Patent ID: 9700847
Date: 2017-07-11
CPC Classifications: A01N,B01D,C02F

Claim:
1. A method of slime control for a reverse osmosis membrane, comprising the step of: adding a combined chlorine agent to a feed water system containing the reverse osmosis membrane, the combined chlorine agent comprising an aqueous agent containing an alkali comprising an alkali metal hydroxide, sulfamic acid or a salt thereof, and a chlorine-containing oxidizing agent, wherein the compositional ratio of the oxidizing agent to the sulfamic acid or salt thereof is in the range from 0.45 to 0.6 by Cl/N molar ratio, the compositional ratio of the oxidizing agent to alkali is in the range from 0.3 to 0.4 by Cl/alkali metal molar ratio, the compositional ratio of sulfamic acid or salt thereof to alkali in the aqueous solution agent is in the range from 0.5 to 0.7 by N/alkali metal molar ratio, the amount of alkali metal contained in the salt of sulfamic acid is calculated as alkali, the pH of the aqueous agent is 13 or more, and the free chlorine concentration in the aqueous agent is no more than 1000 mg/L and 2% by weight of the total chlorine concentration, and the chlorine agent is added to the feed water system containing the reverse osmosis membrane such that the free chlorine concentration in the feed water system is no more than 0.1 mg/L to prevent deterioration of the reverse osmosis membrane.