Browsing by Author "Shimelis, Kebede (PhD)"
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Item The Assessment of Peanut shell and Chat stem as Alternative Energy Source for Cement Industries(AAU, 2018-10) Birhan, Gebregziabher; Shimelis, Kebede (PhD)Cement industries are one of the major energy-intensive industries and heavy polluting process. To reduce the energy cost and environmental impact, cement producers are currently using alternative fuels. This study analyzed the assessment of peanut shell and chat stem as alternative energy source for cement industries. The main objective of this study was to carbonized mixed of a peanut shell and chat stem. The parameters of carbonization process, which affect the calorific value such as temperature (350, 450 and, 450 o C), time (60, 90 and 120min) and mixing ratio (25, 50 and 75%) were optimized via Central Composite Design (CCD). All the necessary analysis that included physiochemical characteristics of peanut shell and chat stem, mixed carbonized and mixed carbonized pellet, then the results were compared with commercial coal. In addition, thermogravimetric analysis were examined the thermal property of peanut shell and chat stem. Based on the result, the optimal conditions were (temperature at 450 o C, time for 60min and mixed ratio 75%) with a maximum calorific value of 6552.6 Cal/g. However, the energy content of sample was comparable with coal, but it needs pellet for suitable storage, handling, transporting. Then the optimum mixed carbonized pellet with 10% of molasses, the calorie develop to 6838.19cal/g. The optimum mixed carbonized pellet showed a decrease in moisture content (2.87%), volatile content (30.75%), Hydrogen (2.95%) and Oxygen (26.19%) while the fixed carbon (57.57%), and carbon (70.86%) increased considerably. Therefore, in this study shows that the mixed carbonized pellet has potential replaced coal as an alternative energy source for cement production due to their calorific value at optimum carbonation condition.Item Characterization and Use of Sewage Sludge Ash as Supplementary Cementitious Material for Concrete(Addis Ababa University, 2019-11) Mohammed, Ali; Shimelis, Kebede (PhD)Disposal of sewage sludge is becoming a serious environmental problem. The incineration process is able to reduce the volume of sewage sludge. It is not a proper solution, so the sewage sludge ash generated after the incineration process, and it must be disposed to landfill. The general objective of this study was to investigate the properties and use of sewage sludge ash as supplementary cementation material for concrete. Sewage sludge was incinerated at temperature of 600 ºC and 800 ºC for 3 & 2.5 hours. The incinerated sewage sludge ash was sieved through size of 75 µm and investigates physical properties, and chemical compositions of sewage sludge ash were carried out. SSA is pozzolanic material satisfied the requirement of ASTM C618. Chemical composition of SSA incinerated at 600 ºC and 800 ºC were determined by Atomic Absorption spectrometer. AAS test has shown that the sewage sludge ash contained primarily these oxides such as SiO2, Al2O3, Fe2O3 and CaO. The concrete specimens were prepared using 5 %, 10 %, 15 %, and 20 % of the two temperatures incinerated sewage sludge ash that is 600 ºC and 800 ºC, and design mix ratio of 1:2:4 with w/c ratio was 0.82. The cubic mold size of 10 cm x 10 cm x 10 cm was used to produce a concrete specimen, and the concrete tests have then been measured both at the fresh and hardened concrete. In the hardened concrete, the results of a concrete have shown that 600 ºC SSA 5% & 800 ºC SSA 10% replacement of OPC by sewage sludge ash achieved a higher compressive strength than the others percentage of set in this research at the age of the 28 days as compared with the control concrete (0 % SSA). The percentage of water absorption increased with increase in sewage sludge ash that incinerated at temperature of 600 ºC & 800 ºC, and all the blended (% SSA) concretes have shown a higher amount of water absorbed as compared with the control concrete (0 % SSA).Item Decolorization of Cane Syrup by Activated Carbon Produced From Peanut Shell(Addis Ababa University, 2019-06) Askal, Haile; Shimelis, Kebede (PhD)Sugar colourants are water soluble compounds present in sugar process products and the most impurities in sugar industry. Syrup decolorization can be achieved by sulphitation process. However, at the same time the formation of fine precipitate of CaSO4 become difficult to eliminate trace of SO2 in final sugar. The aims of this research were to produce activated carbon from peanut shell using KOH as an activating agent for syrup decolorization with lower color and lower residual sulfur dioxide levels and as an alternative waste management method. In this study, the first stage was producing granular activated carbon from peanut shell at different parameters such as: activation temperature (500 o o o C, 600 C and 700 C), KOH concentration (25, 50 and75%wt.) and particle size (0.5, 1.5 and 2.5mm). Low ash content (1.28%) with high percent of methylene blue adsorption (79.4%) of activated carbon was obtained having 0.5mm particle size, 0.26%wt. KOH, and 600 o C of activation temperature was with 0.965 desirability chosen as optimal activation parameter. The activated carbon at optimal condition was characterized in term of ultimate and proximate analysis, FT-IR and methylene blue adsorption efficiency. Using activated carbon, the effect of various process parameters like temperature, activated carbon dosage and time on decolorization of cane syrup was investigated. Under the experimental conditions of 45 o C, 1.4g activated carbon dosage for 75min was found to be the optimal condition for maximum cane syrup decolorization efficiency (75.5%). Consequently, the experimental results indicated that the peanut shell has a potential to be used as an activated carbon for decolorization of cane syrup.Item 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.Item Extraction and Characterization of Essential oil from Thyme (Thymus Schimperi L.) Leaves by using Steam Distillation(Addis Ababa University, 2019-06) Tsige, Tsegay; Shimelis, Kebede (PhD)Essential oils are very interesting natural plant products, and among other qualities they possess various biological properties. This study has been carried out to extract the essential oil from the leaves of thymus schimperi L. using steam distillation. Thyme (thymus schimperi L).is an indigenous plant in Ethiopia and is locally called “Tosign’’ (in Amharic). It is among the commonly occurring thymus species that distributed in different regions of Ethiopia. In this research, thyme leaves were collected from debresina, Tarmaber Woreda. First, the leaf of thyme was dried through partial sun drying. Then the dried thyme leaves were crushed in cross beater mill with sieve size of 2mm and by cutting mill. The sample was sieved using a set of sieves sizes. Next to this, the experimental work was carried out by steam distillation set up. A general factorial design was employed to the extraction process using design expert 7.0 software and linear regression model. This design helped to identify individual effects of extraction time, and particle size, as parameter and their interaction in the entire extraction process. In the extraction experiment, the minimum oil yield of 1.18% was obtained after the extraction time of 60 minutes with particle size of 2 mm and maximum oil yield of 2.12 % was obtained at optimum extraction time of 150 minutes with particle size of 0.5 mm. This shows that, increasing extraction time (optimum of 150 minutes) and decreasing particle size increases the yield of oil. Characterization of the oil was also carried out. Accordingly the yield was found with 1.54 refractive index value, 0.948 �� ����3 specific gravity, and 0.42 degree optical rotation, 6.2 pH, 6.02 mpas dynamic viscosity, 1870C boiling, 101.512ml/g iodine value, 33.6 ml/g saponification value, 5.18 acid value, 28.42 ml/g ester value and 2.605% free fatty acid. The essential oil was analyzed by combined Gas Chromatography and Mass Spectroscopy unit, and it was found to been reached in monoterpenes alcohol and phenolic containing components. Among the major components from the GC-MS analysis were thymol (63.20 %), p-Cymene (11.112%), Carvacrol (8.62%) and Linalool (2.41 %).Item Investigation of the potential of Salt Bridge Mediated Microbial Fuel Cell for Power Generation and Brewery Wastewater Sludge Treatment(Addis Ababa University, 2019-07) Hagos, Mebrahtu; Shimelis, Kebede (PhD)The release of brewery wastewater sludge with high pollutants and soluble organic contents can pose a significant threat to human health and environment due to their toxicity. The present study aims at investigating the potential of Microbial Fuel Cell (MFC) to utilize brewery wastewater sludge as feed stock of electricity generation. The characterization of the brewery wastewater sludge before and after it goes through the microbial fuel cell was analyzed using reactor digestion method, OxiTop BOD5, (HACH method DR890) molybdovanadate method, (HACH method DR 890) TNT per-sulfate digestion method for chemical oxygen demand (COD), biological oxygen demand (BOD), total nitrogen (TN), and total phosphorus (TP) respectively. The effect of varying salt concentrations (1 M, 2M, and 3M) of the salt bridge in MFC have been analyzed with different factors like temperature ranging 20 to 45 °C, and pH ranging from 4 to 10. Results were analyzed in terms of efficiency in chemical oxygen demand (COD), biological oxygen demand (BOD5), total nitrogen (TN), and total phosphorus (TP) removal and capability of energy generation. The optimum temperature was found 32.5 °C, with the optimum pH of 7 and 3 M salt bridge concentration in which the maximum removal percentage and power generation was observed. At the optimum condition the observed power output, removal percentage of chemical oxygen demand (COD), biological oxygen demand (BOD5), total nitrogen (TN), and total phosphorus (TP) were 0.88 V, 93.58%, 93.07%, 1.39%, and 1.19% respectively. Box-Behnken experimental design (BBD) has been used to find the optimum condition for voltage production, chemical oxygen demand (COD), biological oxygen demand (BOD5), total nitrogen (TN), and total phosphorus (TP) removal percentage.Item 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.Item 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 concreteItem Synthesis and Performance Evaluation of Titanium Dioxide Supported Bentonite Composite for Methyl Orange Removal from Wastewater(Addis Ababa University, 2019-06) Abrham, Balew; Shimelis, Kebede (PhD)Dye effluents discharged from different industries causes series damage to aquatic animals as well as human beings by mutagenic and carcinogenic effects. Thus, the effluents needs to be treated before discharged to the environment using advanced oxidation process. TiO2 supported bentonite composite was used in the photocatalytic discoloration of dyes from wastewater i.e., methyl orange (MO). During usage of the composite as a photocatalyst for dye removal, physiochemical characteristics and effect of synthesis and photocatalytic parameters were investigated using Box-Behnkon Design response surface methodology. Characterization of the composite catalyst XRD analysis revealed that, the composite catalyst contains bentonite component (montmorillonite, quartz and feldspar) and TiO2 components (anatase and rutile). The crystal size of raw bentonite and composite were 24.73nm and 53.43nm respectively. In the design of experiment, the efficient catalyst was selected based on its dye removal efficiency via numerical optimization. Calcination temperature 400 C, calcination time 2h and TiO2 to bentonite ratio 0.2 were selected for 96.54% removal efficiency. Also for photocatalytic experiment dye concentration 10mg/L, catalyst dose 1.5g/L and UV irradiation time 2h gave 94.88% removal efficiency. The study justified that, composite photocatalyst titanium dioxide supported with bentonite has many advantages such as improve photocatalytic efficiency, recycling efficiency of the catalyst, improves the recovery rate, save the cost of treatment and improves the light absorption efficiency.Item 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.Item Textile Sludge Based Bricks Production from Hawassa Industrial Park Zero Liquid Discharge Facility(Addis Ababa University, 2018-12) Tsegay, Gebremedhin; Shimelis, Kebede (PhD)Textile sludge is an inevitable byproduct discharged from wastewater treatment plants and becoming a great challenge in today’s industrial parks. Presently, the sludge generated from the ZLD facility is sent and collected inside nearby big constructed shed without any treatment. Since, the sludge is characterized by high level of organic and inorganic components including heavy metals, its accumulation is a burden to the industry and affects the environment and human well-being adversely. Hence, it demands an alternative sludge disposal method. Therefore, the main objective of this study was to investigate the physio-chemical sludge characteristics and suitability of utilizing sludge in the manufacture of bricks replacing natural clay the case of Hawassa industrial park. The test results revealed that concentration of BOD, COD and the principal heavy metals viz. Pb, Zn, Cr & Mn of the textile sludge were 535, 9820 mg/l and 2.25, 30.45, 8.08, 6.75 mg/kg respectively. Additionally, the proximate analysis of the sludge moisture content, VOM, ash and fixed carbon was 82.5, 48.4, 44 and 7.6 percent respectively. Similarly, the quantity of chemical constituents SiO2, Al2O3, CaO and Fe2O3 conducted by using chemical analysis methods, were 16.10, 21.40, 2.56 and 2.32 in percent respectively. The presence of these compounds indicates the potential use of this sludge as partial replacement of building materials. In this work, the effects of sludge proportion 10%, 15% and 20% by dry weight and firing temperature of 800℃, 900℃ and 1000℃, on the quality of the bricks (Water Absorption, and Compressive Strength) were examined and the results were compared with those of controlled bricks. From the results, the minimum values of compressive strength obtained was 2.93 N/mm2 at 20% and 800℃ whereas the maximum amount is 4.2 N/mm2 at 10% sludge mix and 1000℃. Again, the Water Absorption of 21.33% and 12.4% was gained at 20% and 10% sludge content. Moreover, the sludge amended up to 20% mixing ratio shows minimum leachability of heavy metals as performed by ICP-OES and compatible as compared to the USEPA standard. Consequently, the experiment work indicates the potential of textile sludge in the manufacturing of bricks.