JP3967602B2 - Storage method including detoxification process of contaminated soil - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a method for storing pollutants having high toxicity even at low concentrations, for example, contaminated soil containing dioxins while detoxifying them, and a management system therefor.
[0002]
[Prior art]
  Dioxins are generated in the process of incineration of domestic waste and industrial waste in an incinerator, etc., and are discharged together with exhaust gas and waste water. Since dioxins are chemically stable and difficult to be decomposed, dioxins adsorbed on the soil and the like are accumulated almost without being altered or decomposed. Moreover, it is highly toxic even at low concentrations, and when it is ingested by animals such as humans through the food chain, it accumulates in the body, resulting in major social problems such as carcinogenicity and fetal malformation. Yes.
[0003]
  Until now, various methods have been developed as methods for treating contaminated soil with dioxins. These methods can be broadly divided into methods of physical containment, methods of decomposing and detoxifying by physical and chemical means, and methods of decomposing and detoxifying using microorganisms. The following problems have been pointed out.
[0004]
  First, the method of physical containment is to contain the contaminated area in a sealed space such as a barrier layer such as a partition wall or a water-impermeable sheet, and to isolate it from the non-contaminated area. As such a method, a method of excavating contaminated soil or the like, and embedding or embedding it by embankment is adopted. However, this method of containment simply moves the contaminated soil due to dioxins to another location. Therefore, if the leakage and scattering from the isolation space are not completely blocked, new environmental problems will occur at the destination. There is also a risk. Moreover, since this method does not detoxify dioxins, it is not a fundamental solution, and there is a problem that a large amount of contaminated soil must be kept isolated in the future.
[0005]
  As a method of decomposing dioxins by physical means, the melt-solidification (geomelt) method is to put contaminated soil in a container installed in the ground, place an electrode, energize the electrode, and joule heat the soil. Heated and melted by glass to solidify into vitrified, melt-solidified (geomelt) method that thermally decomposes dioxins contained in soil, method of burning contaminated soil at extremely high temperature, and dechlorination of dioxins by ultraviolet irradiation Examples include a method for performing decomposition. Of these, thermal decomposition is an extremely effective method, but it is unsuitable for treating a large amount of soil, and a large amount of energy needs to be input. Become. In addition, irradiation with ultraviolet rays is suitable for purifying dioxins in water, but is not suitable for decomposing dioxins contained in soil because it is decomposed only within the reach of ultraviolet rays.
[0006]
  As a method for decomposing dioxins by chemical means, for example, alkali-catalyzed chemical decomposition (BCD) is a method in which sodium bicarbonate is added to and mixed with a contaminated medium such as soil containing dioxins and indirectly heated. Dechlorinated. However, this method requires a large-scale processing facility such as a chemical mixing / feeding facility, a heating reactor, a gas collection facility, and a collected gas processing facility, and requires a large amount of heat energy. Cost burden is enormous.
[0007]
  The method of decomposing and detoxifying using microorganisms is a method in which dioxins are decomposed by enzymes produced by certain microorganisms, and is expected as a method that can be processed in situ and at low cost. It is difficult to set conditions for predominating microorganisms with a high decomposing ability against the soil in contaminated soil and to maintain them.
[0008]
  In addition, when decontaminating contaminated soil in-situ, in order to prevent the spread of contamination to the surrounding environment, facilities for preventing the scattering of soil dust must be constructed each time and long-term environmental monitoring is required. Become.
[0009]
[Problems to be solved by the invention]
  The present invention has been made in view of the above-described problems, and its technical problem is that dioxins can be processed at low energy and at low cost without taking over the risk of contamination in the future in the treatment of contaminated soil with dioxins and the like. It is to make things harmless.
[0010]
[Means for Solving the Problems]
  In order to effectively solve conventional technical problems, the present invention adopts a method of isolating contaminated soil from dioxins from non-contaminated areas by physical containment, and does not take over the risk of contamination in the future. During this period, the contaminated soil is detoxified with low energy. That is, the storage method including the detoxification process of the contaminated soil according to the invention of claim 1 is isolated from the non-contaminated soil by the water shielding layer and is enclosed in a sealed space with a translucent structure. The contaminated soilThe structure is provided with an ultraviolet irradiation device that irradiates the contaminated soil with ultraviolet rays, collects air in the treatment space, and circulates the air through the contaminated soil to release it to the treatment space. Is what you do.Sunlight that has passed through a light-transmitting structure, especially ultraviolet light contained in sunlight, has a photolytic action on dioxins, etc., so contaminated soil is deposited and stored in a state of being isolated by the water shielding layer and the structure. To decompose surface contaminantsDuring cloudy weather or at night, dioxins on the surface of the soil are decomposed by irradiating ultraviolet rays from an ultraviolet irradiation device. Also, since air in the treatment space is collected and air circulation is performed to vent the air to the contaminated soil and release it to the treatment space, the contaminated soil dust is not diffused outside the structure, By ventilating the soil, it is possible to improve the growth of microorganisms having the ability to decompose pollutants, and the air that has been ventilated to the contaminated soil is once released into the treatment space, and is contained in this air. Soil dust pollutants are decomposed by ultraviolet rays.
[0011]
  The storage method including the detoxification step of the contaminated soil according to the invention of claim 2 is the method of claim 1,A plant having the ability to absorb pollutants is cultivated in the contaminated soil, grown for a required period, and then cut or dug. The vertical distribution of plant roots is limited to the vicinity of the surface layer, but roots have a large surface area by repeatedly branching and generating root hairs. It forms a system suitable for efficiently collecting pollutants such as dioxins diffused in the soil. The pollutant accumulated in the plant body is removed from the soil by cutting or digging after the plant body has grown for a predetermined period. And since ventilation | gas_flowing is performed in soil, the growth of the plant which has the capability to absorb and decompose | disassemble a pollutant can be made favorable.
[0012]
  The storage method including the detoxification step of the contaminated soil according to the invention of claim 3 is the method of claim 1.Or 2In the method described in, the organic solvent or surfactant is sprayed on the contaminated soil in a timely manner to separate the contaminants such as dioxins adsorbed on the soil particles and move them to the soil surface layer.The organic solvent or surfactant that has penetrated to the lowest layer of the contaminated soil is recovered and used for respreading.
[0013]
[0014]
[0015]
[0016]
[0017]
[0018]
[0019]
[0020]
[0021]
  Claim 4The storage method including the detoxification process of the contaminated soil according to the invention ofClaim 2In the method described inA pH sensor for detecting a soil pH value is embedded in the contaminated soil, and a neutralizing agent is added to the contaminated soil through a pump whose drive is controlled by a control device based on the detected value.In other words, plant and soil microorganisms are significantly less active in acidic soils.However, according to the structure of Claim 4, since soil pH is kept at an appropriate value, it can prevent that the activity of a plant or a soil microorganism falls.
[0022]
[0023]
[0024]
[0025]
DETAILED DESCRIPTION OF THE INVENTION
[First form]
  FIG. 1 is an explanatory view showing a first embodiment of a storage method including a detoxification process for contaminated soil according to the present invention. The method of the present invention is also effective for detoxifying soil contaminated with contaminants other than dioxins such as PCBs, but the following description will be made on soil contaminated with dioxins. The dioxins here refer to all dioxins including coplanar PCB.
[0026]
  In FIG. 1, reference numeral 1 denotes a greenhouse structure constructed on the ground 2 in a non-polluted area. This greenhouse structure 1 has a floor portion 1a whose upper layer is made of a concrete floor plate and a lower layer portion made of a clay liner, a lower side wall 1b constructed of concrete or the like so as to surround the periphery thereof, and a glass plate on the glass plate. And a transparent roof 1d in which a glass plate is hermetically combined thereon, and the floor portion 1a is in a position dug down from the ground surface level GL of the ground 2 appropriately. Further, between the floor portion 1a and the lower side wall 1b and the ground 2, a water shielding sheet 1e made of a water shielding material such as synthetic resin or rubber is provided.
[0027]
  The portion surrounded by the lower side wall 1b on the floor portion 1a in the greenhouse structure 1 is a contaminated soil storage portion, that is, the contaminated soil 3 due to dioxins is charged and deposited at a predetermined layer thickness in this portion. Is done.
[0028]
  Below the transparent roof 1d in the greenhouse structure 1,UV light 4Are attached at appropriate intervals.UV light 4Irradiates the surface of the contaminated soil 3 deposited in the contaminated soil storage part of the greenhouse structure 1 with ultraviolet light having a wavelength of 400 nm or less that exerts a photolytic action on dioxins.
[0029]
  A liquid supply pipe 5 in which a plurality of spray nozzles 5 a are arranged at appropriate intervals is provided above the sealed processing space S by the greenhouse structure 1, and an upstream end thereof is connected via a pump 6. It is connected to the additive storage tank 7. The additive storage tank 7 stores an organic solvent or a surfactant. In the case of organic solvents, ethers such as dimethyl sulfoxide, dimethyl ether, and ethyl methyl ether, esters such as ethyl acetate and methyl acetate, ketones such as acetone, methyl butyl ketone, and ethyl methyl ketone, methyl alcohol, isopropyl alcohol, and the like 1 from alcohols, alkanes such as dioxane, normal hexane, heptane and octane, alkenes such as 1-pentene and 1-pentyne, aromatic organic solvents such as benzene, toluene and xylene, and phenols such as phenol and chlorophenol One or more types are selected. In the case of surfactants, anionic surfactants represented by higher fatty acid alkali salts and alkyl sulfonates, nonionic surfactants represented by polyethylene glycol alkyl ethers and fatty acid monoglycerides, and amino acids. One or more amphoteric surfactants are selected. In addition, when using surfactant, water softening agents, such as polyphosphoric acid and sodium sulfate, are used together as needed.
[0030]
  A dust collector 8 is attached to the transparent roof 1 d in the greenhouse structure 1, and the intake port 8 a is open to the processing space S in the greenhouse structure 1. The dust collector 8 is filled with a HEPA filter (High Efficiency Particulate Airfilter) and activated carbon (not shown), and the downstream side thereof is connected to the intake port of the blower 10 via a pipe 9. In the contaminated soil storage part on the floor part 1 a in the greenhouse structure 1, a vent pipe 11 having a large number of vent holes (not shown) is arranged, and an upstream end thereof is connected via a pipe 12. Are connected to the outlet of the blower 10. Moreover, this ventilation pipe 11 is in the state of being buried in the lower layer part of the contaminated soil 3 introduced into the contaminated soil storage unit.
[0031]
  A part of the side wall of the greenhouse structure 1 is provided with an openable / closable entrance for an operator. An air shower device (not shown) is installed at the entrance to prevent dust containing dioxins from diffusing from the processing space S to the external space of the greenhouse structure 1 when opened.
[0032]
  In the above configuration, the contaminated soil storage unit in the greenhouse structure 1 is loaded with the contaminated soil 3 contaminated with dioxins and stored. The greenhouse structure 1 is hermetically sealed, and since a water shielding sheet 1e is provided between the floor 1a and the lower side wall 1b and the ground 2, dioxins in the contaminated soil 3 deposited and stored are present. The contamination is not diffused by leaking outside the greenhouse structure 1.
[0033]
  During a clear day, dioxins on the surface portion of the contaminated soil 3 are photolyzed by the ultraviolet rays in the sunlight SL that has passed through the transparent roof 1d and the transparent side walls 1c in the greenhouse structure 1. Also, when the intensity of ultraviolet rays is low, such as in cloudy and rainy weather, or in the winter when the altitude is low,UV light 4By artificially irradiating with ultraviolet rays, dioxins present on the surface of the contaminated soil 3 are decomposed.
[0034]
  By driving the pump 6, the organic solvent or the surfactant in the additive storage tank 7 is sprayed on the contaminated soil 3 through the spray nozzle 5a in a timely manner. Either or both of the organic solvent and the surfactant may be sprayed simultaneously. Dioxins are poorly hydrophilic and are strongly adsorbed on soil particles, but organic solvents or surfactants release these dioxins from adsorption and are extracted into the soil gap. Dioxins move to the surface of the soil due to vapor pressure and capillary action due to vaporization of organic solvents or surfactants,UV light 4It is decomposed by exposure to ultraviolet rays.
[0035]
  In addition, when a large amount of organic solvent or surfactant is sprayed, dioxins extracted from the contaminated soil 3 penetrate into the bottom layer of the contaminated soil 3 together with the organic solvent or surfactant. Therefore, this is collected from the floor 1a by a collecting means (not shown), sent to the additive storage tank 7, and sprayed in the form of a mist through the spray nozzle 5a.UV light 4It is also possible to configure so that dioxins are photodegraded by ultraviolet rays from the above.
[0036]
  In the contaminated soil 3, air sent by the blower 10 is ventilated toward the soil surface from a number of air holes of the ventilation pipe 11 embedded in the lower layer. For this reason, aerobic microorganisms present in the soil 3 are activated, and in particular, aerobic dioxin decomposition such as Sphingomonas spp., Pseudomonas spp., Terrabacter spp., Alcaligenes spp. Decomposition and activation of microorganisms having ability (hereinafter referred to as dioxin-degrading microorganisms) promotes the decomposition of dioxins. In addition, these dioxin-degrading microorganisms that are originally inhabited in the contaminated soil 3 can be used, but artificially cultured ones may be introduced.
[0037]
  In addition, in the state where dioxins are strongly adsorbed to the soil particles, decomposition by dioxin-degrading microorganisms is not performed efficiently. However, in this embodiment, since the adsorbed state of such dioxins is released by spraying the organic solvent or the surfactant, the contact with the microorganism is efficiently performed and the decomposition is promoted.
[0038]
  The air released from the surface into the treatment space S through the contaminated soil 3 includes soil dust contaminated with dioxins, and organic solvent or surfactant vapor. Soil dust is removed by the HEPA filter that is sucked into the vessel 8 and attached therein, and the organic solvent or surfactant vapor is adsorbed and removed by the activated carbon. The air cleaned by the dust collector 8 passes through the pipe 9, is sent to the ventilation pipe 11 by the blower 10, and is ventilated to the contaminated soil 3. In addition, the soil dust floating in the treatment space S is ultraviolet rays of sunlight SL orUV light 4In this case, some of the dioxins are also decomposed.
[0039]
  Nutrient salts are added to the contaminated soil 3 for the purpose of increasing the decomposition activity of the dioxin-degrading microorganisms. Examples of nutrient salts include ammonium salts such as ammonium nitrate and ammonium sulfate, phosphates such as 1 potassium phosphate and 2 potassium phosphate, potassium salts such as potassium chloride and potassium nitrate, magnesium salts such as magnesium sulfate and magnesium nitrate, chicken manure, Organic fertilizers such as cow dung, swine dung, oil lees, etc., or manure and compost containing the above-mentioned salts can be mentioned. Nutrient salts are mixed when the contaminated soil 3 is put into and deposited in the contaminated soil storage section of the treatment space S. When the contaminated soil 3 is stored and purified for a long period of time, it can be sprayed with an aqueous solution. Depending on the method, it can be additionally supplied in a timely manner.
[0040]
  In addition, it is effective that the contaminated soil 3 is cultivated in a timely manner as a means for moving dioxins in the lower layer of the soil to the surface layer portion. Or the added nutrients can be uniformly mixed in the contaminated soil 3.
[0041]
  Also,If the air in the processing space S is returned to the contaminated soil 3 through the pipe 9, the blower 10, the pipe 12 and the aeration pipe 11 without being attached to the dust collector 8, the contaminated soil 3 is a kind. Acting as a filter, that is, the soil dust is taken into the contaminated soil 3, and the vapor of the organic solvent or surfactant is also returned to the contaminated soil 3 together with the air to be used for extraction of dioxins.
[0042]
[Second form]
  Next, FIG. 2 is explanatory drawing which shows 2nd embodiment of the storage method containing the detoxification process of the contaminated soil based on this invention. Also in this form, the greenhouse structure 1 similar to FIG. 1 described above is constructed on the ground 2 in the non-polluted area.
[0043]
  A liquid supply pipe 5 in which a plurality of spray nozzles 5 a are arranged at appropriate intervals is provided above the processing space S in the greenhouse structure 1, and an upstream end thereof is connected to the additive storage tank 7. Has been. The additive (oxidant or neutralizing agent described later) stored in the additive storage tank 7 is sent to the liquid supply pipe 5 by the pump 6. In addition, a pH sensor 13 for detecting the pH value is embedded in the contaminated soil 3 that is carried in and stored in the contaminated soil storage unit surrounded by the lower side wall 1b on the floor 1a in the greenhouse structure 1. The drive of the pump 6 that sends the additive in the additive reservoir 7 to the liquid supply pipe 5 is controlled by the control device 14 based on the value of the soil pH detected by the pH sensor 13.
[0044]
  A plant 15 having the ability to absorb dioxins is planted in the contaminated soil 3 that is carried into the contaminated soil storage unit in the greenhouse structure 1 and deposited and stored. All plants have some ability to absorb pollutants, but sunflower and cucurbitaceae (cucumber, pumpkin, etc.) plants have a high ability to absorb dioxins. Planting. Various methods such as sowing, transplanting of young seedlings, transplanting of seedlings that have grown to some extent can be considered as the method of planting, but the method by sowing is the easiest. The density of planting (seeding) is set so that the root distribution does not occur and the yield of plants per unit area is maximized in consideration of the rooted area.
[0045]
  The greenhouse structure 1 is provided with an air conditioner 16, and the processing space S in the greenhouse structure 1 is subjected to a temperature suitable for the growth of the plant 15 by the air conditioner 16, that is, 5 to 35 ° C., preferably 15 It can be maintained at ~ 25 ° C.
[0046]
  In the above configuration, the contaminated soil storage section in the greenhouse structure 1 is loaded with the contaminated soil 3 contaminated with dioxins and stored, and the contaminated soil 3 includes sunflower, cucumber, pumpkin, and the like. Plants 15 are planted and cultivated. The treatment space S is hermetically sealed, and a water-impervious sheet 1e is provided between the floor portion 1a and the lower side wall 1b and the ground 2, so that dioxins in the contaminated soil 3 deposited and stored are stored in the greenhouse. The contamination is not diffused by leaking out of the structure 1.
[0047]
  Since the treatment space S is maintained at a temperature suitable for the growth of the plant 15 by the air conditioner 16, the plant 15 planted in the contaminated soil 3 permeates the transparent roof 1d and the transparent side wall 1c of the greenhouse structure 1. Grows in response to sunlight SL. The roots 15a of the plant 15 are distributed to a depth of about 50 cm from the soil surface. In particular, the root hairs are densely distributed near the surface layer, and the dioxins in the contaminated soil 3 are absorbed and accumulated in the body.
[0048]
  In order to increase the activity of the plant 15 and the dioxin-degrading microorganisms in the soil, it is preferable to add nutrient salts as described in the first embodiment to the contaminated soil 3 in a timely manner.
[0049]
  When the dioxin contamination concentration of the contaminated soil 3 is remarkably high, an appropriate amount of an oxidizing agent aqueous solution is sprayed from the additive storage tank 13 in advance from the spray nozzle 5 a of the supply pipe 5 by the pump 6. The oxidizing agent is selected from, for example, hydrogen peroxide, chlorine dioxide, potassium permanganate and the like, and an aqueous solution having a concentration of 2 to 2000 mg / L is used from the viewpoint of safety. The sprayed oxidizing agent oxidizes and decomposes part of dioxins in the contaminated soil 3 to create a soil environment in which plants and dioxin-degrading microorganisms can be easily used.
[0050]
  Moreover, the activity of the dioxin-degrading microorganisms in the plant 15 and soil is significantly reduced in acidic soil. Therefore, an aqueous solution of the neutralizing agent is stored in the additive storage tank 13, and the aqueous solution of the neutralizing agent is supplied from the spray nozzle 5a of the supply pipe 5 based on the value of the soil pH detected by the pH sensor 13. By spraying in a timely manner, the activity of the dioxin-degrading microorganisms in the plant 15 and soil can be maintained.
[0051]
  Dioxins accumulated in the body of the plant 15 are removed from the soil 3 by cutting or digging after the plant 15 has grown for a predetermined period. If the plant 15 that has been cut or dug is accumulated by adding lime nitrogen or the like and composted, the volume is reduced and dioxins are concentrated, and the dioxin-degrading microorganisms that propagate in the composted plant body. Is decomposed and rendered harmless.
[0052]
  By the process as described above, the surface of the contaminated soil 3 is made harmless over time. Therefore, once purification has proceeded to a predetermined contamination concentration or less, the treatment period can be shortened by repeating the above-described steps after removing the soil in the region.
[0053]
  In the second embodiment, as in the first embodiment,UV light 4Irradiation with ultraviolet rays, ventilation to the contaminated soil 3 with the blower 10 and the ventilation pipe 11, removal of suspended dust with the dust collector 8, and the like can be used in combination. Further, as described above, since the roots of the plant 15 are distributed at a high density in the soil surface layer portion, as in the first embodiment, an organic solvent or a surfactant is sprayed to release the dioxin adsorption state. By moving to the soil surface layer, absorption by the plant 15 can be promoted. Further, in the state where the adsorption of dioxins is released by the organic solvent or the surfactant, the contact with the dioxin-decomposing microorganism is also efficiently performed, so that the decomposition by the microorganism is promoted.
[0054]
[Third form]
  As a third form of the storage method including the detoxification process of the contaminated soil according to the present invention, a gas having oxidizing power is passed through the contaminated soil 3 deposited and stored in the contaminated soil storage section of the greenhouse structure 1. Is also effective. That is, in this method, the upstream end portion of the vent pipe 11 similar to that of FIG. 1 described above is connected to a gas supply source (not shown) via a valve or the like. The gas having an oxidizing power supplied from the gas supply source is selected from, for example, chlorine dioxide gas, ozone, and chlorine gas.
[0055]
  Dioxins that are strongly adsorbed to soil particles and organic matter in the soil are carbon dioxide and chlorine by the oxidative decomposition action of chlorine dioxide gas, ozone, or chlorine gas that is ejected from the vent tube 11 and ventilated through the soil particle gaps. These decomposition products are dissolved in the soil 3 to be rendered harmless or released from the surface of the contaminated soil 3 together with aeration gas.
[0056]
  A dust collector 8 is attached to the transparent roof 1d in the greenhouse structure 1 as in FIG. That is, the air in the treatment space S contains soil dust and gas released from the surface through the contaminated soil 3, and the dust collector 8 sucks this air and a HEPA filter attached inside the dust collector 8. In addition to capturing soil dust, the activated carbon filled in the dust collector 8 absorbs and removes the gas.
[0057]
  Sunlight SL orUV light 4In the photodecomposition by, octachloride dioxins, which are generally said to be low in toxicity, become temporarily highly toxic tetrachloride in the process of decomposition. By using together, it is possible to prevent the formation of tetrachloride.
[0058]
  In the third embodiment, the air in the processing space S is returned to the contaminated soil 3 through the pipe 9, the blower 10, the pipe 12, and the ventilation pipe 11 without being attached with the dust collector 8. Anyway. In this way, the contaminated soil 3 acts as a kind of filter, that is, the soil dust is taken into the contaminated soil 3, and the gas having oxidizing power is also returned to the contaminated soil 3 together with the air to oxidatively decompose dioxins. Provided.
[0059]
  In addition, the method according to the third mode is, for example, decomposition by ultraviolet rays, absorption decomposition by plants, decomposition by microorganisms, etc.DetoxificationWhen it does not proceed sufficiently, it can be adopted as a method capable of realizing detoxification in a short period of time.
[0060]
  In each embodiment, after the fully detoxified soil is carried out from the greenhouse structure 1, new contaminated soil 3 is carried into the greenhouse structure 1 and deposited and stored therein. Can be used repeatedly in the detoxification process.
[0061]
[Example]
  A preliminary test was conducted on a soil sample containing dioxins at a concentration of 3000 pg / g · TEQ. In this preliminary test, a storage test involving photolysis and plant degradation of tetra-octaoctachlorodibenzo-p-dioxin and tetra-octaoctachloride bound to a soil sample was considered as greenhouse structure 1 in FIGS. Performed in a quartz glass column. The light source is natural light (sunlight)UV light(UV wavelength 250nm), natural light 8 hours +UV lightIrradiation was for 16 hours. The temperature in the quartz glass column was constant at 20 ° C. Sunflowers, cucumbers and pumpkins were used for the plants grown in the soil.
[0062]
  As a result of the preliminary test, the concentration of dioxins on the surface of the soil sample was reduced by about 80% due to photolysis in the measurement after 4 months from the start of the test compared to the concentration before the start of the test. Moreover, the concentration of dioxins in the region from the soil sample surface to a depth of 50 cm was reduced by about 40% compared to the concentration before the start of the test. In the area below 50 cm deep from the surface of the soil sample, the concentration of nutrients in the soil sample increased by fertilization and accelerated microbial degradation. As a result, the concentration of dioxins was 20% compared to the concentration before the start of the test. The degree was lowered. Together, this resulted in a 84% reduction in dioxin toxicity equivalent (TEQ) in the soil sample during the 4-month storage period.
[0063]
  Next, a detoxification test using an oxidizing agent was performed using the same soil sample and quartz glass column. Hydrogen peroxide water and chlorine dioxide gas were used as the oxidizing agent, and the other conditions were the same as in the preliminary test described above.
[0064]
  As a result of this detoxification test, the concentration of dioxins in the region from the soil sample surface to a depth of 50 cm was reduced by about 60% compared to the concentration before the start of the test. A 92% decrease in dioxin toxicity equivalent (TEQ) was observed, but the input energy (electric power, additives and new equipment) increased by about 20% compared to plant decomposition in the preliminary test.
[0065]
【The invention's effect】
  According to the storage method including the detoxification process of the contaminated soil according to the invention of claim 1, the contamination of the surrounding environment can be increased by isolating the contaminated soil from the non-contaminated area with a water shielding layer and a structure.Prevents aerobic microorganisms in the soil that have the ability to decompose pollutants by preventing and venting the soil without diffusing contaminated soil dust outside the structure In addition, the degradation of pollutants by microorganisms can be promoted, and the soil dust pollutants contained in the air are decomposed by ultraviolet rays by releasing the air aerated in the contaminated soil into the treatment space. , Ultraviolet rays and microorganismsThis energy can be used to detoxify contaminated soil that has been deposited and stored. In addition, the structure, impermeable layer and its associated equipment can be used repeatedly for a long time, so it is low cost and the risk of contamination during storage of contaminated soil is reduced. Is also reduced.In addition, the ultraviolet irradiation device provided in the structure can irradiate the contaminated soil with ultraviolet rays even in cloudy weather or at night to perform photolysis of contaminants on the soil surface.
[0066]
  According to the storage method including the detoxification process of the contaminated soil according to the invention of claim 2, in addition to the effect of the invention of claim 1,The pollutants in the contaminated soil can be transferred to the plant body and removed.
[0067]
  According to the storage method including the detoxification process of the contaminated soil according to the invention of claim 3,Claim 1 or 2In addition to the effects of the present invention, it is possible to move pollutants in the lower part of the contaminated soil to the soil surface irradiated with sunlight or ultraviolet rays by spraying the organic solvent or surfactant on the contaminated soil in a timely manner. , Can promote the photolysis of pollutants.Moreover, dioxins extracted from contaminated soil by spraying organic solvents or surfactants are collected at the bottom layer of the contaminated soil together with organic solvents or surfactants and sprayed into the treatment space, so that ultraviolet rays of sunlight or ultraviolet rays Photolysis of dioxins by ultraviolet rays from the irradiation device can be further promoted.
[0068]
[0069]
[0070]
[0071]
[0072]
[0073]
[0074]
[0075]
[0076]
  Claim 4According to the storage method including the detoxification process of the contaminated soil according to the invention, the pH of the contaminated soil is maintained at a value suitable for the growth environment of plants and microorganisms.Claim 2It is possible to promote absorption of pollutants by plants or decomposition by microorganisms according to the present invention.
[0077]
[0078]
[0079]
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a first embodiment of a storage method including a detoxification process for contaminated soil according to the present invention.
FIG. 2 is an explanatory diagram showing a second embodiment of a storage method including a detoxification process for contaminated soil according to the present invention.
[Explanation of symbols]
1 Greenhouse structure (structure)
1e Impermeable sheet (impermeable layer)
2 Ground in non-polluted areas
3 contaminated soil
4UV light
5a Spray nozzle
11 Vent pipe
15 plants
S processing space

Claims (4)

Contaminated soil is deposited and stored in a treatment space that is isolated from non-contaminated soil by a water shielding layer and hermetically surrounded by a translucent structure, and ultraviolet rays are applied to the contaminated soil. Storage including a detoxification process for contaminated soil, characterized in that an ultraviolet irradiation device for irradiation is provided, air in the treatment space is collected, air circulation is performed to vent the air to the contaminated soil and release it to the treatment space Method. 2. The detoxification process for contaminated soil according to claim 1, wherein a plant having an ability to absorb pollutants is cultivated in the contaminated soil, and the plant is grown for a required period, and then cut or dug. Including storage methods. The organic solvent or surfactant is sprayed on the contaminated soil in a timely manner, and the organic solvent or surfactant that has penetrated to the lowest layer of the contaminated soil is recovered and used for respreading. The storage method including the detoxification process of the contaminated soil of description. A pH sensor for detecting a soil pH value is embedded in the contaminated soil, and a neutralizing agent is added to the contaminated soil via a pump whose drive is controlled by a control device based on the detected value. The storage method including the detoxification process of the contaminated soil of Claim 2 .

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