawi was analyzed using the Mzimba Integrated Rural Water Supply and Sanitation (IRWSS) project as a case in point. Information required for the study was obtained through interviews, administering a set of questionnaires and data collecting from existing documents. The results show that women in decision-making positions at head office of the Ministry responsible for water affairs only constitute about 11.1%. Assessment of the budget allocations has revealed that previously no budgetary allocations were made for gender issues, and that since the 2006/07 fiscal year about US$14,286 was allocated for gender mainstreaming. Women's involvement in local governance institutions and project activities in Mzimba is generally high. Most local water committees have 60% women and 40% men, whereas participation in project activities is highly rated at 97.2%. To improve gender balance, the Ministry responsible for water has to work with stakeholders in the education sector. Besides, great disparities still exist between men's and women's participation in water projects at a local level (97.2% for women) and a person's socioeconomic position greatly affects their inclusion in the local governance structures. Addressing these issues would, therefore, result in better gender integration in the water sector.
Geochemical investigation of geothermal power potential exploration of hot springs in South-western Tanzania
(2010) Mnzava, Lightness J.; Mayo, Aloyce W.
Geochemical investigation of the power potential of Songwe geothermal prospect in south-western Tanzania within the East African Rift Valley was carried out. The thermal geochemistry was studied by collecting and analysing samples from 14 hotsprings. The maximum discharge of thermal water occurs at the northern part of the prospect, at the bottom of a travertine cliff, 35 km above River Songwe level, at a rate of 26 kg/s (T = 80°C, pH = 6.7). The southern springs are discharging between 30 to 50 m above river level. Degassed thermal water (CO2 and H2S) discharges at the river level and cause an increase of about 0.2 to 2°C above the ambient river water temperature (25°C in November), with a maximum spring temperature of 81°C (pH = 6.9). The lowest is Bwana Hutu (3 to 5 m above river level) thermal area where springs are degassing carbon dioxide gas with maximum temperature of 81°C (pH = 7.6). All springs in Songwe are depositing travertine except one spring degassing at (46.7°C, pH = 6.8). The total discharge rate of thermal fluid is between 45 to 75 kg/s with a median temperature of 60.5°C, and an estimated heat transfer of 10 MW. The results showed that the waters are of sodium-bicarbonate type, formed by steam heating below water table at the periphery of a geothermal system. The low predicted subsurface temperature of maximum 152°C (SiO2 no steam loss geothermometer), compared to the earlier prediction of 270°C (unknown geothermometer) is due to great dilution of the deep fluid by percolating rainwater and encroaching ground water (July). This was indicated by high magnesium concentration in the samples of over 8 mg/l compared to deep fluid magnesium level of less than 1 mg/l and also by the chloride-enthalpy plot in which most of the data plotted along the dilution line. The total usable power potential is estimated to be 107 MWe.
Kinetics of Bacterial Mortality in Granular Bed Wetlands
(2004) Mayo, Aloyce W.
Faecal coliform and faecal Streptococci die-off was investigated in the surface flow granular bed constructed wetland cell. The granular bed cell of effective plan area of 7.5 m × 1.5 m and 0.7 m deep was filled with aggregate size 19 mm up to a depth of 0.35 m. The remaining 0.35 m depth was filled with water. To assess the performance of the granular bed, samples were collected at the influent and effluent of the cell for calibration of a mathematical model. The analysis of the model suggests that bacterial mortality rate constant was largely influenced by sunlight intensity, which was responsible for 72.6% of removal. The influence of other parameters such as interception, filtration, dissolved oxygen, temperature, sedimentation on bacterial mortality rate were less significant. For instance, dissolved oxygen and pH contributed 7% and sedimentation only 0.44%. The ratio for the rate constant term to light attenuation coefficient (ks/K) was 1.281 × 10-3 m cm2/cal and the model efficiency was 0.80.
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.
Modeling Coliform Mortality in Waste Stabilization Ponds
(American Society of Civil Engineers, 1995) Mayo, Aloyce W.
The mechanisms of the reduction of fecal coliforms were investigated in pilot-scale and full-scale wastewater stabilization ponds under tropical climatic conditions. Field studies were conducted in pilot and large waste stabilization ponds with pond depths ranging from 1.0 to 1.82 m and hydraulic retention time between 4.3 and 11.2 d, to develop and verify the model. The observation made indicates that sunlight intensity, pond depth, and pH were the key input parameters to the model. In a multifactor developed model, the bacterial mortality rate constant for pH, k(pH) was 0.0135 d-1 and the ratio of rate constant for the light mortality term to light attenuation coefficient k(s)/K was 5.67 x 10(-4) m cm2/cal. The model was successfully verified by simulation with data obtained from field-scale pond systems in Tanzania and from two other pond systems reported in the literature. A brief model application, including the prediction of water pH, is given to aid the designer.
Modeling of Mortality Rate of Heterotrophic Bacteria Due to Chromium in Waste Stabilization Pond
(2013) Ahmed, Masoud G.; Mayo, Aloyce W.
Bacteria play an important role in oxidation and stabilization of organic and inorganic matter in wastewater treatment plant. This paper presents the development of mathematical model to study the effect of chromium on heterotrophic bacteria in waste stabilization pond. The governing equation of the model is based on the Haldane equation. The model developed reflects the mortality rate of heterotrophic bacteria at variable pH and concentration of chromium. To verify the computed results a series of laboratory experiments has been carried out, the predicted mortality rate was obtained from these models and compared with experimental data. The correlation coefficient R2 was 0.87.
Modelling Diurnal Variation of Dissolved Oxygen in Waste Stabilization Ponds
(Elsevier, 2000) Kayombo, S.; Mbwette, T. S. A.; Mayo, Aloyce W.; Katima, Jamidu; Jørgensen, S. E.
The dissolved oxygen sub model was developed in order to depict the combined influence of light, pH, temperature and carbon dioxide on the processes of dissolved oxygen (DO) production and utilization in secondary facultative waste stabilization ponds (SFWSP). The model was formulated based on Chen and Orlob (Chen, C.W., Orlob, G.T., 1975. In: Patten, B.C. (Ed.), Systems Analysis in Ecology, Vol. 3. Academic Press, New York, pp. 476–588.), and was modified to include the influence of pH and carbon dioxide. The forcing functions to the DO model were light intensity, carbon dioxide, temperature and pH. It was found that temperature, light and pH influence the process of photosynthesis based on the multiplicative formulation of forcing functions. The model was calibrated and validated by using the average daily data from SFWSP1 and 11. The model yielded a linear regression coefficient of 0.87 during calibration and 0.78 during validation. Based on the model results the rate of production of DO with relation to dry algal biomass was 1.599 mg DO/mg dry weight, which is equivalent to 35.905 mg DO/mg chlorophyll-a. Such correlation between the observed data and model prediction indicates that the assumption inherent in the mathematical model formulation of the processes is valid for the description of DO production and usage in the ponds.

Browsing by Author "Mayo, Aloyce W."

Results Per Page

Sort Options