Wastewater treatment method

Abstract

To provide a microorganism capable of efficiently degrading wastewater containing an organic acid even in the presence of a bactericidal component, and a wastewater treatment method using the microorganism.SOLUTION: A wastewater treatment method includes contacting wastewater containing organic acids with microorganisms belonging to the genus Enterobacter, and the wastewater treatment agents containing NITE BP-03850 and / or Enterobacter tabaci JCM 19646.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for treating wastewater containing an organic acid, and a wastewater treatment agent for use in said method. [Background technology]

[0002] Bisphenol A is used in many applications as a raw material for plastic products. However, the manufacturing process of these plastic products is prone to produce wastewater containing phenol, methanol, high concentrations of formic acid, etc. Currently, methods for treating such wastewater include dilution, incineration, distillation recovery, and activated sludge.

[0003] The wastewater is generally treated by biological decomposition using the activated sludge method, but there is a concern that the decomposition capacity of the activated sludge will decrease due to the biotoxicity of phenol. In addition, it is known that high concentrations of formic acid are also highly biotoxic and difficult to treat biologically.

[0004] In order to achieve effluent standards for COD(Mn), COD(Cr), etc., wastewater treatment technology that is resistant to the above-mentioned biologically toxic components (bactericidal components) and can break down high concentrations of formic acid is required.

[0005] To date, wastewater treatment using a microorganism belonging to the genus Pseudomonas having phenol decomposition ability, a microorganism belonging to the genus Methylobacterium having formic acid decomposition ability, and a microorganism of the genus Candida having phenol and formic acid decomposition ability has been reported (Patent Document 1). Also, wastewater treatment in a bioreactor using a microorganism Haloferax mediterranei having formic acid decomposition ability has been reported (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2005 / 001066 [Patent Document 2] Special table 2021-506575 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a microorganism capable of efficiently decomposing wastewater containing an organic acid even in the presence of a bactericidal component, and a wastewater treatment method using said microorganism. [Means for solving the problem]

[0008] The inventors have discovered, among microorganisms living in soil, water in storage tanks, and activated sludge, microorganisms capable of efficiently decomposing high concentrations of organic acids and having resistance to phenol and methanol, and have completed the present invention.

[0009] That is, the present invention provides the following [1] to

[10] . [1] A method for treating wastewater, comprising contacting wastewater containing organic acids with a microorganism belonging to the genus Enterobacter. [2] The method for treating wastewater according to [1], wherein the wastewater contains a bactericidal component. [3] The wastewater treatment method according to [1] or [2], wherein the organic acid is a carboxylic acid or dicarboxylic acid having 1 to 6 carbon atoms. [4] The wastewater treatment method according to [3], wherein the organic acid is at least one selected from the group consisting of formic acid, acetic acid, fumaric acid, maleic acid, lactic acid and malic acid. [5] The wastewater treatment method according to any one of [2] to [4], wherein the bactericidal component is phenol and / or methanol. [6] The wastewater treatment method according to any one of [1] to [5], wherein the microorganism belonging to the genus Enterobacter has 16S rDNA consisting of a base sequence having 98% or more identity to the base sequence shown in SEQ ID NO: 1. [7] The wastewater treatment method according to any one of [1] to [6], wherein the microorganism belonging to the genus Enterobacter is NITE BP-03850 and / or Enterobacter tabaci JCM 19646. [8] The wastewater treatment method according to any one of [1] to [7], wherein the wastewater is at least one type of wastewater selected from special wastewater, sewage wastewater, and miscellaneous wastewater. [9] A wastewater treatment agent containing NITE BP-03850 and / or Enterobacter tabaci JCM 19646.

[10] Microorganisms identified in NITE BP-03850. Effect of the Invention

[0010] According to the present invention, it is possible to suppress the decrease in the effectiveness of activated sludge, etc., and to efficiently decompose organic acids contained in high concentrations in wastewater. The microorganisms used in the present invention are highly resistant to bactericidal components such as phenol and methanol, and therefore can be applied to the treatment of industrial wastewater containing such components. [Brief description of the drawings]

[0011] [Figure 1] Figure 1 shows the change in formic acid concentration in wastewater when activated sludge and E. tabaci (JCM 19646) (solid line), or activated sludge only (dashed line) was added to the wastewater. [Diagram 2] FIG. 2 shows the change in formic acid concentration in wastewater when activated sludge and Enterobacter sp. new species strain (solid line), or activated sludge only (dashed line) was added to the wastewater. [Diagram 3] FIG. 3 shows the malic acid concentration and the bacterial cell concentration in the reaction solution before and after the culture. [Figure 4] FIG. 4 shows the fumaric acid concentration and the bacterial cell concentration in the reaction solution before and after the culture. [Diagram 5] FIG. 5 shows the acetic acid concentration and bacterial cell concentration in the reaction solution before and after the culture. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 1. Wastewater treatment method The present invention relates to a wastewater treatment method comprising contacting wastewater containing organic acids with a microorganism belonging to the genus Enterobacter.

[0013] (1) Wastewater to be treated In the present invention, the wastewater to be treated is wastewater containing organic acids. There are no limitations on the origin of the wastewater, so long as it contains organic acids.

[0014] In the present invention, the "organic acid" is not particularly limited as long as it is an organic compound that exhibits acidity. Preferably, the "organic acid" is a carboxylic acid or dicarboxylic acid having 1 to 6 carbon atoms. For example, the "organic acid" may include formic acid, acetic acid, fumaric acid, maleic acid, lactic acid, malic acid, etc.

[0015] The wastewater may contain bactericidal components such as phenol, methanol, etc., in addition to organic acids. These components make biological wastewater treatment difficult, just like organic acids, but the microorganisms used in the present invention are resistant to these bactericidal components and can therefore decompose organic acids in wastewater containing bactericidal components.

[0016] In the present invention, the term "bactericidal component" refers to a component having biotoxicity or bactericidal activity, and examples of the bactericidal component include aliphatic or aromatic alcohols, surfactants, iodine, peroxides, chlorine, aldehydes, etc. Specific examples of the "bactericidal component" include phenol, methanol, benzethonium chloride (hyamine solution), benzalkonium chloride (osvan solution), ethanol, isopropanol, povidone-iodine, iodine, oxidol, sodium hypochlorite, formalin, cresol, etc. Preferably, the "bactericidal component" is phenol and / or methanol.

[0017] The wastewater may be pretreated as necessary before being subjected to microbial treatment. For example, if the wastewater contains a large amount of acidic components and is therefore biased toward acidity, an alkaline component can be added to adjust the pH to 5 to 9, preferably 5.5 to 8.5, and more preferably 6 to 8. The alkaline component used is not limited, and for example, NaOH, KOH, sulfuric acid, ammonium sulfate, etc. (particularly sulfuric acid or ammonium sulfate) can be used in solid or liquid form.

[0018] The wastewater to be treated by the present invention may be any of special wastewater, sewage, and miscellaneous wastewater. As described above, the microorganism of the present invention is resistant to bactericidal components, and therefore can be suitably applied to special wastewater such as industrial water containing such components. Examples of such wastewater include wastewater generated in coke oven plants, coal gasification or liquefaction plants, photographic wastewater, printing wastewater, dyeing wastewater, semiconductor manufacturing plants, petrochemical plants, plastic manufacturing plants, and plastic raw material (such as bisphenol A) manufacturing plants.

[0019] (2) Microorganisms used in wastewater treatment The microorganism used in the present invention (hereinafter sometimes referred to as "the microorganism of the present invention") is "a microorganism belonging to the genus Enterobacter" and is not particularly limited as long as it can decompose organic acids in wastewater.

[0020] The microorganisms used in the present invention may be, for example, microorganisms commercially available or deposited at the Japan Collection of Microorganisms (JCM), the American Type Culture Collection (ATCC), or the NITE Biological Resource Center (NBRC), or may be microorganisms collected from soil, wastewater, etc. In addition, the microorganisms used may be wild-type microorganisms, or genetically modified microorganisms.

[0021] Preferably, the microorganism of the present invention is a microorganism belonging to the genus Enterobacter having a 16S rDNA consisting of a base sequence having 98% or more, preferably 99% or more identity to the base sequence shown in SEQ ID NO: 1. Such a microorganism can be obtained by searching a publicly available database using BLAST or the like. Examples of the microorganism of the present invention are shown in Tables 1 and 2 below.

[0022] [Table 1]

[0023] [Table 2]

[0024] Preferred examples of the microorganism include NITE BP-03850 and / or Enterobacter tabaci JCM 19646.

[0025] NITE BP-03850 is a new strain of Enterobacter sp. discovered by the inventors, which is capable of decomposing and assimilating high concentrations of organic acids. This novel microorganism has the microbiological properties shown in Table 3 below, and has been internationally deposited at the National Institute of Technology and Evaluation, National Patent Microorganism Depositary (NPMD), Biotechnology Center, under the international deposit number NITE BP-03850.

[0026] [Table 3]

[0027] Enterobacter tabaci JCM 19646 is a gram-negative rod-shaped bacterium discovered by Yan-Qing Duan, Xing-Kui Zhou, Li Di-Yan, Qing-Qing Li, and others, and is capable of decomposing and assimilating organic acids. This microorganism is available from the Laboratory of Microorganisms (JCM) (JCM 19646).

[0028] The microorganism of the present invention can be cultured using a medium containing nutrient sources necessary for the growth of ordinary microorganisms and assimilable by the present bacterium, such as a carbon source, a nitrogen source, and inorganic salts. For example, organic acids such as formic acid, malic acid, fumaric acid, and acetic acid, sugars such as glucose, and natural products such as yeast extract can be used as carbon sources. Natural products such as ammonium salts such as ammonium sulfate and peptone can be used as nitrogen sources. Metal ions such as potassium salts, calcium salts, sodium salts, phosphates, and magnesium salts can be used as inorganic components.

[0029] As the medium, for example, commercially available LB medium or 2-YT medium can be used, and inorganic components may be added thereto.

[0030] The microorganism of the present invention is aerobically cultured using the above medium at 10 to 40° C., preferably 20 to 35° C., and at a pH of 5.5 to 8.0, preferably 6.0 to 7.5.

[0031] (3) Wastewater treatment method (3-1) Treatment with microorganisms The wastewater may be treated by contacting the wastewater with the microorganisms. The method for contacting the wastewater with the microorganisms is not particularly limited, and the microorganisms may be added to the wastewater, or the wastewater may be added to the microorganisms. The wastewater may be treated by an activated sludge method or a bioreactor method.

[0032] When the activated sludge method is used, for example, the microorganism of the present invention may be contacted in a tank containing activated sludge mixed with wastewater, or the microorganism of the present invention may be added to activated sludge and then contacted with wastewater.

[0033] When carried out using a bioreactor system, microorganisms are immobilized on an insoluble solid and brought into contact with an aqueous solution (wastewater) containing the organic compounds, thereby decomposing the organic compounds.

[0034] The wastewater treatment using microorganisms may be a continuous reaction or a batch reaction, and those skilled in the art can appropriately select the reaction method depending on the amount and type of wastewater.

[0035] The amount of the microorganisms to be added is not limited and can be appropriately set depending on the amount and quality of the wastewater to be treated, etc. The microorganisms may be added all at once at the start of the reaction, or may be added multiple times.

[0036] When the microorganisms are added multiple times, they may be added at a constant pace, or may be added appropriately while observing the wastewater treatment rate, etc.

[0037] The treatment time with the microorganisms (the time during which the microorganisms are in contact with the wastewater) is not particularly limited, and for example, the treatment can be continued until the compound to be decomposed falls to below the detection limit.

[0038] The temperature of the wastewater during the microbial treatment is not limited as long as the microbial treatment can be carried out efficiently. For example, the wastewater is treated at 10 to 60°C, preferably 15 to 37°C.

[0039] The pH of the wastewater to be treated can be appropriately set so that the treatment by the microorganisms can be carried out efficiently, for example, at pH 5.5 to 9.0, preferably pH 5.5 to 8.5, under aerobic conditions.

[0040] According to the wastewater treatment method of the present invention, wastewater containing formic acid at a high concentration, such as more than 2000 ppm, can be efficiently decomposed.

[0041] (3-2) Use of membrane separation equipment In the wastewater treatment method of the present invention, it is also possible to use (combined use) a membrane separation method. The membrane separation method means a method of separating water (treated water) treated by microorganisms using a separation membrane (in the presence of a membrane separation device). Among them, one of the preferred embodiments of the present invention is a membrane separation activated sludge method (MBR: Membrane Bio Reactor). MBR is a type of activated sludge method, in which treated water and activated sludge are separated using a microfiltration membrane (MF membrane) or an ultrafiltration membrane (UF membrane). By treating wastewater with the microorganisms of the present invention, organic acids in the wastewater are decomposed, the decrease in the capacity of the activated sludge is suppressed, and efficient wastewater treatment is possible.

[0042] In the present invention, the membrane separation device can be installed in a tank in which wastewater is treated by microorganisms, or it can be installed in a tank separate from the tank in which wastewater is treated by microorganisms, and treated water can be introduced into the separate tank for membrane separation. A plurality of separate tanks can also be installed. By treating microorganisms in the presence of the membrane separation device, the reaction efficiency of the microorganisms can be improved. As a result, it is possible to reduce the amount of microorganisms required for wastewater treatment and to shorten the treatment (reaction) time.

[0043] The type and size of the membrane separation device used in the present invention are not particularly limited, and can be appropriately selected depending on the size of the wastewater treatment facility, the amount of wastewater, etc.

[0044] The type of separation membrane used in the membrane separation device is preferably a microfiltration membrane (MF membrane) or an ultrafiltration membrane (UF membrane).

[0045] The shape of the separation membrane may be a hollow fiber membrane, a flat membrane, a tubular membrane, a bag-shaped membrane, etc. Among these, a hollow fiber membrane is preferred because it allows for a high degree of integration of the membrane area when compared on a volume basis.

[0046] Examples of materials for the separation membrane include organic materials (cellulose, cellulose acetate, polyolefins such as polyethylene and polypropylene, aromatic polyamides, polysulfones, polyvinyl alcohol, polymethyl methacrylate, polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, polycarbonate, polytetrafluoroethylene, etc.), metals (stainless steel, etc.), and inorganic materials (ceramics, etc.). The material for the separation membrane is appropriately selected depending on the properties of the wastewater, etc.

[0047] The pore size of the separation membrane may be appropriately selected depending on the purpose of treatment. In the membrane bioreactor (MBR) described below, the pore size of the separation membrane is usually preferably 0.001 to 3 μm. If the pore size is less than 0.001 μm, the resistance of the membrane is likely to be large. If the pore size exceeds 3 μm, the sludge cannot be completely separated, and the quality of the treated water (permeate) may deteriorate. The pore size of the separation membrane is more preferably 0.04 to 1.0 μm, which is the range of a microfiltration membrane.

[0048] In the present invention, the membrane separation device may be prepared using a commercially available separation membrane, or a commercially available membrane separation device may be used. For example, a hollow fiber membrane SADF (trade name "Sterapore SADF") manufactured by Mitsubishi Chemical Corporation may be used. TM "), a module using the DiaFellow membrane separation activated sludge process equipment manufactured by Mitsubishi Chemical Corporation. TM AM, etc. In the wastewater treatment method of the present invention, one or more membrane separation devices may be provided in the wastewater treatment facility.

[0049] The amount of aeration when using the membrane separation device is not particularly limited, and can be appropriately selected depending on the amount and quality of wastewater, the type of microorganisms used, and the like.

[0050] (3-3) Primary treatment Before treating wastewater with microorganisms, it is possible to carry out a process to remove solids from the wastewater (hereinafter referred to as "primary treatment"). Examples of such a process include a screen that uses nets or fences to remove large debris, a grit tank that settles and removes sand, and a primary sedimentation tank that settles and removes mud.

[0051] (3-4) Secondary treatment Following the primary treatment, a treatment (hereinafter referred to as "secondary treatment") may be carried out in which organic matter in the wastewater is removed using microorganisms such as activated sludge.

[0052] (3-5) Tertiary treatment If there are compounds that have not been completely treated by the microorganisms, further treatment (hereinafter referred to as "tertiary treatment") may be carried out after the microbial treatment in order to remove the compounds. By using a tertiary treatment in combination, the quality of the wastewater can be improved and the COD(Mn) or COD(Cr) value described below can be further reduced.

[0053] The type of tertiary treatment is not particularly limited and can be appropriately selected depending on the type of wastewater, the type of compounds that could not be treated by microorganisms, etc. Examples of the tertiary treatment include treatment with activated carbon, treatment with a Fenton catalyst, and treatment with a polycyclic aromatic oxidation catalyst.

[0054] (3-5-1) Activated carbon treatment Activated carbon can remove compounds that could not be completely treated by microorganisms from wastewater by adsorbing them. The activated carbon used is preferably one obtained by carbonizing (heat treating) mineral raw materials such as petroleum pitch, coal, and coke, or plant raw materials such as wood and fruit shells such as coconut shells, or by subjecting them to heat treatment and activation, and commercially available activated carbon for liquid phase can be used.

[0055] The method of treatment with activated carbon is not particularly limited, and can be carried out, for example, by filling the inside of a cylindrical object such as a column with activated carbon and passing the wastewater to be treated through it (activated carbon adsorption tower). The space velocity SV of the water passing through the activated carbon adsorption tower is not particularly limited. For example, the SV can be appropriately determined depending on the ease of adsorption of components contained in the wastewater to activated carbon and the amount of adsorption, the desired water quality requirements after treatment, the effluent standard value, etc. For example, when adsorption to activated carbon is difficult (the amount of adsorption is small) or when the water quality requirements for the wastewater are strict, the SV can be made small and the contact time between the water to be treated (wastewater) and activated carbon can be extended.

[0056] (3-5-2) Fenton catalyst treatment The reaction in which hydrogen peroxide reacts with ferrous ions (iron catalyst) to generate hydroxyl radicals is called the Fenton reaction. Hydroxyl radicals have strong oxidizing power, and this oxidizing power can be used to decompose harmful substances and persistent pollutants and to sterilize. The Fenton catalyst is the iron catalyst used in this Fenton reaction. The Fenton catalyst can remove compounds that could not be completely treated by microorganisms from wastewater by breaking them down with hydroxyl radicals.

[0057] The iron catalyst, which is a Fenton catalyst, is not particularly limited as long as it dissolves in water to generate ferrous ions. For example, ferrous salt or ferrous oxide is preferred. Among them, ferrous sulfate or ferrous chloride is more preferred because it does not need to be managed according to wastewater standards and has excellent solubility.

[0058] The method of treatment using the Fenton catalyst is not particularly limited as long as it can decompose the target compound. For example, an iron reagent is added to the wastewater to be treated while stirring the wastewater as necessary, and then hydrogen peroxide is added to cause a reaction. The amount of the iron reagent added, the amount of hydrogen peroxide added, and the reaction time after adding both can be appropriately selected depending on the type of compound contained in the wastewater to be treated and the amount of the wastewater.

[0059] (3-5-3) Polycyclic aromatic hydrocarbon decomposition enzyme treatment Polycyclic aromatic decomposition enzymes can decompose the persistent polycyclic aromatics that could not be completely treated by microorganisms and remove them from wastewater. The type of polycyclic aromatic decomposition enzyme used is not particularly limited, but it is preferable to use one that has the activity of catalyzing the oxidation and polymerization of persistent polycyclic aromatics such as humins in the presence of hydrogen peroxide. Examples of such polycyclic aromatic decomposition enzymes include peroxidase and laccase.

[0060] As the peroxidase, peroxidase derived from Armorica rusticana of the Brassicaceae family is preferably used, and as the laccase, laccase derived from Trametes versicolor, Rhus vernicifera, Agaricus bisporus, Aspergillus sp., etc. is preferably used.

[0061] The method of treatment with the polycyclic aromatic hydrocarbon decomposing enzyme is not limited, and the enzyme may be added to the wastewater to be treated, or the enzyme may be immobilized as a monomer. The amount of the polycyclic aromatic hydrocarbon decomposing enzyme added to the wastewater is appropriately determined depending on the type and amount of the wastewater, and may be, for example, 0.1 to 300 ppm, preferably 0.5 to 200 ppm, and more preferably 1 to 100 ppm. The treatment time with the polycyclic aromatic hydrocarbon decomposing enzyme is also not particularly limited, and is appropriately determined depending on the amount and quality of the wastewater, the type and quality of the enzyme used, etc.

[0062] (4) Wastewater obtained according to the present invention According to the present invention, organic acids contained in wastewater can be efficiently decomposed. Furthermore, by treating the wastewater after microbial treatment with activated carbon, Fenton's catalyst, polycyclic aromatic decomposition enzymes, etc. (tertiary treatment), substances that could not be removed by the microbial treatment can be removed, and wastewater of higher quality can be obtained.

[0063] COD (chemical oxygen demand) and BOD (biological oxygen demand) are commonly used as indicators of water quality. COD is the amount of oxygen required to oxidize the amount of oxidizable substances in water, while BOD is the amount of oxygen required to oxidize only biodegradable organic matter. COD is measured using potassium dichromate as an oxidizing agent (COD(Cr)), potassium permanganate as an oxidizing agent (COD(Mn)), and alkaline or potassium manganate as COD(Cr). OH etc.

[0064] According to wastewater treatment standards, wastewater treated by the method of the present invention can provide high-quality wastewater in which organic acids have been decomposed.

[0065] 2. Wastewater treatment agents The present invention also provides a microbial preparation (a wastewater treatment agent) for the wastewater treatment method described above. The wastewater treatment agent of the present invention may be a liquid (suspension) or a solid. When the wastewater treatment agent is used as a liquid, the microorganisms are cultured to a desired concentration, and then the wastewater treatment agent can be used as it is or with the addition of additives such as preservatives and stabilizers. In addition, the microorganisms are cultured to a desired concentration, and then, as necessary, separated, washed, purified, concentrated, or the like, or further suspended in an aqueous solution containing a buffer solution or the like, can also be used as the wastewater treatment agent. The microorganisms may be immobilized on a suitable carrier.

[0066] When the wastewater treatment agent is used as a solid, the microorganism is cultured to a desired concentration, and then trehalose, sodium glutamate, skim milk, or the like is added as a freeze-drying protection agent as necessary, followed by freeze-drying. The freeze-dried bacterial cells can be used as they are, or mixed with various additives, as the wastewater treatment agent.

[0067] The wastewater treatment agent of the present invention contains at least one microorganism selected from the genus Enterobacter as an active ingredient. The microorganism preferably has 16S rDNA consisting of a base sequence having 98% or more, preferably 99% or more identity with the base sequence shown in SEQ ID NO:1.

[0068] Specific examples of the above microorganisms are as described in 1(2). Among them, NITE BP-03850 and / or Enterobacter tabaci JCM 19646 are preferred.

[0069] The wastewater treatment agent of the present invention contains the above-mentioned microorganism and components necessary for maintaining the microorganism, and is used by adding it to activated sludge. Alternatively, the wastewater treatment agent may be prepared by mixing the microorganism of the present invention with existing activated sludge. 3.Microbial preparations for decomposing organic acids The present invention also provides the above-mentioned microbial preparation for decomposing an organic acid. The target organic acid is not particularly limited, but examples thereof include carboxylic acids or dicarboxylic acids having 1 to 6 carbon atoms, such as formic acid, acetic acid, fumaric acid, maleic acid, lactic acid, and malic acid.

[0070] The microbial preparation for decomposing organic acids of the present invention contains at least one microorganism selected from the genus Enterobacter and components necessary for maintaining the microorganism, and is used for decomposing organic acids.

[0071] 4. Use of microorganisms for wastewater treatment or decomposition of organic acids. The present invention also provides a use of the microorganism described in (2) of 1 above for treating wastewater containing organic acids or decomposing organic acids. Such use can be carried out according to the description of 1 above. EXAMPLES

[0072] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0073] [Example 1] Formic acid degradation ability of Enterobacter tabaci (JCM 19646) Enterobacter tabaci (JCM 19646) was contacted with wastewater containing phenol or methanol containing formic acid together with activated sludge (hereafter referred to as activated sludge) collected from a phenol wastewater treatment facility in the company, and the formic acid decomposition ability was investigated.

[0074] The components shown in Table 4 below were dissolved in 1 L of distilled water, sterilized in an autoclave at 121°C for 15 minutes, and cooled to room temperature to prepare a culture medium. Sterilized sodium formate was added to the prepared medium to a concentration of 0.3%.

[0075] [Table 4]

[0076] Wastewater containing formic acid at a concentration of 2,000 to 2,500 mg / L together with phenol or methanol was collected and sterilized using a membrane filter with 0.22 μm pores.

[0077] E. tabaci (JCM 19646), which had been cultured in a test tube in advance, was added to 10 mL of activated sludge to a final concentration of OD600 = 0.75, and the sludge and bacteria were washed with PBS. The washed sludge containing the bacteria was suspended in 10 mL of the above wastewater and transferred to a 100 mL shake flask, and degradation treatment was carried out at 30 °C and 180 rpm. The wastewater was replaced with new water every 24 hours, and the degradation test was carried out for 3 days. The formic acid concentration was measured 6 hours and 24 hours after the wastewater replacement. The results are shown in Figure 1.

[0078] [Example 2] Formic acid degradation ability of Enterobacter sp. new species strain (NITE BP-03850) Enterobacter sp. new species strain was contacted with activated sludge and wastewater containing phenol or methanol to which formic acid had been added, and the formic acid decomposition ability was investigated.

[0079] The components listed in Table 3 below were dissolved in 1 L of distilled water, sterilized in an autoclave at 121°C for 15 minutes, and cooled to room temperature to prepare a culture medium. Sterilized sodium formate (final concentration 0.3%) was added to the prepared medium.

[0080] [Table 5]

[0081] Wastewater containing formic acid at a concentration of 2,000 to 2,500 mg / L together with phenol or methanol was collected and sterilized using a membrane filter with 0.22 μm pores.

[0082] A new strain of Enterobacter sp., previously cultured in a test tube, was added to 10 mL of activated sludge to a final concentration of OD600 = 0.75, and the sludge and bacteria were washed with PBS. 10 mL of the above wastewater was suspended in the washed sludge containing the bacteria, transferred to a 100 mL shake flask, and degradation treatment was carried out at 30 °C and 180 rpm. The wastewater alone was replaced with new water every 24 hours, and the degradation test was carried out for 3 days. The formic acid concentration was measured 6 hours and 24 hours after the effluent replacement (Figure 2).

[0083] [Example 3] Malate decomposition ability of Enterobacter sp. new species strain (NITE BP-03850) The ability of Enterobacter sp. new species to degrade and utilize malate was investigated in a mineral salt medium containing malate as the only carbon source.

[0084] The components shown in Table 4 below were dissolved in 1 L of distilled water, sterilized in an autoclave at 121°C for 15 minutes, and cooled to room temperature to prepare a culture medium. After preparation, a sterilized malic acid solution was added to the medium to give a final concentration of 13.5 g / L.

[0085] [Table 6]

[0086] 5 mL of the reaction solution was placed in a test tube, and the bacterial cell solution was added. The mixture was cultured at 30°C for 18 hours at 200 rpm. All of the 13,490 mg / L of malic acid was decomposed and assimilated (Figure 3).

[0087] [Example 4] Fumaric acid degradation ability of Enterobacter sp. new strain (NITE BP-03850) The fumaric acid decomposition and assimilation ability of Enterobacter sp. new species strain was investigated under the same conditions as in Example 3, except that fumaric acid was used instead of malic acid.

[0088] The components listed in Table 4 were dissolved in 1 L of distilled water, sterilized in an autoclave at 121°C for 15 minutes, and cooled to room temperature to prepare a culture medium. After preparation, a sterilized fumaric acid solution was added to the medium to give a final concentration of 6.78 g / L.

[0089] 5 mL of the reaction solution was placed in a test tube, and the bacterial cell solution was added. The mixture was cultured at 30°C for 18 hours at 200 rpm. 6,780 mg / L of fumaric acid was decomposed and assimilated to 0.98 mg / L, which is more than 88% decomposition (Figure 4).

[0090] [Example 5] Acetic acid decomposition ability of Enterobacter sp. new species strain (NITE BP-03850) The acetic acid decomposition and assimilation ability of Enterobacter sp. new species strain was investigated under the same conditions as in Example 3, except that acetic acid was used instead of malic acid.

[0091] The components listed in Table 4 were dissolved in 1 L of distilled water, sterilized in an autoclave at 121°C for 15 minutes, and cooled to room temperature to prepare a culture medium. After preparation, sterilized acetic acid solution was added to the medium to give a final concentration of 9.13 g / L.

[0092] 5 mL of the reaction solution was placed in a test tube, and the bacterial cell solution was added. The mixture was cultured at 30°C for 18 hours at 200 rpm. 9,130 ​​mg / L of acetic acid was decomposed and assimilated to 8,2490 mg / L, with more than 13% being decomposed (Figure 5).

[0093] According to the wastewater treatment method of the present invention, as shown in Examples 1 and 2, 10% or more of formic acid in a 150 mg / L phenol aqueous solution can be decomposed in 6 hours in the presence of sludge, and the decomposition can be continued for 3 days or more even if the wastewater is replaced every 24 hours. Furthermore, according to the wastewater treatment method of the present invention, as shown in Examples 3 to 5, 85% or more of fumaric acid in an aqueous liquid containing no organic matter other than 6800 mg / L fumaric acid can be decomposed within 24 hours. Similarly, 13,400 mg / L of malic acid can be completely decomposed within 24 hours, and 9,100 mg / L of acetic acid can be decomposed by 13% or more within 24 hours. [Industrial Applicability]

[0094] The wastewater treatment method of the present invention can efficiently remove organic acids from wastewater, even when the wastewater contains phenol or methanol. According to the method of the present invention, a decrease in the treatment capacity of activated sludge can be prevented, and high concentrations of organic acids in wastewater can be efficiently decomposed and removed.

[0095] All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety. [Sequence table] SEQ ID NO: 1: 16S rDNA

Claims

1. A method for treating wastewater, comprising contacting wastewater containing an organic acid with a microorganism belonging to the genus Enterobacter.

2. The method for treating wastewater according to claim 1, wherein the wastewater contains a bactericidal component.

3. 2. The wastewater treatment method according to claim 1, wherein the organic acid is a carboxylic acid or dicarboxylic acid having 1 to 6 carbon atoms.

4. 4. The wastewater treatment method according to claim 3, wherein the organic acid is at least one selected from the group consisting of formic acid, acetic acid, fumaric acid, maleic acid, lactic acid and malic acid.

5. 3. The wastewater treatment method according to claim 2, wherein the bactericidal component is phenol and / or methanol.

6. 2. The wastewater treatment method according to claim 1, wherein the microorganism belonging to the genus Enterobacter has a 16S rDNA consisting of a base sequence having an identity of 98% or more with the base sequence shown in SEQ ID NO:

1.

7. The wastewater treatment method according to claim 1, wherein the microorganism belonging to the genus Enterobacter is NITE BP-03850 and / or Enterobacter tabaci JCM 19646.

8. 2. The method for treating wastewater according to claim 1, wherein the wastewater is at least one type of wastewater selected from the group consisting of special wastewater, sewage wastewater and miscellaneous wastewater.

9. A wastewater treatment agent comprising NITE BP-03850 and / or Enterobacter tabaci JCM 19646.

10. A microorganism identified in NITE BP-03850.

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