JP3051047B2 - Purification method and purification system for contaminated soil using soil microorganisms - 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 and a system for purifying contaminated soil using soil microorganisms. More specifically, the present invention relates to a method and a system for purifying contaminated soil that can effectively purify contaminated soil by activating microorganisms capable of decomposing contaminants living in soil in principle.

[0002]

2. Description of the Related Art In recent years, it has been revealed that pollution of underground environment due to volatile organic chlorinated compounds such as trichloroethylene and tetrachloroethylene and petroleum hydrocarbons such as gasoline is spreading worldwide. Is a serious problem on a global scale.

[0003] As a means for removing the contamination of the underground environment, a physical method of adsorbing contaminants on activated carbon or solidifying contaminants with cement, a method of chemically neutralizing or decomposing contaminants, etc. It has been known.

Recently, in addition to these physical or chemical methods, biological methods for decomposing contaminants by the power of microorganisms have attracted attention and are being put to practical use.

[0005] This biological process uses natural processes and therefore requires less energy to treat the pollutants, is economical and decomposes or detoxifies the pollutants, thus generating secondary waste. This is a permanent purification means that does not show any pollution, and has advantages such as the ability to repair contamination in situ or on site.

More specifically, the biological method described above is a “solid phase treatment method” which is a treatment method in which an on-site or off-site soil treatment unit is designed and installed, and in which contaminated soil is purified. The "slurry treatment method" is a treatment method that prepares contaminated soil excavated as slurry in a slurry state and uses a slurry bioreactor to perform microbial decomposition of contaminants in the soil. Three types of in-situ treatment method, which is a treatment method that injects microbial nutrients and oxygen into the ground using wells and watering trenches without excavating the water layer and performs microbial decomposition of pollutants Processing method.

[0007] Among these biological methods, the "in-situ treatment method" is the most cost-effective treatment method, but has many factors depending on the specificity of each contaminated site. And
A circulation mechanism is often used to purify contaminated groundwater pumped up using a bioreactor installed on the ground and re-inject the groundwater after purification treatment into the ground.

At present, in the above-mentioned circulation mechanism in the “in situ treatment method”, a nutrient source of microorganisms capable of decomposing contaminants such as methane is supplied into soil through an injection well or the like, and the microorganisms in the soil are removed. Attempts have been made to activate it to further accelerate the degradation of contaminants by the microorganism.

[0009] However, only the microorganisms near the injection well of the nutrient source grow specifically, and the injection well is clogged with the microorganisms that have excessively grown. There is no denying that they tend to be contaminated instead.

[0010] Therefore, the problem to be solved by the present invention is that even if the nutrient source of soil microorganisms is positively injected, the above-mentioned drawbacks do not occur, and the decomposition of pollutants by soil microorganisms is more effectively promoted. It is to provide a means.

[0012]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems. As a result, it has been found that the above problems can be solved mainly by separating the supply points of the nutrient sources of the microorganisms in the soil for each element of the nutrient sources and by setting the supply points in a specific arrangement. That is, the inventor provides the following inventions.

According to a first aspect of the present invention, there is provided a method for purifying contaminated soil, comprising promoting the growth of microorganisms capable of decomposing contaminants in soil and decomposing the microorganisms into contaminants. A plurality of elements separated at three or more donation points and donated to the soil, and then the elements donated to the soil are moved by the water flow in the aquifer and mixed in the aquifer, and mixed at the mixed point. A method for purifying contaminated soil, comprising activating the microorganism and decomposing contaminants in an activated region of the microorganism.

According to a second aspect of the present invention, in the method for purifying contaminated soil according to the first aspect, a means for generating a water flow for moving a plurality of elements for promoting the growth of microorganisms capable of decomposing contaminants to the confluence point is provided. The present invention provides a method for purifying contaminated soil, characterized in that a plurality of elements for promoting the growth of the microorganisms are moved toward a confluence point by the means.

According to a third aspect of the present invention, in the method for purifying contaminated soil according to the second aspect, a means for generating a water flow for moving a plurality of elements for promoting the growth of microorganisms capable of decomposing contaminants to the confluence point is provided. And a method for purifying contaminated soil characterized by pumping water in an aquifer.

According to a fourth aspect of the present invention, the plurality of elements for promoting the growth of microorganisms capable of decomposing contaminants include an electron donor and an electron acceptor for the microorganisms. A method for purifying contaminated soil according to any one of the preceding claims.

According to a fifth aspect of the present invention, in the method for removing contaminated soil according to the fourth aspect, the point at which an electron donor of a microorganism capable of decomposing contaminants is provided to the soil with reference to the water flow in the aquifer. In the downstream, equidistant points are provided points for donating electron acceptors to a plurality of soils, and the water flow in the aquifer moves the electron donors and the electron acceptors donated into the soil, respectively. A method for purifying contaminated soil, characterized in that the microorganism is activated at a mixed site.

According to the sixth aspect, the method for purifying contaminated soil according to any one of the first to fifth aspects, wherein the microorganism capable of decomposing the pollutant is a methane-utilizing bacterium. provide.

According to a seventh aspect of the present invention, a microorganism capable of decomposing a pollutant in the contaminated area is added to the contaminated area. Provide a purification method.

According to an eighth aspect of the present invention, there is provided a method for purifying contaminated soil according to any one of the first to seventh aspects, wherein the following steps are repeated. A first step of activating a microorganism capable of decomposing contaminants; a second step of decomposing the contaminants into the microorganisms after the first step in a state in which the provision of a plurality of elements for promoting the growth of the microorganisms to the soil is stopped. Step: After the second step, when the activity of the microorganism decreases, a third step of providing the soil with a plurality of factors that promote the growth of the microorganism again.

According to the ninth aspect, the electron donor dissolved water injection means for injecting the electron donor dissolved water supplied by the electron donor dissolved water supply means for microorganisms capable of decomposing the pollutant into the aquifer, and the contaminant Means for injecting the electron acceptor dissolved water supplied from the electron acceptor dissolved water supply means into the aquifer with respect to microorganisms capable of decomposing the water, in the water flow in the aquifer upstream of the contaminated region. And the electron acceptor dissolved water injected into the soil by the electron donor dissolved water injection means and the electron acceptor dissolved water injected into the soil by the electron acceptor dissolved water injection means in the contaminated area. There is provided a purification system for contaminated soil, wherein the electron donor dissolved water injection means and the electron acceptor dissolved water injection means are provided at three or more points so as to be mixed.

According to claim 10, an electron donor dissolved water injection means for injecting an electron donor dissolved water supplied by an electron donor dissolved water supply means for microorganisms capable of decomposing a pollutant into an aquifer, and a contaminant Means for injecting the electron acceptor dissolved water supplied from the electron acceptor dissolved water supply means in the microorganism capable of decomposing the water into the aquifer, and pumping means for pumping water in the aquifer. The water in the aquifer generated by pumping in the pumping means causes the electron donor dissolved water injected into the soil by the electron donor dissolved water injection means and the electron acceptor dissolved water injected into the soil by the electron acceptor dissolved water injection means. The electron donor dissolved water injecting means and the electron acceptor dissolved water injecting means are provided at three or more points in such an arrangement that the injected electron acceptor dissolved water can mix in the contaminated area. And the pumping means is provided, and the water pumped from the pumping means is distributed to the electron donor dissolved water supply means and / or the electron acceptor dissolved water supply means, and the electron donor dissolved water and / or the electron acceptor are supplied. Provided is a purification system for contaminated soil, which contributes to production of body-dissolved water.

According to the eleventh aspect, in the purification system for contaminated soil according to the tenth aspect, means for separating contaminants in groundwater pumped by the pumping means is provided,
The groundwater repurified by the means is supplied to an electron donor dissolved water supply means capable of decomposing pollutants and / or an electron acceptor dissolved water supply means for microorganisms capable of decomposing pollutants, and the electron acceptor dissolved water is supplied. A purification system for contaminated soil characterized by contributing to the production of water and / or the above-described dissolved water of the electron acceptor.

According to the twelfth aspect, a means for injecting dissolved water of an electron donor for microorganisms capable of decomposing pollutants is provided upstream of the groundwater flow in the aquifer, and is equidistant from the point to the downstream of the groundwater flow. The purification system for contaminated soil according to claim 10 or 11, wherein a plurality of electron acceptor dissolved water supply means are provided at the point.

According to the thirteenth aspect, the microorganism according to any one of the eighth to twelfth aspects, wherein a microorganism capable of decomposing the contaminant in the contaminated region is added to the contaminated region. Provide a soil purification system.

Hereinafter, the present invention will be described in detail. A. As described above, the method for purifying contaminated soil according to the present invention relates to a method for purifying contaminated soil in which the growth of microorganisms capable of decomposing contaminants in soil is promoted and the microorganisms decompose contaminants.

FIG. 1 is a schematic diagram illustrating a mechanism for realizing this method of purifying contaminated soil including the prior art.

In FIG. 1, the purification system 10 is pumped by a pumping well 11; a pumping pump 12, which penetrates an aquifer interface 30 in a formation 20 and reaches an aquifer 40.
Pretreatment means 14 for pretreating the groundwater supplied by the water absorption pipe 13 by aeration or the like; adding and mixing nutrients and air to the groundwater supplied by the drainage pipe 13 'and pretreated by the pretreatment means 14; A mixing means 15 for preparing the eutrophic water; and an injection well 16 to which the injection pipe 13 ″ for the eutrophic water supplied by the mixing means 15 communicates. The arrow in FIG. 1 indicates the direction in which the water flows, but the eutrophic water injected into the injection well 16 by the injection pipe 13 ″ is mainly located on the upper layer of the poorly permeable layer 60 generated by pumping in the pump 12. The groundwater flow generated in the located aquifer 40 moves toward the contaminated soil 50. Then, in the contaminated soil 50, the growth of microorganisms capable of decomposing the pollutant is promoted, and the contaminant is decomposed, whereby the contaminated soil 50 can be purified.

As described above, in the prior art, the eutrophic water excessively promotes the growth of microorganisms in the vicinity of the injection well 60, and the injection well 60 is clogged by excessively grown microorganisms. In addition, injection well 6
It cannot be denied that the soil environment near zero tends to be contaminated by the microorganisms.

B. The present invention relates to a method for purifying contaminated soil in which a plurality of elements that promote the growth of microorganisms capable of decomposing contaminants in soil are separated at three or more donor points and provided to the soil. Pollutants to which the present invention is applied include benzene, toluene, ethylbenzene, xylene,
Organic solvents such as trichloroethylene, dichloroethylene, tetrachloroethylene, chloroform, carbon tetrachloride;
Wood preservatives such as creosote and pentachlorophenol; polymeric halogenated aromatics such as polychlorinated biphenyl (PCB); various pesticides; heavy metal ions; The contaminants to which the present invention is applied are not limited to the contaminated substances.

Microorganisms capable of decomposing contaminants in soil are:
It can be appropriately selected according to the type of pollutant to be purified.

For example, when purifying volatile organic chlorine compounds such as trichloroethylene, dichloroethylene and tetrachloroethylene from soil, microorganisms capable of decomposing such volatile organic chlorine compounds, that is, methane assimilating bacteria, Not only aerobic bacteria such as phenol-utilizing bacteria and nitrifying bacteria, but also the above-mentioned volatile organic chlorine compounds, for example, anaerobic bacteria capable of decomposing tetrachloroethylene can be used.

In the present invention, microorganisms which originally inhabit the soil of the contaminated area are used as a contamination means in principle. For example, if the desired microorganism does not exist in the soil to be purified or if it exists, it is weakened. In such a case, the desired microorganisms can be actively replenished from the outside toward the contaminated area.

As the microorganism to be supplemented, not only a microorganism originally existing in nature but also a microorganism created by a genetic engineering technique can be used.

The means for replenishing the contaminated region with microorganisms is not particularly limited. For example, replenishment may be performed together with an element for promoting the growth of microorganisms described later, or an injection port for replenishing microorganisms may be provided separately. It is also possible to refill from the entrance.

The term "plurality of factors promoting the growth of the microorganism" means, literally, a plurality of factors which increase the vitality of the microorganism and promote the growth by being added. Such factors will vary depending on the type of microorganism selected as a means of soil remediation, but will generally be an "electron donor" or "electron acceptor" for the decomposition reaction of contaminants in the microorganism or any other necessary for the growth of the microorganism. (For example, phosphorus-containing compounds, the same applies hereinafter) and the like can be used.

For example, in aerobic methane-utilizing bacteria, the action of soluble methane monooxygenase causes
Methane, which is an “electron donor”, reacts with oxygen, which is an “electron acceptor”, to produce carbon dioxide and water. Then, by a reaction similar to the above by the action of the enzyme, a volatile organic chlorine compound such as trichloroethylene can also be an “electron donor” in such aerobic methane-utilizing bacteria.

In this way, the volatile organochlorine compounds in the soil are decomposed by the aerobic methane-utilizing bacteria.

The component that can be provided as an electron acceptor is generally oxygen in aerobic microorganisms such as methane assimilating bacteria, but the component that can be provided as an electron donor is a component of a microorganism intended to promote growth. A wide variety depending on the type,
It is not particularly limited. For example, examples of the electron donor in the methane-assimilating bacterium include methanol, phenol, tryptophan, and simple hydrocarbons in addition to the above-mentioned methane and volatile organic chlorine compounds. Further, examples of the electron donor of the hydrocarbon-assimilating bacterium include various hydrocarbons such as methane, ethane, and propane.

The specific elements to be provided in the soil are:
It is also determined by the nature of the microorganisms that degrade the pollutant of choice and the soil components that seek to remove the pollutant.

That is, when an aerobic microorganism is selected as a contaminant-degrading microorganism, and when the contaminant does not match the electron donor of the aerobic microorganism, the above element is separated into an electron donor and an electron acceptor. It is preferable to use them. For example, when using aerobic methane-utilizing bacteria for the purpose of purifying trichlorethylene in soil,
It is usually preferable to separate and provide methane as an electron donor and oxygen as an electron acceptor.

On the other hand, even when an aerobic microorganism is selected as a pollutant-degrading microorganism, if the contaminant and the electron donor of the aerobic microorganism match, the above element is used as an electron acceptor and an electron acceptor. It is preferable to use it separately from nutrient sources other than the donor. For example, when degrading phenol in soil using an aerobic phenol-assimilating bacterium, providing more phenol to the soil may further promote phenol contamination in the soil. Therefore, in such a case, it is preferable that nutrient sources other than oxygen and phenol, which are electron acceptors, which can be determined to be relatively deficient in the soil be separated and provided.

Furthermore, when purifying contaminants in the soil, for example, tetrachloroethylene, using methane-utilizing anaerobic bacteria, oxygen cannot be provided to the anaerobic bacteria as an electron acceptor. . In such a case, it is preferable to separate and provide an appropriate electron donor (such as methane in the above example) and other nutrient sources that can be determined to be relatively deficient in the soil.

The form of the element for promoting the growth of microorganisms in the soil, such as the above-mentioned electron donor, to the soil is not particularly limited, but the element is provided in the form of dissolved water in which such an element is dissolved in water. Is preferable in that the above-mentioned elements can be more efficiently supplied to soil.

Further, in the present invention, a plurality of factors for promoting the growth of microorganisms capable of decomposing the above-mentioned pollutants in soil are separated at three or more donor points and provided to the soil. That is, for the microorganisms intended to promote the growth described above, elements such as "electron donors" or "electron acceptors" or other nutrients necessary for the growth of the microorganisms are separated into at least two types, and three or more are provided. Donate into the soil from the point of donation.

This does not mean that it is not always necessary to provide separate donation points for all of the above divided elements and to provide them to the soil. For example, two out of three provided donation points Embodiments are also possible in which the same element is provided in the soil, and the other element is provided in the soil in the remaining one place.

Further, the above separation does not necessarily mean that one element cannot be provided at one donor point. For example, even when an electron donor and an electron acceptor are separated, such an electron donor and an electron acceptor can be separated. It does not exclude the inclusion of other nutrient sources in the electron acceptor.

By providing a plurality of elements in the soil at separate supply points, it is possible to avoid excessive growth of microorganisms near the injection means typified by injection wells. Clogging of the means and microbial contamination of the soil environment of the injection means, ie the above-mentioned disadvantages of the prior art, can be overcome. In addition, as described later, by mixing the plurality of elements in the contaminated region to promote the growth of microorganisms in the contaminated region, it is possible to extremely efficiently remove the contaminants. .

As will be described later, by providing three or more donation points, it is possible to mix the above-mentioned elements for promoting the growth of microorganisms as much as possible in a desired contaminated area. .

C. In the present invention, the element provided to the soil at the above-mentioned donation point is mixed in the aquifer by moving by the water flow in the aquifer, and the microorganism is activated at the mixing point to activate the microorganism. The present invention relates to a method for supplying contaminated soil in which contaminants in an area are decomposed by the microorganism.

As described above, the means for mixing the above-mentioned elements for promoting the growth of the microorganisms provided in the soil at three or more provided donation points may be used when the water flow in the aquifer is not caused separately. In consideration of the direction and velocity of the groundwater flow in the existing aquifer, an element that promotes the growth of each microorganism provided in the soil should be mixed in the desired contaminated area. Set more than one donation point.

For example, when the above-mentioned electron donor and electron acceptor are separated from each other and are donated into the soil from three points, the groundwater flow in the aquifer may be one point. It is preferable to provide two electron acceptor supply points at equidistant points downstream from the electron donor supply point.

Because, as described above, generally, the electron donor to be donated is a substance having explosive properties, a substance which itself can seriously contaminate the soil, and furthermore, because of such properties, it is difficult for the electron donor to be provided in the soil. This is because the donor is required to be decomposed by microorganisms in the soil as efficiently as possible because the donor is a substance whose concentration is often legally regulated.

That is, the factor that promotes the growth of the microorganisms provided in the soil is a spindle-shaped diffusion from the donor point in the direction of the flow due to the water flow in the aquifer. At a concentration that is expected to promote the growth of microorganisms to some extent in the contaminated area downstream of the groundwater flow at the donor point above. In general, it is difficult to mix all the electron donors diffused in the spindle shape with the electron acceptors diffused in the spindle shape, and the electron donors are not easily decomposed by microorganisms. It is difficult to avoid the danger that parts of the body will remain in the soil.

On the other hand, in the groundwater flow in the aquifer, two electron acceptor supply points are set at a position equidistant downstream from one electron donor supply point. By providing such an electron donor, it is possible to assimilate the electron donor to microorganisms in the soil as efficiently as possible in a region where mixing of the electron donor and the electron acceptor is intended.

In the case where nutrient sources of microorganisms other than the electron acceptor and the electron donor are separated and donated to the soil, for example, three donation points are arranged in the same manner as described above (electron donors). Provide nutrients for other microorganisms from upstream of groundwater flow)
By doing so, the nutrient source provided to the microorganisms can be efficiently supplied, and the risk of soil contamination by the nutrient source can be avoided.

D. In the present invention, a means for generating a water flow for moving a plurality of elements for promoting the growth of microorganisms capable of decomposing contaminants to the mixing point is provided, and a plurality of means for promoting the growth of the microorganisms by the means are provided. It is also possible to move the element towards the confluence point.

For example, the water in the aquifer may be positively pumped into the aquifer by an underground water supply means such as a drain pump or the like, or may be generated by a pumping means such as a water pump. To generate a water flow.

In the present invention, as described above, it is necessary that the microorganisms provided to the soil can promote the growth of the microorganisms as efficiently as possible.
It is highly preferred to generate a groundwater flow by the latter pumping means.

As in the example described above, when the electron donor and the electron acceptor are separated and supplied into the soil from three points, the groundwater flow in the aquifer may be:
It is assumed that two electron acceptor supply points are provided at a position equidistant downstream from one electron donor supply point.

In such a case, a groundwater flow is generated from the above-mentioned donation point toward the contaminated area where purification is intended.
In other words, by providing the pumping means so that the point at which the pumping means is provided as a result is located downstream of the generated groundwater flow, in the contaminated area, the electron donor and the electron acceptor can be more efficiently used. Can be mixed to promote the growth of microorganisms in the soil.

In general, microorganisms capable of decomposing contaminants can grow by decomposing the contaminants. However, if the amount of the contaminants is too large, the growth tends to be inhibited. That is, as another meaning of providing the injection means in three or more points in the present invention, when the microorganism growth promoting element is injected into the soil, a purification area mainly by an additional contaminant from the upstream area of the groundwater flow is used. It is possible to prevent the above-mentioned inhibition of the growth of microorganisms capable of decomposing contaminants due to additional contaminants at the time of injection of the microbial growth promoting element. In other words, it is possible to perform the work of purifying the pollutant based on the concentration of the pollutant in the soil at the beginning of the purification.

As described above, as one of means for mixing the above-mentioned elements for promoting the growth of the microorganisms provided to the soil at the three or more providing points, the water flow in the aquifer is separately generated. In such a case, in consideration of the direction and velocity of the groundwater flow in the resulting aquifer, an element that promotes the growth of each microorganism provided in the soil should be mixed in the desired contaminated area. It is preferable to set the above three or more donation points.

In this embodiment using the pumping means, if only two donation points are provided, the above C.I. The same inconveniences as in the case described above occur.

E. In the method for purifying contaminated soil according to the present invention, a first step of activating microorganisms capable of decomposing contaminants, and after the first step, the provision of a plurality of elements for promoting the growth of the microorganisms to the soil is stopped. A second step of decomposing contaminants into the microorganisms in the third step, and after the second step, when the activity of the microorganisms decreases, a third step of providing a plurality of elements for promoting the growth of the microorganisms to the soil again; By repeating the above steps, contaminants can be more efficiently removed from the soil.

That is, in the first step, as described above, an element capable of promoting the growth of a microorganism capable of decomposing contaminants is provided to the soil to activate the microorganism, that is, activate the microorganism. In the second step, promoting the decomposition of the contaminants in the soil by the microorganisms in place of the donated element by stopping the donation of the element in the second step; Activate the exhausted microorganisms; by repeating these steps, contaminants can be more efficiently removed from the soil.

This method is particularly effective when, for example, when methane assimilating bacteria are activated, and when a contaminant intended to decompose an electron donor such as methane and a volatile organic chlorine compound is different from each other. It is.

In each of the above A to E, the specific mode of separation of the element for promoting the growth of the microorganism capable of decomposing the contaminant, the supply amount of the element, and the time required for each step described in E above And the like are items to be individually and specifically determined according to the situation of the area where purification of the pollutant is intended, and are not necessarily limited. Therefore, these matters will be specifically disclosed in examples described later.

F. The present invention provides not only the method for purifying contaminated soil but also a system for purifying contaminated soil for implementing the method. The configuration of the purification system of the present invention basically includes the configuration according to FIG. 1 described above.

That is, the “electron donor dissolved water supply means for microorganisms capable of decomposing pollutants” and the “electron acceptor dissolved water supply means for microorganisms capable of decomposing pollutants” in the purification system of the present invention are shown in FIG. This corresponds to the mixing means 15. Further, the “electron donor dissolved water injection means for injecting the electron donor dissolved water into the aquifer” supplied by the electron donor dissolved water supply means and the “electron acceptor dissolved water supply means” supplied by the electron acceptor dissolved water supply means. "Electron acceptor dissolved water injection means for injecting the electron acceptor dissolved water into the aquifer" corresponds to the injection well 16 in FIG.

Here, it is needless to say that the electron donor dissolved water and the electron acceptor dissolved water contain an electron donor and an electron acceptor which are intended to be supplied to the soil, respectively. It is also possible to include other nutrient sources in these dissolved waters depending on the conditions.

The specific mode of the injection means is not particularly limited as long as the dissolved water can be efficiently supplied to the soil. For example, the injection means may be in the form of an “injection well” as shown in FIG. .

The significance of providing these injection means at three or more points, and in these injection means, the electron donor dissolved water injection means is provided, and the injection means is equidistant from the point to the downstream of the groundwater flow. The significance of providing a plurality of electron acceptor dissolved water supply means at a point has been described above.

The significance of providing pumping means for pumping water in an aquifer typified by a separate pumping well and generating a desired groundwater flow has also been described above.

FIG. 2 is a schematic diagram showing the arrangement of the injection means and the like in one embodiment of the purification system of the present invention.

In FIG. 2, a purification system 100 includes a pumping well 110 for pumping groundwater in an aquifer;
Mixing the groundwater pumped by 10 and supplied by the suction pipe 130 into two parts, one to add and mix electron donors and other nutrients and the other to add and mix electron acceptors and other nutrients Means 150: Piping for electron donor injection 1 for supplying groundwater containing electron donors and other nutrients prepared by mixing means 150
Electron donor injection well 161 through which 31 communicates; mixing means 1
Electron acceptor injection tubing 132 for supplying groundwater containing electron acceptors and other nutrients prepared at 50
Include an electron donor injection well 162 communicating therewith. The small hole 170 in FIG. 2 is an observation well for monitoring the status of contamination of the aquifer at that position. Further, arrow 180 indicates the direction of flow of the groundwater flow.

The purification system 100 includes the water supply pipe 1
As shown in FIG. 1, a pretreatment means for pretreating the groundwater supplied by the water supply pipe 130 by aeration or the like may be provided between the 30 and the mixing means 150 (not shown). Further, if necessary, a port for replenishing microorganisms for replenishing microorganisms capable of decomposing contaminants is provided in the contaminated soil, and desired microorganisms are intentionally replenished in the soil to purify the soil. It is possible to contribute to.

The arrows in FIG. 2 indicate the direction in which water flows, including the arrow 180. Of the two types of eutrophic water prepared by the mixing means 150, eutrophic water containing an electron donor is , Into the soil via the electron donor injection well 161. On the other hand, eutrophic water containing an electron acceptor is supplied to the soil via the electron acceptor injection well 162.

The electron donor and the electron acceptor donated into the soil ride on the groundwater flow 180 toward the pumping well 110 by the pumping power of the pumping well 110, so that the pumping well 11
0 and the contaminated area existing between the injection wells 161 and 162, the growth of microorganisms capable of decomposing the contaminant in the contaminated area can be promoted, and the contaminant can be decomposed.

In the case of performing the series of steps shown in E, each step can be carried out by monitoring the state of contamination of the aquifer at the position by the observation well 170.

As described above, in the present invention, it is possible to biologically purify contaminated soil by increasing the ability of microorganisms in the soil.

[0082]

The present invention will be described more specifically with reference to the following examples. However, the technical scope of the present invention should not be interpreted as being limited by these examples.

<Outline of the area targeted for purification> In 1989, trichlorethylene was detected from a well of a private house in A city, Chiba prefecture.
Soil contamination by trichlorethylene was confirmed. Since 1990, the actual status of pollution has been investigated. As a sample of the contaminated stratum, drilling was performed near the pumping well, and a core of 14 to 23 m was collected from the surface. As the contaminated groundwater, groundwater pumped from a pumping well (14 to 23 m from the strainer depth formation) was collected.

<Pollution and Geological Conditions in the Contaminated Area> Various tests were conducted on the pollution and geological conditions in the above-mentioned contaminated areas. Table 1 shows some of the results.

[Table 1]

<Modeling of the contaminated area> The contaminated area was modeled with reference to the above test results and the like. Modeling was performed in the following procedure.

Selection of Use Model: In this case, the use model is a three-dimensional model, the US Geological Survey (USG).
S) developed MODFLOW (McDonald and Harbaug
h 1988). In addition, the simulation result by the groundwater flow model used MT3D which is a three-dimensional finite element model having a modular structure.

Setting of aquifer specifications: Permeability was estimated from pumping test results. The measured value was used for the hydraulic gradient.
The storage coefficient was estimated from the pumping test results. The effective porosity was estimated to be lower than the porosity. As the total porosity, an actually measured value was used. The upper and lower limits of the aquifer were the average groundwater level and the altitude of the clay layer, which was separated from the aquifer. The bulk specific gravity of the formation was calculated from the porosity of the formation and the specific gravity of the formation components. As the initial concentration of the pollutant, an actually measured value was used. Vertical and horizontal dispersion coefficients were calculated based on the theory of Gelhar et al. (EPRI). As the organic carbon / water partition coefficient, a numerical value from a database of the US EPA was used. As the organic carbon content, an actually measured value was used.

Setting of Finite Element Grid: The modeling target area was set wide enough so that the influence of pumping and injection hardly affected. After that, the modeling target area is set to 10
It was divided into about 0 × 100 grids. At that time, the size of the grid was set large in the periphery and small in the vicinity of the pumping well and injection well.

Setting of boundary condition and initial condition: The flow direction of groundwater in the horizontal axis direction of the finite element grid was made to match. The left and right ends of the finite element grid were used as the pollution source, and the groundwater level was fixed based on the measured values. The initial concentrations of pollutants, oxygen, and methane were set with reference to the results of the sample property analysis.

Groundwater flow / material dynamics simulation: Based on the above, i) groundwater flow simulation in steady state only with pumping well, ii) groundwater flow and material dynamics simulation in steady state with injection well, iii)
A three-stage simulation of the material state simulation in the transition state was performed.

<Arrangement of Wells and the Like> The arrangement of various wells and the like in the purification system of the present invention according to the above-mentioned contaminated area was determined based on the results of the simulation and the like performed above.
FIG. 3 shows such an arrangement.

In FIG. 3, 210 is a pumping well;
Reference numeral 220 denotes an in situ module for preparing electron donor (methane) dissolved water / electron acceptor (oxygen) dissolved water and performing overall control of the purification system of the present invention; 231 denotes an electron donor (methane) dissolved water Supply pipe: 232 is an electron acceptor (oxygen) dissolved water supply pipe; 241 is an electron donor (methane) injection well (Iwj-3); 251 (Iwj-1) and 2
52 (Iwj-2) are both electron acceptor (oxygen) injection wells; 261 (Mw-1) and 262 (Mw-2) are both observation wells; and 270 is a contaminated area.

The horizontal distance between the pumping well 210 and the observation well 262 is 7 m; the horizontal distance between the observation well 262 and the observation well 261 is 3 m50 cm;
The distance in the horizontal axis direction between the 51.252 and the injection well 241 is 1 m40 cm;
cm; the distance between the observation well 261 and the injection well 241 in the horizontal axis direction is 3 m50 cm.

<Operation of in-situ module> (1) Operating conditions: The breeding operation for growing methane assimilating bacteria in soil was performed for 36 days. As shown in FIG. 3, mixed dissolved water of methane and inorganic nutrients was supplied to the soil through the supply pipe 231 and the injection well 241 (Iwj-3). Further, the mixed dissolved water of oxygen and inorganic nutrients is supplied to the supply pipe 2.
32 (two pipes), and the injection wells 251 (Iwj-1) and 2
52 into the soil.

The methane-dissolved water contained 10 ppm of methane, and the methane-dissolved water was injected into the soil at a rate of 0.75 t / hour. In addition, the oxygen-dissolved water contains 20 ppm
Oxygen was dissolved, and this oxygen-dissolved water was injected into the soil at a rate of 0.75 t / hour.

Further, as described above, the following inorganic nutrients were dissolved in each dissolved water. i) Potassium nitrate (KNO ₃ ) _... 95.8 g / h (total of three injection wells) ii) Potassium dihydrogen phosphate (KH ₂ PO ₄ ) _.. 33.8 g / h (same as above) iii ) Sodium carbonate (Na ₂ CO ₃ ) _... 209.0 g / hour (same as above) The pH was adjusted to around 7.0 with sulfuric acid. Further, the pumping speed in the pumping well 210 was 4.2 t / hour. The in-situ module was operated under such conditions.

The decomposition operation for decomposing trichlorethylene in the soil was performed for 54 days. Such a disassembly operation is
In the above-mentioned breeding operation, the injection of methane, oxygen and inorganic nutrients into the soil was stopped.

(2) Monitoring During the above-mentioned breeding operation and the above-mentioned decomposition operation, the amount of dissolved oxygen, inorganic nutrients, and trichloroethylene were analyzed in each monitoring well and the like.

<Results> (1) Mass transfer: In FIG. 4, injection is started on the horizontal axis (proliferation operation).
The vertical axis indicates “concentration in the observation well 262 (Mw-2) / injection well 251 (Iwj-1)” of the electric conductivity and the dissolved oxygen amount. That is, the graph shown in FIG. 4 shows the mass transfer predicted from the simulation of the transition of the dissolved oxygen concentration and the mass transfer estimated from the actually measured electric conductivity (the electric conductivity increases as the amount of oxygen increases).
5 is a graph showing the correlation of the above. As shown in FIG. 4, the mass transfer time expected from the simulation of the change in the dissolved oxygen concentration and the mass transfer time indicating the change in the measured electric conductivity were almost the same. From this, it became clear that the result of the simulation was reflected in the actual groundwater flow.

(2) Movement of inorganic nutrients: FIG. 5 is a graph showing monitoring of the state of movement of inorganic nutrients by measuring electric conductivity in the observation well 262 (Mw-2) as described above. From FIG. 5, it was found that the inorganic nutrients reached the observation well in about 4 days. This result indicates that the inorganic nutrients were sufficiently supplied during the growth operation.

(3) Supply of dissolved oxygen: FIG. 6 shows changes in the amount of dissolved oxygen in the observation wells 261 (Mw-1) and 262 (Mw-2) and the injection well 241 (Iwj-3) after oxygen is injected. 5 is a graph showing the transition of. FIG. 6 revealed that as long as oxygen was injected, sufficient oxygen for the growth of microorganisms was supplied to each of the above points. Before the oxygen injection, the dissolved oxygen concentration at each of the above points is about 5-6.
ppm.

(4) Propagation of microorganisms: FIG. 7 shows the observation wells 261 (Mw-1) and 262 (Mw-2) after starting the injection of oxygen and the like.
It is a graph which shows the change of the number (MPN: MOST PROBABLE NUMBER) of methane assimilating bacteria in injection well 241 (Iwj-3). At each point, sufficient growth of methane-utilizing bacteria was observed. In addition, as a matter of course, it was also shown that the methane-utilizing bacteria start to proliferate in the order close to the injection well.

(5) Microbial degradation of trichlorethylene:
FIG. 8 is a graph showing the results of observing changes in trichlorethylene concentration in all observation wells and injection wells. Under the breeding operation conditions, trichlorethylene in the range of the demonstration tests performed beforehand decreased due to the dilution effect.
Under the decomposition operation conditions, as long as microbial decomposition did not occur, trichloroethylene was replenished from the high-concentration contaminated sites as needed, and the trichlorethylene concentration in wells within the verification test range increased.

The recovery rate of the trichlorethylene concentration in the pumping well by the simulation was 90 to 95% on the 15th day after the start of the decomposition operation. In addition,
This simulation excludes the effects of microbial degradation of trichlorethylene.

However, as shown in FIG. 8, the measured value of the trichlorethylene concentration was
It finally rose about 50 days after the start of the decomposition operation. That is, it was shown that the trichlorethylene concentration increased about 35 days later than the calculation based on the simulation. This clearly indicates that trichlorethylene was decomposed by the grown methane-utilizing bacteria.

According to the present embodiment, it is possible to continuously decompose trichlorethylene repeatedly supplied to the soil by methane-utilizing bacteria by repeating the above-described growth operation and decomposition operation. Also became apparent.

[0107]

According to the present invention, a method and system for purifying contaminated soil that can purify contaminated soil effectively by activating microorganisms capable of decomposing contaminants inhabiting the soil in principle. Was provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a mechanism for realizing a method for purifying contaminated soil including a conventional technique.

FIG. 2 is a schematic view showing an arrangement of an injection means and the like in one embodiment of the purification system of the present invention.

FIG. 3 is a schematic diagram showing a specific arrangement of wells and the like according to the embodiment.

FIG. 4 is a graph showing a correlation between a mass transfer time estimated from a simulation of a change in dissolved oxygen concentration and a mass transfer time indicating a change in an actually measured electric conductivity.

FIG. 5 is a graph showing monitoring of the state of movement of inorganic nutrients by measuring electric conductivity.

FIG. 6 is a graph showing a change in the amount of dissolved oxygen in an observation well or the like after oxygen is injected.

FIG. 7 is a graph showing a change in the number of methane assimilating bacteria in an observation well or the like after the start of injection of oxygen or the like.

FIG. 8 is a graph showing the results of observing changes in trichlorethylene concentration in all observation wells and injection wells.

[Explanation of symbols]

 10, 100 Purification system 11, 110, 210 Pumping well 12 Pumping pump 13, 13 ', 130 Water absorption pipe 13' 'Injection pipe 14 Pretreatment means 15, 150 Mixing means 16, 161, 162, 163 Injection well 20 Formation 30 Aquifer interface 40 Aquifer 50 Contaminated soil 170, 261, 262 Observation well 220 In-situ module 231 Electron donor (methane) dissolved water supply pipe 232 Electron acceptor (oxygen) dissolved water supply pipe 241 Electron donor (methane) Injection well 251, 252 Electron acceptor (oxygen) injection well 270 Contaminated area

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Clay Walton United States 80401 Fes Cure Avenue, Golden City, Colorado 23377 (72) Inventor Nick Cusallas United States of America 80002 Arubada, Colorado AW. Grand View Avenue (58) Fields surveyed (Int. Cl. ⁷ , DB name) B09B 3/00 ZABE

Claims (13)

(57) [Claims] 1. A method for purifying contaminated soil, comprising promoting the growth of microorganisms capable of decomposing contaminants in soil and decomposing the microorganisms into contaminants. The elements are separated and provided to the soil at three or more supply points, and then the elements provided to the soil are mixed by being moved by the water current in the aquifer and mixed in the aquifer. A method for purifying contaminated soil, comprising activating and decomposing contaminants in an activated region of the microorganism. 2. The method for purifying contaminated soil according to claim 1, further comprising means for generating a water flow for moving a plurality of elements for promoting the growth of microorganisms capable of decomposing contaminants to the confluence point. A method for purifying contaminated soil, wherein a plurality of elements for promoting the growth of the microorganisms are moved toward a mixed point by means. 3. The method for purifying contaminated soil according to claim 2, wherein the means for generating a water flow for moving a plurality of elements for promoting the growth of microorganisms capable of decomposing contaminants to the confluence point includes an aquifer. A method for purifying contaminated soil, characterized by pumping water in the inside. 4. The method according to claim 1, wherein the plurality of factors promoting the growth of microorganisms capable of decomposing pollutants include an electron donor and an electron acceptor for the microorganisms. A method for purifying contaminated soil according to the claim. 5. The method for removing contaminated soil according to claim 4, wherein a point at which an electron donor of a microorganism capable of decomposing contaminants is provided to the soil is downstream on the basis of the water flow in the aquifer and A point where an electron acceptor is provided to a plurality of soils at equidistant points, and a point where the electron donor and the electron acceptor donated into the soil move and mix with each other due to the flow of water in the aquifer. , A method for purifying contaminated soil, comprising activating the microorganism. 6. The method for purifying contaminated soil according to claim 1, wherein the microorganism capable of decomposing pollutants is a methane-utilizing bacterium. 7. The method for purifying contaminated soil according to claim 1, wherein microorganisms capable of decomposing contaminants in the contaminated area are added to the contaminated area. 8. The method for purifying contaminated soil according to any one of claims 1 to 7, wherein the following steps are repeated: microorganisms capable of decomposing contaminants. A second step of decomposing contaminants into the microorganisms after the supply of the plurality of factors that promote the growth of the microorganisms to the soil is stopped after the first step; A third step of providing a plurality of elements for promoting the growth of the microorganism to the soil again when the activity of the microorganism decreases. 9. An electron donor dissolved water injection means for injecting an electron donor dissolved water supplied by an electron donor dissolved water supply means for microorganisms capable of decomposing pollutants into aquifer, and capable of decomposing pollutants. An electron acceptor dissolved water injection means for injecting the electron acceptor dissolved water supplied from the electron acceptor dissolved water supply means for the microorganism into the aquifer, upstream of the contaminated region in the water flow in the aquifer, And the electron donor dissolved water injected into the soil by the electron donor dissolved water injection means and the electron acceptor dissolved water injected into the soil by the electron acceptor dissolved water injection means are mixed in the contaminated region. Wherein the electron donor dissolved water injection means and the electron acceptor dissolved water injection means are provided at three or more points. 10. An electron donor dissolved water injection means for injecting an electron donor dissolved water supplied by an electron donor dissolved water supply means for microorganisms capable of decomposing a pollutant into an aquifer, and capable of decomposing a pollutant. An electron acceptor dissolved water supply means for injecting the electron acceptor dissolved water supplied from the electron acceptor dissolved water supply means into the aquifer, and a pumping means for pumping water in the aquifer. The water flow in the aquifer generated by pumping in the means caused the electron donor dissolved water injected into the soil by the electron donor dissolved water injection means and was injected into the soil by the electron acceptor dissolved water injection means. An arrangement in which the electron acceptor dissolved water can mix in the contaminated area, the electron donor dissolved water injection means and the electron acceptor dissolved water injection means are provided at three or more points, and Providing a stage, and further distributing the water pumped from the pumping means to the electron donor dissolved water supply means and / or the electron acceptor dissolved water supply means, and dissolving the electron donor dissolved water and / or the electron acceptor dissolved water. A contaminated soil purification system characterized by contributing to production. 11. A contaminated soil purification system according to claim 10, further comprising means for separating contaminants in the groundwater pumped by the pumping means, wherein the groundwater repurified by the means is capable of decomposing the contaminants. Supplying the donor-dissolved water supply means and / or the contaminant to the electron-acceptor-dissolved-water supply means for decomposable microorganisms to contribute to the production of the electron-acceptor-dissolved water and / or the electron-acceptor-dissolved water; Characterized purification system for contaminated soil. 12. A means for injecting dissolved water of an electron donor for microorganisms capable of decomposing contaminants is provided upstream of a groundwater flow in an aquifer, and a point equidistant from the point to the downstream of the groundwater flow. The purification system for contaminated soil according to claim 10 or 11, wherein a plurality of electron acceptor dissolved water supply means are provided. 13. The contaminated soil purification system according to claim 8, wherein a microorganism capable of decomposing the contaminants in the contaminated region is added to the contaminated region. .