Patent ID: 8685249

Claim:
An operation control method of a multi-stage seawater desalination apparatus that uses a multi-stage seawater desalination apparatus, during a sterilization operation of the high-pressure reverse osmosis device of the multi-stage seawater desalination apparatus, the multi-stage seawater desalination apparatus comprising: a high-pressure pump that is mounted on a raw water line through which raw water is supplied, and increases pressure of the raw water to a predetermined high pressure; a high-pressure reverse osmosis device that includes a high-pressure reverse osmosis membrane for concentrating a salt content in high-pressure feed water whose pressure is increased by the high-pressure pump; a first drain valve that is mounted on a permeated water line through which permeated water that has passed through the high-pressure reverse osmosis device is supplied downstream, and temporarily drains the permeated water of an initial start-up; a low-pressure pump that is mounted on the permeated water line provided downstream of the first drain valve, and reduces pressure of the permeated water to a predetermined low pressure; a low-pressure reverse osmosis device that includes a low-pressure reverse osmosis membrane for concentrating a salt content in low-pressure feed water whose pressure is reduced by the low-pressure pump; and a second drain valve that is mounted on a discharge line on a concentrated water side of the low-pressure reverse osmosis device, and temporarily discharges the low-pressure feed water of the initial start-up supplied to the low-pressure reverse osmosis device; wherein the high-pressure reverse osmosis device is a membrane with chlorine-resistance; the operation control method comprising: a step of supplying raw water to which chlorine (Cl) is added is supplied to the high-pressure reverse osmosis device without feeding a reducing agent from a first reducing agent supplying unit; a step of temporarily draining low-pressure feed water including a reducing agent through the second drain valve, after the reducing agent is added to permeated water with chlorine that has passed through the high-pressure reverse osmosis membrane of the high-pressure reverse osmosis device from a second reducing agent supplying unit; a step of switching operation to a normal operation, by adding a reducing agent from the first reducing agent supplying unit to the raw water, and stopping addition of the reducing agent from the second reducing agent supplying unit, after a predetermined sterilization operation is finished; and a step of producing product water, by switching operation to a rated seawater desalination operation, while closing the second drain valve.