Method for lifting membrane separation apparatus

A method for lifting the membrane separation device immersed in liquid to be treated so as to obtain permeated liquid through a filtration membrane, the method comprising:

• injecting a gas into a predetermined region of the membrane separation device, thereby raising the membrane separation device by a buoyancy generated by the injected gas through the liquid to be treated;
• and
• engaging an engaging portion of a lifting apparatus with an engageable portion provided to an upper portion of the membrane separation device, thereby lifting the membrane separation device,
• wherein the membrane separation device comprises a membrane module, the membrane module including:
• a plurality of membrane elements each having the filtration membrane;
• and
• a liquid collection case coupled to each side of the plurality of membrane elements arranged in parallel to each other, the liquid collection case including a liquid collection space in communication with the flow path of the permeated liquid of each of the membrane elements,
• and wherein the predetermined region is the space forming the flow path of the permeated liquid in the membrane module.