Method for the use of oxidants for microbial control under reducing conditions
View Patent ↗Microbial growth in an aqueous system containing borohydride residues is controlled by adding an aldehyde or aldehyde source, followed by adding an active halogen biocide. The active halogen biocide is preferably stabilized by an N-hydrogen compound.
1. A method for controlling microbial growth in an aqueous system containing borohydride residues, said method comprises adding an aldehyde or an aldehyde source to said aqueous system, followed by adding an oxidant, said oxidant being a source of active halogen, such that a residual oxidant level under reducing conditions is provided.
2. The method of claim 1 , wherein the aldehyde or aldehyde source is added in an amount sufficient to achieve an ORP of greater than −350 mV.
3. The method of claim 2 , wherein the aldehyde or aldehyde source is added in an amount sufficient to achieve an ORP of greater than −300 mV.
4. The method of claim 3 , wherein the aldehyde or aldehyde source is added in an amount sufficient to achieve an ORP of greater than −250 mV.
5. The method of claim 1 , wherein the aldehyde or aldehyde source is selected from the group consisting of dimethyloldimethylhydantoin, glutaraldehyde, triazines, hexamethylenetetramine, formaldehyde, 4,4-dimethyloxazolidine, tetrahydro-3,5-di-methyl-2H-1,3,5-thiadiazine-2-thione, glyoxal, bis(tetrakishydroxymethylphosphonium) sulfate, acetals, and mixtures of the aforementioned.
6. The method of claim 1 , wherein the source of active halogen is selected from the group consisting of elemental chlorine, elemental bromine, bromine chlorides, alkali metal hypohalites, alkaline earth metal hypohalites, alkali or alkaline earth metal hypochlorites combined with bromides, monohalogenated hydantoins, dihalogenated hydantoins, halogenated cyanurates, halogenated cyanuric acids, and mixtures of the aforementioned.
7. The method of claim 6 , wherein the source of active halogen is selected from the group consisting of bromochlorohydantoins, dibromohydantoins, dichlorohydantoins, and mixtures of the aforementioned.
8. The method of claim 6 , wherein the source of active halogen is selected from the group consisting of sodium hypochlorite and sodium hypochlorite/sodium bromide.
9. The method of claim 1 , wherein the source of active halogen is combined with a solution or composition comprising at least one halogen stabilizing compound.
10. The method of claim 9 , wherein the at least one halogen stabilizing compound is an N-hydrogen compound selected from the group consisting of p-toluenesulfonamide, 5,5-dialkylhydantoins, methanesulfonamide, barbituric acid, 5-methyluracil, imidazoline, pyrrolidone, morpholine, acetanilide, acetamide, N-ethylacetamide, phthalimide, benzamide, succinimide, N-methylolurea, N-methylurea, acetylurea, methyl allophanate, methyl carbamate, phthalohydrazide, pyrrole, indole, formamide, N-methylformamide, dicyanodiamide, ethyl carbamate, 1,3-dimethylbiuret, methylphenylbiuret, 4,4-dimethyl-2-oxazolidinone, 6-methyluracil, 2-imidazolidinone, ethyleneurea, 2-pyrimidone, azetidin-2-one, 2-pyrrolidone, caprolactam, phenylsulfinimide, phenylsulfinimidylamide, diarylsulfinimides, dialkylsulfinimides, isothiazoline-1,1-dioxide, hydantoin, glycine, piperidine, piperazine, ethanolamine, glycinamide, creatine, glycoluril, ammonia, ammonium salts, and urea.
11. The method of claim 10 , wherein the at least one halogen stabilizing compound is an ammonium salt selected from the group consisting of ammonium halides, ammonium sulfate, ammonium hydrogensulfate, ammonium bicarbonate, ammonium carbonate, ammonium carbamate, ammonium alkanesulfonates, ammonium alkylsulfates, and ammonium carboxylates, and mixtures of the aforementioned.
12. The method of claim 1 , wherein the molar ratio of borohydride to aldehyde or aldehyde source is from 2:1 to 1:20.
13. The method of claim 12 , wherein the molar ratio of borohydride to aldehyde or aldehyde source is from 1:1 to 1:15.
14. The method of claim 13 , wherein the molar ratio of borohydride to aldehyde or aldehyde source is from 1:2 to 1:10.
15. The method of claim 10 , wherein the molar ratio of active halogen to additional N-hydrogen compound is in the range of 20:1 to 0.1:1.
16. The method of claim 15 , wherein molar ratio of active halogen to additional N-hydrogen compound is in the range of 10:1 to 0.2:1.
17. The method of claim 16 , wherein molar ratio of active halogen to additional N-hydrogen compound is in the range of 5:1 to 2:1.
18. The method of claim 10 , wherein the solution or composition comprising at least one halogen stabilizing compound is an aqueous solution having a pH in the range of 3 to 11.
19. The method of claim 18 , wherein the solution or composition comprising at least one halogen stabilizing compound is an aqueous solution having a pH in the range of 5 to 10.
20. The method of claim 19 , wherein the solution or composition comprising at least one halogen stabilizing compound is an aqueous solution having a pH in the range of 7 to 9.5.
21. The method of claim 10 , wherein the source of active halogen is in an aqueous solution and is admixed with the composition comprising the at least one halogen stabilizing compound.
22. The method of claim 10 , wherein the source of active halogen is in an aqueous solution and is admixed with an aqueous solution comprising the composition comprising the at least one halogen stabilizing compound.
23. The method of claim 10 , wherein the concentration of active halogen (as Cl 2 ) stabilized by the at least one halogen stabilizing compound is 0.1 to 20 ppm in the aqueous system.
24. The method of claim 1 , wherein the aqueous system is selected from the group consisting of pulp and papermaking slurries and liquors, recycle pulp slurries, pulp thick stock, deinking pulp slurries, pulp bleaching slurries and liquids, biomass bleaching slurries and liquids, textile bleaching liquids and clay slurries.