Multistage immersion type membrane separator and high-concentration wastewater treatment facility using same

A multistage immersion type membrane separator in which an air diffuser is disposed under a filtration part immersed in a treatment tank, characterized in that:

• the filtration part has plural plate-like membrane cartridges arranged in a vertically parallel multistage fashion and spaced at intervals for forming a crossflow passage of a predetermined width;
• the plate-like membrane cartridges have a filter supporting plate having rigidity on which a permeated water passage is formed, filtration membranes attached to front and rear of the filter supporting plate, and a permeated water outlet disposed at an upper portion on one side end surface of the filter supporting plate such that it is communicated to the permeated water passage and connected to a collecting means;
• and
• the air diffuser has a diffuser tube disposed sidewardly that has plural blowholes, a flushing pipe that has at its tip an opening serving as an outlet above the diffuser tube, and a flushing valve disposed in the flushing pipe wherein the diffuser tube is communicated at its basal end to an air supply source and at its front-end to the flushing pipe,
• a control means communicating with said flushing valve and said air supply source, and configured such that the flushing valve is opened while supplying air to the diffuser tube, thereby to cause the air supplied to the diffuser tube to pass through the flushing to be exhausted;
• a mixed liquor inside a treatment tank is caused to flow backward from the blowholes into the diffuser tube;
• the flowed mixed liquor is caused to be exhausted after passing through the flushing pipe together with the air as an air-liquid mixed flow;
• and pulsation caused by pressure fluctuations inside the pipe is utilized to repeat intermittent flushing.