Environmental Engineering

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    Adsorption of Heavy Metal from Constituent Waste Water by Tea Waste Adsorbent
    (Addis Ababa University, 2016-06) Oljira, Lalise; Kiros, Solomon (PhD)
    Most industries such as electroplating, textile, fertilizer, batteries, leather, and others in less developed countries discharge huge volumes of untreated wastewater into water bodies. The industrial wastewater may contain toxic chemicals in excess of the threshold level when released into the environment, particularly to the aqueous environment and soil; significantly degrade the quality of the water thereby affecting river health substantially and subsequently human health. There are several techniques for removing toxic chemicals such as ion exchange, membrane filtration, adsorption, irradiation and chemical and biological treatments. However, the adsorption method is believed to be the better option because it is cost-effective, efficient, simple and easy to operate, and environmentally friendly according to many studies. Accordingly, this method can be a preferable option for developing countries like Ethiopia, where advanced treatment technologies for high volumes of toxic industrial waste water are unaffordable. The aim of this work was to determine the potential of tea waste (TW) as a useful adsorbent for the removal of copper and zinc ions from aqueous systems. The study was conducted using batch experiments with constituted wastewater having copper and zinc ion concentration of 1000 mg·L-1. The effects of initial concentration, contact time and pH on adsorption efficiency were investigated. Adsorption isotherm was also studied. Generally, the result showed an increase in removal efficiency with increase in contact time, pH and decrease of initial concentration. The adsorption equilibrium data correlate well with Freundlich model and Langmuir model respectively for zinc removal and copper removal with regression coefficient (R2=0.9913, R2=0.981). The results showed that efficiencies of (TW) for the removal of copper and zinc ion were 95.98% and 99.80% respectively at optimum point of 5pH, 10ppm, and 120min. These results clearly indicate the efficiency of tea waste (TW) as a low-cost adsorbent for treatment of wastewater containing copper and zinc ions. Therefore, it is recommended that tea waste can be used, as a low cost and abundant source for the removal of heavy metals as an alternative to more costly materials. KEY WORDS: Copper, zinc, toxicology, adsorption, tea waste, batch study, atomic adsorption spectrometer.
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    Adsorption of Methylene Blue Dye from Synthetic Wastewater using Chitosan/graphite Composite Adsorbent; Statistical Optimization
    (Addis Ababa University, 2023-11) Soliyana Teshome; Shimelis Kebede (PhD)
    The study aimed to synthesize a chitosan/graphite composite (CGC) for methylene blue dye removal from synthetic wastewater using the impregnation method. Expanded graphite was prepared by reacting graphite with H2SO4 and H2O2 at room temperature, then washed, dried, and heated. The specific surface area of graphite increased from 1193.75m2/g to 1223.648m2/g. The composite adsorbent material was synthesized using the impregnation method, with chitosan to expanded graphite ratio of 75:25. The CGC was characterized using Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer-Emmett-Teller (BET) method, scanning electron microscope (SEM), and point of zero charge analysis. The optimized experimental design resulted in 98.61% removal efficiency at initial concentration of 5.24 mg/L, pH of 9.98 and contact time of 95.43. The adsorption of methylene blue dye onto CGC was best fitted with Langmuir isotherm, with an R2 value of 0.9974 and adsorption capacity of 98g/g. The kinetics of adsorption were best fitted to pseudo-second order with an R2=99.39.
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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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    Application of Hydro-Metallurgy (Wet Etching) To Recovery A Precise Metal (Gold) From A Wasted Printed Circuit Broad (WPCB): Case Study of Ministry of Information Communication and Technology (MICT)
    (Addis Ababa University, 2017-11) Kidist, Wendium; Berhanu, Assefa (PhD)
    This thesis research is undertaken with the main objective of assessing the existing e-waste management in Ethiopia by taking ministry of information and communication technology as a case study and to propose e-waste recycling approach (hydrometallurgy) to recover gold. To meet the research objectives a blend of qualitative and quantitative methods were used where unstructured key informant interviews, Observation of the e-waste disposal site from the selected govermental organization and computer recycling and refurbishment center (CRTC) at Kality were combined with Case study at laboratory scale hydro-metallurgy to recover gold from waste printed circuit boards (PCB).It is found that E-waste is expected to be a huge problem in the future, given the rise in consumption trend of the target institutions and the general importation trend of the country. There is high accumulation of old ICT equipment in the target institutions of the study. Parallel to that, The current trend of lifecycle management of this electronic waste at CRTC and at Addis Ababa University is out date and the precious metals like that of gold are not properly recycled.in addition by applying hydrometallurgical approach (wet etching), from a sample of 500 gm printed circuit board 1.66 gm of gold was recovered with mineral composition of 99.71% Au, 0.12% Ni,0.16% Cu. this research under takes an experimental procedure where, At the start of the experiment 20 gram of fingers was used for on batch. And added to on an empty beaker. The next step will be dilution of the hydrochloric acid, hydrochloric acid with the concentration of 35% will be diluted by adding 57 ml of water on the biker. Finally we can get hydrochloric acid with the concentration of 15% with a volume of 43 ml. next the addition of hydrogen per oxide which has a concentration of 15% with a volume of 50 ml and the reaction proceeds for 6hr after that The combination of hydrochloric acid and hydrogen per oxide will detached the gold fingers from the silicon chips and a film of gold fingers will float, finally Using kitchen strainer and a large coffee filter the gold foils will be filtered out of the acid peroxide solution. The results were obtained by taking Hydrochloric acid to hydrogen per oxide proportion(1:0.5,1:0.4,1:0.9),retention time( 6hr,12hr,21hr) and hydrochloric acid concentration of ( 5%,10%,15%) as factors and on the basses of the study the optimum conditions to get a maximum amount of gold (0.2455 gm) was HCl: H 2 O 2 proportion of (1:0.5), HCl concentration (10%) and retention tine (12hr) .In conclusion, to draft a solution and act accordingly, the government through its instruments should put a system in place.
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    Assesment of Maerua Subcordata Root As Biosorbent for The Removal of Cr (Vi) Ions From Tannery Waste Water
    (Addis Ababa University, 2015-05) Berecha, Mesfin; Negusie, Agizew (PhD)
    Chromium containing wastes are generated by industries such as leather tannery, electroplating, paint and pigment manufacturing. The form of Cr (VI) is responsible for human carcinogen as well as water and soil pollution. The main objective of the present study was to evaluate the possibility of using Maerua Subcordata as a Biosorbent for the removal of Cr (VI) from tannery waste water and aqueous solution. The study was conducted in Addis Ababa university Environmental science laboratory center and Ethiopian leather industry development institute laboratory center, from January to May, 2015. Maerua Subcordata was collected from South Omo Zone DasenechWoreda and cut in to small pieces, dried in the sunlight and grind to produce the powder, treated with H3PO4 (45%w/w). Physical characterization such as moisture content and bulk density of activated Maerua Subcordata was done and it was found low moisture content which indicates high quality of the biosorbent.The Biosorption of Cr (VI) from aqueous solution and real tannery waste water by activated Maerua Subcordata was studied. The biosorbent was characterized by FTIR spectroscopy and characterization of the Maerua Subcordata suggested the possible contribution of carboxyl and hydroxyl groups in Cr (VI) Biosorption. The Biosorption efficiency of the Maerua Subcordata was dependent on the pH of the Cr (VI) solution, with pH 3 being optimal. The removal rate of Cr (VI) ions increased with increase in contact time and remained constant after an equilibrium time of 60 min. The removal of Cr (VI) ions increased with increase in biosorbent concentration with the optimal biosorbent dosage at 125 mg/L. Both Langmuir and Freundlich model were followed by adsorption of Cr(VI) on activated MaeruaSubcordata. But Langmuir model best describes the adsorption data with coefficient of determination (r2) value 0.993.The maximum adsorption capacity obtained from Langmuir model is 4.54mg/g.The RL value obtained from Langmuir model shows the adsorption is favorable. When applying the biosorbent to real waste water 86.5% removal efficiency was obtained. The reduction in efficiency might be due to the presence of interfering ions which compete with Cr (VI) ion for Biosorption. Therefore, the study revealed that the activated Maerua Subcordata could be used as an excellent biosorbent for the removal of Cr (VI) chromium from Tannery wastewater and aqueous solution. Key words: Hexavalent chromium, Activated Maerua Subcordata, Biosorption
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    Assessment and Modeling of Surface Water Quality Dynamics in Awash River basin, Ethiopia
    (Addis Ababa University, 2019) Amare, Shiberu; Zebene, Kiflie (Assoc. Prof.); Agizew, Nigussie (PhD) Co-Advisor
    Awash River has the most important economic values in Ethiopia. However, it has been recognized as being impaired by high amount of various pollutants owing to waste released from different socio-economic activities in its basin since the basin encompasses the main urban, industrial and agricultural centers of the nation. However, investigation of pollution level of the basin is necessary for decision makers to safeguard Awash River and its end users, which has not been addressed yet. This research was therefore aimed at evaluating the status, assessing the spatial-temporal dynamics and modeling surface water quality dynamics in relation to different land use scenarios in Awash River basin. Status of water quality of Awash River was evaluated with respect to drinking and irrigation water uses by choosing 17 sample sites along the River based on accessibility and land use severity and sampling was done twice in each of the dry and wet seasons. Then both onsite and offsite water quality analyses were undertaken following standard procedures. After comparing different water quality indices in use todate, Canadian council of ministers of environment water quality index was applied to compute the water quality indices. The drinking and irrigation water quality indices of the upper basin were 34.79 and 46.39 respectively, which were in the poor and marginal categories of the Canadian water quality ranking. Similarly, the respective indices for the middle/lower basin, which were 32.25 and 62.78, lie in the same ranges of the ranking. Although the difference in the used dataset of the two cases and natural purification in the course of the River might contribute to the difference in WQI, it is generally conceivable that the water quality of the River is below the fair rank. To assess the spatial and temporal variation of water quality in the basin, means of the 9 years’ (2005-2013) water quality dataset of 19 parameters from 10 stations in the basin were used. After validating, normalizing and checking the sampling adequacy and internal consistency of the data, principal component analysis was computed and four principal components were generated. Factor loadings, correlations between variables and the principal factors as well as between sites and the principal factors were tabulated. Agglomerative hierarchical clustering done on the dataset resulted in four clusters based on similarity of water quality characteristics. The Mann-Kendall’s two tailed trend test detected temporal trends for total hardness in February over all sites and for most parameters in the basin in the 9 years period. Spatial analysis of the 14 sampling sites of the basin showed that as one moves from upper to lower parts of the basin, electrical conductivity, total hardness and chloride levels decrease in the dry season. However, total hardness slightly increases and total dissolved solids, chloride, and sulfate content decrease in the rainy season. Cl are maximized respectively at before Beseka and Beseka in both seasons and Beseka, before Beseka and Sodere spring are found to be important sites responsible for the spatial variation. - and EC/TDS/SO4 - To see the relation between land use/land cover (LULC) and water quality in the basin, LULC dynamics was assessed by using cloud-free LS 5 and 7 TM imageries of 1994, 2000 and 2014. The images were captured from EROS center of USGS GloVis viewer and classified by supervised classification coupled with maximum likelihood algorithm in ERDAS Imagine. The dominant LULC of the eight identified land use types were agriculture, barren land, and shrubland in the 3 years’ period. Built-up and water bodies were found to have increased and decreased respectively by about 147% and 63% as one goes from 1994 to 2014. Moreover, in line with the changes in land use specifically of urbanization and agricultural intensification from 2000 to 2014, around which water quality have been analyzed, the parameters EC, TDS, Alkalinity, TH, SO4 2- , and NH3 were found to increase monotonically. Mean values of water quality indicators such as EC, nitrate, and some anions have been compared in the agriculture-dominated, industry-dominated and urban-dominated land uses. As a result, EC within the urban and industrial land uses was found to be maximized. Nitrate, on the contrary, is observed to be higher in agriculture-dominated land uses and higher concentration of anions (bicarbonates and chlorides) and hardness have been generated from urbanized areas. + - , Na + , Cl , K This study also evaluated performance of the Soil and Water Assessment Tool (SWAT) by modeling nitrate and phosphate at the basin scale. First, the model was set up using digital elevation model (DEM), climate, soil, and land use data. Thereafter, overall performance of the model was assessed by linking its outputs to the Sequential Uncertainty FItting Version 2 (SUFI2) procedure of the SWAT Calibration and Uncertainty Program (SWAT-CUP). The most sensitive parameters for the flow and nutrients were identified using t-stat and p-values from global sensitivity analysis of the SWAT-CUP. The goodness-of-fit of the monthly calibration measured by coefficient of determination (R ), Nash-Sutcliffe Efficiency (NSE), and root mean square error-observations standard deviation ratio (RSR) were respectively 0.79, 0.64 and 0.60 for flow; 0.73, 0.71 and 0.54 for nitrate and 0.77, 0.76 and 0.49 for phosphate. During validation, R 2 2 , NSE and RSR were respectively 0.81, 0.52 and 0.70 for flow; 0.68, 0.63 and 0.61 for nitrate and 0.82, 0.81 and 0.44 for phosphate. The results suggested that the model is promising to predict nutrients in the basin. From the modeling, concentrations of nutrients were found to be both seasonally and spatially variable. Sub-basins 4, 8, 13, 21 and 39 were hotspots both in 1994 and 2014 with respect to exporting higher amounts TN and TP. From the temporal investigation of nutrients’ monthly averages in the period from 1997 to 2014 of sub-basin 3, the rainy months (March, July and August) export higher amounts. Basin-wide comparison of the monthly averages of nitrate, phosphate, TN and TP losses from the model simulations with the 2000 and 2014 LU’s indicate that the respective values were generally greater in 2014 than in 2000. From the trends of TN and TP for each of the 53 sub-basins in 1994, 2000 and 2014, slight reduction was observed for the year 2000 as compared to that in 1994. However, since the increment from 2000 to 2014 was significant, the overall trend from 1994 to 2014 was found to be positive (increasing). Results of the study have applications of filling the existing knowledge gap, facilitating informed decision making, using as a customizable framework for similar studies in other river basins of the nation.
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    Assessment of Photo-Fenton Process for The Removal Of Pesticide from Wastewater
    (Addis Ababa University, 2019-12) Bikila, Firdissa; Solomon, Kiros (PhD)
    The main purpose of this work was to study assessment of photo-Fenton process (Fe /H2O2/UV) for the removal of pesticide from wastewater. Synthetic wastewater from 2,4Dichlorophenoxyacetic was prepared and characterized for its organic matter content and also it PH and turbidity which has a significant effect on the degradation process. Box-Benkhen design response-surface methodology was developed to optimize photo-Fenton degradation of 2,4Dichlorophenoxyacetic in which UV light radiation was used as a source of light. The three variables considered in Box-Benkhen design model included initial 2,4-Dichlorophenoxyacetic [2,4-D], hydrogen peroxide [H2O2] and Ferrous iron [Fe 2+ ] concentrations. The removal efficiency was expressed in terms of total organic carbon (TOC) and chemical oxygen demand (COD) percentage removal. The optimum values of 94.7 mg/L 2,4-D, 22.78 mg/L Fe 2+ , 156.4 mg/L H2O2 were obtained by optimizing the variables using Box-Benkhen design that the data was analyzed after carrying out each experiment for 2 hours at room temperature. The photo-Fenton process led to 85% TOC removal and 96% COD removal thereby showing the effectiveness of using photo-Fenton process for the removal of pesticide from wastewater.
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    Assessment of the Current Solid Waste Management Practice: A Case Study of Dukem Town, Central Oromia Region, Ethiopia
    (Addis Ababa University, 2024-06) Ikram Mohammed-Amin; Shimelis Kebede
    Solid waste management is recognized as a global concern that impacts both individuals and governments. Insufficient waste management practices in cities, such as widespread waste dumping in water bodies and along roads and drainage canals, exacerbate sanitation issues in African nations, Ethiopia included. Ethiopia, categorized as a lowincome country, grapples with the repercussions of ineffective management of solid waste, especially in its swiftly urbanizing areas. Dukem is one of the town located in a central Oromia region of Ethiopia facing the problem. The primary objective of this study is to evaluate the present state of solid waste management in Dukem Town. Descriptive survey and Multi-stage sampling technique was employed. The samples were collected from 90 household and from different commercial activities in the study area. The collected samples were sorted into 11 components and measured. Organic wastes represent a significant proportion of the total Solid Waste produced and accounts for about 67.34%. The remaining waste is made up of dense plastic (0.92%), film plastics (5.67%), paper and cardboard (4.08%), metals (1%), special wastes (0.36%), textiles and shoes (1.3%), glass (1.97%), composite products (0.15%) and other wastes (17.21%). According to the study's findings, Dukem Town generates 0.209 kg of solid waste per person every day with a density of 287 Kg/m3. Material flow analysis can be applied in environmental research and it was used as a basis for analyzing and planning waste management and recycling systems and also to evaluate an existing solid waste management practice of Dukem. The analysis of the socio-economic effect evaluation of solid waste management strategies also looked at how it affected the content and amount of solid waste. Due to the wastes high organic content composting is good waste management option that has to be practiced, since there will be better chance of lowering the enormous volume of waste disposed away to disposal site as well as decreasing the Greenhouse gas emission. By composting 50% of the waste designated to the disposal site 39.5% of resource will be managed.
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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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    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.
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    Bioethanol Production from Water Hyacinth by Chemical Hydrolysis (Preliminary Study)
    (Addis Ababa University, 2016-06) Betelihem, Mekonnen; Ojito, Eduardo (Prof.)
    Ethiopia, in order to reduce its dependency on imported petroleum fuels which consumes more than70% of the foreign currency earning, climate change issues and to tackle invasive weed problem such as Water hyacinth through integrated management approach of the concept of waste to Energy, a lot of research needs to be conducted. Bearing this in mind, this study was conducted to conduct preliminary assessment on bioethanol production potential WH by chemical hydrolysis. Water hyacinth was collected from river Awash, the root was cut out and the leaf and stem part were properly washed, dried and chopped for further analyses. Sample characterization result showed that Water hyacinth has high moisture content and the extractive free WH has 30%, 48% and 5% cellulose hemicellulose and lignin respectively. In this study Water hyacinth was hydrolysed with sulfuric acid (2-5 %v/v), temp (116-130 oC) and hydrolysis time (16-60min) and optimal reducing Sugar obtained was 31.152 g/L at acid concentration 3.97% v/v, Temperature at 129.91 oC and 57.82 minutes reaction time. In this study, Ethanol yield obtained is extremely low. Ethanol yield ranges from 0.05% to 0.532% from obtained RS of WH hydrolysate with fermentation parameters of temperature 30oC for 72hr and 150 RPM. The highest ethanol yield was not at the optimal value of factors for maximum reducing sugar but at increased acid concentration but at the lower temperature. This may be due to high content of hemicelluloses and at optimal values of factors pentose sugars are high and at increased acid concentration and temperature partial hydrolysis of the cellulose component has occurred to increase the hexoses sugars that are easily fermentable with the given condition. These results suggest that refinement of the hydrolysis and fermentation process and application of the selected yeast which hydrolyze both hexose and pentose sugars could improve the efficiency of obtaining bioethanol from the water hyacinth.
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    Biogas Production by Anaerobic Co-Digestion of Food Wastes with Goat Manure
    (Addis Ababa University, 2017-12) Gidey, Kiros; Teshome, Worku (Asst. Prof.)
    Due to the rapid population growth and unmanageable urbanization, one of the burning issues faced by the world today is management of all types of wastes. This study has been conducted on the production of biogas by anaerobic co-digestion of food wastes with goat manure. Food waste (FW), goat manure (GM) and their mixtures were anaerobically digested for 40 working days. The proximate composition analysis of the FW and GM had shown that, whereas the GM was higher in TKN value (2.1%), the MFW was higher in C/N ratio (34.0). During this study FW and GM were combined into five MFW to GM mixing ratios of 1:0, 1:1, 2:1, 1:2, and 0:1; and a total of 45 MRs (nine for each mixing system) were prepared in 1-liter plastic bottles. The pH of these MRs was adjusted to 6, 7, and 8 by adding 10 N NaOH. Three water baths were set to three temperature values of 30o C, 35o C and 40o C in which the 45 plastic bottles of 1-liter capacity (15 plastic bottles in each water bath) as main digesters were immersed. The experimental AD of this study took 120 days (40 working days for each experimental setup) to produce biogas. The combination systems of the MFW and GM for co-digestion overcomes the imbalanced C/N ratio of the MFW. The efficiency of the mono-digestion of MFW only, GM only and co-digestion of the MFW with GM were studied and compared. Statistical design of the experiments and data analysis was investigated using the general factorial design. Statistical test had shown that the model "F values" for both the responses, the biogas volume and methane content in the biogas were statistically significant (P<0.05). The optimum MRs between the MFW and GM were found to be the 1:1 and 1:2 MRs at process parameters of 35o C and initial pH of 7.0. The cumulative biogas generated at these conditions were found to be 11.4 and 17.3 liters respectively from the MRs of 1:1 and 1:2. Averagely, higher methane yield of 61.1% and 63.5% respectively was obtained by the codigestion of MFW with GM at 35o C and initial pH value of 7.0 from the MRs of 1:1 and 1:2. The results noted from this study showed that the anaerobic co-digestions of MFW with GM was better than mono-digestion of the single waste alone for biogas generation.
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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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    Biomass Gasifier Process Simulation for Sustaibale Energy Production from Different Biomass Feedstock
    (Addis Ababa University, 2017-11) Seada, Mohammed; Abubeker, Yimam (PhD)
    With the gradual depletion of coal and petroleum resources, biomass is being perceived as a self-sustainable source of energy production. It is cheap and readily available as well. Gasification is one of the potential sources for production of clean and eco-friendly fuel. ASPEN PLUS simulator is a strong tool for investigating the behavior of a process and it can be readily used to access various aspects like feasibility of an operation, effect of operating parameters on the performance of a gasifier. In this paper, steady state simulation model of air gasification has been developed in Aspen plus for fixed bed biomass gasifier using rice husk, coffee husk and saw dust as a fuel and the analysis of fuel samples was done through ultimate and proximate properties of the biomass. Aspen plus is selected as a simulation tool due to its higher capability of handling solid feed using physical models. The fixed bed gasifier used here is an updraft type one with drying, Pyrolysis, gasification, and combustion stages. The gasifier has been modeled based on thermodynamic equilibrium model by Gibbs free energy minimization in four stages. In the first stage moisture content of biomass feed is reduce through drying. In the second stage biomass is decomposed into its elements by specifying yield distribution. In the third and fourth stages gasification and combustion reactions has been modeled using Gibbs free energy minimization approach. Simulation result include; sensitivity analysis of Air to fuel ratio, gasification temperature, gasification pressure, and, steam to biomass ratio have been varied over wide range and the effect of these parameters on syngas composition and lower heating value has been investigated. The sensitivity analysis results indicated that increase in air to fuel ratio decreases the heating value of the producer gas. Temperature increases the production of CO and H2 and enhances the heating value of the producer gas. Higher pressure reduces H2 rich syngas hence decreases the lower heating value of the producer gases. Steam as a gasifying agent favors hydrogen production which results in increase of hydrogen content in the syngas, while increase of the steam to biomass ratio had negative effects on lower heating value of syngas. Based on the simulation results, maximum lower heating value of syngas was found at the gasification temperature of 800ºC, steam flow rate of 0.3 kg/hr, and pressure of 1bar was obtained at air flow rate of 0.5 kg/hr for 1.5 kg/hr of each feed stocks.
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    Biopolymer Based Hydrogel for Adsorption of Heavy Metal Ions from Aqueous Solution: Experimental and Theoretical Investigation
    (Addis Ababa University, 2024-04) Leta Lemma; Zebene Kiflie (Prof.)
    Contamination of water by heavy metal ions, in particular, hexavalent chromium (Cr6+) ion, lead (Pb2+) ion and cadmium (Cd2+) ion, has become one of the most serious issues threatening human health and thus remedial measure have to be taken. Adsorption–based research toward biodegradable polymers for heavy metal ions remediation has received much attention in recent years due to environmental concerns. Polysaccharides in this domain are interesting starting materials for the preparation of novel adsorbents. In this work, novel type of biopolymer–based hybrid hydrogel such as PPSgCG, PCCFG, and CZVI–CS–PVA were designed for removal of Cr6+, Pb2+, and Cd2+ ions from aqueous solution. Polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), acrylamide–grafted native starch (Coccinia abyssinica) (S–g–AAm), chitosan (CS), and graphene oxide (GO) were used to prepare PVA–PVP–S–g–AAm–CS–GO (PPSgCG) hydrogel. L-cysteine–functionalized graphene oxide (CFG), chitosan, and polyvinyl alcohol were used to synthesis polyvinyl alcohol–chitosan–cysteine–functionalized graphene oxide (PCCFG) hydrogel. L–cysteine stabilized zero–valent iron (CZVI), chitosan, and polyvinyl alcohol were used to prepare L–cysteine–zero–valent iron–chitosan–polyvinyl alcohol (CZVI–CS–PVA) hydrogel. Physiochemical properties of freeze–dried hydrogel were characterized by Fourier transform infrared spectroscopy (FTIR; Spectrum 65, PerkinElmer), zetasizer (3000HS), scanning electron microscopy (SEM; JCM-6000 Plus, Japan), energy dispersive X–ray spectroscopy (EDX; JSM–IT 100, JEOL), X-Ray Diffractometer (XRD; XRD–7000, Shimadzu, Japan), and thermogravimetric analysis (TGA/DTA; HCT–1, China). Adsorptions of Cr6+ ion onto PPSgCG and CZVI–CS–PVA hydrogel, and Pb2+ and Cd2+ ions onto PCCFG hydrogel as functions of initial heavy metal ion concentration, pH, time, hydrogel dose, and temperature have been studied by following a one–factor–at–a–time approach. The Cr6+ ions concentration in solution was determined by UV–vis spectrophotometer (Human, X–ma 1200). The Pb2+, Cd2+, and Cu2+ ions concentration in the solution after adsorption was determined by atomic adsorption spectroscopy (AAS; ZEEnit 700p, Analytikajena). The adsorption of Cr6+ onto PPSgCG hydrogel, at optimum conditions: 2, 100 mg l-1, 120 minutes, 3 g l-1, and 25oC of pH, initial Cr6+ ion concentration, hydrogel dose and temperature, respectively; were obtained considering both adsorption capacity and removal efficiency. The adsorption data agree with Langmuir (R2 = 0.99) isotherm at 25°C and follow pseudo–second–order kinetic model (R2 = 0.999) at pH of 2. The maximum adsorption capacity of the PPSgCG hydrogel towards to Cr6+ was 93 mg g−1. The obtained negative standard Gibb‟s free energy (ΔG°= – 1.120 kJ mol−1) and negative enthalpy (ΔH°= – 2.360 kJ mol−1) reveal the spontaneity and exothermic nature of Cr6+ ion adsorption onto the hydrogel. Moreover, the adsorption thermodynamics shows enthalpically favoring host–guest complexion along with decrease in entropy. Furthermore, the effect of common competing ions such as sulfate (SO32-), phosphate (PO43-), nitrate (NO3−), and chloride (Cal−) ions on adsorption efficiency and selectivity of Cr6+ ion on the hydrogel were investigated and the result shows that sulfate ion has a significant effect on the Cr6+ ion adsorption, which might be related to identical chemical properties and geometrical configuration. The adsorption of Cr6+ onto CZVI–CS–PVA hydrogel, at optimum conditions: 3, 45 mg l-1, 90 minutes, 4 g l-1, and 25oC of pH, initial Cr6+ ion concentration, hydrogel dose and temperature, respectively; were obtained considering both adsorption capacity and removal efficiency. The adsorption data agree with Langmuir isotherm (R2 = 0.99) at 25°C and follow pseudo–second order (R2 = 0.999) model at pH of 3. The maximum adsorption capacity of the PPSgCG hydrogel towards to Cr6+ was 15.86 mg g−1. The adsorption of Pb2+ and Cd2+ onto PCCFG hydrogel, at optimum conditions: 5, 225 mg l-1, 50 minutes, 2 g l-1, and 25oC of pH, initial Pb2+ and Cd2+ ion concentration, hydrogel dose and temperature, respectively; were obtained considering both adsorption capacity and removal efficiency. The experimental data well described by a pseudo–second–order kinetic model (R2 = 0.99 for Pb2+ and R2 = 0.98 for Cd2+) and Langmuir isotherm (R2 = 0.980 for Pb2+ & R2 = 0.978) with maximum adsorption capacities of 250 and 192 mg g−1 at 25°C for Pb2+ and Cd2+, respectively. The adsorption capacity of the PCCFG hydrogel increased with the increase in temperature. The value of ΔG° was negative, which shows the spontaneity of the reaction (electron exchange or ion exchange) between the metal ion and electron–rich atoms (–N, –S, –O). The positive ΔH° shows that the adsorption reaction consumes energy and the positive ΔS° shows the strong affinity of PCCFG toward the Pb2+ and Cd2+ ions. Pb2+ had better affinity and less spontaneity than Cd2+. The effect of competing ions was studied in batch adsorption experiments in the solution containing the three metal ions (Pb2+, Cd2+, and Cu2+) and the result shows that the coexistence of metal ions in the solution inhibits the adsorption capacity of the hydrogel compared to solutions containing a single metal ion.Theoretical investigation of adsorption mechanism of Cr6+ and Pb2+: Gauss View 6.0.16 interface were employed to construct the modeled system. The ground state geometry optimization of modeled system were first optimized by Molecular Mechanics (MM) method with aid of Universal Force Field (UFF) followed by Hartree fock (HF) and Density Functional Theory (DFT) method, using Gaussian 09 software package. Moreover, frequency, Natural Bond Orbital (NBO), and energy calculation were done by DFT method with aid of Gaussian 09. Hybrid–generalized gradient approximation (hybrid–GGA), B3PW91–D3 level of theory, where D3 denotes the third–generation dispersion correction by Grimme and basis set, the Stuttgart–Dresden–Boon (SDD) basis set was employed for heavy metal ions, and the 6–31G(d) basis were used for C, N, O, S, and H atoms during geometry optimization, frequency and NBO calculation. Single–point energy calculations were performed using the ωB97XD functional where basis set 6-311+G (d, p) was employed for C, N, O, S, and H atoms, and SDD basis set was employed for heavy metal ions. Solvation effect (H2O) was evaluated with polarizable continuum model (PCM) to mimic the real aqueous solution. The Gaussian simulation result shows that mainly the –N and –O atoms of amine (–NH2), amide (–CONH2), and carboxyl (–COOH) functional group of the hydrogel were responsible for binding of heavy metal ions via electron sharing/covalent bonding.
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    Briquetting of Sawdust using Waste Paper as a Binder
    (Addis Ababa University, 2015-07) Mengist, Muluken; Woldeyes, Belay (PhD)
    This study explored the possibility of producing sawdust briquettes that could be used for energy supply in small factories and for domestic cooking. A briquetting machine suitable for the production of sawdust briquettes on a small scale was constructed. A portion of sawdust was screened in to average diameter of: A (0.5mm), B (1.5mm), C (3mm), D (4.8mm), E (6.8mm) using standard sieves of 1mm, 2mm, 4mm, 5.6mm and 8mm mesh size. The raw sawdust was characterized for the following properties: moisture content (24.43%), density (91.34 kg/m3), volatile matter (94.92%) and ash content (2.6%). Briquettes were produced by mixing sawdust (both screened and raw) with waste paper in weight percentage ratios of 75:25, 70:30, 65:35, 60:40 and 55:45 respectively at three different die diameters. The computed density, porosity index, shatter resistance, volatile matter, ash content, fixed carbon and calorific value for all sawdust briquettes falls in the range of 218.24-322.62kg/m3, 33.97-312.4%, 98.88-99.95%, 70.24-90.56%, 2.33-7.26%, 6.7-24.26% and 14.5019-18.3832MJ/kg respectively. Further more from the results of the Analysis of Variance (ANOVA) carried out, there were no significant difference (p>0.05) in the quality of briquettes bonded with waste paper at different percentages except for percentage volatile matter, ash content and heating value . The effect of die diameter was found to be significant only on the physical properties of sawdust briquettes. A significant effect of average particle size of sawdust was recorded in density, porosity index and volatile matter of the briquettes. However, it was insignificant on shatter resistance, ash content and fixed carbon of the briquettes. The optimum blend of sawdust particle size - waste paper percentage and die diameter- waste paper percentage was assessed on the basis of the briquette properties: density, porosity index, volatile matter, ash content and gross calorific value. The combination of 0.5mm average particle size of sawdust and 30% waste paper gave the optimal density of 270.658kg/m3, porosity index of 29.782%, volatile matter of 86.496%, ash content of 2.829% and gross calorific values of 16.613 MJ/kg. The optimum blend of die diameter and waste paper was obtained at the combination of 6 cm and 25% with optimal values of density of 306.079 kg/m3, porosity index of 35.92%, volatile matter of 83.90%, ash content of 3.05% and gross calorific value of 17.134MJ/kg. It was concluded that the calorific values of briquettes obtained were sufficient to produce heat required for household cooking. Therefore sawdust briquettes can be a very good alternative source of energy for domestic cooking
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    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.
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    Catalytic Oxidation of Phenol in Aqueous Solution using Fe - Sulfonated Carbon Catalyst
    (Addis Ababa University, 2018-07) Tewodros, Geremew; Beteley, Tekola (PhD)
    The main objective of this research was to mineralize phenol in aqueous solution using Fe – Sulfonated carbon catalyst. Two fairly different catalysts (Fe/AC and Fe/AC − SO iii 3 H) in terms of impregnation (FeSO 4 . 7H 2 O for 8hr) and sulfonation (with high concentrated sulfuric acid 98 % for 15hr under N 2 ) were successfully synthesized and compared. The synthesized catalysts were characterized using: pH of zero point of charge, bulk density, total acid density, FT-IR spectroscopy, iron stability, TGA, reusability and performance comparison test with D-optimal experimental design through varying pH of the solution. The result shows that Fe/AC − SO 3 H with maximum acid density, higher iron stability with high reusable capacity. In addition to this, the performance comparison test ensured a maximum phenol removal efficiency and TOC reduction of 8 % and 21.6 % respectively, for Fe/AC − SO 3 H catalyst higher than former catalyst. Thus, from synthesized catalysts Fe/AC − SO 3 H was selected based on the above characterization and further performance analysis was taken place to search for optimal condition. The selected Fe/AC − SO 3 H catalyst was studied for its activity to catalyze mineralization of phenolic aqueous solution using heterogeneous fenton process. Design-Expert 7.0.0 three-levelthree-factor with full factorial was applied for experimental design and statistical analysis using a respective process variables; reaction temperature 30, 60 and 90℃, hydrogen peroxide concentration of 1000, 3500 and 6000 mg/L and 60, 150 and 240 min of reaction time. From the analysis of experimental results the interaction effects were studied and the optimal mineralization reaction process conditions, which will maximize the percentage of TOC reduction, were found to be 57.12 ℃ reaction temperature, 2869.72 mg/L hydrogen peroxide concentration and 119.38 min reaction time which gave 97.94% of TOC reduction. The experimental results were fitted well with the derived response model with the R 2 statistic measure, it is evident that the fit successfully accounted for greater proportion of variance as all the models explained ≈ 98.08 %, 99.8 % and 89.85 % for temperature 30 ℃, 60 ℃and 90 ℃ respectively, of the total variation in the data. In average only 4.09 % of the total variations were not explained by FKM and GLKM. However, as GLKM contains more coefficients than the FKM, R-square statistic, a generally accepted best indicator of the fit quality in the comparison of models with those that are nested, is used.
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    Characterization and Optimization of Alkline Hydrolysis of Waste Human Hair for Production of Nitrogenous Fertilizer
    (Addis Ababa University, 2024-02) Fraol Tesfaye; Brook Tesfamichael (PhD)
    In recent years, the efficient management of organic waste has become a critical concern for sustainable development. This study explores the potential of using waste human hair as a valuable resource for the production of nitrogenous fertilizer through lime treatment. Waste human hair, a readily available and abundantly generated organic waste, has shown promise as a rich source of nitrogen, an essential nutrient for plant growth. The aim of this study was to utilize discarded human hair as liquid organic fertilizers for Swiss chard plants. This was done by investigating the time of solubility of different amounts of hair (2, 4, 6 g) in varying concentrations of CA(OH)2 solutions (0,1g/ml, 0.5g/ml, 1g/ml) at different temperatures (100°C, 110°C, 120°C).For the Swiss chard plants, different treatments was applied at a control group, hydrolyzed hair fertilizer (at rates different rates), and DAP fertilizer. Preliminary results indicate that increasing lime treatment and temperature minimize the hydrolyzing time of waste human hair, in which for lowest lime loading and temperature hydrolyzing time is12 hr and for high lime loading and temperature value hydrolyzing time is 10hr. Furthermore, the resulting nitrogenous fertilizer exhibits desirable nutrient content nitrogen with an optimum yield of 9.54% at an optimum value for the factors temperature (112.37) degree centigrade time (11:27)hr and lime loading( 0.72g/ml) and demonstrates the potential to improve soil fertility, acidity and crop productivity when applied to Swiss chard plant. Biomass analysis obtained for fresh and dry weight value of the Swiss chard was 90g and 25 g respectively. Proximate analysis done on moisture content ,ash content ,crude fiber and total protein was (92.6,9.01,1.80 and 2.5% )respectively This study not only addresses the pressing issue of waste management but also highlights the possibility of converting a waste stream into a valuable resource within the agricultural sector. using the synthesized fertilizer the has altered total nitrogen content of the soil to 1.9%. The findings of this study have the potential to offer valuable insights for waste management strategies and sustainable agricultural practices, promoting the efficient utilization of organic waste resources and fostering a more sustainable future.
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    Characterization and Optimization of Volcanic Ash and Portland Cement blend for Property Enhancement of Concrete
    (Addis Ababa University, 2018-11) Solomon, Zeleke; Hundessa, Dessalegn (PhD)
    Volcanic Ash is one of naturally occurring Pozzolanaic material that was tested in this research work for partial replacement of cement for production of concrete. With respect to reduction of cement consumption for sustainable construction (i.e. reducing GHG emission) evaluation of the strength reduction is crucial as it has a severe impact on the structure under construction. This paper examines the effects of replacing cement by using Lege-Dadi Volcanic Ash on the strength and certain durability characteristics of concrete. The research aims to determine the optimal amount of Volcanic Ash for production of high-grade concrete. Preliminary tests of the different properties of materials used for this research were carried out. The Lege Dadi Volcanic Ash satisfied the requirement of ASTM C618-00.The samples of Volcanic Ash were prepared in five different proportions (0, 5, 10, 15 & 20 wt %) and design mix ratio of 1: 2.9: 3.9 with a 0.61 w/c ratio to make 45 cubic and 27 cylindrical concrete samples. The cubic samples were used to assess compressive strength tests where as the cylindrical samples were used to determine abrasion resistance, water absorbency and acid attack tests. Uniaxial compressive tests were used to examine the strength of concrete achieved after 3, 7 and 28 days of curing. Result of compressive strength show that early strength of concrete samples were low, but as the curing period increases their compressive strength increases.15 % replacement of Volcanic ash was an optimum replacement in this research with compressive strength of 21.3 MPa less than by 4 % with the control (i.e. 0% of Volcanic Ash)and expected to increase in subsequent curing days. The permeability of cylindrical concrete samples decreases as the percentage of volcanic ash in the mix increases, the weight loss due to abrasive force of samples containing volcanic ash were not considered as significant. Acid significantly attacks the surface texture of both control and Volcanic Ash sample concrete cylinders. However, after 28 days of immersion samples contain Volcanic Ash powder reduces the mass loss, compared to the reference control concrete samples.