Composition for removing biofilm in aqueous systems

Abstract

To provide a biofilm removal composition for a water system that can effectively remove a biofilm formed in a water system such as devices and facilities including a water-contacting member such as a water-cooling tower, bathtub piping.SOLUTION: The present invention is a biofilm removal composition for a water system which contains the following component (a), component (b), and component (c), and water, and has a pH at 20°C of 2.5 to 6.5. Component (a): a compound capable of producing hydroxyl radials. Component (b): a reducing agent. Component (c): a mono- or divalent organic acid having a first dissociation constant of 1.2 to 4.6 or a salt thereof.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a biofilm removing composition for use in aqueous systems. [Background technology]

[0002] Biofilms, also called biofilms or slimes, generally refer to structures formed by microorganisms such as bacteria that are produced by microorganisms and grow on the surface of a material, and that encase the microorganisms with polymeric substances such as polysaccharides, proteins, and nucleic acids. When biofilms are formed, various problems occur due to microorganisms, and they are problematic in various industrial fields. For example, when biofilms are formed in the piping of a food plant, the biofilms may peel off and become mixed into the product as foreign matter, or may cause food poisoning due to toxins derived from the bacteria. Furthermore, biofilm formation on metal surfaces may cause metal corrosion and accelerate the aging of equipment.

[0003] Conventionally, systems using aqueous media, such as cooling systems for factory equipment and buildings using water-cooled cooling towers, and cooling pools, have been used. In such systems, microbial contamination of the water used is a problem. For example, in a cooling system using a water-cooled cooling tower, microorganisms mixed in the cooling water form biofilms in the piping, especially in the heat exchanger. The biofilm formed in the heat exchanger reduces the efficiency of heat exchange and increases the power consumption of the cooling system. Periodic water replacement and cleaning are required to prevent biofilm formation, but these increase the maintenance costs of the system. In facilities and devices that use cooling water such as water-cooled cooling towers, microbial bactericides and growth inhibitors called slime control agents are sometimes added to the cooling water to suppress biofilms, but from the viewpoints of safety, corrosion of metal piping, and chemical costs, treatment without using slime control agents is preferable.

[0004] Various proposals have been made so far as measures against contamination caused by microorganisms. US Patent No. 5,399,633 discloses that disinfecting and decontaminating agents including vitamins, metal ions, surface active compounds, and certain antimicrobial agents can be used to break down biofilms. Patent Document 2 discloses a water treatment method for preventing biofilms in a cooling water system in which cooling water cooled in a cooling tower is circulated through a heat exchanger and make-up water is supplied to the cooling tower, the water treatment method removing phosphoric acid from the make-up water and using a non-phosphorus-based corrosion inhibitor as a corrosion inhibitor. Patent Document 3 discloses a biofilm remover composition for hard surfaces, which contains 1 mass % or more and 40 mass % or less of an internal olefin sulfonate. Patent Document 4 discloses a composition for inhibiting biofilm formation, which contains a specific cyclic aldehyde compound and an organic solvent. Patent Document 5 discloses a treatment method comprising the step of contacting a surface affected by a biofilm with a predetermined aqueous alkaline surfactant composition having a surfactant hydroxide molar concentration of 2-9. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2012-512199 [Patent Document 2] JP 2016-102227 A [Patent Document 3] JP 2016-035009 A [Patent Document 4] JP 2018-168097 A [Patent Document 5] Special Publication No. 2017-518432 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a biofilm removal composition for aqueous systems that can effectively remove biofilms that have formed in aqueous systems such as devices and equipment that include components that come into contact with water, such as water cooling towers and bathtub piping. [Means for solving the problem]

[0007] The present invention relates to a composition for removing biofilms in aqueous systems, which contains the following component (a), component (b), component (c), and water, and has a pH at 20°C of 2.5 or more and 6.5 or less: (a) Component: A compound capable of generating hydroxyl radicals (b) Component: Reducing agent (c) Component: a monovalent or divalent organic acid or its salt having a first dissociation constant of 1.2 or more and 4.6 or less.

[0008] The present invention also relates to a kit comprising a plurality of agents containing components selected from the group consisting of component (a), component (b), and component (c), the kit being for producing the biofilm removal composition for aqueous systems of the present invention, in which component (a) and component (b) are contained in separate agents. Effect of the Invention

[0009] According to the present invention, there is provided a biofilm removing composition for aqueous systems that can effectively remove biofilms formed in aqueous systems. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Biofilm Removal Composition for Aqueous Systems> Although the mechanism by which the biofilm removing composition for aqueous systems of the present invention exerts its effect has not been entirely elucidated, it is believed to be as follows. The present inventors have found that biofilms in aqueous systems can be decomposed or dispersed in water by hydroxyl radicals, thereby contributing to the removal of biofilms from equipment. In terms of the efficiency of action between hydroxyl radicals and biofilms formed on equipment, the presence of hydroxyl radicals on the surface of the biofilm is inefficient, and if hydroxyl radicals can be generated widely inside the biofilms formed on the equipment, high biofilm removal efficiency can be expected. The biofilm removing composition for aqueous systems of the present invention does not essentially need to contain metal ions that can also act as a catalyst for generating hydroxyl radicals, so that even if it is dissolved in water that flows, circulates, or remains in the aqueous system, it does not instantly generate hydroxyl radicals, and the (a), (b), and (c) components of the present invention are all low molecular weight, so they tend to move widely inside the biofilms formed on the equipment. Metal ions originating from equipment materials and water supplied to aqueous systems accumulate inside biofilms in the form of salts, oxides, etc., which are insoluble in water. In the composition of the present invention, which has a specific pH range, an organic acid with a specific structure (component (c)) forms a complex, which causes the insoluble metals present in the biofilm to become water-soluble and react with a reducing agent (component (b)) that is thought to be present nearby to become reduced metal ions (for example, Fe 3+ →Fe 2+). It is believed that the reduced metal ions and the compound (component (a)) that is thought to be present in the vicinity and has the ability to generate hydroxyl radicals undergo a Fenton-like reaction to generate hydroxyl radicals, which break the biofilm into pieces large enough to be decomposed or dispersed in water. The metal ions oxidized by the Fenton-like reaction are further reduced by component (b), and the Fenton-like reaction with component (a) occurs continuously, which is thought to result in a sustained biofilm removal effect. As described above, in the biofilm removal composition for aqueous systems of the present invention, explosive generation of hydroxyl radicals does not occur in water, but rather, it is believed that an efficient biofilm removal effect can be obtained by the generation of hydroxyl radicals that occurs continuously in a wide range of the biofilm because the composition utilizes trace amounts of metal ions accumulated in the biofilm. The effects of the present invention are not limited to the above-mentioned mechanism of action.

[0011] [Component (a)] Component (a) is a compound capable of generating hydroxyl radicals. The component (a) may be a compound that generates hydroxyl radicals through a Fenton-like reaction. Examples of the component (a) include one or more compounds selected from hydrogen peroxide, percarbonates, and organic peracids, and from the viewpoints of availability, economy, and hydroxyl radical generating ability, one or more compounds selected from hydrogen peroxide and percarbonates are preferred. Examples of the percarbonates include alkali metal percarbonates such as sodium percarbonate and potassium percarbonate, and from the viewpoints of availability, economy, and hydroxyl radical generating ability, sodium percarbonate is preferred.

[0012] [(b) component] Component (b) is a reducing agent. The component (b) may be a compound having a reducing effect on a metal, for example, iron. The metal on which the component (b) of the present invention exerts a reducing effect refers to a metal in a state that can be reduced. (b) Ingredients include: (b-1) Compounds having an enediol structure: for example, ascorbic acid or a salt thereof, vitamin C extracted from natural products, tannic acid, erythorbic acid or a salt thereof, (b-2) Hydroxylamine: for example, N,N-diethylhydroxylamine, (b-3) Phenol-based reducing agents: for example, gallic acid, methylhydroquinone, dimethylhydroquinone, trimethylhydroquinone, t-butylhydroquinone, methoxyhydroquinone, chlorohydroquinone, (b-4) Other reducing agents: ascorbic acid derivatives or their salts, hydrosulfite, pyrosulfite, sulfite, hydrogen sulfite, thiosulfate, thiourea dioxide, Examples of the salts of these compounds include alkali metal salts such as sodium and potassium, and alkaline earth metal salts such as calcium salt. As component (b), from the viewpoints of availability and enhancing the biofilm removal effect (hereinafter also referred to as biofilm removal property), ascorbic acid or a salt thereof is preferred.

[0013] [(c) component] Component (c) is a monovalent or divalent organic acid or its salt having a first dissociation constant (hereinafter referred to as pKa1) of 1.2 to 4.6. Among such organic acids or their salts, compounds having a reducing action are treated as component (b).

[0014] From the viewpoint of biofilm removing ability, the pKa1 of the component (c) is preferably 1.8 or more, more preferably 2.5 or more, and preferably 3.3 or less.

[0015] The molecular weight of the organic acid of component (c), from the viewpoint of biofilm removing ability, may be, for example, 70 or more, and further 75 or more, further 95 or more, and 200 or less, further 180 or less, further 165 or less, and further 160 or less. From the viewpoint of biofilm removing ability, the organic acid of component (c) has a carbon number of preferably 2 or more, and preferably 8 or less, more preferably 6 or less, and further preferably 4 or less. From the viewpoint of biofilm removing ability, the organic acid of component (c) is preferably a carboxylic acid, and more preferably a monocarboxylic acid or dicarboxylic acid.

[0016] Examples of component (c) include one or more organic acids or salts thereof selected from hydroxymonocarboxylic acids having 2 or 3 carbon atoms and a molecular weight of 70 to 200, and further 180, dicarboxylic acids having 3 or 4 carbon atoms and a molecular weight of 70 to 200, and further 180, hydroxycarboxylic acids having 5 to 8 carbon atoms and a molecular weight of 70 to 200, and further salts thereof.

[0017] Examples of hydroxymonocarboxylic acids having 2 or 3 carbon atoms and a molecular weight of 70 to 200 include glycolic acid (pKa1: 3.83, Mw: 76.1), lactic acid (pKa1: 3.86, Mw: 90.1), and 3-hydroxypropionic acid (pKa1: 4.5, Mw: 90.1).

[0018] Examples of dicarboxylic acids having 3 or 4 carbon atoms and a molecular weight of 70 to 200 include tartaric acid (pKa1:2.98, Mw:150.1), fumaric acid (pKa1:3.02, Mw:116.1), maleic acid (pKa1:1.92, Mw:116.1), malic acid (pKa1:3.4, Mw:134.1), succinic acid (pKa1:4.19, Mw:118.1), and malonic acid (pKa1:2.9, Mw:104.1).

[0019] An example of a hydroxycarboxylic acid having 5 to 8 carbon atoms and a molecular weight of 70 to 200 is gluconic acid (pKa1: 3.86, Mw: 196).

[0020] From the viewpoint of biofilm removal ability, the (c) component is preferably one or more organic acids or salts thereof selected from malonic acid, malic acid, 3-hydroxypropionic acid, succinic acid, lactic acid, tartaric acid, glycolic acid, maleic acid, fumaric acid, gluconic acid, and salts thereof. From the viewpoint of biofilm removing ability, the component (c) is more preferably one or more organic acids or salts thereof selected from tartaric acid, fumaric acid, maleic acid, gluconic acid, and salts thereof.

[0021] Examples of the organic acid salt of component (c) include alkali metal salts such as sodium and potassium, and alkaline earth metal salts such as calcium.

[0022] [Composition, optional ingredients, etc.] In the biofilm removing composition for aqueous systems of the present invention, the concentrations of components (a), (b) and (c) can be set taking into consideration the form of the composition and the like. In the biofilm removal composition for aqueous systems of the present invention, the concentration of component (a) can be set by selecting and combining the upper and lower limit values ​​from, for example, 50 ppm or more, further 60 ppm or more, further 80 ppm or more, and 5000 ppm or less, further 3000 ppm or less, further 1000 ppm or less, further 600 ppm or less, and further 500 ppm or less. In the biofilm removal composition for aqueous systems of the present invention, the concentration of component (b) can be set by selecting and combining the upper and lower limits from, for example, 50 ppm or more, further 60 ppm or more, further 80 ppm or more, and 50,000 ppm or less, further 30,000 ppm or less, further 10,000 ppm or less, further 5,000 ppm or less, further 3,000 ppm or less, further 1,000 ppm or less, further 600 ppm or less, and further 500 ppm or less. In the biofilm removal composition for aqueous systems of the present invention, the concentration of component (c) can be set by selecting and combining the upper and lower limit values ​​from, for example, 50 ppm or more, further 60 ppm or more, further 80 ppm or more, and 5000 ppm or less, further 3000 ppm or less, further 1000 ppm or less, further 600 ppm or less, and further 500 ppm or less.

[0023] From the viewpoint of biofilm removal ability, the biofilm removal composition for aqueous systems of the present invention has a mass ratio (a) / (b) of the concentration of component (a) to the concentration of component (b) of preferably 0.01 or more, more preferably 0.1 or more, and preferably 100 or less, more preferably 10 or less.

[0024] From the viewpoint of biofilm removal ability, the biofilm removal composition for aqueous systems of the present invention has a mass ratio (a) / (c) of the concentration of component (a) to the concentration of component (c) of preferably 0.01 or more, more preferably 0.1 or more, and preferably 100 or less, more preferably 10 or less, even more preferably 9.5 or less, still more preferably 4.5 or less, still more preferably 1.5 or less, and even more preferably 0.5 or less.

[0025] From the viewpoint of biofilm removal ability, the biofilm removal composition for aqueous systems of the present invention has a mass ratio (b) / (c) of the concentration of component (b) to the concentration of component (c) of preferably 0.01 or more, more preferably 0.1 or more, and preferably 100 or less, more preferably 10 or less.

[0026] The biofilm removing composition for aqueous systems of the present invention exhibits an excellent biofilm removing effect even when the concentration of the surfactant is low. For example, the concentration of the surfactant in the biofilm removing composition for aqueous systems of the present invention may be less than 100 ppm, further 50 ppm or less, further 10 ppm or less, or further 0 ppm. The biofilm removing composition for aqueous systems of the present invention may be substantially free of surfactant. Here, substantially free of surfactant may mean that the concentration of the surfactant is within the above range.

[0027] The biofilm removing composition for aqueous systems of the present invention may be free or substantially free of metal ions involved in Fenton-like reactions, specifically, ions of metals selected from iron, scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, and copper. Here, "substantially free of metal ions" may mean that even if the metal ions are contained, the amount is extremely small, and the Fenton-like reaction does not occur sufficiently.

[0028] The composition for removing biofilm for use in an aqueous system of the present invention contains water. The composition for removing biofilm for use in an aqueous system of the present invention is preferably a liquid composition containing water.

[0029] The biofilm removal composition for aqueous systems of the present invention has a pH at 20°C of 2.5 or more, preferably 3.0 or more, from the viewpoint of preventing damage to equipment, and a pH of 6.5 or less, preferably 5.5 or less, from the viewpoint of biofilm removal effect.

[0030] The biofilm removal composition for aqueous systems of the present invention may, for example, have a pH at 20°C of 2.5 or more, preferably 3.0 or more, from the viewpoint of preventing damage to equipment, and may have a pH of 6.5 or less, preferably 5.5 or less, from the viewpoint of biofilm removal effect, when the composition contains 100 ppm of component (a).

[0031] The aqueous system of the present invention is not particularly limited as long as it is a system in which contact with an aqueous liquid occurs, but may be, for example, a system that functions by the circulation or storage of an aqueous liquid, and may be a device composed of a member that comes into contact with water, such as a pipe, a tank, or a pool, and a facility including the device. The water may be water itself, or an aqueous medium containing water and other substances. As an example, the aqueous system is a cooling system equipped with a water-cooled water cooling tower. As another example, the aqueous system may include a hot water piping section selected from a water distribution path such as a water distribution pipe, for example, a hot water piping section of a boiler, and a hot water piping section of a circulating hot water supply pipe to which hot water is supplied from a hot water tank. The aqueous system may also include a water storage tank. Furthermore, other examples of the aqueous system include industrial cooling pools, industrial water supply, storage or drainage paths, drainage treatment facilities, running water heating systems, tanks, pools, baths, filtration facilities, papermaking facilities in paper factories, aquarium tanks and water circulation paths, ultrapure water devices, aquaculture facilities, and plant factories.

[0032] The aqueous system to which the present invention is applied is preferably equipped with a mechanism for contacting with water, such as a mechanism for periodically circulating water or a mechanism for circulating water. In this case, the composition of the present invention can be added to the water to be contacted and the aqueous system can be operated to contact the water, thereby removing the biofilm that has developed in the aqueous system. The water to be contacted may be the composition of the present invention, and in this case, it is preferable to adjust the amounts of the components (a) to (c) to be added so that the concentrations of the components are within the above ranges.

[0033] The present invention provides a method for removing a biofilm that has developed in an aqueous system equipped with a mechanism for contacting water, for example, a mechanism for circulating and / or flowing water, comprising contacting a portion of the aqueous system where a biofilm has developed with a composition for removing biofilm for aqueous systems, the composition for removing biofilm for aqueous systems containing component (a), component (b), component (c) and water and having a pH of 2.5 to 6.5 inclusive. In this method, the composition for removing biofilm for aqueous systems may have a pH at 20°C of 2.5 to 6.5 inclusive. To this method, the matters described above regarding the composition for removing biofilm for use in aqueous systems of the present invention can be appropriately applied. When a biofilm occurs in a mechanism for circulating water, the composition can be brought into contact with the mechanism, thereby bringing the composition into contact with the area where the biofilm occurs. The contact time of the composition is, for example, from 10 minutes to 48 hours. The temperature of the composition to be contacted is, for example, 5°C or higher and 85°C or lower.

[0034] When applying the biofilm removing composition for aqueous systems of the present invention to an aqueous system, a composition prepared in advance as a predetermined composition may be used, or a high-concentration composition of the biofilm removing composition for aqueous systems of the present invention may be used. In addition, the components (a), (b), and (c) may be dissolved individually or as a premix in water flowing, circulating, or remaining in the aqueous system, and the pH may be adjusted to use as the biofilm removing composition for aqueous systems. The components (a), (b), and (c) can be supplied in the form of a liquid, solid, or aqueous solution, depending on the compound. From the viewpoint of the liquid stability of the composition, it is preferable to prepare the composition of the present invention just before application to the aqueous system, or to dissolve it in water flowing, circulating, or remaining in the aqueous system.

[0035] The formulation of the biofilm removal composition for aqueous systems of the present invention may be any formulation, including, for example, a tableted solid formulation, a solid formulation in which a powder is packaged in a water-soluble film, or a paste formulation in which the composition is kneaded with a medium, taking into consideration ease of use depending on the target equipment.

[0036] <Kit> The present invention provides a kit comprising a plurality of agents including components selected from component (a), component (b), and component (c), the kit being a kit for producing the biofilm removal composition for aqueous systems of the present invention, in which the following component (a) and the following component (b) are contained in separate agents:

[0037] Examples of kits of the present invention include: (1) A kit consisting of a preparation containing component (a) but not containing component (b) and a preparation containing components (b) and (c) but not containing component (a). (2) A kit consisting of a preparation containing the components (a) and (c) but not the component (b), and a preparation containing the component (b) but not the component (a). (3) A kit consisting of a preparation containing component (a) but not containing component (b), a preparation containing component (b) but not containing component (a), and a preparation containing component (c) (which preparation may optionally contain component (a) or component (b)). Examples include:

[0038] In the kit of the present invention, it is preferable to store and supply the oxidizing component (a) and the reducing agent (b) separately from the viewpoint of compound stability, and it is preferable to supply the component (c) as a kit of an agent containing the component (a) and an agent containing the components (b) and (c) from the viewpoint of avoiding the oxidation reaction by the component (a) and improving the solubility in water during production. When the components (a) and (c) are solid or liquid, if the reactivity of the components (a) and (c) is low, it is possible to supply the kit of an agent containing the components (a) and (c) and an agent containing the component (b). As a kit, from the viewpoint of the stability and workability of the agent, a kit consisting of an agent containing the component (a) but not the component (b) and an agent containing the components (b) and (c) but not the component (a) is more preferable. Specific examples and preferred examples of the components (a), (b), and (c) are the same as those of the biofilm removing composition for aqueous systems of the present invention. The matters described in the biofilm removing composition for aqueous systems of the present invention can be appropriately applied to the kit of the present invention.

[0039] In each of the agents constituting the kit of the present invention, the content of component (a), component (b), and component (c) may be, for example, an amount such that a biofilm removal composition for aqueous systems of the present invention containing these components at concentrations and mass ratios within the above-mentioned ranges can be produced. EXAMPLES

[0040] <Example 1 and Comparative Example 1> The compositions for removing biofilms in aqueous systems shown in Table 1 were prepared and the following tests were carried out. The results are shown in Table 1. The pH of the compositions in Table 1 was adjusted with 10 mM acetate buffer (to adjust to pH 4.0) or 10 mM phosphate buffer (to adjust to pH 7.0), and then each component was adjusted to a specified concentration. The remainder of the compositions in Table 1 is water.

[0041] [Biofilm removal test (water cooling tower model)] (1) Preparation of biofilm To create the biofilm, we used an aqueous system model using an annular reactor (manufactured by Art Science Co., Ltd.) with a 100 mL culture tank. The culture tank of the annular reactor was equipped with a cylindrical rotor that rotated at a speed of 160 revolutions per minute, and a test piece (SUS304) was attached to this rotor in advance. Cooling water collected from a water-cooled water cooling tower for cooling the reaction tank equipment of a chemical plant was supplied to the annular reactor culture tank (maintained at 30°C), and the culture was continued for 3 weeks to form a biofilm on the test piece.

[0042] (2) Biofilm removal test A test piece on which a biofilm had formed was immersed in each well of a 6-well plate containing 5 mL of the biofilm removal composition for aqueous systems in Table 1 or a control (ultrapure water), and the plate was shaken at 30°C and 60 rpm for 16 hours. Each test piece was stained with 0.1% crystal violet, washed with ultrapure water, and the staining solution was extracted with 1 mL of ethanol, and the absorbance (OD570) was measured. Based on the measured OD570, the biofilm removal rate was measured according to the following formula. The blank refers to the OD570 of ethanol. Biofilm removal rate (%) = {(control OD570 - blank OD570) - (OD570 of the example or comparative example - blank OD570)} x 100 / (control OD570 - blank OD570) In this test, the higher the biofilm removal rate, the greater the effect, and the effect of the present invention can be significantly felt when the rate is 40% or more. In this test, a 5% difference in the biofilm removal rate can be recognized as a significant difference, and a 10% difference can be recognized as a more clear difference.

[0043] [Table 1]

[0044] Component (c') is a comparative compound to component (c). Acetic acid pKa1: 4.76, Mw: 60.1 Citric acid pKa1: 3.09, Mw: 192.1

[0045] <Example 2 and Comparative Example 2> The compositions for removing biofilms in aqueous systems shown in Table 2 were prepared and the following tests were carried out. The results are shown in Table 2. The pH of the compositions in Table 2 was adjusted with 10 mM acetate buffer or 10 mM phosphate buffer, and then each component was adjusted to a predetermined concentration. The remainder of the compositions in Table 2 was water.

[0046] [Biofilm removal test (bathtub piping model)] (1) Preparation of biofilm To prepare the biofilm, an aqueous system model was used using an annular reactor (manufactured by Art Science Co., Ltd.) with a 100 mL culture tank. A cylindrical rotor rotating at a speed of 160 revolutions per minute was installed in the culture tank of the annular reactor, and a test piece (SUS304) was attached to this rotor in advance. Bath water collected from a circulating bath was supplied to the annular reactor culture tank (maintained at 40°C), while R2A medium was added to the supply water as a dirt load treatment so that the concentration increased by 10 ppm every day, and the biofilm was formed on the test piece by culturing for one week.

[0047] (2) Biofilm removal test A test piece on which a biofilm had formed was immersed in each well of a 6-well plate containing 5 mL of the composition for removing biofilms for aqueous systems in Table 2 or a control (ultrapure water), and the plate was shaken at 40°C and 60 rpm for 30 minutes. Each test piece was stained with 0.1% crystal violet, washed with ultrapure water, and the staining solution was extracted with 1 mL of ethanol, and the absorbance (OD570) was measured. Based on the measured OD570, the biofilm removal rate was measured according to the following formula. The blank refers to the OD570 of ethanol. Biofilm removal rate (%) = {(control OD570 - blank OD570) - (OD570 of the example or comparative example - blank OD570)} x 100 / (control OD570 - blank OD570)

[0048] [Table 2]

[0049] <Example 3> A biofilm removal test was carried out in the same manner as in Example 2 using the test piece on which the biofilm was formed as produced in Example 2 and a biofilm removal composition for aqueous systems prepared using the components shown in Table 3. However, the remainder of the composition was ultrapure water, and the cleaning time was 60 minutes. The results are shown in Table 3.

[0050] [Table 3]

Claims

1. The composition contains the following component (a), the following component (b), the following component (c), and water, and has a pH of 2.5 or more and 6.5 or less at 20°C, a mass ratio (a) / (b) of the concentration of the component (a) to the concentration of the component (b) is 0.01 or more and 10 or less; the mass ratio (a) / (c) of the concentration of the component (a) to the concentration of the component (c) is 0.1 or more and 10 or less; A composition for removing biofilm in aqueous systems. Component (a): 50 ppm or more of one or more compounds capable of generating hydroxyl radicals selected from hydrogen peroxide and percarbonates (b) Component: 50 ppm or more of one or more reducing agents selected from ascorbic acid or its salts Component (c): A monovalent or divalent organic acid or a salt thereof having a first dissociation constant of 1.2 or more and 4.6 or less, which is one or more organic acids or salts thereof selected from 3-hydroxypropionic acid, succinic acid, lactic acid, tartaric acid, glycolic acid, maleic acid, fumaric acid, gluconic acid, and salts thereof, in an amount of 50 ppm or more.

2. The biofilm removing composition for aqueous systems according to claim 1, wherein component (a) is a percarbonate.

3. 3. The biofilm removing composition for aqueous systems according to claim 1 or 2, wherein (b) / (c), which is the mass ratio of the concentration of the component (b) to the concentration of the component (c), is 0.01 or more and 100 or less.

4. The biofilm removing composition for aqueous systems according to any one of claims 1 to 3, wherein the component (c) is one or more organic acids or salts thereof selected from tartaric acid and salts thereof.

5. The biofilm removing composition for aqueous systems according to any one of claims 1 to 4, wherein the concentration of the component (a) is 50 ppm or more and 5,000 ppm or less, the concentration of the component (b) is 50 ppm or more and 50,000 ppm or less, and the concentration of the component (c) is 50 ppm or more and 5,000 ppm or less.

6. The biofilm removing composition for aqueous systems according to any one of claims 1 to 5, wherein the concentration of the component (a) is 50 ppm or more and 5,000 ppm or less, the concentration of the component (b) is 50 ppm or more and 5,000 ppm or less, and the concentration of the component (c) is 50 ppm or more and 5,000 ppm or less.

7. The biofilm removing composition for an aqueous system according to any one of claims 1 to 6, wherein the aqueous system is a cooling system equipped with a water-cooled water cooling tower.

8. The composition for removing biofilm for an aqueous system according to any one of claims 1 to 6, wherein the aqueous system includes a water distribution path.

9. A kit comprising a plurality of agents containing components selected from the following component (a), the following component (b), and the following component (c), the kit being for producing a biofilm removal composition for aqueous systems described in any one of claims 1 to 8, the kit comprising the following component (a) and the following component (b) contained in separate agents: Component (a): one or more compounds capable of generating hydroxyl radicals selected from hydrogen peroxide and percarbonates Component (b): One or more reducing agents selected from ascorbic acid or its salts Component (c): A monovalent or divalent organic acid or a salt thereof having a first dissociation constant of 1.2 or more and 4.6 or less, which is one or more organic acids or salts thereof selected from 3-hydroxypropionic acid, succinic acid, lactic acid, tartaric acid, glycolic acid, maleic acid, fumaric acid, gluconic acid, and salts thereof.

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