JP4024658B2 - Purification method and system for contamination by chemical substances - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and a system for purifying a contaminated area containing soil, sediment, sludge and groundwater contaminated with chemical substances, particularly organochlorine compounds, using an oxidizing agent.
[0002]
[Prior art]
Organochlorine compounds such as trichlorethylene (hereinafter sometimes abbreviated as TCE) and tetrachlorethylene (hereinafter also abbreviated as PCE) are widely used in various factories and cleaning stores as cleaning agents for degreasing. Has been. In recent years, contamination of soil and groundwater by these organochlorine compounds is regarded as a problem, and purification measures are being studied. Conventionally, as a general purification measure, mainly containment treatment, excavation / containment treatment of contaminated soil, treatment by a combination of pumping water aeration, vacuum extraction, activated carbon adsorption treatment, and the like have been performed.
[0003]
However, such purification measures are not essentially treatments for decomposing and detoxifying pollutants, the measures using only these treatments require enormous energy and labor, and the purification period is 10 to 20 years. Therefore, there has been a demand for more efficient and inexpensive countermeasure technology. In addition, although the above-mentioned purification measures can purify the contaminated groundwater that has been pumped in particular, it does not actively remove the contamination sources that remain underground or in the groundwater. There is also a problem that the purification period is significantly prolonged from the aspect.
[0004]
In response to these problems, in-situ chemical oxidation methods have recently been developed in which oxidants are directly injected into wells and oxidants are reacted directly in the contaminated area for active purification. is there. For example, in Patent Document 1, an oxidant solution is injected from an injection well into soil contaminated with heavy metals and brought into contact with the contaminated soil, and the oxidant solution after contact with the soil is pumped from a separate pumping well. The purification method to be recovered is described. Patent Document 2 describes a purification method in which an area containing soil or groundwater contaminated with a toxic organic compound is sectioned and persulfate is directly added to the section.
[0005]
[Patent Document 1]
JP 2002-96057 A [Patent Document 2]
JP-A-2002-136916 [0006]
[Problems to be solved by the invention]
However, since the method described in Patent Document 2 basically only adds a persulfate for purification into a predetermined compartment, the recovery process is difficult. Moreover, since the area to be purified is partitioned with a sheet pile or the like, work for that is required. On the other hand, the method described in Patent Document 1 has an advantage that the oxidant solution injected from the injection well is pumped from the pumping well, so that the contaminant can be recovered. Further, for a large contaminated area, for example, by providing a plurality of pumping wells around the injection well, the purification range can be expanded and the purification period can be shortened. However, in this method, an injection well and a pumping well are required, and in some cases, a plurality of pumping wells are required, so that the number of wells to be drilled is increased. Drilling a single well also costs a lot, so this method requires a large investment. Therefore, this method is not necessarily suitable for the case where it is desired to efficiently purify with a small investment amount or the case where the contaminated area to be purified is relatively narrow.
[0007]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a chemical contamination purification method and a purification system capable of efficiently purifying a relatively small contaminated area at a low cost and with a simple method. There is.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a method for purifying contamination by a chemical substance according to the present invention is a method for purifying a groundwater-containing region contaminated by a chemical substance using an oxidizing agent, and a well provided in the contaminated region An oxidant is injected into the well and diffused from the well to the contaminated area to react with the pollutant. After a predetermined period of time, the oxidant diffused into the contaminated area and reacted with the pollutant together with the groundwater It consists of a method characterized in that it is drawn into the same well and recovered by pumping water from the same well .
[0009]
Further, the method for purifying contamination by a chemical substance according to the present invention is a method for purifying a groundwater-containing region contaminated by a chemical substance by using an oxidizing agent, and oxidizes the groundwater pumped from a well provided in the contaminated region. Add oxidant, inject oxidant-added groundwater into the same well, diffuse the oxidant from the well to the contaminated area and react with the pollutant. After a predetermined period of time, it diffuses into the contaminated area and becomes contaminated It comprises a method characterized in that the oxidant reacted with the substance is drawn together with groundwater into the same well and recovered by pumping from the same well .
[0010]
In the purification method for contamination by chemical substances according to the present invention, the oxidant diffused into the contaminated area and reacted with the pollutant is drawn into the same well together with the ground water from the injection or addition of the oxidant to the same well. It is also possible to repeat the steps from pumping up to pumping multiple times. By repeating the purification process for the same contaminated area a plurality of times, the concentration of the contaminant is lowered step by step, and finally it can be brought to a level with no problem.
[0011]
As oxidants, potassium permanganate, hydrogen peroxide, persulfate, hypochlorous acid, perchloric acid, chlorine, ozone, etc. can be used. In view of the above, it preferably contains at least one of potassium permanganate, hydrogen peroxide, and persulfate. In particular, it is preferable to use a persulfate such as sodium persulfate from the viewpoint of stable reactivity to pollutants and low influence on surrounding aquatic organisms.
[0012]
In the above method, at least one treatment of reduction treatment, aeration treatment, and adsorption treatment can be performed on the pumped ground water containing oxidant. By performing such a treatment, it is possible to treat the water quality so that it can be discharged.
[0013]
The system for purifying contamination by chemical substances according to the present invention is a system that uses the above-described method for purifying pollution by chemical substances , and is provided in a contaminated area for injecting oxidant or oxidant-added groundwater and oxidant. An injection / pumping well used for pumping both of the contained groundwater, means for injecting oxidant or oxidant-added groundwater into the well, and means for pumping oxidant-containing groundwater from the well Consists of things.
[0014]
In this system, the oxidant injecting means can be constituted by means for injecting an oxidant substantially directly into the injection / pumping well, or an oxidant is added to the groundwater pumped from the injection / pumping well, It can also comprise a means for injecting oxidant added groundwater into the well.
[0015]
Also in this system, it is preferable that the oxidizing agent contains at least one of potassium permanganate, hydrogen peroxide, and persulfate, and among these, the use of persulfate is preferable.
[0016]
Further, the oxidant-containing groundwater pumping means can be connected to at least one of a reduction processing means, an aeration processing means, and an adsorption processing means, and the processing means can treat the water quality to a dischargeable level. Is possible.
[0017]
In such a purification method and system for contamination by chemical substances according to the present invention, both injection of oxidant and pumping of oxidant-containing groundwater after a predetermined period of time are performed from one same well. There is no need to provide a separate pumping well as in the technique described in Patent Document 1 described above. That is, the injected oxidant is diffused from the well to the contaminated area, reacted with the pollutant in the contaminated area for a predetermined period, and then drawn into the same well together with the groundwater and recovered by pumping water. Therefore, it is possible to perform the in-situ chemical oxidation treatment with only one well on the contaminated area around the well, and it is possible to perform an efficient purification process very easily. In addition, although the well installation cost depends on the depth, it costs about 2 million yen, so in the present invention, the cost is much higher than the case of drilling a plurality of wells with conventional injection wells and pumping wells. Reduction is possible. Moreover, since the oxidant diffused around the well is pumped and recovered around the same well for a relatively small contaminated area, the recovery rate can be kept very high, and the oxidant is Since it does not spread unnecessarily (because it does not move to another site), it is extremely safe. As a result, only the contaminated area can be efficiently and inexpensively purified.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
First, a purification action by a predetermined oxidant on a chemical substance that causes contamination was confirmed. It was confirmed that organic chlorine compounds such as trichlorethylene (TCE) and tetrachlorethylene (PCE) can be decomposed at room temperature with persulfates such as sodium persulfate and potassium persulfate (potassium peroxodisulfate). These oxidizing agents are characterized by a wide range of purification because they are relatively slowly decomposed and have a long reach, and are very effective oxidizing agents for use in the present invention.
[0019]
In the confirmation test of the purification action, 20 g of actual contaminated soil and 180 mL of pure water are placed in a 500 mL vial, and after adding sodium persulfate so that the following conditions are satisfied (blank is no oxidizer added), the vial Was sealed and the treatment was started. And the purification process effect was evaluated by measuring the head space of each vial bottle with time by gas chromatography.
・ Blank (BL): No oxidizer added ・ Test: Sodium persulfate added to a concentration of 500 mg / L [0020]
The test results are shown in FIG. In the test with sodium persulfate added, TCE degradation occurred rapidly and was reduced to a very low concentration in about 1 week, whereas no TCE degradation was observed in the blank. As a result of measuring the persulfuric acid concentration after completion of the reaction, it was confirmed that about 100 mg / L remained.
[0021]
Thus, it has been confirmed that perchlorate can purify an organic chlorine compound over a predetermined time at room temperature.
[0022]
Next, the form at the time of implementing this invention with respect to an actual contamination area | region is demonstrated.
In the present invention, when purifying soil, sediment, sludge, groundwater and the like contaminated with chemical substances using an oxidizing agent, the oxidizing agent concentration (for example, 200 to 5000 mg / L) necessary for the purification is obtained. Injected adjusted water (ground water that has been pumped, industrial water, tap water, etc.) for a certain period of time so that it diffuses from the well into the contaminated area to be purified (for example, about 1 to 7 days), and then decomposes After taking a necessary reaction time (for example, about 1 hour to 1 month, preferably about 1 day to 7 days), the water is pumped by the same amount as that injected from the same well. Preferably, the pollutant in the target region is purified by repeating such a cycle a plurality of times. If the pumped water still contains organochlorine compounds, perform aeration treatment, replenish the oxidant, and reinject. After the purification treatment, the oxidant remaining in the pumped water is discharged after, for example, a reduction treatment.
[0023]
FIG. 2 shows an embodiment of a system for performing the purification process as described above. An injection / pumping well 2 used for both injection of oxidant and pumping of oxidant-containing groundwater is provided in the contaminated area 1 contaminated with a chemical substance. In this embodiment, the injection / pumping well 2 is appropriately used. A monitoring well 3 was provided at a remote location to confirm the effect of purification. However, this monitoring well 3 may be omitted. As means for injecting an oxidant into the injection / pumping well 2, an oxidant adjusting tank 4, and an oxidant adding device for measuring and charging sodium persulfate as an oxidant into the oxidant adjusting tank 4 5. An injection pump 6 for injecting oxidant-containing water adjusted to a predetermined concentration in the oxidant adjusting tank 4 into the injection / pumping well 2 is provided. Further, as a means for pumping the oxidant-containing groundwater from the injection / pumping well 2, a pump 7 disposed in the well 2 is provided. In this embodiment, the pumping line is further provided with an aeration tank 8 for aeration of the oxidant-containing groundwater pumped by the pumping pump 7, and air is supplied from the air supply device 9 to the bottom of the aeration tank 8, Discharged from. In the present embodiment, the aerated water is returned to the oxidant adjustment tank 4, and when the process is repeated, the oxidant is replenished and adjusted again to a predetermined concentration and then injected into the injection / pumping well 2. The When the purification process is completed, a reducing agent is added to the oxidant adjusting tank 4 from the reducing agent addition device 10 and is reduced and discharged. The aeration tank 8 may be disposed at a position after the reduction process.
[0024]
Using such a system, the contaminated groundwater is pumped from the injection and pumping well 2, and after aeration treatment in the aeration tank 8, sodium persulfate is set to 5000 mg / L in the oxidant adjustment tank 4 in the treated water. The oxidant-containing water was added to the injection / pumping well 2 and diffused into the contaminated area 1. After reacting for 3 days, water was pumped up again from the well 2 and subjected to aeration treatment, and the remaining oxidizing agent was reduced with sodium thiosulfate and discharged. Moreover, the said purification process cycle was repeated twice and similarly reduced and aerated, and discharged. As a result of the confirmation in the monitoring well 3, as shown in FIG. 3, the TCE concentration of the groundwater in the monitoring well 3 before the purification treatment was 1.1 mg / L, whereas the purification cycle according to the present invention was performed. When applied once, the TCE concentration decreased to about 0.5 mg / L, and the second time decreased to about 0.1 mg / L. Therefore, while confirming the remarkable effect by the purification process which concerns on this invention, it has confirmed that the effect improved further by repeated process.
[0025]
FIG. 4 illustrates a chemical contamination purification system according to another embodiment of the present invention. In this embodiment, an injection / pumping well 12 used for both the injection of the oxidant and the pumping of the oxidant-containing groundwater is provided in the contaminated area 11 contaminated with the chemical substance. A monitoring well 13 for confirming the effect of purification was provided at a remote position. This monitoring well 13 may be omitted. As means for injecting an oxidant into the injection / pumping well 12, an oxidant adjustment tank 14 into which city water 18 is introduced, and sodium persulfate as an oxidant is measured in the oxidant adjustment tank 14. An oxidizer addition device 15 to be introduced, and an injection pump 16 for injecting the oxidant-containing water adjusted to a predetermined concentration in the oxidant adjustment tank 14 into the injection / pumping well 12 are provided. In addition, as a means for pumping the oxidant-containing groundwater from the injection / pumping well 12, a pumping pump 17 disposed in the well 12 is provided. In the present embodiment, the reducing agent is added from the reducing agent adding device 19 to the oxidizing agent-containing groundwater pumped to the oxidizing agent adjusting tank 14 by the pumping pump 17, and the remaining organic chlorine remains in the activated carbon adsorption treatment device 20. The compound is released after being adsorbed. Even in the system configured as described above, an effect substantially equivalent to that shown in FIG. 3 was obtained.
[0026]
The present invention can be applied not only to purification of contamination by organic chlorine compounds, but also to purification of contamination by other chemical substances such as oil, benzene, toluene, xylene and the like.
[0027]
【The invention's effect】
As described above, according to the purification method and system for contamination by chemical substances according to the present invention, it is possible to easily treat contaminants such as organic chlorine compounds that have been conventionally used for pumping aeration in a short period of time. And it becomes possible to clean up safely. The present invention is extremely effective particularly when a small contaminated area is treated at a low cost. In addition, the present invention is extremely effective in promoting purification of a contaminated area where purification cannot be completed even if conventional aeration processing is performed.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between TCE concentration and time, showing the results of a test conducted to confirm the purification effect of oxide contamination.
FIG. 2 is a schematic configuration diagram of a purification system according to an embodiment of the present invention.
FIG. 3 is a relationship diagram between the TCE concentration and the number of treatments, showing the result of the purification treatment performed using the system of FIG.
FIG. 4 is a schematic configuration diagram of a purification system according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,11 Contamination area | region 2,12 Injection and pumping well 3,13 Monitoring well 4,14 Oxidant adjustment tank 5,15 Oxidant addition apparatus 6,16 Injection pump 7,17 Pumping pump 8 Aeration tank 9 Air supply apparatus 10, 19 Reducing agent addition device 18 City water 20 Activated carbon adsorption treatment device

Claims (7)

A method for purifying a groundwater-containing region contaminated with a chemical substance by using an oxidant, injecting an oxidant into a well provided in the contaminated region, and diffusing the oxidant from the well into the contaminated region. The oxidant diffused into the contaminated area and reacted with the pollutant after a predetermined period of time is drawn into the same well together with the groundwater and recovered by pumping from the same well. To clean up pollution caused by chemical substances. A method for purifying groundwater-containing areas contaminated with chemical substances using an oxidizer, adding oxidizer to groundwater pumped from a well provided in the contaminated area, and injecting oxidizer-added groundwater into the same well The oxidant is diffused from the well into the contaminated area to react with the pollutant, and after a predetermined period of time, the oxidant diffused into the polluted area and reacted with the pollutant is returned to the same well together with the groundwater. A method for purifying contamination caused by chemical substances, wherein the method is drawn and collected by pumping water from the same well . The process from injection or addition of an oxidant to drawing of the oxidant diffused into the contaminated area and reacted with the pollutant into the same well together with groundwater and pumped from the same well is repeated a plurality of times. 2. A method for purifying contamination caused by chemical substances.   The method for purifying contamination by chemical substances according to any one of claims 1 to 3, wherein the oxidizing agent contains at least one of potassium permanganate, hydrogen peroxide, and persulfate.   The purification method of the contamination by the chemical substance in any one of Claims 1-4 which performs at least 1 process of a reduction process, an aeration process, and an adsorption process with respect to the oxidant containing groundwater pumped up. A system using the method for purifying contamination by chemical substances according to any one of claims 1 to 5, wherein the system is provided in a contaminated area, for injecting oxidant or oxidant-added groundwater and for pumping oxidant-containing groundwater. It has an injection and pumping well used for both, means for injecting oxidant or oxidant-added groundwater into the well, and means for pumping oxidant-containing groundwater from the well, Purification system. The system for purifying contamination by chemical substances according to claim 6 , wherein at least one of a reduction processing means, an aeration processing means, and an adsorption processing means is connected to the oxidant-containing groundwater pumping means.

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