JP6155773B2 - Ground purification method - Google Patents

Description

  The present invention purifies the ground by injecting into the ground contaminated with VOC (Volatile Organic Compounds) a nutrient for activating VOC-degrading microorganisms that inhabit the ground. It relates to a purification method.

  There is known a ground purification method for purifying a ground contaminated with VOCs by injecting a nutrient for activating VOC-degrading microorganisms that inhabit the ground. As an example of this nutrient, Patent Document 1 describes that corn steep liquor and a basic pH adjuster are added to contaminated soil.

JP 2007-222823 A

  In the technique of Patent Document 1, the order of addition and mixing of corn steep liquor and basic pH adjuster is not particularly limited, and these addition and mixing may be performed sequentially or simultaneously. Has been.

  Here, corn steep liquor is a by-product when producing corn starch. Specifically, it is a residue produced in an immersion process by acid (sulfurous acid) or lactic acid fermentation for separating corn epidermis. This corn steep liquor is rich in minerals and is acidic. For this reason, when a basic pH adjuster contacts corn steep liquor, SS (Suspended Solid) is aggregated and increased by a neutralization reaction, and there is a problem that the injection well is clogged.

  The present invention has been made in view of such circumstances, and its main purpose is to suppress clogging of the injection well.

In order to achieve the above object, the present invention provides a ground purification method for purifying the ground by injecting a nutrient for activating VOC-degrading microorganisms into the ground contaminated with VOC, and comprising a corn steep liquor stock solution was added an acidic solution with diluted with water, and nutrients material manufacturing process for manufacturing a nutritional material pH of 6 or less, the injection wells provided in the ground, and nutrition material injection step of injecting the nutrient material An alkaline solution injection step of injecting an alkaline solution into the injection well after the nutrient material is injected is performed.

  According to the present invention, since the alkaline solution is injected into the injection well after the nutrient material is injected, the contact opportunity between the nutrient material and the alkaline solution in the injection well can be reduced. Thereby, the neutralization reaction in an injection well is suppressed and SS aggregation and increase can be reduced. As a result, clogging of the injection well due to SS aggregation and increase can be suppressed.

Moreover, since the pH is adjusted to 6 or less by adding an acidic solution to the diluted corn steep liquor with respect to the nutrient material to be manufactured, aggregation and increase of SS in the injection well can be further reduced.

Further, the present invention is a ground purification method for purifying the ground by injecting a nutrient that activates VOC-degrading microorganisms into the ground contaminated with VOC, and in an injection well provided in the ground, A nutrition material injection step for injecting a nutrient material mainly composed of corn steep liquor, and an alkali solution injection step for injecting an alkaline solution into the injection well after the nutrient material has been injected , A confirmation step for confirming whether or not the nutrient material remains is performed after the nutrient material injection step, and the alkali solution injection step is confirmed to be free of the nutrient material in the confirmation step. It is characterized by being performed on the condition. In this purification method, since the alkaline solution is injected with no nutrient remaining, it is possible to prevent aggregation and increase of SS in the injection well. And as this confirmation process, measuring the pH of the liquid stored by the injection well is performed suitably.

Further, the present invention is a ground purification method for purifying the ground by injecting a nutrient that activates VOC-degrading microorganisms into the ground contaminated with VOC, and in an injection well provided in the ground, A nutrition material injection step for injecting a nutrient material mainly composed of corn steep liquor, and an alkali solution injection step for injecting an alkaline solution into the injection well after the nutrient material has been injected , the water injection process for injecting water, performed after said nutritional material injection step, the alkaline solution injection step, and carrying out after the water injection process. In this ground purification method, the nutrient material is pushed out to the contaminated ground by the water injected in the water injection step, so that aggregation and increase of SS in the injection well can be prevented.

Further, the present invention is a ground purification method for purifying the ground by injecting a nutrient that activates VOC-degrading microorganisms into the ground contaminated with VOC, and in an injection well provided in the ground, The nutrient solution injection step of injecting a nutrient material mainly composed of corn steep liquor, and the alkali solution injection step of injecting an alkali solution into the injection well after the nutrient material is injected, the alkali solution injection in step, an alkaline aqueous solution containing a carbon source of the VOC decomposing microorganism, characterized by injecting into the injection wells. In this ground purification method, even if nutrients that have permeated the ground due to the injection of the alkaline solution are poured, this can be compensated by the carbon source.

  According to the present invention, clogging of an injection well can be suppressed while using a nutrient containing corn steep liquor as a main component.

It is a figure which shows the main component and analysis method of corn steep liquor. It is a figure explaining the test conditions in an SS measurement test, and the result. It is an image which shows SS which remained on the sieve. It is a figure explaining the test apparatus of a permeability test. It is a figure which shows the result of a permeability test. It is a figure explaining the test apparatus of a VOC decomposition | disassembly test. It is a figure explaining the test conditions of a VOC decomposition | disassembly test. It is a graph of VOC density | concentration change of sample No1. It is a graph of the VOC density | concentration change of sample No2. It is a graph of the VOC density | concentration change of sample No3. It is a graph which shows a time-dependent change of pH. It is a figure explaining the ground purification method of a 1st embodiment. It is a figure explaining the ground purification method of 2nd Embodiment. It is a figure explaining the ground purification method of 3rd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment described below is characterized in that corn steep liquor is used as a main component as a nutrient for VOC-decomposing microorganisms when the VOC-contaminated ground is purified by VOC-decomposing microorganisms.

  As shown in FIG. 1, the corn steep liquor contained 18% by weight of organic carbon (TOC). Thus, it was confirmed that corn steep liquor is suitable as a nutrient for VOC-degrading microorganisms in that it is rich in organic carbon. The organic carbon was measured by a combustion oxidation-infrared analysis method.

  The corn steep liquor contained 7.7% by weight of ash. The ash is an oxidant generated by burning an inorganic substance (such as mineral) such as phosphorus, potassium, magnesium, calcium, and iron. Inorganic substances constituting ash generally produce a large amount of SS (Suspended Solid) under alkaline conditions. For this reason, it is considered that when an alkaline solution such as a basic pH adjuster is added to corn steep liquor, a large amount of SS is generated and agglomeration occurs, which causes clogging of the injection well. In addition, about ash content, after heating corn steep liquor stock solution at 550 degreeC, the organic substance and the water | moisture content were removed, and the content was calculated | required.

  Next, an SS measurement test was performed to confirm the amount of SS produced from corn steep liquor. In this SS measurement test, an alkaline solution was added to a diluted corn steep liquor to produce SS, and the weight of the produced SS was measured. FIG. 2 is a diagram for explaining test conditions and results in an SS measurement test.

  In this SS measurement test, three samples prepared by diluting 60 g of sufficiently stirred corn steep liquor with water to 150 mL were prepared. And about the 1st sample (No1), the dilution liquid was used as it was. For the second sample (No. 2), 65 mL of a 1 mol / L sodium hydroxide aqueous solution was added to the diluted solution and allowed to stand. For the third sample, 85 mL of a 1 mol / L aqueous sodium hydroxide solution was added to the diluted solution and allowed to stand. When pH was measured about these samples, pH of sample No1 was 3.7, pH of sample No2 was 6.1, and pH of sample No3 was 7.1.

  Samples Nos. 1 to 3 contained SS as a solid content, and the amount of SS was different for each sample. Then, it filtered about sample Nos. 1-3, and measured dry weight of obtained SS. A 75 μm (opening) sieve was used for filtration. Here, since the value of 75 μm corresponds to the particle size of silt, it is considered that the measured SS may impede the flow of nutrients. The dry weight was calculated by subtracting the dry weight of the sieve alone measured in advance from the dry weight of the sieve in which SS remained.

  As shown in FIG. 2, the measured dry weight of SS was 0.56 g for sample No1, 2.3 g for No2, and 6.7 g for No3. The form of the SS remaining on the sieve is shown in FIG. It was confirmed that the amount of SS increased in the order of sample No1, No2, No3. In other words, it was confirmed that the weight of SS produced from corn steep liquor was greatly increased by about 4 times at pH 6.1 and about 10 times at pH 7.1, based on the case of pH 3.7. It was.

  From this result, it is estimated that when a nutrient containing corn steep liquor as a main component and an alkaline pH adjuster are mixed and injected into the injection well, a large amount of SS is generated, causing clogging of the injection well. It was. Moreover, it was estimated that it was the same even if a nutrient and a pH adjuster were mixed in the injection well. In addition, when SS was produced in large quantities, there was a concern that the permeability of nutrients injected from the injection well into the contaminated ground would also decrease. Therefore, in order to verify to what extent the permeability of nutrients is reduced by the generation of SS, a permeability test of nutrients was performed.

  FIG. 4 is a diagram illustrating the configuration of the test apparatus 1 for the permeability test. As shown in the figure, the test apparatus 1 includes a solution column 11 and a receiver 12. The solution column 11 is a cylindrical member made of a transparent resin such as an acrylic resin, and has an inner diameter of 5 cm and an axial length of 30 cm. The solution column 11 is attached in such a direction that the axis is in the vertical direction. The upper end opening 13 of the solution column 11 is opened, and the stopper member 15 is attached to the lower end opening 14 in a liquid-tight state. And the mountain sand 4 is filled into the internal space of the solution column 11 so that a layer thickness may be set to 20 cm. A drainage pipe 16 is inserted into the plug member 15, and the lower end of the drainage pipe 16 is disposed in the internal space of the receiver 12.

  In this test, three types of liquids were used as the test liquid 3. The first liquid was obtained by adding sodium bicarbonate to a 0.6% corn steep liquor diluted solution so that the concentration of the whole solution was 0.3%, and its pH was 6.6. The second liquid was a corn steep liquor diluted solution having a concentration of 0.6%, and its pH was 4.5. The third liquid is tap water as a comparative example. Then, these test solutions 3 were injected from the upper end opening 13 of the solution column 11.

  The injected test liquid 3 passes through the mountain sand 4 by natural flow, flows down the drainage pipe 16, and is stored in the receiver 12. Therefore, the amount of the test liquid 3 stored in the receiver 12 is measured. did. Then, the water permeability coefficient was calculated every time the storage amount of the test liquid 3 increased by a specified amount. In this test, the hydraulic conductivity was calculated every time the storage volume of the test liquid 3 increased by 0.8L.

  FIG. 5 shows the results of the above permeability test. In FIG. 5, the vertical axis represents the water permeability coefficient, and the horizontal axis represents the accumulated water flow rate. Here, the integrated water flow amount is the amount of the test liquid 3 stored in the receiver 12 at the time of calculating the water permeability coefficient. In FIG. 5, “corn steep liquor” indicates the result of the first liquid, and “corn steep liquor (untreated)” indicates the result of the second liquid.

  As shown in the figure, the second liquid, which is a corn steep liquor diluent, has a water permeability of about 0.05 to 0.06 cm / sec, which is equivalent to the third liquid (tap water) over the period of water flow. The coefficient was maintained. In contrast, the first liquid, which is a corn steep liquor neutralized solution neutralized with sodium bicarbonate, has a reduced hydraulic conductivity as the water flow rate increases. And at the time of performing 11.2L water flow, the water permeability coefficient decreased to about 0.002 cm / second and about 1/30 of the second liquid.

  From this result, it was confirmed that the corn steep liquor diluted solution lost its permeability to the ground due to the formation of SS when neutralization treatment with sodium bicarbonate was performed. Therefore, when using a nutrient containing corn steep liquor as a main component, it is better not to neutralize with an alkaline solution until it penetrates into the contaminated ground.

  Here, the corn steep liquor is acidic with a pH of about 3 to 4 (pH 3.7 in the SS measurement test of FIG. 2). On the other hand, the pH suitable for the activity of the VOC degrading microorganism is about 6-8. For this reason, unless neutralization treatment is performed, the VOC-degrading microorganisms in the ground are not easily activated, and the effect of injecting nutrients is not sufficiently exhibited. Therefore, a method is conceivable in which a nutritional material containing corn steep liquor is injected first, and then an alkaline solution is injected for neutralization. In order to verify the validity of this method, a VOC decomposition test was conducted.

  FIG. 6 is a diagram illustrating the test apparatus 2 for the VOC decomposition test. As shown in the figure, the test apparatus 2 includes a test liquid container 21, a liquid feed pipe 22, a tube pump 23, a solution column 24, and a receiver 25.

  The test liquid container 21 is a container for storing a test liquid 7 described later. The liquid feeding tube 22 is a tube for feeding the test liquid stored in the test liquid container 21 to the solution column 24. The tube pump 23 is a device for feeding the test liquid from the test liquid container 21 to the solution column 24.

  The solution column 24 is a cylindrical member made of a transparent resin such as an acrylic resin, and has an inner diameter of 5 cm and an axial length of 30 cm. The solution column 24 is attached in such a direction that the axis is in the vertical direction. A stopper member 26 is attached to the upper end opening of the solution column 24 and a stopper member 27 is attached to the lower end opening in a liquid-tight state. .

  Mountain sand 6 was filled in the internal space of the solution column 24 so that the layer thickness was 20 cm. In addition, the mountain sand 6 collected from Kisarazu was used. Further, the liquid feeding pipe 22 is inserted into the plug member 26, and the upper end of the drainage pipe 28 is inserted into the plug member 27. The lower end of the drainage pipe 28 is disposed in the internal space of the receiver 25.

  In this VOC decomposition test, the tube pump 23 was operated, and the test solution 7 stored in the test solution container 21 was supplied to the solution column 24. And the test liquid 7 stored by the receiver 25 after passing the mountain sand 6 was extract | collected, and pH and VOC density | concentration of the extract | collected test liquid 7 were measured.

  Specifically, as shown in FIG. 7, the 1st test (No1)-the 3rd test (No3) which made the kind and the water flow time of the test liquid 7 to flow through differ were done. Here, the 1st test is a test in the control section which passed tap water. The second test is a test in a test group in which nutrients were continuously injected, and is a comparative example. In addition, the third test is a test in a test section where an alkaline solution was added later, and is an example. Furthermore, in the 1st-3rd test, the water flow of the test solution 7 was divided into the 1st step which flows A liquid, and the 2nd step which flows B liquid. Here, the first stage is a preparation stage for obtaining VOC-contaminated ground, and the second stage is a stage for confirming the decomposition of VOC in the VOC-contaminated ground. Therefore, the second stage corresponds to a VOC decomposition test.

  In the first test of the control group, a 100 mg / L aqueous solution of trichloroethylene (TCE) was used as the A liquid, and tap water was used as the B liquid. In the second test of the comparative example, the corn steep liquor diluted with corn steep liquor stock solution diluted to 1/10 concentration with tap water and added with trichlorethylene so that the concentration would be 100 mg / L as the A liquid. The liquid was used. Moreover, the corn steep liquor dilution liquid which diluted the corn steep liquor stock solution to the 1/20 density | concentration with tap water was used as B liquid. In the 3rd test of an Example, the same corn steep liquor dilution liquid as the 2nd test was used as A liquid, and the sodium bicarbonate solution with a density | concentration of 2% was used as B liquid.

  In each test, in the first stage, 1 L of the solution A was injected 14 days before, 13 days before, and the day of the test. In the second stage, 1 L of B liquid was injected 9 days and 16 days after the start of the test.

  8 to 10 show the change over time in the VOC concentration in each test. In these figures, the “elapsed days” shown on the horizontal axis is “the 0th day” as the last day of the first stage, in other words, the “first day” as the first day of the second stage. Indicates the number of days that have elapsed.

  As shown in FIG. 8, in the first test of the control group, the concentration of trichlorethylene did not fall below about 1 mg / L. On the other hand, almost no increase in cis-dichloroethylene produced by decomposition of trichlorethylene was observed, and the concentration was less than 1 mg / L. Further, trans-dichloroethylene, 1,1-dichloroethylene, and vinyl chloride, which are decomposition products of trichlorethylene, were hardly detected.

  As shown in FIG. 9, in the second test of the comparative example, the concentration of trichlorethylene was maintained around several tens of mg / L and was hardly decreased. The increase in the concentration of cis-dichloroethylene was also slight. Moreover, the density | concentration of 1, 1- dichloroethylene and vinyl chloride was less than 0.1 mg / L over the test period.

  On the other hand, as shown in FIG. 10, in the third test of the example, the concentration of trichlorethylene was confirmed to decrease after adding solution B (bicarbonate solution). For example, it was confirmed that it was less than 0.1 mg / L after 40 days. On the other hand, it was confirmed that the concentration of cis-dichloroethylene increased as the concentration of trichlorethylene decreased. For example, after the addition of solution B, the increase started from about 0.1 mg / L and reached around 10 mg / L after 40 days. In addition, the concentration of 1,1-dichloroethylene was also confirmed to increase after 40 days. From the above, in the third test, it was considered that the decomposition of VOC was progressing. In addition, the clogging of the solution column 22 due to the addition of the sodium bicarbonate solution was not confirmed during the test of the third test.

  In consideration of pH, as shown in FIG. 11, in the third test of the example, the pH increased to about 8.7 with the addition of the alkaline solution on the 9th day, and the 16th day on the elapsed day. When the alkaline solution was added, the pH dropped to about 7.5. Thereafter, the pH was maintained at around 7.5. That is, it can be seen that by adding the sodium bicarbonate solution, the VOC degrading microorganisms are activated. On the other hand, in the 2nd test of the comparative example, it was less than pH6 over the whole period.

  From the above VOC degradation test, a nutrient material mainly composed of corn steep liquor is injected into the ground, and then an alkaline solution such as a sodium bicarbonate solution is injected into the ground, so that the VOC-degrading microorganism can be sufficiently activated. It was confirmed that VOC can be effectively decomposed.

  Next, the ground purification method based on the knowledge obtained in each test will be described. In this ground purification method, a nutrient material manufacturing process, a nutrient material injection process, and an alkaline solution injection process are performed. The nutrient material manufacturing process is a process of manufacturing a nutrient material mainly composed of corn steep liquor, and the nutrient material injection process is a process of injecting the manufactured nutrient material into an injection well provided in the ground. . The alkaline solution injection step is a step of injecting the alkaline solution into the injection well after the nutrient material is injected.

  As shown in FIG. 12A, in the nutrient material manufacturing process, a corn steep liquor stock solution 33 is stored in a corn steep liquor container 31. Then, the corn steep liquor stock solution 33 is delivered to the dilution container 32 by the pump 35 while being stirred by the stirrer 34. The dilution container 32 is diluted 10 times to several tens of times with the industrial water 37 while being stirred by the stirrer 36. Thereby, the corn steep liquor dilution liquid as the nutrient 38 is manufactured.

  Here, when the pH of the manufactured nutritional material 38 (corn steep liquor diluted solution) exceeds 6, the acidic solution 40 may be added to reduce the pH to 6 or less in order to suppress the formation of SS. preferable. From the viewpoint of reliably suppressing the production of SS, when the pH of the nutrient material 38 exceeds 5, it is more preferable to add the acidic solution 40 to make the pH 5 or less.

  As the acidic solution 40, an aqueous solution of an organic acid, a weak acid, or a strong acid can be used. Here, the organic acid is, for example, gluconic acid, citric acid, or acetic acid. The weak acid is, for example, sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium hydrogen sulfite, potassium hydrogen sulfite. Strong acids are, for example, hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid. Among these, an aqueous solution of an organic acid is more preferable.

  If the nutrient material is manufactured, the nutrient material injection process is performed. In this nutrient material injection process, an injection well 41 and a pump 39 are used. Here, the injection well 41 is a perforated pipe installed in the contaminated ground G along the vertical direction. In this embodiment, a horizontal slit type strainer tube having an inner diameter of 50 to 100 mm and a length of 10 to 20 m is used. The horizontal slit formed in the strainer tube has, for example, a frontage length (slot) of 0.5 mm, a slit interval (pitch) of 3 mm, a number of strips of 4, and an opening area ratio of 12.5%. Such a strainer tube is commercially available, for example, under the trade name “lateral slit strainer tube” of Misaki Co., Ltd.

  In the nutrient material injection step, the nutrient material 38 pumped up by the pump 39 is injected into the internal space of the injection well 41 from the upper end of the injection well 41. The injection amount at this time is determined according to the degree of contamination of the ground G. Here, since the pH of the nutrient 38 is adjusted to 5 to 6 or less, excessive generation of SS in the injection well 41 can be suppressed. Thereby, the nutrient 38 can be smoothly injected into the contaminated ground G. The injected nutrient 38 is diffused and penetrated through the ground G by the groundwater of the aquifer 45 or the like. If the nutrient 38 is infiltrated into the contaminated ground G, an alkaline solution injection process is performed.

  As shown in FIG. 12B, an alkaline solution 55 is used in the alkaline solution injection step. The alkaline solution 55 is produced, for example, by stirring the baking soda solution 52 and the industrial water 53 charged in the dilution container 51 with the stirrer 54. Then, the alkaline solution 55 stored in the dilution container 51 is injected into the internal space of the injection well 41 from the upper end of the injection well 41 by the pump 56. The injection amount at this time is set to an amount that can raise the pH of the contaminated ground G to a range where the VOC-degrading microorganisms are activated.

  When the alkaline solution 55 is injected, the inner diameter of the injection well 41 is 50 to 100 mm, which is sufficiently narrow compared to the total length (10 to 20 m), so that the liquid (nutrient 38 or groundwater) in the injection well 41 is alkaline. The solution 55 is pushed out from the lateral slit to the contaminated ground G. Thereby, the contact in the injection well 41 of the nutrient 38 and the alkaline solution 55 can be suppressed to the minimum, and aggregation and increase of SS can be reduced. As a result, clogging of the injection well can be suppressed.

  Thereafter, the alkaline solution 55 penetrates into the contaminated ground G. The alkaline solution 55 performs a neutralization reaction with the nutrient material 38 previously injected, and raises the pH of the ground G. At that time, it is considered that SS is generated inside the contaminated ground G. However, since the generated SS can also be a nutrient source for activating VOC-degrading microorganisms, improvement in purification efficiency can also be expected in this respect.

  For the alkaline solution 55, various water-soluble alkaline substances can be used. For example, sodium hydroxide or potassium hydroxide may be used, or sodium carbonate or potassium carbonate may be used.

  As described above, according to the ground purification method of the present embodiment, the nutrient solution 38 mainly composed of corn steep liquor is injected into the injection well 41 of the contaminated ground G, and then the alkaline solution 55 is added to the injection well 41. Since the injection is performed, the chance of contact between the nutrient material 38 and the alkaline solution 55 in the injection well 41 can be reduced. Thereby, the neutralization reaction in the injection well 41 is suppressed, and clogging of the injection well 41 due to the aggregation or increase of SS can be suppressed. As a result, the nutrient material 38 can permeate a wide range of the contaminated ground G. Moreover, since the pH of the ground G rises by injecting the alkaline solution 55 and the VOC decomposing microorganism is activated, the VOC decomposing efficiency can be increased. In addition, corn steep liquor is a by-product of corn starch production and is very inexpensive, so it can economically purify contaminated ground.

  The above description of the embodiment is for facilitating the understanding of the present invention, and does not limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

  In the first embodiment described above, the alkaline solution injection step is performed following the nutrient material injection step, but the present invention is not limited to this purification method. For example, a confirmation step for confirming whether or not the nutrient material 38 remains in the injection well 41 may be performed between the nutrient material injection step and the alkaline solution injection step. Hereinafter, a second embodiment in which the confirmation process is performed will be described.

  In the ground purification method of the second embodiment, a nutrient material manufacturing process, a nutrient material injection process, a confirmation process, and an alkaline solution injection process are performed.

  The nutrient material manufacturing process and the nutrient material injection process are as described in the first embodiment. That is, as shown in FIG. 13A, in the nutrient material production process, the nutrient corn 38 is produced by diluting the corn steep liquor stock solution 33 with the industrial water 37. In the nutrient material injection step, the manufactured nutrient material 38 is injected from the upper end of the injection well 41.

  The confirmation step is a step for confirming whether or not the nutrient 38 remains in the injection well 41. For example, as shown in FIG. This is done by sampling the stored liquid and measuring the pH of the liquid. That is, the nutrient 38 injected into the injection well 41 in the nutrient injection process flows out into the contaminated ground G by the groundwater in the aquifer 45. For this reason, with the passage of time, the ratio of groundwater in the liquid in the injection well 41 increases. Therefore, the liquid in the injection well 41 is sampled and the pH is measured. If the pH reaches the pH (neutral) of the groundwater, it can be determined that no nutrient 38 remains in the injection well 41.

  In addition, regarding this confirmation process, in the case of the contaminated ground G without the aquifer 45, it may be confirmed whether or not the nutrient material 38 remains based on the liquid level in the injection well 41. . That is, if the entire amount of the nutrient material 38 penetrates into the contaminated ground G, the liquid level in the injection well 41 becomes zero. Therefore, when the liquid level in the injection well 41 has decreased to a level that does not affect the generation of SS, it may be determined that the nutrient material 38 does not remain.

  The alkaline solution injection step is as described in the first embodiment. That is, as shown in FIG. 13C, the alkaline solution 55 is injected into the injection well 41 in the alkaline solution injection step. In this embodiment, the alkaline solution injection step is performed on the condition that no nutrient 38 remains in the confirmation step. Thereby, aggregation and increase of SS in an injection well can be prevented, and the clogging suppression effect of the injection well 41 can be heightened.

  In the second embodiment, the confirmation process is performed. In the third embodiment, the water injection process is performed instead of the confirmation process. As shown in FIG. 14, this water injection step is performed between the nutrient material production step and the nutrient material injection step (see FIG. 14 (a)) and the alkaline solution injection step (see FIG. 14 (c)). Is called. Then, as shown in FIG. 14 (b), in this water injection step, the industrial water 62 stored in the water storage container 61 is pumped out by the pump 63 and injected from the upper end of the injection well 41.

  By performing this water injection step, the nutrient material 38 in the injection well 41 is pushed out to the contaminated ground G by the water 62, and then the alkaline solution 55 is injected. For this reason, aggregation and increase of SS in the injection well 41 can be prevented, and the alkaline solution 55 can be smoothly injected into the contaminated ground G.

  In each of the embodiments described above, an aqueous solution of an alkaline substance such as sodium bicarbonate is used as the alkaline solution 55, but a carbon source (for example, sodium gluconate) of a VOC-decomposing microorganism may be included. If it does in this way, a VOC decomposing microorganism can be activated more and purification efficiency can be improved. In particular, in the contaminated ground G in the vicinity of the injection well 41, there is a possibility that the nutrient 38 will be washed away by the permeation of the alkaline solution 55. For this reason, by adding the carbon source of the VOC-decomposing microorganism to the alkaline solution 55, even if the nutrient 38 that has penetrated into the contaminated ground G is flowed, the carbon source remains and can be supplemented.

  Further, regarding the nutrient material 38, the corn steep liquor diluted solution is used in each of the above-described embodiments, but the corn steep liquor stock solution 33 may be used as the nutrient material 38. Moreover, it is not necessary to manufacture the nutrient material 38 on-site, and the nutrient material 38 manufactured separately may be transported to the site and used.

DESCRIPTION OF SYMBOLS 1 ... Test apparatus of permeability test, 2 ... Test apparatus of VOC decomposition test, 3 ... Test liquid, 4 ... Mountain sand, 6 ... Mountain sand, 7 ... Test liquid, 11 ... Solution column, 12 ... Receptor, 13 ... Upper end opening of solution column, 14 ... lower end opening of solution column, 15 ... stopper member, 16 ... drainage pipe, 21 ... test liquid container, 22 ... liquid feeding pipe, 23 ... tube pump, 24 ... solution column, 25 ... receiving Container, 26 ... stopper member with upper end opening, 27 ... stopper member with lower end opening, 28 ... drainage pipe, 31 ... corn steep liquor container, 32 ... container for dilution, 33 ... corn steep liquor stock solution, 34 ... stirrer, 35 ... Pump, 36 ... Stirrer, 37 ... Industrial water, 38 ... Diluent, 39 ... Pump, 40 ... Acidic solution, 41 ... Injection well, 42 ... Sampling vessel, 43 ... Worker, 45 ... Aquifer, 51 ... Dilution container, 52 ... Baking soda solution, 53 ... Industrial water, 5 ... stirrer, 55 ... alkaline solution, 56 ... pumps, 61 ... reservoir, 62 ... industrial water, 63 ... pump

Claims (6)

A ground purification method for purifying the ground by injecting a nutrient that activates VOC-degrading microorganisms into the ground contaminated with VOC,
A nutrient preparation process for producing a nutrient having a pH of 6 or less by adding an acidic solution while diluting the corn steep liquor stock solution with water,
A nutrient injection step of injecting the nutrient into the injection well provided in the ground;
A ground purification method comprising performing an alkaline solution injection step of injecting an alkaline solution into the injection well after the nutrient material is injected. A ground purification method for purifying the ground by injecting a nutrient that activates VOC-degrading microorganisms into the ground contaminated with VOC,
A nutrition material injection step of injecting a nutrient material mainly composed of corn steep liquor into the injection well provided in the ground,
Performing an alkaline solution injection step of injecting an alkaline solution into the injection well after the nutritional material has been injected;
A confirmation step for confirming whether or not the nutritional material remains in the injection well is performed after the nutritional material injection step,
The alkaline solution injection process and the confirmation process in the land Release purification how to characterized in that it is carried out in condition that has been confirmed that the nutritional material does not remain. The ground purification method according to claim 2 , wherein the confirmation step is a step of measuring the pH of the liquid stored in the injection well. A ground purification method for purifying the ground by injecting a nutrient that activates VOC-degrading microorganisms into the ground contaminated with VOC,
A nutrition material injection step of injecting a nutrient material mainly composed of corn steep liquor into the injection well provided in the ground,
Performing an alkaline solution injection step of injecting an alkaline solution into the injection well after the nutritional material has been injected;
Performing a water injection step of injecting water into the injection well after the nutrient material injection step;
The alkaline solution injection step and the earth plate clean way to and performing after the water injection process. A ground purification method for purifying the ground by injecting a nutrient that activates VOC-degrading microorganisms into the ground contaminated with VOC,
A nutrition material injection step of injecting a nutrient material mainly composed of corn steep liquor into the injection well provided in the ground,
Performing an alkaline solution injection step of injecting an alkaline solution into the injection well after the nutritional material has been injected;
In the alkaline solution injection step, an alkaline aqueous solution containing a carbon source of the VOC decomposing microorganism, land Release purification how to characterized by injecting into the injection wells. Wherein in the alkali solution injection step, soil purification method according to any one of claim 1 to 4, an alkaline aqueous solution containing a carbon source of the VOC decomposing microorganism, characterized by injecting into the injection wells.