OPERATION METHOD OF REVERSE OSMOTIC MEMBRANE DEVICE

PROBLEM TO BE SOLVED: To provide a reverse osmotic membrane device which, always satisfies the water quality standard of permeable water during the operation, can perform the energy-saving operation and the stable supply of the permeable water.SOLUTION: Clear sea water sw after pretreatment stored in a treated water tank 12 is supplied to a reverse osmotic membrane module 14 through a clear sea water supply path 16. Permeable water pw obtained from a preceding stage side reverse osmotic membrane element 36 of the reverse osmotic membrane module 14 is sent to a post process from the permeable water outflow path 46, and the permeable water pw obtained from a post stage side reverse osmotic membrane element 36 is circulated to the treated water tank 12 through a permeable water circulation path 48. While the flow rate of the clear sea water sw supplied to the reverse osmotic membrane module 14 is controlled by a flow rate variable high-pressure pump 22 arranged in the clear sea water supply path 16, the opening of a flow rate regulating valve 68 arranged in the permeable water circulation path 48 is controlled so as to regulate the circulating flow rate of permeable water.