Removal of iron from groundwater by filtration using natural zeolites. The case of assosa town public water supply, benishangul gumuz regional state, western Ethiopia

Abstract

Groundwater is the only Water Supply for Asossa Town. Small amounts of iron are often found in water supply because of the large amount of iron present in the soil and corrosive water will pick up iron from pipes. The problems caused by the presence of large concentration of iron impart a metallic taste to the water, Industrial products such as paper, textiles, or leather may be discolored .Ground water samples collected from Asossa Town deep well relatively with higher iron (Fe) concentration than the permissible limits as specified in WHO. The naturally available environmentally and economically acceptable zeolites were obtained from the surrounding area of the Town. It was a powerful Adsorbent for the removal of iron. The aim of study was to design the most efficient, easily available, economical and environmentally acceptable iron removal technology from ground water using natural zeolites. The study was carried on Laboratory-scale columns experiment by sand filters with variable depths of 10, 15, 20, 25, 30 cm and three graded types of sand (course, fine and graded) were used. The course sand (E=1.0 mm, U=1.117, depth of sand =30cm, filtration rate 2.4 m3 /m2 /hr.) was the best type of filter media. Iron concentration measured in groundwater was 5.15 mg/l before filtration and decreased to concentration of 0.85 mg/l following filtration. Hence, iron removal efficiency of 83.49 % with a correlation coefficient of R 2>0.98 was obtained during aeration process. The result compared with chlorination and aeration depending on sand filtration, chlorination was better removal efficiency in natural zeolites than aeration filtration process. According to Ethiopian standard water quality procedure and WHO guideline states that Fe concentration <0.3 mg/l is permissible level for drinking water. In this study also chlorination treated water initial concentration 6.20 mg/l after sand filtration 0 mg/l iron concentration ,then the removal efficiency of course sand was 100% , its correlation coefficient,R2>0.97. Advantage of such treatment were simplicity, easily available natural zeolites, low cost design at house hold and a community level, and without the need of chemical addition. Finally, periodic washing for sand filter or replacement of sand by other sand was needed in order to get sufficient flow rate.