Method of use of compositions of biocides and fluorescent indicators to control microbial growth

A method for determining the consumption of biocide for controlling growth of microbiological organisms within a fluid system containing said microbiological organisms which comprises the steps of:

• a) adding to said fluid system containing microbiological organisms an amount of a composition comprising a biocide/inert fluorescent compound combination of a known weight ratio selected from the group consisting of glutaraldehyde/1,5 naphthalene disulfonic acid, glutaraldehyde/1,3,6,8 pyrene tetrasulfonic acid, mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one/1,5 naphthalene disulfonic acid, mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one/1,3,6,8 pyrene tetrasulfonic acid, glutaraldehyde/fluorescein, alkyl dimethyl benzyl ammonium chloride quaternary/2-naphthalene sulfonic acid and 2-(decylthio)-ethanamine/2-naphthalene sulfonic acid, wherein said inert fluorescent compound is present in from 0.0005 to 10 percent by weight based on the weight of active biocide;
• b) determining the amount of biocide added to the system at an initial time by measuring the intensity of the fluorescence of the fluorescent compound present in the system and calculating the mount of biocide using the known weight ratio;
• c) determining the amount of biocide present in the system at a second time by measuring the intensity of the fluorescence of the fluorescent compound and calculating the amount of biocide at said second time using the known weight ratio;
• and
• d) subtracting the actual amount of biocide present as determined in step (c) from the total amount of biocide added as determined in step (b), which yields the amount of biocide consumed.

A method for maintaining the concentration of a biocide for controlling growth of microbiological organisms in an industrial fluid system containing said microbiological organisms which comprises the steps of:

• a) adding to said industrial fluid system containing microbiological organisms an amount of a composition comprising a biocide/inert fluorescent compound combination of a known weight ratio selected from the group consisting of glutaraldehyde/1,5 naphthalene disulfonic acid, glutaraldehyde/1,3,6,8 pyrene tetrasulfonic acid, mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one/1,5 naphthalene disulfonic acid, mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one/1,3,6,8 pyrene tetrasulfonic acid, glutaraldehyde/fluorescein, alkyl dimethyl benzyl ammonium chloride quaternary/2-naphthalene sulfonic acid and 2-(decylthio)-ethanamine/2-naphthalene sulfonic acid, wherein said inert fluorescent compound is present in from 0.0005 to 10 percent by weight based on the weight of active biocide;
• b) determining the amount of biocide added to the system at an initial time by measuring the intensity of the fluorescence of the inert fluorescent compound present in the system and calculating the amount of biocide using the known weight ratio;
• c) determining the amount of biocide present in the system at a second time by measuring the intensity of the fluorescence of the fluorescent compound and calculating the amount of biocide at said second time using the known weight ratio;
• d) subtracting the actual amount of biocide present as determined in step (c) from the total amount of biocide added as determined in step (b), which yields the amount of biocide consumed;
• and
• e) adding to the industrial fluid system an amount of biocide to maintain the biocide at a specified concentration which inhibits microbial growth.