Improved module cleaning method

A/back washing device with ventilating of porous membrane filter assembly (5) adopts a (16), comprising the vertical distance one or more isolating film of the upper end cover (7) and lower end cover (8) extending longitudinally (6), wherein the isolating film the end part is mounted in the upper and lower end cover of the. With penetrable wall isolating film (6) and filter operation when using, and a feeding of contaminants to a voltage isolating film of one side, wherein liquid from other side of the isolating film wall alkali. The ventilated/to back washing device (16) is made at least a rotary part one part of each separation membrane component (5), and comprises a through hole (18,19) is chamber is provided is separated (17), wherein a through hole with of the chamber (17) and a isolating film assembly (5) liquid is provided with a. The use, supply to the gas the chamber (17); through the through hole (18,19) is configured the gas and isolating film assembly (5), connected in order to the isolating film ventilating the isolating film assembly, through the through hole (5) is suction of the isolating film assembly the backwash and chamber (17) and/or supply of the isolating film assembly (5).