Method for the sterilization of ultrapure water line
AssigneeMorita Kagaku Kogyo Co., Ltd.
InventorsToshio Tatsuno, Mitsuo Miyamoto, Yoshiharu Ohta, Koichi Sawada
Life of this patent
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Abstract
Periodical sterilization is usually needed in the ultrapure water line provided in an ultrapure water-producing system or plant to kill some occasionally occurring viable cells of microorganisms in the ultrapure water as produced or being produced and thereby keep the ultrapure water under germ-free conditions. Now, it is discovered that an aqueous solution containing 1 to 100 ppm of hydrofluoric acid is effective to sterilize the ultrapure water line and is advantageous over the conventional sterilization agents such as aqueous hydrogen peroxide and sodium hypochlorite which were employed normally for the sterilization of the ultrapure water line.
Claims5
A method for the sterilization of an ultrapure water line provided in an ultrapure water-producing system, which comprises passing through the ultrapure water line an aqueous solution containing hydrofluoric acid as a sole sterilizing agent at a concentration of 1-10 ppm, so that the ultrapure water line is sterilized.
A method for the sterilization of an ultrapure water line provided in an ultrapure water-producing system, said ultrapure water line comprising an ion exchange resin unit as well as an inlet-side conduit section and an outlet-side conduit section as connected to an inlet and an outlet of the ion exchange resin unit, which method comprises:
- (a) disconnecting from the ion exchange resin unit and connecting the inlet-side conduit section and the outlet-side conduit section directly to each other to form a bypass circuit and to permit bypassed feeding of water through said bypass circuit without passing the water through the ion exchange resin unit provided in the ultrapure water line;
- (b) passing an aqueous solution containing hydrofluoric acid at a concentration of 1-100 ppm, through the ultrapure water line which has been rearranged by the direct connection of the inlet-side conduit section to the outlet-side conduit section to form the bypass circuit and permit the bypassed feeding of said solution without passing said solution through the ion exchange resin unit, whereby the sterilization is effected in the so rearranged ultrapure water line;
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- (c) allowing the aqueous solution of hydrofluoric acid to remain within the ultrapure water line having been so rearranged to have the bypass circuit, until the sterilization has been completed in said ultrapure water line.
Dependencies are inferred from the claim text.