Filtration membrane cartridge

A plurality of filtration membrane cartridges submerged for use in a raw liquid processing tank, each of said cartridges comprising:

• a fusible resin membrane-supporting plate,
• a filtration membrane disposed on the surface of the resin membrane-supporting plate,
• the membrane-supporting plate having a plurality of interconnecting linear gutters and channels for permeated liquid formed on the surface of the membrane-supporting plate facing the filtration membrane;
• the filtration membrane comprising a nonwoven fabric support member on the side thereof abutting on the membrane-supporting plate, the surface of said support member being impregnated with a membrane to form the filtration membrane;
• and
• said filtering membrane being peripherally fused to said membrane-supporting plate by a main fusible domain and a plurality of subordinate fusible domains defining a sealed border enclosing an effective filtration area free of said main and subordinate fusible domains,
• said main fusible domain being formed peripherally in a continuous line adjacent to but spaced from the peripheral edges of the filtering membrane, said plurality of subordinate fusible domains being formed intermittently in a non-continuous line extending along and disposed closely adjacent to the main fusible domain, the resin of the resin-membrane-supporting plate and the nonwoven fabric of the filtration membrane being fused together so that the filtration membrane is bonded to the membrane supporting plate,
• said line of subordinate fusible domains being formed along the side of said main fusible domain away from the peripheral edges of the filtering membrane.