Separating film, separating film element, separating film module, sewage and waste water treatment device, and separating film manufacturing method

A separation membrane comprising a porous substrate and a porous resin layer on at least one surface of the porous substrate, the porous substrate comprising an organic fiber and having a density of 0.7 g/cm3 or less, the porous resin layer comprising a resin, part of the resin permeating into the porous substrate to form a composite layer with the porous substrate, wherein

• B≧0.2×A, and
• C/B≧0.1
• wherein A represents the thickness of the porous substrate, B represents the thickness of the porous resin layer, and C represents the thickness of the composite layer, and wherein the porous resin layer has macrovoids having short diameters of 0.05×A or more, and the rejection of micro particles having an average particle size of 0.9 μm is at least 90%.

A separation membrane comprising a porous substrate and a porous resin layer on at least one surface of the porous substrate, the porous resin layer comprising a resin and permeating into part of the porous substrate to form a composite layer with the porous substrate, wherein

• B≧0.2×A, and
• C/B≧0.1
• wherein A represents the thickness of the porous substrate, B represents the thickness of the porous resin layer and C represents the thickness of the composite layer, and wherein the porous resin layer has an average pore size in the range of 0.01 to 0.2 μm and a standard variation of the pore size of 0.1 μm or less at the surface.

A separation membrane element comprising a separation membrane comprising a porous substrate and a porous resin layer on at least one surface of the porous substrate, the porous resin layer comprising a resin, part of the resin permeating into the porous substrate to form a composite layer with the porous substrate, wherein the porous resin layer has an average pore size in the range of 0.01 to 0.2 μm and a standard variation of the pore size of 0.1 μm or less at the surface.

A separation membrane module comprising a plurality of separation membrane elements and a housing containing the separation membrane elements, each separation membrane element comprising a separation membrane comprising a porous substrate and a porous resin layer on at least one surface of the porous substrate, the porous resin layer comprising a resin, part of the resin permeating into the porous substrate to form a composite layer with the porous substrate, wherein the porous resin layer has an average pore size in the range of 0.01 to 0.2 μm and a standard variation of the pore size of 0.1 μm or less at the surface.

A sewage treatment apparatus comprising a separation membrane module comprising a plurality of separation membrane elements and a housing containing the separation membrane elements, each separation membrane element comprising a separation membrane comprising a porous substrate and a porous resin layer on at least one surface of the porous substrate, the porous resin layer comprising a resin, part of the resin permeating into the porous substrate to form a composite layer, wherein the porous resin layer has an average pore size in the range of 0.01 to 0.2 μm and a standard variation of the pore size of 0.1 μm or less at the surface, the separation membrane module being immersible into sewage to be treated in use.

A method for making a separation membrane comprising the steps of:

• applying a solvent solution containing a resin, a pore-forming agent, and a solvent onto at least one surface of a porous substrate having a density of 0.7 g/cm3 or less to form a coating film and to impregnate the porous substrate with the solvent;
• and
• immersing the porous substrate into a coagulation bath containing a non-solvent to coagulate the resin and to form a porous resin layer on the surface of the porous substrate.