Browsing by Author "Alemayehu, Esayas (Professor)"
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Item De-Fluoridation of Ground Water Using Raw and Modified Bentonite Clay(Addis Ababa University, 2022-06-12) Woldemedhin, Adane; Alemayehu, Esayas (Professor)The presence of fluoride in groundwater sources of drinking water has posed a concern to global public health, particularly in the East African Rift Valley (EARV). The study's ultimate objective was twofold. First, investigate low-cost, locally available adsorbents for fluoride adsorption that could be used in Ethiopia's Rift Valley (which is the country's most fluorotic region), and second, contribute to the search for an appropriate and long-term fluoride removal technology for the treatment of fluoride-contaminated groundwater for drinking water for developing countries. Due to cultural beliefs and the terrible odor they emit, the use of bone char and the Nalgonda process for de-fluoridation is being rejected by users in the study area. Several researchers have advocated for the use of non–conventional low–cost adsorbents, such as natural materials and waste/byproducts from agriculture and industry, as effective adsorbents for the removal of fluoride from aqueous solution in recent years. Low–cost adsorbents, such as clay minerals, have emerged as a viable remediation technique for removing fluoride from polluted ground water. However, only a few clay minerals have been studied and investigated for their usefulness in removing fluoride from polluted water, either as is or after slight alteration. As a result, a new, cost-effective technology of fluoride removal is required. Therefore, in this study, the feasibility of fluoride adsorption from aqueous solutions using naturally available bentonite clay in both modified and unmodified forms is investigated. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy analysis was applied to describe the structure and nature of modified and unmodified bentonite clay. The physicochemical characteristics of the adsorbent were also investigated for moisture content, pH, apparent density, specific surface area, cation exchange capacity and its point-of-zero charge. Results obtained from these studies are presented and discussed. These effects of treatment or modification have been discovered. The EDX analysis reveals a significant silica and alumina content, as well as trace amounts of Fe+3, Ca+2, and Mg+2. The presence of the primary minerals, silica and alumina, with a minor amount of hematite, was revealed by XRD analysis. Furthermore, the silica and alumina levels have increased due to modification of the original material. SEM scans revealed considerable alterations in the original pore structure. The research involves a series of adsorption experiments in a column mode to evaluate the ability of the adsorbents for fluoride removal from polluted water. The column operations were used to investigate the practical application of the produced low–cost adsorbents for removal effectiveness at greater fluoride concentrations under an ideal pH setting of 7.2, which is suitable for drinking. Under the optimized values of the process parameters of initial fluoride concentration (mg/L), Flowrate (mL/min) and bed depth (cm) under continuously flowing fixed bed column was determined. At optimized conditions, RB have shown very low fluoride removal efficiency (47.19%), whereas, modification of the clay surface with HCl and aluminum oxide, on the other hand, increased fluoride removal efficiency to 79.77% and 94.38%, respectively for the 5mg/L of initial fluoride concentration, 10cm bed depth and 15mL/min flowrate. The statistical model, central composite design (CCD) and mathematical models were applied to evaluate the column adsorption performance. The adsorption modelling study reveals that for all models such as Thomas, Clarck, Yoon-nelson and Adam-Bohart, the lower the flow rates with higher bed height leads to maximum fluoride uptake on to adsorbent. The analysis of variance was used to determine the importance of independent variables and their interactions on adsorption capacity and Fluoride removal. All the R2 values indicate that the models match the experimental data well. Moreover, the study investigated the effects of co-existing ions in water on the performance of ALUM-MBENT, in column mode, the effects of anions on fluoride adsorption were investigated using concentrations of each anion of 0.1, 10, and 100 mg/L. When competing anions are present, the adsorption capacity of the adsorbent reduces, according to the findings. Multi-valent anions are more easily absorbed than monovalent anions. Carbonates and phosphate are the main anions that have the greatest influence on the fluoride adsorption. The fluoride adsorption is strongly affected by the concentrations of competing anions. Phosphate, bicarbonate, and sulfate greatly reduced fluoride adsorption. However, chloride had little effect on the sorption. The impact of major anions on fluoride adsorption followed the order of Cl-Item Distillery Stillage Water Pollution Control: An Integrated Approach for Efficient Treatment and Recovery(Addis Ababa University, 2021-05-26) Dagnew, Getachew; Alemayehu, Esayas (Professor); Chebude, Yonas (Professor); Mekonnen, Andualem (Professor)In spite of the increasing demand for potable and fuel ethanol, the distillery industries continue to be a major source of surface water and soil pollution, especially to developing nations, due to the release of a highly organic and complex byproduct- the stillage. Stillage contains solids, recalcitrant organics, persistent color, sulfate, chlorides, phosphorus and nitrogen, whose recovery and treatment plays a major role in environmental sustainability. In most cases, the application of single stillage treatment technology did not succeed. The objective of this study was to quantify molasses and stillage byproducts in Ethiopia and examine the feasibility of an integrated treatment approach towards sustainability. Standard methods were applied, beginning from a systematic literature review through primary data collection, stillage sampling and conducting a series of experiments. The trials were set-up based on a sound design followed by standard analytics and a statistical analysis of the results. The experiments started with determining the biochemical methane potential (BMP) test and then undertaking a mild iron oxide coated sand (IOCS) based wet air pretreatment (WAp) through anaerobic digestion (AD), adsorption and a polishing aerobic degradation. From a quantitative characterization study, Ethiopia currently produces close to 1.8 million tons of cane sugar, with the release of over 300,000 tons of molasses as a by-product. Using cane molasses as a raw material and with the release of 431,000 m3 of stillage into the environment, the potable ethanol industry in the country produces over 33,000 m3 of ethanol annually. According to the BMP test run for 45 days at mesophilic condition, molasses stillage has the potential of giving 139 NmlCH4/g-COD with 68% purity. A mild IOCS based WAp of the stillage sample at 3.5% IOCS loading, a temperature of 60 oC, which was held for four hours at atmospheric pressure brought the desirable effect in detoxification. The result observed following comparison of raw and treated stillage from E. coli incubation at 37 oC and 86 revolutions per minute of shaking demonstrated a statistically significant difference (p-value = 0.02) in toxicity. Successively, the consequence of a mild, IOCS based WAp on the methane (biogas) yield as well as the biochemical oxygen demand (BOD) and COD removal was compared with the raw counterpart using batch mesophilic (35±2 oC) AD of stillage. Further, the effect of applying scoria (a highly vesicular igneous rock) support on AD process stability and performance was assessed for the first time. Consequently, a statistically significant (p-value < 0.05) difference in the cumulative specific raw without scoria support, raw with scoria support and WAOp scoria supported stillage AD subsequently. The soluble COD (CODsol) after AD of stillage with scoria, without scoria and with scoria and WAp in mg/l was 30041.7, 30666.7, and 13375.0 respectively. With the WAOp and scoria supported stillage AD a BOD and COD reduction of ≈100% and 92% were achieved. These achievements are unique in stillage recovery and pollution remediation findings so far. Further, the biogas yield with respect to the reaction days (within 18 days) with a relatively stable process (average pH=7.7, 6.8 and 6.7 for pretreated and untreated stillage with scoria and without scoria) was hastened due to pre-treatment. Regarding the adsorption trial on stillage after the batch AD, all the significant COD removals were observed after three hours of contact time for all doses of the treated scoria adsorbent. Maximum removal rate was at 0.03 mg/ml of scoria dosing and in three hours contact time whereby the final COD of the stillage did go lower only to 7500 mg/l. In a related experiment, the effect of organic loading rate (OLR) and stillage WAp was studied in a continuous AD in scoria-packed column reactors. The removal of stillage COD was significantly better (p-value = 0.036), with an average of 13% difference, due to pre-treatment of stillage with an increased OLR to 2000 mg/L-d. In a further polishing aerobic treatment trial of the effluent from the stillage batch AD, a complete removal of the BOD and significant removal of COD, with an average effluent COD of 2278 mg/L was achieved. In fact, 68% of the COD removal occurred within eight hours of digestion. Despite the persistence of color, the removal of organics with bioenergy recovery from integrating the WAp, the batch AD and the aerobic remediations (˜99% COD and 100% BOD removals) of stillage appear to be a promising technique in its sustainable management while adhering to the regulators’ discharge limits.Item Drinking Water Quality and Management Practices From Source to Household: The Case of Kombolcha Town, Ethiopia’(Addis Ababa University, 2020-06-13) Tesfaye, Bezawit; Alemayehu, Esayas (Professor); Zewge, Feleke (PhD)This research focuses on investigation of the existing drinking water quality of Kombolcha town from the source to points of household tap in relation to safety and acceptability for users concerning water quality parameters. The town gets its water supply from groundwater sources. A total of 45 water samples were selected and collected from boreholes, reservoirs, distribution mains and households. The pH, Turbidity, Total Dissolved Solids (TDS), Electrical Conductivity (EC), Temperature, Total hardness, free chlorine residue, Manganese, Nitrate and Iron and Microbiological (Total Coliform and fecal Coliform) parameters were determined. The result was then compared with the WHO and Ethiopian water quality standards. The results obtained show that for physical analysis except temperature the rest all parameters were within the WHO permissible limit. The results for temperature were found between the ranges of 22.5°C - 26.1°C. Based on laboratory analysis of chemical parameters the result shows that total hardness is above the permissible limit set by the guidelines. Also, all chlorine residual of the samples were found to be below the recommended values of WHO and national guidelines except seven of samples. However manganese, iron and nitrate were within the permissible limit. The result of bacteriological analyses indicated that Fecal coliform of all samples were zero meeting WHO and national guidelines. But Total coliform of nine samples were above the guideline`s limit ranging between 1-4 CFU/100ml. In summary, with regard to the Physico-chemical parameters the water is safe and there is no significant effect on the health of the users. The results of bacteriological analyses have shown that some of the sample points are at risk. To overcome these problems regular chlorination is recommended. It is also recommended that sampling and monitoring at different times is essential and analysis of additional water quality parameters should be undertaken.Item Performance Evaluation of Water Treatment Plants (Wtps): a Comparative Study Between Gaborone and Mmamashia Wtps (Botswana)(Addis Ababa University, 2020-07-07) Tshepho, Josephine; Alemayehu, Esayas (Professor)One of the ways to protect public health and environment by the elimination of waterborne diseases and pathogens is water undergoing treatment before consumption, making this process very important. Hence there is a need for regular monitoring of the performance of water treatment plants as this will ensure public water supply quality control management, consequently ensuring consumers’ safety. Performance evaluation of a water treatment plant (WTP) is a process to measure the functioning efficiencies based on some established performance indicators such as turbidity, color, suspended impurities, E-coli, Total Dissolve Solid, Residual Chlorine. Therefore, the overall objective of this study was to evaluate the performance of Gaborone and Mmamashia treatment plants (Botswana) with regard to their ability to produce quality water and control pathogens. The water parameters, pH, Total Coliform, E-coli, turbidity and conductivity, were analyzed based on the years 2019 and 2020 Autumn season. Secondary data was obtained for the year 2019 while sampling and standard laboratory tests and analysis were done for the year 2020. One hundred and twenty samples were collected from each water treatment plant (WTP) for five weeks. Samples were taken from raw water entering the water treatment plants and after disinfection stage. The weighted arithmetic water quality index method was used to classify the quality of treated water. The log removal value and turbidity removal efficiency were determined using the respective formulas. Correlation statistical technique was carried out to find out if there was any direct or indirect relationship between the parameters. The results from the study showed that, all the water parameters analyzed after disinfection stage for both treatment plants fall within the permissible limit for World Health Organization and Botswana bureau of standards. The water quality index for both plants was below 50 hence the water quality was classified as excellent. Overall, log removal value for Mmamashia, for the years 2019 and 2020 were, 1.96 and 1.3 respectively, for Gaborone, the values obtained were 2.24 and 1.52. Overall turbidity removal efficiency for Mmamashia for the years 2019 and 2020 was, 98.34% and 83.04% respectively while for Gaborone, 99.31% and 96.83% values were obtained for the years 2019 and 2020. There was significant correlation between parameters for both treatment plants. The treatment plants were found to be doing well with respect to providing the public with safe water and there was no significant difference between the v treatment plants except for the quality of raw water each is receiving. This study, therefore, acts as a baseline for further research regarding the efficiency of the Gaborone and Mmamashia treatment plants.Item Sustainability Assessment of Urban Water Distribution System a Case of Bahir Dar City Ethiopia(Addis Ababa University, 2021-10-11) Antehun, Yirged; Alemayehu, Esayas (Professor); Mekonnen, Andualem (PhD)One of the most fundamental requirements of human life is water. As a result, everybody should have access to adequate and safe water on a continuous basis. For adequate and safe water supply, proper design and execution of the new distribution and the operation of the existing distribution network is needed. The study aimed to assess the sustainability of Bahir Dar City's pressure zone-1 water supply distribution system. For assessing the hydraulic sustainability, an analytical model (WaterGEMS V8i) was used to model the WDN and produce hydraulic parameters (velocity and pressure). Sustainability indicators (reliability, resilience, and vulnerability) were calculated based on these parameters and used to determine the sustainability index. The WaternetGEN tool was used to assess the distribution network's hydraulic performance. A geographic positioning system (GPS) and Arc GIS 10.4.1 was used to check the existing layout and to generate the study area. The results showed that; the distribution system has overall sustainability indexes of 0.71 for the current peak hour demand, with sustainability indexes of 0.97 and 0.43 for pressure and velocity, respectively. Based on the result of this analysis the distribution network sustainability is acceptable for current demand. However, the overall sustainable indexes for forecasted demand has been reduced to 0.32, which is in the medium range but unacceptable. It is found that also Pressure in a WDN had a technical performance index of 86.53 %, while the performance indexes of velocity in the distribution system is 57.86% after optimization of the hydraulic parameters in WDN. Water age was determined at low demand hour. Analysis for water age was based on assumption that the distribution system was loaded with continuous flow. The maximum water age in the distribution system is 19.93 hour which is less than a day and acceptable. In general, the result of this study showed that the current distribution network is sustainable for the current water demand.