JP2007237035A - Treating method of waste filtrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provided a treating method of waste filtrate easily removing fine powder of resin contained in waste filtrate containing an organic solvent and water, after separating slurry-like suspension of resin into solid matter and liquid, without requiring any special device, and also separating a small amount of a generated organic phase and a water phase having an electrostatic capacitance roughly equal to that of the organic phase. <P>SOLUTION: In this treating method of waste filtrate, waste filtrate (α<SB>0</SB>°C) containing the organic solvent and water after separating slurry-like suspension of resin into solid matter and liquid, is heated to (α<SB>0</SB>+5)°C to (α<SB>0</SB>+40)°C, to separate into the organic solvent phase containing fine powder of resin and the water phase. An interface of the organic solvent phase containing fine powder of resin and the water phase is detected by a differential pressure of the upper and lower pressures of a vertical transfer pipe provided at a lower part of a separation tank, for separation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for treating filtrate wastewater, in which fine powder of resin contained in a filtrate is removed from filtrate wastewater containing an organic solvent and water after solid-liquid separation of a slurry suspension of resin.

  As a method for treating wastewater containing an organic solvent, for example, there is a method of recovering an organic solvent by distillation, but when the wastewater contains resin fine powder, if distillation is carried out as it is, clogging in the distillation tower, Since problems such as sticking of the resin to the reboiler may occur, it is desirable to remove the resin fines in the waste water in advance.

  As a method of removing resin fines in the waste water, it is common to remove it using a filter, but it cannot be completely removed, and the filter is frequently washed and replaced, and the collected resin is removed. It is not preferable because it takes time and effort.

  As a method for removing suspended solids (SS) in the waste water, a method is known in which salt, acid, or a flocculant is added, and then precipitated or floated. For example, there is a pressure levitation method (see, for example, Patent Document 1). However, since this method requires a special levitation tank, there is a problem that the installation location is large and the equipment cost is increased. Further, when the resin is recovered by such a method, it is difficult to reuse the recovered resin as it is because the added salt, acid, or flocculant becomes an impurity.

  To remove harmful chemical substances in the wastewater, the ultrafine particulate organic solvent is jetted into the wastewater by rotating the capsule at a high speed in a stirring and mixing tank equipped with a rotating shaft with a capsule at the tip. Discloses a method of dissolving a harmful chemical substance in an organic solvent, and toluene, thinner, acetone, or the like is used as the organic solvent (see, for example, Patent Document 2). According to this method, resin fine powder is also collected in the organic solvent, and it seems that the fine powder can be removed. However, it is necessary to create an ultrafine particulate organic solvent with a special device, which increases the equipment cost. There is.

  As a method of separating two liquids in a tank, for example, a light liquid of an organic solvent phase and a heavy liquid of an aqueous phase, a method of controlling the interface position between the organic phase and the aqueous phase using a differential pressure transmitter is disclosed. (For example, refer to Patent Document 3). In this method, the differential pressure of the liquid phase between two points sandwiching the interface between the upper layer and the lower layer separated in the mixing tank is detected, and the level of the interface calculated from the detected value of the differential pressure is kept constant. Since it is a continuous separation method for extracting the upper layer and the lower layer, for example, it is not suitable for a batch system in which a light liquid is extracted and then a heavy liquid is recognized and extracted to another place. Furthermore, there is a problem that the interface cannot be recognized because the differential pressure cannot be obtained in a system in which the upper layer light liquid or the lower layer heavy liquid does not exist sufficiently.

In addition, as a method of recognizing light liquid and heavy liquid while being discharged from the mixing tank after being separated from the mixing tank and extracting them to different places, a method of separating using a capacitance type interface detector for the pipe is generally used. However, this method is used in systems where the electrostatic capacity of the heavy liquid and the light liquid is approximately the same, or the organic solvent that is a light liquid is partially dissolved in the aqueous phase of the heavy liquid and the electrostatic capacity is approximately the same. There was a problem that it was not possible.
Japanese Patent Publication No.56-23668 JP 2004-24935 A JP-A-6-107571

  The object of the present invention is to easily remove the resin fine powder contained in the filtrate drainage containing the organic solvent and water after solid-liquid separation of the resin slurry suspension without the need for special equipment. It is another object of the present invention to provide a method for treating filtrate wastewater, and further to provide a method for separating and recovering a small amount of an organic solvent phase that is generated and an aqueous phase having a capacitance substantially equivalent to that of the organic phase.

  In order to solve the above-mentioned problems, the present inventors have intensively studied, and as a result, completed the present invention shown below.

That is, according to the present invention, the filtrate drainage (temperature: α ₀ ° C.) containing the organic solvent and water after solid-liquid separation of the resin slurry suspension is changed to (α ₀ +5) ° C. or more and (α ₀ +40 ) A method of treating filtrate wastewater that is heated to a temperature of less than or equal to ℃ and separates into an organic solvent phase containing fine resin powder and an aqueous phase, the interface between the organic solvent phase containing fine resin powder and the aqueous phase at the bottom of the separation tank The present invention relates to a method for treating filtrate wastewater, characterized in that it is detected and separated by a differential pressure above and below a vertical transfer pipe provided in the above.

  In a preferred embodiment, the content of the organic solvent in the filtrate waste water is in the range of 10% by weight to 30% by weight, and the water content is in the range of 70% by weight to 90% by weight. The present invention relates to a method for treating the filtrate drainage.

  A preferred embodiment relates to the method for treating filtrate wastewater according to any one of the above, wherein the content of the resin in the filtrate wastewater before heating is in the range of 0.01% by weight to 5% by weight. .

  A preferred embodiment relates to the method for treating filtrate wastewater according to any one of the above, wherein the content of the resin in the filtrate wastewater before heating is in the range of 0.01 wt% or more and 2 wt% or less. .

A preferred embodiment relates to the method for treating filtrate wastewater according to any one of the above, wherein the filtrate wastewater is heated to a range of (α ₀ +10) ° C. or higher and (α ₀ +30) ° C. or lower.

  A preferred embodiment relates to the method for treating filtrate waste water according to any one of the above, wherein the organic solvent is methyl ethyl ketone.

  A preferred embodiment relates to the method for treating filtrate waste water according to any one of the above, wherein the difference in capacitance between the organic solvent phase containing fine resin powder and the aqueous phase is within 35 PF.

  A preferred embodiment relates to the method for treating filtrate waste water according to any one of the above, characterized in that the distance between the differential pressure detection parts above and below the vertical transfer pipe provided in the lower part of the separation tank is 2 m or more.

  According to the method of the present invention, the resin fine powder contained in the filtrate drainage containing the organic solvent after solid-liquid separation of the resin slurry suspension is easily removed without the need for a special apparatus. For example, it is also possible to separate and recover a small amount of the generated organic solvent phase and an aqueous phase having substantially the same capacitance as the organic solvent phase. Furthermore, the resin in the waste water can be recovered in a usable state.

  The present invention relates to a method for treating filtrate wastewater that can remove resin fines in filtrate wastewater by heating a filtrate wastewater containing an organic solvent and water after solid-liquid separation of a slurry suspension of resin.

  In the present invention, the resin that can be used is not particularly limited. For example, rubber obtained by graft polymerization on rubber particles formed of a polymer mainly composed of an elastomer or a rubber-like polymer. Examples thereof include a core-shell polymer in which a part or the whole of the particle surface is covered with a graft component. Among these, ABS (acrylonitrile butadiene styrene) resin, MBS (methyl methacrylate butadiene styrene) resin, acrylic rubber-containing graft copolymer, polyorganosiloxane-containing graft copolymer are used because they are industrially useful core-shell polymers. A polymer etc. can be illustrated preferably.

  The resin can be produced by a known method such as emulsion polymerization, suspension polymerization, microsuspension polymerization, solution polymerization and the like. Among them, the production of the core-shell polymer is most commonly industrially emulsion polymerization.

  The resin obtained by the production method is often obtained as an aqueous latex. For example, by mixing an organic solvent having partial solubility in water with the aqueous latex, the emulsion stability of the latex of resin particles can be improved. A method of obtaining an aggregate of the resin by reducing the concentration and then adding water to the mixed solution of the organic solvent and latex, for example, is disclosed (for example, see JP-A-2005-248109).

  In the present invention, for example, as described above, a liquid in which a resin aggregate is suspended is generally referred to as a slurry suspension. Although there is no restriction | limiting in particular in the slurry-like suspension of resin which can be used in this invention, For example, it is preferable that solid content in a suspension is the range of 5 to 30 weight%. If the solid content in the slurry suspension is less than 5% by weight, the amount of resin is small relative to the volume, and the productivity may be low. On the other hand, when it exceeds 30% by weight, the viscosity of the slurry-like suspension is increased, so that the fluidity is low and liquid feeding may be difficult. The slurry suspension usually contains an anionic surfactant derived from emulsion polymerization, such as ABS (side chain alkylbenzene sulfonate), LAS (linear alkylbenzene sulfonate). AOS (α-olefin sulfonate), AS (alkyl sulfate ester salt), AES (alkyl ether sulfate ester salt) and the like are included.

  The method of solid-liquid separation of the slurry suspension is not particularly limited, and examples thereof include sedimentation filtration using a perforated plate, a metal mesh or a filter cloth, or vacuum filtration. The solid content concentration of the cake remaining on the sieve by filtration is preferably 25% by weight or more. When the solid content concentration of the cake is less than 25% by weight, the filtration efficiency may deteriorate due to the large amount of moisture and organic solvent in the resin.

  The filtrate drainage after solid-liquid separation that can be used in the present invention is not particularly limited as long as it contains an organic solvent and water, but in particular, slurry suspension preparation and resin fines in the filtrate drainage are removed. From the viewpoint, it is preferable that the content of the organic solvent in the filtrate waste water is in the range of 10% by weight to 30% by weight and the water content is in the range of 70% by weight to 90% by weight.

  Although it does not restrict | limit especially as said organic solvent, From a viewpoint of slurry-like suspension preparation and removal of the fine powder of the resin in waste_water | drain, the solubility with respect to the water in 20 degreeC is 5 weight% or more and 40 weight% or less. A certain organic solvent is preferable, and methyl ethyl ketone is particularly preferable. For example, in the case of methyl ethyl ketone, the solubility of methyl ethyl ketone in water can be lowered by raising the temperature in the range of 0 ° C. to 70 ° C. Thus, by reducing the solubility of the organic solvent by controlling the temperature, the fine powder of the resin in the filtrate waste water can be removed by utilizing the property that the organic solvent that becomes supersaturated in the filtrate waste water causes phase separation as droplets.

  The particle diameter of the resin fine powder is generally in the range of 1 to 1000 μm. The content of the resin in the filtrate drainage is not particularly limited, but in the filtrate drainage treatment method of the present invention, the resin is contained in the filtrate drainage in the range of 0.01 wt% to 5 wt%. It is preferable that the solid-liquid separation is performed in a range of 0.01% by weight to 2% by weight. If the amount of resin fines in the filtrate drainage is less than 0.01% by weight, the amount of fines can be considered as a very small amount, and therefore the demand for further processing is reduced. On the other hand, when the amount of resin fines in the filtrate drainage exceeds 5% by weight, the amount of resin fines is large, so that it is difficult to completely remove fines by a single treatment.

In the present invention, the filtrate drainage (however, the temperature before treatment is α ₀ ° C.) is in the range of (α ₀ +5) ° C. to (α ₀ +40) ° C., more preferably (α ₀ +10) ° C. As described above, by heating in the range of (α ₀ +30) ° C. or less, the fine resin particles in the filtrate wastewater can be collected in the organic solvent phase and removed from the filtrate wastewater. Although this mechanism is not always clear, heating the filtrate wastewater reduces the solubility of the organic solvent in water, causing the supersaturated organic solvent to phase-separate as fine droplets. It is estimated that a good resin can be collected in the organic solvent phase. If the temperature of the filtrate drainage after heating is less than (α ₀ +5) ° C., the organic solvent phase in the filtrate drainage is less likely to occur, and the fine powder removal effect tends to be reduced. When α ₀ +40) ° C. is exceeded, fine powder can be removed, but the vapor pressure increases with temperature, so that the airtightness and pressure resistance of the equipment must be maintained, and the equipment cost tends to increase.

  The heating method of the filtrate drainage is not particularly limited, and examples thereof include a jacket, a heat transfer heater, and steam blowing. Although it is effective to install a device for stirring the filtrate waste water as a means for increasing the heating efficiency, the stirring device is not particularly limited and may not be installed.

After raising the filtrate drainage to a predetermined temperature, that is, (α ₀ +5) ° C. or more and (α ₀ +40) ° C. or less, it is desirable that the filtrate drainage is allowed to stand for 10 minutes or longer as necessary. Furthermore, standing for about 30 minutes is more preferable. If the standing time is less than 10 minutes, there is a concern that resin fines cannot be completely removed from the filtrate drainage. Since the organic solvent phase containing the resin fine powder in the filtrate waste water after the heat treatment forms a light liquid phase, the light liquid can be separated from the aqueous phase.

  Operations related to the supply of filtrate wastewater, heating, and removal of the organic solvent phase containing resin fines may be performed by heating, standing, and separating from the lower part of the tank, and a series of operations. May be performed continuously.

  For example, an apparatus for separating and recovering an organic solvent phase and an aqueous phase by a batch method includes a method of controlling the interface position between the organic solvent phase and the aqueous phase in the separation tank using a differential pressure. However, when there is little light liquid isolate | separated in the separation tank, since the thickness of a light liquid is small, there exists a tendency for the detection in a tank to be difficult. In the present invention, even if the thickness of the light liquid is small, the thickness of the light liquid phase is increased in the vertical transfer pipe provided in the lower part of the separation tank to detect the differential pressure above and below the pipe. It is characterized in that the organic solvent phase and the aqueous phase can be recognized and separated and recovered by the change in pressure. In general, a capacitance type interface detector is exemplified as a method of detecting in the pipe, but it is difficult to apply because the detection is difficult when the capacitance of the organic solvent phase and the water phase is close. However, the present invention can be preferably applied to a system in which the difference in capacitance between the organic solvent phase and the aqueous phase is within 35 PF (picofarad).

  The position of the transfer pipe installed in the lower part of the tank in the present invention is not particularly limited, but in order to maintain the interface between the light liquid and the heavy liquid separated in the separation tank, it is provided vertically in the lower part of the separation tank. It is desirable. The diameter and length of the vertical pipe are not particularly limited, but are preferably 2 m or more, and more preferably 3 m or more, between the differential pressure detectors above and below the pipe. If the distance between the differential pressure detectors above and below the pipe is less than 2 m, it may not be possible to recognize the difference in pressure difference between light and heavy liquids. There is no particular limitation on the length of the short pipe of the differential pressure detection part at the top and bottom of the pipe, but 20 mm or less is preferable. More preferably, it is 10 mm or less. If the length of the short pipe of the differential pressure detection port at the top and bottom of the pipe exceeds 20 mm, it takes time to replace the liquid in the short pipe, and there is a possibility that a response delay may occur when detecting heavy liquid and light liquid.

  The method for detecting the differential pressure is not particularly limited. For example, a differential pressure transmitter is exemplified, and when a differential pressure transmitter is used, a pressure guideless type is preferable. In the case of a pressure guiding tube type, clogging may occur due to the presence of solids in the light liquid. The flow rate in the vertical pipe when detecting the differential pressure is not particularly limited, but a linear velocity of 0.04 m / sec or less is preferable. More preferably, it is 0.02 m / sec or less. When the flow velocity in the vertical pipe exceeds 0.04 m / sec, when the interface between the aqueous phase and the organic solvent phase passes through the vertical pipe, the interface may be disturbed, resulting in a response delay in the detection of heavy liquid and light liquid. .

  The organic solvent phase containing the recovered resin fine powder does not increase impurities because no acid, salt, flocculant or the like is added to the resin. Therefore, it is possible to reuse the recovered resin by volatilizing the organic solvent. The filtrate drainage containing the organic solvent from which the fine resin powder has been removed can be reused, for example, by collecting the organic solvent by distillation.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

  In the following, the solid content concentration in the filtrate waste water was measured by the heating loss method. Moreover, the organic solvent density | concentration in filtrate waste_water | drain was measured with the gas chromatography method. The number average particle size of the fine powder in the filtrate drainage was measured with a particle size distribution measuring device. The filtrate drainage contains an anionic surfactant, and the amount thereof was measured by the methylene blue method.

  Prior to the examples, the analytical measurement method used in the present invention will be described below.

(1) Measurement of solid content concentration in filtrate drainage A predetermined amount of filtrate wastewater is collected and dried at 105 ° C. for 30 minutes using a hot air dryer, and the solid content concentration in the filtrate drainage is determined from the weight change before and after drying. Was calculated.

(2) Measurement of concentration of organic solvent in filtrate wastewater 0.3g of filtrate wastewater was collected, diluted with 3 ml of acetone, which is a dilution solvent containing internal standard chlorobenzene, and from the peak area of the organic solvent by gas chromatography. The concentration was calculated.

(3) Measurement of number average particle diameter of fine powder in filtrate drainage The number average particle diameter of fine powder in filtrate drainage was measured by using a laser diffraction type particle size distribution measuring apparatus, Microtrack 9320-X100 type.

(4) Measurement of anionic surfactant in filtrate drainage The amount of anionic surfactant in filtrate drainage was measured with the anionic surfactant using the methylene blue method (JIS K0102) used for anionic surfactant analysis. Chloroform colored by the extracted methylene blue was measured with a spectrophotometer at a wavelength of 650 nm.

(5) Measurement of specific gravity of organic solvent phase and aqueous phase in filtrate drainage The specific gravity of organic solvent phase and aqueous phase in filtrate drainage was calculated from volume and weight using a 20 ml hole pipette.

(Example of filtrate drainage preparation)
20 kg of latex (solid content 30% by weight) of MBS resin obtained by emulsion polymerization was placed in a stirring tank and mixed with 20 kg of methyl ethyl ketone. Next, 29 kg of water was added and agglomerated by stirring at 120 rpm to obtain a slurry suspension of the obtained resin. This slurry suspension was subjected to solid-liquid separation with a metal filter 32 mesh (aperture 500 μm) to obtain filtrate drainage.

Example 1
60 L of filtrate waste water containing 1.0% by weight of MBS resin fine powder (number average particle size 100 μm), 23% by weight of methyl ethyl ketone and 76% by weight of water is placed in a separation tank and heated from room temperature 25 ° C. (temperature before treatment) When the temperature reached 50 ° C., the heating was stopped and the mixture was allowed to stand for 30 minutes. 1200 ml of a light liquid phase of methyl ethyl ketone containing the resin was generated, and the specific gravity was 0.84. The specific gravity of the heavy liquid was 0.97. When a pipe with an inner diameter of 23 mm and a length of 2 m is installed vertically in the lower part of the separation tank, and the output value when the pipe is filled with heavy liquid above and below it is 100%, filled with light liquid A differential pressure transmitter (pressure tube-less type) manufactured by Yokogawa Electric Co., Ltd. set to 0% was attached, and the liquid was discharged so that the linear velocity in the pipe was 0.04 m / sec. The output of the differential pressure transmitter that is discharging the heavy liquid phase is 100%, and when it reaches 0%, it was collected in a separate container, and it was confirmed whether there was an interface between the heavy liquid side and the light liquid side. There was no interface between the heavy and light liquids, and the light and heavy liquids were separated and recovered. Moreover, it was 0.2 weight% as a result of measuring the solid content density | concentration of a heavy liquid. The heavy liquid phase contained an anionic surfactant derived from MBS resin latex, and its concentration was measured and found to be 0.2% by weight. That is, it was confirmed that the solid content in the heavy liquid phase after the heat treatment was an anionic surfactant, and the MBS resin fine powder was removed from the filtrate drainage.

(Example 2)
60 L of filtrate wastewater containing 0.5% by weight of MBS resin fine powder (number average particle size 150 μm), 23% by weight of methyl ethyl ketone, and 76.5% by weight of water is placed in a separation tank and heated from room temperature of 25 ° C. (temperature before treatment). When the temperature reached 45 ° C., the heating was stopped and the mixture was allowed to stand for 30 minutes. 900 ml of a light liquid phase of methyl ethyl ketone containing resin was generated and the specific gravity was 0.84. The specific gravity of the heavy liquid was 0.97. When a pipe with an inner diameter of 23 mm and a length of 2 m is installed vertically in the lower part of the separation tank, and the output value when the pipe is filled with heavy liquid above and below it is 100%, filled with light liquid A differential pressure transmitter (pressure tube-less type) manufactured by Yokogawa Electric Co., Ltd. set to 0% was attached, and the liquid was discharged so that the linear velocity in the pipe was 0.04 m / sec. The output of the differential pressure transmitter that is discharging the heavy liquid phase is 100%, and when it reaches 0%, it was collected in a separate container, and it was confirmed whether there was an interface between the heavy liquid side and the light liquid side. There was no interface between the heavy and light liquids, and the light and heavy liquids were separated and recovered. Moreover, as a result of fractionating a heavy liquid phase and measuring solid content concentration, it was 0.2 weight%. The heavy liquid phase contained an anionic surfactant derived from MBS resin latex, and its concentration was measured and found to be 0.2% by weight. That is, it was confirmed that the solid content in the filtrate drainage after the heat treatment was an anionic surfactant, and the MBS resin fine powder was removed from the filtrate drainage.

(Comparative Example 1)
60 L of filtrate waste water containing 1.0% by weight of MBS resin fine powder (number average particle diameter 100 μm), 23% by weight of methyl ethyl ketone, and 76% by weight of water is placed in a separation tank having a diameter of 400 mm and heated from room temperature of 25 ° C. (temperature before treatment). When the temperature reached 50 ° C., the heating was stopped and the mixture was allowed to stand for 30 minutes. 1200 ml of a light liquid phase of methyl ethyl ketone containing the resin was generated, and the specific gravity was 0.84. The specific gravity of the heavy liquid was 0.97. Although the differential pressure transmitter was attached to the light liquid phase and heavy liquid phase of the tank, the thickness of the light liquid phase in the tank is about 10 mm, and the change in the differential pressure between the light liquid and heavy liquid in the tank is recognized. I couldn't.

(Comparative Example 2)
60 L of filtrate waste water containing 1.0% by weight of MBS resin fine powder (number average particle size 100 μm), 23% by weight of methyl ethyl ketone and 76% by weight of water is placed in a separation tank and heated from room temperature 25 ° C. (temperature before treatment) When the temperature reached 50 ° C., the heating was stopped and the mixture was allowed to stand for 30 minutes. 1200 ml of a light liquid phase of methyl ethyl ketone containing the resin was generated, and the specific gravity was 0.84. The specific gravity of the heavy liquid was 0.97. A capacitive interface detector was installed at the bottom of the separation tank to discharge the liquid. Although the heavy liquid phase was changed to the light liquid, the capacitive interface detector did not respond.

  As described above, a light liquid (organic solvent phase) and a heavy liquid (water) are detected by detecting the organic solvent phase containing resin fines and the aqueous phase by the differential pressure above and below the vertical transfer pipe provided at the bottom of the separation tank. Phase).

An example of a device with differential pressure detectors above and below a vertical transfer pipe at the bottom of the separation tank

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Separation tank 2 Differential pressure detection part 3 Piping installed vertically 4 Organic solvent phase recovery port 5 Water phase recovery port

Claims (8)

The filtrate drainage (temperature: α ₀ ° C) containing the organic solvent and water after solid-liquid separation of the resin slurry suspension is in the range of (α ₀ +5) ° C to (α ₀ +40) ° C. A method for treating filtrate wastewater that is heated and separated into an organic solvent phase containing a fine resin powder and an aqueous phase, wherein the interface between the organic solvent phase containing the fine resin powder and the aqueous phase is provided at the bottom of the separation tank. A method for treating filtrate drainage, characterized by detecting and separating the pressure difference between the upper and lower pipes.   The organic solvent content in the filtrate waste water is in the range of 10 wt% or more and 30 wt% or less, and the water content is in the range of 70 wt% or more and 90 wt% or less. The method for treating filtrate waste water according to 1.   The method for treating filtrate wastewater according to claim 1 or 2, wherein the content of the resin in the filtrate wastewater before heating is in the range of 0.01 wt% to 5 wt%.   The method for treating filtrate wastewater according to any one of claims 1 to 3, wherein the resin content in the filtrate wastewater before heating is in the range of 0.01 wt% to 2 wt%. The method for treating filtrate wastewater according to any one of claims 1 to 4, wherein the filtrate wastewater is heated to a range of (α ₀ +10) ° C to (α ₀ +30) ° C.   The method for treating filtrate wastewater according to any one of claims 1 to 5, wherein the organic solvent is methyl ethyl ketone.   The method for treating filtrate wastewater according to any one of claims 1 to 6, wherein the difference in capacitance between the organic solvent phase containing fine resin powder and the aqueous phase is within 35 PF.   The method for treating filtrate wastewater according to any one of claims 1 to 7, wherein a distance between the differential pressure detection parts above and below the vertical transfer pipe provided in the lower part of the separation tank is 2 m or more.

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