Method of waste water/water treatment in a submerged membrane bioreactor is disclosed. The bioreactor includes a tank containing a mixed liquor having microorganism; porous carriers in the mixed liquors; and a filtration module immersed in the mixed liquor and having a permeate side into which fluid can flow only through the filtration module. The method includes introducing an influent into the tank; applying a negative pressure source to the permeate side so that liquid in the tank penetrates the filtration module into the permeate side and flows out from the tank; and aerating the mixed liquor in the tank so that the porous carriers keep contact with the filtration module, and thus reduce fouling of the filtration module.