JP2008161778A - Soil purifying method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soil purifying method which utilizes carbon dioxide produced by metabolism of microorganisms, less influences the environment by the use of naturally existing substances and produces no harmful substances even in the circumference of improved ground and after ground improvement. <P>SOLUTION: A silica compound and microorganisms are injected into ground 6 containing a harmful substance 20, and carbon dioxide produced through the metabolism of the microorganisms is used to solidify the silica compound and decompose the harmful substance with the microorganisms at the same time. If necessary, carbon dioxide or its aqueous solution is used together to promote the degree of initial improvement. A composition containing nutrient sources for microorganisms as effective ingredients, a polyvalent metal compound or a gelling adjusting agent may be used together. The harmful substance 20 in the ground 6 is contained in the solidified product 21 of the injected solution injected through an injection channel 19. The silica compound in the injected solution is solidified by the microorganisms and made harmless through reaction with an agent purifying the harmful substance in the injected solution. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a soil consolidation method that improves the ground or consolidates discharged soil and the like, and relates to a method that has little influence on the surrounding environment even after the improvement. In addition, the present invention relates to a method for treating a building frame or a method for fixing harmful substances in soil and purifying harmful substances.

  Conventionally, water glass and cement have been used to improve the ground. Since these injection materials use strong alkalis or strong acids, handling is necessary, and the ground that can be used is limited.

  The present inventors can obtain a long gelation time and a stable gel even if the amount of acid or alkali is reduced by using activated silica, water glass, or colloidal water glass. Thus, a grout having a small influence on the environment has been developed (for example, see Patent Document 1: Japanese Patent Application Laid-Open No. 2005-075899).

  Further, Patent Document 2 (Japanese Patent Publication No. 7-57870) by the present applicant is already known. In the invention described in Patent Document 2, water glass and carbon dioxide are pressurized and supplied at a constant ratio, and a water glass aqueous solution in which carbon dioxide is absorbed is discharged to obtain a ground injecting chemical solution.

  An object of the present invention is to produce insoluble silica by generating carbon dioxide through metabolism by microorganisms. In addition, in the ground to be purified, there has been a problem that when the ground improver is injected, it is diffused by the groundwater in the ground and cannot be injected into the target ground, and the contaminants and the decomposing microorganisms are difficult to contact.

Japanese Patent Laying-Open No. 2005-075899 Japanese Patent Publication No. 07-057870 JP 07-289290 A

  The object of the present invention is to pursue a reduction in environmental impact, and to develop a ground improvement method that uses only substances that exist in the natural state and does not generate harmful substances around the improved ground and after ground improvement. There is. Then, it set as the subject to solidify without adding a strong acid or a strong alkali to a silica compound, and to improve the ground.

  In order to solve this problem, the present invention provides a method of utilizing carbon dioxide gas generated by microbial metabolism, and further solidifies by adding silica, or solidifies soil and waste containing harmful substances by microbial metabolism. In addition, the present invention provides a method for decomposing harmful substances in soil and waste by microbial metabolism.

Therefore, since the carbon dioxide dissolves in water and lowers the pH, the present researchers have determined that the nutrient source is decomposed into ethanol and carbon dioxide by microbial metabolism in the method of curing and gelling the silica compound. It has been found that the ground can be improved without using a large-scale device or chemicals, and that there is little impact on the environment around the ground improvement area.
C ₆ H ₁₂ O ₆ → 2C ₂ H ₅ OH + 2CO ₂

  In other words, when silica compounds and microorganisms are injected into the ground, the microorganisms metabolize and release carbon dioxide, which causes the silica compounds to react with carbon dioxide and gel, thereby solidifying the soil particles and improving the ground. To do. Alcohols also have a function of gelling a silica solution such as water glass.

  At this time, although water glass is mentioned as a silica compound, it can be made to gelatinize reliably by using silica compounds, such as active silica and colloidal silica, in addition. Moreover, gel time can also be accelerated | stimulated by using the thing which added the trace amount acid to water glass and made it colloid.

  Furthermore, by injecting microorganisms and organic substances simultaneously, or in the ground containing many microorganisms, injecting organic substances into the ground regulates the respiration of microorganisms, regulates the amount of carbon dioxide generated, and gels of silica compounds Promote or regulate crystallization.

  Further, by simultaneously injecting gas such as carbon dioxide and oxygen, it is possible to adjust metabolism and promote or regulate gelation.

  The gelation time can also be adjusted by adding a gel compound that has little influence on microorganisms as a gelation accelerator or regulator for the silica compound. Examples include inorganic salts such as potassium chloride and sodium chloride, trace amounts of acids, and organic salts. In addition, by adding calcium compounds and magnesium compounds, carbon dioxide released by the metabolism of microorganisms reacts with polyvalent metal compounds to form insoluble polyvalent metal carbonates, and not only the gelation time can be adjusted. It is also possible to increase the strength of the injection material.

  Due to the above, the substances used according to the present invention are generally present in nature, hardly affect the surrounding ground even after ground improvement, and rarely contaminate groundwater and soil, so conventional ground improvement In the method, the ground is effectively improved in a place where unreacted products are difficult to diffuse and a place where the environment is delicate, and there is no fear of environmental pollution after the improvement.

  Since there is no need to use large-scale equipment or harmful chemicals, it can be easily installed at construction sites for ground improvement. In particular, it is also suitable for seismic reinforcement in conditions where there are many underground burials such as gas, electricity, and water pipes under the foundation of structures, such as liquefaction countermeasures.

  Furthermore, the gelation time can be adjusted or the strength of the improved ground can be increased by injecting one or a plurality of calcium compounds, nutrients, carbon dioxide, and gelation regulators.

  Furthermore, it is a purification treatment method that focuses on fixing of harmful substances and decomposition of harmful substances by solidifying soil and industrial waste containing harmful substances by applying microbial metabolism.

  The method of concrete implementation of the present invention will be described.

  The silica compound used in the present invention may be any one of water glass, activated silica, silica colloid and the like. In addition, since it is necessary to adjust the pH to activate the combined microorganism, a small amount of pH adjusting material may be used. Silica colloid is colloidal and is stable for a long time at a neutral pH due to its low Na content, and it is gelled with a small curing agent (see Patent Document 1, etc.), which is suitable for the present invention. .

  In addition, the gelation time can be adjusted by using a colloid obtained by adding a small amount of acid to a silica compound.

  Since the silica in the present invention is accompanied by gelation, it can be consolidated within a predetermined range due to the provision of water-stopping property, a rapid consolidation effect, and a gelling time adjusting function.

  The microorganism used in the present invention can be used as long as it hardly affects the human body and the environment. In particular, those used in conventional foods such as lactic acid bacteria, natto bacteria, baker's yeast and brewer's yeast, and those existing in large amounts in general ground can be used. For example, soil and sand from the field may be collected and the mixed solution or the supernatant thereof may be used. In metabolism by lactic acid bacteria, lactic acid is produced to lower pH and promote or regulate gelation.

  Currently, a method of injecting nutrient sources in the contaminated soil, growing the microorganisms in the soil, and decomposing the pollutants is used, so that microorganisms with the desired resolution are isolated from the microorganisms collected from the field. It can also be cultured and used.

  The calcium salt precipitated according to the present invention is calcium carbonate, calcium hydroxide, calcium chloride, calcium nitrate, aluminum dioxide or the like, and is influenced by microorganisms to be injected or microorganisms that inhabit the ground.

  The microbial nutrient source is a microbial nutrient source, and is preferably a saccharide that is metabolized and decomposed by microorganisms in the soil. Examples include monosaccharides such as glucose and fructose, disaccharides such as sucrose, maltose and galactose, other oligosaccharides, polysaccharides such as starch and maltodextrin, and other saccharides.

  In addition, by using a reaction product of water glass such as glyoxal or organic acid esters such as carbonic acid and acetic acid as nutrients, the reaction product after gelation of water glass can be used as a nutrient source for microorganisms. Can help to break down.

  Since the metabolic rate varies depending on the microorganism or organic nutrient source, it is necessary to select the soil according to the construction site.

  Examples of the polyvalent metal compound in the present invention include calcium salts such as calcium chloride, polyvalent metal salts such as magnesium chloride, calcium hydroxide, and the like, fine particle lime, fine particle cement, fine particle slag, gypsum, calcium carbonate and the like. . In addition, calcium such as shells contained in the ground, lime, etc. also affect the reaction. In the present invention, the combined use of silica and calcium brings about an increase in strength due to the formation of calcium silicate.

  In the present invention, the infusion solution of the present invention is infiltrated, mixed, or coated in soil or waste containing harmful substances to prevent diffusion of contaminated areas from harmful substances and waste, and microorganisms in the infused liquid, Alternatively, by injecting microorganisms or soil purification materials, the ground can be limited and purified, which is effective.

  In addition, when silica is not used, water permeability is reduced by depositing calcium carbonate between the soil particles to give water tightness, but since it does not involve gelation, it can be stopped by repeatedly injecting it. Can be improved. However, when silica is used in combination, gelation occurs, so that water permeability can be lowered and consolidated even with a single injection. Of course, if the injection is repeated many times, the improvement effect is further improved.

  Moreover, since the ground after purification is solidified, it is possible to contain injected microorganisms and detoxified pollutants and collect them after purification. Microorganisms that have grown in the ground due to soil purification are also difficult to diffuse into the surrounding ground and can be recovered after purification, avoiding secondary contamination such as excessive growth of microorganisms and contamination of groundwater. it can.

  The hazardous substances in the present invention are heavy metals such as hexavalent chromium, mercury, lead and cadmium, waste mud generated by civil engineering, incinerated ash, sludge, industrial waste, environmental hormones, agricultural chemical residues, organic solvents, organic Organic compounds such as detergents, dioxins and other soils that contain harmful substances that adversely affect the human body and the environment. Examples include alkyl mercury, total mercury, cadmium, lead, organic phosphorus, hexavalent chromium, arsenic, cyanide, PCB, and trichlorethylene. , Tetrachloroethylene, dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,3 dichloropropene , Thiuram, simazine, thiobencarb, benzene, selenium and the like.

  Specific examples of the soil purification agent in the present invention include inorganic reducing agents such as ferrous sulfate, ferrous chloride, sodium hydrogen sulfite, potassium hydrogen sulfite, sodium sulfite, and potassium sulfite. Agents and organic matter degrading microorganisms are also used.

が挙げられる。 As the chelating agent, for example, a liquid chelate compound having a pyrrolidine skeleton, specifically, a pyrrolidine sulfur compound

Is mentioned.

  It is very easy to bind to these heavy metals and instantly binds to form a metal chelate compound that is insoluble in water. This metal chelate compound has a strong binding force, and once bonded, the compound does not dissolve in water and becomes a very stable chelate compound. Therefore, even if a compound combined with heavy metal ions is disposed of in landfills, it does not re-dissolve in rainwater, acid rain, or organic acids or alkaline substances caused by organic matter decay, and does not cause any secondary pollution. It is a fixative.

In addition, imine sulfur compounds such as

等が挙げられる。 Carbamate-based sulfur compounds, such as

Etc.

  An example of decomposition by microorganisms is as follows.

  Organic matter in industrial waste is decomposed by microorganisms such as bacteria and filamentous gold fungi. Ammonia involved in the production of trihalomethane, which is a carcinogen, is decomposed by nitrifying bacteria, and industrial solvent trichlorethylene is decomposed by ammonia oxidizing bacteria. In addition, agricultural chemicals are decomposed by filamentous fungi, bacteria, and radioactive bacteria in the soil.

  For example, parathion is degraded by the collaboration of Pseudomonas stuzeri and Pseudomonas aeruginosa. Carbamate insecticides are degraded by Penicillium and Trichoderma. Further, PCB is decomposed by Pseudomonas and Alcaligenes, and chlorobenzene is also decomposed by Pseudomonas.

  In the injection material according to the present invention, one or more of the compositions shown in the following (1) to (6) can be used in combination, whereby the strength and water stoppage are further improved.

(1) Composition containing water glass as an active ingredient This is, for example, a composition containing water glass and a curing agent as active ingredients. Water glass exhibits a molar ratio of SiO ₂ / Na ₂ O = 1 to 6 and is industrially produced, powder or liquid, or is obtained by adding caustic alkali thereto. When used, it is diluted with water.

  Hardeners include inorganic salts such as bicarbonate, calcium chloride, sodium bisulfate, sodium aluminate, sulfate band, and alum, carbonic acid, carbon dioxide, carbonated water, sulfuric acid, phosphoric acid, hydrochloric acid and other inorganic acids, acetic acid, etc. Organic acids, esters such as diacetin, triacetin and ethylene carbonate, cements such as glyoxal and fine particle cement, slags such as fine particle slag, and alkaline agents such as slaked lime and caustic alkali.

  Any method may be used as a method of using the composition, but the method is used by infiltrating the injection solution according to the present invention before and after injection.

(2) Curable compositions other than water glass Specific examples include curable resin compositions such as epoxy resins and polyester resins.

(3) Composition comprising a hardly soluble calcium compound as an active ingredient In the present invention, the hardly soluble calcium compound is preferably a calcium compound having a solubility in water (20 ° C.) of 5% by weight or less, specifically, calcium carbonate, Cements, slags, limes and the like can be mentioned. As this combination method, it is preferable to use the combination mainly for the purpose of preventing the deviation when the injection liquid according to the present invention deviates due to uneven ground. Specifically, it can be used together before and after injecting the injection solution according to the present invention, but it can also be used as a primary injection material. Moreover, the calcium containing liquid produced | generated with the supernatant liquid of the hardly soluble calcium compound as mentioned above can be used for this invention.

(4) Composition containing fine particle slag or fine particle cement as an active ingredient As these fine particle slag and fine particle cement, those having an average particle diameter of 10 μm or less and a specific surface area of 5000 cm ² / g or more are used. This case can also be used in the present invention as in the case of (3).

(5) Composition containing alkali agent as active ingredient As the alkali agent, slaked lime, caustic alkali or the like is used.

(6) Composition containing active silica or colloidal silica as an active ingredient Active silica obtained by removing alkali from water glass using an ion exchange resin or ion exchange membrane, acid radicals of acidic water glass, Examples include activated silica obtained by removing an alkali metal with an ion exchange resin and an ion exchange membrane, colloidal silica obtained by concentrating and granulating active silica. Or the silica solution which mixed water glass with these may be sufficient. As the curing agent, inorganic salts such as sodium chloride and potassium chloride, and acids or alkalis are used for adjusting the curing rate and pH, and they can be used in the alkali to acidic region.

(7) Carbon dioxide gas or carbonated water in which carbon dioxide gas is dissolved in water Carbon dioxide gas may be injected by injecting into the polyvalent metal compound and microorganisms and / or nutrient sources, and carbon dioxide gas may be injected later. It may be injected into the ground to accelerate solidification by precipitation of silica gel or calcium carbonate in the initial stage, and in the long term, silica gel or calcium carbonate may be formed by reaction of carbon dioxide gas due to microbial metabolism.

  A method and apparatus for blowing carbon dioxide or a mixture of carbon dioxide and water glass into the ground has already been developed by the present applicant (see, for example, Patent Document 2: Japanese Patent Publication No. 7-57870).

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited by these Examples.

[Reaction experiment between carbon dioxide and silica compound]
10 ml each of colloidal silica, activated silica and water glass as silica compounds were put into a test tube, and carbon dioxide gas was sent with a hose. Carbon dioxide gas was obtained by vaporizing dry ice and allowed to stand at room temperature for 24 hours. After 24 hours, all silica compounds were gelled.

Water glass: No. 5 water glass Colloidal silica: Commercially available colloidal silica (SiO ₂ concentration: 30.0 wt%, pH around 10; particle size: 10 to 20 nm) was used. The active silica may be stabilized with water glass or caustic soda and aged for one week to form a colloid.
Active silica: An active silica having a pH of 2.7, a specific gravity of 1.03, and an SiO ₂ concentration of 4 wt% obtained by treating a solution obtained by diluting No. 3 water glass with water through a cation exchange resin.

[Gelification of yeast and colloidal silica]
The presence or absence of gelation was examined when microorganisms were added to the silica colloid used in Example 1.

Yeast as the microorganism in colloidal silica 10 ml (Nisshin Foods Corporation, Nisshin super Camellia) 0.6 g, glucose C ₆ H ₁₂ O ₆ 0.3g as a nutrient source in the formulation of Table 1 was added to screw-cap test tube, The mixture was mixed well and allowed to stand at room temperature in the atmosphere for 24 hours. After 24 hours, the test tube was turned upside down to check for gelation.

  In Comparative Examples 1 and 2 to which no yeast was added, no gel product was observed, but in the present invention 1 and 2 containing yeast, the contents did not fall even when the test tube was inverted, and the silica colloid gelled by microorganisms. confirmed.

  In addition, in the test tube in which only microorganisms were added to the colloidal silica of the present invention 2, gelation was partially observed, whereas in the test tube in which microorganisms and nutrients were added to the colloidal silica of the present invention 1, the colloidal silica solution From the fact that the whole gelled, it was found that carbon dioxide released by the metabolism of microorganisms was involved in gelling, and in particular, “gelling can be promoted by a nutrient source”.

  Experiments were conducted in which microorganisms, calcium compounds, and gelation modifiers were reacted with silica compounds.

(1) Materials used Water glass: JIS No. 5 water glass: specific gravity (20 ° C.) 1.32, SiO ₂ 25.5%, Na ₂ O 7.03%, molar ratio 3.75.
Colloidal silica: Commercially available colloidal silica (SiO ₂ concentration 30.0 wt%, pH around 10; particle size 10-20 nm) was used. The active silica may be stabilized with water glass or caustic soda and aged for one week to form a colloid.
Microorganisms: Yeast (Nisshin Foods Co., Ltd., Nissin Super Camellia)
Nutrients: glucose
4% AS: Silica concentration adjusted to 4% by adding a small amount of 75% phosphoric acid to JIS No. 5 water glass.
8% AS: Silica concentration adjusted to 8% by adding a small amount of 75% phosphoric acid to JIS No. 5 water glass.

  With the formulation shown in Table 2, the presence or absence of gelation after 24 hours was observed.

1. In the case where yeast was added to colloidal silica (No. 1), gelation was observed within 1000 minutes. In addition, the formulation (No. 2) with an increased amount of glucose showed gelation within 1000 minutes.
2. In the case where yeast was added to water glass (No. 3), yeast did not dissolve and gelled. The formulation (No. 4) in which yeast was diluted with water and added to water glass did not gel within 1000 minutes, but gelled in about 4000 minutes.
3. The formulation (Comparison 1 and 2) in which a small amount of 75% phosphoric acid was added to water glass diluted to a silica concentration of 4% and 8% (Comparative 1 and 2) did not gel after 1000 minutes, but gelled in about 200 minutes when yeast was added ( No. 5, 6).

  From the above, the following in the present invention was verified.

1. When yeast is added to colloidal silica, carbon dioxide is generated due to the metabolism of microorganisms after compounding, and gelation occurs because the pH in the chemical solution is lowered. The water glass itself is difficult to gel because yeast does not dissolve easily.
3. The diluted water glass gels even when yeast is added, but the gelation time becomes longer.
4). When a small amount of a curing agent is added to diluted water glass and yeast is added, gelation time can be shortened compared to when yeast is not added or when yeast is added to diluted water glass.

  FIG. 1 is a flow sheet for explaining a method of mixing carbon dioxide gas in the actual ground in the present invention. Mainly, A and B liquid feed pipe lines 5 and a plurality of systems (two systems in FIG. 1) carbon dioxide gas. It is configured to include a pressure feeding line, that is, a high-pressure carbon dioxide pressure feeding line 12 and a low-pressure carbon dioxide pressure feeding line 14, and an injection pipe 7 inserted into the ground 6.

  The A and B liquid feed pipe lines 5 are piped from the water glass aqueous solution storage tank 1 to the injection pipe 7 inserted into the ground 6 and, as shown in FIG. A pump 3 and a flow meter 4 are arranged in the pipeline 5.

  The high-pressure carbon dioxide pressure feeding line 12 is connected to the high-pressure carbon dioxide container 8-1 through the connection pipe 9-1 and is connected to the injection pipe 7. An electromagnetic valve 10-1, a pressure reducing valve 11-1, and a carbon dioxide blowing nozzle 13 are disposed in the pipe 12 respectively. Although not shown, the carbon dioxide blowing nozzle 13 can be provided in the injection pipe 7.

  The low-pressure carbon dioxide gas feed line 14 is connected to the reduced-pressure high-pressure carbon dioxide container 8-1 and the connection pipe 9-2 in the same manner as the high-pressure carbon dioxide pressure feed line 12, and the water glass aqueous solution storage tank 1 Alternatively, the water glass aqueous solution feeding pipe 5 is piped to the upstream side a of the gas-liquid mixing device 2. Similarly to the above, an electromagnetic valve 10-2, a pressure reducing valve 11-2, and a carbon dioxide blowing nozzle 15 similar to the above are arranged in the pipe line 14, respectively.

  According to the apparatus of the present invention having the above-described configuration, the low-pressure carbon dioxide container 8 is connected to the upstream side a of the water glass aqueous solution feeding pipe 5 or the water glass aqueous solution storage tank 1 via the low-pressure carbon dioxide feeding pipe 14. -2 through the electromagnetic valve 10-2, the pressure reducing valve 11-2, and the carbon dioxide blowing nozzle 15, the carbon dioxide gas is injected into the water glass aqueous solution, and then the water glass aqueous solution and the carbon dioxide gas are sufficiently mixed by the gas-liquid mixing device 2. Then, the absorption rate of carbon dioxide gas into the water glass aqueous solution is increased, and the water glass aqueous solution in which the carbon dioxide gas is absorbed by the injection pump 3 is sent to the injection pipe 7 through the water glass aqueous solution supply pipe 5.

  Further, carbon dioxide is injected into the injection pipe 7 from the high-pressure carbon dioxide container 8-1 through the electromagnetic valve 10-1, the pressure reducing valve 11-1, and the carbon dioxide blowing nozzle 13 via the high-pressure carbon dioxide pressure feed line 12.

  According to the present invention, the harmful substance 20 in the ground 6 shown in FIG. 2 (a) is encapsulated by the solidified product 21 of the injected liquid injected through the injection line 19, as shown in FIG. 2 (b). The silica compound in the injection liquid is solidified by microorganisms and reacts with the harmful substance purifier contained therein to render it harmless.

  At this time, as shown in FIG. 3 (a), the caking material is injected through the injection pipe 5 around the harmful substance 20 in the ground 6, and an impermeable shielding wall 22 is formed in advance. In this state, as shown in FIG. 3 (b), if the injection liquid containing the purification liquid is injected through the injection pipe 19, the detoxification process is more effective as described above.

  In the present invention, as shown in FIG. 3 (a), first, an impervious shielding wall 22 is formed around the harmful substance 20 in the ground 6 by using a caking material to enclose the harmful substance. Water is poured into the area surrounded by the shielding wall 22, or a harmful substance purifying agent or an injection solution or a caking agent containing the purifying agent is injected to transfer the harmful substance into water, dehydrated to the ground, and detoxified. You can also

  Here, as mentioned above, harmful substances are heavy metals such as hexavalent chromium, mercury, lead, cadmium, etc. that have a negative effect on the human body and the environment, waste mud, incinerated ash, sludge, industrial waste, domestic wastewater, etc. The material purification agent is the same inorganic or organic reducing agent or chelating agent as described above, or bacteria, and the caking agent is the same material as described above.

[In-situ purification method for soil contaminated with organic compounds]
The soil purification method using this invention in the ground contaminated with trichlorethylene (TCE) is shown.

1. Earthen tank A simple earthen tank with a diameter of 1 m and a height of 1 m was filled with dredged sand and adjusted so that the porosity was 40% and the water content was 20%.
Trichlorethylene (TCE) concentration of 0.1 mg / l was infiltrated into the center of the simple soil tank by about 30 cm in diameter to create contaminated soil (see FIG. 4).

2. Soil purification method TCE in the ground was decomposed by the following method.
The present invention: A barrier wall was made around the contaminated soil with a mixed solution of the silica compound and microorganisms shown in Table 3, and ferrous sulfide was injected into the contaminated ground (see FIG. 5).
Comparative Example 1: Ferrous sulfide was injected into the contaminated ground (see FIG. 6).

3. Results After soil purification, the amount of TCE in the improved ground was measured. The results are shown in Table 3.

  From the results, it was found that the TCE amount after soil purification was smaller when the present invention was used. Thus, by using the present invention, the soil purifier can be prevented from spreading by surrounding the contaminated ground and the ground can be purified efficiently. Since the microorganism-containing water glass of the present invention is cured by carbon dioxide due to the metabolism of microorganisms, it is alkaline and hardly reacts with a soil purifier like conventional acidic silica sols.

  The soil purification method by the water glass liquid containing the sclerosing | hardenable microorganisms of this invention in the ground contaminated with the trichlorethylene (TCE) is shown.

1. Earthen tank A simple earthen tank with a diameter of 1m and a height of 1m was filled with dredged sand and adjusted so that the porosity was 40% and the water content was 20%.
Contaminated soil was prepared by infiltrating a trichlorethylene (TCE) concentration of 0.1 mg / l about 30 cm in diameter into the center of a simple soil tank (see FIG. 4).

2. Collection of TCE-degrading bacteria Colonies grown in a malt extract medium containing 100 ppm of TCE from on-site collected sand were cultured in a liquid medium.

  Degrading bacteria can be collected by collecting sand from contaminated ground and screening. The method differs depending on the pollutants of each ground (see Patent Document 3: Japanese Patent Laid-Open No. 07-289290, etc.).

3. Formulation The degrading bacterium obtained in 2 above was dissolved in 100 ml of ion-exchanged water in which 10 g of glucose was dissolved, and was allowed to stand at 40 ° C. until the aqueous solution became pH 4.2 or lower. Thereafter, 60 ml of No. 5 water glass, 10 ml of colloidal silica, and 30 ml of ion-exchanged water were mixed. In the same manner, 4 l of the mixed solution was prepared.

4). Injection The compounded liquid of the above 3 was injected around the TCE-contaminated sand prepared in 1 above to create a barrier wall.
The liquid mixture of the above 3 was injected inside the barrier wall, and the TCE amount after one month was measured (see FIG. 5).

5. Results After soil purification, the amount of TCE in the improved ground was measured. The results are shown in Table 4.
From the results of Table 4, it can be seen that the improvement effect was obtained by the injection material of the present invention.

It is explanatory drawing of one specific example of the injection apparatus of the injection material concerning this invention. It is explanatory drawing which processes a harmful | toxic substance, Comprising: (a) represents the harmful | toxic substance in the ground, (b) is explanatory drawing of the state which solidified and wrapped up the harmful | toxic substance with the caking material. It is explanatory drawing of the process using a shielding wall, Comprising: (a) represents before a process, (b) represents after a process. It is explanatory drawing of the contaminated ground created in the simple earth tank. It is explanatory drawing which performs soil purification effectively by consolidating the contaminated ground periphery with the injection liquid of this invention, and inject | pouring a soil purification agent into a contaminated ground. It is explanatory drawing which inject | pours the injection liquid of this invention into the contaminated ground periphery and the contaminated ground, and performs soil purification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aqueous solution storage tank 2 Mixing tank 3 Injection pump 4 Flowmeter 5 Aqueous solution liquid supply line 6 Ground 7 Injection pipe 8 Carbon dioxide container 9 Connecting pipe
10 Solenoid valve
11 Pressure reducing valve
12 High-pressure carbon dioxide gas supply line
19 Injection line
20 Toxic substances
21 Solidified material
22 Shielding wall

Claims (4)

A soil purification method for ground containing harmful substances, wherein the soil purification method is characterized by injecting a caking agent into the ground to decompose harmful substances in the ground.
(1) A method of decomposing harmful substances with a soil purification agent together with a method of injecting a silica compound and a microorganism, or a silica compound and a microorganism and a nutrient source as the caking agent, and solidifying by microbial metabolism.
(2) A method of injecting a silica compound and a microorganism or a silica compound, a microorganism and a nutrient source as the caking agent to solidify the ground and decompose harmful substances.   2. The soil remediation method according to claim 1, wherein the soil surrounds the harmful substances in the ground or encloses and solidifies the harmful substances, and then injects a soil purification agent into the inside thereof to decompose the harmful substances.   The soil purification method according to claim 1 or 2, wherein the initial improvement degree is promoted by using carbon dioxide gas or carbonated water together. The soil purification method according to any one of claims 1, 2, and 3, further comprising using a polyvalent metal compound or a gelling regulator.

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