JP3295741B2 - How to clean contaminated soil - Google Patents

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 contaminated soil located below an impermeable layer deeper than a groundwater level.

[0002]

2. Description of the Related Art Most conventional methods for purifying contaminated soil have mostly been directed to contaminated soil above the level of groundwater. As a method for treating contaminated soil below the groundwater level, for example, there is a process described in JP-A-3-202586, which is a system for simultaneously sucking gas extracted from contaminated soil and groundwater.

[0003]

Problems to be Solved by the Invention The above-mentioned conventional method for purifying contaminated soil has the following problems. <A> Conventionally, since a system extracts gas and groundwater from a single well, the purifying range is limited. <B> In addition to the well for extracting gas, it is necessary to provide a well for lowering the groundwater level and a well for injecting air, which is extremely uneconomical.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has as its object to provide the following method for purifying contaminated soil. <A> A purification method capable of efficiently purifying a wide area. <B> A purification method that can minimize the number of drilled wells.

[0005]

Means for Solving the Problems In order to achieve the above object, a method for purifying contaminated soil according to the present invention is a method for purifying contaminated soil at a position lower than the level of groundwater. In a state surrounding the area, a pumping system for suctioning groundwater is installed to a position lower than the contaminated layer, and the contaminated stratum is forcibly formed as a ventilation layer by sucking groundwater with this pumping facility group. A method for purifying contaminated soil is provided in which compressed air is supplied to the ventilation layer, and the compressed air that has passed through the contaminated formation layer that has become the ventilation layer is suctioned to the ground. Furthermore, the method for purifying contaminated soil according to the present invention is a method for purifying contaminated soil at a position lower than the water level of groundwater, in a state surrounding the contaminated area, for sucking groundwater to a position lower than the contaminated layer. Pumping facilities will be installed, and some pumping facilities will have sand columns around the water intake pipes.
Compressed air is supplied to the ground through this sand column, and an intake pipe is installed at a substantially central position surrounded by pumping equipment to extract air, and the groundwater level is raised by the pumping equipment from the contaminated soil to be purified. The contaminated soil is supplied to the contaminated soil from sand columns around the pumping equipment, and the compressed air that has passed through the contaminated soil is taken out to the ground by an intake pipe. It is a characteristic.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for purifying contaminated soil according to the present invention will be described below with reference to the drawings. <A> Preconditions The purification method of the present invention is intended for a case where a contaminated soil layer exists at a position lower than the natural groundwater level W1. In addition, an impermeable layer such as a clay layer exists underground,
This corresponds to the case where a contaminated layer with good air permeability such as a gravel layer exists below the impermeable layer.

<B> Installation of Pumping Equipment The method of the present invention is not a method of simultaneously sucking groundwater and an extracted gas, but a method of separately suctioning them to the ground. As the pumping equipment, ordinary pump drainage called deep well and other well-known equipment can be adopted, but a well point will be described as an example. For that purpose, first, a well point is set as the pumping equipment 1 to a position lower than the contaminated layer while surrounding the contaminated area. This pumping equipment 1
Is a device for sucking groundwater, which consists of a pipe for water absorption and a point at the tip. The point is a nozzle with a small hole, which sucks groundwater from the point at the tip of the underground by applying a negative pressure to the ground side of the water absorption pipe.

For this purpose, a cylindrical hole is previously opened in the ground, a point is suspended in the cylindrical hole, and the periphery of the pipe is fixed to the vicinity of its tip by a solidified wall 11 such as cement grout. However, only near the tip of the pipe, if the surroundings are solidified, groundwater cannot be sucked. Therefore, the area around the tip is a permeable wall 1 such as sand.
Surrounded and protected by 2. This group of pumping facilities is arranged so as to surround the contaminated area. Other methods can be widely used as long as the equipment can expect the same operation as the well point.

<C> Sand Pillar Among a group of many pumping facilities, a pipe arranged on the outer periphery of the contaminated area is constituted as a pumping / injecting pipe 2. The pipe 2 is a cylindrical body having a sand column 21 provided around a water absorption pipe of the water pumping facility 1. That is, after the pipe of the pumping equipment 1 is inserted into the hole, sand, gravel, etc. are thrown around the pipe and the
Form one. The sand column 21 supplies compressed air into the ground, but it is necessary to supply compressed air only from the lower part thereof to only the contaminated layer to be purified. For this purpose, a steel pipe 22 is arranged on the upper part of the sand column 21 to insulate the sand column 21 from the ground, and only the lower part of the sand column 21 is exposed and located in the contamination layer. The upper end of the steel pipe is closed so that a required amount of compressed air can be supplied through the valve 23 into the steel pipe 22, that is, into the sand column 21.

<D> Intake Pipe An intake pipe 3 for extracting air is installed at a substantially central position of the contaminated area surrounded by the group of pumping facilities. This pipe constitutes a hollow part 31 having an upper part hardened by cement grout or the like, and a pipe containing a filter 32 at its lower end part. This filter 32 is placed and installed in the target contaminated layer.

[Usage method] Next, an actual purification method will be described.

<a> Decrease in groundwater level A negative pressure is supplied to a group of pumping facilities surrounding the contaminated area to lower the natural groundwater level W1 to a position W2 lower than the contaminated soil to be purified. By lowering the groundwater level, the contaminated layer that previously existed in the groundwater became
Ventilation is possible. In other words, the contaminated layer is forcibly formed as a ventilation layer by sucking groundwater by the group of pumping equipment.

<B> Supply of compressed air When the groundwater level drops to a position lower than the contaminated soil, the sand column 2 of the pumping / air injection pipe 2 arranged on the outer periphery of the area
From 1 supply compressed air to the contaminated soil. Since the periphery of the upper part of the sand column 21 is protected by the steel pipe, the compressed air supplied to the pumping / inlet pipe 2 is supplied from the tip of the sand column 21 to the contaminated layer having improved air permeability after drainage. .

<C> Intake of contaminated air When air passes through contaminated soil, contaminants in the contaminated layer are extracted and move in the contaminated layer together with compressed air. This contaminated air is taken out to the ground via the filter 32 of the intake pipe 3. The contaminated air taken out to the ground is supplied to various known processing apparatuses such as activated carbon adsorption equipment for processing. In this way, the substance in the contaminated layer is recovered as gas on the ground, and the contaminated layer is gradually purified.

[0014]

As described above, the method for purifying contaminated soil according to the present invention has the following effects. <B> A contaminated area that is deeper than the groundwater level is formed as a layer that can be forcibly ventilated by lowering the water level. Therefore, efficient purification of pollution can be easily performed. <B> Contaminated groundwater and contaminated gas are separately discharged to the ground for treatment. Therefore, since the processing after being taken out to the ground is easy, the equipment can be operated simply and economically. <C> Since the entire purification range is formed as an unsaturated region by a method of lowering the groundwater level, purification over a wide range can be performed efficiently. <D> Since the well for lowering groundwater and the well for injecting air can be used in common, the number of wells can be reduced, which is extremely economical. <E> If a valve is attached to the pumping / injection pipe, control can be easily performed so as to supply a uniform air flow to the entire area to be purified. Further, purification can be performed efficiently by making the length of the pipe reach the depth of the contamination source.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method for purifying contaminated soil according to the present invention.

FIG. 2 is an explanatory view of a method for purifying contaminated soil according to the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-202586 (JP, A) JP-A-4-309526 (JP, A) JP-T4-501231 (JP, A) JP-T-4- 501893 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B09C 1/00-1/08 B09B 3/00 E02D 3/10

Claims (2)

(57) [Claims] 1. A method for purifying contaminated soil at a position lower than the water level of groundwater, comprising installing a pumping facility for sucking groundwater to a position lower than the contaminated layer while surrounding the contaminated area. By drawing groundwater with this pumping equipment group, the contaminated formation is forcibly formed as a ventilation layer, and compressed air is supplied to the ventilation layer. A method for cleaning contaminated soil by suction. 2. A method for purifying contaminated soil at a position lower than the water level of groundwater, comprising installing a pumping facility for sucking groundwater to a position lower than the contaminated layer while surrounding the contaminated area. However, some pumping facilities are provided with a sand column around the suction pipe, supply air into the ground through the sand column, and install an intake pipe to draw air at a substantially central position surrounded by the pumping facility. After the groundwater level is lowered to a level lower than the contaminated soil to be purified by the pumping equipment, compressed air is supplied to the contaminated soil from sand columns around the pumping equipment, and the compressed air that has passed through the contaminated soil is A method for purifying contaminated soil by taking it to the ground through an intake pipe.