JP2006130395A - Treatment apparatus of contaminated soil and treatment method of contaminated soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment apparatus of contaminated soil capable of efficiently and certainly separating an organochlorine compound from contaminated soil to detoxify the same, and a treatment method of contaminated soil. <P>SOLUTION: The treatment apparatus 1 of the contaminated soil is constituted of a separator 2 for separating the organochlorine compound from contaminated soil and a detoxifying device 3 for detoxifying the separated organochlorine compound. In the separator 2, a surfactant or a solvent is mixed with a solution W1 or ultrasonic waves are generated to accelerate the separation of soil particles and the organochlorine compound. On the other hand , In the detoxifying device 3, ultrasonic waves are generated in the solution to accelerate the electrolysis of the organochlorine compound. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a contaminated soil treatment apparatus and a contaminated soil treatment method for separating and detoxifying organochlorine compounds such as polychlorinated biphenyl (PCB) contained in contaminated soil, and in particular, efficiently treating organochlorine compounds. The present invention also relates to a contaminated soil treatment apparatus and a contaminated soil treatment method that can be reliably rendered harmless.

  Soil pollution is added as a factor in determining real estate prices due to the obligation to conduct pollution surveys when certain facilities are abolished by the enforcement of the Soil Contamination Countermeasures Law (February 2003) and the revision of real estate appraisal standards (January 2003). In Japan, the problem of soil contamination and groundwater contamination tends to become apparent. There are a variety of substances that cause soil contamination and groundwater contamination. Among them, the ratio of volatile organic chlorine compounds such as dichloromethane and TCE, and organic chlorine compounds such as PCB and dioxin is high.

  PCB, which is one of the organic chlorine compounds, is a substance that has been widely used as an insulating oil, a heat medium, and the like because of its insulating properties and chemical stability. Its toxicity became apparent in the wake of the environmental pollution problem that occurred in the Showa 40s, and its manufacture and use were prohibited by the Ordinance of the Ministry of International Trade and Industry in 1972. However, an effective treatment method has not been established, and the waste has been stored for more than 30 years. The “Stockholm Convention on Persistent Organic Pollutants (POPs Convention)” was adopted in 2001, and Japan has already ratified it, but it came into effect in May 2004 with over 50 countries ratified. Yes. Under this treaty, PCB is designated as one of the nine substances whose production and use are prohibited, and appropriate disposal targets are set up until 2016. In Japan, the “PCB Waste Special Measures Law” was enacted, and it was determined that these PCBs would be processed by 2016. Currently, the country is promoting the establishment of a regional wide-area treatment facility utilizing the Environmental Rehabilitation and Conservation Organization, and promoting the commercialization of PCB waste disposal.

  On the other hand, looking at PCBs that have already been released into the environment, air and water quality are the main measures for constant monitoring and emission control. However, for soil (or sediment), there are active purification measures. desired. However, since the target concentration range reaches a low concentration range of about several pg / g in terms of CoQPC TEQ value, the processing similar to the PCB stock solution is inefficient in terms of both cost and energy, high temperature and high pressure Or, because it involves the use of special chemicals, 6 technologies established in the “Processing Standards for Waste PCB, etc.” from the aspect of environmental assessment: (1) High-temperature incineration, (2) Dechlorination decomposition, (3) Hydrothermal oxidation decomposition, As for (4) reducing thermochemical decomposition, (5) photolysis, and (6) plasma decomposition, it is difficult to apply on-site. In the case of soil contamination, the same treatment as the stock solution is extremely inefficient in terms of energy, and there is a problem that costs increase. In addition, technologies involving high temperature and pressure may cause by-products or exhaust gas generation, and there are problems such as it being difficult to obtain local government approval and understanding from the surrounding residents in terms of environmental assessment.

  With respect to the above problem, Patent Document 1 discloses an invention relating to a PCB processing apparatus and a PCB processing method that can be rendered harmless by electrolyzing a PCB.

Japanese Patent Laid-Open No. 2002-349591

  According to the PCB processing apparatus and the PCB processing method disclosed in Patent Document 1, it is possible to promote the decomposition of pollutants at room temperature, and to eliminate the concern of secondary contamination such as exhaust gas. However, it does not correspond to the treatment of contaminated soil. Therefore, the process of washing and separating PCB from the contaminated soil, the functional attenuation of ultrasonic waves by parallel processing of electrolysis, and the presence of soil particles It is considered that this is an inhibiting factor of electrolysis due to blocking, and therefore, it is considered that the energy efficiency of the PCB detoxification treatment is greatly reduced.

  The contaminated soil treatment apparatus and the contaminated soil treatment method of the present invention have been made in view of the above-described problems, and by separating the organic chlorine compound from the contaminated soil as a pre-stage of the detoxification treatment of the organic chlorine compound. An object of the present invention is to provide a contaminated soil treatment apparatus and a contaminated soil treatment method capable of detoxifying organochlorine compounds efficiently and reliably.

  In order to achieve the above object, a contaminated soil treatment apparatus according to the present invention is a contaminated soil treatment apparatus for separating and detoxifying organochlorine compounds such as polychlorinated biphenyl (PCB) contained in contaminated soil, It is characterized by comprising a separation device for separating an organic chlorine compound from contaminated soil and a detoxification device for detoxifying the separated organic chlorine compound.

  The detoxification device of the present invention is detoxified by separating organochlorine compounds such as PCB attached to contaminated soil from soil particles with a separation device and dechlorinating the separated PCB (in the case of PCB) To harmless biphenyl).

  In another embodiment of the contaminated soil treatment apparatus according to the present invention, the separation device includes a container that contains a solution containing the contaminated soil, a stirring member, and an oscillation member that generates ultrasonic waves in the solution. At least, the solution is stirred by a stirring member while generating ultrasonic waves in the solution, and a supernatant liquid containing an organic chlorine compound is sent out to the detoxifying device.

  By generating ultrasonic waves in the solution, the organic chlorine compound attached to the soil particles can be easily separated from the soil particles. By making the organic chlorine compound easy to separate from the soil particles by ultrasonic waves and stirring the solution, the soil particles and the organic chlorine compound can be completely (or almost completely) separated. By leaving the mixture for a predetermined time after stirring, the soil particles from which the organic chlorine compound has been separated are deposited in the container, and the sparingly soluble organic chlorine compound is suspended in the supernatant.

  As an embodiment of the separation device, for example, a vertical partition is provided in the container, a stirring member and an oscillation member provided with a propeller at the tip are installed on one side of the partition, and the other side of the partition Has a submersible pump installed. Water is already contained on one side of the partition wall, and contaminated soil is introduced from the earth and sand introduction hopper. The organic chlorine compound is separated from the contaminated soil, and the supernatant liquid is allowed to flow from the upper part of the partition wall to the other side when the supernatant liquid in which the organic chlorine compound floats is formed. This supernatant liquid can be sent to the detoxifying device while being pumped up by a submersible pump.

  In addition, when introducing contaminated soil from the earth and sand charging hopper, it is desirable to screen the contaminated soil with a vibration sieve or the like in advance and make the maximum particle size as small as possible. This is because, in the case of performing electrolysis, which will be described later, as a method for detoxifying an organic chlorine compound, the smaller the particle size, the higher the decomposition efficiency.

  In another embodiment of the contaminated soil treatment apparatus according to the present invention, the separation apparatus includes a container that contains a solution containing the contaminated soil, a stirring member, and a solution mixed with a surfactant or a solvent. At least, the solution is stirred by a stirring member, and a supernatant liquid containing an organic chlorine compound is sent out to the detoxifying device.

  By adding a surfactant to the solution and stirring, the organic chlorine compound can be easily dispersed in water. Moreover, when using a solvent, solvents, such as n-hexane, isopropyl alcohol, and methanol, can be used, for example.

  Further, in another embodiment of the contaminated soil treatment apparatus according to the present invention, the detoxification apparatus forms a container containing a solution containing an organic chlorine compound, and an anode and a cathode for electrolyzing the organic chlorine compound. And at least an electrode member.

  Since it is a solution containing the organic chlorine compound separated from the soil particles by the separator, electrolysis of the organic chlorine compound is efficiently promoted by energizing the solution. By electrolysis, the harmless biphenyl dechlorinated adheres to the cathode, and a chloride compound composed of chlorine ions and calcium or potassium in water adheres to the anode.

  Moreover, as a preferred embodiment of the contaminated soil treatment apparatus according to the present invention, the detoxification apparatus further includes an oscillating member that generates ultrasonic waves in the solution.

  By generating ultrasonic waves in the solution, for example, PCB can be emulsified in water to promote electrolysis of the PCB. In addition, cavitation occurs when bubbles generated by ultrasonic waves collapse, and there is an effect of assisting dechlorination.

  In another embodiment of the contaminated soil treatment apparatus according to the present invention, the solution after the detoxification treatment in the detoxification device can be reused as the solution in the separation device.

  For example, the partition which consists of a semipermeable membrane of a perpendicular direction is provided in the container which comprises a detoxification apparatus. An electrode member for forming a cathode and an oscillation member are installed on one side of the partition wall, and a supernatant liquid containing an organic chlorine compound is allowed to flow in. On the other hand, an electrode member for forming an anode and a submersible pump are installed on the other side of the partition wall. The aqueous solution on the other side of the partition wall does not contain an organic chlorine compound. Therefore, the aqueous solution is formed by pumping up this aqueous solution with a submersible pump and returning it to the container constituting the separation device. It can be reused.

  Further, another embodiment of the contaminated soil treatment apparatus according to the present invention is characterized in that the soil in the separation apparatus from which the organochlorine compound has been separated can be recovered.

  The collected earth and sand is recovered by pumping up the earth and sand separated from the organic chlorine compounds deposited in the container that constitutes the separation device, for example, with a sand pump installed in the container. It can be effectively used for returning soil.

  In addition, the method for treating contaminated soil according to the present invention is a method for treating contaminated soil that separates and detoxifies organic chlorine compounds such as polychlorinated biphenyl (PCB) contained in the contaminated soil. And water are mixed to form a solution, and the solution is stirred while generating ultrasonic waves in the solution, and the supernatant solution containing the organochlorine compound in the stirred solution is put in a separate container. And a second step of dechlorination by electrolyzing the organic chlorine compound by energizing the container.

  In the first step, it is possible to easily separate the organochlorine compound adhering to the soil particles from the soil particles by generating ultrasonic waves in the solution. In addition, by electrolyzing the organochlorine compound separated from the soil particles, it is possible to shorten the time required for electrolysis.

  Another embodiment of the method for treating contaminated soil according to the present invention is a method for treating contaminated soil that separates and detoxifies organic chlorine compounds such as polychlorinated biphenyl (PCB) contained in the contaminated soil, A contaminated soil and water are mixed in a container to form a solution, a surfactant or solvent is mixed in the solution, and the solution is stirred, and among the stirred solutions, an organochlorine compound is added. It is characterized by comprising a second step of dechlorination by transferring the contained supernatant to a separate container and energizing the container to electrolyze the organic chlorine compound.

  As described above, the organic chlorine compound can be easily dispersed in water by adding the surfactant to the solution and stirring. In addition, it becomes possible to further promote the separation of the organic chlorine compound from the soil particles by mixing the above-described surfactant or solvent into the solution and stirring the solution while generating ultrasonic waves. .

  Furthermore, another embodiment of the method for treating contaminated soil according to the present invention is characterized in that in the second step, the organic chlorine compound is electrolyzed while generating ultrasonic waves in the container.

  In the second step, electrolysis can be promoted by electrolyzing the organic chlorine compound while generating ultrasonic waves.

  As can be understood from the above description, according to the contaminated soil treatment apparatus and the contaminated soil treatment method of the present invention, it is possible to promote the decomposition of pollutants at room temperature, and there is a concern about secondary pollution such as exhaust gas. Therefore, safety during and after construction can be ensured. Therefore, it becomes easier for residents to understand the construction. Moreover, according to the contaminated soil processing apparatus and the contaminated soil processing method of the present invention, the organochlorine compound can be separated from the contaminated soil efficiently and reliably and detoxified.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing a contaminated soil treatment apparatus of the present invention, and FIG. 2 is a graph showing experimental results. In the illustrated embodiment, the detoxification device shows that the organic chlorine compound is electrolyzed, but the detoxification device is not limited to such an embodiment. Further, in the figure, the separating device is provided with the oscillating member, but in the case where a surfactant or solvent is mixed in the solution in the separating device, an embodiment in which the oscillating member is not provided may be used. .

  FIG. 1 shows a treatment apparatus 1 for contaminated soil. The contaminated soil treatment device 1 is mainly composed of a separation device 2 and a detoxification device 3.

  In the separation device 2, a partition wall 22 is provided inside the container 21. A plurality of oscillating members 4 and 4 and a stirring member 5 are installed on one side of the partition wall 22 and a solution W1 formed by mixing a surfactant or a solvent in water is accommodated. The contaminated soil that has been passed through the vibrating screen through the earth and sand injection hopper 6 is introduced into the solution W1 (arrow X direction). The contaminated soil is dispersed in the soil particles S, S,. Here, the stirring member 5 is rotated while generating ultrasonic waves from the tips of the oscillation members 4, 4, and the solution W <b> 1 is stirred with the stirring blade 51 attached to the tip.

  The organic chlorine compound C adhering to the soil particles S can be easily separated from the soil particles S by the surfactant (or solvent) mixed in water and the ultrasonic waves.

  After stirring the solution W1 with the stirring blade 51 and leaving it for a predetermined time, a supernatant liquid W2 in which the organic chlorine compound C floats is formed in the upper layer of the solution W1, and the soil particles from which the organic chlorine compound C has been separated are formed. S deposits on the bottom of the container 21.

  By opening the opening 22 a provided in the upper part of the partition wall 22, the supernatant liquid W <b> 2 flows into the other side of the partition wall 22. A submersible pump 81 is installed on the other side of the partition wall 22, and a water distribution pipe 83 communicated with the submersible pump 81 leads into the container 31 constituting the detoxifying device 3. The supernatant liquid W2 stored on the other side of the partition wall 22 is pumped up by the submersible pump 81, whereby the supernatant liquid W2 is fed into the container 31 (in the arrow Y direction).

  A semipermeable membrane partition wall 32 is provided inside the container 31 of the detoxifying device 3. On one side of the partition wall 32, an electrode member 71 forming a cathode, a stirring member 5, and an oscillation member 4 are provided. On the other hand, an electrode member 72 for forming an anode is provided on the other side of the partition wall 32, and the electrode members 71 and 72 are connected to a power source.

  When a predetermined amount of the supernatant liquid W2 is stored in the container 31, an electric current is passed through the solution. During energization, ultrasonic waves are generated in the solution and stirring by the stirring member 5 is performed. The organochlorine compound C floating in the solution by electrolysis is electrolyzed. When the organic chlorine compound C is, for example, PCB, chlorine ions are separated from the cathode and replaced with hydrogen ions generated by electrolysis of water to form harmless biphenyl h. On the other hand, the chlorine ions pass through the partition wall 32 of the semipermeable membrane, move to the anode side, and precipitate or dissolve as the chlorine compound f. At this time, since biphenyl h cannot pass through the partition wall 32 of the semipermeable membrane, resynthesis of PCB is not performed.

  The solution around the anode does not contain organochlorine compound C and dechlorinated organic compound. When this solution (water) is reused for the next treatment of contaminated soil, the submersible pump installed It can be fed into the container 21 through a water distribution pipe 84 communicating with 81 (in the direction of arrow Z).

  Further, the earth and sand composed of the soil particles S, S,... Separated from the organic chlorine compound C and deposited in the container 21 is pumped up by the sand pump 82 installed at the bottom of the container, and is discharged to the outside through the discharge pipe 85. Discharge (arrow T direction). The earth and sand discharged to the outside are the ones from which the organic chlorine compounds have been removed, and therefore can be reused as backfill soil for construction work.

  The outline of the experiment by the inventors and the result of the experiment are shown below. In this experiment, the processing time required to set the PCB concentration in the muddy water to be equal to or lower than the wastewater standard (0.003 mg / L) based on the “Ministry of the Environment Ordinance for Establishing Wastewater Standard” was obtained.

  The experimental apparatus used is composed of a separation device (pretreatment device) and a detoxification device (ultrasonic electrolysis tank), and the general configuration is shown in FIG. The separation device includes a 50 L water tank, a stirring member (stirrer), and an oscillation member (ultrasonic generator). This ultrasonic generator is adjusted to an ultrasonic frequency of 20000 Hz and an ultrasonic output of 2000 W. With this separation device, PCB is washed and extracted from the contaminated soil.

  On the other hand, the detoxification device is composed of a 50 L water tank, a stirrer, an ultrasonic generator, an electrode, and a semipermeable membrane. This ultrasonic generator is adjusted to an ultrasonic frequency of 20000 Hz, an ultrasonic output of 2000 W, an electrolysis voltage of 20 V, and a current of 50 A. By this detoxification device, the supernatant liquid after the PCB is extracted by the separation device is dechlorinated.

  The submersible pump in the separation device is adjusted to a water supply rate of 9 L / min, and the submersible pump in the detoxification device is adjusted to a water supply rate of 10 L / min. Water is to be sent.

  The contaminated soil to be treated is PCB-contaminated soil, and dry soil with an initial PCB concentration of 2000 mg / kg is used. In addition, this contaminated soil is screened in advance when it is introduced into the separation device, and the particle size of the introduced soil particles is adjusted to 2 mm or less.

  The solution in the water tank uses tap water, and caustic soda is added as an electrolyte. In this experiment, 40 L of tap water is filled in both the water tank of the separation device and the water tank of the detoxification device, and 160 g of caustic soda is added to both water tanks.

  In the experiment method, first, 600 g of PCB-contaminated soil is put into the separation device, the stirrer and the ultrasonic generator of the separation device and the detoxification device are operated, and the detoxification device further energizes between the electrodes. The submersible pumps of the separation device and the detoxification device are simultaneously operated to circulate cleaning water (treated water) in the contaminated soil treatment device. In the experiment, the muddy water in the separation apparatus was sampled every 30 minutes, and the PCB concentration in the muddy water was measured.

  Here, as a method for analyzing PCB concentration, first, 100 g of muddy water was sampled, 200 cc of n-hexane was added to the sampling sample, and three sets of shaking treatment for 10 minutes were performed. The sample after the shaking treatment was measured with a gas chromatograph mass spectrometer (GC / MS), and the PCB concentration in the sample was measured.

  The experimental results are shown in Table 1 and FIG.

  As can be seen from Table 1 and FIG. 2, according to the treatment apparatus composed of the separation apparatus (pretreatment apparatus) and the detoxification apparatus of the present invention, the PCB contamination far exceeds the drainage standard (0.003 mg / L). Even in soil, it can be reduced to below the drainage standard in about 4 hours.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

The schematic diagram which showed the processing apparatus of the contaminated soil of this invention. The graph which shows an experimental result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Contaminated soil processing apparatus, 2 ... Separation apparatus, 3 ... Detoxification apparatus, 4 ... Oscillation member, 5 ... Stirring member, 6 ... Sediment injection hopper, 21, 31 ... Container, 22, 32 ... Septum, 71, 72 ... Electrode member, W1 ... Solution, W2 ... Supernatant

Claims (10)

An apparatus for treating contaminated soil for separating and detoxifying organochlorine compounds such as polychlorinated biphenyl (PCB) contained in contaminated soil,
The contaminated soil treatment apparatus comprises a separation apparatus for separating an organic chlorine compound from the contaminated soil and a detoxification apparatus for detoxifying the separated organic chlorine compound.   The separation device includes at least a container that contains a solution containing contaminated soil, a stirring member, and an oscillation member that generates ultrasonic waves in the solution, and the stirring member generates ultrasonic waves in the solution. The contaminated soil treatment apparatus according to claim 1, wherein the solution is stirred, and a supernatant liquid containing an organic chlorine compound is sent out to the detoxification device.   The separation device includes at least a container for storing a solution containing contaminated soil, a stirring member, and a solution mixed with a surfactant or a solvent. The stirring member is used to stir the solution, and the The processing apparatus of contaminated soil of Claim 1 which sends out the supernatant liquid containing an organic chlorine compound to the said detoxification apparatus.   2. The detoxification device comprises at least a container for storing a solution containing an organic chlorine compound and an electrode member for forming an anode and a cathode for electrolyzing the organic chlorine compound. The processing apparatus of the contaminated soil in any one of -3.   The contaminated soil treatment apparatus according to claim 4, wherein the detoxification device further includes an oscillation member that generates ultrasonic waves in the solution.   The contaminated soil treatment device according to any one of claims 1 to 5, wherein the solution after the detoxification treatment in the detoxification device can be reused as a solution in the separation device.   The contaminated soil treatment apparatus according to any one of claims 1 to 6, wherein the soil in the separation apparatus from which the organic chlorine compound has been separated can be collected. A method for treating contaminated soil that separates and detoxifies organochlorine compounds such as polychlorinated biphenyl (PCB) contained in contaminated soil,
A first step of mixing a contaminated soil and water in a container to form a solution, stirring the solution while generating ultrasonic waves in the solution, and a supernatant liquid containing an organochlorine compound among the stirred solutions And a second step of dechlorination by electrolyzing the organic chlorine compound by transferring the water to a separate container and energizing the container. A method for treating contaminated soil that separates and detoxifies organochlorine compounds such as polychlorinated biphenyl (PCB) contained in contaminated soil,
In the container, contaminated soil and water are mixed to form a solution, a surfactant or solvent is mixed in the solution, and the solution is stirred, and among the stirred solutions, an organochlorine compound is added. Transferring the contained supernatant to a separate container and energizing the container to conduct dechlorination by electrolyzing the organochlorine compound, and a contaminated soil comprising Processing method.   The method for treating contaminated soil according to claim 8 or 9, wherein in the second step, the organic chlorine compound is electrolyzed while generating ultrasonic waves in the container.

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