Removal of iron and manganese from micro-polluted surface source water using bio-sand filtration system

Bio-sand filter was adopted to study the iron and manganese removal from micro-polluted surface source water, and the effect by biofilm formation method, dissolved oxygen (DO) and water temperature on iron and manganese were analyzed. The results demonstrate that natural start-up and inoculm start-up methods of filters both have a high removal of iron and manganese. The former method is better than the latter one on iron and manganese removal, but it is less stable. When the DO in water are 1.5–2.5mg/L, 3.0–5.0mg/L, 5.5–6.5mg/L and 7.0–8.0mg/L, the average removal rate of iron are 62.11%, 82.95%, 83.08% and 70.81%, respectively, and removal of manganese are 74.89%, 80.30%, 75.44% and 71.46% respectively. Changing DO values under 4.0–5.0mg/L had no remarkable effect on the removal rate. When the value is about 4.0mg/L, the DO is enough to remove manganese and iron. The temperature of water is a significant factor on the manganese removal. When it is below 15°C and 20–26°C, the average removal rate of iron are 70.88% and 82.17%, and the removal of manganese are 64.46%, 78.95%, respectively. The most suitable environmental temperature is about 22°C when iron and manganese coexists. We can reduce the filtration rate to improve the removal efficiency at low temperature. When bio-sand filtration is added after the process of coagulation and sedimentation, the efficiency of removing iron and manganese would be further improved. The concentration of iron and manganese in the effluent is much lower than 0.3mg/L and 0.1mg/L which achieve drinking water-quality standards.