Bioremediation accelerator, method of manufacturing the same, method of purifying contaminated ground

Abstract

To provide a novel bioremediation accelerator, a method of manufacturing the bioremediation accelerator, and a method of purifying contaminated soil.SOLUTION: A bioremediation accelerator includes rice malt.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a bioremediation promoter, a method for producing the same, and a method for purifying contaminated ground. [Background technology]

[0002] Bioremediation and other methods have been known for some time as methods for purifying ground contaminated by volatile organic compounds (hereinafter also referred to as "VOCs") and the like. Bioremediation is a method of using microorganisms to decompose and detoxify contaminants in the ground. Examples of bioremediation include a method of purifying contaminants by multiplying and activating microorganisms that decompose contaminants that are originally present in the contaminated ground (see, for example, Patent Document 1), and a method of introducing externally cultured microorganisms that decompose contaminants into the contaminated ground and then multiplying and activating these microorganisms within the ground to purify the contaminants (see, for example, Patent Document 2).

[0003] Bioremediation has the advantage of being able to purify pollutants under mild conditions and at low cost. However, in soils where VOC-degrading microorganisms are relatively scarce, it takes time to create an anaerobic environment in which VOC-degrading microorganisms can grow, resulting in a long remediation process. Therefore, there is a need for a new method of promoting bioremediation that can be used in soils where VOC-degrading microorganisms are relatively scarce. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4529667 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-301178 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above circumstances, an object of the present invention is to provide a novel bioremediation promoter, a method for producing the same, and a method for purifying contaminated ground. [Means for solving the problem]

[0006] As a result of extensive research to solve the above problems, the inventors discovered that the purification of pollutants by bioremediation can be promoted by adding rice koji to a bioremediation promoter, and thus completed the present invention.

[0007] That is, the present invention relates to the following inventions. [1] A bioremediation accelerator containing rice koji. [2] The bioremediation accelerator according to [1], wherein the mass ratio of rice koji to water (rice koji (dry mass):water) is 1:10 to 1:40. [3] A method for purifying contaminated ground, comprising a step of supplying the bioremediation promoter according to any one of [1] and [2] to the contaminated ground. [4] A method for producing a bioremediation promoter, comprising a step of dissolving rice koji in water. [5] The bioremediation promoter according to [4], further comprising a step of adding a microbial growth inhibitor in the step of dissolving rice koji in water. [Effects of the Invention]

[0008] The present invention provides a novel bioremediation accelerator, a method for producing the same, and a method for remediating contaminated ground. The bioremediation accelerator, the method for producing the same, and the method for remediating contaminated ground according to the present invention alleviate the disadvantage of the time required to create an anaerobic environment conducive to the proliferation of VOC-degrading microorganisms, which has traditionally taken time to decompose VOCs. Furthermore, the bioremediation accelerator, the method for producing the same, and the method for remediating contaminated ground according to the present invention are based on the discovery that bioremediation can be effectively promoted by using rice koji, which is rich in amino acids and vitamins. This allows the use of readily available, inexpensive rice koji as a bioremediation accelerator, thereby offering the advantage of low-cost remediation of contaminants. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a graph showing the change in each VOC concentration (mg / L) over time in control area 1-1. [Figure 2] FIG. 2 is a graph showing the change in each VOC concentration (mg / L) over time in control area 1-2. [Figure 3] FIG. 3 is a graph showing the change in each VOC concentration (mg / L) over time in Test Area 1-1. [Figure 4] FIG. 4 is a graph showing the change in each VOC concentration (mg / L) over time in Test Area 1-2. [Figure 5] FIG. 5 is a graph showing the change in each VOC concentration (mg / L) over time in Test Area 2-1. [Figure 6] FIG. 6 is a graph showing the change in each VOC concentration (mg / L) over time in Test Area 2-2. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present invention will be described in detail below, but the present invention is not limited to the following embodiments.

[0011] As used herein, "bioremediation" refers to reducing the concentration of pollutants in contaminated ground by using microorganisms that purify the pollutants. Furthermore, the bioremediation promoter and contaminated soil purification method according to this embodiment can be applied to both biostimulation, which utilizes purification microorganisms that are originally present in the contaminated ground, and bioaugmentation, which introduces microorganisms cultivated outside to purify contaminants into the contaminated ground.

[0012] (Bioremediation accelerator) The bioremediation accelerator according to this embodiment contains rice koji and preferably contains water, and may further contain other components as required.

[0013] <Rice Koji> In this specification, "rice koji" refers to rice that has been steamed and then cultured with koji mold. This "rice koji" is the same as that used to make sake, soy sauce, miso, etc. The rice koji used in this embodiment is not particularly limited and can be selected appropriately depending on the purpose, including dried rice koji, as long as it is generally produced and sold as rice koji.

[0014] <Water> The water used in this embodiment is not particularly limited and can be appropriately selected depending on the purpose. Examples include tap water, groundwater, and distilled water.

[0015] There are no particular restrictions on the mass ratio of rice koji to water in the bioremediation accelerator (rice koji (dry mass):water), and it can be set appropriately depending on the concentration of contaminants in the ground to be purified, the type of ground, the soil quality, etc. The mass ratio of dried rice koji (water content: approximately 3%) to water (rice koji (dry mass):water) is preferably 1:10 to 1:40.

[0016] <Other ingredients> The other components are not particularly limited as long as they are contained in ordinary bioremediation promoters and can be selected appropriately depending on the purpose, and examples thereof include carbon sources, nitrogen sources, phosphorus sources, inorganic ions, vitamins, etc.

[0017] Examples of carbon sources include sugars such as glucose, sucrose, lactose, galactose, fructose, arabinose, maltose, and starch; alcohols such as ethanol, glycerol, mannitol, and sorbitol; organic acids such as gluconic acid, lactic acid, fumaric acid, citric acid, malic acid, and succinic acid; organic acid salts such as sodium salts, potassium salts, and calcium salts of organic acids; gluconic acid derivatives such as gluconic acid amide, gluconic acid ester, and gluconic acid anhydride; fatty acids such as palmitic acid, stearic acid, and linoleic acid; fatty acid salts such as sodium salts, potassium salts, and calcium salts of fatty acids; and fats such as soybean oil, sunflower seed oil, peanut oil, and coconut oil.

[0018] Examples of nitrogen sources include nitrogen-containing organic compounds such as amino acids such as asparagine, glutamine, arginine, lysine, tryptophan, and histidine; urea derivatives such as urea, biuret, triuret, and N-substituted C1-C6 alkyl urea; ammonium salts such as ammonium chloride, ammonium carbonate, ammonium hydrogen carbonate, ammonium sulfate, ammonium nitrate, ammonium acetate, triammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate; nitrates such as ammonium nitrate, sodium nitrate, and potassium nitrate; and nitrites such as sodium nitrite and potassium nitrite.

[0019] Examples of phosphorus sources include trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, triammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate.

[0020] The content ratios of the carbon source, nitrogen source, and phosphorus source are not particularly limited and can be appropriately set depending on the concentration of contaminants in the ground to be purified, the type of ground, soil quality, etc. The molar ratio of C:N:P contained in the carbon source, nitrogen source, and phosphorus source is preferably 20-60:1-6:0.1-0.6, and more preferably 20-50:2-5:0.2-0.5.

[0021] Examples of inorganic ions include potassium, magnesium, and calcium. Examples of vitamins include vitamins A, B, E, biotin, and thiamine.

[0022] The contents of other components are not particularly limited and can be appropriately selected depending on the purpose.

[0023] The formulation of the bioremediation accelerator according to this embodiment is not particularly limited, and any known and commonly used formulation can be selected depending on the intended use. Examples of formulations of the bioremediation accelerator include solution, slurry, suspension, gel, paste, semi-solid, powder, and the like.

[0024] (Method for producing bioremediation accelerator) The method for producing a bioremediation promoter according to this embodiment preferably includes a step of dissolving rice koji in water, and if necessary, a step of adding a microbial growth inhibitor, and further includes other steps as necessary.

[0025] <Process for dissolving rice koji in water> The step of dissolving rice koji in water is a step of dispersing and dissolving rice koji in water to obtain a rice koji solution, for example, by adding dried rice koji to water and mixing them. The mixing method is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include stirring and shaking.

[0026] <Step of adding microbial growth inhibitor> The step of adding a microbial growth inhibitor is a step of adding a microbial growth inhibitor to a rice koji solution. The step of adding a microbial growth inhibitor may be carried out either before or after the step of dissolving rice koji in water, but is preferably carried out simultaneously with the step of dissolving rice koji in water.

[0027] <<Microbial growth inhibitor>> As used herein, the term "microbial growth inhibitor" generally refers to a substance that acts to stop the movement of microorganisms.

[0028] The microbial growth inhibitor is not particularly limited as long as it has the effect of stopping the movement of microorganisms, and can be appropriately selected depending on the purpose, and examples thereof include alkaline agents that become basic when dissolved in water, such as sodium carbonate and sodium hydroxide.

[0029] The content of the microbial growth inhibitor is not particularly limited and can be appropriately selected depending on the purpose. The microbial growth inhibitor may be removed by the microbial growth inhibitor removal step described below, or may be left remaining in the bioremediation promoter.

[0030] <Other processes> The other processes are not particularly limited as long as they do not inhibit the effect of the bioremediation promoter of the embodiment, and can be selected appropriately depending on the purpose. For example, a microbial growth inhibitor removal process, a filtration process, a pH adjustment process, etc. can be included.

[0031] The microbial growth inhibitor removal step can be carried out, for example, by adding a compound that adsorbs the microbial growth inhibitor to the bioremediation promoter.

[0032] The filtration step is a step for removing large particles contained in the bioremediation accelerator. Because the bioremediation accelerator according to this embodiment contains rice koji, there is a possibility that residues that do not dissolve in water may remain during the dissolution process. If the bioremediation accelerator contains insoluble residues, there is a possibility that the injection well may become clogged when the bioremediation accelerator is injected into the ground from the injection well. For this reason, it is preferable to perform a filtration step.

[0033] The pH adjustment step is a step in which the acidity caused by the anaerobic microbial decomposition of rice koji during the bioremediation process is neutralized using a known, commonly used pH adjuster, such as sodium bicarbonate or disodium hydrogen phosphate.

[0034] (Methods for remediating contaminated ground) The method for purifying contaminated ground according to this embodiment includes a step of supplying the bioremediation promoter to the contaminated ground, and may further include other steps as necessary.

[0035] In this specification, "contaminated ground" refers to ground contaminated with volatile organic compounds (VOCs), such as tetrachloroethylene, trichloroethylene, 1,1-dichloroethylene, 1,2-dichloroethylene, chloroethylene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,2-dichloroethane, carbon tetrachloride, dichloromethane, 1,3-dichloropropene, benzene, o-dichlorobenzene, m-dichlorobenzene, and p-dichlorobenzene. In particular, the method for purifying contaminated ground according to this embodiment can be suitably used as a method for purifying tetrachloroethylene, trichloroethylene, 1,1-dichloroethylene, 1,2-dichloroethylene, chloroethylene, and the like.

[0036] <Step of supplying bioremediation accelerator> The method for supplying the bioremediation accelerator to the contaminated ground is not particularly limited, and any known or commonly used method can be used, including, for example, digging a trench on the ground surface, storing the bioremediation accelerator in the trench, and allowing it to permeate into the contaminated ground from the surface, injecting the bioremediation accelerator into the contaminated ground from an injection well, and stirring and mixing the bioremediation accelerator with the contaminated ground using a backhoe, power blender, stabilizer, deep stirring and mixing machine, etc.

[0037] <Other processes> The other steps are not particularly limited and can be selected appropriately depending on the purpose. [Example]

[0038] EXAMPLES The present invention will be specifically explained below by showing examples, but the present invention is not limited to these examples.

[0039] [Evaluation of the mass ratio of rice koji to water] Dried rice koji (Miyako Koji, sold by Ise-So Co., Ltd., moisture content 3.4%) and tap water were placed in a 120 mL medium bottle at the dilution ratio shown in Table 1, and the mixture was allowed to soak in water for two days at room temperature (25°C) using a reciprocating shaker with an amplitude of approximately 5 cm and a shaking frequency of approximately 180 times per minute, to obtain a rice koji solution. The dilution ratio is the mass of tap water divided by the mass of rice koji (dry mass).

[0040] [Table 1]

[0041] The total organic carbon (TOC) concentration (mg / L) in the resulting rice koji lysate was measured using a total organic carbon meter (TOC-L CPH, Shimadzu Corporation). The measurement was performed on the clear supernatant of the rice koji lysate. The amount of dissolved TOC (g) in the solution was calculated from the measured TOC concentration (mg / L), specifically, by multiplying the solution volume (mL) by the TOC concentration (mg / L). Next, the relationship between the amount of TOC dissolved in the solution and the amount of rice koji added to the rice koji solution (TOC dissolution rate: amount of TOC dissolved in solution (g) / amount of rice koji added (g) × 100) is shown in Table 2. The more rice koji components are dissolved in water, the higher the TOC dissolution rate.

[0042] [Table 2]

[0043] The amount of dissolved TOC in a solution generally increases with the amount of rice koji in the solution, i.e., the lower the dilution ratio. However, when comparing the amount of dissolved TOC in the solution per unit of dry rice koji added (TOC dissolution rate), a 10-fold dilution resulted in a higher TOC dissolution rate than a 5-fold dilution. Furthermore, increasing the dilution rate beyond 10-fold tends to result in a gradual decrease in the TOC dissolution rate. Therefore, a 10-fold to 40-fold dilution of rice koji (rice koji (dry mass):water = 1:10 to 1:40) is considered favorable in terms of the dissolution of most rice koji components in water, and is also reasonable in terms of allowing the use of a smaller dissolution vessel.

[0044] [Test Example 1. Evaluation of the VOC decomposition promoting effect of rice koji] The effect of rice koji in promoting VOC decomposition was evaluated by comparing the effects on the time-dependent changes in the concentration of trichloroethylene (hereinafter referred to as "TCE"), a VOC, and the concentration of its decomposition products (1,2-dichloroethylene, 1,1-dichloroethylene, chloroethylene) between a control area that did not contain rice koji and a test area that did contain rice koji.

[0045] <Preparation of control and test plots> 100 mL of tap water was added to 10 g of dried rice koji, and the mixture was shaken for two days in a shaker (amplitude approximately 5 cm, shaking rate approximately 100 times / min) to prepare a rice koji lysate with a mass ratio of rice koji (dry mass):water of 1:10. The TOC concentration in the supernatant of the resulting rice koji lysate was measured and found to be approximately 38 mg / mL. 50 g (wet weight) of mountain sand (produced in Aichi Prefecture) was added as soil to a 130 mL glass medium bottle. Next, the specified amount of deionized water shown in Table 3 was added, followed by the amount shown in Table 3 of rice koji solution or chloroclean (10% wet weight aqueous solution). 0.2 mL of a cultured solution of VOC-degrading bacteria collected from a VOC-contaminated site was added as a source of VOC-degrading bacteria, followed by 1 mL of a saturated TCE solution. Then, 10 mL of a 5% aqueous solution of sodium bicarbonate (hereinafter also referred to as "sodium bicarbonate") was added as a pH adjuster to create control plots 1-1 and 1-2 and test plots 1-1 and 1-2.

[0046] In the test plots containing only rice koji lysate, chloroclean, or a combination of rice koji lysate and chloroclean (control plot 1-2, test plots 1-1 and 1-2), the amount of additive was adjusted so that the TOC amount was 90 mg / experimental plot.In the test plot containing rice koji lysate and chloroclean (test plot 1-2), the amount of additive was adjusted so that the organic carbon derived from the rice koji lysate was 30 mg, the organic carbon derived from chloroclean was 60 mg, and the TOC amount was 90 mg / experimental plot. In addition, in control areas 1-1 and 1-2 and test areas 1-1 and 1-2, the amount of VOC-decomposing bacteria culture solution added was about 1 / 10 of that used in normal experiments, assuming ground with very little VOC-decomposing bacteria.

[0047] [Table 3]

[0048] Details of each component listed in Table 3 are as follows. Chloroclean®: A material containing sodium gluconate, urea, and sodium dihydrogen phosphate in a weight ratio of 93:6:1, with a total organic carbon concentration of 31% (by dry weight) (C:N:P (molar ratio) = 34:3:0.3) Dried rice koji (Miyako koji, sold by Iseso Co., Ltd.)

[0049] <Measurement of various VOC concentrations> The solutions from each control and test group were collected with a syringe, and the concentrations of trichloroethylene (TCE), 1,2-dichloroethylene (1,2-DCE), and chloroethylene (CE) were measured using a gas chromatograph (PID detector). The results are shown in Figures 1 to 4.

[0050] Figure 2 shows that in the control area 1-2 containing chloroclean, the TCE concentration decreased rapidly after 20 days, while the 1,2-DCE concentration increased. However, no increase in CE was observed, indicating that 1,2-DCE decomposition did not progress in the control area 1-2. Therefore, it was found that decomposition of volatile organic compounds (VOCs) did not progress in the control area 1-2.

[0051] On the other hand, Figure 3 shows that in Test Area 1-1, TCE decreased rapidly from the early stage and was almost completely decomposed by about 15 days. The amount of 1,2-DCE increased from the early stage, peaked at about 15 days, and was almost completely decomposed by about 40 days. CE began to be generated at about 15 days and was almost completely decomposed by about 40 days. Furthermore, Figure 4 shows that in test area 1-2, TCE decreased rapidly from the early stage and was almost completely decomposed by about 30 days. The amount of 1,2-DCE increased from the early stage, peaked at about 20 days, and was almost completely decomposed by about 60 days. CE began to be generated at about 30 days and was almost completely decomposed by about 70 days. Therefore, it was found that decomposition of volatile organic compounds (VOCs) progressed in test plots 1-1 and 1-2.

[0052] [Test Example 2. Evaluation of the VOC decomposition promotion effect by using a microbial inhibitor] In Test Example 1, when the results of the test section containing only rice koji lysate and the test section containing only chloroclean (control section 1-2, test section 1-1) were compared, it was found that VOCs were decomposed more quickly with rice koji lysate alone. This is thought to be because rice koji contains more useful components that activate VOC-decomposing microorganisms than chloroclean. Therefore, we added a microbial inhibitor to the rice koji lysate during the dissolution process to suppress the activity of koji mold during the dissolution process, and then investigated it.

[0053] <Preparation of test plots> 10 g of dried rice koji, 1 g of sodium carbonate as a microbial inhibitor, and 100 mL of tap water were added, and the mixture was shaken for two days in a shaker (amplitude approximately 5 cm, shaking frequency approximately 100 times / min). The TOC concentration in the supernatant of the rice koji solution was measured and found to be approximately 12 mg / mL. In the same order and manner as in Test Example 1, mountain sand (produced in Aichi Prefecture), deionized water, rice koji dispersion with added sodium carbonate (a 10-fold diluted solution to which sodium carbonate was added), chloroclean (a 10% aqueous solution by wet weight), VOC-decomposing bacterial solution, TCE saturated aqueous solution, and 5% aqueous solution of sodium bicarbonate were added in the amounts shown in Table 4 to 130 mL glass medium bottles to prepare Test Areas 2-1 and 2-2.

[0054] [Table 4]

[0055] <Measurement of various VOC concentrations> The solution from each test area was collected with a syringe, and the concentrations of trichloroethylene (TCE), 1,2-dichloroethylene (1,2-DCE), and chloroethylene (CE) were measured using a gas chromatograph (PID detector). The results are shown in Figures 5 and 6.

[0056] Comparing test plots 1-1 (Figure 3) and 2-1 (Figure 5), it was found that none of TCE, 1,2-DCE, and CE were detected, i.e., the time until TCE was completely decomposed was approximately 40 days in test plot 1-1 and approximately 35 days in test plot 2-1. From these results, it can be said that adding the microbial inhibitor accelerated VOC decomposition by approximately one week. Next, comparing test plots 1-2 (Figure 4) and 2-2 (Figure 6), it was found that none of TCE, 1,2-DCE, and CE were detected, i.e., the time until TCE was completely decomposed was approximately 70 days in test plot 1-2 and approximately 40 days in test plot 2-2. From these results, it can be said that in the system containing rice koji lysate and chloroclean, adding rice koji lysate containing a microbial inhibitor during the rice koji dissolution process accelerated VOC decomposition by approximately one month. From the above, it is thought that by suppressing the activity of koji mold attached to the surface of rice koji with sodium carbonate, the consumption of useful components contained in rice koji by koji mold is reduced, and these useful components are consumed to improve the activity of VOC-decomposing bacteria, resulting in promoted VOC decomposition.

Claims

1. A bioremediation promoter containing rice koji.

2. Further containing water, 2. The bioremediation accelerator according to claim 1, wherein the mass ratio of the rice koji to the water (rice koji (dry mass) : water) is 1:10 to 1:

40.

3. A method for remediating contaminated ground, comprising: The method includes a step of supplying the bioremediation promoter according to claim 1 or 2 to the contaminated ground. Methods for purifying contaminated ground.

4. A method for producing a bioremediation promoter, comprising a step of dissolving rice koji in water.

5. 5. The method for producing a bioremediation promoter according to claim 4, further comprising the step of adding a microbial growth inhibitor.

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