Sewage/wastewater treatment system using granular activated sludge and membrane bio-reactor and sewage/wastewater treatment method using the same

The present disclosure relates to a sewage/wastewater treatment system using granular activated sludge and a membrane bio-reactor and a sewage/wastewater treatment method using the same that are configured to effectively remove pollutants contained in raw water through a granulation tank in which the granular activated sludge is contained and to allow the raw water to be filtered through movable membranes located on the upper portion of the granulation tank. The system includes: an indirect aeration tank adapted to supply air thereto to allow dissolved oxygen contained in raw water to reach a saturation concentration; a granulation tank adapted to allow floating microorganisms contained in the treated water passing through the indirect aeration tank to be granulated and having a sludge blanket formed thereon; and movable membranes located on the upper portion of the granulation tank in such a manner as to be movable in the granulation tank.