JP7147662B2 - Purification method and equipment for contaminated soil, incineration ash or sludge - Google Patents

Description

The present invention relates to a purification method and purification facility for contaminated soil, incineration ash or sludge, and particularly to a purification method for contaminated soil, incineration ash or sludge contaminated with harmful metals such as heavy metals and pollutants such as halogens and boron. and purification equipment.

When construction and civil engineering works such as tunnels, dams, and land preparation are carried out, excavation muck is generated as excavated surplus soil.
Such excavation muck may contain harmful metals and their compounds, which are natural or artificial contaminants. cannot be brought into
In addition, since toxic metals and the like are contained in the soil of abandoned factory sites, etc., it is necessary to remove the toxic metals and the like from the contaminated soil to satisfy the second elution standard.

For example, in Japanese Patent No. 4970627, granules to which contaminants such as contaminated soil and incineration ash are attached are refined, and contaminants such as heavy metals and dioxins adhering to the surface of the granules are A cylindrical rotating drum having a plurality of outer blades axially mounted on the inner peripheral surface and protruding in the central direction, and a rotating drum axially mounted on the outer peripheral surface and protruding radially in order to release the A single grain refining means having a rotor rotating in the opposite direction to the rotating drum, which has a plurality of inner blades and is mounted eccentrically with respect to the rotating drum inside the rotating drum, The granules with contaminants adhering to them are put into the gap between the rotating drum and the rotor, which is the processing gap of the granulation means. In the method for treating the granular material to which contaminants are attached, the granular material is separated into independent granular materials, and the contaminant adhering to the surface of the granular material is separated. It is put into the same grain refining means again and re-processed, and at the time of re-processing, the eccentricity of the rotor is made larger than the previous time to make the processing gap smaller than the previous time, or the rotating drum and the rotor are made smaller than the previous time. or making the eccentric amount larger than the previous time and the rotation speed higher than the previous time, so that the stress applied to the granular material is made larger than the previous time. A method for treating particulates with attached contaminants is described.
However, the above method for treating contaminated soil requires high cost and high energy.

In recent years, as a method for treating contaminated soil, from the viewpoint of low cost and low energy consumption, a method has been proposed in which heavy metals, etc. are dissolved in an aqueous solution as chelate compounds by wet cleaning using a chelating agent, and removed from the contaminated soil. there is

For example, Japanese Patent Laid-Open No. 2018-8222 describes the treatment of contaminated soil contaminated with harmful substances in order to remove harmful substances present as anions from the liquid phase generated after wet washing of contaminated soil. A treatment method, comprising: a washing step of adding a chelating agent to the contaminated soil and wet washing; a separation step of solid-liquid separation of the contaminated soil after wet washing; A solid-phase treatment step in which a solid-phase solidifying material or a lime-based solidifying material is added to modify the properties, and a solid-liquid-separated liquid phase is added with a solidifying material and an additive containing iron (III) to precipitate the harmful substances. and a liquid-phase treatment step of removing the contaminated soil from the liquid phase.

However, the method of treating contaminated soil using a chelating agent has a problem with long-term stability because the chelating agent is an organic substance, and if it decomposes over time, the heavy metals will be re-eluted.
In addition, in the method of treating contaminated soil using cement or slaked lime, since cement and slaked lime are alkaline, the treated soil becomes alkaline, making reuse difficult.

Furthermore, the method of removing harmful metals, etc. from contaminated soil using a flocculating agent may not satisfy the first elution standard of the Soil Contamination Countermeasures Act (Ministry of the Environment), and chelating agents alone can sufficiently remove harmful metals, etc. In some cases, the second dissolution criterion could not be satisfied.

Therefore, there is a demand for a new method for remediation of contaminated soil that removes contaminants such as harmful metals contained in the contaminated soil and that satisfies the second elution standard and can be brought into the final disposal site.

Patent No. 4970627 JP 2018-8222 A

The object of the present invention is to provide harmful metals such as heavy metals, halogens, boron contained in the Type 2 specified hazardous substances stipulated in the Soil Contamination Countermeasures Act, and contaminants such as these compounds (hereinafter referred to as "contaminants"). ) containing polluted soil, incineration ash or sludge (hereinafter referred to as “contaminated soil, etc.”), effectively adsorb contaminants, and treat them with washing water containing adsorbents so as to satisfy the second elution standard. It is to provide a novel method for remediation of contaminated soil and the like.
In particular, it is an object of the present invention to provide a remediation method for effectively removing contaminants from contaminated soil containing a large amount of contaminants and having fine particle diameters and reusing the entire amount of the contaminated soil.

Another object of the present invention is to provide equipment for remediation of contaminated soil, etc., which can effectively carry out the above-described method for remediation of contaminated soil, etc., which is contaminated with contaminants.

(1) The method for purifying contaminated soil, etc. of the present invention comprises:
Contaminated soil, incinerated ash or sludge, an adsorption additive containing an adsorbent and a flocculant, a pH adjuster and water are mixed to adsorb pollutants to the adsorbent, and the pH is adjusted to 5.8 to 8.6. A mixing / coagulation sedimentation step for adjusting to and coagulating and sedimenting the solid content,
A solid-liquid separation step of separating the coagulated and sedimented water-containing solids from the liquid and dehydrating the water-containing solids to obtain a dehydrated cake;
A classification step of classifying the dehydrated cake so that it can be used for multiple purposes, and
The method for remediation of contaminated soil, etc. is characterized by comprising a reflux step of refluxing the liquid from the solid-liquid separation step to the mixing/aggregating/sedimentation step.

In the method for purifying contaminated soil, etc., in (1) above , part of the liquid in the mixing/coagulation-sedimentation step is taken out and mixed with a chelating agent, and the chelating agent mixture is returned to the mixing/coagulation-sedimentation step. A method for purifying contaminated soil or the like, characterized by:

( 2) Preferably , in the method for remediation of contaminated soil, etc. of (1) above, the contaminated soil is characterized by further comprising a crushing step of crushing the contaminated soil, etc. before the mixing/coagulating sedimentation step. This is a method for purifying soil and the like.

( 3 ) More preferably, in the method for remediation of contaminated soil or the like of (1) or (2) above, the adsorbent is in the form of a powder having an average particle size of 3 to 100 μm and contains a dolomite compound and an acid sulfate. However, the dolomite compound contains CaMg(CO ₃ ) ₂ , MgO, CaCO ₃ , and the acid sulfate is contained in a ratio of 1 to 23% by mass in the total amount of the dolomite compound and the acid sulfate. A method for remediation of contaminated soil, etc., characterized in that 14 to 25% by mass of MgO is contained in the soil.

( 4 ) The facility for purifying contaminated soil, etc. of the present invention is
Contaminated soil, incinerated ash or sludge, an adsorption additive containing an adsorbent and a flocculant, a pH adjuster and water are mixed to adsorb pollutants to the adsorbent, and the pH is adjusted to 5.8 to 8.6. A mixing / coagulating sedimentation device that adjusts to and coagulates and sediments the solid content,
A solid-liquid separation device that separates the water-containing solid content and the liquid content that have aggregated and sedimented, dewatering the water-containing solid content to obtain a dehydrated cake,
A classifier for classifying the dehydrated cake so that it can be used for multiple purposes, and
The facility for purifying contaminated soil, etc. is characterized by comprising a first recycling device for recycling the liquid from the solid-liquid separation device to the mixing/coagulating sedimentation device.

The purification equipment of ( 4 ) above includes a chelate treatment device that takes out a part of the liquid from the mixing/coagulation-sedimentation device and mixes it with a chelating agent, and a chelating agent mixture for introducing the chelating agent mixture into the mixing/coagulation-sedimentation device. A purification facility for contaminated soil, incineration ash or sludge, characterized by comprising a second recycling device of

( 5 ) Preferably , the facility for purification of contaminated soil, etc. in (4) above further comprises a crushing device for crushing the contaminated soil, etc.
(6) More preferably, in the facility for purifying contaminated soil, incineration ash, or sludge of (4) or (5) above, the adsorbent is in the form of a powder having an average particle size of 3 to 100 μm, and contains a dolomite compound and an acidic It contains a sulfate, the dolomite-based compound includes CaMg(CO ₃ ) ₂ , MgO, and CaCO ₃ , and the acid sulfate is contained in a proportion of 1 to 23% by mass in the total amount of the dolomite-based compound and the acid sulfate. , a purification facility for contaminated soil, incineration ash or sludge, characterized in that the adsorbent contains 14 to 25% by mass of MgO.

The method for remediation of contaminated soil, etc. of the present invention is used for pollutants such as harmful metals such as heavy metals, halogens, boron contained in the Type 2 specified hazardous substances stipulated in the Soil Contamination Countermeasures Act, and these compounds. By effectively adsorbing the pollutants from the contaminated soil, etc., it becomes possible to obtain soil that satisfies the second elution standard.
In addition, the equipment for purifying contaminated soil, etc. of the present invention includes contaminants such as harmful metals such as heavy metals, halogens, boron contained in the Class 2 specified hazardous substances stipulated in the Soil Contamination Countermeasures Law, and compounds of these substances. It is possible to effectively carry out a method for remediation of contaminated soil, etc. contaminated with.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically an example of purification facilities, such as contaminated soil of this invention.

The present invention is illustrated by the following preferred examples, but is not limited thereto.
The method for purifying contaminated soil or the like of the present invention comprises:
Contaminated soil, incinerated ash or sludge, an adsorption additive containing an adsorbent and a flocculant, a pH adjuster and water are mixed to adsorb pollutants to the adsorbent, and the pH is adjusted to 5.8 to 8.6. A mixing / coagulation sedimentation step for adjusting to and coagulating and sedimenting the solid content,
A solid-liquid separation step of separating the coagulated and sedimented water-containing solids from the liquid and dehydrating the water-containing solids to obtain a dehydrated cake;
A classification step of classifying the dehydrated cake so that it can be used for multiple purposes, and
The method for remediation of contaminated soil, etc., has a reflux step of refluxing the liquid from the solid-liquid separation step to the mixing/aggregating/sedimentation step.

In addition, the equipment for purifying contaminated soil etc. of the present invention is
Contaminated soil, incinerated ash or sludge, an adsorption additive containing an adsorbent and a flocculant, a pH adjuster and water are mixed to adsorb pollutants to the adsorbent, and the pH is adjusted to 5.8 to 8.6. A mixing / coagulating sedimentation device that adjusts to and coagulates and sediments the solid content,
A solid-liquid separation device that separates the water-containing solid content and the liquid content that have aggregated and sedimented, dewatering the water-containing solid content to obtain a dehydrated cake,
A classifier for classifying the dehydrated cake so that it can be used for multiple purposes, and
A purification facility for contaminated soil, etc., comprising a first recycling device for recycling the liquid from the solid-liquid separation device to the mixing/coagulating sedimentation device.

Specifically, it will be described below with reference to FIG.
FIG. 1 is a diagram schematically showing a purification facility 1 for contaminated soil or the like of the present invention.
The method for remediation of contaminated soil etc. of the present invention is firstly carried out with contaminants such as harmful metals such as heavy metals, halogens, boron contained in the type 2 specified hazardous substances stipulated in the Soil Contamination Countermeasures Law, and these compounds. It can be applied to polluted contaminated soil 2 or the like.
Here, the type of contaminated soil contaminated with pollutants, etc. 2 is not particularly limited, and surplus soil generated from construction and civil engineering work sites such as tunnels, dams, and land development, excavated surplus soil such as factory sites, and output from power plants Incinerated ash and sewage sludge fall under this category.
Also, the type of soil includes rock, stone, gravel, sand, silt, etc., and is not particularly limited.

Contaminated soil or the like 2 is introduced into a mixing/coagulation-sedimentation device 3 and mixed with an adsorption additive containing an adsorbent and a coagulant, a pH adjuster, and water (mixing/coagulation-sedimentation step).
Before subjecting the contaminated soil, etc. 2 to the mixing and agglomeration process, if necessary, a crushing step for the contaminated soil, etc. 2 is provided, and the contaminated soil, etc. 2 is introduced into the crushing device 8 and crushed. (Crushing step) and then introduced into the mixing/agglomerating device 3 for processing, it is possible to efficiently remove contaminants from the contaminated soil 2 such as rocks and large stones. It is desirable because it is possible to obtain a large amount of contaminated treated soil that satisfies the second elution standard that can be brought into the final disposal site. Further, when performing the crushing treatment, it is more preferable to use crushing water such as water, for example, in order to improve the efficiency of the crushing treatment.

Before being introduced into the mixing/coagulation-sedimentation device 3, the adsorbent and the coagulant are mixed in advance before the adsorbent and the coagulant that adsorb the contaminants and the adsorption additive containing the coagulant are introduced into the mixing/coagulation-sedimentation device 3. Either the adsorbent, the coagulant, and water are mixed in advance to prepare the adsorbent additive washing water before introduction, or the adsorbent and the coagulant are added to the mixing/coagulating sedimentation device 3. Even if it is added directly to the mixing/coagulating sedimentation device 3 together with the contaminated soil 2, any blending method can be used. It is desirable to mix the agent and water to prepare the adsorbent additive washing water in order to shorten the time for uniform mixing with the contaminated soil 2 .

The adsorbent for adsorbing contaminants contained in the adsorption additive used in the present invention is not particularly limited, and known contaminant adsorbents can be used.
Preferably, the adsorbent is in the form of powder because it can be uniformly and widely dispersed in the washing water. In addition, it is possible to rapidly react with polluted soil and the like by making it powder form in washing water, and it is possible to efficiently adsorb and capture contaminants.
The average particle diameter of such powder is preferably 3 to 100 μm, more preferably 30 to 100 μm, from the viewpoint of uniform dispersibility in washing water.

As the adsorbent capable of adsorbing contaminants contained in the adsorption additive, any known adsorbent can be used. In particular, an adsorbent containing a dolomite-based compound effectively traps contaminants. It is desirable because it can be adsorbed and fixed.

Here, the contaminants refer to harmful metals such as heavy metals, halogens, boron contained in Class 2 specified hazardous substances stipulated in the Soil Contamination Countermeasures Act, and compounds thereof. For example, heavy metals include: For example, one or more of manganese, chromium, copper, cadmium, mercury, selenium, lead, arsenic, etc., and heavy metal simple substances and their compounds can be exemplified. The compounds can be exemplified, but are not limited to these.

A dolomite-based compound suitably used as an adsorbent contains MgO, CaMg(CO ₃ ) ₂ and CaCO ₃ as essential main components.
Examples of dolomite-based compounds containing such components include semi-baked dolomite containing MgO, CaCO ₃ , and CaMg(CO ₃ ) ₂ as main components.
Any commercially available dolomite can be used, regardless of the place of production.
In addition, any semi-baked dolomite available on the market, or semi-baked dolomite obtained by firing any dolomite available on the market can be used as the semi-baked dolomite. I don't mind. Semi-calcined dolomite is not obtained by calcining dolomite until the decomposition reaction is completely completed, but contains MgO, CaMg(CO ₃ ) ₂ and CaCO ₃ as essential components.

Dolomite has a double salt structure in which the molar ratio of limestone CaCO ₃ and magnesite MgCO ₃ is 1:1, and Ca ²⁺ ions and Mg ²⁺ ions are alternately layered with CO ₃ ²⁻ groups in between. In general, it means that the proportion of MgCO ₃ is 10 to 45% by mass. Dolomite is abundant in Japan, and an adsorbent using dolomite is advantageous in terms of cost and environmental load.

As the semi-baked dolomite, the content x of the residual CaMg(CO ₃ ) _two -phase in the dolomite calcined product analyzed by the Rietveld method based on powder X-ray diffraction is 0.4 ≤ x ≤ 35.4 (mass %) can be suitably used.
By quantifying the CaMg(CO _{3 ) 2 phase contained in the semi-baked dolomite and suitably using the semi-baked dolomite with the CaMg(CO 3 ) 2 phase residual} amount within the above range, the production area of the raw dolomite ore It is possible for dolomite to have the best contaminant adsorption performance regardless of the difference in composition due to calcination and the setting of calcination conditions such as calcination temperature.

Dolomite exhibits a decomposition reaction represented by CaMg(CO ₃ ) ₂ →MgO+CaCO ₃ +CO ₂ by firing. In addition, it is considered that pores are formed by the thermal decomposition of dolomite due to calcination, and the contaminant trapping performance is exhibited.
Preferably, the dolomite-based compound is obtained by analyzing the residual amount of the dolomite phase (CaMg(CO ₃ ) ₂ phase) in semi-baked dolomite obtained by calcining the dolomite by the Rietveld method using powder X-ray diffraction, and residual CaMg (CO ₃ ) The content x of the _two phases is 0.4 ≤ x ≤ 35.4 (% by mass), preferably 1.8 ≤ x ≤ 17.4 (% by mass), so that contaminants are particularly preferably removed. , a better capture can be realized.

For example, such a suitable semi-baked dolomite is such that the content x of the residual CaMg(CO ₃ ) ₂ phase in the dolomite calcined product analyzed by the Rietveld method by powder X-ray diffraction is preferably 0.4 ≤ x ≤ 35.4 (% by mass), more preferably 1.8≦x≦17.4 (% by mass).
The temperature at which dolomite is fired is not particularly limited, and it can be fired at a temperature at which dolomite is normally fired to produce semi-fired dolomite, for example, 650 to 1000°C. The firing time is not limited as long as the content of the residual CaMg(CO ₃ ) ₂ phase is 0.4≦x≦35.4 (mass %).

The MgO content in the adsorbent containing the dolomite compound is preferably 14 to 25% by mass, more preferably 14 to 23% by mass, as analyzed by the Rietveld method using powder X-ray diffraction. .
The MgO in the adsorbent is derived from the contained dolomite-based compound, specifically derived from semi-calcined dolomite obtained by calcining dolomite, and more preferably semi-calcined dolomite. belongs to.
If the MgO content in the adsorbent is less than 14% by mass, the adsorption capacity for lead, fluorine, etc. may decrease. The pH of water, such as rain water, shows alkalinity of 10 or more, which is not desirable.

The dolomite-based compound contained in the adsorbent contained in the adsorption additive used in the present invention includes one and/or two or more materials such that the essential ingredients MgO, CaMg(CO ₃ ) ₂ and CaCO ₃ are included. can be mixed arbitrarily.
As an example, when semi-calcined dolomite containing 21% by mass of MgO is used, by setting the blending ratio of semi-calcined dolomite in the adsorbent to 80 to 99% by mass, the amount of MgO in the adsorbent used in the present invention is The content can be 14 to 25% by mass, but the above mixing ratio is not restricted depending on the dolomite-based material used.

Further, the adsorbent in the adsorbent additive used in the present invention includes acid sulfate.
Examples of acidic sulfates include ferrous sulfate and aluminum sulfate, and ferrous sulfate is preferably contained.
By containing acidic sulfate, it is possible to more effectively capture harmful metals such as arsenic and hexavalent chromium due to its high reducing action like ferrous sulfate, and it is acidic. By adjusting the blending ratio of the materials contained in other dolomite-based compounds, it is possible to maintain the wash water obtained using the adsorbent near neutrality.

The acidic sulfate contained in the adsorbent preferably contains 1 to 23% by mass, preferably 14 to 21% by mass, of the total amount of the dolomite compound and the acidic sulfate. Therefore, it is preferable that the adsorbent contains the dolomite compound and the acid sulfate in the above ratio.

An example of the adsorbent includes a dolomite-based compound and an acid sulfate, as described above, and the acid sulfate is contained in a proportion of 1 to 23% by mass in the total amount of the dolomite-based compound and the acid sulfate, and , an adsorbent containing 14 to 25% by mass of MgO in the adsorbent can be preferably used.

The adsorbent contained in the adsorption additive used in the present invention contains the above-mentioned dolomite-based compound and acid sulfate, and by setting the content of each of these within the above range, more effectively captures pollutants and the like. can do.

Also, the adsorption additive used in the present invention includes a flocculating agent.
The flocculant is not particularly limited. Examples of inorganic flocculants include aluminum sulfate, polyaluminum chloride (PAC), iron-containing compounds such as iron sulfate or iron chloride, or calcium-containing compounds such as quicklime or slaked lime. , polyaluminum chloride, slaked lime, and ferric chloride. On the other hand, examples of organic flocculants include anionic polymer flocculants such as polyacrylamide, nonionic polymer flocculants, cationic polymer flocculants, and amphoteric polymer flocculants.

The adsorption additive containing the suitable adsorbent containing the dolomite-based compound used in the present invention has a medium pH of the test solution prepared by the method in accordance with the Environmental Agency Notification No. 46 (issued on August 23, 1991). (Ministry of the Environment uniform effluent standards (5.8 to 8.6)).

Further, by using an adsorption additive containing the above suitable adsorbent, the pH of the wash water mixed with water finally reaches an equilibrium state of 8 to 10, preferably 9 to 10, more preferably after 28 days. is 8 to 10, preferably 9 to 10. Further, it is desirable that the pH of the initial washing water obtained by mixing the adsorbent and water is 6-8.

In addition to the adsorption additive, a pH adjuster is added to the mixing/aggregating/sedimenting device 3 .
As such a pH adjuster, for example, an acid component such as dilute sulfuric acid or sodium hydroxide or an alkaline component is added to adjust the pH in the mixing/coagulating sedimentation device 3 to a neutral level of 5.8 to 8.6 in the waste water standard. Adjust to range.

By adding a pH additive to adjust the pH in the mixing/coagulating sedimentation device 3 to neutrality, and mixing the contaminated soil etc. 2 and the adsorption additive in such a neutral region, Contaminants are adsorbed by the adsorbent contained in the adsorption additive, and flocs can be aggregated and precipitated in the washing water in the mixing/aggregating device 3 .

Next, the water-containing solid content (sludge) introduced into the solid-liquid separation device 4 from the mixing/aggregation-sedimentation device 3 and the liquid content containing flocs are filtered by, for example, a known solid-liquid separation device 4 by filtration such as a filter press. Solid-liquid separation treatment is performed at (solid-liquid separation step).
The solid-liquid-separated liquid component is refluxed to the mixing/coagulation-sedimentation device 3 through, for example, a conduit (first reflux device) 6 (first reflux step), and recycled in the solid-liquid/coagulation-sedimentation device 3 as a washing liquid. used.
In addition, if necessary, if a crushing step for the contaminated soil 2 is provided before the mixing/coagulation sedimentation step, the liquid content is transferred to the crushing device 8 through the conduit (third recycling device) 10, for example. (third reflux step), and reused as crushing water that can be preferably added in the crushing step when the contaminated soil or the like is crushed.

The dehydrated cake, which is a solid content separated by the solid-liquid separator 4, is obtained as a solid content that satisfies the second elution standard.
Next, the dehydrated cake is classified by introducing it into a classifier 5 (eg, 5-1, 5-2, 5-3).
The classification treatment in such a classification step is, according to the desired use of the soil, for example, as shown in FIG. By performing the classification process 5-2 and then performing the tertiary classification process 5-3, etc., the treated soil is classified according to the grain size according to the application.
As a result, it becomes possible to reuse the treated soil for multiple purposes according to the particle size of the treated soil.
Examples of reuse applications include backfilling materials for structures, backfilling materials for civil engineering structures, road embankment materials, river embankment materials, materials for building land, materials for water surface reclamation, and vegetation materials.
According to the present invention, pollutants can be effectively adsorbed and captured, for example, even in soil containing a large amount of pollutants and having a small particle size, incineration ash, or the like.

In addition, if necessary, when the concentration of contaminants in the contaminated soil 2 is extremely high during the mixing treatment in the mixing/coagulating sedimentation device 3, for example, in the case of incineration ash containing a high concentration of contaminants If necessary, part of the liquid in the mixing/coagulating/sedimentation device 3 is taken out and mixed with a chelating agent in the chelating treatment device 7, and the obtained chelating agent mixture is fed to the mixing/coagulating/sedimentation device 3. It is also possible to collect contaminants by refluxing them to the mixing/coagulation-sedimentation device 3 through a conduit (second reflux device) 9, but in the present invention, the chelating treatment is not essential, and the chelating agent mixture Using is not a mandatory configuration.
In addition, in the present invention, the chelating agent that has captured contaminants is mostly recovered in the dehydrated cake finally produced in the solid-liquid separation step.

Chelating agents used in the chelating treatment include, for example, EDTA (ethylenediaminetetraacetic acid), HIDS (3-hydroxy-2,2'-iminodisuccinic acid), IDS (2,2'-iminodisuccinic acid), MGDA (methylglycine diacetic acid), sodium salt of EDDA (ethylenediaminediacetic acid) or GLDA (L-glutamic acid diacetic acid).

In purifying various contaminants in contaminated soil, etc. contaminated with contaminants, etc., there were cases where the contaminated treated soil could not satisfy the second elution standard in the conventional purification method, but according to the present invention, the contaminated soil The treated soil after purification treatment of contaminated soil or the like contaminated with substances can reduce the above-mentioned various contaminants to the extent that the second elution standard is satisfied.

Therefore, with conventional remediation, it was difficult to reduce the amount of elution to below the second elution amount standard based on the Soil Contamination Countermeasures Act (Ministry of the Environment), and contaminated treated soil could not be brought to the final disposal site. Even soil, etc. can be treated effectively to satisfy the second elution standard, so it is possible to produce a large amount of contaminated treated soil that can be brought to the final disposal site and be treated at the final disposal site. becomes.
In addition, as described above, by classifying the contaminated soil, it becomes possible to use it for multiple purposes, such as backfilling materials for structures, backfilling materials for civil engineering structures, road embankment materials, river embankment materials, It can be used as a material for building land, a material for land reclamation, etc. In particular, the present invention makes it possible to bring contaminated soil, etc. of less than 0.075 mm to a final disposal site, so that the entire amount of contaminated soil, etc. can be reused. is possible.
In particular, when a dolomite-based adsorbent is used as the adsorbent, the treated soil subjected to the pollution treatment of the present invention is neutral and can be reused as soil for vegetation and the like.

The method for purifying contaminated soil and the like of the present invention can be applied to excavated soil such as excavated muck and sludge generated in construction and civil engineering work, contaminated soil such as factory sites, and incineration ash. of pollutants can be effectively captured and removed.

1...Contaminated soil purification device 2...Contaminated soil etc. 3...Mixing/coagulation sedimentation device 4...Solid-liquid separation device 5, 5-1, 5-2, 5- 3 Classification device 6 First reflux device 7 Chelate treatment device 8 Crushing device 9 Second reflux device 10 Third reflux device

Claims (6)

A method for purifying contaminated soil, incineration ash or sludge,
Contaminated soil, incinerated ash or sludge, an adsorption additive containing an adsorbent and a flocculant, a pH adjuster and water are mixed to adsorb pollutants to the adsorbent, and the pH is adjusted to 5.8 to 8.6. A mixing / coagulation sedimentation step for adjusting to and coagulating and sedimenting the solid content,
A solid-liquid separation step of separating the coagulated and sedimented water-containing solids from the liquid and dehydrating the water-containing solids to obtain a dehydrated cake;
A classification step of classifying the dehydrated cake so that it can be used for multiple purposes;
A reflux step of refluxing the liquid from the solid-liquid separation step to the mixing/aggregation/sedimentation step , and
A step of taking out a part of the liquid in the mixing/aggregating/sedimentation step, mixing it with a chelating agent, and refluxing the chelating agent mixture to the mixing/aggregating/sedimentation step.
A method for purifying contaminated soil, incineration ash or sludge, characterized by comprising The method for purifying contaminated soil, incinerated ash, or sludge according to claim 1 , further comprising a crushing step of crushing the contaminated soil, incinerated ash, or sludge before the mixing/aggregating/sedimentation step, A method for purifying contaminated soil, incineration ash or sludge. 3. The method for purifying contaminated soil, incinerated ash or sludge according to claim 1 or 2 , wherein the adsorbent is in the form of powder having an average particle size of 3 to 100 μm and contains a dolomite compound and an acid sulfate, contains CaMg(CO ₃ ) ₂ , MgO, and CaCO ₃ , the acid sulfate is contained in a proportion of 1 to 23% by mass in the total amount of the dolomite compound and the acid sulfate, and the adsorbent contains 14 to 14% of MgO. A method for purifying contaminated soil, incineration ash or sludge, characterized by containing 25% by mass. Equipment for purifying contaminated soil, incineration ash or sludge,
Contaminated soil, incinerated ash or sludge, an adsorption additive containing an adsorbent and a flocculant, a pH adjuster and water are mixed to adsorb pollutants to the adsorbent, and the pH is adjusted to 5.8 to 8.6. A mixing / coagulating sedimentation device that adjusts to and coagulates and sediments the solid content,
A solid-liquid separation device that separates the water-containing solid content and the liquid content that have aggregated and sedimented, dewatering the water-containing solid content to obtain a dehydrated cake,
A classifier for classifying the dehydrated cake so that it can be used for multiple purposes ;
a first reflux device for refluxing the liquid from the solid-liquid separation device to the mixing/coagulating sedimentation device ; and
A chelating treatment device for taking out part of the liquid from the mixing/coagulation/sedimentation device and mixing it with a chelating agent, and a second reflux device for introducing the chelating agent mixture into the mixing/coagulation/sedimentation device. A purification facility for contaminated soil, incineration ash or sludge, characterized by: 5. The facility for purifying contaminated soil, incineration ash or sludge according to claim 4 , further comprising a crusher for crushing the contaminated soil, incineration ash or sludge. 6. The facility for purifying contaminated soil, incineration ash or sludge according to claim 4 or 5, wherein the adsorbent is in the form of powder having an average particle size of 3 to 100 μm and contains a dolomite compound and an acid sulfate, and the dolomite compound is CaMg(CO ₃ ) ₂ , MgO, CaCO ₃ Contaminated soil characterized in that the acid sulfate is contained at a rate of 1 to 23% by mass in the total amount of the dolomite compound and the acid sulfate, and the adsorbent contains 14 to 25% by mass of MgO. , incineration ash or sludge purification equipment.

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