Removal of Iron and Manganese from Groundwater by Oxidation-Filtration Hybrid System
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Date
2021-01
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Addis Ababa University
Abstract
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.
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Keywords
filtration, sodium hypochlorite, air flow rate, oxidation