| 摘要 |
PROBLEM TO BE SOLVED: To facilitate a back washing and at the same time, improve the recovery rate a water permeation by the back washing and further, enable a stable filtering capability to be maintained for a long time by arranging a filtered water flow path and an injection channel under a filter membrane face and at the same time, not allowing at least the injection channel of a cleaning medium to come into contact with a filter membrane. SOLUTION: A filter membrane element 10 is formed in a four-tier structure and two flat membranes 14, 15 are firmly attached to the outside face of a support frame 12, and at the same time, other flat membranes 21, 22 are firmly attached to the inside face of the support frame 12. Further, a single filtered water flow path 30a is formed in a gap between both flat membranes 14, 21 and another filtered water flow path 30b is formed in a gap between both flat membranes 15, 22. In addition, an injection channel 31 of a cleaning medium is formed in a gap between both flat membranes 21, 22. Consequently, the filter membrane element 10 which is shared by only an inlet and an outlet for the supply of the cleaning medium and for the drainage of filtered water, can be constituted, although the filtered water flow path 30b and the injection channel 31 of the cleaning medium are mutually different, by connecting both filtered water flow paths 30a, 30b and the injection channel 31 of the cleaning medium to a single filtered water nozzle.
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