Patent ID: 8377225

Claim:
A method for cleaning an air diffusing apparatus of a submerged membrane separation apparatus comprising: a separation membrane module which is placed in a treatment tank in which a liquid to be treated is to be stored; at least one air diffusing apparatus which is disposed below the separation membrane module and has a first connecting port a and a second connecting port b; and a gas supplying apparatus which supplies gas to the air diffusing apparatus through a as supplying pipe; wherein when at least one air diffusing apparatus is arranged in one treatment tank, a first header pipe A and a second header pipe B are placed as the gas supplying pipes, the first connecting port a and the first header pipe A and the second connecting port b and the second header pipe B for each air diffusing apparatus are respectively connected, on-off valves are arranged in four parts: a first upstream side A 1 and a second upstream side B 1 of the connection point of the first and second header pipes A and B and the first air diffusing apparatus and a first downstream side A 2 and a second downstream side B 2 of the connection point of the first and second header pipes A and B and the last air diffusing apparatus one by one, and the downstream ends of the first and second header pipes A and B being open to the atmosphere; the method comprising: alternately providing a valve state 1 where on-off valves A 1 and B 2 are opened and on-off valves B 1 and A 2 are closed and a valve state 2 where the on-off valves A 1 and B 2 are closed and the on-off valves B 1 and A 2 are opened in a state where the filtration operation is stopped and the gas supplying apparatus is driven when the air diffusing apparatus in the submerged membrane separation apparatus is cleaned; further comprising providing a valve state 3 where all of the on-off valves are opened.