ES2595491T3 - A synergistic biocide and process to control the growth of microorganisms - Google Patents

Abstract

A method of controlling the growth of microorganisms in an aqueous system, comprising adding an effective amount of a combination of monohaloamine and dihaloamine in an aqueous system, where the ratio of monohaloamine to dihaloamine is selected as a result of a synergistic index of the system lower than 1, and where the aqueous system is a water system of a pulp and paper mill.

Description

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DESCRIPTION

A synergistic biocide and process to control the growth of microorganisms Technical field

The present invention relates to a method for controlling the growth of microorganisms in aqueous systems, more particularly in industrial process waters with the use of synergistic mixtures (or combinations) of haloamines.

Background of the invention

The uncontrolled growth of microorganisms in industrial production systems can have serious consequences, such as reduced product quality, product degradation or deterioration, product contamination, and interference with a wide range of important industrial processes. The growth of microorganisms on surfaces exposed to water (for example, recycling systems, heat exchangers, open circuit heating and cooling systems, pulp and papermaking process systems, etc.) can be especially problematic, since many of these systems provide a suitable environment for the growth of bacteria and other types of microorganisms. Industrial process waters often provide temperature conditions, nutrients, pH, etc., which allow the abundant growth of microorganisms. The uncontrolled growth of microorganisms is often manifested in the water column with large amounts of (planktonic) cells that float freely, as well as in submerged surfaces in which conditions favor the formation of biofilms.

The process that leads to the formation of biofilms is described in detail as indicated below. The first stage of biofilm formation is the contact of the planktonic cells with submerged surfaces either as a result of the turbulence in the water flow or by the active movement towards the surface. If the physical and chemical characteristics of the surface, including the surface-water interface, are favorable for growth, the microorganisms can adhere to the surface, grow and begin to produce exopolysaccharides that provide three-dimensional integrity to the biofilm. Over time, the biofilm becomes thicker and internally complex when cells reproduce and produce more exopolysaccharides. The microbial community of a biofilm can consist of single or multiple species.

Apparently biofilms are ubiquitous in all natural, medical and industrial fields where bacteria exist. Microorganisms can form biofilms on a wide variety of hydrophobic and abiotic hydrophilic surfaces, including glass, metals and plastics.

Numerous types of processes, systems and products can be adversely affected by the uncontrolled growth of microorganisms in biofilms and in industrial process waters. Such problems include accelerated corrosion of metals, accelerated decomposition of wood and other biodegradable materials, restricted flow through pipes, obstruction or fouling of valves and flow rates, and reduced efficiency of thermal exchange or cooling on thermal exchange surfaces. Biofilms can also be problematic in terms of cleaning and sterilization in medical equipment, breweries, wineries, dairy plants and other industrial process water systems for the manufacture of food and beverages. Moreover, sulfate reducing bacteria are often problematic in waters used for secondary oil recovery or for oil exploration in general. Although sulfate reducing bacteria can form biofilms in equipment and in tubenas, the significant problem caused by these bacteria is that they generate metabolic by-products that have very unpleasant odors, are toxic and can cause corrosion of metallic surfaces by accelerated galvanic action. For example, these microorganisms reduce the sulfates present in the injection water by generating hydrogen sulfide, a highly toxic gas that has a very unpleasant smell (i.e. rotten egg smell), is corrosive and reacts with metal surfaces to form products of insoluble iron sulfide corrosion.

Paper production is particularly susceptible to the adverse effects of biofilms. The waters of papermaking processes have conditions (for example, temperature and nutrients) that favor the growth of microorganisms in water and on exposed surfaces. The biofilms on the surfaces of papermaking process systems can be very thick and contain paper fiber and other materials used in paper production; said resulting material is referred to as silt or silt deposits. Slime deposits can be detached from the surfaces of the system and incorporated into the paper, which causes an increase in breaks and tears in the sheet. In addition, the slime can cause antishetical stains or holes in the final product, causing a lower quality product or rejection of the product. This requires stopping paper production to clean the equipment, resulting in the loss of production time.

In order to control the problems caused by microorganisms in industrial process waters, numerous antimicrobial agents (i.e. biocides) have been used to eliminate, inhibit or reduce microbial growth. Biocides are used alone or in combination to prevent or control problems caused by the

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microorganism growth Biocides are often added directly to a process water stream or to a material used in the process. When used to prevent the formation of biofilms, the typical method of addition is such that the biocide is distributed throughout the entire process system. In this way, planktonic and existing microorganisms in biofilms can be controlled on surfaces in contact with the process water.

Numerous organic and inorganic substances are used as biocides in industrial process systems. The type of biocide used in a given system will depend on many factors, including, but not limited to, the nature of the medium to which the biocide is added, the problematic microorganism (s), as well as the specific requirements of the industry, including safety and regulatory considerations. Not all biocides are interchangeable. A biocide that works well in one environment may not work in another environment. For example, biofilm-forming organisms are difficult to control because many biocides cannot penetrate the envelope formed around the organism.

Depending on their chemical composition and mode of action, biocides are classified as oxidizing or non-oxidizing. Oxidizing and non-oxidizing biocides can be used alone or in combination depending on the application. Oxidizing biocides have been widely used in industry for decades, especially in pulp and paper production, in which strong oxidants have been used to control microbial populations. Oxidizing biocides, such as chlorine gas, sodium hypochlorite, hypobromous acid, and chlorine dioxide are widely used as biocides to treat recycled water in many types of industries. Two of the main reasons for using these and other oxidizing biocides are that these oxidants are: (1) economical; and (2) non-specific with respect to what types of microorganisms are inhibited; if sufficient concentrations of oxidizing biocides are reached, practically all microorganisms can be inhibited.

Of the oxidizing biocides, chlorine is the most widely used in the treatment of recycled water systems. The chemistry of chlorine is well known. Other halogens, such as bromine, fluorine and iodine are known to possess antimicrobial activity. When added to water, chloride can exist in one of these two forms, HOCl and OCl-, depending on the pH. Bromine reacts with water similar to chlorine. These chemical species of chlorine, also referred to as "free chlorine," react with a wide variety of compounds in aqueous systems.

HOCl (hypochlorous acid) is much more effective as a disinfectant than OCl- (hypochlorite). When HOCl contacts a microorganism, the oxidant can quickly interact with any of a series of cellular constituents that result in growth inhibition. It has been reported that a very short contact time (i.e., <0.1 s) is required to inhibit a cell. Chlorine in contact with a microorganism can quickly cause a Fenton-like reaction in which hydroxyl radicals are generated and those radicals are responsible for inhibitory effects.

The highly reactive nature of chlorine can also be a drag, since some of the oxidizers will be used (for example, consumed) during reactions with the non-biological material. Therefore, in order to provide sufficient oxidant to react with microorganisms in a process stream, the total amount of oxidant necessary to inhibit microorganisms will include that used in reactions with non-biological components of the system. The reactions with non-biological components of the process water not only increase the cost of the treatment, but can also generate unwanted by-products and negatively affect other additives present in the process stream.

Process currents, such as in paper mills, are especially problematic for highly reactive oxidants due to high concentrations of dissolved and particulate inorganic and organic materials. The waters of these processes exhibit a very high "demand" for oxidant. "Demand" is defined as the amount of chlorine that reacts with substances other than the target microorganisms in the process water. In order to maintain an effective concentration of chlorine in an aqueous system to inhibit microorganisms, an amount greater than demand has to be applied. The types and quantities of inorganic and organic materials in a process stream will define the demand for an oxidant. For example, many substances that react with chlorine and cause the chlorine to be non-biocidal are known; such substances include sulfides, cyanides, metal ions, lignin and, among others, various water treatment chemicals (for example, some scale-forming and corrosion inhibitors).

Although effective as biocides, strong oxidants, such as sodium hypochlorite, can cause many problems in an industrial process stream, such as increased corrosion rate, increased consumption of wet end additives, and, among others. , decrease in the duration of the felt used in paper machines.

Due to the intrinsic reactivity of chlorine and strong oxidants related to non-biological organic and inorganic materials, it is desirable that the oxidant has a form with antimicrobial activity, but is less reactive with non-biological materials. The chloramination process has been used to avoid some of the problems associated with the use of strong oxidants. Chloramination can occur in various ways (1)

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adding chlorine to an aqueous system that contains a known low concentration of ammonia, or (2) adding ammonia to a water system that contains a known low concentration of chlorine. In any situation, the chlorine and the amomac react in situ forming a chloramine. Chloramines generated by chlorine and amomac reaction include monochloramine (NH2Cl), dichloramine (NHCh), and trichloramine (NCh). Two of the important parameters that determine which chloramine species will exist in a system are the pH and the ratio of Cl to N.

Typically, chlorine, in gaseous or liquid form, and ammonia combine to form chloramines. Other halogens, such as bromine, can be substituted with chlorine. Other substances that contain an amine group (RNH2) can also form haloamines, such as chloramines. The antimicrobial activity of a chloramine depends on the chemical nature of the amine-containing compound. For example, ammonium hydroxide can react with a halogen donor oxidant, such as sodium hypochlorite, to form monochloramine; This chloramine will be an effective biocide. However, if an amino acid, such as glycine (NH2CH2COOH), reacts with sodium hypochlorite, the amine group will be chlorinated to form mono- or di-chloramine species. Chlorinated glycine has a lower antimicrobial activity compared to monochloramine generated from ammonium hydroxide.

Chloramines are attractive for water treatment due to their in situ stability, ease of application, control, low investment and operational cost. Although laboratory studies have shown that free chlorine is more effective than chloramines in the inactivation of microorganisms, studies have also documented that chloramine's antimicrobial activity is higher at a lower pH as well as higher temperatures and concentrations.

Methods for the production of chloramines in highly concentrated form, including anhydrous chloramine, have been patented (US Pat. Nos. 2,678,258; 2,837,409; 3,038,785; 2,710,248; and 3,488,164).

Monochloramine is the preferred chemical species to disinfect a water supply. Dichloramine is described as being a superior disinfectant but has negative properties, such as high volatility and odor. The difference in reactivity and specificity of chlorine and monochloramine allows the latter to penetrate a biofilm and react with the inhabitants while the former is consumed in non-specific reactions with materials in the water or with abiotic components of the biofilm before fully penetrating The biofilm.

Monochloramine is used as a unique asset for water treatment to control the growth of microorganisms in water and wastewater systems. Studies have shown that the pH of an aqueous system affects the efficacy of monochloramine; Efficiency increases as the pH decreases. Other physical and chemical parameters of a system can affect the effectiveness of chloramines by influencing the stability of the compounds. For example, it has been shown that parameters such as pH, temperature and presence of other chemicals influence the stability of monochloramine in water, monochloramine has a significantly greater stability at 4 ° C than at 35 ° C.

WO 2004/007378 A2 discloses a method and apparatus for implementing the reduction of pathogens in a poultry processing or food processing plant that uses water that has been treated with chloramines in an advantageous dosage before being introduced into the production process in the processing stages. Water treated with chloramines can come from a source of fresh water or reclaimed water from the processing plant. The reintroduction of the treated regenerated water advantageously causes a dramatic reduction in the levels of microorganisms associated with poultry processing, while substantially conserving water consumption.

Wared et al. (NR Ward, RL Wolfe and BH Olson, Appl. Environ. Microbiol. 1984, vol. 48, No. 3, 508-514) disclose the influence of pH, application technique, and the weight ratio of chlorine to nitrogen in the bactericidal activity of the inorganic chloramine compounds, which were determined with stem and environmental strains of Escherichia coli, Salmonella spp., Pseudomonas aeruginosa, Klebsiella pneumoniae, and Enterobacter cloacae. The inactivation rate increased from 1.5 to 2 times when the weight ratio of chlorine to nitrogen was adjusted from 2: 1 to 5: 1, 5 to 6 times as the pH decreased from 8 to 6, and 5 to 6 times as the concentration increased from 1 to 5 mg / liter. Additions other than free chlorine and ammonia (simultaneous addition and pre-ammonia) in water impregnated at a pH equal to or less than 7.5 resulted in destruction comparable to that observed with free chlorine (99% inactivation in less than 20 s). At pH 8, inactivation by different additions was considerably slower and was comparable to that of previously reacted chloramine compounds (99% inactivation in 25 to 26 min). The determination of the effectiveness of inorganic chloramine compounds as primary disinfectants for drinking water must take into account the method of application, the pH and the concentrations of chlorine and ammonia.

Although widely practiced for the treatment of municipal water distribution systems, chloramines are not commonly used in industrial systems. In papermaking systems, chlorine (in bleach or chlorine gas) was used in combination with amomac. In later years, in papermaking systems, there has been a tendency towards the use of other oxidizing and non-oxidizing biocides. However, recently it seems that interest in the use of chloramines in papermaking systems has been revived (see, U.S. Patent Nos. 6,478,973; 6,132,628; 5,976,386).

For example, it has been shown that ammonium bromide activated with sodium hypochlorite produces a biocide

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effective for industrial applications. In addition, this biocide is especially effective for the control of problems associated with microbial growth in process waters in the production of pulp and paper that have a pH in the alkaline range. The biocide generated from ammonium bromide, described as a "bromide activated chloramine" effectively reduces the total microbial community in a system (that is, associated with a biofilm, as well as planktonic bacteria) in which the pH ranges from neutral to alkaline. The preferred pH of the receiving water must be in the range of 7 to 9; The biocide is effective in waters of the alkaline papermaking process but does not interfere with other pulp and papermaking processes and with functional additives (for example, dry and wet strength additives, sizing agents, dyes, etc. ), unlike other common oxidants.

Improved biocides that are effective in harsh environmental conditions, such as those in the paper industry and other industrial processes, are still necessary.

Summary of the invention

The present invention relates to methods for preventing the growth of microorganisms in industrial process waters through the use of certain mixtures (or combinations) of haloamines.

More specifically, the present invention is directed to the use of synergistic mixtures (or combinations) containing monohaloamine and dihaloamine, examples of these are monochloramine and dichloramine. In the invention, microbial populations of aqueous industrial process waters are controlled by administration to aqueous systems of effective amounts of monohaloamine and dihaloamine, the result is synergistic.

The processes (methods) that incorporate the composition of the present invention show unexpected synergistic activity against microorganisms.

Brief description of the figures

Figure 1 Effect of pH on the synergy between monochloramine and dichloramine.

Figure 2 Synergy of monochloramine and dichloramine.

Figure 3 Synergy of monochloramine and bromamine at pH 8.

Figure 4 Synergy of monochloramine and bromamine at pH 7.

Figure 5 Synergy of monochloramine and bromamine at pH 8.

Detailed description of the invention

For the purposes of this invention, haloamines are defined as chemical products with a composition that includes one or more halogen atoms associated with an amine group and which possess antimicrobial activity. Nitrogen may or may not bind to another atom other than hydrogen. Halogen atoms include chlorine, fluorine, bromine, and iodine. Chlorine is the most preferred halogen used in the present invention.

The present invention is directed to a method for controlling the growth of microorganisms in aqueous systems, which comprises adding in an aqueous system an effective amount of a combination of a monohaloamine and dihaloamine, such as monochloramine and dichloramine. These innovative synergistic biocide mixtures (or combinations) when used in combination in an aqueous system are effective in inhibiting or controlling the growth of microorganisms in the aqueous system. The present invention is directed to a method for inhibiting or controlling the growth of microorganisms by administering or adding an effective amount of monohaloamine and an effective amount of dihaloamine, producing a synergy index less than 1 defined herein, and where the aqueous system is an aqueous system for the pulp and paper factory. Preferred haloamines are chloramines and bromamine.

Monohaloamine, when used with dihaloamine in aqueous systems, unexpectedly provided improved biocidal activity, which is greater than that of the individual components. The microbicidal mixtures (or combinations) of the present invention possess a high degree of antimicrobial activity that could not have been predicted from the known activities of the individual ingredients comprising the combinations. The improved activity of the mixtures (or combinations) allows a significant reduction of the total amount of biocide required for an effective treatment of an aqueous system.

The aqueous systems to be treated have pH values between 4 and 10, preferably between 5 and 9.

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Monohaloamine, when used with dihaloamine in aqueous systems, unexpectedly provided improved biocidal activity, which is greater than that of the individual components. Examples of monohaloamines and dihaloamines include chloramines, bromamines, and iodamines. The microbicidal mixtures (or combinations) of the present invention possess a high degree of antimicrobial activity that could not have been predicted from the known activities of the individual ingredients comprising the combinations. The improved activity of the mixtures (or combinations) allows a significant reduction in the total amount of biocide required for an effective treatment of an aqueous system.

Due to the intrinsic reactivity of halogens, for example chlorine, and strong oxidants related to non-biological organic and inorganic materials, it is desirable that the oxidant has a form with antimicrobial activity, but is less reactive with non-biological materials. The chloramination process has been used to avoid some of the problems associated with the use of strong oxidants. The chloramination process can generate chloramines including monochloramine (NH2Cl), dichloramine (NHCh), and trichloramine (NCh). Two of the important parameters that determine which chloramine species will exist in a system are the pH and the ratio of Cl to N. As the pH of the aqueous system decreases, the monohaloamine species will become a dihaloamine species. As the amount of chlorine in the system increases with respect to the amount of the available amine source, the balance drives the monohaloamine species to a dihaloamine species.

Typically, chlorine, in gaseous or liquid form, and ammonia combine to form chloramines. However, other substances that contain an amine group can also form chloramines or haloamines. The antimicrobial activity of a haloamine, such as chloramine, depends on the chemical nature of the amine-containing compound. For example, ammonium hydroxide can react with a halogen donor oxidant, such as sodium hypochlorite, to form monochloramine; This chloramine will be an effective biocide. However, if an amino acid, such as glycine (NH2CH2COOH), reacts with sodium hypochlorite, the amine group will be chlorinated to form mono- or di-chloramine species. Chlorinated glycine has a lower antimicrobial activity compared to monochloramine generated from ammonium hydroxide.

The present invention relates to a method, which uses synergistic mixtures (or combinations) containing monohaloamine and dihaloamine. Haloamines, both monohaloamine and dihaloamine, can be produced by combining an amine source or ammonium source with a halogenated oxidant. An amine source or ammonium source can be combined with a non-halogenated oxidant to form a haloamine if the system also contains a halogen source. Examples of halogen sources include, among others, a halogen containing salt or acid. Examples of haloamines are chloramines (monochloramine or dichloramine) and bromamines (monobromamine and dibromamine). The haloamine mixture can be adjusted to obtain the desired monohaloamine to dihaloamine ratio by adjusting the pH and / or the halogen to nitrogen ratio. Once monochloramine has been converted to dichloramine, it is stable and cannot easily be converted again.

Dichloramine can be produced from a monochloramine solution. One method of producing dicloramine from monochloramine is to reduce the pH of the monochloramine solution. Another method of producing a dichloramine from a monochloramine solution is to adjust the ratio of chlorine to nitrogen in the solution, for example by adding additional chlorine to the monochloramine solution. Once monochloramine has been converted to dichloramine, it is stable and cannot easily be converted again. The pH and Cl to N ratios can be equilibrated to produce the desired combination of mono and dichloramines. Monobromamine is easily converted to dibromamine at a pH lower than 12. In most conditions, at a pH of 10 or less, bromoamine will exist as dibromamine.

For the purposes of this invention, any method that can be used to produce a haloamine is contemplated as a possible source of haloamine. The ratio of monohaloamine to dihaloamine can be adjusted by known methods to achieve the desired ratio that produces a synergistic biocidal effect.

In a variant of the invention, a source of amine or ammonium reacts with a halogen containing oxidant to produce monohaloamine. The pH of monohaloamine is then adjusted to achieve the desired ratio of mono to dihaloamines.

In another variant, a source of amine or ammonium reacts with a halogen containing oxidant to produce monohaloamine. The chlorine to nitrogen ratio of monohaloamine is then adjusted to achieve the desired ratio of mono to dihaloamines.

In a third variant, a source of amine or ammonium reacts with a halogen containing oxidant to produce monohaloamine. A portion of the monohaloamine is then separated and adjusted to produce dihaloamine. Dihaloamine and monohaloamine are used in a relationship in the system to be treated to achieve the desired ratio of mono to dihaloamines.

In a fourth variant, monohaloamine and dihaloamine are produced separately and are contacted with the aqueous system to be treated separately or in a common duct. The amounts of mono and dichloramines are selected to achieve the desired ratio of mono to dihaloamines to produce the synergistic effect.

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Amine sources or ammonium sources used in the present invention include, among others, amomac, ammonium salts and amines. What is meant by ammonium salts are those salts that have an NH / cation and a related anion. Examples of ammonium salts include, but are not limited to, ammonium acetate, ammonium bicarbonate, ammonium bifluoride, ammonium bromide, ammonium carbonate, ammonium chloride, ammonium citrate, ammonium fluoride, ammonium hydroxide, ammonium iodide, ammonium molybdate, ammonium nitrate, ammonium oxalate, ammonium persulfate, ammonium phosphate, ammonium sulfate, ammonium sulphide, ferric ammonium sulfate, ferrous ammonium sulfate and ammonium sulfamate. Preferred ammonium salts are ammonium carbonate, ammonium citrate, ammonium hydroxide, ammonium sulfate and ammonium chloride. Quaternary ammonium salts are not considered amine sources in the present invention and ammonium salts are not included in the term for the purposes of this invention.

The useful amines sources in the present invention can also be primary amines (RNH2), secondary amines (R2NH) or tertiary amines (R3N). Sources of ammonium and / or amine further include amomaco, dimethylamine, ethanolamine, ethylenediamine, diethanolamine, triethanolamine, dodeciletanolamina, hexdeciletanolamina, oleic acid ethanolamine, triethylenetetramine, dibutylamine, tributylamine, glutamine, dilaurylamine, distearylamine, tallow-methylamine, coco-methylamine, n-alkylamines, n-acetylglucosamine, diphenylamine, ethanol methylamine, diisopropanolamine, n-methylaniline, n-hexyl-n-methylamine, n-heptyl-n-methylamine, n-octyl-n-methylamine, n-nonyl-n-methylamine, n-decyl-n-methylamine, n-dodecyl-n-methylamine, n-tridecyl-n-methylamine, n-tetra-decyl-n-methylamine, n-benzyl-n-methylamine, n-phenylethyl-n-methylamine, n-phenylpropyl-n-methylamine, n-alkyl-n-ethylamines, n-alkyl-n-hydroxyethylamines, n-alkyl-n-propylamines, n-propylheptyl-n-methylamine, n-ethylhexyl-n-methylamine, n- ethylhexyl-n-butylamine, n-phenylethyl-n-methylamine, n-alkyl-n-hydroxypropylamines, n-alkyl-n-isopropylamines, n-alkyl-n-butylamines and n-alkyl-n-isobutylamines, n -alkyl-n-hydroxyalkylamines, hydrazine, urea, guanidines, biguanidines, polyamines, primary amines, secondary amines, cyclic amines, bidcyclic amines, oligodyl amines, aliphatic amines, aromatic amines, polymers containing primary and secondary nitrogen. Quaternary amines are not included in the amine source useful in this invention. Quaternary amines are saturated and not reactive with oxidants. They do not react sufficiently to produce the biocide of the present invention.

The oxidants react with the amine source producing useful biocides in the present invention. The oxidants used in the present invention include, among others, chlorine, hypochlorite, hypochlorous acid, chlorine dioxide, chlorinated isocyanurates, bromine, hypobromite, hypobromous acid, bromine chloride, electrolytically generated chlorites, electrolytically generated bromites, halogenated hydatoms, ozone, and peroxy compounds, such as perborate, percarbonate, persulfate, hydrogen peroxide, percarboxylic acid, and peracetic acid.

In a particular advantageous embodiment of the invention, the source of ammonium and / or amine is ammonium hydroxide and the oxidant is sodium hypochlorite.

In another particular advantageous embodiment of the invention, the source of ammonium and / or amine is ammonium sulfate and the oxidant is sodium hypochlorite.

The methods of this invention are effective for controlling and inhibiting the growth and reproduction of microorganisms in aqueous systems and aqueous systems of additives. Aqueous systems include industrial water systems, such as cooling water systems, pulp and paper processing systems, oil operations, lubricants and industrial refrigerants, lagoons, lakes and ponds. Aqueous systems include aqueous additive systems. In addition, the aqueous systems in which the present invention can be used include, among others, in particular, paints, leather, wood, wood pulp, wood chips, starch, clays, retention favors, sizing agents, defoamers , dry and wet strength additives, pigment suspensions (for example, precipitated calcium carbonate), protein materials, wood, animal skins, vegetable fork liquors, cosmetics, formulations for personal hygiene items, emulsions, adhesives, coatings , metallurgical fluids, pool water, textiles, heat exchangers, pharmaceutical formulations, geological drilling lubricants, and agrochemical compositions.

An aqueous additive system is an aqueous system that is added or added to a larger aqueous system. Such aqueous additive systems in the pulp and paper industry include, among others, retention favors, sizing agents, antifoams, dry and wet strength additives and pigment suspensions.

The dosed amounts of monohaloamine and dihaloamine required for efficacy in this invention generally depend on the nature of the aqueous system being treated, the level of organisms present in the aqueous system, and the level of inhibition desired. A person skilled in the art, using the information disclosed herein, can determine the amount needed without undue experimentation.

Effective concentrations of monohaloamine, such as monochloramine, on an active level basis, range from about 0.01 milligrams per liter (mg / l) to about 1,000 mg / l by weight, (i.e., based on the weight of monohaloamine measured by the amount of available chlorine [in mg / l]), preferably from about 0.05 to about 200 mg / l, more preferably from about 0.1 mg / about 100 mg / l, more preferably from about 0.1 mg / l about 10 mg / l and even more preferably about 0.1 mg / l about 5 mg / l. The amount of dihaloamine,

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on an active level basis, it is from about 0.01 parts per million (mg / l) to about 1,000 mg / l by weight (i.e., based on the weight of dihaloamine measured by the amount of available chlorine [in mg / l]), and preferably from about 0.05 to about 200 mg / l, more preferably from about 0.1 mg / about 100 mg / l, more preferably from about 0.1 mg / about 10 mg / l and even more preferably about 0.1 mg / l about 5 mg / l. Therefore, with respect to biocides, the lower and upper limits of the required concentrations depend substantially on the system to be treated.

The ratio of monohaloamine to dihaloamine is from about 400: 1 to about 1: 100, preferably from about 200: 1 to about 1: 100, preferably from about 20: 1 to about 1: 5.

In one embodiment of the invention, monohaloamine is added to the aqueous system before dihaloamine. In another embodiment of the invention, dihaloamine is added before monohaloamine. In another embodiment of the invention, monohaloamine and dihaloamine are added simultaneously to the system to be treated.

In another embodiment, after the addition of monohaloamine, dihaloamine is added to the aqueous system. The time lag between the addition of monohaloamine and dihaloamine can be, among others, up to 30 minutes, or up to 15 minutes, or up to 5 minutes, or up to 1 minute.

In another embodiment, after the addition of dihaloamine, monohaloamine is added to the aqueous system. The time lag between the addition of dihaloamine and monohaloamine can be, among others, up to 30 minutes, or up to 15 minutes, or up to 5 minutes, or up to 1 minute.

In another embodiment, monohaloamine and dihaloamine are added to the aqueous system simultaneously.

In another embodiment, the combination of mixed haloamine can be produced in situ by the addition of a source of ammonium or amine and halogenated oxidant to the process water to cause the formation of monochloramine, after which a measurable amount of acid is added to the water. to lower the pH to a sufficient point to cause the formation of dichloramine.

In any embodiment, monohaloamine may be added in accordance with any known method that provides the desired concentration of monohaloamine in the aqueous system. Similar to monohaloamine, in any embodiment, dihaloamine can be added in accordance with any known method that provides the desired concentration of dihaloamine in the aqueous system. Either monohaloamine and dihaloamine can be supplied continuously, intermittently, or alternatively, to aqueous systems.

Haloamines may be added to the system as independent material (s) or in combination with other materials that are added to the aqueous system being treated. For example, a synergistic combination of monohaloamine and dihaloamine can be added with starch, clay, pigment suspensions, precipitated calcium carbonate, retention favors, sizing agents, dry and / or wet strength additives, defoamers or other additives used in the manufacture of pulp or paper products.

Haloamines can be added continuously, intermittently, or alternatively, to aqueous systems and / or additives. The above supply strategies for biocidal addition depend on the growth of the microbial population, the type of problematic microorganisms and the degree of surface fouling in a particular system. A combination of monohaloamine and dihaloamine can be used in the treatment of additive systems, (i.e. starch solutions, retention-enhancing solutions, precipitated calcium carbonate suspensions, etc.) or other supply points in the aqueous system (it is ie, short or long circuit, recycled pulp tank, fiber collectors, dense paste, combination tub, input box).

Examples

The efficacy of the active materials and combinations were determined using a dose protocol. The assets were evaluated in synthetic white water (see, Smith et al., U.S. Patent No. 6,361,963) with pH values of 5.5 and 8.0. The materials were tested against multiple species of the bacterial consortium (also referred to as artificial consortium) containing approximately equal numbers of six bacterial strains. Although the test strains are representative of organisms present in paper mill systems, the effect is not limited to these bacteria. Two of the strains were Klebsiella pneumonia (CACT 13883) and Pseudomonas aeruginosa (CACT 15442). The other four strains were isolated from paper mill systems and identified as Curtobacterium flaccumfaciens, Burkholderia cepacia, Bacillus maroccanus and Pseudomonas glathei. Each strain was grown on soybean tripticase agar overnight at 37 ° C. Sterile cotton swabs were used to aseptically transfer cells to a sterile saline solution. Each cell suspension was prepared in a desired concentration, measured by turbidity, before combining identical volumes of each of the strains to prepare the consortium. The bacterial consortium was distributed in the wells of a microtiter plate before adding monohaloamine and / or dihaloamine. The microtiter plates were incubated at 37 ° C. The

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Optical density (OD) readings at 650 nm were taken initially (to) and after 4 hours (T4) of incubation.

The raw data is converted to "bacterial growth inhibition percentages" according to the following formula:

% inhibition = [(a-b) a] * 100

in which:

a = (OD of control in tn) - (OD of control in to) b = (OD of treaty in tn) - (OD of treaty in to)

Inhibition values can be represented against the dosage for each asset and the particular combination. This results in a dose response curve from which the dose can be calculated to produce a 50% inhibition (I50). In the examples (tables) below, the I50 values are expressed as mg / l of active material.

The synergy index (SI) was calculated using the following equation and is based on the amount needed to cause a 50% inhibition of bacterial growth.

Synergy Index (IS) = (CA 4- Ca) + (CB 4- Cb)

in which:

CA = amount of compound A in mixture, which produces the evaluation criteria

Ca = amount of compound A, acting alone, that produces the evaluation criteria

CB = amount of compound B in mixture, which produces the evaluation criteria

Cb = amount of compound B, acting alone, that produces the evaluation criteria

If IS is less than 1, there is synergy; if IS is greater than 1, there is antagonism; If IS is equal to 1, there is an additive effect.

The antibacterial efficacy of monochloramine and dichloramine, alone and in combination, was compared in a conventional exposure test. To carry out the test, artificial bacterial consortia were prepared using the same species as those in microtiter assays. A solution of mineral salt was prepared by combining K2HPO4 (1.2 mg / l), KH2PO4 (0.624 mg / l), (NH4) 2SO4 (0.05 g / l), and NaCl (0.1 mg / l). This solution was sterilized by autoclave treatment (121 ° C, 15 min) and, after cooling, was modified with the following: 10 ml / l of sterile solution by filtration of 0.5% (w / v) CaChO ^ OR; 10 ml / l of sterile solution by filtration of MgSO4-7H2O at 2%; sterilized glucose by filtration, (0.01 g / l, final concentration); 1 ml of a sterilized solution by filtration containing Na2EDTA (ethylenediaminetetraacetate) (1.58 g / 100 ml), ZnSO4-7H2O (0.7 g / 100 ml); MnSO4-H2O (0.18 g / 100 ml); FeSO4 7H2O (0.16 g / 100 ml); CoChO-6H2O (0.052 g / 100 ml); NaMoO4-2H2O (0.042 g / 100 ml); and CuSO4.5H2O (0.047 g / 100 ml). Identical volumes of cell suspensions of each of the strains were then combined to prepare the consortium. The bacterial consortium was distributed in sterile glass containers and was immediately used in exposure studies. To determine the effect of the pH of the mineral salt solution on the efficacy of monochloramine, dichloramine, and combinations thereof, the pH of the cell suspension was adjusted to the desired levels using dilute solutions of sodium hydroxide or phosphoric acid, as appropriate. The pH values tested in the exposure studies were 5.0, 6.0, 7.0 and 8.0. The pH values represent the typical white water pH of the mayone of the paper mills.

The presence of the active chemical species was demonstrated with a scanning spectrophotometer measuring the absorbance of light in the range of 200 nm to 350 nm. To determine the absorbance spectrum, an amount of monochloramine and / or dichloramine in solution was added to a quartz cuvette and scanned in the spectrophotometer. The spectral profile resulting from the solution demonstrated the presence of one or both active chemical species and is consistent with the published spectra of monochloramine and dichloramine.

The height of the absorbance peak at 244 nm was linearly related to the concentration of monochloramine in the solution. Likewise, the absorbance peak at 295 nm was linearly related to the concentration of dichloramine in solution. Peak height control allowed the concentrations of monochloramine and dichloramine to be verified in the test solutions. UV absorption for NHBr2 is known to be at 350 nm, NH2Br is at 278 nm, OCl- is at 292 nm and OBr- is at 329 nm.

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After preparing the monohaloamine solution, the amount necessary to reach a desired final concentration was transferred to the previously prepared bacterial consortium. Samples of the bacterial consortium were collected immediately before adding monochloramine and after contact times, usually 1, 10, and 20 minutes. The controls were untreated cell suspensions.

The use of the term "percentage" in reference to the concentration of chemical products is based on a weight per volume basis.

The concentrations of monochloramine and dichloramine described herein are expressed in units of milligrams per liter as Cl2. The units, milligrams per liter according to Cl2 (or mg / ml as Cl2 or mg / ml), were determined based on the total concentration of chlorine available in a sample according to the Hach DPD (Hach Company, Chlorine Assay). Loveland, Colorado). Total available chlorine refers to the amount of chlorine in a sample that reacts with N, N-diethyl-p-phenylenediamine oxalate, the indicator used in the Hach test. In order to determine the amount of monochloramine or dichloramine in a sample, an algae of the samples was transferred to a clean container, diluted with deionized water, as appropriate, and tested according to the Hach DPD chlorine test. The test measures the total amount of chlorine that can react with the indicator reagent. The reaction is measured by determining the light absorbance at 530 nm. Therefore, for the purposes of this invention, an amount of monochloramine or dichloramine presented in units of mg / l means the amount of monochloramine or dichloramine that contains the designated amount of milligrams of reactive chlorine per liter. Consequently, for example, a sample treated with 1 mg / l of monochloramine or dichloramine will contain a total available chlorine concentration of 1 mg / l. Similarly, a sample treated with 0.5 mg / l of monochloramine and 0.5 mg / l of dichloramine will contain a total available chlorine concentration of 1 mg / l.

The use of the term "ratio" in relation to the active molecules tested is based on the amount of each of the assets in one milligram per liter base. For example, a solution containing monochloramine to dichloramine in a 1: 1 ratio contains X mg / l (as Ch) of monochloramine and X mg / l (as Ch) of dichloramine, where X = a fraction or whole number. Similarly, a solution containing monochloramine to dichloramine in a 5: 1 ratio contains 5X mg / l (as Ch) of monochloramine and X mg / l (as Ch) of dichloramine, where X = a fraction or whole number.

Monochloramine can be generated using amine sources, such as ammonium bromide, ammonium sulfate, ammonium hydroxide, ammonium phosphate, ammonium chloride, etc. Ammonium hydroxide was used as the amine source to generate haloamine in the present examples.

To carry out an exposure study, the monochloramine was prepared at a desired concentration by mixing adequate amounts of 30% ammonium hydroxide and 6.2% sodium hypochlorite in a volume of deionized water in such a way to achieve equimolar ratios of Cl and NH2. After the preparation of the monochloramine solution, the purity of the solution was verified by determining its absorbance spectrum. To prepare a dichloramine solution, the pH of a monochloramine solution was reduced to 5.0. This guaranteed the conversion of monochloramine to dichloramine. The spectral characteristics of the dichloramine solutions showed that lowering the pH of a solution of monochloramine in deionized water resulted in the formation of dichloramine. The concentrations of monochloramine and dichloramine in the solutions were confirmed by measuring the total chlorine concentration by the Hach DPD chlorine assay.

Spectral analysis was used to verify the conversion of monochloramine to dichloramine when the pH was adjusted.

The following examples are intended to be illustrative of the present invention. However, these examples are not intended to limit in any way the scope of the invention or its protection. The examples illustrate the synergistic relationship obtained with the compositions of the present invention.

Example 1

A measured amount of monochloramine and a measured amount of dichloramine were added to a suspension of bacteria and the cell suspension was incubated for a selected period of time. The efficacy of the combination of the biocides was determined by measuring the growth or lack thereof after an additional time of appropriate incubation. This example illustrates the synergistic activity between monochloramine and dichloramine in a concurrent delivery strategy against an artificial bacterial consortium in synthetic white water at pH 5.5 and 8.0. A synergistic index value of <1.00 indicates a synergistic effect between the two assets.

_____Table 1. Synergistic indices of the combinations of monochloramine and dichloramine ._____

NH2Cl and NHCI2 at pH 5.5

 mg / l NHCI2

 mg / l NH2CI NHCI2 ratio: NH2CI% inhibition Synergistic index

 17.23

 0.00 - 50 1.00

 15.13

 0.73 20.8: 1.0 50 0.92 *

 14.03

 1.45 9.7: 1.0 50 0.89 *

 13.45

 2.91 4.6: 1.0 50 0.94 *

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 NH2CI and NHCI2 at pH 5.5

 mg / l NHCI2

 mg / l NH2CI NHCh ratio: NH2Cl% inhibition Synergistic index

 11.38

 3.75 3.0: 1.0 50 0.87 *

 8.87

 5.81 1.5: 1.0 50 0.83 *

 5.69

 9.00 1.0: 1.6 50 0.82 *

 3.34

 11.63 1.0: 3.5 50 0.83 *

 2.84

 12.29 1.0: 4.3 50 0.84 *

 1.42

 14.59 1.0: 10.3 50 0.88 *

 0.71

 15.60 1.0: 21.5 50 0.88 *

 0.36

 15.85 1.0: 44.6 50 0.89 *

 0.18

 15.28 1.0: 85.9 50 0.85 *

 0.09

 15.60 1.0: 175.6 50 0.86 *

 0.04

 15.82 1.0: 356.1 50 0.87 *

 0.00

 18.21 - 50 1.00

 NH2CI and NHCI2 at pH 8.0

 mg / l NHCI2

 mg / l NH2CI NHCh ratio: NH2Cl% inhibition Synergistic index

 0.59

 0.00 - 50 1.00

 0.57

 0.73 1.0: 1.3 50 1.05

 0.48

 1.45 1.0: 3.0 50 0.99 *

 0.36

 2.14 1.0: 6.0 50 0.87 *

 0.29

 2.91 1.0: 10.2 50 0.85 *

 0.18

 3.86 1.0: 21.7 50 0.78 *

 0.09

 5.22 1.0: 58.8 50 0.81 *

 0.07

 5.81 1.0: 88.8 50 0.84 *

 0.04

 6.88 1.0: 154.7 50 0.94 *

 0.00

 7.96 - 50 1.00 *

Table 1 shows a synergy between monochloramine and dichloramine. Synergy is affected by pH. For example, the synergistic ratio of monochloramine to dichloramine was much broader at pH 8 than at pH 5. At higher pH, monochloramine could be in a ratio less than 1: 1 or greater than 1: 1 and still be synergistic. At pH 5, the ratios greater than 1: 1 (monochloramine to dichloramine) were synergistic. The lower pH provides greater synergy.

Example 2

In this example, a measured amount of monochloramine and a measured amount of dichloramine were added to a consortium of bacteria prepared at a density of approximately 1 x 10 6 cells per milliliter and the cell suspension was incubated for a selected time. The bacteria consortium has been described above. The efficacy of the combination of the biocides was determined by measuring the number of bacteria that survived after the contact time. The efficacy of monochloramine, dichloramine, and combinations of the two active ingredients were compared at different pH values. Bacterial consortia were prepared in solutions of mineral salts with pH adjusted to selected values and exposed with monochloramine and dichloramine and combinations thereof. Samples to list the number of surviving bacteria were collected at selected time intervals.

Table 2. Number of surviving bacteria after a contact time of 20 minutes with monochloramine (MCA), dichloramine (DCA) and combinations thereof. The numbers are transformations in log-io and represent the

average of the three values

 PH

 0.5 mg / l MCA 1.0 mg / l MCA 0.5 mg / l DCA 1.0 mg / l DCA 0.5 mg / l MCA + 0.5 mg / l DCA

 5.0

 4.97 3.94 5.58 4.47 0.00

 6.0

 5.14 5.14 5.17 3.62 3.06

 7.0

 5.47 5.17 5.52 5.40 3.95

 8.0

 5.74 5.71 5.62 5.26 4.49

As is evident in Table 2, a combination of monochloramine and dichloramine in a 1: 1 ratio was more effective in destroying bacteria of the species defined in the consortium than any single asset. The table also indicates the effect of pH on the efficacy of monochloramine and dichloramine and the synergistic effect. The effect of pH on the synergy between monochloramine to dichloramine is evident by comparing efficacy (as indicated by the number of surviving bacteria after a contact time of 20 minutes) as a function of pH. That the synergy was evident at pH 5 to 8 is illustrative of the potential utility in using both assets at the same time.

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Example 3

Although synergy was detected when monochloramine and dichloramine were combined in a 1: 1 ratio, the results of Example 1 illustrate that the optimal ratios were greater than 1: 1 (monochloramine to dichloramine). In this example, the bacterial consortia were prepared with the pH of the mineral salt solution adjusted to selected levels immediately before adding the cells. The monochloramine was prepared in a desired concentration by mixing suitable amounts of 30% ammonium hydroxide and 6.2% sodium hypochlorite in a volume of deionized water in such a way to achieve equimolar ratios of Cl- and NH2 +. After the preparation of the monochloramine solution, the purity of the solution was verified by determining its absorbance spectrum. To prepare a dichloramine solution, the pH of a monochloramine solution was reduced to 3.0. This guaranteed the conversion of monochloramine to dichloramine. The spectral characteristics of the dichloramine solutions showed that lowering the pH of a solution of monochloramine in deionized water resulted in the formation of dichloramine. The concentrations of monochloramine and dichloramine in the solutions were confirmed by measuring the total chlorine concentration by the Hach DPD chlorine assay. Selected ratios of monochloramine and dichloramine were added and the number of bacteria that survive after a contact time of 20 minutes was determined. In this study, 0.5 mg / l of monochloramine and 0.5 mg / l of dichloramine were tested. In addition, the ratios of monochloramine to dichloramine were adjusted by varying the amount of each asset added to the cell suspension, maintaining the total amount of chloramine added at 0.5 mg / l. For example, by adding 0.4 mg / l of monochloramine and 0.1 mg / l of dichloramine, the total amount added was 0.5 mg / l (as Ch), but the ratio was changed to 4: 1 .

Figure 1 shows that the ratio of monochloramine to dichloramine affects synergy. As the ratio of monochloramine to dichloramine decreases, the synergistic effect is greater. The lower pH increases the synergistic effect.

Figure 1 shows the effect of pH on the synergy between monochloramine and dichloramine. The bacteria were exposed to the designated concentrations for 20 minutes before determining the number of survivors. MCA = monochloramine, DCA = dichloramine.

Example 4

In another dose exposure study using the dose protocol, the range of desired ratios of monochloramine to dichloramine, as well as individual assets is extended from 1: 1 to 10: 1 (monochloramine to dichloramine). After a contact time of 20 min, the number of surviving bacteria was determined. In this experiment, all systems were exposed to 0.5 mg / l (as Ch) of active. As illustrated in Figure 2, as the ratio of monochloramine to dichloramine increased from 1: 1 to 10: 1, so did the synergy, regardless of pH.

Figure 2 shows the effect of pH and the ratios of monochloramine to dichloramine selected in bacterial consortia. The bacteria were exposed to the designated combinations of monochloramine and dichloramine for 20 minutes before determining the number of survivors.

The results presented in Figure 2 are illustrative of the potential utility in employing the two assets together to treat recycling waters through a range of pH values.

Example 5

Monochloramine and bromamine were tested using the dose protocol and conventional exposure test. In this example, bromamine was prepared by reacting hypobromous acid (HOBr) with ammonium hydroxide forming monobromamine. Since monobromamine is rapidly converted to dibromamine in solution at a pH below 10, the bromamine used in the synergy test consisted mainly of dibromamine. In this example, a range of monochloramine to bromamine ratios was tested. The results demonstrated synergy with combinations of monochloramine to bromamine in the range of 15 parts of monochloramine: 1 part of bromamine to 1 part of monochloramine: 50 parts of bromamine. Relations with more than 15 parts of monochloramine to 1 part of bromamine are expected to show synergy.

Figure 3 shows the results of the synergy test between monochloramine and bromamine at pH 8.0.

Figure 4 shows the results of the synergy test between monochloramine and bromamine at pH 7.0.

Figure 5 shows the results of the synergy test between monochloramine and bromamine at pH 8.0.

Claims (21)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 60 65 1. A method for controlling the growth of microorganisms in an aqueous system, comprising adding an effective amount of a combination of monohaloamine and dihaloamine in an aqueous system, where the ratio of monohaloamine to dihaloamine is selected as a result of a synergistic system index. less than 1, and where the aqueous system is a water system of a pulp and paper factory. 2. The method of claim 1, wherein the monohaloamine is produced by contacting a source of ammonium or amine with a halogenated oxidant or alternatively in contact with the source of ammonium or amine with an oxidant in the presence of a halogen source. 3. The method of claim 2, wherein the monohaloamine comprises monochloramine. 4. The method of claim 1, wherein dihaloamine is produced by reacting a source of ammonium or amine with a halogenated oxidant. 5. The method of claim 1, wherein dihaloamine is produced by lowering the pH of a solution containing monohaloamine. 6. The method of claim 1, wherein dihaloamine is produced by changing the ratio of halogen to nitrogen in a solution containing monohaloamine. 7. The method of claim 1, wherein monohaloamine is produced from an amine or ammonium source comprising ammonia or ammonium hydroxide. 8. The method of claim 1, wherein monohaloamine is produced from an amine or ammonium source comprising an ammonium salt. 9. The method of claim 8, wherein the ammonium salt is selected from the group consisting of ammonium sulfate, ammonium acetate, ammonium bicarbonate, ammonium carbonate, ammonium chloride, ammonium citrate, ammonium iodide, ammonium molybdate, ammonium nitrate, ammonium oxalate, ammonium persulfate, ammonium phosphate, ammonium sulfate, ammonium sulphide, ammonium sulfamate and combinations thereof. 10. The method of claim 1, wherein the amine source is selected from the group consisting of polyamines, primary amines, secondary amines, cyclic amines, aliphatic amines, aromatic amines, polymers containing primary and secondary nitrogen and combinations of the same. 11. The method of claim 1, wherein the amine source or ammonium source is selected from the group consisting of dimethylamine, ethanolamine, ethylenediamine, diethanolamine, triethanolamine, dodecyl ethanolamine, hexdecyl ethanolamine, oleic acid of ethanolamine, triethylenetetramine, dibutylamine, tributylamine, glutamine, dilaurylamine, distearylamine, tallow-methylamine, coco-methylamine, n-alkylamines, n-acetylglucosamine, diphenylamine, ethanol methylamine, diisopropanolamine, n-methylaniline, n-hexyl-n-methylamine, n-heptyl-n-methylamine n-octyl-n-methylamine, n-nonyl-n-methylamine, n-decyl-n-methylamine, n-dodecyl-n-methylamine, n-tridecyl-n-methylamine, n-tetra-decyl-n-methylamine, n-benzyl-n-methylamine, n-phenylethyl-n-methylamine, n-phenylpropyl-n-methylamine, n-alkyl-n-ethylamines, n-alkyl-n-hydroxy-ethylamines, n-alkyl-n-propylamines, n-propylheptyl-n-methylamine, n-ethylhexyl-n-methylamine, n-ethylhexyl-n-butylamine, n-phenylethyl-n-methylamine, n-alkyl-n-hydroxypropylamines, n-alkyl- n-isopropylamines, n-alkyl-n-butylamines and n-alkyl-n-isobutylamines, n-alkyl-n-hydroxyalkylamines, hydrazine, urea, guanidines, biguanidines, and combinations thereof. 12. The method of claim 2, wherein the halogenated oxidant is selected from the group consisting of chlorine, hypochlorite, hypochlorous acid, chlorinated isocyanurates, bromine, hypobromite, hypobromous acid, bromine chloride, halogenated hydatoms, and combinations thereof . 13. The method of claim 2, wherein the halogenated oxidant is selected from the group consisting of chlorine, hypochlorite, hypochlorous acid, chlorinated isocyanurates, and combinations thereof. 14. The method of claim 13, wherein the source of ammonium or amine is an ammonium salt or amomac. 15. The method of claim 2, wherein the oxidant is selected from ozone, a peroxy compound or combinations thereof. 16. The method of claim 2, wherein the halogenated oxidant comprises hypochlorous acid or hypochlorite. 17. The method of claim 1, wherein the ratio of monohaloamine to dihaloamine is from 200: 1 to 1: 100. 18. The method of claim 1, wherein the ratio of monohaloamine to dihaloamine is from 20: 1 to 1: 5. 19. The method of claim 1, wherein the amount of monohaloamine, on an active level basis, ranges from 0.01 to 1,000 mg / l as Cl2 based on the volume of the aqueous system being treated and the amount of dihaloamine. , on an active level basis, ranges from 0.01 to 1,000 mg / l as Cl2 based on the volume of the aqueous system being treated. 5 20. The method of claim 1, wherein the amount of monohaloamine ranges from 0.05 to 200 mg / l as Ch on an active level basis, and the amount of dihaloamine ranges from 0.05 to 200 mg / l as Cl2 On an active level basis. The method of claim 1, wherein monohaloamine and dihaloamine are added continuously, continuously. intermittent, or alternatively to the aqueous system. 22. The method of claim 1, wherein the aqueous system has a pH of 4 to 10. 23. The method of claim 1, wherein the aqueous system has a pH of 5 to 9.