WO2010150790A1

WO2010150790A1 - Suction filtration/concentration method and suction filtration/concentration device

Info

Publication number: WO2010150790A1
Application number: PCT/JP2010/060574
Authority: WO
Inventors: 正國谷
Original assignee: メタウォーター株式会社
Priority date: 2009-06-23
Filing date: 2010-06-22
Publication date: 2010-12-29
Also published as: JP2012035262A; JPWO2010150790A1; JP5324636B2; JP4902814B2

Abstract

Disclosed is a suction filtration/concentration method for filtrating and concentrating suspension by a suction method, which comprises a step in which water content in the suspension is passed through filter cloth (18) in the shape of a bag by sucking the suspension through a filtering chamber (76) formed in the interior of the filter cloth (18), while solids in the suspension are attached to the surface of the filter cloth (18). The suction filtration/concentration method has a step for selecting first suspension containing solid content capable of blocking the mesh of the filter cloth (18), a cake thin layer forming step for forming a cake thin layer on the surface of the filter cloth (18) by filtrating and concentrating the first suspension by the suction method, and a filtration/concentration step for filtrating and concentrating second suspension having concentration lower than the concentration of the first suspension through the cake thin layer by the suction method. The method and a device therefor make it possible to concentrate sludge of low concentration of not more than 1% by mass, which is produced in a filter plant or the like, in a short time and in an efficient manner.

Description

Suction filtration concentration method and suction filtration concentration device

The present invention relates to a suction filtration concentration method and a suction filtration concentration device. More specifically, the sludge (suspension) containing solids that cannot be captured by the filter cloth efficiently forms a state that can be filtered by such a filter cloth, resulting in clogging. The present invention relates to a suction filtration concentration method and apparatus capable of performing filtration without any problems.

Conventionally, sludge generated at water purification plants has been concentrated stepwise mainly from the viewpoint of reducing energy consumption mainly due to concentration, and finally disposed. As a typical example, sludge (suspension) generated in a water purification plant or the like is precipitated in a coagulation sedimentation tank using a coagulant. The settled sludge is further introduced into a gravity sedimentation tank and settled by the action of gravity. In this gravity settling tank, for example, sludge having a concentration of 1% by mass or less is concentrated to a concentration of more than 1% by mass to about 2% by mass. Next, the sludge settled on the bottom of the gravity sedimentation tank is further concentrated using a suction filtration concentration apparatus using a suction filtration concentration technique. This suction type filtration concentration apparatus is provided with a filtration concentration tank for allowing sludge to flow in and filtering and concentrating. Further, the filtration and concentration tank is provided with a bag-like filter cloth that forms a filtration chamber therein, and suction means for sucking sludge outside the filter cloth through the filtration chamber. And the sludge which flowed in the filtration concentration tank from the gravity sedimentation tank is attracted | sucked by a suction means. Thereby, moisture in the sludge passes through the filter cloth and is collected in the filtration chamber, while solids in the sludge adhere to the outer surface of the filter cloth. Thus, the sludge is further concentrated. In general, this suction filtration concentrator can concentrate sludge having a concentration of about 1% by mass to 2% by mass to a concentration of about 3% by mass to 5% by mass. Further, the concentrated sludge adhering to the outer surface of the filter cloth is discharged to the outside from the filtration and concentration tank, and water is further removed by a dehydrator, a dryer or sun drying. By this water removal, the above-mentioned concentrated sludge is further concentrated. In this way, the concentrated sludge is formed into a cake and is finally reused for landfill disposal or horticultural soil.

However, if the sludge with a low concentration of 1% by mass or less generated at a water purification plant as mentioned above is concentrated by direct dehydrator, dryer or sun drying, the energy consumption of the dehydrator or dryer The cost increases. On the other hand, in the sun drying, a considerable time is required until drying. Therefore, it is not practical.

Furthermore, recently, water purification treatment with high treatment capacity is required in water purification plants by mixing microorganisms and bacteria such as Cryptosporidium into the purified water. Therefore, the amount of generated sludge increases due to an increase in the amount of coagulant added in the coagulation sedimentation tank, and the efficiency of water purification treatment at the water purification plant is an urgent issue. On the other hand, the sludge treatment in the gravity settling tank uses the natural sedimentation of the sludge due to gravity, and it takes a long time, for example several days, for the sludge to settle and concentrate. Moreover, when using a gravity sedimentation tank, in order to discharge | emit the naturally settled sludge reliably, agitation of the sludge is also performed in the gravity sedimentation tank lower part. However, in such a case, extra energy is required for stirring. Furthermore, the installation of the gravity settling tank requires a huge installation space and requires a large-scale civil engineering work. As described above, the treatment of sludge in the gravity sedimentation tank has been an obstacle to the efficiency of the water purification treatment.

In this regard, among the suction filtration and concentration techniques, a siphon filtration and concentration device is known that can achieve a high energy saving effect by using a suction power as a siphon.

For example, Patent Document 1 discloses a siphon type suction filtration and concentration apparatus. Since this suction-type filtration concentration apparatus includes a bag-like filter cloth that forms a filtration chamber, the suction sludge (sludge before concentration) is separated into moisture and concentrated sludge. That is, the moisture contained in the sludge is guided into the filtration chamber and collected as a filtrate by passing through countless pores of the filter cloth. In addition, the sludge from which moisture has been removed and concentrated is attached to the outer surface of the filter cloth, and then is subjected to a peeling treatment and discharged to the outside of the suction filtration concentration device.

Incidentally, when the concentrated sludge adhering to the outer surface of the filter cloth is peeled off from the filter cloth, the following processes (S1) to (S4) have been conventionally performed. First, unconcentrated sludge in the filtration and concentration tank is discharged to the outside and temporarily stored (S1). This is to prevent the concentrated sludge from being reduced in concentration by dissolving the concentrated sludge into the unconcentrated sludge. Next, air of a predetermined pressure (air) is pumped from the inside of the filter cloth to the outside through the filtration chamber (S2). Concentrated sludge adheres to the entire outer surface of the filter cloth, and countless pores of the filter cloth are blocked. Therefore, by sending air, the filter cloth bulges outward and deforms, and when the air passes through numerous pores, the concentrated sludge can be forcibly peeled outward. It becomes. Next, the concentrated sludge is discharged to the outside (S3). From (S2) described above, the peeled concentrated sludge accumulates at the bottom of the filtration concentration tank. Therefore, it is performed to remove concentrated sludge from the filtration concentration tank. Next, unconcentrated sludge is filled into the filtration and concentration tank (S4).

As described above, the separation processing steps (S1) to (S4) using the conventional suction type filtration concentration apparatus are completed.

By the way, when performing such peeling treatment steps (S1) to (S4), the low-concentration sludge precipitated in the coagulation sedimentation tank is directly used by using a suction filtration concentrator without using the gravity sedimentation tank. If it is filtered and concentrated by a suction method, a filter cloth with a small eye must be adopted. In such a case, the filter cloth is clogged in a short time by filtering and concentrating the sludge, and it is necessary to stop the filter concentration and wash the filter cloth. As a result, the operating rate is lowered and a separate cleaning cost is incurred. On the other hand, as an alternative to the suction-type filtration concentration apparatus using such a filter cloth, it has been studied to perform filtration concentration using a membrane module such as MF or UF, but the membrane module itself is very expensive. At the same time, chemicals and high-pressure pumps are required to clean the membrane, resulting in high costs.

In this regard, for example, Patent Document 2 discloses a suspension concentration device that forms a thin cake layer on the surface of a filter body by using sludge (suspension) that is a subject of filtration concentration. This suspension concentrating device includes a sludge tank filled with sludge to be filtered and concentrated, a filter body that is disposed near the upper surface of the sludge tank, circulates, and sludge toward the surface of the filter body. Sludge supply means for supplying water, permeated water discharge means for discharging permeated water that has passed through the traveling filter body to the outside of the tank, and means for returning the concentrated sludge to the sludge tank. Then, as a pre-filtration, the amount of the filter body is filtered, a cake thin layer is formed on the filter body as a filter layer for filtration, and the main suspension is suspended in the filter body with the cake thin layer formed Is filtered. According to such a suspension concentrating device, it is possible to prevent clogging while using a relatively coarse and inexpensive filter body without separately pre-coating the surface of the filter body.

However, such a suspension concentration apparatus has the following technical problems. First, it is difficult to efficiently form a cake thin layer as a filtration layer on the surface of the filter body. That is, when the filtration is divided into the preliminary filtration and the main filtration, the cake thin layer is formed by using the sludge that is the object of filtration concentration as it is not only in the main filtration but also in the preliminary filtration. On the other hand, in the traveling filter body, the area used for forming the cake thin layer is limited to only a part of the track on the loop of the traveling filter body. Therefore, it is necessary to reduce the rotational speed of the traveling filter body, and it takes time to form the cake thin layer, which is inefficient. More specifically, since the area used for forming the cake thin layer is limited, it takes time to apply the stock solution over the entire area and form the cake thin layer. Further, when forming the cake thin layer, it is necessary to supply a sufficient amount of the stock solution to the traveling filter body in order to concentrate the solid content in the stock solution in a limited area. Therefore, it is necessary to reduce the rotational speed of the traveling filter body, and it takes time to form a cake thin layer on the entire traveling filter body.

Second, it is difficult to control the thickness of the cake thin layer. More specifically, the traveling filter body travels on the loop track, and a thin cake layer is formed at the front portion of the loop track (preliminary filtration). Furthermore, the activated concentrated sludge trapped by the cake thin layer is accumulated in the rear liquid reservoir (main filtration). On the other hand, at the bottom of the loop trajectory, the suspension is concentrated so that the excess cake thin layer on the filter cloth surface is dropped using the filtrate after the cake thin layer is formed (the solution after the suspension is filtered). The device is configured. Therefore, it is difficult to control the amount and thickness of the cake to be peeled, and the cake thin layer may be peeled more than necessary. On the other hand, it hardly peels off and may peel off at a certain timing. In the former case, it is necessary to operate the traveling filter again at a low speed to form a cake thin layer, but it is difficult to predict when such a situation will occur. Moreover, since the concentration process must be stopped each time, the concentration efficiency is reduced. On the other hand, in the latter case, an excessively thick cake layer is already formed in the liquid reservoir. Therefore, there is a case where the filtrate does not pass through the cake thin layer and cannot be concentrated, and if the cake thin layer is peeled off together at a certain timing, the thickness of the cake layer becomes non-uniform on the entire filter cloth surface, causing variation in filtration capacity. . Furthermore, at the lower part of the loop orbit, it is configured to drop the filtrate after the cake thin layer is formed and drop the excess cake thin layer on the filter cloth surface. First, it will be immersed in between. Therefore, before the outer surface located on the lower side of the cake thin layer is peeled off, it is highly likely that peeling will start between the filter cloth surface and the inner surface located on the upper side of the cake thin layer. The layer itself is difficult to maintain.

Thirdly, since a filter body that circulates and travels is adopted, energy consumption accompanying the drive of the filter body is large, and the drive unit tends to cause a failure. In addition, the maintenance cost is high, and the portion of the main filtration that is substantially filtered as a filter body is limited to a part on the upper side of the trajectory of the filter body.

Further, Patent Document 3 discloses a tank containing a fluid containing a colloidal object to be removed, a first filter immersed in the tank, and a second filter comprising a gel film adsorbed on the surface thereof. And a filter device including the filter device formed by the above. In this apparatus, a gel film made of an object to be removed is used as a filter, and many gaps formed in the filter are used as fluid passages. And the to-be-removed thing which becomes the cause of clogging can be spaced apart from a filter, and it can implement | achieve maintenance of filtration capability. Therefore, the filtration technique described in Patent Document 3 falls into the category of conventionally known “dynamic filtration”.

However, in the filtration device disclosed in Patent Document 3, the fluid as the stock solution to be filtered and the fluid for forming the second filter are the same in that they are colloidal objects to be removed. The concentration of the fluid containing the removal product is the same. Furthermore, the average particle diameter of the removal target contained is also the same. Therefore, even if this filtration device is used, it is not possible to efficiently concentrate sludge having a low concentration of 1% by mass or less generated in a water purification plant or the like as described above in a short time.

Thus, none of Patent Documents 1 to 3 is still sufficient, and further improvements are required.

Japanese Patent No. 4164498 JP 2001-120915 A JP 2004-321997 A

In view of the technical problems described above, the object of the present invention is to efficiently establish a state in which a suspension containing solids that cannot be captured by a filter cloth can be filtered by such a filter cloth. An object of the present invention is to provide a suction filtration concentration method and a suction filtration concentration apparatus that can be formed and filtered without causing clogging. In view of the above technical problems, the object of the present invention is to form a cake thin layer that can easily maintain and control the thickness on the surface of the filter cloth, thereby containing a solid that cannot be captured by the filter cloth. An object of the present invention is to provide a suction filtration concentration method and a suction filtration concentration apparatus capable of filtering a turbid liquid.

Furthermore, in view of the above technical problems, the object of the present invention is to substantially eliminate the need for sludge agitation in a gravity settling tank for sludge (suspension) generated at a water purification plant or the like. An object of the present invention is to provide a suction filtration concentration method and a suction filtration concentration device capable of collecting and treating sludge filtered and concentrated by the filter body together with sludge used as the filter body while being used as a filter body.

Furthermore, in view of the technical problems described above, the object of the present invention is to apply sludge (suspension) generated in a water purification plant or the like to a gravity settling tank, thereby reducing the equipment space and efficiently. Another object of the present invention is to provide a suction filtration concentration method and a suction filtration concentration apparatus capable of performing a concentration treatment for a long time.

[1] A suction-type filtration and concentration method for filtering and concentrating a suspension by a suction method, wherein the suspension is sucked through a filtration chamber formed in a bag-shaped filter cloth. In the suction filtration concentration method, which has a step of allowing water in the filter cloth to pass through the filter cloth while allowing the solid matter in the suspension to adhere to the surface of the filter cloth, the solid content capable of closing the eyes of the filter cloth Selecting a first suspension containing a cake thin layer forming step of forming a cake thin layer on the surface of the filter cloth by filtering and concentrating the first suspension by a suction method, and the first suspension And a filtration concentration step of filtering and concentrating the second suspension having a concentration lower than the concentration of the one suspension through the cake thin layer by a suction method.

[2] The cake thin layer forming step is performed by allowing the first suspension to flow into a filtration and concentration tank and using a filter cloth disposed in the filtration and concentration tank, and filtering the second suspension. The concentration step is a suction filtration concentration method according to [1], wherein the first suspension is discharged from the filtration concentration tank and then the second suspension is allowed to flow into the filtration concentration tank.

[3] The cake thin layer forming step is performed by allowing the first suspension to flow into a filtration and concentration tank and using a filter cloth disposed in the filtration and concentration tank, and filtering the second suspension. In the concentration step, the second suspension is discharged while discharging the first suspension from the filtration concentration tank so that the filter cloth is not exposed from the liquid surface of the first suspension filled in the filtration concentration tank. The suction filtration concentration method according to [1], which is performed by flowing a turbid liquid into the filtration concentration tank.

[4] The peeling step of peeling the concentrated sludge composed of the cake thin layer by the first suspension and the concentrated layer by the second suspension attached to the outer surface of the cake thin layer from the filter cloth is performed by filtration. The suction filtration and concentration method according to any one of [1] to [3], which is performed by pumping water from the inside of the filter cloth in an unconcentrated suspension filled in the concentration tank.

[5] The suction according to [4], further including a step of discharging and storing the separated concentrated suspension from the filtration concentration tank to the outside, and using the stored concentrated suspension as the first suspension. Formula filtration concentration method.

[6] After the cake thin layer forming step, the first suspension is discharged from the filtration concentration tank and stored, and after the peeling step, the first suspension is supplied to the filtration concentration tank. The suction filtration concentration method according to [5], comprising steps.

[7] The step of feeding the lower suspension in the gravity sedimentation tank to the filtration and concentration tank as a first suspension, and the first suspension sent to the liquid are placed inside the filtration and concentration tank. And filtering and concentrating with a suction method using a bag-like filter cloth that forms a filtration chamber inside, forming a cake thin layer by adhering to the outer surface of the filter cloth, and the upper part of the gravity settling tank A step of feeding the suspension as a second suspension to the filtration and concentration tank; a step of filtering and concentrating the second suspension at the top of the gravity settling tank sent through the cake thin layer; and Removing the concentrated sludge adhering to the outer surface of the filter cloth by pumping the peeling medium through the filtration chamber.

[8] A suction type filtration concentration apparatus installed downstream of the gravity sedimentation tank, which is disposed inside the filtration concentration tank and the filtration concentration tank into which the suspension in the gravity sedimentation tank flows. A bag-shaped filter cloth forming a filtration chamber, suction means for sucking the suspension in the filtration and concentration tank through the filtration chamber, and a lower portion of the gravity sedimentation tank and the filtration and concentration tank are connected to each other. 1 sludge supply pipe, a first liquid feeding means for feeding the first suspension settled in the lower part of the gravity sedimentation tank through the first sludge supply pipe to the filtration and concentration tank, an upper part of the gravity sedimentation tank, A second sludge supply pipe for connecting the filtration and concentration tank; a second liquid feeding means for feeding the second suspension at the top of the gravity sedimentation tank to the filtration and concentration tank through the second sludge supply pipe; In the filtration and concentration tank, the concentrated sludge adhering to the surface of the filter cloth is peeled off by the suction means. Having a concentrated sludge separating means for suction type filtering concentrator.

[9] Further, a concentrated sludge storage tank that stores a first suspension having a concentration that can be captured by the filter cloth, and a third sludge supply pipe that connects a lower portion of the filtration and concentration tank and the concentrated sludge storage tank. And a third liquid feeding means for feeding the concentrated sludge separated by the concentrated sludge peeling means and accumulated at the bottom of the filtration and concentration tank through the third sludge supply pipe to the concentrated sludge storage tank, and the concentrated sludge The concentrated sludge stored in the concentrated sludge storage tank through a fourth sludge supply pipe connecting the storage tank and the middle of the first sludge supply pipe, and the fourth sludge supply pipe and the first sludge supply pipe. And a fourth liquid feeding means for feeding the liquid to the filtration / concentration tank.

[10] A gravity sedimentation tank into which a suspension to be filtered and concentrated is passed, and a partition extending in the vertical direction in the gravity sedimentation tank. An opening that communicates between one space of the partitioned gravity settling tank and the other space, a bag-like filter cloth that forms a filtration chamber therein, and the filtration A suction means for sucking the suspension in the one space through the chamber, and further, the second suspension in the upper part in the other space is liquidated to the one space through the upper opening. An upper sludge liquid feeding means for feeding, and a lower sludge liquid feeding means for feeding the lower first suspension in the other space to the one space through the lower opening. A suction type filtration concentration apparatus having

[11] Furthermore, it has a concentrated sludge storage tank that is connected to the downstream side of the gravity settling tank and stores the first suspension in the one space, and the first suspension in the one space is The suction filtration concentration device according to [10], wherein the suction sludge storage tank is supplied to the one space.

[12] Further, a sludge storage tank for storing the second suspension is provided in a lower part of the other space, and the second suspension in the lower part of the other space is removed from the sludge storage tank. The suction filtration concentration apparatus according to [10], which is supplied to one space.

According to the suction filtration concentration method and apparatus according to the present invention, the first suspension containing the solid content having the predetermined particle diameter and the predetermined content is selected according to the size of the filter cloth, and the first When the suspension is filtered and concentrated by the suction method, the yarn that forms the filter cloth is caused by the bridge formation due to the solid content, the intermolecular force between the solid content, or the suction force caused by the rapid flow of fluid between the solids. When the solid content is densely packed in the space between the yarn and the yarn, the filter cloth eyes are closed and a cake thin layer is formed, so even if such solid contents are not necessarily larger than the filter cloth eyes, It is possible to efficiently form a cake thin layer on the surface of the filter cloth. Therefore, even if it is a 2nd suspension which has a density | concentration lower than the density | concentration of a 1st suspension, by utilizing this cake thin layer as a pseudo filter body, a 2nd suspension is made into a cake thin layer. The second suspension can be filtered and concentrated without clogging the filter cloth. From this, sludge having a low concentration of 1% by mass or less generated at a water purification plant or the like can be concentrated efficiently in a short time.

It is a schematic block diagram of the waste water treatment facility which concerns on 1st Embodiment of this invention. It is a schematic front view of the filter plate of the suction filtration concentration apparatus of the wastewater treatment facility according to the first embodiment of the present invention. It is the schematic which shows the state in the bulging about the filter plate of FIG. It is the schematic which shows the state in filtration about the filter plate of FIG. It is the schematic which shows the effect | action of the suction filtration concentration apparatus of the waste water treatment facility which concerns on 1st Embodiment of this invention. It is the schematic which shows the effect | action of the suction filtration concentration apparatus of the waste water treatment facility which concerns on 1st Embodiment of this invention. It is the schematic which shows the suction filtration concentration apparatus of the waste water treatment facility which concerns on 2nd Embodiment of this invention. FIG. 7 is a view similar to FIG. 6 according to a modified embodiment of the present invention. FIG. 7 is a view similar to FIG. 6 according to a modified embodiment of the present invention. FIG. 7 is a view similar to FIG. 6 according to a modified embodiment of the present invention. It is the schematic which shows the experimental method of the suction filtration concentration of sludge. It is a graph of the experimental result which shows the change by the filtration time of the amount of filtrates in low concentration sludge and high concentration sludge. It is a graph which shows the particle size distribution of the solid content contained in concentrated sludge for reference. It is a graph which shows the relation between the amount of filtrate and filtrate time for reference.

Embodiments of the suction filtration concentration method and apparatus according to the present invention will be described in detail below with reference to the drawings, but the present invention is not limited to these embodiments. In addition, below, it demonstrates as an example the case where it applies to a water-purification processing equipment targeting sludge.

[1] Configuration of the suction filtration concentration method of the present invention:
The suction filtration concentration method of the present invention is a suction filtration concentration method in which a suspension is filtered and concentrated by a suction method, and the suspension is sucked through a filtration chamber formed inside a bag-like filter cloth. Thus, in the suction filtration concentration method, the moisture content in the suspension is allowed to pass through the filter cloth while the solid matter in the suspension is adhered to the surface of the filter cloth. A step of selecting a first suspension containing a solid that can close the eyes, and filtering and concentrating the first suspension by a suction method to form a cake thin layer on the surface of the filter cloth. A suction filtration concentration method comprising: a layer formation step; and a filtration concentration step of filtering and concentrating a second suspension having a concentration lower than the concentration of the first suspension through the cake thin layer by a suction method. .

According to the suction type filtration concentration method having the above configuration, the water in the suspension is passed through the filter cloth by suction through the filtration chamber formed inside the bag-like filter cloth, while the suspension It is possible to concentrate the suspension by filtration by adhering the solid matter to the surface of the filter cloth.

Furthermore, once the first suspension containing solids that can be captured by the filter cloth is filtered and concentrated by a suction method, the surface of the filter cloth has an efficiency even if such solids are not necessarily larger than the eyes of the filter cloth. A thin cake layer is formed. Even the second suspension having a concentration lower than that of the first suspension is filtered by this cake layer, and a cake layer is further formed on the filter cloth.

More specifically, in the present invention, the first suspension containing a solid content having a predetermined particle diameter and a predetermined content according to the size of the filter cloth so that the filter cloth can be closed. Selecting a suspension. After passing through the step of selecting the first suspension, it has a cake thin layer forming step of forming a cake thin layer on the surface of the filter cloth by filtering and concentrating the selected first suspension by a suction method. become. Here, the cake thin layer is composed of the yarn and yarn constituting the filter cloth due to the bridge formation due to the solid content, the intermolecular force between the solid content, or the suction force caused by the rapid flow of fluid between the solids. It is formed by solidifying the solid content in the space between the filter cloths and closing the eyes of the filter cloth. Furthermore, it has the filtration concentration stage which carries out filtration concentration of the 2nd suspension which has a density | concentration lower than the density | concentration of the said 1st suspension through the said cake thin layer by a suction system. The filtration concentration step is a step of filtering and concentrating the second suspension through the cake thin layer by a suction method by using the cake thin layer as a pseudo filter body. Here, although the eyes of the filter cloth are closed through the cake thin layer formation stage, this closed state is a blockage that allows the moisture of the second suspension to pass through. Therefore, in the filtration concentration in the filtration concentration step in the present invention, the second suspension can be filtered and concentrated without causing clogging of the filter cloth.

In the present invention, the first suspension contains a solid content capable of closing the filter cloth, but more clearly, the first suspension is “can close the filter cloth. Thus, it contains a solid content having a predetermined particle diameter and a predetermined content according to the size of the filter cloth. Usually, the meaning of “contains a solid content that can close the eyes of the filter cloth” means that the solid content has a particle size larger than that of the filter cloth or the solid content (suspension The concentration) is equal to or higher than a predetermined value.

Further, in the present embodiment, there is a filtration and concentration step of “concentrating the second suspension having a concentration lower than the concentration of the first suspension by suction through the cake thin layer”. This is because, as shown in the particle size distribution measurement diagram of FIG. 12, all of the solid content and the like contained in the suspension that is the stock solution of the first suspension and the second suspension are all sucked in this embodiment. This means that the filtration and concentration treatment can be carried out by the expression filtration and concentration method. That is, as shown in FIG. 12, in the conventional so-called membrane filtration concentration sludge treatment, for example, when using a membrane having an eye size of 10 μm, the particle size in the Y region of 10 μm or more (10 to 100 μm). ). On the other hand, in the conventional so-called cake filtration (filtering is carried out by holding the filter medium on the filter cloth, which means dynamic filtration), the solid content having a particle size (1 to 10 μm) in the X region of 10 μm or less. Was targeted. Therefore, for example, in membrane filtration concentration sludge treatment, when filtering solid content having a particle size in the Y region, or when simultaneously filtering solid content having a particle size in the Y region together with the particle size in the X region. Clogging occurred immediately, and long-time treatment and continuous treatment could not be performed.

Details of the suction filtration concentration method of the present invention will be described together with the suction filtration concentration device of the present invention described below. In the suction filtration concentration method of the present invention, a siphon suction filtration method or a suction filtration method using a suction pump can be adopted. Here, a siphon suction filtration concentration method and apparatus are used. I will explain.

[2] Configuration of the suction filtration concentration apparatus of the present invention:
As shown in FIGS. 1, 2, 3 </ b> A and 3 </ b> B, the suction type filtration concentration apparatus of the present invention is installed on the downstream side of the gravity settling tank 12. The filtration and concentration tank 83 that flows into the filtration and concentration tank 83, the bag-like filter cloth 18 that is disposed inside the filtration and concentration tank 83 and forms the filtration chamber 76 therein, and the suspension in the filtration and concentration tank 83 through the filtration chamber 76. A suction means for sucking turbid liquid, a first sludge supply pipe 80 connecting the lower part of the gravity sedimentation tank 12 and the filtration and concentration tank 83, and a lower part of the gravity sedimentation tank 12 through the first sludge supply pipe 80. A first liquid feeding means 82 for feeding the settled first suspension to the filtration and concentration tank 83; a second sludge supply pipe 90 for connecting the upper part of the gravity sedimentation tank 12 and the filtration and concentration tank 83; A second suspension at the top of the gravity settling tank 12 is passed through the second sludge supply pipe 90. Second liquid feeding means 91 for feeding the liquid to the filtration and concentration tank 83, and concentrated sludge peeling for peeling the concentrated sludge adhered to the surface of the filter cloth 18 by the suction means in the filtration and concentration tank 83. And a suction filtration and concentration device 10 having a means.

According to the suction type filtration concentration apparatus having the above-described configuration, the suspension is sucked through the filtration chamber formed inside the bag-shaped filter cloth in the filtration concentration tank, thereby filtering the water in the suspension. The suspension can be filtered and concentrated by allowing the solids in the suspension to adhere to the surface of the filter cloth while passing through the cloth.

Specifically, in the present embodiment, among the sludge (suspension) filled in the gravity sedimentation tank, the high-concentration sludge (first suspension) settled in the lower part of the gravity sedimentation tank is used. The liquid is fed to the filtration and concentration tank through the first sludge supply pipe by one liquid feeding means. A thin slurry layer is formed on the surface of the filter cloth by adhering the liquid-concentrated sludge (first suspension) to the surface of the filter cloth by suction means. Further, in this state, out of the sludge (suspension) filled in the gravity sedimentation tank, the sludge having a low concentration (second suspension) in the upper part of the gravity sedimentation tank is secondly fed by the second liquid feeding means. Liquid is sent to the filtration and concentration tank through the sludge supply pipe. The low-concentration sludge (second suspension) sent by liquid can be filtered and concentrated by sucking it through the filter cloth and cake thin layer by suction means. Along with this, a high-concentration sludge that forms a cake thin layer attached to the surface of the filter cloth (first suspension) and a low-concentration sludge that adheres to the surface of the cake thin layer (second suspension) The concentrated sludge can be separated from the surface of the filter cloth at once by the concentration peeling means and recovered.

In particular, when suction filtration concentration is performed on activated sludge generated at a sewage treatment plant or the like, the activated sludge having a lower moisture content and a higher concentration tends to have a higher content of fibrous coarse suspended solids contained in the sludge. is there. If sludge having such a high concentration is used, it becomes possible to efficiently form a cake thin layer on the surface of the filter cloth without causing clogging of the filter cloth. At the same time, both the activated sludge with low shape-retaining property and the activated sludge with high concentration that forms a cake thin layer with high shape-retaining properties can be obtained by increasing the suction pressure and performing suction filtration. As activated sludge having a low concentration adhering to the surface of the layer, it is possible to catch it on the surface of the filter cloth at one time and further peel it off from the surface and collect it.

(Purified water treatment equipment)
Specifically, as shown in FIG. 1, the water purification treatment facility 1 includes a water purification tank 2 for separating the raw water A into purified water B and sludge C, and a gravity settling tank 12 that receives the separated sludge C. The suction-type filtration concentration device 10 for filtering and concentrating the sludge in the gravity sedimentation tank 12 by a suction method and the dehydrator 3 for dewatering the sludge filtered and concentrated.

(Water purification tank and sludge (suspension))
The water purification tank 2 may be a conventionally known one, and receives the raw water A and separates the raw water A into purified water B and sludge C by adding, for example, a flocculant into the water purification tank 2. For this reason, it can be said that the water purification tank 2 is also a coagulation sedimentation tank. Further, the separated purified water B is further processed on the downstream side, and is used as drinking water, for example. On the other hand, as will be described below, the separated sludge (suspension) C is gradually concentrated on the downstream side and finally disposed.

(Gravity sedimentation tank)
The gravity sedimentation tank 12 is provided separately from the water purification tank 2. The gravity sedimentation tank 12 is a container having a bottomed circular cross section. The sludge (first suspension) having a high concentration is received at the bottom of the tank by receiving sludge inside and allowing it to settle naturally by the action of gravity. It is trying to accumulate. Further, the gravity settling tank 12 is provided with a conventionally known stirrer 4 in the gravity settling tank, and the vertical axis of the stirrer 4 is rotated by the motor 5 so that the sludge in the tank is stirred. Thus, by providing the stirrer 4 and the like, the sludge (first suspension) settled on the bottom of the gravity settling tank 12 can be scraped and collected and discharged.

(Second suspension, second sludge supply pipe and second liquid feeding means)
In addition, one end of a sludge supply pipe 24 for supplying sludge into the gravity settling tank 12 communicates with the side wall 22 of the gravity settling tank 12, and through a sludge supply valve 26 provided in the middle of the sludge supply pipe 24, A sludge supply pump 28 is connected. Thereby, the sludge supply valve 26 is opened and the sludge supply pump 28 is operated to supply the sludge from the water purification tank 2 into the gravity settling tank 12. Furthermore, one end of a second sludge supply pipe 90 is connected to the upper part of the gravity settling tank 12. The other end of the second sludge supply pipe 90 is disposed so as to face an upper opening of a filtration and concentration tank 83 to be described later via a pump 91 as a second liquid feeding means. As a result, the sludge having a low concentration (second suspension) before being concentrated by sedimentation in the gravity sedimentation tank 12 is directly supplied to the filtration and concentration tank 83 through the second sludge supply pipe 90. For example, the suction filtration concentration method of the present invention corresponds to the step of selecting a second suspension having a concentration lower than that of the first suspension.

Further, one end of a supernatant liquid discharge pipe 21 that discharges the supernatant liquid in the gravity settling tank 12 is connected to the side wall 22 of the gravity settling tank 12 so as to communicate therewith. A supernatant liquid discharge valve 23 is provided in the middle of the supernatant liquid discharge pipe 21. Further, a supernatant liquid discharge pump 25 is connected via the supernatant liquid discharge valve 23. Then, by opening the supernatant liquid discharge valve 23 and operating the supernatant liquid discharge pump 25, the supernatant liquid is discharged from the gravity settling tank 12 and returned to the upstream side of the water purification tank 2. As a modification of the second sludge supply pipe described above, the one end connected to the upper part of the gravity settling tank 12 is connected to the sludge supply pipe 24 to constitute the second sludge supply pipe 90, and the sludge supply The pump 28 may be configured as a second liquid feeding means (not shown). As a result, the suspension can be directly fed from the water purification tank 2 to the filtration and concentration tank 83 without going through the gravity settling tank 12. The upper sludge in the gravity sedimentation tank 12 is a supernatant liquid before sedimentation or after sedimentation and does not change the concentration of sludge (suspension) before flowing into the gravity sedimentation tank 12 or settles in the gravity sedimentation tank 12. Since the concentration is lower than the sludge (first suspension), it can be said that using this as the second suspension is also a preferable mode.

(First suspension selection stage, first suspension, first sludge supply pipe, and first liquid feeding means)
Furthermore, one end of a first sludge supply pipe 80 that connects a lower part of the gravity sedimentation tank 12 and a filtration and concentration tank 83 described later is connected to the bottom of the gravity sedimentation tank 12. Further, a first sludge supply pump 82 as a first liquid feeding means is connected via a first sludge supply valve 81 provided in the middle of the first sludge supply pipe 80. Thereby, the sludge (first suspension) settled in the lower part of the gravity sedimentation tank 12 through the first sludge supply pipe 80 is sent to the filtration and concentration tank 83. In addition, the processing process demonstrated as mentioned above is equivalent to the step which selects the 1st suspension containing solid content which can block | close the filter cloth in the suction type filtration concentration method of this invention, for example. .

(Schematic configuration of suction filtration and concentration device)
As shown in FIG. 1 and FIG. 2, the suction type filtration concentration apparatus 10 includes a filtration concentration tank 83 that stores sludge (suspension) that is a target for filtration concentration, and a filter plate disposed in the filtration concentration tank 83. 14, a suction part 16 that is a suction means for sucking sludge (suspension), and a concentrated sludge that peels off the concentrated sludge attached to the outer surface of the filter cloth 18 provided on the filter plate 14 by the suction part 16. It consists of the peeling part 20 and the concentrated sludge discharge part 123 which discharge | releases the concentrated sludge of the cake-like piece which peeled by the concentrated sludge peeling part 20 and accumulated on the bottom of the filtration concentration tank 83.

(Filtration concentration tank and concentrated sludge storage tank)
The filtration concentration tank 83 is a container having a bottomed rectangular cross section, and has a volume capable of installing a filter plate 14 to be described later. An upper opening of the filtration and concentration tank 83 is installed so that the other end of the first sludge supply pipe 80 faces. Then, the sludge (first suspension) settled in the lower portion of the gravity sedimentation tank 12 through the first sludge supply pipe 80 is supplied from the upper opening of the filtration concentration tank 83 to the inside of the filtration concentration tank 83. . On the other hand, one end of a first concentrated sludge discharge pipe 84 is connected to the bottom of the filtration and concentration tank 83. The first concentrated sludge discharge pipe 84 is connected to the concentrated sludge storage tank 86 via the first concentrated sludge discharge pump 85. Further, the first concentrated sludge discharge pipe 84 branches downstream of the first concentrated sludge discharge pump 85 and is connected to the gravity settling tank 12 as an unconcentrated sludge discharge pipe 119, and both are switched by

valves

150 and 151. Yes. One end of a second concentrated sludge discharge pipe 87 is connected to the concentrated sludge storage tank 86, and the second concentrated sludge discharge pipe 87 is provided in the middle of the first sludge supply pipe 80 via a second concentrated sludge discharge pump 88. It is connected. Here, the non-concentrated sludge is sludge existing around the filter cloth 18 in the filtration concentration layer 83, and the first suspension and the second suspension are not considered.

As described above, the concentrated sludge that has been filtered and concentrated by the filter plate 14 and separated by the filter plate 14 and accumulated at the bottom of the filter and concentration tank 83 is discharged by the first concentrated sludge discharge pump 85. The concentrated sludge is sent to the concentrated sludge storage tank 86 through the pipe 84 and stored in the concentrated sludge storage tank 86, and independently, the concentrated sludge stored in the concentrated sludge storage tank 86 is the second concentrated sludge. A discharge pump 88 is sent from the concentrated sludge storage tank 86 to the first sludge supply pipe 80 through the second concentrated sludge discharge pipe 87, and is supplied to the filtration and concentration tank 83 through the first sludge supply pipe 80.

The first concentrated sludge discharge pipe 84 is branched and connected to the gravity settling tank 12 as an unconcentrated sludge discharge pipe 119 in order to continuously concentrate sludge (suspension). is there. That is, when the sludge (suspension) is continuously concentrated, the unconcentrated sludge in the filtration and concentration tank 83 is returned to the gravity settling tank 12 through the unconcentrated sludge discharge pipe 119, and then the filtration and concentration tank 83. The first sludge is fed to the cake, and a cake thin layer is formed as a pseudo filter, and the concentration process is continuously performed. After this processing step, a concentrated sludge peeling process for peeling the cake layer is performed by a concentrated sludge peeling unit described later. The above-described processing step is performed, for example, in the suction filtration concentration method of the present invention, in which a cake thin layer is formed on the surface of the filter cloth by filtering and concentrating the first suspension by a suction method. Corresponds to the formation stage.

(Suction unit / suction means)
As shown in FIGS. 1 and 2, the filtration plate 14 is connected to an inverted U-shaped distribution pipe 34 at an upper portion thereof, and the distribution pipe 34 extends vertically downward outside the filtration concentration tank 83 and is in the middle. A filtrate discharge valve 40 is provided. The lower end of the distribution pipe 34 is installed so as to face the filtrate reservoir 114. Further, the filtrate reservoir 114 is configured to return the filtrate to the upstream side of the water purification tank 2 through a filtrate return pipe 89 provided with a filtrate return pump 116 on the way. Thereby, the filtrate filtered in the filtration concentration tank 83 is discharged out of the filtration concentration tank 83 using the principle of siphon. Independently of this, the filtrate stored in the filtrate reservoir 114 is sent to the upstream of the water purification tank 2 through the filtrate return pipe 89 by the filtrate return pump 116 and flows into the water purification tank 2 again. .

Furthermore, a suction pipe 31 is branched and connected to the distribution pipe 34, and a vacuum pump 35 is connected to the suction pipe 31 via a suction valve 33 provided in the middle. Thus, by operating the vacuum pump 35 with the suction valve 33 open, the liquid to be processed in the filtration and concentration tank 83 is sucked into the distribution pipe 34, and the distribution pipe is utilized using the principle of siphon. Through 34, preparations for discharging the filtrate to the outside can be made.

This siphon suction pressure is determined according to the level difference between the lower end and the top of the distribution pipe 34. However, when the suction filtration concentration apparatus 10 is practically used, it is preferably 0.02 MPa to 0.08 MPa. By continuously sucking the sludge (suspension) in the filtration and concentration tank 83 under such a relatively low suction pressure, the concentrated sludge can adhere to the outer surface of the filter cloth 18. At that time, even if the concentrated sludge is peeled off from the filter cloth 18 by the concentrated sludge peeling unit 20 described later in the unconcentrated sludge (in the suspension) in the filtration and concentration tank 83, it is kept as a cake-like piece. It is possible to secure an adhesive force that can maintain the shape.

(Concentrated sludge stripping part)
The concentrated sludge stripping section 20 is generally composed of a distribution pipe 34, a water inflow pipe 42, a water inflow valve 44, and a liquid feed pump 46. Then, the concentrated sludge stripping unit 20 pumps the stripping medium from the inside of the filter cloth 18, so that the cake thin layer by the first suspension and the cake thin layer attached to the outer surface of the cake thin layer are formed. The stage which peels the concentrated sludge which consists of a concentrated layer by two suspensions from a filter cloth will be performed.

Specifically, as shown in FIGS. 2, 3A, and 3B, one end of a water inflow pipe 42 is connected to the distribution pipe 34 through a water inflow valve 44 provided in the middle thereof. It is connected to the liquid feed pump 46. Therefore, when the liquid feed pump 46 is operated with the water inflow valve 44 opened, water is supplied through the water inflow pipe 42 and the distribution pipe 34 to the filtration chamber 76 (described later) formed inside the filter plate 14. Is done. The supplied water causes the filter cloth 18 to bulge, and the concentrated sludge is peeled off from the filter cloth 18. In this case, the peeling pressure and / or the peeling time is adjusted by using the liquid feed pump 46 and the water inflow valve 44 so that the concentrated sludge adhering to the surface of the filter cloth 18 is peeled off from the filter cloth 18 as a cake-like piece. It is preferred that

In this way, by feeding the release medium from the inside of the filter cloth, the cake thin layer by the first suspension and the concentrated layer by the second suspension adhering to the outer surface of the cake thin layer are filtered. When peeling from the cloth, the concentrated layer held on the surface of the filter cloth until the peeling medium is pumped can be peeled at once, and the cake thin layer by the first suspension is peeled off every time it is peeled off. Since the thickness of the cake thin layer is mainly determined by the combination of the concentration of the first suspension and the filtration time of the first suspension, it is easy to control the thickness of the cake thin layer. It becomes.

Furthermore, the peeling step is preferably performed by pumping water from the inside of the filter cloth in an unconcentrated suspension filled in the filtration concentration tank. About this point, when this inventor makes filtration concentration object sludge, even if it peels the concentration sludge adhering to the filter cloth in unconcentrated sludge (in suspension), concentrated sludge is in unconcentrated sludge ( In order to maintain the shape retention as a cake-like piece without being dissolved in the suspension), it is important that the water as the peeling medium is not intermittently pumped continuously over a predetermined time. I have confirmed.

Here, “shape retention” refers to the degree to which the concentrated sludge attached to the filter cloth maintains the plate-like form (size, thickness, etc.) at the time of attachment. For example, when the concentrated sludge at the time of peeling peels off as a large lump and the shape does not collapse so much at a later stage, it can be determined that the shape retention is good. On the other hand, when it becomes a small lump at the time of peeling, a lump after peeling breaks down into a small lump, or melts and becomes extremely small, it can be said that the shape retention is poor.

In addition, it is also preferable to use the filtrate collected in the filtration chamber 76 by filtering the sludge (suspension) with the filter cloth 18 as the water as the stripping medium for the concentrated sludge. However, it is not limited to this. Further, the “non-concentrated suspension” here is synonymous with the “non-concentrated suspension” described above.

(Filter plate)
As shown in FIG. 2, the filter plate 14 includes a filter frame 48, a support plate 50 disposed inside the filter frame 48, and a filter cloth 18 having a bag shape so as to accommodate the support plate 50 therein. , And a plurality of coil springs 54 provided between the filter frame 48 and the support plate 50. The filter frame 48 has a hollow rectangular shape and has both

sides

60 and 62 between the upper side 56, the lower side 58, and the upper and lower sides. The filter plate 14 is suspended and supported from the inner side surface of the filtration concentration tank 83 by both end portions of the upper side 56.

(Support plate)
The support plate 50 is made of a net or mesh net, has a rectangular shape, and an infinite number of small openings are provided in the support plate 50. An uneven portion (not shown) extending in the vertical direction is provided on the surface of the support plate 50, and a filtrate extending in the vertical direction of the support plate 50 is provided between the concave portion of the support plate 50 and the inner surface of the filter cloth 18. A plurality of the flow paths are formed. The support plate 50 is made of resin, and specifically, for example, made of polyethylene or EVA resin is preferable. By adopting such a material, when the filter cloth 18 is immersed in sludge for a long time or when the filter cloth 18 is expanded, the tension acting on the filter plate 14 by the coil spring 54 described later is always maintained. It becomes possible to make it substantially constant.

(Filter cloth)
The filter cloth 18 is preferably made of chemical fiber or metal, and is particularly preferably nylon, polyester, polypropylene or the like. For example, the filter cloth 18 is formed by overlapping a pair of rectangular cloth bodies to sew the peripheral edges, or by bending a single rectangular cloth body so that opposing edges overlap each other, and the peripheral edges are separated. It is good to form in a bag shape by sewing. A plurality of eyelets 78 are provided around the filter cloth 18, and one end of the coil spring 54 is hooked to the eyelets 78.

The filter cloth 18 is provided with a plurality of seams 74 extending in the vertical direction of the filtration and concentration tank 83, and the filter cloth 18 is stitched together with the support plate 50 accommodated therein by each seam 74. . As shown in FIGS. 2 and 3, a filtration chamber 76 partitioned by adjacent seams 74 is formed inside the filter cloth 18. A horizontal pipe 15 provided at an upper portion in the filter cloth 18 is connected to the tip of the distribution pipe 34. Further, the horizontal pipe 15 is provided with an outflow hole (not shown) communicating with each filtration chamber 76 downward, and water as a peeling medium passes through the outflow holes provided in the distribution pipe 34 and the horizontal pipe 15. In addition, the pressure is fed into each filtration chamber 76.

In particular, when the length of the filter cloth 18 in the vertical direction is long and the difference in the hydraulic pressure due to the sludge in the filtration and concentration tank 83 is large, the water supply pipes are set at different levels in the height direction of the filter cloth 18. It is also preferable to provide it. When water as a peeling medium is pumped and the concentrated sludge adhering to the filter cloth 18 is peeled off, the hydraulic pressure due to the sludge (suspension) in the filtration concentration tank 83 loaded on the filter cloth 18 fluctuates in the height direction. As a result, it is possible to prevent a situation in which the concentrated sludge cannot be uniformly peeled in the height direction of the filter cloth 18 and is difficult to peel as cake pieces. In this case, for example, water having a relatively low water pressure is sent to the upper part of the filter cloth 18 having a low hydraulic pressure, and water having a relatively high water pressure is sent to the lower part of the filter cloth 18 having a high hydraulic pressure. Good.

(coil spring)
As shown in FIG. 2, the plurality of coil springs 54 are between the side 60 of the filter frame 48 and the side 61 of the filter cloth 18, and between the side 62 of the filter frame 48 and the side 63 of the filter cloth 18. The filter frame 48 is disposed between the lower side 58 of the filter frame 48 and the lower side 59 of the filter cloth 18 and between the upper side 56 of the filter frame 48 and the upper side 57 of the filter cloth 18. What is necessary is just to set suitably the space | interval of the adjacent coil springs 54 each installed in the both sides and upper and lower sides of the filter frame 48 according to the magnitude | size of the filter cloth 18, the amount of concentrated sludge adhering. More specifically, one end of each coil spring 54 is hooked to the eyelet 78 of the filter cloth 18, and the other end is fixed to the side sides 60 and 62, the upper side 56 and the lower side 58 of the filter frame 48. Yes. The plurality of coil springs 54 are preferably made of SUS from the viewpoint of corrosion resistance, and several tens of the coil springs 54 are arranged around the periphery of the filter plate 14. Instead, it is better to use standard products.

(Concentrated sludge discharge part)
The concentrated sludge discharge part in this embodiment is provided in order to discharge the peeled concentrated sludge to the outside of the filtration concentration tank 83. Specifically, as shown in FIG. 1, the concentrated sludge discharge part 123 is generally constituted by a concentrated sludge valve 118 and a third concentrated sludge discharge pipe 93. By opening the concentrated sludge valve 118, the concentrated sludge is fed from the filtration concentration tank 83 to the dehydrator 3 through the third concentrated sludge discharge pipe 93 connected to the dehydrator 3.

(Dehydrator)
The dehydrator 3 may be a conventionally known one such as a belt press, a belt filter, a centrifugal dehydrator, or a rotary press, and is appropriately selected in consideration of the concentration of concentrated sludge sent to the dehydrator 3, the cohesiveness of sludge, and the like. do it. The dehydrator 3 is connected to the lower part of the filtration and concentration tank 83 via the third concentrated sludge discharge pipe 93, and the concentrated sludge accumulated in the lower part of the filtration and concentration tank 83 is transferred to the dehydrator 3 through the third concentrated sludge discharge pipe 93. I am trying to supply. A dryer may be used as an alternative to the dehydrator 3.

(Operation method of water purification equipment)
About the water purification processing equipment 1 which has the structure demonstrated so far, the effect | action including a driving | operation method is demonstrated below. The raw water A is introduced into the water purification tank 2, and the flocculant is added in the water purification tank 2. Thereby, the raw water A is separated into the purified water B and the sludge C, and the purified water B is separately processed on the downstream side. Next, the sludge supply valve 26 is opened and the sludge supply pump 28 is operated, whereby the separated sludge (suspension) is introduced into the gravity settling tank 12 through the sludge supply pipe 24.

Next, the first sludge supply valve 81 is opened and the first sludge supply pump 82 is operated. Thereby, the first sludge (first suspension) having a relatively high concentration (for example, 1% by mass) accumulated at the bottom of the gravity settling tank 12 is passed through the first sludge supply pipe 80 to the level at the top of the filter plate 14. Until it is introduced into the filtration and concentration tank 83.

In this case, the concentrated sludge stored in the concentrated sludge storage tank 86 is sent to the first sludge supply pipe 80 through the second concentrated sludge discharge pipe 87 by the second concentrated sludge discharge pump 88, and the first sludge from the gravity settling tank 12 is sent. One sludge (first suspension) may be merged and supplied to the filtration and concentration tank 83 as first sludge (first suspension).

More preferably, a concentrated sludge storage tank that stores a first suspension having a concentration that can be captured by the filter cloth, and a third sludge supply pipe that connects the lower part of the filtration and concentration tank and the concentrated sludge storage tank. A third liquid feeding means for feeding the concentrated sludge separated by the concentrated sludge peeling means and accumulated at the bottom of the filtration and concentration tank to the concentrated sludge storage tank through the third sludge supply pipe; and the concentrated sludge storage The concentrated sludge stored in the sludge storage tank is passed through the fourth sludge supply pipe connecting the tank and the middle of the first sludge supply pipe, the fourth sludge supply pipe and the first sludge supply pipe. And a fourth liquid feeding means for feeding the liquid to the filtration and concentration tank. By being configured in this way, the concentrated sludge having a higher concentration than the first suspension and the first suspension can be mixed to adjust the concentration as the first suspension having a new concentration. The cake thin tank can be formed in a short time, and continuous sludge treatment can be reliably performed.

Specifically, as shown in FIG. 1 and FIG. 2, a concentrated sludge storage tank 86 for storing a first suspension having a concentration that can be captured by the filter cloth 18, a lower part of the filtration and concentration tank 83, and a concentrated sludge. A first concentrated sludge discharge pipe 84 is provided as a third sludge supply pipe that connects to the storage tank 86. Further, the concentrated sludge is fed to the concentrated sludge storage tank 86 through the first concentrated sludge discharge pipe 84 as the third sludge supply pipe. Here, this concentrated sludge is peeled off by the concentrated sludge peeling part 20 configured as a concentrated sludge peeling means. The peeled concentrated sludge collects at the bottom of the filtration and concentration tank 83. Thus, the concentrated sludge is sent to the concentrated sludge storage tank 86 by the first concentrated sludge discharge pump 85 and the concentrated sludge discharge valve 120 as the third liquid feeding means. Furthermore, the 2nd concentrated sludge discharge pipe 87 as a 4th sludge supply pipe which connects the concentrated sludge storage tank 86 and the middle of the 1st sludge supply pipe 80 is provided. Then, the concentrated sludge stored in the concentrated sludge storage tank 86 is sent to the filtration and concentration tank 83 through the second concentrated sludge discharge pipe 87 and the first sludge supply pipe 80 as the fourth sludge supply pipe. A second concentrated sludge discharge pump 88 is provided as a four-liquid feeding means. An example of the suction type filtration concentrator configured as described above can be given. However, it is not limited to this.

Next, preparation for filtering and concentrating the first sludge (first suspension) in the filtration and concentration tank 83 by a siphon method is performed. More specifically, as shown in FIGS. 1 to 3A and 3B, the suction valve 33 is opened and the vacuum pump 35 is operated. Thereby, the liquid (filtrate) in the filter cloth 18 is sucked into the distribution pipe 34. That is, according to the level difference between the end of the distribution pipe 34 on the filter plate 14 side and the top, the filtrate introduced into the filtration chamber 76 by siphon action is discharged outside through the distribution pipe 34 and stored in the filtrate. It is stored in 114 and returned to the upstream side of the water purification tank 2 through the filtrate return pipe 89 by the filtrate return pump 116.

Next, the first sludge (first suspension) in the filtration and concentration tank 83 is sucked toward the outer surface of the filter cloth 18 by the siphon principle. At that time, moisture in the first sludge (first suspension) passes through the filter cloth 18 and is guided to the filtration chamber 76 in the filter cloth 18 as a filtrate. In this way, the first sludge (first suspension) is dehydrated and concentrated and adheres to the outer surface of the filter cloth 18 to form a cake thin layer. Even if it is continuous suction at a relatively low pressure by a siphon type, or even if the concentrated sludge adhering to the outer surface of the filter cloth 18 is peeled off in the unconcentrated sludge, the shape retaining property can be maintained as a cake-like piece. The first sludge (first suspension) can be attached to the outer surface of the filter cloth 18 in the form of a dehydrated and concentrated cake thin layer with the adhesive force of

Note that tension is always applied to the filter plate 14 by a coil spring 54 from the periphery thereof. Therefore, the filter plate 14 is maintained in an immobile stationary state. Thereby, as will be described later, the concentrated sludge adhering to the outer surface of the filter cloth 18 is prevented from peeling off from the outer surface of the filter cloth 18 due to the filter plate 14 flapping or wobbling. Is possible.

As shown in FIG. 4, the first sludge (first suspension) dehydrated and concentrated adheres to the outer surface of the filter cloth by such suction filtration, thereby forming the cake thin layer K. Is done. The supply of the first sludge (first suspension) is stopped when the filtrate becomes almost transparent based on the turbidity of the filtrate. Alternatively, since the flow rate of the filtrate decreases with the formation of the cake thin layer, the supply of the first sludge (first suspension) may be stopped based on the flow rate of the filtrate.

In this embodiment, the filter plate 14 is not a traveling type as found in the prior art but a fixed type. Further, since the entire filter cloth 18 is filled with the stock solution (suspension), the formation of the cake thin layer K on the entire filter plate 14 is started at the same time. Therefore, the formation time of the cake thin layer K is greatly shortened, and it is not necessary to move the filter plate for forming the cake thin layer. As a result, energy can be saved.

Next, as shown in FIG. 1, the concentrated sludge discharge valve 120 is opened and the concentrated sludge valve 118 is closed. In this manner, the first sludge (first suspension) in the filtration and concentration tank 83 is sent to the concentrated sludge storage tank 86 through the first concentrated sludge discharge pipe 84 by the first concentrated sludge discharge pump 85.

In addition, the cake thin layer forming step is performed by using the filter cloth 18 disposed in the filtration concentration tank 83 by allowing the first suspension to flow into the filtration concentration tank 83, and performing the filtration concentration step of the second suspension. Is preferably performed by discharging the first suspension from the filtration concentration tank 83 and then allowing the second suspension to flow into the filtration concentration tank 83. This is because versatility is improved. Even when the second suspension is allowed to flow into the filtration and concentration tank 83 after the first suspension is discharged from the filtration and concentration tank 83 in this way, the first sludge ( The first suspension) may be sent to the concentrated sludge storage tank 86 through the first concentrated sludge discharge pipe 84 by the first concentrated sludge discharge pump 85.

Next, the second sludge (second suspension) is introduced into the filtration and concentration tank 83 from the upper opening of the filtration and concentration tank 83 through the second sludge supply pipe 90 from the upper part of the gravity settling tank 12 or the water purification tank 2. .

As another form, the cake thin layer forming step is performed by using the filter cloth 18 disposed in the filtration concentration tank 83 by allowing the first suspension to flow into the filtration concentration tank 83 and the second suspension. In the filtration and concentration stage of the turbid liquid, the first sludge (first suspension) is stored from the bottom of the filtration and concentration tank 83 while adjusting the liquid level in the filtration and concentration tank 83 so that the filter plate 14 is not exposed. It is also preferable to supply the second sludge (second suspension) from the upper part of the gravity sedimentation tank 12 or the purified water tank 2 from the upper part of the filtration and concentration tank 83 while returning to the tank 86. As a result, the discharge of the first sludge (first suspension) settled in the filtration and concentration tank 83 and the supply of the second sludge (second suspension) having a low concentration proceed in parallel. The suction filtration is not interrupted by the replacement work of the first and second suspensions in the concentration tank 83, and continuous filtration can be performed. Therefore, the time can be shortened.

That is, as shown in FIGS. 3 and 5, the water in the sludge (suspension) is allowed to pass through the filter cloth 18 by suction through a filtration chamber 76 formed in the bag-shaped filter cloth 18. On the other hand, the second sludge (second suspension) can be filtered and concentrated in a suction manner by attaching the solid matter in the second sludge (second suspension) to the surface of the filter cloth 18. .

By doing in this way, even if it is the 2nd sludge (2nd suspension) which has a density | concentration lower than a 1st sludge (1st suspension), utilizing a cake thin layer as a pseudo filter body. It is possible to concentrate by filtration. That is, a thin cake layer is efficiently formed on the surface of the filter cloth 18 by first filtering and concentrating the first sludge (first suspension) having a concentration that can be captured by the filter cloth 18 by a suction method. The By using this cake thin layer, the second sludge (second suspension) can be filtered and concentrated through the cake thin layer by a suction method. Moreover, the second sludge (second suspension) can be filtered and concentrated without clogging the filter cloth 18. In the suction filtration concentration method of the present invention, the processing step described above is performed by sucking a second suspension having a concentration lower than that of the first suspension through the cake thin layer. This corresponds to the filtration concentration step of concentration by filtration.

In particular, the solid content contained in the second sludge (in the second suspension) can pass through the eyes of the filter cloth 18 and the second sludge (second suspension) cannot be captured by the filter cloth 18. Even if it has the density | concentration of 2nd, the 2nd sludge (2nd suspension) can be suction-filtered by utilizing the cake thin layer formed with a 1st sludge (1st suspension) as a filter body. . That is, the water contained in the second suspension is collected in the filtration chamber 76 as a filtrate, while the solids contained in the second suspension can be attached as concentrated sludge to the surface of the cake thin layer. It is.

More preferably, the second suspension has a concentration that cannot be captured by the filter cloth. Even the second suspension having a concentration that cannot be captured by the filter cloth can be filtered through the cake thin layer of the first suspension as described above. Two suspensions having different concentrations, different amounts of solids, different particle sizes, and the like are preferable because they can be filtered and concentrated at the same time.

Furthermore, it is preferable that the start of the supply of the second suspension into the filtration and concentration tank is determined by the turbidity of the filtrate of the first suspension. When the supply of the second sludge (second suspension) is started when the filtrate becomes transparent based on the turbidity of the first suspension, a desired cake thin film is formed on the filter cloth. Since the layer is formed, sufficient filtration and concentration treatment can be performed.

In addition, it is preferable that the start of the supply of the second suspension into the filtration and concentration tank is determined by the flow rate of the filtrate of the first suspension. Since the flow rate of the filtrate decreases with the formation of the cake thin layer, the supply of the second sludge (second suspension) may be started based on the flow rate of the filtrate.

(Peeling process)
Next, the filter cloth 18 is expanded to peel the concentrated sludge adhering to the filter cloth 18 (the first sludge cake thin layer and the second sludge concentrated sludge adhering to the surface of the cake thin layer). More specifically, the water inflow valve 44 is opened, and water is pumped from the liquid feed pump 46 into the filtration chamber 76 of the filter plate 14 through the water inflow pipe 42, the distribution pipe 34 and the horizontal pipe 15. That is, after being concentrated by filtration, water is continuously pumped from the side opposite to the surface to which the concentrated sludge is adhered in the unconcentrated sludge toward the filter cloth 18 for a predetermined time. At that time, the pumped water tends to flow into the unconcentrated sludge through the countless pores of the filter cloth 18. On the other hand, the concentrated sludge adheres to the entire outer surface of the filter cloth 18 and closes countless pores of the filter cloth 18. Further, the liquid pressure of the unconcentrated sludge is uniformly applied to the outer surface of the filter cloth 18 to which the concentrated sludge has adhered. For this reason, at least until the hydraulic pressure of the unconcentrated sludge is overcome, the water pressure of the pumped water in the filtration chamber 76 presses the concentrated sludge adhering to the surface of the filter cloth 18 into the unconcentrated sludge. Become. That is, the concentrated sludge is not peeled off from the surface of the filter cloth 18 at least until the liquid pressure of the unconcentrated sludge is overcome. Therefore, the pressure of the pressure-feeding water in the filtration chamber 76 increases, and the filter cloth 18 swells with it (see FIG. 3A).

Here, since the pumped water is liquid water, it has an incompressible property compared to a gas such as air. Therefore, it is possible to prevent a situation caused by the conventional separation by air in the atmosphere. That is, in the case of conventional pneumatic feeding, the concentrated sludge adhering to the surface of the filter cloth 18 from the filter cloth 18 near the portion is partially treated due to a local pressure increase in the filtration chamber 76. It is pressed toward the liquid (in the suspension). It is possible to prevent the situation where the pressed concentrated sludge is peeled off from the surface of the filter cloth and the air continues to flow out only from the open pores. In other words, in the present invention, the concentrated sludge adhering to the surface of the filter cloth is removed over the entire filter cloth when the pressure of the pumped water reaches a predetermined pressure uniformly in the filter chamber 76. It is possible to press toward the liquid to be treated at the same time. Therefore, it becomes possible to peel the concentrated sludge uniformly from the surface of the filter cloth in the circumferential direction.

In particular, in the present embodiment, the surface of the filter cloth 18 has a concentrated layer (cake thin layer) of the first sludge (first suspension) and a concentrated layer of the second sludge (second suspension). Laminated laminated sludge will adhere. However, the concentrated sludge in which the concentrated layer (cake thin layer) by the first sludge (first suspension) and the concentrated layer by the second sludge (second suspension) are laminated differs from the case of the precoat. The same kind of sludge (suspension) is laminated and adhered. However, when the concentrated sludge is peeled off from the filter cloth by using pump water, the concentrated layer (cake thin layer) by the first sludge (first suspension) and the concentrated by the second sludge (second suspension). There is little risk of peeling off the layers separately.

Preferably, the first suspension and the second suspension are supplied from the same suspension source, the first suspension is supplied from the bottom of the suspension source, and the second suspension is suspended. It is supplied from the upper part of the turbid liquid source. The first suspension having a high concentration is settled at the lower part in the gravity sedimentation layer in which the same suspension source is stored. On the other hand, the second suspension having a low concentration accumulates in the upper part of the gravity sedimentation layer. Therefore, by adopting the configuration as described above, the suspension can be easily selected and supplied according to the processing step.

Furthermore, the concentrated sludge adhering to the outer surface of the filter cloth 18 in unconcentrated sludge (in suspension) may be peeled off. Thereby, concentrated sludge becomes easy to peel as a cake-like piece with shape retention. Furthermore, the concentrated sludge of the cake-like pieces falls in the unconcentrated sludge (in the suspension) while receiving the action of buoyancy toward the bottom of the filtration concentration tank 83, so that the impact when colliding with the bottom can be mitigated. . This prevents the cake-like pieces from being broken into small pieces, prevents the concentrated sludge from dissolving into the unconcentrated sludge (in the suspension), and prevents the concentration of the concentrated sludge from decreasing. is there. Further, it is possible to discharge the concentrated sludge accumulated at the bottom of the filtration and concentration tank 83 to the outside as cake pieces.

According to the above structure, the water which is a peeling medium is pumped from the inside of the filter cloth 18, and thereby the cake thin layer by the first sludge (first suspension) and the second surface attached to the outer surface of the cake thin layer. The concentrated layer of sludge (second suspension) can be peeled off from the filter cloth 18 together. Since it restarts from the formation of the cake thin layer by 1st sludge (1st suspension) whenever it peels, the thickness control of a cake thin layer becomes easy. That is, the thickness of the cake thin layer predicts the turbidity and concentration of the filtrate mainly from the combination of the concentration of the first sludge (first suspension) and the filtration time of the first sludge (first suspension). Can be controlled.

Next, the peeled concentrated sludge is discharged to the outside of the filtration and concentration tank 83. More specifically, the concentrated sludge discharge valve 120 is closed, the concentrated sludge valve 118 is opened, and the liquid is fed to the dehydrator 3 through the third concentrated sludge discharge pipe 93. At this time, since the concentrated sludge can be retained as cake-like pieces in the unconcentrated sludge (in the suspension) until it is taken out to the outside after being peeled off, before the concentrated sludge is discharged, Solid-liquid separation can be easily performed in unconcentrated sludge (in suspension) without having to discharge the concentrated sludge (suspension) to the outside. This completes the sludge filtration and concentration operation. It should be noted that the concentrated sludge around the concentrated sludge of the peeled cake piece, that is, only the “peeled concentrated suspension” is concentrated through the first concentrated sludge discharge pump 85 and the first concentrated sludge discharge pipe 84. You may return to the storage tank 86 as a 1st suspension liquid.

When the sludge (suspension) is continuously concentrated, the unconcentrated sludge (suspension) in the filtration and concentration tank 83 is returned to the gravity settling tank 12 through the unconcentrated sludge discharge pipe 119, What is necessary is just to supply a 1st sludge (1st suspension) to the filtration concentration tank 83, and to form a cake thin layer.

The concentrated sludge discharged to the outside of the filtration concentration tank 83 is further concentrated separately by the dehydrator 3 to be formed into a cake and subjected to incineration or landfill disposal.

As described above, supply of the first sludge (first suspension) to the filtration and concentration tank 83, formation of a cake thin layer on the surface of the filter cloth 18 by the first sludge (first suspension), and filtration Discharge of the first sludge (first suspension) from the concentration tank 83, supply of the second sludge (second suspension) to the filtration concentration tank 83, suction filtration of the second sludge (second suspension) A series of cycles consisting of concentration, exfoliation of the concentrated sludge adhering to the surface of the filter cloth 18 and discharge of the concentrated sludge from the filtration and concentration tank 83 is caused by an increase in the thickness of the concentrated sludge adhering to the surface of the filter cloth 18. As long as the filtration performance deteriorates but the thickness of the concentrated sludge is within an allowable range, supply of the second sludge (second suspension) to the filtration concentration tank 83 and suction filtration of the second sludge (second suspension) are performed. It is possible to repeat the concentration. In this case, the supply of the second sludge (second suspension) to the filtration concentration tank 83 may be performed while performing suction filtration concentration of the second sludge (second suspension), or in batch. Also good.

Thus, among the sludge (suspension) filled in the gravity sedimentation tank 12, the high concentration sludge (first suspension) settled in the lower part of the gravity sedimentation tank 12 is removed by the first liquid feeding means. Liquid is fed to the filtration and concentration tank through the first sludge supply pipe. Then, the high-concentration sludge (first suspension) fed to the liquid is adhered to the surface of the filter cloth by suction means. Thereby, a cake thin layer is formed on the surface of the filter cloth. In this state, among the sludge (first suspension) filled in the gravity sedimentation tank 12, the low concentration sludge (second suspension) in the upper part of the gravity sedimentation tank 12 is obtained by the second liquid feeding means. Liquid is fed to the filtration and concentration tank through the second sludge supply pipe 90. The liquid-concentrated sludge (second suspension) can be filtered and concentrated by sucking it through the filter cloth and cake thin layer by the suction means. At the same time, the highly concentrated sludge (first suspension) that forms a cake thin layer attached to the surface of the filter cloth and the low concentration sludge (second suspension) attached to the surface of the cake thin layer are concentrated. It is possible to peel off from the surface of the filter cloth at once by the peeling means and collect it. In addition, since sludge having a low concentration that contains solid matter that cannot be captured by the filter cloth can be filtered and concentrated, the rate of increase in the thickness of the concentrated sludge that adheres to the surface of the filter cloth And can be filtered and concentrated efficiently over a long period of time.

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. Hereinafter, the features of the second embodiment of the present invention will be described.

The feature of the second embodiment of the present invention is that, in the first embodiment, a filtration concentration tank 83 separate from the gravity settling tank 12 is provided on the downstream side of the gravity settling tank 12, and a siphon is provided inside the filtration concentration tank 83. In contrast to the arrangement of the suction suction device 10 (see FIG. 1), in the present embodiment, the siphon suction filtration device 10 is placed inside the gravity sedimentation tank 212 corresponding to the gravity sedimentation tank 12 in the first embodiment. The siphon type suction filtration device 210 corresponding to the above is disposed (see FIG. 6).

More specifically, as shown in FIG. 6, the gravity settling tank 212 into which the suspension to be filtered and concentrated is provided with a partition 100 that extends in the vertical direction in the gravity settling tank 212. In addition, the partition 100 is provided with an opening formed in the upper part and the lower part thereof so as to communicate between one space 102 and the other space 104 of the gravity settling tank 212 partitioned by the partition 100 ( Upper opening, lower opening) are provided. In one space 102 of the gravity settling tank 212, there are a bag-shaped filter cloth 18 that forms a filtration chamber 76 therein, and suction means for sucking the suspension in the one space 102 through the filtration chamber 76. Be placed. Further, a communication pipe 126 as an upper sludge liquid feeding means is provided in the upper opening, and an adjustment valve 106 is provided in the communication pipe 126. By this upper sludge liquid feeding means, the second suspension at the upper part in the other space 104 can be fed to one space 102 through the upper opening. Further, a communication pipe 121 and a communication pipe 122 are provided in the lower opening. The communication pipe 121 is provided with a first liquid feed pump 124 for feeding the lower sludge (first suspension) in the other space 104 to one space 102, and the communication pipe 122 has one space 102. A second liquid feed pump 108 for feeding the lower sludge inside to the other space 102 is provided. That is, the space 102 has the same function as the filtration concentration tank 83 of the first embodiment.

From the above, the adjustment valve 106 is closed and the first liquid feed pump 124 is operated. As a result, the high-concentration sludge (first suspension) in the lower part of the other space 104 is sent to the filter plate 14 through the communication pipe 121. On the other hand, by opening the regulating valve 106 and operating the second liquid feed pump 108, low concentration sludge (second suspension) in the upper part of the other space 104 is sent to the filter plate 14 through the communication pipe 126. It is possible to be According to the pump capable of rotating in the forward and reverse directions, it is possible to serve as both the first liquid feed pump 124 and the second liquid feed pump 108 with a single pump.

As in the first embodiment, the suction means has a siphon-type suction tube. One end of the siphon-type suction tube communicates with the filtration chamber 76 from above, and the other end extends downward outside the gravity settling tank 12. An inverted U-shaped tube is preferred. By doing in this way, an energy-saving effect can be realized highly.

The operation of the suction filter device having the above configuration will be described below. First, the regulating valve 106 is closed, and the first sludge (first suspension) having a relatively high concentration (for example, 1 mass%) settled in the gravity sedimentation tank 212 is connected to the communication pipe 121 by the first liquid feed pump 124. Then, the liquid is fed from the other space 104 to the one space 102. As a result, as in the first embodiment, suction filtration is performed by the filter plate 14 disposed in one space 102, and a cake thin layer K is formed on the surface of the filter cloth 18. Note that the suspended water is replenished from the lower part of the water purification tank 2 to the extent that the water level in the other space 104 has decreased.

Next, the regulating valve 106 is opened, and the sludge (first suspension) in one space 102 is fed from one space 102 to the other space 104 through the communication pipe 122 by the second liquid feed pump 108. . As a result, the water level in the gravity sedimentation tank 212 rises, and the second sludge (second suspension) having a relatively low concentration (for example, 0.1 mass%) in the upper part thereof passes through the communication pipe 126 to the other space. It flows from 104 to one space 102. Thus, as in the first embodiment, the second sludge (second suspension) can be suction filtered through the cake thin layer K formed by the first suspension adhering to the filter cloth surface. Is possible.

Next, the concentrated sludge adhering to the filter cloth, that is, the concentrated layer of the cake thin layer formed by adhering the first sludge (first suspension) to the filter cloth surface, and the surface of the concentrated layer of the cake thin layer Further, the concentrated sludge composed of the concentrated layer formed by the attached second sludge (second suspension) is peeled off from the surface of the filter cloth. Similar to the first embodiment, this peeling process is performed by continuously pumping water in the liquid through the filtration chamber 76 for a predetermined time. In addition, about the replacement | exchange method of the 1st suspension liquid and the 2nd suspension liquid in one space 102, it is the same as that of the case of the filtration concentration tank 83 in 1st Embodiment.

Next, the concentrated sludge of the peeled cake pieces is accumulated at the bottom of the gravity settling tank 212, and the accumulated concentrated sludge is discharged to the outside.

By repeating these steps, it is possible to concentrate the relatively low concentration sludge (second suspension) by suction filtration. In addition, whenever it repeats suction filtration concentration in this way, the cake thin layer by the 1st sludge (1st suspension) is formed, and the 2nd sludge (2nd suspension) of the cake thin layer adhered to the surface A concentrated layer is formed. Furthermore, since such a concentrated layer (concentrated sludge) is peeled off together and discharged to the outside as concentrated sludge, there is a situation where the first sludge (first suspension) necessary during operation is insufficient. Can occur. In such a case, for example, a mixing tank (not shown) is provided on the upstream side of the gravity settling tank, and the concentrated sludge discharged to the outside in this mixing tank is the second sludge (the second sludge in the gravity settling tank). Suspension) and a predetermined concentration (at least a concentration higher than the second sludge (second suspension)) may be mixed and replenished as the first sludge (first suspension).

As described above, according to the second embodiment of the present invention, the existing gravity settling tank 212 can be used without significantly modifying the existing gravity settling tank 212. This eliminates the need for expansion of equipment space. Further, the concentration rate of the thickened sludge adhering to the surface of the filter cloth is increased by suction filtration concentration of the sludge having a relatively low concentration without waiting until the sludge naturally settles in the gravity settling tank 212 as in the prior art. Therefore, it is possible to concentrate sludge efficiently and over a long period of time.

Furthermore, as a modification of the second embodiment of the present invention, as shown in FIG. 7, when siphon type suction filtration is difficult due to the restriction of the installation level of the gravity sedimentation tank 212, a suction pump 110 is used. Then, suction filtration may be performed. In this case, by adjusting the suction strength of the suction pump 110, the concentrated sludge adhering to the filter cloth is peeled off from the filter cloth and can be held in a piece of cake even in a state where it accumulates at the bottom of the gravity sedimentation tank 212. Therefore, for example, the screw feeder 112 may be used to discharge the concentrated sludge to the outside.

As a further modified example, it has a concentrated sludge storage tank that is connected to the downstream side of the gravity settling tank and stores the first suspension in the one space, and the first suspension in the one space is It is also preferable that the suction sludge concentrating device is supplied from the concentrated sludge storage tank to the one space. By comprising in this way, the 1st sludge for cake thin layer formation can be stored, and a concentrated sludge process can be performed continuously. Specifically, as shown in FIG. 8 or FIG. 9, the concentrated sludge storage tank 86 is provided separately from the gravity sedimentation tank 312, and the concentrated sludge in one space 102 is recovered in the concentrated sludge storage tank 86. Alternatively, the first sludge for forming the cake thin layer may be supplied to one space 102. Here, FIG. 8 shows a case where the concentrated sludge storage tank 86 is provided above the gravity settling tank 312, and FIG. 9 shows that the concentrated sludge storage tank 86 is provided below the gravity settling tank 312 and is recovered from one space 102. The case where the 1 mass% sludge which was done is returned to one space again through the filtrate return pump 153 and the filtrate return rod 154 is illustrated. However, it is not limited to this.

Furthermore, it has the 2nd suspension sludge storage tank which stores 2nd suspension in the lower part in the other space, and the 2nd suspension of the lower part in the other space is 2nd suspension. It is also preferable to be configured as a suction filtration and concentration device configured to be supplied from the sludge storage tank to one space. By comprising in this way, a 2nd suspension liquid can be stored and a concentrated sludge process can be performed continuously.

Furthermore, as a modification, instead of filtering and concentrating sludge in the gravity sedimentation tank 12, when the filtrate is used by suction filtration of the suspension filled in the tank, the sludge is placed in the lower part in the tank. A thin cake layer is formed on the surface of the filter cloth using the relatively concentrated first suspension located, and then the cake thin layer is used as a pseudo filter to be positioned at the top in the tank. The second suspension having a relatively low concentration may be suction filtered. In this case, the gravity settling tank 12 requires several days for the settling and separation of purified water, but in the case of a tank having a relatively small volume or a relatively shallow depth, the first suspension is used in the tank. Before the cake thin layer is formed, the solid content of the suspension may settle below the filter plate in the tank. Therefore, before the cake thin layer is formed using the first suspension, the suspension in the tank is once stirred so that the suspension has a uniform concentration in the tank. A thin cake layer may be formed using the suspension. After the cake thin layer is formed on the surface of the filter cloth, from the viewpoint of energy saving, the stirring is stopped, and suction filtration may be performed for a low concentration suspension that naturally settles in the tank, Suction filtration may be performed while stirring continuously.

According to such a suction type filtration concentration method, the water in the suspension is passed through the filter cloth by suction through the filtration chamber formed inside the bag-like filter cloth in the gravity settling tank, while the suspension is suspended. The suspension can be filtered and concentrated in a suction manner by adhering solid matter in the suspension to the surface of the filter cloth.

In this case, among the sludge filled in the gravity settling tank, even if it is a sludge having a low concentration that contains solids that cannot be captured by the filter cloth, it contains solids that can be captured by the filter cloth. It is possible to filter and concentrate through the cake thin layer by forming a cake thin layer on the surface of the filter cloth using sludge having a high concentration of and using this cake thin layer as a pseudo filter. It is possible to filter and concentrate efficiently without having to wait until the sludge filled in the gravity settling tank settles, while the concentration is low enough to contain solids that cannot be captured by the filter cloth. Since it is possible to concentrate by filtration even if it is sludge having a filter, it is possible to suppress the increase rate of the thickness of the concentrated sludge adhering to the surface of the filter cloth, and to concentrate by filtration over a long period of time. It is also possible

Furthermore, it is preferable to have a step of peeling the concentrated sludge adhering to the outer surface of the cake thin layer from the filter cloth together with the cake thin layer adhering to the filter cloth.

As shown in FIG. 10, the present inventor installed a filter plate 14 directly in the gravity settling tank 12 and conducted a confirmation test as to whether or not sludge can be filtered and concentrated. The test apparatus and test method are as follows.

1. Test subject: Sludge: Sakai water purification plant sludge Test apparatus: Suction-type filtration concentration apparatus Filtration area of the filter plate 14: 0.12 m ²
Filter cloth 18: Made of nylon, sewn together on the support plate Suction pressure: -33kPa

3. Test method:
(1) Filtration concentration method:
Suction filtration concentration was performed continuously for 8 hours on the raw sludge by suction filtration concentration.
Specifically, as shown in FIG. 10, first, filtration and concentration are started with a stock solution (sludge: corresponding to the first suspension) (T1). Next, after the start of filtration, when the turbidity of the filtrate F becomes transparent, the stock solution (sludge) is discharged from the lower part of the tank (T2), and 10-fold diluted liquid (corresponding to the second suspension) from the upper part of the tank. (T3). Then, after discharging the stock solution, the filtration concentration is continued only with a 10-fold diluted solution (T3).

(2) Stripping method:
Next, as shown in FIG. 10, after the unconcentrated sludge in the tank is discharged to the outside (T4), air is pumped through the filtration chamber 76 to peel the concentrated sludge W adhering to the filter cloth 18 from the filter cloth 18. (T5).

The experimental results are shown in Table 1 and FIG. It took about 1 minute for the filtrate F to become transparent. As shown in Table 1 and FIG. 11, in Comparative Example 1, according to the filtration concentration in the stock solution, the stock solution concentration was 1.12%, the filtrate concentration was 0.05%, and the concentrated sludge concentration was 8.29%. While the magnification is 7.40, in Example 1, according to the low-concentration sludge with the 10-fold diluted solution, the stock solution concentration is 0.108%, the filtrate concentration is 0.014%, and the concentrated sludge concentration is 6.69. % And the concentration factor was 61.94. In addition, a density | concentration shows the mass%.

From this result, firstly, even if the concentration of raw sludge is low, there is no significant difference in the concentration of concentrated sludge. Second, at T3 shown in FIG. 10, the amount of filtrate and the filtrate in FIG. As shown by the line S indicating the time relationship, it can be confirmed that the filtration performance does not deteriorate even after 8 hours, that is, continuous operation can be performed without backwashing. Thirdly, the required time is 1 minute to form a cake thin layer with the stock solution, 9 minutes to replace sludge, 470 minutes to filter and concentrate low-concentration sludge, and after washing the filter plate Since it took 20 minutes to return to the first step, the ratio of the effective filtration time to the total filtration time reached 94%, and fourthly, it is necessary to stop the filtration step when stripping the concentrated sludge, It was confirmed that the time required for stripping only accounts for several percent of the filtration concentration time of the low-concentration sludge, and does not hinder the overall concentration efficiency.

From the above, the present inventor puts a filter plate directly in the gravity settling tank 12 and uses sludge with a high concentration to adhere the solid content to the surface of the filter cloth, so that the sludge is concentrated and filtered. Got the prospect of being possible.

The embodiment of the present invention has been described in detail above, but various modifications or variations can be made by those skilled in the art without departing from the scope of the present invention. For example, in the first embodiment, the case where the target of filtration and concentration is sludge has been described. However, the present invention is not limited thereto. For example, the target of filtration and concentration includes incineration ash, milk, juice, and the like contained in an alkaline solution. There are foreign matters contained in the beverage, turbid water in the turbid water, etc., depending on the subject of filtration concentration, as long as the conditions such as the type of filter cloth 18, the size of the pore diameter, the suction force, etc. are appropriately set, The suction type filtration concentration apparatus according to the present invention is applicable to these. In this case, the first suspension is required for forming the cake thin layer, but in the first embodiment, the first sludge that has settled in the gravity sedimentation tank is used as the target of filtration and concentration. However, when such a first suspension cannot be used immediately, the first suspension may be generated by drying or concentration by sunlight or heat, concentration using a membrane filtration device, or concentration by vacuum evaporation. .

In the first embodiment, water is used as a stripping medium in unconcentrated sludge to separate the concentrated sludge from the filter cloth. However, without being limited thereto, the unconcentrated sludge is once removed from the filtration and concentration tank. After discharging to the outside, peeling may be performed using air as a peeling medium.

Furthermore, in the first embodiment, the concentrated sludge stored in the concentrated sludge storage tank 86 is used for the formation of a cake thin layer in the filtration and concentration tank 83. In addition, the same kind of properties may be used for forming a cake thin layer in other suction filtration concentration.

The suction filtration concentration method and apparatus according to the present invention can be applied not only to water treatment technical fields including clean water, middle water and sewage but also to a wide range of technical fields such as food and chemical industries. Among them, it is particularly useful as a suction filtration concentration method and apparatus applied in a concentration process of sludge generated in a water treatment process such as a water purification plant.

1: Water purification equipment, 2: Water purification tank, 3: Dehydrator, 4: Stirrer, 5: Motor, 10, 210: Suction filtration concentration device (siphon type filtration concentration device), 12, 212, 312: Gravity sedimentation layer , 14: filter plate, 15: horizontal pipe, 16: suction section, 18: filter cloth, 20: concentrated sludge stripping section, 21: supernatant liquid discharge pipe, 22: side wall, 23: supernatant liquid discharge valve, 24: sludge supply 25: supernatant discharge pump, 26: sludge supply valve, 28: sludge supply pump, 31: suction pipe, 33: suction valve, 34: distribution pipe, 35: vacuum pump, 36: filtrate storage tank, 40: filtrate Drain valve, 42: Water inflow pipe, 44: Water inflow valve, 46: Liquid feed pump, 48: Filtration frame, 50: Support plate, 54: Coil spring, 56: Upper side, 57: Upper side, 58: Lower side, 59: Lower side , 60, 61, 62, 63: side, 74: seam 76: filtration chamber, 78: eyelet, 80: first sludge supply pipe, 81: first sludge supply valve, 82: first liquid feeding means (first sludge supply pump), 83: filtration concentration tank, 84: first Concentrated sludge discharge pipe, 85: first concentrated sludge discharge pump, 86: concentrated sludge storage tank, 87: second concentrated sludge discharge pipe, 88: second concentrated sludge discharge pump, 89: filtrate return pipe, 90: second sludge Supply pipe, 91: pump, 93: third concentrated sludge discharge pipe, 100: partition, 102: one space, 104: other space, 106: regulating valve, 108: second liquid feed pump, 110: suction pump, 112: Screw feeder, 114: Filtrate reservoir, 116: Filtrate return pump, 118: Concentrated sludge valve, 119: Unconcentrated sludge discharge pipe, 120: Concentrated sludge discharge valve, 121: Communication pipe, 122: Communication pipe, 123: Concentration Sludge discharge part, 1 4: first liquid feed pump, 126: communication pipe, 153: filtrate return pump, 154: filtrate return Kan, K: Cake thin layer, W: concentrated sludge.

Claims

A suction filtration concentration method of filtering and concentrating a suspension by a suction method,
By sucking the suspension through a filtration chamber formed inside a bag-shaped filter cloth, moisture in the suspension is passed through the filter cloth, while solids in the suspension are passed through the filter cloth. In a suction filtration concentration method having a step of adhering to the surface of a filter cloth,
Selecting a first suspension containing solids capable of closing the eyes of the filter cloth;
A cake thin layer forming step of forming a cake thin layer on the surface of the filter cloth by filtering and concentrating the first suspension by a suction method;
A filtration and concentration step of filtering and concentrating a second suspension having a concentration lower than that of the first suspension through the cake thin layer by a suction method;
A suction filtration concentration method.
The cake thin layer forming step is performed by using the filter cloth disposed in the filtration concentration tank, and the first suspension is allowed to flow into the filtration concentration tank.
The filtration concentration step of the second suspension is performed by discharging the first suspension from the filtration concentration tank and then flowing the second suspension into the filtration concentration tank. The suction filtration concentration method.
The cake thin layer forming step is performed by using the filter cloth disposed in the filtration concentration tank, and the first suspension is allowed to flow into the filtration concentration tank.
In the filtration concentration step of the second suspension, the first suspension is placed in the filtration concentration tank so that the filter cloth is not exposed from the liquid surface of the first suspension filled in the filtration concentration tank. The suction-type filtration concentration method according to claim 1, wherein the second suspension is introduced into the filtration concentration tank while being discharged from the filter.
The stripping step of peeling the concentrated sludge composed of the cake thin layer by the first suspension and the concentrated layer by the second suspension attached to the outer surface of the cake thin layer from the filter cloth is performed in the filtration concentration tank. The suction filtration concentration method according to any one of claims 1 to 3, which is carried out by pumping water from the inside of the filter cloth in an unconcentrated suspension filled with the above.
The exfoliated concentrated suspension is further discharged from the filtration concentration tank to the outside and stored.
The suction filtration concentration method according to claim 4, wherein the stored concentrated suspension is used as the first suspension.
After the cake thin layer forming step, discharging and storing the first suspension from the filtration concentration tank;
The suction filtration concentration method according to claim 5, further comprising a step of supplying the first suspension to the filtration concentration tank after the peeling step.
A step of feeding the suspension in the lower part of the gravity sedimentation tank to the filtration and concentration tank as a first suspension;
The outer surface of the filter cloth is obtained by filtering and concentrating the liquid-supplied first suspension by a suction method using a bag-like filter cloth disposed inside the filtration and concentration tank and forming a filtration chamber inside. Forming a thin layer of cake by adhering to
Feeding the suspension at the top of the gravity sedimentation tank to the filtration and concentration tank as a second suspension;
Filtering and concentrating the second suspension at the top of the liquid gravity sedimentation tank passed through the cake thin layer;
Peeling the concentrated sludge adhering to the outer surface of the filter cloth by pumping the peeling medium through the filtration chamber;
A suction filtration concentration method.
A suction filtration and concentration device installed downstream of the gravity sedimentation tank,
A filtration and concentration tank into which the suspension in the gravity settling tank flows, and
A bag-like filter cloth disposed inside the filtration concentration tank and forming a filtration chamber therein;
A suction means for sucking the suspension in the filtration and concentration tank through the filtration chamber;
A first sludge supply pipe connecting the lower part of the gravity sedimentation tank and the filtration and concentration tank;
A first liquid feeding means for feeding a first suspension settled in a lower part of the gravity sedimentation tank through the first sludge supply pipe to the filtration and concentration tank;
A second sludge supply pipe connecting the upper part of the gravity sedimentation tank and the filtration and concentration tank;
Second liquid feeding means for feeding the second suspension at the top of the gravity sedimentation tank to the filtration and concentration tank through the second sludge supply pipe;
In the filtration and concentration tank, concentrated sludge stripping means for stripping the concentrated sludge adhered to the surface of the filter cloth by the suction means;
A suction filtration and concentration apparatus.
Furthermore, a concentrated sludge storage tank for storing a first suspension having a concentration that can be captured by the filter cloth,
A third sludge supply pipe connecting the lower part of the filtration and concentration tank and the concentrated sludge storage tank;
Third liquid feeding means for feeding the concentrated sludge separated by the concentrated sludge peeling means and accumulated at the bottom of the filtration and concentration tank to the concentrated sludge storage tank through the third sludge supply pipe;
A fourth sludge supply pipe connecting the concentrated sludge storage tank and the middle of the first sludge supply pipe;
A fourth liquid feeding means for feeding the concentrated sludge stored in the concentrated sludge storage tank to the filtration and concentration tank through the fourth sludge supply pipe and the first sludge supply pipe;
The suction filtration concentration apparatus according to claim 8, wherein
A gravity settling tank into which the suspension to be filtered and concentrated, and
A partition extending vertically in the gravity settling tank,
The partition has an opening that communicates between one space and the other space of the gravity settling tank partitioned by the partition at each of an upper part and a lower part thereof,
In the one space, a bag-shaped filter cloth that forms a filtration chamber therein, and a suction means for sucking the suspension in the one space through the filtration chamber are arranged,
Furthermore, an upper sludge liquid feeding means for feeding the upper second suspension in the other space to the one space through the upper opening,
A suction-type filtration and concentration apparatus, comprising: a lower sludge liquid feeding means for feeding the lower first suspension in the other space to the one space through the lower opening.
Furthermore, it has a concentrated sludge storage tank that is connected to the downstream side of the gravity settling tank and stores the first suspension in the one space, and the first suspension in the one space has the concentration The suction type filtration concentration apparatus according to claim 10, wherein the suction filtration concentration apparatus is supplied to the one space from a sludge storage tank.
Furthermore, it has a sludge storage tank which stores 2nd suspension in the lower part in said other space, and the 2nd suspension of the lower part in said other space is said one space from said sludge storage tank. The suction filtration concentration apparatus according to claim 10, wherein the suction filtration concentration apparatus is supplied.