JP2007209915A - Cleaning system for volatile organic compound-contaminated soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning system for volatile organic compound-contaminated soil capable of efficiently cleaning the contaminated soil containing the volatile organic compound. <P>SOLUTION: The cleaning system 1 is provided with an ultrasonic washing/decomposition apparatus 3 and a solid/liquid separation apparatus 4. The ultrasonic washing/decomposition apparatus 3 has a treatment tank 31 for storing a mixture of the contaminated soil E1 containing VOC and washing water W1, and extracts the VOC from the contaminated soil E1 side to the washing water W1 side by irradiating the inside of the mixture with an ultrasonic wave 10 of 20 kHz to wash the contaminated soil E1. The solid/liquid separation apparatus 4 separates the soil particles contained in the washing water W1 discharged from the ultrasonic washing/decomposition apparatus from the washing water W1 and returns the separated washing water W1 to the treatment tank 31. The ultrasonic washing/decomposition apparatus 3 decomposes the VOC by irradiating the inside of the washing water W1 returned from the solid/liquid separation apparatus 4 to the treatment tank 31 with an ultrasonic wave 10 of 500 kHz to detoxify it. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a purification system for volatile organic compound-contaminated soil that uses ultrasonic waves to detoxify volatile organic compounds in contaminated soil.

  Conventionally, volatile organic compounds (VOC) have been widely used in solvents, adhesives, cleaning agents, and the like. However, many of these VOCs are highly toxic, and are known to cause photochemical smog and suspended particulate matter in the atmosphere.

  VOCs discharged during factory operation are accumulated and concentrated in the contaminated soil of the factory site, and there is concern about causing health damage via groundwater and air. For this reason, the Soil Contamination Countermeasures Law was enacted in February 2003, and the Air Pollution Control Law was revised in June 2004 to strengthen VOC emission standards. Therefore, it is desired to decontaminate contaminated soil such as factory ruins and recycle it as purified soil containing no VOC.

  As the VOC treatment in soil, purification methods such as physical / chemical treatment, heat treatment, biological treatment (bioremediation), etc. are known. Physical and chemical treatments include a method of decomposing with ultraviolet rays or an oxidizing agent (oxidation-reduction decomposition treatment), a classification cleaning with particles, a method of separation with high-pressure water or a surfactant (soil cleaning treatment), and a gas provided with a suction well. And the separation method (gas suction, aeration treatment) and the like. The heat treatment is a method of volatile separation at 200 ° C. to 600 ° C. (thermal desorption treatment), a method of incineration at 800 ° C. to 1000 ° C. (thermal decomposition treatment), a method of melting at a high temperature of 1200 ° C. or higher (melt solidification treatment), etc. is there. Biological treatment is a method of degrading with bacteria at a contaminated site or on a ground plant.

  Moreover, the technique which purifies contaminated soil as mentioned above is disclosed by patent documents 1-3. Specifically, Patent Document 1 discloses a soil purification method in which mud water obtained by mixing contaminated soil mixed with VOC and water is aerated to volatilize VOC from the soil. Patent Document 2 discloses a purification method in which contaminated soil is heated to extract a gas containing VOC, and the VOC is decomposed with ozone. In this method, combined use of ultraviolet irradiation and addition of hydrogen peroxide increases the oxidizing power and enhances the decomposition efficiency of VOC. In Patent Document 3, a well for sucking contaminated air is provided in soil, the contaminated air is sucked using a vacuum pump, and VOC contained in the contaminated air is removed by an adsorption device made of activated carbon. A purification method has been proposed.

  Furthermore, in recent years, a cleaning apparatus that cleans contaminated soil using ultrasonic waves (see, for example, Patent Document 4) and a processing apparatus that renders VOCs contained in an aqueous solution harmless by using ultrasonic waves (for example, see Patent Document 5). ) Has been proposed.

  In the purification apparatus described in Patent Document 4, water is supplied to the contaminated soil to perform ultrasonic cleaning, and further, ultrasonic cleaning is performed while circulating the washed slurry-like soil, thereby purifying the contaminated soil. is doing.

In the processing apparatus described in Patent Document 5, a catalytic material made of a basic metal salt is added to an aqueous solution containing VOC, and ultrasonic waves with a relatively low frequency (for example, 20 kHz to 100 kHz) are irradiated. When ultrasonic waves are irradiated into an aqueous solution, bubbles called cavitation are generated, and a reaction field of several thousand degrees and several thousand atmospheres called a hot spot is locally formed through compression and collapse processes. And it is thought that VOC is thermally decomposed in this extreme reaction field.
JP 2002-59151 A JP 2004-321919 A JP 2005-87809 A JP 2005-81247 A JP 2005-169389 A

  By the way, in the purification method of patent documents 1-3, it is difficult to comprise a purification system so that the extracted VOC may not leak outside, and there are concerns about air pollution etc. Furthermore, when the extracted VOC is adsorbed on activated carbon or the like to be processed, there is a problem that the cost is increased because the activated carbon is discarded. Further, when the soil purification method by heat treatment is adopted, there are problems that the equipment becomes large and cannot be purified at the site such as a factory site, and that the running cost of the equipment becomes high. Furthermore, a biological treatment or a purification method in which a suction well is provided and separated into gas is not practical because the treatment time becomes long.

  Moreover, in the purification apparatus of patent document 4, since the ultrasonic wave of a comparatively low frequency (20kHz-40kHz) is irradiated, contaminated soil can be purified efficiently. However, since the harmful substances contained in the cleaning water cannot be decomposed, a separate drainage treatment for the cleaning water is required.

  For example, if a soil purification system is comprised by the purification apparatus of patent document 4, and the processing apparatus of patent document 5, and the washing water discharged | emitted by the purification apparatus of patent document 4 is processed with the processing apparatus of patent document 5, washing water It is considered possible to decompose harmful substances contained in However, in the processing apparatus of Patent Document 5, since the decomposition process of the organic compound is performed by adding a catalyst substance, the processing cost increases. Furthermore, since such a soil purification system has a complicated configuration and becomes a large-scale system, there is a problem that the equipment cost increases.

  The present invention has been made in view of the above problems, and its purpose is to purify volatile organic compound-contaminated soil with a simple configuration and capable of efficiently purifying contaminated soil containing volatile organic compounds. To provide a system.

  In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that the treatment tank containing a mixture of contaminated soil containing volatile organic compounds and washing water, and the treatment for irradiating ultrasonic waves into the mixture. An ultrasonic vibrator provided in the tank, and irradiates the mixture with ultrasonic waves of less than 100 kHz from the ultrasonic vibrator to wash the contaminated soil, thereby volatilizing from the contaminated soil side to the washing water side. Volatile equipped with an ultrasonic cleaning and decomposing apparatus for decomposing and detoxifying the volatile organic compound by irradiating ultrasonic waves of 100 kHz or higher into the cleaning water from the ultrasonic vibrator after extracting the volatile organic compound The gist is the purification system for organic compound contaminated soil.

  According to the first aspect of the present invention, when a relatively low ultrasonic wave of less than 100 kHz is irradiated into a mixture of contaminated soil containing a volatile organic compound and washing water in the treatment tank, the ultrasonic wave is It acts on the soil particles in the mixture, and the contaminated soil is washed by the vibrational energy of the ultrasonic waves. At that time, volatile organic compounds contained in the contaminated soil are extracted to the washing water side. Thereafter, when a relatively high ultrasonic wave of 100 kHz or higher is irradiated into the cleaning water, cavitation (bubbles) is generated in the cleaning water, and a high-temperature and high-pressure reaction field is formed. Here, since the volatile organic compound is hydrophobic, it spontaneously gathers around the cavitation (interface between the washing water and the bubbles), and further volatilizes and enters the cavitation. As a result, the volatile organic compound can be thermally decomposed and rendered harmless by the action of a high-temperature and high-pressure reaction field. Therefore, in the purification system of the present invention, the volatile organic compound extracted from the contaminated soil can be detoxified without using an additive such as a special drug, and the washed soil can be reused. Further, in this purification system, the contaminated soil can be washed and the volatile organic compound can be decomposed in one treatment tank, so that the system can be downsized. Moreover, since the ultrasonic wave of the frequency suitable for each process can be irradiated, the soil purification process can be performed efficiently in a short time, and the running cost of the purification system can be suppressed.

  In addition, as a volatile organic compound in this invention, trichloroethylene, tetrachloroethylene, benzene, toluene, xylene, acetone, etc. can be mentioned.

  The invention according to claim 2 is characterized in that, in claim 1, a discharge port for discharging the contaminated soil is provided at the bottom of the treatment tank, and the contaminated soil cleaned by irradiation with ultrasonic waves of less than 100 kHz is After discharging from the discharge port, the gist is to irradiate the cleaning water in the treatment tank with ultrasonic waves of 100 kHz or more.

  According to invention of Claim 2, since the discharge port is provided in the bottom part of a processing tank, the soil wash | cleaned by ultrasonic irradiation can be discharged | emitted efficiently. And the ultrasonic wave of 100 kHz or more is irradiated with respect to the washing water left in the processing tank. In this case, since the soil particles hardly remain in the wash water, the ultrasonic waves propagate efficiently. As a result, more cavitation effective for decomposing volatile organic compounds can be generated, and volatile organic compounds can be efficiently decomposed. In addition, in this structure, it is preferable to provide the water storage tank which once stores the wash water which wash | cleaned the contaminated soil. In this case, after storing the wash water in the water storage tank, the soil particles remaining in the treatment tank can be reliably discharged from the discharge port. And if the washing water of a water storage tank is returned to a processing tank and an ultrasonic wave of 100 kHz or more is irradiated, a volatile organic compound can be decomposed | disassembled efficiently.

  The invention according to claim 3 is the ultrasonic vibration according to claim 1, wherein an ultrasonic transducer for irradiating the ultrasonic wave of less than 100 kHz is provided outside the lower part of the processing tank and irradiates the ultrasonic wave of 100 kHz or more. The gist is that the child is provided outside the upper part of the treatment tank.

  According to the invention described in claim 3, since the ultrasonic vibrator is provided on the outer surface side rather than the inner surface side of the treatment tank, the unevenness on the inner surface side of the treatment tank is reduced, and the ultrasonic wave is not contained in the cleaning water in the treatment tank. Sound waves can be propagated uniformly. In addition, since the soil particles sink to the bottom in the treatment tank, it is possible to reliably irradiate the soil particles collected at the bottom with ultrasonic waves of less than 100 kHz, and increase the cleaning efficiency of the contaminated soil. Furthermore, it is possible to reliably irradiate the cleaning water of the supernatant in the treatment tank with an ultrasonic wave of 100 kHz or more, and to efficiently decompose the volatile organic compound contained in the cleaning water.

  A fourth aspect of the present invention provides the cleaning water according to the first aspect, wherein the cleaning water is supplied by cleaning the contaminated soil by the irradiation of the ultrasonic wave of less than 100 kHz, and the soil particles and the cleaning water contained in the cleaning water are separated. The gist of the present invention is that it further comprises a solid-liquid separation device for returning the washing water to the treatment tank.

  According to invention of Claim 4, the wash water which wash | cleaned the contaminated soil in a processing tank is supplied to a solid-liquid separator, and the soil particle and wash water are isolate | separated by the solid-liquid separator, The removed washing water is returned to the treatment tank. In this way, since ultrasonic waves of 100 kHz or higher propagate efficiently in the wash water, more cavitation can be generated and volatile organic compounds can be efficiently decomposed. Moreover, since the newly contaminated soil can be washed by reusing the wash water returned to the treatment tank, the concentration of the volatile organic compound in the wash water can be increased. If it does in this way, the decomposition | disassembly efficiency of the volatile organic compound by irradiation of an ultrasonic wave can be improved.

  According to a fifth aspect of the present invention, in the fourth aspect, the ultrasonic cleaning / disassembling apparatus is provided in a pair, and the cleaning water is circulated between the solid-liquid separation apparatus and the processing tank in one ultrasonic cleaning / decomposing apparatus. When the contaminated soil is washed by irradiating the ultrasonic wave of less than 100 kHz, the volatile organic compound is decomposed by irradiating the ultrasonic wave of 100 kHz or higher in the other ultrasonic washing and decomposing apparatus. The gist of this is

  According to the fifth aspect of the present invention, when the contaminated soil is being washed, the volatile organic compound can be decomposed in parallel with the washing, so that the processing efficiency of the entire system is increased. Can do.

  As described in detail above, according to the first to fifth aspects of the present invention, it is possible to efficiently perform the purification treatment of contaminated soil containing a volatile organic compound with a simple configuration.

[First Embodiment]

  Hereinafter, a first embodiment in which the present invention is embodied in a purification system for volatile organic compound-contaminated soil will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing the contaminated soil purification system.

  As shown in FIG. 1, the purification system 1 of the present embodiment includes a hopper 2, an ultrasonic cleaning / decomposing apparatus 3, a solid-liquid separation apparatus 4, and a control apparatus 7. The purification system 1 purifies contaminated soil containing a volatile organic compound (VOC) such as trichlorethylene (TCE) at a contaminated site such as a factory site, and decomposes and detoxifies the VOC extracted from the contaminated soil. It is a system for. The purification system 1 is a portable system having a size that can be mounted on a vehicle such as a truck. Of course, the purification system 1 may be a fixed system that is not particularly intended for conveyance.

  Specifically, the contaminated soil E1 excavated by an excavator (not shown) is put into the hopper 2, mixed with the hopper 2, and then supplied to the ultrasonic cleaning and decomposing apparatus 3.

  The ultrasonic cleaning / decomposing apparatus 3 includes a treatment tank 31 for containing a mixture (muddy water) of the contaminated soil E1 and the washing water W1, a stirrer 32 for stirring the contaminated soil E1 and the washing water W1 in the treatment tank 31, A first ultrasonic transducer 33 and a second ultrasonic transducer 34 that irradiate the cleaning water W1 in the treatment tank 31 with the ultrasonic wave 10, and oscillation circuits 35 and 36 for driving the ultrasonic transducers 33 and 34, respectively. With. The treatment tank 31 of the present embodiment has a box shape having a pair of inclined surfaces (tapered surfaces) 37 facing the bottom thereof, and is formed so that the width of the bottom is gradually narrowed. In the treatment tank 31, the first ultrasonic transducer 33 is provided outside the inclined surface 37 at the bottom, and the second ultrasonic transducer 34 is provided outside the side surface 38.

  The treatment tank 31 has a capacity of 110 liters, and in one washing treatment, for example, 10 kg of contaminated soil E1 and 100 liters of washing water W1 are placed. And by stirring with the stirrer 32, soil particles are disperse | distributed in the washing water W1. In addition, as washing water W1 supplied to this processing tank 31, cheap water, such as a tap water, is used. Of course, use of water other than tap water (for example, rainwater, seawater, etc.) is allowed.

  The first ultrasonic transducer 33 is made of a plate-shaped piezoelectric ceramic, and outputs the ultrasonic wave 10 having a low frequency (specifically, 20 kHz) in the thickness direction thereof based on the oscillation signal of the oscillation circuit 35. In the ultrasonic cleaning / disassembling apparatus 3 according to the present embodiment, the first ultrasonic transducer 33 is provided on the inclined surface 37 at the bottom of the processing tank 31, and the first ultrasonic transducer 33 is superposed obliquely upward from the first ultrasonic transducer 33. A sound wave 10 is irradiated. At this time, the ultrasonic wave 10 acts on the soil particles in the washing water W1, and the contaminated soil E1 is ultrasonically cleaned by the vibration energy of the ultrasonic wave 10. At that time, VOC is extracted from the contaminated soil E1 side to the wash water W1 side.

  The second ultrasonic transducer 34 is made of a plate-shaped piezoelectric ceramic, and outputs a high-frequency (specifically, 500 kHz) ultrasonic wave 10 in its thickness direction based on the oscillation signal of the oscillation circuit 36. In the ultrasonic cleaning / disassembling apparatus 3 of the present embodiment, the second ultrasonic transducer 34 is provided on the side surface 38 of the processing tank 31, and the ultrasonic wave 10 is directed from the second ultrasonic transducer 34 to the side. Is irradiated. By irradiation with this ultrasonic wave 10, cavitation at the nano level to micron level is generated in the cleaning water W1, and a reaction field of high temperature and high pressure is formed. As a result, VOC contained in the cleaning water W1 is thermally decomposed and rendered harmless. As a specific example, for example, when VOC is trichloroethylene or tetrachloroethylene, chlorine ions and harmless hydrocarbons are generated.

  Moreover, the lower end of the bottom part in the processing tank 31 is provided with a discharge port 39 for discharging the cleaned contaminated soil E2. The discharge port 39 is connected to the solid-liquid separator 4 via a discharge pipe 40, and an open / close valve 41 and a discharge pump 42 are provided in the middle of the discharge pipe 40. Then, when the opening / closing valve 41 is opened and the discharge pump 42 is driven, the washing water W1 containing soil particles is discharged from the discharge port 39, and the discharge pipe 40 is pumped to the solid-liquid separator 4. To be supplied.

  The solid-liquid separation device 4 includes a cylindrical separation tank 44 and a filter body 45 provided at the center of the separation tank 44. The washing water W1 pumped from the ultrasonic washing / decomposing apparatus 3 to the solid-liquid separation apparatus 4 passes through the filter body 45 of the separation tank 44, whereby the soil particles and the washing water W1 are separated. The soil E2 separated in the solid-liquid separation device 4 is drained from the discharge port 46 to the outside of the device after moisture is removed by a dryer (not shown) and reused as purified soil containing no VOC. The solid-liquid separation device 4 is connected to the treatment tank 31 via a circulation pipe 48, and the wash water W 1 from which soil particles have been removed in the solid-liquid separation apparatus 4 is treated via the circulation pipe 48. It is comprised so that it may return to 31.

  The control device 7 is constituted by a known microcomputer including a CPU 71, a ROM 72, a RAM 73, an input / output port (not shown), and the like, and is electrically connected to the agitator 32, the oscillation circuits 35 and 36, the open / close valve 41, and the discharge pump 42. It is connected to the. The ROM 72 constituting the control device 7 stores a control program, and the CPU 71 uses the RAM 73 to execute the control program. As a result, the control device 7 outputs various control signals to control the entire system in an integrated manner.

  Here, the operation of the purification system 1 in the present embodiment will be described.

  The operator operates the operation unit (not shown) of the control device 7 to operate the purification system 1 and supplies a predetermined amount (for example, 100 liters) of cleaning water W1 to the treatment tank 31 of the ultrasonic cleaning / decomposing device 3. At the same time, a predetermined amount (for example, 10 kg) of contaminated soil E1 is introduced from the hopper 2. Then, the control apparatus 7 starts a soil purification process.

  Specifically, the control device 7 rotates the stirrer 32 by outputting a control signal to the stirrer 32. Thereby, the mixture of the contaminated soil E1 and the washing water W1 is stirred, and the soil particles are dispersed in the washing water W1. Next, the control device 7 outputs a control signal to the oscillation circuit 35 and causes the oscillation circuit 35 to output an oscillation signal. As the first ultrasonic transducer 33 vibrates based on this oscillation signal, the 20 kHz ultrasonic wave 10 is irradiated to the mixture (muddy water) in the treatment tank 31 for a predetermined time (specifically, 15 minutes). Thereby, the ultrasonic wave 10 acts on the soil particles in the mixture, and the contaminated soil E1 is washed by the vibration energy of the ultrasonic wave 10. In the treatment tank 31 of the present embodiment, the first ultrasonic transducers 33 are respectively provided on the two inclined surfaces 37 facing each other at the bottom, and the ultrasonic waves 10 are irradiated from different directions toward the soil particles in the mixture. Therefore, the synergistic effect by superimposing the ultrasonic waves 10 can be obtained, and the contaminated soil E1 is efficiently washed.

  In this cleaning process, VOC contained in the contaminated soil E1 is extracted to the cleaning water W1 side. Here, for example, 150 mg of trichlorethylene (TCE) is extracted from 10 kg of contaminated soil E1 placed in the treatment tank 31 into the wash water W1 (100 L). In this case, the TCE concentration of the cleaning water W1 is 50 times (1.5 mg / L) the environmental reference value (0.03 mg / L).

  Thereafter, the control device 7 outputs a control signal to open the on-off valve 41, and further drives the discharge pump 42 to contain soil particles from the treatment tank 31 to the separation tank 44 of the solid-liquid separation apparatus 4. The cleaning water W1 is pumped. The solid-liquid separation device 4 separates the soil particles contained in the washing water W1 from the washing water W1, and after drying the separated soil E2, discharges it from the discharge port 46 to the outside of the device. The washing water W1 (100 liters) separated by the solid-liquid separation device 4 is returned to the treatment tank 31 again via the circulation pipe 48.

  In the ultrasonic cleaning and decomposing apparatus 3, new contaminated soil E <b> 1 is supplied from the hopper 2, and the cleaning water W <b> 1 supplied from the solid-liquid separator 4 is reused to perform the cleaning process on the contaminated soil E <b> 1. That is, the contaminated soil E1 and the washing water W1 are agitated by the agitator 32, and the ultrasonic treatment is performed for a predetermined time from the first ultrasonic transducer 33 to perform the washing process. Further, after the cleaning process is completed, the cleaning water W1 containing soil particles is pumped from the processing tank 31 to the separation tank 44, and a solid-liquid separation process for separating the soil particles and the cleaning water W1 is performed.

  In the present embodiment, the VOC concentration contained in the cleaning water W1 is increased to 30 mg / L by repeatedly performing the cleaning process and the solid-liquid separation process as described above 20 times.

  Then, after the cleaning water W1 (100 L) containing the high-concentration VOC is returned to the treatment tank 31, the decomposition process of the VOC is started. That is, the control device 7 outputs a control signal to the stirrer 32 and rotates the stirrer 32 to stir the cleaning water W <b> 1 in the treatment tank 31.

Then, the control device 7 outputs a control signal to the oscillation circuit 36 and causes the oscillation circuit 36 to output an oscillation signal. As the second ultrasonic transducer 34 vibrates based on this oscillation signal, the ultrasonic wave 10 of 500 kHz is irradiated for a predetermined time (specifically, 5 hours). Here, since the washing water W1 in the treatment tank 31 contains almost no soil particles, the high-frequency ultrasonic wave 10 propagates efficiently in the washing water W1. Therefore, more cavitation at the nano level to micron level is generated, and a high temperature / high pressure reaction field is formed in a wide range in the cleaning water W1. Since VOC is hydrophobic and volatile, it spontaneously gathers around the cavitation (interface between the cleaning water W1 and the bubbles), and further volatilizes and enters the cavitation. As a result, the VOC is thermally decomposed and rendered harmless by the action of the high-temperature and high-pressure reaction field, and the VOC concentration in the cleaning water W1 is reduced to the environmental standard value (0.03 mg / L) or less.
Then, the cleaning water W1 after the VOC decomposition process is left in the processing tank 31 as it is, and is reused for the next cleaning process. Of course, you may comprise so that the wash water W1 after this decomposition process may be drained as sewage.

  Therefore, according to the present embodiment, the following effects can be obtained.

  (1) In the purification system 1 of the present embodiment, the VOC extracted from the contaminated soil E1 can be rendered harmless only by irradiation with the ultrasonic wave 10 without using an additive such as a special drug. Furthermore, since the washed contaminated soil E1 can be reused, the environmental load can be reduced. Moreover, in this purification system 1, since the ultrasonic wave 10 of the frequency suitable for each process can be irradiated by the soil particle washing process and the VOC decomposition process, the soil purification process can be efficiently performed in a short time. Can do.

  (2) In the purification system 1 of the present embodiment, the contaminated soil E1 can be completely detoxified without producing waste. Further, it is possible to construct a closed system in which VOC does not leak to the outside of the apparatus during the soil purification treatment, and there is no problem of air pollution due to VOC.

  (3) In the purification system 1 according to the present embodiment, since the soil purification treatment can be efficiently performed using the ultrasonic wave 10, the portable system that can be mounted on a vehicle by reducing the size of the ultrasonic cleaning / disassembling apparatus 3. Can be realized. Therefore, the in-situ processing of the contaminated soil E1 can be performed by moving the vehicle equipped with the purification system 1 to a factory site or the like.

  (4) In the purification system 1 of the present embodiment, the washing water W1 and the soil particles can be separated by the solid-liquid separator 4 and the washing water W1 from which the soil particles have been removed can be returned to the treatment tank 31. Accordingly, since almost no soil particles remain in the washing water W1, the ultrasonic wave 10 can be efficiently propagated to generate more cavitation, and the VOC can be reliably decomposed.

  (5) In the purification system 1 of the present embodiment, the washing water W1 separated by the solid-liquid separator 4 is returned to the treatment tank 31 and reused for washing the contaminated soil E1, whereby the VOC in the washing water W1. The concentration can be increased. Thereby, the decomposition efficiency of VOC by ultrasonic irradiation can be improved.

  (6) In the purification system 1 of the present embodiment, the cleaning water W1 that has been made harmless by decomposing VOC can be reused, and the running cost of the purification system 1 can be reduced. In particular, even when the washing water W1 cannot be sufficiently secured in a factory site or the like, the contaminated soil E1 can be continuously purified by reusing the washing water W1.

  (7) In the ultrasonic cleaning / decomposing apparatus 3 of the present embodiment, since the ultrasonic transducers 33 and 34 are provided not on the inner surface side of the processing tank 31 but on the outer surface side, there are few irregularities on the inner surface side of the processing tank 31. Therefore, the ultrasonic wave 10 can be uniformly propagated in the cleaning water W1, and the cleaning process of the contaminated soil E1 and the decomposition process of the VOC can be performed efficiently. Moreover, since the unevenness | corrugation in the inner surface side of the processing tank 31 decreases, a soil particle can be reliably discharged | emitted from the discharge port 39. FIG.

(8) In the case of this embodiment, since the cleaning water W1 in the treatment tank 31 is stirred using the stirrer 32, the VOC contained in the cleaning water W1 is homogenized, and the reaction frequency between VOC and cavitation is increased. In addition to becoming higher, the effective cavitation due to the VOC reaction is increased. Therefore, VOC contained in cleaning water W1 can be decomposed efficiently and in a short time.
[Second Embodiment]

  Next, a second embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 2, the purification system 81 of the present embodiment includes two ultrasonic cleaning / decomposing apparatuses 3, a solid-liquid separation apparatus 4, and a control apparatus 7. In this purification system 81, the discharge pipe 40 of each ultrasonic cleaning / disassembling apparatus 3 is connected to the solid-liquid separator 4 via a flow path switching valve (switching means) 82, and the circulation pipe 48 is used for switching the flow path. It is connected to the solid-liquid separator 4 via a valve (switching means) 83. The flow path switching valves 82 and 83 are electrically connected to the control device 7, and are cleaned on the ultrasonic cleaning / disassembling device 3 side during the cleaning process based on a control signal output from the control device 7. The flow path of the water W1 is switched. In this purification system 81, each ultrasonic cleaning / decomposing apparatus 3, solid-liquid separation apparatus 4, and control apparatus 7 have the same configuration as that of the first embodiment, and include a pair of ultrasonic cleaning / decomposing apparatuses 3. This is different from the first embodiment in that the flow switching valves 82 and 83 are provided in the discharge pipe 40 and the circulation pipe 48.

  In the purification system 81 of the present embodiment, in one ultrasonic cleaning / decomposing apparatus (for example, the apparatus on the left side in FIG. 2), the cleaning water W <b> 1 is circulated between the solid-liquid separator 4 and the treatment tank 31. The contaminated soil E1 is washed by irradiating the ultrasonic wave 10 of 20 kHz from the first ultrasonic transducer 33. At this time, the other ultrasonic cleaning / decomposing apparatus (for example, the apparatus on the right side of FIG. 2) 3 irradiates the ultrasonic wave 10 of 500 kHz from the second ultrasonic transducer 34, thereby decomposing the VOC in the cleaning water W1. Is done.

  Then, when the cleaning process of the contaminated soil E1 is completed in one ultrasonic cleaning / decomposing apparatus 3 and the VOC decomposing process is completed in the other ultrasonic cleaning / decomposing apparatus 3, each of the flow path switching valves 82 and 83 is operated. The flow path is switched to the opposite device side. Then, the VOC is decomposed by irradiating the ultrasonic wave 10 of 500 kHz in one ultrasonic cleaning / decomposing apparatus 3, and the other ultrasonic cleaning / decomposing apparatus 3 performs a separation between the solid-liquid separation device 4 and the processing tank 31. The contaminated soil E1 is washed by irradiating the ultrasonic wave 10 of 20 kHz while circulating the washing water W1.

  If comprised in this way, since the ultrasonic cleaning decomposition | disassembly apparatus 3 can perform the decomposition | disassembly process of VOC, when the cleaning process of the contaminated soil E1 is performed in one ultrasonic cleaning decomposition apparatus 3, the system Overall processing efficiency can be improved. Moreover, since the solid-liquid separation device 4 can be used in common, the equipment cost can be reduced as compared with a system including the solid-liquid separation device 4 for each ultrasonic cleaning and decomposing device 3.

  Furthermore, in the purification system 81 of the present embodiment, when one ultrasonic cleaning / decomposing apparatus 3 performs the VOC decomposition process, the other ultrasonic cleaning / decomposing apparatus 3 and the solid-liquid separation apparatus 4 perform cleaning. It is also possible to repeat the treatment and the solid-liquid separation treatment a plurality of times. If it does in this way, the VOC density | concentration in the washing water W1 can be raised, and the decomposition | disassembly efficiency of VOC can be improved.

  In addition, you may change each embodiment of this invention as follows.

  In each of the above embodiments, the solid-liquid separation device 4 that separates the washing water W1 and the soil particles is provided, but the present invention is not limited to this. For example, it is good also as a structure provided with the water storage tank 92 instead of the solid-liquid separator 4 like the purification system 91 shown in FIG. Specifically, in the purification system 91, a drainage port 93 is provided in the treatment tank 31 of the ultrasonic cleaning / decomposing apparatus 3, and the drainage port 93 is connected to a water storage tank 92 via a transfer pipe 94. An opening / closing valve 95 is provided in the middle of the transfer pipe 94. Furthermore, a circulation pipe 96 for returning the cleaning water W1 to the treatment tank 31 is connected to the water storage tank 92, and a pump 97 for pumping the cleaning water W1 is provided in the middle of the circulation pipe 96. It has been.

  In the purification system 91, the ultrasonic cleaning / disassembling apparatus 3 and the control apparatus 7 have the same configuration as the above embodiment. The control device 7 drives the agitator 32 to agitate the contaminated soil E1 and the washing water W1, and also irradiates the ultrasonic wave 10 of 20 kHz from the first ultrasonic vibrator 33 to wash the contaminated soil E1. . Thereafter, the control device 7 stops the stirrer 32, stops the irradiation of the ultrasonic wave 10 by the first ultrasonic vibrator 33, and ends the cleaning process. Then, in the treatment tank 31, the soil particles sink to the bottom thereof, and the washing water W1 accumulates above the soil particles. Here, the control device 7 opens the open / close valve 95 of the transfer pipe 94 to temporarily store the cleaning water W <b> 1 accumulated as a supernatant in the treatment tank 31 in the water storage tank 92. Next, the control device 7 discharges the soil particles remaining in the treatment tank 31 from the discharge port 39 by opening the open / close valve 41 of the discharge pipe 40.

  After that, the control device 7 drives the pump 97 with the open / close valves 41 and 95 closed, thereby returning the cleaning water W1 of the water storage tank 92 to the treatment tank 31 again, so that the second ultrasonic transducer 34 generates 500 kHz. Ultrasonic 10 is irradiated. In this way, since there are almost no soil particles in the washing water W1 in the treatment tank 31, the ultrasonic wave 10 propagates efficiently in the washing water W1. As a result, more cavitation can be generated in the cleaning water W1, and the VOC can be reliably decomposed. Even if the purification system 91 is configured in this manner, the VOC extracted from the contaminated soil E1 can be rendered harmless without using special additives such as special agents, as in the above embodiment, and the cleaned contamination The soil E1 can be reused. Also in this purification system 91, since the ultrasonic wave 10 having a frequency suitable for each processing can be irradiated in the soil particle cleaning process and the VOC decomposition process, the soil cleaning process can be performed efficiently.

In the first embodiment, the cleaning process and the solid-liquid separation process using low frequency ultrasonic irradiation are repeated 20 times, and then the VOC decomposition process using high frequency ultrasonic irradiation is performed. However, the present invention is not limited to this. For example, the cleaning process and the solid-liquid separation process and the VOC decomposition process may be alternately performed.
In the first embodiment, the solid-liquid separation process is performed after the cleaning process using the low-frequency ultrasonic irradiation. However, the VOC decomposition process may be performed after the cleaning process. . Specifically, after the cleaning process is completed, the soil particles sink to the bottom of the processing tank 31 with the passage of time, and the cleaning water W1 accumulates above the soil particles. For this reason, when a predetermined time has elapsed after the end of the cleaning process, the ultrasonic wave 10 of 500 kHz is irradiated from the second ultrasonic transducer 34 toward the cleaning water W1 accumulated as a supernatant in the processing tank 31, and the cleaning water Decompose VOC in W1. Thereafter, the soil particles and the cleaning water W1 are supplied to the solid-liquid separation device 4 to separate the soil particles and the cleaning water W1. Even in this way, the contaminated soil E1 can be purified and reused.
In each of the above embodiments, the ultrasonic wave 10 of 20 kHz is irradiated from the first ultrasonic vibrator 33 in order to clean the contaminated soil E1, but the present invention is not limited to this frequency. For example, the frequency of the ultrasonic wave 10 can be appropriately changed according to the particle size of the contaminated soil E1. However, if the frequency of the ultrasonic wave 10 is too high, the cleaning efficiency is lowered. Moreover, in the said embodiment, in order to decompose | disassemble VOC, the ultrasonic wave 10 of 500 kHz was irradiated from the 2nd ultrasonic transducer 34, However, It is not limited to this frequency. The ultrasonic wave 10 for decomposing VOC may have a frequency of 100 kHz to 1000 kHz, more preferably 200 kHz to 600 kHz, and particularly preferably 400 kHz to 500 kHz.

  In each of the above embodiments, the first ultrasonic transducer 33 for low frequency and the second ultrasonic transducer 34 for high frequency are used. However, the present invention is not limited to this. For example, an oscillation circuit having a function of switching the frequency of the oscillation signal may be used, and low frequency and high frequency ultrasonic waves may be emitted from a common ultrasonic transducer based on each oscillation signal of the oscillation circuit. Good.

  -In above-mentioned embodiment, although the processing tank 31 had the two inclined surfaces 37 in the bottom part, it is not limited to the shape, A rectangular parallelepiped shape without the inclined surface 37 may be sufficient. A cylindrical shape may be used.

  Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the embodiment described above are listed below.

  (1) In claim 2, a water storage tank is provided, and after the wash water that has washed the contaminated soil is temporarily stored in the water storage tank, the soil particles remaining in the treatment tank are discharged from the discharge port. Purification system for soil contaminated with volatile organic compounds.

  (2) In Claim 5, provided in the middle of a flow path for connecting each of the ultrasonic cleaning and decomposing apparatus and the solid-liquid separation apparatus, any one of the ultrasonic cleaning and decomposing apparatuses and the A volatile organic compound-contaminated soil purification system comprising switching means for switching the flow path so as to connect to a solid-liquid separator.

  (3) A treatment tank containing a mixture of contaminated soil containing volatile organic compounds and washing water, and provided in the treatment tank, washing the contaminated soil and extracting volatile organic compounds from the contaminated soil side to the washing water side In order to do so, the first ultrasonic vibrator that irradiates the mixture with ultrasonic waves of less than 100 kHz, and the treatment tank, the volatile organic compound in the washing water is decomposed and detoxified to make the washing water harmless. And a second ultrasonic transducer for irradiating ultrasonic waves of 100 kHz or higher.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram which shows the purification system of 1st Embodiment which actualized this invention. The schematic block diagram which shows the purification system of 2nd Embodiment which actualized this invention. The schematic block diagram which shows the purification system of another embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,81,91 ... Purification system of soil contaminated with volatile organic compounds 3 ... Ultrasonic cleaning and decomposing device 4 ... Solid-liquid separation device 10 ... Ultrasonic 31 ... Treatment tank 33, 34 ... Ultrasonic vibrator 39 ... Discharge port E1 ... Contaminated soil W1 ... Wash water

Claims (5)

  A treatment tank containing a mixture of contaminated soil containing volatile organic compounds and washing water; and an ultrasonic vibrator provided in the treatment tank for irradiating the mixture with ultrasonic waves. A volatile organic compound is extracted from the contaminated soil side to the wash water side by irradiating the mixture with ultrasonic waves of less than 100 kHz from the vibrator to wash the contaminated soil, and then the wash water from the ultrasonic vibrator. A volatile organic compound-contaminated soil purification system comprising an ultrasonic cleaning and decomposing apparatus that decomposes and detoxifies volatile organic compounds by irradiating them with ultrasonic waves of 100 kHz or higher.   A discharge port for discharging the contaminated soil is provided at the bottom of the treatment tank, and after the contaminated soil washed by irradiation with ultrasonic waves of less than 100 kHz is discharged from the discharge port, the washing water in the treatment tank 2. The purification system for volatile organic compound-contaminated soil according to claim 1, wherein ultrasonic waves of 100 kHz or more are irradiated to the volatile organic compound-contaminated soil.   The ultrasonic vibrator for irradiating the ultrasonic wave of less than 100 kHz is provided on the lower outer side of the processing tank, and the ultrasonic vibrator for irradiating the ultrasonic wave of 100 kHz or higher is provided on the upper outer side of the processing tank. The volatile organic compound-contaminated soil purification system according to claim 1.   A solid-liquid separation device is further provided that is supplied with wash water for washing contaminated soil by irradiation with ultrasonic waves of less than 100 kHz, separates soil particles and wash water contained in the wash water, and returns the wash water to the treatment tank. The volatile organic compound-contaminated soil purification system according to claim 1, which is provided.   Contained soil by irradiating ultrasonic waves of less than 100 kHz while circulating the cleaning water between the solid-liquid separation device and the treatment tank in one ultrasonic cleaning / decomposing device. 5. The volatilization according to claim 4, wherein the volatile organic compound is decomposed by irradiating the ultrasonic wave of 100 kHz or higher with the other ultrasonic cleaning and decomposing apparatus. System for soil contaminated with organic organic compounds.

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