Feleke Zewge | Addis Ababa University (original) (raw)

Papers by Feleke Zewge

Chemosphere

The hybrid electrocoagulation-electrooxidation (EC-EO) process was evaluated for its capability t... more The hybrid electrocoagulation-electrooxidation (EC-EO) process was evaluated for its capability to remove color, total organic carbon (TOC), and chemical oxygen demand (COD). Aluminum (Al/Al) and iridium dioxide-coated onto titanium (IrO2/Ti) electrodes were selected as anode/cathode for EC and EC-EO experiments, respectively. The box-Behnken statistical experimental design was used to optimize different operating conditions of the processes. The selected EC operating parameters are the concentrated dye concentration, applied current density, electrolysis time, and pH. The three chosen operating conditions for hybrid EC- EO processes are applied current density, pH, and electrolysis time. The results were evaluated based on the interaction effects of operating parameters of the treatment methods on the percentage of COD, TOC, and color removal. The EC process achieved 89% color and 76% COD removal rate at the optimum operating conditions. Likewise, the hybrid EC-EO process obtained 97% COD and color removal efficiency. FT-IR and 1H and 13C NMR spectroscopy combined approach was employed to analyze the dye degradation extent. Both analysis results confirm the complete degradation of the organic contaminants into carbon dioxide and water. Thus, this study discloses that the treatment method using mesh IrO2/Ti electrodes is a promising technology that could reach the discharge limit for industrial effluents. In addition, the optimum operating conditions are tested for real industrial wastewater effluents and show excellent performance in removing pollutants. Furthermore, the treatment method's mineralization study and economic analysis were performed and compared to other studies.

Water Practice and Technology

Ever-increasing coffee consumption results in the generation of a significant amount of solid res... more Ever-increasing coffee consumption results in the generation of a significant amount of solid residue in the form of spent coffee ground and its subsequent disposal cause environmental pollution. Valorization of spent coffee ground (SCG) through pyrolysis could be one of the solutions to this challenge. Pristine biochar of SCG shows less efficiency to remove dyes from aqueous solutions. Herein, iron(III) salt was used as a catalyst during the carbonization of SCG and has a good graphitization efficiency and thus enhanced the formation of aromatic structures which provide adsorption sites for the dye. The physical characteristics of the prepared biochar were analyzed by FTIR, XRD, and BET. A predictive model for the removal of the dye was investigated with the Design Expert 11.0 software through the central composite design (CCD) - response surface methodology (RSM) by conducting a batch adsorption study and the suggested optimum values of the CCD were 10 ppm initial dye concentratio...

Water Science and Technology, 2022

In this study, the performance of the electrocoagulation (EC) process was evaluated for its capab... more In this study, the performance of the electrocoagulation (EC) process was evaluated for its capability to remove color, total organic carbon (TOC), chemical oxygen demand (COD) using aluminium electrodes. Response surface methodology based on Box-Behnken design was used to optimize different operating conditions of the processes. The interaction effects of four independent variables such as dye concentration, applied current density, electrolysis time, and pH on the percentage of COD, TOC, and color removal were investigated by the EC process. ANOVA analysis was made to examine the significance of input parameters and their interaction effect on responses. At the optimum operating conditions, 89% of color, 47% of TOC, and 76% of COD removal rate were achieved using the EC process. Different research works have been reported on the treatment of textile wastewater by the EC process. However, these researches vary regarding working conditions such as dye type, concentration, current de...

Journal of Water and Health, 2022

In developing countries, the evaluation of disinfection by-products in drinking water has been ne... more In developing countries, the evaluation of disinfection by-products in drinking water has been neglected because most water utility companies focus on microbial elimination. As a result, this study aimed at evaluating trihalomethane formation, the relation between water quality parameters and trihalomethane formation, and the estimation of the associated potential health risks in drinking water. The headspace purge and trap coupled with a gas chromatography–mass spectrometry technique was used to quantify trihalomethane. The concentrations of trihalomethane found in the water were within the National Water and Sewerage Corporation, World Health Organization guidelines, and the United States Environmental Protection Agency standards. Total organic carbon, ultraviolet absorbance at 254 nm, bromide concentration, and the temperature had a positive and significant correlation, pH had a positive but non-significant correlation, while the residual chlorine had a negative but significant c...

PLOS Neglected Tropical Diseases, 2020

Background Schistosomiasis is a water-based disease acquired through contact with cercaria-infest... more Background Schistosomiasis is a water-based disease acquired through contact with cercaria-infested water. Communities living in endemic regions often rely on parasite-contaminated freshwater bodies for their daily water contact activities, resulting in recurring schistosomiasis infection. In such instances, water treatment can provide safe water on a household or community scale. However, to-date there are no water treatment guidelines that provide information on how to treat water containing schistosome cercariae. Here, we rigorously test the effectiveness of chlorine against Schistosoma mansoni cercariae. Method S. mansoni cercariae were chlorinated using sodium hypochlorite under lab and field condition. The water pH was controlled at 6.5, 7.0 or 7.5, the water temperature at 20˚C or 27˚C, and the chlorine dose at 1, 2 or 3 mg/l. Experiments were conducted up to contact times of 45 minutes. 100 cercariae were used per experiment, thereby achieving up to 2-log 10 inactivations of cercariae. Experiments were replicated under field conditions at Lake Victoria, Tanzania. Conclusion A CT (residual chlorine concentration x chlorine contact time) value of 26±4 mg�min/l is required to achieve a 2-log 10 inactivation of S. mansoni cercariae under the most conservative condition tested (pH 7.5, 20˚C). Field and lab-cultivated cercariae show similar chlorine sensitivities. A CT value of 30 mg�min/l is therefore recommended to disinfect cercariainfested water, though safety factors may be required, depending on water quality and operating conditions. This CT value can be achieved with a chlorine residual of 1 mg/l after a contact time of 30 minutes, for example. This recommendation can be used to provide safe water for household and recreational water activities in communities that lack safe alternative water sources.

Journal of Water Supply: Research and Technology-Aqua, 2021

AQUA: Water Infratructure, Ecosystems and Society issues a formal retraction in relation to the a... more AQUA: Water Infratructure, Ecosystems and Society issues a formal retraction in relation to the above article by Muluwork Maru, et al. The publisher issues this retraction due to concerns over the originality of the authors’ work.

Indoor and Built Environment, 2019

A total of 45 households were selected to participate in a study to assess indoor exposure to par... more A total of 45 households were selected to participate in a study to assess indoor exposure to particulate matter (PM) and total volatile organic compounds (TVOC) while cooking a widely consumed Ethiopian traditional stew sauce (Wot, in Amharic). The geometric mean (GOM) concentrations of PM 1 , PM 2.5 and PM 10 when electricity, kerosene and charcoal fuel sources were used during the wet season ranged 11.4-151 mg.m À3 , whereas the GOM concentrations during the dry season ranged 7.7-222 mg.m À3. The GOM of TVOC during the wet and dry seasons using electricity, kerosene and charcoal fuel ranged 350-812 mg m À3. The health risks associated with exposure to PM 2.5 , PM 10 and total suspended particulate matter (TSP), either as a single pollutant or cumulative based on the hazard quotient (HQ) or hazard index (HI) calculation by U.S. Environmental Protection Agency, indicate that exposure to PM 2.5 , PM 10 or TSP while cooking Wot using electricity, kerosene and charcoal fuels may not cause health problems to a healthy adult. However, long-term exposure to high levels of PM 10 emissions when charcoal fuel is used is considered to be unsafe. The exposure to all the emitted pollutants during the use of any of the three fuels sources may also pose a human health impact to individuals near the sources.

African Journal of Environmental Science and Technology, Sep 30, 2014

Adsorption techniques are widely used to remove certain groups of pollutants such as dyes which a... more Adsorption techniques are widely used to remove certain groups of pollutants such as dyes which are not amenable to biodegradation and environmentally very problematic. Although commercial activated carbon is a preferred sorbent for color removal, its widespread use is restricted due to high cost. As such, alternative non-conventional sorbents should be investigated. It is well-known that natural materials, waste materials from industry and agriculture, and bio sorbents can be obtained without a cost, therefore could be employed as inexpensive sorbents. Therefore the present investigation reports the adsorptive capacity of an industrial residue for the removal of azo dyes. Batch experiments were carried out for the sorption of the dye onto the adsorbent. The influence of contact time, adsorbent dose, pH and initial dye concentration on the adsorption capacity of the material was studied. Kinetics and adsorption isotherms were also studied to evaluate the rate of dye removal and the capacity of the adsorbent. The equilibrium data best fits freundlich isotherm equation. Adsorption capacity (K f) and intensity of adsorption (n) as determined by fitting the equilibrium data to freundlich isotherm equation are calculated to be 0.26 and 0.82, respectively. The adsorption process was found to undergo via a pseudo-second-order adsorption kinetics with a rate constant of 3.81×10-3 (g /mg / min). The removal of dye was not affected for the initial dye concentration range of 15 to 256 mg/L. An adsorption process; requiring an equilibrium time of 30 h with optimum adsorbent dose of 19 g/L for 77.4% dye removal efficiency was observed at near neutral pH. However, as the pH of water is adjusted from 7 to 9, the dye removal efficiency was greater than 90%. The overall result shows that the industrial by product investigated in this study exhibited a high potential for the removal of dye from aqueous solution.

Toxicological & Environmental Chemistry, 2010

The accuracy of the Content should not be relied upon and should be independently verified with p... more The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.

Bulletin of the Chemical Society of Ethiopia, 2018

This study focuses on the chemical modification of Ethiopian bentonite and commercial montmorillo... more This study focuses on the chemical modification of Ethiopian bentonite and commercial montmorillonite with aluminum oxi-hydroxide (AO) for the purpose of defluoridation from aqueous solution. The chemical modification was achieved by preparing AO-modified adsorbents at different pH values. The adsorbent materials were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and point of zero charge (PZC). From the modified adsorbents, AO-Mont at pH 5 (AO-Mont 5) showed a slight shift of d001 at 2θ = 7.5º reflection toward the lower angle 2θ = 7.0º as a result of the Al2O3 insertion into interlayer space. The elemental composition from XRF further showed the increment of Al content accompanied with a decrease in the exchangeable cations in the modified samples and higher content of Al was observed in AO-Mont 5. In addition, the PZC initially 8.5 and 2.5 for raw bentonite and montmorillonite clays were increased to 10 and 8.5 in AO-Bent 5 and AO-Mont 5, respectively. Adsorption of fluoride on these modified adsorbents was studied as a function of preparation pH, contact time, solution pH and co-existing anions. AO-Mont prepared at pH 5, which contained higher content of Al resulted better fluoride removal performance. AO-Bent 5 and AO-Mont 5 have shown five and nine fold increase in fluoride removal capacity, respectively as compared to their respective unmodified clays. The experimental data fitted well with Freundlich adsorption isotherm model which indicated that the surface of the adsorbent is heterogeneous and adsorption of fluoride followed a multilayer sorption. Hence AO-modified Bent and Mont adsorbents prepared at pH 5 can be considered as potential adsorbents for defluoridation from drinking water.

Lake Ziway is shallow freshwater located in Northern part of Ethiopian Rift Valley. It is charact... more Lake Ziway is shallow freshwater located in Northern part of Ethiopian Rift Valley. It is characterized as semi-arid to sub-humid type of climate. Expansions of the flower industry, widespread fisheries, intensive agricultural activities, fast population growth lead to deterioration of water quality and depletion of aquatic biota. In this study, spatial and temporal variations of selected water quality parameters of Lake Ziway were evaluated using multivariate statistical techniques in the study periods of 2014 and 2015. Monthly water quality data were collected from nine sampling stations during dry and wet seasonal basis for analysis of 15 water quality parameters. Mean nutrient concentrations showed increasing trend and were higher in Floriculture effluent (Fb) and Floriculture effluent after mixing in the lake (Fa) in all seasons. These sites were also characterized by high electrical conductivity (EC) and total dissolved solid (TDS). All the nine sampling sites were categorized...

ABSTRACT. The fluoride contents in the infusions of 21 commercially available Ethiopian and impor... more ABSTRACT. The fluoride contents in the infusions of 21 commercially available Ethiopian and imported black and green tea brands; in leaf and bag forms was determined by a fluoride ion-selective electrode method. Of the samples analyzed twelve were products from Ethiopia and the remaining nine were imported tea brands. The effect of brewing time on fluoride release from tea was assessed. Results showed that fluoride release increased with increasing brewing time (3, 5 and 10 min). Fluoride level after 5 min brewing for black tea leaves, green tea bags, and black tea bags was in the range of 117–682 mg/kg, 111–190 mg/kg and 141–246 mg/kg, respectively. The WHO guideline for daily fluoride intake is 2 mg for children and 4 mg for adults. Assuming that one consumes 4 cups of tea everyday (400 mL) and each cup uses 2.5 g of tea leaves, the daily fluoride intake from black tea leaves may be in the range between 1.11 and 6.82 mg. For the same condition, if consumption of one green tea bag ...

ABSTRACT: The objective of the present study was to evaluate the potential use of water hyacinth ... more ABSTRACT: The objective of the present study was to evaluate the potential use of water hyacinth for the removal of chromium (Cr) from tannery wastewater. This experiment was performed using healthy, young and acclimatized water hyacinth collected from unpolluted Awash River. Cr concentrations of 3, 5, 7, 10 and 20 mg/L were added to five different polyethylene tanks, containing 40 litre tap water cultured with Hoagland’s solution. A sixth tank containing Cr-free water was used as a control group. Six plants of equal wet mass (each 12.5 ± 2 g), shoot length (11 ± 2 cm) and root length (6 ± 2 cm) were transferred into each tank and allowed to grow in a greenhouse for 42 days. From each tank plants were harvested randomly every week. Bioaccumulation factor, translocation factor, shoot and root length; wet biomass and dry weight of the shoot and root were measured, and relative growth rate, tolerance index of the root and tolerance index of wet mass were analyzed. The maximum accumulat...

Separation Science and Technology

The objective of the present study was to evaluate the potential use of water hyacinth for the re... more The objective of the present study was to evaluate the potential use of water hyacinth for the removal of chromium (Cr) from tannery wastewater. This experiment was performed using healthy, young and acclimatized water hyacinth collected from unpolluted Awash River. Cr concentrations of 3, 5, 7, 10 and 20 mg/L were added to five different polyethylene tanks, containing 40 litre tap water cultured with Hoagland’s solution. A sixth tank containing Cr-free water was used as a control group. Six plants of equal wet mass (each 12.5 ± 2 g), shoot length (11 ± 2 cm) and root length (6 ± 2 cm) were transferred into each tank and allowed to grow in a greenhouse for 42 days. From each tank plants were harvested randomly every week. Bioaccumulation factor, translocation factor, shoot and root length; wet biomass and dry weight of the shoot and root were measured, and relative growth rate, tolerance index of the root and tolerance index of wet mass were analyzed. The maximum accumulation of 2.5...

The main objective of this study was to determine the levels of fluoride in cereals (tef, wheat, ... more The main objective of this study was to determine the levels of fluoride in cereals (tef, wheat, corn and barley) and legumes (pea, lentil and chickpea) produced in selected areas of Ethiopia. The samples were collected from the rift valley and outside rift valley areas of Ethiopia: Arsi Negele, Adola, Wonji, Ada, Gonder, Bure (Gojam) and Dessie towns. The samples were collected from local markets in the areas where they are cultivated in large amount. Levels of total fluoride in cereal and legume grain samples were determined by fluoride ion selective electrode. Fluoride levels in cereals were found between 0.98 mg/kg in corn from Adola and 10.98 mg/kg in tef from Wonji. Fluoride levels in legumes ranged from 1.52–11.07 mg/kg both in the pea with the lowest and highest levels from Bure and Ada, respectively. Fluoride levels in cereals from rift valley areas were higher than those from outside the rift valley areas. Generally, cereal samples from Arsi Negele and Wonji were found to ...

Journal of Water Supply: Research and Technology-Aqua

Nitrogen and phosphorus removal and recovery are considered as one of the interventions to contro... more Nitrogen and phosphorus removal and recovery are considered as one of the interventions to control water bodies' eutrophication by application of various methods. Adsorption is an effective method for phosphate and nitrate removal from wastewater. It is efficient, quick, easy, low-cost and environmentally friendly. Even though different adsorbents have been developed with excellent properties, lack of compilation, lack of consistency in operational conditions, and lack of other important parameters used for direct comparison and practical use selection were observed. The first aim of this review is to provide facts and figures on novel adsorbents used for nitrate, phosphate, and simultaneous nitrate-phosphate removal and recovery. Second, various adsorbents applied for nitrate and phosphate removal have been compared in terms of the number of cycles that the adsorbent used; retained removal capacity (RR); the removal capacity of the adsorbent considering the threshold limit sett...

Water Supply

Schistosomiasis is a water-based neglected tropical disease that is prevalent in over 78 countrie... more Schistosomiasis is a water-based neglected tropical disease that is prevalent in over 78 countries. It affects communities that are reliant on freshwater bodies contaminated with schistosome cercariae for their daily water activities. Whilst treatment with the drug praziquantel is relatively effective, it does not prevent reinfection. One option for reducing schistosomiasis infection is providing at-risk communities with treated water, thereby reducing contact with cercaria-infested water for activities such as bathing or doing laundry. This study aims to establish design guidance for sand filtration to remove schistosome cercariae from water. Four sand filters were tested, varying from 300 to 2,000 μm in sand grain size. Each filter was tested with a sand depth of 20 cm, which was increased until no cercariae were detected in the effluent. The required filter depth to remove 100% of cercariae ranged between 40 and 70 cm depending on sand grain size. Cercaria removal was more effect...

Cleaner Engineering and Technology