| abstract |
PROBLEM TO BE SOLVED: To extend a chemical cleaning interval by efficiently removing contaminants adhering to a primary membrane surface of a membrane separation device by backwashing. SOLUTION: An internal pressure hollow fiber type, tubular type or spiral type membrane separation device 2 for supplying raw water to one side 2A of a separation membrane 2M and obtaining permeated water from the other side 2B. Means 14 and 21 for directly introducing gas from one end of raw water side 2A of separation membrane 2M And a means 20 for introducing backwash water into the permeated water side 2B, and a gas-liquid discharge means 22 provided at the other end of the raw water side 2A. At the time of backwashing, backwash water and gas are simultaneously supplied to efficiently wash the separation membrane. |