Abstract: Provided is a cartridge-type hollow fiber membrane module including a hollow fiber membrane unit module with a free end and a cartridge frame and a submerged water treatment apparatus including an air diffuser apparatus capable of intermittent and continuous aeration disposed below the hollow fiber membrane module, wherein the cartridge-type membrane module with the free end using the coarse bubble generating air diffuser apparatus capable of intermittent/continuous aeration in conjunction with an air accumulation pipe may control aeration/non-aeration cycles through adjustment of the volume of an air chamber and an amount of inflow air and carry out continuous aeration based on changes in raw water load and a concentration of solids in a membrane separation tank.

Abstract: Disclosed is a diffuser installation structure capable of improving uniformity of air bubbles discharged from air bubble discharge holes, restricting the formation of dead zone air bubble discharge holes, and having the tolerance against design deviation. In the installation structure for a diffuser including at least one air feeding port and an air bubble discharge wall having a plurality of air bubble discharge holes, the air bubble discharge wall is inclined upward in the direction of increasing distance relative to the air feeding port.