Patent ID: 7579018

Claim:
A method of achieving an effective “free chlorine” level in treating with a biocide water that is in contact with biofilm or that comes into contact with biofilm, which method comprises introducing into said water a biocidally effective amount of at least one 1,3-dibromo-5,5-dialkylhydantoin wherein said amount (i) provides in the water a biocidally effective “free chlorine” level that is higher than would be provided by an equimolar quantity of N,N′-bromochloro-5,5-dimethylhydantoin, (ii) results in eradication or at least effective biocidal challenge of said biofilm, and (iii) enables the rate of biocide consumption in treating said water to be reduced as compared to N,N′-bromochloro-5,5-dimethylhydantoin, said at least one 1,3-dibromo-5,5-dialkylhydantoin that is introduced into said water being characterized in that one of the alkyl groups in the 5-position is a methyl group and the other alkyl group in the 5-position has in the range of 1 to 4 carbon atoms, and wherein said at least one 1,3-dibromo-5,5-dialkylhydantoin that is introduced into said water is introduced in the form of granules which are devoid of binder and wherein prior to introduction into said water said granules of said at least one 1,3-dibromo-5,5-dialkylhydantoin have an average size in the range of about 40 U.S. standard mesh size to about ⅜-inch and have an average crush strength of at least about 15 pounds per inch of thickness.