Abstract: Fe and Mn removal from groundwater by a contact oxidation process and the effects of backwash were studied. It takes 9 days to have stable Fe removal with a filter chamber filled with sand and 2 days for the filter chamber of manganese mineral filtration. Forty-ight days are needed to have stable Mn reinoval with a filter chamber filled with sand, and 2 days for a filter chamber of manganese mineral filtration. Forty minutes and eighty minutes are needed for the filter chamber filled with sand to recover the ability of Fe and Mn removal after backwash. Twenty minutes and forty minutes are needed for the filter chamber of manganese mineral filling to recover the ability of Fe and Mn removal after backwash. SEM photographs show that floculations adhere to the surface of the filter membrane, that is the basis for quick recover of Fe and Mn after backwashing. Manganese mineral can be replaced by the cheaper sand as filling. In doing so, the investment can be greatly decreased.

Key words: iron removal, manganese removal, contact oxidation process, sand, manganese mineral