BIOCIDAL METHOD OF CIRCULATING WATER SYSTEM IN OPEN TYPE WATER COOLING TOWER

PROBLEM TO BE SOLVED: To provide a biocidal method for efficiently annihilating not only microorganisms such as bacterium and true fungus but also comparatively large-sized organisms such as algae and young shellfish in a circulating water system of an open type water cooling tower.SOLUTION: In the circulating water system of the open type water cooling tower, hypochlorite ion or hypobromite ion of sufficient concentration for annihilating shellfish in replenishing water is made to be present in the replenishing water and further hypochlorite ion or hypobromite ion in the circulating water is maintained so that free residual chlorine (bromine) concentration in the circulating water is in a range where concentration necessary for sterilization of the circulating water is a lowest limit and concentration not promoting corrosion of a metal coming into contact with the circulating water is a highest limit. Thus biocidal method of the circulating water system of the open type water cooling tower is provided.