JP6750865B2 - Countermeasures against soil pollutants - Google Patents

Description

The present invention relates to a method for coping with soil pollution during operation by a business operator handling hazardous substances.

The soil pollution control business in Japan began to enter the industry by many related companies in the 1990s, and since then the related laws have been enacted, and it was actively implemented until around 2010, but due to the Lehman shock. The industry was heading for a shrinking trend as companies withdrew due to the stagnation of land flow and the decrease in the number of large-scale contaminated sites with large profits.
As a result, in about 20 years from the creation of the industry to the present day, measures for about 10% of contaminated sites have been completed, but about 90% of contaminated sites still remain.

This residual polluted site is a case where the project is ongoing and purification is not progressing as expected, and it is a land with bad debts called brown field which is abandoned due to high pollution control costs and difficult land sale There are also many.
Although the land is in a so-called "salted state", the total amount of bad debts that may cause brownfield in Japan is estimated to be about 11 trillion yen, promoting land mobilization and regional redevelopment during economic recovery. It has been recognized as a new social problem that will be an obstacle to doing so (Intermediate report on the actual situation of the Brownfield problem concerning soil pollution / Document 5 (March 2007)).

In this way, the soil pollution countermeasure costs will be large, and if it becomes difficult to sell the land after the project is completed and it is left unattended and becomes brownfield, such a brownfield countermeasure is a budget that is commensurate with the expected land sale price. It is necessary to carry out brownfield prevention measures within the scope in advance from the start of operation before the end of the project, or to wait for the launch of inexpensive and effective brownfield countermeasure technology. However, in the present situation, the latter is not even promising, and there is only the option of focusing on the measures of the former.

The former measures include "prevention of pollution leaks" before brownfield due to the spread of pollution, and "early detection of pollution leaks and prevention of migration/diffusion of leaked pollutions (including local A series of brownfield preventive measures based on the fail-safe concept against pollution leakage, such as "low elution and pollution decomposition", and "continuation of purification measures during operation" if pollution still occurs. , Especially important.
As for the technical/policy approach regarding the “prevention of pollution leakage”, the revised Water Pollution Control Law enforced in 2012 is a measure to prevent soil and groundwater pollution. The standards for the structure, equipment, and method of use were provided, and legally binding measures were taken.
In addition, in "Implementation of purification measures during operation", there are some effective countermeasure techniques for in-situ purification techniques in conventional pollution purification techniques, and they contribute to a certain extent to brownfield prevention measures. ..
As described above, in the efforts to prevent brownfield conversion against pollution leaks, the introduction of "prevention of pollution leaks" and the final stage "implementation of purification measures from the start of operation" are almost ready. there were.

However, it is a technology that connects the introduction and the last stage, that is, a technology that guarantees preventive measures from the viewpoint of fail-safe and leads to full-scale measures, such as "early detection of pollution leakage and suppression of migration/diffusion of leakage pollution (including : Localized low elution/pollution decomposition) technology is still under development, and there was a situation where complementation by such relay technology was desired in a series of brownfield prevention measures.
As related arts related to "early detection of pollution leakage" in such "early detection of pollution leakage and movement/diffusion suppression of leakage pollution (including local low elution and pollution decomposition)", there are Patent Documents 1 to 1. There is a technology shown in 3. Further, as related arts related to “movement/diffusion suppression of leaked pollution (including: local low elution/decomposition of pollution)”, there are technologies shown in Patent Documents 4 to 6.

Japanese Patent No. 5789289 Patent No. 5339176 Japanese Patent No. 4702669 Patent No. 5596936 Japanese Patent No. 3079260 Japanese Patent No. 5218853

However, as a conventional technique related to "early detection of pollution leak" in "early detection of pollution leak and movement/diffusion control of leaked pollution (including local low elution and pollution decomposition)", Patent Document 1 The techniques shown in to 3 have various problems as described later.

Patent Document 1 is a technique for capturing pollutants in the injected inspection fluid and collecting groundwater containing the inspection fluid to detect contamination. However, when the groundwater depth is deep, the drilling machine is used for mesh investigation. Therefore, it was necessary to install a large number of observation wells using the above, and there was a difficulty in practicality and versatility from the cost.
In addition, the present technology is a study that assumes that the injected test fluid spreads evenly around the periphery and returns reliably, but this premise requires that the stratum be homogeneous and In such an ideal condition, there can hardly exist. The present technology is highly dependent on the environment, and there is a concern that contamination may be overlooked or underestimated depending on how the inspection fluid spreads.

Moreover, although patent document 2 is a technique which estimates the existence of pollution from the concentration distribution of the ion species used as the respiration source of various microorganisms in groundwater, like patent document 1, when groundwater depth exists deeply, a mesh investigation will be carried out. Since it was necessary to install a large number of observation wells, there was difficulty in practicality and versatility in terms of cost.
In addition, if nitrate ions and sulfate ions, which are respiration sources of pollutant-degrading microorganisms, do not exist at the survey site under the initial conditions in a substantially uniform concentration, it is not possible to appropriately carry out a quantitative evaluation according to the amount of contamination. It was also a technology with uncertainty, such as being difficult to underestimate pollution or making a mistake.
In general, the present technology is highly environment-dependent and has an uncertainty of underestimating the pollution or making a mistake.

Furthermore, Patent Document 3 is an investigation method using surface gas, and is an embodiment in which construction is easy and low cost can be expected. If there is no shortage and basic conditions to ensure microbial metabolism are not in place, it is difficult to properly carry out an evaluation according to the amount of pollution, and it was also a technique with the uncertainty of underestimating pollution. ..
In general, the present technology is also highly dependent on the environment and has an uncertainty of underestimating or misidentifying pollution.

As described above, the conventional technologies related to “early detection of pollution leakage” in “early detection of pollution leakage and movement/diffusion control of leakage pollution (including local low elution and pollution decomposition)” are all It was a highly expensive technology, which is highly dependent on the environment and could cause pollution to be overlooked or underestimated.

By the way, in the "Early detection of pollution leakage and migration/diffusion control of leakage pollution (including local low elution and pollution decomposition)" technology, "Movement/diffusion suppression of leakage pollution (including local low elution/local decomposition)" The technologies disclosed in Patent Documents 4 to 6, which are conventional technologies related to "decomposition of pollution", also have various problems as described below.

For example, as in the technique disclosed in Patent Document 4, as a method for suppressing migration/diffusion of pollutants from soil pollution by organic compounds (including local low elution and pollution decomposition) A method for reducing elution using a material containing activated carbon has been proposed.

However, a method for suppressing migration/diffusion of pollutants (including: local low elution/pollution decomposition) using a tablet-shaped active carbon-containing material disclosed in Patent Document 4 is a contaminated surface layer. It is a technology for countermeasures by spraying on soil or river bottom mud, and in order to apply it to a polluted saturated zone having a geological structure, it is necessary to use a method such as excavating and mixing from the shape of tablet-like activated carbon-containing material. It was a technology with limited and limited applicability.
In addition, this technology is a technology that simply adsorbs contaminants to activated carbon tablets to achieve local low elution, and is not a purification technology that can reduce contaminants, that is, reduces the content of contaminants. It was a difficult technique to do.

Further, the difficulty of reducing the contamination content is also the same as the contamination countermeasure technology using fine carbon-based particles having a contamination adsorbing ability of Patent Document 5.
That is, if there is no function of decomposing and removing the contaminants adsorbed on the fine carbon-based particles having a contaminant adsorption capacity, the dispersed fine carbon-based particles having a contaminant adsorption capacity eventually reach the limit of the adsorption amount, and in that case, It was a technique that could result in an uneconomical treatment, such as repeatedly charging fine carbonaceous particles having a contaminant adsorption capacity.

The method for preventing recontamination after purification of contaminated soil shown in Patent Document 6 is a technique aimed at inadvertent contamination elution after soil groundwater pollution countermeasures. Zeolite is used only for the adsorption of pollutants, and even in the present technology, there is no function of decomposing and removing the contaminants adsorbed by the adsorbent particles having a contaminant adsorbing ability. The technique reached the limit, and in that case, the technique could be an uneconomical treatment such as repeatedly introducing adsorbent particles having a contaminant adsorption ability.

Generally speaking, the technology of adding fine carbon particles with various adsorption capacity to soil for conventional soil pollution and implementing countermeasures against pollution is "movement/diffusion suppression/low elution" for a certain amount of pollution. Although it is possible to achieve this, it was not a technology that has both continuity of effects and cost-effectiveness in consideration of “decomposition” that reduces the pollutant content.

From such a background, the purpose of the present invention is to reduce the risk of underestimation of pollution, to provide an inexpensive “early detection of pollution leakage” technology with low environmental dependency, and to prevent migration/diffusion suppression/low elution. , It was set as the market launch of the technology of "movement/diffusion control of leaked pollution (including: local low elution/pollution decomposition)" in consideration of pollution decomposition to reduce the pollution content.

In order to solve the above-mentioned problems, the inventors of the present invention have eagerly developed the bio-prevention method applying the function of the iron-reducing bacteria (biological The following inventions have been achieved to achieve "early detection of pollution leakage and suppression of migration/diffusion of leakage pollution (including local low elution and pollution decomposition)" by means of the Pollution Prevention Law) It was
That is, the gist of the present invention is the following (1) to (14).

(1) A material containing a porous carbon-based material that mediates extracellular electron transfer of iron-reducing bacteria at least partly in a site where biodegradable pollutants including harmful substances are handled or planned And, a culture substrate is added to the soil to be treated, a three-dimensional conductive net that communicates is formed in the ground, and a contact is made with a microbial community including iron-reducing bacteria that conducts to the three-dimensional conductive net and contaminants, metabolism or degradation of the pollutants to a countermeasure method of FIG Ru soil contaminants, achieving generation and accumulation of insoluble iron compounds derived from the metabolism of the iron-reducing bacteria, to encourage blockage of soil pore, said pollution The method for controlling soil pollutants, which aims to suppress the migration of the pollutants and further metabolizes or decomposes the pollutants whose migration is suppressed .

( 2 ) On the site, a microbial community including the steric conductive net and iron-reducing bacteria is formed for a soil-contaminated area where soil contamination by the pollutant is known and its surrounding area ( This is the countermeasure method for soil pollutants described in 1 ) .

( 3 ) A microorganism that can metabolize the pollutant and/or a material containing at least a part of a porous carbon-based material that mediates extracellular electron transfer of the iron-reducing bacterium by separately culturing the iron-reducing bacterium And/or, together with the culture substrate, the method for controlling soil pollutants described in at least one of (1) to ( 2 ), which is added to the soil to be treated.

(4) an electron donor according to the microorganism metabolism, and / or an electron acceptor, which is according to at least one of adding to the soil measures a subject from and wherein (1) and (3) Soil This is a countermeasure for pollutants.

( 5 ) The material containing a porous carbon-based material that mediates extracellular electron transfer of iron-reducing bacteria in at least a part thereof is activated carbon, according to at least one of (1) to ( 4 ). This is a countermeasure method for the listed soil pollutants.

( 6 ) The operation of accelerating the metabolism and decomposition of pollutants under reducing conditions by adding the activated carbon and iron powder, and a material containing a fat-soluble organic material as at least a part of the culture substrate, is performed . It is the method for controlling soil pollutants described in ( 5 ), which is carried out at any time.

( 7 ) An operation of adding the activated carbon and iron powder to the soil to be treated, and further adding a material containing at least a part of peroxide to accelerate the metabolism and decomposition of pollutants under oxidizing conditions , is been countermeasures soil contaminants described which comprises carrying out at the timing of arbitrary (5).

( 8 ) It is characterized in that a gas containing air or oxygen is supplied to the soil to be treated for the purpose of supplying electron acceptors and/or activating electron acceptors used by the iron-reducing bacteria. It is the method for controlling soil pollutants described in at least one of (1) to ( 7 ).

(9) Material via wells like structures, with the addition of the peroxide into the soil measures a subject, comprising at least a portion of the porous carbonaceous material which mediate extracellular electron transfer of the iron-reducing bacteria The method for remedying soil pollutants described in at least one of (1) to ( 8 ) is characterized in that the operation for regenerating the functional deterioration due to the adherent substance is carried out.

( 10 ) The well-like structure is composed of one tube structure, and has a function of observing well and a function of injecting a peroxide solution and/or gas from the strainer section into the soil to be treated. The method for controlling soil pollutants described in ( 9 ) is characterized by disposing strainers for at least two sections.

( 11 ) The method for preventing soil pollutants according to at least one of ( 7 ), ( 9 ), or ( 10 ), wherein the peroxide is a persulfate compound.

( 12 ) The concentration of at least one underground gas component containing at least carbon dioxide gas generated through the metabolism of a microbial community including the iron-reducing bacteria is measured, and the underground leakage of the pollutant is determined from the concentration distribution of the gas component. the estimation of the location, a countermeasure soil pollutants according to at least one of which comprises carrying out pressurized strong point (1) (11).

( 13 ) The method for controlling soil pollutants described in at least one of (1) to ( 12 ), wherein the harmful substance is 1,4-dioxane.

Hereinafter, the present invention will be described in more detail.
In the present invention, a bioprevention method applying the function of an iron-reducing bacterium by utilizing a steric conductive network of a material containing at least a part of a porous carbon-based material that mediates extracellular electron transfer of the iron-reducing bacterium. (Biological Pollution Prevention Law) and its incidental countermeasure technology group to implement a series of pollution countermeasures such as "early detection of pollution leakage and suppression of migration/diffusion of leakage pollution (including local low elution and pollution decomposition)" It is assumed to be implemented.

According to the method for controlling soil pollutants according to (1) of the present invention, a material containing a porous carbon-based material that mediates extracellular electron transfer of iron-reducing bacteria in at least a part and a culture base are used as a target land. By adding it to the saturated or unsaturated zone of spores to form a communicating steric conductive network in the ground, it is biodegradable and harmful by the metabolism of a microbial community including iron-reducing bacteria that conducts to the steric conductive network. It is possible to promote metabolism of pollutants including substances and reduce pollutants.

Even if abundant trivalent iron is present in soil, there are three parties, "iron-reducing bacteria (including microbial community),""pollutants," and "electron acceptor" at the same location. Without it, high metabolic activity cannot be obtained. Furthermore, even if these three are present at the same point, if the metabolism progresses over time and the relative amount becomes "pollutant">"electronacceptor", the "electron acceptor" As a result, the metabolism of "iron-reducing bacteria (including microbial community)" is lowered and the metabolism of "pollutants" is stopped.
However, according to the present invention, by spreading a communicating three-dimensional conductive network in the soil, at least "iron-reducing bacteria (including microbial community)", "pollutants" and "three-dimensional conductive network" can be obtained. If a person exists at the same point, this steric conductive network mediates the transfer of electrons from iron-reducing bacteria to many electron acceptors in the vicinity.
Furthermore, as the culture progresses and the amount of iron-reducing bacteria increases, the three-dimensional conductive networks that are not in conduction are brought into conduction by the intermediary of iron-reducing bacteria, and the three-dimensional conduction networks are organically linked to each other. It becomes possible to utilize the ferric iron in the range where the three-dimensional conductive network is laid as a general electron acceptor.
By installing the three-dimensional conductive network according to the present invention in the ground by such a mechanism, the relative amount in the metabolic balance becomes “pollutant”<“electron acceptor”, and therefore pollutants due to iron-reducing bacteria etc. Metabolism continues on the spot, and more pollutants can be continuously purified.

By the way, by laying a three-dimensional conductive network according to the present invention, by the metabolism of a microbial community including iron-reducing bacteria, in the process of decomposing and purifying pollutants that exhibit biodegradability and include harmful substances, carbon dioxide Various iron compounds derived from iron and trivalent iron accumulate in the surrounding soil voids.

If the former accumulated carbon dioxide is used, the soil gas is collected through the underground hole that communicates with the ground, which is the method according to ( 12 ), and the concentration of one or more gas components containing at least carbon dioxide. By measuring periodically, the underground leakage of the pollutant and its leakage point can be detected early from the concentration distribution of the gas component concerned, so a series of subsequent measures for soil pollutants will be implemented effectively and effectively. be able to.
In addition, by conducting underground leakage surveys of such pollutants with high accuracy and regularity, the presence and location of the contamination leakage can be detected at the very early stage of the leakage, so that it can be moved/extended to a wide area/deep area. However, it is possible to avoid the risk of causing serious pollution damage, and as a result, it is possible to implement pollution control measures that significantly reduce purification cost.
Actually, excavation and removal of contaminated soil of 1 cubic meter in the shallow layer costs tens of thousands of yen. Assuming that the groundwater flow velocity is 0.3 m/day and the vertical/horizontal movement speed is 1/10 of this, if left unattended for 1 year, the pollution length will exceed 100 m and the pollution depth/width will exceed 10 m. Simply, about 0.5 to 10,000 cubic meters of contaminated soil will be produced in one year, and this treatment will result in a serious damage situation in which a loss of 100 million units is expected if left unattended for at most one year.

On the other hand, the latter iron compounds derived from ferric iron do not always accumulate at the site where decomposition and purification of pollutants are achieved by metabolism of the microbial community including iron-reducing bacteria due to the function of the above-mentioned steric conductive network. .. Many of them are composed of various ferric iron-derived iron compounds in the periphery where microbial communities including iron-reducing bacteria are present, at the part where the steric conductive network comes into contact with the soil near the oxidizing environment where ferric iron exists. Accumulation is planned.
That is, in the method according to ( 1 ), various iron compounds derived from ferric iron, such as magnetite, oxygen and divalent iron, are present in the vicinity of the oxidative environment existing around the anaerobic environment. By accumulating insoluble iron compounds such as iron hydroxide generated in the reaction, the soil voids near the contamination are promoted to be blocked, and microorganisms containing iron-reducing bacteria while suppressing migration/diffusion of contaminants. The pollutants in the vicinity of the crowd can be retained, and the pollutants can be efficiently reduced by metabolism of the microbial community including the iron-reducing bacteria.

In addition, although the migration of pollutants becomes extremely slow due to the blockage of the soil gap, since the metabolic rate of pollutants by the microbial community including iron-reducing bacteria does not change, the carbon dioxide concentration in the surroundings can be maintained at a high spot. The accuracy of detection of a pollution leak point by soil gas survey, which is the method according to ( 12 ), can be significantly increased by this mechanism.

By the way, according to the method for controlling soil pollutants according to ( 2 ), even when the pollution is already known, as in the unknown case, it is a porous medium that mediates extracellular electron transfer of iron-reducing bacteria. A material containing at least part of a carbonaceous material and a culture substrate are added to a saturated zone or an unsaturated zone of the target land to form a communicating three-dimensional conductive network in the ground, thereby conducting the three-dimensional conductive network. Metabolism of contaminants in microbial communities, including iron-reducing bacteria, allows for purification of known contaminants while preventing further contamination migration/diffusion.

Furthermore, according to the method for controlling soil pollutants according to ( 5 ), the porous carbonaceous material is more preferably activated carbon to increase the adsorption ability of pollutants, resulting in higher accuracy. It is possible to suppress migration/diffusion of pollutants and reduce elution from soil.

By the way, if soil contamination is known at a site where there is a history of handling pollutants, it is preferable to preferentially purify this known contamination in consideration of the timing at which purification measures are realized.
According to countermeasures soil contaminants in this invention is that where the (6) (7), at the timing of the arbitrary, selected activated carbon and iron powder as a conductive material, if necessary peroxidation It is possible to effectively carry out spot purification inexpensively and promptly by utilizing things and the like together.

In addition, according to the method for controlling soil pollutants according to ( 3 ), the present invention can be performed by separately culturing a microorganism that controls microbial metabolism of a pollutant and/or the iron-reducing bacterium and adding the soil-reducing bacteria to the soil. It is possible to further strengthen and surely carry out migration/diffusion control of pollution and microbial decomposition in the target area to be deployed.

By the way, according to the method for controlling soil pollutants according to ( 4 ), the electron donors and/or electron acceptors of the microorganisms and iron-reducing bacteria that control the microbial metabolism of pollutants are not insufficient in the soil to be purified. By adding, it is possible to more surely carry out microbial decomposition of contamination in the target area to which the present invention is applied, and migration/diffusion suppression by iron-reducing bacteria.

Further, according to the method for controlling soil pollutants according to ( 8 ), by supplying a gas containing air or oxygen to the soil, anaerobic iron-reducing bacteria are activated by oxidation of electron acceptors. On the other hand, oxygen is supplied as an electron acceptor to aerobic iron-reducing bacteria and aerobic microorganisms, and by this one-step operation, both anaerobic/aerobic regions in soil can be obtained. Microbial decomposition of pollutants can be very efficiently promoted.

For example, benzene can be biodegraded by both anaerobic iron-reducing bacteria and aerobic bacteria, but in the prior art, soil is mainly excavated to form static piles, etc. Purification was achieved by aerobic decomposition by continuous inhalation from.
However, it is almost impossible to evenly ventilate the inside of the static pile by pure aerobic decomposition using this static pile, which is the conventional technique. It became a way and was only implemented locally. Therefore, continuous aeration is used to dry the soil with oxygen supply, and the pile cutting operation is repeated at regular intervals to further crush the aggregated structure and soil mass of the soil in a dry state. It was essential to combine the work so that oxygen was evenly distributed throughout the soil.
However, by forming a three-dimensional conductive network in the soil, which is the present invention, the ferric iron present in the soil, which is an electron acceptor for iron-reducing bacteria, can be fully utilized. , Which was essential for aerobic decomposition, can be used to purify benzene pollution by turning work to spread oxygen electron acceptors evenly throughout the contaminated soil and by greatly reducing continuous intake. it can.

In this case, the inversion (ventilation) using heavy-duty heavy-duty turning and a large air supply device is performed at the minimum number of times when most of the ferric iron, which is an electron acceptor of iron-reducing bacteria, is reduced. By reoxidizing a part of the reduced iron compound with oxygen to regenerate trivalent iron, which is an electron acceptor of iron-reducing bacteria, purification with low energy and low cost is performed. Can be implemented.

As described above, by properly installing the three-dimensional conductive network of the present invention, more ferric iron in the soil can be utilized as an electron acceptor, which is a normal pollutant concentration, If the soil contains valent iron, it will be contaminated with minimum man-hours including mixing work in the initial installation of the three-dimensional conductive network without special turning back or intake (aeration) using a large air supply device. Purification can be carried out.
Theoretically, from the content of trivalent iron contained in general soil, there is an electron acceptor amount satisfying the anaerobic metabolic decomposition of benzene present at a maximum concentration of 1 g/kg. This is a much higher concentration than that found in benzene-contaminated soils commonly found.

By the way, in the environment where both oxygen and trivalent iron are present as described above, it is possible to specifically promote the growth of some iron-reducing bacteria that can use both of them as electron acceptors.
Some of these iron-reducing bacteria produce ferric iron and organic acids when ferric iron is used as an electron acceptor, while hydrogen peroxide is produced when oxygen is used as an electron acceptor. In the method for controlling soil pollutants according to ( 8 ), which is known in nature and is the present invention, by supplying air or a gas containing oxygen to the soil to be countermeasured at regular intervals, By forming the timing when ferric iron, an organic acid and hydrogen peroxide are present at the same time, it is possible to promote the decomposition of further pollutants by the Fenton reaction which is a chemical oxidation mechanism based on these products.

Further, according to the countermeasures soil contaminants shown in (9) and (10), wells like structures, preferably, consists of one tube structure, with observation wells functions, from the strainer section, By using a well-like structure having a function of injecting a peroxide solution and/or a gas into the soil to be treated, the peroxide can be effectively and evenly added to the soil to be treated. the porous carbon-based materials that mediate extracellular electron transfer iron-reducing bacteria to allow regeneration of reduced function by adhesive substance of the material comprising at least a portion, it is possible to maintain the normal operation.

Furthermore, in the method for controlling soil pollutants shown in ( 7 ), ( 9 ) and ( 10 ), by using a persulfate compound as a peroxide, a better pollution purification/washing effect can be obtained. ..

By the way, 1,4-dioxane, which has been environmentally standardized by the Ministry of the Environment Notification in 2009, is a harmful substance that has generally been evaluated to have low biodegradability, and there are no particular findings regarding bio-purification measures. There were still few situations.
According to the method for controlling soil pollutants shown in ( 13 ), which is the present invention, it is possible to detect early detection of pollution leakage and transfer of leakage pollution by utilizing iron-reducing bacteria against 1,4-dioxane, which is a harmful substance. /Diffusion suppression (including: local low elution and pollution decomposition)" can be implemented.

According to the present invention, the known or unknown soil pollution by the statutory first class specific harmful substances and similar harmful substances is applied to the function of the iron-reducing bacteria by utilizing the three-dimensional conductive network of the conductive material. A series of "early detection of pollution leak and suppression of migration/diffusion of leak pollution (including local low elution and pollution decomposition)" by the bioprevention method (biological pollution prevention method) and its incidental countermeasure technology group Can be achieved with.

It is a schematic diagram which shows the basic concept of the soil pollution countermeasure method in this invention. It is a schematic diagram which shows the basic concept of the surface layer gas investigation method in this invention. It is a schematic diagram of the microbial community including the iron reducing bacteria in the present invention. It is a schematic diagram which shows the basic concept of the well-like structure in this invention. 3 is a graph showing the amount of CO 2 generated in each test section in Example 1. 5 is a graph showing the treatment performance of pollutants in each test section in Example 2. It is the graph which used for the purification capacity of the test area 1 in Example 2 for comparison with other elements. 7 is a graph showing changes in supply pressure in each test section in Example 2.

Hereinafter, a basic embodiment representative of the present invention will be described with reference to the drawings of FIGS. 1 to 3.
In particular, the gist of the present invention is that the conductive material 1 forms a communicating steric conductive network 2 in the ground, and the metabolism of the microbial community 3 including iron-reducing bacteria is biodegradable with the steric conductive network 2. By activating the pollutant 4 including the toxic substance in a range where it coexists, a series of pollution countermeasures including the following elements are taken against leakage pollution.

(A) Estimating the location of pollution leaks, preferably early detection of leaks.
(B) Suppression of migration/diffusion of contamination due to generation of insoluble iron compound or the like.
(C) Low elution of harmful substances from soil.
(D) Bioprevention by a microbial community including iron-reducing bacteria.
(E) Spot purification using a conductive material against known contamination that is easy to approach.

It should be noted that the pollutant 4, which leaks on the surface of the earth 17 and exhibits biodegradability and contains harmful substances, traces the process of penetrating from the leak point 12 to the unsaturated zone 18 and from the unsaturated zone 18 to the saturated zone 20. Generally, if the pollutant 4, which reaches the saturation zone 20 and exhibits biodegradability and contains harmful substances, flows down according to the natural groundwater flow direction and causes wide-area pollution, it becomes a more serious problem.
The three-dimensional conductive net 2, which is the gist of the present invention, can be formed in any soil section from the ground surface 17 to the unsaturated zone 18 and further to the saturated zone 20, but here, it is more serious. Such an embodiment will be described below by taking as an example the application in the saturation zone 20 where various problems are concerned.

By the way, the microbial community 3 including the iron-reducing bacteria present in the saturated zone 20 becomes oxidative soil particles 5 composed of trivalent iron compounds such as goethite and ferrihydrite in the saturated zone anaerobic environment. On the other hand, by directly or indirectly imparting electrons, breathing is performed to generate iron compounds containing divalent iron such as divalent iron ions and magnetite.

If the steric conductive net 2 is present together with the microbial community 3 containing the iron-reducing bacteria, the electrons imparted to the steric conductive net 2 from the microbial community 3 containing the iron-reducing bacteria are all in contact with the steric conductive net 2. It becomes possible to donate electrons to the oxidative soil particles 5, and the oxidative soil particles 5 that function as an electron acceptor serving as a respiratory source are used in abundance, and thus pollutants 4 that are biodegradable and include harmful substances Purification is achieved, and further, by the electron donation, a reductive insoluble iron compound 11 and divalent iron ions are generated.

The initial state of pollution is a situation in which the pollutant 4, which is biodegradable and contains harmful substances, has infiltrated into the soil gap that is exactly composed of the oxidative soil particles 5. At this point, the oxidative soil particles are 5. Pollutants 4, which are biodegradable and contain harmful substances, and microbial communities 3, which contain iron-reducing bacteria, exist at almost the same point, and insoluble iron compounds 11 and divalent iron ions are produced at this point.

On the other hand, when the metabolism of pollutants in the microbial community 3 including iron-reducing bacteria progresses over time, the oxidative soil particles 5 at the pollution leak point are used as a respiratory source for the microbial community 3 including iron-reducing bacteria. Then, it changes into reducing soil particles 6, and finally the respiratory source at this point is depleted. At this point, electron-releasing respiration starts via the three-dimensional conductive network 2 and to the surrounding oxidative soil particles 5.

As a result, the insoluble iron compound 11 is produced and accumulated in the boundary area with the surrounding saturated zone aerobic environment area 8 instead of the saturated zone anaerobic environment area 7 where the microbial community 3 including iron-reducing bacteria grows. As a result of this accumulation, the closure of the soil gap is promoted. In addition, regarding the divalent iron ions generated together, the insoluble iron compound 11 that is a trivalent iron compound is produced from the reaction with the molecular oxygen contained in the surrounding clean surface groundwater 9, and the iron-reducing bacteria are included. The insoluble particle group promotes the clogging of the soil gap in combination with the bacterial cells of the microbial community 3 that grow.

By the way, according to the Ministry of the Environment "Survey of the Soil Contamination Countermeasures Act of 2008 and the results of surveys on soil pollution surveys and cases of countermeasures," soil pollution is generally a cause of temporary damage such as pipe damage or improper handling. It has been shown that it is often caused by sexual problems, and the proportion of continuous and continuous leakage cases such as infiltration of drainage underground is low.

As described above, as one of the causes for the temporary trouble to progress to the serious pollution in which the brown field is feared, in the conventional technology, the temporary pollution that cannot be prevented in advance. On the other hand, there is no suitable technology for early detection and movement/diffusion suppression.
As a result, even if a temporary leak of a small amount of pollution occurs, if it is overlooked and the pollution spreads, depending on the elapsed time, the cost of countermeasures that cannot be imagined as described above will be applied to serious pollution. And it progresses.
Therefore, it is important to detect how quickly a temporary small-scale leakage problem occurs and to control the movement/diffusion to prevent serious pollution, that is, to prevent brownfield. Becomes

The early detection of leakage pollution according to the present invention is caused by activation of metabolism of the microbial community 3 including iron-reducing bacteria, triggered by the leakage of the pollutant 4 which is biodegradable and includes harmful substances. The large amount of carbon dioxide gas 13 is used as an index to estimate (A) the pollution leakage point.

For example, assuming that about 0.1 L of benzene stock solution leaked into the ground and was completely decomposed to carbon dioxide gas 13 by the microbial community 3 including iron-reducing bacteria, 1 mol of benzene up to 6 mol of dioxide. Since carbon is generated, the carbon dioxide gas 13 generally exceeds 100 L.
Then, the carbon dioxide of the surface underground gas gradually diffuses to the surroundings while generating a concentration distribution with the maximum concentration around the leakage point 12 by gas exchange with the atmosphere caused by the atmospheric pressure change.

If this diluted and diffused carbon dioxide gas 13 is to be accurately measured, for example, on the order of 10 ppm, it will be diluted several hundred times at the maximum, that is, several tens of cubic meters of ground, which is several hundred times the volume of the original carbon dioxide produced. Even when diluted with medium gas, a carbon dioxide concentration distribution 14 in the underground gas having a wide dynamic range and having a significant difference from the atmospheric concentration level is generated.

From the principle of formation of this carbon dioxide gas concentration distribution 14, a carbon dioxide gas concentration point having a significant difference from the atmospheric concentration level is detected, and from this point, the point with a higher concentration is further narrowed to a system In pursuit of the leakage point 12.

Hereinafter, the actual surface soil gas survey representing the present invention will be described with reference to FIG.

Specifically, the target site is divided by the survey mesh 15, the survey point 16 is set on the ground surface 17, the sampling hole 19 having a depth of about 1 m is created in the unsaturated zone 18, and the underground gas is sampled. The concentration of the carbon dioxide gas 13 in the medium gas is measured, and the concentration points of relatively high concentration in the basic mesh are extracted from the carbon dioxide gas concentration distribution 14 on the mesh, and the target mesh is determined from the gas concentration of each point. The carbon dioxide gas concentration distribution 14 above is clarified. In addition, when the saturation zone 20 exists in a shallow layer and the sampling hole 19 of a predetermined depth cannot be installed, the sampling hole 19 is installed in a shallower depth, and underground gas is sampled.

Next, according to the gas concentration distribution on the survey mesh 15, the mesh width around the maximum concentration point is further divided into ½ (X1 point in the figure) and ¼ (Y1 point and Y2 in the figure). Point)), and the detection point of the highest maximum carbon dioxide concentration is further pursued and narrowed down to estimate the leakage point 12.

Here, more specifically, in the surface soil gas investigation using the carbon dioxide gas 13 according to the present invention, an 8 m mesh is empirically used as the basic mesh. In this way, if the initial mesh is set to 8 m, even if the mesh is narrowed down to 3 levels of 8 → 4 → 2 → 1 m, the scale of the measure at the subsequent spotting can be easily set with an integer value of m unit. , Make the mesh setting like this to improve the efficiency of the survey.
Further, for areas where it is assumed that the pollutant 4 exhibiting biodegradability and containing harmful substances is hardly used or leaked, 16 m or 32 m, which is a multiple of 8 m, may be adopted.

In the surface gas investigation, which is the present invention, the drilling work on the ground, the sampling work of the gas sample, etc. are the same as those of the soil gas investigation (the Ministry of the Environment Notification No. 16 investigation) under the above-mentioned soil pollution control method. It is possible to substitute gas survey equipment (drilling machine, gas sampling pipe, sampling bag, etc.) according to the method.

In the surface gas investigation, not only the carbon dioxide gas concentration but also a benzene-like leaking substance such as benzene can be targeted with benzene gas detector tubes, PID detectors, FID detectors, The benzene gas concentration in the ground may be measured together with the carbon dioxide gas concentration using an IR absorption detector or the like.

However, the volatilized benzene gas dilutes and diffuses as underground gas in the same behavior as the carbon dioxide gas described above, but the theoretical maximum generation amount of benzene gas is 1% of the above carbon dioxide generation amount. Only about /6. It should be noted that benzene gas is likely to be easily decomposed by soil microorganisms to be converted to carbon dioxide gas and disappear during the dilution and diffusion process.

Empirically, the horizontal distribution of carbon dioxide gas tends to be clearly wider than the horizontal distribution of volatile pollutant gas, and in fact, it is detected that the volatile pollutant gas is not in the immediate vicinity of the leakage point 12. It is often not done. Therefore, the measurement using volatile pollutant gas together starts with the step of narrowing down the mesh, and generally conducts an efficient survey.
Further, if the purpose of measuring the gas concentration of volatile pollutants is positioned as a cross-check for confirming the leakage point 12, it will be a meaningful measurement for verifying the carbon dioxide gas survey results. Since the carbon dioxide gas survey is highly accurate, carbon dioxide gas derived from non-pollutants generated by the decomposition of organic substances other than pollutants may be detected. Is an important operation.

As is clear from the above, in terms of selection of the carbon dioxide gas 13 as the measurement target, accuracy of the investigation mesh 15, implementation of the work of narrowing down the leakage point 12, or by using the three-dimensional conductive net 2 composed of the conductive material 1. In terms of the metabolic utilization of the microbial community 3 including the iron-reducing bacteria of the present invention, and the aim of maintaining the high concentration of leakage pollution by promoting the soil gap clogging by the metabolites, the surface gas investigation according to the present invention is the official investigation Phase 2 It is significantly different from the soil gas survey (Ministry of the Environment Notification No. 16 survey) and conventional surface gas survey methods.

The surface gas investigation method which is the present invention is to carry out highly accurate estimation of a series of pollution mechanisms, such as detection of leakage pollution in pollutant 4 which is biodegradable and includes harmful substances, and estimation of leakage pollution points. It is positioned as a survey method with a focus on.
In addition, this method has a feature that it is possible to detect the presence of the pollutant 4 that exhibits biodegradability and includes harmful substances and the leakage point with higher accuracy than the official phase 2 soil gas survey. It is preferable to use it as the basic information for the official phase 2 soil gas survey countermeasures, which will be described later, and to effectively use it for the design of all subsequent pollution countermeasures.

Hereinafter, an embodiment representative of the present invention for systematically addressing a series of soil pollution countermeasures from the stage of operation of factories, business establishments, etc. that handle first-class specified hazardous substances will be described.

As will be described later, the Soil Contamination Countermeasures Act is used when factories and business establishments that handle hazardous substances such as Class I Specified Hazardous Substances are abolished, when the site area changes due to construction, and when the soil is dug up. If the prescribed requirements are met, the prescribed investigation prescribed in the law is mandatory.
If there is a point of "concentration detection above the lower limit of quantification" in the Phase 2 soil gas survey, the presence of contamination is confirmed by the boring survey in Phase 3 and the contaminated area is designated according to the contamination level. After that, it is obliged to implement a series of purification measures for the purpose of removing the area, and under the administrative guidance, purification measures costs of several million to several hundred million yen, labor and time-consuming business burden are required. The possible rails will be laid according to the prescribed procedure and the guidance of the supervision office.

First of all, in consideration of clearing the Phase 2 soil gas survey, the method of countermeasures for pollutants (A) to (D) according to the present invention is used to systematically tackle soil pollution countermeasures from the stage of operation. It is preferable to take a series of pollution countermeasures from the viewpoint of early detection of soil pollution and early countermeasures.

By the way, the most preferable method of operating the pollution control according to the present invention is to start the pollution control from the state of vacant land where the handling of Class I specified hazardous substances is planned for the future. It is to be.

Specifically, the soil on the surface of the site where the Class 1 Specified Hazardous Substances are scheduled to be handled is improved efficiently by using heavy equipment such as backhoes, power blenders, trencher type stabilizers, general-purpose stabilizers, etc. An electrically conductive material and a culture substrate are mixed in the surface soil to form a three-dimensional conductive network that communicates with the surface soil.

In addition, when adding conductive materials to a large site in this way, use inexpensive civil engineering materials that contain a large amount of conductive magnetite (sand iron), such as sea sand, which has a strong black color, to reduce the price. Make sure that the three-dimensional conductive net is installed.

After that, the above-mentioned surface gas survey will be carried out regularly, and the leakage countermeasure will be carried out in real time when the carbon dioxide gas or the pollutant gas significantly exceeding the atmospheric level is detected in the soil gas.
If the surface gas measurement point exists in the building, or on the pavement or covered surface, a gas sampling hole such as a leak detection hole installed around the underground tank of the gas station is permanently installed. However, after that, it is preferable to carry out an efficient periodical surface gas survey, in which only soil gas sampling and analysis are performed without drilling work each time.

By the way, if the building already exists and the handling of harmful substances etc. has begun, first, after spraying the aqueous solution containing the culture base material with the conductive material on the ground surface, after a certain time has elapsed The surface gas investigation, which is the present invention, is carried out.
In the situation where the handling of Class I specified harmful substances has started and there is a high possibility that leakage pollution has already occurred, large-scale addition of conductive materials will be carried out to greatly disturb the soil gas at the site. If this happens, the leak point information, which is the original purpose of the investigation, may be lost, so caution should be exercised in the construction priority here.

In the area where the presence of pollution leakage is denied in the surface gas survey, a self-propelled boring machine or a percussion-type simple mechanical boring machine is used to remove an aqueous solution containing conductive materials in a dispersed state. It may be injected into the soil through the gap between the saturated zone and the unsaturated zone of the site to form a three-dimensional conductive network that communicates with the soil over a wide area in the ground, or particulate conductive material etc. may be used as a backhoe, power blender, or trencher type. It is also possible to use a heavy machine such as a stabilizer or a general-purpose stabilizer to mix with the soil to form a three-dimensional conductive network that communicates with the soil in the surface soil. Select conductive materials and construction equipment according to the situation of the construction site, and install an appropriate three-dimensional conductive net.

Finally, in an area where the presence of contamination leakage has already been recognized, it is preferable to first actively perform spot purification using an electrically conductive material against known contamination that is easy to approach (E).
On the other hand, for pollution that is difficult to approach at present, for the soil around it, low elution type conductive material etc. such as activated carbon or porous graphite, which is the present invention, is applied to the soil in the above manner. (B) Suppression of migration/diffusion of pollution due to generation of insoluble iron compounds, etc., (C) Low elution of harmful substances from soil, (D) ) Bio-prevention by a microbial community including iron-reducing bacteria.
After such construction, regular surface gas surveys will be conducted to further detect early leakage pollution and early countermeasures, and in the areas where purification construction has been carried out, the purification progress will be observed through gas surveys.

In the case of pollution containing a volatile organic compound such as a first-class specified harmful substance, the high-concentration region at the central part of the pollution is often accompanied by cutting oil, grease, or the like. For the pollution of the central part with a large amount of oil content, the construction considering the oil pollution mainly consisting of porous graphite, and the pollution mainly flowing only the harmful substances that flowed down by the groundwater flow in the saturated zone For example, select a porous carbon-based conductive material that has the optimum adsorption capacity for pollutants depending on the polluted state, such as performing construction mainly on activated carbon.

Regarding the selection and blending ratio of these, it is necessary to carry out a preliminary test in a laboratory in advance.Also, at the time of on-site construction, conduct regular checks to ensure more reliable construction. aim to do.

In addition, fertilizer materials, electron donors, electron acceptors, etc. to be added are adjusted so that decomposition by a microbial community including iron-reducing bacteria is optimal depending on the type of harmful substance. For example, if the harmful substance is an organochlorine tetrachloroethylene, decomposition by a microbial community including iron-reducing bacteria will proceed by a dechlorination reaction coupled with respiration, and depending on the relative concentration of each, reduction of trivalent iron will occur. There is also the possibility of competing with the reaction. If such a phenomenon is observed in the laboratory, the dechlorination reaction by microorganisms other than iron-reducing bacteria in the microbial community including iron-reducing bacteria should also be considered, and appropriate electron donors and decomposition Consider adding bacteria.

By the way, even in the case of a site where the handling or management of harmful substances has already been completed or is scheduled to be completed, it is judged that there is a high risk of contamination, and countermeasures will be taken in the same way as above.

This series will be implemented as a measure to clear the Phase 2 study, which is an official study that will be implemented after the project is completed.

In addition, if the specified standard value is not exceeded in the Phase 2 soil gas survey, the polluted area judgment, which is the official survey, will be completed, and it will be possible to use land in the same way as land without pollution regarding land use and sale. Become.

On the other hand, there are points that were screened as "detection of concentration above the lower limit of quantitation" in this Phase 2 soil gas survey, and after the contamination was confirmed in the Phase 3 survey, the "measured area" or If the “Notification Required Area for Character Change” is designated, further purification measures will be implemented with the aim of releasing this series of areas.

Specifically, the present invention includes (B) suppression of migration/diffusion of pollution due to generation of insoluble iron compounds, (C) low elution of harmful substances from soil, and (D) iron-reducing bacteria. Continuation of bioprevention by microbial communities that carry out, and (E) if necessary, spot purification using electrically conductive materials against known contamination with an easy approach is carried out. It is preferable to take purification measures aiming at the sequential removal of areas, such as changing from the "measure area" to the "notification area required for changing traits", and then releasing the "notification area requiring notification when changing traits".

In addition, when various surveys under the Soil Contamination Countermeasures Law clearly indicate the contaminated section, if the (A) pollution leakage point of the present invention is not estimated, the pollution leakage point is In order to confirm the above, a surface soil gas survey according to the present invention is carried out, and the pollution leak point is always included in the purification target.

In the purification measures after the enforcement of the current Soil Contamination Countermeasures Act, some construction companies do not confirm the pollution leak point, but grasp the pollution leak point based on the Phase 2 soil gas survey result and the Phase 3 boring survey result. There are many cases where purification measures are planned and implemented without being omitted.
As a result, after the purification of the polluted point area confirmed by the official survey results was completed, and after a while, pollution was detected again at the same point, and there are also disputed cases where construction defects are asked.
Contamination has a cause and produces a result, and it is a typical purification that can occur if the cause is not determined, by dealing with it only by looking at the result of the contamination investigation from another viewpoint where the contamination mechanism cannot be understood. This is a negligent case of a contractor. It should be noted that the survey on the Soil Contamination Countermeasures Law at this time is a survey conducted for the purpose of investigating the presence or absence of pollution on the site and does not clearly reflect the pollution mechanism.
If the leak point is not clear, the (A) pollution leak point, which is the present invention, is estimated or applied to implement a highly accurate purification measure with a clear pollution mechanism.

In addition, in such a situation that the presence of contamination is already clear, as a conductive material to be added to the soil, by using a porous carbon-based conductive material, such as porous graphite, by constructing a three-dimensional conductive network. In addition to the effect of suppressing the migration/diffusion of pollution due to the formation of the insoluble iron compound that occurs, the substance adsorption capacity of the porous carbonaceous material is taken into consideration to further reduce the pollution from soil. As for the construction method, as described above, an appropriate method is selected according to the construction site and the pollution situation.

In particular, if the target area is designated as a "required measure area", it is required to take measures to block the ingestion route that meets the prescribed elution criteria, and the administrative response is to restrict drinking and use of the contaminated groundwater. On the other hand, on the business side, on the other hand, the measures to prevent the migration/diffusion of such pollution and to reduce the amount of soil from the soil satisfying the second elution standard and to purify the same can be achieved with the accuracy of the countermeasure method according to the present invention. We will implement it at a high cost, and first try to quickly change the category from the "measure area" to the "notification area required for changing traits".

By changing the classification from the "necessary measure area" to the "characteristic change required notification area", the regulatory requirements for entering the area and changing the character such as building construction are substantially exempted. Enables commercial production activities. Such commercial production activities will be promptly resumed in the target area, and after that, aggressive commercial development will be carried out to reduce the burden of purification costs in the future.

Further, in order to release the "notification area required for changing traits" thereafter, further purification up to a predetermined elution standard concentration is required and a prognosis study for a certain period is required. In this case, according to the present invention, (C) the low elution of harmful substances from soil, (D) bioprevention by a microbial community including iron-reducing bacteria is continued, and (E) ) We will carry out spot purification using a conductive material against known pollution that is easy to approach, pursuing purification that meets prescribed elution standards, and aiming to release the area designation after a certain period of time.

Depending on the degree of contamination, completion of such biological purification generally takes from half a year to several years. In the situation of "notification area required for change of characteristics", improvement of land use, such as resumption of substantial commercial production activities, and reduction of burden of purification costs, If it is possible to wait for the completion of biological purification in a state, it is a cost-effective purification measure that promptly takes a step away from the “mainly required area” which is currently the mainstream , There is no need to spend a huge amount of money.

In addition, if the cost of cleanup measures exceeds 20% of the land price of the target area, a market survey showing the possibility that the land will be salted and becomes brownfield without the sale of land after implementing the cleanup measures. There is a result.

If it is assumed in advance that there is a concern that there will be brownfield conversion of hazardous substances, from the stage of operation of the project dealing with hazardous substances, first, the official test phase after the project is completed. Prior to the investigation, the soil pollution countermeasures (A) to (E) of the present invention, which are characterized by early detection and early countermeasures, which are determined to be “no pollution” in the soil gas survey 2) It is extremely important to implement this systematically and systematically.

Here, as the conductive material according to the embodiment, specifically, for example, if it is a mineral-based conductive material, magnetite, hematite, lepidocrocite, goethite, etc., if it is a metal-based conductive material, iron powder. If aluminum, aluminum powder, magnesium powder, etc. are carbon-based conductive materials, powders of graphite, carbon black, black charcoal, white charcoal, ogre charcoal, bamboo charcoal, biochar, etc., or fiber-like products thereof, porous carbon-based particles Although it is possible to use a barrel of activated carbon or the like, any conductive material that exhibits conductivity and can mediate electron transfer on the cell surface of iron-reducing bacteria can be used in the present invention. The materials are not limited to those specifically shown. Further, needless to say, a material containing other electrically conductive materials and partially containing these electrically conductive materials can be used as the electrically conductive material in the present invention.

Here, according to the embodiment, the shape of the conductive material is an atypical type in which there are various sizes depending on the soil to be developed and the forming conditions, but the conductive material adheres to the surface of the soil particles, and in the soil gap. Have a common property that they form the basis of a three-dimensional conductive network by communicating with each other, and are expanded and reinforced by mediating iron-reducing bacteria on the surface of soil particles. If this soil gap is compared to a tunnel, a three-dimensional conductive network is formed along the inner wall surface of this tunnel.
Further, the three-dimensional appearance shape of the three-dimensional conductive network is similar to the sponge resin shape. The original sponge resin has a mesh-like resin structure that encloses a large number of voids, but the appearance of the three-dimensional conductive net and the soil gap can be similar to that of the mesh-like resin. Incidentally, the resin forming the actual sponge does not have a hollow structure, but assuming that it has a hollow structure, the approximated soil gap corresponds to this hollow part, and the similarly approximated three-dimensional conductive network is It corresponds to the outer surface defining the hollow.
That is, the three-dimensional conductive net, the shape of which is approximated to the boundary shape between the soil gap and the soil particles, the three-dimensional object in which the appearance is approximated to the sponge resin structure, is a hollow tunnel-shaped net thread. Described as a structure as formed.

Further, here, as the culture substrate according to the embodiment, nitrogen fertilizer (ammonium salt, nitrate, urea, etc.), phosphate fertilizer (phosphate, superphosphate, etc.), potassium fertilizer, various metal salts (magnesium) , Manganese, molybdenum, cobalt, etc.), vitamins, and other medium components, as well as mineral particles (zeolite, Kanuma soil, talc, etc.) for adsorbing and gradually releasing these medium components, and electron donors. (Organic substances, metal particles such as zero-valent iron, etc.), electron acceptors (organic substances, nitrates, sulfates, iron compounds, manganese compounds, organic acids such as humic acid, carbonic acid compounds, etc.) can be used, Any material that promotes the growth and metabolism of a microbial community including iron-reducing bacteria can be used in the present invention, and is not limited to the materials specifically shown above. In addition, it goes without saying that other materials can be mixed and used as a culture substrate in the present invention as long as they are materials containing a part of these culture substrates.

Furthermore, as the harmful substances according to the embodiment, carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethylene, cis-1,2, which are the first-class specified harmful substances in the Soil Contamination Countermeasures Act, are used. -Dichloroethylene, 1,3-dichloropropene, dichloromethane, tetrachloroethylene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene, and benzene can be mentioned, and they can be the object of the present invention. In addition, 1,4-dioxane, vinyl chloride monomer, etc., which are defined in the water quality environmental standard and the soil environmental standard, are also applicable in the measure of the present invention. Note that, in addition to the above-mentioned Class I specified harmful substances, if the pollution containing the target substances specified by the Chemical Substances Control Law, etc. is biodegradable, it shows the mode of pollutants including harmful substances. However, it goes without saying that the chemical substances are not limited to the chemical substances specifically shown above.

Here, as the iron-reducing bacteria that can be used in the present invention, specifically, for example, Geobacter bacteria, Perobacter bacteria, Felimonas bacteria, Schwanella bacteria, Rhodoferrax bacteria, and Ferribacterium. Bacteria, Anaeromyxobacter bacteria, Desulfromus bacteria, Desulfromonas bacteria, Desulfitobacterium bacteria, Geoglobus bacteria, Bacillus bacteria, Ferroglobus bacteria, Geobacillus bacteria, and Geoslix bacteria and the like. ..
It should be noted that any microorganism capable of electron transfer to a conductive material or another bacterium through a cell constituting organ such as a cell surface or a conductive wire can be used in the present invention, and is specifically described above. It is not limited to the microorganisms shown.

Further, one of the gist of the present invention is to achieve biological purification by a microbial community 3 including iron-reducing bacteria, including other anaerobic bacteria having a symbiotic relationship with iron-reducing bacteria. Hereinafter, details of the microbial community including the iron-reducing bacteria, which is the present invention, will be described with reference to FIG.

The iron-reducing bacteria group 23 forms a biomat together with other anaerobic (symbiotic) bacteria group 24 in the environment, and uses the pollutant 4 that is biodegradable and contains harmful substances as an electron donor or as an electron donor. It is consumed as an acceptor. By promoting this consumption, purification of pollutants can be achieved.
As the expression "pollutant 4 which is biodegradable and contains harmful substances" indicates that the pollutant is composed of a complex substance containing at least one or more kinds of harmful substances, and it is necessary for the comprehensive metabolism of this complex substance. In the present invention, which needs to be dealt with by the functions of various bacteria, the microbial community mainly including the iron-reducing bacteria group 23 and including the anaerobic (symbiotic) bacteria group 24 is used to achieve such comprehensive metabolism.

Here, for example, if the target is an organic chlorine compound contamination, in addition to the iron-reducing bacteria group 23, a sulfate-reducing bacteria group, a methane bacteria group, a dechlorinating bacteria group such as dehalococcoides, or a vitamin B12-producing bacteria, etc. Dechlorination is achieved by the microbial community 3 including iron-reducing bacteria, which is composed of the anaerobic (symbiotic) bacteria group 24.
Here, as the dechlorinating bacterium of an organic chlorine compound other than iron-reducing bacteria that can be used in the present invention, specifically, for example, Dehalococcocides bacteria, Methanosarcina bacteria, Desulfitobacterium Genus bacterium, Dehalobacterus bacterium, etc. are used, which utilize an organochlorine compound as an electron acceptor and dechlorinate an organochlorine compound by supplying an appropriate electron donor and a culture base together. It has the characteristic of purifying (by coexistence with vitamin B12-producing bacteria).

Here, by making the microbial community mainly composed of the iron-reducing bacteria group 23, transfer of such electrons is performed through a part of the anaerobic (symbiotic) bacteria group 24, the cell surface, the conductive wire 22, and other conductive substances. It is hoped that this will lead to energy-efficient bio-purification.
For example, a microbial community 3 that includes iron-reducing bacteria with which a closer symbiotic relationship is established through electron transfer between the dechlorinating bacteria existing as a part of the anaerobic (symbiotic) bacteria group 24 and the iron-reducing bacteria 3 To conduct biostimulation by constructing a local indigenous flora, or to obtain in advance an integrated culture system in which a symbiotic system capable of electronic transfer is established and to develop a bioaugmentation method on site. Therefore, energy-efficient dechlorination biopurification in which electrons generated from iron-reducing bacteria are used for dechlorination of dechlorination bacteria is expected.

Further, for example, when the target is gasoline pollution, benzene in gasoline is decomposed by the iron-reducing bacteria group 23 in the biomat, while other gasoline components are nitrate-reducing bacteria group in the biomat and sulfuric acid reduction. Degradation is achieved by the anaerobic (symbiotic) bacterial group 24 composed of bacterial groups, methane bacterial groups, and the like. In this way, for gasoline pollution, biological purification through various microorganisms by the microbial community 3 including iron-reducing bacteria is attempted.

It is also known that a part of the iron-reducing bacteria group 23 can transfer electrons to molecular oxygen through the conductive wire 22 extending near the biomat boundary 21. , It enables diverse and unique electron transfer in a wide range of environments from aerobic to anaerobic environments.

By the way, regarding purification of fuel oil pollution, there are many actual cases of purification by not only anaerobic oil-decomposing bacteria but also aerobic oil-decomposing bacteria. When carrying out a hybrid purification under anaerobic/aerobic conditions using an anaerobic iron-reducing bacterium and an aerobic oil-degrading bacterium according to the present invention, under the condition that migration/diffusion suppression of pollution is secured. , The target polluted soil is intermittently ventilated with a gas containing oxygen that does not inhibit anaerobic decomposition, to regenerate the electron acceptor of the reduced iron-reducing bacteria and to aerobic oil-degrading bacteria. Supplies oxygen as an electron acceptor to carry out efficient purification.

When performing this hybrid purification, it is preferable to excavate the target soil, form the excavated soil into a pile, and install an appropriate ventilation (intake) pipe, if possible, but at the original position. Purification can be achieved by taking a sufficient amount of time even by simply performing a cut-back to perform soil improvement and performing intermittent ventilation with a simple ventilation device.

By the way, as the aerobic microorganism capable of decomposing fuel oil and fats and oils usable in the present invention, specifically, for example, Rhodococcus, Gordonia, Nocardia, Pseudomonas, Mycobacterium, No Cardioides genus, Plaucerella genus, Burkholderia genus, Alkaniborax genus, Xanthomonas genus, Acinetobacter genus, Ralstonia genus, Oleophilus genus, Thalassolitas genus, Xanthobacter genus, Acidis faera genus, Bacillus genus, Geobacillus genus Examples include genus bacteria. It should be noted that any aerobic microorganism capable of decomposing fuel oil or fat and oil can be used in the present invention, and is not limited to the bacteria group specifically shown above.

Thus, even in the case of complex pollution containing benzene, various purification methods can be proposed by the microbial community 3 including iron-reducing bacteria, which is a combination of iron-reducing bacteria and various microbial groups.
Appropriate purification design will be carried out, such as confirmation of the site situation, contamination resolution of indigenous microorganisms, confirmation of effectiveness of degrading bacteria addition in the lab before construction, etc., as well as optimal purification in view of delivery time and purification cost Like that.

Although it is a special case, if some iron-reducing bacteria such as Schwanella bacteria that can use both oxygen and trivalent iron as respiratory substrates can be applied in the field, air or gas containing oxygen can be used. Are supplied to the soil to be treated at regular intervals. As a result, such a special iron-reducing bacterium produces hydrogen peroxide during the time period when oxygen is used as a respiratory substrate, and it is reduced during the time period when anaerobically using ferric iron as a respiratory substrate. It produces valent iron and organic acids.
By repeating this operation alternately, a time zone in which divalent iron, organic acid, and hydrogen peroxide simultaneously exist is formed, and the Fenton reaction, which is a non-biological chemical oxidative decomposition based on these products, is performed. Set conditions that are likely to occur and try to promote further purification of pollutants.

As described above, the mode and the embodiment for carrying out the invention of the present invention according to the assumed pollution situation and the purpose of the countermeasure have been described, but at least the conductive material and the culture substrate are used to communicate with the soil to be the countermeasure. basic to form a three-dimensional conductive network in the ground, FIG metabolism and decomposition of pollutants through contact with including microbial community the iron-reducing bacteria and contaminants Luba Io prevention technology (biological pollution prevention technologies) to if that is contamination countermeasures to the configuration and it is needless to say that also included in the present invention there are changes or additions without departing from the scope of the present invention.

Further, with regard incidental art purification Mitigation later (reproduction technique conductive material using a decontamination technology and well-like structures at any time), changes and additions without departing from the scope of the present invention Needless to say, these are included in the present invention.

In the case of carrying out pollution purification at an arbitrary timing, which is an accompanying technique, activated carbon and iron powder are selectively used as the conductive material. In this case, the chemical oxidative decomposition method and the reductive dechlorination method can be selected as the pollution purification method, but the method must be selected by conducting an applicability test before construction, confirming its efficacy and applying the necessary materials. To decide.

In the chemical oxidative decomposition method, in addition to the conductive material, the types of peroxides and organic acids are examined and appropriate conditions are set. Examples of peroxides include materials containing hydrogen peroxide, ozone, hypochlorite, permanganate, magnesium peroxide, persulfate, and the like. These peroxides may be used alone or in combination of two or more. As the peroxide, it is particularly preferable to use a persulfate compound.
Further, as the organic acid, for example, an organic acid selected from succinic acid, citric acid, pyruvic acid, maleic acid, fumaric acid, lactic acid, acetic acid, formic acid, oxalic acid, malic acid, gluconic acid, tartaric acid or a salt thereof. The contained materials may be used alone or in combination of two or more.
It should be noted that any material containing peroxide and/or organic acid capable of decomposing pollutant/hazardous substances by the combination of activated carbon and iron powder can be used in the present invention. It is not limited to the materials shown.

Further, in the reductive dechlorination method, in addition to the conductive material, a material containing a fat-soluble organic material in at least a part thereof is added to set an appropriate condition. The advantage of using a fat-soluble organic material is that it can minimize the flow down and outflow due to the infiltration of groundwater and rainwater, and in the implementation of the reductive dechlorination method, which requires a relatively long period of time, the supply of this product to contaminated soil over a long period of time. Used for the purpose of
On the other hand, when the soil environment to be developed is in an oxidizing atmosphere and it is necessary to shift to reducing conditions in a short period of time, etc., the structure is mainly composed of fat-soluble organic materials, and some of them may contain water-soluble organic substances. A method of implementing the reductive dechlorination method with various material configurations may be adopted.
As fat-soluble organic materials, vegetable oil (rapeseed oil, soybean oil, corn oil, sesame oil, rice oil, waste oil of such vegetable oil, etc.), animal oil (lard, beef fat, waste oil of such animal fat, etc.), fatty acid, etc. May be used, or two or more kinds may be used in combination.

A method of regenerating a conductive material, which is another accessory technique, will be described with reference to the schematic view of the well-like structure shown in FIG.
The well-like structure is partitioned by the multiple distribution joint 25 shown in 4a, and the peroxide solution and/or the gas is transferred from the strainer (perforated) pipe 26 arranged in the partitioned section to the fluid transfer pipe 27. It has the function of injecting it into the soil of the countermeasure target via. The injected peroxide solution causes a stirring flow 29 of the injected peroxide solution by the injection gas flow 28, and permeates and diffuses into the aquifer, which is the target soil. The stirring of the peroxide solution using this gas can have a wider influence range when a plurality of strainers are arranged in one well.

One well in which a plurality of strainers are arranged has a plurality of multiple distribution joints 25 arranged in one well as shown in 4a and 4b, and a plurality of partitioned strainer sections are installed to further carry out fluid transfer. A fluid transfer pipe 27 having a multiple pipe structure including an outer pipe group 30 and a fluid transfer inner pipe 31 is connected to a multiple distribution joint 25 and a strainer (perforated) pipe 26, and then fixed by a fluid transfer pipe fixture 32. Finally, the strainer (perforated) pipe 26 and the non-perforated pipe 33 are fixed and manufactured (4c).

The peroxide solution that has permeated and diffused into the target soil is used to wash and decompose the functionally damaging substances adhering to the conductive material, and to determine the function of the conductive material, such as the conductive characteristics, surface adsorption characteristics, and spatial characteristics. To restore various functions. Examples of peroxides include materials containing hydrogen peroxide, ozone, hypochlorite, permanganate, magnesium peroxide, persulfate, and the like. These peroxides may be used alone or in combination of two or more. However, it is particularly preferable to use a persulfate compound as the peroxide.

This well-like structure will be used as an observation well in each strainer section during the period when the conductive material is not regenerated, and highly accurate monitoring will be carried out by monitoring multiple sections. If the well-like structure is to be applied to contaminated soil that has an alternating structure in which the stratum structure is not destroyed, the multiple strainer sections that are characteristic of the well-like structure should By distributing and arranging, it will be utilized as a multi-purpose well that can carry out individual monitoring for each layer and fluid injection/recovery operations specialized for each layer.

Although the embodiments and examples for carrying out the invention of the present invention have been described above, the specific configurations are not limited to the above-described embodiments and examples, and modifications and additions are made within the scope not departing from the gist of the present invention. Even so, it is included in the present invention.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following Examples.

In this experiment, loam soil with different amounts of conductive materials added was placed in a container, and a mixed oil of kerosene/gasoline was added to a part of the soil to determine the difference in respiration rate due to iron-reducing bacteria. It was evaluated from the carbon dioxide concentration.

The test procedure is shown below.
(A) In the anaerobic glove box in which the nitrogen gas was replaced, the basic culture soil was adjusted with respect to 1 L of the loamy soil, a medium for iron-reducing bacteria (dechlorination tap water 100 m1, NH ₄ Cl: 0.15 g, NaH ₂ PO ₄ : 0.06 g, CaCl ₂ ·2H ₂ O: 0.01 g, KCl: 0.01 g, MgCl ₂ ·6H ₂ O: 0.2 mg) were added and mixed to prepare.
Subsequently, in the same glove box, this basic culture soil was divided into 5 equal parts, and 4 mg of the test soil to which 10 mg, 50 mg, 100 mg, and 500 mg of nano activated carbon (<1 nmφ) were added per 1 kg of soil, and 1 strain of the Activated carbon-free soil was created, and each test soil was filled in a 500 ml glass bottle having a gas discharge/collection hole partitioned by a septum.
Then, in the center of the filled soil, 1 ml of mixed oil of kerosene and gasoline mixed 1:1 was slowly spiked so that it spreads vertically from the surface of the center of the bottle to the surroundings, Furthermore, a lid was attached while being careful not to disturb the entire soil structure, and the culture test was performed in a static state in an incubator at 15°C.

(B) Subsequently, for each elapsed time, 0.5 ml of gas was sampled from the gas release/collection hole of each test section with a gas tight syringe and subjected to TCD gas chromatography to measure the carbon dioxide concentration in the sampled gas. I asked.

The above experimental results are shown in FIG.
As is clear from the graph of FIG. 4, it was found that the higher the activated carbon concentration, the earlier the carbon dioxide concentration rises. Further, although there was a difference in arrival time, the arrival concentration of carbon dioxide concentration remained almost unchanged when the amount of activated carbon added exceeded 50 mg, and reached a peak around 80 to 90%.

At the end of the test, the test soil was frozen and fixed, then taken out of the container, thawed and subjected to observation. In the test section where the amount of activated carbon added exceeded 50 mg, the test soil had a dark brown color at the beginning of the test. It was observed that the soil color that had existed changed to blue, which was black over the entire surface of the test soil. On the other hand, in the non-addition group and the 10 mg addition group, no blue color change was observed on the entire surface, and the bluing was limited to the vicinity of the central portion. In addition, a plurality of thread-shaped blue lines extending radially were observed at the boundary between the blue part and the brown part in the 10 mg addition group.

From these experimental results, at least, by appropriately mixing the activated carbon with the soil to form a three-dimensional conductive network in the soil, it is possible to utilize not only the contaminated portion but also the electron acceptor at a remote place. , It was found that the metabolic activity of iron-reducing bacteria in the whole system can be enhanced. It was also confirmed that such metabolism is accompanied by remarkable generation of carbon dioxide.

In Example 1, generation of carbon dioxide and evaluation of formation of a three-dimensional conductive network were carried out, but in Example 2 concerned, pollution transfer/diffusion suppression, reduction from soil as an effect of using a conductive material. The soil column test was used to evaluate elution and microbial purification.

The test procedure is shown below.
(A) Prepare three simulated soil columns with an inner diameter of φ5 cm×1 m effective length and a temperature control jacket, in which glass beads having a weight ratio of 95 and a particle diameter of 0.1 mm and well-known soil having a weight ratio of 5 are well mixed and packed, and subsequently, The anaerobic dechlorinated tap water, which has been subjected to boiling/deaeration treatment and activated carbon treatment and deoxygenation through a pre-column filled with steel wool, is adjusted in the anaerobic glove box and the column gap volume is adjusted using a syringe pump. Conditioning was carried out by passing water in an amount of 3 times the amount of the above. In the conditioning, the flow rate of the syringe pump was adjusted so that the linear velocity passing through the column was approximately 30 cm/day.

(B) In addition, 1,4-dioxane was added to the above-mentioned "anaerobic dechlorinated tap water" to a concentration of 1 mg/L, and two types of feed solutions were added depending on whether nutrient salts were added or not, It was prepared in an anaerobic glove box and provided for each column test section. Table 1 shows the difference in the culture conditions in each test section.

Incidentally, nutrients, compared solution _{1L, NH 4 Cl: 1.5g,} NaH 2 PO 4: 0.6g, CaCl 2 · 2H 2 O: 0.1g, KCl: 0.1g, MgCl 2 · 6H 2 O: 2 mg and Fe(III)-EDTA: 2.5 g were added, and the pH was adjusted to 7 before the experiment.
By the way, originally, natural soil contains a considerable amount of insoluble trivalent iron, and it is not always necessary to supply the ferric iron component through the medium, but this time, from the middle of the test, iron In order to evaluate the contribution of reducing bacteria, experiments were carried out in a system in which a soluble iron component was supplied in addition to water.
The water flow in each test section was set so that the initial column passing linear velocity was approximately 30 cm/day, but assuming that the supply pressure increased with the passage of time, the supply pressure was 50 kPa. Automatic water supply was stopped, and intermittent water supply was set by adjusting the pressure so that when the pressure drops to 10 kPa, the water supply automatically returns. The column temperature was adjusted to a constant temperature of 15°C through a temperature control jacket.
Under these settings, conditioning was carried out for 10 days, and the 1,4-dioxane concentration in the water passing through the column was measured over time by the headspace method using PID/GC.

(C) After conditioning for 10 days, a nano activated carbon slurry solution having a concentration of 5% by weight, which is 0.1 times the column volume, was passed through each column of the test section 1 and the test section 2 to remove the activated carbon particles. The operation of adsorbing on the surface of the glass beads was performed.

(D) After that, the 1,4-dioxane concentration in the water passing through the column with time was continuously measured by the headspace method using PID/GC. In addition, for 10 days from 90 days to 100 days after the addition of activated carbon, test solution 1 was passed through a solution obtained by removing Fe(III)-EDTA from the nutrient salt of the passing solution, and The concentration of 4,4-dioxane was observed.

The results are shown in the graphs of FIGS. FIG. 5 is a concentration ratio calculated from the 1,4-dioxane concentration supplied in each test section and the 1,4-dioxane concentration in the column outflow water over time. From -10th day to 0th day, each test section was in the conditioning period before the addition of activated carbon, and for test sections 1 and 2, the addition of activated carbon was carried out on the 0th day.

As is clear from FIG. 5, with regard to the test groups 1 and 2 which are the activated carbon-added groups, the concentration ratio changed to a decreasing tendency several days after the addition of the activated carbon, and the detection was almost observed after several days. I can no longer. Specifically, the test plot 1 had a water environmental standard of 0.05 mg/L or less on the 34th day after the addition of activated carbon and the test plot 2 on the 56th day. After that, the test section 1 achieved the standard value or less by the 97th day and the test section 2 by the 57th day for two days.

The difference in the number of days until the groundwater standard is reached and the duration of these two test plots is the difference in the presence or absence of the addition of nutrient salts, which is associated with the growth of iron-reducing bacteria or microbial communities including iron-reducing bacteria. It was inferred that this was due to the presence or absence of decomposition of 1,4-dioxane.
Regarding the change in the concentration ratio of test area 2 which is assumed to have almost no involvement in microbial degradation, it is assumed that the 1,4-dioxane concentration decreases mainly due to the adsorption effect of activated carbon, but it is observed after 70 days. It is speculated that the rapid increase in the 1,4-dioxane concentration ratio that is caused is the result of reaching a breakthrough state where the adsorption capacity of the added activated carbon reaches its limit.

On the other hand, in Test Zone 1, the environmental standard value is still maintained even after 70 days. From the comparison of such phenomena, iron-reducing bacteria or iron-reducing bacteria can be used for the decomposition and purification of 1,4-dioxane. A certain contribution of microbial communities, including bacteria, is suggested.
In order to further clarify the contribution of this iron-reducing bacterium, etc., a test in which Fe(III)-EDTA was removed from the water flow was carried out for 10 days from 90th day to 100th day, and the peak was found on the 111th day. A temporary return of the 1,4-dioxane concentration ratio was observed, and iron-reducing bacteria, etc., contributed to a certain degree of contribution in keeping the 1,4-dioxane concentration in the column effluent below the environmental standard value. It became clear that it fulfilled.

By the way, although the test section 3 is a test section in which nutrient salts are present in the column water as in the test section 1, no clear decrease in the 1,4-dioxane concentration as observed in the test section 1 is observed. It was The difference between the conditions of test section 3 and test section 1 is the presence or absence of addition of activated carbon, but in the comparison of the 1,4-dioxane removal ability shown in FIG. 6, the removal of test section 1 and the sum of test sections 2 & 3 Comparing the performances, the latter shows a sharp decline in capacity after the 74th day, while the former maintains a high removal capacity even after the 74th day (for another purpose, with the negative peak on the 111th day). (Excluding the evaluation period) is clearly shown.
These results show that 1,4-dioxane removal effect by adsorption of activated carbon shown in test section 2 and 1,4-dioxane removal effect by decomposition of iron-reducing bacteria shown in test section 3 It was clarified by the comparison with the results shown in Test Group 1 that the above-mentioned effect is caused by the combination of activated carbon and iron-reducing bacteria.
In this experiment, since the electron acceptor is continuously supplied from the water flow liquid, it is not the difference due to the rate-determining electron acceptor caused by the difference in the degree of formation of the steric conductive network. Contamination concentration effect by activated carbon, or promotion effect of adhesion and biomat formation, etc. contributed to the promotion and decomposition of iron-reducing bacteria. It

In addition, comparing the changes over time in the supply pressure of each column shown in FIG. 7, there was no change in the supply pressure of the test section 2 to which only activated carbon was added, and to the supply pressure of the test section 3 to which only nutrient salts were added. Although a slight increase tendency was observed, the increase in the supply pressure in the test area 1 was the most remarkable.
It is speculated that the difference in the increase in pressure was caused by the formation of insoluble iron compounds generated by the metabolism of the iron-reducing bacteria and the clogging of the soil gap by the proliferated iron-reducing bacteria, and the metabolism of the iron-reducing bacteria and the like in test section 1. It is considered that the activity was more remarkable as compared with the test group 3.

In general, the addition of activated carbon to the system, together with the formation of a steric conductive network, has the effect of enhancing the metabolic activity of iron-reducing bacteria and the like in the entire system, which improves the 1,4-dioxane purification capacity and soil pores. It was conjectured that the permeability coefficient, which is a blockage, would be reduced, and that the flow rate of harmful substances contained in contaminated groundwater would be suppressed, including migration/diffusion suppression (including local low elution and pollution decomposition). ..

Based on the results of Example 2, 1,4-dioxane was changed to benzene or tetraethylene, the composition of the culture solution was changed to a composition suitable for each decomposition, and the same test as in Example 2 was carried out. , Both harmful substances showed almost the same results as 1,4-dioxane, and it was shown that the same effect can be reproduced by replacing the harmful substance species with aromatic hydrocarbon compounds and organic halogen compounds ( No data).

In this experiment, a three-dimensional conductive net using magnetite (sand iron) as a conductive material is formed in the ground, and a microbial community including conducting iron-reducing bacteria is utilized to utilize hydrogen peroxide, divalent iron, and organic acids. The verification of the method that promotes the generation of methane, induces the Fenton reaction, and decomposes the hardly biodegradable pollutants was conducted.

The test procedure is shown below.
(A) As a soil containing hardly biodegradable pollutants, it is a C heavy oil contaminated soil that has a history of aerobic bioremediation, and uncontaminated soil (pollution concentration: Approximately 3000 mg/kg) was selected. Rice bran and magnetite (sand iron) were added to the soil containing the hardly biodegradable oil at a weight ratio of 0.2%, respectively, and nitrogen and phosphorus were added at a ratio of 0.01% (urea as a nitrogen fertilizer, Calcium superphosphate was used as phosphorus fertilizer) to prepare the test soil.

(B) Subsequently, the test soil was loaded up to the mouth of five stainless steel containers of 2 L volume to set up test sections of 5 lines, and the test soil was cultured in an incubator at a culture temperature of 20 degrees. .. After the start of culture, the oil concentration in each test section was measured over time.
Further, after the start of the test, using a soil sample (about 500 ml) in a test section where a decrease in oil content was observed, in order to determine that the decomposition effect is a decomposition reaction derived from a hydroxy radical generated in the Fenton reaction, Mannitol (as a scavenger for hydroxy radicals: masking test) was added in an amount of 0.5% of the soil weight, and then filled in a 500 ml container, and incubation and subsequent aging were performed under the same operation as the test conditions. The oil concentration was measured (it was confirmed that the addition of mannitol did not change the respiratory activity of soil microorganisms before and after addition).

The results of the above experiment are shown in Table 2. As is clear from Table 2, the result that the purification performance of the C heavy oil was different depending on the ventilation condition was obtained. In the aeration cycle of the test section 2 in which the stirring was performed every day, the decomposition of the hardly biodegradable pollutant derived from the C heavy oil-contaminated soil could be most remarkably achieved.

In addition, as a result of performing a hydroxyl radical masking test using a soil sample one month after the test section 2 in which the decomposition was remarkable, the decrease in the oil content after the addition of mannitol was observed. It was suggested that it was highly likely that the remarkable decomposition reaction observed in the test section 2 was derived from the hydroxy radical, because it was extremely clearly blunted as compared with the change.

In Example 5, the pollution purification performance was evaluated in the case where materials (peroxides, organic acid iron, fatty acids) used for decomposing various pollutants and typical conductive materials (activated carbon, iron powder) were combined. Table 3 shows the outline. Test sections 1 to 3 were set up with a system containing only activated carbon, test sections 7 to 9 were set up with a system containing only iron powder, and test sections 4 to 6 were set up with a system combining iron powder and activated carbon.

The detailed settings for each test section are as follows. In 100 ml of groundwater containing 50% by weight of black soil, in the test of "adding hydrogen peroxide + iron citrate", the final concentrations were hydrogen peroxide concentration: 10 g/L, iron citrate concentration: 1 g/ L was added to the test system. In the test of the "sodium persulfate addition" system, the final concentration was added to the test system so that the sodium persulfate concentration was 10 g/L. In the test of the "fatty acid addition" system, a commercially available fatty acid material, Amteclean P (manufactured by Panasonic Environment Co., Ltd.): 10 g/L was added to the test system as a final concentration. Then, iron powder and activated carbon were added so that the total final concentration was 10 g/L, and IMK medium (manufactured by Wako Pure Chemical Industries, Ltd.): 252 mg/L as a culture substrate was added to all systems. did.

After adjusting each reaction solution, 100 ml of the reaction solution was placed in a 500 ml capacity sealed bottle, and for the reducing system sealed bottle, the gas phase was replaced with pure nitrogen gas and then the bottle was sealed, and the tetrachloroethylene concentration was 40 mg/ The tetrachloroethylene standard solution (1 mg/ml) was added to the test system in a 500 ml capacity sealed bottle so as to give L and stored in an incubator kept at 15° C. to start the test. Then, 10 and 30 days after the reaction was started, the chlorine ion concentration of each test system was measured with an ion electrode, and the degree of decomposition of tetrachloroethylene to chlorine ion in each test system was observed. The results are shown in Table 4.

In Table 4, the data for test plots 1, 4, and 7 are shown in parentheses. However, this was immediately after the start of the test and suffered from rapid foaming, and the test system could not be opened and kept sealed. It is shown as data. Further, from the foaming phenomenon, a problem in practical use of hydrogen peroxide was pointed out.
In the present 30-day test, in all test systems, significant decomposition of tetrachloroethylene, which produces chlorine ions, was observed in comparison with the respective control groups, although there was a difference in degree depending on the decomposition rate and the end point concentration. Further, from the comparison of each test section, remarkable decomposition of tetrachloroethylene was observed in the test system in which both activated carbon and iron powder were present, as compared to the test system in which activated carbon or iron powder was added alone, and especially sodium persulfate was added. Significant degradation was observed in the system.

The concentration of tetrachlorethylene under the condition of 40 mg/L, the chlorine ion concentration generated by complete decomposition is theoretically calculated to be 34.2 mg/L, but after 30 days of test groups 2, 5, and 8 to which sodium persulfate was added, Regarding the chlorine ion concentration, a concentration close to the complete decomposition was observed. In addition, it was found that the system containing these sodium persulfates had the best decomposition rate in the test system in which both activated carbon and iron powder were present as far as the results on the 10th day were seen.

In this way, since tetrachloroethylene reached a state close to complete decomposition in the presence of activated carbon, it was suggested that sodium persulfate added also decomposed tetrachloroethylene adsorbed on the activated carbon. That is, it was found that the activated carbon can be regenerated by adding sodium persulfate.

In general, as a result of evaluating the pollution purification performance by combining materials used for decomposing various pollutants (peroxides, organic acid iron, fatty acids) and typical conductive materials (activated carbon, iron powder), as a conductive material It is possible to further promote pollution purification by adding materials (peroxides, organic iron oxides, fatty acids) used in the decomposition of various pollutants under the condition that both activated carbon and iron powder are present. Also, it was found that sodium persulfate is preferable as the peroxide, and the use of this agent makes it possible to regenerate the activated carbon having adsorbed the pollution.

In Example 6, an evaluation was carried out regarding aeration/agitation operation when the well-like structure was used to regenerate the functional deterioration of the conductive material due to the adherent substance.

(Experiment 1) This experiment was conducted in order to obtain a consideration on the range of the influence of ventilation from the strainer in multiple sections of the well-like structure.
A 25 cm strainer is located at a site with a groundwater level of GL-1.8 m and a GL-9.5 m clay silt layer as the base and a first aquifer mainly composed of fine sand to medium sand. A φ50 mm well-like structure having four sections (from the bottom of the well, section A: 25-50, section B: 100-125, section C: 175-200, section D: 250-275 cm) was installed.
In addition, observation wells having all-layer strainers were installed at positions of 0.5 m, 1.0 m, 1.5 m, and 2.0 m in a linear distance from the well-like structure. Subsequently, the air flow rate from each strainer was adjusted using compressed air using a mass flow meter so that the strength was 10 L/min. Under the above settings, ventilation was sequentially performed from the bottom strainer, and the ventilation influence range under each ventilation condition was determined from the foaming condition in the observation well after one day and night.
In addition, after conducting a series of tests as described above, an experiment was also conducted in which ventilation was performed from only section A at a strength of 40 L/min. The results are shown in Table 5.

As a result of the above test, it was found that the ventilation influence range can be set wider by performing the same amount of ventilation as the total amount by using the strainers of multiple sections than by performing the constant amount of ventilation by the strainer of the single section.

(Experiment 2) Subsequently, for the purpose of verifying the stirring effect by aeration from the well-like structure, 400 L of a 1% saline solution was prepared as a substitute for the peroxide, and each strainer from the 4 sections before the start of aeration was used. After injecting 100 L, ventilation was performed from a strainer in 4 sections so that the strength was 10 L/min. After that, the electrical conductivity of each observation well was measured at each elapsed time, and the stirring effect of aeration was considered.

As a result, it was found that the electric conductivity in each observation well converges in the range of 50 to 100 μS/cm after about 3 days under the test conditions, and the gas aeration from the well-like structure having a multi-section strainer It was shown that stirring within a certain area is possible.

Although the embodiments of the present invention have been described above, the specific configuration is not limited to the above-described embodiments, and modifications and additions within the scope of the present invention are included in the present invention. ..

The present invention achieves fail-safe against unanticipated measures that enables early detection of early pollution and early migration/dispersion suppression measures against unknown soil pollution caused by legally designated Class I specified harmful substances and similar substances. It can be applied especially as an emergency measure technology.
In addition, regarding known pollution, it is especially applied as an emergency measure technology for suppressing migration/diffusion of harmful substances, low elution from soil, bioprevention by iron-reducing bacterial flora, and spot purification using conductive materials. be able to.

DESCRIPTION OF SYMBOLS 1... Conductive material 2... Steric conductive net 3... Microbial community 4 containing iron-reducing bacteria 4... Pollutant 5 exhibiting biodegradability and containing harmful substances 5... Oxidizing soil particles 6... Reducing soil particles 7... Saturation zone Anaerobic environment area 8... Saturated zone Aerobic environment area 9... Clean surface groundwater 10... Natural groundwater flow direction 11... Insoluble iron compound 12... Leakage point 13... Carbon dioxide gas 14... Carbon dioxide gas concentration distribution 15... Survey mesh 16... Survey point 17... Surface 18... Unsaturated zone 19... Collection hole 20... Saturation zone 21... Biomat boundary 22... Conductive wire 23... Iron-reducing bacteria group 24... Anaerobic (symbiotic) bacteria group 25... Multiple distribution joint 26... Strainer (perforated) pipe 27... Fluid transfer pipe 28... Injection gas flow 29... Stirring flow of injected peroxide solution 30... Fluid transfer outer tube group 31... Fluid transfer inner tube 32... Fluid transfer tube fixture 33... No hole tube

Claims (13)

Materials and culture medium containing porous carbon-based materials that mediate extracellular electron transfer of iron-reducing bacteria at least partly at the site where biodegradable pollutants including harmful substances are handled or planned. Material is added to the soil to be treated, a three-dimensional conductive net that communicates with the soil is formed in the ground, and through contact with the microbial community including the iron-reducing bacteria that conducts to the three-dimensional conductive net and the pollutant, metabolism and degradation a countermeasure method of FIG Ru soil contaminants, achieving generation and accumulation of insoluble iron compounds derived from the metabolism of the iron-reducing bacteria, to encourage blockage of soil pore, movement of the contaminants A method for coping with the soil pollutant, which aims to suppress the pollutant, and further promotes microbial metabolism and decomposition of the pollutant whose migration is suppressed . In the premises, as a target the pollutants soil contamination and soil contamination areas known its periphery, to claim 1, characterized in that forming the encompassing microbial community of the three-dimensional conductive network and iron-reducing bacteria Countermeasures against listed soil pollutants. A microorganism capable of metabolizing the pollutant, and/or a material in which the iron-reducing bacterium is separately cultured and at least a part of which contains a porous carbon-based material that mediates extracellular electron transfer of the iron-reducing bacterium, and/or Alternatively, the method for controlling soil pollutants according to at least one of claims 1 to 2 , which is added to the soil to be treated together with the culture substrate. An electron donor in accordance with the microorganism metabolism, and / or an electron acceptor, the soil pollutants according to at least one of claims 1 to 3, characterized in that added to the soil measures target Countermeasure. The material containing a porous carbon-based material that mediates extracellular electron transfer of iron-reducing bacteria in at least a part thereof is activated carbon, according to at least one of claims 1 to 4 . Countermeasures against soil pollutants. Said activated carbon and iron powder, also by adding a material comprising at least a portion of the fat-soluble organic material as the culture substrate, the operation for promoting the metabolism and breakdown of pollutants under reducing conditions, arbitrary timing 6. The method for controlling soil pollutants according to claim 5 , wherein Adding the activated carbon and iron in the soil measures a subject, further by adding a material comprising at least a portion of the peroxide, an operation to promote the metabolism and breakdown of pollutants under oxidizing conditions, arbitrary The method for controlling soil pollutants according to claim 5 , which is carried out at a timing. A gas containing air or oxygen, which is used by the iron-reducing bacteria, for the purpose of supplying an electron acceptor and/or activating an electron acceptor, is supplied to the soil to be treated. 7. The method for controlling soil pollutants according to at least one of claims 7 to 10. Via wells like structures, with the addition of the peroxide into the soil measures a subject, adhesion of the material comprising at least a portion of the porous carbonaceous material which mediate extracellular electron transfer of the iron-reducing bacteria The method for coping with soil pollutants according to at least one of claims 1 to 8 , wherein an operation for regenerating a functional deterioration due to a substance is performed. The well-like structure is composed of a single tubular structure, and has a function of observing wells and a function of injecting a peroxide solution and/or gas from the strainer section into the soil to be treated, at least The method for preventing soil pollutants according to claim 9 , wherein a strainer having two or more sections is provided. Characterized in that said peroxide is persulfate compound, according to claim 7, claim 9, some have the countermeasures soil pollutants according to at least one of claims 10. The concentration of at least one underground gas component containing at least carbon dioxide gas generated through metabolism of a microbial community including the iron-reducing bacteria is measured, and the underground leakage point of the pollutant is estimated from the concentration distribution of the gas component. and it has been countermeasures soil contaminants according to claim 1, at least one of claims 11, wherein the carrying out pressurized forte. The method for controlling soil pollutants according to at least one of claims 1 to 12 , wherein the harmful substance is 1,4-dioxane.