JP2017136515A - Apparatus and method for decontaminating contaminated earth - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable installing and removing by a simple configuration, establishing unmanned decontamination operation, and further widening a decontamination coverage to an earth deep layer part.SOLUTION: An apparatus 1 for decontaminating contaminated earth includes: an electrode sheet 2 for laying on earth surface; a plurality of electrode poles 3 for insetting into an earth in a region to be decontaminated piercing the electrode sheet 2; a penetration liquid for penetrating into a contaminated earth D; and a water stop agent for stopping diffusion of the penetration liquid of the contaminated earth D. The electrode sheet 2 includes a conductive material, and a contamination substance adsorbent or a contamination substance decomposer. In an electrode pole 3, an inlet opening 12c communicates with an outlet opening 10a, a bolt terminal 12b of an upper end is electrically conductive to an electrode part 11 of a tip end, and an insulation coated part 13 is provided on a side surface except for a tip end part. A pushing piece 12a for pinioning the electrode sheet 2 through a rubber bush 13b is projected at an upper end part of the insulation coated part 13, and the bolt terminal 12b is disposed. A DC voltage is impressed between the electrode sheet 2 and the electrode poles 3 to induce a contamination substance in the contaminated earth D to the electrode sheet 2 by an electrokinetic phenomenon.SELECTED DRAWING: Figure 1

Description

  The present invention is an apparatus for decontaminating soil by adsorbing and recovering or decomposing soil contaminants contaminated with radioactive contaminants, heavy metals, agricultural chemicals, oil, volatile organic compounds, soil contaminants such as salt damage caused by tsunami, etc. And a method.

  Conventionally, the decontamination apparatus described in Patent Literature 1 includes a negative electrode sheet-like electrode member integrally provided with a solar cell film on the front surface and a radioactive substance adsorbent attached to the conductive layer on the back surface, and the sheet-like electrode member. A plurality of anode piles planted at a distance from each other and electrically insulated from the conductive layer, and a water supply device for moistening the radioactively contaminated soil. A sheet-like electrode member is laid so as to cover the soil decontamination target region. When a voltage is applied between the sheet electrode member and the anode pile due to the power generation of the solar cell film, the sheet electrode member acts as a cathode and generates an electric field in the contaminated soil around the anode pile, resulting in an electrokinetic phenomenon. As a result of promoting the ionization of radioactive substances contained in the soil surface layer by electrolysis and attracting radioactive substances ionized by electrophoresis or electroosmotic flow to the conductive layer of the sheet-like electrode member, the sheet-like electrode When the radioactive substance is adsorbed on the member and the sheet-like electrode member is removed, the radioactive substance can be recovered.

JP 2014-228360 A

In the above conventional decontamination equipment, it has been studied as an urgent measure against the Fukushima Daiichi nuclear accident, and the radioactive material derived from the accident has penetrated into the shallow surface of the soil about 5 cm from the ground surface. Paying attention to the above, a relatively short anode pile is inserted to decontaminate radioactively contaminated soil near the ground. Therefore, although this decontamination apparatus is effective for recovering radioactive materials having a shallow penetration depth of radioactive pollutants, it is difficult to effectively decontaminate soil contamination in which the contamination range extends from the ground to the deep layer.
Therefore, the present invention extends the decontamination target range for efficiently collecting the pollutants to the deep layer, and in this case, it can be installed easily and in a short time with a relatively simple configuration. It is an object of the present invention to provide a decontamination apparatus and a decontamination method for contaminated soil that does not stay at the site to be dyed.

  In order to solve the above problems, the present invention provides a conductive electrode sheet 2 laid on the soil surface of a decontamination target area in a decontamination apparatus 1 for contaminated soil that collects or decomposes contaminants from contaminated soil D. A plurality of electrode piles 3 penetrating through the electrode sheet 2 into the soil of the decontamination target area at intervals, an infiltrated solution that penetrates into the contaminated soil D and promotes a conductive phenomenon, and penetrates into the soil And a water-stopping agent that stops the downward diffusion of the penetrant. The electrode sheet 2 contains a contaminant adsorbent or a contaminant decomposer. An electrode portion 11 to which a voltage is applied is provided between the electrode pile 3 and the lower end portion of the electrode pile 3. The water-stopping agent permeates the soil near the electrode portion 11 of the electrode pile 3 to stop the downward diffusion of the permeate. A voltage is applied between the electrode sheet 2 and the electrode pile 3, and the contaminant is attracted to the electrode sheet 2 by electrolysis, electrophoresis or electroosmotic flow of the electrokinetic phenomenon that occurs in the contaminated soil D, and is absorbed and recovered. Or disassemble with an electrode sheet.

  In the present invention, a voltage is applied between the electrode sheet laid on the ground surface and the tip of the electrode pile inserted into the soil, and the electrokinetic phenomenon attracts and adsorbs or decomposes contaminants. The decontamination target range can be expanded to the depth of the soil up to the insertion depth, pollutants can be efficiently recovered, and installation and recovery operations can be completed easily and in a short time. This has the effect of reducing the risk of contact with pollutants without having to stay on site for a long time.

It is a schematic block diagram of the decontamination apparatus concerning 1st Example of this invention. It is sectional drawing of an electrode pile. It is explanatory drawing of the decontamination apparatus of the process of forming a hardly water-permeable layer. It is explanatory drawing of the decontamination apparatus of the process of forming a conductive layer. It is explanatory drawing of the decontamination apparatus of the process of applying a voltage.

An embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, a decontamination apparatus 1 for contaminated soil includes an electrode sheet 2 and an electrode pile 3 connected to a direct-current power supply 4, a water-stopping agent tank 5 connected to the electrode pile 3 via a pump 7, and an infiltration. A liquid tank 6, a sheet pile 8 that partitions the decontamination target range, and a residual water tank 9 to which a pump 9 a is connected are provided.

  The electrode sheet 2 is developed so as to cover the ground in the decontamination target range, and is connected to one electrode of the power source 4. This electrode sheet 2 is obtained by mixing a powdered conductive material and a harmful substance adsorbent or a harmful substance decomposing agent in a bag-like casing that can be developed into a sheet shape by a woven or non-woven fabric such as natural plant fiber or synthetic fiber. Composed. The electrode sheet 2 may be held by impregnation, adhesion, etc. by mixing a fibrous sheet material such as natural plant fiber or synthetic fiber with a granular conductive material and a harmful substance adsorbent or a harmful substance decomposition agent. . The conductive material is, for example, activated carbon, charcoal, iron powder, or the like, or a granular material in which two or more of these are mixed. The harmful substance adsorbent is, for example, zeolite, layered clay mineral, activated carbon, lignite, ferrocyanide compound, ion exchange resin, chelating agent, or a mixture of two or more of these. The harmful substance decomposing agent is an acid, an alkali, an oxidizing agent or a reducing agent, for example, nitric acid, oxalic acid, sodium hydroxide, titanium dioxide, hypochlorous acid, iron powder, sodium thiosulfate, or a combination thereof. It is a granular material mixed with seeds or more.

  The electrode pile 3 penetrates the electrode sheet 2 and is inserted into the ground. As shown in FIG. 2, the electrode pile 3 includes a steel pipe part 10, an electrode part 11 connected to the lower end part of the steel pipe part 10, a cylinder lid part 12 connected to the upper end part of the steel pipe part 10, and a steel pipe part. It is comprised with the insulation coating part 13 of 10 side surfaces. The steel pipe part 10 is a conductive long cylindrical pipe, and includes a plurality of discharge ports 10a at equal intervals around an axis projecting to the outside communicating with the lower end part. The electrode portion 11 is made of a conductive steel material, and includes a connecting tube portion 11b that is screwed into the lower end portion of the steel pipe portion 10, and a conical pointed portion 11a that easily penetrates into the soil. The cylinder lid portion 12 is made of a conductive steel pipe material having a lower end opened and screwed around the upper end portion of the steel pipe portion 10. A bolt terminal 12 b to which a cord connected to the power source 4 is connected is screwed into the closing lid of the tube lid portion 12. An inlet 12c to which a hose connected to the water-stopping agent tank 5 and the osmotic liquid tank 6 is protruded from the upper part of the side surface of the tube lid 12 and communicates with the hollow interior. The insulation coating portion 13 is configured by an insulation sleeve, a heat shrinkable tube, or the like that covers the steel pipe portion 10 in order to ensure insulation from the electrode sheet 2 and the soil except for the electrode portion 11. The lower end portion of the insulating coating portion 13 is provided with an injection hole 13a for opening the discharge port 10a. On the upper part of the insulating coating part 13, a pressing piece 12 a that horizontally protrudes laterally through a rubber bush 13 b around the base part for insulating the steel pipe part 10 and presses the electrode sheet 2 extends. A bolt terminal 12d to which a cord connected to the other electrode of the power supply 4 is connected is screwed into the presser piece 12a.

  The power source 4 applies a DC voltage between the electrode sheet 2 and the electrode pile 3, and each electrode is selected to have a polarity in which the electroosmotic flow between the electrode pile 3 and the electrode sheet 2 is directed upward from below. The The applied voltage may be continuous or intermittent.

  The connection between the water-stopping agent tank 5 and the permeate tank 6 and the electrode pile 3 is switched by a switching valve of the pump 7. The water-stopping agent in the water-stopping agent tank 5 forms a hardly water-permeable layer 14 that stops the permeation of the permeated liquid in order to prevent contaminants from penetrating and diffusing underground with the permeated liquid from the decontamination target range. The water-stopping agent injected from the injection port 12c of each electrode pile 3 is ejected from the injection hole 13a of the discharge port 10a to the contaminated soil, and permeates and diffuses horizontally in the deep layer of the contaminated soil to form the hardly water-permeable layer 14. To do. The permeation liquid is injected and held above the hardly water-permeable layer 14 to form a conductive layer 15 having higher conductivity by holding more soil moisture than other parts, and the electrode sheet 2 and the conductive layer 15 are simulated. As a parallel electrode plate, a vertical electric field is generated between them to promote the movement of pollutants due to electrokinetic phenomena. The waterstop agent is one of bentonite, starch paste, glue, polyvinyl acetate, polyion, or the like, or a mixture of two or more thereof. Polyion includes cationized cellulose, carboxymethylcellulose (CMC), polydiallyldimethylammonium chloride, polyacrylic acid sodium salt, and the like, and can be biodegraded by microorganisms in soil. CMC and polyacrylic acid sodium salt have high water absorption and are suitable for retaining moisture in the conductive layer 15 formed immediately below the bottom of the contaminated soil D in the decontamination target range.

  The permeate in the permeate tank 6 promotes the elution of pollutants in the soil and the electroosmotic flow, and uses water, dilute acid, alkali, salt, chelate, surfactant and the like. The osmotic solution is injected from the osmotic solution tank 6 to the injection port 12c of each electrode pile 3 via the pump 7, and is discharged to the contaminated soil D from the injection hole 13a of the discharge port 10a. The permeate penetrates and diffuses into the soil and promotes the movement of pollutants by electrokinetic phenomena. In order to further promote the electrokinetic phenomenon, the penetrant controls the zeta potential of the contaminant particles by adding salts, adjusting the pH, or the like as necessary. During the construction period, the permeate is supplied to the contaminated soil D continuously or intermittently.

In this decontamination apparatus 1, as shown in FIG. 1, the electrode sheet 2 is spread on the soil surface in the decontamination target area, the electrode pile 3 is penetrated through the electrode sheet 2, and is inserted almost vertically downward into the ground, and the presser piece 12a Embed until the electrode sheet 2 is pressed down. Before inserting the electrode pile 3, an insertion hole may be drilled in the soil with an electric hammer or the like. As shown in FIG. 3, a hose is connected to the injection port 12 c of the electrode pile 3, a water stop agent is injected from the water stop agent tank 5 through the pump 7, and sprayed from the discharge port 10 a through the steel pipe part 10. A hardly permeable layer 14 is formed immediately below the bottom of the deepest layer of the contaminated soil D. Next, as shown in FIG. 4, the valve of the pump 7 is switched to inject the osmotic solution from the osmotic solution tank 6 into the injection port 12 c of the electrode pile 3, and then injected from the injection hole 13 a of the discharge port 10 a through the steel pipe part 10. The permeate is permeated and diffused into the contaminated soil D. When the contaminated soil D is in a proper wet state, the conductive layer 15 is formed on the upper part of the hardly water-permeable layer 14. When the electrode sheet 2 becomes excessively immersed in the osmotic solution moved by the electroosmotic flow, the excess of the osmotic solution is recovered in the residual water tank 9 by the pump 9a, and the adsorbent, decomposition agent, pH adjuster or Add a flocculant and detoxify properly. This treated water may be used again for adjusting the penetrant. Next, as shown in FIG. 5, a power source 4 is connected to the electrode sheet 2 and the electrode pile 3, and a DC voltage is applied to the contaminated soil D. The voltage is applied continuously or intermittently during the decontamination period as necessary. When a voltage is applied between the electrode sheet 2 and the electrode pile 3, the electric field formed in the contaminated soil D between the electrode sheet 2 and the conductive layer 15 causes electrolysis, electroosmosis, electrophoresis, etc. An electric phenomenon occurs, and the contaminant moves toward the electrode sheet 2. The contaminants attracted in the vicinity of the electrode sheet 2 are adsorbed and accumulated by the adsorbent contained in the electrode sheet 2 or decomposed by the decomposition agent. If necessary, collect the soil in the decontamination target area and analyze it to confirm the decontamination effect. The electrode sheet 2 used for the decontamination work is appropriately treated as industrial waste or radioactive waste according to the pollutant.
In addition, the decontamination target range of the contaminated soil D may be prevented from leaking in the horizontal direction due to penetration of the permeate by partitioning and surrounding with the sheet pile 8 in advance.

  The electrode sheet 2 is preliminarily formed in the previous embodiment and carried into the decontamination site. In addition, the electrode sheet 2 decontaminates the granular material mixed with the conductive material and the harmful substance adsorbent or the harmful substance decomposition agent at the decontamination site. A thin layer of powder is applied to the soil surface of the target area, and starch paste, synthetic glue, glue, polymer ion complex, etc. are additionally sprayed on the soil surface, and dried to form a thin layer of granular material on the soil surface. It may be formed by fixing.

DESCRIPTION OF SYMBOLS 1 Decontamination apparatus 2 Electrode sheet 3 Electrode pile 4 Power supply 5 Water stop agent tank 6 Osmotic liquid tank 7 Pump 8 Sheet pile 9 Residual water tank 9a Pump 10 Steel pipe part 10a Discharge port 11 Electrode part 11a Pointed part 11b Connection cylinder part 12 Tube lid Part 12a Presser piece 12b Bolt terminal 12c Inlet 12d Bolt terminal 13 Insulation coating part 13a Injection hole 13b Rubber bushing 14 Water-impermeable layer 15 Conductive layer D Contaminated soil

Claims (10)

In decontamination equipment for contaminated soil that collects or decomposes pollutants in contaminated soil,
A conductive electrode sheet that includes a pollutant adsorbent or a pollutant decomposer and is laid on the soil surface of the decontamination target area;
An electrode pile having an electrode portion that penetrates the electrode sheet while being insulated and is inserted into the soil of the decontamination target area at intervals, and a DC voltage is applied to the lower end portion between the electrode sheet and ,
An osmotic solution that penetrates into the soil and promotes electrokinetic phenomena;
Penetrating into the soil in the vicinity of the electrode portion of the electrode pile, and comprising a waterstop agent that stops the downward diffusion of the permeate,
A DC voltage is applied between the electrode sheet and the electrode pile, and the contaminant is adsorbed to the electrode sheet by an electroosmotic flow of electrokinetic phenomenon generated in the soil and recovered or decomposed by the electrode sheet. Decontamination equipment for contaminated soil. The electrode pile has an inlet at the upper end for injecting the permeate and water-stopping agent,
An outlet at the lower end communicating with the inlet and discharging the penetrant and water-stopper into the soil;
A connection terminal at an upper end electrically connected to the electrode portion and connected to one electrode of a DC power source;
While fixing the electrode sheet to the soil surface, a presser piece having a connection terminal connected to the other electrode of the DC power supply,
2. The decontamination apparatus for contaminated soil according to claim 1, further comprising an insulating covering portion that is electrically insulated from the electrode sheet and soil except for the electrode portion.   3. The decontamination apparatus for contaminated soil according to claim 1, wherein the electrode sheet is made of a fibrous sheet material holding a powdered conductive material and the contaminant adsorbent or contaminant decomposer. 4.   3. The soil removal according to claim 1, wherein the electrode sheet comprises a sheet-like bag body containing a mixture of a granular conductive material and the contaminant adsorbent or contaminant decomposer. Dyeing equipment.   The electrode sheet includes the particulate conductive material and the pollutant adsorbent or the pollutant decomposing agent sprayed on the soil surface, and a binder material sprayed on and dried to fix them. The decontamination apparatus for contaminated soil according to claim 1 or 2.   The pollutant adsorbent for the electrode sheet contains at least one kind of zeolite, layered clay mineral, activated carbon, lignite, ferrocyanide compound, ion exchange resin or chelating agent. Decontamination equipment for contaminated soil according to crab.   6. The contaminated soil decontamination apparatus according to claim 1, wherein the contaminant decomposing agent for the electrode sheet is an acid, an alkali, an oxidizing agent, or a reducing agent.   The decontamination apparatus for contaminated soil according to any one of claims 1 to 7, further comprising a pressing piece projecting to a side portion to press the electrode sheet against a soil surface at an upper portion of the electrode pile.   The decontamination apparatus for contaminated soil according to any one of claims 1 to 8, further comprising a sheet pile embedded in a boundary portion of the decontamination target region and preventing diffusion of the permeate. A decontamination method using the decontamination apparatus according to claim 1,
Injecting and infiltrating the water-stopper into the soil to form a poorly water-permeable layer;
Injecting and infiltrating the permeate into the soil and diffusing above the poorly permeable layer;
Applying a voltage between the electrode sheet laid on the soil surface and the electrode pile inserted through the electrode sheet, and eluting pollutants by electrokinetic phenomena such as electrolysis, electrophoresis, electroosmosis, A method of decontaminating contaminated soil, comprising the steps of attracting the electrode sheet and adsorbing the contaminant with the contaminant adsorbent contained in the electrode sheet or decomposing the contaminant with the contaminant decomposer.

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