JP4702671B2 - In-situ purification method for contaminated soil and contaminated groundwater - Google Patents

Description

  The present invention relates to a contaminated soil and contaminated groundwater in-situ purification method that purifies soil and groundwater contaminated with volatile organic compounds such as tetrachloroethylene and trichlorethylene in situ by microorganisms.

  Conventionally, a method generally called bioremediation has been used as one of the methods for purifying soil and groundwater contaminated with volatile organic compounds (volatile organochlorine compounds) such as tetrachloroethylene and trichlorethylene in situ. ing. In this bioremediation, nutrient sources such as nitrogen and carbon are injected into contaminated areas contaminated with volatile organic compounds to activate indigenous microorganisms (anaerobic microorganisms), or microorganisms are injected directly into contaminated areas. The soil and groundwater contaminated by decomposing volatile organic compounds with these microorganisms are purified.

  At this time, for example, when purifying soil or groundwater contaminated with tetrachlorethylene, tetrachlorethylene is decomposed into trichlorethylene and thus cis-1,2-dichloroethylene by reductive dechlorination reaction by anaerobic microorganisms activated in the contaminated area. Is done. When cis-1,2-dichloroethylene is decomposed into carbon dioxide via vinyl chloride, it is completely detoxified and the purification process of the contaminated area is completed.

  However, in such bioremediation, it is possible to decompose tetrachloroethylene to trichlorethylene and cis-1,2-dichloroethylene by anaerobic microorganisms, but trichlorethylene and cis-1,2- which are difficult to become substrates of anaerobic microorganisms. It was difficult to further decompose dichloroethylene into vinyl chloride or carbon dioxide, and even if it could be decomposed, there was a problem that it took a long time to complete the complete purification treatment.

On the other hand, in order to solve the above problems, for example, in the method disclosed in Patent Document 1 (contaminated soil and contaminated water purification method), tetrachloroethylene is decomposed into trichlorethylene and cis-1,2-dichloroethylene by anaerobic microorganisms. After that, a gas such as air is vented to the contaminated area (gas aeration process), and the contaminated area is changed from an anaerobic condition to an aerobic condition. And, by indigenous aerobic microorganisms activated by this gas aeration process and newly aerobic microorganisms injected into the contaminated area, trichloroethylene and cis-1,2-dichloroethylene, which are difficult to decompose by anaerobic microorganisms, are decomposed into carbon dioxide. Like to do. In addition, the anaerobic microorganism treatment process, the gas aeration process, and the aerobic microorganism treatment process are sequentially repeated, or each process is performed a plurality of times so that the volatile organic compounds in the contaminated area can be efficiently and reliably purified. I have to.
JP 2005-205299 A

  However, in the purification method disclosed in the above-mentioned Patent Document 1, it is necessary to change the entire contaminated area from anaerobic conditions to aerobic conditions by the gas aeration step, especially as the contaminated area is wide. There was a problem that it took a lot of time to change to anaerobic or aerobic conditions. For this reason, there has been a strong demand for a method that can more effectively purify soil and groundwater contaminated with volatile organic compounds using microorganisms.

  In view of the above circumstances, the present invention provides in-situ purification of contaminated soil and contaminated groundwater capable of purifying contaminated soil and groundwater by decomposing volatile organic compounds reliably and more efficiently using microorganisms. An object is to provide a processing method.

  In order to achieve the above object, the present invention provides the following means.

  The in-situ purification method for contaminated soil and contaminated groundwater according to the present invention is a method for in-situ purification of soil and groundwater contaminated with volatile organic compounds by microorganisms, and contaminated with the volatile organic compounds. A pumping well is disposed in the contaminated area, a first injection well is disposed on one contaminated area side, and a second injection well is disposed on the other contaminated area side. An anaerobic decomposition in which the volatile organic compound is decomposed by activated anaerobic microorganisms into the one contaminated region by the first circulation of the groundwater supplied from the first circulation region and pumped in the pumping well. Forming a region, supplying the second contaminated well, circulating the other contaminated region, and pumping the pumped well through the second circulation of the groundwater into the other contaminated region with activated aerobic microorganisms And forming aerobic degradation region to decompose-volatile organic compounds.

  In the present invention, an anaerobic decomposition region is formed in one contaminated region by the first circulation of groundwater, so that volatile organic compounds can be decomposed by the anaerobic microorganisms activated in this region. In addition, since the second circulation of groundwater forms an aerobic decomposition region in the other polluted region, volatile organic compounds that have not been decomposed until detoxified in the anaerobic decomposition region are grounded in this aerobic decomposition region. By being distributed together, it can be decomposed until it is rendered harmless by aerobic microorganisms.

  According to the in-situ purification method for contaminated soil and contaminated groundwater of the present invention, groundwater containing a volatile organic compound as compared with the conventional purification method for changing the entire contaminated region from anaerobic conditions to aerobic conditions. The volatile organic compounds can be decomposed until they are rendered harmless by a simple operation of pumping up the water from the pumping well and sequentially circulating it through the anaerobic and aerobic decomposition regions, so that the purification process can be performed reliably and efficiently. It becomes possible.

  Hereinafter, with reference to FIG. 1, an in-situ purification method for contaminated soil and contaminated groundwater according to an embodiment of the present invention will be described. The present embodiment relates to an in situ purification method for contaminated soil and contaminated groundwater, in which soil and groundwater contaminated with volatile organic compounds are purified in situ by microorganisms.

  As shown in FIG. 1, the purification treatment apparatus (purification treatment equipment) A used in the in-situ purification treatment method for contaminated soil and contaminated groundwater of this embodiment is disposed in a contaminated region R contaminated with a volatile organic compound. The pumping well 1, the first injection well 2 disposed on the one contaminated area R1 side with the pumping well 1 interposed therebetween, and the second injection well 3 disposed on the other contaminated area R2 side with the pumping well 1 interposed therebetween. And is configured. Further, the pumping well 1 is provided with a slit portion 1a for allowing the surrounding groundwater W to permeate inside at the lower end side thereof, and the groundwater is driven through the slit portion 1a by driving a pumping pump 1b inserted therein. It is configured to collect W and pump it to the ground. On the other hand, the first injection well 2 and the second injection well 3 are provided with slit portions 2a and 3a on the lower end side, respectively, and the ground water W pumped up by the pumping well 1 is the first injection well 2 and the second injection well. 3, the groundwater W can be returned to the ground through the slit portions 2 a and 3 a when supplied to the inside of each. In FIG. 1, the pumping well 1, the first injection well 2, and the second injection well 3 are illustrated as being provided one by one. A plurality of two injection wells 3 may be provided.

  Furthermore, in the purification treatment apparatus A of the present embodiment, the pipe 4 connected to the pump 1b of the pumping well 1 is bifurcated on the ground, and one branch pipe 5 is connected to the nutrient solution addition tank 6 and the other is added. The branch pipes 7 are respectively connected to the aeration tank 8. Moreover, the nutrient solution addition tank 6 and the first injection well 2, the aeration tank 8 and the second injection well 3 are connected via pipes 9 and 10, respectively.

  When purifying contaminated soil and contaminated groundwater by the purification treatment apparatus A configured as described above, the pumping pump 1b inserted into the pumping well 1 is driven, and the surroundings through the slit portion 1a of the pumping well 1 are driven. Pumping groundwater W to the ground while collecting water. When the groundwater W is pumped up from the pumping well 1 in this way, a groundwater flow T1 flowing from the first injection well 2 side toward the pumping well 1 is generated in one contaminated region R1, and the other contaminated region R2 has A groundwater flow T2 flowing from the second injection well 3 side toward the pumping well 1 is generated.

  In the present embodiment, the groundwater W collected from one contaminated area R1 and the groundwater W collected from the other contaminated area R2 are mixed in the pumping well 1 and pumped to the ground. Then, a part of the groundwater W pumped up to the ground is sent to the nutrient solution addition tank 6 through one branch pipe 5, and in this nutrient solution addition tank 6, for example, a nitrogen nutrient source, a carbon nutrient source, Nutrients such as organic acids, inorganic salts and vitamins are added. The groundwater W to which the nutrient is added in this way is supplied to the first injection well 2 through the pipe 9, and is returned to the ground again from the slit portion 2a of the first injection well 2. The returned groundwater W containing the nutrient is passed through the one contaminated region R1 by the groundwater flow T1 flowing through the one contaminated region R1, and collected in the pumping well 1 again. As a result, the pumping well 1 is placed on one side of the contaminated area R1 between the pumping well 1 to the nutrient addition tank 6, the nutrient addition tank 6 to the first injection well 2, and the first injection well 2 to one side. A first circulation S1 of the groundwater W that circulates again to the pumping well 1 through the contaminated region R1 is formed.

  And by the 1st circulation S1 of the groundwater W formed in this way, while the groundwater W containing a nutrient passes sequentially one pollution area | region R1, indigenous microorganisms are activated and oxygen in soil and groundwater is consumed. In addition, an anaerobic decomposition region P1 in which indigenous anaerobic microorganisms are activated is formed on one contamination region R1 side.

  On the other hand, the groundwater W pumped up by the pumping well 1 and sent to the aeration tank 8 through the other branch pipe 7 is aerated in the aeration tank 8, and the amount of dissolved oxygen is increased. That is, the groundwater W is treated so as to increase the dissolved oxygen concentration. And the groundwater W in which the dissolved oxygen concentration became high in this way is supplied to the 2nd injection well 3 via the piping 10, and is returned in the ground again from the slit part 3a of this 2nd injection well 3. FIG. The returned groundwater W having a high dissolved oxygen concentration passes through the other contaminated region R2 by the groundwater flow T2 flowing through the other contaminated region R2, and is collected in the pumping well 1 again. Thus, the pumping well 1 is passed through the other contaminated area R2 from the pumped well 1 to the aeration tank 8, the aeration tank 8 to the second injection well 3, and the second injection well 3 to the other contaminated area R2. A second circulation S2 of the groundwater W that circulates again to the pumping well 1 is formed.

  Then, by the second circulation S2 of the groundwater W thus formed, the groundwater W having a high dissolved oxygen concentration sequentially passes through the other contaminated region R2, and the indigenous microorganisms are activated, and the other contaminated region R2 side is activated. In this case, an aerobic degradation region P2 in which native aerobic microorganisms are activated is formed.

  For example, when the first circulation S1 and the second circulation S2 are formed in the contaminated region R contaminated with tetrachloroethylene (volatile organic compound) and the groundwater W is circulated, the anaerobic decomposition region formed in the first circulation S1. At P1, it is decomposed into trichlorethylene and thus cis-1,2-dichloroethylene by a dechlorination reaction by an anaerobic microorganism in which tetrachloroethylene is activated. Furthermore, the volatile organic compound thus decomposed into trichlorethylene and thus cis-1,2-dichloroethylene is pumped from the pumping well 1 together with the ground water W by the first circulation S1. Subsequently, the groundwater W containing trichlorethylene and thus cis-1,2-dichloroethylene is sent to the second circulation S2, and flows from the second injection well 3 to the aerobic decomposition region P2. As a result, the volatile organic compound decomposed to trichlorethylene and thus cis-1,2-dichloroethylene by the anaerobic microorganism in the anaerobic decomposition region P1 is chlorinated by the dechlorination reaction by the aerobic microorganism activated in the aerobic decomposition region P2. It is decomposed into carbon dioxide via vinyl.

  Here, in this embodiment, the groundwater W pumped up by the pumping well 1 is the groundwater W in the first circulation S1 that has passed through the anaerobic decomposition region P1, and the groundwater W in the second circulation S2 that has passed through the aerobic decomposition region P2. Are mixed in the pumping well 1. Then, the water is pumped up to the ground and distributed to the first circulation S1 and the second circulation S2 by one branch pipe 5 and the other branch pipe 7. For this reason, a part of the volatile organic compound decomposed to the trichlorethylene and thus cis-1,2-dichloroethylene through the anaerobic decomposition region P1 again passes through the anaerobic decomposition region P1 by the first circulation S1. It will be circulated. However, by continuously pumping up the ground water W in the pumping well 1 and distributing it to the first circulation S1 and the second circulation S2, all of the tetrachlorethylene in the contaminated region R is passed through the anaerobic decomposition region P1 and the aerobic decomposition region P2. Passes through and gradually decomposes to carbon dioxide and is rendered harmless. Thereby, the contaminated soil and contaminated groundwater contaminated with tetrachlorethylene in the entire contaminated region R are reliably purified. At this time, by measuring the concentration of volatile organic compounds in the groundwater W pumped up in the pumping well 1, the degree of purification of the contaminated soil and the contaminated groundwater can be confirmed.

  Therefore, in the in situ purification method for contaminated soil and contaminated groundwater of the present embodiment, the anaerobic decomposition region P1 is formed on the one contaminated region R1 side by the first circulation S1 of the groundwater W. Thereby, a volatile organic compound can be decomposed | disassembled by the anaerobic microorganisms activated in this area | region P1. Further, an aerobic decomposition region P2 is formed on the other contaminated region R2 side by the second circulation S2 of the groundwater W. As a result, the volatile organic compound that has not been decomposed until it is detoxified in the anaerobic decomposition region P1 flows along with the groundwater W to the aerobic decomposition region P2, so that the volatile organic compound is surely obtained by the aerobic microorganism. Can be broken down until detoxified.

  Therefore, in comparison with the conventional purification method that changes the entire contaminated region R from anaerobic conditions to aerobic conditions, groundwater W containing volatile organic compounds is pumped from the pumping well 1 and is more favorable than the anaerobic decomposition region P1. By a simple operation of sequentially flowing to the gas decomposition region P2, the volatile organic compound can be decomposed until it is rendered harmless, and the purification process can be performed reliably and efficiently. In addition, a highly reliable purification process can be easily performed at an early stage, and the cost for the purification process can be reduced.

  As mentioned above, although one embodiment of the in-situ purification method of the contaminated soil and the contaminated groundwater according to the present invention has been described, the present invention is not limited to the above-described one embodiment, and is appropriately within a range not departing from the gist thereof. It can be changed. For example, in this embodiment, the anaerobic decomposition region P1 in which indigenous anaerobic microorganisms are activated is formed by returning the groundwater W added with nutrients from the first injection well 2 to the ground, An aerobic decomposition region P2 in which indigenous aerobic microorganisms are activated is formed by returning groundwater W having an increased dissolved oxygen concentration from the second injection well 3 to the ground. Anaerobic microorganisms are added to the groundwater W supplied to the well 2 or aerobic microorganisms are added to the groundwater W supplied to the second injection well 3, so that these groundwaters W are in one contaminated area R1 and the other contaminated area R2. The anaerobic microorganisms may be supplied to the anaerobic decomposition region P1 and the aerobic microorganisms may be supplied to the aerobic decomposition region P2.

  In the present embodiment, the nutrient water is only added to the groundwater W pumped up in the pumping well 1 and returned from the first injection well 2. For example, the pumped-up groundwater W is sent to a deaeration device or the like. The groundwater W having a reduced dissolved oxygen concentration may be returned from the first injection well 2. Accordingly, the anaerobic decomposition region P1 can be reliably formed by the first circulation S1, and the anaerobic microorganism can be reliably activated to decompose the volatile organic compound.

  Further, in the present embodiment, the groundwater W that has passed through the anaerobic decomposition region P1 and the aerobic decomposition region P2 is pumped up while being mixed in the pumping well 1, but the groundwater W that has passed through the anaerobic decomposition region P1, The groundwater W that has passed through the aerobic decomposition region P2 may be pumped up to the ground while being divided. In this case, it is possible to send all the groundwater W that has passed through the anaerobic decomposition region P1 to the aeration tank 8, and to send all the groundwater W that has passed through the aerobic decomposition region P2 to the nutrient solution addition tank 6. That is, the groundwater W can be circulated by one-system circulation connecting the first circulation S1 and the second circulation S2. In this case, all the volatile organic compounds decomposed to trichlorethylene and thus cis-1,2-dichloroethylene in the anaerobic decomposition region P1 can be sent to the aerobic decomposition region P2 in the next step. The purification process can be performed more efficiently than in the present embodiment.

  Moreover, in this embodiment, although it demonstrated so that the aeration tank 8 of 2nd circulation S2 might be used only for raising the dissolved oxygen concentration of groundwater W, while aeration groundwater W was aerated in the aeration tank 8, At least a part of the volatile organic compound contained in the groundwater W is volatilized and diffused in the gas phase in the aeration tank 8. For this reason, for example, a purification treatment apparatus A is configured by connecting an adsorption tank containing an adsorbent such as activated carbon to the gas phase of the aeration tank 8, and the gas phase of the aeration tank 8 is sent to the adsorption tank together with the aeration. You may make it collect the volatile organic compound volatilized in the phase with an adsorbent. In this case, volatile organic compounds can be decomposed by underground microorganisms to purify contaminated soil and contaminated groundwater, and at the same time, volatile organic compounds can be removed from groundwater W pumped up on the ground. Therefore, the purification process can be performed more efficiently.

  Further, in the present embodiment, the volatile organic compound that contaminates the soil and groundwater has been described as being tetrachloroethylene (including trichloroethylene and cis-1,2-dichloroethylene). For other volatile organic compounds such as 1-trichloroethane, dichloromethane, carbon tetrachloride, 1,1-dichloroethylene, 1,2-dichloroethane, 1,1,2-trichloroethane, 1,3-dichloropropene, benzene, By applying the in-situ purification method of the contaminated soil and contaminated groundwater of the present invention, it is possible to perform the purification treatment in the same manner as in this embodiment. In addition, for example, in the case of complex pollution in which heavy metals such as mercury, selenium, hexavalent chromium, cadmium, lead, and arsenic coexist with these volatile organic compounds, the groundwater W pumped in the pumping well 1 The volatile organic compounds are decomposed while removing other pollutants by returning the groundwater W, which has been insolubilized, etc., and removed other pollutants such as heavy metals from the wells 2 and 3 to the ground. Can be processed.

It is a figure which shows the in-situ purification process method of the contaminated soil and contaminated groundwater which concern on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pumping well 1b Pumping pump 2 1st injection well 3 2nd injection well 6 Nutrient addition tank 8 Aeration tank A Purification processing equipment (purification processing equipment)
P1 Anaerobic decomposition region P2 Aerobic decomposition region R Contaminated region R1 One contaminated region R2 Other contaminated region S1 First circulation S2 Second circulation T1 Groundwater flow T2 Groundwater flow W Groundwater

Claims (1)

A method of purifying soil and groundwater contaminated with volatile organic compounds in situ by microorganisms,
A pumping well is disposed in a contaminated area contaminated with the volatile organic compound, and a first injection well is provided on one contaminated area side and a second injection well is provided on the other contaminated area side. Arranged,
By the first circulation of the groundwater supplied from the first injection well and circulated through the one contaminated area and pumped by the pumping well, the volatile organic compound is activated in the one contaminated area by activated anaerobic microorganisms. Forming an anaerobic decomposition region to decompose,
The volatile organic compound is activated by activated aerobic microorganisms into the other contaminated area by the second circulation of the groundwater supplied from the second injection well, distributed through the other contaminated area and pumped up by the pumping well. An in-situ purification method for contaminated soil and contaminated groundwater, comprising forming an aerobic decomposition region for decomposition.

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