Method for cleaning separation membrane

Abstract

Pulse back washing for applying a back pressure from the filtrate side to the raw water side of the membrane is repeated plural times for recovering a TMP during usual main back washing applied by suspending membrane filtration, when the TMP is increased when tank water extracted out of a biological treatment tank 1 is filtrated through the membrane by a cross-flow method. Pulse back washing is applied at a stage when the TMP is 80% or less of the permissible TMP to peel the deposits on the membrane surface, and the peeled deposits are returned to the biological treatment tank concomitantly with a circulating flow. Clogging substances on the separation membrane is removed in a direction opposite to the direction of pulse back washing by selecting the destination of discharge of back wash drain to be the inlet side of the separation membrane in the main back wash step.

Dependencies are inferred from the claim text.