Water Supply and Environmental Engineering

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    Assessment of Lead Contamination via Soil and Water in Addis Ababa Daycares
    (Addis Ababa University, 2023-04) Eden Belete; Zerihun Getaneh (PhD)
    Lead exposure can come from different environmental media soil, water and air impose negative health effects if ingested by humans, children’s are the most vulnerable. The objective of the study were to investigate i) lead level in water and soil of daycares facilities in Addis Ababa, ii) lead level in water sources (both surfaces and ground water) that supply water sources to Addis Ababa city. Graphite Furnaces Atomic Absorption Spectroscopy were used to analyze the concentration of lead in soil and tap water of 28 day cares. Samples were taken from 11 sub cities, sample size were determined based on the number of daycares in each sub city. Sample from sources (ground and surfaces) of water supply were also analyzed. The result indicated that the mean level of lead in soil and water of day cares were 2.37 and 8.26μg/l are within the permissible value of 10μg/L according to WHO standard. The result from sources of water shows that the lead level in surfaces water sources before treatment were above the permissible value (10μg/L ) whereas the ground water sources were within in the acceptable limits . Integrated exposure uptake bio-kinetic model were used to determine the blood lead level of children’s below 4 year of age. The mean blood lead level were 1.78μg/dl. Even if the BLL were below the blood reference value of 3.5μg/dl (according to CDC) there is no safe blood lead level value low lead level can have adverse effects in children. Lead level in drinking water from daycare centers is greater than the lead concentration from water sources this shows that there is sources of lead in between water sources and daycare tap water.
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    Impact Assessment of Koshe (ቆሼ) Open Dump Site Leachate on Ground Water Quality, Addis Ababa
    (Addis Ababa University, 2023-04) Tarekegn Tadesse; Zerihun Getaneh (PhD)
    One of the primary threats to the quality of groundwater is thought to be open dump sites. The study focused on Koshe open dump site which is the official active Open dump site for Addis Ababa city. The main purpose of this study was to assess the impact of Koshe open dump site leachate on groundwater quality around the dump site. The study was conducted from November 2022 to May 2023 giving a total of thirty-eight (38) parameters of the six (6) groundwater samples and one (1) leachate sample. Judgment sampling was used for data gathering. Physico-chemical parameters were analyzed at Horticoop Ethiopia (Horticulture) PLC Soil, Water, and Plant Analysis Laboratory. Samples of leachate and groundwater were analyzed to evaluate the impact of leachates on groundwater through the comparison of their physicochemical nature. Groundwater and leachate samples were collected and analyzed for selected water quality parameters and compared to the Ethiopian Water Quality Standard, EPA, and WHO Guidelines for drinking-water quality fourth edition WHO. The physicochemical characteristics of the groundwater samples around the Koshe open dump sites indicated high concentrations of Electrical conductivity, Potassium, Iron, Chromium, Lead, Mercury, Total Alkalinity, Nitrate, Phosphate, Cadmium, Bicarbonates, Arsenic, Salinity, Cobalt, and Silicon above the Ethiopian standard, WHO, and EPA thresholds for acceptable drinking water quality. Because of the distance and located on upstream of Koshe, the well located in Ayer Tena high school was all most in all parameters, especially in parameters that indicate the impact of leachate on groundwater quality(Arsenic, cadmium, chromium, Lead, Mercury, molybdenum, nitrate, potassium & phosphate) shown significantly low concentration relative to the other wells. The leachate quality analysis revealed an extensive range of different contaminants that affect groundwater quality. Parameters such as; Electrical conductivity (EC), Total suspended solids (TSS), Turbidity, Total dissolved solids (TDS), Dissolved oxygen (DO), Potassium, Sodium, Iron, Manganese, Lead, Mercury, Total Alkalinity, Chloride, Ammonia, Phosphate, Sodium, Boron, Arsenic, Cobalt, BOD, and COD fall in the red category of Effluent & Solid Waste Disposal Regulations SI6 which is referred to as being a high environmental hazard. According to the National sanitation foundation water quality index (NSFWQI), The Weighted arithmetic index method (WAIM), and The Canadian Council of Ministers' environment water quality index (CCME WQI) analysis of the water quality status of groundwater well samples fall in poor quality and unfit to drink category. Nemerow's pollution index (NPI) analysis indicated that the contributing parameters which are responsible for polluting water quality in all groundwater well samples are Hydrogen ion (pH), Electrical conductivity (EC), Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), iron, Phosphate, Molybdenum, Temperature, Bicarbonates, Nitrate, Cadmium, Ammonia, Total Alkalinity, Arsenic, and Mercury. The result of the correlation analysis indicated a strong positive and negative association between parameters at a 0.01 and 0.050 confidence level. The presence of physicochemical parameters such as Arsenic, cadmium, chromium, Lead, Mercury, molybdenum, nitrate, potassium & phosphate in groundwater wells which are located around open dump sites can lead to the conclusion that indicated there is a significant impact of the Koshe dumpsite on the groundwater quality.
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    Performance Assessment of Sewer Network in Addis Ababa: The Case of Kality Catchment
    (Addis Ababa University, 2023-12) Getye Fekadu; Agizew Nigussie (PhD)
    Urban development usually exerts enormous pressure on the existing sewer network systems. The deficiency in the performance of the sewer network becomes one of the most critical issues in the sewer system sector that requires immediate action. Kality Catchment sewer system has problems related to sewer system coverage, manholes overflow, and capacity deficiency. The main objective of this study is to assess the performance of existing sewer network in Kality’s Catchment with respect to pipe capacity (depth/rise), and surcharge using Bentley SewerGEMS CONNECT. Both primary and secondary data were collected and TOOLS such as Arc GIS, AutoCAD, Microsoft Office Excel, and Geographic positioning system (GPS) were used. Model analyses were conducted under three possible scenarios. The wastewater generations for the first and second scenarios were estimated based on water consumption bill data by considering active and potential sewer customers for both scenarios, respectively. Additionally, a projected wastewater generation was derived from land use data for the third scenario. The sewer system coverage in the Kality Catchment was estimated to be 17.63%, showing only the proportion of active sewer customers relative to water customers in the study area. The steady-state analysis of the sewer network, considering peak flow conditions, revealed that approximately 1.01%, 1.49%, and 4.16% of pipes exceeded their capacity (d/D) (>90%) values. This accounts for lengths of 5,415.10m, 7,956.20m, and 22,249.10m for the first, second, and third scenarios respectively. Additionally, approximately 2.88%, 3.74%, and 8.35% of pipes experienced surcharge, accounting for lengths of 15,372.40m, 20,019.10m, and 44,654.50m for the respective scenarios. The pipe capacity (d/D) exceeded when the d/D ratio reached 0.9(90%), and surcharge occurred when the water level rose above 15cm of the manhole rim elevation during peak flow conditions. These locations with deficiencies in both pipe capacity (d/D) and surcharge covered lengths of 1,691.90m, 5,334.80m, and 17,577.50m for the first, second, and third scenarios respectively. It is recommended that the utility upgrade the existing sewer network, as well as expand a new sewer system and connect to the system unserved areas and customers.
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    Development of Rainfall Intensity Duration Frequency Curves for the City of Addis Ababa under the Changing Climate
    (Addis Ababa University, 2023-09) Lideya Abdissa; Agizew Nigussie (Phd)
    Hydrologic design of water management infrastructures is on the basis of specific design storms derived from historical rainfall events available in the form of intensity-duration-frequency (IDF) curves. However, it is expected that the frequency and magnitude of future extreme rainfalls will change due to the increase in greenhouse gas concentrations in Earth’s atmosphere. Developing intensity, duration, and frequency (IDF) of rainfall with the reflection of future climate change is required for designing and managing water infrastructures. Thus, this study presents a rainfall Intensity-Duration-Frequency (IDF) curves for Addis Ababa city under base and climate change scenarios. For this purpose, historical daily rainfall data was collected from Ethiopian National Meteorological Service Agency and bias-corrected CORDEX rainfall data for RCP 8.5 climate scenario was used. Appropriate methods for filling of rainfall data gaps and calculating areal rainfall were employed. Rainfall data tests for independence, stationarity, homogeneity, trend and outliers were also conducted using relevant methods. The data were found to be independent, stationary, homogenous with no trend and outliers. By using EasyFit computer program, the probability distribution that best fits the historical and future rainfall data was selected The Generalized Extreme Value (GEV) distribution was found to be the best fit distribution. Daily historically rainfall and climate scenario data were generated and disaggregated in to hourly basis using the method indicated in ERA Drainage Manual. Expected rainfall quantiles (XT) for 10min up to 180min durations were computed for return periods of 2, 5, 10, 25, 50, and 100 years using general extreme value (GEV) frequency analysis. Future Rainfall intensities under climate change scenario RCP8.5 were found to be greater than the historical rainfall intensities by 27%–79% in the period2010-2039; 37%-88% in 2040-2069; and 55%-104% in 2069-2099.; Hence, intense rainfall events are expected in the future and design of stormwater management systems should take this into account.
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    Effects of Ineffective Wastewater Drainage System on Quantity of Wastewater Reaching Rivers and Treatment Plants in Addis Ababa
    (Addis Ababa University, 2021-12) Sisay, Dula; Geremew, Sahilu (PhD)
    There have been rapid land use change both in the center and in the outskirts of Addis Ababa. However, the existing conventional wastewater drainage system has been in use in the central part for around 40 years while sewer system has not yet developed in the expanding residential areas. In view of that, this research was conducted to identify how ineffective existing sewer system and onsite wastewater management facilities are contributing for the discharge of untreated wastewater into rivers in addition to assessing inflow and infiltration quantity in the existing sewer. For these purposes, Senga Tera and Tulu Dimtu study areas were selected to represent urban densification and urban expansion respectively. The existing land use plans of both areas, and as-built data and sewer master plan for the existing sewer system were collected and reviewed. Flow rate were manually measured at selected manholes on field for model calibration in addition to analyzing six months of ArcGIS water use data’s. Moreover, the number of stories and floor areas of high-rise buildings which are now under construction were surveyed in Senga Tera. Similarly, field research was conducted to identify the existing onsite wastewater management facilities inTulu Dimtu. Then, steady state analysis and modeling for the existing sewer system and for the proposed nonconventional sewer system in Tulu Dimtu were conducted using Sewer GEMS V8i. Accordingly, it was revealed that 87% and 53% of the existing manholes in in Senga Tera could be surcharged and overflowing due to rapid land use change during wet weather season respectively. It was also found that around 15.59 l/s of wastewater was cross connected into the nearby storm water drainage system. As a result, overflows and leakage through the walls of the existing cesspools in Tulu Dimtu and Sanitary Sewer Overflows (SSOs) from manholes and sewer cross connections in Senga Tera area have been found to be factors for the discharge of untreated wastewater first into the nearby storm water drainage system and then outfall into nearby rivers. Moreover, the quantity of average inflow and infiltration which was estimated in Senga Tera was around 71%. This in turn could contribute to induce SSOs on the existing sewer system in addition to become a factor for the hydraulic overloading of the existing Kality Wastewater Treatment Plant. Therefore, it is recommended to enhance the existing sewer system through master plan review and to use non- conventional sewer system instead of cesspools in the expansion areas.
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    Optimum Coagulant Dose Prediction for Water Treatment using Artificial Neural Network (Case of Legedadi Water Treatment Plant)
    (Addis Ababa University, 2022-04) Eyerusalem, Alemayehu; Agizew, Nigussie (PhD)
    Water obtained from surface or subsurface sources is crucial for life. But direct use of raw water has serious health risks. Different water treatment processes can be used to make the raw water safe for domestic purposes. Coagulation and Flocculation is one of the treatment stages used to remove colloidal particles through the use of chemicals (coagulants) that enable the formation of larger flocs that can be easily removed by sedimentation and filtration. Determination of the optimum coagulant dosage is important to meet the required water quality. For instance, a high coagulant dosage may lead to high residual chemical in the treated water, high sludge volume, and increased load on the filter units. All these can result in poor water treatment performances, high operational costs, and process complications. Jar test has been used widely to determine the optimal coagulant dosage for a given water quality. However, this practice has some drawbacks such as it is time-consuming, the probability of making errors is high and it is impractical for highly variable raw water turbidity. Consequently, the need to develop new tools and techniques to determine optimum coagulant dosage becomes important. However, quantifying the relationship between the process inputs and output in the water treatment unit process is very difficult with the existing process model. Thus, Artificial Neural Network was used to develop the models in this research as it is a robust technique that allows the development of a multi-variable and complex non-linear relationship. ANN Multi-Linear Perceptron type with one hidden layer was used to simulate the jar test for the optimum coagulant dosage forecasting. Two models were developed and their performances were evaluated based on Root mean squared error (RMSE) and coefficient of determination (R 2 ). The first model which enables prediction of turbidity for a given coagulant dosage and other factors was the process model. The second model which allows determination of optimum coagulant dosage to attain the desired turbidity level is the Inverse Process Model. The RMSE and R 2 values were found to be 0.0748 NTU and 0.6121, respectively for the Process model. For the Inverse Process model the RMSE and R 2 values were found to be 0.225mg/l and, 0.9823, respectively. These indicate that a good performance of the ANN-based model to simulate the jar test could be obtained. The models can be used to optimize the coagulation process within the available raw water turbidity range of Legedadi Water Treatment Plant.
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    Assessment of reasons for Yield Decrease of Water Wells in Akaki Well Field based of Design, Construction and Operation
    (Addis Ababa University, 2022-03) Bethelhem, Kena; Mebruk, Mohammed (PhD)
    Groundwater is of paramount importance for the city of Addis Ababa and the majority of the groundwater supplied to the city comes from drilled wells in and around Akaki-Kality sub city. Even though numerous water wells are built over the years, the majority of the wells fell to provide anticipated design yield. The study mapped 70 wells found in Akaki Phase I, Akaki Phase II, Akaki Phase IIIA & Akaki Phase IIIB on ARCMAP to see the spatial distribution of wells and their performance over the years. From the map, some wells were observed to perform better than their neighboring wells and some wells were found to perform worse than the neighboring wells. Therefore the research engrossed in understanding the reason behind this phenomenon mainly by focusing on the design, construction, and operation of selected wells from all phases of Akaki well field. The selected 35 wells were grouped in accordance with their performance. Data from the well-completion report was organized and analyzed to identify the possible reason for the decrease in yield. Parameters used to compare the grouped wells were depth, elevation, screen arrangement, geologic medium, filter material used, construction process, year of construction, and the drilling contractor. The result showed bottom elevation of some better performing wells is deeper than those in a worse condition which means they are tapping water from a deeper aquifer. Another finding was 60% of the study wells have 30-50% of their casing screened. Some wells perform worse than their surrounding wells because their screened section is lower. For these wells, it can be suggested to increase the screen section in accordance with the water-bearing formation. From the analysis done using the Cooper Jacob method, it was found that the majority of the wells are developed within the radius of influence of one another meaning pumping water from one well is affecting the neighboring wells. Another finding of the research is the drawdown result from single and multiple well tests which showed 100% of the wells are being affected by the surrounding wells which supports the result obtained on the radius of influence of those same wells.
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    Assessment of Pipe Failure Causes (Case Study on Chiro Town Water Supply Distribution System), Ethiopia
    (Addis Ababa University, 2021-09) Masho, Dekamo; Geremew, Sahilu (PhD)
    Intermittent water distribution is the key problem of many water authorities in developing countries including Ethiopia. Hence, this research was conducted to carry out a risk assessment of water supply pipe failure (burst) in the water supply system of Chiro town which is located in the eastern Oromia Region of Ethiopia. To investigate the cause of pipe burst in the town water supply distribution network, physical, pipe installation condition investigations of the distribution system and water GEMS modeling were utilized. Chiro town water supply distribution system was constructed in 2013 to 2015. More pipes were laid from 2014 to 2015 especially uPVC pipe and HDPE, but more pipe bursts were observed in uPVC pipe and HDPE pipe. According to pipe failure (burst) history recorded in the town water supply distribution system, more types of pipe burst were found in plastic pipe (uPVC pipe and HDPE) than the other types of pipe (DCI and GI pipes). The water supply distribution piping is mainly of plastic pipes (89.17%) and 10.83 % other types. According to Chiro town’s water distribution system, the investigation of the factors causing pipe failure in the system was based on considering three factors (pipe condition assessment) such as physical factors (types of pipe materials, pipe diameter, pipe installation years), environmental factors or pipe installation conditions (pipe cover, pipe bedding and backfill practiced conditions) and hydraulic parameters (internal water pressure, transient pressure and also velocity). As per the research results, the main causes of pipe burst in the water supply system were the type of pipe materials and its PN, water pressure, poor pipe installation practices, absence of selected material pipe bedding specially at rocky area and also absence of sufficient pipe cover and back fill for plastic pipe or uPVC and HDPE pipes. In general, frequent pipe burst in the system leads to water losses and this contributes to interruptions (intermittent) of water supply in the town. Based on pipe condition/situation assessment and the relation between the parameters which contributes to pipe failure, identify which parameter/s are more related to the cases of pipe failure than the others and develop equation based on their relationship of the parameters with the probability of pipe failures. This is significant to rehabilitate /replacement/repair and improve the reliability of town water distribution system and providing more attention to pipe burst reduction strategies which are vital for remedial measures.
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    Comparative Assessment of Low Impact Development Controls on Flood Mitigation (The Case of Wollo Sefer to Gotera Route, Addis Ababa)
    (Addis Ababa University, 2021-11) Biniam, Berhe; Geremew, Sahilu (PhD)
    Urbanization alters hydrological cycle and increases runoff by changing permeable surfaces into impermeable ones. In Addis Ababa, which is found in Awash catchment; rapid urbanization and development is altering permeable surfaces into impermeable ones; including impermeable roof surfaces. This phenomenon lowers the capacity of the land to infiltrate and store stormwater, and contributes in increased runoff volume and rate; causing flood damage as a result; which is not adequately managed by the current conventional drainage systems of the city. The study area which is the route from Wollo sefer to Gotera is one of the areas found in the city affected by flood due to immense urbanization. By decreasing runoff volume and increasing storage and infiltration, Low Impact Development (LID) practices are capable of minimizing and even avoiding flood risk if integrated with the existing drainage system. The objectives of the study are, evaluating the performance of the existing drainage system of the study area, apply four hypothetical LID controls (bio-retention cells, rain barrels, green roofs, and permeable pavements) to see the difference, comparing the LID controls on the basis of avoiding flood with a minimum area of application, and selecting the feasible one using storm water management modeling (SWMM) tool. The study revealed that the area has eleven subcatchments and flooding problem exists in it; because the drainage system is not found to adequately prevent this issue solely. Calibration of the model resulted in R2 = 0.9714, and RMSE = 4.867; which proved a good agreement between the model and the actual values. Trials and errors testified that the minimum area on which LID controls can be applied to avoid flood risk was 58320m² (36%) of the area of the third subcatchment. If the aforementioned LID controls except green roofs were applied on such an area, flood problems would be avoided. Since, building areas were found to cover 60% of the third subcatchment, rain barrels were chosen as the feasible LID controls that can be installed on the least area possible to avoid flooding problems.
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    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.
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    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.
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    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.
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    Utilization of Underground Solid Waste Management System for Addis Ababa City, Ethiopia: Case study on ‘Lideta’ Sub-City Condominium
    (Addis Ababa University, 2021-05) Mahlet, Abreham; Mebruk, Mohammed (PhD)
    Managing wastes has become a problem especially in highly urbanized areas. There are a lot of human activities that contribute to waste generation. If these waste materials failed to be disposed in the proper manner and in the proper place, create a serious problem to humans and threat to nature. Solid Waste Management plays a big role on the preservation of life and nature. Ethiopia is considered as the tiger economy of Africa for its fast growth and development, this advancement also affects a solid waste management. There had been some attempt to implement policies to promote proper solid waste management. This study is concerned on the implementation of underground waste management system for a more efficient, economical and environmentally-friendly waste management solution. Design of UGSWM has been proposed based on varies parameter including solid waste generation, number of population, area of existing bin, number of building. Analytical formula are applied to compute different solid waste rates. A case study is conducted for reasonably selected (i.e., Lideta sub city condominium) site and proper design had investigated to meet the required objectives on various components of the system used for installation process. In conducting this study, interview questionnaires were answered by 60 household residents, 2 hospitals and 6 business/commercial establishments’ respondents of Addis Ababa community. The survey was conducted to gather information on the knowledge and practices respondents have on solid waste management. The awareness of the residents in the Addis Ababa about solid waste management is low. The practices and compliance of residents indicates the knowledge and training they have acquired. Solid waste management is a human obligation to fulfill. The inefficiency and failure to sustain proper solid waste management is a societal, environmental, economic, and political issue. This paper concludes that a truly integrated solid waste management system could be realized by implementing underground solid waste management and should be implemented to Addis Ababa city to ensure for healthy environment, economically.
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    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.
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    Removal Efficiency of Chromium Using Coffee Husk Activated Carbon in Hawassa Industrial Park Waste Water Treatment
    (Addis Ababa University, 2021-02) Mihretabe, Negash; Alemtsehay, Gebremeskel (PhD)
    In this study, the potential of activated carbon coffee husk for removal of chromium were examined. The influence of contact time, PH, adsorbent dosage, initial concentration and adsorption equilibrium were studied at batch experiments at room temperature. The modification process was done by treating the coffee husk with different chemicals and activation. Maximum sorption was found to be at pH 2. The biosorption was rapid for the first 45 minutes of contact, removing more than 75% and equilibrium has attained in 120 minutes. Kinetic studies demonstrate good correlation coefficient (R2) for a pseudo second order kinetic model. The biosorption capacity was found to increase with higher initial Cr( VI) concentration and lower solution pH. Langmuir model fitted the equilibrium data better. The calculated biosorption free energies from the D-R isotherm model indicated that the biosorption process proceeds via chemisorptions. Optimization using response surface methodology (RSM) indicated an initial metal ion concentration, solution pH; biosorbent dose and contact time played an important role for the biosorption of Cr (VI). The study concluded that coffee husk activated carbon could be applied as a low cost alternative biosorbent to remove Cr (VI) from aqueous solution.
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    Assessment of Storm Water Drainage System Performance of Mojo Town, Central Ethiopia
    (Addis Ababa University, 2020-12) Mezmur, Hawaz; Geremew, Sahilu (PhD)
    The main objective of this study was to assess the existing storm water drainage performance of Mojo town and to provide the possible recommendations or engineering measures that enables to alleviate the prevailing problems. Storm Water Management Model (SWMM), which is a dynamic rainfall runoff simulation model widely applied for urban drainage, was chosen for the performance evaluation to assess the triggering factors as well. The model was developed based on a selected area of 354 ha, that has been a flood prone area mainly due to the construction of two mega projects. The model area is divided in to 45 sub catchments with a drainage network of 94 conduits, 74 junctions and 2 outfalls. Three important inputs for the model were organized: Rainfall, infiltration and physical characteristic of the model area. 1. Rainfall depths of twenty-one years (1997-2017) of Mojo metrology station were obtained from National Metrological Agency. An IDF curve for different return periods (2,5,10,25,50,100yrs) formulated by Log person type III distribution method was used as an input for the model due to its slightly better coefficient of determination than Gumbel method.2. Infiltration of the model area is represented by Green-Ampt equation.3 Physical characteristics of the sub catchments including topography of the model area was analyzed using Global mapper, ArcGIS software. Besides, three successive Google earth images were used to analyze the land use land cover change of the model area through 11 years (2009-2019) period. Based on the inputs the model is built and model parameters were derived based on characteristics of the sub catchments and drains infrastructures. According to the sensitivity analysis, catchment width and Manning roughness coefficient for pervious areas were found the most sensitive parameters. Three drains (D_48, D_89 & D_90) were selected for calibration and validation. Three rainfall event observations for calibration and one event for validation were used on the two most sensitive parameters until the simulated and observed values reached at acceptable level. The performance of SWWM is insured based on an evaluation that is made by coefficient of determination (R2) and Nash-Sutcliffe Efficiency Coefficient (NSE). The model is simulated for one rainfall event, for different return periods and 3 hours rainfall duration. According to 10 years return period of simulation regarding storm water discharge, 25 conduits and 28 junctions were flooded which is 27.0 % and 37.8% respectively. An increment in terms of Peak runoff, total runoff & peak discharge is observed due to LULC change. The other important issue is a significant proportion of the drainage system is subjected to below 0.9m3/s flow velocity that insists deposition of solid material in drains which affects the system performance. Among the various low impact development (LID) structural measures, Bio retention and Infiltration trench are incorporated and simulated in the model. Based on 10 yrs & 25 yrs return period simulation for LID, improvements in terms of peak discharges decrease and elongated peak time discharge were observed where LID is applied. Regarding 10 yrs period ,the magnitude of peak discharge of drains is decreased with the minimum of 1.5% and maximum of 35.1.Generally, the drainage system of the town is not suffice for the runoff generated from the town because of intensive land use/land cover (LULC) change as well as lack of green areas in required proportion. The major source of overflow of drains is highly related to the construction of the two mega projects. Minimum flow velocity, which is below cleansing velocity, is the other problem that affects the drainage system performance. In terms of quality, different studies verified that storm water of Mojo town is highly polluted due to mainly industrial pollution. This study mainly recommends proper implementation of the town master plan in such a way to regulate reasonable land use land cover. Redesigning of drains and related drainage infrastructure is critically required in such a way to meet the minimum limit of flow velocity and to use as remedy for the problem of overflow of drains. Diversified application of structural and nonstructural measures of LID help to alleviate the prevailing drainage problem of the town.
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    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.
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    Hydraulic Performance of Gimbi Town Water Distribution Network
    (Addis Ababa University, 2020-01) Lencho, Legese; Fiseha, Behulu (PhD)
    Assessment of hydraulic performance of water supply distribution system to address water distribution bottlenecks within an urban water supply system is important. This can be achieved through investigating the status of the existing distribution system of the network. The main objectives of this study is to assess sustainability and to identify the challenges of Gimbi town WDS. The major problem found in this area is bursting and leakage problem of the pipe system in the distribution network resulting the system to deliver insufficient amount of water to the consumer. To examine the hydraulic performance of the water distribution network, water GEMS modeling was used and the model result is compared with the allowable pressure value and velocity in the distribution system. From the hydraulic analysis all of the velocity in the system is less than 0.6 m/s. It is also identified that 48% of the Nodes in the distribution system has maximum pressure head above 70m and 1% of the Nodes has minimum pressure less than15m. From the detailed analysis, the estimated current (2019) maximum water demand of Gimbi town is 5351 m3/d (62 l/s). However, the current (2019) existing surface horizontal centrifugal types of pumps has only maximum capacity 20 l/s. Further, the analyzed water losses result in Gimbi town indicates that about 55% of production is non-revenue water and 60% of non -revenue water is estimated as a real lose. In general, rising in water demand, small capacities of existing pump and large volume of water loss leads to intermittent water supply in Gimbi town. Hence, most of resident are not satisfied from the town water service. To solve this problem, it is significant to rehabilitate the old pipe from distribution network that are more vulnerable by the current pressure and providing pressure reducing valve in the link having high pressure in distribution network to minimize the pressure to an acceptable level that reduce water losses in the distribution network. Accordingly, installation of 4 PRV in the model at different location in the distribution network reduces the system pressure to an acceptable range of pressure value (15m-70 m). Providing water pump that deliver the current maximum day demand of the water (62 l/s) for the town solves water scarcity in the town. Finally, it was recommended for water utility to give more attention to water losses reduction policies and strategies to minimize water loss in the town.
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    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
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    Impact of Flood in Urban Drainage System and Identifying Cause of Storm Water Flooding: - The Case of Gurd Shola Area
    (Addis Ababa University, 2021-03) Assmamaw, Assefa; Mebruk, Mohammed (PhD)
    Disasters like flooding have changed dimensions of urban areas. The urban flooding in cities is mainly in the form of flash floods and water logging of streets due to high intensity short spell rainfall. But the levels of damage to these disasters have increased over time in the urban areas because of increased rainfall runoff volume. However, it is clearly evident that different level of exposure and different extents of flood hazard characteristics vary the urban flood risk nature from city to city. Addis Ababa is one of the fastest growing cities in Africa and urbanization is known to increase the amount of runoff generated from the urban catchment. Due to urbanization and lack of proper design and management, the city’s’ transport infrastructure has experienced frequent flooding. The objective of this research is to identify the drainage condition of Gurd shola area, which is one of the villages found in in Addis Ababa with respect to the hydrology, hydraulic and operation and maintenance features. In this study, the impacts of important factors on flooding in urban drainage system of Gurd Shola area were evaluated using primary and secondary data collection systems. For the analysis of rainfall data and their probability distribution Gumbel and log Pearson’s III distribution statistical methods were used. In order to see the impact, runoff coefficient for different time interval year 2004 and 2019 was used and also the rainfall intensities for different duration was analyzed for a period of 1988-2017. The rational formula and Bentley Civil Storm software were used to compute the peak flood estimation for (T= 10 years) and to determine the hydrological peak flow respectively. The analysis from the frequency distribution indicates that Gumble Extreme Value distribution was to be a good fit. The finding of the study shows that, the flooding problem mainly arises due to improper cleaning and storm water management. Slops also should be clearly checked in order avoid unwanted storm water accumulation on the road surface.