Environmental Engineering

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    Assessment of the Current Solid Waste Management Practice; Case Study of Bishoftu Town, East Shewa Zone of the Oromia Region, Ethiopia
    (Addis Ababa University, 2024-05) Mahelet Admassu; Birhanu Assefa (PhD)
    The success of waste management requires reliable data on waste generation and composition, which is critical for making decisions about the best waste management system. There is currently no data on Municipal Solid Waste (MSW) generation and composition collected in Bishoftu town. In order to provide baseline data for the establishment of a municipal solid waste management system, the primary goal of this study is to analyse the rate of generation and composition of municipal solid waste. The samples were collected from the household from 4 Keble’s and from different commercial activities like hotels, resorts, restaurants and cafeterias, open market, super market and mini markets found in the town. The collected sample was sorted out in to various components. Subsequently, the weight of each component were measured and recorded. The daily generation of MSW works out to be 0.31 Kg /day/person with a density of 306 Kg/m3.The study results reveal that the MSW stream has the largest proportion of biodegradable waste (69 %) followed by other waste (18 %) containing ash material and different solid waste types. From the socio-economic analysis, middle socioeconomic group and lower socioeconomic group generate more waste due to more family members and energy type used for cooking while socioeconomic characteristics like education level, occupation, age, gender, and housing condition have no relationship with solid waste management practices. Understanding the movement of waste in an urban area is crucial for identifying the main problems and opportunities for improvement in the efficient handling of waste. Assessment instruments like material flow analysis (MFA), a technique that is widely used in waste management research, offer an organized and objective assessment procedure to best describe the waste management system, identify its strengths and weaknesses, and suggest feasible alternatives. In order to assess the current waste management strategy used by the City of Bishoftu, this study uses material flow analysis. Due to the waste's high organic content If waste management options such as composting and recycling are implemented in the future, there is a greater possibility of reducing the amount of waste stream that is disposed of in landfills as well as lowering greenhouse gas emissions, which is a current global issue. By composting 50 % of the waste designated to the disposal site 47.9 % of resource is managed which have an increment of 78.1 % than the current SWM practice and a total reduction of 35.35 % in GHG emission.
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    Statistical Optimization of Electrooxidation Process for the Removal of Paracetamol from Synthetic Wastewater
    (Addis Ababa University, 2024-03) Bereket Adinow; Shimelis Kebede (PhD)
    Over the past few decades, there has been a growing interest among researchers and scientists worldwide in removing toxic substances from wastewater. Micro pollutants, in particular, have become a major public concern due to their ability to accumulate in the environment, their carcinogenic properties, and their harmful effects even at low concentrations. In this particular study, the focus was on degrading and mineralizing paracetamol, a commonly found micro pollutant, in synthetic wastewater using the electro oxidation process. To achieve this, a Ti/IrO2 coated anode and a stainless-steel cathode were utilized, and the efficiency of paracetamol removal was measured by analyzing changes in absorption spectra using a UV-VIS spectrophotometer. The researchers conducted preliminary experiments to understand the impact of various operating parameters, such as pH, paracetamol concentration, electrode distance, and current density, on the efficiency of paracetamol removal. Once the individual effects were studied, the interaction effect of these parameters and optimized them using a statistical tool called central composite design (CCD), which is a type of response surface methodology (RSM). This allowed them to determine the optimal conditions for the electro oxidation process. Based on the findings of this study, it can be concluded that the electro oxidation process using a Ti/IrO2 anode and a stainless-steel cathode presents a viable alternative treatment technology for mitigating the environmental issues caused by paracetamol contamination. The oxidation process was carried out within a pH range of 3-5, a current density range of 5-7 mA/cm2, an electrode distance range of 1-2 cm, and an initial paracetamol concentration range of 20-50 mg/L. Through the optimization process, it was found that 97.3% of paracetamol could be removed at an optimum pH of 3.7, a current density of 6.47 mA/cm2, an electrode distance of 1.12 cm, and an initial paracetamol concentration of 21.14 mg/L. However, even under these optimized conditions, only 60% of the average total organic carbon (TOC) could be removed after 40 minutes of electrolysis.
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    Electrolytic Silver Recovery from Photographic Fixer Solution: Berhanena Selam Printing Enterprise
    (Addis Ababa University, 2023-05) Selamawit Teshome; Abubeker Yimum (PhD)
    The goal of the study is to develop an electrolysis process for recovering silver from waste photographic fixer. Brehanena Selam Printing Enterprise provided the samples for the investigation. The experimental runs are randomized, and suitable software is used for the analytical process. Portal for Design Expert 6.0.8: Box-Behnken Design was used during this study statistical method of surface response methodology (SRM) was used for analyzing of laboratory result of silver recovery. The amount of the variable used in the study was selected after considering the effects of each parameter on the results. Ph (4-8), current density (2-5), and time (20-90).17 different laboratory experiments were carried out within these specified ranges. ANOVA results, fitness graphs, and 3D graphs of operational parameters were examined using BBD (Box-Behnken Design) of RMS (Response Surface Methodology) and fit summery and also XRD analysis and XRF analysis. The three parameter investigated that the result showed pH at 6 and current density at 5A and contact time at 1:30hr gives silver yield of 97.295%. This is my optimum result. So the result of the study showed that electrolysis process on silver recovery from photographic waste is technically feasible.
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    Cleaner Production Assessment in The Ethiopian Alcohol Industries A Case Study in The Sebata Alcohol & Liquor Factory
    (Addis Ababa University, 2007-07) Belay Teffera; Berehanu Assefa (PhD)
    Sebeta Alcohol and Liquor Factory (SALF) is a sister company of National Alcohol and Liquor Enterprise (NALE). The factory was established in 1914 in Sebeta town and uses molasses as raw material for the production of potable and technical alcohols. It consists of a distillery and filling plants. Its installed daily production capacity is 2500 liters of potable alcohol and about 5000 liters of various liquors. The current production capacity was found to be on average 2100 liters of 95.7oGL potable (fine) and 250 liters of 93oGL technical alcohols per day when the factory was running normally. Water balance, material balance and energy balance were drawn only for the distillery plant for the filling section was under maintenance during sampling. The molasses, water and energy consumption were found to be 6.3 kg, 168 liters and 22.12 MJ liters per liter of 96oGL alcohol. The average BOD, COD and TDS in the wastewater were 20,866, 53,514 and 19000 mg/l respectively. The total alcohol loss from the fermentation, decantation and distillation process units was significant with the value of 13.22 %. The stillage from mash column is found a severe source of water pollution. The fermentation efficiency (78.02%), alcohol recovery at distillation unit (83.3%) and overall alcohol conversion efficiency (65.0%) were found to be low compared to values of similar technologies in India, South Africa and Brazil. The steam generation and distribution systems were studied and the boiler combustion efficiency was found extremely low (29%) resulting from excess air supply. Similarly, other sources of heat loss were identified and carefully examined The cleaner production options were generated, selected and evaluated for the distillery plant. CO2 Recovery, Cooling water recycling, lost heat recovery in the stillage and spent lee, indirect heating, generation of methane and fertilizer from stillage were considered for improving resource utilization and reducing pollution loads. Other GHK practices were recommended to bring overall efficiency in the plant.
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    Coupling Bio-electro Hetero-Fenton Oxidation Processes for Textile Wastewater Treatment
    (Addis Ababa University, 2023-12) Redae Nuguse; Hyunook Kim (Prof.); Joon Wun Kang (Prof); Shimelis Kebede (PhD)
    Discharging colored industrial wastewater effluents into natural water bodies is one of the main sources of environmental contamination globally and locally. The textile industry is one of the main water consuming and wastewater producing industries that needs serious attention. Conventional industrial textile wastewater treatments are not designed to treat emerging organic dyes (EODs). These compounds mainly remain unaffected even after the secondary biological treatment processes. Advanced oxidation processes (AOPs) are thought to be a successful and promising method of removing EODs. These processes rely on in situ liberation of reactive oxygen species (ROS), which have an active role in the degrading of EODs. The integration of wastewater treatment systems, which calls for knowledge in interdisciplinary domains, is a current focus. Although integrating wastewater treatment systems are challenging endeavors in the field of wastewater technology, various coupled systems have been developed. For example, systems such as bio-electrochemical system (BES) and electro-Fenton systems (EFS) for oxidation combine biological and electrochemical processes. The objective of the study was to combine the high oxidation power of EFS and cost-effectiveness of BES to oxidize textile wastewater effluents. Hence, a coupled system of BES-EFS oxidation system was developed in four phases to optimize the treatment process and offer a potential solution to oxidize EODs. To begin, different sized Fe3O4 nanoparticles (INPs) were synthesized using modified co-precipitation method. The synthesized INPs (C, S, and M) possessed an average hydrodynamic diameter of 23, 17 and 48 nm with a saturation magnetization of 76 ± 2.4, 79 ± 2.6 and 66 ± 2.8 emu g 1 respectively and fluidized microelectrodes were prepared from each INPs (C, S, and M). The fluidized electrodes were tested for catalytic degradation of Acid orange 7 and 89.4 ± 1.7%, 93.2 ± 1.5% and 83.7 ± 2.3% degradation efficiency was determined respectively. On a second phase, a carbon felt (CF) was activated to synthesize activated functional cathode (ACF). The cathode was checked to have carboxyl functional groups (-C =O-OH) to drive H2O2 generation during EF oxidation. The selectivity of ACF toward H2O2 generation, i.e., two electron oxygen reduction reaction (2e-ORR) was estimated to be more than 89 ± 3.1%. Over 40-min of EF reaction test and 94.3 ± 1.7% removal efficiency for Congo red (CR) was achieved. Similarly, total organic carbon (TOC) and mineralization current efficiency were achieved as 82.7 ± 2.8% and 58 ± 2% over 40-min, respectively. The chemical quenching, LC-MS and IC analysis confirmed the role of ∙OH and O2-. radicals in CR degradation into NO3- and SO42- ions. On third phase, functional composite electrode (Fe3O4/CNT/ACF) was synthesized and characterized. Fe3O4 and carbon nanotubes (CNTs) were used as surface modifiers, i.e., to ease charge-transfer by forming multilayered channels and to enhance the thermal and structural strength of the electrode respectively. Using Fe3O4/CNT/ACF cathode, 93.7 ± 3.7% methylene blue (MB) removal was obtained within 1 h, following 2.7  10−2 M−1 min−1 pseudo-second-order rate kinetics. Based on TOC analysis, 57.8 ± 2.9% of MB could be mineralized. On fourth phase, a four-electrode-based coupled BEF system with ACF and iron strips as cathode and anode of BES and polarizable Fe3O4@ACF and iron strip as cathode and anode of EFS was developed. Methyl orange (MO) was used as a model pollutant for oxidation. After stabilization of the BES about 275.23 ± 9.4 mW cm-2 power density was generated, which could drive the EFS. At 20 mg L-1 of MO concentration, an external resistance of 100 Ω, a catholyte pH of 3.5, and an aeration rate of 300 mL min-1, 82.5 ± 4.3% removal efficiency was achieved over 40 hours. Simultaneously, sewage wastewater was oxidized and accompanied with TOC, COD and NH4+-N removal efficiencies of 67.4 ± 3.6%, 71.2 ± 3.8% and 69.3 ± 3.7%, respectively. The results showed that the coupled BES-EFS system achieved satisfactory MO oxidation efficiency, indicating the synergistic effect of combining these two systems. Finally, the BES-EFS system was assessed for actual textile wastewater degradation which showed to be an effective system for industrial applications. Thus, the overall study provides an insight for an innovative mechanism of well-performing and easily recyclable composite electrodes and stable BEF system for degradation of recalcitrant EODs.
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    Removal of Lead Metal Ion from Paint Industries Wastewater by Mango and Avocado Seed Waste
    (Addis Ababa University, 2024-02) Tseganesh Kegne; Belay Weldeyes (Prof.)
    In this study, the effectivity of Mango and Avocado Seed Waste as an adsorbent an inexperienced science in the removal of lead metal ion from paint industry wastewater is analyzed. The adsorbent was once characterized the use of physico-chemical residences such as moisture content, ash content, volatile matter and iodine number. The surface morphology of mango and avocado seed adsorbent was once characterised with the aid of SEM, FTIR and BET. Experimental consequences confirmed that mango and avocado seed adsorbent may want to operate successfully inan extensive vary ofexperimentalconditions.Thewastewatersamples havebeen physicochemically characterized earlierthan andafter remedy inaccordance to well-known system the usage of mango and avocado seed adsorbent. Batch adsorption experiments have been performed to consider the impact of contact time, pH and adsorbent dose of adsorbate had been studied, and the adsorption isotherms and kinetics of on Pb (II) elimination have been determined. To set up optimal adsorption conditions, Design Expert version 13 Software was once used. To decide the ultimate setting, a central composite design under response surface methodology to be used. The most elimination effectivity of Pb2+ions through mango and avocado seed adsorbent used to be got most advantageous pH 5.5, foremost adsorbent dose of 1.25g, and the most advantageous contact time of 120 min; in these highest quality stipulations the elimination effectivity was once 99.5%. The effects have been additionally verified that the adsorption method follows Langmuir isotherm model with a higher sorption fit and supported for the monolayer adsorption of Pb+2ions on mango and avocado seed adsorbent. The kinetic model of this learn about indicates a pseudo-second order kinetic model with top correlation coefficient. Based on the outcomes obtained, the mango and avocado seed adsorbent produced from Mango and Avocado Seed waste has a suitable functionality in elimination of the lead metal ions from the Paint industry wastewater.
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    (Addis Ababa University, 2023-07) Alemshet Ghion; Zebene Kifle (Prof.)
    the objective of this study was to investigate the lead (II) ion removal efficiency of modified kaolin (zeolite X) from wastewater. By using batch experiments, zeolite-X was synthesized, characterized, and applied to adsorb lead from wastewater. In this study, the synthesis of zeolite-X was performed at 600 0C for 1 h in a muffle furnace from kaolin formed as meta-kaolin and then mixed with NaOH. The adsorbent was characterized using XRD, FTIR, SEM, and BET. The concentration of the lead ion was determined using atomic absorption spectrophotometer (AA 2400FS Varian. The XRD revealed that zeolite-X synthesized has a faujasite (FAU) phase, composed of cubic, rectangular, and irregular crystallite shapes as seen by SEM. The FTIR analysis revealed the presence of functional groups Si-O bonds associated with zeolite. The BET analysis show that the adsorbent is porous and has good surface area to adsorb lead. The effects different factors on the Lead (II) ion removal efficiency was studied in batch adsorption experiments. Results show that Lead (II) ion the removal efficiency of the prepared adsorbent was dependent on the pH, contact time, adsorbent dosage and Lead (II) ion initial concentration. Experiment results showed that maximum removal of lead (II) ion by zeolite-X at optimum condition ( 5.2 pH, 51.8min contact time, 4.506 g adsorbent dose and 12.8mg/L initial concentration of lead(II)ion) is 98.2 %..Adsorption data were interpreted in terms of Langmuir and Freundlich isotherms. It was observed that the experimental data fitted better to Langmuir model with a correlation factor (R2) value of 0.99996 compared to Freundlich with R2 value of 0.85075and the maximum adsorption capacity of the material was 39.67 mg of Pb/g of zeolite-X. The kinetic processes of Lead (II) ion adsorption on zeolite -X were described by applying pseudo-first-order and pseudo-second-order kinetic models. The kinetic data for the adsorption process obeyed a pseudo-second-order kinetic model with regression coefficients value of 0.999561, suggesting that the adsorption process is chemisorption. The synthesized zeolite -X showed good potential for the removal of Lead (II) ion from aqueous solution and it also removes lead (II) ion from the real Nefas silk paint industry waste water about 90.9%.
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    Biogas Production from Mixture of Water Hyacinth and Tannery Flesh Waste Using Inoculum from Cow Dung
    (Addis Ababa University, 2021-12) Wondmeneh, Hadgu; Jabasingh, Anuradha (PhD)
    Disposal of untreated tannery wastes into land and water bodies results in water pollution and air pollution which in turn leads to greenhouse gases. With increased emphasis on climate change mitigation, waste management and, re-use of waste as a resource new environment friendly technological approach such as anaerobic digestion has received increased attention. This research presents the experimental results of anaerobic digestion of tannery solid waste and water hyacinth in different proportions. Four bench scale anaerobic digesters with different feedstock composition of 100%, 75gram:25gram, 50gram:50gram, and 25gram:75gram (Tannery solid waste to Water hyacinth) have been used in the experiment. The retention time of the experiment ranged 82 days for the digester containing 75gram Tannery solid waste and 25gram Water Hyacinth at ambient temperature of 37 o C and pH of 7. Estimation of biogas produced and its quality was determined by the water displacement method using the biogas analyzer for each digester. It was found that, the highest volume of biogas was 6540Lit and with a methane content of 72.05% this produce produced by the digester containing 75% Water Hyacinth waste and 25% tannery solid waste. The lowest biogas concentration (2540Lit) of methane concentration 68.06% was produced by digester containing tannery solid waste alone.
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    Study on the Competitive Removal of Heavy Metals (Cr+6 and Pb+2) from Wastewater By Using Activated Coffee Husk
    (Addis Ababa University, 2022-02) Godana, Dese; Shimelis, Kebede (PhD)
    Due to the release of toxic heavy metals from various industries, water pollution has been a major challenge to environmental engineers today. Among various heavy metals, Pb(II) and Cr(VI) are considered as highly toxic due to their carcinogenicity and various health disorders. This study aimed was to investigate the competitive removal of heavy metal ions (cr+6 and pb+2) from aqueous solutions by using activated carbon prepared from the coffee husk. The initial work involves the optimization of process parameters involved in the preparation of activated carbon by chemical activation using H3PO4. The effects of activation temperature and concentration of H3PO4 at 2h contact times on the yield and MBN of prepared activated carbon were investigated. The highest yield (73%) of activated carbon was obtained at 400 0C temperatures and 30% H3PO4 concentrations while the highest removal efficiency (52%) was observed at 600 0C temperatures and 30% H3PO4 concentration. The prepared activated carbons were characterized for different physicochemical properties. The surface and structural properties of the adsorbent were studied using FTIR spectrometer and X- XRD analysis. The characterization result showed that the coffee husk-activated carbon has good properties and is compared favorably with other reference activated carbons. A series of batch adsorption of Cr(VI), as a single component, on ACs were carried out and the effect of experimental parameters on the removal efficiency were studied. The maximum removal efficiency of Cr(VI) was 98.1%. The competition of ions to active sites was studied and the result showed that the removal efficiency of Cr(VI) from binary solution was decreased to 94.77% compared to the removal efficiency (98.1% ) of Cr(VI) as a single component at the same conditions. The linear form of Langmuire and Freudlich models were applied to analyze adsorption data and the equilibrium data of Cr(VI) were well fitted to Langmuir isotherm model with R2 of 0.98. Two kinetic models were used to determine the adsorption mechanism and the kinetic data were correlated (R2 =0.998) well with the pseudo second order kinetic model for the adsorption study of Cr(VI) which implies that adsorption follows second order kinetics.
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    Integration of Fenton Oxidation and Biological Process with Sequencing Batch Reactor for the Treatment of Textile Wastewater
    (Addis Ababa University, 2020-02) Desta, Solomon; Zebene, Kiflie (PhD); Hulle, Stijn Van (PhD) Co-Advisor
    study was mainly aimed to investigate the treatment efficiency of the integrated system of biological oxidation and homo catalytic advanced oxidation process for the treatment of textile wastewater. Mineralization of a methyl orange dyes using artificial solar Fenton oxidation, degradation of a Basic Blue 41 dyes and real textile waste water with conventional Fenton oxidation were examined at laboratory scale in batch experiments using Box–Behnken statistical experiment design. Dyestuff, hydrogen peroxide (H2O2) and ferrous ion dose (Fe2+) concentrations were selected as potential independent factors for simulated dye aqueous solutions while for real wastewater Fenton reagents (H2O2 and Fe2+ ) and pH were selected as independent potential factors. Besides, color and total organic carbon (TOC) removal were measured as desired response functions for artificial solar Fenton oxidation while color and chemical oxygen demand (COD) were selected as desired response for conventional Fenton oxidation processes. The total time of irradiation used in the case of artificial solar Fenton oxidation for all the experimental runs were 20 minutes while the total reaction time for conventional Fenton oxidation processes was 1hour. Perturbation plots showed that iron dosage was the key process factor on the responses for both solar and conventional Fenton processes. At constant dye stuff dose, color, TOC and COD removal increased with increasing H2O2 and Fe2+ concentrations up to a certain level. High concentrations of H2O2 and Fe2+ for a constant dye stuff dose did not result in better removal of color ,TOC and COD. The optimum ratio of Fe2+ / H2O2 /dyestuff which gives a complete color removal and 96% TOC removal for the highest level of dye dose for artificial solar Fenton was found to be 72 /1386 / 255 (mg/L). In this regard, Percent color removal was higher than TOC removal. During degradation of Basic Blue 41 dye, the optimum ratio of H2O2/Fe2+/dyestuff which gives a complete color removal and 95% COD removal was found to be 1195mg/L /90mg/L /255mg/L while in the case of real wastewater degradation, the optimum ratio of that gives 87% color removal and 79% COD removal were Fe2+/H2O2/pH (500.4mg/L/5187.6mg/L/2.9). In this regard,, Fenton oxidation using optimum Fenton reagents at a pH of 2.9 is effective for the treatment of acrylic fiber processing textile wastewater. Subsequently, real textile wastewater was taken and treated with a sequencing batch reactor (SBR) using a biomass taken from domestic wastewater treatment plant. Cycle period, air flowrate and sludge retention time (SRT) were initially optimized using the response surface methodology (RSM). The optimum ratio of cycle period/ air flowrate/SRT which indicated 57% COD removal and 54% color removal was found to be 25 h /15L/h /16d. Two types of wastewater substrate concentrations and various hydraulic retention time (HRT) were used at optimized conditions. COD removal, color removal, sludge volume index (SVI) and mixed liquor suspended solid (MLSS) were measured. The maximum COD removal (73%) and color removal (65.8%) were obtained at an organic loading rate of 0.078 kg COD/m3d. SVI at the optimized condition was found to be 90-92 mL/g. A first order kinetic model was used to represent the degradation of textile wastewater. Finally, the removal of COD and color studied on a real textile wastewater using a single stage of Fenton oxidation, (SBR) and also with the combination of SBR with Fenton oxidation. Optimum amount of chemical reagents and SBR process factors were used. The effluent obtained from SBR at steady state conditions indicated a maximum COD and color removal of 74.1% and 64.6% respectively. The effluent obtained from Fenton followed by SBR (Fenton +SBR) at steady state conditions indicated a maximum COD and color removal efficiency of 86.3% and 84% respectively. while SBR followed by Fenton (SBR+ Fenton) for three Fenton oxidation experimental runs indicated a maximum COD and color removal of 80.2% and 73.6% respectively
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    Environmental Life Cycle Assessment of Ethiopian Electricity Generation Systems: A Case of Hydro and Wind Power
    (Addis Ababa University, 2020-11) Belay, Teffera; Berhanu, Assefa (PhD)
    Electricity is one of the most vital elements in modern society. Despite its significance to improve human life, there are concerns on its environmental impacts. Life Cycle Assessment (LCA) is a well-established tool for assessing the environmental burdens of products (goods and services) throughout their life cycles. Several LCA studies were conducted for electricity generation and supply systems. However, the LCA data of electricity systems are country specific in their nature. In addition, existing LCA and inventory modeling efforts are limited to the circumstances of the developed world. Therefore, the need to evaluate the environmental performance and to develop country specific LCA data that describe actual electricity systems remains important. This thesis provides a picture of current electricity system and presents for the first time the LCA results of hydro and wind power systems in Ethiopia. The assessment aims to model existing hydro and wind energy systems and develop LCI and LCA datasets of the country per 1 kWh electricity generated. For both case studies, process-based attributional LCA has been applied using SimaPro software version 8.0.1 and ReCiPe 2008 as impact assessment method. The main midpoint environmental impacts of Ethiopian hydropower system consisting of eleven hydropower plants operational in 2013-2017 were: climate change(CC): 32 g CO2 eq., fossil depletion (FD): 0.82 g oil eq., freshwater eutrophication (FWEU): 0.000132 g P eq., human toxicity (HT): 0.58 g 1, 4-DCB eq., metal depletion (MD):1.04 kg Fe eq., marine ecotoxicity (MET): 0.01 kg 1,4-DCB eq., natural land transformation (NLT): 8.3E-04 m2 eq., particulate matter formation (POF): 0.15 g PM10 eq., photochemical oxidant formation (POF): 0.03 g NMVOC eq., terrestrial acidification (TA): 0.02 g SO2 eq. and freshwater ecotoxicity (FWET): 0.005 g 1,4-DCB eq. per 1kWh electricity generated. The major midpoint environmental impacts of Ethiopian wind farms composed of 3 wind farms operational in 2015-2017 were: climate change (CC):33.36 g CO2 eq., fossil depletion (FD): 8 g oil eq., freshwater ecotoxicity (FWET): 0.023 g 1,4-DCB eq., freshwater eutrophication (FWEU): 0.005 g N eq., human toxicity (HT): 9.9 g 1,4-DCB eq., metal depletion (MD): 18.7 g Fe eq., marine ecotoxicity (MET):0.098 g 1,4-DCB eq., particulate matter formation (PMF): 0.097 g PM10 eq., photochemical oxidant formation (POF): 0.144 g NMVOC eq., terrestrial acidification (TA): 0.21 g SO2 eq. and natural land transformation (NLT): 1.4E-06 m2 eq. per 1 kWh electricity generated. The cumulative energy demand and the energy return on investment (EROI) are 0.393 MJ/kWh and 9.2 respectively. The contribution analysis shows that the pre-operation phase of hydropower plants contributes the highest share (62-99%) in most impact indicators, with the exception that the operation and maintenance phase accounts for about 50 and 90% share in POF and CC respectively. Moreover, medium-scale hydropower plants have higher potential environmental impacts when compared to large-scale hydropower plants. Similarly, the pre-operation phase of wind power is the largest contributor to all the environmental impacts, with the shares ranging between 82 and 96%. In addition, the sensitivity and scenario analyses indicate that the changes in lifespans, exchange rates for parts, capacity factors, transport routes and treatment activities would result in significant changes in the LCA results The results of the assessment show that the lifecycle of wind power generation has more impacts in most impact categories than hydropower generation, except particulate matter formation (PMF), natural land transformation (NLT) and water depletion. In many cases, a single impact category is caused by many processes associated with few lifecycle stages. This demands the engagement of many stakeholders including academia, researchers, developers, operators and policy and decision-makers. In general, these studies would give insight for operators and developers to pay proper attention on determination of sites, capacities and lifespans of power plants and end-of-life waste management options. More importantly, this study can serve as an input to a comprehensive life cycle assessment database of the national energy system in Ethiopia, which is in turn vital to develop communication metrics such as Environmental Product Declarations (EPDs) for economically significant export products in Ethiopia, including electricity itself. However, the results of this study should be interpreted within the context of the data limitations encountered during the course of the research, namely, lack of local datasets for electricity, transport and waste treatment activities relevant to local conditions. Future efforts in Ethiopia should, therefore, be dedicated to undertaking the creation of life cycle inventory databases with a focus on such background systems that will serve as a backbone for all kinds of LCAs in the country, and in and beyond the Horn of Africa region at large.
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    Anaerobic Co-Digestion of Slaughterhouse Wastewater with Water Hyacinth (Ecchornia Crassipes) For Biogas Production Using Rumen Fluid as Inoculum: Characterization and Parametric Optimization
    (Addis Ababa University, 2021-10) Rakeb, Kifle; Zebene, Kiflie (PhD)
    The purpose of the present study was to characterize and optimize the co-digestion of Slaughterhouse wastewater with Water Hyacinth (WH) for biogas production using rumen fluid as inoculum. The slaughterhouse wastewater and water hyacinth were first characterized to determine their potential for biogas production. Water Hyacinth reducing sugar content was determined (11.94 g/L) using dinitrosalicylic acid (DNSA). Co-digestions were carried out in batch reactors. The effects of substrate composition (ratio of WH to SWW), hydraulic retention time and pH on methane production and COD removal efficiency were investigated and optimized using RSM-Optimal (custom) design. Accordingly, the optimum methane production and COD removal efficiency were found to be 76.2% and 59.1%, respectively at HRT of 40 days, a substrate composition of 50%SWW: 50%WH and a pH of 7. Furthermore, the bio-digestate was investigated for fertilizer potential. Results show its nutrient values were below the FAO suggested values. FAO suggests a minimum of 5% sum (N+P+S) for an organic fertilizer. Results show that co-digestion of SWW with WH is promising way for producing biogas and simultaneously to control the spread of WH. In addition, it is suggested to blend the bio-digestate with organic manure for enhancement of fertilizer potential.
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    Investigation of Quality Briquette Fuel from Brewery Waste Water Sludge and Spent Grains
    (Addis Ababa University, 2021-09) Bontu, Teshome; Berhanu, Assefa (PhD)
    Brewery wastes such as spent grain and brewery wastewater sludge are abundant brewing byproducts and have energy potential due to their high carbon contents. The objective of this study was to produce and evaluate solid fuel/briquette fuel from spent grains and brewery wastewater sludge using molasses as a binder. The carbonization process parameters were temperature (350℃, 400℃, and 450℃), time (60 min, 90 min, 120 min), and mixing ratio of BSG to BWWS (25%, 50%, and 75%). These process parameters which affect the process response (Calorific value) were optimized using Central Composite Design (CCD) of Response surface methodology (RSM). In this study, physicochemical characterizations of BSG, BWWS, Sawdust, carbonized mixed samples, carbonized mixed briquette, the non-carbonized mixed briquette was conducted, and then the results were compared with Sawdust briquette. The results of the proximate and ultimate analysis indicated that the potential use of the BSG and BWWS as a replacement for household energy use. The optimal conditions of the carbonization process were temperature at 350 ℃, time at 60 min, and mixing ratio of 75%BSG to 25%BWWS with a calorific value of 4761.10 Cal/g. The carbonized mixed samples were densified using 20% molasses for suitable handling, transporting, and enhancing the calorific value. The calorific value increased to 5385.72 Cal/g due to the addition of binder for briquetting process. The experimental work indicated that the BSG and BWWS can be used as good resource in the manufacturing of quality briquette fuel. In addition, the carbonization process and application of binder increases the energy density of the briquette. The produced briquette can be excellent household fuel alternative source.
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    Studies on Nitrification-Denitrification and Sludge Granulation Processes in Sequencing Batch Airlift Reactor for the Removal of Nitrogen from Tannery Wastewater
    (Addis Ababa University, 2020-12) Aysanew, Gorems; Berhanu, Asefa (PhD); Srinivasan, S.V. (PhD)
    Tannery wastewater is characterized by high organic carbon and nitrogenous compounds due to the raw hides/skins and chemicals used in making leather. The present study employed sequencing batch airlift reactor (SBAR) system to develop the simultaneous removal of nitrogen and organic carbon from synthetic tannery wastewater. The reactor (working volume of 5 L) was run for 250 d at different operational conditions by automated control of the SBR cycles, pH, DO and temperature and constant 50% volume exchange ratio. The performance of the reactor was evaluated in terms of TCOD, sCOD, TKN, NH4-N, NO3-N, NO2-N, DO and pH profile. The reactor was initially run at SRT of 7 d, MLSS of 3.5-4 g/L, pH in the range of 7.25-7.3 and DO of 2 mg/L for 129 days. The startup of nitrification process took about 30 days. During this time, the reactor showed almost complete organic carbon removal and unstable partial nitrification to nitrite with very less conversion to nitrate. Later the reactor operation was changed to different operating conditions: constant SRT of 20 d, resulting in MLSS of 10-11 g/L, DO of 1 mg/L and pH in the range of 7.25-7.3 and different cycle times of 18, 12, 10 and 8 h. The reactor was run for a minimum of two weeks for each cycle times. The result showed stable nitrification and denitrification with 97% removal in terms of COD and a 94% removal in terms of ammonical nitrogen. The total nitrogen removal was observed to increase as the cycle time increases. The total nitrogen removal efficiencies for 18, 12, 10 and 8 h cycle times were, 69, 58, 53 and 43 % respectively. The COD, DO and nitrogen species profiles showed that the removal of nitrogen was observed during the feeding and initial phase of the aeration due to denitrification. It was also observed that the remaining nitrogen in the effluent was more in the form of nitrate at higher cycle times and in the form of nitrite for lower cycle times. Kinetics study also showed that maximum removal of COD and ammonical nitrogen in 8 h cycle time under controlled condition. In addition, cycle time control to change the characteristics of the effluent from complete nitrification to partial nitrification which is one of the important steps to link the reactor with anammox reactor system where in the presence of nitrite, ammonical nitrogen is anaerobically oxidized to nitrogen gas by anammox bacteria. Whole metagenome-16S rRNA sequencing of the bacteria population diversity of initial seed and reactor sludge after 200 d showed that the dominant bacteria were proteobacteria and the reactor sludge showed higher nitrifies and anammox population compared to seed sludge. Further experiments were conducted to change the flocculent sludge to granular sludge and improve the overall efficiency of the reactor. A COD loading rate of 6.3 kg/m3.d and nitrogen loading rate of 0.425kg/m3.d were first applied to the reactor for 105 days by using simulated tannery wastewater. The flocculent sludge was transformed to granular sludge when the operating settling time was reduced sequentially. The granules formed were having a final MLSS of 12.3 g/L, biomass density of 6.1 gVSS/L granule, settling velocity of 30-40 m/h, SVI of 16-20 ml/g TS and size distribution in the range 1.8-3.2 mm. Evaluation of the performance of the reactor showed a very good quality effluent with average COD, NH4-N and TN removal of 97.7±1.5 (%), 87.1±11.8 and 74.43±11.7 (%) respectively. The effect of settling time on the existence and relative abundance of selected bacteria gene involved in nitrogen cycle is analyzed by PCR and qPCR. The result confirmed the existence of AOB-amoA, nirK and PLA46amx820 gene. The qPCR result also confirmed that the relative abundance of AOB-amoA and PLA46amx820 was higher in the reactor compared to the control. Biological transformation of nitrogen results in generation of sludge which needs sustainable solution. Anaerobic digestion of these sludge yield energy and reduce the sludge volume significantly. The digestion of excess sludge from the SBAR reactor in this particular study yield biogas yield of 193.2 ml/g VSS and the digester reached steady state in about 30 days. However, the supernatant after anaerobic digestion contains significantly high concentration of ammonia (i.e., 1097 mg/l) which again need sustainable solution. Partial nitrification (PN) of the supernatant after anaerobic digestion is a sustainable alternative to remove the nitrogen either through partial nitrification-denitrification route or through partial nitrification-anammox route. Though the PN-denitrification route may result in generation of unwanted N2O gas. Therefore, the PN-anammox route is more sustainable. For the PN-anammox route, the NH4-N in the wastewater need to be partially nitrified to NO2-N in the ratio of 1:1. As a result, the SBAR reactor was operated at SRT of 7 days, DO of 1 mg/L, pH of 8, at ambient temperature and cycle time of 8 h to start up the PN process and the reactor was started up in 30 days with the required NO2-N: NH4-N ratio for anammox reactor feed. Moreover, the effect of various operational factors on the response variable (NO2N: NH4-N) was studied by considering seven operational factors (i.e. pH, DO, temperature, Cycle time, C/N, MLSS and aeration strategy (intermittent and continuous)). Fractional factorial design (Placket-Burman) was used to study the effect of the seven operational factors. The study showed that the individual factors considered for the study are not significant but the interactions between the factors are more significant. The results from experimental runs showed that it is possible to reach a stable partial nitrification with high pH (7.60), low C/N (0.5), high cycle time (10 h), low DO concentration (1 mg/L), low MLSS/MLVSS (3500 mg/L), high temperature (32ºC) and intermittent aeration.
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    Production, Characterization and Optimization of Bricks made from a Mixed Tannery Sludge and Municipal Waste Incineration Bottom Ash (MWI-BA)
    (Addis Ababa University, 2021-09) Helina, Asfaw; Shegaw, Ahmed (PhD)
    Clay has been used to make bricks for thousands of years and a continuous exploitation of the top soil makes the soil loss its fertility. The chemical composition of tannery waste water treatment plant sludge is very similar to that of brick clay. As a result, the tannery sludge could be a potential substitute for brick clay. The sludge produced by the tannery waste water treatment process must be disposed of in an environmentally friendly manner. Most sludge created in treatment systems across the world is released into an open dump site, resulting in carbon emissions and harmful heavy metal leaching into the environment. The use of sludge in the production of constructional materials is regarded the most cost-effective and environmentally friendly alternative among all disposal methods. One of the waste materials emanated from waste to energy facility, which contain high silica content, and might be incorporated with tannery sludge in brick production, is bottom ash (BA). As a result, this trend offers an environmentally friendly way to reuse bottom ash. The study looked into using a mixture of tannery sludge and bottom ash to partially replace clay soil. In this study, fifteen different proportions of tannery sludge (TS) to bottom ash (BA) were investigated, with replacement levels ranging from 10% to 30% for each waste and firing temperatures of 800°C, 900°C, and 1000°C. The Ethiopian standard (ES) and the American society for testing and materials standards (ASTM) were used to determine and evaluate the engineering qualities of the bricks. In addition to this the TS-BA amended clay bricks were also compared with the control clay bricks. After the production was optimized the best conditions for producing TS-BA amended clay bricks were found to be 11.69 % tannery sludge (TS), 10.16 % bottom ash (BA), and a firing temperature (FT) of 800°C. Based on the findings, it was determined that the majority of the TS-BA amended clay bricks met both Ethiopian and ASTM specifications for fired clay bricks.
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    Synthesis of Silica Xerogel from Bottom Ash of Reppi Waste to Energy as A Methylene Blue Adsorbent on Textile Wastewater
    (Addis Ababa University, 2021-08) Amsal, Getahun; Shimelis, Kebede (PhD)
    Dyes are water soluble complex organic compounds, it present in the textile dyeing process and they are nonbiodegradable waste in the textile wastewater. In Ethiopia, most textile factories are located nearby water bodies and they discharge their color effluent to canals, rivers, lakes, and streams without treatment. Those Effluents can harm all forms of living things. Among those dyes discharging MB dye without treatment can affect human life and aquatic life. The aims of this research were to synthesis silica xerogel from bottom ash by the sol-gel process to treat dyehouse waste. In this study the first stage was the leaching treatment to reduce heavy metal elements and to increase silica extraction, the second step was extraction process was employed to synthesize sodium silicate at different parameters such as extraction time (1, 2, and 3h), NaOH concentration (1, 2 and3M) and solid to liquid (wt: vol) ratio (1:1, 1:2 and1:3) with constant temperature 750c. Since the sol-gel process for all extracted sodium silicate were done at the same parameter such at room temperature, hydrosol pH 3, the addition of water 40mL slow constant stirring, 18h aging time, drying at 1050c for 24 hr and final silica gel pH7. The High percent of purity (84.1321%) of silica gel was obtained with the ratio 1:1.5, 2:5hr, and 2M of NaOH concentration with 0.901 desirability chosen as optimal sodium silicate extraction parameter. The physical and chemical characteristics of the mesoporous silica materials were analyzed using BET, FTIR and also their purity, moisture content, and bulk density was characterized. The results indicated that the BET surface area and pore diameter of the synthesized silica materials were 253.1 m2/g and 18.38Å; respectively. The FTIR spectra confirmed the existence of a surface hydroxyl group and the occurrence of symmetric Si–O stretching. The results indicate that purity, moisture content, and bulk density were 84.13, 5.26%, and 0.73gm/cm3 respectively. Under the experimental conditions at 30.85 min, 0.1g silica gel dosage for 13.94mg/L dye concentrations were found for maximum dye removal efficiency (86.101%) with0.99desirability. The optimal condition was checked on textile dye house water, which dye concentration was 14.81mg/L, the result becomes 84.62% dye removal efficiency. Consequently, the experimental results indicated that the bottom ash has the potential to be used as silica gel for dye removal.
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    Electrolysis Sodium Hypochlorite Generation from Sodium Chloride Solution
    (Addis Ababa University, 2021-01) Tsegaye, Assefa; Shimelis, Kebede (PhD)
    The scarcity of fresh-water has become one of humanity's most pressing problems today. Chlorine was chosen as the disinfection of choice because it was cost-efficient, effective, and easy to use. Chlorine was introduced to water as a gas or a liquid (NaOCl). For safety reasons, NaOCl was frequently used instead of chlorine gas. It was a viable disinfectant for controlling microbial growth and sanitizing inert surfaces. One of the alternate ways used as value-added disinfection was on-site electrolytic NaOCl production. To achieve the goal, a batch laboratory-scale reactor was used, with a Ti/IrO2 anode and stainless-steel cathode. To find the best optimal conditions, the RSM experimental design was used. The effects of the most important variables, the creation of optimal conditions, and the construction of the optimum sodium hypochlorite concentration were studied. The experiment was carried out with a variety of variables, including NaCl content, electric potential, electrode gap, and electrolysis time. At 32g NaCl, 7v, 2.5cm electrode gap, and 70min with pH of 11 and ambient temperature of 25°C, 7.2g Cl2/l of NaOCl was created under the best-optimized circumstances for NaOCl generation. The results show that the NaOCl generated can disinfect water and inert surfaces.
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    Study on the Possibility of using Municipal Solid Waste Incineration Bottom Ash as Partial Replacement of Aggregates in Concrete Mixes (The case in Repie waste to energy plant)
    (Addis Ababa University, 2021-07) Abiy, Tirfe; Shimelis, Kebede (PhD)
    A huge sum of civil strong waste (MSW) are created each year. The most way of Waste administration and utilization are major concern in numerous parts of the world. Because it may generate power from garbage, burning could be an important process for handling municipal solid waste (MSW). Specifically, municipal solid waste incineration (MSWI) generates two types of ash: bottom ashes (BA) and fly ashes (FA). The lack of space for land fill and the resulting natural pollution is the primary drawback of incineration technology, thus the use of MSWI ash displays a tremendous dedication to waste reduction and asset conservation. This research paper investigated to study the possibility of the Repie waste to energy incinerator plant bottom ash to produce the concrete materials by partial replacement of aggregates in the standards of concrete mix ratio. First the physical and chemical properties of the Repie MSWI BA was investigated in detail and the result obtained with the moisture content of the ash was 30.76wt % having high moisture content. Its particle size distribution was in the range of coarse to fine. The most abundant oxide composition in the bottom ash was found to be SiO2 which reaches up to 48.88%. From the experiment all the three parameters, substitution ratio, particle size and curing time had significant effect on the compressive strength. The optimum condition for maximum CS of 21.21MPa were 10% ratio substitution, with particle size 3.01mm and 28th days curing time for the concrete
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    Removal of Iron and Manganese from Groundwater by Oxidation-Filtration Hybrid System
    (Addis Ababa University, 2021-01) Lemlem, Belay; Shimelis, Kebede Kassahun (PhD)
    Groundwater is naturally available water that exists in pore spaces and fractures in rock and sed-iment beneath the earth's surface that fills the opening in beds of rocks and sand. In developing countries both groundwater and surface water are used for irrigated agriculture and urban water supply. In Ethiopia groundwater is mostly utilized for drinking and industrial utility. In deeper wells the natural presence of metallic elements iron and manganese together is common .Their presence in limited amount is essential for all living organisms. However, the existence of iron and manganese are considered as contaminants above the limited concentration of 0.3mg/L and 0.1mg/L respectively. From many wells found in and around Addis Ababa some of them have high iron and manganese concentration which is found to be a problem on using groundwater to supply the high-water demand in the city. The aim of this study was removal of iron and manganese from groundwater by oxidation by air and sodium hypochlorite followed by sand filtration. Experimental set up was done at AAiT 5 kilo campus. The sand bed was prepared for filtration process with bed depth 0.6m and grain size of ES=0.71mm, UC=1.70 and d60=1.2mm. Electrolytic sodium hypochlorite Produced using ti-tanium and stainless steel electrodes at electrolytic reaction time 72 min in one liter electrolytic cell 2 cm gape and 7volte. The result hypochlorite resulted had concentration of 4.183 g/lit. Removal efficiency of the system tested using synthetic water resulted removal efficiency of 95.76333% for iron and 95.65% for manganese. For actual groundwater from Sambanekersa with 5.162mg/l iron and 0.607mg/l manganese concentration oxidation filtration process was performed at optimal point of 7.02mg/l NaOCl, 77min and 1.5 l/min air flow rate the resulted removal efficiency is 87.14% for iron and 26.41% for manganese.
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    Removal of Chromium from Painting Industry Wastewater Using Bioelectrochemical Fuel Cell Technology
    (Addis Ababa University, 2021-07) Diriba, Amsalu; Shimelis, Kebede Kassahun (PhD)
    Chromium is heavy metal that released as waste dominantly from chemical industries and causes chronic and acute health problems on human beings and other living environments. From different industrial sector in Ethiopia Painting industries are developing but their wastewater treatments are not get attention. This was one of the reason to select the sector for the removal of chromium from their wastewater using Bioelectrochemical Fuel Cell Technology (BECFC). The technology is an effective, efficient, and environmental-friendly that remove chromium without using external energy. The methodology can generate electrical energy from wastes that helps it to avoid the cost of energy during treatment. The sub objectives of this research were synthesizing chromium wastewater using APHA methodology, constructing set up of BECFC, enumerating Bacillus Ceruse. And others were investigating the efficiency of the methodology by varying three parameters at three different operational level, using statistical method of RSM optimizing operation parameters and verified on synthetic wastewater. Also characterizing real wastewater and verifying again optimum operation parameters on real wastewater were sub-objectives of the research. BECFC remove chromium from wastewater when electro-active bacterial like Bacillus Cereus metabolize organic waste in anodic chamber and release electrons during the process. Then generated electrons are transferred to the cathodic chamber through the external wire. Then after chromium is reduced, attached on electrode, detached and settle to the bottom of cathodic chamber. To see results of the research, over all above 95% efficiencies of removal of chromium were achieved. The highest efficiency of removal achieved was 99.6% at a concentration of 15 mg/L, pH of 9, and time of treatment 16hrs. The efficiency of optimum operation parameter was 98.1% and current density generated was 17.51mA/m2 with an optimum concentration of 9mg/L, pH 7, and optimum time of 17.357hrs. And the efficiency of removal of chromium from real wastewater of (3400mg/L SS, 2164NTU turbidity, 738mg/L COD and 148mgg/L BOD) was 84%. In conclusion, BECFC is a promising technology, but more research in full facilitated laboratories are requested to make the methodology applicable on real wastewater.