JP4821097B2 - Water flow anaerobic biosystem and its treatment method - Google Patents

Description

  The present invention relates to a water flow anaerobic biosystem for efficiently purifying soil contaminated with an organic chlorine compound and a treatment method thereof.

  Tetrachloroethylene, trichlorethylene, and dichloroethylene, which are volatile organic chlorine compounds, are used in the degreasing and washing of metals, washing in dry cleaning, refrigerants, etc., and they have high industrial utility value. It becomes a harmful substance that causes Therefore, soil and groundwater contamination by these organochlorine compounds is a serious social problem.

There are many techniques for decomposing these organic chlorine compounds and purifying contaminated soil and groundwater, one of which is a purification method by pumping water aeration treatment. This is because the contaminated groundwater is pumped, the volatile organochlorine compounds contained in the groundwater are vaporized by aeration treatment, and the vaporized volatile organochlorine compounds are adsorbed on activated carbon and removed to remove contamination. This is a method of purifying the groundwater that has been removed (for example, Patent Document 1). As another technique, a method for purifying contaminated soil and groundwater by reductive dechlorination treatment by anaerobic microorganisms has been developed. This is a method of purifying contaminated soil and groundwater by substituting the chlorine of the organochlorine compound with hydrogen using anaerobic microorganisms present in the contaminated soil and groundwater (for example, Patent Document 2 or 3). ).
JP 2003-154356 A JP-A-10-216694 JP 2000-263032 A

  In the pumping process, groundwater is pumped from the aquifer, so if the contamination with volatile organochlorine compounds reaches the aquifer and volatile organochlorine compounds are not contained in the aquifer, an efficient removal effect is achieved. Is not expected. For example, since tetrachlorethylene and trichlorethylene are hydrophobic, they do not dissolve in groundwater, and therefore are not efficient because removal by pumping treatment is ineffective and takes time.

  In the reductive dechlorination treatment by anaerobic microorganisms, tetrachloroethylene and trichlorethylene can be easily decomposed, but there are very few anaerobic microorganisms capable of decomposing dichloroethylene produced by their decomposition, Purifying groundwater takes time and this process is not efficient.

  For this reason, when pumping treatment and reductive dechlorination treatment are carried out independently, it takes a long time to purify contaminated soil and groundwater, and it may take 10 years or more. In order to solve this problem, an object of the present invention is to provide a water flow anaerobic biosystem for efficiently purifying soil contaminated with an organic chlorine compound and a treatment method thereof.

In order to solve the above problems, a water-flowing anaerobic biosystem according to the present invention is a water-flowing anaerobic biosystem for purifying soil contaminated with organochlorine compounds that are decomposed into volatile water-soluble substances by anaerobic microorganisms. A decomposition accelerator storage tank for storing an anaerobic microbial decomposition accelerator that is a hydrogen donor or iron powder in a reductive dechlorination reaction that replaces chlorine and hydrogen in an organic chlorine compound; In order to add the anaerobic microbial degradation promoter transferred from the degradation promoter storage tank to the contaminated soil, it is provided on the upstream side of the groundwater flowing in the soil, and promotes the anaerobic microbial degradation in the groundwater. An injection well for injecting an agent, and an underground containing the volatile water-soluble substance generated by the anaerobic microorganisms in soil contaminated with the organochlorine compound In order to remove the volatile water-soluble substances from the groundwater that is provided on the downstream side of the groundwater that flows in the soil, and for taking in the groundwater, and groundwater that is taken in the water intake well Further, the aeration apparatus for aeration treatment of groundwater taken in the intake well with nitrogen gas, and the volatile vaporized from the mixed gas of the volatile water-soluble substance vaporized by the aeration treatment and the nitrogen gas A purification device for removing the water-soluble substance; and a gas transfer device for transferring the nitrogen gas after the vaporized volatile water-soluble substance is removed by the purification device to the aeration device. In addition, it is preferable that the said system is further provided with the groundwater transfer means for transferring the aerated groundwater to the said injection well, and inject | pouring it into the said soil. The organic chlorine compound is preferably one or more compounds selected from the group consisting of tetrachloroethylene or trichloroethylene. The volatile water-soluble substance is preferably dichloroethylene.

Furthermore, the water-flowing anaerobic biotreatment method according to the present invention is a water-flowing anaerobic biotreatment method for purifying soil contaminated with organochlorine compounds that are decomposed into volatile water-soluble substances by anaerobic microorganisms, Injecting an anaerobic microbial degradation promoter that is a hydrogen donor or iron powder in a reductive dechlorination reaction that replaces chlorine and hydrogen of an organochlorine compound, upstream of the groundwater flowing in the contaminated soil; Taking the groundwater in which the volatile water-soluble substance generated from the organochlorine compound by the anaerobic microorganisms is dissolved in the contaminated soil at the downstream side of the groundwater flowing in the contaminated soil; A process of aeration of the groundwater taken with nitrogen gas in an aeration apparatus to evaporate the volatile water-soluble substance, and before vaporization by the aeration process The step of removing the vaporized volatile water-soluble substance from the mixed gas of the volatile water-soluble substance and the nitrogen gas, and the nitrogen gas after the vaporized volatile water-soluble substance is removed to the aeration apparatus Transferring. Preferably, the water flow anaerobic biotreatment method further includes a step of injecting and circulating the aerated groundwater to the upstream side of the groundwater flowing through the contaminated soil. The organic chlorine compound is preferably one or more compounds selected from the group consisting of tetrachloroethylene or trichloroethylene. The volatile water-soluble substance is preferably dichloroethylene.

  The present invention provides a water flow anaerobic biosystem for efficiently purifying soil and groundwater contaminated with volatile organochlorine compounds and a treatment method thereof.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The objects, features, advantages, and ideas of the present invention will be apparent to those skilled in the art from the description of the present specification, and those skilled in the art can easily reproduce the present invention from the description of the present specification. it can. The embodiments and specific examples of the invention described below show preferred embodiments of the present invention and are shown for illustration or explanation, and the present invention is not limited to them. It is not limited. It will be apparent to those skilled in the art that various modifications and variations can be made based on the description of the present specification within the spirit and scope of the present invention disclosed herein.

=== Outline of water anaerobic biosystem and its treatment ===
Degradation of organochlorine compounds by anaerobic microorganisms includes tetrachloroethylene (hereinafter abbreviated as “PCE”) to trichlorethylene (hereinafter abbreviated as “TCE”), dichloroethylene (hereinafter abbreviated as “DCE”), and vinyl chloride (hereinafter referred to as “VC”). The reaction proceeds in the order of ethylene (hereinafter abbreviated as “ETY”), ethane (hereinafter abbreviated as “ETA”) (see FIG. 1). In actual polluted soil, as long as the organochlorine compound that is the pollutant is PCE or TCE, it is easily decomposed because there are anaerobic microorganisms that decompose them, but PCE and TCE are decomposed. When DCE is a volatile water-soluble substance, DCE tends to accumulate because there are few anaerobic microorganisms that can decompose DCE.

  However, while PCE and TCE are hydrophobic, DCE is hydrophilic and has high solubility in water. Therefore, there is a high possibility that DCE is contained in the groundwater flowing in the contaminated soil, and it is possible to efficiently remove DCE by collecting the groundwater and subjecting it to aeration.

  Therefore, in the contaminated soil, DCE precursors PCE and TCE are decomposed into volatile water-soluble DCE by anaerobic microorganisms, and dissolved in groundwater flowing in the contaminated soil, and the DCE is dissolved. By recovering the groundwater contained therein and subjecting it to aeration treatment, it becomes possible to efficiently remove organochlorine compounds from contaminated soil.

=== Configuration diagram of a water anaerobic biosystem ===
FIG. 3 shows a configuration diagram of a water flow anaerobic biosystem 100 described as an embodiment of the present invention.

  As shown in FIG. 3, a water flow anaerobic biosystem 100 according to the present invention is anaerobic to a decomposition accelerator storage tank 10 for storing an anaerobic microbial decomposition accelerator and groundwater flowing in soil contaminated with an organic chlorine compound. An injection well 20 for injecting a microbial decomposition accelerator, an intake well 30 for taking ground water containing volatile water-soluble substances generated by anaerobic microorganisms, and aeration treatment of ground water taken by the intake well 30 Thus, an aeration apparatus 40 for transferring to the injection well 20 after purification is provided.

  The pump 12 installed in the vicinity of the decomposition accelerator storage tank 10 plays a role of transferring the anaerobic microbial decomposition accelerator in the decomposition accelerator storage tank 10 to the injection well 20. The injection well 20 is provided on the upstream side of the groundwater flowing through the soil in order to add the anaerobic microbial degradation promoter to the contaminated soil, and injects the anaerobic microbial degradation promoter into the groundwater. The anaerobic microbial decomposition accelerator promotes the decomposition of the organic chlorine compound by the anaerobic microorganisms, thereby generating a volatile water-soluble substance as a decomposition product. A water intake well 30 for taking groundwater in which the volatile water-soluble substance is dissolved is provided on the downstream side of the groundwater flowing in the soil. The groundwater containing volatile water-soluble substances taken in the intake well 30 is transferred to the aeration apparatus 40.

  Hereinafter, an apparatus configuration provided around the aeration apparatus 40 in order to purify the groundwater taken from the intake well 30 will be described. First, the gas tank 50 which supplies the gas required for aeration processing with respect to the aeration apparatus 40 is provided. In addition, a purification device 60 is provided to render the volatile water-soluble substance vaporized by the aeration device 40 harmless. A gas-liquid separation tank 62 is provided in the middle of the path for transferring gas from the aeration device 40 to the purification device 60 to separate liquid components mixed in the gas from the aeration device 40. The separated liquid component may be collected and transferred to the aeration apparatus 40. In addition, the compressor 42 is connected to the purification device 60 and serves to transfer the gas released from the purification device 60 to the aeration device 40 for reuse. Furthermore, the aeration apparatus 40 can discharge the groundwater purified by the aeration process to the water injection well 20. These devices may be connected by a transport pipe for transferring gas or liquid, but may be directly connected, or a plurality of devices such as providing a gas tank 50 inside the aeration device 40. May actually hold as one device. In the present specification, “original position” means “contaminated soil location”.

=== Water Anaerobic Biotreatment Method ===
The following steps are carried out in a water-flowing anaerobic biotreatment method for purifying soil contaminated with organochlorine compounds that are decomposed into volatile water-soluble substances by anaerobic microorganisms.

(1) First, an anaerobic microbial degradation promoter that promotes the decomposition of organochlorine compounds into volatile water-soluble substances by anaerobic microorganisms is injected into the upstream side of groundwater flowing in the contaminated soil. The anaerobic microbial decomposition accelerator is transferred from the decomposition accelerator storage tank 10 to the injection well 20 by means for transferring the anaerobic microbial decomposition accelerator. And an anaerobic microbe decomposition | disassembly promoter is inject | poured from the injection well 20 in the upstream of the groundwater which flows in the contaminated soil.

As a means for transferring the anaerobic microbial degradation promoter, for example, a pump 12 or the like can be considered. The anaerobic microorganism decomposition accelerator, to provide a hydrogen by a chemical reaction with the hydrogen donor or water to provide a necessary hydrogen chlorine and hydrogen organic chlorine compounds to promote the reductive dechlorination of replacing Iron powder is used. Examples of the hydrogen donor include alcohols such as methanol or ethanol, low-molecular organic substances such as glucose or sucrose, lower fatty acids such as acetic acid, propionic acid, lactic acid, or butyric acid, or HRC (Hydrogen Release Compound) that is a polylactic acid ester. : Hydrogen donor compound) and the like. If the amount of groundwater flowing through the soil is small or almost absent, the soil is contaminated by dissolving or diluting the anaerobic microbial degradation promoter in water to facilitate injection. You may pass water. The organochlorine compound that is the subject of pollution purification is preferably a compound containing one or more types of PCE or TCE, but any substance that is decomposed into volatile water-soluble substances by anaerobic microorganisms can be purified. Is possible. Further, DCE includes trans-dichloroethylene (hereinafter abbreviated as “trans-DCE”) or cis-dichloroethylene (hereinafter abbreviated as “cis-DCE”), while cis-DCE is soluble (solubility in water: cis- DCE is more preferable because 6300 mg / l) is high.

  By injecting the anaerobic microbial degradation promoter from the injection well 20, the anaerobic microbial degradation promoter efficiently penetrates into the contaminated soil. Therefore, the reductive dechlorination of organochlorine compounds by the anaerobic microorganisms is efficient. Implemented. Moreover, compared to the degradation of PCE and TCE into VC or ETY by anaerobic microorganisms, the degradation to DCE is short (see FIG. 2), so there is no need to repeatedly inject an anaerobic microbial degradation promoter, The amount used is also small and efficient compared to the amount required for decomposition into VC or ETY by ordinary anaerobic microorganisms. In addition, the range in which the concentration of organochlorine compounds in the contaminated soil is extremely high or the concentration of substances that inhibit the action of anaerobic microorganisms such as oxidants is diluted by passing water. Degradation of PCE and TCE into DCE by sex microorganisms is promoted.

Next, groundwater in which volatile water-soluble substances generated from organochlorine compounds by anaerobic microorganisms in the contaminated soil are dissolved is taken downstream of the groundwater flowing in the contaminated soil. Decomposition of organochlorine compounds by anaerobic microorganisms in normal contaminated soil takes time until it is decomposed to ETY. Therefore, before DCE that is a volatile water-soluble substance is decomposed into ETY by decomposition products of PCE and TCE. And the anaerobic microbial degradation accelerator diffuses, causing a problem that it cannot be efficiently processed. However, in this invention, since it decomposes | disassembles to DCE in a short period of time, an anaerobic microbial degradation promoter is used effectively and prevents spreading | diffusion. Even if DCE, which is a volatile water-soluble substance, flows into the groundwater, there is no problem because water can be taken in the intake well 30.

(3) The groundwater taken is aerated to vaporize volatile water-soluble substances. The aeration process is, for example, supplying gas to the groundwater in order to vaporize DCE contained in the groundwater taken in the intake well 30. By supplying this gas, DCE which is a volatile water-soluble substance is vaporized. Gas used, in order to decompose the DCE as possible collected water was present in the ground water to promote the activity of anaerobic microorganisms might be remaining in the groundwater PCE and TCE, etc., is an inert gas Nitrogen is used . Further, the vaporized volatile water-soluble substance is transferred to the purification device 60 via the gas-liquid separation tank 62. The gas-liquid separation tank 62 is preferably an apparatus having a function of separating gas and liquid, for example, a gas-liquid separation membrane, in order to reliably transfer only gas to the purification device 60.

(4) Then, the volatile water-soluble substance vaporized by the aeration process is detoxified. In the purification device 60, since the gas used for the aeration process and the vaporized volatile water-soluble substance are mixed, a process for separating them is performed. As a means for the separation treatment, activated carbon is used, but a gas separation membrane such as a ceramic separation membrane capable of isolating a volatile water-soluble substance may be used. The gas detoxified by removing the volatile water-soluble substance in this way is reused and returned to the aeration apparatus 40 by the compressor 42. The compressor 42 is preferably a device that can transfer the gas to be reused to the aeration device 40, such as an air compressor.

  Next, aerated groundwater is injected and circulated upstream of the groundwater flowing through the contaminated soil. The purified groundwater is harmless and can be discharged anywhere. However, it is preferable to transfer the soil to the original position to establish a purification cycle for contaminated soil and groundwater. Furthermore, when this transfer route and the route for injecting the anaerobic microbial degradation accelerator from the degradation accelerator storage tank 10 to the injection well 20 are combined, the route for transferring purified groundwater to the original position and anaerobic by one route. It is possible to play two roles of the route for injecting the microbial degradation accelerator, which is very efficient and preferable. In addition, when nitrogen gas is used in the aeration process described above, the purified groundwater is anaerobic due to oxygen being degassed, and when returned to its original position, the original position becomes more anaerobic, which is preferable for anaerobic microorganisms. It becomes the environment. Furthermore, when the above-mentioned path | routes were merged into one, it is still better because an anaerobic microbial degradation promoter can be inject | poured into the water of the anaerobic state.

  Usually, when an in-situ anaerobic microorganism is decomposed, the presence of anaerobic microorganisms capable of decomposing organochlorine compounds into contaminated soil and groundwater (specifically, the presence of anaerobic microorganisms capable of decomposing DCE) It is necessary to carry out an applicability evaluation test (treatability test) for confirming the above, but it is not necessary to carry out this test by carrying out the water anaerobic biotreatment method of the present invention. This is because there are many types of anaerobic microorganisms that degrade PCE and TCE, and they inhabit almost all soils and groundwaters, so it is not necessary to confirm their existence again. That is, the present invention can be applied even in soil where there are no anaerobic microorganisms capable of degrading DCE, which is very efficient. Furthermore, since the above-mentioned aeration treatment is performed in parallel while the PCE and TCE are being decomposed by the anaerobic microorganisms in the contaminated soil, the present invention can be applied to normal soils contaminated by the anaerobic microorganisms or pumping treatment. Faster and more efficient than purification.

  For the soil contaminated with organochlorine compounds, the following experiment was conducted to compare the number of days related to the decomposition of PCE and TCE into DCE and the number of days in which DCE is decomposed using an applicability evaluation test.

  Add 100g of soil containing organochlorine compound and 100ml of groundwater containing organochlorine compound to 100ml brown screw mouth bottle, add 50ppm hydrogen donor, and then inject nitrogen gas into the upper part of screw mouth bottle Then, anaerobic state was created by substituting oxygen. Then, the screw mouth bottle was sealed with a Teflon-coated cap with a silicon septum, and the substances contained therein were mixed, followed by stationary culture at 25 ° C. After that, sample the gas in the gas phase in the screw bottle every few days, using a gas chromatograph (GC-8610, JEOL Datum) (detector: DELCD, separation column: stainless capillary column NBW-310SS30), Analysis of organochlorine compounds (PCE, TEC, cis-DCE, VC) was performed. The result is shown in FIG.

  The PCE decreased immediately after the start of the experiment, and became less than the environmental standard value (0.01 mg / l) after 5 days. The TCE produced by the decomposition of PCE also fell below the environmental standard value (0.03 mg / l) after 5 days. However, the cis-DCE produced by the decomposition of TCE gradually increased until about the 30th day, and finally began to decrease from the 30th day. Since it takes time for all of the soil and groundwater PCE and TCE used in the experiment to be decomposed into cis-DCE (including those that adhere to soil organic matter and did not dissolve in water), cis-DCE It took time to increase. On reaching day 65, cis-DCE decreased to 0.01 mg / l or less. Moreover, VC gradually increased from around the 15th day, and continued to increase in the inverse proportion to cis-DCE after the 30th day. This indicates that cis-DCE was decomposed into VC. From this, it became clear by the present invention that the process required for about 65 days can be shortened to 5 days too much.

It is the figure which showed the reductive dechlorination reaction of an organic chlorine compound, and its product with the reaction process. In one Example of this invention, it is the graph which showed the process in which the organochlorine compound contained in soil and groundwater was decomposed | disassembled with progress of time by the applicability evaluation test. It is a figure which shows the structure of the water flow anaerobic biosystem demonstrated as one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Decomposition accelerator storage tank 12 Pump 20 Injection well 30 Intake well 40 Aeration apparatus 42 Compressor 50 Gas tank 60 Purification apparatus 62 Gas-liquid separation tank 100 Water flow anaerobic biosystem

Claims (6)

A flow-through anaerobic biosystem for purifying soil contaminated with organochlorine compounds that are decomposed into volatile water-soluble substances by anaerobic microorganisms,
A decomposition accelerator storage tank for storing an anaerobic microbial decomposition accelerator which is a hydrogen donor or iron powder in a reductive dechlorination reaction for replacing chlorine and hydrogen of an organic chlorine compound;
In order to add the anaerobic microbial decomposition accelerator transferred from the decomposition accelerator storage tank to the soil contaminated with the organic chlorine compound, provided on the upstream side of the groundwater flowing in the soil, the groundwater An injection well for injecting an anaerobic microbial degradation promoter;
In order to recover the groundwater containing the volatile water-soluble substance generated by the anaerobic microorganisms in the soil contaminated with the organic chlorine compound, the groundwater is provided on the downstream side of the groundwater flowing in the soil, A water intake well for taking water,
An aeration apparatus for aeration treatment of the groundwater taken in the intake well with nitrogen gas in order to remove the volatile water-soluble substances from the groundwater taken in the intake well;
A purification device for removing the vaporized volatile water-soluble substance from a mixed gas of the volatile water-soluble substance and the nitrogen gas vaporized by the aeration treatment;
A water transfer anaerobic biosystem comprising: a gas transfer device that transfers the nitrogen gas after the vaporized volatile water-soluble substance is removed by the purification device to the aeration device.   The water flow biosystem according to claim 1, further comprising groundwater transfer means for transferring the aerated groundwater to the injection well and injecting it into the soil.   The water-permeable anaerobic bio of claim 1 or 2, wherein the organic chlorine compound is one or more compounds selected from the group consisting of tetrachloroethylene or trichloroethylene, and the volatile water-soluble substance is dichloroethylene. system. A flow-through anaerobic biotreatment method for purifying soil contaminated with organochlorine compounds that are decomposed into volatile water-soluble substances by anaerobic microorganisms,
Injecting an anaerobic microbial degradation promoter that is a hydrogen donor or iron powder in a reductive dechlorination reaction that replaces chlorine and hydrogen of an organochlorine compound, upstream of the groundwater flowing in the contaminated soil; ,
Taking groundwater in which the volatile water-soluble substances generated from the organochlorine compounds by the anaerobic microorganisms are dissolved in the contaminated soil downstream of the groundwater flowing in the contaminated soil;
Aerating treatment of the taken groundwater with nitrogen gas in an aeration apparatus to vaporize the volatile water-soluble substance;
Removing the vaporized volatile water-soluble substance from a mixed gas of the volatile water-soluble substance and the nitrogen gas vaporized by the aeration treatment;
Transferring the nitrogen gas after the vaporized volatile water-soluble substance is removed to the aeration apparatus;
A method for treating anaerobic bioanalyses, comprising:   5. The water flow biotreatment method according to claim 4, further comprising a step of injecting and circulating the aerated groundwater into an upstream side of the groundwater flowing through the contaminated soil. 6. The water-permeable anaerobic bio of claim 4 or 5, wherein the organic chlorine compound is one or more compounds selected from the group consisting of tetrachloroethylene or trichloroethylene, and the volatile water-soluble substance is dichloroethylene. Processing method.