JP2524290B2 - Method and apparatus for insolubilizing heavy metals in contaminated soil - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a soil contaminated in situ without excavating or moving the contaminated soil when heavy metals which cause pollution are present in the soil and the soil is contaminated. TECHNICAL FIELD The present invention relates to a method and an apparatus for insolubilizing heavy metals in contaminated soil, which enables waste water to be drained, insoluble heavy metals in the ground to be treated, and soil to be reused.

[0002]

2. Description of the Related Art On the ground of factories of various industries that handle heavy metals that cause pollution, as conventional treatment methods when soil is polluted by heavy metals leaked from these facilities or by industrial waste, Contamination by excavating the contaminated soil and carrying it out to the other, or by pulverizing the excavated soil and mixing it with a stabilizer in a mixer to backfill it, or replacing it with new soil brought in from another place The method of regenerating the area of soil was used.

[0003]

As described above, conventionally,
There is no way to treat the soil contaminated by heavy metals in-situ and recycle it, therefore the contaminated soil should be excavated, taken out and finely ground and mixed with stabilizers before filling it. Either returning or transporting the contaminated soil to another treatment facility and then importing new soil from another to backfill and replace it, but during excavation, mixing or unloading There was a problem that contaminated soil was scattered in the area, and there were problems such as noise during the work and secondary pollution to surrounding residents when carrying in and out.

The present invention is intended to provide a method for treating contaminated soil and an apparatus thereof for the purpose of solving the above conventional problems.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a plurality of hollow tubes having a large number of water passage holes which also serve as electrodes of an anode and a cathode are bored to form a row of tubes facing each other for the anode and the cathode. While forming and penetrating deeper than the depth of the contaminated soil, while installing so that the polarity of the anode and the cathode can be switched, a direct current is applied to each of the electrodes to apply a direct current voltage to the anode tube. An aqueous solution of sodium sulfide or iron sulfate is injected into the electrode, and the electroosmosis phenomenon that acts on the contaminated soil between the two electrodes is used to discharge the aqueous solution from the anode tube through the water holes to evenly distribute it in the contaminated soil. In contact with the heavy metal in the contaminated soil to cause an insolubilizing chemical reaction, and contaminated soil water or excess insolubilizing aqueous solution is passed through the water holes to the cathode tube. After collecting water and then inspecting water quality, the specified water quality standard value is reached. In, by adopting a means of repeated collecting water discharged from the anode tube of the aqueous solution, the penetration and cathode tubes to contaminated soil, has solved the above problems.

[0006]

According to the present invention having the above-described structure, the anode row and the cathode row are installed to penetrate deeper than the pollution depth of the contaminated soil so that the anode row and the cathode row are opposed to each other in the soil area contaminated by heavy metals. Then, by applying a direct current to this and utilizing the electroosmosis phenomenon that acts in the contaminated soil between the two electrodes, an aqueous solution of sodium sulfide or iron sulfate necessary for insolubilization of heavy metals from the anode side tube row is obtained. Discharge, by uniformly permeating the aqueous solution into the contaminated soil by the electroosmosis phenomenon, by further repeating the cycle of collecting the aqueous solution in the tube row on the cathode side, in addition to the chemical reaction of insolubilization by the aqueous solution, In-situ insolubilization of heavy metals by utilizing redox reaction by electrochemical action.

[0007]

EXAMPLE The method of the present invention is contaminated by forming a plurality of hollow tubes having a large number of water passage holes, which also serve as anode and cathode electrodes, facing each other for the anode and the cathode to form a row of tubes. While being installed deeper than the depth of the soil, while being installed so that the polarity of the anode and cathode can be switched, a DC voltage is applied to each of the electrodes by applying a DC current, and sodium sulfide in the anode tube or By injecting an aqueous solution of iron sulfate, and utilizing the electroosmosis phenomenon that acts on the contaminated soil between the two electrodes, the aqueous solution is discharged from the anode tube through the water passage holes to allow it to penetrate into the contaminated soil evenly. , Contacting the heavy metal in the contaminated soil to cause a chemical reaction of insolubilization, contaminated soil water, or excess surplus of the insolubilizing aqueous solution to collect water into the cathode tube through the water holes, After that, a water quality test is performed and the water-soluble Discharged from the anode tube, by repeating the collecting water to penetrate and cathode tubes to contaminated soil is to insolubilize the heavy metals in contaminated soil. The above method and apparatus will be described in detail below with reference to the drawings.

In the area of the contaminated soil 1 contaminated by heavy metals, the soil engineering characteristics of the soil are investigated, and the anode is set at intervals based on the value of the hydraulic conductivity of the soil constituting the ground. A plurality of bottomed hollow tubes 2 which also serve as cathode electrodes are formed so as to face each other for the anode and the cathode to form a row of tubes and penetrate into the ground deeper than the depth of the contaminated soil 1.

A large number of water passage holes 3 are formed on the outer peripheral wall surface of the hollow tube 2 so that an aqueous solution of sodium sulfide or iron sulfate can be discharged into the soil and the aqueous solution in the soil can be collected. At the same time, the connection device 4 such as a connection terminal is attached to the portion of each hollow tube 2 protruding from the surface of the earth.

Of the two sets of hollow tubes 2a and 2b which are installed in the contaminated soil 1 as two pairs of tube rows A and B facing each other as electrodes for anode and cathode, respectively, 2 In each hollow tube 2a constituting the row A of tubes for the anode, a cock 7 projecting from a water supply conduit 6 having one end communicating with the water tank 5 is projected from an upper portion of each hollow tube 2a. The water supply conduit 6 is connected and fixed by connecting the connected communication pipes 8, and the lead wire 11 drawn from the connection device 4 of each hollow pipe 2a of the anode side tube row A is connected to the anode side cord 10 of the DC power supply 9. Connect.

Each of the hollow tubes 2b constituting the two rows of cathode tubes B is connected to the steam / water separation tank 12 at one end thereof by a cock 7 projecting from another water collecting conduit 13, The water collection conduit 13 is connected and fixed by connecting the communication pipes 8 projecting from the upper portion of each hollow pipe 2b, and further the cord 14 on the cathode side of the DC power supply 9 is connected.
The lead wire 15 drawn from the connecting device 4 of each hollow tube 2b of the tube row B on the cathode side is connected to.

Although two sets of tube rows A and B are shown in FIGS. 1 and 2, more tube rows are arranged when the processing area is large. In the figure, 16 is a water supply tank 5 and a water supply conduit 6.
A gate valve 17 is provided between the water vapor separation tank 12 and the water collecting conduit 13.

The air / water separation tank 12 is connected to a settling tank 20 by a drainage connecting pipe 19 with a drainage pump 18 interposed, and the settling tank 20 is adsorbed by a water supply connecting pipe 22 with a water feeding pump 21. Further, the adsorption tank 23 is connected to the water supply tank 5 by a water supply connection pipe 25 having a water supply pump 24 interposed, and the water supply tank 5 is connected to the water supply conduit 6 via the gate valve 16 as described above. It is connected. These are installed so as to form a cycle in series, and the contaminated soil water in the contaminated soil 1 and the aqueous solution of sodium sulfide or iron sulfate sent from the water supply tank 5 to the water supply conduit 6 are water quality standards. It is installed so that it is not discharged until it is cleared.

On the other hand, a dissolution tank 26 for adjusting the concentration of sodium sulfide or iron sulfate to an appropriate concentration is connected to the water supply tank 5 by a liquid supply connecting pipe 28 with a liquid supply pump 27 interposed in between. The aqueous solution of sodium sulfide or iron sulfate adjusted to an appropriate concentration in the dissolution tank 26 is sent to the water supply tank 5 by the liquid supply pump 27 via the liquid supply connection pipe 28, and further, the gate valve 16 is supplied from the water supply tank 5 to the water supply tank 5. Through the communication pipe 8 through the cock 7 attached to the water supply conduit 6, and discharged into the contaminated soil 1 from the water passage hole 3 of each hollow tube 2a of the anode side tube row A. In contact with heavy metals present in the contaminated soil 1 where the electroosmosis phenomenon is occurring, a chemical reaction of insolubilization is generated, and contaminated soil water or excess insolubilizing aqueous solution is used on the cathode side tube. Is it the water passage hole 3 of the hollow tube 2b in row B? Catchment to the respective hollow tube 2b.

The contaminated soil water collected in each hollow tube 2b or the surplus insolubilizing aqueous solution is pumped and sent to the water collecting conduit 13 through the communicating pipe 8 and the cock 7. Further, it flows into the steam separation tank 12 via the gate valve 17. Then, the aqueous solution separated from the air by the air-water separation tank 12 flows into the settling tank 20 by the drainage pump 18 through the drainage connecting pipe 19, and is contained in the aqueous solution by the treatment of the settling agent in the settling tank 20. The water solution is separated from the fine soil particles and the like, and only the aqueous solution is supplied to the adsorption tank 23 by the water supply pump 21 through the water supply connecting pipe 22.
In the adsorption tank 23, extremely fine particles of heavy metals mixed in the aqueous solution are adsorbed, and the treated aqueous solution enters the water supply tank 5 via the water supply connecting pipe 25 by the water supply pump 24, and the The concentration is adjusted and water is again fed to the gate valve 16, the water supply conduit 6, the cock 7, the communication pipe 8 and each hollow pipe 2a on the anode side, and while repeating the same cycle as described above, the heavy metals in the soil are removed. The process of insolubilization is repeated.

In the soil in which the electroosmosis phenomenon occurs, the area of the anode becomes the acidic area and the area of the cathode becomes the alkaline area, so that the substance between both electrodes undergoes a redox reaction, and this phenomenon occurs. Therefore, heavy metals in soil are also affected, and it exerts a strong effect on the chemical reaction with the aqueous solution of sodium sulfide or iron sulfate infiltrated by the electroosmosis phenomenon. For this reason, in the case of a long energization time, it is sometimes necessary to freely change the polarities of the tube rows A and B at any time to efficiently insolubilize heavy metals in the contaminated soil. In this case, it is shown in the figure. At the same time, the polarity is changed by the conversion device, and at the same time, the injection of the aqueous solution of sodium sulfide or iron sulfate into each hollow tube on the anode side is stopped, and only the action of redox due to the electrical action acts on the contaminated soil 1. Let

When the water quality inspection is appropriately performed by repeating the above cycle and a predetermined water quality reference value is reached, these series of operations are stopped and the insolubilization treatment of heavy metals in the contaminated soil is completed.

[0018]

Since the present invention is as described above, it is possible to insolubilize heavy metals in contaminated soil in its original position without affecting other operations such as conventional soil replacement. In addition, hollow tubes for anode and cathode are installed deeper than the depth of pollution in the area of contaminated soil, and electroosmosis phenomenon occurs only in the area of the area surrounded by this hollow tube. As it works, it does not flow pollutants to areas outside this range. Further, according to the present invention, since excavation, mixing, and carrying-in / out of contaminated soil are unnecessary, there is no scattering of contaminated soil, no noise due to work, and no secondary pollution to workers and neighboring residents. Is played.

[Brief description of drawings]

FIG. 1 is a schematic plan view of the entire device of the present invention.

FIG. 2 is a vertical cross-sectional view of the device of the present invention.

[Explanation of symbols]

1 contaminated soil, 2 hollow tubes, 2a hollow tubes on the anode side, 2b hollow tubes on the cathode side, 3 water holes, 5 water supply tanks, 6 water supply conduits, 7 cocks, 8 communication tubes,
9 DC power source, 12 steam separation tank, 13 water collection conduit, 16, 17 gate valve, 20 sedimentation tank, 2
6 Dissolution tank, A anode side tube row, B cathode side tube row.

Claims (2)

(57) [Claims] 1. A plurality of hollow tubes having a large number of water holes that also serve as electrodes for an anode and a cathode are formed to form a row of tubes facing each other for the anode and the cathode, and Along with deeply penetrating the installation, the anode and the cathode are installed so that the polarity can be switched, while a DC current is applied to each of the electrodes to apply a DC voltage, and an aqueous solution of sodium sulfide or iron sulfate in the anode tube. Is injected, and by utilizing the electroosmosis phenomenon that acts on the contaminated soil between the two electrodes, the aqueous solution is discharged from the anode tube through the water passages and uniformly permeated into the contaminated soil, By contacting heavy metals in contaminated soil and causing insolubilization chemical reaction, contaminated soil water or excess insolubilization aqueous solution is collected in the cathode tube through the water hole, and then water quality Perform an inspection and check whether the above-mentioned aqueous solution anode tube A method for insolubilizing heavy metals in contaminated soil, characterized by repeating discharge from the contaminated soil, permeation into the contaminated soil, and water collection to the cathode tube. 2. A plurality of hollow tubes having a large number of water passage holes which also serve as electrodes of an anode and a cathode are formed to form a row of tubes facing each other for the anode and the cathode, and Along with deeply penetrating the installation, the anode and the cathode are installed so that the polarity can be switched, while the anode tube is connected and fixed to a water supply conduit having one end connected to a water tank through a gate valve. A water collecting conduit, one end of which communicates with a gas / water separation tank via a gate valve, is connected and fixed to the cathode tube, and a precipitation tank and an adsorption tank are further disposed between the water / water separation tank and the water supply tank. Along with fixing the dissolution tank for sending water by adjusting the concentration of sodium sulfide or iron sulfate to an appropriate concentration in the water supply tank, further connecting the anode tube to the anode side of direct current, and to the cathode side of the direct current. Heavy metal in contaminated soil characterized by connecting the cathode tube A device to insolubilize genera.