JP5340813B2 - Screw press dehydrator, sludge treatment system, and method of operating sludge treatment system - Google Patents

Description

  The present invention relates to an improvement of a screw press dehydrator used as a sludge dehydrator in the sewerage treatment field and the industrial wastewater treatment field, a sludge treatment system using the screw press dehydrator, and an operation method of the sludge treatment system.

  Conventionally, a screw press dehydrator used as a sludge dehydrator in the sewerage treatment field and the industrial wastewater treatment field is a screw auger and an outer cylinder screen arranged around the screw auger in order to condense the sludge, etc. The main structure is composed in combination. The filter material (filter) of the outer cylinder screen uses a metal filter (punching metal, etc.), and the opening is φ0.5 mm to φ1.5 mm, which is a fibrous filter cloth used in belt press dehydrators and the like. Since it is large in comparison, the solid matter that cannot be trapped during dehydration and is discharged outside the machine, so-called suspended solids (SS) increases, and the SS recovery rate is about 90 to 95%. It is generally said that the SS recovery rate is poor compared to other models (see Non-Patent Document 1, for example).

  Therefore, in order to solve this problem, the SS content in the filtrate discharged from the screw press dehydrator is recovered, returned to the sludge storage tank in the previous stage of dehydration, and supplied again to the dehydrator to improve the SS recovery rate. A filtrate separating apparatus has been proposed (see, for example, Non-Patent Document 2).

"Guide to using polymer flocculants" (Tokyo Sewer Service Co., Ltd., issued in March 2002) High-efficiency press-fitting screw press dehydrator Technical Manual March 2006 (Issued date: March 31, 2006, Issued by Sewerage New Technology Promotion Organization) Pages 187-191

  However, the filtrate separation device disclosed in Non-Patent Document 2 has a problem that it is a large-scale device, costs are considerably increased, and operation control is complicated.

  The present invention was made in order to solve such a conventional problem, and its purpose is to collect SS in a dehydrator body, settle SS and separate SS, and discharge the clear filtrate. An object of the present invention is to provide a screw press dehydrator, a sludge treatment system, and a method for operating the sludge treatment system that can improve the rate.

The screw press type dehydrator according to claim 1 is provided with an outer cylinder screen having a cylindrical shape and a spiral screw blade on an outer periphery of a tapered shaft, and is rotatably disposed in the outer cylinder screen. A screw whose outer peripheral end face is substantially in contact with the outer cylinder screen, a sludge supply port provided on the small-diameter portion side of the screw, which is the lower portion of the screw, and a large-diameter portion side of the screw, which is the upper portion of the screw A cake outlet provided above, an outer cylinder provided on the outer periphery of the outer cylinder screen for receiving the filtrate squeezed from the outer cylinder screen , and a clear filtrate in the outer cylinder located at the upper part of the outer cylinder screen discharged, and the outer cylinder above the clear provided filtrate outlet, intermittently discharging a high filtrate of SS concentration accumulated in said outer cylinder downward, the outer Characterized in that it comprises a filtrate outlet provided below.

The screw press type dehydrator according to claim 2 is the screw press type dehydrator according to claim 1, wherein an opening / closing valve is provided at the filtrate discharge port provided below the outer cylinder, and the opening / closing valve is provided. By closing, the filtrate is stored in the filtration chamber formed between the outer cylinder and the outer cylinder screen, and the SS in the filtrate in the filtration chamber is settled and separated, so that the clear filtrate is discharged. A clear filtrate is discharged from the outlet, and the on-off valve is intermittently opened to discharge a high-concentration filtrate accumulated below the filtration chamber from the filtrate outlet .

The screw press-type dehydrator according to claim 3 is the screw press-type dehydrator according to claim 2, wherein the on-off valve has a cycle of 20 to 30 minutes during operation in which sludge is compressed and dehydrated and discharged. It is characterized by being operated to open for 3 minutes and close otherwise .

The screw press type dehydrator according to claim 4 is provided with a cylindrical outer cylinder screen and a spiral screw blade on an outer periphery of a tapered shaft, and is rotatably arranged in the outer cylinder screen. A screw whose outer peripheral end surface is substantially in contact with the outer cylinder screen, a sludge supply port provided on the small-diameter portion side of the screw, a cake outlet provided on the large-diameter portion side of the screw, and the outer cylinder screen An outer cylinder that is provided on the outer periphery and receives the filtrate squeezed from the outer cylinder screen, a clear filtrate discharge port that is provided in the outer cylinder and discharges the clear filtrate in the outer cylinder, and is provided in the outer cylinder. be supplied and the screw press type dehydrator, the sludge in the screw press type dehydrator and a intermittently discharged to the filtrate outlet of the high filtrate of SS concentration accumulated in the outer tube A sludge supply device, a sludge supply passage connecting the sludge supply port of the screw press dehydrator and the sludge supply device, and sending the sludge to the screw press dehydrator, and a filtrate discharge section of the screw press dehydrator And a sludge return path for feeding a filtrate having a high SS concentration accumulated in the screw press type dehydrator to the sludge supply apparatus.

  The sludge treatment system according to claim 5 is the sludge treatment system according to claim 4, wherein the sludge supply device is a sludge storage tank, a sludge supply pump for sending sludge from the sludge storage tank, and sludge sent by the sludge supply pump. A sludge agglomeration device that aggregates by adding a flocculant, the sludge supply path connects the sludge agglomeration device and the sludge supply port of the screw press dehydrator, and the sludge return path is the filtrate of the screw press dehydrator It is characterized by connecting the discharge part and the sludge storage tank.

  The operation method of the sludge treatment system according to claim 6 is the method of operating the sludge treatment system according to claim 4 or 5, wherein the sludge sent from the sludge supply device is introduced into the outer cylinder screen, During the process of squeezing and dewatering gradually with the outer cylinder screen and the process of squeezing and dewatering and discharging the sludge, the filtrate outlet is closed and the filtrate is stored in the outer cylinder and contained in the filtrate. The step of precipitating and separating the solid matter (SS), the step of discharging the clear filtrate produced during the step of precipitating and separating the solid matter (SS) contained in the filtrate, and the outer cylinder A step of intermittently discharging the filtrate having a high SS concentration accumulated in the filtrate from the filtrate discharge port, and a step of returning the filtrate having a high SS concentration discharged intermittently from the filtrate discharge port to the sludge storage tank. It is characterized by providing.

The operation method of the sludge treatment system according to claim 7 is the operation method of the sludge treatment system according to claim 6, wherein the step of intermittently discharging the filtrate having a high SS concentration accumulated in the outer cylinder from the filtrate outlet. Measures the turbidity of the clear filtrate with a turbidimeter, opens the filtrate outlet when the measured value exceeds the threshold, and after the filtrate outlet is opened, there is filtrate collected in the outer cylinder It is operated so that a filtrate discharge port may be closed after the time required for discharging a certain amount.
The operation method of the sludge treatment system according to claim 8 is the operation method of the sludge treatment system according to claim 6, wherein the filtrate having a high SS concentration accumulated in the outer cylinder is intermittently discharged from the filtrate discharge port. Is characterized in that it is operated based on the time for opening and closing the filtrate outlet determined by the trial operation of the sludge treatment system.

According to the present invention, the SS recovery rate of a screw press dehydrator can be improved to 98 to 99% with a simple apparatus and operation method.
According to the present invention, as a secondary effect, it is possible to operate without worrying about the SS recovery rate, so cake moisture content priority operation, throughput priority operation or low chemical injection rate operation is possible, Dehydration performance can be improved.

It is a lineblock diagram showing the vertical screw press type dehydrator concerning one embodiment of the present invention. It is explanatory drawing which shows the sludge processing system which concerns on one Embodiment of this invention. It is explanatory drawing which shows the operating method of filtrate discharge | emission in the sludge processing system shown in FIG. It is a graph which shows the comparison by the filtrate level of the cake moisture content in a sewage mixing raw sludge. It is a graph which shows the comparison by the filtrate level of the moisture content of the cake in sewage digestion sludge.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 shows a vertical screw press dehydrator 1 according to an embodiment of the present invention.
The screw press type dehydrator 1 according to the present embodiment is provided with an outer cylindrical screen 3 having a vertical cylindrical shape, and screw blades 9 that are spiral and have the same outer shape of each blade on the outer periphery of a tapered shaft 7. A tapered screw 5 that is rotatably disposed in the outer cylinder screen 3 with the small shaft diameter portion 7a at the bottom, a sludge supply port 13 provided on the small shaft diameter portion 7a side of the screw 5, and a large shaft diameter of the screw 5. The cake outlet 15 provided in the part 7b side, the outer cylinder 17 which is provided in the outer periphery of the outer cylinder screen 3, receives the filtrate squeezed from the outer cylinder screen 3, and the motor 21 which rotationally drives the screw 5 are provided. .

  For the outer cylinder screen 3, for example, a SUS304 wire mesh or a punching plate is used. And as for the filtration hole, the hole diameter of the concentration zone mentioned later is 1.0-1.5 mm, the hole diameter of a filtration zone is 0.7-1.0 mm, and the hole diameter of a pressing zone is 0.5-0. It is set to 6 mm. In this embodiment, the hole diameter of the concentration zone is 1.2 mm, the hole diameter of the filtration zone is 0.8 mm, and the hole diameter of the pressing zone is 0.5 mm. The length and the diameter of the outer cylinder screen 3 are arbitrary, but in this embodiment, the length of the outer cylinder screen 3 is 660 mm and the diameter of the outer cylinder screen 3 is 200 mm.

The screw 5 is made of, for example, SUS304 material. The shaft 7 of the screw 5 is directed from the sludge input side to the dewatered cake discharge side so that the filter chamber 11 formed between the outer cylinder screen 3 continuously decreases in volume toward the dewatered cake discharge side. The taper is thickened.
As with the shaft 7, the pitch of the screw blades 9 is set so as to decrease from the sludge input side to the dewatered cake discharge side so that the volume of the filter chamber 11 continuously decreases toward the dewatered cake discharge side. Has been. The pitch of the screw blades 9 is substantially the same as that in Non-Patent Document 1.

  The outer cylinder screen 3, the screw 5, and the outer cylinder 17 are erected on the pedestal 23 using a watertight mechanism via a receiving portion 25 communicating with the sludge supply port 13. The receiving part 25 has a short cylindrical shape, and the upper side thereof is the lower surface of the outer cylinder 17, and the outer cylinder screen 3 has a watertight seal on the inner surface of the hole whose upper side is opened by a coaxial small-diameter circle. This prevents the sludge in the receiving portion 25 from short-passing to the outer cylinder 17. The screw 5 passes through a hole opened by a coaxial small-diameter circle on the lower side of the receiving portion 25 at the lower end of the shaft 7 through a water-tight seal, and has a lower end portion of the small-diameter portion 7a in the lower part thereof. The space between the outside of the shaft 7 of the screw 5 and the screw blade 9 communicates with the receiving portion 25.

  A shaft 27 is attached to the screw 5 so as to pass through the receiving portion 25 from the lower end portion of the small shaft diameter portion 7a of the screw 5 and protrude into the mount 23, and is supported by a bearing (not shown) so as to be rotatable. A sprocket 33 is attached to the shaft 27, and is connected via a chain 35 to a sprocket 39 provided on a drive shaft 37 of the motor 21 installed on the mount 23. Here, the drive device of the screw 5 includes a motor 21 installed on the mount 23, a sprocket 33 provided on the shaft 27 of the screw 5, a sprocket 39 provided on the drive shaft 37 of the motor 21, and sprockets 33, 39. It is comprised with the chain 35 stretched over.

  A hollow shaft 31 is attached to the lower end portion of the outer cylinder screen 3 and is connected to a metal fitting 29 for receiving the outer cylinder screen 3, and is coaxially disposed outside the shaft 27 of the screw 5. A sprocket 41 is attached in the vicinity of the lower end of the hollow shaft 31 and is connected to a sprocket 47 provided on the drive shaft 45 of the motor 43 of the outer cylinder screen 3 installed on the mount 23 via a chain 49. Here, the driving device for the outer cylinder screen 3 includes a motor 43 installed on the gantry 23, a sprocket 41 provided on the hollow shaft 31 of the screw 5, a sprocket 47 provided on the driving shaft 45 of the motor 43, The chain 49 extends between the sprockets 41 and 47.

  The outer cylinder 17 is provided with a clear filtrate outlet 18 for discharging a low-concentration clear filtrate at the upper part, and a filtrate outlet 19 for discharging a high-concentration filtrate at the lower part. Yes. The filtrate outlet 19 is provided with an open / close valve 20 driven by a motor. By closing the on-off valve 20, the filtrate is stored in the filtration chamber 79 formed in the outer cylinder 17, and the SS in the filtrate in the filtration chamber 79 is settled and separated. Then, the clear filtrate is discharged from the upper clear filtrate outlet 18. Further, by opening the on-off valve 20 intermittently, the high-concentration filtrate accumulated below the filtration chamber 79 is discharged from the lower filtrate outlet 19.

In the outer cylinder 17, a plurality of water spray nozzles 51 are installed vertically to perform back washing of the outer cylinder screen 3 when the operation is stopped between the dehydration operation and the dehydration operation. In the back washing of the outer cylinder screen 3, the outer cylinder screen 3 is washed with a cleaning spray using pressure water when the operation is stopped. The entire outer surface of the screen 3 is cleaned.
On the upper side of the outer cylinder 17, a cylinder part 53 that covers the terminal end side of the large-diameter part side 7 b of the screw 5 is provided. The cylinder portion 53 is provided with an outlet pressure sensor 55.

An outlet cone 57 is installed at the end of the screw 5 in the cylindrical portion 53. The outlet cone 57 adjusts the discharge amount while pressing the dehydrated cake discharged from the cylindrical portion 53 by the outlet control cylinder 61 installed on the shaft 59 provided at the terminal portion of the screw 5. The outlet control cylinder 61 communicates with a compressed air supply source (not shown) via a compressed air pipe 63.
Around the outlet cone 57, a dewatered sludge storage portion 65 connected to the tube portion 53 is formed, and a rotary cake scraping blade 67 is rotatably arranged. The rotary cake scraping blade 67 is hung on a doughnut-shaped rack internal gear 71 rotatably supported on the inner periphery of the dewatered sludge storage portion 65, and a spur gear 73 meshing with the rack internal gear 71 is provided. The provided shaft 75 is attached to the dewatered sludge storage portion 65 via a bearing, and a spur gear 77 is provided on the shaft 75, and the spur gear 77 is provided on a shaft 59 connected to the terminal end of the screw 5. By meshing, the inside of the dewatered sludge container 65 can be rotated in synchronization with the rotation of the screw 5.

The dehydrated sludge storage unit 65 is provided with a cake outlet 15.
In the screw press type dehydrator 1 according to this embodiment, as shown in FIG. 1, a concentration zone (moisture 98 to 95%), a filtration zone (from the small shaft diameter portion 7 a to the large shaft diameter portion 7 b of the screw 5). The filter chamber 11 is formed so as to constitute a pressing zone (moisture of 88 to 75%).

FIG. 2 shows a sludge treatment system 100 according to an embodiment of the present invention using the vertical screw press dehydrator 1 according to the embodiment of the present invention shown in FIG.
In the sludge treatment system 100 according to the present embodiment, the sludge supply port 103 of the sludge supply device 101 that supplies the sludge to the screw press dehydrator 1 is connected to the sludge supply port 13 of the screw press dehydrator 1, and the screw press The sludge return path 105 for sending the filtrate having a high SS concentration accumulated in the screw press dehydrator 1 to the sludge supply device 101 is connected to the filtrate outlet 19 of the screw dehydrator 1. The low-concentration clear filtrate discharged from the clear filtrate outlet 18 provided at the upper part of the outer cylinder 17 is configured to be sent to a water treatment facility (not shown).

Here, the sludge return path 105 is configured to send the filtrate having a high SS concentration accumulated in the screw press dehydrator 1 by the transfer pump 106 to the sludge supply device 101. In addition, when the filtrate with a high SS concentration collected in the screw press type dehydrator 1 by natural flow can be sent to the sludge supply apparatus 101, the transfer pump 106 can be omitted.
The sludge supply apparatus 101 includes a sludge storage tank 107, a sludge supply pump 109 that sends out sludge from the sludge storage tank 107, and a sludge aggregation apparatus 111 that aggregates the sludge sent by the sludge supply pump 109 by adding a flocculant. ing.

The sludge storage tank 107 is configured to store sludge sent from a concentration facility (not shown) by the concentrated sludge extraction pump 113. The sludge storage tank 107 includes a stirring blade 108 driven by a motor.
The sludge aggregating device 111 stores the polymer flocculant dissolved from the flocculant dissolution tank 115 that dissolves the polymer flocculant by the flocculant supply pump 117 and the sludge sent from the sludge storage tank 107 by the sludge supply pump 109. It is configured as follows. The sludge aggregating apparatus 111 includes a stirring blade 112 driven by a motor. The flocculant dissolution tank 115 includes a stirring blade 116 driven by a motor to dissolve the polymer flocculant.

  In the present embodiment, the water spray nozzle 51 provided in the outer cylinder 17 of the screw press dehydrator 1 is supplied with cleaning water sent from the water supply tank 119 by the cleaning water pump 121, and the outlet control cylinder 61 is supplied to the outlet control cylinder 61. The compressed air sent from the air compressor 123 is supplied.

FIG. 3 shows an example of an operation method for discharging the filtrate in the sludge treatment system 100 shown in FIG.
Next, a method of operating the sludge treatment system 100 according to the present embodiment based on the screw press dehydrator 1 shown in FIG. 1, the sludge treatment system 100 shown in FIG. 2, and the filtrate discharge operation method shown in FIG. explain.
First, the screw press dehydrator 1 and the sludge supply device 101 are driven. At that time, the on-off valve 20 of the filtrate outlet 19 at the bottom of the screw press type dehydrator 1 is closed.

  Then, the flocculant added with a flocculant in the sludge aggregating apparatus 111, for example, the agglomerated sludge made of solid matter of 2 to 3 mm is, for example, 30 to 50 KPa by the sludge supply pump 109 through the sludge supply path 103. It is introduced into the outer cylinder screen 3 from the sludge supply port 13 under pressure, and is formed between the outer cylinder screen 3 by the screw blades 9 in the concentrating zone by the screw 5 of ultra-low speed rotation (0.08 to 1 rpm). Transport while dehydrating in the chamber 11.

  The moisture content of the inlet sludge in the concentration zone is 98% to 95% (in other words, the solid concentration is 2% to 5% (weight ratio)), and the sludge introduced into the screw press dehydrator 1 is pressurized. Attaching and depositing on the inner surface of the outer cylinder screen 3 on the flow flowing from the high filter chamber 11 to the space between the outer cylinder 17 and the outer cylinder screen 3 on the outside of the outer cylinder screen 3, the screw blade 9 Therefore, it adheres to the blade surface on the upstream side in the traveling direction of the screw 5 and is transported to the subsequent filtration zone. As soon as the screw blades 9 pass, the outer cylinder screen 3 is exposed, and the water in the filter chamber 11 between the blade pitches flows into the filtration chamber 79 formed between the outer cylinder 17 at once.

Then, the dewatered sludge flows into the dewatered sludge storage 65 while receiving the pressing force by the outlet cone 61 from the compression zone, and is discharged from the cake outlet 15 by the rotary cake scraper 67.
On the other hand, the opening / closing valve 20 of the lower filtrate discharge port 19 is opened for 3 minutes, for example, as shown in FIG. In order to close the other, the filtrate is stored in the filtration chamber 79 of the outer cylinder 17, and the solid (SS) contained in the filtrate is precipitated and separated.

And the clear filtrate (for example, SS density | concentration 150-300 mg / L) produced | generated at the time of carrying out the precipitation separation of the solid substance (SS) contained in a filtrate is discharged | emitted as overflow from the upper clear filtrate discharge port 18. And sent to the water treatment facility.
Next, the opening / closing valve 20 of the lower filtrate discharge port 19 is opened for only 3 minutes, for example, as shown in FIG. The filtrate with high SS concentration (for example, 0.002 m ³ per discharge, SS concentration of 4000 to 8000 mg / L) accumulated in the filtration chamber 79 of the outer cylinder 17 is discharged from the filtrate discharge port 19.

And the filtrate with high SS density | concentration discharged | emitted intermittently from the filtrate discharge port 19 is returned to the sludge storage tank 107 via the sludge return path 105. FIG.
In addition, discharge of the filtrate with high SS concentration from the filtrate discharge port 19 controls the on-off valve 20 based on the time to open and close the filtrate discharge port 19 obtained by the trial operation of the sludge treatment system 100. Is done by. Further, the turbidity of the clear filtrate is measured with a turbidimeter, and when the measured value is equal to or higher than a threshold value (for example, the SS concentration is 300 mg / L or higher), the filtrate outlet 19 is opened. After the release valve 20 is opened, the time required to discharge a certain amount of the filtrate accumulated in the outer cylinder 17 (required to discharge 4/5 of the filtrate storage height of the outer cylinder, for example) The on-off valve 20 may be controlled so as to close the filtrate outlet 19 after elapse of time, for example, in the case of this apparatus, for example, for 3 minutes.

Next, the effect of the filtrate level on the cake moisture content in the screw dehydrator 1 will be described.
1-1. Experimental data of sewage mixed raw sludge Figure 4 shows a comparison of cake moisture content according to the filtrate level.
In this figure, ■ is data on the moisture content of the cake when the normal filtrate is discharged without accumulating, and ◆ indicates that the lower filtrate discharge port 19 is fully closed, the filtrate is accumulated, and the upper clear filter is collected. It is the data of the cake moisture content when it is made to overflow from the liquid drain port 18. FIG.
Table 1 shows the sludge concentration, chemical injection rate, coagulator rotation speed, screw rotation speed, and outlet pressure at that time.

[Discussion]
When the on-off valve 20 of the lower filtrate outlet 19 is fully closed, the filtrate is kept at the entire outer cylinder level, overflowed from the clear filtrate outlet 18, and the dehydrated portion is immersed in the filtrate, and the lower filter When the on-off valve 20 of the liquid discharge port 19 was fully opened and the filtrate in the outer cylinder was discharged to expose the dewatered portion, there was no particular effect on the moisture content of the cake.

1-2. Experimental data of sewage digestion sludge Figure 5 shows a comparison of cake moisture content according to the filtrate level.
In this figure, ■ is data on the moisture content of the cake when the normal filtrate is discharged without accumulating, and ◆ indicates that the lower filtrate drain 19 is fully closed, the filtrate is accumulated, and the upper clear filter is collected. It is the data of the cake moisture content when it is made to overflow from the liquid drain port 18. FIG.
Table 2 shows the sludge concentration, chemical injection rate, coagulator rotation speed, screw rotation speed, and outlet pressure at that time.

[Discussion]
When the on-off valve 20 of the lower filtrate outlet 19 is fully closed to keep the filtrate at the entire outer cylinder level and overflowed from the clear filtrate outlet 18, the on-off valve 20 of the lower filtrate outlet 19 is fully opened. When the filtrate in the outer cylinder was discharged, the moisture content of the cake tended to be slightly lower when overflowing.

From the above results, it was confirmed that the moisture content of the cake was not adversely affected even when the on-off valve 20 of the lower filtrate outlet 19 was fully closed and the dehydrated portion was immersed in the filtrate.
That is, it was confirmed that the fluid moves from a high pressure to a low pressure, but the reverse is not possible. The internal pressure of the dehydrator is lower: around 30 KPa and upper: around 100 KPa, whereas the pressure generated at the filtrate head is lower: about 10-20 KPa and upper: 0 KPa. It was confirmed that does not adversely affect the moisture content of the cake.

Next, the influence of the return of the high concentration filtrate on the sludge concentration in the sludge storage tank 107 will be described.
The sludge having a sludge concentration of 20000 mg / L is supplied from the concentration facility to the sludge storage tank 107 by the concentrated sludge extraction pump 113. Here, let sludge supply amount be Q1.
The amount Q2 of sludge drawn out from the sludge storage tank 107 by the sludge supply pump 109 is set to 0.6 m ³ / h.

The amount of filtrate discharged per discharge from the lower filtrate outlet 19 is set to 0.002 m ³ . The SS concentration of the filtrate is set to 4000 to 8000 mg / L (average 6000 mg / L). Let Q3 be the amount of high concentration filtrate returned.
Based on these, the sludge concentration in the sludge storage tank is calculated.
Sludge supply amount: Q1 = Q2-Q3
Sludge extraction amount: Q2 = 0.6 m ³ / h
High concentration filtrate return amount: Q3 = 0.002 m ³ × 60 minutes / 25 minutes = 0.05 m ³ / h
However, one cycle time (average) is 25 minutes.

Therefore, the sludge supply amount and the sludge concentration of sludge extraction are as follows.
Sludge supply rate: Q1 = Q2-Q3 = 0.6m 3 /h-0.05m 3 /h=0.55m 3 / h
Sludge extraction sludge concentration = (Q1 x 20000 + Q3 x 6000) / Q2
= (0.55 x 20000 + 0.05 x 6000) /0.6
= 18830 mg / L
Therefore, the sludge concentration of 20000 mg / L supplied to the sludge storage tank 107 is gradually diluted when the high-concentration filtrate is returned, and finally the concentration is reduced to 18830 mg / L. However, such a change is a range that occurs on a daily basis, and it is extremely unlikely that the operation of the screw press type dehydrator 1 will be hindered.

  In the above embodiment, the screw press type dehydrator according to the present invention has been described as a vertical type, but it can also be used as a horizontal type or an inclined type.

DESCRIPTION OF SYMBOLS 1 Screw press type dehydrator 3 Outer cylinder screen 5 Screw 7 Shaft 7a Shaft small diameter part 7b Shaft large diameter part 9 Screw blade 11 Filter chamber 13 Sludge supply port 15 Cake outlet 17 Outer cylinder 18 Clear filtrate discharge port 19 Filtrate discharge port 20 On-off valve 21 Motor 79 Filtration chamber 100 Sludge treatment system 101 Sludge supply apparatus 103 Sludge supply path 105 Sludge return path 106 Transfer pump 107 Sludge storage tank 109 Sludge supply pump 111 Sludge aggregation apparatus 115 Coagulant dissolution tank 117 Coagulant supply pump 119 Water supply tank

Claims (8)

An outer cylinder screen having a cylindrical shape;
A screw provided on the outer periphery of the tapered shaft, and a screw that is rotatably arranged in the outer cylinder screen, and an outer peripheral end surface of the screw blade substantially contacts the outer cylinder screen;
A sludge supply port provided on the small-diameter portion side of the screw, which is the lower portion of the screw;
A cake outlet provided on the upper side of the large-diameter portion of the screw that is an upper portion of the screw;
An outer cylinder that is provided on the outer periphery of the outer cylinder screen and receives the filtrate squeezed from the outer cylinder screen;
A clear filtrate outlet provided above the outer cylinder for discharging the clear filtrate in the outer cylinder located at the upper part of the outer cylinder screen ;
A screw press-type dehydrator comprising: a filtrate discharge port provided below the outer cylinder for intermittently discharging a filtrate having a high SS concentration accumulated in the lower part of the outer cylinder . In the screw press type dehydrator according to claim 1,
The filtrate outlet provided below the outer cylinder is provided with an on-off valve,
By closing the on-off valve, the filtrate is stored in the filtration chamber formed between the outer cylinder and the outer cylinder screen,
The SS in the filtrate in the filtration chamber is separated by settling, so that the clear filtrate is discharged from the clear filtrate outlet,
A screw press type dehydrator characterized in that a high-concentration filtrate collected below the filtration chamber is discharged from the filtrate outlet by opening the on-off valve intermittently . In the screw press type dehydrator according to claim 2,
The on-off valve is operated when the sludge is compressed and dehydrated and discharged.
A screw press-type dehydrator that is operated to open for 3 minutes and to close for the other period of 20 to 30 minutes . An outer cylinder screen having a cylindrical shape and a spiral screw blade on the outer periphery of a tapered shaft are rotatably disposed within the outer cylinder screen, and an outer peripheral end surface of the screw blade is substantially in contact with the outer cylinder screen. A screw, a sludge supply port provided on the small-diameter portion side of the screw, a cake outlet provided on the large-diameter portion side of the screw, and provided on the outer periphery of the outer cylinder screen and squeezed out of the outer cylinder screen An outer cylinder that receives the filtrate, a clear filtrate outlet that is provided in the outer cylinder and discharges the clear filtrate in the outer cylinder, and a high SS concentration filter that is provided in the outer cylinder and accumulates in the outer cylinder. A screw press dehydrator comprising a filtrate outlet for intermittently discharging the liquid ;
A sludge supply device for supplying sludge to the screw press dehydrator;
A sludge supply path for connecting the sludge supply port of the screw press type dehydrator and the sludge supply device and sending the sludge to the screw press type dehydrator;
A sludge return path that connects the filtrate discharge section of the screw press type dehydrator and the sludge supply device, and sends the filtrate having a high SS concentration accumulated in the screw press type dehydrator to the sludge supply device. Characteristic sludge treatment system. In the sludge treatment system according to claim 4,
The sludge supply device includes a sludge storage tank, a sludge supply pump that sends out sludge from the sludge storage tank, and a sludge aggregation device that aggregates by adding a flocculant to the sludge sent by the sludge supply pump,
The sludge supply path connects the sludge aggregation device and the sludge supply port of the screw press type dehydrator,
The sludge return path connects the filtrate discharge section of the screw press dehydrator and the sludge storage tank. In the method of operating the sludge treatment system according to claim 4 or 5,
The step of introducing the sludge sent from the sludge supply device into the outer cylinder screen, gradually squeezing and dewatering with the screw and the outer cylinder screen, and discharging,
During the step of pressing and dewatering and discharging the sludge, closing the filtrate outlet, storing the filtrate in the outer cylinder, and precipitating and separating solids (SS) contained in the filtrate;
Draining the clear filtrate produced during the step of precipitating and separating solids (SS) contained in the filtrate from the clear filtrate outlet;
A step of intermittently discharging the filtrate having a high SS concentration accumulated in the outer cylinder from the filtrate outlet;
And a step of returning the filtrate having a high SS concentration that is intermittently discharged from the filtrate discharge port to the sludge storage tank. In the operation method of the sludge treatment system according to claim 6,
In the step of intermittently discharging the filtrate having a high SS concentration accumulated in the outer cylinder from the filtrate outlet, the turbidity of the clear filtrate is measured with a turbidimeter, and the measured value exceeds a threshold value. The filtrate outlet is opened, and after the filtrate outlet is opened, the filtrate outlet is closed after elapse of time required for discharging a certain amount of filtrate accumulated in the outer cylinder. A method for operating a sludge treatment system, characterized in that In the operation method of the sludge treatment system according to claim 6,
The step of intermittently discharging the filtrate having a high SS concentration accumulated in the outer cylinder from the filtrate discharge port includes the time for opening and closing the filtrate discharge port determined by the trial operation of the sludge treatment system. A method for operating a sludge treatment system, characterized in that it is operated based on

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