JP2018126703A - Decomposition purification method of hardly decomposable organic compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively decompose and purify contaminated soil mainly containing silt or clay contaminated by a contaminant consisting of a hardly decomposable organic compound such as oil.SOLUTION: A process (S1-1 to S1-4) for decomposing and crashing contaminated soil 200 to make mud water, a process (S2-1 to S2-2) for supplying hydroxy radical to the mud contaminated soil 200, and a process (S3) for decomposing a hardly decomposable organic compound adhered to the contaminated soil 200 by the hydroxy radical for cleaning the contaminated soil 200 which is contaminated by a contaminant consisting of the hardly decomposable organic compound and mainly contains at least silt or clay and decomposing the contaminant.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for decomposing and purifying hardly decomposable organic compounds, for example, a method for efficiently decomposing and purifying silt and clay contaminated with contaminants such as oil.

  As a method for treating oil-contaminated soil, a soil cleaning method and a microbial decomposition method are generally performed. When the soil washing method is applied to soil with a high content of silt and clay, it is possible to collect uncontaminated gravel and sand, but because pollutants such as oil are concentrated in silt and clay. Separately, contaminated silt and clay must be treated. Moreover, in soil with a high content of silt or clay, it is difficult to maintain an aerobic environment that is a condition for microbial treatment, so the microbial decomposition treatment method is not applicable.

  Therefore, the soil cleaning method and the microbial decomposition method cannot be applied to soils with a high content of silt or clay contaminated with oil, etc., and are subject to off-site disposal, solidification treatment or insolubilization treatment. In the current situation, heat treatment and incineration are being carried out.

  In recent years, hydroxyl radical treatment has attracted attention as a method for treating hardly decomposable organic compounds. The method of treating a hardly decomposable organic compound with a hydroxyl radical is said to be able to effectively treat a hardly decomposable organic compound by using a hydroxyl radical having a higher oxidation potential than chlorine or ozone that has been used conventionally. There are advantages. As a technique for treating an organic substance with a hydroxyl radical or a hydroxyl radical, there are techniques described in Patent Document 1 and Patent Document 2, for example.

  The technique described in Patent Literature 1 is a technique related to a purification device that decomposes organic substances contained in a purification target gas with hydroxy radicals. This purification apparatus includes a water storage tank for storing stored water therein, bubble forming means for forming fine bubbles of the gas to be purified containing organic matter in the stored water, and radical generating means for generating hydroxy radicals in the stored water. ing. And the organic substance in a bubble is decomposed | disassembled by the hydroxyl radical produced | generated around the bubble. As a device for this purpose, the outlet for blowing the purification target gas separated from the stored water into the room, the cooling means for cooling the indoor gas, and the condensed water generated when the cooling means cools the indoor gas are stored. Condensed water introducing means for introducing into the tank.

  The technique described in Patent Document 2 is a soil remediation that pays attention to the fact that hydroxyl radicals generated when hydrogen peroxide is catalytically decomposed by ferrous ions and pollutants are chemically harmless. It is about the method.

Japanese Patent No. 5870828 Japanese Patent No. 3192020

  By the way, when applying a technique for solidifying and insolubilizing silt and clay contaminated with oil or the like, a separate land for storing and managing the solidified and insolubilized residual soil is required. In particular, in Japan, it is difficult to secure a disposal site for the remaining soil. As for off-site disposal, the remaining capacity of the final disposal site tends to decrease, and it is difficult to secure a final disposal site near the contaminated soil generation site. For this reason, the cost concerning transport of the remaining soil becomes expensive, and the disposal cost becomes expensive.

  Moreover, since the processing method of the contaminated soil by heat processing is a processing method which oxidizes and decomposes the oil in the contaminated soil by heating the contaminated soil, the energy cost is high and the environmental load countermeasure becomes a big problem.

  Moreover, the processing method which incinerates contaminated soil is a method of incinerating using contaminated soil as a cement raw material. For this reason, there is a problem that the amount of contaminated soil that can be treated is controlled by cement demand and is not suitable for mass treatment.

  Furthermore, as a problem common to each processing method described above, the contaminated soil must be carried out of the field, so that there is always a risk that the contaminant is scattered when the contaminated soil is transported.

  In addition, although the technique described in each patent document mentioned above is the method of processing organic substance with a hydroxyl radical or a hydroxyl radical, the silt and clay which were contaminated with contaminants, such as oil which are the main characteristics of this invention. There is no disclosure of a technique for efficiently decomposing and purifying these.

  The present invention has been proposed in view of the above-described circumstances, and can efficiently decompose and purify contaminated soil mainly composed of silt or clay contaminated with a pollutant composed of a hardly decomposable organic compound such as oil. It is an object of the present invention to provide a method for decomposing and purifying possible hardly decomposable organic compounds.

  The method for decomposing and purifying a hardly decomposable organic compound according to the present invention has the following features in order to achieve the above-described object. That is, the method for degrading and purifying a hardly decomposable organic compound according to the present invention is a method for cleaning a contaminated soil contaminated with a pollutant composed of a hardly decomposable organic compound and containing at least one of silt or clay as a main component. It is a method for disassembling.

  The method of degrading and purifying the hardly decomposable organic compound includes a step of crushing contaminated soil to make muddy water, a step of supplying hydroxyl radicals into the muddy water, and a difficulty of attaching to the contaminated soil by hydroxyl radicals. And a step of decomposing the organic compound.

  Further, in the step of supplying hydroxyl radicals in the muddy water contaminated soil, a step of generating a hydroxyl radical by a cavitation phenomenon generated by rotating a propeller in a water tank storing the muddy water contaminated soil, and rotating the propeller, An ultrasonic generator is installed in the tank that stores the muddy water, and hydroxyl radicals are generated by the cavitation phenomenon caused by the generation of ultrasonic waves. The muddy water is supplied to the pipe where the orifice is installed. Then, the step of generating hydroxyl radicals by the cavitation phenomenon when the muddy water passes through the pipe, the micro bubble generator is installed in the water tank storing the muddy water, and the micro bubble generator is driven. Generates hydroxyl radicals by cavitation At least one step of generating hydroxyl radicals by adding hydrogen peroxide and an aqueous iron salt solution to the muddy water contaminated soil and mixing them to generate a Fenton reaction. It is.

  In addition, as a post-treatment step for decomposing the hard-to-decompose organic compounds adhering to the contaminated soil, a dehydration treatment step is performed, and at least one of microbial decomposition treatment and sun drying treatment is performed on the contaminated soil after the dehydration treatment. It is preferable that the contaminated soil after treatment is reused as general residual soil.

  Moreover, it is preferable to reuse the filtrate generated in the dehydration process in the step of crushing the contaminated soil to make it muddy.

  According to the method for degrading and purifying a hardly decomposable organic compound according to the present invention, the soil contaminated with a pollutant comprising the hardly decomposable organic compound and crushing the contaminated soil containing at least one of silt or clay as a main component is made muddy water. By doing so, the soil particles can be uniformly dispersed in the solvent. And the decomposition reaction of a hardly decomposable organic compound is accelerated | stimulated by making a hydroxyl radical act with respect to the silt particle | grains or clay particle disperse | distributed uniformly.

  Thereby, it is possible to purify the contaminated soil by decomposing a hardly decomposable organic compound such as oil. The hardly decomposable organic compound to be decomposed and purified according to the present invention may be not only oil but also harmful substances such as PCBs and DXNs.

  In addition, the process for generating hydroxyl radicals may be performed by selecting a preferable process corresponding to the state of the contaminated soil to be purified from a plurality of processes, or by combining a plurality of processes. Therefore, the hydroxyl radical can be made to act reliably according to the state of the contaminated soil, and the contaminated soil can be purified appropriately and reliably.

  Moreover, the contaminated soil after purification can be effectively reused as general residual soil by dehydrating the contaminated soil and subjecting it to microbial decomposition treatment and sun drying treatment as necessary.

  Moreover, the water used for a purification process can be effectively ensured by reusing the filtrate generated by the dehydration process in the step of crushing the contaminated soil to make muddy water.

Process drawing of the decomposition purification method of the hardly decomposable organic compound which concerns on embodiment of this invention. The apparatus block diagram used for the decomposition | disassembly purification method of the hardly decomposable organic compound which concerns on embodiment of this invention. Schematic diagram of a cavitation tube.

  Hereinafter, a method for decomposing and purifying a hardly decomposable organic compound according to an embodiment of the present invention will be described with reference to the drawings. 1 to 3 illustrate a method for decomposing and purifying a hardly decomposable organic compound according to an embodiment of the present invention. FIG. 1 is a process diagram, FIG. 2 is an apparatus configuration diagram, and FIG. 3 is a schematic diagram of a cavitation tube. is there.

<Outline of decomposition and purification method for persistent organic compounds>
The method of degrading and purifying a hardly decomposable organic compound according to an embodiment of the present invention targets a contaminated soil mainly composed of silt or clay such as red soil contaminated with oil or the like, by allowing hydroxyl radicals to act, This is a method of purifying by promoting the decomposition reaction of the hardly decomposable organic matter. Refractory organic substances are not limited to oil, and can decompose and purify harmful substances such as PCBs and DXNs adhering to soil.

  Hydroxyl radicals are generated by the self-crushing action of microbubbles (fine bubbles) generated by the cavitation phenomenon or the like. That is, the fine bubbles are locally in a high energy state when self-crushing due to a pressure change. At this time, hydroxyl radicals are generated in water as the water is decomposed. Since the generated hydroxyl radical has a very high reactivity, it is possible to promote the decomposition of organic substances existing on the surface of the soil particles in the muddy water. In the present embodiment, hydroxyl radicals can also be generated by causing the Fenton reaction by adding and mixing hydrogen peroxide and an iron salt aqueous solution into muddy water contaminated soil.

<Process of decomposition and purification method of hardly decomposable organic compound>
As shown in FIG. 1, the method for degrading and purifying a hardly decomposable organic compound according to an embodiment of the present invention includes a muddy water step (S1-1 to S1-4), a hydroxyl radical supply step (S2-1 to S2-2). ), And can be roughly divided into organic compound decomposition step (S3), and further, a dehydration step (S4) and a reuse step (S5-1 to S5-2) are performed as a post-treatment of the organic compound decomposition step Is preferred. Hereinafter, each step will be described with reference to FIGS.

<Muddy water process>
The muddy water treatment step is a step of crushing contaminated soil containing at least one of silt or clay as a main component to make muddy water. For example, as shown in FIGS. 1 and 2, the excavated contaminated soil 200 is crushed with a bucket or the like of the backhoe 10 (S1-1), and the belt conveyor 20 is used to agitate the liquid such as fresh water or seawater. It puts in the water tank 30 (S1-2). And if the submersible pump 90 installed in the stirring water tank 30 is driven (S1-3), the lump of silt and clay will be finely ground by the impeller etc. of the submersible pump 90 (S1-4), and mud density 1.02- It becomes about 1.4 muddy water.

  The submersible pump 90 used in the muddy water process may be, for example, an underwater agitation pump, an aeration agitation ejector pump, a vertical or horizontal submersible mixer that rotates rotating blades such as a ship screw, and the like.

  By carrying out this mudification process, the soil particles are uniformly dispersed in the liquid, and the soil particles and the hydroxyl radicals are reliably in contact with each other. In the subsequent hydroxyl radical supply process and the organic compound decomposition process, the pollutant Can be promoted.

<Hydroxyl radical supply process>
A hydroxyl radical supply process is a process of supplying a hydroxyl radical in the contaminated soil 200 made muddy. In the hydroxyl radical supply step, the muddy soil is transferred to the reservoir 40 (S2-1), and microbubbles are supplied into the reservoir 40 to generate hydroxyl radicals (S2-2). In order to generate microbubbles, any one of the following steps is performed alone or in combination. At this time, when seawater is used as the liquid (solvent), chlorine ions in the seawater generate chlorine radicals, so that an effect of promoting oxidative decomposition of organic substances such as oil can be expected.

<Step (1)>
By installing a super cavitation propeller (not shown) that actively generates a cavitation phenomenon in the water tank (reservoir tank 40) that stores the muddy water 200, the cavitation phenomenon is reduced. Cause it to occur. Then, hydroxyl radicals are generated by the self-crushing action of microbubbles (fine bubbles) generated by the cavitation phenomenon.

<Step (2)>
An ultrasonic generator (not shown) is installed in a water tank (reserved water tank 40) for storing the muddy water 200 and the cavitation phenomenon is generated. Then, hydroxyl radicals are generated by the self-crushing action of microbubbles (fine bubbles) generated by the cavitation phenomenon.

<Step (3)>
As shown in FIGS. 2 and 3, the sludge contaminated soil 200 is sucked by the underwater sand mixer 100 and supplied into the pipe (cavitation pipe 50) where the orifice 51 is installed, and the negative pressure generated on the back surface of the orifice 51. Causes cavitation. Then, hydroxyl radicals are generated by the self-crushing action of microbubbles (fine bubbles) generated by the cavitation phenomenon.

<Process (4)>
Microbubbles are supplied into the contaminated soil 200 made muddy. In order to supply microbubbles, a method of adding fresh water or seawater in which microbubbles are generated to muddy contaminated soil 200, or a microbubble generator in muddy water 200 as shown in FIG. The method of operating the microbubble generator 60 by installing 60 can be used. Then, hydroxyl radicals are generated by the self-crushing action of the supplied microbubbles (fine bubbles). In addition, as shown in FIG. 2, the purification target mud water containing microbubbles is sucked by the underwater sand pump 110, and a mechanical cavitation phenomenon is generated in the underwater sand pump 110, thereby increasing the generation amount of hydroxyl radicals. Countermeasures can also be implemented.

<Step (5)>
Hydroxyl radicals are supplied into the contaminated mud water by adding and mixing hydrogen peroxide and an aqueous iron salt solution in the mud contaminated soil 200 and causing a Fenton reaction. The hydrogen peroxide and the iron salt aqueous solution are added using a chemical material adding device 80 as shown in FIG.

<Organic compound decomposition process>
The organic compound decomposition step (S3) is a step of decomposing the hardly decomposable organic compound attached to the contaminated soil 200 (silted silt or clay) by the action of hydroxyl radicals. The method of treating a hardly decomposable organic compound with a hydroxyl radical is characterized by the use of a hydroxyl radical having a higher oxidation potential compared to chlorine and ozone that have been used in the past. Can be processed.

<Dehydration process>
The dehydration process (S4) is a process performed as a post-treatment process of the organic compound decomposition process (S3). As the dehydration method, for example, as shown in FIG. 2, a method of dehydrating using a screw decanter 70, a method of dehydrating using a filter press (not shown), submerging soil particles using gravity sedimentation, and removing the supernatant A removal method or the like can be used. Dehydration may be performed by any one of these methods, or may be performed by appropriately combining a plurality of methods.

  The treated soil (contaminated soil 200) after the dehydration process is then backfilled in the field or reused as general residual soil through post-treatment (S5-1) such as microbial decomposition or sun drying. (S5-2). In addition, the filtrate produced in the dehydration process is reused in the muddy water process.

<Degradation and purification equipment for persistent organic compounds>
With reference to FIG.2 and FIG.3, the apparatus for enforcing the decomposition | disassembly purification | cleaning method of the hardly decomposable organic compound mentioned above is demonstrated. As shown in FIG. 2, the hardly decomposable organic compound decomposition and purification apparatus conveys the backhoe 10 that crushes the generated contaminated soil 200 as main components and the crushed contaminated soil 200 to the stirred water tank 30. Belt conveyor 20, agitation water tank 30 provided with an underwater pump 90 therein, a storage water tank 40 provided in communication with the agitation water tank 30, a cavitation tube 50 and a microbubble generator 60 provided in the storage water tank 40. A chemical material adding device 80 for supplying chemical materials such as hydrogen peroxide and an iron salt aqueous solution into the storage water tank 40, a dehydrating device (for example, screw decanter 70) for dehydrating the purified muddy water, and after dehydration A mud tank 300 and a filtrate tank 400 for storing the mud and filtrate respectively are provided.

  The number of submersible pumps 90 installed in the stirred water tank 30 is not limited, and an appropriate number can be installed according to the capacity of the stirred water tank 30, the properties of the contaminated soil 200, and the like. Further, an underwater sand mixer 100 for supplying the muddy water 200 is connected to the cavitation tube 50 and the microbubble generator 60. Further, an underwater sand pump 110 for stirring the muddy water 200 is installed near the outlet side of the cavitation pipe 50.

  As shown in FIG. 3, the cavitation tube 50 is configured by installing a plurality of orifices 51 in a pipe. The cavitation phenomenon occurs due to the change in the flow velocity at the installed portion of the orifice 51. The number of orifices 51 is not limited, and an appropriate number can be installed according to the properties of the contaminated soil 200.

  In addition, the decomposition and purification apparatus of the hardly decomposable organic compound is not limited to the configuration shown in FIG. 2, and other types are selected according to the nature and amount of the contaminated soil 200 to be purified, the environment in which the apparatus is installed, and the like. Devices may be added, or only necessary devices may be configured. Further, in the configuration shown in FIG. 2, not all devices used in the above-described microbubble generation process are illustrated, but devices other than the illustrated devices may be added, or the illustrated devices may be added to other devices. It may be replaced.

DESCRIPTION OF SYMBOLS 10 Backhoe 20 Belt conveyor 30 Stirring water tank 40 Storage water tank 50 Cavitation pipe 51 Orifice 60 Micro bubble generator 70 Screw decanter 80 Chemical material addition apparatus 90 Underwater pump 100 Underwater sand mixer 110 Underwater sand pump 200 Contaminated soil 300 Mud tank 400 Filtrate tank

Claims (4)

A method for degrading the pollutant by washing contaminated soil mainly composed of at least one of silt or clay and contaminated with a pollutant composed of a hardly decomposable organic compound,
Crushing the contaminated soil to muddy water,
Supplying hydroxyl radicals in the muddy water contaminated soil;
Decomposing the hardly decomposable organic compound adhering to the contaminated soil by the hydroxyl radical;
A method for decomposing and purifying a hardly decomposable organic compound, comprising: In the step of supplying hydroxyl radicals into the muddy water contaminated soil,
A step of installing a propeller in a water tank storing the muddy water contaminated soil and generating hydroxyl radicals by a cavitation phenomenon generated by rotating the propeller, an ultrasonic generator in the water tank storing the muddy water contaminated soil The process of generating hydroxyl radicals by the cavitation phenomenon caused by the generation of ultrasonic waves, supplying the muddy contaminated soil into the pipe where the orifice is installed, and the cavitation phenomenon when the muddy water passes through the pipe A step of generating hydroxyl radicals, a step of installing a microbubble generator in a water tank for storing the muddy water contaminated soil, and driving the microbubble generator to generate hydroxyl radicals by a cavitation phenomenon, the muddy water Hydrogen peroxide and contaminated soil Performing at least one step of the step of causing the Fenton reaction generating hydroxyl radicals by mixing with the addition of iron salt solution,
The method for decomposing and purifying a hardly decomposable organic compound according to claim 1. As a post-treatment step of decomposing the hardly decomposable organic compound adhering to the contaminated soil, a dehydration treatment step is performed,
Performing at least one of microbial decomposition treatment or sun drying treatment on the contaminated soil after the dehydration treatment, and reusing the treated contaminated soil as general residual soil;
The method for decomposing and purifying a hardly decomposable organic compound according to claim 1 or 2.   The method for decomposing and purifying a hardly decomposable organic compound according to claim 3, wherein the filtrate generated in the dehydration step is reused in a step of crushing the contaminated soil to make muddy water.

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