METHOD AND APPARATUS FOR BACKWASHING MEMBRANE MODULE FOR REMOVING TURBIDNESS

PROBLEM TO BE SOLVED: To provide a method for backwashing a membrane module for removing turbidness, by which the flux through the membrane module can be made high and the membrane module can stably be operated continuously for a long period of time. SOLUTION: Raw water 1 is filtered by using the membrane module 5 consisting of a hollow fiber membrane to obtain a filtrate. This method for backwashing the module 5 is carried out by combining a filtration step to obtain the filtrate by making the water 1 pass through the module 5 with a backwashing step to backwash the module 5 by the germicide 8-injected backwashing water and another backwashing step to backwash the module 5 by the acid 9-injected backwashing water. Citric acid, ammonium dihydrogen citrate or a mixed acid of citric acid and glycolic acid is used as the acid 9 and is injected so that the citric acid concentration in the module 5 becomes 50-1,500 mg/L. Otherwise, an inorganic acid is used as the acid 9 and is injected so that the pH in the module 5 becomes 1.0-3.0. COPYRIGHT: (C)2004,JPO&NCIPI