Chemical cleaning method of immersing the membrane element

The organic waste water containing manganese 1 mg / L or more, the submerged membrane element used in the activated sludge treatment and biological treatment in the bath, then the membrane separation activated sludge process of solid-liquid separation by the installed membrane filtration units in the processing bath a method of chemical cleaning, a first solution containing an oxidizing agent is injected from the secondary side of the submerged membrane element on the primary side, after holding a predetermined time, and sucked and discharged from the secondary side of the submerged membrane element to the outside of the system, then by injecting a second liquid comprising an acid from the secondary side of the submerged membrane element on the primary side, after holding a predetermined time, by performing suction filtration operation, the organic wastewater membrane bioreactor containing a high concentration of manganese when chemical cleaning of the submerged membrane element for use in the treatment with activated sludge treatment tank, the organic decomposition and manganese removal, carried out efficiently at the same time, without adversely affecting the microorganisms in the activated sludge, high dose Effect can be obtained.