JP2001149913A - Cleaning method of contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To clean the soil contaminated with oil and heavy metals, etc., on the spot easily and inexpensively. SOLUTION: This cleaning method of contaminated soil comprises a process for stirring and mixing the contaminated soil and cleaning liquid, a process for classifying coarse particles from the mixture of the contaminated soil and the cleaning liquid, a process for further cleaning the coarse particles with the cleaning liquid and separating the contaminated material together with the cleaning liquid by using a classifier 11, a process for precipitating the residual fine particles after classifying the coarse particles with a precipitation unit 8 and performing solid-liquid separation and a process for recovering the cleaning liquid, separating, treating or disposing the contaminated material. When the contaminated material is oil, water and water glass are used as the cleaning liquid. When the contaminated material is heavy metals, water and an acidic solution or alkaline solution are used as the cleaning liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning and contaminating soil contaminated with oil such as kerosene, light oil, heavy oil, or heavy metals.

[0002]

2. Description of the Related Art In recent years, a situation often arises in which crude oil or heavy oil that has flown to the sea due to a tanker accident or the like drifts on the shore and causes environmental pollution. In such cases, caustic soda, hydrogen peroxide,
Alternatively, a method of separating and removing oil from contaminated soil using kerosene or a surfactant has been attempted.

[0003] When soil is contaminated with harmful heavy metals, an effective and appropriate method for separating and removing heavy metals from the contaminated soil has not yet been established. In order to prevent this, measures have been taken to strictly contain them.

[0004]

However, the conventional cleaning method for oil-contaminated soil as described above cannot be carried out simply and inexpensively on site, and it is fundamental to simply contain heavy metal-contaminated soil. From the above, it is urgently necessary to develop effective means for easily and inexpensively cleaning soil contaminated with oil, heavy metals, and the like.

[0005]

SUMMARY OF THE INVENTION The invention of claim 1 is a method for cleaning and cleaning contaminated soil, comprising the steps of stirring and mixing the contaminated soil and the cleaning liquid; A step of classifying coarse particles from the mixture, a step of further washing the coarse particles with a washing liquid and separating contaminants together with the washing liquid by a classifier, and a step of sedimenting the remaining fine particles obtained by classifying the coarse particles in a sedimentation device to form a solid-liquid And a step of collecting a cleaning liquid to separate and treat or dispose of contaminants.

According to a second aspect of the present invention, in the first aspect of the invention, water and water glass are used as the cleaning liquid when the contaminant is oil.

According to a third aspect of the present invention, in the first aspect of the invention, when the contaminant is a heavy metal, water and an acid or alkali solution are used as the cleaning solution.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A cleaning method according to a first embodiment of the present invention will be described with reference to FIG. The first embodiment is intended for soil contaminated with oil such as kerosene, light oil, or heavy oil, and uses water and water glass (sodium silicate solution) as a cleaning liquid.

In the first embodiment, contaminated soil excavated at the site is put into a receiving hopper 1 and supplied to a mixing device 2 by a conveyor such as a belt conveyor. A pulverizer or a stirrer can be suitably used as the mixing device 2, and washing water is supplied to the mixer to stir and mix.

After stirring and mixing for a predetermined time, the mixture is transferred to a sieve device 3 to remove debris and the like having a large particle size (those having a particle size of about 2 mm or more). The fine earth and sand that has passed through the sieve device 3 is sent from the primary receiving tank 4 to the classifying device 5, where washing water is added.

In the classifier 5, coarse particles (mainly sand) having a size of about 74 μm or more are classified and sent to the secondary receiving tank 6. Silt and clay, which are the remaining fine particles, are sent to the muddy water receiving tank 7 together with washing water. send.

A coagulant (PAC or the like) is added to the fine particles sent to the muddy water receiving tank 7 and sent to a sedimentation device 8 where the fine particles are settled for a predetermined time, and the sedimented fine particles are compressed by a compression device such as a filter press. After being compressed by 9 to remove water, it is recovered. The oil separated from the fine particles and floated on the liquid surface of the sedimentation device 8 is collected and disposed, and the washing water from the sedimentation device 8 is collected and treated in the primary washing water receiving tank 10 together with the washing water from the compression device 9. Then, it is circulated and used with newly supplied washing water.

On the other hand, the coarse particles are mixed with water glass as a cleaning liquid in the secondary receiving tank 6 and sent to a classification device 11 by a pump. A drum type classifier having a washing chamber can be suitably used as the classifier 11, and when the coarse particles and the washing liquid are mixed with stirring, the oil is separated from the soil by washing with water glass. And a washing liquid containing oil, which is a separated contaminant, is sent to the secondary washing water receiving tank 12. In the secondary washing water receiving tank 12, if necessary, a new washing liquid is added to adjust the pH to 10
As described above, the concentration of the water glass is adjusted to 1% or more to be used in circulation. The separated oil floats on the liquid surface of the secondary cleaning liquid receiving tank 12 and is collected and disposed.

According to the cleaning method of the first embodiment, the oil-contaminated soil is divided into coarse particles (mainly sand) and fine particles (silt or clay), and the coarse particles are separated by washing with water glass. The oil is separated by the secondary washing water receiving tank 12, and the fine particles are washed with water and subjected to solid-liquid separation in the sedimentation device 8, so that a sufficient washing effect can be obtained and, moreover, simple and efficient on-site implementation The soil after washing can be returned to the site as it is, and water or water glass as a washing liquid can be regenerated and reused repeatedly, and thus the washing cost can be sufficiently reduced.

[0015] In the above method, for example, the highly contaminated soil of about 5% by heavy fuel oil A can be cleaned to a residual concentration of about several hundred ppm. The soil may be subjected to a more advanced cleaning treatment, for example, a bioremediation treatment.

Next, a cleaning method according to a second embodiment of the present invention will be described with reference to FIG. The second embodiment is directed to a soil contaminated with heavy metals, and uses water and an acid solution such as hydrochloric acid or sulfuric acid, or an alkaline solution such as caustic soda or sodium silicate as the washing liquid.

In the second embodiment, contaminated soil excavated at the site is put into a receiving hopper 21 and supplied to a mixing device 22 by a conveyor such as a belt conveyor. A pulverizer or a stirrer can be suitably used as the mixing device 22, and an acid or alkali solution as a cleaning liquid is supplied to the mixing device 22 for stirring and mixing.

After stirring and mixing for a predetermined time, the mixture is transferred to a sieve device 23 to separate debris and the like having a large particle size. The washing solution is washed away in a water washing device 24, and then collected and backfilled on site. The washing water used here is collected in the secondary washing water receiving tank 25 and reused.

The fine earth and sand that has passed through the screen device 23 is:
The cleaning liquid is sent from the primary receiving tank 26 to the classification device 27,
The cleaning liquid is also added to the classifier 27.

In the classifier 27, coarse particles (mainly sand) of about 74 μm or more are classified and sent to the secondary receiving tank 28, and the remaining fine particles such as silt and clay are sent to the muddy water receiving tank 29 together with the washing liquid. .

The pH of the fine particles sent to the muddy water receiving tank 29 is adjusted as required, and a coagulant (PAC or the like) is added to the fine particles and sent to the sedimentation device 30, where the fine particles are allowed to stand for a predetermined time.
The sedimented fine particles are compressed by a compression device 31 such as a filter press to remove water, and then collected and backfilled on site. The cleaning liquid containing the contaminants separated from the fine particles in the sedimentation device 30 and the cleaning liquid from the compression device 31 are collected in the primary cleaning water receiving tank 32, and the heavy metals as the contaminants are separated and removed in the heavy metal treatment device 33 to the disposal facility. The washing water collected here is regenerated and recycled.

On the other hand, the coarse particles are mixed with the washing water in the secondary receiving tank 28 and sent to a classifier 34 by a pump. As the classifying device 34, a drum type classifier having a washing room can be suitably adopted. When the coarse particles and the washing water are mixed with stirring, the pollutants are separated from the soil by washing with the washing water. The coarse particles after washing are collected and backfilled at the site, and the washing water containing the heavy metals as the separated contaminants is sent from the secondary washing water receiving tank 25 to the heavy metal processing device 33, and the above-mentioned primary washing liquid receiving tank 32 And heavy metals are separated and removed.

In the second embodiment, an excellent cleaning effect can be obtained by using an appropriate acid solution or alkali solution according to the heavy metal to be treated, and, as in the first embodiment, simple and efficient on-site. It can be implemented at reasonable cost.

FIG. 3 shows a third embodiment of the present invention. The third embodiment targets heavy metal-contaminated soil similarly to the second embodiment, and similarly uses water and an acid solution or an alkali solution as a cleaning solution. (Mainly sand) is thoroughly washed with a cleaning solution and backfilled at the site, and relatively small amounts of debris and fine particles (silt, clay) are disposed of only after washing with water. .

In the third embodiment, the contaminated soil is supplied from the receiving hopper 41 to the mixing device 42, and is mixed with the washing water by stirring.

After stirring and mixing for a predetermined time, debris and the like having a large particle diameter are separated and disposed by the sieve device 43, and the fine earth and sand that has passed through the sieve device 43 is sent from the primary receiving tank 44 to the classification device 45 together with the washing water. Wash water is also supplied to the classifier 45.

The classifier 45 classifies coarse particles (mainly sand) having a size of about 74 μm or more and sends them to the secondary receiving tank 46, and the remaining fine particles such as silt and clay are transferred to the muddy water receiving tank 47 together with the washing water. send.

The fine particles sent to the muddy water receiving tank 47 are added to a coagulant (PAC or the like) and sent to a sedimentation device 48, where they are allowed to stand for a predetermined time, and the sedimented fine particles are compressed by a compression device 49 such as a filter press. After removing water by compressing, collect and dispose. The washing water containing the contaminants separated from the fine particles in the sedimentation device 48 and the washing water from the compression device 49 are collected in the primary washing water receiving tank 50, and the heavy metal as the contaminant is separated and removed in the heavy metal treatment device 51 for disposal. The collected washing liquid and washing water are regenerated and recycled.

On the other hand, when the coarse particles are stirred and mixed with the cleaning liquid in the secondary receiving tank 46, the contaminants are separated from the soil by the cleaning with the cleaning liquid. After rinsing, backfill at the site. The cleaning liquid containing contaminants from the classification device 52 is sent from the secondary cleaning liquid receiving tank 54 to the heavy metal processing device 51, and the washing water from the water cleaning device 53 is also sent to the heavy metal processing device 51, where heavy metals are separated and removed. Regenerate and recycle the cleaning solution.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the details of the steps, the cleaning liquid to be used, and the apparatuses are appropriately designed without departing from the gist of the present invention. Naturally, it is possible to make objective changes.

[0031]

According to the first aspect of the present invention, the contaminated soil is divided into coarse particles and fine particles, and the coarse particles are washed with a cleaning liquid, and the contaminants are separated and removed together with the cleaning liquid by a classifier. Particles are separated into solids and liquids in the sedimentation device, so that sufficient washing effects can be obtained and contaminated soil can be cleaned, and in addition, simple, inexpensive, and efficient washing can be performed locally, and oil and heavy metals can be removed. It is suitable to be applied when a large amount of soil contaminated with water is treated.

According to the second aspect of the present invention, since water and water glass are used as the cleaning liquid when the contaminant is oil, an excellent cleaning effect on the oil by the water glass is obtained, and the cleaning liquid is regenerated and recycled. It is economical because it is possible.

According to the third aspect of the present invention, when the contaminant is a heavy metal, water and an acid solution or an alkali solution are used as the cleaning liquid. Therefore, an appropriate acid solution or alkali solution is selected and used according to the heavy metal to be treated. Thereby, an excellent cleaning effect can be obtained, and the cleaning liquid can be regenerated and recycled.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a first embodiment of the present invention.

FIG. 2 is a system diagram showing a second embodiment of the present invention.

FIG. 3 is a system diagram showing a third embodiment of the present invention.

[Explanation of symbols]

 2 Mixing device 3 Screening device 5 Classification device 8 Sedimentation device 11 Classification device 22 Mixing device 23 Screening device 27 Classification device 30 Sedimentation device 33 Heavy metal processing device 34 Classification device 42 Mixing device 43 Screening device 45 Classification device 48 Precipitation device 51 Heavy metal processing device 52 Classification device 53 Water washing device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takuro Odawara 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation (72) Inventor Chiaki Niwa 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation In-house F term (reference) 4D004 AA41 AB02 AB03 AC07 CA07 CA10 CA13 CA15 CA35 CA40 CC03 CC12 CC13 CC20 DA02 DA10 4D071 AA01 AA42 BB13 DA03

Claims (3)

[Claims] 1. A step of stirring and mixing contaminated soil and a washing liquid; a step of classifying coarse particles from a mixture of the contaminated soil and the washing liquid; a step of further washing the coarse particles with the washing liquid; and separating the contaminants together with the washing liquid by a classifier. Performing a sedimentation process, sedimenting the remaining fine particles in a sedimentation apparatus to separate solid and liquid, and collecting a washing liquid to separate and treat or dispose of contaminants. How to clean contaminated soil. 2. The method for cleaning contaminated soil according to claim 1, wherein the contaminant is an oil component, and water and water glass are used as the cleaning liquid. 3. The method for cleaning contaminated soil according to claim 1, wherein the contaminant is a heavy metal, and water and an acid solution or an alkaline solution are used as the cleaning liquid.