JP2008272530A - Polluted soil decontaminating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polluted soil decontaminating method for return change in an ecosystem caused by an anaerobic microorganism charged after decontamination and an anaerobic microorganism produced in a decontamination process to a state before decontamination, in a bio-augmentation of a pollutant harmful to a human body or an organism, and returning change in the environmental due to the anaerobic microorganisms to the state before decontamination. <P>SOLUTION: In the polluted soil decontaminating method, ozone water 17 produced from the ozone water making machine 15 and water tank 14 on the ground is injected in polluted oil from an injection well 5 after the pollutant is removed to increase the concentration of oxygen in a decontaminating target region. By this method, the anaerobic microorganism charged for decontamination and the anaerobic microorganism produced or propagated in the decontamination process are sterilized to detoxify the harmful anaerobic microorganism after decontamination. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for purifying soil or groundwater contaminated mainly by volatile organic chlorine compounds.

  In recent years, environmental pollution by volatile organochlorine compounds, which are hardly decomposable and harmful in the environment, has become a major problem. At present, volatile organic chlorine compounds that cause contamination have been widely used in industry as raw materials for dry cleaning solvents, metal degreasing, refrigerants, insecticides, and the like. So far, detoxification treatment has been carried out at the stage of discarding volatile organic chlorine compounds, but at that time, it was not recognized that it was a hazardous substance, so it could not be said that it was completely treated. Moreover, when it spills on the floor during use as a solvent, it is considered that volatile organic chlorine compounds such as tetrachloroethylene and trichlorethylene have permeated into the soil in the factory premises. In fact, soil contamination by such volatile organochlorine compounds has already been reported. In addition, since volatile organochlorine compounds are heavier than water, groundwater contamination has been reported one after another. These volatile organochlorine compounds are said to have penetrated into the soil and will be dissolved in groundwater by rainwater, etc. and spread throughout the surrounding area. Since such compounds are relatively stable in the environment and some of them are suspected to be carcinogenic, soil contamination especially near the groundwater basin used as a drinking water source is a major social problem. Has been.

  For this reason, the purification of contaminated soil by the decomposition and removal of volatile organic chlorine compounds, the purification of aqueous media such as contaminated groundwater, and the accompanying purification of the surrounding gas phase are important for maintaining the health of the general population and protecting the environment. From the viewpoint of this, it is an important issue, and technologies necessary for purification have been developed.

  For example, physical and chemical adsorption treatment represented by activated carbon, decomposition treatment with electromagnetic waves and heat, etc. have been studied, but it should satisfy all aspects such as cost, operability and decomposition efficiency. I can't say that. On the other hand, if microbial decomposition of volatile organochlorine compounds such as tetrachloroethylene, which is stable in the environment, is reported and there are indigenous microorganisms that decompose volatile organochlorine compounds at the site of contamination, the area subject to pollution purification A method called biostimulation has been put into practical use, in which a nutrient source for indigenous microorganisms is added to the substance to activate the indigenous microorganisms to promote the degradation of pollutants. There is also a technique called bioaugmentation in which microorganisms that are artificially cultivated with high decomposability to volatile organochlorine compounds are cultivated and administered to contaminated sites to purify them.

  Dechlorination of volatile organochlorine compounds by microorganisms can be broadly classified into dechlorination by aerobic microorganisms and dechlorination by anaerobic microorganisms.

  Dechlorination by an aerobic microorganism can cause co-metabolism by supplying toluene, phenol, methane as an electron donor, and oxygen as an electron acceptor to the ground. Dechlorination by aerobic microorganisms has a high rate of dechlorination, but because microbial growth and dechlorination are independent, it acquires extra energy to grow microorganisms apart from dechlorination It is inefficient because it requires a carbon source.

  Therefore, dechlorination by anaerobic microorganisms is attracting attention. In the case of dechlorination by anaerobic microorganisms, energy is acquired in conjunction with dechlorination by halogen respiration, so there is no need for a carbon source to acquire extra energy for growth like co-metabolism. However, it is expected as a dechlorination favorite. As shown in FIG. 8, it has been observed that dechlorination by anaerobic microorganisms is dechlorinated from tetrachloroethylene to trichlorethylene, dichloroethylene, vinyl chloride, and ethylene in soil and groundwater. Alcohols, sugars, organic acids, etc. in the soil are used as electron donors, and a mechanism in which chlorine is replaced with hydrogen by halogen respiration, in which organochlorine compounds act as electron acceptors, is considered to be promising.

  However, in the anaerobic microorganisms, free oxygen in the atmosphere inhibits the survival or growth, and thus it is necessary to remove the free oxygen for the survival or growth of the anaerobic microorganisms. Aerobic bacteria have enzymes such as catalase and superoxide dismutase necessary for decomposing free oxygen toxic substances, while anaerobic bacteria do not have these enzymes, and active oxygen acts lethally.

  Therefore, sugar and organic acids are added to grow indigenous aerobic microorganisms that exist in the ground, and anaerobic conditions are created by aerobic respiration of indigenous aerobic microorganisms that are supersaturated. In addition, the development of materials for dechlorination by anaerobic microorganisms has also progressed. Once injected into the ground, polylactic acid continues to generate hydrogen ions by gradually anaerobic decomposition of lactic acid into pyruvic acid and acetic acid for 6 to 12 months. Materials mainly composed of glycerin esters have been commercialized. As described above, an environment that is optimal for anaerobic microorganisms to be dechlorinated is provided by making the target area for contamination purification anaerobic. At the same time, sterilizing protozoa and aerobic microorganisms that may prey on dechlorinated anaerobic microorganisms administered by eliminating oxygen, which is an electron acceptor, by putting them in an anaerobic state in the pollution control area Can do.

  In this way, the contaminated soil is purified by dechlorination from tetrachloroethylene to ethylene by anaerobic microorganisms.

  However, in bioaugmentation, when injecting microorganisms that dechlorinate volatile organochlorine compounds into soil or groundwater at high concentrations, the safety of the microorganisms to be administered and the fluctuations in the field after administration are fully predicted. Even so, there is the possibility of changing the balance of the microbial ecosystem in the pollution control area by administration of a high concentration of microorganisms.

  In order to solve these problems, in the purification method that decomposes pollutants with microorganisms, microorganisms that are highly auxotrophic are used as microorganisms to be administered to the target areas for pollution purification, and the amount of the required substances to be nourished is adjusted. There is a technique of controlling the duration of microorganisms to be administered and treating the administered microorganisms after contamination purification (see, for example, Patent Document 1). Hereinafter, a method for controlling microorganisms to be administered to the contamination purification target area will be described with reference to FIG.

  Nutrients required by highly auxotrophic microorganisms are added and cultured until a certain number of bacteria is reached. The microorganism having a high auxotrophy is a microorganism that cannot grow unless a specific nutrient that is not so much present in the environment is administered. Next, this culture solution was divided into two equal parts, A and B, and the required nutrients were continuously supplied in the A solution as before, but no required nutrients were supplied in the B solution thereafter.

  As can be seen from FIG. 9, it is understood that the number of bacteria decreases with time in the liquid B in which the nutrients to be supplied are not supplied. In other words, the microorganism can be treated by using a highly auxotrophic microorganism as the microorganism to be administered to the contamination purification target area and not supplying the required substance required by the microorganism after purification.

  As described above, the technique such as Patent Document 1 takes into consideration not only the treatment of contaminants but also the treatment of microorganisms administered for contamination purification.

  However, if the object of pollution purification is a volatile organochlorine compound such as tetrachloroethylene or trichlorethylene, and anaerobic microorganisms are used for dechlorination, the above-mentioned pollution purification method is artificially anaerobic during the process of pollution purification. In the state of the state, the excessive anaerobic state cannot activate the anaerobic microorganisms other than the anaerobic microorganisms to be administered for dechlorination and cause them to proliferate.

  Some anaerobic microorganisms have the property of producing malodorous or toxic substances as their products, causing changes in the environment of the purification target area that has been artificially anaerobic, There is also the possibility of causing harm to humans.

  Examples of harm caused by the products of the anaerobic microorganisms are given below. Clostridium tetani tetanus toxin includes muscle stiffness in the vicinity of the infected lesion, jaw-to-neck stiffness, opening disorder, limb tonic convulsions, dyspnea (convulsive), increased excitability to stimulation, anti-bow tension (opisothonus), etc. Cause the symptoms. Clostridium botulinum also produces toxins that cause flaccid paralysis, causing botulism, wound botulism, and infant botulism. Wound botulism is infected by contaminating the wound site with Clostridium botulinum. Infant botulism is transmitted when an infant ingests Clostridium botulinum spores. Clostridium perfringens also produces at least 12 toxins. Among them, alpha toxin is a toxin found in gas gangrene and has a tissue destruction action. If inhaled, it may cause fatal lung damage. In addition, cases of anthrax caused by infection with Bacillus anthracis, a spore-producing facultative anaerobic gram-positive gonococcus, are classified into skin anthrax, lung anthrax, and intestinal anthrax. Especially, skin anthrax accounts for 95% or more. Infection through small wounds in the skin, forms redness, edema and blisters locally. Heales in many cases, but if left untreated, it may enter the blood further from local lymph nodes and develop into sepsis. Lung anthrax is due to inhalation of spores, and intestinal anthrax occurs mainly by eating meat from animals infected with anthrax. Both have a high fatality rate. Similarly, Bacillus cereus, a spore-producing facultative anaerobe, produces toxins such as cereulide and enterotoxin, causing symptoms such as vomiting and diarrhea.

  In addition, an excessively anaerobic state artificially sterilizes indigenous aerobic microorganisms, causing unnecessary concerns that the balance of the ecosystem in the area to be purified is lost due to the generation or growth of anaerobic microorganisms. It might be.

However, the danger described above decreases as the excessive anaerobic state in the soil is alleviated with the diffusion of oxygen in the air. Moreover, it is thought that the possibility that a general consumer will be infected with the pathogenic bacteria shown above by the improvement of the sanitary environment in recent years is low.
Japanese Patent Laid-Open No. 06-134433

  However, the environmental changes and ecosystem changes described above are not preferable from the viewpoint of environmental conservation, and when the pollutants are decomposed and removed, there are no pollutants in the area to be purified, and there are no pollutants. It is preferable to quickly return the environmental change due to excessive anaerobic conditions in the contaminated target area that occurs during the process of decomposition and removal to the state before purification, and contamination that occurs during the process of decomposition and removal of contaminants It is necessary to return the changes in the ecosystem due to the growth and generation of anaerobic microorganisms other than the anaerobic microorganisms administered in the purification target area and the sterilization of the aerobic microorganisms to the state before the purification.

  The present invention solves such a conventional problem, returning the change in the ecosystem due to an anaerobic microorganism generated in the process of decontamination and the administered microorganism after the decontamination, to the state before the decontamination, In other words, it is possible to maintain a balance between aerobic microorganisms and anaerobic microorganisms, and to return the environmental changes caused by these anaerobic microorganisms to the state prior to purification, thereby eliminating the products of anaerobic microorganisms. It aims to provide a method.

  In order to achieve the above object, the pollution purification method of the present invention is a method for making the environment in the purification target area incapable of growing anaerobic microorganisms after purification of the pollutants.

  By this means, it is possible to return the changes in the ecosystem due to anaerobic microorganisms generated in the process of decontamination and administered microorganisms after decontamination, that is, to maintain a balance between aerobic microorganisms and anaerobic microorganisms, Moreover, the pollution purification which can return the environmental change by these anaerobic microorganisms to the state before purification | cleaning, ie, can eliminate the product of anaerobic microorganisms, is obtained.

  ADVANTAGE OF THE INVENTION According to the present invention, it is possible to return the changes in the ecosystem that have occurred in the process of decontamination to the natural state before the decontamination, maintain the balance between the aerobic microorganisms and the anaerobic microorganisms and It is possible to provide a pollution purification method that is effective in detoxifying various anaerobic microorganisms.

  Further, according to the present invention, in the method for rendering the environment in the pollution target area incapable of growing anaerobic microorganisms, changes in the ecosystem generated during the process of cleaning up pollution by increasing the oxygen concentration in the pollution control target area, It is possible to provide an effective pollution purification method capable of returning environmental changes to the state before purification, and detoxifying harmful anaerobic microorganisms after pollution purification.

  Further, according to the present invention, in the method of generating oxygen, sterilization can be promoted by its strong oxidizing power by injecting ozone water into the pollution purification target area, and anaerobic generated in the process of pollution purification. Deodorize / decompose the product of sexual microorganisms. Furthermore, since it is returned to water by several tens of minutes due to the unstable nature of ozone, it does not remain in the treated water, so that it is possible to provide a pollution purification method that is effective for safe treatment.

  Further, according to the present invention, by injecting hydrogen peroxide water into the pollution target region in the method of generating oxygen, sterilization is promoted by generated OH radicals, and anaerobic microorganism products can be deodorized and decomposed. The effect of increasing the amount of catalyst added to promote the foaming of oxygen and reducing the amount of oxygen or delaying oxygen generation by adding no catalyst to increase the diffusibility of hydrogen peroxide water in the soil It is possible to provide a contamination purification method.

  Further, according to the present invention, by injecting a mixture containing oxygen molecules into the contamination purification target region in the method of supplying oxygen, no chemical reaction other than oxidation occurs in the contamination purification target region, so that it is possible to work safely. An effective pollution purification method can be provided. The mixture containing oxygen molecules is an aqueous solution or gas gas containing oxygen molecules.

  Further, according to the present invention, in the method for making the environment in the contaminated target area incapable of growing anaerobic microorganisms, by improving the circulation of air in the soil and the atmosphere in the polluted target area, special gas, aqueous solution Therefore, it is possible to provide a pollution purification method that can be realized at low cost because facilities are unnecessary.

  The invention according to claim 1 of the present invention is a soil purification method for purifying soil contaminated with harmful substances with anaerobic microorganisms so that the environment in the soil is returned to a state before purification with anaerobic microorganisms. This is a method for decontamination that is characterized by reducing the anaerobic microorganisms administered for decontamination and the anaerobic microorganisms that have been generated or proliferated during the decontamination process. It has the effect of returning to the state before purification by anaerobic microorganisms.

  According to a second aspect of the present invention, in the method for purifying soil contaminated with harmful substances with anaerobic microorganisms, the anaerobic microorganisms cannot grow in the environment in the soil after the anaerobic microorganisms are administered to the soil. It is a method for decontamination that is characterized by the condition of anaerobic microorganisms that are administered for decontamination and anaerobic microorganisms that are generated or proliferated during the decontamination process. It has the effect | action of returning to the state before purifying by anaerobic microorganisms.

  Further, the invention according to claim 3 of the present invention is a contamination purification method characterized in that after the anaerobic microorganisms are administered to the soil, the oxygen concentration of the soil is increased, and oxygen molecules are contaminated. It has the effect of causing cell damage of anaerobic microorganisms administered for purification and anaerobic microorganisms generated or propagated in the process of decontamination.

  The invention according to claim 4 of the present invention is a method for purifying soil, wherein oxygen is generated in the soil in a method for purifying soil contaminated with harmful substances with anaerobic microorganisms. The generated oxygen molecules have the effect of causing cell damage of anaerobic microorganisms administered for decontamination and anaerobic microorganisms generated or proliferated in the process of decontamination.

  The invention according to claim 5 of the present invention is a method for purifying soil contaminated with harmful substances with anaerobic microorganisms, and injecting ozone water into the soil after administering the anaerobic microorganisms to the soil. It is characterized by the fact that ozone is dissociated into oxygen and generated, and has the effect of oxidizing bacteria by its strong oxidizing power.

  According to a sixth aspect of the present invention, in the method for purifying soil contaminated with harmful substances with anaerobic microorganisms, hydrogen peroxide water is added to the soil after the anaerobic microorganisms are administered to the soil. The hydrogen peroxide solution has an action of foaming oxygen and generating OH radicals.

  The invention according to claim 7 of the present invention is a method for purifying soil contaminated with harmful substances with anaerobic microorganisms, and after administering the anaerobic microorganisms to the soil, Manganese dioxide is injected, and the manganese dioxide has an action of promoting the foaming of oxygen of the hydrogen peroxide solution.

  The invention according to claim 8 of the present invention is a method for purifying soil contaminated with harmful substances with anaerobic microorganisms, wherein oxygen molecules are injected into the soil after the anaerobic microorganisms are administered to the soil. The oxygen molecules have the effect of causing cell damage of anaerobic microorganisms and increasing the oxygen concentration of the soil.

  The invention according to claim 9 of the present invention is a method for purifying soil contaminated with harmful substances with anaerobic microorganisms, and injecting an oxygen-containing substance into the soil after administering the anaerobic microorganisms to the soil. The oxygen molecules contained in the oxygen-containing water cause cell damage of anaerobic microorganisms and increase the oxygen concentration of the soil.

  According to a tenth aspect of the present invention, in the method for purifying soil contaminated with harmful substances with anaerobic microorganisms, the gas containing oxygen molecules in the soil after the anaerobic microorganisms are administered to the soil. The oxygen molecules contained in the gas cause the cell damage of the anaerobic microorganisms and increase the oxygen concentration of the soil.

  The invention according to claim 11 of the present invention is a method for purifying soil contaminated with harmful substances with anaerobic microorganisms, wherein the aqueous solution containing oxygen molecules in the soil after the anaerobic microorganisms are administered to the soil. The oxygen molecules contained in the aqueous solution or the oxygen molecules foamed from the aqueous solution cause cell damage of the anaerobic microorganisms and increase the oxygen concentration of the soil.

  The invention according to claim 12 of the present invention is characterized in that oxygen molecules are saturated or supersaturated in a mixture containing oxygen molecules, and the oxygen molecules contained in the mixture prevent cell damage of anaerobic microorganisms. It has the effect of promoting and increasing the oxygen concentration of the soil.

  Further, the inventions according to claims 13 to 15 of the present invention are methods for purifying pollution characterized by improving circulation of air in the soil and in the atmosphere, and oxygen contained in the atmosphere can be rapidly introduced into the soil. Has the effect of diffusing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
In the method of the present invention, the harmful substances are volatile organic chlorine compounds and the like, which are hardly decomposable harmful substances that are difficult to be completely decomposed and detoxified by aerobic microorganism treatment. Examples of such harmful substances include chemical substances such as tetrachloroethylene (PCE), trichlorethylene (TCE), cis-1,2-dichloroethylene (cis-1,2-DCE), and vinyl chloride (VC).

  The purification method of the present invention is characterized by increasing the oxygen concentration in the soil contaminated with the contaminant, and after the contaminant purification by the dechlorinated anaerobic microorganisms administered to purify the contaminant, the soil By increasing the oxygen concentration in the medium, the anaerobic microorganisms generated or proliferated in the process of purifying the administered anaerobic microorganisms and contaminants are killed. In addition, in this invention, if it is a place contaminated with the pollutant, it shall not be limited to soil, but shall be applied also to groundwater.

  In the present invention, the timing for increasing the oxygen concentration in the soil is not only at the stage where purification is completed after administration of anaerobic microorganisms, but at the stage immediately after administration or during purification after administration if anaerobic microorganisms are administered. Even if it exists, the same effect can be acquired. If the purification by anaerobic microorganisms is interrupted for some reason, the oxygen concentration in the soil may be increased immediately after the administration of the anaerobic microorganisms. In addition, when changing to another purification method because the effect of purification by anaerobic microorganisms is not seen in the middle of purification, the oxygen concentration in the soil can be increased by increasing the oxygen concentration in the soil during the purification. The environment can be returned to the state before purification by anaerobic microorganisms.

  When anaerobic microorganisms are used for decontamination, it is necessary to first put the anaerobic microorganisms to be administered in an anaerobic state so that the anaerobic microorganisms to be administered can be proliferated without problems in the contaminated areas and efficiently purified. When nutrient sources for aerobic microorganisms such as sugar and organic acids are added to the pollution control area, the aerobic microorganisms proliferate and the aerobic breathing action reduces oxygen in the pollution control area and creates an anaerobic state. Can do. Control during anaerobic treatment can be handled by constantly monitoring the oxygen gas concentration or liquid concentration, and controlling the amount of nutrient source added to the aerobic microorganism based on these measured values. The target control level is that the oxidation-reduction potential is −10 0 mV or less under the conditions in the liquid, and the nutrient source of the aerobic microorganism is added as needed to control to this level.

  As a specific example of the anaerobic microorganism injection device that can be realized by the purification method of the present invention, FIG. 1 shows a case where anaerobic microorganisms to be dechlorinated are injected into an injection well. 1 is soil, 2 is contaminated soil, 3 is a poorly permeable layer, 4 is pollutant, and 5 is an injection well.

  An injection well 5 reaching the underground contaminated soil 2 is provided in the vicinity of the storage location of the pollutant 4, and a water injection pipe 6 for injecting an anaerobic microorganism 13 to be dechlorinated is inserted into the injection well 5. On the ground, an anaerobic culture tank 8 for culturing anaerobic microorganisms 13 to be dechlorinated and a nutrient storage tank 11 for storing nutrients thereof are installed. The anaerobic microorganism 13 to be dechlorinated cultured in the anaerobic culture tank 8 is supplied to the water injection pipe 6 through the microorganism supply pipe 9 by the first pump 7 and injected into the soil from the injection well 5. Further, nutrients for activating the anaerobic microorganisms 13 injected into the contaminated soil 2 are supplied from the nutrient storage tank 11 to the water injection pipe 6 through the nutrient supply pipe 12 by the second pump 10, and from the injection well 5. It is injected into the contaminated soil 2. In this apparatus, the water supply equipment such as the microorganism supply pipe 9 and the water injection pipe 6 through which the anaerobic microorganisms 13 pass has an airtight structure.

  As anaerobic microorganisms used for decontamination, preferably, the genus Methanarcarcina, Methanococcus, Methanobacterium, Methanobrevibater, Methanogenium, Desobacterium, Clostridium, and Clostridium, However, it is not necessarily limited to the above microbiological classification as long as it is an anaerobic microorganism and has the ability to dechlorinate volatile organochlorine compounds.

  In addition, the anaerobic microorganisms to be administered may be allowed to act alone or in appropriate combinations.

  The amount of the anaerobic microorganism to be administered can be determined so as to obtain a desired purification result in consideration of the type of anaerobic microorganism to be administered and the degree of contamination in the contamination purification target area.

  In addition, when adding arbitrary microorganisms, it is possible to use microorganisms that have already been isolated or newly screened according to the purpose in the environment. It does not matter even if it is a system. It is also possible to use microorganisms that have undergone artificial mutation or microorganisms that have been genetically modified. It is also possible to use microorganisms immobilized on a carrier such as ceramics.

  Nutrients injected into the soil from the nutrient storage tank include, but are not limited to, culture solutions that promote the growth of anaerobic microorganisms to be dechlorinated, glucose solutions, unsaturated fatty acids, amino acids, manganese sulfate, and the like. .

  In order to further efficiently purify the contamination purification target region, the anaerobic microorganisms to be administered and nutrients thereof may be added to the contaminated soil as needed.

  As described above, the pollution control target area is adjusted to an optimum environment for anaerobic microorganisms, and the dechlorination of volatile organic chlorine compounds and the like by the anaerobic microorganisms is promoted. As a result, the anaerobic microorganisms to be dechlorinated are activated and propagated, but anaerobic microorganisms other than the anaerobic microorganisms administered therewith are also activated and propagated.

  Anaerobic microorganisms other than the above-mentioned anaerobic microorganisms include Clostridium genus, Propionibacterium genus, Arachnia genus, Bifidobacterium genus, Lactobacillus genus, Actinomyces genus, Eubacterum genus, Eubacterium genus, Lactonobacterium, Genus, Bilophila, Dichelobacter, Fibrobacter, Megamonas, Mitsukella, Porphyromonas, Prevotella, Rikenella, Ruminobacter, Sebaldella Tissierella genus, Butyrivibrio genus, Anaerobiospirillum genus, Succinivibrio genus, Succinimonas genus, Anaerovibrio genus, Selenomonas genus, Pectinatus genus, Wolinella spp., Campylobacter spp., Treponema species, Borrelia spp., Sarcina genus, microorganisms and the like belonging to such Coprococcus genus.

  As soon as it can be confirmed that it is below the environmental standard, the oxygen concentration in the contamination purification target area is increased. As an index for confirming pollution purification, soil in a pollution purification target area is collected, and volatile chlorine compounds contained therein are measured by gas chromatography or the like. In addition, when the dechlorination by anaerobic microorganisms is interrupted for some reason, the oxygen concentration in the contamination purification target region can be increased immediately after administration of the anaerobic microorganisms to be dechlorinated.

  In order to increase the oxygen concentration, ozone water is injected into the contamination purification target area. Therefore, a dissolved ozone generator is installed on the ground, and water is injected from the injection well using an airtight water supply facility so that the dissolved ozone does not escape to the outside air. The dissolved ozone maker may include an ozone generator and a dissolved ozonation tank. There are three types of ozone generation methods for the dissolved ozone generator or the ozone generator: an ultraviolet type, a discharge type, and a water electrolysis type, and any method can be adopted. A relatively low-cost ultraviolet type may be used, or a large-scale discharge type ozonizer may be used.

  As a specific example of the contamination purification apparatus that can be realized by the purification method of the present invention, FIG. 2 shows a case where water is injected into ozone water and an injection well.

  A water injection pipe 6 for injecting ozone water 17 is inserted into the injection well 5 reaching the contaminated soil 2. On the ground, an ozone water production machine 15 and a water storage tank 14 are installed, and ozone water 17 is produced by dissolving ozone in the water supplied from the water storage tank 14. The ozone water 17 is supplied to the water injection pipe 6 through the water supply pipe 16 by the first pump 7 and injected into the contaminated soil 2 from the injection well 5. In this apparatus, the water supply equipment such as the water supply pipe 16 through which the ozone water 17 passes has an airtight structure.

  The dissolved ozone concentration at the time of injection into the injection well 5 can be arbitrarily changed according to the restoration environment and the restoration scale, but it is desirable that the dissolved ozone concentration is 4 mg / L or more. In fact, both bacteria and viruses are almost completely killed by contact with 4 mg / L of ozone water for several seconds. Moreover, the higher the setting of the dissolved ozone concentration, the higher the equipment cost of the necessary ozone-related equipment, which is uneconomical.

  In addition, when inject | pouring ozone in the pollution purification object, you may inject | pour as gas and may make it melt | dissolve in the water | moisture content in soil or soil.

  In addition, when ozone water is a method in which gaseous ozone generated by various ozonizers is dissolved in a dissolved ozonizer, the dissolved oxygen concentration at the time of aeration is lower than before aeration depending on the ability of the ozonizer There is also a possibility. Even in such a case, the dissolved ozone replaced from the dissolved oxygen is gradually decomposed into oxygen in the process of diffusion after being injected into the soil, so that the actual amount of oxygen to be supplied does not decrease.

  Ozone is an allotrope of oxygen in which one molecule is composed of three oxygen atoms, and is present in a trace amount (0.1 ppm or less) in the atmosphere. It is a gaseous substance with a unique odor and gradually decomposes back to complete oxygen at room temperature. In order to return the anaerobic atmosphere generated in the process of decontamination from the excessive anaerobic state to the state before the purification, the property that ozone returns to oxygen and the administration that became unnecessary at the end of purification due to its strong oxidizing power It utilizes the property to sterilize anaerobic microorganisms and anaerobic microorganisms generated in the process of decontamination.

  Further, Bacillus and Clostridium, which are anaerobic microorganisms that may live in contaminated soil, may form spores in the cells when the oxygen concentration in the contamination purification area increases. Spores are extremely resistant to physicochemical treatment and can withstand heating at 100 ° C. There are also examples that are resistant to drying and have not been killed for decades in a dry state. A spore is a kind of bacteria that is formed when the growth conditions are poor, such as when the oxygen concentration is high, and all metabolism stops, but life is maintained and an appropriate environment such as when the oxygen concentration is low Then, it will be restored to bacteria and proliferate again. Ozone is also effective against these bacterial spores.

  In addition, using a machine such as a shovel car to improve the circulation of air in the soil and air in the contaminated area, and to quickly diffuse oxygen contained in the air in and into the soil. Dig up the soil.

  FIG. 3 is a schematic diagram of soil deposits before digging up the soil. The soil mainly contains solid matter 18, gas 19, and moisture 20. The gas 19 contains nitrogen, oxygen, and the like. When the soil is in an anaerobic state, the gas 19 may contain a product of anaerobic microorganisms. The pores in the soil are made up of a relatively large space and a small space. The small space is filled with moisture 20 by the capillary pressure, and air cannot enter or exit.

  FIG. 4 is a schematic diagram of soil deposits obtained by digging up soil using a machine such as an excavator. By digging up the soil and creating relatively large pores in the soil, the capillary pressure is reduced, moisture is eliminated, and oxygen-containing gas is included in that portion. In addition, air can be made in and out by eliminating moisture contained in the pores, and air circulation in the soil and the atmosphere can be improved.

  Further, in order to efficiently diffuse oxygen contained in the soil in the contaminated area and the air in the atmosphere, a vent pipe 21 as shown in FIG. 5 may be installed in the soil. The ventilation pipe has a cylindrical shape and a ventilation hole at the center in the axial direction, from which air in the atmosphere directly touches the contaminated soil. One or more vent pipes 21 may be installed depending on the range of the contamination purification target area.

  Control during aerobic treatment can be handled by constantly monitoring the oxygen gas concentration or in-liquid concentration, and controlling the amount of ozone water added to the contamination purification target region based on these measured values. The target control level is that the oxidation-reduction potential is preferably +100 mV or more and +400 mV or less in the liquid condition, and the ozone water is added as needed to control to such a level.

(Embodiment 2)
As a specific example of the contamination purification apparatus that can be realized by the purification method of the present invention, FIG. 6 shows a case where hydrogen peroxide water is injected into the injection well.

  As shown in FIG. 6, after the decomposition of the pollutant by the anaerobic microorganism to be administered is completed, the hydrogen peroxide solution 22 is injected into the contaminated soil 2 from the hydrogen peroxide solution storage tank 23 through the water injection pipe 6.

When the hydrogen peroxide solution 22 is injected from the water injection pipe 6 into the contaminated soil 2, the hydrogen peroxide solution 22 is diluted to an appropriate concentration and injected from the situation of acidification of the soil, peripheral effects of the hydrogen peroxide solution 22 and the like. There is a need. The proper conditions for injection must be found by prior treatability tests, but the injection concentration range is 15% (H ₂ O ₂ ) or less.

  When foaming of oxygen from the hydrogen peroxide solution 22 is desired to be performed with high efficiency, an aqueous solution in which manganese dioxide 24 as a catalyst is dissolved is injected after the hydrogen peroxide solution 22 is injected into the contaminated soil 2. Alternatively, the hydrogen peroxide solution 22 may be injected after the catalyst is injected into the contamination target region. However, since oxygen is generated early and the hydrogen peroxide solution 22 may be consumed before reaching a place having a distance, it is not preferable. Further, since oxygen is generated early even when an excess catalyst is added, generation of oxygen can be delayed by refraining from adding the catalyst.

  In addition, an aqueous solution of sodium permanganate, calcium permanganate, vitamin C, glutathione peroxidase, peroxidase, catalase, or the like can be substituted for a catalyst that increases the reaction rate of oxygen generation in hydrogen peroxide 22.

When it is desired to generate OH radicals from the hydrogen peroxide solution 22 with high efficiency, ferrous sulfate is added to the hydrogen peroxide solution 22 to cause the Fenton reaction. However, Japan's main alluvial and diluvial deposits often contain moderate amounts of sulfide minerals in the fine-grained phase and a considerable amount of iron in the soil. When the hydrogen peroxide solution 22 is injected, iron in the soil or sulfide mineral and the hydrogen peroxide solution 22 react to produce ferrous sulfate (FeSO ₄ ), and finally the Fenton reaction is established. In many cases, it is not necessary to add a large amount of iron. In addition, OH radicals may be generated early due to the addition of an excess amount of iron and may be consumed before reaching a contamination source having a distance. When there is a distance between the injection well 5 and the contamination source, generation of OH radicals can be delayed by refraining from adding iron. Furthermore, it is necessary to avoid excessive foaming of oxygen from the hydrogen peroxide solution 22 as much as possible. Excessive bubbling of oxygen from the hydrogen peroxide solution 22 inhibits the generation control of OH radicals. In addition, other major causes of foaming are cases where organic substances such as humic substances (humic substances etc.), volcanic ash soil such as Kanto Loam, loose cohesive soil, manganese components, oil contamination, etc. are in the pollution control area. .

  In order to achieve the target oxidation-reduction potential, the hydrogen peroxide solution 22 and manganese dioxide 24 are added as needed.

  Further, in order to efficiently diffuse oxygen contained in the air in the soil 1 in the contamination target area, by digging up the soil using a machine such as a shovel car or installing a vent pipe 21 in the soil, Oxygen contained in air in the atmosphere may be efficiently diffused into the soil 1 in the contamination target area.

(Embodiment 3)
As a specific example of the contamination purification apparatus that can be realized by the purification method of the present invention, FIG. 7 shows a case where water containing oxygen is injected into an injection well.

  As shown in FIG. 7, after the decomposition of the pollutant by the anaerobic microorganism to be administered is completed, the oxygen-containing water 25 is injected into the contaminated soil 2 from the oxygen-containing water storage tank 26 through the water injection pipe 6.

  The periphery of the soil 1 is blocked by an air-impermeable layer 27 that reaches the underground water-impermeable layer 3 and covered with an air-impermeable sheet 28 on the soil 1 inside.

  If necessary, the pressure is reduced by pumping water from the water absorption pipe 29 to enhance the diffusibility of oxygen and oxidize anaerobic microorganisms.

  In the above purification method, the oxygen-containing water 25 is preferably oxygen-saturated water, particularly supersaturated water. The higher the oxygen concentration, the higher the oxygen concentration increase rate.

  The oxygen-containing water 25 generally has 5 to 200 mg oxygen, preferably 8 to 150 mg oxygen, in 1 liter of water. The supersaturated water and saturated water of oxygen can be obtained, for example, by injecting oxygen gas from the water injection pipe while keeping the container with the water injection pipe containing water in a pressurized state. Instead of the oxygen-containing water 25, oxygen gas may be directly injected into the soil, but the efficiency generally decreases.

  Oxygen-containing water 25 is not as reactive as ozone water or hydrogen peroxide water, and its sterilizing effect is weak, but it is less reactive than ozone and hydrogen peroxide, and is therefore more diffusible in the soil. High diffusivity.

  Further, after injecting the oxygen-containing water 25 into the contamination target region, preferably by reducing the pressure by pumping water, the oxygen in the oxygen-containing water 25 becomes supersaturated, and oxygen that cannot be dissolved in the oxygen-containing water starts to foam. Since the foamed oxygen passes through even the poorly water-permeable layer 3, such a contaminated layer can be purified. In addition, the various water-permeable layers 3 may accumulate | store various substances, and may be purified only by passage of oxygen.

  In order to achieve the target oxidation-reduction potential, the oxygen-containing water 25 is added as needed.

  Further, in order to efficiently diffuse oxygen contained in air in the soil 1 in the contamination target area, the soil is excavated by using a machine such as a shovel car, or the ventilation pipe 21 is installed in the soil. Oxygen contained in air in the atmosphere may be efficiently diffused into the soil 1 in the target region.

  When administering anaerobic microorganisms capable of decomposing compounds that are toxic to the human body or organisms, the area to be decontaminated is made anaerobic in order to increase the activity of the anaerobic microorganisms. It can also be applied to soil purification and groundwater purification.

Sectional drawing which shows the outline of the apparatus which inject | pours the anaerobic microorganisms in Embodiment 1 of this invention. Sectional drawing which shows the outline of the apparatus which inject | pours the ozone water in Embodiment 1 of this invention Schematic diagram of soil deposit before digging up soil in Embodiment 1 of the present invention Schematic diagram of soil deposit after digging up soil in Embodiment 1 of the present invention Sectional drawing which shows the outline of the vent pipe in Embodiment 1 of this invention Sectional drawing which shows the outline of the apparatus which inject | pours the hydrogen peroxide solution in Embodiment 2 of this invention Sectional drawing which shows the outline of the apparatus which inject | pours oxygen-containing water in Embodiment 3 of this invention Outline of dechlorination of tetrachlorethylene Explanatory diagram showing the remaining number of auxotrophic microorganisms

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Soil 2 Contaminated soil 3 Impervious layer 4 Pollutant 5 Injection well 6 Injection pipe 7 1st pump 8 Anaerobic culture tank 9 Microorganism supply pipe 10 2nd pump 11 Nutrient storage tank 12 Nutrient supply pipe 13 Anaerobic microorganism 14 Water storage Tank 15 Ozone water production machine 16 Water pipe 17 Ozone water 18 Solid 19 Gas 20 Moisture 21 Vent pipe 22 Hydrogen peroxide solution 23 Hydrogen peroxide solution storage tank 24 Manganese dioxide 25 Oxygen-containing water 26 Oxygen-containing water storage tank 27 Non-ventilated Layer 28 Air-impermeable sheet 29 Water absorption pipe

Claims (15)

In a soil purification method for purifying soil contaminated with harmful substances with anaerobic microorganisms, the environment in the soil is returned to a state before purification with anaerobic microorganisms after the anaerobic microorganisms are administered to the soil. A method for purifying contaminated soil. A soil purification method for purifying soil contaminated with harmful substances with anaerobic microorganisms, characterized in that after the anaerobic microorganisms are administered to the soil, the environment in the soil is brought into a state where the anaerobic microorganisms cannot survive. To clean up contaminated soil. The method for purifying contaminated soil according to claim 1 or 2, wherein the oxygen concentration in the soil is increased after the anaerobic microorganism is administered to the soil. The method for purifying contaminated soil according to any one of claims 1 to 3, wherein oxygen is generated in the soil. The method for purifying contaminated soil according to any one of claims 1 to 4, wherein ozone water is injected into the soil. The method for purifying contaminated soil according to any one of claims 1 to 4, wherein hydrogen peroxide is injected into the soil. The method for purifying contaminated soil according to any one of claims 1 to 4, wherein hydrogen peroxide and manganese dioxide are injected into the soil. The method for purifying contaminated soil according to any one of claims 1 to 3, wherein oxygen is injected into the soil. The method for purifying contaminated soil according to claim 1, wherein a mixture containing oxygen molecules is injected into the soil. The method for purifying contaminated soil according to any one of claims 1 to 3, 8, or 9, wherein a gas containing oxygen molecules is injected into the soil. 10. The method for purifying contaminated soil according to claim 2, wherein an aqueous solution containing oxygen molecules is injected into the soil. The method for purifying contaminated soil according to any one of claims 9 to 11, wherein oxygen is saturated or supersaturated in the mixture containing oxygen molecules. The method for purifying contaminated soil according to any one of claims 1 to 3, wherein air circulation in soil and air is improved. 14. The method for purifying contaminated soil according to claim 1, wherein the soil is dug up. The method for purifying contaminated soil according to any one of claims 1 to 3, wherein a ventilation pipe is installed in the soil.

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