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EP-3967664-B1 - BIOFILM REMOVAL METHOD

EP3967664B1EP 3967664 B1EP3967664 B1EP 3967664B1EP-3967664-B1

Inventors

  • HOSOKAWA, Kento
  • CHIBA, MASASHI
  • YAMAMOTO, TETSUJI
  • TANAKA, TAKANORI

Dates

Publication Date
20260506
Application Date
20200428

Claims (10)

  1. A method for removing a biofilm containing a metal and formed in a water system, wherein the biofilm is brought into contact with a liquid composition containing a component (a), a component (b), a component (c) and water, wherein component (a) is one or more compounds selected from hydrogen peroxide and percarbonate salts, component (b) is ascorbic acid or a salt thereof, and component (c) is one or more selected from tartaric acid, maleic acid, fumaric acid, gluconic acid and salts thereof, and wherein, in the liquid composition, the concentration of component (a) is 50 ppm or more and 5,000 ppm or less, the concentration of component (b) is 50 ppm or more and 5,000 ppm or less, the concentration of component (c) is 50 ppm or more and 5,000 ppm or less, and a primary dissociation constant of component (c) is 1.2 or more and 4.6 or less.
  2. The method for removing a biofilm according to claim 1, wherein the liquid composition has a pH of 2.0 or more and 10.0 or less.
  3. The method for removing a biofilm according to claim 1 or 2, wherein the components (a), (b) and (c) are brought into contact at a pH of 2.0 or more and 10.0 or less.
  4. The method for removing a biofilm according to any one of claims 1 to 3, wherein the components (a) and (c) are brought into contact at a mass ratio of component (a)/component (c) of 0.01 or more and 100 or less.
  5. The method for removing a biofilm according to any one of claims 1 to 4, wherein the components (b) and (c) are brought into contact at a mass ratio of component (b)/component (c) of 0.01 or more and 100 or less.
  6. The method for removing a biofilm according to any one of claims 1 to 5, wherein the components (a) and (b) are brought into contact at a mass ratio of component (a)/component (b) of 0.01 or more and 100 or less.
  7. The method for removing a biofilm according to any one of claims 1 to 6, wherein the biofilm contains one or more metals selected from iron, manganese, nickel and copper.
  8. The method for removing a biofilm according to any one of claims 1 to 7, wherein the biofilm contains, per mg of the biofilm in a wet state, the metal in an amount of 0.5 ng or more and 50000 ng or less.
  9. The method for removing a biofilm according to any one of claims 1 to 8, wherein the water system is a cooling system comprising a water-cooled cooling tower.
  10. The method for removing a biofilm according to any one of claims 1 to 9, wherein the water system comprises a water flow path and/or a water storage tank.

Description

Field of the Invention The present invention relates to a biofilm removing method for removing a biofilm produced in a water system. Background of the Invention A biofilm is also called a microbial film or slime, and generally refers to a structure formed to encapsulate microorganisms such as bacteria or the like in polymeric substances such as polysaccharides, proteins, nucleic acids and the like produced by the microorganisms when the microorganisms adhere to surfaces of substances to grow. The formation of a biofilm causes many kinds of problems due to microorganisms, thus posing problems in various industrial fields. For example, when a biofilm is formed within piping of a food plant, this biofilm peels off to be mixed as a foreign substance into products, to cause the occurrence of food poisoning due to toxins derived from bacteria, or the like. Further, the formation of a biofilm onto metal surfaces causes metal corrosion and accelerates the deterioration of equipment. Systems utilizing aqueous media, such as cooling systems for plant equipment or buildings using water-cooled cooling towers, cooling pools, or the like have conventionally been used. In such systems, the microbial contamination of water used is problematic. For example, in a cooling system using a water-cooled cooling tower, microorganisms mixed into cooling water form a biofilm inside piping, particularly in a heat exchanger. The biofilm formed in the heat exchanger decreases the efficiency of heat exchange and increases the amount of electricity used in the cooling system. In order to prevent the biofilm from being formed, the periodical replacement and cleaning of water are required, but they increase maintenance costs of the system. While, in equipment, apparatuses or the like using cooling water, such as water-cooled cooling towers or the like, antimicrobial agents or growth inhibitors called slime control agents may sometimes also be added to the cooling water to inhibit a biofilm, treatment using no slime control agents is more desirable from the viewpoint of safety, the corrosion of metal piping, chemical agent costs or the like. Various kinds of proposals have conventionally been offered as measures against contamination incurred due to microorganisms or the like. JP-A 2012-512199 discloses that a disinfection/decontamination agent containing vitamin, a metal ion, a surface-active compound and a predetermined antimicrobial active substance can be used for the degradation of biofilms. JP-A 2016-102227 discloses a method for preventing a biofilm in a cooling water system in which cooling water cooled in a cooling tower is circulated to a heat exchanger and the cooling tower is supplied with supplementary water, wherein water in the cooling water system is treated by removing phosphoric acid in the supplementary water and using a non-phosphoric corrosion inhibitor as a corrosion inhibitor. JP-A 2016-035009 discloses a biofilm removing agent composition for hard surfaces containing 1 mass% or more and 40 mass% or less of internal olefin sulfonates. JP-A 2018-168097 discloses a biofilm formation inhibiting composition containing a specific cyclic aldehyde compound and an organic solvent. JP-A 2017-518432 discloses a method for treating a biofilm-affected surface including the step of contacting the affected surface with a predetermined aqueous alkali surfactant composition having a surfactant hydroxide molarity of from 2 to 9. WO 2004/035718 A2 relates to a composition comprising: 0.1 to 40 wt. % of at least one oxidation-stable, at least mono-unsaturated, substituted or unsubstituted organic acid, 0.1 to 40 wt. % of at least one oxidation-stable, saturated, substituted or unsubstituted organic acid, up to 30 wt. % of hydrogen peroxide and/or at least one inorganic and/or organic peroxide compound and up to 2 wt. % of an oxidation-stable complexing agent. Said composition is said to be an effective, widely applicable disinfecting, antibacterial and pharmaceutical agent, characterized by a good shelf life. WO 2009/028757 A1 describes a cleaning agent composition for cleaning indoor water supply pipes that comprises 5 to 10% by weight of citric acid, 1 to 10% by weight of oxalic acid, 1 to 10% by weight of malic acid, 0.1 to 1% by weight of phosphoric acid, 5 to 15% by weight of hydrochloric acid, 1 to 2% by weight of hydrogen peroxide, 0.01 to 0.1% by weight of lauryl alcohol ethoxylate (LEA), 0.01 to 0.1% by weight of ascorbic acid, and the remaining weight percentage of water, based on a total of 100% by weight of the composition. KR 101 140 217 B1 describes n detergent composition for cleaning a water reservoir that comprises 1- 10wt% of citric acid, 1-10 wt% of malic acid, 1-10 wt% of oxalic acid, 1-2 wt% of hydrochloric acid (HCI), a non-ionic alcohol surfactant, and 0.01-1 wt% of hydrogen peroxide, and the components are mixed into water at room temperatures. JP S56 78695A describes a cleaner for sticking material in a distribu