JP2001300506A - Method for cleaning contaminated ground components - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cleaning contaminated ground components, such as soil and ground water, contaminated by organic composition and more particularly organic chlorine compounds. SOLUTION: Contaminated soil is taken out of the ground contaminated with the organic compounds by a back hoe 1 and are fed into a treating vessel 3. In this treating vessel 3, the contaminated soil is brought into contact with an organic pollutant elution accelerator to elute the organic pollutants and thereafter the eluted organic pollutants are brought into contact with an oxidizing agent and are thereby decomposed.

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 soil and other soil constituents such as groundwater contaminated with organic compounds, especially organic chlorine compounds.

[0002]

2. Description of the Related Art As is well known, organic chlorine compounds represented by trichloroethylene, tetrachloroethylene, trichloroethane, carbon tetrachloride and the like have a wide range of uses as solvents, cleaning agents, anti-inflammatory agents, and the like. , These compounds are produced, used, stored, transported, etc.
Due to leakage, scattering, accidents, etc., it is released to the environment and penetrates into the ground, thus polluting the environment.

[0003] These compounds, which have penetrated into the ground, have a high density, a high volatility, and exhibit a complicated behavior because they are slightly soluble in water. Some are absorbed by organic matter and clay minerals in the ground, or are accumulated in gaseous form in the ground, but most of them reach the aquifer and migrate and diffuse over a wide area due to groundwater. Become. The presence of these compounds in such aquatic areas not only adversely affects the aquatic ecosystem, but also poses a major obstacle to the toxicity of the compounds when groundwater is used for drinking, irrigation or industrial purposes. It is. Therefore, ground, groundwater and the like contaminated with such compounds must be purified immediately.

[0004] Such organic contaminants in the ground are generally chemically stable in many cases, and are extremely difficult to treat. Therefore, a method of removing contaminated soil and replacing it with new soil may be adopted. However, because the contaminated area extends in the horizontal and vertical directions, groundwater containing organic matter is usually pumped up and absorbed by an adsorbent such as activated carbon or removed by aeration. The method is taken. Further, a method may be adopted in which the contaminated area is heated by utilizing the volatility of the contaminated organic matter or removed by reducing the pressure. In addition, by passing groundwater through a layer mainly composed of granular or powdered iron, a method of reducing organic compounds and converting them to harmless compounds, or by so-called bioremediation of supplying microorganisms, enzymes, etc. to the contaminated area. Also, a method of mineralizing contaminants is being studied.

[0005]

However, the above-mentioned conventional method takes too long to complete the purification and repair of the contaminated ground (it may take several years to several tens of years depending on the repair method). There was a problem. The inventors of the present invention have conducted intensive studies on the reason, and as a result, it has been confirmed that the conventional method is not high in processing efficiency in principle and that the solubility of the contaminating organic compound in water is low.

[0006] Further, the cause of the decrease in the processing efficiency is not limited to this. That is, the contaminating organic compounds are present only in the groundwater up to a predetermined equilibrium concentration, and the rest is contained in the groundwater or adsorbed or absorbed by soil constituents (specifically, particles of clay minerals and organic substances). When the organic matter in the water was removed by any of the conventional methods described above, if the amount of the dissolved compound in the water was reduced, the amount of the compound was replenished from the above-mentioned ground components, and as a result, the purification process was prolonged. Was confirmed.

Therefore, even if the purification is performed by the conventional method, the contaminants will be supplied to the water soon, and after a predetermined period of time, the contaminants between the water and the solid substance will have a predetermined concentration. Until then, the concentration in the water will rise.
For example, in the case of trichlorethylene, it takes about 5 to 15 days to reach the certain concentration. Such a rebound phenomenon may be repeated indefinitely as long as the organic substance is absorbed or adsorbed on the solid phase. Therefore, it was desired to propose an effective purification treatment for not only groundwater but also soil. Note that this rebound phenomenon is remarkably observed in the case of an organic chlorine compound, but is also observed in the case of an organic compound that is soluble in water even in a small amount.

[0008] Therefore, a main object of the present invention is to provide a purification method capable of completing a purification restoration process in a short period of time.

[0009]

Means for Solving the Problems According to the first aspect of the present invention which has solved the above-mentioned problems, the present invention relates to an organic pollutant by contacting contaminated ground constituents contaminated with an organic compound with an organic pollutant elution accelerator. A method for purifying contaminated soils, comprising eluting substances and decomposing the eluted organic pollutants by contacting them with an oxidizing agent.

[0010] According to the second aspect of the present invention, a contaminated ground component including at least contaminated soil is taken out of a ground contaminated with an organic compound and put into a processing vessel. A method for purifying contaminated ground constituents, comprising: contacting an organic contaminant to elute organic contaminants; and contacting the eluted organic contaminants with an oxidizing agent to decompose them.

According to a third aspect of the present invention, an organic pollutant elution accelerator is supplied to a ground contaminated with an organic compound, and at least contaminated ground constituents including contaminated soil are contacted with the organic pollutant elution accelerator. And elute organic contaminants by supplying an oxidizing agent into the ground, and contacting the eluted organic contaminants with the oxidizing agent to decompose the contaminated soil constituents. is there.

According to a fourth aspect of the present invention, the elution treatment and the decomposition treatment are performed on both the contaminated soil and the contaminated groundwater contained in the site to be subjected to the purification treatment of the ground contaminated with the organic compound. This is a method for purifying contaminated ground components.

The invention according to claim 5 is the method for purifying contaminated ground constituents according to any one of claims 1 to 4, wherein a surfactant is used as the organic pollutant elution accelerator.

The invention according to claim 6 is the method for purifying contaminated ground components according to any one of claims 1 to 5, wherein an organic solvent is used as the organic pollutant elution accelerator.

According to a seventh aspect of the present invention, an oxidizing agent containing hydrogen peroxide as a main material is used as the oxidizing agent.
The method for purifying contaminated ground constituents according to any one of the above.

<Effect> The soil constituents, especially soil, which are contaminated with organic matter are related to the content of clay minerals and organic matter, etc. They often absorb high concentrations of organic matter,
Even if such water is removed, for example, by pumping, the contaminants in the soil are left as they are. After this, even if groundwater flows into the ground, organic pollutants usually have low solubility in water, so the transfer of contaminants from soil to water is extremely low,
In our investigations, more than one week is required to reach equilibrium.

Therefore, even if only the groundwater is purified while the ground is contaminated, the groundwater eventually returns to the soil containing a high concentration of contaminants, and is contaminated to almost the original concentration.

The organic contaminants absorbed and adsorbed in the soil are bound to the above-mentioned clay minerals, organic substances, etc. even if they attempt to decompose using a chemical reaction, or enter the gaps between the particles. May be protected by these factors and are very difficult to decompose. That is, even if the soil and the contaminated water are decomposed together by simply using a strong oxidizing agent, even if a decomposition rate of 100% of organic matter in water and 98% or more as a whole is achieved, the remaining 2% or less of soil remains in the soil. Due to the rebound of the organic substance, the concentration of the organic substance in the water layer portion eventually increases.

However, according to the present invention, the contaminated ground constituents are brought into contact with an organic pollutant elution accelerator to elute the organic pollutants, and the eluted organic pollutants are brought into contact with an oxidizing agent to decompose them, thereby obtaining soil particles and the like. Not only can the contaminants adsorbed on the surface be eluted, but the eluted contaminants are easily decomposed, so that they can be easily decomposed and made harmless. As a result, the subsequent rebound can be kept low. This effect is evident from the examples described below. For example, even when the aqueous layer portion reaches equilibrium at a very high concentration of an organochlorine compound of 10 mg / l, the rebound does not increase when treated by the method of the present invention. Even after 7 days when it has occurred and reached equilibrium,
The concentration of the aqueous layer could be maintained at about 0.01 mg / l, and the environmental standard value could be 0.03 mg / l.

As described above, the greatest advantage of the present invention is that the contaminated ground constituents can be purified and repaired not only in the groundwater but also in the soil in a short time. That is, with the conventional restoration method
Even if it takes more than a year, it can be repaired within a few days. The contaminated ground components whose restoration has been completed can be used as they are for the original purpose.

Further, in the present invention, the soil suspension water and the soil in which the organic pollutant elution accelerator is present can be oxidatively decomposed as they are, and the operation is very simple. Furthermore, there are few by-products in the present invention, and the processing of by-products is simple.

In concrete treatment, ground components such as contaminated soil are purified in a treatment vessel installed on the ground (claim 2), or an elution accelerator and an oxidizing agent are supplied in situ. Then, it is recommended that the in-situ purification process be performed (claim 3). In the former case, the processed ground components can be returned to the original ground.

On the other hand, the organic pollutant elution accelerator used in the present invention is versatile as fibers, papermaking, pigments, paints, oils, dispersants, wetting agents and the like in the synthetic resin industry, It is used in a wide range of fields such as cosmetics and the like, has no problem in terms of safety, and is easy to use at a low price.

[0024]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. <First Embodiment> FIG. 1 shows a flow of a purification process. The first embodiment is suitable when the contaminated soil is located at a relatively shallow position such as excavation. First, the corresponding contaminated soil is excavated with a backhoe 1 or the like, and if necessary, a belt conveyor 2 is used.
And transferred into a container 3 having a stirrer 3A installed on the ground, adding an elution medium such as water as needed, and further adding an organic pollutant elution accelerator for a predetermined time. Stir to elute the organic contaminants into the elution medium phase. If the suspension composed of the surfactant and the soil in the container is almost homogeneously mixed, stirring for 10 to 60 minutes is sufficient. Note that the dissolution medium such as water and the dissolution promoter can be filled in the container 3 before the excavation is charged.

Thereafter, an oxidizing agent was added to the contents of the container (water or a slurry of water and soil concentrated by elution of contaminants) while an organic contaminant elution accelerator was left, and eluted. Oxidatively decomposes pollutants. At this time, the organic pollutant elution accelerator is also oxidatively decomposed.

Although not shown, after the addition of the elution accelerator, the mixture is allowed to stand once to settle the solid content in the soil, and the supernatant is transferred to another container, to which an oxidizing agent is added, and the eluted contaminants are added. Can be oxidatively decomposed. Further, at the time of the oxidation treatment, an oxidative decomposition can be promoted by adding an oxidation promoting aid described below, irradiating ultraviolet rays, or bubbling ozone.

Thus, the soil and water after the purification treatment are buried back in the original position.

<Second Embodiment> The second embodiment is suitable for the case where the ground where the contaminant exists is located at a deep position, while rotating a stirring rod having a stirring blade and a discharge port. And agitating while injecting or spraying a required chemical into the ground from the discharge port into the ground, and sequentially performs elution treatment and oxidative decomposition treatment in situ.

FIG. 2 has a tip discharge port 11 and a plurality of agitating blades 12, 12,.
It shows an example in the case of using a known intrusion discharge type stirring and mixing rod 10 having the following, when rotating into the ground while rotating the stirring rod 10, reaches the contaminated ground portion X,
Starting to supply the dissolution accelerator into the ground from the tip discharge port 11,
Agitates with in-situ ground components (ground soil, groundwater) to elute pollutants. In addition, since there is a certain waiting time for the elution, the soil in the ground and the elution promoting material are sequentially stirred and mixed in the adjacent ground in the same manner. Thereafter, although not shown, the oxidizing agent is applied to the ground where stirring and mixing of the elution accelerator have been performed, as well as the R that penetrates while rotating the stirring rod and reaches the corresponding ground, as in the case of the elution acceleration processing. Is discharged from the discharge port, and the oxidizing agent is stirred and mixed with the mixture of the in-situ elution accelerator and the ground constituents. Thus, the oxidizing agent is brought into contact with the eluted contaminants to cause oxidative decomposition. In this way, the soil or water constituting the contaminated ground is brought into contact with the surfactant, and in this process, the contaminated organic matter is extracted from the components constituting the soil particles into the aqueous phase.

In the illustrated example, the processing example of the discharge type at the time of penetration is shown. However, a processing apparatus and procedure of a known stirring and mixing processing method (a so-called deep mixing processing method and the like) may be applied. For example, using a stirring rod having a stirring blade on the distal end side and a drug discharge port on the base end side, discharge the medicine when pulling up while rotating the rod, and the in-situ substance and the discharged medicine A method of stirring and mixing can also be adopted.

Also, in the oxidation treatment in the second embodiment, an oxidation promoting aid is supplied or ozone is bubbled by oxidative decomposition by the same supply method to the ground as the elution accelerator and the oxidizing agent. Can be promoted.

<Third Embodiment> A known chemical liquid injection method is applied, and instead of a ground improvement material (hardening agent), an elution accelerator and an oxidizing agent of the present invention are sequentially injected into the ground to perform elution treatment. More oxidative decomposition treatment can be performed. In this case, stirring is not performed at the time of supplying the elution accelerator and the oxidizing agent, but if necessary, stirring can be performed at a time other than the time of supplying the drug by using a separate stirring device.

<Specific Examples of Organic Pollutant Elution Accelerator> The organic pollutant elution accelerator in the present invention is not particularly limited as long as it has water-soluble or water-dispersible properties. When the target is an object, for example, an organic halogen compound, a surfactant is preferable. Examples of the surfactant include a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant. Among them, a nonionic surfactant is particularly preferable. As the nonionic surfactant, for example, higher alcohols, phenols, fatty acids, alkylamines, fatty acid amides, and the like, obtained by addition polymerization of ethylene oxide, copolymers of ethylene oxide and propylene oxide, esters of sorbitan and various fatty acids, and the like are used. Can be. Examples of the anionic surfactant include alkali salts of higher fatty acids, acyl sarcon, sodium alkyl sulfate, and alkylbenzene sulfonate. Examples of the cationic surfactant include amine salts, quaternary ammonium salts, and quaternary ammonium salts. 3
Grade compound sulfonium salts, quaternary phosphonium salts, and the like can be used, and as the amphoteric surfactant, amino acids, phospholipids, and the like can be used.

These surfactants are preferably used in the form of a 0.01 to 1% aqueous solution and have the ability to elute organic compounds in the target soil into water. If this concentration is low, the ability to elute contaminants from soil will be reduced, making it difficult to achieve the object of the present invention. On the other hand, using a high concentration of surfactant
In the next step, the amount of the oxidizing agent used for decomposing the contaminants is increased, and the surfactant is not desirable because it inhibits the oxidative decomposition. A particularly preferred aqueous solution concentration of the surfactant is 0.05 to 0.5%.

The surfactant may be added directly to the contaminated aqueous solution or slurry to be treated, but it is preferable to use a solution once dissolved in water in order to perform the treatment quickly.

On the other hand, as the organic pollutant elution accelerator of the present invention, an organic solvent such as acetone, ethanol, hexane and the like can be used.

<Specific Examples of Oxidizing Agent> The oxidizing agent used for oxidatively decomposing the extracted contaminants is not particularly limited, but it is preferable to use hydrogen peroxide as the main agent. The concentration of hydrogen peroxide varies depending on the type and amount of contaminants to be treated, the amount and type of surfactant used, and the like. Typically 0.0% in aqueous surfactant solution to be treated
Adjusted to be 5-10%. However, when this concentration is low, it becomes difficult to completely decompose the contaminants,
Further, when the organic contaminant elution accelerator is also oxidatively decomposed, there is a problem that the residual amount thereof becomes large.

In the present invention, when hydrogen peroxide is used as an oxidizing agent, a mixture of hydrogen peroxide and ground constituents is irradiated with ultraviolet rays in order to positively generate hydroxyl radicals generated by decomposition of hydrogen peroxide. Irradiation or ozone can be blown into a system for performing the oxidation. Further, it is more preferable to use an oxidizing agent obtained by mixing a transition metal compound catalyst with hydrogen peroxide, for example, a Fenton's reagent using an iron salt as a catalyst. When an iron salt is used, the degree of treatment for generating these hydroxyl radicals and the amount of the auxiliary agent are not particularly limited, but the hydroxyl radicals are blended so that the generation continues for 5 minutes or more, preferably 10 minutes or more. Preferably, when the target is an organochlorine compound, the pH of the suspension is also kept acidic or neutral.

Depending on the soil constituting the ground, a certain amount of an iron compound suitable for oxidative decomposition may be present. In such a case, it is not necessary to add the above-mentioned auxiliary agent. Or it can be reduced. When the above-mentioned auxiliary is used, it is also a preferable embodiment to adopt a method of supplying the compound into the container or the ground together with the organic compound elution accelerator or the oxidizing agent.

The effects of the present invention will be clarified with reference to the following examples.

[0041]

<Example of the present invention> To a container made of Teflon (registered trademark), water contaminated with Kashima silica sand No. 6, trichloroethylene (TCE) was added, and the mixture was shaken for 6 hours on a vibrating device. The contaminated quartz sand was adjusted. The finally obtained contaminated sand is 100 parts, 28 parts of water, T
The concentration of CE was 15.5 mg / l.

Into 10 parts of the above contaminated sand, 1 part of a 0.2% by weight aqueous solution of Pelesoft 207, an alkyl ether type nonionic surfactant obtained by addition polymerization of ethylene oxide, manufactured by Miyoshi Yushi Co., Ltd. was sealed. The sample was transferred to a glass bottle and placed on a vibrator for 30 minutes and shaken.

Next, 0.55 parts of a 100 g / l aqueous solution of ferrous sulfate and 0.9 part of 10% by weight of hydrogen peroxide were rapidly added to the bottle, and the mixture was placed on a vibrator and shaken for 10 minutes. After that, the sample was allowed to stand still, and the water layer portion was appropriately sampled, and the TCE concentration in the portion was analyzed.

<Comparative Example> TCE adjusted in the above-mentioned present invention example
A similar test was conducted using contaminated sand without adding a nonionic surfactant and then adding an oxidizing agent to the contaminated sand in the same manner as in the above-mentioned present invention.

<Test Results> Table 1 shows the test results of the examples of the present invention.
Table 2 shows the test results of Comparative Examples and Comparative Examples. The environmental standard value (concentration) of the aqueous layer with respect to TCE is 0.03 mg / l.
Day)), while the comparative example shows the effect of oxidative decomposition,
Not only was the TCE concentration immediately after the end of the oxidative decomposition high, but also the concentration of the aqueous layer when the equilibrium was reached (after 4 days) exceeded the environmental standard value, and was about six times that of the present invention.

[0046]

[Table 1]

[0047]

As described above, according to the present invention, there are provided advantages such that the purification process can be completed in a very short period of time and the process can be simplified.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first processing mode.

FIG. 2 is a schematic diagram showing a second processing mode.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Backhoe, 2 ... Belt conveyor, 3 ... Container, 10
... Stirring rod, 11 ... Discharge port, 12 ... Stirring blade.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) C02F 1/72 (72) Inventor Kaichi Michichika 4-35, Kudankita, Chiyoda-ku, Tokyo Light Industry F term (for reference) 2E191 BA12 BB01 BC01 BC05 BD11 4D004 AA41 AB06 AC05 AC07 CA15 CA36 CA40 CC03 CC04 CC05 CC11 4D038 AA02 AA10 AB14 BB05 BB16 4D050 AA02 AA20 AB19 BB09 CA05

Claims (7)

[Claims] 1. A method for dissolving organic contaminants by contacting contaminated ground constituents contaminated with organic compounds with an organic contaminant elution accelerator, and decomposing the eluted organic contaminants by contact with an oxidizing agent. A method for purifying contaminated ground components. 2. Contaminated soil components including at least contaminated soil are taken out of the soil contaminated with an organic compound and placed in a treatment vessel. In the treatment vessel; A method for purifying contaminated ground constituents, comprising eluting substances and decomposing the eluted organic pollutants by contacting them with an oxidizing agent. 3. An organic pollutant elution accelerator is supplied to the ground contaminated with an organic compound, and at least contaminated ground constituents including contaminated soil are brought into contact with the organic pollutant elution accelerator to remove organic pollutants. A method for purifying contaminated ground constituents, comprising eluting, supplying an oxidizing agent into the ground, and bringing the eluted organic pollutant into contact with the oxidizing agent to decompose. 4. The elution treatment and the decomposition treatment for both contaminated soil and contaminated groundwater contained in a site to be treated for purification of ground contaminated with an organic compound.
The method for purifying contaminated ground constituents described in the above. 5. The method according to claim 1, wherein a surfactant is used as the organic pollutant elution accelerator. 6. The method for purifying contaminated ground constituents according to claim 1, wherein an organic solvent is used as the organic contaminant elution accelerator. 7. The method for purifying contaminated ground constituents according to claim 1, wherein an oxidizing agent containing hydrogen peroxide as a main material is used as the oxidizing agent.