JP2000176487A - Method of remediation of contaminated groundwater and contaminated bed and remediation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the remediation period of a contaminated site. SOLUTION: Plural injection wells 12 for dissolving an inducible substrate for inducing decomposing enzymes for chemical substances in groundwater drawn from a pumping well 10 to feed them to a contaminated site are arranged around the pumping well 10 put between the injection wells 12. Therefore, the groundwater injected to the injection wells 12 flows toward the pumping well 10 from the periphery of the pumping well 10. Then, bacterial for decomposing the contaminated chemical substances can be increased in the periphery of the pumping well 10. And the groundwater flowing into the pumping well 10 is that which has passed through a bed in which these bacteria grow up. In this way, the polluting chemical substances in the groundwater circulated to the pumping well 10 can be effectively removed to allow the purifying period of the contaminated site to be sharply shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a system for purifying groundwater contaminated with a chemical substance, particularly an organochlorine compound such as trichlorethylene, a contaminated groundwater for purifying a formation, and a contaminated formation.

2. Description of the Related Art Organochlorine compounds such as trichlorethylene and tetrachloroethylene are widely used as cleaning agents for degreasing in various factories and cleaning shops. However, it is suspected that these organochlorine compounds have carcinogenicity, and groundwater and soil pollution by these organochlorine compounds have become a serious social problem.

[0002] Contamination groundwater and contaminated stratum formed by chemical substances such as organochlorine compounds have been pursued as a purification measure so far. Examples of the method include backfilling with non-contaminated soil, pumping and aeration using a combination of vacuum extraction and activated carbon adsorption, and the like, including pumping and aeration after groundwater is pumped and then aerated to dissipate pollutants into the atmosphere. However, these physicochemical methods are effective for high-concentration pollution, but are inefficient for low-concentration and wide-range pollution due to high equipment costs and operating costs. Also,
Since it is not a technology to decompose and detoxify pollutants, there was a problem of secondary pollution by pollutants.

Therefore, as a treatment method for decomposing contaminant chemicals such as organochlorine compounds using microorganisms, in situ bioremediation technology carried out at contaminated sites has been developed. In the method of purifying stratum and groundwater by the in situ bioremediation technique, a specific microorganism is proliferated in the stratum at a contaminated site, and the microorganism is used to decompose an organic chlorine compound.

Here, when biologically treating contaminant chemicals such as organochlorine compounds, there are no bacteria capable of directly assimilating the contaminants. Therefore, bacteria that assimilate methane, toluene, phenol and ammonia are used. A treatment method using oxidation is being studied. That is, nutrients at the contaminated site,
Inject methane, toluene, phenol, ammonia, etc., which are substrates for decomposing enzymes of contaminant chemicals such as oxygen and organochlorine compounds. Decompose.

[0005] Fig. 6 shows an example of a conventional bioremediation purification system in which methane is used as an induction substrate to decompose trichlorethylene (hereinafter referred to as TCE). Thus, one pumping well 1
One injection well 2 is arranged at a predetermined interval. Then, oxygen O ₂ , nitrate NO ₃ , and methane CH ₄ are dissolved in the groundwater pumped from the pumping well 1 and supplied to the injection well 2.
As a result, methane assimilating bacteria proliferate in the stratum between the injection well 2 and the pumping well 1, and the action of the methane assimilating bacteria can decompose and remove contaminant chemicals in groundwater circulating therethrough.

[0006] Such in situ bioremediation technology is disclosed in JP-A-9-206789, JP-A-9-234490, and JP-A-9-253.
No. 688, for example.

[0007]

Here, considering the flow and spread of the injected groundwater in this system,
The zone (bio zone) 4 where methane assimilating bacteria grow and TCE is decomposed expands in several years,
As shown in the figure, it spreads radially from the injection well 2 to its periphery, and a part of the shape is narrowly extended toward the pumping well 1.

On the other hand, the groundwater pulled up in the pumping well 1 is from the periphery of the pumping well 1, and of the groundwater pumped in the pumping well 1, only a small part of the groundwater passing through the biozone 4 is used. is there. For this reason, the effect of decomposition of TCE through the biozone is not easily reflected on the TCE concentration of the pumped ground water, and it takes several years before a decrease in the TCE concentration is observed. As a result, long periods of several years or more were required to clean up the entire contaminated site.

In the treatment method utilizing co-oxidation, a co-oxidation system using a substrate of an aromatic compound such as phenol or toluene has a higher decomposition efficiency of an organic chlorine compound than a system using methane. It has been known.

However, when a private house is close to a contaminated site, as in Japan, injecting highly toxic aromatics poses a safety problem. At present, bioremediation using methane is not practical in Japan. There is a great demand, and in this bioremediation purification system using methane, there is a particularly great demand to shorten the purification period.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a method and a system for purifying contaminated groundwater and a contaminated stratum capable of shortening the period for purifying a contaminated site.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a method of purifying groundwater, a contaminated groundwater for purifying a stratum, and a method of purifying a contaminated stratum at a polluted site contaminated by a chemical substance, wherein the groundwater is pumped from a pumping well provided at the polluted site. In the pumped ground water, an inducing substrate for inducing the enzyme for decomposing the chemical substance is dissolved, and the obtained inducing substrate dissolved ground water is injected into a plurality of injection holes arranged around the pumping well. Injected into the well, the inducer diffuses from the pumping well to the pumping well and decomposes the chemical using enzymes generated from the inducer by bacteria growing around the pumping well It is characterized by the following.

As described above, according to the present invention, a plurality of injection wells for dissolving an inducing substrate for inducing the enzyme for decomposing the above-mentioned chemical substance and supplying them to the contaminated site are dissolved in the groundwater pumped from the pumping well. It is located around the pumping well. Therefore, the groundwater injected into the injection well flows from the periphery of the pumping well toward the pumping well. Therefore, bacteria used for co-oxidation of polluting chemicals can be grown around the pumping well. The groundwater flowing into the pumping well passes through the stratum where this fungus is growing. This makes it possible to effectively remove contaminant chemicals in the groundwater circulating in the pumping well, thereby greatly shortening the purification period of the contaminated site.

The chemicals to be treated include not only organic chlorine compounds such as trichlorethylene and tetrachloroethylene, but also oils such as benzene and xylene.

It is preferable that the groundwater pumped from the pumping well dissolves nutrients, oxygen, etc. in addition to the substrate for decomposing enzymes. By injecting the groundwater in which these are dissolved from the injection well, bacteria that assimilate the induction substrate can be grown around the injection well, particularly in the stratum in the area toward the pumping well.

As the derivatized substrate, methane, toluene, phenol, ammonia and the like can be used. In addition, nitric acid and the like are used as nutrients, and oxygen can be supplied as air, but pure oxygen having a high oxygen concentration is more effective.

Preferably, the chemical substance is an organic chlorine compound, and the derivatized substrate is methane. Methane is a safe substance and can be used at polluted sites near private houses.

Further, oxygen and nutrients are further supplied to the groundwater from the pumping well, and injections into the groundwater are mutually delayed so that three of the derived substrate, oxygen and nutrients are not supplied simultaneously. It is preferable to perform it intermittently. When the groundwater, in which the derived substrate, oxygen, and nutrients are dissolved at once, is injected into the injection well,
Bacteria grow easily. For this reason, bacteria grow on the inner surface of the injection well and the injection well is clogged, so that diffusion to the vicinity of groundwater cannot be performed. By making the injection intermittent, the environment for bacterial growth is not sufficient in the injection well, and clogging in the injection well can be suppressed.

It is preferable that hydrogen peroxide is further added to the groundwater from the pumping well. Hydrogen peroxide has a bactericidal activity, and the addition thereof can suppress the growth of bacteria and the occurrence of clogging in the injection well.

The present invention is also a purification system for contaminated groundwater and soil that purifies groundwater and soil at a contaminated site that has been contaminated by chemical substances. A dissolving means for dissolving a substance necessary for decomposing the chemical substance into the pumped ground water, and a plurality of injection wells for supplying ground water after dissolving the substance to a contaminated site; It is characterized in that wells are arranged around pumping wells. With this system, the above-described bioremediation can be performed.

It is preferable that this system be one unit and a plurality of such units be arranged along the flow of groundwater. As a result, the entire contaminated site can be effectively purified.

[0022]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.
Here, in this embodiment, trichloroethylene (TCE) is produced by bioremediation using methane.
It is described as purifying the contaminated site.

FIG. 1 is a diagram showing a conceptual configuration of the present embodiment. As described above, in the present embodiment, a plurality of injection wells 12 are arranged around the pumping well 10 so as to surround the pumping well 10 when performing bioremediation. Then, oxygen O ₂ , nitrate NO ₃ as a nutrient, and methane CH ₄ are dissolved in the groundwater pumped from the pumping well 10 to inject the well 1
Feed to 2.

FIG. 2 shows a conceptual diagram of a cross section of the contaminated site along a line connecting the pumping well 10 and one injection well 12. Thus, the pumping well 10 extending from the ground to the inside of the groundwater flow
A pump 14 is disposed at the bottom of the inside. Although a submersible pump is used as the pump 14, a pump of a type that is arranged on the ground and sucks groundwater in the pumping well 10 may be used.

The groundwater pumped by the pump 14 is supplied to the injection well 12 through the dissolving device 16. The dissolving device 16 is supplied with nutrients and the like from a nutrient salt supply device 18, and these are mixed and dissolved in groundwater in a pipe leading to the injection well 12.

Various in-line mixers such as an ejector can be used as appropriate for the dissolving device 16. Also,
Not limited to the inline mixer, other mixing devices can be used. The nutrient supply device 18 supplies oxygen O ₂ , nitrate NO ₃ , and methane CH ₄ , and selects and appropriately supplies these. Oxygen O ₂ and methane CH
Reference numeral ₄ denotes a gas body supplied by a cylinder or the like. NO ₃ nitrate is an aqueous solution, and a sodium salt or the like is used.

As shown in FIG. 1, eight injection wells 12 are provided on a circle to dissolve oxygen, nutrients, and methane in groundwater and supply the dissolved water to the contaminated site. The groundwater pumped from one pumping well 10 is supplied to a distributor 20.
, And is supplied to each injection well 12. The distributor 20 may be a distributor that constantly distributes the incoming groundwater into eight or a distributor that switches over time to distribute the groundwater as long as it distributes eight.

The number of the injection wells 12 is sufficient if they are arranged with the pumping well 10 interposed therebetween. However, it is preferable to arrange about 4 to 10 injection wells 12 on a circle and arrange the pumping well 10 for pumping groundwater at the center of the circle.

With such a system, groundwater pumped from the pumping well 10 is supplied to a plurality of surrounding injection wells, so that groundwater in which oxygen, nutrients, and methane are dissolved diffuses from the plurality of injection wells 12. Most of these flow toward the pumping well 10.

Therefore, as shown in FIG. 1, groundwater in which oxygen, nutrients, and methane are dissolved diffuses in a substantially circular area surrounding the plurality of injection wells 12, and methane-utilizing bacteria proliferate there. A biozone 24 is formed.

As a result, the groundwater pulled up by the pumping well 10 is almost occupied by the groundwater passing through the biozone 24. Therefore, by arranging the pumping well 10 and the injection well 12 such that an appropriate biozone 24 conforming to the contaminated site is formed, the biozone 24 can be effectively spread to the contaminated site,
By circulating the groundwater intensively at the contaminated site, the TCE at the contaminated site can be effectively decomposed and removed.

The monitor well 22 is for taking groundwater therefrom and analyzing and measuring TCE in the groundwater.

With such a configuration, the effect reduced by bioremediation is directly reflected on the TCE concentration of the groundwater collected at the monitor well 22, and the TCE
Is observed to decrease significantly. As a result, the entire contaminated site can be purified in a short period of time, from several months to one year.

Here, the injection of oxygen, nutrients and methane into the groundwater in the dissolving device 16 is preferably performed intermittently and alternately. This is because oxygen, nutrients, and methane are mixed in the injection well 12, so that methane assimilating bacteria grow excessively on the inner surface and around the injection well 12, and block the aquifer in which the injection well or the groundwater flows. It is for suppressing that it does. That is, the intermittent injection prevents the methane-utilizing bacteria from growing excessively only around the injection well 12 and allows the methane-utilizing bacteria to grow relatively uniformly throughout the wide biozone 24. Accordingly, it is possible to suppress blocking of the aquifer through which the groundwater flows in or around the injection well 12.

Further, it is also effective to inject hydrogen peroxide H ₂ O ₂ to suppress the excessive growth of microorganisms. Hydrogen peroxide has a bactericidal action, which can suppress the overgrowth of methane-utilizing bacteria around the injection well 12. In this case, hydrogen peroxide (preferably 5 to 5)
It is effective to inject 100 mg / l continuously.

The chemicals to be treated include not only organic chlorine compounds such as trichloroethylene and tetrachloroethylene, but also oils such as benzene and xylene.

FIG. 3 shows a system for repairing a wide range of contaminated sites by the bioremediation of the present invention.

In this system, a purification system in which a plurality of injection wells are arranged on a circle and a pumping well for pumping groundwater is arranged at the center of the circle is defined as one unit 30.
Four units 30 are arranged from the pollution source 32 to the downstream of the pollution along the groundwater flow. In each unit 30, the same effective removal of contaminant chemicals as in the case described above is performed.
The biozone 24 can be spread over the entire contaminated site. As a result, it is possible to purify the entire contaminated site within a short period of one year or less. In this system, the size of one unit is increased toward the downstream of the contamination to cope with low-concentration contamination.

[0039]

FIG. 4 shows the change over time of TCE when the TCE treatment is performed by the bioremediation purification system shown in FIGS.

In this example, the groundwater pumped in the pumping well 10 contains oxygen 10 mg / l, nitric acid 10 mg / L, methane 4
mg / L was dissolved and supplied to eight injection wells. From this, it is understood that a sufficient decrease in TCE can be obtained in any of the groundwater collected in the pumping well 10 and the monitor well 22. That is, TC which was initially 1.0 mg / L
E can be reduced to 0.03 mg / L or less after one year.

FIG. 5 shows the rise in pressure of the injection pump when oxygen, nitric acid, and methane are intermittently injected into groundwater, and when hydrogen peroxide is continuously used in addition to the intermittent injection.

The intermittent injection is performed by using 30 mg / L of oxygen and 3 mg of nitric acid.
0 mg / L for 4 hours, groundwater only for 2 hours, methane 10
This was repeated with one cycle of injection of mg / L for 4 hours and groundwater only for 2 hours. In addition, a continuous injection of 50 mg / l of hydrogen peroxide was performed.

From these results, it has been clarified that the intermittent injection and the continuous injection of hydrogen peroxide are effective in suppressing an increase in pressure of the injection pump due to excessive growth of microorganisms.

(Comparative Example) FIG. 7 shows the change over time of TCE by the conventional bioremediation purification system shown in FIG. In this conventional example, the groundwater pumped in the pumping well 1 has oxygen 10 mg / L, nitric acid 10 mg / L, methane 4 m
g / L was dissolved and supplied from the injection well 2 to the contaminated site.

In this case, the groundwater that has passed through the biozone is only a part of the groundwater that is pulled up by the pumping well. Is not reflected, and a decrease in TCE concentration is not observed much in one year. That is, the TCE concentration, which was initially 1 mg / L,
Even after one year, it is still 0.7 to 0.9 mg / L. Therefore, it takes a long period of several years or more to clean the entire contaminated site.

[0046]

As described above, according to the present invention, by arranging a plurality of injection wells with a pumping well interposed therebetween, in remediation of groundwater and soil contamination, the purification period is short and bioremediation that can be put to practical use is realized. Law can be provided. In addition, clogging in an injection well or the like can be suppressed by intermittent injection of nutrients or the like or supply of hydrogen peroxide. Furthermore, by providing a plurality of units each including one pumping well and a plurality of injection wells, effective bioremediation can be performed even on a wide range of contaminated sites.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a bioremediation purification system according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a schematic cross-sectional configuration of a bioremediation purification system according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of application to a wide-area contamination site.

FIG. 4 is a diagram showing a change with time of the TCE concentration in the purification system of the present invention.

FIG. 5 is a diagram showing a change over time of an infusion pump pressure.

FIG. 6 is a diagram showing a change over time of a TCE concentration in a conventional purification system.

FIG. 7 is a diagram showing a change in TCE concentration in a conventional purification system.

[Explanation of symbols]

10 pumping wells, 12 injection wells, 14 pumping pumps, 16
Dissolving device, 18 nutrient supply device, 20 distributor,
22 monitor wells, 24 biozones, 30 units, 32 pollution sources.

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[Procedure amendment]

[Submission date] November 4, 1999 (1999.11.
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

[0012]

SUMMARY OF THE INVENTION The present invention relates to a method of purifying groundwater, a contaminated groundwater for purifying a stratum, and a method of purifying a contaminated stratum at a polluted site contaminated by a chemical substance, wherein the groundwater is pumped from a pumping well provided at the polluted site. In the pumped ground water, an inducing substrate for inducing the enzyme for decomposing the chemical substance is dissolved, and the obtained inducing substrate dissolved ground water is injected into a plurality of injection holes arranged around the pumping well. Injected into the well, the derived substrate is diffused from the periphery of the pumping well toward the pumping well, and the chemical substance is decomposed by utilizing the enzyme generated from the derived substrate by bacteria growing around the pumping well. It is characterized by the following.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

The present invention is also a purification system for contaminated groundwater and soil that purifies groundwater and soil at a contaminated site that has been contaminated by chemical substances. A dissolving means for dissolving a substance necessary for decomposing the chemical substance into the pumped ground water; and a plurality of injection wells for supplying ground water after dissolving the substance to a contaminated site; It is characterized in that wells are arranged around pumping wells. With this system, the above-described bioremediation can be performed.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

FIG. 2 shows a conceptual diagram of a cross section of the contaminated site along a line connecting the pumping well 10 and one injection well 12. Thus, the pumping well 10 extending from the ground to the inside of the groundwater flow
A pump 14 is disposed at the bottom of the inside. Although a submersible pump is used as the pump 14, a pump of a type that is arranged on the ground and sucks groundwater in the pumping well 10 may be used.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3 is a diagram showing an example applied to a wide-area contamination site.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] Fig. 6

[Correction method] Change

[Correction contents]

FIG. 6 is a diagram showing a schematic configuration of a conventional purification system.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] Fig. 7

[Correction method] Change

[Correction contents]

FIG. 7 is a diagram showing a change over time of a TCE concentration in a conventional purification system.

[Procedure amendment 8]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

[Procedure amendment 9]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

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Claims (6)

[Claims] Claims: 1. A method for purifying groundwater, a contaminated groundwater at a contaminated site contaminated by a chemical substance, and a method for purifying a contaminated stratum, comprising the steps of: pumping groundwater from a pumping well provided at the contaminated site; Dissolving an induction substrate for inducing a chemical substance-degrading enzyme, and injecting the obtained ground substrate-dissolved groundwater into a plurality of injection wells arranged around the pumping well and performing the induction Contaminated groundwater characterized in that the substance is diffused from the periphery of the pumping well toward the pumping well, and the chemical substance is decomposed by utilizing enzymes generated from the inducer by bacteria growing around the pumping well; and How to clean contaminated strata. 2. The method according to claim 1, wherein the chemical substance is an organochlorine compound, and the derivatized substrate is methane. 3. The method according to claim 1, wherein oxygen and nutrients are further supplied to the groundwater from the pumping well, and three of the induction substrate, oxygen and nutrients are not supplied simultaneously. A method for purifying a contaminated groundwater and a contaminated stratum, wherein the injection into the groundwater is carried out intermittently at different times. 4. The method according to claim 1, further comprising adding hydrogen peroxide to groundwater from the pumping well. 5. A purification system for contaminating groundwater at a contaminated site contaminated by a chemical substance, contaminated groundwater for purifying soil, and a contaminated stratum, wherein a pumping well for pumping groundwater at the contaminated site, and groundwater pumped from the pumping well. A dissolving means for dissolving a substance necessary for decomposing the chemical substance, and a plurality of injection wells for supplying groundwater after dissolving the substance to a contaminated site, wherein the plurality of injection wells are pumped wells. A purification system for contaminated groundwater and a contaminated stratum, wherein the system is disposed around the periphery of the groundwater. 6. A purification system for contaminated groundwater and contaminated stratum that purifies groundwater and soil at a contaminated site contaminated by a chemical substance, wherein the system according to claim 5 is defined as one unit and is used as a groundwater flow. A system for purifying contaminated groundwater and a contaminated stratum, wherein a plurality of contaminated groundwaters and contaminated strata are arranged along the ground.