Water Supply and Environmental Engineering

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Investigation on Storm Drainage Problem of Addis Ababa (Case Study at Gotera – Wollo Sefer, Saris - Gotera And Ring Road)
(Addis Ababa University, 2011-07) Desalegn, Getachew; Yilma, Seleshi (PhD)
Proper drainage system is required in developing urban areas. In Addis Ababa, drainage problem become an issue during rainy season. This study deals with investigation of storm drainage problem of Addis Ababa and a possible mitigation measure to overcome the problem. Despite there are many places in the city facing storm drainage problem; Ethio china road (Gotera – Wollo sefer), Saris Gotera road (Debrezeit road) and Ring roads are areas selected for this study. Based on primary and secondary data collected, the problems in the areas are categorized as construction, management and design problem. The method used to investigate management problem is direct field data collection and site visit but the construction problem is analyzed using field survey as well as comparison of design with what is implemented in the ground. Design of the study area is evaluated by redesigning of the system using the computation sheet used in American Federal Highway Administration (FHWA) urban drainage design manual and Addis Ababa City Road Authority (AACRA) urban drainage design manual with some modification. Design of storm drainage system evaluated in this research includes inlet spacing, pipe sizing and inlet type selection. The Values of inlet spacing and pipe sizing obtained by redesigning is compared with the original design. The result of this paper shows that the problem in Gotera - Wollo Sefer and Ring road is caused by insufficient drainage operation, over spaced inlet spacing and minimum pipe size is used. The investigation in Saris – Gotera road also shows; the curb inlets are over spaced and constructed with very small opening, the operation system of the drainage is in sufficient and curbs are not constructed according to the design.Finally, based on the result obtained a possible mitigation measures is recommended.
Impact of Built Environment on Hydrological Regimes of Addis Ababa
(Addis Ababa University, 2011-09) Getahun, Habtamu; Semu, Ayalew (PhD)
Urbanization takes place takes place in Ethiopia early 1900‟s. The rate is different from place to place; this is mainly due to social and economic influences. Among the big cities of Africa Addis Ababa is the one with high population low planned urbanization influence. This lack of proper settlement plan of the city influences its hydrological regimes due to influence on main streams of the city The built environment of Addis Ababa includes Asphalt roads, paved roads, residential areas, commercial and industrial areas and other big infrastructures. The purpose of this study was to show the impact of built environment on hydrological regimes of Addis Ababa through defining hydrological parameters by using SCS (soil conservation Service) method to evaluate surface runoff generated as result of rainfall and it is impact on streams. The study focused on the city of Addis Ababa without considering the entire Akaki watershed. Three periods of land use maps were considered in the analysis. The land use periods are 1984, 1986 and 2002, the first two maps was obtained from Ethiopian mapping agency and the 2002 one is from Addis Ababa city Administration which developed by City master plan office. The land use maps were digitized using GIS. Based on the three periods the land uses types categorized as Asphalt, Agriculture, Forest, Paved, Built and Park and Cemetery. Using parameter,curve number for each land use types surface runoff was calculated. Accordingly it was found out that since 1984 the runoff potential has changed from 0.28 in 1984to 0.45 in 2002. This is due to the expansion of the city and increasing of built environment, which was expressed by composite Curve Number and Soil Retention. The composite curve number has changed from 84.6 in 1984 to 91.1 in 2002. This change has been also observed when we delineated twelve sub catchments using ARC SWAT and GIS . Based on the analysis we found change of surface runoff was observed. The characteristics of streams which found in the delineated sub catchments also changed .The time of concentration for streams in delineated sub catchments reduced by twenty seven percent in small streams (intermittent). Therefore it is important to consider the impact of land use change in planning and design of urban infrastructure.
Assessment on The Performance of AAWSA Controlled Sewerage System - The Case of Arada Sub city
(Addis Ababa University, 2011-11) Rekik, Tsegaye; Habtamu, Hailu (PhD)
Wastes originating from domestic, commercial, and industrial sources (often mixed with storm water) are collected, treated, and discharged back into the environment. The purpose of sanitary service is to prevent ground water pollution and minimize water borne diseases. The city of Addis Ababa provides sewerage service to its inhabitants by connecting their internal sewer lines to the sewerage network; however the level of service is still regarded as very low. This paper is therefore meant to assess the performance of the existing sewerage system both in technical and economic efficiency terms specifically in the Arada sub city, Addis Ababa. To achieve this, different evaluation methods were used. The methods comprise field visits (accompanied by capturing some pictures of the problem areas), cost analysis and comparison of the two common waste disposal techniques used in the city, Viz. vacuum truck and sewer line, gathering  from customers in order to identify the satisfaction level and finally evaluation of the sewerage network using sewer CAD version 4.3 to check and compare the existing hydraulic capacity and the future expectations. From the field visits different problems are identified which include manhole rising, manhole overflow, manhole loss and infrastructure problems. From cost analysis and , it was identified that there is lack of awareness and interest by the customers to connect their waste disposal point to the sewerage line. However, it was found out that sewer line is efficient than vacuum truck service considering cost and service efficiency. Finally the sewer cad analysis indicated that the existing sewer network can serve under capacity if the upstream area loads are excluded. However, the inclusion of the upstream area (Merkato site) to the Lideta existing sewerage system resulted in a complete system failure. The identified problems associated with sewerage system can therefore be overcome through having efficient operation and maintenance services in cooperation with other infrastructure agencies and through awareness creation.
The Application of High Rate Tube Settler - The Case of Legadadi Water Supply Treatment Plant
(Addis Ababa University, 2015-06) Obsa, Bayissa; Esayas, Gebreyouhannes (PhD)
In modern water supply treatment plant high rate settler units achieve effective settling process than conventional sedimentation tank. This high rate settler can be considered during the new sedimentation tank construction and also existing sedimentation tanks can be modified by including such units. This study was aimed at the assessment and evaluation of the application of high rate tube settlers in the case of Legadadi Water Supply Treatment plant by two main methods. The first one is by comparing and evaluating the performance of settling process of the sedimentation tank that the high rate tube settler is provided for it and the one without it. The second method contained the pilot scale experiment developed at this treatment plant to evaluate and asses the performance of the existing one. The comparatives and experimental results concluded optimistically that the high rate tube settler can provide better performance than that of the conventional sedimentation tanks. The comparative results indicates that the performance in production efficiency increase by 34.5% and the effects of HRTS on filtration units saves 35.11% water use for filter back washing. Additionally the pilot experimental result due to high rate tube settlers’ shows that the production efficiency increased by 35.30%, detention time decreased by 33.7%, turbidity reduction is increased by 76.65% and the chemical amount required is reduced significantly. Therefore; from the results of the two study it is possible to conclude that the application of high rate tube settlers provides effective sedimentation process ,positive effect on filtration unit, and cost effective in(structural and land cost of sedimentation tank, chemical cost and other operational costs). The results of the study offered to recommend that the Legadadi Water Supply treatment can upgrade and improve the efficiency of process relative to the pilot scale results and; Other Water Supply institutions have to use this high rate tube settler to gain all important advantageous to be achieved.
Assessments of Urban water Supply and Loss Managements, the case of Adama Town
(Addis Ababa University, 2015-12) Siraj, Abduro; Geremew, Sahilu (PhD)
The aims of this research is to assess the situation of the urban water supply and demand, total water loss in distribution system and build a model to provide possible scenario in order to meet water supply with demand by reducing pressure effect in the system to minimize water loss in the town. Whereas, the significance of the study is to make responsible body to be aware in order to satisfying the water demand in Adama town water supply scheme. Water production and consumption, the pressure zones or topography and customers‟ meter reading (water billed) approaches was used to evaluate the water loss. The distribution of water connection per family, per capital consumption and the level of mode of services have been used in assessment of water supply coverage in study area. In process of evaluating, model building and analysis; tools such as Microsoft excel, Auto CAD and Water CAD v6.5 was used. The existing water supplying situation; the distribution of mode of service in the town house connection, yard connection and public taps were 5%, 60% and 35% respectively. Also average per capital consumption is 34.5L/c/d, whereas the average of water connection per family was 0.527 (52.7%) connection/family. On the other hand, water loss is analyzed in sampled kebeles and town levels, by using different methods like, percentage of loss and loss per number of connections. So at town level, currently in average, 34.05% of produced water is lost from the system due to many reason, effect of pressure, aged pipe, lack of good maintenance etc. In the modeling, the system has been modified using the design criteria of velocity and pressure. Areas with high pressures in the existing system have been identified and solution was established using pressure-reducing valves, which used to reduce effect of pressure and minimize water loss. In Adama town, due to different reason; water supply is not satisfying the demand of the town, currently, Adama Town Water Supply and Sewerage Enterprise produce treated water only 233L/s whereas the water demand is 364L/s, from this result, a gap between supply- demand is 131L/s. The impact of leakage in distribution system is high; to minimize the breakage of pipe lines and physical loss, the old aged water pipe lines should be replaced in order to improve the adequacy of urban water supply of the town.
Study on Storm Water Drainage Situation in Addis Ababa “Case Study for Jemo-Iii Condominium Site near Glass Factory Area”
(Addis Ababa University, 2016-03) Tillahun, Tessema; Meron, Mebrahtu (Ms.)
Flooding has long been recognized as the most damaging and costly natural hazard in many countries considering the frequency and influencing extent. Due to the rapid urbanization and the global climate change in the urban areas, the frequency of devastating floods tends to be higher and the loss of human lives and property show no sign of decreasing. In order to decide on minimizing the impact of floods an effective flood volume estimation model is required. The proper design of any storm drainage system involves the accumulation of certain basic data, familiarity with the project site, and a basic understanding of the hydrologic and hydraulic principles and drainage standards associated with that design. The rational method is the most common method in use for the design of storm-water drains, where the momentary peak flow rate is desired. The method provides peak runoff rates for small urban and rural catchment areas, less than 50 hectares (0.5 km2), but is best suited to urban storm-water drain systems and rural ditches. It shall be used with caution if the time of concentration exceeds 30 minutes. For the study area the storm-water sewer network has been analyzed based on the selected outfall facilities, selected network schematization and agreed designed criteria using interactive mathematical model on Excel. This study shall contribute a lot to control the flooding problems of the study area and enhances the ability of planners, researchers and city development actors to formulate and implement sound policies to minimize undesirable future flooding impacts and management alternatives.
Development of a Planning Strategy for Sustainable Water Systems Using the Life Cycle Assessment a Case of Ethiopian Emerging Town
(Addis Ababa University, 2017) Kidist, Wondimu; Mebrate, Taffesse (PhD)
Purpose: the objective of this paper is to develop a planning strategy of emerging towns water supply system based on the sustainability assessment tool called Life cycle assessment (LCA). The analysis applied to one of the Ethiopian small town called Fitche Methods: the method utilized in this paper is fragmented life cycle assessment for each component of the water supply systems based on well-known EPD (Environmental Product declaration), simplified CMLCA tool and, excel tools. Result and discussion: after complete assessment of the small-town water supply system, the borehole water abstraction has more impact (45-50%) on the system than the stream water utilization, Using hydroelectric is much better (85-95%) than using the diesel pumps, Less mineral content of the borehole water treatment has less impact (5-10%) than treatment of the spring water, The water supply infrastructure developed at the very initial stage of design affects the environment, Pit latrine coverage of the town is significantly high, so it increases of the borehole water contamination level directly related with it,The absence of liquid waste disposal system is the main risk of the spring water contamination. . Conclusion: in respect of the planning strategy; the results obtained from the LCA, which is basically from the most defined and relevant impact categories, known as GWP-CC (global warming potential and the climate change), nonrenewable energy source, and water consumption are good indicators of an emerging town water supply system impact. Therefore, it is essential to formulate the planning strategy of the water supply system of an emerging town based on carbon foot print and water foot print
Decision Support System Tool for the Evaluation of Sustainability of Rural Water Supply Services
(Addis Ababa University, 2017) Alazar, Negash; Geremew, Sahilu (PhD)
Since the globe managed to deliver the Sustainable Development Goals (SDGs) to the platform to replace the Millennium Development Goals (MDGs), Sustainability has become a global concern. Even though the world achieved in meeting the MDG target for drinking water, we have to sustain the water supply services, especially the rural water supply services to ensure a change in the livelihood of the rural poor. The main objective of this study is to formulate a DSS tool that can aid the rural water supply engineer and planner in decision making regarding to the sustainability of rural water supply services. Three modules that comprises functionalities for data input, data analysis (data query) and display of results are employed in the computer program development using visual basic programming language by Microsoft Visual Studio Express. A user-friendly interface helps the navigation of the software easy. The DSS tool identifies the sustainability status of a particular water supply services and further goes to identify the factors behind it from the most affecting factor to the least affecting factor in a descending order. The DSS tool further scrutinizes and contrasts between different water supply sources in a district to decide which water source is more sustainable than other water sources presented in a woreda/district. The Rural Water Supply Sustainability Evaluation DSS tool is applied on specific sites. The results are sustainability scoring values per the FIETS factor, per date, location and per administrative area (zone, district or sub-district levels).The results show increased social participation contributing to increased sustainability, schemes with distribution are more sustainable than isolated on spot schemes and increased cost recovery of the services contributing to increased sustainability of the rural water supply services. It is recommended that, community contribution and social participation, ensuring cost recovery and developing services with distribution schemes than isolated spot schemes should be practiced to ensure sustainability of rural water supply services.
Water Supply Quality Problem and its Impact of Agaro Town
(Addis Ababa University, 2017-03) Rezika, Dafiro; Geremew, Sahilu (PhD)
Agaro Town has been experiencing the problem of potable water supply in adequate quality even if the modern water supply system was installed since in 1961 and expanded its service by drilling a number of boreholes, it is common to see red water color in different interval of months .Still a number of people do not have access adequate amount of potable water and also they are not used for all home consumption. This research has focused on Water quality problems in town and its impact different bodies. Laboratory analysis characterizing and evaluating its quality by comparing with WHO and Ethiopian Standards is used in this research for identifying water quality problems in the town. By preparing Questionnaires with the aim of recognizing impact of water quality problems , for different people that cannot used distributed water for all home consumptions like merchant of the town that can partake coffee and tea, and people that can follow Muslim religion they cannot used for preparation of soup in the month of Ramadan. Economical loss by requiring another source of water is described in this body of this study. TWATER CAD software is used in water distribution system to analyze pressure and velocity and Pressure measurement was taken in different location of distribution system for the purpose of calibration. The parameters like Iron, Electrical conductivity, Total coli form, Turbidity, Dissolved oxygen and E. coli are not within the maximum permissible limit prescribed by WHO and Ethiopian drinking water quality standard. The max and min pressure by WATER CAD is at 7 and 10 junction respectively and max and min velocity is at 5 and 21 links respectively, whereas by Gagged pressure at sample location point is 3 junction low pressure observed . The total simulation accuracy of pressure in the network systems as assessed by statistical methods, R =0.899 Generally it can be concluded that the source of water supply contain high level of iron, it affects color of coffee, tea and soup this results affect high cost loss in merchant of the town that participate on preparation of coffee and tea , the people that follow Muslim region because of soup is prepared during the month of Ramadan, high level of iron contain high corrosive problem it affect pipes and pumps in the borehole . The other is as they not used pre and post chlorination total coli form and ecoli is show above permissible limit because this water born and water related disease is the first top ten diseasesshown in the town.Aeration, chlorination and house hold water treatment like boiling is the most recommended for removal of these contaminants in the town water supply system. KEY WORD:-water quality parameters, physical, chemicaland biological, water cad pressure and velocity, Agaro East of Ethiopia.
Alternate Solution to Lake Beseka Water Level Rise Containment
(Addis Ababa University, 2017-06) Lulit, Habte; Mebruk, Mohammed (PhD)
Environmental change that has taken place over the last few decades is an essential task to understand the impacts that natural processes and anthropogenic factors have on hydrological settings and ecosystems. Environmental concern regarding the expansion of Lake Beseka has become a major issue. The expansion of Lake Beseka has caused an irreversible damage to the nearby Awash River which is a resource for the surrounding irrigation schemes and downstream water supply. This paper tried to predict the maximum possible Lake level so that it is contained in its territory to control the contamination of Awash River. A numerical groundwater model, TAGSAC, has been used for predicting this maximum possible Lake level rise. For the identification, a steady state groundwater model was first created and calibrated for the inventoried wells. The model is conceptualized by considering a constant head boundary condition for the Awash River in locations where the river is perennial. The calibration of the model was made by changing the recharge and hydrogeologic parameters of the basins. The goodness of fit indicators (GoFIs) showed that the measured and simulated heads of the model have a better match. The maximum Lake level rise was determined by raising the lake water level where the flow was reversed away from the Lake by assuming the Lake is contained in its territory. As the result of this study indicates the maximum Lake level where the flow completely reversed is 12m.
Performance Evaluation and Model-Based Optimization of Membrane Bioreactors: The Case of Addis Ababa Package Treatment Plant
(Addis Ababa University, 2017-11) Mahlet, Melaku; Agizew, Nigussie (PhD)
Addis Ababa Water and Sewerage Authority invested 750 million ETB for installing membrane bioreactor units in the city. This new technology is expected to double the wastewater treatment capacity of the city. Evaluating the performance of the units is necessary in estimating the likelihood of meeting this expectation and predicting the sustainability of the treatment plants. This research explores performance of the installed plants and suggests optimal operational strategies to enhance the denitrification capacity of the plant while minimizing energy cost. Measures of performance were effluent quality and membrane filtration processes. In order to evaluate the effluent quality, samples were collected both in dry and wet seasons. The MBR module was evaluated using recorded data of Transmembrane Pressure (TMP), flux & permeability of five-month operation. Activated sludge model no1 based simulation was used to determine the optimal operation strategy. To ensure energy reduction while improving the treated water quality; the suitability of intermittent aeration was explored using the developed model. The average COD removal efficiency was 97%. The ammonium effluent concentration was always lower than 0.5 mg/L. However, absence of anoxic tank resulted in poor denitrification with consequently increase nitrate effluent concentration over 100 mg/l. The treated wastewater was found to be completely clear of fecal coliform; making the treated water suitable for reuse. The MBR filtration showed stable but low permeability condition. The average operational TMP was less than 20mbar. However, flux and permeability plot showed the plant was operating with decreasing trend over time and maximum of 80LMH/bar. This suggests the need for frequent cleaning or construction of a primary tank. Results from the ASM1 simulation indicated that intermittent aeration with aerobic-anoxic cycle of 43/54 min was the optimum duration. The proposed operational strategy increased the total nitrogen removal efficiency from 42% to 71% without affecting COD removal. These results indicate that creating optimal aerobic/anoxic conditions within the existing reactor is the most competitive solution to upgrade the MBR treatment plant.
Effects of Pressure Change on Water Quality: Case of Akaki Phase 3B Water Supply Distribution System in Addis Ababa, Ethiopia
(Addis Ababa University, 2017-12) Yetnayet, Tsegaye; Agizew, Nigussie (PhD)
Water network performance is defined as the ability to deliver a required quantity of water under sufficient pressure and an acceptable level of quality. Systems that have big transmission line may have problem on changes of pressure in the distribution system. Because pressure rate changes have been too much between water treatment plant and dead ends in distribution system. This study is to analyze the effects pressure changes on the water quality in water distribution systems for case study of Akaki phase 3B water supply system was assessed. Efforts were also made to identify the relationship between the residual chlorine and pressure in the distribution of the water supply network systems using Water Cad software /tool to model water distribution system. Accordingly, simulation results show that, for maximum and minimum pressures were used as base to evaluate the hydraulic performance; and simulation results for minimum residual chlorine were used as base to assess water quality transformation in distribution system. Pressure has a direct relationship with residual chlorine. Pressure change has been causing to increase chlorine consumption more. The result of pressure changes among others can decrease in chlorine content and hydraulic factors, because the systems may be extensive and thus possess complex networks and hangs in quantity cause pressure of flow. Hence hydraulic changes (pressure) could affect of water quality in the water distribution system.
nvestigating the Efficacy of the Indigenous Water Purification Method Using African Spear Plant Case: Konso Community
(Addis Ababa University, 2018) Sokate, Aylate; Alemtsehay, Gebremeskel (PhD)
Water supply and environmental engineering primary concern should be making potable water available to the community at large. Among the many topics addressed in the discipline, water purification method is of paramount issue to be addressed. Water purification can be undertaken in more sophisticated method and traditional way. An indigenous method used by Konso community to purify water using African spear plant was investigated in this research. Lab scale study was conducted to assess the efficacy of African spear plant to purify water in terms of water quality parameters such as PH, Turbidity and Bacteria presence. The study has used triangulation approach, means, qualitative and quantitative approach. The qualitative approach is used for the exploration of the method being used by the society by interviewing significant people in the community and observation of the practice in the society and to know the situation in which the community uses this traditional method. The quantitative method was used for measurement of African Spear plant efficacy in terms of water quality parameters such as PH, Turbidity and Bactria presence. The study found that, when the water is stirred with a crashed African Spear plant for about 1 minute and kept for about 10-15 minutes, African Spear plant has the capacity to reduce the turbidity of water, capacity to reduce the level of bacteria in the water and reduce the PH of the water but if it is kept for long time in the water, the African Spear plant makes the water media more favorable for bacteria and the color of the water is changed to the color of the plants. Wet African spear plant has much effect than dry plant in purifying water.
Performance Assessment of Stormwater Drainage System in Alamata Town
(Addis Ababa University, 2018) Ashenafi, Zinabie; Geremew, Sahilu (PhD)
Urbanization of an area invariably leads to increase in overall imperviousness of the area. When land becomes impervious,stormwater will stagnate on the surface thereby affecting the infrastructure, transportation and causing inconvenience to general populace. Stormwater drainage problem is one of the major challenges facing many countries in Ethiopia in general and Alamata town also faced the problem. This study has investigated the overall challenges of the stormwater drainage system in Alamata town.Rapid expansion of built environment, poor urban drainage managements and location of Alamata town being at the foothills of mount Gra-Kahsu are the major problems in the study area. The objective of this study is to evaluate the current stormwater drainage systems and associated problems. This research involves collection of both primary and the secondary data and the collected raw data was edited, coded, classified, and tabulated in order to make it ready for analysis. Furthermore, spatial analyses was conducted using Arc GIS, Bentley Flow master, Google Earth pro, and Auto CAD software’s as analytical tools. The land use land cover image was processed for the years 2008 and 2018 by using Arc GIS.10.4.1 and Google earth pro then for each land use/land cover, annual stormwater runoff volume was calculated and digital change detection were evaluated. The results indicate that Annual runoff volume of Built -up area in the study area has increased from 162129.6m in 2018 which accounts for 13.35% of the total Annual runoff volume. The Vegetation has decreased from 15616.8m 3 in 2008 to 183772.8 m 3 in 2008 to 4568.4m 3 in 2018 which accounts for 70.75%. The Bare Land area has increased from 8286.3m 3 3 in 2018 which accounts for 153.08%. The existing depth and width of the stormwater drainage channel were measured for all sub catchments of the town and used to determine the existing drainage capacity using Bentley Flow master. The hydrological analysis was computed by the SCS method and rational method. The computed discharge values, which were determined by both SCS method and rational method, were compared by dividing the watershed area according to their area of application. The existing condition drainage channel depths of sub-catchments 6,7 and 8 Increase by 68.40%, 160.20% and 121.07%; and the widths by 55.44%, 116.83% and 100.98%, and the Design discharge was also 9.29m in 2008 to 20970.9m 3 /s and 9.13m 3 3 /s, 16.47m 3 /s respectively.
Sustainable Urban Drainage Options for Mekelle City
(Addis Ababa University, 2018-03) Teamir, Abraha; Geremew, Sahilu (PhD)
Flood generation became a common incident in Mekelle because of low vegetation cover and the vastly spreading land cover that accompanies development also results in less water being available for infiltration into the ground. Moreover, the increasingly constructing impervious structures facilitate more flood to be produce and overloading the conventional system of drainage in the city. Therefore, the existing flooding impacts on the conventional system studied and parameterized with help of Geographical information system (GIS) application. The paper also presents a diverse stormwater management technique that potentially could be implement in a case study area and evaluate their sustainability using Analytical Hierarchy Process (AHP) decision support tool. Five alternatives for stormwater management in the selected site evaluated according to 4 main criteria and 11 sub criteria using an Analytical Hierarchy Process type called MCDA model. The model, which applies quantitative scoring and experts invited to conduct the scoring and weighting elements of the method. Again, SWMM tool is applied to compute the rainfall-runoff simulations with in Subcatchments located in the city of Mekelle (Northern Ethiopia).Finally, comparisons takes place between different Hydrologic and hydraulic parameters produced by a design storm before and after installing SWMM-LID control components. The result showed that the best sustainable stormwater management solution after analysis of the Multi Criteria Analysis weightage tends to Rain garden (A2), and infiltration trench (A3) with overall aggregate weight of 0.489 and 0.232 respectively which employs main criteria such as technical, Environmental impact, social impact, and economic impact. Following weightage for the best management types a moderate-weight to Bio-cells (A1) scoring 0.190, 0.18 to Vegetation swale (A5) and finally lowest priority of 0.166 to Permeable pavement (A4). With installing of LID-controls that displace equal amount of area covered by impermeable ground, runoff on affected Subcatchments S80 & S81, high imperviousness, with initial flow rates of 3.16m 3 /s and 3 3.34 m /s respectively reduced and controlled. As recommendation, some relevant LID- components are allocated considering the suitability criteria of construction of different site in Mekelle city.
Artificial Neural Network and Fuzzy Logic for Water Demand forecasting (In case of Mekelle city)
(Addis Ababa University, 2018-05) Gebrewahid, Adhana; Mebrate, Taffese (PhD)
The methodology emphasizes the importance of the new predictive model development, and to account for water demand uncertainty, through evaluation of the reliability of model predictive. In this thesis Artificial Neural Networks (ANN) and fuzzy logic models were used for Mekelle city water consumption predictions analysis. Water consumption data collected from Mekelle city water and sewerage authority and independent monthly climate data were obtained from the National Metrological Agency. Sensitivity analysis was applied to selection most relevant minimum explanatory variables in the forecasting process. These data were used in both ANN and the fuzzy model setting up, testing and validation. To build ANN model the available dataset were divided into 3 subsets: 70% of the data for model development; (15%) of the data are used for training; and (15%) of the data are used validation to determine the optimal number of inputs and optimal number of hidden neurons. Both input variables and the output variable of the water consumption were fuzzified and triangular fuzzy membership functions were created. The Mamdani fuzzy rules in If–Then format with the centroid defuzzification method were employed. Seven ANN model were developed with different weather combination as input variable and Model one were found best with a root mean square error (RMSE) of 30.96, mean absolute percentage error (MAPE) 2.54, correlation coefficient (R2) of 0.98 and 97.46% of forecasting accuracy. The average absolute percentage error of the fuzzy model was found as 19.2%. Therefore, in this research ANN model is successfully presented for predicting water consumption in Mekelle city with climate inputs, cost of water and population compared with the fuzzy prediction system.
Recovery of Phosphorus and Nitrogen from Source-Separated Urine: Process Optimization in Bench-Scale
(Addis Ababa University, 2018-06) Johnny, Girma; Agizew, Nigussie (PhD); Zerihun, Getaneh (Mr.) Co-Advisor
The main focus of this research is to investigate about the possibility of Nutrient recovery in the form of Magnesium Ammonium Phosphate (Struvite) by determining optimum PH, optimum dosage, suitable mixing time, mixing speed , precipitation time ,and storage time from source separated stored human urine. A laboratory test was conducted using Jar test for the stored human urine. Struvite formation was PH dependent reaction and the experiment was started with PH optimization having six different pH values from PH 6 to 11. The experimental result showed that at PH 10 the percentage removal for N -N and PO4-P was 87.07% and 91.55% respectively, which is greater than other PH’s which implied that the optimum PH was PH 10. Using PH 10 as optimum PH, the determination of optimum dosage (P04-p:M )ratio was conducted using six different mass ratios, i.e. 1:1, 1:2, 1:3, 1:4, 1:5 and 1:6. The result of the experiment showed that, at PH10 and P04-P:M dosage of 1:1, the percentage removal of NH4-N and P04-P was 90.54% and 77.49% respectively which showed the optimum dosage was 1:1. Laboratory tests were also done to determine the optimum mixing time and mixing speed and found to be 30minutes and 60rpm respectively .Two samples were tested to determine the optimum incubation period to recover nitrogen and phosphorus for 25 and 30 days and found to be on 20th and 19th day respectively. Furthermore Basaka water was also used as source of Mg +2 to recover Nitrogen and Phosphorus and about 36% of Phosphorus was recovered and ultimately struvite was produced by the designed stirred reactor.
Assessment of Cactus Biosorption Potential in The Removal of Hexachromium Ions from Synthetic and Tannery Waste Water
(Addis Ababa University, 2018-06) Getahun, Mebrate; Geremew, Sahilu (PhD)
Chromium (VI) is environmentally mobile owing to its high solubility in water. Its pollution is largely attributed by discharge of inadequately treated effluents of chrome utilizing industries. Discharges of such effluents pose a potential threat to human health unless are treated properly before its disposal. Adsorption using activated carbon prepared from biomaterials is a new technology for the treatment of heavy metals rich industrial effluents. Opuntia Ficus Indicus (OFI) activated with H3PO4 (45%) was evaluated for Cr (VI) removal capability from both synthetic and tannery waste water. The present work was aimed at assessing the biosorbent capability of OFI in removal of Cr (VI) from synthetic aqueous solution and tannery waste water. OFI was activated with H3PO4 (45%) and carbonized at 450 o C in muffle furnace for 1hr and its different physical properties such as bulk density and moisture content was determined. Besides; the sorbent characterized by FTIR spectroscopy test analysis before and after adsorption processes, suggested possible key contributions of hydroxyls and carboxyls in the sequestering of Cr(VI) on OFI. Maximum Cr(VI) removal efficiency of 99.5% was achieved by OFI under different study parameters. The percentage removal of Cr (VI) ions increased with increase of the amount of sorbent concentration for which the Optimum removal of Cr (VI) was observed at sorbent dose of 125 mg. The adsorption efficiency of Cr (VI) on OFI was increased at low pH values between 2 and 3, attending its optimum at pH of 2. Percentage removal was observed to increase, while decreasing the initial concentration of Cr (VI) to which 6mg/l was the minimum of adsorption system. Whereas; the removal was increased with increasing the agitating speed and its corresponding contact time, whereby; the optimal adsorption reached at 60 minutes at 150rpm agitating speed. Both Langmuir and Freundlich models and followed adsorption process with high regression correlation coefficient (R 2 ) values of 0.999 and 0.956 respectively. But, Langmuir isotherm with higher R 2 was best fitted to the experimental values, with monolayer adsorption capacity of 4.587mg/l. Besides; the RL values were obtained in range of 0 < RL < 1 that confirmed the favorability of adsorption process. The optimized parameters were applied to the real waste water resulted in 88.7% of optimal adsorption removal efficiency. The reduction in percentage of removal might be due the matrix effect of the competing ions present the chrome liquor spent. Adsorbent used in present study was prepared at laboratory scale and observed to hold distinct position for its efficient removal of Cr (VI) both from synthetic aqueous solution and tannery waste water and could be an alternative promising plant based biosorbent in field.
Wetlands as Nature Based Solutions for In Situ Water Purification: The Case of Urban Wetlands, Jimma, Ethiopia
(Addis Ababa University, 2018-07) Adey, Sileshi; Agizew, Nigussie (PhD)
Nature provides valuable solution to tackle different socio- environmental challenges. Wetlands have a potential to purify water which is mainly influenced by its hydro-system, including landform setting and the water regime, and different biogeochemical processes. In East Africa, it’s estimated that approximately 80% of wastewater is discharged untreated or partially treated. Although there are some studies dealing with the water purifying effect of wetlands, its application for in-situ water purification is still in its infancy. The main objective of this study is to determine the effect of natural riverine wetlands to reduce nutrient and organic pollutant concentrations. And to assess the difference among the study wetlands. A cross sectional study on water samples collected from different locations before entering the wetlands, within the wetlands and after passing through the wetlands, was conducted between February 5 and February 25, 2017. Data collection check list and standard field protocol were used to collect data from three urban wetlands (urban downstream wetland and two urban upstream wetlands). After compiling, data analysis was done using R statistical software. The results of this study showed a lower concentration of nutrients, and BOD in sites after joining the wetlands compared to those before the confluence of the wetland. This implied the presence of pollution attenuation by the wetlands. Among the three wetlands, the one located in the urban downstream revealed a higher level pollution. The PCA model showed nutrient and pollution gradient along its axis. Urban downstream wetland was positively correlated with nutrients as shown in the PCA biplot. In conclusion, the study revealed the potential of urban wetlands to reduce/ attenuate pollution from the water which passes through them. However, discharging unlimited amount of nutrients and other toxicants to wetlands may affect the functioning of wetlands
Assessment of Impacts of Urbanization on Surface Water Quality, The Case of Keha River, Gondar Town
(Addis Ababa University, 2018-10) Amsalu, Alemu; Geremew, Sahilu (PhD)
This study assessed the impacts of urbanization on surface water quality and identify the sources of pollution on Keha River in Gondar town. Urbanization and anthropogenic activities are the key factor causing water quality degradation as we go downstream along Keha River. Based on Keha watershed land use land cover in1999,2004,2006 and 2017, it is shown that there is significant land use change of the bare land, grassland and agricultural land converted into urban land use and Keha River water quality has deteriorate in the past 15 years. The critical source of pollutions are industries like Moha soft drink industry, Gondar hospital, Kedame Gebeya Commercial market, a lot of hotels and restaurants among others. To analyze the river water quality fourteen (14) different strategic sampling sites were selected. The analysis consisted of in situ and laboratory analysis of samples using standard methods. The result indicated that the range of PH (5.9-8.97mg/l), Conductivity (142-1231 us/cm), Turbidity (8-1072 NTU), Dissolved Oxygen (7.4-2.1mg/l), BOD (4.1-217mg/l), TDS (102-1298mg/l), Alkalinity (89-508mg/l), Total Hardness(103283mg/l), Iron(0.15-0.76), Chromium(0.02-0.42), Manganese(0.02-3.9), Phosphate(1.3732.7mg/l), Nitrate(35.4-178mg/l), Total coliform counts(2.9-495) and E.Coli counts (2273.8) for rainy and dry seasons. At all sampling sites except upstream of Keha River the Physico- chemical and bacteriological results of water samples were above the Ethiopian and WHO standard limit indicated that Keha River was polluted. Except upstream of Keha River, at all sites the Dissolved Oxygen (DO) is less than 5 mg/l that is below the WHO and Ethiopian minimum standard limit. High nitrate and phosphate cause of eutrophication, high total coliform and high E.coli lead to water borne disease and the death of the communities especially children because some people like the daily laborers and street children were used for drinking this polluted River within the study area. It is therefore concluded that the river in the study area is polluted and not fit for domestic use. It is recommended that the water of Keha River should not be used directly for domestic purposes. It is also recommended that an IWRM approach be used in order to solve the pollution problem. Keha River health restorative work is require for multiple importance such as ecosystem regeneration, water quality improvements, reduce any negative impacts on the water resources and aquatic life of Keha River.

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