Browsing by Author "Shimelis, Kebede Kassahun (PhD)"

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    Removal of Chromium from Painting Industry Wastewater Using Bioelectrochemical Fuel Cell Technology
    (Addis Ababa University, 2021-07) Diriba, Amsalu; Shimelis, Kebede Kassahun (PhD)
    Chromium is heavy metal that released as waste dominantly from chemical industries and causes chronic and acute health problems on human beings and other living environments. From different industrial sector in Ethiopia Painting industries are developing but their wastewater treatments are not get attention. This was one of the reason to select the sector for the removal of chromium from their wastewater using Bioelectrochemical Fuel Cell Technology (BECFC). The technology is an effective, efficient, and environmental-friendly that remove chromium without using external energy. The methodology can generate electrical energy from wastes that helps it to avoid the cost of energy during treatment. The sub objectives of this research were synthesizing chromium wastewater using APHA methodology, constructing set up of BECFC, enumerating Bacillus Ceruse. And others were investigating the efficiency of the methodology by varying three parameters at three different operational level, using statistical method of RSM optimizing operation parameters and verified on synthetic wastewater. Also characterizing real wastewater and verifying again optimum operation parameters on real wastewater were sub-objectives of the research. BECFC remove chromium from wastewater when electro-active bacterial like Bacillus Cereus metabolize organic waste in anodic chamber and release electrons during the process. Then generated electrons are transferred to the cathodic chamber through the external wire. Then after chromium is reduced, attached on electrode, detached and settle to the bottom of cathodic chamber. To see results of the research, over all above 95% efficiencies of removal of chromium were achieved. The highest efficiency of removal achieved was 99.6% at a concentration of 15 mg/L, pH of 9, and time of treatment 16hrs. The efficiency of optimum operation parameter was 98.1% and current density generated was 17.51mA/m2 with an optimum concentration of 9mg/L, pH 7, and optimum time of 17.357hrs. And the efficiency of removal of chromium from real wastewater of (3400mg/L SS, 2164NTU turbidity, 738mg/L COD and 148mgg/L BOD) was 84%. In conclusion, BECFC is a promising technology, but more research in full facilitated laboratories are requested to make the methodology applicable on real wastewater.
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    Removal of Iron and Manganese from Groundwater by Oxidation-Filtration Hybrid System
    (Addis Ababa University, 2021-01) Lemlem, Belay; Shimelis, Kebede Kassahun (PhD)
    Groundwater is naturally available water that exists in pore spaces and fractures in rock and sed-iment beneath the earth's surface that fills the opening in beds of rocks and sand. In developing countries both groundwater and surface water are used for irrigated agriculture and urban water supply. In Ethiopia groundwater is mostly utilized for drinking and industrial utility. In deeper wells the natural presence of metallic elements iron and manganese together is common .Their presence in limited amount is essential for all living organisms. However, the existence of iron and manganese are considered as contaminants above the limited concentration of 0.3mg/L and 0.1mg/L respectively. From many wells found in and around Addis Ababa some of them have high iron and manganese concentration which is found to be a problem on using groundwater to supply the high-water demand in the city. The aim of this study was removal of iron and manganese from groundwater by oxidation by air and sodium hypochlorite followed by sand filtration. Experimental set up was done at AAiT 5 kilo campus. The sand bed was prepared for filtration process with bed depth 0.6m and grain size of ES=0.71mm, UC=1.70 and d60=1.2mm. Electrolytic sodium hypochlorite Produced using ti-tanium and stainless steel electrodes at electrolytic reaction time 72 min in one liter electrolytic cell 2 cm gape and 7volte. The result hypochlorite resulted had concentration of 4.183 g/lit. Removal efficiency of the system tested using synthetic water resulted removal efficiency of 95.76333% for iron and 95.65% for manganese. For actual groundwater from Sambanekersa with 5.162mg/l iron and 0.607mg/l manganese concentration oxidation filtration process was performed at optimal point of 7.02mg/l NaOCl, 77min and 1.5 l/min air flow rate the resulted removal efficiency is 87.14% for iron and 26.41% for manganese.