High quality drinking water can be produced by membrane separation process. A major problem in the current system is a membrane fouling control. In order to investigate membrane fouling due to E.coll crmoval, lab scale experiment using MF and UF and semi pilot plant experiment using UV radiation or not was performed. AS a result, the possibility of membrane fouling control by repressing of micro-organ-ism on the membrane surface was clearly verified. But it was not clearly verified in this experiment the combined effect with other factors such as Turbidity, organic and inorganic matters