WO2016140006A1

WO2016140006A1 - Sludge volume reduction device and sewage treatment system comprising same

Info

Publication number: WO2016140006A1
Application number: PCT/JP2016/053132
Authority: WO
Inventors: 佐々木　洋
Original assignee: 株式会社日立製作所
Priority date: 2015-03-03
Filing date: 2016-02-03
Publication date: 2016-09-09
Also published as: JP2018086601A

Abstract

The purpose of the present invention is to provide a sludge volume reduction device capable of effectively reducing the volume of even highly fluid sludge, and a sewage treatment system using same. To solve said problem, this sludge volume reduction device 2 is provided with: a sludge collection tank 25 for collecting sludge after moisture removal; an endless belt-shaped resin sheet 21, which is rotated by multiple rollers 22, 23, 23a and has a continuous porous structure capable of absorbing moisture in the sludge 16 that is placed on the surface thereof; and a pressurizing roller 24, which is disposed at a position where the resin sheet 21 is driven so as to double back near the sludge collection tank 25. Moisture in the sludge 16 is absorbed by conveying the resin sheet 21 towards the sludge collection tank 25 with the sludge in an unpressurized state, and moisture is discharged from the resin sheet after moisture absorption by the pressurizing roller 24 and collected in a moisture collection tank 26.

Description

Sludge volume reduction device and sewage treatment system having the same

The present invention relates to a sludge volume reducing device that removes moisture in sludge generated during sewage treatment and reduces the sludge volume, and a sewage treatment system having the same.

The sludge generated at the sewage treatment plant is generally treated as follows. First, water in the sludge is separated to some extent using centrifugation or the like. As a result, the sludge becomes clay-like, but contains about 80% of moisture in terms of weight. This is heated to vaporize the moisture and then incinerated. Incineration ash is entrusted to an industrial waste disposal company for disposal. However, when there are few heavy metals in sludge, it is diverted to fertilizer etc. after heat drying. However, in any case, enormous energy is required to volatilize the water in the sludge, and the fuel cost accounts for a considerable proportion of the entire sewage treatment system.
Therefore, Patent Document 1 has been proposed as a technique for reducing moisture without going through a heating step. In patent document 1, it comprises the structure which makes the hydrophilic resin of a dewatering belt absorb the water | moisture content in a sludge by carrying out the compression contact of the sludge to a dewatering belt formed with hydrophilic resin with a pressing roll. That is, the hydrophilic resin absorbs moisture while pressurizing sludge.

JP 2012-139648 A

In patent document 1, it is the structure which makes the water | moisture content in sludge absorb in the dehydration belt formed with hydrophilic resin, pressurizing sludge. However, sludge containing a large amount of moisture has high fluidity and may leak from the dewatering belt due to pressurization, making it difficult to effectively reduce the volume of sludge by removing moisture.
Then, this invention is providing the sludge volume reducing apparatus which can perform volume reduction effectively also to sludge with high fluidity, and a sewage treatment system using the same.

In order to solve the above-mentioned problems, the sludge volume reduction device of the present invention is a sludge recovery tank for recovering sludge after moisture removal, and a plurality of rollers that are rotationally driven and put moisture in the sludge placed on the surface thereof. An endless belt-shaped resin sheet having a continuous porous structure capable of absorbing; and a pressure roller disposed at a position where the resin sheet is driven to be folded in the vicinity of the sludge collection tank, and the resin sheet is By conveying the sludge to the sludge collection tank in a non-pressurized state, the moisture in the sludge is absorbed, and the moisture is discharged from the resin sheet after the moisture absorption by the pressure roller. .
In addition, the sewage treatment system of the present invention includes a first sedimentation basin that separates organic substances from inflowing sewage by gravity sedimentation, and a biological treatment that performs nitrification and denitrification on the sewage flowing from the first sedimentation basin by using sludge containing microorganisms. A tank, a final sedimentation tank installed on the downstream side of the biological treatment tank, having a sludge scraper and sinking the sludge from the sewage flowing from the biological treatment tank, and separating the supernatant, and the final sedimentation tank A dehydrator for separating water from the sludge extracted from the sludge, and a sludge volume reducing device for removing water from the dewatered sludge, wherein the sludge volume reducing device collects the sludge after moisture removal. A sludge collection tank, an endless belt-shaped resin sheet having a continuous porous structure that is rotationally driven by a plurality of rollers and is placed on the surface of the sludge, and the resin sheet is in the vicinity of the collection tank In A pressure roller disposed at a position to be driven back, and by absorbing the moisture in the sludge by conveying the resin sheet to the sludge collection tank without pressing the sludge, Water is discharged from the resin sheet after moisture absorption by the pressure roller.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the sludge volume reduction apparatus which can perform volume reduction effectively also to sludge with high fluidity, and a sewage treatment system using the same.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

1 is an overall configuration diagram of a sewage treatment system according to an embodiment of the present invention. It is a schematic block diagram of the sludge volume reduction apparatus shown in FIG. FIG. 3 is an AA cross-sectional arrow view of the sludge volume reducing device shown in FIG. 2. It is a figure which shows the other structural example of a sludge volume reduction apparatus, and is a side view and an AA cross-sectional arrow view. It is a figure which shows the other structural example of a sludge volume reduction apparatus. It is an enlarged view of the area | region B of the sludge volume reduction apparatus shown in FIG. It is a top view in the area | region B shown in FIG. It is the external view and sectional drawing of the water | moisture-content absorber which comprise a sludge volume reduction apparatus. It is a schematic block diagram of the sludge supply part vicinity which comprises a sludge volume reduction apparatus.

In the present specification, the “endless belt-shaped resin sheet” to be described later is not limited to a so-called seamless belt, but may be any belt as long as it can continuously travel on a circular track. Depending on the length of the sheet, in the running direction of the above-mentioned orbit, the resin sheet is bonded at both ends with a metal joint, or a plurality of divided resin sheets are held in resin or non-resin Also included are those that are joined by members and formed into an endless belt shape.

In FIG. 1, the whole block diagram of the sewage treatment system which concerns on one Embodiment of this invention is shown. The sewage treatment system 1 treats sewage (hereinafter referred to as treated water) such as domestic wastewater or industrial wastewater through a biological reaction tank that treats sewage with sludge containing microorganisms (activated sludge). . As shown in FIG. 1, the sewage treatment system 1 includes a first sedimentation basin 3, an aerobic tank 4, a nitrification denitrification tank 5, a final sedimentation basin 6, a centrifugal separator, and the like that separate organic matter from the treated water 15 by gravity sedimentation. The dehydrator 7 used, the sludge volume reducing device 2, and the control unit 13 for controlling them are provided. An aerobic tank aeration tube 8 is provided in the aerobic tank 4, and a stirrer 9 is provided in the nitrification denitrification tank 5. The aerobic tank diffusing tube 8 is connected to the blower 10 via an air volume adjusting valve 11. The control unit 13 controls the blower 10 and the air volume adjusting valve 11 so as to obtain a desired aeration air volume. Further, the control unit 13 controls the stirring intensity such as the rotational speed of the stirring blade constituting the stirrer 9. When the dehydrator 7 is, for example, a centrifugal dehydrator, the control unit 13 rotates the speed of a screw conveyor drive motor (not shown) constituting the dehydrator 7 and will be described in detail later. The sludge volume reducing device 2 is controlled. In addition, in FIG. 1, although the combination of the aerobic tank 4 and the nitrification denitrification tank 5 is shown as a biological treatment tank, it is not restricted to this, For example, the biological treatment tank which consists of various combinations including an anaerobic tank etc. is applied suitably it can.
Here, the control unit 13 includes, for example, a storage device such as a ROM, a RAM, and an external storage device (not shown), reads out and executes various programs stored in the ROM, and is data or execution results in the program execution process. It is comprised from processors, such as CPU which stores an arithmetic processing result in RAM or an external storage device.

The control unit 13 controls the stirring intensity of the stirrer 9 provided in the nitrification denitrification tank 5 based on the measurement result of ammonia nitrogen (NH ₄ -N) concentration by an ammonia sensor (not shown) and a predetermined set value, The amount of aeration air supplied by lending the aerobic tank aeration pipe 8 to the aerobic tank 4 installed upstream of the nitrification denitrification tank 5 is controlled. Further, convection is generated in the nitrification denitrification tank 5 by the stirrer 9 to the water 15 to be treated. That is, the command value of the stirring intensity output to the stirrer 9 output from the control unit 13 is such that sludge containing microorganisms (activated sludge) is almost uniformly dispersed in the water to be treated in the nitrification denitrification tank 5. Stirring intensity. Thereby, sedimentation of activated sludge on the bottom surface of the nitrification denitrification tank 5 can be prevented.

In the final sedimentation basin 6, activated sludge is gravity settled from the treated water 15 flowing from the nitrification denitrification tank 5, and the supernatant liquid is separated and discharged as treated water. In the final sedimentation basin 6, a sludge scraping machine 60 that scrapes sludge containing microorganisms that settle on the bottom surface (activated sludge) is provided.
The sludge scraper 60 is provided at both ends of a drive shaft to which rotational force is transmitted by a plurality of flights 62 attached to the chain 61 at predetermined intervals and a drive device 64 installed on the water surface of the final sedimentation basin 6. The driven sprocket wheel 63a, the driven sprocket wheel 63b provided at both ends of the intermediate shaft disposed on the downstream side of the driving sprocket wheel 63a, and the downstream side of the driven sprocket wheel 63b and disposed near the bottom surface of the final sedimentation basin 6. A driven sprocket wheel 63c provided at both ends of the tail shaft, and a driven sprocket wheel 63d provided at both ends of the head shaft disposed near the bottom surface of the final sedimentation basin 6 and upstream of the driven sprocket wheel 63c. A chain 61 to which a plurality of flights 62 are attached at predetermined intervals is stretched in parallel with the drive sprocket wheel 63a and the driven sprocket wheels 63b to 63d, and is circulated by the drive device 63. The flight 62 has a flat plate shape that is attached at a predetermined interval so as to cross the chain 61 stretched in parallel with the two strips.

Then, when the chain 61 moves along the direction of the arrow F1 (the direction from the downstream side to the upstream side), the microorganisms that settle on the bottom surface of the final sedimentation basin 6 are sludge (activated) by the flight 62 attached to the chain 61. Sludge) is scraped to the sludge pit P1 side. Further, when the chain 61 moves in the direction of the arrow F2 (in the direction from the upstream side to the downstream side) near the water surface position of the final sedimentation basin 6, the scum that floats on the water surface by the flight 62 attached to the chain 61 is on the scum skimmer 65 side. It is scraped and discharged.
Sludge containing microorganisms (activated sludge) scraped to the sludge pit P1 side by the sludge scraper 60 is returned to the aerobic tank 4 by the sludge return pump 12. Below, the activated sludge which is the sludge containing the microorganisms which settle to the bottom face of the final sedimentation basin 6 is included, and is only called sludge.

As described above, the sludge settled on the bottom surface of the final sedimentation basin 6 is scraped to the sludge pit P1 and then returned to the aerobic tank 4 by the sludge return pump 12, but during the operation time of the sewage treatment system 1. Accordingly, the amount of sludge that settles on the bottom surface of the final sedimentation basin 6 and is scraped to the sludge pit P1 increases. Therefore, the sludge 16 raked into the sludge pit P1 is pulled out and introduced into the dehydrator 7 installed at the subsequent stage of the final sedimentation basin. For example, in the centrifugal dehydrator 7, as described above, the rotational speed of the motor that rotationally drives the screw conveyor (not shown) is controlled by the control unit 13, and the sludge 16 containing a large amount of moisture is By the rotational drive, it is centrifuged into sludge 16 from which clarified water and moisture have been partially removed. Although the sludge 16 centrifuged by the dehydrator 7 becomes a clay, it still contains about 80% water by weight. The sludge 16 centrifuged by the dehydrator 7 is supplied to the sludge volume reducing device 2 installed at the subsequent stage of the dehydrator 7.

In FIG. 2, the schematic block diagram of the sludge volume reduction apparatus 2 is shown. The sludge volume reducing device 2 mounts a driving roller 22 driven by a motor 28 and a transport roller composed of a plurality of driven

rollers

23 and 23a and a sludge 16 supplied from the dehydrator 7 and circulates by the transport roller. Endless belt-shaped resin sheet 21 having a continuous porous structure traveling on a track, sludge recovery tank 25 for recovering sludge 17 whose moisture has been absorbed and reduced by resin sheet 21, pressure roller 24, pressure roller 24, and A water recovery tank 26 is provided for recovering water 27 released from the resin sheet 21 after moisture absorption by being pressurized by the driven roller 23.
In the example shown in FIG. 2, the driving roller 22 driven by the motor 28 rotates in the clockwise direction. In accordance with the rotation of the driving roller 22, the plurality of driven

rollers

23 and 23a are also rotated in the clockwise direction. Due to the rotation of these transport rollers, the resin sheet 21 having a continuous porous structure travels in a clockwise direction on an elliptical orbit. Thereby, the endless belt-shaped resin sheet 21 is folded at the position of the driven roller 23 a disposed above the sludge collection tank 25, and the pressure roller 24 disposed above the moisture collection tank 26 and the pressurization. It passes between the driven rollers 23 arranged to face the roller 24 and travels toward the drive roller 22 side.

Thus, when the resin sheet 21 having a continuous porous structure travels, the sludge 16 placed on the resin sheet 21 is conveyed in the direction indicated by the arrow S. Hereinafter, for the sake of convenience, the drive roller 22 side is referred to as the upstream side and the driven roller 23a side is referred to as the downstream side along the conveying direction S of the sludge 16. While the sludge 16 placed on the resin sheet 21 is transported to the position of the driven roller 23a disposed at the downstream end, the water in the sludge 16 has a continuous porous structure. The volume of the sludge 16 is gradually reduced. That is, the sludge 16 is reduced in volume. Here, the resin having a continuous porous structure is also called a hydrophilic resin having open cells, and in particular, as a result of the inventor's diligent efforts, a resin having a hydroxyl group and having a continuous porous structure is particularly pressurized. It has been found that moisture can be trapped in the continuous porous material. The material for the resin sheet having a continuous porous structure will be described later.

As shown in FIG. 2, while reaching the driven roller 23 a arranged at the downstream end, the sludge 17 that has absorbed and reduced the moisture is detached from the resin sheet 21 by folding the resin sheet 21, It falls to the sludge collection tank 25 arranged below and is collected. The resin sheet 21 folded back by the driven roller 23a and having a continuous porous structure after moisture absorption in the sludge 16 travels to the pressure roller 24 and the driven roller 23 arranged to face the pressure roller 24. . Moisture 27 pressurized by the pressure roller 24 and the driven roller 23 and absorbed by the resin sheet 21 having a continuous porous structure is pushed out from the continuous porous body and in a moisture recovery tank 26 disposed below. Collected. The recovered water is mixed with sewage and treated as sewage. The resin sheet 21 having a continuous porous structure after passing through the pressure roller 24 is regenerated to a state in which the moisture in the sludge 16 can be absorbed again, as the absorbed moisture is discharged.
The volume-reduced sludge 17 collected in the sludge collection tank 25 is subjected to normal processing. If the heavy metal concentration in the sludge 17 whose volume has been reduced is high, the sludge 17 burns and the burned material is treated as industrial waste. If the heavy metal concentration is low, it is used as a fertilizer for agricultural products.
Thus, according to the sludge volume reduction apparatus 2, the water | moisture content in the sludge 16 is especially sent to the resin sheet 21 which has a continuous porous structure with respect to the sludge 16 supplied from the dehydrator 7, without requiring a pressurization. Since it is absorbed, it is possible to effectively reduce the volume of sludge containing a large amount of water, that is, sludge having high fluidity.

Here, the chemical structure and porosity of the resin sheet 21 having a continuous porous structure will be described. As described above, a polymer having a large number of hydrophilic substituents such as hydroxyl groups, carboxyl groups, sulfonic acid groups, and amino groups in the molecule is used as a resin having a continuous porous structure, also called a hydrophilic resin having open cells. . Of these, carboxyl groups and sulfonic acid groups dissociate in water, and the water in contact with them exhibits acidity. Moreover, the hydroxyl group directly bonded to the aromatic structure, such as the hydroxyl group of phenol, also dissociates, and the water in contact with it exhibits acidity. On the other hand, the amino group is also dissociated in water, and the water in contact with the amino group is basic. Therefore, these may cause corrosion of the metal parts in the sludge volume reducing device 2 and are not preferable.
Compared to this, the alkyl chain or the hydroxyl group directly bonded to the alkylene chain hardly dissociates, and hardly changes the liquidity of water in the sludge to be treated. Therefore, there is almost no fear of corroding the metal parts in the sludge volume reducing device 2, which is preferable.
Specific examples of such a hydroxyl group-containing resin include copolymers of water-soluble resins such as polyethylene glycol and polyvinyl alcohol, and resins such as polyalkyl acrylate, polymethacrylate, and polystyrene that hardly dissolve in water. In addition, a polymer having a sugar skeleton such as cellulose is also included. By using a continuous porous body of these resins, a large amount of water can be adhered (absorbed) not only on the surface but also on the inside, so that the amount of water absorption per unit volume increases.
Cellulose has a structure in which sugars are connected in a straight line and is insoluble in water. However, since a substance with a helical structure like starch is soluble in water, it forms water by forming a copolymer with a monomer such as acrylonitrile. Use in a structure that is insoluble in.

The higher the void ratio, the larger the internal void ratio, so that the water absorption rate per unit volume also tends to increase. Since a material having a porosity of at least about 70% can be manufactured in a normal porosification process, the lower limit is preferably about 70%.
However, if the porosity is increased too much, specifically, if the porosity is 98% or more, the physical strength is remarkably reduced, so that the fracture occurs with a slight force.
On the other hand, the physical strength varies depending on the type of resin. Cellulose resin with a repeating unit of sugar or sugar derivative skeleton, and starch copolymer are more physical than resins having a structure such as polyvinyl alcohol whose main chain is hydrocarbon and polyalkylene glycol whose main chain is polyalkylene oxide. High strength and difficult to break. This is considered that the physical strength is increased by hydrogen bonding between a large number of hydroxyl groups in cellulose.

From the above, the porosity is approximately 70 to 97% when the main chain of the resin has a cellulose skeleton, approximately 70 to 96% of the copolymer of starch as the main chain of the resin, and hydrocarbon chains as the main chain of the resin. Approximately 70 to 95% is preferable.
The resin having a continuous porous structure so that the porosity falls within a desired range as described above can be obtained, for example, by controlling the temperature and pressure of a reaction vessel containing a mixture of the resin and the volatile solvent. It is done. Here, with respect to the mixture of the resin and the volatile solvent, the temperature increase and pressurization conditions in the case of producing a resin having a continuous porous structure are repeatedly performed by changing the temperature increase and pressurization conditions repeatedly. can get. By controlling the reaction vessel under the obtained temperature rise and pressure conditions, a resin having a continuous porous structure can be produced with good reproducibility. For example, a volatile solvent having a boiling point of 70 ° C. to 80 ° C. is used to mix with the above resin in the reaction vessel. Thereafter, the temperature of the reaction vessel is raised until the temperature of the mixture of the volatile solvent and the resin reaches 70 ° C. to 80 ° C. As a result, the volatile solvent in the mixture evaporates, and voids are formed in the resin where the volatile solvent previously existed. By combining these voids, a continuous porous structure is obtained.

FIG. 3 is a cross-sectional view of the sludge volume reducing device 2 shown in FIG. As shown in FIG. 3, the driven roller 23 has a recess formed in a substantially central portion in the axial direction. In other words, the driven roller 23 has a shape in which the outer diameter decreases from the predetermined position toward the center from both ends in the axial direction. By adopting such a shape, the sludge 16 containing a large amount of moisture with high fluidity overcomes the tension of the resin sheet 21 having a continuous porous structure due to its own weight, and is a shape simulating a recess formed in the driven roller 23. It becomes. As a result, the sludge 16 placed on the resin sheet 21 and conveyed to the driven roller 23a disposed at the downstream end leaks from both ends of the resin sheet 21 orthogonal to the sludge conveyance direction S. Can be prevented.
In addition, it is desirable that the degree of depression of the recess formed in the driven roller 23 is made larger as the driven roller 23 arranged on the upstream side. This is because, in the resin sheet 21 having a continuous porous structure running on the driven roller 23 arranged on the upstream side, the degree of moisture absorption in the sludge 16, that is, the volume reduction of the sludge 16 is low. by. Moreover, about the driven roller 23a distribute | arranged to a downstream edge part, it is preferable to set it as a cylindrical roller without providing a recessed part.

FIG. 4 is a diagram showing another example of the configuration of the sludge volume reducing device 2. The left diagram is a side view, and the right diagram is a sectional view taken along the line AA. The resin sheet 21 having a continuous porous structure has a large number of pores. When the resin sheet 21 having a continuous porous structure is operated for a long time by the transport roller composed of the driving roller 22 and the driven

rollers

23 and 23a shown in FIG. There is a possibility that breakage will occur. Therefore, in the configuration shown in FIG. 4, the resin sheet 21 having a continuous porous structure is fixed to a belt 29 having a high physical strength, and the belt 29 is caused to travel by a driven roller 23b. As the belt 29, for example, a belt made of an elastic body such as rubber or a belt made of a non-porous resin is used. Thereby, the tensile stress concerning the resin sheet 21 which has a continuous porous structure is reduced. Moreover, the resin sheet 21 having a continuous porous structure can be used without breakage for a long time by reducing the tensile stress.
As shown in FIG. 4, a plurality of convex portions extending in the axial direction are formed on the outer peripheral surface of the driven roller 23b at predetermined intervals in the circumferential direction. In addition, a plurality of concave portions extending in a direction (width direction of the belt 29) perpendicular to the sludge conveyance direction S are formed on the inner surface of the belt 29 at predetermined intervals. The convex portions of the driven roller 23b and the concave portion of the belt 29 mesh with each other, so that the rotational force of the driving roller (not shown) and the driven roller 23b constituting the transport roller can be efficiently transmitted to the belt 29. Yes.

In addition, as shown in the AA cross-sectional arrow view of FIG. 4, the convex portion of the driven roller 23b has a uniform height in the axial direction, but is not limited thereto. For example, as shown in FIG. 3 described above, the height of the convex portion may be configured to decrease from a predetermined position toward the central portion from both axial end portions. Thereby, the sludge 16 containing a lot of fluid with high fluidity overcomes the tension of the resin sheet 21 having a continuous porous structure and the elastic force of the belt 29 by its own weight, imitating the convex portion formed on the driven roller 23b. It becomes a shape.

FIG. 5 is a diagram illustrating another configuration example of the sludge volume reducing device 2. In contrast to the configuration shown in FIG. 4, the resin sheet 21 having a continuous porous structure is a resin sheet 21 a having a plurality of continuous porous structures divided into a predetermined length along the sludge transport direction S. Is different. FIG. 6 shows an enlarged view of a region B surrounded by a dotted line in FIG. 5, and FIG. 7 shows a top view of the region B shown in FIG. As shown in FIG. 6, the divided resin sheets 21 a having a plurality of continuous porous structures are each held by a resin sheet holding member 30 formed on the outer surface of the belt 29. Each resin sheet 21a is mounted by being pushed in the depth direction in FIG. As shown in FIGS. 6 and 7, each resin sheet holding member 30 has an inverted L-shaped longitudinal section and a shape extending in the width direction of the belt 29 (direction perpendicular to the sludge transport direction S). Have. Two resin sheet holding members 30 are located between resin sheets 21a having a continuous porous structure arranged adjacent to each other. The resin sheet holding member 30 is formed of, for example, an elastic body made of rubber or a non-porous resin like the belt 29.
By using the resin sheet 21a having such a continuous porous structure, if any of the resin sheets 21a having the continuous porous structure is damaged, only the damaged resin sheet 21a is replaced. It can respond. Therefore, the operation cost at the time of operation of the sludge volume reducing apparatus 2, especially the maintenance cost can be reduced.

In FIG. 8, the external view and sectional drawing of the water | moisture-content absorber which comprise the sludge volume reduction apparatus 2 are shown. As shown in the external view shown in the left diagram of FIG. 8 and the cross-sectional view shown in the right diagram, the moisture absorbing material is formed by covering a resin sheet 21 a having a continuous porous structure with a mesh-like cloth 31.
Here, the mesh-like cloth 31 is desirably a cloth made of polyethylene, polypropylene, or nylon that does not absorb moisture. This is because it is difficult to remove moisture from the mesh-like cloth 31 only by applying pressure by the above-described pressure roll 24 and the driven roller 23 facing the pressure roll 24. Rather, polyethylene and polypropylene having a hydrophobic hydrocarbon structure that hardly absorbs moisture are desirable. Nylon also absorbs moisture per unit weight slightly higher than polyethylene and polypropylene, but has a higher physical strength than polyethylene and polypropylene, and is therefore preferable because of its high strength as a cloth. Thus, by setting the resin sheet 21a having a continuous porous structure to be covered with the mesh-like cloth 31, resistance to tensile stress can be improved, and the resin sheet 21a having the continuous porous structure can be damaged. Can be reduced.
Embodiments of the present invention will be described below with reference to the drawings.

The sludge 16 is placed flat on the resin sheet 21 having a continuous porous structure constituting the sludge volume reducing device 2 shown in FIG. At this time, the thickness of the sludge 16 was about 4.5 mm and the width was 1 m. The water in the sludge 16 was 80% by weight, the water other than the water in the sludge 16 was 20% by weight, and the specific gravity was about 2. From this, the moisture per unit area of the sludge 16 immediately after being placed on the resin sheet 21 having a continuous porous structure is about 0.4 g / cm ² , and other than the sludge 16 is about 0.1 g / cm 2. ² .
On the other hand, the resin sheet 21 having a continuous porous structure of the sludge volume reducing device 2 has a width of 1.1 m and a length of 10 m. Here, the length of the resin sheet 21 having a continuous porous structure is the length from the position where the sludge 16 is placed to the position on the driven roller 23a disposed at the downstream end in FIG. And the rotation speed of the motor 28 which rotationally drives the drive roller 22 was set from the control part 13 (FIG. 1) so that the resin sheet 21 which has a continuous porous structure may drive | work on a conveyance roller at 2.5 m / m. Therefore, the time for which the sludge 16 is in contact with the resin sheet 21 having a porous structure is 4 minutes. As the resin having a continuous porous structure, a cellulose resin having a porosity of 93% was used, and the resin sheet 21 was not covered with the mesh-like cloth 31.

After 4 minutes, the sludge 16 reached the follower roller 23a disposed at the downstream end shown in FIG. 2, and the sludge 16 at this time had a thickness of about 1.5 mm. Then, as a result of measuring the water | moisture content in the sludge collect | recovered by the sludge collection tank 25, it was 50 weight%. From the above, the moisture per unit area of the sludge immediately before being collected in the sludge collection tank 25, that is, the volume of the sludge 17 reduced in volume is about 0.1 g / cm ² , and other than the sludge is about 0.1 g / cm ^2. Will remain.

Moisture in the sludge 16 immediately after being placed on the resin sheet 21 having a continuous porous structure was reduced to ¼ by contact with the resin sheet 21 having a continuous porous structure. In terms of the volume of the sludge 16, the thickness immediately after being placed on the resin sheet 21 having a continuous porous structure (about 4.5 mm) and the thickness of the sludge immediately before being collected in the sludge collection tank 25 (about 1. It was clarified that the volume of sludge can be reduced to 1/3 by converting from the change of 5 mm).
Here, as described above, the configuration of the sludge volume reducing apparatus 2 that flatly places the sludge 16 on the resin sheet 21 having a continuous porous structure will be described. FIG. 9 is a schematic configuration diagram in the vicinity of the sludge supply unit constituting the sludge volume reducing device 2.
As shown in FIG. 9, the sludge volume reducing device 2 places the sludge 16 supplied from the dehydrator 7 (FIG. 1) on the resin sheet 21 having a continuous porous structure. Is provided. The sludge supply unit 32 has a supply port 33 that rotates up and down in an arc shape around the fulcrum C. The opening degree of the supply port 33 is adjusted by the control unit 13 (FIG. 1) on the resin sheet 21 having a continuous porous structure so that the sludge having a desired thickness is orthogonal to the width direction of the resin sheet 21 (the sludge transport direction S In the direction of movement) to be substantially uniform. The portion of the supply port 33 that contacts the resin sheet 21 having a continuous porous structure has a rounded shape so as not to damage the resin sheet 21. Further, as shown in FIG. 9, the position of the supply port 33 in contact with the resin sheet 21 having a continuous porous structure is arranged upstream in the sludge transport direction S among the plurality of driven rollers 23 constituting the transport roller. It becomes the upper part of the driven roller 23 vicinity. That is, the supply port 33 is positioned downstream of the drive roller 22.

According to this embodiment, it is possible to reduce the volume of highly fluid sludge containing 80% by weight of water supplied from the dehydrator to 1/3.

In the present embodiment, a plurality of resin sheets 212 having different arithmetic surface roughness (Ra) on the surface in contact with the sludge of the resin sheet 21 having a continuous porous structure are used using the sludge volume reducing apparatus 2 of the above-described first embodiment. Using.
When the arithmetic surface roughness (Ra) of the resin sheet 21 having the continuous porous structure is 2 mm, the sludge remaining on the surface of the resin sheet 21 having the continuous porous structure is not recovered into the sludge recovery tank 25. The average was about 2% by weight. Further, when the arithmetic surface roughness (Ra) was 1.4 mm, the average amount of sludge remaining on the surface of the resin sheet 21 having a continuous porous structure was about 1% by weight.

On the other hand, when the arithmetic surface roughness (Ra) was 1.2 mm, the sludge remaining on the surface of the resin sheet 21 having a continuous porous structure was reduced to 0.1% by weight or less on average. Further, when the arithmetic surface roughness (Ra) was set to 1.0 mm, the remaining amount ratio was almost the same as when the arithmetic surface roughness (Ra) was set to 1.2 mm.
From this, it was found that the arithmetic surface roughness (Ra) of the surface in contact with the sludge of the resin sheet 21 having a continuous porous structure is desirably 1.2 mm or less.

According to the present embodiment, the arithmetic surface roughness (Ra) of the surface in contact with the sludge of the resin sheet 21 having a continuous porous structure is 1.2 mm or less, so that the fluidity supplied from the dehydrator 7 is reduced. It is possible to effectively reduce the volume of high sludge and improve the recovery rate of the reduced sludge.

In this embodiment, the sludge volume reducing device including the cylindrical driven roller 23 shown in FIG. 2 and the sludge volume reducing device in which the driven roller 23 has the shape shown in FIG. 3 are used. A comparative experiment was conducted.
When the moisture in the sludge supplied from the dehydrator 7 (FIG. 1) is about 80% by weight, the sludge has a viscosity of soft clay, and both can reduce the sludge appropriately.
However, when the water content in the sludge is 90% by weight, the sludge volume reducing device provided with the cylindrical driven roller 23 shown in FIG. 2 used in Example 1 has sludge on the resin sheet 21 having a continuous porous structure. Was driven, and the transport roller composed of the driving roller 22 and the driven

rollers

23 and 23a was driven to run the resin sheet 21 having a continuous porous structure. Then, the phenomenon that sludge leaks out from both ends of the resin sheet 21 having a continuous porous structure in a direction orthogonal to the sludge conveyance direction S (dripping down the resin sheet 21) occurred. This is because when the moisture in the sludge is too much, the viscosity of the sludge decreases and the fluidity of the sludge becomes extremely high, so that it wets and spreads on the resin sheet 21 having a continuous porous structure, and from both ends of the resin sheet 21 It is thought that leaked downward.

On the other hand, in the sludge volume reducing device having the driven roller 23 having a shape (recessed portion) whose outer diameter decreases from the predetermined position toward the central portion from the axial end portions shown in FIG. Even in the case of 90% by weight, sludge did not leak out from both ends in the width direction of the resin sheet 21 having a continuous porous structure. This is because when sludge is placed on the resin sheet 21 having the continuous porous structure, the sludge overcomes the tension of the resin sheet 21 having the continuous porous structure by its own weight, and is formed on the outer peripheral surface of the driven roller 23. It bends into a shape simulating a concave part. Accordingly, the sludge placed on the resin sheet 21 having a continuous porous structure is suitably held on the resin sheet 21 while being transported above the driven roller 23a disposed on the downstream end. It was confirmed that sludge can be prevented from flowing out (leaking out).

According to the present embodiment, the use of the driven roller 23 having the shape shown in FIG. 3 makes it possible to effectively sludge, particularly when the water content in the sludge is as high as 90% by weight or more and the sludge has extremely high fluidity. Can be reduced, and the recovery rate of sludge after volume reduction can be improved.

In this example, the durability test of the resin sheet 21 having a continuous porous structure was performed using the sludge volume reducing apparatus 2 shown in FIG. 2 used in Example 1 described above. The resin sheet 21 having a continuous porous structure was allowed to travel 200 times on an elliptical orbit around the transport roller composed of the driving roller 22 and the driven

rollers

23 and 23a shown in FIG. When the resin sheet 21 having a continuous porous structure after running for 200 revolutions was confirmed, fine cuts started to appear at the ends. After that, the resin sheet 21 having a continuous porous structure was run for 100 rotations on the elliptical orbit, and sludge volume reduction was performed. The resin sheet 21 having a continuous porous structure was broken and dropped from the transport roller after running a total of 300 revolutions and an elliptical circular orbit.

On the other hand, as shown in FIG. 8, a cellulose resin having a continuous porous structure was used as the resin sheet 21 a, the resin sheet 21 was covered with a polyethylene mesh cloth 31, and a long elliptical orbit was run by the transport roller. . At this time, the mesh interval of the polyethylene mesh cloth 31 was set to 200 μm, and the thickness of the fibers forming the mesh was set to 100 μm.
As a result of checking the ellipsoidal orbit after traveling 300 revolutions, a fine cut was not generated. After that, the slender volume reduction process was continued by traveling on the long elliptical circular orbit, and when it was confirmed after traveling a total of 1000 revolutions, the occurrence of a break was confirmed for the first time. In addition, about the volume reduction rate of sludge, the difference was not recognized with the case where volume reduction processing was performed only with the resin sheet 21 which has a continuous porous structure, without covering with the mesh-like cloth 31. FIG.
Further, when the mesh-like cloth 31 was made of polypropylene, the mesh interval was 100 μm, and the thickness of the fibers forming the mesh was 50 μm, almost the same result was obtained.

According to the present embodiment, as shown in FIG. 8, the continuous porous structure is maintained while maintaining the volume reduction rate by covering the resin sheet 21a having the continuous porous structure with the mesh cloth 31. It is possible to extend the life of the resin sheet 21a having

In addition, this invention is not limited to the above-mentioned Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace the configurations of other embodiments with respect to a part of the configurations of the embodiments.

DESCRIPTION OF SYMBOLS 1 ... Sewage treatment system 2 ... Sludge volume reduction apparatus 3 ... First sedimentation tank 4 ... Aerobic tank 5 ... Nitrification denitrification tank 6 ... Final sedimentation tank 7 ... Dehydrator 8 ... Aerobic tank diffuser tube 9 ... Stirrer 10 ... Nitrification Denitrification tank blower 11 ... Air volume adjustment valve 12 ... Sludge return pump 13 ... Control unit 15 ... Water to be treated 16 ... Sludge 17 ...

Volumetric sludge

21 and 21a ... Resin sheet 22 ...

Drive rollers

23, 23a and 23b ... Follower rollers 24 ... Pressure roller 25 ... Sludge collection tank 26 ... Moisture collection tank 27 ... Moisture absorbed 28 ... Motor 29 ... Belt 30 ... Resin sheet holding member 31 ... Mesh cloth 32 ... Sludge supply part 33 ... Supply port 60 ... Sludge Scraper 61 ... Chain 62 ... Flight 63a ... Drive

sprocket wheel

63b, 63c, 63d ... Driven sprocket wheel 64 ... Drive device 65 ... Scum clearance

Claims

A sludge collection tank for collecting the sludge after moisture removal;
An endless belt-like resin sheet having a continuous porous structure that is rotationally driven by a plurality of rollers and can absorb moisture in sludge placed on the surface thereof,
A pressure roller disposed at a position where the resin sheet is driven back in the vicinity of the sludge collection tank, and
By transporting the resin sheet to the sludge collecting tank side in a non-pressurized state, the resin sheet absorbs moisture in the sludge and discharges moisture from the resin sheet after moisture absorption by the pressure roller. A sludge volume reduction device characterized by that.
In the sludge volume reduction apparatus of Claim 1,
The sludge volume reducing device according to claim 1, wherein a material of the endless belt-shaped resin sheet having the continuous porous structure is a cellulose structure.
In the sludge volume reduction apparatus of Claim 1 or Claim 2,
The plurality of rollers include a driving roller and a plurality of driven rollers arranged on the downstream side of the driving roller,
Among the plurality of driven rollers, a predetermined number of driven rollers have a shape in which an outer diameter decreases from a predetermined position toward a central portion from both ends in the axial direction.
In the sludge volume reduction apparatus of Claim 3,
The sludge volume reducing device characterized in that the driven roller disposed at the downstream end and above the sludge recovery tank and the driving roller have a cylindrical shape with a uniform outer diameter in the axial direction. .
In the sludge volume reduction apparatus of Claim 1 or Claim 2,
The outer peripheral surface is fixed to the inner peripheral surface of the endless belt-shaped resin sheet having the continuous porous structure, and the inner peripheral surface has a fixed belt that comes into contact with the outer peripheral surfaces of the plurality of rollers,
The sludge volume reducing device, wherein the belt is formed of an elastic body or a non-porous resin.
In the sludge volume reduction apparatus of Claim 5,
A plurality of resin sheet holding members that are spaced apart at predetermined intervals in the longitudinal direction of the fixed belt and extend in the width direction of the fixed belt;
A sludge volume reducing device, wherein a resin sheet having the divided continuous porous structure is disposed between adjacent resin sheet holding members.
In the sludge volume reduction apparatus of Claim 1 or Claim 2,
An endless belt-like resin sheet having the continuous porous structure is covered with a mesh-like cloth.
In the sludge volume reduction apparatus of Claim 7,
The sludge volume reducing device, wherein the mesh cloth is made of polyethylene, polypropylene, or nylon.
In the sludge volume reduction apparatus of Claim 1 or Claim 2,
An arithmetic surface roughness of a surface in contact with the sludge of the endless belt-shaped resin sheet having the continuous porous structure is 1.2 mm or less, and the sludge volume reducing device.
An initial settling basin that separates organic matter from the incoming sewage by gravity settling;
A biological treatment tank for nitrifying and denitrifying the sewage flowing from the first sedimentation basin by sludge containing microorganisms;
A final settling basin installed on the downstream side of the biological treatment tank, having a sludge scraper and settling the sludge from the sewage flowing from the biological treatment tank, and separating the supernatant liquid;
A dehydrator for separating water from the sludge drawn from the final sedimentation basin;
A sludge volume reduction device that removes moisture from the sludge after dehydration,
The sludge volume reduction device is:
A sludge collection tank for collecting sludge after moisture removal, an endless belt-like resin sheet having a continuous porous structure that is rotationally driven by a plurality of rollers and is capable of absorbing moisture in the sludge placed on its surface; A pressure roller disposed at a position where the resin sheet is driven back in the vicinity of the sludge collection tank, and by conveying the resin sheet to the sludge collection tank side without pressurizing the sludge A sewage treatment system that absorbs moisture in the sludge and discharges moisture from the resin sheet after moisture absorption by the pressure roller.
The sewage treatment system according to claim 10,
The sewage treatment system, wherein a material of the endless belt-shaped resin sheet having the continuous porous structure is a cellulose structure.
The sewage treatment system according to claim 10 or 11,
The plurality of rollers include a driving roller and a plurality of driven rollers arranged on the downstream side of the driving roller,
Of the plurality of driven rollers, a predetermined number of driven rollers have a shape in which an outer diameter decreases from a predetermined position toward a central portion from both ends in the axial direction.
The sewage treatment system according to claim 10 or 11,
The outer peripheral surface is fixed to the inner peripheral surface of the endless belt-shaped resin sheet having the continuous porous structure, and the inner peripheral surface has a fixed belt that comes into contact with the outer peripheral surfaces of the plurality of rollers,
The sewage treatment system, wherein the belt is formed of an elastic body or a non-porous resin.
The sewage treatment system according to claim 13,
A plurality of resin sheet holding members that are spaced apart at predetermined intervals in the longitudinal direction of the fixed belt and extend in the width direction of the fixed belt;
A sewage treatment system, wherein a resin sheet having the divided continuous porous structure is disposed between adjacent resin sheet holding members.
The sewage treatment system according to claim 10 or 11,
A sewage treatment system, wherein the endless belt-like resin sheet having the continuous porous structure is covered with a mesh cloth.