A series of experiments to demonstrate the applicability of micro- and ultra-filtration technology for purification of the public water supply were conducted using slightly polluted river water. The result of the first and second runs of the experiment was satisfactory from the viewpoints of treatment efficiency and effectiveness of contaminant rejection. There was almost no difference in the performance between MF and UF membranes. However, when an MF membrane was used, pretreatment by coagulation was necessary to maintain a high flux with the untreated water.