JP2008200542A - Method and system for treating polluted soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide of a treatment method of polluted soil capable of effectively purifying polluted water produced accompanying the treatment of polluted soil to effectively utilize the purified water without discharging the same to the outside, and a treatment system of polluted soil. <P>SOLUTION: The treatment method of polluted soil has a soil excavation process (S 130) for excavating fluorine containing polluted soil, a water treatment process (S 200) for mixing magnesium oxide or an additive material based thereon and magnesium chloride with the fluorine-containing polluted water bled when the polluted soil is excavated in the soil excavation process (S 130) to subject fluorine in the polluted water to insolubilization treatment, and an insolubilization treatment process (S 330) for mixing the treated water purified in the water treatment process (S 200), magnesium oxide or the additive material based thereon and the magnesium chloride solution with the polluted soil excavated in the soil excavation process (S 130) to subject fluorine in the polluted soil to insolubilization treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a contaminated soil treatment method and treatment system for insolubilizing fluorine contained in soil.

  Environmental standards related to water pollution as of February 22, 1999 (Environment Agency Notification No. 59 December 1986) and environmental standards related to groundwater pollution (Environment Agency Notification No. 10 March 1997) Was revised, and fluorine was added to the items of environmental standards related to human health protection, along with nitrate nitrogen, nitrite nitrogen, and boron. Along with this, in March 2001, fluorine was newly added to the soil environmental standards.

  Fluorine may be present in the soil due to natural origin, drainage from factories, etc., but if fluorine in the soil enters groundwater or the like due to rain or the like, it may be mixed into drinking water. If excessive fluorine is taken into the human body by ingesting such drinking water, it may cause patchy teeth, skeletal fluorine poisoning (gait disorder), fluorine deposition disease, etc. It has become a very important technology in terms of environmental conservation.

  Therefore, regarding the treatment of fluorine-contaminated soil, a technique for insolubilizing fluorine in the fluorine-contaminated soil by adding and mixing magnesium oxide and magnesium chloride to the fluorine-contaminated soil has been proposed (see Patent Document 1, etc.).

JP 2005-324083 A

  In the field of soil contamination, contamination often spreads deeper than the groundwater level, and it is not uncommon for contaminants to elute into the groundwater. Therefore, when excavating contaminated soil to make it insoluble, it is necessary to treat contaminated water generated during excavation.

  However, it is actually expensive to purify contaminated water to a level where a dedicated plant is installed and allowed to drain into the surrounding environment (meeting environmental standards). If a dedicated treatment plant cannot be installed, there are many cases where contaminated water must be treated as waste.

  The present invention has been made in view of such circumstances, and there is provided a processing method and a processing system for contaminated soil that can effectively purify contaminated water generated in the treatment of contaminated soil and effectively use it without taking it outside. The purpose is to provide.

  (1) In order to achieve the above object, the present invention provides a drilling process for excavating contaminated soil containing fluorine, and magnesium oxide in contaminated water containing fluorine exuded when excavating contaminated soil in the excavating process. Or, an additive containing this as a main component and magnesium chloride are mixed to insolubilize fluorine in the contaminated water, and treated water purified in this water treatment step, magnesium oxide or an additive containing this as a main component A material and a magnesium chloride solution are mixed with the contaminated soil excavated in the excavation step, and an insolubilization process step of insolubilizing fluorine in the contaminated soil is included.

  (2) In the above (1), preferably, the treated water is mixed with the contaminated soil as a solvent of a magnesium chloride solution.

  (3) In the above (1) or (2), preferably, the treated water is mixed with the contaminated soil as moisture for adjusting the water content ratio.

  (4) In any one of the above (1) to (3), preferably, the water treatment step includes a step of allowing contaminated water to stand to precipitate contaminated soil particles, wherein the contaminated soil is precipitated. The particles are insolubilized in the insolubilization process together with the contaminated soil excavated in the excavation process.

  (5) In order to achieve the above object, the present invention also stores a drilling device for excavating contaminated soil containing fluorine, and contaminated water containing fluorine that has exuded when excavating contaminated soil with the drilling device. A water tank for mixing magnesium oxide or an additive containing the same as a main component, a water tank for storing the contaminated water and mixing magnesium chloride, and an additive containing magnesium oxide or a main component thereof A mixing device that mixes the material with the contaminated soil excavated by the excavating device, treated water in which magnesium oxide or an additive containing magnesium oxide as a main component and magnesium chloride are mixed and insolubilized in the water tank, and a magnesium chloride solution And a mixing device for mixing the contaminated soil excavated by the excavating device.

  According to the present invention, similarly to the treatment of contaminated soil, magnesium oxide (or an additive based on this) and magnesium chloride are mixed to purify the contaminated water, thereby chemically treating the contaminated soil and the treated soil. Treated water whose balance does not change can be obtained. This treated water is suitable as contaminated soil treatment water, and the treated water can be effectively used for treating contaminated soil. Therefore, the contaminated water can be effectively purified and effectively used without being taken outside.

Embodiments of contaminated soil treatment according to the present invention will be described below.
[1] Basic Principle of Insolubilization Process First, the basic concept of the fluorine insolubilization process of the present invention will be described.
The contaminated soil treatment according to the present invention can be applied to all contaminated soil containing fluorine, but particularly when fluorine-contaminated soil exhibiting alkalinity exceeding pH 10 is treated as compared with other methods. Has a remarkable effect. Representative examples of the fluorine-contaminated soil exhibiting alkalinity include, for example, casting sand to which magnesium oxide is added as a hardener, soil in which fluorine is mixed into modified soil to which calcium is added as an improving material, and the like. The present invention is not limited to these cases, and the present invention is also suitable for treating fluorine-contaminated soil that has become alkaline by containing magnesium oxide or calcium or other substances due to natural origin or other factors.

  In the method for treating contaminated soil according to the present invention, the fluorine-contaminated soil exhibiting alkalinity as described above is additive containing magnesium oxide or magnesium oxide as a main component (hereinafter simply referred to as “magnesium oxide” or “insolubilizer” as appropriate). And a mixing process. As long as the fluorine is insolubilized to a level that satisfies the soil environmental standard value (fluorine elution amount in the test solution prepared from the soil by the official method is 0.8 mg / L or less), the mixing effect of magnesium oxide alone has a corresponding effect. Play. Magnesium oxide is mixed in a powder state, but in some cases, it can be added to the contaminated soil in a mixed state with a liquid. However, a powder having a particle size of 1 mm or less, more preferably 10 μm or less is preferable. The powdered magnesium oxide is preferably high-purity or a large specific surface area.

  Moreover, in addition to the mixing process of magnesium oxide, the process of mixing magnesium chloride with the contaminated soil is performed, thereby further stabilizing the insolubilization reaction of fluorine. Magnesium chloride is added to contaminated soil in the form of a solution, but in some cases it may be added in the form of powder (hereinafter, magnesium chloride may be described as “insolubilizer” together with magnesium oxide). ). The mixing step of magnesium chloride can be carried out at the same time regardless of before and after the mixing step of magnesium oxide.

In the process of mixing magnesium oxide (MgO) into the contaminated soil,
MgO (solid) + F- → MgO ... F-
As shown, fluorine ions that existed in a state that can be insolubilized in the contaminated soil are adsorbed on the solid surface of magnesium oxide to be insolubilized. The symbol “...” In the above formula schematically represents the adsorbed state.

In the step of mixing magnesium chloride (MgCl2),
3MgO (solid) + MgCl2 + nH2O → 3MgO · MgCl2 / nH2O
As shown, magnesium oxide reacts with magnesium chloride to produce magnesia cement. At this time, the fluorine adsorbed on the solid surface of magnesium oxide is taken into the cement structure of magnesia cement, so that the fluorine is more stably insolubilized. In addition, with the generation of magnesia cement, the treated soil is solidified to a certain extent, and after a predetermined curing period, it can be used as it is as a backfill soil without any further strength improvement (as backfill soil). Can be secured).

[2] Whole process Next, embodiment of the contaminated soil processing which concerns on this invention is described using drawing.
FIG. 1 is a process flow diagram schematically showing the entire process of an embodiment of the contaminated soil treatment according to the present invention.
As shown in FIG. 1, the contaminated soil treatment in the present embodiment occurs in the excavation / backfill process (S100) for excavating contaminated soil and backfilling the treated soil, and the excavation / backfill process (S100). A water treatment step (S200) for purifying the contaminated water and a soil treatment step (S300) for treating the excavated contaminated soil. Each of these steps 100 to 300 will be described.

(2-1) Excavation and backfilling process Although not shown in particular, it is necessary to conduct a preliminary survey of the contamination status of the soil contamination site before constructing the excavation and backfilling process (S100). Sampling and measuring the amount of fluorine eluted from the sampled soil. The method for measuring the fluorine elution amount is not limited. For example, the fluorine concentration in the test solution prepared based on the official method is measured. As a result, when the elution amount of fluorine in the treatment target soil exceeds the soil environmental standard value, the soil at the sampling location is identified as the contaminated soil to be treated.

FIG. 2 is a schematic diagram of an underground section of contaminated soil.
Contaminated soil C in which the fluorine content exceeds the soil environment standard value is distributed in the clean soil S in which the content of fluorine as a contaminant is within the soil environment standard value. In the model diagram of FIG. 2, the contaminated soil C extends to the lower side of the groundwater W. An impermeable layer I that is difficult to pass through the groundwater W exists below the groundwater W. Pollution situations like this model are common when pollutants are buried underground. In the case of such a contamination situation, there is a high possibility that fluorine is eluted in the groundwater W. Fluorine ions dissolved in the groundwater W move with the groundwater W. However, compared to VOC (volatile organic compounds, terachlorethylene, etc.), the movement distance is short because of restrictions on the potential in the soil and organic matter.

  When the contaminated soil C as exemplified in FIG. 2 is targeted, in the excavation / backfilling step (S100), first, the impervious work (S110) is started, and the sheet pile F that blocks the flow of groundwater is started from the ground surface. Drive over impermeable layer I. As a result, the groundwater W in the contaminated area is separated from the surrounding groundwater W (see FIG. 3).

  In the subsequent groundwater pumping work (S120), a well B (generally called “Kamaba”) for pumping up the groundwater W is dug into the contaminated soil C, and the contaminated water (exudate) oozing into the well B is pumped out. Pump up. Thereby, the water level of the contaminated soil C is lowered and the contaminated soil C is easily excavated. In addition, the well B may be a boring well, or may be a dent excavated with a heavy excavator (such as a hydraulic excavator). The contaminated water pumped up from the well B is treated in a water treatment step (S200) described later.

  In the soil excavation step (S130), the excavated heavy machine such as a hydraulic excavator excavates the contaminated soil C and the surrounding clean soil S, and the excavated contaminated soil C is transferred and processed in the soil treatment step (S300).

  After excavating the contaminated soil C, as shown in FIG. 4, the soil layer L is formed by laying clean earth and sand on the excavation site in the subsequent spreading step (S140), and the procedure is transferred to the backfilling step (S150). Then, the treated soil R treated in the soil treatment step (S300) is spread on the soil layer L. When the treated soil R is backfilled in the excavation site in this way, the surface of the treated soil R is covered with the covered soil H in the last soil covering step (S160), and is compacted as necessary. When the soil covering process (S160) is completed, the sheet pile F is pulled out, and the entire process related to the contaminated soil treatment shown in FIG.

  In the above, the so-called covering / laying earth method is adopted, and the case where the treated soil R is surrounded by the covering soil L and the covering soil H to suppress the movement of soil particles in the treated soil R is shown as a preferable example. However, the treated soil R that has been subjected to the soil treatment step (S300) may simply be backfilled to the excavation site without depending on the soil covering / laying earth method, as long as the fluorine is sufficiently insolubilized.

(2-2) Water treatment process In this water treatment process (S200), the groundwater pumped up in the excavation and backfilling process (S100) (S120), that is, may contain fluorine as a contaminant. Purify highly contaminated water. The contaminated water purification method in the water treatment step (S200) is essentially the same as the contaminated soil purification method, in which magnesium oxide and magnesium chloride are mixed with the contaminated water, and the fluorine dissolved in the contaminated water is insolubilized. .

  The procedure of the water treatment process (S200) will be described with reference to FIG. 1. First, in the coagulation sedimentation process process (S210), the contaminated water pumped up by the pump P in the groundwater pumping work (S120) is the water tank T1 (FIG. 5). The sediment is stored in the water tank T1, and the soil and the like pumped together with the contaminated water is precipitated by leaving the contaminated water in the water tank T1. The settled sediment is sent to the soil treatment step (S300) together with the contaminated soil excavated in the soil excavation step (S130). At this time, FIG. 1 illustrates an example in which the sediments and the like that have been precipitated are subjected to the insolubilization treatment step (S330) in the soil treatment step (S300). It is desirable to use earth and sand for the pretreatment step (S320).

  In the subsequent insolubilization process (S220), the contaminated water separated from the earth and sand after the coagulation sedimentation process (S210) is transferred from the water tank T1 to another water tank T2 (see FIG. 5), where it is insolubilized. Agents (magnesium oxide and magnesium chloride) are added and mixed (both insolubilizers may be added separately in different tanks without adding both insolubilizers in water tank T2). Fluorine is precipitated by the reaction with these insolubilizing agents, and the supernatant liquid in the water tank T2 becomes clean treated water. The contaminated water pumped in the groundwater pumping step (S120) has the same pH as the contaminated soil C, and the contaminated water pumped up at the excavation site of the alkaline fluorine-contaminated soil has a pH of about 10 at the time of pumping. There are many cases. Even if this pH is insolubilized in the insolubilization process (S220), it is weakly alkaline with approximately the same pH of about 10. In addition, although the state of the insolubilizer used at this process is not specifically limited, What is necessary is just to divert what is prepared at a soil treatment process (S300).

  In the subsequent analysis step (S230), the fluorine elution amount of the treated water in the water tank T2 is analyzed. The analysis method may be the same as the method used for the examination of the test solution in the above-described preliminary investigation process performed prior to the excavation / backfill process (S100). As a result of the analysis, if the fluorine elution amount in the treated water is not less than or equal to the soil environment standard value, the treated water is reprocessed, for example, by adding an insolubilizing agent to the water tank T2. If the analysis result of the fluorine elution amount in the treated water is below the soil environmental standard value, the treated water (supernatant liquid) in the water tank T2 is further transferred to another water tank T3. At this time, in this embodiment, since the treated water that satisfies the soil environment standard value in the water tank T2 is used as a solvent of the magnesium chloride solution used in the soil treatment process (S300) or the present process (S200), the water tank T3 is used. A part of the treated water (or treated water moved to the water tank T3) transferred to is supplied to the magnesium chloride solution generation step (S310) of the soil treatment step (S300). The precipitate may be mixed in the contaminated soil to be treated in the soil treatment step (S300) or may be disposed of separately.

  Of the treated water transferred to the water tank T3 that satisfies the soil environmental standard value, treated water that has not been used as a solvent for magnesium chloride may be discharged. In this case, as a subsequent neutralization step (S240) It is necessary to neutralize the treated water in the water tank T3 by adding and mixing a neutralizing agent (hydrochloric acid or the like). Then, in the subsequent analysis step (S250), the pH of the treated water is analyzed, and as a result of the analysis, if the pH of the treated water is not neutralized to the pH within the set range, the water tank T3 is further neutralized. To neutralize the treated water again. If the analysis result of the pH of the treated water is within the set pH range, the treated water in the water tank T3 is discharged to the outside as required (S260).

(2-3) Soil treatment step In this soil treatment step (S300), a magnesium chloride production step (S310) for producing a magnesium chloride solution for insolubilization of fluorine, the contaminated soil is classified to a target particle size, or finely divided. Pretreatment step (S320), magnesium oxide and magnesium chloride are added to and mixed with pretreated contaminated soil to insolubilize fluorine in the contaminated soil (S330), fluorine elution of the treated soil after insolubilization treatment The analysis process (S340) etc. which analyze quantity are included as a main process.

i) Magnesium Chloride Solution Generation Step In this magnesium chloride solution generation step (S310), treated water in which the fluorine elution amount satisfies the environmental standard in the analysis step (S230) of the water treatment step (S200) is used as a solvent. That is, treated water is added to a powdered magnesium chloride solution or a magnesium chloride solution having a concentration higher than a set value to produce a magnesium chloride solution having a magnesium chloride concentration within a set range. Although the means for preparing the magnesium chloride solution of the set concentration is not shown in the figure, the magnesium chloride and the treated water are simply put in a suitable container such as a tank and stirred manually or by a stirring device, so that the magnesium chloride concentration becomes uniform. This is enough. Of course, a mixing device having a stirring device in a container (however, a container capable of storing a liquid), such as a mixing device 515 described later, can also be used. The magnesium chloride solution created in this step is appropriately transferred to a storage tank 553 (described later with reference to FIG. 14) and used in the insolubilization treatment step (S330).

ii) Pre-treatment step In this pre-treatment step (S320), the contaminated soil is classified according to the particle size, so that the larger and smaller particles are selected, and the contaminated soil having a larger particle size than the target particle size is crushed. To do. In order for the insolubilizing agent (magnesium oxide and magnesium chloride) to permeate the entire contaminated soil in the subsequent insolubilization treatment step (S330), it is desirable that the particle size of the contaminated soil be appropriately small. Therefore, in the present embodiment, prior to the insolubilization process, a pulverization process (S325) is provided in the pretreatment process to refine the contaminated soil, but it is necessary to make the grain size smaller than the target grain size. Contaminated soil with no waste is sorted in advance and only the contaminated soil with the target particle size or more is crushed to eliminate unnecessary treatment amount.

  At this time, in the crushing step (S325), the contaminated soil contains gravel in addition to refining the contaminated soil of the target particle size or more, which may not be effectively insolubilized as it is, into the target particle size or less. In some cases, at least part of the gravel should be subdivided. This crushing step is performed by a crushing device 603 (see FIG. 18) of a crushing machine 600 described later, but a jaw crusher (such as a crushing machine 400 described later, see FIG. 12) may be used if necessary. . Other crushers such as impact crushers and shredders are also applicable.

  In addition, the contaminated soil of the target particle size or less selected in the selection process and the crushed contaminated soil may be separately insolubilized, but in this embodiment, the crushed contaminated soil is directly subjected to the insolubilization treatment. After mixing the contaminated soil selected below the target particle size, it is subjected to insolubilization treatment. When there is no or insufficient contaminated soil having a target particle size or less to be mixed with the contaminated soil after pulverization, it may be replaced with other clean soil or treated soil that has been insolubilized.

FIG. 6 is a process flow diagram of the pretreatment process (S320).
As shown in FIG. 6, in the pretreatment step (S320), the contaminated soil excavated in the soil excavation step (S130) is selected based on the selected particle size G1 (for example, about 100 mm) (S321). A block of soil whose grain size G selected in the sorting step (S321) is larger than the selected grain size G1 is supplied to the crushing step (S322), and is crushed by a crusher such as a jaw crusher or impact crusher together with rocks and gravel contained therein. The

  The contaminated soil after the crushing process is further selected based on the selected particle size G2 (<G1) together with the contaminated soil smaller than the selected particle size G1 selected in the selection step (S321) (S323). The selected particle size G2 means a particle size that can be uniformly mixed with the insolubilizing agent at a certain level or more in the insolubilization step (S330). A lump larger than the selected grain size G2 selected in the selection step (S323) is returned to the crushing step (S322) and crushed.

  The contaminated soil of the sorting particle size G2 or less sorted in the sorting step (S323) is further sorted based on the target particle size G3 (<G2) in the subsequent sorting step (S324). Contaminated soil larger than the target particle size G3 selected in the selection step (S324) is supplied to the pulverization step (S325), and is crushed into small pieces together with the contained soil blocks and gravel. On the other hand, the contaminated soil having the target particle size G3 or less is subjected to a subsequent insolubilization process (S330). At this time, in this Embodiment, a part of contaminated soil below the target particle size G3 is mixed with the contaminated soil after the crushing process (S325) (S326). By passing through this mixing step (S326), the contaminated soil that is likely to contain a relatively large amount of gravel broken in S325 is given a particle size distribution, and then insolubilized treatment step (S330). ).

  The “target particle size G3” mentioned above is a particle size that is more uniformly mixed with the insolubilizing agent than the contaminated soil of the selected particle size G2, and if it is finer than this, the added / mixed insolubilizing agent is the entire contaminated soil. Refers to a particle size that is sufficiently diffused into the surface. Strictly speaking, the target particle size G3 depends on the performance of the mixing means such as the mixing device 515 (see FIG. 13) used in the insolubilization step (S330) and the properties of the insolubilizing agent. The current minimum value that can ensure efficiency is, for example, about 20 mm. Needless to say, it is of course better if it is finer, but in the screening method using a sieve, if a sieve with a finer mesh than 20 mm is used, the sorting operation itself is difficult depending on the state of contaminated soil (water content ratio, soil quality, etc.). There is a case. A method of sorting contaminated soil with warm air while drying and crushing is also conceivable, but this method normally processes tons of contaminated soil because of the large amount of energy consumed with respect to the amount processed. Then, the cases that can be applied are limited. Although application of wet classification is also conceivable, enormous energy or sun drying time is required to lower the water content later.

iii) Insolubilization treatment process / analysis process In the insolubilization treatment process (S330), the contaminated soil of the target particle size G3 or less selected in the selection process (S324), the contaminated soil obtained through the mixing process (S326), or the contaminated soil obtained by mixing them. Fluorine insolubilization treatment is performed on the subject ("contaminated soil" described in the description of the present step 330 is a generic name thereof). As described above, the insolubilization method is to mix magnesium oxide and magnesium chloride solution into contaminated soil.

FIG. 7 is a process flow diagram of the insolubilization process (S330) and the analysis process (S340).
In the insolubilization treatment step (S330), the contaminated soil that has undergone the pretreatment step (S320) and the sediment that has settled in the water tank T1 in the coagulation sedimentation treatment (S210) are treated. The earth and sand precipitated in the water tank T1 may be used for the pretreatment step (S320) together with the excavated contaminated soil if it contains relatively large gravel.

  As shown in FIG. 7, the contaminated soil that has finished the pretreatment step (S320) is transferred to the insolubilization treatment step (S330), and after mixing magnesium oxide (powder) in the step of S331, the step of S332 is further performed. The magnesium chloride (solution) is mixed with. As described above, the order of mixing the magnesium oxide and the step of mixing the magnesium chloride may be performed at the same time. If the process of S332 is completed, it will move to the process of S333 and will cure the processing soil which mixed the insolubilizing agent in a predetermined place. The curing method is not particularly limited, and it is sufficient to use natural drying.

  When the treated soil is cured for a predetermined period (for example, about one day), the process proceeds to the analysis step (S340). In this analysis step (S340), first, the elution amount of fluorine in the treated soil is measured in step S341. This measuring method is not particularly limited, but may be a method of measuring the fluorine content (concentration) in the test solution prepared based on the official method in the same manner as the fluorine elution analysis method described above.

  Then, in the subsequent analysis step (S342), it is determined whether or not the amount of fluorine eluted from the treated soil is equal to or less than the soil environment reference value. When the fluorine elution amount of the treated soil exceeds the soil environment reference value in this analysis step (S342), the procedure is returned to S331 to insolubilize the treated soil again. On the other hand, if the fluorine is sufficiently insolubilized and the fluorine elution amount of the treated soil is below the soil environmental standard value, the treated soil is subjected to the above-described backfilling step (S150) and backfilled to the excavation site, etc. The process ends.

[3] Operational Effects The operational effects of the contaminated soil treatment method in the present embodiment described above will be sequentially described below.

(3-1) Basic action In the case of fluorine-contaminated soil that contains a large amount of magnesium oxide or calcium and exhibits alkalinity, mineral acids such as sulfuric acid (H2SO4) and hydrochloric acid (HCl) are added to make it acidic and insolubilized. It is common to perform processing. However, in this case, the following phenomenon occurs.

For example, in the case of soil containing a large amount of magnesium oxide, apart from the insolubilization reaction of fluorine in a state where it can be eluted, the reaction between magnesium oxide and mineral acid that originally adsorbed a part of fluorine on the solid surface. Proceeds as shown below, and magnesium ions (Mg2 +) are dissolved.
MgO (solid) + H2SO4 → Mg2 +++ SO42− + H2O
MgO (solid) + 2HCl → Mg2 +++ 2Cl− + H 2 O
As a result of the dissolution of magnesium, a part of the fluorine adsorbed on the solid surface of magnesium oxide is released and dissolved (becomes eluting).

  That is, when a mineral acid is added and an insolubilization reaction proceeds in an acidic region, a reaction between the substance adsorbing fluorine and the mineral acid occurs in parallel with this, and a part of the fluorine that was originally insolubilized can be eluted. The insolubilization reaction may become unstable as a whole. Moreover, since the soil originally contains a substance that tilts the pH to the alkali side, the treated soil after the insolubilization treatment returns to alkalinity, and there is a possibility that a part of the fluorine in the insolubilized state may be eluted. . Therefore, when alkaline fluorine-contaminated soil is targeted, it has been difficult to insolubilize fluorine to a level that satisfies the soil environmental standard value by the conventional method using a mineral acid.

  On the other hand, according to this embodiment, the fluorine existing in a state that can be eluted in the contaminated soil (in the retained water of the contaminated soil) by adsorbing fluorine to the solid surface of the mixed magnesium oxide as described above. Can be insolubilized. At this time, the fluorine-contaminated soil exhibiting alkalinity is not acidified and mixed with magnesium oxide so that fluorine is insolubilized in the alkali region, so that the substance that adsorbed fluorine is not changed and is originally insolubilized. It is possible to prevent the fluorine existing in the contaminated soil from changing to a normal state where it can be eluted. In addition, since fluorine is insolubilized in the alkali region, it does not return to a state in which the insolubilized fluorine can be eluted again in the process in which the treated soil returns to the alkali region. Therefore, fluorine can be insolubilized to a level that satisfies the soil environment standard value for fluorine-contaminated soil exhibiting alkalinity.

  In addition, since the insolubilization treatment is carried out while maintaining the pH of the contaminated soil alkaline, not dissolving minerals present in the soil also contributes to the reliable insolubilization of fluorine. That is, for example, magnesium carbonate (MgCO 3) or the like may be present in the minerals in the soil, which is a reaction between magnesium oxide and carbon dioxide (CO 2), or magnesium hydroxide (Mg (OH) 2) and carbon dioxide. It is produced by the reaction. When a mineral acid is added to this magnesium carbonate, a reaction of decarbonation gas easily occurs and dissolves. As a result, fluorine adsorbed on the solid surface of magnesium oxide may be released, but this does not occur in this embodiment.

  Also, by mixing magnesium chloride in addition to magnesium oxide, when magnesium oxide reacts with magnesium chloride to become magnesia cement, the fluorine adsorbed on the solid surface of magnesium oxide is taken into the cement structure. And the fluorine insolubilization reaction can be further stabilized.

(3-2) Effects of water treatment In soil contamination sites, contamination often spreads not only to soil contamination but also to surrounding groundwater. However, it is very expensive to install a dedicated treatment plant for contaminated water. As a highly versatile method, there is a method of adding a chelating agent to contaminated water and adsorbing the pollutant to the chelating agent to collect it, but fluorine is less likely to be adsorbed by the chelating agent than other pollutants, and the processing efficiency It is difficult to secure enough. Therefore, when a treatment plant is not installed, it is a fact that the contaminated water must be treated as waste. When a large amount of contaminated water is generated, the treatment cost becomes large.

  Therefore, in this embodiment, the method for insolubilizing contaminated soil is applied to the method for treating contaminated water as it is, and magnesium oxide and magnesium chloride are added to the contaminated water to insoluble and precipitate fluorine in the contaminated water. In the present water treatment step (S200), since the contamination source of the contaminated water is the same as the contamination source of the contaminated soil at the soil contamination site, the inventor of the present application can insolubilize the contaminants by the same method as the contaminated soil. It was conceived based on such findings.

  Moreover, the treated water obtained by purifying the contaminated water contaminated by the same pollution source as the contaminated soil by the same treatment as the contaminated soil has the same degree of pH as the contaminated soil and treated soil as well as the used insolubilizer. This is realized by the insolubilization method (mixing of magnesium oxide and magnesium chloride) of the present embodiment in which the pH of the contaminated soil and the treated soil before the treatment does not change.

  And according to this Embodiment, since an original chemical balance is not destroyed in a water treatment process (S200), reaction is carried out by utilizing the treated water whose chemical balance is the same as soil for soil insolubilization treatment. The effect of improving long-term stability can also be expected. If there is a difference in pH between the contaminated soil before the treatment and the treated soil, there is a possibility of returning to the soil pH before the treatment in the long term. That is, the soil insolubilization effect may be reduced in the future, and the properties of moisture used in the soil insolubilization treatment may affect the long-term treatment stability.

  In addition, if the treated water treated in the water treatment step (S200) is discharged to the outside, the treated water must be neutralized, but it is not necessary for the amount used in the insolubilized treatment step of the contaminated soil, In addition to the effects of treatment stability and effective use of contaminated water, it can also be expected to reduce wastewater, reduce man-hours, and reduce costs, thereby effectively purifying contaminated water generated by contaminated soil treatment. However, there is a great merit that it can be used effectively without taking it outside. Another advantage is that the cost of water for treatment is reduced.

  In this embodiment, treated water is used as a magnesium chloride solvent, but treated water has the same pH conditions using the same insolubilizing agent as the contaminated soil and treated soil. It can be used in any way as moisture to be used. For example, it can be naturally used for the moisture supplied to the contaminated soil for adjusting the water content ratio, or the moisture sprayed for preventing the scattering of soil particles and insolubilizing agents.

(3-3) Effect of Pretreatment Step FIG. 8 is a microscopic view of the soil model.
It is considered that normal soil is formed by gathering gravel and fine soil particles, etc., and in a state after removing large gravel by passing through a sieve (for example, a state provided for the crushing step (S325)), As shown in FIG. 8, A: gravel alone, B: soil particles alone, C: aggregates of soil particles, and D: aggregates formed by adhering soil particles to gravel can be mixed.

  In the insolubilization treatment of the present embodiment, magnesium oxide powder that adsorbs fluorine in the water retained in the contaminated soil and an aqueous magnesium chloride solution that prevents elution of fluorine in the soil are used. However, powdered magnesium oxide tends to adsorb moisture in the soil, but magnesium chloride in aqueous solution may not easily penetrate the entire soil depending on the nature of the contaminated soil.

  For example, in FIG. 8, a magnesium chloride solution easily spreads over a relatively small soil block formed by adhering soil particles or a single soil particle, but magnesium chloride is present inside a relatively large soil block. The solution is difficult to reach. When soil particles adhere to gravel and a clod is formed, if fluorine is held between the gravel and the clod, it is difficult for the magnesium chloride solution to reach the contamination source location. The same applies when fluorine or fluorine-contaminated soil has entered a gravel crack (see FIG. 8).

  Even if these contaminated soils are subjected to insolubilization treatment as they are, when officially analyzing the treated soils, the treated soil is treated when the sample soil (treated soil) is loosely crushed with a mortar to create a sample for analysis (under 2 mm). The surface that is not insolubilized may be exposed and fluorine may be eluted. If the results of the elution inspection of the treated soil do not meet the soil environment standard value, it is natural that the treated soil must be insolubilized again, and even after reprocessing, a lot smaller than usual from the viewpoint of reliability. In addition, since it is necessary to perform an elution amount inspection of the treated soil, not only the efficiency of the insolubilization work but also the reliability is significantly reduced.

Therefore, a case is considered in which the following measures are taken in order to effectively spread the magnesium chloride solution.
(Part 1) Make the contaminated soil as fine as possible.
(Part 2) A large amount of water is added to the contaminated soil to form a mud.
(Part 3) Dry sufficiently to make the clot easy to collapse.

  However, if the contaminated soil is made finer to a certain particle size as in (Part 1), the processing time of the finely divided and screening becomes extremely long, and the processing efficiency cannot be ensured. Moreover, it takes a lot of labor and time to reduce the total amount of contaminated soil to a target particle size or less. Next, when the amount of water is increased as in (No. 2), the handleability of the treated soil is poor and the subsequent curing process is prolonged. In the case of (Part 3), sun drying is the best way to keep the energy consumption low, but it takes a long time to dry the contaminated soil to the sun, and it is turned over with a hydraulic excavator etc. But it takes time. In addition, it is necessary to secure a large place for the contaminated soil to be treated, which leads to expansion of the occupied space of the contaminated soil treatment system.

  On the other hand, in this embodiment, in the pretreatment step (S320), contaminated soil larger than the target particle size G3 and small contaminated soil are selected. The contaminated soil smaller than the target particle size G3 is used as it is, and the contaminated soil larger than the target particle size G3 is separately subjected to the pulverization step (S325) and crushed, and then subjected to the insolubilization treatment step (S330). In this way, the total treatment amount of the contaminated soil is not made smaller than the target particle size G3, but the soil that is larger than the target particle size G3 but smaller than the selected particle size G2 is subjected to sufficient pulverization processing for the crushing step (S325). By applying, it is possible to improve the work efficiency by switching to a sorting process with a target particle size or less. The contaminated soil which is smaller than the target particle size G3 and does not need to be refined is selected in advance, and only the contaminated soil having the target particle size G3 or more is subjected to the crushing step (S325). The quantity is also optimized.

  In addition, by providing the pulverization step (S325) in the pretreatment step (S320), not only the crushed soil mass of the target particle size or more, which is difficult to effectively insolubilize fluorine as it is, but below the target particle size, The effect of crushing gravel contained in contaminated soil can also be expected. In the case where fluorine is held between gravel and soil particles, the fluorine particles are exposed by scraping the soil particles from the gravel in the crushing step, and the magnesium chloride solution can be brought into sufficient contact. In addition, even when fluorine or fluorine-contaminated soil has invaded the gravel crack, etc., if the crushing action is applied to the gravel, the gravel will be crushed by the crack, and the magnesium chloride solution is exposed by exposing the fluorine that has entered the crack. Can be fully contacted.

  By performing the crushing step prior to the insolubilization treatment in this way, even when fluorine is contained in the gravel or the clot, by actively exposing the fluorine and making it easy to contact the insolubilizing agent, It is possible to improve the stability and certainty of fluorine insolubilization treatment by spreading the insolubilizing agent to every corner of the contaminated soil. In addition, the effect of improving the reliability and work efficiency of the insolubilization treatment is great, and it greatly contributes to cost reduction by shortening the construction period.

  Further, in the pretreatment step (S320), the contaminated soil (mixed soil) that has undergone the pulverization step (S325) is mixed with the contaminated soil after the pulverization in the mixing step (S326). An appropriate particle size distribution can be provided. As a result, the magnesium chloride solution and other moisture retention (water retention) necessary for insolubilization treatment can be imparted to the mixed soil, further improving the mixability between contaminated soil and the insolubilizing agent, and thus the certainty of the insolubilization treatment. Can be made. In addition, when there is no or insufficient contaminated soil having a target particle size or less to be mixed with the crushed contaminated soil, other clean soil or insolubilized treated soil may be substituted.

(3-4) Speeding up of treatment Since this embodiment is a mixture of magnesium oxide and magnesium chloride in fluorine-contaminated soil, for example, unlike ordinary fluorine insolubilization technology in which an aluminum salt, an iron salt or the like is added, the treated soil is treated. Fluorine ion concentration can be measured without distilling the test solution extracted from the sample. In the ordinary fluorine insolubilization technique, the sample solution must be distilled because ions that interfere with the measurement of the fluorine ion concentration are contained in the treated soil by the insolubilizing agent. Usually, since the test solution cannot be distilled at the insolubilization treatment site, when the test solution is distilled, the elution amount of fluorine cannot be measured unless the test solution is taken from the site.

  On the other hand, in this embodiment, since the test solution does not need to be distilled, the fluorine ion concentration can be easily measured by using, for example, a measuring device using an ion electrode for the test solution prepared from the treated soil. . Therefore, on-site analysis of the fluorine elution amount of the treated soil becomes possible, and it is easy to determine whether the treated soil can be reused as backfill soil or whether insolubilization is required again. Therefore, the process can be quickly transferred to the backfilling process, and the processing can be speeded up.

  In addition, since fluorine can be reliably insolubilized by only two steps of mixing magnesium oxide and mixing magnesium chloride, it can be processed at a high speed and in large quantities on the spot.

  Furthermore, when magnesium chloride is mixed, magnesium oxide and magnesium chloride react to produce magnesia cement. The hardening reaction of this magnesia cement is a common calcium oxide cement (for example, portland cement, blast furnace). Advancing speed is faster than the curing reaction of Cement B). Thereby, a curing period can be shortened to about 1/5 to 1/2 in the case of solidifying treated soil using a general calcium oxide cement. Therefore, the treated soil after curing can be immediately used for backfilling, which contributes to faster processing.

(3-5) Improvement of safety In general fluorine insolubilization technology, mineral acid and alkali are added in order to promote pH insolubilization reaction by adjusting pH. In this embodiment, it is not necessary to add mineral acids or alkalis that are highly dangerous to the environment for such pH adjustment. Magnesium oxide is generally used as a food additive, fertilizer, and the like, and magnesium chloride is generally used as a food additive, an antifreezing agent, and the like. Therefore, the fluorine-contaminated soil can be safely insolubilized, and the effect of reducing the environmental load is great.

[4] Configuration Examples of Use Device Several configuration examples of the device for carrying out the above contaminated soil treatment method will be described below.

(4-1) Analyzer FIG. 9 is a schematic diagram showing a configuration example of the analyzer.
The analysis apparatus 100 shown in FIG. 9 can be applied to the previous analysis process (S230, S250, S340) and the measurement of the fluorine elution amount when the contaminated soil to be treated is specified. This analyzer 100 is composed of a potentiometer or an ion concentration meter, and is connected to an ion electrode 103 and a comparison electrode 104 immersed in a predetermined volume of a test solution 102 in a container 101 prepared based on an official method. .

  The ion electrode 103 has a sensitive film (not shown) that responds to fluorine ions (F−) to be measured. When this sensitive film part comes into contact with the fluorine ions in the test solution 102, the ion activity depends on the ion activity. A membrane potential is generated. By measuring the potential difference between the ion electrode 103 and the reference electrode 104 with the analyzer 100, the fluorine ion concentration in the test solution 102 is measured, and the fluorine per unit volume eluted in the test solution 102 is measured. The amount (fluorine ion concentration) can be known. The analyzer 100 also includes a thermometer 105 that measures the water temperature of the test solution 102 and a stirrer 106 that stirs the test solution 102.

  In addition, although the analyzer by the ion electrode method was illustrated in FIG. 9, the measuring method by an absorptiometry is applicable, for example. The results of on-site analysis are regularly checked by comparing with the results of official methods to ensure reliability.

(4-2) Sorting Machine FIG. 10 is a side view showing an example of the configuration of the sorting machine.
The sorting machine 200 (strictly, the sorting apparatus 201) shown in FIG. 10 can be applied to the sorting process (S321 / S323 / S324) of the pre-processing process (S320). The sorting machine 200 receives the contaminated soil and sorts it into a component larger and smaller than the set particle size, and a transporter that transports the contaminated soil from which the large gravel and the lump are removed by the sorting device 201. And a conveyor 202.

  The sorting device 201 is a so-called vibrating sieve, and a lattice (sieving member) 204 having a predetermined eye size is fixed inside a frame body 203 constituting the main body. The frame body 203 is supported on the main body frame 205 through a spring 206 so as to vibrate. The frame 203 is vibrated together with the frame body 203 by a vibration exciter (not shown), thereby A portion larger than the size of the grid 204 is removed from the inside, and the contaminated soil passing through the grid 204 is guided downward. A tilt 208 is provided above the main body frame 205 via a support post 207. The tilt 208 is for reliably introducing contaminated soil into the sorting device 201 and is located above the sorting device 201.

  The conveying conveyor 202 is supported by the supporting members 210 and 211 so that the frame 209 is inclined upward from the lower side of the sorting device 201 toward the downstream side in the carrying direction (right side in FIG. 10) in accordance with the tilt of the sorting device 201. It is supported. In addition, in this Embodiment, although the structure which provided the conveyance conveyor 202 directly in the downward direction of the sorting apparatus 201 was illustrated, in order to prevent scattering of contaminated soil reliably, between the sorting apparatus 201 and the conveyance conveyor 202, It is even better to provide an upwardly expanding hopper (chute).

  In addition, since the sorting machine 200 of FIG. 10 has only one grid 204, the sorted grain size of the contaminated soil is sorted into two contaminated soil groups based on the grid 204 eyes. In addition, there are those that select three soil particle groups according to the particle size. This type is also applicable.

(4-3) Excavation / Throwing Device FIG. 11 is a side view showing a configuration example of the excavation / throwing device.
The excavation / loading device 300 can be applied to various operations such as excavation / backfilling of contaminated soil, loading of excavated contaminated soil into other processing devices such as the sorting machine 200, rolling, and land change. 11 is a hydraulic excavator (hereinafter referred to as a hydraulic excavator 300). The hydraulic excavator 300 includes a traveling device 302 having an endless track crawler 301, a revolving body 303 that is pivotably provided on the upper portion of the traveling device 302, and an articulated front that is pivotally connected to the revolving body 303. Device 304. The front device 304 includes a boom 305 whose base end is pivotally supported by the swing body 303, an arm 306 that is pivotally connected to the boom 305, and a bucket 307 that is pivotally connected to the arm 306. It has. With such a configuration, a desired operation is performed by appropriately operating the traveling operation by the traveling device 302, the revolving operation of the revolving structure 303, and the excavation / loading operation by the front device 304.

(4-4) Crushing machine FIG. 12 is a side view showing a configuration example of the crushing machine.
The crushing machine 400 shown in FIG. 12 crushes and crushes large gravel or a lump when they are contained in contaminated soil. For example, the crushing process (S322) of the pretreatment process (S320). ) Etc. The crushing machine 400 shown in FIG. 12 illustrates a so-called jaw crusher.

  The crushing machine 400 conveys the traveling device 401, a hopper 402 that receives contaminated soil as an object to be crushed, a crushing device (jaw crusher) 403 that crushes contaminated soil, and 109 that is received by the hopper 402 to the crushing device 403. A grizzly feeder 404, a discharge conveyor 405 that conveys the crushed contaminated soil and discharges it outside the machine, and a power unit (power unit) 406 with a built-in power source.

  The crushing device 403 includes swinging moving teeth 407 and fixed teeth 408, and the contaminated soil introduced between the moving teeth 407 and the fixed teeth 408 is crushed by the swinging motion of the moving teeth 407. It comes to handle. The maximum particle size of the contaminated soil after crushing generally depends on the setting of the exit gap between the moving teeth 407 and the fixed teeth 408.

  The grizzly feeder 404 has a plurality of plates arranged in a step shape with comb-like tips, and the contaminated soil introduced through the hopper 402 is sequentially applied to the crushing device 403 by vibrating these plates. Transport and supply. The grizzly feeder 404 also extracts fine particles contained in the contaminated soil being conveyed from the comb teeth at the tip of the plate and introduces them into the side conveyor 411 via the chute 410. When the fine particles are combined with the contaminated soil after the crushing treatment, the optional side conveyor 411 is removed and the fine particles are guided to the discharge conveyor 405 by the chute 410.

  With the above-described configuration, the contaminated soil received by the hopper 402 is guided to the crushing device 403 by the grizzly feeder 404, where it is crushed and guided onto the discharge conveyor 405. Then, the contaminated soil (and fine particles introduced through the chute 410) crushed by the crushing device 403 is conveyed by the discharge conveyor 405 and discharged outside the machine.

(4-5) Insolubilization processing machine FIG. 13 is a side view showing a configuration example of the insolubilization processing machine, and FIG. 14 is a diagram showing an extracted main part of one configuration example of the insolubilization processing machine.
The insolubilization processing machine 500 shown in FIGS. 13 and 14 is applied to the insolubilization processing step (S330) and the like, and includes a soil improvement machine 510 and a liquid supply device 550. The soil improvement machine 510 includes a traveling device 511, a sieve device 512, a hopper 513, a transport conveyor 514, a mixing device 515, a powder supply device 516, a discharge conveyor 517, a power device (power unit) 518, and a main body frame 519 that supports each device. The liquid supply device 550 is generally configured by a pump unit 551, a supply system 552, and the like.

FIG. 15 is a side view showing a detailed structure near the sieve device 512 and the hopper 513.
The sieve device 512 plays a role of receiving and classifying contaminated soil excavated by the hydraulic excavator 300 or the like, for example. A frame body 520 constituting the main body of the sieving device 512 is elastically supported by a support member 522 provided on the main body frame 519 via a support post 521 via a spring 523. A vibrating shaft (not shown) of the lattice member 524 mounted in the frame 520 is inserted into the rotating drum 525, and the rotating shaft is rotated by the rotating drum 525 being driven by a driving device (not shown). Then, the sieve device 512 is vibrated. As a result, components smaller than the eyes of the lattice member 524 are selected and introduced into the lower hopper 513. At this time, since the frame body 520 is disposed such that the front side (left side in FIG. 15) is lower than the rear side (right side in FIG. 15), the frame body 520 is larger than the eyes of the lattice members 524 in the contaminated soil. If foreign matter such as stone is included, the foreign matter moves forward on the lattice member 524 and is discharged out of the machine (in this case, the left side in FIG. 15). A tilt 526 is provided on the upper part of the sieving device 512.

  The hopper 513 is a frame-shaped member that functions as a means for receiving contaminated soil, and is formed to expand upward so as to reliably receive the contaminated soil that has passed through the sieve device 512, and the support member 522. It is fixed to. An arch breaker 527 is provided inside the hopper 513. The arch breaker 527 includes a rotation shaft 528 that is rotatably supported by the hopper 513 and a plurality of stirring rods 529 provided at a predetermined pitch with respect to the rotation shaft 528. The driving device 530 of the arch breaker 527 is directly connected to the end portion (the right end in FIG. 15) of the rotating shaft 528. When the arch breaker 527 is rotationally driven by the driving device 530, the contaminated soil introduced into the hopper 513 is agitated by the agitation bar 529, which is useful for preventing the occurrence of cross-linking in the hopper 513 and promoting the crushing of the soil mass.

FIG. 16 is a diagram illustrating a detailed structure in the vicinity of the downstream side of the conveyor 514.
The transport conveyor 514 serves as a transport means for transporting the contaminated soil received by the hopper 513 to the mixing device 515, and is mounted on the front side (left side in FIG. 13) end of the main body frame 519. The conveyor frame 531 of the transfer conveyor 514 supports a driving wheel 532 at a downstream end (right side in FIG. 16) and a driven wheel (not shown) at an upstream end (left end in FIG. 16). A conveyor belt 533 is wound between 532 and a driven wheel (not shown). With this configuration, the conveyor 514 rotates the drive wheels 532 with a driving device (not shown) to drive the conveyor belt 533 in a circulating manner. At this time, an opening 534 having a predetermined opening area is provided on the downstream side wall surface of the hopper 513, and the contaminated soil transported by the transport conveyor 514 is cut out to the outside of the hopper 513 through the opening 534 by a certain amount. 515. The conveyor 514 is provided with a regulation plate 535 that prevents spillage of contaminated soil from the hopper 513 to the mixing device 515.

  The powder supply device 516 adds and supplies an insolubilizing agent (magnesium oxide powder) to the contaminated soil. The storage tank 536 for storing the insolubilizing agent and the insolubilizing agent in the storage tank 536 are led downward. It consists of a feeder 537. The feeder 537 is a rotary feeder that receives the insolubilizing agent in the storage tank 536 between the partition walls of the rotor and sequentially adds it to the contaminated soil on the conveyor 514, but it may be replaced with a screw feeder.

  As shown in FIG. 14, the liquid supply device 550 supplies an insolubilizing agent (magnesium chloride solution) and water (treated water) in a liquid state, and supplies these magnesium chloride solution and treated water to the contaminated soil. A supply system 552 and a pump unit 551 for supplying a liquid insolubilizer to the supply system 552 are provided. In the present embodiment, a configuration example in which the liquid supply device 550 is separate from the soil improvement machine 510 is illustrated. However, when the pump unit 551 is relatively small, the liquid supply device is added to the soil improvement machine 510. 550 may be attached and insolubilization processing machine 500 may be constituted.

  The pump unit 551 has a storage tank 553 for storing the magnesium chloride solution generated in the magnesium chloride solution generation step (S310), a storage tank 554 for storing the treated water (or other water) generated in the water treatment step (S200), A pump 555 for discharging the magnesium chloride solution in the storage tank 553, a pump 556 for discharging treated water in the storage tank 554, a control panel (not shown), and a base frame 557 (see FIG. 13) on which these are mounted. Has been.

  The supply system 552 distributes the treated water discharged from the pump 556 and guides it to a desired location, an open / close valve 559 for opening and closing the flow path of the supply line 558, and the magnesium chloride solution discharged from the pump 555. A supply line 560 that circulates and leads to a desired location, and an on-off valve 561 that opens and closes the flow path of the supply line 560.

  In the present embodiment, the case where water is sprayed into the hopper 513 of the soil improvement machine 510 by the supply pipe 558 is illustrated, but the water supply place is not particularly limited as long as it is upstream of the mixing device 515. For example, water may be sprayed in the vicinity of the inlet 538 (see FIG. 16) of the mixing device 515, or may be appropriately branched to supply water to a plurality of locations. Further, in the present embodiment, treated water is appropriately supplied to the contaminated soil in order to adjust the water content ratio, but it may be considered that water is supplied for other purposes such as handling operation.

  The same applies to the supply pipe 560, and the supply location of the magnesium chloride solution may be on the upstream side of the mixing device 515. In the present embodiment, the case where the magnesium chloride solution is supplied to the contaminated soil in the vicinity of the inlet 538 (described later) of the mixing device 515 by the supply pipe 560 is illustrated, but for example, water is sprayed into the hopper 513 of the soil improvement machine 510. Alternatively, it may be divided and supplied at a plurality of locations. In the present embodiment, the supply pipe 560 is connected to the supply pipe 562 (see FIG. 16). The supply pipe 562 is supported by a frame 563 that spans the regulation plate 535 of the conveyor 514 and the inlet 538 of the mixing device 515.

FIG. 17 is a diagram illustrating the structure of the supply pipe 562.
As shown in FIG. 17A, the supply pipe 562 is, for example, a pipe whose ends are closed in a “U” shape, and a central portion 564 to which the supply pipe 560 is connected, and the central portion 564 It has an end portion 565 formed by bending both sides, and a plurality of holes 566 are provided inside the center portion 564 and the end portion 565, respectively. The distance between both end portions 565 (that is, the length of the central portion 564) is substantially equal to the width dimension of the inlet 538 of the mixing device 515, the hole 566 of the central portion 564 is opposed to the conveyor 514, and is almost directly above the inlet 538. It arrange | positions so that it may be located. However, the shape or the like of the supply pipe 562 is not limited, and may be a linear shape as shown in FIG.

  Returning to FIG. 13, the mixing device 515 is mounted approximately on the center in the longitudinal direction of the main body frame 519, and an inlet 538 (see FIG. 16) for contaminated soil or the like on the upper side of one side (left side in FIG. 13) and the other side (FIG. 13). A middle soil outlet (not shown) is provided at the bottom. This mixing device 515 is provided with a plurality of paddle mixers (not shown, may be a single unit) provided in parallel as a stirring means inside, and the contaminated soil and the insolubilizing agent introduced through the inlet 538 are mixed with the paddle mixer. While stirring and mixing uniformly, the mixture is transferred to the outlet side, and the treated soil is led out from the outlet.

  The discharge conveyor 517 is a discharge unit that conveys the processing soil discharged from the mixing device 515 and discharges the treated soil to the outside of the machine. The discharge conveyor 517 is a predetermined distance from the lower side of the outlet (not shown) of the mixing device 515 toward the other side (right side in FIG. 13). After extending substantially horizontally, it extends in an upward slope from below the drive device 36 of the mixing device 515.

  Although not specifically shown, the power unit 518 is an engine as a power source of the drive device of each device described above, a hydraulic pump driven by the engine, and pressure oil supplied from the hydraulic pump to the drive device of each device. A plurality of control valves and the like to be controlled are incorporated, and are provided at the other end in the longitudinal direction of the main body frame 519 (right side in FIG. 13).

  In the case of insolubilizing contaminated soil with the insolubilization processing machine 500 having the above-described configuration, for example, when contaminated soil excavated by the hydraulic excavator 300 or the like is put into the sieve device 512, components larger than the size of the lattice member 524 are removed, and the lattice Contaminated soil components that have passed through the member 524 are introduced into the hopper 513. This classification makes the particle size distribution of the contaminated soil uniform and facilitates mixing with the insolubilizing agent. Further, a part of the soil block larger than the eyes of the lattice member 524 is jumped up by the vibration of the lattice member 524 and falls again on the lattice member 524. By repeating this, there is also an effect of crushing the soil mass due to the impact at the time of jumping up and the edge effect of the net (or blade) of the lattice member 524.

  Treated water in the storage tank 554 is supplied to the contaminated soil received by the hopper 513 through the supply pipe 558 as necessary, and is uniformly stirred by the arch breaker 527 to adjust the water content. When the contaminated soil in the hopper 513 is stirred by the arch breaker 527 as described above, even if a relatively large soil block remains, the soil block is crushed here, and a new soil block is generated in the hopper 513. An effect such as prevention can be expected.

  The contaminated soil in the hopper 513 is cut out by a certain amount outside the hopper 513 through the opening 534 (see FIG. 16) on the conveyor 514, and then magnesium oxide from the powder supply device 516 is supplied during the transportation. Further, it is introduced into the mixing device 515 together with magnesium chloride from the liquid supply device 550. The contaminated soil introduced into the mixing device 515 is uniformly stirred and mixed by the paddle mixer together with these insolubilizing agents. Then, the treated soil mixed by the mixing device 515 is led out onto the discharge conveyor 517 and discharged outside the machine. The discharged treated soil is appropriately cured and backfilled if the fluorine elution amount is below the soil environmental standard value.

(4-6) Crushing Machine FIG. 18 is a side view showing a configuration example of the crushing machine.
The crushing machine 600 shown in FIG. 18 is a machine that crushes clots, gravel, etc. into small pieces and makes them fine, and can be applied, for example, in the crushing step (S325) of the pretreatment step (S320). . This is also useful when disposing of the treated soil by disposing it in the subsequent stage of the insolubilization processing machine 500 in the insolubilization processing step (S330).

  The crushing machine 600 includes a hopper 601 that receives a material to be crushed such as contaminated soil or treated soil (hereinafter represented by contaminated soil), a conveyor 602 that conveys the contaminated soil received by the hopper 601, and contamination on the conveyor 602. A crushing device 603 and the like for crushing the soil during transportation are provided. Although the case where two crushing apparatuses 603 are provided is illustrated in FIG. 18, three or more crushing apparatuses 603 may be provided, or only one may be provided.

  The conveyor 602 is supported by the frame 604 on the upstream side (left side in FIG. 18) of the contaminated soil and supported by the legs 605, and is inclined upward toward the downstream side (right side in FIG. 18). It is arranged. A driven wheel 607 and a driving wheel 608 are respectively provided at both ends of the conveyor frame 606 of the transport conveyor 602, and the driving wheel 608 and the driven wheel 607 are rotated by driving the driving wheel 608 with a driving device (not shown). The conveyor belt 609 wound around is circulated.

  The hopper 601 is supported by the frame 604 via the support member 610 so as to be positioned on the upstream end of the transport conveyor 602. Although not shown, a cutout facing the conveyor belt 609 is cut out on the downstream side wall of the hopper 601, and contaminated soil conveyed by the conveyor 602 is cut out of the hopper 601 through the cutout. . The amount of contaminated soil transported by the transport conveyor 602 is determined by the opening area of the exit and the transport speed of the transport belt 609.

19 is a side view showing the detailed structure of the crushing device 603, FIG. 20 is a cross-sectional view taken along the line XX-XX in FIG. 19, and FIG. 21 is a cross-sectional view taken along the line XXI-XXI in FIG.
As shown in FIGS. 19 to 21, the crushing device 603 is supported on a conveyor frame 606 via a support frame 611. The support frame 611 includes a frame 612 attached on the conveyor frame 606 and a bracket 613 provided on the frame 612. A swing member 615 is attached to the support frame 611 with the upper end connected to the bracket 613 via a support shaft 614. The swing member 615 swings with respect to the support frame 611 together with the rotating body 616 attached to the tip. The rotating body 616 crushes the contaminated soil, and includes both ends of a rotating shaft 618 held by a swing member 615 via a bearing 617 and a plurality of blades 619 provided radially on the rotating shaft 618.

  The blades 619 are attached to a mounting plate 620 fixed to the rotating shaft 618 by bolts 621 and are curved in the axial direction of the rotating shaft 618, respectively. The bending direction is staggered between the blades 619 adjacent to each other in the circumferential direction. Further, as shown in FIG. 21, the blade 619 rotates to face the conveyance direction of the conveyance belt 609, but is along the direction opposite to the rotation direction toward the outer peripheral side. By adopting such a curved shape, the contact frequency between the contaminated soil on the conveyor belt 609 and the blades 619 is increased.

  A driving device 622 for driving the crushing device 603 is provided on the bracket 613. A sprocket 624 is provided at the end of the output shaft 623 of the driving device 622, and a chain 626 is wound around the sprocket 625 provided at the end of the sprocket 624 and the rotating shaft 618. As a result, the driving force of the driving device 622 is transmitted to the rotating shaft 618 via the chain 626, and the rotating body 616 rotates. The rotational speed of the driving device 622 can be adjusted.

  Further, the rotating body 616 is covered with a cover 627, and the contaminated soil splashed up by the rotating body 616 is prevented from scattering by the cover 627. The cover 627 is swingably supported by the rotation shaft 618 and has a center of gravity on the downstream side of the rotation shaft 618 in the transport direction. At this time, a plate 629 having a groove 628 formed in an arc shape with the rotation shaft 618 as the radius center is attached to the side surface of the cover 627. A pin 630 provided on the side surface of the swing member 615 is loosely fitted in the groove 628 of the plate 629, thereby restricting the range of swing operation of the cover 627. A pin 631 is driven into the bracket 613, and the lower limit of the swing range of the swing member 615 is regulated by the pin 631.

  As a result, even if large foreign matter is mixed in the contaminated soil on the conveyor belt 609, the swinging member 615 swings to separate the rotating body 616 from the transport belt 609, and the transport belt 609 and the rotating body 616 are separated. It is possible to prevent foreign matter from being caught between them. Further, when the swinging member 615 swings and the cover 627 is separated from the transport belt 609, the cover 627 swings and the gap between the transport belt 609 is kept as narrow as possible and scattering of contaminated soil is prevented.

  When the contaminated soil is crushed by the pulverizing machine 600 having the above-described configuration, for example, when the contaminated soil is put into the hopper 601 with the hydraulic excavator 300 or the like, the contaminated soil put into the hopper 601 is sequentially transferred to the hopper by the conveyor 602. 601 is conveyed outside. The contaminated soil on the conveyor 602 is crushed by the blades 619 of the crushing device 603 during conveyance and then discharged from the downstream end of the conveyor 602.

[5] System Configuration Examples Several systems using the above-described devices and the like are illustrated below with reference to the drawings. In the following drawings, the members and devices already described or those having the same functions as those described above are denoted by the same reference numerals as those in the above-described drawings, and the description thereof is omitted.

FIG. 22 is a diagram illustrating a configuration example of the preprocessing system.
The system illustrated in FIG. 22 excavates the contaminated soil C1 by the hydraulic excavator 300 and inputs it into the sorting machine 200a, and sorts the contaminated soil containing gravel larger than the selected grain size from the smaller contaminated soil by the sorting device 201. , The contaminated soil containing gravel larger than the selected particle size is crushed by the crushing device 403 of the crushing machine 400, for example, the sorting step (S321) and the crushing step (S322) in the pretreatment step (S320) illustrated in FIG. ).

  The sorting machine 200a is equipped with a sorting device 201 and a conveyor (not shown) on a traveling device 250 together with a power unit (not shown), and further a component having a size equal to or larger than the sorting particle size sorted by the sorting device 201 is laterally arranged. A side conveyor 260 is provided. Since FIG. 22 shows the state seen from the rear of the sorting machine 200a, the components below the sorting particle size are conveyed to the back side in the direction perpendicular to the paper surface by the conveyor, and the components above the sorting particle size are laterally conveyed by the side conveyor 260. It is thrown into the arranged crushing machine 400. The contaminated soil C2 crushed by the crushing machine 400 is again sorted into the sorting machine 200a (or other sorting machine).

FIG. 23 is a diagram illustrating another configuration example of the preprocessing system.
In the system illustrated in FIG. 23, the contaminated soil C3 is excavated by the hydraulic excavator 300 and put into the sorting machine 200b, and the contaminated soil containing gravel larger than the target grain size is contaminated by the sorting apparatus 200 within the target grain size. , And pulverizing the contaminated soil having a particle size larger than the selected particle size by the pulverization device 603 of the pulverization machine 600. Used in (S325).

  As with the sorting machine 200a, the sorting machine 200b is equipped with the sorting device 201 and the transfer conveyor 202 on the traveling device 250 together with the power unit 270, and further, the components of the target particle size or more sorted by the sorting device 201 are laterally added. A side conveyor 260 is provided for transporting to the side. Since FIG. 23 illustrates the state as viewed from the rear of the sorting machine 200b, the components smaller than the target particle size are conveyed to the far side in the direction perpendicular to the paper surface by the conveyor 202, and the components larger than the target particle size are laterally conveyed by the side conveyor 260. To the crushing machine 600 disposed in Contaminated soil C4 crushed by the pulverizing machine 600 is mixed with, for example, contaminated soil of a target particle size or less selected by the sorting device 201 (S326), and is supplied to the insolubilization process (S330). The soil improvement machine 510 (or the mixing device 515 alone) can be used for the mixing step (S326).

  According to the present system, since the blade 619 (see FIG. 20) provided in the crushing machine 600 strikes at a high speed, the crushing action of not only the earth block but also the gravel can be expected. Even when it is difficult to wrap around, it is possible to expose the location where fluorine is present and make it easy to contact the insolubilizing agent by crushing, which greatly contributes to the certainty and stability of the insolubilizing treatment. Further, when the crushing machine 600 is used, the crushing apparatus 603 uses a thin blade 619 that is curved as shown in FIG. The certainty of the crushing effect is also high.

FIG. 24 is a diagram illustrating a configuration example of an insolubilization processing system.
In the system illustrated in FIG. 24, the excavated soil C5 is excavated by the hydraulic excavator 300 and introduced into the insolubilization processing machine 500, the insolubilization processing machine 500 mixes the insolubilizing agent with the contaminated soil, and the processing soil is crushed by the machine 600 For example, it is used in the steps S331 and S332 in the insolubilization step (S320) illustrated in FIG. Moreover, in this system example, the discharged treated soil R is finely divided by the crushing process of the crushing machine 600, and is in contact with a lot of air and mixed uniformly. Thus, the process of crushing treated soil may be implemented. If necessary, the crushing machine 600 may be provided with a traveling device so that it can run on its own.

  Here, according to the official method, the test solution for evaluating the insolubilization state of fluorine stipulated in the soil environment standard is 50 g of the sample collected from the air-dried, granulated, and granulated particles. The sample is prepared from a sample solution obtained by mixing the sample with a solvent by a predetermined method. In an actual soil contamination site, although the contaminated soil to be treated is generally in the ton order, only 50 g of the sample is used for preparing the test solution. Therefore, even if the soil environment standard value is sufficiently cleared for the treated soil as a whole, if the mixed state of the contaminated soil with the insolubilizer is uneven, the soil environment is limited to 50 g treated soil provided to the sample. There may also be cases where the reference value is not met.

  On the other hand, in this example, a so-called mixing type mixing device 515 provided with a paddle mixer as a stirring means is used. The mixing device 515 has a paddle mixer in which a large number of stirring blades (paddles) are implanted around the rotation axis in the main body. By rotating the paddle mixer, the contaminated soil introduced into the main body is stirred and crushed. While sufficiently mixing with the insolubilizer. In addition, since the paddle mixer has a function of transferring the mixture, if it is operated with the outlet open, continuous processing to discharge the contaminated soil while mixing is possible. Can also be improved.

  Thus, the contaminated soil and the insolubilizer can be more reliably mixed by using the mixing type mixing device 515 as in this example. This mixing performance is extremely useful in reliably clearing the soil environment standard value. However, this does not limit the contaminated soil treatment method of the present invention by the configuration and type of the mixing device, and other types of mixing devices such as a screw mixer and a stabilizer can also be applied. Furthermore, manual mixing may be performed as long as the uniformity of stirring and mixing can be ensured.

  In the case of this example, two insolubilizing agents, magnesium oxide and magnesium chloride, can be added to and mixed with the contaminated soil by a single insolubilization processing machine 500, so that the system can be configured extremely compactly. This is a great merit of the contaminated soil treatment method of the present invention in which fluorine is insolubilized by simply mixing magnesium oxide and magnesium chloride into the contaminated soil.

  Further, since the system can be configured compactly, it is easy to carry in and out the system, so that labor and time required for construction and withdrawal of the system are greatly reduced. As a result, it is also advantageous to ensure the operating time as long as possible even in an overcrowded construction schedule. Since the system is compact, the system can be constructed even in a narrow space, and it is easy to relocate and has a high degree of freedom in layout. The layout is further improved by giving each device constituting the system a self-propelled function. The compact system also has the advantage that it is easy to take measures to prevent contaminated soil from scattering.

FIG. 25 is a diagram illustrating another configuration example of the insolubilization processing system.
In the system illustrated in FIG. 25, two soil conditioners 510 are arranged, and each mixing device 515 is assigned a magnesium oxide mixing step (S331) and a magnesium chloride mixing step (S332). When the excavated soil C5 is excavated by the excavator 300 and put into the soil improvement machine 510, the contaminated soil and the magnesium oxide powder are mixed by the mixing device 515 of the previous soil improvement machine 510, and then the subsequent soil improvement machine 510. The magnesium chloride solution from the pump unit 551 is further mixed by the mixing device 515 of the (insolubilization processing machine 500). The system that shares the mixing process of the insolubilizer is effective when it is desired to ensure the time from mixing magnesium oxide to mixing magnesium chloride in addition to mixing each insolubilizing agent carefully with contaminated soil. is there. Moreover, since the two soil conditioners 510 are arranged, the number of the powder supply devices 516 becomes two, so that magnesium chloride can be added as a powder. However, in the case of using an insolubilizer in which magnesium oxide and magnesium chloride are mixed in a powder state in advance, one powder supply device 516 is sufficient.

FIG. 26 is a diagram illustrating still another configuration example of the insolubilization processing system.
The system illustrated in FIG. 26 is a system in which the mixing step of magnesium oxide (S331) and the mixing step of magnesium chloride (S332) are shared by two mixing devices 515 as in the system of FIG. 551 is connected to the former soil conditioner 510 and mixed with magnesium oxide after mixing with magnesium chloride. Moreover, the conveyor apparatus 700 is arrange | positioned between the two soil improvement machines 510, and the addition order of the insolubilizing agent is not limited to this, but the time from the first insolubilizing agent mixing to the second insolubilizing agent mixing is further increased. The configuration is secured. Although a general belt conveyor is sufficient for the conveyor device 700, as shown in the figure, by providing a hopper 701 with an arch breaker (similar to the hopper 513 in FIG. 15), the mixing property of the insolubilizer is further improved. If necessary, a conveyor device having a traveling device may be arranged.

FIG. 27 is a diagram illustrating still another configuration example of the insolubilization processing system.
In the system illustrated in FIG. 27, the mixing device 515 of the two soil improvement machines 510a shares the magnesium oxide mixing process (S331) and the magnesium chloride mixing process (S332), but the soil improvement machine 510a is a fixed type. It is. These soil improvement machines 510a may have independent configurations, but in this example, they are fixed to a common problem and constitute an insolubilization processing machine 500a integrated with the pump unit 551. It is also conceivable to configure the system for performing the insolubilizing agent mixing step of S331 and S332 in this way.

  In addition, although the case where the contaminated soil is supplied by the hydraulic excavator 300 is illustrated in each system of FIGS. 22 to 27, the contaminated soil may be supplied by a belt conveyor (or a screw conveyor). Moreover, you may make it supply directly from the discharge conveyor of the apparatus which bears the most downstream process of a previous process.

  For example, the soil conditioner 510 is arranged at the next stage of the crushing machine 600 of the system of FIG. 23, and further, the soil conditioner 510 having a different particle size or less discharged from the transfer conveyor 202 of the sorting machine 200b through the other route. By arranging the belt conveyor to be supplied to the system, it is possible to construct a system for executing the processes of S324 to S326 in FIG. And if the contaminated soil discharged | emitted from the discharge conveyor of the soil improvement machine 510 of the system is directly thrown into the 1st soil improvement machine 510 of any insolubilization processing system of FIGS. 24-27, It is also possible to construct a system that continuously processes most of the steps from the pretreatment step (S320) to the insolubilization treatment step (S330). Thus, the system for carrying out the contaminated soil treatment method of the present invention can be configured in a wide variety and flexibility.

  Each device provided with the traveling device is not limited to a so-called crawler-type traveling device provided with an endless track, and may be replaced with a so-called wheel-type traveling device, or may be a fixed device.

It is a process flow figure showing roughly the whole process of one embodiment of a contaminated soil treatment of the present invention. It is a schematic diagram of the underground cross section of contaminated soil. It is a schematic diagram showing the state of pumping up contaminated water. It is a cross-sectional schematic diagram of the excavation location after refilling process soil. It is the schematic diagram showing the mode of purification processing (water treatment) of contaminated water. It is a process flow figure of a pretreatment process. It is a process flow figure of the insolubilization process part and analysis process part in the contaminated soil processing method of the present invention. It is the model figure of the soil seen microscopically. It is the schematic diagram showing the example of 1 structure of the analyzer. It is a side view showing an example of 1 composition of a sorting device. It is a side view showing an example of 1 composition of excavation / throwing device. It is a side view showing an example of 1 composition of a crushing device. It is a side view showing the example of 1 structure of the insolubilization processing apparatus. It is the figure which extracted and represented the principal part of one structural example of the insolubilization processing apparatus. It is a side view showing the detailed structure of the sieve apparatus with which the insolubilization processing apparatus was equipped, and the hopper vicinity. It is a figure showing the detailed structure of the downstream vicinity of the conveyance conveyor with which the insolubilization processing apparatus was equipped. It is a figure showing the structure of the supply pipe with which the insolubilization processing apparatus was equipped. It is a side view showing an example of 1 composition of a crushing device. It is a side view showing the detailed structure of the crusher with which the crushing apparatus was equipped. FIG. 20 is a cross-sectional view taken along the line XX-XX in FIG. 19. It is XXI-XXI arrow sectional drawing in FIG. It is a figure showing the example of 1 structure of a pre-processing system. It is a figure showing the other structural example of a pre-processing system. It is a figure showing the example of 1 structure of the system of the insolubilization process process part in the contaminated soil processing system of this invention. It is a figure showing the other structural example of the system of the insolubilization process process part in the contaminated soil processing system of this invention. It is a figure showing the further another structural example of the system of the insolubilization process process part in the contaminated soil processing system of this invention. It is a figure showing the further another structural example of the system of the insolubilization process process part in the contaminated soil processing system of this invention.

Explanation of symbols

300 Hydraulic Excavator 500 Insolubilization Treatment Device 500a Insolubilization Treatment Device 515 Mixing Device C Contaminated Soil C1-5 Contaminated Soil S130 Excavation Step S200 Water Treatment Step S210 Aggregation Precipitation Treatment Step S310 Magnesium Chloride Solution Generation Step S330 Insolubilization Treatment Step T1-3 Water Tank

Claims (5)

An excavation process for excavating contaminated soil containing fluorine;
A water treatment step of insolubilizing fluorine in contaminated water by mixing magnesium oxide or additive containing magnesium oxide and magnesium chloride in the contaminated water containing fluorine exuded when excavating contaminated soil in this excavation process; ,
Insolubilization treatment that insolubilizes fluorine in the contaminated soil by mixing the treated water purified in this water treatment process, magnesium oxide or an additive mainly composed thereof, and the magnesium chloride solution into the contaminated soil excavated in the excavation process. A contaminated soil treatment method comprising: a treatment step.   The contaminated soil treatment method according to claim 1, wherein the treated water is mixed with the contaminated soil as a solvent of a magnesium chloride solution.   The contaminated soil treatment method according to claim 1 or 2, wherein the treated water is mixed with the contaminated soil as moisture for adjusting the water content ratio.   The contaminated soil treatment method according to any one of claims 1 to 3, wherein the water treatment step includes a step of allowing contaminated water to stand to precipitate contaminated soil particles, wherein the contaminated soil particles thus precipitated are excavated. A method for treating contaminated soil, comprising performing insolubilization treatment in the insolubilization treatment step together with contaminated soil excavated in the process. A drilling device for drilling contaminated soil containing fluorine;
A water tank for storing contaminated water containing fluorine exuded when excavating contaminated soil with this excavator and mixing magnesium oxide or an additive based on this, and
A water tank for storing the contaminated water and mixing the magnesium chloride;
A mixing device for mixing magnesium oxide or an additive mainly composed thereof with contaminated soil excavated by the excavating device;
Treated water in which magnesium oxide or an additive containing magnesium oxide as a main component and magnesium chloride are mixed and insolubilized in the water tank, and a mixing device for mixing the magnesium chloride solution with the contaminated soil excavated by the excavator. Contaminated soil treatment system characterized by that.

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