Environmental Engineering

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Characterization of Physicochemical Parameters for Tap Water and Removal of Hardness Using Moringa Stenopetala seed as Natural Absorbent The Case of Mekelle Town, Tigray Ethiopia
(Addis Ababa University, 2007-06) Mesfin, Amhagiyorgis; Assefa, Berhanu (PhD)
The physicochemical examination of tap water used for domestic purposes in Mekelle town was carried out to ascertain their suitability for consumption. Water softening experiments were also conducted to observe the changes in total hardness, with varying dosages of a natural coagulant. The natural coagulant was extracted from Moringa stenopetala seed A total of twenty (20) water samples were collected from various parts of the town tap water used for domestic purposes and characterized for their physicochemical parameters, arising public interest. The physicochemical implications render Mekelle’s tap water unfit for human consumption, though it can be used for other purposes. Tap water samples containing high concentration of hardness from Mekelle town, Enda Mariam and Enda Giyorgis areas were used for hardness removal mechanism part of this study. The optimum hardness removal efficiency for Mekelle tap water sample produced from ground water source was approximately 58 % (from initial total hardness of 523.25 to final hardness result of 220.3 which is within Ethiopian and WHO standard, i.e. below 300 mg/l as CaCO3) which was attained at M.Stenopetala dosage of 200 mg/l. The optimum hardness removal efficiency for synthetic hard water analysis done by taking two factors, coagulant dose concentration and PH as independent factors was approximately 49 % (from 500 to 256.6 mg/l as CaCO3) which was attained at M.Stenopetala dosage of 200 mg/l and 6.5 PH value. The mechanism for hardness removal in hard water seems to be precipitation of insoluble products of the reaction between M.Stenopetala extract and the hardness causing ions. Even at a relatively higher dosage of the M.Stenopetala coagulant compared to the chemical softening, natural coagulant is preferred for economic use, health and environmental safety. Key words: Water Hardness, coagulant protein, Moringa Stenopetala, physicochemical parameters, Tap water
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.
Impact Assessment on Solid Health-Care Waste Management in Addis Ababa, And Identification of Energy Recovery Possibility
(Addis Ababa University, 2008-05) Temesgen, Tatek; Gessesse, Nebiyeleul(PhD)
In recent world the best way of protecting community health mainly depends on preventive methods rather than curative means. Due to this reason, having good solid health-care waste management and disposal in every health-care center is inevitable. The present study is conducted in five systematically selected sample hospitals in Addis Ababa. The main objective of the study was to assess the impacts arose from the current health-care solid waste management, predict proper treatment and disposal mechanism and check the possibility of heat recovery during treatment of waste. The sampling method used is two-stage cluster sampling with 90 % confidence level. In these sample hospitals, solid waste was collected for one week from 84 randomly selected beds of the total occupied 505 beds. The mean waste generation rate for the city was estimated to be 1.227± 0.253 Kg/ day. bed, like wise the generation rate for the private and governmental hospitals were estimated applying the same data. To achieve these results different statistical estimation methods are used. On top of this, proper on site sorting was done in order to perform proximate analysis to seven waste categories. Based on this analysis the maximum infected hospital waste in the city was estimated to be 662 Kg/day. Additionally, an attempt is done to address the overall solid waste management trend all over the routes to disposal. Possible Environmental, health and social impacts are identified for every waste management route. Analyzing the data found, health, environmental and social impact has 37.7, 35.6, and 26.7% impact contribution respectively. To identify the energy recovery of the treatment plant, secondary data from WHO that gives the minimum calorific value for infectious waste and estimated total generation rate of infectious waste in the city was used to determine the energy generation to be 104 Kg/hr, which is less than the capacity of medium sized steam generator. Since the capacity of the energy is less, possible ways of utilizing this small energy was suggested. Finally, based on the results and findings of the present study, certain solid waste management, treatment and disposal recommendations are forwarded to improve the management and minimize the impact of solid health-care waste in Addis Ababa.
Modeling of Air Pollutant Dispersion and Analysis
(Addis Ababa University, 2010-11) Anteneh, Muheye; Teshome, Worku (Asst. Prof.)
This work has been carried out to develop a three dimensional modeling program for pollutant dispersion. The program solves partial differential equation by integrating into one mathematical equation and then various data are taken from literature s and primary sources for verification of the program. The effects of meteorological and stack parameters on dispersion of pollutants ,like wind velocity, ambient air temperature, atmospheric stability, exit temperature, velocity ,concentration and stack height were studied and considered in the program. Several illustrations for reducing maximum ground level concentration using the program are given. The output results from the program are presented in different forms. Different simulation runs and observations were made that clearly illustrate the utility of the program in helping decision makers about air pollution control and effects of different variables in pollution.
Design and Performance Evaluation of Biomass Gasifier Stove
(Addis Ababa University, 2011-06) Shiferaw, Yohannes; Worku, Teshome (PhD)
With respect to global issues of sustainable energy and reduction in greenhouse gases, biomass energy as one of the key sources of renewable energy is getting increased attention as a potential source of energy in the future. This work has been carried out to develop, design and manufacture an applicable type biomass gasifier stove for the production of producer gas using locally available biomass fuels like bamboo, eucalyptus and prosopies Juliflora. The gasifire is produced and tested on three trial test runs by conducted caloric value, moisture content and ash content at dry base of each biomass is measure, and is conducted at different time with bamboo, eucalyptus and prosopies Juliflora biomass feeding. First batch fed gasifier reactor having an internal diameters of 39cm was designed and fabricated, operating period of 25-35min, amount of biomass fuel consumed of 4.5kg, temperature at various points of 560 – 7350C were monitored and analyzed. Important parameter such as: manufacturing materials and technique, operation, fuel type, smoke and primary and secondary air inlet were evaluated using water boiling test and controlled cooking test methods by actually boil and cooking food. The results obtained from this study shows that the gasifier performance and operating conditions are good with thermal efficiency around 31.8%. So the out put can provides modern energy services for basic needs and productive applications in the areas. Key words: Biomass, gasification, producer gas, fuel efficiency, ash.
Water and Wastewater Minimization in Tannery by Using Water Pinch Technology Case Study (Ethio Leather Industry (ELICO) Glove and Hide Unit(Ethio Leather Industry (ELICO) Glove and Hide Unit
(Addis Ababa University, 2011-07) Gutama, Moroda; Nurelegn, Tefera (PhD)
In tanneries, the phases of conditioning and preparing the hide/skin for tanning, as well as the transportation and fixation of tanning substances are all carried out in aqueous media. Most of the steps of these processes are carried out with fresh water. This leads to the generation of high wastewater flowrates which will have to be treated due to the relatively high concentrations of pollutants. The high effluent volume requires huge investments for effluent treatment plants in order to meet the required specification for the discharge of liquid effluents to various water bodies. In this study the total water consumption reduction of the case study tannery is investigated by using water reuse technique in some stages of the process. For the systematic design of water reuse networks, the theory of the water pinch methodology is described, which are proved to be effective in identifying water reuse opportunities. Experimental results on pilot scale are shown that the methodology is demonstrated to be successful. Water reuse reduces the load of the wastewater treatment plant as well as it reduces the costs. During the analysis, it was tested that 100% of the effluent from de-liming discharge can be reused for presoaking and main soaking stages, reuse in bating washing-1 100% and bating washing-2 75% from bating washing-3, and the reuse of 80% of washing after shaving for tanning float. The physical and chemical parameters analyzed in the processes and for the products with reuse practice did not present any considerable difference when compared with the conventional process. This demonstrates the viability of reuse practice in tanning industry. This study identified a potential scope of reducing both freshwater and wastewater by 44%. In turn the water reduction represents a total potential annual savings of 307200 Birr, taking into account the raw water and wastewater treatment costs, labor cost, electrical and chemical costs.
A Case of Pawe And Mandura Woredas, North Eastern Part of Benishangul Gumuz Regional State, Ethiopia
(Addis Ababa University, 2012-11) Mebrahtu, Meron; Yayehyirad, Gashaw(PhD)
A recent development of the CMP approach, to implement rural water supply projects has been piloted in five woredas of the Metekel zone in Benishangul Gumuz regional state located at the Western part of Ethiopia. The assessment on the efficiency of the approach has been carried out in two woredas of the Northern part of Metekel Zone, namely, Mandura and Pawe woredas. First, it was checked if efforts have been put in to place and its applicability before evaluating accomplished results. In the second part, effectiveness of the approach was evaluated. In this research, the approach is supposed to effective if implementation is efficient, if the built schemes are going to sustain and if schemes are providing proper and adequate services. Accordingly, a rural water supply system is supposed to be sustainable up on achieving determinants of sustainability. In this research, these aspects are taken as factors that indicate effectiveness, which is a means to measure advancement of the approach towards meeting objectives. Major findings of the research were, elements of the approach were practiced as required except participating communities in technology option selection and post construction support. From the identified causes, it was recognized that there were no evidences found to articulate inappropriateness of any elements of the approach for the study areas. Finally, the effectiveness of the approach, evaluated using averaging the scores attributed to indicators showed above average value that is, 68.61% and 76.70% for Mandura and Pawe woredas respectively. This is interpreted as its application has shown promising result, which only requires some adjustment and efforts for its complete implementation and better output. And it appeared that more effort is needed to secure spare part availability and improve efficiency of community financing. And in general terms, other factors to be given due consideration include skill and awareness of community, especially in Mandura woreda where the socio economic situation is relatively poorer. Recommendations are made on how to deal with the gaps that has been identified for further accomplishments and stress on implementation procedures, which need focus for proper operation and maintenance so as to assure sustainability of schemes.
Performance Evaluation of Drinking Water Treatment Plant (Case Study: Gambella Town Drinking Water Treatment Plant)
(Addis Ababa University, 2013-01) Tariku, Gebretsadik; Berhanu, Assefa (PhD)
The conventional water treatment plant, especially in developing countries, faces major challenges in terms of assessing its operation and performance due to inappropriate technologies, insufficient equipment and deficiency in skilled expertise. Simple but efficient technologies are therefore necessary for reasonable evaluation of the daily performance of the plant. Turbidity is thought of as a convenient surrogate to give favorable indication of the biological and physical quality of the treated water thus by extension provide a fair gauge of the performance of the treatment plant with respect to water purification. Besides, it is fairly simple to measure, cheap and can easily be understood by the operators. In this study the performance of Gambella town water treatment plant was assessed. The study was conducted by assessing unit process capability, design, operation and maintenance potential to meet optimized goals. From results of the assessments, root factors limiting optimum performance were identified and improvement options were proposed. Major unit processes were evaluated to project their design capabilities to meet current peak water demand by selecting appropriate loading rates as basis criteria. The results of the assessment found that all units had the capability to satisfactorily treat water at peak daily demand of 2000 m /day. The study assessed turbidity performances of sedimentation and filtration units by setting optimized turbidity goals. The assessment results indicated that, settled water turbidity was measured less than 10 NTU. And filter turbidity spike of 6.5 NTU following backwash with a reduction to 0.6 NTU after one hour was observed. Generally optimized performance goals were not being achieved. This indicated high risk of microbial pathogens that could pass the filtration barriers in the finished water. Jar test experiments were conducted to evaluate the effectiveness of Aluminum Sulphate (recently used by the treatment plant), Ferric chloride and Ferric Sulphate by comparing the optimum dose at optimum pH for highest turbidity removal and relative costs. From the jar test results Aluminum Sulphate was found to be the effective chemical with 45 mg/l optimum dose at pH 7.1 and the treatment plant was recommended to continue using Aluminum Sulphate at the optimum dose for the raw water characteristics during the evaluation period. Treated water samples were collected from the clear-water well to test 14 water quality parameters according to the standard methods for water and waste water examinations. The collected samples were intended to show the characteristics of the finished water only during the evaluation period. The samples were analyzed at the laboratory of GWTP and results were compared with WHO standards and guidelines for drinking water. Results of the analysis showed that all of the measured parameters were within the acceptable range. In the assessment of factors limiting performance of the treatment plant; major factors were categorized as design, operational and maintenance. No single factor was responsible for poor plant performance, although in general the study found that all factors influence the plant’s ability to work properly. Some of the primary operational problems and the intake structure’s adequacy significantly affected performance. Operational factors were found to have the highest rank. This finding, coupled with the fact that the plant had adequate capability, indicates that improving process control could significantly improve performance.
Horizontal Subsurface Constructed Wetland for Removal of Heavy Metals from Leachate Using Phragmites Australis (A Case of Addis Ababa Solid Waste Open Dump)
(Addis Ababa University, 2013-04) Bahre, Mesele; Worku, Teshome (Ass. professor)
Heavy metals were present at relatively high concentrations in the landfill leachate. The disposal of heavy metals into the environment is of great concern due to their serious effects on food chain and furthermore on animal and human health. Constructed wetlands have played a significant role in treatment of domestic, agricultural and industrial wastewater containing heavy metals effectively. This study focused on the efficiency of horizontal subsurface constructed wetland with Phragmites australis in the removal of heavy metals in landfill leachate. Where, it also determines the amount of heavy metals uptake by Phragmites australis and the amount of heavy metals retained in the soil media. In this work a laboratory-scale study was conducted on HSSF constructed wetland systems which comprises one planted and one control system. The systems operated identically at a flow rate of 22L /d and HRT 4 days for about 28 days treatment period. The result shows the heavy metals composition of the leachate of “reppi” open dump was significant in both season with more slightly higher in wet season. The experimental study shows higher removal of heavy metals by the planted compared to unplanted system. A removal efficiency of 99.33% Fe, 93.67% Mn, 89.24% Pb, 96.14% Cu and 98.33% Zn were achieved in the planted system at the 28th day. While removal efficiency of 98.43% Fe, 91.66% Mn, 85.01% Pb, 90.70% Cu and 85.19% Zn were observed in the control system at the 28th day of the treatment period. The plants uptake of Pb and Cu were also analyzed. The results show that uptake on roots for both heavy metals were high comparing the uptake on leaves and stems. The ability of soil to accumulate Pb and Cu was analyzed. Soil samples were taken from the inlet, middle and outlet of control and planted system. The result shows that accumulation of Pb was highest on inlet part of both systems while accumulation of Cu was highest on the outlet part of both systems. This study concludes that HSSF constructed wetland with Phragmite australis plant and red ash gravel can remove heavy metals from leachate. Keywords: Landfill leachate, Constructed wetland, heavy metals removal, Plant uptake, Soil media
Liquid Fuel Production Through Pyrolysis of Khat and plastic waste mixture
(Addis Ababa University, 2014-02) Abdulhafiz, Yishak; Kiflie, Zebene(PhD)
A good portion of the Ethiopian population, especially of the youth, has taken up the habit of chewing Khat (scientific name: Catha edulis Forsk). Growing use of the stimulant is obviously generating a huge amount of waste making the already-bad situation of solid waste management in Addis Ababa worse. On the other hand, the disposal of plastics is also affecting the environment negatively and in no less a degree. With the expected increase in the consumption of both items, the problem will certainly grow correspondingly especially given the trend that khat is almost always sold in plastic bags. This study investigated the potentials of khat waste to be mixed with high-density polyethylene (HDPE) for use as a raw material in pyrolysis to produce liquid fuel. The results showed that khat waste can be used in pyrolysis, solely and in a mixture with waste HDPE, to yield liquid fuel. A maximum of 26%.wt of liquid yield was achieved. Produced data on characteristics of khat waste that were not available until now showed that khat waste had 76.3% moisture (as discarded); 5.31% ash (dry basis); 59% cellulose; 31.7% lignin; 47.12% C; 6% H; 45.65% O; 1.23% N; HHV of 17.5 MJ/kg; and LHV of 12.6 MJ/kg. A dark brownish liquid that had smoky odor was produced from all runs. An average liquid yield of 15.57% was obtained while the minimum and maximum values were 3% and 26%, respectively. The experiment studied respective influences from varying amount of khat in feed; pyrolysis temperature; and total pyrolysis time. It was seen that pyrolyzing khat waste alone and in higher percentages gave better results. Lower amount of khat (30%) in the feed composition led to higher yield at 550OC. However, pyrolysis at the remaining temperatures studied (650OC and 750OC) showed corresponding increase in yield with increasing amount of khat (70% and 100%). As respective decomposition of its lignocellulosic components took place at higher temperatures (> 300OC for cellulose, and > 500OC for lignin), more amount of khat in the feed led to increased amount of liquid yield. Variation in the total pyrolysis time between 30 and 60 min did not have any significant effect. Following the similarity between elemental composition of bio-oil from pyrolysis and the parent biomass, the HHV and LHV of liquid product were calculated to be 17.1 MJ/kg and 15.05 MJ/kg, respectively. In general, the expected enhancement in liquid yield from presence of plastic was not observed. In the study, pyrolysis of khat waste alone (0% HDPE) gave the maximum percentage yield for liquid product. However, it would not be plausible to conclude that addition of plastic does not bring any benefit at all – only percentage yields but not qualities of liquid produced with and without HDPE in the feed were compared.
Life Cycle Analysis (LCA) and Emission Reduction Evaluation of Compost from Floriculture Waste
(Addis Ababa University, 2014-02) Getu, Abeba; Kaba, Tasissa
Global climate change has increasingly gained worldwide attention. The concentration of greenhouse gases in our atmosphere is becoming an issue of increasing concern. To address this problem, it is believed that examining greenhouse gas emissions from different sources is important .Quantification of greenhouse gas emissions from composting facilities is necessary to quantify actual emissions from these systems and which requires a life cycle (cradle to grave) approach. This thesis identifies, quantifies, evaluates and recommends the environmental impact (global warming potential) associated with the flower farm waste composting process using life cycle analysis (LCA) according to ISO14000(2004). The system considered in this study include receipt of source from the farm , transport to the compost production area , production of mature compost and application of compost to a soil for subsequent agricultural application by planting a plant .Under composting emission (Etotal);Transport emission (Te), Process emission (Pe) and Fugitive emission (Fe) were the three Composting system emissions. The result demonstrates that from the three emission categories, transportation is the highest emitter with 59% CO2 eq than fugitive and process emissions. The results for CO2, CH4, and N2O indicate that CO2 is the most significant contributor in all three emission categories with values of 145.26 kg/ton for transport emissions, 90.75 kg/ton for fugitive emissions, and 11.18 kg/ton for process emissions. Compared to CO2 the contributions of CH4 and N2O are insignificant with values running from 0 to 8.09E-03 for CH4 and 0 to 3.66E-03 for N2O. In general composting emission (Etotal) the benefit of post application impact (Btotal) and the Compost Emission Reduction Factor (CERF) became 249.403 kg CO2 eq, 653.44 kgCO2eq and 404.037 CO2eq per ton of feedstock respectively. The results of this study indicates significant environmental benefits arise from the commercial composting system, including net greenhouse benefits, even where the compost is transported significant distances (200kms radius) for agricultural application. Key words: greenhouse gas emissions, global warming potential, cradle to grave, fugitive emission, Transport emission, Process emission, Composting emission, Emission Reduction Factor
Energy Potential of Municipal Solid Waste for Incineration: Reppi Open Dump Site, Addis Ababa
(Addis Ababa University, 2014-04) shiferaw, Getachew; Worku, Teshome
Solid waste handling and disposal are the pressing problems in Addis Ababa City. Millions of tons of municipal solid waste, hazardous/industrial wastes and commercial xi wastes are handled daily throughout municipal areas. Addis Ababa cleansing management agency confronted with great challenges in disposing of solid wastes in an efficient, cost effective and environmentally safe manner. The total quantity of MSW generated at the site was 3800m3/day or 760 ton/day, annually 1,387,000 m3 Based on the results obtained, I recommended that the municipal solid waste at Reppi Dump Site is feasible for incineration as a strategy to reduce the amount of disposed waste and energy recovery.. Knowledge of the energy potential of MSW for incineration is necessity, in order to plan for energy recovery from MSW. Energy potential from municipal solid waste for incineration was done in an area called Reppi /Koshe, which is the only dumpsite in the city, with objective of evaluating energy potential (heating value) of municipal solid waste and feasibility for incineration. Solid waste sampling and laboratory analysis were carried out according to the random sampling method based on American Society of Testing and Materials (ASTM) standards to determine the waste compositions and proximate analysis. The laboratory work undertaken at school of chemical and bioengineering and Arat kilo chemistry department. According to the weekly analysis the main compositions of the generated MSW in the site were food waste, chat waste and fruit waste which accounted 65% by weight. In this work an average calorific value of 19.78 MJ/kg with variable high water content of 44-65% was determined. Based on the average calorific value, moisture content and MSW removed the net energy potential is 7.68 MJ/Kg with 84.5% energy efficiency.
Investigation of Environmental and Economic Benefits Of Bioslurry From Coffee Husk Relative to Chemical Fertilizer
(AAU, 2014-06) Takele, Uma; Berhanu, Assefa (PhD); Mr. Zerihun, Abate (Mr.) Co-Advisor
Agriculture dominates the Ethiopian economy. It is the major supplier of raw materials to food processing, beverage and textile industries. Application of fertilizer is one of the major interventions made by the government to increase the productivity of the sector. The government focuses on productivity improvement of smallholder agriculture through diffusion of fertilizers and improved seeds. However, the price of chemical fertilizer is increasing from time to time which results in shortage of the supply and unaffordable to smallholder farmers. The objective of the study was to (i) to see the effect of bioslurry from coffee husk on the macro nutrients of the soil (ii) to assess the influence of bioslurry from coffee husk on soil organic carbon content (iii) to compare the effect of bio slurry on yield and yield components of the test crop (iv) To compare the economic benefit of bio slurry application from yield perspective. In order to achieve the stated objectives, a pot study was conducted under greenhouse condition. Seven treatments were designed with combined and sole application rates of bioslurry and urea to 5 kg soil pot -1 using wheat as a test crop. The results of the study revealed that combined and sole application of the bioslurry with chemical fertilizer positively increased the yield, yield component of the test crop and organic carbon soil. The conjugate application of bioslurry with chemical fertilizer at (3.1m bioslurry +62 kg urea) ha -1 gave the highest yield (4368.2 kgha -1 ) and highest spike length was also recorded with this treatment. The high application rate of bioslurry at (6.2m 3 ) increased the soil organic carbon content over 100% compared to the control without any amendment. The simple economic calculation based on economic efficiency indicated that the combined application of bioslurry with chemical fertilizer at (3.1 m 3 +62 kg urea) ha- 1 gave a net benefit of 23, 460.8 ETB. The study showed that the appropriate utilization of bioslurry as soil amendment not only increases soil fertility but also plays a great role in alleviation of climate change through increment of soil organic carbon which in turn serves as a carbon pool of planet earth.
Upgrading Biogas Produced from Biogas Pilot Plant through Absorption
(Addis Ababa University, 2014-06) Assefa, Gizachew; Assefa, Berhanu(PhD)
Biofuels derived from biomass are considered as good alternative to petroleum fuels. Biogas is produced by anaerobic digestion of various organic substances such as food waste, agricultural waste, municipal solid waste (MSW), cow dung (CD) etc., which offers low cost and low emissions than any other secondary fuels. It can be a supplemented to liquefied petroleum gas (LPG) and compressed natural gas (CNG), if it is used in compressed form in cylinders. Ethiopia is among the developing countries where biogas upgrading system doesn’t include in biogas production plants. The use of unrefined biogas has several social and environmental impacts such as GHG emissions, the incombustible part of biogas, CO2, lowers its calorific value, the presence of hydrogen sulphide forms sulphuric acid with water, which is highly corrosive, rendering the biogas unusable. Furthermore, the use of biogas has remained near to the generating plants and compression requirement is high. This paper examines the effect of raw biogas flow rate, water flow rate and water head on methane enrichment of biogas; using water scrubbing which is based on the physical effect of dissolving gases in liquids. In a scrubber, CO2 as well as the H2S, dissolves into the water while CH4 does not because of their difference in solubility. This makes it a very simple process. There is a lot of potentials in terms of increased energy per unit volume, wider application and ease of handling if biogas is upgraded to >95% CH4. Raw biogas methane content in the studied pilot biogas plant ranged from 45 % to 56 %, carbon dioxide from 39 % to 50 % and trace amount of hydrogen sulphide. Oxygen content in all the measured raw biogas was < 2%. A counter-current absorption process upgraded the pilot plant gas near to 80 % methane content. The carbon dioxide content of the product gas ranged from 17 to 35 %. Hydrogen sulphide was removed from the raw pilot plant gas with over 90 % efficiency with the upgrading system. Removal of contaminants (CO2 and H2S) from biogas through upgrading was conducted at a water head of (80, 110 and 140 cm), water flow rate of (8, 16 and 25 l/min) and gas flow rate of (1, 1.5 and 2 l/min). In all cases, the increase in water head from 80 to 140 cm and the increase in water and gas flow rates increased the methane concentration. The highest methane content (80 %) was obtained at the highest water head (140 cm) and water flow (25 l/min) and when the gas flow was maintained at 1.5 l/min. The resulted CH4 enriched product gas implies that carbon dioxide and hydrogen sulphide gases have been trapped in the absorbent water with higher removal efficiency (60 and >90 % respectively). Keywords: biogas; methane; upgrading: Anaerobic digestion: enrichment: biofuel
Biodiesel Production from Consortium of Microalgae
(Addis Ababa University, 2014-07) Ayalew, Birhanu; Kiflie, Zebene(PhD)
The aim of the research work is to determine and analyze the factors that affect the yield of biodiesel production from algal biomass and to optimize the processing conditions. Microalgae oil was extracted from dried and grinded consortium microalgae through soxhlet extraction method and the physicochemical properties were determined. Design Expert 7.0.0 software application was used to statistically analyze data obtained from experimental work. The factors that affect the biodiesel yield were investigated. The density, viscosity, acid value, saponification value and free fatty acids were recorded as 0.94g/ml, 41.85mm2/s, 4.63mgKOH/g of oil, 201.72mg/g of oil, and 2.32% respectively. Alkali catalytic methanol transesterification method was employed to produce biodiesel from the oil and to improve the physicochemical properties of the oil. Temperature is found to be the factor that highly affects the yield of biodiesel. An optimum yield of 89.61% (44.8ml) biodiesel was obtained at reaction temperature of 53.270c, 1.99% catalyst and 6.18 alchol to oil molar ratio. The physicochemical properties of the optimum obtained biodiesl were determined and the results were compared with the ASTM and EN standards. The physicochemical properties were recorded as density (0.89g/ml), viscosity (5.5mm2/s), acid value (0.78mgKOH/g of oil), moisture content (0.026%w/w), ash content (0.022%), free fatty acid (0.39%). The results showed that the fuel properties are within the ASTM and EN standards and it suggests the potential of algal oil as a feedstock for biodiesel industry which could be exploited as an alternative source of fuel. Key Words: Biodiesel, Algal Biomass, Soxhlet Extraction, Transesterification & Physicochemical Properties.
Organic Matter Removal to Reduce Disinfection By-products Precursors A Case study in “Legedadi Water Treatment Plant”
(Addis Ababa University, 2014-07) Kebede, Getahun; Kaba, Tassisa (PhD)
The main aim of this study was the use of enhanced coagulation method to reduce DBPs precursors from surfaces raw water source to control the formation of DBPs in drinking water. Jar test experiments were conducted to study the effectiveness of enhanced coagulation for removal of DBPs precursors from Legedadi reservoir, which is the major water supply to Addis Ababa Metropolitan the capital city of Ethiopia. In this study, for the removal of turbidity and organic matter polyelectrolyte, PACl, and alum were used. The performance of the three coagulants with varying dose level were assessed through treated water turbidity measurement and content of organic matter measured by surrogate parameters of total organic carbon value. These coagulants showed almost similar turbidity removal value. The results were indicated by TOC tested the optimum factorial combination of 1.75* optimum dose of PACl, which gave better resulting with optimum response values of 98.80 % organic matter removal efficiency, whereas Alum, and polyelectrolyte at 1.5*optimum dose showed optimum response value of 96.20, and 96.70 % organic matter removal efficiency respectively. The result showed that 84 % organic matter removal efficiency was obtained in conventional treatment, where as enhanced coagulation process showed an efficiency of 98.08 %. .Since organic matter is a large contributor in the formation of THMs, lower TOC values will likely indicate a lower potential for formation of disinfection by-products. This indicated that enhanced coagulation process is an effective means for removing organic matter present in drinking water if the coagulant dose and pH condition are adjusted to optimum condition. In general, TOC removal enhanced with increasing coagulant dose. However, further increases in coagulant dose beyond the optimal value had little negative effect on DBPs precursors’ removal Key words: Enhanced Coagulation, Organic Matter (DBPs Precursor), Total Organic Carbon, Organic Carbon Removal, Addis Ababa, Legedadi Water Treatment Plant, Ethiopia
Life Cycle Assessment of Kitchen Cabinet: The case of Finfine Furniture Factory (3F)
(Addis Ababa University, 2014-10) Tekle, Hiluf; Kaba, Tassisa (PhD)
A life cycle assessment (LCA) is conducted for kitchen cabinet manufacturing in Finfine Furniture Factory (3F). The LCA methodology is used to assess the environmental impacts and explore ways alleviating environmental burdens at the kitchen cabinet production stages. The assessment covered the cradle-to-gate production of major inputs to 3F including their transportation to the factory gate. Primary data were collected on materials and resources used as inputs to, and on the product outputs from the factory. Data for the production of upstream inputs and supplements were taken from the USLCI and ELCD databases. The collected data were imported in, and analyzed with the Open LCA software. Emissions from transportation of raw materials were quantified based on emission factors from various studies and guidelines. Thereafter, the resulting life cycle inventory (LCI) table was evaluated with the CML 2001 baseline characterization method to quantify the contribution of the kitchen cabinet manufacturing chain in nine environmental impact categories. The study result indicated that there is an intensive use of particleboard, medium density fiberboard, lumber, and polyvinyl chloride. There is also large environmental impact contribution from the production and use of these materials. The production of particleboard generates significant potentials of Acidification, Terrestrial Eco Toxicity, and Eutrophication with magnitudes of 1.7 kg SO2-eq, 0.04 kg -1,4- DCB-eq, 0.3 kg PO4-eq, respectively. The emissions from the production of MDF cause Human Toxicity and Stratospheric Ozone Depletion with magnitudes of 213.1 kg-1,4-DCB-eq and 3.7x10-6 kg CFC-11 eq, respectively. There is visible contribution from the harvesting stage to Freshwater Aquatic Eco-toxicity and Global Warming with magnitudes of 10.2 kg-1,4-DCB eq and 45.2 kg CO2 eq. The kitchen cabinet production stage is also another important contributor to Photochemical Ozone Creation, Abiotic Depletion and Terrestrial Eco Toxicity with magnitudes of 0.1 kg ethylene eq, 0.52 kg 1,4-DCB eq and 0.04 kg 1,4-DCB eq, respectively. The results of this study clearly indicated that non renewable energy use and emissions from formaldehyde use are the major issues to be prioritized for environmental optimization of the kitchen cabinet manufacturing chain in the factory. Therefore, making energy conservation, using biomass as source of energy and substituting toxic resin (UF) by less toxic resins can minimize the environmental burdens caused by the manufacturing of kitchen cabinet at 3F. Keywords: Life cycle inventory, kitchen cabinet, medium density fiberboard, particle board, impact assessment, urea formaldehyde
Reuse of Textile Dye house Wastewater by Removal of Reactive Dye Using Nano Membrane
(Addis Ababa University, 2014-10) Aberra, Daniel; Assefa, Berhanu(PhD)
This study was devoted to provide good understanding of the operating characteristics and their effects on NF membranes system, to utilize in the treatment of wastewater containing synthetic reactive dyes which are common in Ethiopia. The effectiveness of NF systems in rejection of reactive dyes was evaluated under different operating conditions, such as working pressure, feed flow rate and dye concentration keeping feed temperature and pH constant. All experiments were conducted on RO/NF pilot scale plant including facility of feeding and product tank, on line measurement of flow rate and pressure. Wastewater containing reactive Dye was brought from Yirgalem Textile factory and its characteristics were analyzed. The result shows that dye-house wastewaters, containing reactive dyes, are hazardous to the environment since their COD, BOD, TS and pH values are higher than the free discharge limit values and also they are highly colored. It is found that all the three parameters affect the permeate flow and dye removal significantly. The increase of both inlet flow rate and working pressure has positive effect on the permeate flow rate. But increase in dye concentration generally shows negative impact. On the other hand, the increase of inlet flow rate, dye concentration and working pressure increases percent of dye removal. In this investigation, greater than 99% dye removal and maximum permeate flow rate within the minimum fouling rate was obtained at feed flow rate of 0.86m3/h, working pressure of 20 bars, and dye concentration 146.1mg/L. Keywords: Membrane separation, Synthetic dyes, Nano filtration, Wastewaterreuse
Recycling of Used Lubricating Oil Using Acid-Clay Treatment Process
(Addis Ababa University, 2014-10) Andargachew, Hayalu; Yimam, Abubeker (PhD)
Numerous industries are emerging in Ethiopia and urban developments are accelerated giving rise to multiple waste generations. As used lubrication oil is one of the hazardous wastes generated at different development sectors, it should not be utilized and/or disposed in ways which are unsafe to the environment hence calling for its proper management. This study primarily focuses on the recycling of used oil by applying acid-clay treatment process. Used engine oil properties gave expected undesired characteristics caused by oil deterioration. The characterization was indicative to the sources of contaminations from conditions during the oils application period. For instance, the lower flash point (132°C) indicated light fuel contamination effect; increased density (0.93 g/ml) and viscosity (kinematic Viscosity @ 40 °C was 126.41 cSt) showed possible oxidation and polymerization products dissolved and suspended in the used oil; and ash content (2.3%) indicated contamination from incombustible solid particles of dirt, dust, grit and metallic fragments. Similarly, deviations of other parameters also referred different contamination sources. Recycling experiments utilized 15, 20 and 25% acid and adsorbent (Bentonite clay) ratios with different combinations. Nine combinations with their respective triplicates were conducted. The experiments showed that the acid-clay treatment process was effective in recovering valuable oil from used oil samples with comparable qualities. From the twenty seven runs performed, yields within the range of 55% to 74.7 % was obtained. The run with acid percentage of 20% and adsorbent percentage of 15% was chosen as the optimum combination using statistical analysis that considered selected quality parameters of recovered oil i.e. density, kinematic viscosity @ 40 °C and ash content. The optimum combination gave a 69% yield; density of 0.886 g/ml; kinematic viscosity @ 40 °C of 94 cSt; and 0.34% ash content. Eight to ten percent of valuable light fuel was also recuperated from the vacuum distillation step of the process. The preliminary cost analysis showed, an estimated sum amount of 22.86 birr is expected to recover a liter of usable oil which is 61.64 birr less, relative to the amount required to import the original fresh oil that costs 84.5 birr/liter.
Optimization ofMunicipal SolidWaste Vermicomposting Parameters
(Addis Ababa University, 2014-11) Gebrekrstos, Teklebrahan; Worku, Teshome (Ass. professor)
Today, increasing population and rapid development are resulting for generation of large amount of solid wastes in developing countries. Most of these wastes are usually disposed in open dumping site, open spaces, rivers or burned in the streets without any treatment due to lack of proper management techniques, awareness and commitment of the society and the government, which creates severe environmental pollution and health hazards, hence it was thought to attempt use of municipal solid waste for cheap and ecofriendly treatment methods like vermicomposting. It is the process of compost formation by earthworms. Optimization of process parameters for the vermicomposting of municipal solid waste using Esenia fetida was investigated using response surface methodology (RSM). The three parameters and their ranges namely moisture content (60-90%), C/N ratio (20-30), and worm stocking density (0.8-2.0 kg/m2) were chosen from the previous study of vermicomposting. The experimental data on the quantity of N, P and K were fitted into a quadratic polynomial model using multiple regression analysis. The experimental results and software predicted N, P and K values were comparable. The individual parameters effect as well as effect of interactions between the vermicomposting parameters on N, P and K was analysed using various graphical representations. A three-level three factorial Box-Behnken design technique under RSM using numerical optimization method was used to optimize their interactions, which showed that a moisture content of 74.62%, C/N ratio of 23.21, and worm stocking density of 2 kg/m2 were the best conditions. Under these conditions, the maximum predicted yield of N, P and K was 2.82%, 1.58% and 1.28%, respectively. The produced vermicompost was found to be better in desired level of composition of macro-nutrients i.e., N, P and K and the efficacy of the prepared vermicompost has been studied on the spinach vegetable plant. A plastic pot set-up with soil was used to determine the effects and efficiency level of vermicompost on the yields of spinach. The study was conducted through effect of increasing concentration of Vermicompost (0% (control), 50% and 100% w/w) in target plant growth. Total leaves wet weight and number of leaves has been studied. Results showed that the number of leaves produced using 100% VC was 2.67 times greater than the number of leaves produced using 0% VC and 1.6 times greater than produced using 50% VC and leaf wet weight of the spinach plant produced using 100% VC was 2.2 times greater than produced using the control (soil) and 1.2 times greater than produced using 50% VC. Thus, vermicomposting of municipal solid waste is an excellent and ecofriendly method of municipal solid waste management. Key words: Optimization; vermicomposting; municipal solid waste; Esenia fetida; response surface methodology; spinach

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