JP2006116397A - Washing method and washing apparatus of contaminated soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a washing method and a washing apparatus of contaminated soil stripping and separating contaminants firmly adhering on surface of earth and sand, and improving quality of washed soil. <P>SOLUTION: In this washing method of contaminated soil, contaminated soil containing toxic contaminants is washed and separated into washed soil and condensed residue containing condensed contaminants, the washed soil is recycled, and the condensed residue is recovered for treatment. The method comprises processes for: adding water to the contaminated soil, classifying it by wet screening to separate gravel and coarse sand to form slurry earth and sand; adding a dispersant to the slurry earth and sand, mixing and agitating to strip the contaminants from the surface of the earth and sand; treating the slurry earth and sand by a hydrocyclone to classify into sand/fine sand and fine particles containing the contaminants; separating metal contaminants by gravity type separation of the classified sand/fine sand; obtaining washed earth and sand through dewatering process of the sand/fine sand and separating separated fine particles into settled sludge and water by coagulation settling; dewatering the settled sludge and separating into the condensed residue and water, to obtain the condensed residue. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for cleaning contaminated soil containing harmful pollutants and a cleaning device used in this cleaning method, and in particular, mineral oil, polycyclic aromatic hydrocarbons (PAHs), heavy metals, cyan and the like. A method for cleaning contaminated soil in which contaminated soil containing harmful pollutants is washed, separated into washed soil and concentrated residue of pollutants, the treated soil is reused, and the concentrated residue is recovered. And a cleaning apparatus.

  In general, various purification techniques are applied to the purification and repair of contaminated soil depending on the type of the pollutant. The cost of purification is minimized when the most appropriate purification technology is selected for the subject pollutant. However, actual sites are often contaminated with multiple chemicals (eg oil and heavy metals). For this reason, a purification technique with low cost and wide application range is desired.

Among them, it has been reported that the soil washing method is widely applicable to many substances such as volatile organic compounds (VOCs), PCBs, agricultural chemicals, heavy metals, and cyan (see, for example, Non-Patent Document 1). . This soil cleaning technology can be applied to many substances such as (1) high cleaning efficiency, (2) high processing capacity, (3) mineral oil, PAHs, heavy metals, cyanide, etc. (4) Contamination cleaning processing Since the re-use rate of the later soil is as high as about 70%, it has an excellent ability such as low-cost treatment.
Hitoshi Tanaka, Mitsuo Mori, Shinsei Kumamoto, Yoshiharu Haneda, Masaki Imazawa, Purification of Contaminated Soil by High Efficiency Soil Cleaning Plant (MRP), Soil Environment Center Technical News, September 2003, No. 7, p. 36-38

  However, contaminants that are firmly attached to the surface of the earth and sand due to electrostatic interaction or the like cannot be separated or removed from the surface of the earth and sand even by the soil washing method according to Non-Patent Document 1, and the washing process It was often attached to the soil until the end. For this reason, there existed a problem that the quality of the washing process soil fell.

  In view of the above-mentioned problems of the prior art, the present invention is used in a method for cleaning contaminated soil, which peels and separates contaminants firmly attached to the surface of the soil and improves the quality of the cleaned soil, and this cleaning method. An object is to provide a cleaning device.

To solve this problem,
The invention according to claim 1 is for cleaning contaminated soil containing harmful pollutants, separating the soil into wash-treated soil and a concentrated residue obtained by concentrating the pollutants, supplying the washed-treated soil for reuse, and concentrating the soil. A method for cleaning contaminated soil in which a residue is subjected to a recovery process, wherein water is added to the contaminated soil, and wet sieving classification is performed to separate gravel and coarse sand to form slurry-like soil (A-1 ), Adding a dispersant to the slurry-like earth and sand, mixing and stirring, separating the contaminants from the surface of the earth and sand (A-2), and hydrolyzing the slurry-like earth and sand, A step of classifying fine sand and fine particles containing contaminants (A-3), a step of separating the classified sand and fine sand by gravity, and further separating metal contaminants (A- 6) and step (A-7) of dehydrating the sand / fine sand Then, while obtaining the said washing process soil, the process (B-1) which carries out the aggregation precipitation of the said fine particle isolate | separated at the said process (A-3), and isolate | separates it into a precipitated sludge and water, and dehydrates this precipitated sludge. It is the washing | cleaning method of the contaminated soil characterized by obtaining the said concentration residue through the process (B-2) which processes and isolate | separates into the said concentration residue and water.

  According to a second aspect of the present invention, contaminated soil containing harmful pollutants is washed, separated into washed treated soil and concentrated residue of the pollutants, the washed treated soil is reused, and the concentrated A method for cleaning contaminated soil in which a residue is subjected to a recovery process, wherein water is added to the contaminated soil, and wet sieving classification is performed to separate gravel and coarse sand to form slurry-like soil (A-1 ), Adding a dispersant to the slurry-like earth and sand, mixing and stirring, separating the contaminants from the surface of the earth and sand (A-2), and hydrolyzing the slurry-like earth and sand, A step of classifying fine sand and fine particles containing contaminants (A-3), a step of adding a collecting agent to the classified sand and fine sand, and mixing and stirring (A-4); The mixed and agitated sand and fine sand are separated by foam floating method to remove contaminants. Separating step (A-5), separating the sand / fine sand separated by gravity and further separating metal contaminants (A-6), and dehydrating the sand / fine sand. The step (A-7) is followed by the step (B-1) of obtaining the washing treated soil and coagulating and precipitating the fine particles separated in the step (A-3) into separated sludge and water. ) And the step (B-2) of dehydrating the precipitated sludge and separating the concentrated sludge into water and the concentrated residue to obtain the concentrated residue.

  According to a third aspect of the present invention, contaminated soil containing harmful pollutants is washed, separated into washed treated soil and concentrated residue of the pollutants, the washed treated soil is reused, and the concentrated A device for cleaning contaminated soil for collecting residue, a wet sieving device (10) for separating gravel and coarse sand from the contaminated soil to which water has been added to form slurry-like soil, and the slurry-like soil Mixing and stirring device (20) for adding a dispersing agent to the earth and sand, mixing and stirring to separate the contaminants from the surface of the earth and sand, and the slurry-like earth and sand into sand and fine sand and fine particles containing the contaminants Hydrocyclone device (30) for classifying treatment, gravity type separation device (60) for further separating metal contaminants from the classified sand and fine sand, dewatering the sand and fine sand, and the washing treated soil Dehydration cyclone equipment (7 And a coagulating sedimentation device (100) for coagulating and precipitating the separated fine particles to separate the separated sludge and water, and a press dehydrating device for dehydrating the precipitated sludge to obtain the concentrated residue (200). A cleaning apparatus for contaminated soil.

  According to a fourth aspect of the present invention, contaminated soil containing harmful pollutants is washed, separated into washed treated soil and concentrated residue of the pollutants, the washed treated soil is reused, and the concentrated A device for cleaning contaminated soil for collecting residue, a wet sieving device (10) for separating gravel and coarse sand from the contaminated soil to which water has been added to form slurry-like soil, and the slurry-like soil A mixing and stirring device (20) for adding a dispersant to the earth and sand, mixing and stirring, and separating the contaminants from the surface of the earth and sand, and further adding the slurry-like earth and sand to the sand and fine sand and fine particles containing the contaminants From the hydrocyclone device (30) for classifying into the sand, the mixing and stirring device (40) for adding and collecting the collecting agent to the classified sand and fine sand, and the mixed and stirred sand and fine sand Bubble floating separator for separating pollutants 50), a gravity separator (60) for further separating metal contaminants from the separated sand / fine sand, and a dewatering cyclone device (70) for dehydrating the sand / fine sand to obtain the washed soil And a coagulating sedimentation device (100) for coagulating and precipitating the separated fine particles and separating them into a precipitated sludge and water, and a press dehydrating device for dehydrating the precipitated sludge to obtain the concentrated residue ( 200), and a contaminated soil cleaning apparatus.

  According to the method and apparatus for cleaning contaminated soil of the present invention, by adding a dispersant to the sand and mixing and stirring, the contaminants firmly attached to the surface of the sand can be separated and separated, The quality of the cleaning soil can be improved.

  Hereinafter, a cleaning method for contaminated soil and a cleaning device used in the cleaning method according to an embodiment of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic view of a contaminated soil cleaning apparatus according to the first embodiment. The cleaning apparatus according to the present embodiment corresponds to the invention described in claim 3, and the cleaning method corresponds to the invention described in claim 1.

  In addition, the contaminated soil cleaning apparatus according to the present embodiment cleans contaminated soil containing harmful pollutants, separates the soil into cleaned treated soil and concentrated residues of pollutants, and reuses the cleaned soil. The concentrated residue is subjected to a recovery process. This device separates gravel and coarse sand from contaminated soil to which water has been added to form a slurry-like sand, and adds a dispersant to the slurry-like sand and mixes and stirs. A mixing and stirring device (20) for separating contaminants from the surface of the soil, a hydrocyclone device (30) for classifying the slurry-like soil into sand / fine sand and fine particles containing the contaminant, and classification Gravity type separation device (60) that further separates metal contaminants from the treated sand / fine sand, dehydration cyclone device (70) that dehydrates the sand / fine sand to obtain washed soil, and separated fine particles The coagulation sedimentation apparatus (100) which coagulates and precipitates and isolate | separates into precipitation sludge and water, and the press dehydration apparatus (200) which dehydrates this precipitation sludge and obtains a concentrated residue is comprised roughly.

  Contaminated soil to be cleaned contains harmful pollutants. Such harmful pollutants include organic pollutants such as mineral oil, polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), PCBs, dioxins, pesticides, heavy metals, cyanides, and inorganic pollution. Substances. Moreover, the contaminated soil is soil of all land such as agricultural land, industrial land, urban area, residential area and the like. It may be a soil such as a factory site that is artificially contaminated with harmful pollutants at a high concentration, or may be a soil such as a naturally contaminated farmland.

  First, after adding water, the contaminated soil is sent to a wet sieving device (10). This wet sieving device (10) sorts foreign matter by vibration sieving, ultrasonic sieving, specific gravity sorting, etc., and classifies it into gravel / crude sand exceeding 2 mm and slurry-like earth and sand below it, It has a mesh surface inside. A commercially available well-known apparatus can be used for this wet sieving apparatus (10). After adding water, the contaminated soil is classified by the wet sieving apparatus (10) and classified into gravel / crude sand exceeding 2 mm and slurry earth and sand of 2 mm or less (step (A-1)). Most harmful pollutants adhere to and adsorb on fine particles, and the amount of pollutants contained in large gravel and coarse sand exceeding 2 mm is below the environmental standard value. Can be reused together with the washed soil after separation. Further, by separating in advance gravel / crude sand exceeding 2 mm, the washing efficiency of earth and sand can be improved. The amount of water added to the contaminated soil is preferably 2.5 to 5 times (mass ratio) that of the soil from the viewpoint of slurrying.

  The classified slurry-like earth and sand is sent to the mixing and stirring device (20). The mixing and stirring device (20) is provided with a stirring tank and a stirring blade. In this apparatus, after adding a dispersant to the slurry-like earth and sand, the slurry-like earth and sand are rubbed together by mechanically mixing and stirring using a stirring blade or the like, thereby firmly attaching to the surface of the earth and sand. It is for exfoliating and separating contaminants. A commercially available well-known apparatus can be used for this mixing and stirring apparatus (20). The slurry-like earth and sand classified in the step (A-1) is added with a dispersant, mixed and stirred by the mixing and stirring device (20), and the contaminants are separated from the surface of the earth and sand (step (A -2)). As the dispersant, a surfactant is preferable, and among them, a polyphosphate-based surfactant is more preferable. Moreover, although the addition amount of a dispersing agent changes with the abundance of a contaminant, it is preferable that it is 0.01-0.1 mass% with respect to the whole. Even if the slurry-like soil is simply mechanically mixed and stirred without adding the dispersant, it is difficult to peel the contaminants from the surface of the soil. This is because the surface charge of the pollutant is different from that of the earth and sand, and the pollutant is firmly attached to the earth and sand surface by electrostatic interaction. By adding a dispersing agent, these surface charges change, so that contaminants can be easily peeled off. The separated contaminants are classified as an overflow together with fine particles in the next step, so that they do not remain in the cleaning soil.

  Then, this slurry-like earth and sand is sent to a hydrocyclone apparatus (30). This hydrocyclone device (30) is composed of a container having a conical structure at the bottom of the cylinder, and includes an upper inlet for introducing slurry mixed with earth and sand, a lower outlet for taking out underflow, and an upper part for taking out overflow. And an outlet. The slurry-like earth and sand that has entered from the upper inflow port is rotated at a high speed in the circumferential direction of the cylindrical container, thereby causing a rotational motion, which becomes a rotational flow and proceeds toward the top of the cone. At this time, particles having a high specific gravity in the slurry gather on the peripheral wall due to centrifugal force, gradually move toward the underflow outlet (lower outlet), and are concentrated and discharged. On the other hand, particles having a low specific gravity with the liquid rise as a vortex in the center of the cylindrical container and are discharged from the overflow outlet (upper outlet). Specifically, sand / fine sand of 63 μm to 2 mm is classified as underflow, and fine particles and contaminants of less than 63 μm are classified upward as an overflow (step (A-3)). A commercially available well-known apparatus can be used for this hydrocyclone apparatus (30). Since the contaminants adhere to and adsorb on the fine particles, most of the contaminants can be removed from the cleaning soil by classification with the hydrocyclone device (30). This classification treatment is preferably performed once or more.

  The classified sand / fine sand is sent to the gravity separation device (60). This gravitational separation device (60) has a structure in which soil and sand together with water are spirally flowed from above to below, and is classified by the difference in speed when particles settle in the liquid by gravity. Heavy metal contaminants gather inside the spiral, light sand / fine sand separates with the water to the outside of the spiral, and the sand / fine sand is taken out from below. A commercially available well-known apparatus can be used for this gravity-type separation apparatus (60). Metal contaminants are separated from the sand / fine sand by a gravity separator (60) (step (A-6)). Examples of such metal contaminants include shotgun bullets. Moreover, since a metal contaminant and water contain the contaminant, they are sent to the coagulation sedimentation apparatus (100).

  Sand and fine sand are sent to a dehydration cyclone device (70). The dehydration cyclone device (70) has the same structure as the hydrocyclone device (30). Sand and fine sand are separated into washing soil and water by a dehydration cyclone device (70) (step (A-7)). Analyze the residual concentration of pollutants in the washed soil obtained and confirm that it is below the environmental standard value. This cleaning soil can be reused for backfilling and the like because the concentration of contaminants is below the environmental standard value. Moreover, water is sent to a storage tank and reused as water added to the wet sieving apparatus (10) as circulating water.

  On the other hand, fine particles containing contaminants separated by the hydrocyclone device (30) are sent to the coagulation sedimentation device (100). This coagulation sedimentation device (100) is equipped with a sedimentation tank, and aggregating agent is added to and stirred in suspension water containing fine particles, and fine suspended matter in water is precipitated as a large sedimentation sludge to separate clear treated water. (Step (B-1)). A commercially available well-known apparatus can be used for this coagulation sedimentation apparatus (100). As such flocculants, inorganic flocculants and organic flocculants can be used alone or in combination. Examples of the inorganic flocculant include aluminum sulfate, polyaluminum chloride, and iron salt. Examples of the organic flocculant include polyacrylamide and polyacrylic acid. The addition amount of the flocculant is adjusted according to the suspended solid (SS) concentration of the suspension water. Moreover, the water isolate | separated from the sedimentation sludge is sent to a storage water tank, and is reused as water added to a wet sieving apparatus (10) as circulating water.

  Since this precipitated sludge contains a large amount of moisture, it is sent to the press dewatering device (200) and dehydrated. The press dewatering device (200) is a known pressure filtration device (belt filter press) or the like, and includes a filter made of a filter cloth or the like and a press machine. By filtering the precipitated sludge with a press dehydrator (200) for dehydration, a concentrated residue having a water content of 40 to 50% by mass can be obtained on the filter (step (B-2)). This concentrated residue consists of fine particles of less than 63 μm, and since the contaminants are concentrated, they are taken out and disposed of. If the particle size composition (dry weight ratio) of the original contaminated soil is gravel / crude sand 25%, sand / fine sand 50%, fine particle 25%, the resulting washed soil is 75%, concentrated residue Becomes 25%, and the reuse rate of the cleaning soil can be increased.

  Moreover, in this embodiment, since the water used by the whole apparatus is circulated and reused, the secondary pollution by waste_water | drain does not generate | occur | produce and the cost of water treatment can be reduced.

  In this embodiment, by providing a mixing and stirring device (20) for adding and mixing and stirring a dispersing agent, it is possible to peel and separate contaminants firmly attached to the surface of the earth and sand. Can improve the quality.

  Moreover, in this embodiment, most soil particles up to 4 mm are washed by classification and processing into gravel / coarse sand exceeding 2 mm, sand / fine sand of 63 μm to 2 mm, and fine particles of less than 63 μm. Can be processed.

[Second Embodiment]
FIG. 2 is a schematic view of a contaminated soil cleaning apparatus according to the second embodiment. The cleaning apparatus according to the present embodiment corresponds to the invention described in claim 4, and the cleaning method corresponds to the invention described in claim 2. In this embodiment, between the hydrocyclone device (30) and the gravity separation device (60), a mixing and stirring device (40) for adding and collecting and stirring a collecting agent to the classified sand and fine sand Since it is the same as that of the first embodiment except that the foam floating type separation device (50) for separating contaminants from the sand / fine sand is provided, the description thereof is omitted.

  The mixing and stirring device (40) has the same structure as the mixing and stirring device (20), but the added drug is not a dispersant but a collecting agent (collector). In this mixing and stirring device (40), a trapping agent that selectively adheres only to the contaminant is added to the sand / fine sand by utilizing the fact that the surface charges of the contaminant and the sand surface are different. Mixing and stirring are performed to attach the scavenger to the contaminant (step (A-4)). This pollutant is separated from the earth and sand in the next bubble floating separator (50). The type and concentration of the collection agent are appropriately selected according to the target contaminant.

  This sand / fine sand is sent to the bubble floating separator (50). This bubble floating type separation device (50) includes a flotation cell and a rotor therein, and the upper liquid surface of the cell is composed of a rotating blade for removing bubbles with the liquid surface and the horizontal direction as a rotation axis. A scraper is provided. The slurry containing sand and fine sand is introduced into the flotation cell of the foam floating separator (50), the foaming agent is added, and the rotor is rotated to introduce air into the cell bottom. Bubbles generated from the rotor trap the contaminants with the trapping agent and rise to the liquid level at the top of the cell together with the bubbles, and are scraped off by the scraper as froth together with the bubbles from the liquid level (step (A -5)). The foam and water are sent to the coagulation sedimentation device (100), and the separated sand / fine sand is sent to the gravity separation device (60).

  In this embodiment, by providing the collection agent mixing and stirring device (40) and the bubble floating separation device (50) between the hydrocyclone device (30) and the gravity separation device (60), the remaining The contaminants to be removed can be removed and the quality of the cleaning soil can be further improved.

It is the schematic of the cleaning apparatus of the contaminated soil which concerns on 1st Embodiment. It is the schematic of the cleaning apparatus of the contaminated soil which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Wet sieving apparatus 20, 40 Mixing and stirring apparatus 30 Hydrocyclone apparatus 50 Foam floating type separation apparatus 60 Gravity type separation apparatus 70 Dehydration cyclone apparatus 100 Coagulation sedimentation apparatus 200 Press dehydration apparatus

Claims (4)

Contaminated soil that cleans contaminated soil containing harmful pollutants, separates it into washed treated soil and concentrated residue of the pollutant, recycles the washed soil, and collects the concentrated residue for recovery processing Cleaning method,
Adding water to the contaminated soil, separating the gravel and coarse sand by wet sieving classification (A-1),
A step of adding a dispersant to the slurry-like earth and sand, mixing and stirring, and peeling the contaminant from the earth and sand surface (A-2);
The slurry-like earth and sand is subjected to a hydrocyclone treatment to classify it into sand / fine sand and fine particles containing contaminants (A-3),
A step (A-6) of separating the metallic contaminants by subjecting the classified sand and fine sand to a gravity separation treatment;
Through the step (A-7) of dehydrating the sand and fine sand, the washing soil is obtained,
A step (B-1) of coagulating and precipitating the fine particles separated in the step (A-3) and separating them into precipitated sludge and water;
A method for washing contaminated soil, characterized in that the precipitated residue is obtained through a step (B-2) in which the precipitated sludge is dehydrated and separated into the concentrated residue and water. Contaminated soil that cleans contaminated soil containing harmful pollutants, separates it into washed treated soil and concentrated residue of the pollutant, recycles the washed soil, and collects the concentrated residue for recovery processing Cleaning method,
Adding water to the contaminated soil, separating the gravel and coarse sand by wet sieving classification (A-1),
A step of adding a dispersant to the slurry-like earth and sand, mixing and stirring, and peeling the contaminant from the earth and sand surface (A-2);
The slurry-like earth and sand is subjected to a hydrocyclone treatment to classify it into sand / fine sand and fine particles containing contaminants (A-3),
A step (A-4) of adding a collecting agent to the classified sand and fine sand and mixing and stirring;
A step (A-5) of separating the contaminants by subjecting the mixed and stirred sand / fine sand to a foam floating type separation treatment;
A step (A-6) of subjecting the separated sand / fine sand to a gravity separation process to further separate metal contaminants;
Through the step (A-7) of dehydrating the sand and fine sand, the washing soil is obtained,
A step (B-1) of coagulating and precipitating the fine particles separated in the step (A-3) and separating them into precipitated sludge and water;
A method for washing contaminated soil, characterized in that the precipitated residue is obtained through a step (B-2) in which the precipitated sludge is dehydrated and separated into the concentrated residue and water. Contaminated soil that cleans contaminated soil containing harmful pollutants, separates it into washed treated soil and concentrated residue of the pollutant, recycles the washed soil, and collects the concentrated residue for recovery processing A cleaning device of
A wet sieving device (10) for separating gravel and coarse sand from the contaminated soil to which water has been added to form slurry-like soil;
A mixing and stirring device (20) for adding a dispersing agent to the slurry-like earth and sand, mixing and stirring, and separating contaminants from the surface of the earth and sand;
A hydrocyclone apparatus (30) for classifying the slurry-like earth and sand into sand / fine sand and fine particles containing contaminants;
A gravity separator (60) for further separating metal contaminants from the classified sand and fine sand;
A dehydration cyclone device (70) for dehydrating the sand and fine sand to obtain the washed soil;
And the coagulation sedimentation apparatus (100) which coagulates and precipitates the separated fine particles and separates it into sedimentation sludge and water,
An apparatus for cleaning contaminated soil, comprising: a press dewatering apparatus (200) for dewatering the precipitated sludge to obtain the concentrated residue. Contaminated soil that cleans contaminated soil containing harmful pollutants, separates it into washed treated soil and concentrated residue of the pollutant, recycles the washed soil, and collects the concentrated residue for recovery processing A cleaning device of
A wet sieving device (10) for separating gravel and coarse sand from the contaminated soil to which water has been added to form slurry-like soil;
A mixing and stirring device (20) for adding a dispersing agent to the slurry-like earth and sand, mixing and stirring, and separating contaminants from the surface of the earth and sand;
Furthermore, the hydrocyclone apparatus (30) for classifying the slurry-like earth and sand into sand / fine sand and fine particles containing contaminants;
A mixing and stirring device (40) for adding and mixing and stirring a collecting agent to the classified sand and fine sand;
A bubble floating separation device (50) for separating contaminants from the mixed and stirred sand and fine sand;
A gravity separator (60) for further separating metal contaminants from the separated sand and fine sand;
A dehydration cyclone device (70) for dehydrating the sand and fine sand to obtain the washed soil;
And the coagulation sedimentation apparatus (100) which coagulates and precipitates the separated fine particles and separates it into sedimentation sludge and water,
An apparatus for cleaning contaminated soil, comprising: a press dewatering apparatus (200) for dewatering the precipitated sludge to obtain the concentrated residue.

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