PURPOSE: To carry out stable water treatment over a long time and to obtain treated water with high purity, by stacking a filter membrane layer formed by entangling a cation exchange fiber and a fine granular ion exchange resin on a filter membrane layer comprising a fine granular cation.anion exchange resin.
CONSTITUTION: Fine granular ion exchange resins A, C with particle size of 2W 250μm are mixed with water and the obtained mixture is precoated on a filter support 11 to form a filter membrane layer. On the other hand, a cation exchange fiber D of which thickness is 2W200μm and length is two times or more of the thickness and fine granular ion exchange resins A, C with particle size of 2W250μm are mixed in water to be entangled mutually and the rsulting mixture is further precoated on the previous filter membrane layer to obtain a double filter membrane layer. This filter layer hardly generates crack because has an integral tough structure ad contamination and clogging of a filter element are eliminated as well as high purity treated water is obtained.
YOSHIDA YASUSHI
OOKI TOSHIYUKI
