| 摘要 |
PURPOSE:To permit execution of backwashing with a simple device, and to eliminate opportunity of contamination of permeate by pressurizing the permeate side by transmittig the pressure of feed liquid to the permeate side through a stretchable or flexible member in the stage of backwashing of a filter medium. CONSTITUTION:A feed liquid line is separated from a permeate line by a flexible member 6-6, and a volume of permeate corresponding to the volume of deformation of the flexible member 6-6 (i.e. the volume corresponding to the deformation of the flexible member expressed by the dotted line 6-6 from a downwardly convex condition to an upwardly convex condition) flows backward through a filter medium 4-4 to the feed liquid side causing backwashing effect without causing mutual intermixing of the feed liquid and the permeate. And the pressure of the feed liquid serves as the driving force for causing the back flow of the permeate. As a result, the backwashing of the filter medium 4-4 is executed with a simple device and without fear of causing contamination of the permeate by pressurizing the permeate side.
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