Removal of iron from ground water by coagulation and sedimentation

Abstract

Ground water is a major source of safe water for drinking and other domestic purposes for the rural I urban population of Bangladesh which may have iron content in excess of 5 mg/L. This study is an experimental investigation to observe the effect of different factors in iron removal and also to develop simple and cost effective iron removal method. Relevant literature on chemistry of iron content water and unit processes of iron removal have been reviewed, and water use pattern and distribution of iron in ground water have also been focused. Investigations were made at laboratory condition on artificial iron content water and natural ground water collected from tubewells of iron prone areas to find out effect of different unit processes and other related factors on iron removal. Experimental results shows that filtration is an effective mode of iron removal. However, considering the frequent cleaning of the filter bed and low yield, in this study emphasis have been given on sedimentation, for effective and efficient iron removal. As an aid in improving settling characteristics of the precipitated iron, coagulation is observed to be an important tool. Aeration, coagulation and 30 min sedimentation can reduce iron concentration to allowable limit of 1 mg/L. However, the analysis also shows that iron removal increases with an increase in anion concentration. More pronounced effect is observed when the added anion is common to the anion already in solution, due to common ion effect. Alum used as coagulant is observed to be more effective than lime in iron removal. Whereas, the coagulant cost involved using alum as coagulant is 191.7% higher than lime.