JP2020192517A - Method for recycling contaminated soil - Google Patents

Abstract

To provide a novel soil dispersant that clears various problems of concern with pearlite used as a soil dispersant in the conventional method, and is suitable for soil contamination countermeasure excellent at low cost.SOLUTION: Starting with the modification of a silt and clay-containing contaminated soil using an inexpensive inorganic porous body that is a colored and highly rigid soil dispersant suitable for soil contamination countermeasure; achieving decontamination and drying with enhanced efficiency in the manufacturing process; finally converting to a decontaminated and dried granulated soil, which is an extremely inexpensive soil dispersant having soil dispersion performance derived from contaminated soil.SELECTED DRAWING: Figure 1

Description

The main purpose of the present invention is to recycle contaminated soil, and in particular, the contaminated soil is reformed by using an inorganic porous body instead of pearlite, which has the ability to disperse contaminated soil particles, and the contaminated soil is decontaminated and constant. The present invention relates to a method for recycling contaminated soil into a soil dispersant derived from the contaminated soil through a drying step of the contaminated soil under the conditions.

Conventionally, the method of implementing purification measures for soil contaminated with VOC (volatile organic compounds) and oil containing a large amount of silt and clay has been extremely limited, and as construction conditions, large heavy machinery and large soil If the land is accessible to transport vehicles and the contamination is at an excavable depth, then in most cases a combination of excavation removal and clean soil replacement will be considered.

However, the method that combines excavation removal and clean soil replacement is particularly expensive among purification measures, and even if the above construction conditions are satisfied, there are many cases where the construction cost cannot be met. If there is no contact with a contractor who can implement a special purification method as described later, there are many cases where the pollution is left as it is and the land is not utilized (for example, Non-Patent Document 1).

As a special purification method that is technically more advanced than excavation removal and clean soil replacement, but can be carried out at a relatively low cost, the purification chemical solution from the injection well causes cracks in the silt and clay-rich formation. (For example, Patent Document 1) and a method for forcibly mixing the purifying agent by kneading by vertical shaft mixing using a columnar improver (for example, Patent Document 2) can be mentioned.

The former is a construction method in which the injection of the press-fitting liquid depends on the cracks generated in the stratum, and if the crack formation due to the inhomogeneity of the stratum is biased, the purification tends to be extremely uncertain, and the latter is the reliable construction. Although the property is extremely high, since long rods are installed upright, the size of the carry-in path is a condition, and a construction space up to a height of about 10 m is required inside the building, so the application is extremely limited. It was.

In addition, although it is more limited and uncommon, if the soil is contaminated with almost no silt or clay, so to speak, mainly composed of sand, fluid can be easily taken in and out through the soil gap. It is also possible to select a remarkably inexpensive purification measure method such as performing pile aeration treatment (for example, Patent Document 3) on-site for the excavated contaminated soil.

However, it can be said that there is no case in the current pollution purification industry where such pile aeration treatment is selected for contaminated soil containing silt or clay above a certain level, but as a patented technology, An aerobic biopurification technique has been proposed in which pearlite is used as a soil conditioner for contaminated soil containing a certain amount of silt or clay to improve air permeability (for example, Patent Document 4). However, pearlite was also a material for which the adsorption ability of heavy metals was reported (for example, Non-Patent Documents 2 and 3).

Japanese Patent No. 3735644 JP-A-2007-283229 Japanese Patent No. 6055233 Japanese Patent No. 4767472

Tetsuo Hodaka, Doctoral Dissertation, Yokohama National University Graduate School March 2007 T. Mathialagan, T.M. Viraraghavan, Adsorption of cadmium from solutions by perlite, Journal of Hazardous Materials, Vol. 94, (3), 2002, P291-303. H. Ghassabzadeh, M.D. Torab-Mostadei, A.M. Mohaddespour, M. et al. G. Maragheh, S.M. J. Ahmadi, P.I. Zaheri, characterizations of Co (II) and Pb (II) removal process from solution solutions using expanded perlite, Desalination, Vol. 261 (1-2), 2010, P73-79.

As a conventional technique, an aerobic biopurification technique (for example, Patent Document 4) in which air permeability is improved by using pearlite as a soil conditioner for contaminated soil containing silt or clay above a certain level has already been published. Although it has been proposed, it has not yet become widespread to the extent that it can be said that there are no cases in which such technology has been introduced in the subsequent pollution purification industry.

Although the technology exists as a proposal in this way, the following are assumed as the reasons why it has not become widespread in the purification industry.
First, pearlite is very expensive to use as a soil improvement material for soil purification, and because of its irreversible ionic adsorption of heavy metals, local soil contamination formation due to heavy metal accumulation is promoted. Or, the concern of bringing it in cannot be dispelled, and in addition, when pearlite is added to the soil, the fragile porous part of pearlite is destroyed by the soil pressure, and the soil improvement state is lost over the course of construction. There is concern about continuity, the texture of pure white pearlite deviates from the texture of the target contaminated soil, and due to the light specific gravity, pearlite floats on the soil surface during rainfall and accumulates near the surface soil to blow powder. There are many concerns about the use of pearlite as a countermeasure against soil contamination, such as the concern that the finished quality may be impaired, such as the appearance of soil.

As a contaminated soil countermeasure technology that has the potential to be an extremely inexpensive purification work, it is desirable to apply pile aeration treatment for contaminated soil containing silt and clay, but soil is required for the completion and dissemination of this technology. It has the ability to disperse soil by absorbing the moisture in the gaps and promoting the improvement of ventilation in the gaps, and after clearing various problems that are concerned about the use of pearlite, it is also excellent in its low price, for soil contamination countermeasures. A new soil dispersant was essential.

The gist of the present invention for achieving the above-mentioned object lies in the following invention.
An inorganic porous body is added in an amount of 0.1 part by mass or less to 1 part by mass of contaminated soil containing fine particles such as silt and clay, and a soil mass having a particle size of 20 cm or less depending on the content of the fine particles. Has a process to disperse to
A method for reusing contaminated soil, wherein the inorganic porous body is colored particles having a water absorption rate of 30% or less, a specific gravity of 0.5 or more, and an average particle diameter of 5 mm or less.

According to the method for recycling contaminated soil according to the present invention, various problems of pearlite used as a soil dispersant in the conventional method are solved, and a new method suitable for soil pollution countermeasures, which is excellent at low cost, is solved. It becomes possible to provide a soil dispersant.

This is a list comparing the properties of pearlite pearlite used in the conventional method, the inorganic porous body used and manufactured in the present invention, and the decontaminated and dried granulated soil. It is a figure which shows the typical structure of the intake pipe shown in (8) used at the time of the soil gas suction in this invention.

Hereinafter, embodiments representing the present invention will be shown and described together with examples.
The method for reusing contaminated soil into a soil dispersant according to the present embodiment is a method of recycling contaminated soil into a soil dispersant, which is contaminated with silty or clay using an inorganic porous body which is a colored and highly rigid soil dispersant suitable for soil contamination countermeasures. Beginning with soil reforming, decontamination and drying with improved efficiency in the manufacturing process are aimed at, and finally it is converted to decontamination and drying granulated soil with soil dispersion performance and concentrated for recycling for purification measures. Will be done.

FIG. 1 shows various properties of pearlite used in the conventional method, an inorganic porous body used and manufactured in the present invention, and decontaminated and dried granulated soil. Compared with the pearlite used in the conventional method, the soil dispersant used and manufactured in the present invention shows a difference in various properties except for the particle size, and this difference is the soil dispersion required for soil contamination countermeasures. It was a property as a material.

That is, the difference in water absorption performance and specific gravity indicates the high rigidity of the soil dispersant used / manufactured in the present invention, and the difference in color tone is different from the target soil of the soil dispersant used / manufactured in the present invention. It shows the synchrony of the texture, and the difference in heavy metal absorption capacity dispels the concern of heavy metal contamination accumulation in the soil dispersant used and manufactured in the present invention.

In addition, the overwhelming difference between the pearlite used in the conventional method and the soil dispersant used / manufactured in the present invention lies in their unit price. The price of the inorganic porous material used in the initial process of the present invention is about 1/2 that of pearlite, and the price of the decontamination-dried granulated soil manufactured and used in the subsequent process is 1/10 of that of pearlite. Since the present invention is provided at a reasonable price, it has become possible to provide the market with extremely inexpensive pollution purification measures.

By the way, the target soils in the present invention are specifically classified by soil type, such as sand soil (Sand), loam sand soil (Loamy Sand), sand loam soil (Sandy Loam), and loam soil (Loam). Silt Loam, Sandy Clay Loam, Clay Loam, Silt Clay Loam, Sandy Clay, Sandy Clay, Sandy Clay, Of the silty clay and heavy clay, unless it is a solidified soil that requires physical crushing, the soil containing silty or clay is particularly limited to that type. Not done.

Further, the scope of application of the soil water content, which is closely related to soil dispersion, is not particularly limited in the present invention, and an inorganic porous body or decontaminated and dried granulated soil is applied at an appropriate dose according to the soil quality and water content. It suffices to improve the soil used as the soil dispersion.

Further, as contaminated soil suitable for the present invention, chloroethylene, carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, 1,3-, which are defined by the Soil Contamination Countermeasures Law and the like. Soil contaminated with dichloropropene, dichloromethane, tetrachloroethylene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichlorethylene, benzene, 1,4-dioxane, crude oil, heavy oil, light oil, kerosene, etc. Oils with a composition equivalent to gasoline, waste cutting oil used for metal processing and equipment maintenance, waste lubricating oil, grease, etc., monocyclic aromatic hydrocarbons such as toluene, xylene, ethylbenzene, phenol, trinitrotoluene, etc. Examples include polycyclic aromatic hydrocarbons such as naphthalene, anthracene, phenanthrene, pyrene, fluorantene, chrysene, benzofluorantene, and benzopyrene, and soil contaminated with dioxin, PCB, and the like.

Here, in the case of the recycling of contaminated soil containing silty and clay using the inorganic porous body of the present invention into a soil dispersant, the contamination purification project was carried out by following this conversion process. It is shown with an example.

The target contaminated soil has a yellow-orange light brown color, contains silt and clay in a proportion of 68%, and contains a high concentration of tetrachlorethylene, and is contaminated soil derived from the contaminated center of the cleaning factory premises (elution). Concentration: 32 mg / L). The water content was 19.6%, and the soil was contaminated with strong plasticity forming large soil masses.

To add the inorganic porous body, the soil mass excavated using a backhoe was further cut with a bucket to make a soil mass of about 5 cm or less, and a 20 cubic meter suction pile with a plurality of intake pipes shown in FIG. 2 installed in the center was created. An inspiratory treatment was carried out (the inorganic porous body used in the treatment of this 20 cubic meters was finally about 2.8 tons).

Since the construction was carried out in winter, the entire pile was placed in a simple tent using a single scaffolding pipe and a sheet, and the air inside the tent was heated and cured with a hot air blower. For the convenience of installing this tent, the pile was purified by itself.

The day after the start of ventilation, the temperature distribution of the soil mass gap in the intake path from the pile surface to the intake surface located in the center of the pile was confirmed, and although a temperature drop of about 10 degrees Celsius was confirmed as a temperature difference. The gradient was a discontinuous situation in which no temperature change was observed within a range of 50 cm to the intake surface. This discontinuity of temperature change continued for 17 days thereafter.

After 3 weeks of aeration, the elution concentration of tetrachlorethylene was still above the standard of 0.42 mg / L, but the soil mass was dried to the inside, so the pile was broken and the backhoe caterpillar was used. The decontaminated and dried soil mass was granulated by rolling compaction using. After confirming that the soil mass became fine particles of about 5 mm or less, piles were formed again using these fine particles and suction was performed.

About 6 weeks after the tetrachlorethylene contamination concentration was not detected in the elution concentration, the aeration was stopped to obtain decontaminated and dried granulated soil.

In this series, the drying period took longer than expected, but the reason for this is that the amount of ventilation is small compared to the surface area of the soil mass, so the humidity of ventilation quickly reaches saturation and the temperature due to latent heat due to evaporation. It was pointed out that the decline stagnated and a part of the pile that was not dried was formed in the pile. According to this consideration, the diameter of the soil mass is increased several times, the surface area is reduced to about 1/30, and the space between the soil masses is increased to improve the ventilation to generate a continuous temperature decrease gradient. And said.

As a treatment for this new contaminated soil, the addition of the soil dispersant, which is the decontamination and dry granulated soil, was carried out in the excavation hole using a backhoe. This time, the soil mass cut out to a width of 20 cm or less (for example, about 20 cm) is further cut with a skeleton bucket to make a soil mass of about 10 to 20 cm, and after sprinkling an inorganic porous body on the surface, excess inorganic material is used with the skeleton bucket. After sieving off the porous material and small lumps, they were carried out from the excavation hole, transported to the pile yard as they were, and loaded. The decontaminated and dried granulated soil used for the treatment of 20 cubic meters was finally about 0.8 tons).

The day after the start of ventilation, the temperature distribution of the soil mass gap in the intake path from the pile surface to the intake surface located in the center of the pile was confirmed, and although a continuous temperature decrease gradient was confirmed, the temperature difference was 8 degrees Celsius. Since the temperature was about the same, when the maximum suction was further performed using a spare suction blower, intake (0.4 vvm) was achieved until the temperature difference became 5 degrees Celsius or less.

After 7 days of aeration, the elution concentration of tetrachlorethylene was still above the standard of 0.31 mg / L, but the soil mass was dried to the inside, so the pile was broken and the backhoe caterpillar was used. The decontaminated and dried soil mass was granulated by rolling compaction using. After confirming that the soil mass became fine particles of about 5 mm or less, piles were formed again using these fine particles and suction was performed.

The day after the tetrachlorethylene contamination concentration was not detected in the elution concentration, the aeration was stopped and new decontaminated and dried granulated soil was obtained.

After that, the treatment using decontaminated and dried granulated soil as a soil dispersant was repeated, and the pollution purification measures with a total target soil amount of 57 cubic meters were completed.

The target contaminated soil was a contaminated soil containing oil and trichlorethylene, which had a blackish color containing organic substances and contained silt and clay at a ratio of 33%. The water content was 17%, and by adding 2% w / w of the inorganic porous body, soil particles were dispersed in a state of less than 1 cm small lumps. Since the target soil amount was 98 cubic meters, first, 20 cubic meters of this was filled in a suction facility equipped with an intake pipe on the bottom of a steel tank imitating pile ventilation, and intake treatment was performed.

One week after aeration, the soil mass was dried, and when the trichloroethylene contamination concentration (initial contamination concentration: elution concentration 0.93 mg / L) was not detected at the elution concentration, the aeration was stopped and the decontaminated dried soil particles were aerated. (At this point, the soil particles had already become soil particles centered on the main particle size distribution of about 2 to 3 mm). However, at this time, the TPH concentration remained at 2010 mg / kg as the oil content (the initial value of the TPH concentration was 3240 mg / kg).

With reference to the purification method described in Japanese Patent No. 4695666, defatted rice bran with adjusted moisture, chemical fertilizer, etc. are added to the decontaminated dry soil particles where this oil contamination remains, and the same steel tank suction is performed again. The equipment was filled and the decontaminated dried soil particles were decomposed and dried by thermophilic oil-degrading bacteria under composting and heating. After 5 days, the soil temperature reached the maximum temperature of 75 degrees Celsius, and when it dropped to 50 degrees Celsius after 4 days, dry soil particles were collected and the TPH as an oil concentration decreased to 850 mg / kg. After confirming that the trichlorethylene elution value was not detected, the suction operation was completed to obtain decontaminated and dried granulated soil.

A ratio of 0.9 parts by mass of new contaminated soil was mixed with 0.1 part by mass of this decontaminated and dried granulated soil, and all the remaining contaminated soil was subjected to a steel tank intake treatment. After that, the same operation as the previous one was repeated to dry it, and the batch work of 20 cubic meters was repeated to reduce the oil content to 1000 mg / kg or less and the trichlorethylene elution value to the standard value or less, and to take a series of pollution countermeasures. Completed.

During this repeated operation, the period for reaching the maximum temperature of the composting temperature rise was shortened each time, and finally it was 35 hours. It was speculated that this phenomenon was caused by the increase in the concentration of thermophilic bacteria contained in the decontaminated and dried granulated soil and the stabilization of the flora by the repeated operation.

Example 1 is a typical example of recycling a series of contaminated soil into a soil dispersant, which is the present invention. However, as in Example 2, the present invention depends on the implementation situation. Needless to say, it is within the scope of the present invention even if the process is simplified as long as it does not deviate from the main point of the above.

In addition, Example 3, which will be described later, is an example implemented as an emergency measure in the event of kerosene leakage due to damage to kerosene pipes that occurred outdoors, and this is a case that does not deviate from the main point of the present invention depending on the site conditions and circumstances. This is an example in which a part of the invention is omitted.

Such applications are used when the amount of soil for countermeasures that does not require repetition is extremely small, when there is a risk of pollution dispersal or precipitation infiltration during outdoor purification countermeasure construction, or when the countermeasure period is extremely limited in an emergency. It is often planned for special circumstances such as high-quality construction.

The target soil was an embankment impregnated with high-concentration kerosene, mainly black soil. One day has passed since the leak, and a leak of more than 200 L is expected. On the other hand, due to daily rainfall, oil slicks were observed not only at the leaked points but also everywhere on the local ground surface, and kerosene contamination was secondarily diffused by the inadvertent entry of people.

As an emergency response, we proposed the addition of an inorganic porous material and powdered activated carbon, and sprayed it on the topsoil of the leaked part and the surrounding oil film. In addition, the oil film and oil odor are masked under the condition that a part of the soil sample directly under the leaked part is taken and the inorganic porous body and powdered activated carbon are added at 2% w / w respectively, and benzene. It was confirmed by a simple elution / GC analysis in the field that the elution value was not detected, and the mixture of the inorganic porous body with the design concentration and the powdered activated carbon was improved in the depth direction of the leaked part. Emergency measures were taken at night to prevent the spread of pollution in the depth direction.

Approximately one week later, at the time when the local rainwater pool was pulled out, the re-excavation of the countermeasures department and the secondary construction to confirm the contamination status on the side of the excavation bottom were carried out. As a result, excess benzene was found on some of the excavated sides, and after excavating, conducting a side survey again and confirming no detection, materials for emergency measures were taken for newly excavated contaminated soil. Similar to the design conditions, the inorganic porous body and powdered activated carbon were added and mixed.

Subsequently, a chemical fertilizer was added and mixed with the oil and benzene of the soil maintained in a low concentration equilibrium adsorption state by activated carbon in order to decompose and purify by bioremediation, and then the suction tube shown in FIG. Was returned to the backhoe excavation hole installed on the bottom side surface, the construction site was cured with a sheet, and an intake operation with a suction intensity of 0.1 vvm was performed using a turbo blower.

In a follow-up survey two months later, it was confirmed that the benzene elution value was below the standard value and the TPH concentration was 1000 mg / kg or less, suction was stopped, the suction tube was extubated, and purification measures were completed.

The soil after purification is composed of dry particles of approximately 2 mm or less, including a soil mass of up to 5 cm in part, and can be used as decontamination and dry granulated soil by performing an operation to adjust the particle size. Was being dried. However, in this case, there is no contaminated soil that requires further countermeasures, and the countermeasure project was completed without reusing the generated dry soil for decontamination and dry granulation soil for pollution purification. It was.

In the case of Example 3, if the addition / construction range of the inorganic porous body implemented at the time of emergency measures is limited to a part, and the measures for the remaining contaminated soil are set to multiple measures by sliding the time, In the next construction, the decontaminated and dried soil particles generated in the contaminated soil treatment in the range of the first addition of the inorganic porous body will be used as a substitute for the inorganic porous body in the decontaminated and dried granulated soil generated in the previous construction. I was able to do it.

However, due to the fact that the entire construction had to be carried out in a short period of time as an emergency response, and under the condition that the low concentration of equilibrium adsorption was maintained by activated carbon, the lengthening of the construction period made the purification treatment batch period longer. In view of the above, the reuse of the decontaminated and dried granulated soil, which is a part of the present invention, is omitted (despite the fact that it has sufficient potential for reuse as decontaminated and dried soil particles). It was a completed case.

As described above, it goes without saying that the process of the present invention may be partially simplified in view of the implementation situation as long as it does not deviate from the main purpose of the present invention, but it is within the scope of the present invention.

Activated carbon not only prevents the penetration and diffusion of contamination in the rainy weather construction shown in Example 3, but also VOC contamination in an open system in a situation where it is difficult to prevent diffusion such as setting up a tent outdoors. It will also be used for the purpose of preventing the diffusion of VOCs around when implementing measures that involve excavation of soil. As described above, it is advisable to add not only the inorganic porous body but also the pollution control material such as activated carbon as needed.

By the way, when activated carbon is partly contained as a pollution control material, purification measures are taken against the pollution adsorbed on the surface of the activated carbon and the pollution maintained in a low concentration equilibrium adsorption state by the activated carbon and gradually released at a low concentration. It is important to add the purification material that can be used as a countermeasure soil to the countermeasure soil.

As a purification method applicable to the former contamination adsorbed on the surface of activated carbon, a chemical oxidation method that generates sulfuric acid radicals and hydroxyl radicals that can be effectively decontaminated in a short period of time is effective. On the other hand, for contamination that is maintained in an equilibrium adsorption state at a low concentration by activated carbon and is gradually released at a low concentration, biological treatment utilizing a degrading microorganism having long-term continuity is effective.

If the pollution control material contains a liquid regardless of the presence or absence of activated carbon, at least the addition of this liquid component is the addition of soil particles in the process (4) after the soil mass has been dried. The permeation of the purification agent into the soil particles extends to the inside of the soil particles, contributing to highly accurate pollution purification without omission.

The following invention concept is derived from the embodiments and examples described above.
(1) To 1 part by mass of contaminated soil containing fine particles such as silt and clay, an inorganic porous body is added in an amount of 0.1 part by mass or less, and the particle size is 20 cm or less depending on the content of the fine particles. It has a process to disperse it into the soil mass
A method for reusing contaminated soil, wherein the inorganic porous body is colored particles having a water absorption rate of 30% or less, a specific gravity of 0.5 or more, and an average particle diameter of 5 mm or less.

(2) The method for recycling contaminated soil according to (1) above, wherein a contamination countermeasure material is added in addition to the inorganic porous body.

(3) The method for reusing contaminated soil according to (2) above, wherein the soil mass is loaded to prepare a molded soil mass, and an intake operation is performed from the bottom surface of the molded soil mass.

(4) The above-mentioned (3) is characterized in that the intake operation is set to an intake speed at which the temperature distribution of the soil mass gap in the intake path in the molded soil mass forms a continuous temperature decrease gradient within 5 degrees Celsius. It is a method of recycling contaminated soil described in.

(5) After the granulated soil having a particle size of 5 mm or less is produced by destroying the molded soil mass, the anti-contamination material is added and mixed with the granulated soil to form a new molded soil mass and removed. The method for reclaiming contaminated soil according to (3) or (4) above, which comprises a step of producing a soil dispersant which is a dye-dried granulated soil.

(6) The temperature in the new molded soil mass is set to a high temperature environment exceeding 55 degrees Celsius.
The above (5), which comprises a step of promoting the decomposition of the hydrocarbon compound by the metabolism of a thermophilic microorganism assimilating the hydrocarbon compound which is a pollutant in the granulated soil in the high temperature environment. ) Is the method for recycling contaminated soil.

(7) The intake operation is carried out by using an intake pipe in which the circumference of a double pipe composed of an inner pipe having pores and an outer pipe having a mesh-like surface is further covered with a filter material. The method for recycling contaminated soil according to any one of (3) to (6) above.

(8) The above-mentioned (2), wherein the pollutant purification material contains a powdered activated carbon having a specific surface area of more than 900 m ² / g, and the powdered activated carbon is added in an amount of 0.05 parts by mass or less. This is the method for reclaiming contaminated soil according to any one of (7).

(9) The above-mentioned (1) to (8), wherein the inorganic porous body is a fired product containing clean colored waste glass powder or a clean material containing colored minerals as a part of a raw material. It is the method for recycling contaminated soil according to any one of the above.

(10) A method for recycling contaminated soil, which comprises using the soil dispersant according to (5) above as a substitute for the inorganic porous body.

Next, the effects of the above-mentioned invention concept will be described.
According to the method for reclaiming contaminated soil according to (1) of the present disclosure, 0.1 part by mass or less of the inorganic porous body is used for 1 part by mass of the contaminated soil containing fine particles such as silt and clay. If the soil mass is dispersed in a particle size of 20 cm or less according to the content of the fine particles, the rejoining of the soil mass is reduced, and a communicative soil mass gap space having good fluid permeability can be secured.

As a result, the surface of the soil mass is promoted to dry, and the moisture and contamination inside the soil mass are rapidly transferred to the surface of the soil mass in a dry state through the capillary phenomenon generated inside the soil mass, and the drying effect and volatile pollutants throughout the soil mass are produced. The decontamination effect by transferring to the surface of the material can be dramatically enhanced.
At this time, especially in the case of soil containing a large amount of fine particles such as silt and clay, if the size of the soil mass does not exceed 20 cm and efforts are made to form a larger soil mass, a well-ventilated continuous soil mass Gap space is secured, and extremely efficient drying of the soil mass surface can be promoted.

In addition, with such a large soil mass, the surface area of the soil mass is smaller than the soil volume, and the amount of the inorganic porous body used by adhering to the soil mass surface is significantly saved, which is cost-effective. It is possible to promote the drying of the surface of soil with a high surface area.

In addition, the specific surface area and water absorption rate per mass are clearly inferior to those of general porous materials such as pearlite, and the strength of the porous structure, which is the particle strength of the properties of water absorption rate of 30% or less and specific gravity of 0.5 or more, is high. By using only the inorganic porous material which is particularly stable in the present disclosure, the porous body is less damaged by the soil pressure when the soil masses come into contact with each other or when the soil masses are loaded, and the rejoining of the soil masses is suppressed. , It is possible to continuously secure a well-ventilated space between soil masses.

In addition, by using an inorganic porous material that is a colored particle with a higher specific gravity than pearlite, the finish quality such as texture change and floating and accumulation on the soil surface during rainfall that occur when pearlite is added Concerns can be dispelled.

In addition, according to the method for reclaiming contaminated soil according to (2) of the present disclosure, when a contamination countermeasure material is added as necessary, the contamination exuded to the surface of the soil mass due to the capillary phenomenon together with water is discharged to the surface of the soil mass. Since it is possible to implement pollution countermeasures such as disassembling the soil, it is possible to implement safe pollution countermeasures in which the spread of pollution around the construction area is reduced.

Further, according to the method for recycling contaminated soil according to (3) of the present disclosure, a soil mass is loaded to create a molded soil mass, and an intake operation is positively performed from the bottom surface of the molded soil mass. , The drying effect over the entire soil mass and the decontamination effect by transferring volatile pollutants to the surface can be dramatically enhanced.

Further, in the intake operation in the molded soil mass, according to the method for reclaiming contaminated soil according to (4) in the present disclosure, the temperature distribution in the soil mass gap in the intake path in the molded soil mass is continuous within 5 degrees Celsius. By setting the intake intensity to form a temperature decrease gradient, there is no yield such as shrinkage or clogging of the soil mass caused by the increase in plasticity of the soil mass under the condition of excessive humidity of the soil gap when the gradient is not formed, and it is extremely efficient. An inspiratory operation that enables the recovery and dehydration of good volatile pollutants is achieved, and decontaminated and dried soil mass can be produced extremely efficiently without stagnation.

Subsequently, according to the method for recycling contaminated soil according to (5) of the present disclosure, after the soil mass is destroyed to produce granulated soil having a particle size of 5 mm or less, the granulated soil is contaminated and purified. By adding and mixing materials and performing an appropriate intake operation, further purification against residual volatile and non-volatile contamination is achieved, and the water absorption performance is slightly inferior to that of the inorganic porous body, but it is an alternative. Possible recycling of decontaminated and dried granulated soil into new soil dispersants can be achieved.

Subsequently, according to the method for recycling contaminated soil according to (6) of the present disclosure, the granulated soil is dried and volatile pollutants are recovered, and the contamination on the surface of the granulated soil is decomposed and adsorbed. The method to be combined is the pollution purification method accompanied by the temperature rise of composting disclosed in Japanese Patent No. 4695666, so that the temperature of the soil grain gap is increased by the temperature rise of composting and the relative humidity of the gap air is lowered. Highly efficient drying can be achieved by increasing the effect and the amount of evaporation. In addition, the contaminated soil can be purified extremely efficiently by the decontamination and metabolism of thermophilic degrading bacteria, which is said to double the metabolic activity when the temperature rises by 10 degrees under high temperature conditions.

Further, according to the method for recycling contaminated soil according to (7) of the present disclosure, in the intake operation, a double pipe composed of an inner pipe having pores and an outer pipe having a mesh-like surface. By using an intake pipe whose circumference is further covered with a filter material, the intake pipe is clogged with fine-grained soil exfoliated from the soil mass in the drying process or soil fine particles generated when granulating to a particle size of 5 mm or less. It is possible to avoid adverse effects on the intake system consisting of the activated coal tank and blower after the intake pipe, and it is stable with an extremely simple system that does not require the introduction of a dust removal system to the exhaust. It is possible to carry out various intake operations.

Further, according to the method for reclaiming contaminated soil according to (8) of the present disclosure, a powder having a specific surface area of more than 900 m ² / g at a ratio of 0.05 parts by mass or less as a part of the anti-contamination material. By adding activated charcoal to contaminated soil containing volatile components such as VOC contamination, deodorization and elution of contaminated soil with sufficiently reduced desorption / leaching rate of volatile components such as VOC can be achieved by equilibrium adsorption of activated charcoal. It is possible to achieve pollution control measures to prevent the spread of pollution to the surrounding environment and recycling of soil dispersants.

In addition, according to the method for reclaiming contaminated soil according to (9) of the present disclosure, the inorganic porous body uses clean colored waste glass powder or a clean material containing colored minerals as a part of the raw material. Since it is a calcined product containing heavy metals, its surface structure becomes a vitreous smooth structure with less adsorption and accumulation of heavy metals, there is no concern about organic contamination due to high temperature conditions, and heavy metals are contained when selecting raw materials. It is possible to minimize the risk of soil contamination derived from this material when adding this material to contaminated soil, because heavy metals can be brought in to the minimum by selecting and using raw materials that do not have any.

Furthermore, inorganic porous materials produced using inexpensive raw materials such as clean colored waste glass powder and soil containing colored minerals are extremely inexpensive as compared with existing pearlite, and are therefore specified in the present disclosure. By using the inorganic porous material, it is possible to carry out inexpensive soil improvement with extremely little concern about recontamination and ensuring safety.

Further, according to the method for recycling contaminated soil according to (10) of the present disclosure, the inorganic porous body is obtained by using the soil dispersant according to (5) as a substitute for the inorganic porous body. It is possible to continuously produce decontaminated and dried granulated soil, which is an extremely inexpensive material that can be used as a substitute for the above, at the site where the required decontamination and purification target area is required, while pursuing decontamination and purification.

As described above, the present disclosure can provide the market with an inexpensive pollution purification method using two types of new soil dispersants for soil contamination countermeasures, an inorganic porous body and a decontaminated and dried granulated soil.

In addition, the operation of adding decontaminated and dried granulated soil, which is a soil dispersant derived from this contaminated soil, to the new contaminated soil is a new contamination of a part of the old treated soil from the viewpoint of a series of purification construction processes. It is nothing but returning it to the soil. By following this process in bioremediation using aerobic pollutant-degrading bacteria, it is natural to inoculate a part of the old treated soil, which is rich in pollutant-degrading bacteria, as a starter for new contaminated soil. Therefore, it is possible to carry out bioremediation construction at a significantly lower cost than in the past, which does not require the purchase of new pollutant-degrading bacteria materials and soil dispersants.

Further, according to the method for reclaiming contaminated soil according to the present disclosure, the inorganic porous body according to the present disclosure is compared with the conventional method in which it is necessary to purchase a porous body according to the amount of contaminated soil. The purchase of is reduced only to the first time in a series of purification works, and in the subsequent pollution purification works, decontamination and dry granulated soil derived from contaminated soil is used as a substitute for the inorganic porous body, so that fine grains such as silt and clay are used. It has become possible to carry out extremely inexpensive soil contamination countermeasure construction using intake system purification technology such as pile construction for contaminated soil that includes the amount of soil.

Although embodiments and examples of the present invention have been described above, the specific configuration is not limited to the above-mentioned disclosure, and the present invention may be changed or added without departing from the gist of the present invention. include.

It can be particularly applied in the purification of contaminated soil having a series of processes for carrying out the purification operation through ventilation and the like.

1 ... Perforated PVC pipe 2 ... Resin underdrain pipe 3 ... Felt-like sheet

Claims (10)

An inorganic porous body is added in an amount of 0.1 part by mass or less to 1 part by mass of contaminated soil containing fine particles such as silt and clay, and a soil mass having a particle size of 20 cm or less depending on the content of the fine particles. Has a process to disperse to
A method for recycling contaminated soil, wherein the inorganic porous body is colored particles having a water absorption rate of 30% or less, a specific gravity of 0.5 or more, and an average particle diameter of 5 mm or less. The method for recycling contaminated soil according to claim 1, wherein a contamination countermeasure material is added in addition to the inorganic porous body. The method for recycling contaminated soil according to claim 2, wherein the soil mass is loaded to prepare a molded soil mass, and an intake operation is performed from the bottom surface of the molded soil mass. The contamination according to claim 3, wherein the intake operation sets the temperature distribution of the soil mass gap in the intake path in the molded soil mass to an intake speed that forms a continuous temperature decrease gradient within 5 degrees Celsius. Soil recycling method. After the molded soil mass is destroyed to produce a granulated soil having a particle size of 5 mm or less, the anti-contamination material is added and mixed with the granulated soil to form a new molded soil mass, and decontamination and drying are performed. The method for reusing contaminated soil according to claim 3 or 4, wherein the step of producing a soil dispersant as a grain soil is included. The temperature in the new molded soil mass was set to a high temperature environment exceeding 55 degrees Celsius.
5. A claim is characterized by comprising a step of promoting decomposition of the hydrocarbon compound by metabolism of a thermophilic microorganism assimilating the hydrocarbon compound which is a pollutant in the granulated soil in the high temperature environment. Recycling method of contaminated soil described in. The intake operation is performed by using an intake pipe in which the circumference of a double pipe composed of an inner pipe having pores and an outer pipe having a mesh-like surface is further covered with a filter material. The method for recycling contaminated soil according to any one of claims 3 to 6. Any of claims 2 to 7, wherein the pollutant purification material contains powdered activated carbon having a specific surface area of more than 900 m ² / g as a part thereof, and the powdered activated carbon is added in an amount of 0.05 parts by mass or less. The method for reclaiming contaminated soil described in item 1. The invention according to any one of claims 1 to 8, wherein the inorganic porous body is a clean colored waste glass powder or a fired product containing a clean material containing a colored mineral as a part of a raw material. How to recycle contaminated soil. A method for recycling contaminated soil into a soil dispersant, which comprises using the soil dispersant according to claim 5 as a substitute for the inorganic porous body.