JP2003080273A - Ground water cleaning technology - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground water cleaning technology which is capable of efficiently cleaning contaminated water by using simple cleaning walls. SOLUTION: The ground water cleaning technology of a type to build up the continuous cleaning walls in underground by using a multispindle auger includes an excavating and mixing process of continuously discharging iron powder from an excavating head of the auger during the excavating process step by the auger and agitating and mixing the iron powder and excavated soil in a present position, in which the cleaning walls consisting of the underground continuous walls by the soil mixed with the iron powder are constituted by repeating the above process and the contaminated water is cleaned by permeating the streams of the contaminated water through the cleaning walls. The above cleaning walls have a width and depth sufficient for the streams of the contaminated water to be cleaned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying groundwater contaminated with organochlorine compounds, and more particularly, to groundwater pollution caused by underground soil as a pollutant, by removing iron powder mixed with soil in the groundwater area. The present invention relates to a method for purifying by using.

[0002]

2. Description of the Related Art As a method for purifying halogen-containing pollutants in groundwater utilizing the reducing action of iron powder or the like, for example, a method as disclosed in Japanese Patent Publication No. 5-501520 is known.
In order to purify polluted groundwater in front of the well, for example, a purification means main body in which iron powder and sand are mixed in advance is installed in the groundwater upstream side of the pumped well in order to purify polluted groundwater. It is installed and performed.

In the case of such a purification method, the mixture of iron powder or steel wool and sand as the main body of the purification means is the purification means before the contaminated groundwater reaches the well due to the groundwater flow generated by the pumping well. Since the purification treatment is performed by passing through the main body, it is necessary to install the purification means main body at a specific front of the well or around the well. As the laying method, a trench (a digging groove) is excavated in a necessary portion, and a mixture of iron powder or steel wool and sand, which is a purification means main body, is filled in the trench, and the purification means main body and air are filled. It is a method of covering the upper part with excavated soil so as to cut off the contact of the above.

As another method, in order to construct a purification means body similar to the above in the groundwater upstream side of the pumping well, a large number of cylindrical holes are drilled and at the same time, the mixture of iron powder and sand is added to the cylindrical holes. It is considered to fill the inside and arrange such cylindrical holes in a staggered manner to form a wall. In these conventional purification methods, contaminated groundwater passes through the wall formed by the purification means main body, and the reducing action of the iron powder or the like detoxifies the pollutant, for example, a halogen substance. It is something.

[0005]

When the above-mentioned known method is used, since it is necessary to fill the trench with a mixture of iron powder or the like, which is the main body of the purifying means, and sand, it is difficult to perform the construction in a place where the groundwater level is low. is there. That is, a trench excavator is usually used to construct such a trench, but high-depth trench excavation is extremely difficult, and it is difficult to lay the purification means main body when the contaminated water basin is deep. . Further, in a method of excavating a large number of cylindrical holes and filling the mixture of iron powder and sand, which is a purifying means, into the cylindrical holes, it is necessary to cope with the above-mentioned deep groundwater level. Is relatively easy. However, in this method, for example, the surroundings of the pumping well are staggered to form holes, and the purifying means main body is filled, so that the contact efficiency of iron powder or the like with the contaminated water flow is poor, and as a result, it is effective. There was a drawback that could not be called a proper method.

The present invention eliminates such drawbacks and provides a groundwater purification method capable of efficiently purifying contaminated water by an extremely simple construction method using a purification wall. Furthermore, contaminated groundwater flowing out from a relatively wide contaminated soil,
This method provides a groundwater purification method in which the efficiency of iron powder purification is extremely high by guiding the water to the purification wall using an impermeable wall laid underground.

[0007]

The present invention is a groundwater purification method of the type in which a continuous purification wall is constructed underground by using a multi-axis auger, the method being a head for excavating the auger during an excavation process by the auger. Including a drilling and mixing process that continuously discharges iron powder and stirs and mixes iron powder and excavated soil at the current position, and by repeating this process, a purification wall consisting of a continuous underground wall of iron powder mixed soil is constructed. However, the contaminated water flow passes through the purification wall for purification, and the purification wall has a sufficient width and depth with respect to the contaminated water flow to be purified. Further, water blocking walls for guiding the contaminated water flow to the purification wall may be laid on both ends of the purification wall. In this case, the purification walls are arranged in upstream and downstream sides of the groundwater flow and are constructed in a plurality of rows. . Further, in the groundwater purification method, the purification wall is constructed at a depth reaching at least the groundwater level to the impermeable layer.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows various planar shapes of a purification wall 10 constructed in a groundwater purification method according to an embodiment of the present invention. FIG. 1 (A) shows a purification wall 10 having a linear cross-section which is constructed so as to be substantially orthogonal to the contaminated groundwater streamline indicated by the arrow X. The same figure (B) shows the purification wall 10 whose cross-sectional shape is also arcuate with respect to the contaminated groundwater streamline X, and further, the same figure (C) is the purification wall whose cross-sectional shape is also roughly pot-bottom shaped. 10 is shown. However, such a shape of the purification wall 10 itself is not a special feature of the present invention, and the point is that the purification wall 10 is orthogonal to the streamline X of the contaminated groundwater flow as much as possible, and the contaminated groundwater is, as will be described later. It is important to have a structure in which the flow reliably passes through the purification wall body without bypassing the outside of the purification wall 10.

FIG. 2 shows the purification wall 10 as shown in FIG.
The vertical cross-sectional shape and the state of the underground soil on which the purification wall 10 has been constructed are shown. The soil area 20 in which the contaminated groundwater in which the purification wall 10 of the present invention is constructed is present in a shape that blocks the contaminated groundwater flow zone 23 between the ground surface 21 and the impermeable layer 22 existing at a certain depth underground. Built in. That is, the upper end 10A of the purification wall 10 is located at least above the groundwater level 24 in the construction area, and the lower end 10B thereof is located.
Reaches the inside of the impermeable layer 22 through at least the contaminated groundwater flow zone 23, whereby the contaminated groundwater flow is surely passed through the purification wall body.

FIG. 3 shows the arrangement of the purification wall 10 according to the second embodiment of the present invention, and further, it is constructed in a substantially eight shape from both sides of the purification wall 10 in plan view toward the upstream of the groundwater flow, for example. The impermeable walls 30 and 30 are shown, and an opening 30A is formed with respect to the contaminated groundwater streamline X. Further, in this embodiment, as shown in FIG. 1 (A), double purification walls 10 each having a linear cross section are provided. This is a structure for sufficiently purifying a large amount of contaminated running water collected toward the purification wall 10 by the impermeable walls 30, 30 as described later.

FIG. 4 shows a purification wall 10 (2 having the structure shown in FIG.
It shows the cross-sectional state of the underground soil area 20 including the row construction), and is in the same mode as in FIG. Impermeable wall 3 shown by broken lines
As in the case of FIGS. 1 and 2, the purification walls 10 and 10 constructed at the intermediate openings of 0 and 30 (see 30A in FIG. 3) sufficiently cover the contaminated groundwater flow zone 23 so that the groundwater level. It is provided across 24 and the impermeable layer 22.

In this way, the purification wall 1 according to each embodiment
0 is laid across the groundwater level 24 and the impermeable layer 22 so as to cover the contaminated groundwater flow zone 23, but the depths of the groundwater level 24 and the impermeable layer 22 are the soil areas of the contaminated groundwater. Obviously, it depends on the conditions in.
Further, although a portion above the upper end 10A of the purification wall 10 will be described later, normal soil is restored once it is excavated without being mixed with iron powder.

The structure and construction method of the impermeable walls 30, 30 in FIGS. 3 and 4 are also provided so as to completely block at least the contaminated groundwater flow zone 23, as will be described later. Even if the upper end of the water wall reaches the ground surface 21, there is no problem. Since the function of the impermeable wall is simply to collect the contaminated groundwater flow to be purified in the purifying wall portion, no particular strength condition is required and the impermeable performance is sufficient.

5 to 7 are explanatory views of a multiaxial auger for constructing the purification wall 10 and the impermeable wall 30 in the groundwater purification method of the present invention, and a process of constructing the wall body by the auger. As is apparent from FIG. 5, a conventionally known multi-axis auger 1 has, for example, three excavating shafts 3 and 3 which are rotationally driven by a drive device 2, and the excavating heads 4 and 4 are respectively provided at the tips of the excavating shafts. 4 are provided. The various excavating heads 4 and 4 are of a type capable of ejecting various fluids.

FIG. 6 shows a state in which a part of the purification wall 10 is constructed. The excavating shaft 3 of the triaxial auger shown in FIG. 5 advances while being rotationally driven by the drive device 2, and the discharge of the iron powder is started from the position of the upper end portion 10A of the purification wall 10 shown. In this case, the upper end 1 where the construction of the purification wall 10 is started
The position of 0A is at least above the groundwater level as described above.

In FIG. 6, the purification wall 1 shown by reference numeral 10A.
From the excavation head 4 that has been dug up to the upper end position of 0, the discharge of the iron powder for forming the purification wall is started, and the discharge of the iron powder is continued at least to the lower end portion 10B of the purification wall that penetrates the impermeable layer. In the iron powder discharge area, the excavated soil and the iron powder can be stirred and mixed by rotating the excavating shaft 3 of the auger up and down as necessary. In this case, the discharged iron powder amount in this case is about 10% in weight ratio with the excavated soil to be mixed, but this value itself is not strict and should be increased to about 15%, for example. Is also possible.

Strictly explaining the discharge start position of the iron powder, the volume of the mixed soil forming the purification wall 10 increases by the amount of the iron powder mixed, so that the upper end of the purification wall that is actually required is increased. It is possible to start the discharge of the iron powder from a position slightly lower than the part position 10A. More specifically, 3
The outer diameter of the excavating head 4 of the shaft auger is φ650 to φ850, and the purification wall formation depth, that is, the upper end portion 1 of the purification wall 10.
The depth of 0A is about 10m, and the depth of the lower end 10B is about 60m.
However, these numerical values are merely examples, and are values determined by the conditions of the contaminated groundwater flow zone to be purified.

FIG. 7 shows an excavation procedure for constructing a purification wall for implementing the groundwater purification method of the present invention using a triaxial auger. A triaxial auger, which is a normal multiaxial auger, has three excavation axes A, B, and C. Then, from the left side of the figure, the excavation process is carried out in this order, and each time, the iron powder is discharged and mixed with the excavated soil.

In FIG. 7, in the first excavation step, a purification wall for a continuous excavation hole portion by the excavation axes A, B, C is constructed. This is excavation and discharge of iron powder as described above.
It is performed according to a technique such as stirring and mixing. The next excavation process is carried out in the same manner, but an interval for one excavation shaft is provided between the excavation position of the C axis in the excavation process and the excavation position of the A axis in the excavation process. There is. Then, the respective excavation axes A and C in the excavation process are installed in the portion of the axis C of the process and the axis A of the process at the already excavated position, and the process is performed in the same manner as the process of It is something. Therefore, the hatched excavation position shown in FIG. 7 indicates a site excavated in duplicate,
In this way, the overlapping excavated portion functions as a guide for the auger shaft in each of the steps, and the like, while sequentially advancing the steps of, and.

In the above purification wall construction process,
As mentioned above, in each step of
A required amount of iron powder is discharged and mixed from all the excavating heads B and C at a required time. However, in the steps (1) and (2), the discharge of the iron powder from the excavation axes A and C is stopped, and the iron powder is ejected only from the central excavation axis B under the same conditions as above and mixed with the excavated soil. Is done. In this way, it is possible to create a purification wall in which the amount of iron powder mixed is uniform and without waste.

Next, the process of constructing the impermeable wall 30 will be described. The impermeable walls 30, 30 shown in FIGS. 3 and 4 are constructed so as to reach from the ground surface 21 to the impermeable layer 22, or at least from the groundwater level 24 to the impermeable layer 22 as described above. Then, using the above-mentioned triaxial auger 1, FIG.
Although the excavation work is carried out by the procedure shown in FIG. 3, in the case of the impermeable wall 30, the excavated soil and the solidifying material such as cement milk are discharged from the excavating head of the auger shaft.

That is, the impermeable wall 30 is constructed by a conventionally known method for constructing an underground continuous wall, for example, S.M. M. W. It can be carried out extremely rationally by adopting the construction method. However, the S. M. W. Since the construction method is a well-known construction method for a continuous underground wall, detailed description thereof will be omitted, but for example, at the position of the excavation axis A or C that overlaps in each construction process shown by diagonal lines in FIG. It is not necessary to stop the discharge of cement milk even in the steps of ,.

By such a procedure, the impermeable walls 30, 30
As shown in FIG. 3, is constructed by opening in a substantially eight-shape toward the contaminated groundwater streamlines X, X, and is connected to the end of each impermeable wall at the position of the opening 30A, the purification wall 10, Ten are created. Therefore, for example, the two purification walls 10 and 10 can purify the contaminated groundwater flow in a portion corresponding to a width approximately 2 to 3 times the width, but the purification wall 10 depends on the flow rate of the collected contaminated groundwater. Of course, it is possible to adjust the amount of iron powder composing No.

[0024]

According to the purification method of the present invention, a purification wall for a contaminated groundwater flow in a high-depth region can be formed extremely efficiently, and by using a continuous purification wall, expensive iron powder for pollution purification is not wasted. Can prevent use. In addition, by using the impermeable wall and multiple purification walls together, extremely reliable and efficient purification of contaminated groundwater could be implemented, and the construction period could be shortened. Furthermore, according to the purification method of the present invention, the above-mentioned purification wall with good purification efficiency enables normal iron powder to be used at a weight ratio of about 10%. Could be very low.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a purification wall according to a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of the underground where the purification wall of FIG. 1 is formed.

FIG. 3 is a cross-sectional view of a purifying wall and a water blocking wall according to a second embodiment of the present invention.

FIG. 4 is a vertical cross-sectional view of the underground where the purification wall of FIG. 3 is formed.

FIG. 5 is a side view of a triaxial auger forming the purification wall of the present invention.

FIG. 6 is an explanatory diagram of a purification wall forming process using a triaxial auger.

FIG. 7 is an explanatory diagram of a procedure of a purification wall creating process.

[Explanation of symbols]

10 Purification wall 20 Contaminated area soil 21 Ground surface 22 Impermeable layer 23 Contaminated groundwater basin 24 Groundwater level 30 impermeable wall

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nobuo Hamamoto             3-1-2 Iwamotocho, Chiyoda-ku, Tokyo Naruko             Business Tokyo branch F-term (reference) 4D050 AA20 AB19 BA02 BD03

Claims (4)

[Claims] 1. A groundwater purification method of the type in which a continuous purification wall is constructed underground by using a multi-axis auger, the method comprising continuously feeding iron powder from a drilling head of the auger during a drilling process by the auger. It includes a drilling and mixing step of discharging and stirring and mixing the iron powder and the excavated soil at the current position, and by repeating this step, a purification wall consisting of a continuous underground wall of the iron powder mixed soil is formed, and the purification wall is contaminated. A method for purifying groundwater, characterized in that it is purified by the passage of a water stream, and the purification wall has a sufficient width and depth for the contaminated water stream to be purified. 2. The groundwater purification method according to claim 1, wherein both sides of the purification wall are laid with impermeable walls for guiding a contaminated water flow to the purification wall. Groundwater purification method. 3. The groundwater purification method according to claim 2, wherein the purification walls are arranged in a plurality of rows on the upstream and downstream sides of the groundwater flow. 4. The groundwater purification method according to claim 1, wherein the purification wall is constructed at a depth reaching at least the groundwater level to the impermeable layer. Construction method.