JP2006007182A - In situ bioremediation construction method accompanied by preculture, and system therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an in situ bioremediation construction method accompanied by preculture, allowing efficient and inexpensive cleaning of polluted soil or polluted underground water, and reducing influence on environment or human bodies, and a system used therefor. <P>SOLUTION: The system comprises a water intake well 1 excavated and installed at a downstream side of a polluted area for the purpose of pumping up polluted underground water from the underground polluted area 10 polluted with benzene; a culturing plant 2 provided on the ground for the purpose of cultivating the polluted underground water pumped up from the intake well 1 under aerobic conditions; an injection well 3 excavated and installed at an upstream side of the polluted area for the purpose of returning cultured solution cultured in the culturing plant 2 to the polluted area; and an oxygen supply pump 4 installed by excavating in the polluted area for the purpose of keeping the whole in situ underground polluted area aerobic. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention improves the microbial decomposition activity with the ability to decompose pollutants contained in contaminated soil / contaminated groundwater by culturing and in situ with pre-culture for purifying contaminated soil / contaminated groundwater in situ The present invention relates to a bioremediation method and its system.

  In recent years, environmental pollution of soil and groundwater by pollutants has become a serious problem. In particular, since volatile organic compounds such as benzene are hardly decomposable, they penetrate into the soil, dissolve in groundwater without being decomposed, and expand the contaminated area through the groundwater. For this reason, it is necessary to decompose and remove these pollutants, purify contaminated soil and contaminated groundwater, and restore the environment.

  Conventionally, as a purification method for removing pollutants from contaminated soil and contaminated groundwater, the microorganisms with the ability to decompose pollutants contained in the contaminated soil and contaminated groundwater are improved by culturing them, and the contaminated soil and contaminated groundwater are removed. There is an in-situ bioremediation method with pre-culture that purifies in-situ. For example, after culturing a microorganism having the ability to decompose pollutants in a medium containing at least some of the elements of the environment in which the microorganism lives, the cultured microorganism is brought into contact with an organic compound in the environment. Thus, there is a technique for restoring the environment (for example, see Patent Document 1).

Such a conventional in-situ bioremediation method with pre-culture is intended to improve the microbial degradation activity by culturing outside the in-situ location of a ground plant or the like. Compared with an in-situ bioremediation method that does not involve pre-culture that improves the in-situ degradation activity of microorganisms, it is easier to prepare appropriate conditions for activating the microorganisms.
Japanese Patent Laid-Open No. 11-90411

  However, in the conventional in-situ bioremediation method with pre-culture, the object to be cultured is not the contaminated soil / contaminated groundwater but the microorganism itself.

  For this reason, it is necessary to screen specific microorganisms before culturing, and there is a problem that the purification of contaminated soil and contaminated groundwater is inefficient, and the cost for that is high.

  In addition, when introducing microorganisms to be cultivated from the outside, there is a problem that a serious influence on the environment, the human body, etc. cannot be denied.

  Therefore, the present invention is an in-situ bioremediation method with pre-culture that can efficiently and inexpensively purify contaminated soil / contaminated groundwater, and that can reduce the impact on the environment, human body, etc. The purpose is to provide a system.

  In order to solve the above-mentioned problems, the present invention improves the decomposition activity of microorganisms having the ability to decompose pollutants contained in contaminated soil / contaminated groundwater, and purifies the contaminated soil / contaminated groundwater in situ. In-situ bioremediation method with pre-culture for the purpose of collecting a part of contaminated soil / contaminated groundwater from the in situ, and the contaminated soil / contaminated groundwater collected in the sampling process with a culture solution or medium Culture process for culturing, supply process for reducing and supplying the culture medium or medium cultured in the culture process to the original position, and decomposing pollutants contained in the contaminated soil and contaminated groundwater supplied in the original process into microorganisms And a purification process for purifying contaminated soil and contaminated groundwater in situ.

  Furthermore, the culture process in the present invention may include a step of adding a contaminant as a decomposition substrate to the culture solution or the culture medium.

  In addition, the present invention provides a sampling device that collects a part of contaminated soil and contaminated groundwater containing aerobic microorganisms that are contaminated with volatile organic compounds and has the ability to decompose organic compounds, and a sampling device. Of the contaminated soil and contaminated groundwater from a culture device that is cultured under aerobic conditions together with a neutral culture solution or medium containing an organic compound as a decomposition substrate, and the culture solution or medium cultured in the culture device An aeration treatment device that performs aeration treatment to remove organic compounds, a supply device that supplies and supplies the culture solution or culture medium that has been aerated by the aeration treatment device in a reduced state, and diffused and mixed in the supply device. And an oxygen supply device for supplying oxygen for decomposing organic compounds contained in the contaminated soil and groundwater in the original position into aerobic microorganisms.

 Furthermore, the supply device according to the present invention may have a control means for controlling the culture solution or the medium aerated by the aeration treatment device so as to reduce and supply the culture solution or culture medium together with the injected water to the original position. .

  Furthermore, the organic compound in the present invention is an aromatic compound such as benzene, phenol, benzoic acid, toluene, xylene, cresol, or an organic chlorine compound such as dichloroethylene, trichloroethylene, tetrachloroethylene, tetrachloroethane, vinyl chloride, dioxin, It may be characterized by containing at least one or more.

  According to the present invention, it is possible to purify contaminated soil and contaminated groundwater efficiently and inexpensively, and to reduce the influence on the environment, the human body, and the like.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic cross-sectional view showing an in-situ bioremediation system with pre-culture according to an embodiment of the present invention, for taking contaminated groundwater from a contaminated area 10 contaminated with benzene (underground) and pumping it to the ground. A water intake well 1 excavated downstream of the contaminated area, a culture plant 2 provided on the ground for culturing contaminated groundwater pumped from the water intake well 1 under aerobic conditions, and a culture plant 2 In order to reduce and supply the culture broth cultured in the contaminated area, an injection well 3 excavated upstream of the contaminated area, and in the contaminated area to bring the entire original underground contaminated area into an aerobic state. And an oxygen supply pump 4 provided by being excavated in the cylinder.

  As shown in FIG. 1, the underground pollution region 10 is composed of a saturated layer 11 through which groundwater flows, an unsaturated layer 12 thereabove, and an impermeable layer 13 below the saturated layer 11. Contaminants such as benzene are present in the saturated layer 11, the unsaturated layer 12, and the water-impermeable layer 13, particularly at the boundary portions of the layers, and are present in a state where they are difficult to separate. Contaminants such as benzene are likely to be adsorbed by the clay and organic matter in the soil contained in the formation, and therefore, in the saturated layer 11, the contaminants are gradually released into the groundwater, Benzene).

  In addition to benzene, which is a volatile organic compound, the pollutants in the present invention include aromatic compounds such as phenol, benzoic acid, toluene, xylene, cresol, dichloroethylene, trichloroethylene, tetrachloroethylene, tetrachloroethane, and chloride. At least one of organic chlorine compounds such as vinyl and dioxin may be contained.

  In addition, the microorganism in the present invention may be any microorganism that is contained in contaminated soil / contaminated groundwater and has the activity of degrading the contaminant, such as Pseudomonas mendocina, P. putida F1, Nitrosomonas europaea, Mycobacterium sp. Aerobic microorganisms, Methanosarucina sp., Methanosarucina metai, Methanosarucina acetivorans, Methanothrix sp., Dechlorinating bacterium DCB-1, Methanosarucina sp.DCM Methanococcusthermolithotropiumum It may be an anaerobic microorganism such as.

 In the present invention configured as described above, the intake well 1 functions as a collection device for collecting a part of contaminated groundwater containing aerobic microorganisms having the ability to decompose benzene, which is a volatile organic compound, from its original position. In addition, the sampling device in the present invention is not necessarily limited to the sampling device such as the intake well 1, and a sampling device such as a drilling device that excavates a part of the contaminated soil in the underground contaminated area from the original position. It may be. Such intake well 1 makes it difficult to optimize the culture conditions of aerobic microorganisms in the in-situ underground contaminated area, but it is easy to optimize the culture conditions in a ground plant other than the original position. Become.

 The culture plant 2 includes a culture tank 21 and an aeration tank 22, and the former culture tank 21 is a neutral culture containing a degradation substrate (benzene) for contaminated groundwater collected by a collection device (intake well 1). The latter aeration tank 22 functions as an aeration treatment apparatus that performs aeration treatment to remove benzene remaining in the culture medium cultured in the culture tank 21. To do.

FIG. 2 is a schematic sectional view showing the culture plant 2 including the culture tank 21 and the aeration tank 22.
The culture tank 21 is in a sealed state as shown in FIG. 2, after neutralizing the contaminated groundwater pumped from the intake well 1 by pH adjustment (pH 6-8), and further, a volatile organic compound Benzene (10 to 50 ppm, a small amount of tar and a large amount of benzene, etc.) is added as a decomposition substrate. In addition, a stirring pump is provided at the bottom of the culture tank 21, and the microorganisms contained in the pumped contaminated groundwater and benzene are mixed thoroughly and cultured under optimum culture conditions (aerobic conditions, etc.). Can be done. Other factors for optimizing the culture conditions include, for example, temperature (20 to 40 ° C., preferably 25 to 35 ° C.), nutrients (nitrogen, phosphorus, etc.), activation promoters, and the like. In addition, the culture tank 21 is preferably provided with a culture solution collection port (not shown) for collecting a sample in order to perform quality control of the culture solution.

 Note that the present invention is not necessarily limited to the case of culturing in a culture solution as in the above embodiment, and for example, even when culturing in a medium such as bouillon medium, M9 medium, L medium, and MY medium. Good. Furthermore, the present invention is not necessarily limited to culturing contaminated groundwater, but may be a case where contaminated soil is cultivated in a slurry state. In addition, it goes without saying that such culture may be repeated a plurality of times (for example, prior culture etc.).

 The factors that improve the benzene decomposing activity of microorganisms by such a culture tank 21 include that the benzene decomposing performance and proliferation performance of microorganisms are promoted, or that resistance to microbial growth inhibitory factors is acquired. In addition, an increase in the half-life of a protein or the like having the ability to decompose benzene produced by microorganisms can be cited as such a factor. Furthermore, a plurality of such factors may be combined to contribute to the improvement of benzene decomposition activity by microorganisms. Moreover, when the inhibitory factor and other indigenous bacteria contained in the contaminated groundwater are reduced or removed, it becomes easier to further improve the benzene decomposition activity of the culture solution.

 On the other hand, in the aeration tank 22, volatile benzene contained in the culture solution transferred from the culture vessel 21 by the pump diffuses into the air, so that benzene is completely removed from the culture solution. . For this reason, when reducing and supplying the culture solution to the original position, the original position is not contaminated again by benzene, which is a contaminant contained in the culture solution. Benzene diffused in the air is recovered and processed by a well-known method.

 In addition, the injection well 3 is supplied to the original plant in order to diffuse and mix the culture solution cultured in the culture plant 2 and aerated, into the entire underground contaminated area (including contaminated soil and contaminated groundwater). Functions as a device. Such an injection well 3 makes it possible to return the contaminated groundwater collected and cultured from the original position to the original position again. At this time, various methods such as a batch method, a semi-continuous method, and a continuous method may be used. Alternatively, a method may be used in which the cultured microorganisms are returned to their original positions in a semi-fixed state or in a state where they are supported on an appropriate carrier.

 The injection well 3 is provided with a control means (not shown) for controlling the culture solution aerated in the aeration tank to be reduced and supplied to the original position at a ratio optimal for purification such as 1/100 together with the injected water. It is preferable to have. Such a control means makes it possible to optimize the amount of the culture solution supplied to the original position. In addition, out of contaminated groundwater that is pumped in the intake well 1 and not cultivated in the culture plant 2, water that passes through a water treatment device (not shown) that removes harmful substances such as arsenic is used as part of the injected water. You can also.

 The oxygen supply pump 4 is an oxygen supply device that supplies oxygen to decompose benzene contained in the in-situ contaminated soil / contaminated groundwater into aerobic microorganisms having benzene decomposition performance activated in the culture plant 2. Function as. Unlike the ground-polluted area, the in-situ underground polluted area is generally in a state deficient in oxygen, so such an oxygen supply pump 4 provides an aerobic condition by supplying fresh air from the ground. Aerobic microorganisms contained in contaminated soil and contaminated groundwater can be activated. Furthermore, by adding nutrients (nitrogen, phosphorus, etc.), the microorganisms grown in the culture plant 2 can survive for a certain period of time after returning to the original underground contaminated environment. As a result, it is possible to effectively reduce and remove benzene, which is a contaminant, even in situ. In addition, since the microorganisms which decomposed | disassembled benzene return to an anaerobic state under the anaerobic condition of an underground polluted environment, and decrease / disappear, there is little influence on an environment or a human body.

 Furthermore, in order to implement the present invention having the above-described configuration, it is necessary to satisfy at least the following conditions (i) to (iv). (I) Contaminated groundwater contaminated with benzene contains aerobic microorganisms (hereinafter referred to as “benzene-degrading bacteria”) having benzene-degrading performance (collection process). (Ii) It is possible to activate the benzene-degrading ability of benzene-degrading bacteria by culturing without separating and isolating from contaminated groundwater (culturing step). (Iii) The culture solution can be injected into the original position and mixed by diffusion (feeding step). (Iv) The benzene decomposing activity of the culture solution injected into the in-situ can be maintained even in an underground contaminated area where the activity conditions are severe (purification process).

 Among the above conditions, conditions (i) and (iii) can be confirmed by laboratory tests, and the applicability in field tests is also well known. And about condition (ii), it was able to confirm by the preceding laboratory test. Therefore, the applicability in laboratory tests and field tests to confirm condition (iv) will be described below.

=== Applicability in the confirmation test of the condition (iv) and in the field test ===
First, Table 1 shows the test conditions of the culture test performed to confirm the condition (iv).

  In the culture test, the same soil and water as those used in the preceding laboratory test were used. It was a sample with high pH for both soil and water. The test was carried out on a case where the cells were cultured while being alkaline (culture test 1) and a case where the pH was adjusted before the culture (culture test 2).

The measurement result of the benzene concentration in the culture broth performed under such test conditions is shown in FIG.
FIG. 3 is a graph showing the change over time of the benzene concentration in the culture test. (A) shows the change over time of the benzene concentration in the culture test 1 (alkaline), while (b) shows the culture test 2 (medium The change with time in the benzene concentration is shown.

  As shown in FIG. 3, when the culture solution is not added with only soil and medium, the culture is performed under the same conditions as in the sterilized case and the preceding laboratory test, and the decrease in benzene concentration with time is not seen. The result was similar to the laboratory test. In addition, in the case where the culture solution was added to the soil and culture medium, the benzene concentration decreased rapidly even in the presence of local soil and water. By comparing these test results, it is difficult to activate the benzene-degrading bacteria in the soil used in the main culture test, but the inhibitory action is strong enough to immediately kill the activated benzene-degrading bacteria. I found that there was no.

  In addition, as shown in FIGS. 3 (a) and 3 (b), similar results were obtained in culture test 1 (alkaline, pH 9.5 to 10) and culture test 2 (neutral, pH 7.5). It was. From these results, it was found that the culture broth with enhanced benzene decomposition activity was not affected by the inhibitory action under high pH conditions (alkaline). In the above test, contaminated groundwater is targeted, but such results are also valid for contaminated soil.

  From the above, it has been shown that the injected culture broth is likely to grow for a certain period of time and maintain benzene decomposition activity even in an underground contaminated area (ground) with severe active conditions. That is, it can be said that the main culture test confirmed that the condition (iv) was satisfied, and that the applicability in the field test was high.

It is a schematic sectional drawing which shows the in-situ bioremediation system with the preculture in embodiment of this invention. It is a schematic sectional drawing which shows the culture plant in embodiment of this invention. It is a graph which shows a time-dependent change of the benzene density | concentration in a culture test.

Explanation of symbols

1 Intake Well 2 Culture Plant 3 Injection Well 4 Oxygen Supply Pump 21 Culture Tank 22 Aeration Tank

Claims (5)

In-situ bioremediation with pre-culture to improve the microbial degradability of contaminated soil and contaminated groundwater by culturing microorganisms with the ability to degrade pollutants and purify the contaminated soil and contaminated groundwater in situ Construction method,
A collecting step of collecting a part of the contaminated soil / contaminated groundwater from an original position;
A culture step of culturing the contaminated soil / contaminated groundwater collected in the collection step in a culture solution or medium;
A supply step of reducing and supplying the culture solution or medium cultured in the culture step to the original position;
A purification step of decomposing the pollutants contained in the contaminated soil / contaminated groundwater supplied in the supply step into the microorganisms and purifying the contaminated soil / contaminated groundwater in situ. In-situ bioremediation method with pre-culture. The culture step includes
The in-situ bioremediation method with pre-culture according to claim 1, further comprising the step of adding the contaminant as a degradation substrate to the culture solution or the culture medium. A collection device for collecting a part of contaminated soil / contaminated groundwater containing aerobic microorganisms contaminated with volatile organic compounds and capable of decomposing the organic compounds;
A culture apparatus for culturing the contaminated soil / contaminated groundwater collected by the collection apparatus under aerobic conditions together with a neutral culture solution or medium containing the organic compound as a decomposition substrate;
An aeration treatment apparatus for performing an aeration treatment to remove the remaining organic compound from a culture solution or a medium cultured in the culture apparatus;
A supply device for reducing and supplying the culture solution or culture medium aerated by the aeration treatment device so as to diffuse and mix in the original position;
An oxygen supply device for supplying oxygen to decompose the organic compound contained in the in situ contaminated soil / contaminated groundwater mixed and diffused by the supply device into the aerobic microorganisms In-situ bioremediation system with The supply device includes:
4. The pre-culture according to claim 3, further comprising control means for controlling the culture solution or the medium aerated by the aeration treatment apparatus so as to be reduced and supplied to the original position at a constant rate together with the injected water. In-situ bioremediation system with The organic compound is
It contains at least one of aromatic compounds such as benzene, phenol, benzoic acid, toluene, xylene, cresol, and organic chlorine compounds such as dichloroethylene, trichloroethylene, tetrachloroethylene, tetrachloroethane, vinyl chloride, and dioxin. In-situ bioremediation system with pre-culture according to claim 3 or 4.

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