Coupling Technique for Deep Removal of Manganese and Iron from Potable Water

Abstract

Although many treatment methods have been employed to remove soluble Fe(II) and Mn(II) from water, for some smaller water treatment plants or under emergent circumstances such as sharp increase of iron and manganese concentrations in source water during summer, traditional physicochemical removal methods are more flexible and effective. In this article, a coupling technique of chlorine dioxide (ClO2) preoxidation and manganese sand filtration for iron and manganese removal from potable water have been proposed. Fe(II) and Mn(II) removal efficiencies of different filter materials (natural manganese sand, quartz sand, and fiber bundle filter (FBF) material) were compared. Influences of ClO2 dosage, liquid flow rate, particle size of filter material, and thickness of filter bed on removal efficiency were also examined. In addition, performance of ClO2 preoxidation–manganese sand filter technique was investigated under the optimum operating conditions to remove Fe(II) and Mn(II). Results indicated that natural manganese sand filter showed higher capability of removing Fe(II) and Mn(II) than quartz sand filter and FBF. It was found that manganese removal efficiencies increased with higher dosage of preoxidant, lower liquid flow rate, smaller sand particle diameter, and thicker filter bed. When initial concentrations of Mn(II) and Fe(II) in feed water were 1.5 and 1.0 mg/L, respectively, ClO2 dosage was 0.99 mg/L, liquid flow rate was 282.6 mL/min, sand particle diameter was 0.6–1.2 mm, and filter bed thickness was 60 cm, the process showed good performance of Fe(II) and Mn(II) removal with both removal rates more than 95%.