JP2002136962A - Decontamination method for contaminated soil and system therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a system, which can surely remove contaminants from contaminated soil and efficiently treat a large volume of waste water generated when the soil is decontaminated. SOLUTION: This soil decontamination system having a soil decontamination process 1 for decontaminating soil 20 contaminated with polycyclic aromatic hydrocarbons by using a surfactant, is provided with a surfactant separation means 14 for separating waste water, which is generated after the soil decontamination process 1 and contains the surfactant involving the polycyclic aromatic hydrocarbons, into the polycyclic aromatic hydrocarbons and the surfactant by cooling the temperature of the waste water to the Krafft temperature of the surfactant or below and raising the temperature to the cloudpoint or above or by using ultrasonic waves, a freeze concentration means 13b for cooling and freezing waste water 31 containing the separated polycyclic aromatic hydrocarbons, an ice separating and melting means 13c for separating and melting ice which is generated by the freezing and does not contain the polycyclic aromatic hydrocarbons, and a wash water regulator 15 for generating wash water, which is supplied to a soil cleaner, by using the separated surfactant and water generated when the ice is melted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating and removing harmful substances from soil contaminated with harmful substances against ecosystems, and more particularly to a method for separating harmful substances against ecosystems from soil using a surfactant. And a method for purifying contaminated soil.

[0002]

2. Description of the Related Art Conventionally, soil is contaminated by improper handling of industrial waste, transportation accidents, ignorant use of pesticides and other chemical substances, and the like, resulting in harmful effects on ecosystems including animals and plants. I have. Even nontoxic hydrocarbons and oils, as well as highly toxic and mutagenic chemicals, destroy ecologically friendly environments and threaten the survival of living organisms. These harmful substances include, for example, heavy metals such as lead, hexavalent chromium and mercury, organometallic compounds and organic chlorides derived from pesticides and pesticides, organic chlorides such as PCB and trichlene discharged from the electric industry, and incinerators. Dioxins contained in the residual ash, cutting oil and lubricating oil discharged by the machinery industry, crude oil from tanker accidents, various by-products and tar from the crude oil refining industry, and so on. In particular, soil contaminated with polycyclic aromatic hydrocarbons generated from city traffic, coke production, aluminum smelting, and the like is considered to be extremely toxic. These harmful substances not only harm plants and organisms in the soil, but also dissolve in groundwater and rivers and contaminate water quality, and volatilize and diffuse into the air to pollute the air. Other organisms are also adversely affected. In particular, in recent years, an increase in the amount of polycyclic aromatic hydrocarbons released into the environment from plants for producing fossil fuels such as petroleum and coal has been recognized, and the carcinogenicity of the polycyclic aromatic hydrocarbons has been recognized. There is a concern about the effects on humans and the environment of gender or mutagenicity that induces mutations.

Conventionally, for such soil contamination, an air drying method in which the contaminated soil is removed by pulverizing the contaminated soil and passing air, a solidification and stabilization method in which the contaminated soil is sealed with concrete, or a method using a low or high temperature. Thermal decomposition and thermal desorption methods of heat treatment, and microbial decomposition treatment methods of supplying water, nutrients, air, and the like to contaminated soil to decompose them by indigenous microorganisms have been used. However, in the air drying method, not only harmful substances may remain in soil but also cause air pollution. The solidification and stabilization methods have a problem that it is necessary to monitor the leakage of contaminants after the treatment over time, and that it is difficult to treat a large amount of soil. In the thermal decomposition and thermal desorption methods, dioxin generated by the combustion of the organic chloride-based compound must be treated, which increases the cost. Further, the microbial decomposition treatment method is low in cost but long in treatment time, and is not practical.

Accordingly, as a method for treating harmful organic compounds in such soil, a method has been proposed in which a surfactant, an alkali, or the like is added to excavated contaminated soil, washed with water, and contaminants are extracted. . As one of them, JP-A-9-7
No. 5907 proposes a soil purification method using a surfactant. This is to excavate soil contaminated with organic compounds, add a surfactant solution of a predetermined concentration to the excavated soil in a stirring tank, stir and mix to desorb contaminants, and after the desorption is completed,
This is a method for separating a surfactant solution from soil by a solid-liquid separation device. The soil from which the surfactant solution has been separated in this way is returned to the excavation site, and the surfactant solution is reused after removing pollutants in an activated carbon adsorption tank.

In the treatment method using such a surfactant,
In the case of soil purification treatment, it is inexpensive and simple treatment is possible, but on the other hand, there is a problem that a large amount of contaminated water is generated when soil is washed. It is necessary to add a wastewater treatment facility equipped with To solve such a problem, Japanese Patent Application Laid-Open No. H10-2166
In No. 93, as shown in FIG. 3, the contaminated soil B is accommodated in the cleaning tank 02 filled with the cleaning water W to which the chemical cleaning agent has been added, and the contaminated soil A is separated from the contaminated soil B by chemical cleaning. After that, supersaturated water in which the gas component in the air is excessively dissolved is supplied into the cleaning tank 02 to generate fine bubbles in the cleaning water W. A method of separating contaminants that floats on the surface of the washing water W and recovers the pollutants is proposed.

[0006]

However, in such a method, the facility cost can be greatly reduced by the simplified cleaning system as described above, but depending on the type of soil, air bubbles in the cleaning tank may be reduced. As a result, the soil is suspended and collected together with the contaminants, and the final treatment amount of the contaminants is increased. There is a possibility that they will remain slightly, and they are not suitable for treating very toxic contaminants even in trace amounts, such as the polycyclic aromatic hydrocarbons to be treated in the present invention. Accordingly, the present invention has been made in view of the problems of the related art, and it is possible to reliably separate harmful substances from a large amount of wastewater discharged by soil washing using a surfactant, and to circulate water used for washing. It is an object of the present invention to provide a method and an apparatus for contaminated soil purification that can efficiently perform soil purification treatment including wastewater treatment.

[0007]

In order to solve the above-mentioned problems, the present invention provides a washing step for washing soil contaminated with harmful substances against ecosystems using an aqueous solution of a surfactant, and a solid phase comprising purified soil. And a solid-liquid separation step of solid-liquid separation into a liquid phase comprising a surfactant aqueous solution containing an emulsion incorporating the harmful substance, wherein the solid-liquid separated liquid phase is cooled and frozen. Concentrating the harmful substance in the liquid phase by generating ice, melting the ice from which the harmful substance has been removed, and recycling the generated water for the soil washing. I do.

[0008] The harmful substances against ecosystems referred to herein are chemical substances having acute toxicity, mutagenicity and teratogenicity, and adhere to or invade organisms, and are useful for sustaining life such as respiration, sweating, exercise, digestion and absorption functions. A substance that inhibits various necessary functions. Those belonging to the former include, for example, lead, mercury, inorganic substances such as hexavalent chromium, organometallic compounds such as organic mercury and organotin compounds, trichloroethylene, tetrachloroethylene,
Organic chlorides such as polychlorinated biphenyls and hexachlorobenzenes; polycyclic aromatic hydrocarbons such as anthracene, phenanthrene, pyrene, fluoranthene, chrysene, benzopyrene and perylene; those belonging to the latter, for example, crude oil, crude oil refining There are crude oil derived substances such as distillate, mineral oil and tar.

Although the above harmful substances include water-soluble substances, many of them are water-insoluble substances. In any case, since the harmful substances are adsorbed on soil particles, the soil can be removed for a limited time and with water. In order to wash, surface activity has the function of increasing the wetting of the soil particle surface, removing adsorbed harmful substances, dissolving or emulsifying and dispersing in the aqueous phase, and reducing the concentration of harmful substances on the surface of soil particles. The use of agents is essential.

As the surfactant, any of generally known anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants can be used. More specifically, for example, fatty acid sodium, alkyl sulfate, alkyl polyoxyethylene sulfate, alkyl benzene sulfonate, α-olefin sulfonic acid,
Anionic surfactants, such as cationic surfactants, such as alkyltrimethylammonium salts, triethanolamine / difatty acid ester quaternary salts, zwitterions, such as alkyldimethylamine oxides, alkylcarboxybetaines, and amide amino acid salts Can be selected from nonionic surfactants such as surfactants, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, fatty acid polyoxyethylene esters, and fatty acid sorbitan esters, and use in combination of two or more. Can also.

In particular, calcium ions and the like in the soil
Since metal ions are included, such as lowering the Kraft point of the surfactant and reducing its functional effect, it is also preferable to use a sequestering agent such as a chelating agent or zeolite having high reactivity with these metal ions. .

According to the present invention, the wastewater containing harmful substances separated from the soil by the surfactant is cooled and frozen by a refrigerator or the like to produce true ice free of impurities, thereby producing the surfactant and the harmful wastewater. By concentrating impurities such as substances and recycling the water generated by melting the true ice for soil washing, it is possible to reliably separate water, surfactants and harmful substances. Since re-use can be easily performed, cost can be reduced and efficient soil cleaning can be performed. When the wastewater is frozen, fine bubbles are preferably released into the wastewater and constantly stirred and shaken by air. By doing so, mass transfer is always carried out frequently around the nucleus of the water crystal in the wastewater, so that the crystal to be subsequently purified is only pure water crystal, thereby efficiently concentrating impurities in the wastewater and purifying efficiently. Done.

Further, in the method for purifying contaminated soil according to the present invention, the separated liquid phase is cooled to a temperature lower than the Kraft point of the contained surfactant, heated to a temperature higher than the cloud point, or irradiated with ultrasonic waves. The solubilization or emulsification of the liquid phase harmful substance is destroyed and the upper layer and the lower layer are separated into two layers, and the lower layer containing the harmful substance is cooled and frozen to form ice to concentrate the harmful substance in the lower layer. And melting the ice from which the harmful substances have been removed, and recycling the generated water for the soil washing.

[0014] This is because the wastewater after washing the contaminated soil with the surfactant is cooled to a point below the Kraft point before freezing, thereby greatly reducing the solubility of the ionic surfactant due to micelle formation. And the step of separating the surfactant. The Krafft point is, as is well known, a temperature at which the solubility of a surfactant due to micelle formation in water sharply increases. Usually, if the surfactant is not used at a temperature higher than this temperature, the solubility is small and useless.
On the other hand, the solubility of the nonionic surfactant rapidly decreases at a temperature higher than the cloud point.

The surfactant separated in this way has a lower specific gravity than water and accumulates in the upper layer. On the other hand, harmful substances or water-soluble harmful substances having a specific gravity higher than water migrate to the lower layer and are separated into two layers. The upper layer containing the surfactant in the waste water can be recycled and used again, so that the cost can be reduced. Furthermore, since the harmful substance and the surfactant are separated, the treatment of the harmful substance in the next step becomes easy. That is, a further feature of the method for purifying contaminated soil of the present invention is that the two-layer separated surfactant from which harmful substances have been removed is recycled and used for the soil washing.

When the harmful substance in the liquid phase containing the harmful substance obtained by the solid-liquid separation is water-insoluble and has a specific gravity smaller than water, the temperature is lowered to the Kraft point of the surfactant contained. When an operation of separating or depositing a surfactant and a harmful substance by the action of ultrasonic waves is performed, the harmful substance moves to the upper layer together with the surfactant. In this case, it is necessary to separate the surfactant and the harmful substance by another method, or to transfer the surfactant and the upper layer surfactant separately to a decomposing step to make them harmless.

Further, in the soil washing treatment according to the present invention, a desired purification may not always be obtained by a single batch operation depending on treatment conditions. That is, the size of the processor,
Depending on the amount of soil to be treated at one time, the amount of available water limited by this, the capacity and concentration of the surfactant, the treatment rate ((initial soil contamination concentration-soil contamination concentration after treatment)) x 10
0 / initial soil contamination concentration) is not 100% and varies depending on conditions. In such a case, the processing object can be achieved by multi-stage processing in which washing is repeated a plurality of times according to the set final arrival contamination concentration of the soil. That is, a further feature of the method for purifying contaminated soil of the present invention is to perform multi-stage washing in which the solid-liquid separated solid phase is returned to the washing step, and the washing step and the solid-liquid separation step are repeated a plurality of times. .

For example, due to the above-mentioned constraints, only 90% of the reaching processing rate can be obtained by one cleaning processing,
1pp contaminated soil contaminated with ppm contaminant concentration
When it is desired to perform the multi-stage cleaning to be repeated n times or more when it is desired to reduce the concentration to the final attainment concentration of m or less, (1-0.9) n × 1000 ppm ≦ 1 ppm 10−n ≦ 10−3 ∴n ≧ 3 The purpose can be achieved by washing three or more times.

As an invention of an apparatus for effectively implementing these inventions, the present invention relates to a soil purification apparatus provided with a soil washing means for washing soil contaminated with ecologically harmful substances using an aqueous solution of a surfactant. A freeze-concentrating means for cooling and freezing wastewater containing the surfactant incorporating the harmful substance after the soil washing, and ice for separating and melting the surfactant-free true ice generated by freezing Separating and melting means, and water produced by the ice separating and melting means is returned to the soil washing means for reuse.

Further, the present invention provides a soil purification apparatus provided with soil washing means for washing soil contaminated with ecologically harmful substances using an aqueous solution of a surfactant, Freeze-concentrating means for cooling and freezing wastewater containing a surfactant incorporating the harmful substance, and ice separation and melting means for separating and melting true ice free of surfactant generated by freezing. With
The water generated by the ice separating and melting means is returned to the soil washing means for reuse.

Further, in the above-mentioned contaminated soil purification apparatus, the present invention is further characterized in that the freeze-concentrating means and the ice separating / thawing means are performed in the same tank by a heat radiation / heat absorption cycle of a heat pump. With this configuration, a heat pump cycle / refrigeration cycle is alternately formed in a tank having both the freeze-concentrating means and the ice separating / thawing means. Reduce.

Still further, according to the present invention, ice is melted on the condenser side by the ice separation and melting means, and wastewater is frozen on the evaporator side by the freeze concentration means. The melting water of the ice is used for cooling the wastewater containing the surfactant to a temperature below the Kraft point, and the heat of condensation at the time of the freeze concentration is heated by the heating heat source of the washing water regulator and the surfactant separating means. It is characterized by being connected by a heat pump used to raise the temperature of the wastewater containing surfactant to a temperature higher than the cloud point.

The washing water conditioner must be maintained at a temperature higher than the Kraft point in order to increase the solubility of the surfactant. On the other hand, the surfactant separating means requires a temperature lower than the Kraft point to suspend and separate the surfactant. Alternatively, it must be kept at the cloud point. Therefore, in this invention, when an ionic surfactant is used, heat of condensation at the time of generation of ice is led to the washing water regulator to raise the temperature, and low-temperature molten water generated by melting of ice When the non-ionic surfactant is used, the heat is condensed during the formation of ice, and the soil is purified with high thermal efficiency. A device can be provided. Incidentally, apart from the method of cooling the surfactant separating means using the cold heat from the melting water of ice as described above, it is also possible to use a method of cooling using the heat of melting when melting the ice. Good.

Further, the contaminated soil purification apparatus of the present invention returns the solid-liquid separated solid phase to the washing step between the washing step and the solid-liquid separation step, and repeats the washing step and the solid-liquid separation step a plurality of times. A return means for performing multi-stage cleaning is provided.

The return means includes a transfer means such as a belt conveyor, a screw conveyor, a bucket conveyor, etc., which is connected to the solid phase discharge port of the solid-liquid separator and guides the solid phase to the soil input port of the soil washer. can do.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the invention thereto, unless otherwise specified, and are merely illustrative examples. Not just. FIG. 1 is an overall configuration diagram of a soil purification device according to a first embodiment of the present invention, and FIG. 2 is an overall configuration diagram of a second embodiment. As shown in FIG. 1, the soil purification apparatus according to the first embodiment of the present invention includes a soil washing step 1 and a freeze concentration step 3, and the soil washing step 1 is a soil washing machine 1
0, solid-liquid separators 11, 12 and return means 35. The freeze-concentration step 3 comprises a harmful substance separation means 13 comprising a storage tank 13a, a freeze-concentration means 13b and an ice separation / thaw means 13c.
And a refrigeration / heat pump device 16.

In the soil washing step, the soil washer 10
For example, using a screw feeder that moves the contaminated soil 20 introduced from the inlet of the contaminated soil 20 containing harmful substances to the downstream side by rotating a helical screw, supplies washing water to the downstream side of the soil washer 10. An opening is provided, and the washing water 21 and the surfactant are caused to flow to the side of the soil input port so that the contaminated soil is washed. Also, the solid-liquid separator 11
It is preferable to use a filter thickener or the like provided downstream of the soil washer 10, that is, on the side of the soil discharge port, for removing the liquid component from the soil washed by the soil washer 10 by filtration. The solid-liquid separated soil is configured to be returned to the soil washer again by the return means 35 such as a bucket conveyor, and the washing can be repeated. further,
On the downstream side, a solid-liquid separator 12 for separating the soil remaining in the wastewater by settling is provided.

The freeze-concentration step is a step of separating pure water from wastewater containing a surfactant containing harmful substances. The storage tank 13a, the freeze-concentration means 13b, and the ice separation / thaw means 1
The refrigeration / heat pump device 16 includes a toxic substance separation means 13 provided with 3c. The freeze concentration means 13b
Has a configuration in which a refrigeration cycle 16a is formed on the evaporator side of the refrigeration / heat pump device 16, and the pure water is frozen and separated from impurities by cooling the wastewater stored in the freeze-concentrating means 13b. It has become. On the other hand, the ice separation and melting means 13c is located on the condenser side of the refrigeration /
As a result, the purified water 29 is circulated to the soil washer 10 for reuse.

The surfactant contained in the washing water 21 may be any of an anionic surfactant, a cationic surfactant, and a nonionic surfactant. For example, alkyl benzene sulfonate, abieticin A surfactant suitable for pollutants and soil is used in combination with one or more of acid salts, fatty acid soaps, polyoxyethylene alkyl ether, polyoxyethylene nonylphenyl ether, and the like.

Next, the step of purifying contaminated soil in the first embodiment will be described. First, the contaminated soil 20 containing a harmful substance is put into the soil washer 10, and the harmful substance is separated from the contaminated soil 20 by mixing with the washing water 21 supplied from the downstream side. The liquid is introduced into the solid-liquid separator 11 which is vertically separated by a filter to remove the liquid. If the concentration of the harmful substance does not fall to a predetermined value by one washing, the separated soil is returned to the soil washer again by the return means 35, and the washing is repeated. Then, the purified soil 24 is returned to the environment by being returned to the excavation site or transported to a soil use place. On the other hand, wastewater 23 containing a surfactant that has taken in harmful substances through the soil washer 10 is guided to the solid-liquid separator 12 together with the liquid component 26 separated from the purified soil by the solid-liquid separator 11,
Here, after the purified soil 25 remaining in the liquid is precipitated and separated, it is sent to the freeze concentration step 3.

The wastewater 27 containing harmful substances discharged from the soil washing step 1 is temporarily stored in the storage tank 13a of the harmful substance separation means 13 by the pump 18 with the valves a and c opened. When the amount is stored, it is supplied to the freeze concentration means 13b. And the freeze concentration means 13b
Since pure water freezes on the refrigerant pipe of the refrigeration cycle 16a formed by the refrigeration / heat pump device 16,
The wastewater in which the surfactant containing the harmful substance is concentrated is collected in the lower part of the freeze concentration means 13b, and the harmful substance concentrated wastewater 30 is pumped by the pump 18 with the valves a and c closed and the valves b and e open. And discharged to the decomposition process. After the drainage 30 is completely discharged, the valves b and e are closed,
The heat pump cycle 16
By forming b and functioning as the ice separating and melting means 13c, ice frozen in the refrigerant tube can be melted to obtain pure water. The pure water 29 obtained here is returned to the soil washing step and reused.

As described above, by alternately forming the refrigeration / heat pump cycle by the refrigeration / heat pump device 16, pure water can be generated in one tank as shown in FIG. As shown in FIG. 2, two or more tanks are installed and the freeze concentration means 13b and the ice separation and thawing means 13c are provided with a time difference, respectively, so that a large amount of wastewater discharged from the soil washing step 1 can be efficiently removed. The heat energy can be effectively used on the evaporator side and the condenser side of the refrigeration / heat pump device 16, and waste of power can be reduced.

The second embodiment of the present invention shown in FIG. 2 is an apparatus in which a step of separating a surfactant and a harmful substance is further provided in the first embodiment described above. 3 and a surfactant recycling step 2. In the second embodiment, the soil washing step 1 has the same configuration as that of the first embodiment. In the surfactant recycling process, if the used surfactant is ionic, the aqueous solution is cooled below the Kraft point to separate it, and if the used surfactant is nonionic, the aqueous solution is heated to the cloud point or higher. Need to be separated. The surfactant recycling step 2, which is a processing step of the harmful substance-containing wastewater 27 discharged from the soil washing step 1, includes a surfactant separating means 14 and a washing water adjuster 15, and the surfactant separating means Numeral 14 is maintained below the Kraft point or above the cloud point of the surfactant used, and the washing water regulator 15 is maintained above the Kraft point or below the cloud point. As a result, the surfactant is separated in the surfactant separating means 14 because the solubility of the surfactant is very low. On the contrary, the surfactant is dissolved in the washing water regulator 15. In the subsequent freeze concentration step 3, the impurities in the waste water are concentrated and separated to obtain pure water, as in the first embodiment.

To explain the flow of the second embodiment,
The wastewater 27 discharged by the cleaning treatment of the contaminated soil in the soil cleaning step 1 as in the first embodiment is guided to the surfactant separating means 14 by opening the valve a, where the surfactant is separated by floating. At the same time, in the case of this example, the harmful substance has a specific gravity higher than that of water, so that the harmful substance settles below the surfactant separating means 14. The separated surfactant 33 is used as the washing water conditioner 1
The wastewater guided to 5 and containing the harmful substances settled in the lower part is sent to the storage tank 13a in the freeze concentration step 3 by the pump 18 with the valves d and c open. The surfactant separating means 14 can also apply ultrasonic waves or fine bubbles accompanied by ultrasonic waves to the inside of the tank, and separate the surfactant and the harmful substance by the fine bubbles or ultrasonic waves. In the case of the nonionic surfactant, it is also possible to raise the temperature to be higher than the cloud point by the effect of increasing the temperature by ultrasonic waves when separating by heating. When a certain amount of wastewater stored in the storage tank 13a accumulates, the wastewater is transferred to the freeze concentration means 13b. The freeze concentration means 1
In 3b, since the pure water portion freezes due to the refrigeration cycle 16a formed by the refrigeration / heat pump device 16,
The harmful substance is concentrated and accumulates in the lower part, and the three-way valve 19 and the valves b and e are opened to send the concentrated harmful substance concentrated wastewater 34 to equipment provided with a harmful substance decomposition treatment process or the like.
At this time, the heat of condensation at the time of ice formation is reduced by the washing water regulator 15.
And the heat of condensation is used to maintain the temperature of the washing water regulator 15 above the Kraft point of the surfactant used. That is, the refrigeration cycle 16a is provided on the freeze concentration means 13b side.
A heat pump cycle 16 is provided on the washing water regulator 15 side.
By configuring the refrigeration / heat pump device 16 so as to form b ′, it becomes possible to efficiently operate such a soil cleaning device.

After the harmful substance concentrated wastewater 34 is completely discharged from the freeze-concentration means 13b, a heat pump cycle 16b is formed in the freeze-concentration means 13b and transferred to the ice separation and thawing means 13c, whereby the frozen ice is melted. Pure water can be obtained. The molten water 29 obtained here is
The three-way valve 19 is opened in the direction of the washing water regulator 15, and the three-way valve 19 is fed to the washing water regulator 15. At this time, the low-temperature molten water 29
The cooling of the surfactant separating means 14 is performed by utilizing the cold heat. Thereby, heat exchange can be efficiently performed by the surfactant separating means 14, and when the washing water regulator 15 into which the purified water 29 whose temperature has been raised is introduced is heated to a temperature higher than the Kraft point of the used surfactant, Alternatively, less heat energy is required for cooling to below the cloud point of the surfactant used. In addition, as a cooling method of the surfactant separating means 14,
As mentioned above, besides utilizing the melting water or heat of condensation,
A refrigeration cycle formed using heat of evaporation at the time of melting the ice in the ice separating and melting means 13c may be used.

In the washing water regulator 15 to which the waste water containing the surfactant 33 separated by the surfactant separating means 14 and the pure water 29 generated in the freeze concentration step 3 are supplied, these are mixed. Washing water suitable for soil washing is adjusted and supplied to the soil washing step 1 to reuse the washing water. This will reduce the amount of wastewater discharged in large quantities,
Recycling of surfactant and water becomes possible, leading to cost reduction. The water separated from the surfactant and the harmful substance by the surfactant separating means 14 is the pure water 29.
In addition, it is preferable to use the cleaning water regulator 15.

[0037]

As described above, according to the present invention, it is possible to reliably remove harmful substances from a large amount of wastewater used for cleaning soil contaminated with ecological harmful substances, It is possible to provide an inexpensive and low-cost soil purification method and apparatus by circulating and using water and a surfactant used for washing. Further, in the freeze-concentration step used in the present invention, by effectively utilizing the refrigeration / heat pump cycle, a device having high thermal efficiency can be provided, and waste of power can be eliminated.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a soil purification device according to a first embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a soil purification device according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram showing an embodiment of a conventional contaminated soil purification device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Soil washing process 2 Surfactant recycling process 3 Freeze-concentration process 10 Soil washer 11, 12 Solid-liquid separator 13 Hazardous substance separation means 13a Storage tank 13b Freeze-concentration means 13c Ice separation / thaw means 15 Washing water regulator 16 Freezing / Heat pump device 18 Pump 19 Three-way valve 20 Contaminated soil 29 Melted water (pure water) 34 Concentrated wastewater of harmful substances 35 Return means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B09C 1/04 C02F 1/36 1/08 B09B 3/00 304K C02F 1/22 ZAB 1/24 5/00 S 1/36 (72) Inventor Takeo Kanazawa 2-13-1, Botan, Koto-ku, Tokyo Inside the Maekawa Works Co., Ltd. (72) Inventor Shinichi Yamagami 2-3-1 Botan, Koto-ku, Tokyo Co., Ltd. Maekawa Corporation Inside the factory (72) Inventor Keisuke Iwahori 519-1-201 Orito F-term (reference) 4D004 AA41 AB02 AB03 AB06 CA13 CA40 CA45 CB44 CB50 CC03 CC05 4D037 AA11 AB06 AB08 AB14 BA01 BA11 BA26 CA06

Claims (9)

[Claims] 1. A washing step for washing soil contaminated with ecological harmful substances using an aqueous solution of a surfactant, a surfactant comprising a solid phase comprising purified soil and an emulsion incorporating the harmful substances. A solid-liquid separation step of solid-liquid separation into a liquid phase composed of an aqueous solution, wherein the solid-liquid separated liquid phase is cooled and frozen to generate ice, thereby converting the harmful substance into the liquid phase. A method for purifying contaminated soil, characterized in that the ice, from which the harmful substances have been removed, is melted, and the generated water is recycled for the soil washing. 2. A washing step for washing soil contaminated with ecologically harmful substances using an aqueous solution of a surfactant, and a surfactant comprising a solid phase composed of purified soil and an emulsion incorporating the harmful substances. A solid-liquid separation step of solid-liquid separation into a liquid phase comprising an aqueous solution, wherein the separated liquid phase is cooled below the Kraft point of the contained surfactant and above the cloud point of the contained surfactant By heating or irradiating ultrasonic waves to break up the solubilization or emulsification of harmful substances in the liquid phase and separate into two layers, an upper layer and a lower layer.The lower layer containing the harmful substances is cooled and frozen to form ice Contaminating the harmful substance in the lower layer by melting, melting the ice from which the harmful substance has been removed, and recycling the generated water for the soil washing. 3. The method for purifying contaminated soil according to claim 1, wherein the surfactant separated from the two layers to remove harmful substances is recycled for the soil washing. 4. The multi-stage washing in which the solid-liquid separated solid phase is returned to the washing step, and the washing step and the solid-liquid separation step are repeated a plurality of times. Contaminated soil purification method. 5. A soil purification apparatus provided with a soil washing means for washing soil contaminated with ecologically harmful substances using an aqueous solution of a surfactant, wherein the surfactant containing the harmful substances after the soil washing is used. A freeze-concentrating means for cooling and freezing the wastewater containing the agent; and an ice separation and melting means for separating and melting the true ice free of surfactant generated by freezing, and the ice separation and melting means. A contaminated soil purification device, wherein the generated water is returned to the soil washing means for reuse. 6. A soil purification apparatus provided with a soil washing means for washing soil contaminated with ecologically harmful substances using an aqueous solution of a surfactant, wherein the surfactant containing the harmful substances after the soil washing is taken. Cool the wastewater containing the agent below the Kraft point of the surfactant contained, raise the temperature above the cloud point, or irradiate ultrasonic waves to destroy the emulsification of the liquid phase and form two layers, an upper layer and a lower layer. A two-layer separating means for separating, a freeze-concentrating apparatus for cooling and freezing the separated lower layer containing the harmful substance, and an ice separating and melting means for separating and melting ice from which the harmful substance generated by freezing is removed. A contaminated soil purification device, comprising: a cleaning water preparation device that prepares cleaning water to be supplied to a soil cleaning device using the separated surfactant and water generated by melting of ice. . 7. The contaminated soil purification apparatus according to claim 5, wherein the freeze concentration means and the ice separation / thawing means are performed in the same tank by a heat radiation / endothermic cycle of a heat pump. 8. The method of melting ice on the condenser side by the ice separating and thawing means, freezing the waste water on the evaporator side by the freeze concentrating means, and removing the surfactant by the surfactant separating means. The melting water of the ice is used for cooling the wastewater containing water to a temperature lower than the Kraft point, and the heat of condensation at the time of freeze concentration includes the heating heat source of the washing water preparation device and the surfactant in the surfactant separating means. The contaminated soil purification apparatus according to any one of claims 5 to 7, wherein the apparatus is connected by a heat pump used to raise the temperature of the wastewater to a temperature higher than the cloud point. 9. A return means for performing multi-stage washing, wherein the solid-liquid separated solid phase is returned to the washing step, and the washing step and the solid-liquid separation step are repeated a plurality of times. 9. A contaminated soil purification apparatus according to any one of claims 8 to 8.