Patent ID: 9649602
Date: 2017-05-16
CPC Classifications: B01D,C02F

Claim:
1. A method of sewage treatment comprising: immersing a separation membrane module into wastewater which includes activated sludge and is contained in a reservoir, wherein the separation membrane module comprises a plurality of separation membrane elements, and a housing containing the separation membrane elements, wherein each separation membrane element comprises a supporting plate, a separation membrane and a filtered water outlet and wherein the separation membrane is a flat membrane and is arranged on at least one face of the supporting plate; separating the wastewater into filtered water and suspended solids by having the water wastewater permeate through the separation membrane; and having the filtered water flow toward the exterior from the filtered water outlet; wherein the flat separation membrane of each separation membrane element comprises a nonwoven fabric and a porous resin layer on at least one surface of the nonwoven fabric; the porous resin layer comprises a resin; a part of the resin permeates into the nonwoven fabric to form a composite layer with the nonwoven fabric; the porous resin layer has at its surface, pores having an average pore size in the range of 0.01 to 0.2 μm and a standard variation of pore sizes of 0.1 μm or less; and the nonwoven fabric has a thickness A of from 50 μm to 1 mm, the porous resin layer has a thickness B and the composite layer has a thickness C; and wherein the separation membrane satisfies: macrovoids are present in the porous resin layer and have larger diameters than the diameter of pores at the surface and have a short diameter of 0.05×A or more; and supplying air from an air diffuser to the surfaces of the separation membranes of the separation membrane elements.