LIQUID PERMEATING METHOD

PURPOSE:To perform effective liquid permeation by inhibiting back flow of liquid permeate from permeate side to circulating liquid side and to enhance backwashing effect by decelerating the increasing rate of permeation resistance by controlling the circulating liquid amt. so as to maintain the exit pressure of the circulating liquid to above the pressure of the permeate. CONSTITUTION:The circulating liquid flow rate V is controlled to above the minimum flow rate Vmin of the circulating liquid necessary for inhibiting deposition of contaminant, etc., to a liquid permeating element 7, and the flow rate V of the circulating liquid and the flow rate F of the permeate measured by a flow meter 13 and 16, and the exit pressure Po and permeate pressure Pf measured by a pressure gauge 18 and 19 are inputted to an operation control device 21 while regulating Po>=Pf. Thus, the degree of opening of a flow control valve 12 or 15 is controlled basing on the result of the operation.