HOLLOW YARN MEMBRANE FILTER

PURPOSE:To reduce the amt. of a waste liq. discharged from a filter and to reduce the frequency of the exchange of the hollow yarn membrane filter by providing a gas storage part for regulating pressure, and regulating optionally the amt. of compressed gas for backwashing by the amt. of the gas stored in the gas storage part. CONSTITUTION:A separate tank 4 having a gas storage part 3 for regulating pressure is connected to the lower side part of the main body 2 of a hermetic vessel contg. a hollow yarn membrane filter 5. When a clad in a waste liq. is deposited on the surface of the filter 5 during the filtration of the waste liq., a valve 16 is opened to supply compressed gas from a gas supply pipe 11 into the main body 2 of the hermetic vessel until the pressure in the main body 2 becomes equal to the pressure of compressed gas, and then the valve 16 is closed. The volume of the gas stored in the gas storage part 3 is reduced as the pressure in the hermetic vessel 2 increases, the treating liq. equivalent to the reduced volume is refluxed to the surface from the inside of the filter 5, and the clad deposited on the surface of the filter 5 is removed. The amt. of the treating liq. to be refluxed can be controlled by regulating previously the amt. of gas to be stored in the gas storage part 3.