Patent ID: 9458034
Filing Date: 2016-10-04
CPC Classification: B01D,C02F

Claim Text:
1. A method of membrane separation, comprising the successive steps of: supplying a water to be treated to a membrane separation apparatus having a membrane for a non-addition period in which a combined chlorine treating agent is not added and supplying a water to be treated to the membrane separation apparatus for an intermittent addition feeding period in which a combined chlorine treating agent is added, wherein the combined chlorine treating agent is an aqueous agent containing an alkali metal hydroxide, a sulfamic acid compound, and a chlorine-based oxidizing agent, a viable cell count, log CFU/mL, of the water to be treated is 3 or more, the non-addition feeding period is for 6-120 hours and the intermittent addition feeding period commences during the formation of a biofilm on the membrane and is for 0.5-40 hours, the concentration of the combined chlorine treating agent in the water to be treated in the intermittent addition feeding period is 0.5-20 mg/L as total chlorine for exfoliating the biofilm formed on the membrane while the biofilm is in a non-adhesive condition, and the combined chlorine treating agent is added during the intermittent addition feeding period at an additive amount R in which R, represented by the following formula (4) is 3 or more,