JP4670570B2 - Purification method for contaminated soil - Google Patents

Description

  The present invention relates to a purification technique for soil contaminated with harmful substances, and more particularly to a purification process for soil contaminated with an organic chlorine compound such as PCB (polychlorinated biphenyl).

  Soil contaminated with organochlorine compounds represented by PCBs and the like is present in the ground such as a factory site without being decomposed so much.

  Further, the PCB or the like is excavated from the ground for soil purification and stored in a container such as a drum can.

  In particular, the excavated contaminated soil is stored in large quantities without being subjected to purification treatment, and the purification treatment is urgently needed.

Conventionally known methods include, for example, a thermal decomposition method, an iron powder method, an alkali catalyst chemical decomposition method, and a melt solidification method.

  However, it is desired to develop a method in which contaminated soil is purified so as to satisfy environmental standard values and the number of treatment steps is small.

  Among the various processing methods, the following are known as typical solutions.

  There are electrical parts such as transformers and capacitors that contain difficult-to-decompose harmful substances such as PCB, waste liquid, and waste oil as constituent members or parts thereof.

  This harmful substance is stored in various containers such as drums and boxes, charged into a melting furnace as fuel, and melted at a high temperature to thermally decompose the harmful substance (see, for example, Patent Document 1). ).

  Further, there is a method of excavating soil contaminated with an organic halogen compound, mixing iron powder into the excavated soil, and stacking it on the ground in a pile shape and leaving it for several days to several months.

  There is also a method of decomposing pollutants and mixing them with hydrocarbons such as ethane and ethylene by mixing iron powder into excavated soil and backfilling it underground.

Furthermore, there is a treatment method for preventing recurrence of contamination due to contaminants remaining in the surrounding soil (for example, see Patent Document 2).
Further, dioxin-contaminated solids are pulverized with a pulverizer, the atmosphere of the pulverized material is replaced with an inert gas, and a reducing metal is introduced into the pulverized material and mixed.

The pulverized dioxin-contaminated mixture obtained from the pulverized material and the reducing metal is transferred to the dehalogenation reactor while maintaining the inert gas atmosphere, and the pulverized material is reduced with the reducing metal. Thus, a dehalogenation reaction of dioxins is performed (see, for example, Patent Document 3).
JP 2004-154666 A JP 2001-577 A JP 2003-190932 A

  However, what is described in Patent Document 1 is a thermal decomposition process, which requires a high-temperature incinerator, which complicates equipment and becomes large-scale.

  Hazardous substances in this thermal decomposition treatment include devices such as PCBs, waste liquids, waste oils, etc. that are difficult to decompose (hereinafter referred to as PCBs) or contaminated with PCBs, articles such as parts, PCBs, etc. Contaminated soil, contaminated water, etc. mixed with or a container such as a drum can.

  Further, since combustion is performed while maintaining a high temperature in a high-temperature incinerator, continuous operation is required, and the amount of fuel consumed increases.

  There is also a problem of undecomposed by combustion and dioxins in the middle of decomposition.

  Next, the thing of patent document 2 mixes iron powder with excavated soil, piles up the obtained mixture in the shape of a pile (pile), hangs a sheet, and is left still for several days to several months. is there.

  When excavating this contaminated soil, the soil excavated from the contaminated site contains large contaminants such as stones and glass, and components having greatly different particle sizes.

  For this reason, when mixing iron powder with excavated soil, it is difficult to disperse | distribute iron powder uniformly in excavated soil.

  In addition, a mixture of iron powder near the excavation site is piled up on the ground in piles and hung on a sheet, and left still, but the lower part of the mountain is in contact with the ground. May leak the mixture.

  Moreover, it is difficult for the hills formed of the mixture to break down due to weathering or the like and maintain the initial shape, and the mixture is easily exposed from the sheet.

  Furthermore, the required amount of water in the mixture necessary for preventing oxidation by contact of iron powder with air and promoting reductive decomposition of the organic halogen compound cannot be maintained.

  In other words, the evaporation of water due to the drying of the mixture changes the balance between the oxidation rate of iron powder and the desalination reaction rate of PCB and the like, and it is difficult to perform reductive decomposition of a stable organochlorine compound over a certain period.

  Moreover, the thing of patent document 3 requires the grinder which grind | pulverizes a contaminated solid substance, and also mixes the reducing metal of metallic sodium with the grind | pulverized substance grind | pulverized with the grinder, and makes a dehalogenation process reaction. .

  At this time, an apparatus for maintaining an inert gas or a reducing atmosphere is necessary, which complicates the entire system, resulting in a problem that the operating cost increases.

  The present invention solves the above-mentioned conventional problems, and excavated soil contaminated with PCB or the like is reliably (here, the certainty is below a reference value that conforms to environmental standards), and further has a zero value. By effectively using the amount of treatment agent, which is a metal reducing agent containing iron powder, the running cost can be reduced as a result, and a method for purifying contaminated soil that meets environmental standards (detoxification) is provided. The purpose is to do.

The present invention Oite drilling soil contaminated with organic chlorine compounds, in the range water content of the excavation soil 15% to 85%, three times the soil in inverse proportion to the magnitude of the water content to 1 After supplying water adjusted to double the weight, a kneading step of mixing to obtain a slurry soil, and separating the slurry soil into at least a coarse particle soil and a plurality of particle size groups of fine particle soil A separation step, and a mixing step in which the separated fine-grained soil, a metal reducing agent containing zero-valent iron powder, and water are mixed by stirring to form a slurry mixture, and the slurry mixture is stored in a container. The organic chlorine compound is detoxified by curing in a sealed container for a certain period of time.

  According to the contaminated soil purification treatment apparatus of the present invention, excavated soil contaminated with organochlorine compounds such as PCBs can be treated with reduced amount of treatment agent and contaminated soil that conforms to environmental standards. .

A first aspect of the present invention is Oite drilling soil contaminated with organic chlorine compounds, in the range water content of the excavation soil 15% to 85%, three times the soil in inverse proportion to the magnitude of the water content A kneading step of supplying water adjusted to a weight of ˜1 and then mixing to obtain slurry-like soil, and said slurry-like soil into at least a plurality of particle size groups of coarse-grained soil and fine-grained soil A separation step for separating, and a mixing step for stirring and mixing the separated fine-grained soil, a metal reducing agent containing zero-valent iron powder, and water to form a slurry-like mixture, and the slurry-like mixture in a container The organochlorine compound is detoxified by being stored in a sealed and sealed container for a certain period of time.

In this way, by adjusting the amount of water supplied to the soil according to the moisture content of the excavated soil, even when the moisture content of the soil is low, it is possible to break down and refine the soil mass that encloses stones, etc. Moreover, when the moisture content of the soil is high, slurry-like soil can be obtained without greatly increasing the total amount.
Moreover, a fine-grained soil having a large surface area and a high contamination concentration per unit mass can be separated, and the fine-grained soil, a metal reducing agent containing zero-valent iron powder, and water can be uniformly stirred and mixed.

  Further, the contact between the organochlorine compound adhering to the soil surface and the metal reducing agent is promoted, and a stable decomposition reaction can be caused by curing in a sealed container.

Therefore, the excavation soil contaminated with organochlorine compounds represented by PCBs, etc. is treated with certainty, and the iron powder oxidation reaction and slurry are processed by minimizing the amount of metal reducing agent containing zero-valent iron powder. The dechlorination reaction of the mixture can be made efficient.

The second invention is the mixing step of the first invention , wherein the fine-grained soil, the metal reducing agent, and water are stirred and mixed, and then the coarse-grained soil having a larger particle size than the fine-grained soil is mixed. It is cured in a container to treat organochlorine compounds below the environmental standard value.

  Thereby, by mixing an appropriate amount of coarse-grained soil, even if the fine-grained soil is fine soil particles, it prevents clay from becoming aggregated or solidified in the container, The decomposition efficiency of the organic chlorine compound adhering to the fine soil particles during the curing period can be further improved.

  Moreover, when it is backfilled to the excavation site after the curing period, it can be prevented from becoming clayey in the ground.

According to a third aspect of the present invention, in the kneading step of the first aspect of the present invention, a kneading device is used for removing a large contaminant from the excavated soil contaminated with the organochlorine compound by a primary separation device. In the separation step, small contaminants are removed from the slurry soil, and small contaminants removed soil containing water passing through the sieve is passed through the sieve in the separation step. separated into, the small decontamination soil containing the sieve pass water separated by the secondary separation device, separated into coarse fraction soil and fine fraction soil tertiary separation device, separated by a cubic separator was by then stored separated into supernatant water and fine fraction soil aggregate precipitator the fine fraction soil containing the separated water, the plurality of grains of said drilling soil and coarse fraction soil the fine fraction soil Detoxify the organochlorine compounds by separating into diameter groups It is something to process.

  This separates and removes large contaminants such as stones and glass from the excavated soil, supplies water to the soil, dissolves the massive soil as a mixed slurry, and passes through a plurality of separation steps. It can isolate | separate reliably for every some particle size group of coarse-grained soil and fine-grained soil. Further, it is possible to separate and capture fine particle soil contained in water, and to detoxify organochlorine compounds such as PCB adhering thereto.

  Here, the presence or absence of harm means the environmental standard value of pollutants or less.

  Hereinafter, a soil purification method according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a conceptual diagram of a soil treatment system according to an embodiment of the present invention, and FIG. 2 is a flowchart showing processing steps corresponding to FIG. Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  First, the separation step for separating the excavated soil in the container into at least a plurality of particle size groups of coarse-grained soil and fine-grained soil will be described.

  In FIG. 1 and FIG. 2, excavated soil in a container 1 contaminated with an organic chlorine compound such as PCB is conveyed to a primary separator 2 having a vibrating sieve 2a and a vessel 2b.

  In this primary separation device 2, the mesh of the vibration sieve 2a is set to about 30 mm, for example, and a large contaminant 3 such as a relatively large stone or glass mixed in the soil on the vibration sieve 2a. Is separated. The excavated soil contaminated with the organochlorine compound shaken down through the vibrating sieve 2a is accommodated in the vessel 2b (FIG. 2, S100).

  Note that the primary separation device 2 may be a jumping screen that wave-moves the screen mat surface or a multilayer screen that is gradually made finer.

  Further, depending on the state of the excavated soil, visual separation may be used. Moreover, the primary separation apparatus 2 may use a means for fixing the sieve and moving the excavated soil on the sieve or a means for applying vibration to the soil.

  Next, the soil in the vessel 2b from which the large contaminants 3 such as stone and glass are removed is conveyed to the kneading device 4 that is a mixer.

  Water is supplied from the water supply line 5 to the soil in the kneading apparatus 4 to forcibly wet and knead (S101).

  As a result, the soil becomes a slurry, and the soil lump enveloping the lump of soil, pebbles and the like is separated and released to be refined.

  The kneading device 4 includes a rotary blade (not shown) driven by a motor, and rotates the rotary blade at, for example, about 5 to 10 rotations per minute.

  Thereby, an impact will be given to a soil lump and it will become easy to unravel.

  If the amount of water supplied to the soil is too small, it will not be possible to make it finer, and there will be a situation in which the soil mass that has wrapped stones and the like cannot be unraveled. If the amount of water is too large, the total amount will increase.

  The amount of water supplied to the soil may be adjusted according to the moisture content of the excavated soil.

  As a result of obtaining the optimum mixing ratio of soil and water, it varies depending on the moisture content of the soil. For example, for soil having a moisture content of 60%, by supplying 1.5 times the weight ratio of water, Soil can be obtained. Moreover, with respect to the soil whose water content exceeds 85%, slurry-like soil can be obtained by supplying water at a weight ratio of 1 times.

  Furthermore, for soil having a water content of 15% or less, slurry-like soil can be obtained by supplying three times the water by weight.

  Moreover, the water used for supply water includes the water containing a soil dispersing agent other than general water, such as river water, ground water, and tap water.

  The soil dispersant can be appropriately selected according to the state of the soil such as the type of soil and the degree of compression.

  Next, the slurry soil kneaded by the kneading device 4 is conveyed to the secondary separation device 6. The secondary separation device 6 is a rotary separator (Trommel) having a cylindrical rotary sieve 6a, and the cylindrical rotary sieve 6a is positioned so that the soil inlet side 6b is higher than the outlet side 6c. It is inclined like this.

  The rotary sieve 6a is driven by a driving means (not shown) having a speed reduction mechanism, and the rotary sieve 6a is rotated at a low speed of about 5 revolutions per minute, for example.

  In the present embodiment, the mesh of the rotary sieve 6a is set to about 5 mm, for example, and the slurry-like soil thrown into the cylindrical rotary sieve 6a moves within the inclined cylindrical rotary sieve 6a. The contaminants 7 such as pebbles and gravel remaining in the rotary sieve 6a without passing through the mesh of the rotary sieve 6a are discharged from the outlet side 6c and separated.

  The soil containing water that has passed through the mesh accumulates in the lower part of the secondary separation device 6.

  At this time, slurry adhering to the surface of pebbles, gravel, etc. is removed by passing the slurry-like soil containing water through the mesh (S102).

  As described above, first, the primary separation device 2 removes large contaminants 3 such as stones and glass, and then supplies water to form a slurry-like soil, which is further driven by a kneading device 4 and a rotary sieve 6a that are driven at a low speed. By the secondary separator 6, the soil lump that has wrapped the lump of soil, pebbles, gravel, etc. is further detached, unraveled and refined.

  Next, the soil containing water separated through the rotary sieve 6a of the secondary separator 6 is conveyed to the tertiary separator 8 having the vibrating sieve 8a and the vessel 8b. In the tertiary separation device 8, the mesh of the vibration sieve 8a is set to about 0.75 mm, for example, and coarse soil 9 such as sand is stored on the vibration sieve 8a. Fine-grained soil such as viscous soil containing water that has passed through the vibrating sieve 8a having a mesh size of 0.75 mm and is shaken down is accommodated in the vessel 8b (S103).

  Note that the tertiary separation device 8 may use a jumping sieve that wave-moves the sieve surface, or a multilayer sieve that gradually becomes finer.

  The mesh size of the vibrating screen 2a of the primary separator 2 and the mesh size of the rotary screen 6a of the secondary separator 6 is the size and size of the excavated soil and the size of the contaminants. The optimum conditions may be set as appropriate according to the soil contamination state and the like.

  Next, fine-grained soil such as viscous soil containing water in the vessel 8 b separated by the tertiary separation device 8 is conveyed to the coagulation sedimentation device 10. In the coagulation sedimentation apparatus 10, the fine-grained soil settles down due to the specific gravity difference, and is separated into the supernatant water and the fine-grained soil (S104).

  The supernatant water is supplied to the water storage tank 13 through the supply pipe 11 and the pump 12 and stored in a certain amount (S105). Further, the stored water in the water storage tank 13 is supplied to the filtration device 16 having activated carbon through the supply pipe 14 and the pump 15 to be detoxified and discharged from the discharge pipe 17 (S106). The stored water is supplied to the filtration device 16 continuously or intermittently by detecting the water level in the water storage tank 13. The filtration device 16 mainly detoxifies organochlorine compounds contained in moisture in excavated soil.

  Further, the stored water in the water tank 13 is supplied to the kneading device 4 through the supply pipe 18 and the pump 19, and the primary separation device 2 forcibly removes the soil from which the large contaminants 3 such as stone and glass are removed. Wet and knead. Further, treated water treated by the filtration device 16 may be supplied to the kneading device 4. Thereby, the supply amount of water such as tap water from the water supply line 5 can be reduced.

  Moreover, the stored water in the storage tank 13, the stored water processed by the filtering device 16, or the water from the water supply line 5 may be appropriately selected and supplied to the soil, or each water may be mixed and supplied in advance. .

  In addition, each connection of the water storage tank 13 and the kneading device 4, the water storage tank 13 and the filtration device 16, the coagulation sedimentation device 10, the water storage tank 13, and the coagulation sedimentation device 10 is constituted by a supply pipe and a pump. You may give and supply, and you may carry in a container.

  Further, the primary separation device 2 and the kneading device 4, the kneading device 4 and the secondary separation device 6, the secondary separation device 6 and the coagulating sedimentation device 10 are each conveyed in a container and conveyed by a moving means. A method such as conveying and sucking means may be used as appropriate by giving a height difference of 5 mm.

  This separates and removes large contaminants 3 such as stones and glass that do not contain contaminants from the excavated soil, supplies water to the soil, dissolves the massive soil as a mixed slurry, and further separates the soil By passing through the steps, it is possible to select and separate at least a plurality of particle size groups of coarse-grained soil and fine-grained soil.

  Moreover, the soil of fine particles contained in water can be separated and captured.

  As described above, the basic separation step for separating the excavated soil in the container 1 into a plurality of particle size groups of at least coarse-grained soil and fine-grained soil has been described. A basic processing step of stirring and mixing the metal reducing agent and water and storing in a container will be described.

  The finely divided soil separated and settled by the coagulation sedimentation apparatus 10 is supplied to the reducing agent mixing tank 22 by the pump 21 through the supply pipe 20. Based on the fine-grained soil in the reducing agent mixing tank 22 and zero-valent fine-particle iron powder, water is supplied from a metal reducing agent and a water supply line 24 and stirred by a stirring means 23 composed of rotor blades driven by a motor. These are mixed to obtain a mixture (S107). The supplied water contains the amount of saturated water or more in order to prevent the metal reducing agent from being oxidized and to disperse the metal reducing agent uniformly throughout the soil.

  In addition, you may supply the treated water processed with the filtration apparatus 16 to the reducing agent mixing tank 22. FIG.

  Thereby, the supply amount of water such as tap water from the water supply line 24 can be reduced.

  Moreover, the stored water in the storage tank 13, the treated water processed by the filtering device 16, or the water from the water supply line 24 may be appropriately selected and supplied to the soil, or the respective waters may be mixed and supplied in advance. .

  Next, the mixture is stored in a container 25, the upper opening of the container 25 is sealed with a lid 25a, and cured for a certain period (for example, left for several months) and detoxified by a dechlorination reaction. Yes (S108). Organochlorine compounds receive electrons on the iron powder surface (reduced) and change to a chlorine-free compound such as acetylene to be rendered harmless.

  As the container 25, it is preferable to use, for example, a stainless steel material or a drum can with an inner surface coated with a resin, thereby preventing leakage of the stored mixture due to corrosion.

  Further, the mixture may be stored inside the drum can through a resin bag.

  In this storage, it is desirable to seal the mixture so that it does not come into direct contact with the outside air in order to cut off the oxygen source, which is a factor that inhibits the decomposition action of the contaminants by the metal reducing agent. It is preferable to fill the upper space portion.

  As described above, the mixture is stirred and mixed by the stirring means 23 in the reducing agent mixing tank 22 to form a mixture and conveyed to the container 25. However, the fine soil, the metal reducing agent, and water may be stirred and mixed in the container 25. Good.

  In this case, the stirring means 23 is provided in a member separate from the lid 25a of the container 25 to perform stirring and mixing, and after stirring and mixing, the upper opening of the container 25 is sealed with the lid 25a. Thereby, the whole apparatus can be simplified.

  As the metal reducing agent, zero-valent fine particle iron powder is used as a main component. For example, the iron powder may be fine particles having an average particle size of about 70 μm, and the decomposition reactivity of the organic chlorine compound can be improved by increasing the surface area of the zero-valent fine particle iron powder.

  Further, nickel alloy, carbon-coated iron powder or the like may be blended and used.

  Moreover, the addition amount of the metal reducing agent to the soil is about 1 to 10% by weight with respect to the soil, and when the addition amount is less than 1% by weight, the decomposition rate is remarkably reduced.

  Moreover, you may supply and mix solvents, such as surfactant and alcohol, with a metal reducing agent and water with fine grain soil. In this case, detachment and elution of the organic chlorine compound from the soil surface can be promoted, and the decomposition efficiency can be further improved.

As described above, Oite drilling soil contaminated with organic chlorine compounds, in the range water content of the excavation soil 15% to 85%, three times the soil in inverse proportion to the magnitude of the water content - A kneading step of supplying water adjusted to a weight of 1 and then mixing to obtain slurry-like soil, and separating the slurry-like soil into at least a plurality of particle size groups of coarse-grained soil and fine-grained soil And a mixing step of stirring and mixing the separated fine-grained soil and the metal reducing agent containing zero-valent iron powder to form a slurry mixture, and storing the slurry mixture in a container The method for purifying contaminated soil is characterized in that the organochlorine compound is detoxified by curing in a sealed container for a certain period of time.

  In addition, the soil excavated from the contaminated site contains large contaminants such as stones and glass, and components having greatly different particle sizes.

  Therefore, it is difficult to uniformly disperse the metal reducing agent in the excavated soil when mixing the metal reducing agent that is fine particle iron powder into the excavated soil, but in this example, the surface area is large and the unit mass is large. A fine-grained soil having a high permeation concentration can be separated, and the fine-grained soil, metal reducing agent, and water can be mixed uniformly.

  Further, the contact between the organochlorine compound adhering to the soil surface and the metal reducing agent is promoted, and a stable decomposition reaction can be caused by curing in a sealed container.

  Therefore, the excavated soil contaminated with an organic chlorine compound typified by PCB or the like can effectively use the amount of zero-valent fine iron powder used, and can be rendered harmless.

  The reason is that zero-valent fine-particle iron powder, which is a metal reducing agent, reacts with water in the slurry-like soil and releases hydrogen ions.

  By replacing this hydrogen ion with chlorine of an organic chlorine compound typified by PCB (dechlorination reaction), the organic chlorine compound typified by PCB or the like is reduced in molecular weight and can be rendered harmless.

  Next, after stirring and mixing the metal reducing agent and water into the fine-grained soil, the coarse-grained soil having a larger particle size than the fine-grained soil is mixed and cured in the container 25 to render the organochlorine compound harmless. A method of processing will be described.

  The fine soil settled and separated by the coagulation sedimentation apparatus 10 is supplied to the reducing agent mixing tank 22 by the pump 21 through the supply pipe 20.

  A metal reducing agent and water are supplied to the fine-grained soil in the reducing agent mixing tank 22, and the mixture is stirred and mixed by stirring means 23 composed of rotating blades driven by a motor. After the metal reducing agent and water are stirred and mixed in the fine-grained soil, a part of the coarse-grained soil separated in the tertiary separation step is supplied to the reducing agent mixing tank 22 and mixed, and this mixture is put into the container 25. It is housed, and the upper opening of the container 25 is sealed with a lid 25a, cured for a certain period, and detoxified by a dechlorination reaction.

  Thus, by mixing a suitable amount of coarse-grained soil with a mixture obtained by uniformly stirring and mixing a metal reducing agent and water with fine-grained soil, even if the fine-grained soil is fine soil particles, Prevents the agglomeration and solidification of clay and promotes the contact between the soil particles and the metal reducing agent, and decomposes organic chlorine compounds adhering to the finely divided soil particles during the curing period Can be further improved. Moreover, when it is backfilled to the excavation site after the curing period, it can be prevented from becoming clayey in the ground. The mixing amount of the coarse-grained soil may be a minimum amount capable of preventing agglomeration and solidification by becoming clayey in the container 25.

  Next, the separated fine-grained soil is mixed with a metal reducing agent and water, and further mixed with the coarse-grained soil with a metallic reducing agent and water. A method of detoxifying the organic chlorine compound by storing each of the mixed fine-grained soil and the coarse-grained soil mixture in different containers 25 and curing in a container 25 for a certain period of time will be described.

The finely divided soil settled and separated by the coagulating sedimentation apparatus 10 is supplied to the reducing agent mixing tank 22 by the pump 21 through the supply pipe 20. Wherein the fine soil of the reducing agent in the mixing tank 22 to supply the metal reducing agent and water, and mixtures thereof are mixed with stirring means 23 constituted by the rotor blades driven by a motor. The coarse-grained soil separated in the tertiary separation step is supplied to the reducing agent mixing tank 22.

Wherein the coarse fraction of soil reducing agent in the mixing tank 22 to supply the metal reducing agent and water, and mixtures thereof are mixed with stirring means 23 constituted by the rotor blades driven by a motor.

  And each of the mixture of the fine-grained soil and the coarse-grained soil mixed with the metal reducing agent and water is stored in different containers 25 and cured in each container 25 for a certain period to detoxify the organic chlorine compound. It is.

  As a result, the excavated soil can be separated into particle size groups having different specific surface areas and contamination concentrations, and the optimum supply amount of reduced metal and water can be selected and mixed uniformly for each particle size group.

  Furthermore, the contact with the organic chlorine compound adhering to the soil surface and the metal reducing agent is promoted, and a stable decomposition reaction can be caused by curing in a sealed container different for each particle size group.

  Therefore, excavated soil contaminated with an organic chlorine compound typified by PCB or the like can be reliably treated and rendered harmless.

  In addition, iron powder and water, which are reducing agents, are supplied to the fine-grained soil settled and separated by the agglomeration sedimentation apparatus 10 and mixed to form a mixture. The mixture is stored in the container 25, and the upper opening of the container 25 is opened. The part was sealed with a lid and cured for a certain period of time, but a metal reducing agent was supplied to fine-grained soil such as viscous soil containing water in the vessel 8b separated by the tertiary separator 8 and stirred and mixed. The mixture may be stored in the container 25, and the upper opening of the container 25 may be sealed with a lid and cured for a certain period.

  In addition, the metal reducing agent and water are stirred and mixed in the fine-grained soil containing water separated in the tertiary separation step to obtain a mixture, and the metal reducing agent and water are stirred and mixed in the coarse-grained soil separated in the third separation step. Then, as a mixture, each of the mixture of the fine-grained soil and the coarse-grained soil in which the metal reducing agent and water are mixed may be stored in different containers 25 and cured in each container 25 for a certain period of time. .

  As described above, according to the present invention, excavated soil contaminated with an organic chlorine compound typified by PCB or the like can be detoxified with a small amount of treatment agent used.

  It can be applied to a wide range of uses in the purification of soil contaminated with harmful substances.

The block block diagram of the soil treatment system of Example 1 of this invention Flow chart showing processing steps corresponding to FIG.

Explanation of symbols

1 Container 2 Primary Separator 2a Vibrating Sieve 2b Vessel 3 Stone, Glass (Large Contamination)
4 Kneading device 5 Water supply line 6 Secondary separation device 6a Rotary sieve 6b Input side 6c Outlet side 7 Pebbles, gravel (contamination)
8 Tertiary separator 8a Vibrating sieve 8b Vessel 9 Sand (coarse grained soil)
DESCRIPTION OF SYMBOLS 10 Coagulation sedimentation apparatus 11 Supply pipe 12 Pump 13 Water tank 14 Supply pipe 15 Pump 16 Filtration apparatus 17 Discharge pipe 18 Supply pipe 19 Pump 20 Supply pipe 21 Pump 22 Mixing tank 23 Stirring means 24 Water supply line 25 Container 25a Lid

Claims (3)

In the excavated soil contaminated with organochlorine compounds, the moisture content of the excavated soil was adjusted to the weight of 3 to 1 times the soil in inverse proportion to the size of the moisture content in the range of 15% to 85%. A kneading step of mixing water to obtain slurry-like soil, a separation step of separating the slurry-like soil into at least a plurality of particle size groups of coarse-grained soil and fine-grained soil, and the separation A mixing step in which the finely divided soil, the metal reducing agent containing zero-valent iron powder and water are mixed by stirring to form a slurry mixture, the slurry mixture is stored in a container, and the container is sealed A decontamination treatment method for contaminated soil, wherein the organochlorine compound is detoxified by curing for a certain period of time. In the mixing step, followed by stirring and mixing the water the the fine fraction soil and the metal reducing agent, a mixture of large the coarse fraction of soil particle size than the fine fraction soil was cured at the container The method for purifying contaminated soil according to claim 1, wherein the organochlorine compound is detoxified. In the kneading step, the from the excavated soil contaminated with organic chlorine compounds in large decontamination soil removing large contaminants in the primary separation device, water is supplied mixed with a slurry soil kneading apparatus And none,
In the separation step, small contaminants from said slurry soil secondary separation apparatus and is separated into a small decontamination soil containing sieve passing water passed through the sieve, the sieve pass water separated by the secondary separation device in the small decontamination soil, separated into a coarse fraction soil and fine fraction soil tertiary separator, coagulation sedimentation device the fine fraction soil containing the separated water separated in the tertiary separation device comprising by separating the reservoir to the supernatant water and fine worth soil,
The method for purifying contaminated soil according to claim 1, wherein the excavated soil is separated into a plurality of particle size groups of the coarse-grained soil and the fine-grained soil.

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