JP4372067B2 - Contaminated soil continuous cleaning method - Google Patents

Description

  The present invention relates to a contaminated soil continuous washing method for obtaining washed soil by continuously subjecting contaminated soil slurry to settling and separation.

  At present, soil pollution is attracting attention as a serious environmental problem following air pollution and water pollution as environmental pollution. The problem of soil contamination is that the existence of the contaminated soil itself is a problem, as well as water pollution of the water that has passed through the soil, air pollution due to the diffusion of harmful volatile substances from the soil, etc. It has a great negative effect.

  Examples of methods for avoiding such adverse environmental impacts caused by soil contamination include excavation and disposal of contaminated soil, incineration of contaminated soil, cleaning treatment of contaminated soil, chemical extraction of contaminants, and biomedation. It is done. These methods are selected and implemented in consideration of the characteristics of the pollutant, the nature of the contaminated soil, the environment, treatment costs, construction period, and the like.

  However, in reality, the above-described method has a major drawback. For example, in many cases, the excavation and disposal method of contaminated soil is merely transfer of pollutants, and environmental pollution spreads instead. Since the incineration method incinerates the soil, enormous loss of energy occurs, and at the same time, the soil changes due to heat.

  In the soil cleaning treatment method, water or a cleaning agent is used. In the case of water washing, in order to use, for example, a cyclone as described in Patent Document 1 to separate soil and contaminants, fine particles in the soil composition are also discarded together with the contaminants. For this reason, some tens of percent of the soil is discarded.

In the soil cleaning treatment, many cleaning methods using a cleaning agent are also disclosed.
In the method described in Patent Document 2, for example, for washing oil-contaminated soil, water corresponding to the soil weight and a nonionic surfactant are added and washed for 10 minutes. Next, for rinsing and washing after dehydration, the same amount of water as that of the previous time is added and stirring and washing is performed for 10 minutes.

In the method described in Patent Document 3, for example, a soil cleaning agent 5 times the mass of the contaminated soil is added and stirred for 15 minutes. After that, it is dehydrated and further washed with water 3 times the mass of the soil.
In a method described in another document, as a method for washing soil with poorly water-soluble organic matter, a nonionic surfactant is added to the washing water and washed, and then further treated with iron salt and high salt to treat the contaminated water. A molecular flocculant is added.

As described above, the use of a cleaning agent and a long processing time are economically disadvantageous.
In addition, in the chemical extraction treatment method, there is a possibility that the soil is further contaminated with a cleaning agent or an extractant, and in biomedation, the work period is prolonged due to the delayed effect.

As described above, there are many problems with the conventionally known soil cleaning methods, but the preconditions for soil treatment such as the types of pollutants in the contaminated soil and the contaminated environment may be complicated, so the cost of soil purification is high. Currently, the method is employed, and there is a demand for a soil remediation method that can realize cost reduction.
JP 2003-251330 A JP 2003-1238 A JP 2003-119495 A

  The present invention has been made to solve the conventional problems as described above, and after the slurry is made with the contaminated soil and the diluted water, the slurry is purified and contaminated by continuously settling and separating the slurry. Water that is washed with soil that has almost the same composition as the soil and has no change in quality, and that treats contaminated water that contains pollutants and effectively circulates the collected water as dilution water for use. The purpose is to reduce the amount of

  As a result of diligent research to solve the above-mentioned problems, the present inventor uses only water as a cleaning medium in consideration of the influence on the environment, and dilutes contaminated soil with water to form a slurry. As a result, the present inventors have completed the present invention.

That is, the present invention is as follows.
(1) (a) A slurrying step in which diluted water is added to contaminated soil composed of soil particles, contaminants, and contained water to form a slurry in which the contaminants are uniformly dispersed in the diluted water and the contained water.
(B) The slurry is divided into a downward flow in which soil particles are mainly present in the settling tank and an upward flow in which dilution water containing pollutants is mainly present, so that the soil particles and the contaminants are continuously separated. Sediment that separates and discharges soil containing entrained water in which contaminants are dispersed continuously from the lower part of the separation tank, and continuously discharges contaminated water in which contaminants are dispersed from the upper part of the separation tank Separation process,
Contaminated soil continuous washing method characterized by having.

(2) The contaminated soil continuous washing method according to the above (1) having a plurality of sedimentation separation steps in order to add dilution water to the washing soil again to form a slurry and to repeatedly perform the sedimentation separation operation.
(3) In the plurality of sedimentation separation steps, each sedimentation separation tank is sequentially disposed below, and the slurry is transferred to the next sedimentation separation tank by using gravity. The contaminated soil continuous cleaning method described.

(4) The method for continuously washing contaminated soil according to (1) above, wherein contaminants are removed from the contaminated water discharged from the settling tank and used as a dilution water for making a slurry.
(5) The contaminated soil continuous cleaning method according to (1), wherein the slurrying step includes a slurrying device and a slurry transfer device.

(6) In the slurrying step, when the total volume of soil particles contained in the unit volume of the contaminated soil is S, the volume of water contained is G, and the volume of the pollutant is P, the volume of contaminants remaining in the washed soil is volume. In order to reduce to P1, the continuous washing | cleaning method of the contaminated soil as described in said (1) characterized by operating on the conditions where the volume W of the water added to a contaminated soil satisfies the following (c) and (d).
(C) W ≧ (P / P1-1) × G
(D) (G + W) /S≧1.5

  (7) The sedimentation separation tank has a slurry injection port, a contaminated water discharge port, and a slurry sediment discharge port, and when the diameter or equivalent diameter of the sedimentation separation tank is D, the sedimentation tank is provided at the top of the sedimentation separation tank. The method for continuously washing contaminated soil according to (1) above, wherein the slurry inlet is installed below the contaminated water outlet by 0.2D or more.

  (8) The sedimentation separation tank has a slurry injection port, a contaminated water discharge port, and a slurry sediment discharge port. When the diameter or equivalent diameter of the sedimentation separation tank is D, the sedimentation tank is provided at the bottom of the sedimentation separation tank. The method for continuously washing contaminated soil according to (1) above, wherein the slurry inlet is installed above the slurry sediment outlet by 0.2D or more.

  (9) The contaminated soil continuous washing method according to the above (7) or (8), wherein the sedimentation separation tank has a control means for retaining the soil particle sediment at the upper part of the slurry sediment discharge port.

Hereinafter, the present invention will be described in detail.
The invention according to the above (1) includes a slurrying step in which a soil contaminated with oil, heavy metals, organic compounds, inorganic compounds and their combined contaminants is mixed with stirring water and stirred to form a slurry; It is characterized by having a sedimentation separation process in which the sedimentation is continuously separated and separated into slurry sediment as washing soil and contaminated water containing contaminants.

  The contaminated soil to be cleaned is composed of soil particles, water contained therein, and contaminants. In many cases, the volume of the soil particles and the volume of the contained water are substantially the same. Dilution water is added to this contaminated soil to make a slurry. Although it does not specifically limit as dilution water to be used, As mentioned later, the water which removed the contaminant from the contaminated water discharged | emitted from a sedimentation tank can be used. Most of the contaminants in the contaminated soil before washing are present between the soil particles, and the amount of the contaminants entering the soil particles is small. Therefore, contaminants that enter the soil particles and are present can be ignored as objects to be cleaned.

  The soil particle size is distributed from about 20000 microns to a particle size of 1 micron or less. Similar to liquid contaminants, heavy metals are present between soil particles in the form of fine particles or metal compounds of several micron diameter metals themselves, depending on the production process.

  When making a slurry by adding dilution water to the contaminated soil, the slurry is passed through a water jet pump, slurry pump, or stirring device to obtain a homogeneous slurry of soil particles, contained water, contaminants and dilution water. I can do it. In the slurry, the contaminants form a homogeneous dispersion in the contained water and dilution water. In this state, the total amount of contained water and dilution water compared to the concentration of contaminants in the contained water before washing. It is diluted in inverse proportion to. Such a state is the slurrying step.

  Next, the slurry is continuously transferred to a sedimentation tank. The transferred slurry is poured into the sedimentation tank and flows out into the staying slurry. The slurry that has flowed into the settling tank is divided into a downward flow and an upflow at a flow rate that is inversely proportional to the inner diameter of the settling tank. In the downflow, there are mainly soil particles whose specific gravity is greater than that of water. There are accompanying flows in the soil particles. On the other hand, most of the diluting water is present in the upward flow, accompanied by soil fine particles corresponding to the flow velocity of the upward flow. By continuously injecting the slurry transferred from the previous step, the downward flow and the upward flow can be continuously maintained.

  Contaminants uniformly dispersed in the contained water and the dilution water are proportionally distributed to the amount of water in the downward flow and the upward flow and are discharged from the sedimentation separation tank. Most of the soil is discharged out of the tank as a downflow, but at the same time there are dilute and reduced pollutants in the accompanying flow. As a result, pollutants in the soil are reduced and a washed soil is obtained.

  If the specific gravity of the pollutant is significantly different from the specific gravity of water, it will not be proportionally distributed between the descending flow rate and the ascending flow rate, but it may be dealt with by adjusting the flow rate by adjusting the amount of dilution water. For example, in the case of heavy metal contamination, the specific gravity difference with water is large, but as the contamination situation, the heavy metal is minute and adheres to the soil particles to form a colloid with water, so it is proportional to the descending flow rate and the rising flow rate Allocated, the diluted cleaning effect is the same. The sedimentation separation as described above is performed in the sedimentation separation step.

  The invention according to the above (2) is carried out in order to further reduce the amount of pollutants because the cleaning soil obtained in (1) contains dilute pollutants in the accompanying flow. That is, after further adding dilution water to the washing soil obtained in (1) to form a slurry by stirring and mixing operation, sedimentation separation is performed, which is performed continuously in the sedimentation separation step of (1). It is a process. It is preferable to install a plurality of the same sedimentation separation steps and perform sedimentation separation continuously, so that washing can be enhanced and contaminants in the washing soil can be further reduced.

  When a plurality of sedimentation separation steps are installed in this way, it is also preferable to arrange the sedimentation tanks in multiple stages and sequentially below and transfer the slurry using gravity.

  In the present invention, the contaminated water continuously discharged from the sedimentation tank is subjected to water treatment corresponding to the contaminated contaminants. For example, in the case of oil contamination, the oil can be removed from the water by floating separation. In the water, there are permissible oil and soil fine particles accompanying the upward flow of the settling tank. The invention according to the above (4) circulates and uses the water as the diluting water in the slurrying step, thereby reducing the amount of diluting water used in the slurrying step and improving the economic efficiency.

  In the invention according to the above (5), the slurrying step includes a slurrying device and a slurry transfer device. Examples of the slurrying device include a water jet pump, a slurry pump, a line mixer, a stirring device, and the like, and a slurry can be made from contaminated soil and diluted water using these. Examples of the slurry transfer device include a slurry pump and a snake pump. In this slurrying step, it is also possible to combine slurrying and slurry transfer like a water jet pump.

The invention relating to the above (6) will be described.
In the present invention, the slurry produced in the slurrying process is transferred to the next sedimentation and separation process, and continuously settled and separated in the sedimentation tank, so that most of the soil particles become a downward flow, and the pollutants are separated from the soil particles. Contaminated water containing water is discharged out of the tank as an upward flow. The concept of this phenomenon is as follows.

The mass balance of the soil slurry fluid in the settling tank is shown in FIG.
In FIG. 2, the flow rate (V) of slurry continuously flowing into the settling separation tank, the flow rate of contaminated water discharged continuously from the upper part of the settling separation tank (V2), and continuously discharged from the lower part of the settling separation tank. The flow rate (V1) of the washed soil is as follows.

V = S + G + W + P
V2 = S2 + W2 + P2
V1 = S1 + G + W1 + P1
V = V1 + V2
In addition, the symbol of a soil slurry fluid is as follows (a unit is a volume per time).

V: Flow rate of slurry continuously flowing into the settling tank (ie, V1 + V2)
V1: Flow rate of washing soil continuously discharged from the lower part of the settling separation tank V2: Flow rate of contaminated water discharged continuously from the upper part of the settling separation tank S: Total volume of soil particles in the contaminated soil (ie, S1 + S2) )
S1: Total volume of soil particles continuously discharged from the lower part of the sedimentation tank S2: Total volume of soil particles continuously discharged from the upper part of the sedimentation tank

P: Total volume of pollutants in the contaminated soil (ie, P1 + P2)
P1: Total volume of contaminants continuously discharged from the lower part of the sedimentation tank P2: Total volume of contaminants continuously discharged from the upper part of the sedimentation tank W: Total volume of diluted water added to the contaminated soil ( That is, W1 + W2)
W1: Total volume of diluting water continuously discharged from the lower part of the settling separation tank W2: Total volume of diluting water continuously discharged from the upper part of the settling separation tank G: Present along with contaminated soil before washing Soil-containing water volume T: Total amount of water in the unit soil in the slurry at the inlet of the settling tank (ie, contained water G + diluted water W)

Further, symbols other than the slurry fluid are as follows.
u1: Average speed when the fluid V1 flows down the sedimentation tank (ie, V1 / A)
u2: Average speed when the fluid V2 moves up the sedimentation tank (ie, V2 / A)
This u2 is equal to the sedimentation speed R of the soil particle diameter at which the amount of accumulated fine particles of the soil becomes S2.

A: Area of the cross section of the sedimentation tank (the cross sectional area that realizes U2)
D: Diameter or equivalent diameter of the cross section of the sedimentation tank L1: Vertical section length of the sedimentation tank in the range where the fluid V1 flows down L2: Vertical section length of the sedimentation tank in the range where the fluid V2 rises R: Soil Particle settling velocity

The conditions for transferring the slurry are preferably (G + W) /S≧1.5 in order to secure the fluidity of the slurry and transfer the piping.
In order to realize the pollutant P1 of the cleaning soil from the pollutant content P per unit volume of the contaminated soil, the conditions of the dilution water W are as follows.

P1 / P = G / T
T = (P / P1) × G
W = TG = (P / P1-1) × G
Therefore, it is desirable that the amount of dilution water satisfies the following conditions.
W ≧ (P / P1-1) × G

  The invention according to the above (7) or (8) relates to the position of the slurry inlet in the sedimentation tank. The sedimentation tank has a slurry inlet, a polluted water outlet, and a slurry sediment outlet. The slurry injected into the sedimentation tank is divided into a downward flow and an upward flow, and the upward flow velocity is the upward flow. It becomes below the sedimentation rate of the soil particles inside. The upward flow speed is determined by setting the cross-sectional area A of the sedimentation tank so as to realize the speed at which the soil particles contained in the contaminated water become S2. Specifically, In other words, A is determined from V2 / A, which is equal to the sedimentation velocity R of the soil particles in the water where the cumulative amount of soil particles in the soil soil distribution in the contaminated soil is S2. However, the upward flow velocity varies depending on the shape of the soil particles, the property of the pollutant, the shape of the sedimentation separation tank, and the like, and is an approximate numerical value as an operating index.

  In (7) above, when the diameter or equivalent diameter of the cross section of the settling tank is D, the slurry inlet to the settling tank is at the liquid level at the discharge port of the upward flow (that is, above the settling tank). It is preferable to be installed at a distance of 0.2D or more from the position of the contaminated water discharge port provided. When the slurry inlet is installed at the above position, a transition zone is secured so that the streamline of the upward flow is as vertical as possible, and sedimentation separation is performed efficiently.

In the present invention, the equivalent diameter of the cross section of the sedimentation separation tank refers to the diameter of the circle when assuming a circle having an area equal to the cross-sectional area of the sedimentation separation tank.
The shape of the sedimentation tank used in the present invention is not particularly limited as long as the slurry can be circulated. The cross-sectional shape may be any shape such as, for example, a circle, a quadrangle, or a triangle, and the vertical cross-sectional shape may be, for example, a quadrangle, an inverted triangle, a combination of a quadrangle at the top and a triangle at the bottom, a square at the top, and a semicircle at the bottom. Any shape such as a combination of semi-elliptical shapes may be used. Moreover, the slurry inlet and the contaminated water outlet of the settling tank may be divided into a plurality.

In (8) above, when the diameter or equivalent diameter of the cross section of the sedimentation separation tank is D, the slurry injection port to the sedimentation separation tank is at the liquid level at the discharge port of the downflow (that is, at the bottom of the sedimentation separation tank). It is preferable to be installed above 0.2D or more from the position of the provided slurry sediment outlet. When the slurry inlet is installed at the above position, a transition zone is secured so that the streamline of the downward flow is as vertical as possible, and sedimentation separation is performed efficiently.
Also, the downflow fluid is a slurry of soil particles and water, and sedimentation is efficiently performed, and at the same time smooth discharge of the slurry is important, so an oblique streamline toward the sediment outlet is secured. It is also important to do. This sediment discharge port may be divided into a plurality.

  The invention according to the above (9) is characterized in that the sedimentation separation tank has a control means for retaining the soil particle sediment at the upper part of the slurry sediment discharge port. By providing such a flow rate control means, it is possible to prevent the slurry injected into the sedimentation separation tank from flowing out directly from the discharge port at the bottom of the sedimentation separation tank, and the washing soil that has settled after a certain residence time has passed. In order to increase the soil density to a target value, for example, the pressure at the bottom of the storage tank can be detected and the flow rate can be controlled to be within a certain pressure range.

  The contaminated soil continuous cleaning method of the present invention is compact in terms of equipment, and by using only water, the target cleaned soil is obtained due to the effect of diluting water, and additives such as surfactants and cleaning agents are unnecessary. is there. Furthermore, since most of the water to be used can be reused as circulating water, it can be said that it is an economically advantageous and environmentally friendly cleaning method. Moreover, the composition of the obtained washing soil is substantially the same as the soil composition before washing, and is not subjected to any treatment such as heating, and therefore has no alteration. Therefore, there is an advantage that it can be backfilled in the original soil.

Hereinafter, the present invention will be described more specifically based on the drawings.
FIG. 1 is a schematic view showing an example of the contaminated soil continuous cleaning method of the present invention.

  The soil receiving tank 3 mixes the contaminated soil 1 with the diluting water that circulates internally from the slurry receiving tank 5 through the pipe 6 to form a slurry. The water jet pump 4 further refines the slurry and transfers it to the slurry receiving tank 5. The transfer pump 7 transfers the slurry from the slurry receiving tank 5 to the sedimentation tank 9. The sedimentation / separation tank 9 separates and separates the slurry into washing soil 11 and contaminated water 12 which are slurry sediments. The slurry pump 10 discharges the slurry sediment (washing soil) 11 separated in the sedimentation tank 9. The polluted water 12 that is discharged after rising in the settling tank 9 is separated by the separating device 13 and circulated and reused as dilution water. This shortage of dilution water is supplied from makeup water 18.

Since the purpose of the soil receiving tank 3 is to add fluidity by mixing contaminated soil and water, it is preferable to hold a stirrer inside the tank. In order to promote slurrying, it may be fluidized with a water spray while the contaminated soil is transferred to a soil receiving tank by a conveyor or the like, and a method of adding water using a horizontal rotating drum as the soil receiving tank is also possible. .
It is desirable to remove large gravels having a diameter of 20 mm or more in the contaminated soil before putting them into the soil receiving tank 3.

  The water jet pump 4 serves to refine and transfer the slurry of the contaminated soil and water produced in the soil receiving tank 3, but instead of the water jet pump, the slurry is refined using a line mixer. It is also possible to use a process that combines the transfer using In each of the above methods, it is preferable to increase the number of stages according to the necessity of making the slurry fine.

Since the slurry receiving tank 5 needs to hold the slurry in a homogeneous state, a stirrer can be installed inside the slurry receiving tank, or a rotating drum storage tank or the like can be used.
The sedimentation / separation tank 9 is preferably a tank in which a vertical circular cylinder part and a conical part are combined, but a rectangular cylinder tank is also possible. A screw may be installed in the conical portion and a discharge mechanism may be installed.

The separation device 13 is preferably a horizontal floating separation tank, but water and contaminants can also be separated by a centrifuge.
Examples of soil contaminants include oil, heavy metals, organic matter, and complex contaminants. The contaminated soil continuous cleaning method of the present invention can be applied to any contaminant.

Next, the case where oil contaminated soil is washed will be described as an example.
The oil-contaminated soil 1 is made into a small lump and put into a soil receiving tank 3 and mixed with dilution water to become a slurry. The slurry is sucked and transferred by the water jet pump 4 and stored in the slurry receiving tank 5. Dilution water flows into the water jet pump 4 from the pipe 19 and is mixed with the slurry. At that time, the small lump of soil in the slurry becomes a slurry dispersed to the level of soil particles. At this time, the oil existing between the soil particles is peeled off and dispersed in water. Therefore, it becomes a relatively homogeneous slurry composed of the three components of soil particles, water and oil. The amount of dilution water 20 necessary to achieve the target cleaning is added to adjust the oil concentration of the slurry.

  The slurry is constantly circulated and stirred by the slurry pump 7 so as not to settle and separate. A part of the circulating slurry is continuously supplied quantitatively to the sedimentation tank by the FIC 21 of the flow rate indicating control valve. The slurry supply port is located in the middle part of the sedimentation separation tank 9, and the soil particles settle down and move downward while being deposited at the bottom of the sedimentation separation tank, and are discharged as slurry sediment. At that time, diluted oil exists in the accompanying water. The slurry sediment 11 is discharged by the slurry pump 10 controlled by the PIC 22 of pressure instruction control so that the pressure in the tank at the bottom of the settling separation tank 9 becomes constant, and washing soil is obtained.

  On the other hand, dilution water, oil, and fine soil particles that rise without settling are discharged out of the settling separation tank as contaminated water 12. The discharged contaminated water is discharged through the water / oil separator 13 as waste oil (pollutant) 14 from the upper part of the separator. From the lower part of the separation device, purified water containing soil fine particles accompanying the contaminated water is obtained and becomes the circulating water 15. The circulating water is boosted by the pump 16 and used as the driving water for the dilution water 20 and the water jet pump 4.

  When oil-contaminated soil was washed using the contaminated soil continuous washing method of the present invention, the following results were obtained.

The composition of the treated amount 1 m ³ / hr of the contaminated soil 1 was soil particles 0.48 m ³ / hr, contained water 0.50 m ³ / hr, and oil 0.02 m ³ / hr. This is put into a 500 liter earth receiving tank 3 to form a slurry, and further, the driving water 19 of the water jet pump 4 is added with ³ m ³ / hr and 1.5 m ³ / hr of the dilution water 20 to add slurry. after the result of the sedimentation in the settling tank 9 of a cylindrical conical volume of 100 liters diameter 500 mm, soil particles 0.46 m ³ / hr as a cleaning soil 11, entrained water 0.55 m ³ / hr and the oil 0.002m ³ / hr was obtained.

On the other hand, the contaminated water 12, to obtain an aqueous 4.45m ³ / hr, soil particles 0.02 m ³ / hr and the oil 0.018 m ³ / hr fluid mixture. Following this contaminated water, and separated by the water-oil separation device 13, waste oil 0.018 m ³ / hr and entrained water 0.05 m ³ / hr and the circulating water 4.40m ³ / hr and circulated water to soil particles 0 0.02 m ³ / hr was recovered. As a result, the oil in the cleaning soil was reduced to almost 10%.

It is the schematic which shows an example of the contaminated soil continuous washing | cleaning method of this invention. It is a figure which shows the mass balance of the soil slurry fluid in a sedimentation tank.

Explanation of symbols

3 Soil receiving tank 5 Slurry receiving tank 9 Sedimentation separating tank 13 Separator

Claims (5)

(A) a slurrying step of adding diluted water to contaminated soil comprising soil particles, contaminants and contained water to form a slurry in which the contaminants are homogeneously dispersed in the diluted water and the contained water;
(B) The slurry is divided into a downward flow in which soil particles mainly exist in the settling separation tank and an upward flow in which dilution water containing pollutants mainly exists, and the pollutants are in the downward flow and upward flow. Proportionally distributed to the amount of water, and the soil particles and pollutants are not separated from the swirl flow as an external force, but use the settling action due to the dead weight of the soil particles, and are accompanied by the contained water in which the pollutants are dispersed. A sedimentation step of continuously discharging the washing soil from the lower part of the sedimentation tank, and continuously discharging the contaminated water in which the pollutants are dispersed from the upper part of the sedimentation tank;
Have a further, said settling tank slurry inlet, a contaminated water outlet and the slurry sediment outlet, the upper part of the slurry sediment outlet, the soil particles sediment the precipitated separation tank bottom A method for continuously washing contaminated soil, comprising means for controlling the slurry sediment discharge flow rate so as to stay and detect the pressure at the bottom of the sedimentation tank to be within a certain pressure range .   The method for continuously washing contaminated soil according to claim 1, comprising a plurality of sedimentation separation steps in order to add dilution water to the washing soil again to form a slurry and to repeatedly perform the sedimentation separation operation.   3. The contaminated soil continuation according to claim 2, wherein in each of the plurality of sedimentation separation steps, the sedimentation separation tanks are sequentially disposed below, and the slurry is transferred to the next sedimentation separation tank using gravity. Cleaning method.   The contaminated soil continuous cleaning method according to claim 1, wherein the contaminated soil is removed from the contaminated water discharged from the settling tank and circulated as dilution water for making a slurry.   The contaminated soil continuous cleaning method according to claim 1, wherein the slurrying step includes a slurrying device and a slurry transfer device.

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