JP2013188725A - Solid-liquid separation apparatus and solid-liquid separation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain clean treatment liquid by separating a solid from wastewater that contains the solid at low cost without adding any additive and any external energy.SOLUTION: A solid-liquid separation apparatus includes a first solid-liquid separator that subjects a first solid, having a first particle size in a liquid to be treated, to solid-liquid separation; a second solid-liquid separator that is connected with the first solid-liquid separator through a first transfer line, supplies a first treatment liquid obtained by separating the first solid from the liquid to be treated through the first transfer line, and subjects a second solid having a second particle size to solid-liquid separation from the first treatment liquid; and a third solid-liquid separator that is connected with the second solid-liquid separator through a second transfer line, supplies a second treatment liquid obtained by separating the second solid from the first treatment liquid through the second transfer line, and subjects a third solid having a third particle size to solid-liquid separation from the second treatment liquid. The solid-liquid separation apparatus is composed to satisfy the relation: (first particle size)≥(second particle size)≥(third particle size).

Description

  The present invention relates to a solid-liquid separation device and a solid-liquid separation method.

  Various apparatuses and methods are used for the treatment of wastewater containing sludge depending on the type of the wastewater. For example, oil field accompanying water contains sludge such as dissolved organic compounds, and in waste liquids from nuclear power plants, nuclear facilities, etc., in addition to fine precipitates such as iron oxide and iron hydroxide, powder ion exchange Solid wastes such as resins and granular ion exchange resins are also included.

  A solid-liquid separation method using a sedimentation separation tank is used for treatment of wastewater containing various solids that do not require decomposition of organic compounds and the like. This method is a simple solid-liquid separation system that uses gravity sedimentation of solid particles due to the density difference between the solid particles and the liquid, so it is widely used in various fields that discharge wastewater as described above. .

  However, solids with a small particle size and solids with a low density cannot be efficiently separated with a short sedimentation time and a low tank height because of their low sedimentation speed. Therefore, in order to obtain a clear liquid, it is common to add a flocculant to agglomerate solids, increase the particle size, and separate by sedimentation.

  In addition, a treatment liquid (supernatant liquid) that satisfies the required specifications cannot often be obtained only by sedimentation separation, and when the water quality of the supernatant liquid after sedimentation separation is to be reduced to a lower solids concentration, a filtration device is used as a post-treatment. It is possible to install it, and sand filtration is generally used. Furthermore, in order to obtain a treatment solution with a low solids concentration, diatomaceous earth as a filter aid in the filter element of the filtration device and additives such as pulp, activated carbon, granite, ceramic, various resins, glass, metal, metal oxides, etc. A method of using a back-washable filter for pre-coating the fine particles and powders is proposed.

  Furthermore, a method of separating into distilled water and concentrated liquid using an evaporative concentration apparatus as another post-treatment for lowering the water quality of the supernatant liquid after sedimentation separation has been disclosed.

  However, since any of the above-described techniques uses a flocculant, when the solid matter in the wastewater is waste, the amount of waste increases by the amount of the flocculant added, and the solid matter is the product. In some cases, there was a problem that a separate process of product solids and added flocculant was required.

  Moreover, diatomaceous earth as a filter aid and additives as a filter aid are pre-coated with fine particles and powders such as pulp, activated carbon, granite, ceramic, various resins, glass, metal, and metal oxides. As described above, if the solid is a waste, the amount of the waste is increased by the amount of the additive. If the solid is a product, a separate process for separating the product solid and the additive is required. It becomes.

  Furthermore, when using an evaporative concentrator, it is necessary to supply heat energy for evaporating water from the outside in order to separate it into distilled water and concentrate, and it is necessary to secure a separate energy source for generating heat energy Therefore, there was a problem that it was against the demand for energy conservation.

Japanese Patent No. 3864518 JP 2010-119982 A JP2011-167582A

  The subject of this invention is isolate | separating a solid substance at low cost from the waste_water | drain containing a solid substance, without adding an additive substance and external energy, and obtaining a clean process liquid.

  One aspect of the present invention includes a first solid-liquid separator that solid-liquid separates a first solid having a first particle size in a liquid to be treated, and a first transfer line connected to the first solid-liquid separator. A first processing liquid that is connected and separated from the liquid to be processed is supplied via the first transfer line, and a second solid having a second particle size is supplied from the first processing liquid. A second solid-liquid separator for solid-liquid separation, and a second transfer line connected to the second solid-liquid separator via the second transfer line, and the second solid matter from the first processing liquid via the second transfer line And a third solid-liquid separator for supplying the second processing liquid separated from the second processing liquid and solid-liquid separating the third solid material having the third particle diameter from the second processing liquid. The present invention relates to a solid-liquid separator characterized by satisfying a relationship of particle size ≧ third particle size.

  According to the present invention, a clean treatment liquid can be obtained by separating solids from wastewater containing solids at low cost without adding additive substances and external energy.

It is a figure which shows schematic structure of the solid-liquid separation apparatus of 1st Embodiment. It is a figure which shows schematic structure of the solid-liquid separation apparatus of 2nd Embodiment. It is a graph which shows the solid content rate in the simulation liquid used in the Example. It is a graph which shows the solid content rate in the treated water obtained in the Example. It is a graph which shows the solid content rate in the simulation liquid used in the Example.

(First embodiment)
FIG. 1 is a diagram showing a schematic configuration of the solid-liquid separation device of the present embodiment.
A solid-liquid separator 10 shown in FIG. 1 includes a first solid-liquid separator 11, a second solid-liquid separator 12, and a third solid-liquid separator 13, and the first solid-liquid separator 11 and the second solid-liquid separator 11 are arranged. The liquid separator 12 is connected via the first transfer line 15, and the second solid-liquid separator 12 and the third solid-liquid separator 13 are connected via the second transfer line 16, and the third solid-liquid separator 12 is connected. The liquid separator 13 and the first solid-liquid separator 11 are connected via a third transfer line 17.

  The first solid-liquid separator 11 is a solid for removing a solid (first solid) having a relatively large particle size, that is, a particle size (first particle size), from waste water containing solids that are liquids to be treated. The coarse separator is preferably composed of, for example, a vibration sieve or a rotary drum type solid-liquid separator.

  When using a vibration sieving machine, select a sieve with an opening according to the first particle size of the first solid, and select the optimum vibration application method from ultrasonic, three-dimensional, centrifugal force, etc. . In addition, since the vibration sieve machine which is equipped with the sieve of various mesh diameters and to which the various vibration systems are applied is marketed, it can also be used selecting from such a commercially available vibration sieve machine suitably. When a rotary drum type solid-liquid separator is used, a screen with an opening corresponding to the first particle size of the first solid is selected to control the residence time of the waste water in the separator.

  The second solid-liquid separator 12 is a solids separator for removing solids (second solids) having a medium particle size, that is, a particle size (second particle size), from the waste water, and is a gravity sedimentation separator. Or a centrifugal sedimentation separator. As the gravity settling separator, a general-purpose one can be used, and in particular, from the viewpoint of improving the processing efficiency, a structure capable of storing several tens to several hundred batches of solids at the bottom is preferable. Centrifugal sedimentation separators can also be constructed from general-purpose types such as a cylindrical type, a separator plate type, a decanter type, etc., and the equipment dimensions and rotation speed are set appropriately according to the density difference between the second solid matter in the waste water and the liquid To do.

  The third solid-liquid separator 13 is a solid separator for removing a solid (third solid) having a small particle size, that is, a particle size (third particle size), from the waste water. Although it depends on the size of the third particle size, it is preferable to use a filter. The type of filter is not particularly limited as long as the third solid matter can be removed and separated. For example, a ceramic filter can be used in addition to an endren filter that is widely used as a drainage filter. When using a ceramic filter, the pore diameter and the number of pores of the filter, and the thickness (length) of the filter are appropriately selected and set according to the size and amount of the third solid to be removed.

  As is clear from the above description, the first solid, the second solid, and the third solid satisfy the relationship of the first particle size ≧ the second particle size ≧ the third particle size with respect to their sizes. To do.

  Next, a method for removing solid matter from the wastewater that is the liquid to be treated using the solid-liquid separator 10 shown in FIG.

  First, the waste water W0 is introduced into the first solid-liquid separator 11 via the waste water supply line 21, and for example, while vibrating a vibrating screen or the like by a predetermined vibration application method, By letting the drainage water W0 pass through the sieve with openings, the first solid matter having the largest particle size is removed from the wastewater W0 by solid-liquid separation. The removed first solid matter is discharged to the outside from a discharge line 18 provided at the bottom of the first solid-liquid separator 11, and is used for disposal or the like. The discharge line 18 is not necessarily connected to the bottom, and may be connected to the upper part of the first transfer line 15.

  Next, the first treatment liquid W <b> 1 after the first solid is separated from the waste water W <b> 0 is introduced into the second solid-liquid separator 12 via the first transfer line 15. In the second solid-liquid separator 12, for example, the first processing liquid W1 is stored for a predetermined time (several hours to several tens of hours) in a gravity sedimentation separator or the like, and is a medium size contained in the first processing liquid W1. The second solid material is allowed to settle. The settled second solid matter is discharged to the outside from a discharge line 19 provided at the bottom of the second solid-liquid separator 12, and is used for disposal or the like. The discharge line 19 is not necessarily connected to the bottom, and may be sucked out from the top.

  Next, the second processing liquid W <b> 2 after the second solid is separated from the first processing liquid W <b> 1 is introduced into the third solid-liquid separator 13 via the second transfer line 16. In the third solid-liquid separator 13, for example, the second processing liquid W <b> 2 is passed through a ceramic filter or the like, and small third solids contained in the second processing liquid W <b> 2 are collected by the filter to be solid-liquid separated. To do. The treatment liquid W3 after the third solid matter is separated and removed from the second treatment liquid W2 is discharged to the outside from the treatment liquid discharge line 22, and is reused as a water resource or the like.

  Next, the third solid-liquid separator 13 is washed through a pipe (not shown), and the third solid matter collected in the third solid-liquid separator 13 is washed and discharged. For example, when the third solid-liquid separator 13 is a ceramic filter or the like, the ceramic filter or the like is back-washed. As described above, when the inside of the third solid-liquid separator 13 is washed, the obtained waste liquid W4 contains solids that are agglomerated by the aggregation of the third solids. Therefore, in the present embodiment, the waste liquid W4 is introduced into the first solid-liquid separator 11 via the third transfer line 17.

  As described above, in the first solid-liquid separator 11, the waste liquid W <b> 4 is applied to the sieve having a predetermined opening disposed in the apparatus while vibrating a vibration sieve machine or the like by a predetermined vibration application method. By allowing the water to flow, the aggregated and enlarged third solid in the waste liquid W4 can be removed by solid-liquid separation. The removed aggregates of the third solid matter are discharged to the outside from a discharge line 18 provided at the bottom of the first solid-liquid separator 11 and used for disposal or the like.

  The processing liquid in each transfer line can be transferred using a pump or the like (not shown), or a transfer device (not shown) using a negative pressure caused by a fluid such as a steam jet. ) Can also be used.

  Thus, according to the present embodiment, for example, the first solid-liquid separation device 11 configured by a vibrating sieve or a rotary drum type solid-liquid separator, for example, a gravity sedimentation separator or a centrifugal sedimentation separator is configured. A second solid-liquid separator 12 and a third solid-liquid separator 13 composed of, for example, an endren filter or a ceramic filter, and a drainage supply line 21, a first transfer line 15 and a second By introducing the waste water W0 through the transfer line 16, a relatively large solid (first solid), a medium-sized solid (second solid) and a small solid (second solid) in the waste water W0. 3 solids) can be separated and removed.

  That is, according to the solid-liquid separation device 10 of the present embodiment, the solid waste of various sizes contained in the waste water W0 can be obtained by simply transferring the waste water W0 introduced into the solid-liquid separation device 10 through the device. Can be separated and removed. Therefore, it is possible to obtain a clean processing liquid by separating solids at a low cost without adding an additive material such as a flocculant and external energy such as thermal energy.

  In addition, by introducing the waste liquid W <b> 4 that has washed the third solid-liquid separator 13 into the first solid-liquid separator 11 through the third transfer line 17, the third collected by the third solid-liquid separator 13. Solids can be easily separated and removed.

(Second Embodiment)
FIG. 2 is a diagram showing a schematic configuration of the solid-liquid separation device of the present embodiment.
2 is different from the solid-liquid separator 10 shown in FIG. 1 in that the first solid-liquid separator 11 and the first transfer line 15 and the discharge line 18 associated therewith are omitted. The other configurations are the same. In FIG. 2, the same reference numerals are used for the similar or identical components to those shown in FIG.

  Therefore, the second solid-liquid separator 12 can be configured similarly to the second solid-liquid separator 12 in the first embodiment, and the third solid-liquid separator 13 is the third solid-liquid separator in the first embodiment. The configuration can be the same as that of the separator 13.

  In addition, since the solid-liquid separator 20 of this embodiment does not have the 1st solid-liquid separator 11 unlike the solid-liquid separator 10 of 1st Embodiment, the waste_water | drain W0 which should be introduce | transduced is 1st solid. It can be suitably used when it does not have a relatively large solid such as a product.

  Next, a method for removing solid matter from the waste water W0, which is the liquid to be treated, using the solid-liquid separation device 20 shown in FIG. 2 will be briefly described.

  First, the wastewater W0 is introduced into the second solid-liquid separator 12 via the wastewater supply line 21, and the wastewater W0 is stored in a gravity sedimentation separator or the like for a predetermined time (several hours to several tens of hours). The second solid contained in W0 is allowed to settle. The settled second solid matter is discharged to the outside from a discharge line 19 provided at the bottom of the second solid-liquid separator 12, and is used for disposal or the like. As described above, the discharge line 19 does not necessarily have to be connected to the bottom, and may be sucked out from the top.

  Next, the second treatment liquid W <b> 2 after the second solid matter is separated from the waste water W <b> 0 is introduced into the third solid-liquid separator 13 via the second transfer line 16. In the third solid-liquid separator 13, for example, the second processing liquid W2 is passed through a ceramic filter or the like, and the third solid contained in the second processing liquid W2 is collected and solid-liquid separated by the filter. . The treatment liquid W3 after the third solid matter is separated and removed from the second treatment liquid W2 is discharged to the outside from the treatment liquid discharge line 22, and is reused as a water resource or the like.

  Next, the third solid-liquid separator 13 is washed through a pipe (not shown), the third solid matter collected in the third solid-liquid separator 13 is washed and discharged, and the obtained waste liquid W4 is discharged. It introduces into the second solid-liquid separator 12 via the third transfer line 17.

  As described above, in the second solid-liquid separator 12, for example, by storing in a gravity sedimentation separator or the like, the agglomerated third solid matter in the waste liquid W4 can be separated by solid-liquid separation and removed. it can. The removed agglomerates of the third solid matter are discharged to the outside from a discharge line 19 provided at the bottom of the second solid-liquid separator 12 and used for disposal or the like.

  Thus, according to the present embodiment, for example, the second solid-liquid separation device 12 configured by a gravity sedimentation separator or a centrifugal sedimentation separator, and the third solid configuration configured by, for example, an endren filter or a ceramic filter. By preparing the liquid separator 13 and introducing the waste water W0 to the liquid separator 13 via the waste water supply line 21 and the second transfer line 16, a medium-sized solid matter (second solid matter) in the waste water W0. ) And small solids (third solids) can be separated and removed.

  That is, according to the solid-liquid separation device 20 of the present embodiment, the solid waste of various sizes contained in the waste water W0 can be obtained simply by transferring the waste water W0 introduced into the solid-liquid separation device 20 through the device. Can be separated and removed. Therefore, it is possible to obtain a clean processing liquid by separating solids at a low cost without adding an additive material such as a flocculant and external energy such as thermal energy.

  In addition, the waste liquid W4 washed by the third solid-liquid separator 13 is introduced into the second solid-liquid separator 12 via the third transfer line 17, whereby the third solid-liquid separator 13 collected. Solids can be easily separated and removed.

Example 1
In this example, the solid-liquid separation apparatus 10 shown in FIG. 1 was used to separate and remove solids from the waste water.

  First, as a drainage simulation liquid, a solid having a particle size of 10 μm or less, a solid having a particle size of 10 μm to 200 μm, a solid having a particle size of 200 μm to 2 mm (particle size of 200 μm or more and less than 2 mm). A suspension containing a solid substance having a particle diameter of 2 mm or more and a ratio as shown in FIG. 3 was prepared. The solid having a particle size of less than 200 μm was composed of zirconia oxide particles, and the solid having a particle size of 200 μm or more was composed of stainless steel.

  In addition, content (mass%) of each solid substance in the said simulation liquid and content (mass%) of each solid substance in each process liquid shown below filter a predetermined quantity of liquid with the filter paper for analysis, The mass of the solid separated into solid and liquid was measured with a balance and divided by the volume of the treatment liquid to obtain the solid concentration in the treatment liquid.

  Further, as the first solid-liquid separator 11, a three-dimensional vibration sieve including a sieve having a nominal size (opening) of 212 μm is used, and a gravity sedimentation separator having an effective sedimentation depth of 750 mm is used as the second solid-liquid separator 12. A ceramic filter made of alumina was used as the third solid-liquid separator 13. A ceramic filter having 19 channels with an inner diameter of 4 mm was used.

  The simulated liquid described above was introduced into the first solid-liquid separator 11 from the drainage supply line 21, and all of the simulated liquid was passed through a sieve of a vibrating sieve that was the first solid-liquid separator 11. As a result, it was found that all solids having a particle size of 200 μm or more were removed from the first processing liquid W1 from the first solid-liquid separator 11.

  Next, the first processing liquid W1 was introduced into the second solid-liquid separator 12 via the first transfer line 15 and allowed to stand for 6 hours, and then the supernatant liquid (second processing liquid W2) was extracted. In addition, the ratio of the solid substance in the 2nd process liquid W2 became a thing as shown in FIG. As apparent from FIG. 4, in the second solid-liquid separator 12, although solids having a particle size of 2 μm or more remain, at least most of the solids having a particle size of 10 μm to 200 μm are separated and removed. I understand.

Next, the second processing liquid W2 was introduced into the third solid-liquid separator 13 via the second transfer line 16. In addition, the process flow rate per unit filtration area of the ceramic filter which comprises the 3rd solid-liquid separator 13 was 0.2 m < ³ > / h / m < ² >. Moreover, the process by the 3rd solid-liquid separator 13 was performed until the filtration differential pressure (filter inlet pressure-filter outlet pressure) of the ceramic filter became about 0.2 MPa. As a result, the solid concentration in the third treatment liquid W3 after the treatment is reduced to 0.1 ppm or less, and most of the solid contained in the second treatment liquid W2 is separated and removed. There was found.

  The solid concentration in the third treatment liquid W3 is determined by measuring the mass of the solid obtained by filtering a predetermined amount of the treatment liquid with a filter paper for analysis and separating the solid and liquid with a balance, and dividing by the volume of the treatment liquid. The solids concentration was

  From the above, it has been found that in this embodiment, the solid waste of various sizes contained in the waste water W0 can be separated and removed only by transferring the waste water W0 introduced into the solid-liquid separation device 10 through the device. . Therefore, it is possible to obtain a clean processing liquid by separating solids at a low cost without adding an additive material such as a flocculant and external energy such as thermal energy.

  Subsequently, the ceramic filter was back-washed, and the obtained waste liquid W4 was introduced into the first solid-liquid separator 11 via the third transfer line 17. The waste liquid W4 was filtered with a filter paper for analysis, and the solid matter on the solid-liquid separated filter paper was observed with a microscope, and as a result of analysis by dimension measurement, the waste liquid W4 was separated and removed by the third solid-liquid separator 13 It turned out that the aggregate of the diameter of 1 mm or more of a solid substance was contained. On the other hand, as a result of the solid-liquid separation as described above in the first solid-liquid separator 11, most of the aggregate in the drainage liquid W4 was separated and removed.

  Therefore, in the present embodiment, the waste liquid W4 washed by the third solid-liquid separator 13 is introduced into the first solid-liquid separator 11 via the third transfer line 17, and is thereby captured by the third solid-liquid separator 13. It was found that the collected third solid matter can be easily separated and removed.

(Example 2)
In this example, the solid-liquid separation device 20 shown in FIG. 2 was used to separate and remove solids from the waste water.

  First, as a drainage simulation liquid, a solid having a particle size of 2 μm or less, a solid having a particle size of 2 μm to 10 μm, a solid having a particle size of 10 μm to 100 μm (particle size of 10 μm or more and less than 100 μm) A suspension containing a solid and a solid having a particle size of 100 μm or more was prepared at a ratio shown in FIG. All solids were composed of oxidized zirconia particles.

  In addition, content (mass%) of each solid substance in the said simulation liquid and content (mass%) of each solid substance in each process liquid shown below filter a predetermined quantity of liquid with the filter paper for analysis, The mass of the solid separated into solid and liquid was measured with a balance and divided by the volume of the treatment liquid to obtain the solid concentration in the treatment liquid.

Moreover, the 2nd solid-liquid separator 12 and the 3rd solid-liquid separator 13 used the same thing as Example 1. FIG.
The simulated liquid described above was introduced into the second solid-liquid separator 21 from the waste water supply line 21 and allowed to stand for 6 hours, and then the supernatant liquid (second processing liquid W2) was extracted. Similar to the first embodiment, it was found that the second solid-liquid separator 12 separated and removed most of the solids having a particle size of 10 μm to 200 μm in the simulated water.

Next, the second processing liquid W2 was introduced into the third solid-liquid separator 13 via the second transfer line 16. In addition, the process flow rate per unit filtration area of the ceramic filter which comprises the 3rd solid-liquid separator 13 was 0.2 m < ³ > / h / m < ² >. Moreover, the process by the 3rd solid-liquid separator 13 was performed until the filtration differential pressure (filter inlet pressure-filter outlet pressure) of the ceramic filter became about 0.2 MPa. As a result, the solid concentration in the third treatment liquid W3 after the treatment is reduced to 0.1 ppm or less, and most of the solid contained in the second treatment liquid W2 is separated and removed. There was found.

  The solid concentration in the third treatment liquid W3 is determined by filtering a predetermined amount of the treatment liquid with an analytical filter paper, measuring the mass of the solid separated by solid-liquid separation with a balance, and dividing by the volume of the treatment liquid. The solids concentration was

  As described above, in this embodiment, it was found that the solid waste of various sizes contained in the waste water W0 can be separated and removed only by transferring the waste water W0 introduced into the solid-liquid separation device 20 through the device. . Therefore, it is possible to obtain a clean processing liquid by separating solids at a low cost without adding an additive material such as a flocculant and external energy such as thermal energy.

  Subsequently, the ceramic filter was back-washed, and the obtained waste liquid W4 was introduced into the second solid-liquid separator 12 through the third transfer line 17. The waste liquid W4 was filtered with a filter paper for analysis, and the solid matter on the solid-liquid separated filter paper was observed with a microscope, and as a result of analysis by dimension measurement, the waste liquid W4 was separated and removed by the third solid-liquid separator 13 It turned out that the aggregate of the diameter of 1 mm or more of a solid substance was contained. On the other hand, as a result of the solid-liquid separation as described above in the second solid-liquid separator 12, most of the aggregates in the drainage liquid W4 were separated and removed.

  Therefore, in the present embodiment, the waste liquid W4 washed by the third solid-liquid separator 13 is introduced into the second solid-liquid separator 12 via the third transfer line 17 so as to be captured by the third solid-liquid separator 13. It was found that the collected third solid matter can be easily separated and removed.

  As mentioned above, although several embodiment of this invention was described, these embodiment was posted as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

10, 20 Solid-liquid separation device 11 First solid-liquid separator 12 Second solid-liquid separator 13 Third solid-liquid separator 15 First transfer line 16 Second transfer line 17 Third transfer line 18, 19 Discharge line W0 Drainage W1 First treated water W2 Second treated water W3 Third treated water W4 Waste liquid

Claims (11)

A first solid-liquid separator for solid-liquid separation of a first solid having a first particle size in the liquid to be treated;
The first solid-liquid separator is connected via a first transfer line, and the first processing liquid from which the first solid matter is separated from the liquid to be processed is supplied via the first transfer line, A second solid-liquid separator for solid-liquid separating a second solid having a second particle size from one treatment liquid;
Connected to the second solid-liquid separator via a second transfer line, supplying the second processing liquid from which the second solid matter is separated from the first processing liquid via the second transfer line, A third solid-liquid separator for solid-liquid separation of the third solid having the third particle size from the second treatment liquid,
A solid-liquid separation device satisfying a relationship of first particle size ≧ second particle size ≧ third particle size.   The first solid-liquid separator and the third solid-liquid separator are connected to each other, and the aggregate of the third solid matter after the solid-liquid separation is supplied to the first solid-liquid separator to be removed. The solid-liquid separator according to claim 1, comprising three transfer lines.   The solid-liquid separator according to claim 1 or 2, wherein the first solid-liquid separator is a vibrating sieve or a rotary drum type solid-liquid separator.   The solid-liquid separator according to claim 1, wherein the second solid-liquid separator is a gravity sedimentation separator or a centrifugal sedimentation separator.   The solid-liquid separator according to any one of claims 1 to 4, wherein the third solid-liquid separator is a filter. A first solid-liquid separator for solid-liquid separation of a first solid having a first particle size in the liquid to be treated;
The liquid to be treated is connected to the first solid-liquid separator via a first transfer line, connected to the first solid-liquid separator via a second transfer line, and the liquid to be processed via the first transfer line. The processing liquid from which the first solid is separated is supplied from the solid, and the second solid having the second particle size is solid-liquid separated from the processing liquid, and the aggregate of the second solid after the solid-liquid separation. A second solid-liquid separator for supplying and removing to the first solid-liquid separator via the second transfer line,
A solid-liquid separator characterized by satisfying a relationship of first particle size ≧ second particle size.   The solid-liquid separator according to claim 6, wherein the first solid-liquid separator is a gravity sedimentation separator or a centrifugal sedimentation separator.   The solid-liquid separator according to claim 6 or 7, wherein the second solid-liquid separator is a filter. Solid-liquid separation of a first solid having a first particle size in the liquid to be treated by a first solid-liquid separator;
The first processing liquid from which the first solid is separated from the liquid to be processed is supplied to a second solid-liquid separator via a first transfer line, and has a second particle size from the first processing liquid. Solid-liquid separation of the second solid material;
The second processing liquid from which the second solid is separated from the first processing liquid is supplied to a third solid-liquid separator via a second transfer line, and has a third particle size from the second processing liquid. Solid-liquid separation of the third solid matter,
A solid-liquid separation method characterized by satisfying a relationship of first particle size ≧ second particle size ≧ third particle size.   Supplying the first solid-liquid separator to the first solid-liquid separator through a third transfer line to remove the aggregate of the third solid matter separated by solid-liquid separation by the third solid-liquid separator. The solid-liquid separation method according to claim 9. Solid-liquid separation of a first solid having a first particle size in the liquid to be treated by a first solid-liquid separator;
A treatment liquid from which the first solid is separated from the liquid to be treated is supplied to a second solid-liquid separator via a first transfer line, and a second solid having a second particle size is obtained from the treatment liquid. A solid-liquid separation step;
Supplying the first solid-liquid separator to the first solid-liquid separator via a second transfer line to remove the aggregate of the second solid substance solid-liquid separated by the second solid-liquid separator;
A solid-liquid separation method characterized by satisfying a relationship of first particle size ≧ second particle size.

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