JP2005349304A - Method and apparatus for volume reduction of surplus sludge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a practical method and apparatus for volume reduction of surplus sludge which can crush the surplus sludge stably at high crushing efficiency to solubilize it, and has a high volume-reduction ratio and high energy efficiency. <P>SOLUTION: In the surplus sludge volume reduction method which enables the biological treatment of organic wastewater in a biological treatment tank, at least a part of the surplus sludge generated by the biological treatment is crushed, and the crushed surplus sludge is returned to the biological treatment tank to be biologically treated again, the surplus sludge with a volume of 1.2-3.8 times of surplus sludge generated from the organic wastewater is agitated by a rotary vane 45, and passed through holes 46a foamed in screens 46 disposed around the rotary vane 45 to be sheared and crushed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an excess sludge volume reduction method and an excess sludge volume reduction apparatus that reduce the volume of sludge produced by biological treatment of organic wastewater.

  Conventionally, raw sludge generated from wastewater treatment facilities such as sewage treatment plants and surplus sludge produced by biological treatment of organic matter are disposed of as industrial waste by incineration or landfill after concentration and / or dehydration. It has been. However, incineration as industrial waste requires evaporation of moisture in the process of burning sludge, which requires a large amount of heat and is not economical. In addition, it has been difficult to secure a landfill site for industrial waste reclamation. For these reasons, volume reduction of excess sludge has been demanded.

In recent years, solubilization treatment has been developed and attracted attention as a treatment method for excess sludge generated from wastewater treatment facilities and the like. This sludge solubilization process is a process in which surplus sludge is solubilized (liquefied) by crushing or damaging the cell wall of surplus sludge (microorganisms) by mechanical, physical, chemical, or biological techniques.
Here, as a mechanical method, a wet medium stirring mill (see Patent Document 1), a rotary blade (see Patent Document 2), a rotating disk (see Patent Document 3), a homogenizer (see Patent Document 4), or the like is used. And a method of crushing sludge.
Examples of physical methods include ozone treatment (see Patent Document 5), jetting treatment by a pressurizing part, a constriction part, and a low pressure part (see Patent Document 6), ultrasonic treatment (see Patent Document 7), and the like.
Chemical methods include alkali treatment (see Patent Literature 8), acid treatment (see Patent Literature 9), radical reaction treatment (see Patent Literature 10), sterilization treatment (see Patent Literature 11), and pulse discharge treatment (Patent Literature 12). And high temperature treatment (see Patent Document 13).
Biological techniques include solubilizing enzyme treatment (see Patent Documents 14 and 15).
If surplus sludge solubilized by such a technique is biologically treated again, the amount of surplus sludge discharged from the waste water treatment facility or the like can be reduced to zero or extremely small.
JP-A-11-300393 JP 2000-343098 A JP 2001-70993 A JP 2000-24698 A Japanese Patent No. 2973761 JP 2001-314877 A Japanese Patent No. 3212969 JP-A-11-188399 JP 2003-1300 A JP 2001-96291 A Japanese Patent Laid-Open No. 11-277087 JP 11-179391 A Japanese Patent Laid-Open No. 9-276887 Japanese Patent No. 3176563 Japanese Patent No. 3267935

  However, among the above-described sludge solubilization treatments, the physical method, particularly the ozone treatment, has a problem that the equipment cost is high, and the medium-scale equipment has a small cost merit. In the chemical method, since the chemicals are continuously added, the treatment tends to be complicated. Biological techniques cannot be sufficiently solubilized, and the aeration blower amount must be increased and the temperature needs to be adjusted. This requires running costs, and the biological treatment tank has to be managed more strictly. Therefore, neither method is practical.

The mechanical method has the advantage that the excess sludge can be solubilized with inexpensive equipment compared to other methods. However, in the crushing by a ball mill or a wet medium agitation type mill, not only the crushing efficiency of surplus sludge is remarkably lowered due to cavitation generated in these apparatuses, but also it is difficult to remove the generated cavitation out of the system. Moreover, the crushing efficiency decreased with time due to wear of the apparatus. Therefore, since it is difficult to stably crush and solubilize excess sludge with high efficiency, the volume reduction rate of excess sludge was low.
In addition, the crushing using ultrasonic waves is not practical due to problems such as noise caused by micro-vibration generated from the apparatus itself, short life of the ultrasonic generator, and difficulty in manufacturing a large-capacity crushing apparatus.
By crushing with a homogenizer or a mixer, crushing to fine particles (less than 5 μm) is difficult, and it is not practical as a solubilization treatment of excess sludge.
In addition, the mechanical method has a problem of low energy efficiency.
The present invention has been made in view of the above circumstances, can stably crush and solubilize excess sludge with high crushing efficiency, has a high volume reduction rate of surplus sludge, and has high energy efficiency, An object is to provide a practical method and apparatus for reducing excess sludge volume.

The surplus sludge volume reduction method of the present invention is a method of biologically treating organic wastewater in a biological treatment tank, crushing at least a part of surplus sludge generated by the biological treatment, In the excess sludge volume reduction method of returning to the biological treatment tank and biologically treating it again,
The excess sludge of 1.2 to 3.8 times the volume of surplus sludge generated due to organic wastewater is stirred by a rotary blade, and the penetration formed in a screen arranged around the rotary blade It is characterized by shearing and crushing by passing through a hole.
The surplus sludge volume reduction device of the present invention includes a biological treatment tank for biologically treating organic waste water, a sludge crusher for crushing at least a part of excess sludge generated in the biological treatment tank, and a sludge crusher. In the surplus sludge volume reducing device comprising a crushed sludge return pipe for returning the crushed surplus sludge to the biological treatment tank,
A sludge crusher is attached to a rotating shaft, a rotating blade for stirring excess sludge, a screen disposed in the vicinity of the rotating blade and having a large number of through holes, and a driving means for rotationally driving the rotating shaft. It is characterized by comprising.

  In the surplus sludge volume reduction method and surplus sludge volume reduction device of the present invention, the excess sludge can be stably crushed and solubilized with high crushing efficiency, the excess sludge volume reduction rate is high, and the energy efficiency Is high and practical.

Hereinafter, an embodiment of an excess sludge volume reduction method and an excess sludge volume reduction device of the present invention will be described.
In FIG. 1, the excessive sludge volume reduction apparatus of this embodiment is shown. The surplus sludge volume reducing device 1 is transferred from the biological treatment tank 10 and the biological treatment tank 10 for biologically treating the organic wastewater supplied from the drainage supply pipe 11 in an aerobic state by the standard activated sludge method. A sedimentation tank 20 for precipitating and separating sludge, an uncrushed sludge return pipe 30 for returning a part of the sludge as it is from the sedimentation tank 20 to the biological treatment tank 10, and a part of the remaining sludge (surplus sludge). Sludge crusher 40, crushing sludge return pipe 50 for returning surplus sludge crushed by sludge crusher 40 to biological treatment tank 10, air supply means 60 for supplying air to the bottom of biological treatment tank 10, and excess sludge The surplus sludge discharge pipe 70 which discharges the remainder of this to the outside of the excess sludge volume reduction apparatus 1 is comprised.
In addition, the biological treatment tank 10 and the sedimentation tank 20 are connected by the first connection pipe 12, and the sedimentation tank 20 and the sludge crusher 40 are connected by the second connection pipe 41, and the second connection pipe 41. Is attached with a sludge supply pump 42 for supplying excess sludge to the sludge crusher 40. Furthermore, a supernatant water discharge pipe 21 for discharging the supernatant water is connected to the upper part of the precipitation tank 20.

As shown in FIGS. 2 and 3, the sludge crusher 40 in the excess sludge volume reducing device 1 is provided with a rotating shaft 44, a rotating blade 45 attached to the rotating shaft 44, and the vicinity of the rotating blade 45. A conical screen 46 in which a large number of through-holes 46a, 46a,... Are formed, a cylindrical casing 47 serving as a surplus sludge flow path, and a rotating shaft 44. And a driving means 48 for rotationally driving. Further, the rotary blade 45 has a shape that decreases in diameter along the shape of the screen 46. Further, the through hole 46 a of the screen 46 is elongated in the direction from the casing 47 side toward the tip of the screen 46.
The sludge supply pump 42 in the excess sludge volume reducing device 1 is not particularly limited as long as it can transfer excess sludge.

In the surplus sludge volume reduction method using the excess sludge volume reducing device 1 of FIG. 1, first, organic waste water is continuously supplied from the waste water supply pipe 11 to the biological treatment tank 10 charged with activated sludge. To do. Here, the organic wastewater is wastewater containing organic matter, and examples thereof include sewage, rural village wastewater, and organic industrial wastewater. The organic waste water may be diluted with water.
Next, air is supplied to the lower part of the biological treatment tank 10 by the air supply means 60 to activate the activated sludge and stir the organic waste water. Then, the organic waste water is retained in the biological treatment tank 10 for a predetermined time, and is biologically treated by the action of activated sludge to decompose the organic matter in the organic waste water.

Next, the sludge mixed liquid containing sludge and water is continuously transferred to the sedimentation tank 20 through the first connection pipe 12. Then, using the specific gravity difference in the sedimentation tank 20, sludge is precipitated to separate sludge and water from the sludge mixture, and the treated water, which is the supernatant water, is passed through the supernatant water discharge pipe 21 to the excess sludge. It discharges continuously from the volume reduction device 1.
Next, a part of the sludge separated in the sedimentation tank 20 (separated sludge) is continuously returned as it is to the biological treatment tank 10 via the uncrushed sludge return pipe 30 as it is. The return sludge amount is adjusted so that the activated sludge amount (MLSS) in the biological treatment tank 10 becomes a predetermined value.
Further, a part of the remaining sludge (surplus sludge) is continuously transferred to the sludge crusher 40 by the sludge supply pump 42 via the second connection pipe 41, and the remaining surplus sludge is discharged to the surplus sludge discharge pipe. 70 is continuously discharged from the excess sludge volume reducing device 1.

In the sludge crusher 40, the sludge is sent to the vicinity of the rotary blade 45 through the casing 47 and stirred by the rotary blade 45 that is driven to rotate by the driving means 48. The agitation imparts outward kinetic energy to the surplus sludge, and passes the surplus sludge at a high speed through the through-holes 46 a of the screen 46 disposed in the vicinity of the periphery of the rotary blade 45. Then, the excess sludge is crushed by the shearing force generated at that time and simultaneously discharged from the sludge crusher 40 (see FIGS. 2 and 3).
Subsequently, the crushed surplus sludge (crushed sludge) is returned to the biological treatment tank 10 through the crushed sludge return pipe 50. Then, the crushed sludge returned to the biological treatment tank 10 is biologically treated again together with the newly supplied organic waste water and the returned sludge.

When the crushed surplus sludge is biologically treated again, 25-40% is mineralized (water, carbon dioxide, etc.), and 60-75% becomes surplus sludge again. Considering this amount of mineralization, in this surplus sludge crushing method, the volume of surplus sludge to be crushed is 1.2 to 3.8 times the amount of surplus sludge generated due to organic waste water. .
On the other hand, if the volume of crushed sludge is less than 1.2 times the amount of excess sludge generated due to organic wastewater, the amount of crushed excess sludge to be biologically processed will be reduced, and surplus Since the volume reduction effect of sludge becomes low, it is not practical, and if it is more than 3.8 times, the load of activated sludge in the biological treatment tank 10 increases and the capacity of biological treatment decreases, so treated water May cause deterioration of water quality.

  Moreover, in this surplus sludge crushing method, although the density | concentration of the sludge discharged | emitted from the sedimentation tank 20 should just be a fluid grade, it is preferable that it is 8 mass% or less, and it is more preferable that it is 0.2-7 mass%. It is preferably 0.4 to 6% by mass. When the sludge concentration exceeds 8% by mass, practicality is low because there is almost no sludge fluidity. On the other hand, when the sludge concentration is less than 0.2% by mass, the operation cost and the equipment cost are increased with respect to the sludge treatment amount, which tends to be uneconomical. However, even if the sludge has a concentration that does not flow, it can be flowed if diluted with treated water or the like.

In the excess sludge volume reducing device 1 and the excess sludge volume reduction method described above, the excess sludge separated in the sedimentation tank 20 is stirred by the rotary blade 45 of the sludge crusher 40 to impart kinetic energy, and the rotary blade It passes through a through hole 46 a of a screen 46 arranged around 45. At that time, the moving speed of the excess sludge increases and shear force is generated. The excess sludge is crushed by the shear force, the microorganisms in the excess sludge are crushed together with the cell wall, and the intracellular substrate components are extracted, and the cell wall Is decomposed to ultrafine. In this method, since the rotating blades 45 do not contact anything other than the excess sludge as compared with other mechanical methods, it is possible to prevent a reduction in crushing efficiency and crushing energy efficiency. Moreover, since the abrasion of the sludge crusher 40 can be prevented, even if excess sludge is crushed for a long time, the crushing efficiency is hardly lowered and is stable. That is, surplus sludge can be crushed and solubilized more stably with high efficiency. Moreover, since the power cost can be reduced, the energy efficiency is high and the running cost is low.
Moreover, since the crushed sludge returned to the biological treatment tank 10 is decomposed and is easily biologically processed, it is easily biologically processed in the biological treatment tank 10 so as to have carbon dioxide gas and water. And decomposed. And in this excess sludge volume reduction method, since the excess sludge is further solubilized with high efficiency, the speed of biological treatment can be increased and the volume reduction rate of the excess sludge can be increased.

Moreover, in the said excess sludge volume reduction method, since the surplus sludge of a volume 1.2 to 3.8 times the surplus sludge amount which originates in organic waste water is crushed and solubilized, surplus sludge The volume reduction effect is high and practical. In addition, since the ability of biological treatment in the biological treatment tank 10 can be prevented from being lowered, the quality of treated water can be prevented from being lowered.
Further, in the above-described excess sludge volume reduction method, sludge is crushed by a mechanical method, so that a sufficient fine crushing effect can be obtained regardless of the sludge concentration, the treatment time is short, and surplus sludge is economically used with small-scale equipment. Can be reduced in volume. Moreover, since it is the surplus sludge crushing method which does not accompany generation | occurrence | production of a hard-to-decompose component, the quality of the treated water which biologically processed the sludge was favorable.

  The present invention is not limited to the above-described embodiment example. In the above-described embodiment, biological treatment is performed in the biological treatment tank by the standard activated sludge method, but biological treatment may be performed by other methods. However, the biological treatment in the biological treatment tank is preferably an aerobic treatment, and specifically, an activated sludge method or a biofilm method is preferred. Here, as the activated sludge method, in addition to the standard activated sludge method, for example, oxygen activated sludge method, re-aeration method, long-time aeration method, oxidation ditch method (oxidation ditch method), batch activated sludge method, membrane The separation activated sludge method and the like can be mentioned. In particular, in the membrane separation activated sludge method, the biological treatment tank can be used as a membrane separation activated sludge tank, and in this case, the sedimentation tank can be omitted. Examples of the biofilm method include a trickling filter method, a rotating contact body (rotating disk) method, a contact aeration method, a biofiltration method, a carrier method, and the like. Even if any of these biological treatment methods are employed, the volume of excess sludge can be reduced.

Hereinafter, the present invention will be specifically described by way of examples.
(Example 1)
Using the excess sludge volume reduction apparatus 1 shown in FIG. 1, first, the biochemical oxygen consumption (BOD) is 1,000 mg / L, the chemical oxygen consumption (COD) is 600 mg / L, and the suspended solids amount is 150 mg. Sewage (organic wastewater) adjusted to / L was quantitatively supplied to the biological treatment tank 10 at 1,000 L / day. Here, the biological treatment tank 10 is a treatment tank for aerobically biologically treating sewage by a standard activated sludge method, and has an effective capacity of 1,000 L. The residence time for biological treatment was 24 hours.
The inside of the biological treatment tank 10 is aerated and stirred by the air supply means 60, and the residual oxygen concentration is 2.0 mg / L while sufficiently stirring the activated sludge, so that the MLSS in the biological treatment tank 10 is 4,000 mg / L. Biological treatment was performed as follows. Next, sludge and water were continuously transferred from the biological treatment tank 10 to the settling tank 20 via the first transfer pipe 12 and separated into sludge and water in the settling tank 20 due to the difference in specific gravity. And the supernatant water was continuously discharged | emitted from the excess sludge volume reduction apparatus 1 via the supernatant water discharge pipe 21. FIG.
On the other hand, a part of the separated sludge separated in the sedimentation tank 20 is continuously returned to the biological treatment tank 10 through the uncrushed sludge return pipe 30 as it is, and the remaining sludge is used as surplus sludge as an excess sludge discharge pipe 70. Through the excess sludge volume reduction device 1.
Here, when the return rate of the returned sludge was 100%, the sludge concentration in the sedimentation tank 20 was 8,000 mg / L. Under this condition, the excess sludge generated due to the organic waste water was 450 g / day as a dry mass and 56.2 L / day as a volume.

Next, 2.6 times the surplus sludge amount (56.2 L / day) generated due to organic wastewater, that is, 146.12 L / day surplus sludge is sludge crusher by the sludge supply pump 42. 40 and crushed for 4 hours.
Here, CLM-0.8S made by M Technique Co., Ltd. was used as the sludge crusher 40. The sludge crusher 40 includes a rotary shaft 44, a rotary blade 45 attached to the rotary shaft 44, a conical screen 46 disposed in the vicinity of the periphery of the rotary blade 45, and a screen 46 attached to the tip. A cylindrical casing 47 and driving means 48 connected to the rotating shaft 44 are provided. Further, the rotary blade 45 has a shape that decreases in diameter along the shape of the screen 46. Further, the through hole 46 a of the screen 46 is elongated in the direction from the casing 47 side toward the tip of the screen 46.

The crushed surplus sludge was returned to the biological treatment tank 10 via the crushed sludge return pipe 50, and biological treatment was performed again together with the newly supplied sewage and return sludge. The MLSS in the biological treatment tank 10 at this time was also set to 4,000 mg / L.
In this way, when the surplus sludge was biologically treated while being crushed, the quality of the treated water from the sedimentation tank 20 was as shown in Table 1, BOD 19 mg / L, COD 41 mg / L, suspended matter The amount was 12 mg / L. Then, when biological treatment and sludge crushing were continued for 30 days under the same conditions, the quality of the treated water was not changed. Moreover, the excess sludge discharged | emitted from the excess sludge volume reduction apparatus in 30 days was 540g as dry mass, and the volume reduction rate of the excess sludge was 96%.

(Example 2)
In Example 1, the volume amount of surplus sludge to be crushed is 1.4 times that of surplus sludge generated due to organic wastewater, that is, 78.68 L / day. Similarly, the wastewater was biologically treated. As a result, as shown in Table 1, the quality of the treated water from the settling tank 20 was 17 mg / L for BOD, 36 mg / L for COD, and 10 mg / L for the amount of suspended solids. Then, when biological treatment and sludge crushing were continued for 30 days under the same conditions, the quality of the treated water was not changed. Moreover, the excess sludge discharged | emitted from the excess sludge volume reduction apparatus in 30 days was 1,620g as dry mass, and the volume reduction rate of the excess sludge was 78%.

(Example 3)
In Example 1, the volume of surplus sludge to be crushed is 3.2 times that of surplus sludge generated due to organic wastewater, that is, 179.84 L / day. Similarly, the wastewater was biologically treated. As a result, as shown in Table 1, the quality of the treated water from the precipitation tank 20 was 22 mg / L for BOD, 42 mg / L for COD, and 13 mg / L for the amount of suspended solids. Then, when biological treatment and sludge crushing were continued for 30 days under the same conditions, the quality of the treated water was not changed. Moreover, the excess sludge discharged | emitted from the excess sludge volume reduction apparatus in 30 days was 135g as dry mass, and the volume reduction rate of the excess sludge was 99%.

Example 4
Membrane separation activated sludge method was adopted as a biological treatment method by biological treatment tank. The membrane used at that time was a hollow fiber membrane having a nominal pore size of 0.4 μm manufactured by Mitsubishi Rayon Co., Ltd., and the membrane filtration flux was 0.4 m ³ / (m ² · day).
And the MLSS in the biological treatment tank 10 is set to 8,000 mg / L, and the sewage is the same as in Example 1 except that the excess sludge is directly transferred from the biological treatment tank 10 to the sludge supply pump without using the sedimentation tank 20. Of biological treatment. As a result, as shown in Table 1, the water quality of the treated water was 9 mg / L for BOD, 24 mg / L for COD, and 0 mg / L for the amount of suspended solids. Then, when biological treatment and sludge crushing were continued for 30 days under the same conditions, the quality of the treated water was not changed. Moreover, the excess sludge discharged | emitted from the excess sludge volume reduction apparatus in 30 days was 270g as dry mass, and the volume reduction rate of the excess sludge was 98%.

(Example 5)
The biofilm method was adopted as a biological treatment method using the biological treatment tank 10. As a biofilm carrier, a power tube manufactured by Mitsubishi Rayon Engineering Co., Ltd. (polypropylene, 6φ × 6 mmL) is used, and 20% by volume (200 L) of the effective capacity of the biological treatment tank 10 is filled to acclimate the organism. did.
The quality of the treated water after the completion of the acclimatization was 22 mg / L for BOD, 44 mg / L for COD, and 10 mg / L for the amount of suspended solids. Moreover, the excess sludge generated at that time was 400 g / day in terms of dry mass, and the sludge concentration in the sedimentation tank 20 was 8,000 mg / L.
Next, 2.4 times the surplus sludge generated due to organic wastewater (50 L / day) from the sedimentation tank 20, that is, 120 L / day of surplus sludge is sludge crusher by a sludge supply pump 42. The excess sludge was crushed for 3 hours. Then, the crushed surplus sludge was returned to the biological treatment tank 10 through the crushed sludge return pipe 50, and biological treatment was performed again together with newly supplied sewage and return sludge.
As a result, as shown in Table 1, the quality of the treated water from the settling tank 20 was 24 mg / L for BOD, 48 mg / L for COD, and 17 mg / L for the amount of suspended solids. Then, when biological treatment and sludge crushing were continued for 30 days under the same conditions, the quality of the treated water was not changed. Moreover, the excess sludge discharged | emitted from the excess sludge volume reduction apparatus in 30 days was 480g as dry mass, and the volume reduction rate of the excess sludge was 96%.

(Comparative Example 1)
In Example 1, the wastewater was biologically treated in the same manner as in Example 1 except that a general homogenizer was used as the sludge crusher.
As a result, as shown in Table 1, the quality of the treated water from the settling tank 20 was 75 mg / L for BOD, 120 mg / L for COD, and 45 mg / L for the amount of suspended solids. Then, when biological treatment and sludge crushing were continued for 30 days under the same conditions, the quality of the treated water was not changed. Moreover, the excess sludge discharged | emitted from the excess sludge volume reduction apparatus in 30 days was 13,100g as dry mass, and the volume reduction rate of the excess sludge was 3%.

(Comparative Example 2)
In Example 1, the biological treatment of sewage in the same manner as in Example 1 except that the volume of excess sludge to be crushed was 0.6 times the amount of excess sludge generated due to organic wastewater. Did. As a result, as shown in Table 1, the quality of the treated water from the settling tank 20 was 21 mg / L for BOD, 43 mg / L for COD, and 45 mg / L for the amount of suspended solids. Then, when biological treatment and sludge crushing were continued for 30 days under the same conditions, the quality of the treated water was not changed. Moreover, the excess sludge discharged | emitted from the excess sludge volume reduction apparatus in 30 days was 10,950g as dry mass, and the volume reduction rate of the excess sludge was 18.9%.

(Comparative Example 3)
Biological treatment of sewage in the same manner as in Example 1 except that the volume of surplus sludge to be crushed is 4.0 times the amount of surplus sludge generated due to organic wastewater. Did. As a result, as shown in Table 1, the water quality of the treated water from the sedimentation tank 20 was 115 mg / L for BOD, 207 mg / L for COD, and 81 mg / L for the amount of suspended solids. Then, when biological treatment and sludge crushing were continued for 30 days under the same conditions, the quality of the treated water was not changed. Moreover, the excess sludge discharged | emitted from the excess sludge volume reduction apparatus in 30 days was 4,560g as dry mass, and the volume reduction rate of the excess sludge was 66.2%.

In Examples 1 to 5, excess sludge having a volume of 1.2 to 3.8 times the amount of excess sludge generated due to organic wastewater is stirred by a rotary blade and arranged around the rotary blade. The resulting screen was sheared and crushed by passing it through a through-hole formed in the screen. Therefore, the excess sludge volume reduction rate was high, and the quality of the treated water was good.
On the other hand, in Comparative Example 1, surplus sludge was crushed with a homogenizer, so crushing was insufficient, and the excess sludge volume reduction rate was low.
In Comparative Example 2, surplus sludge having a volume of less than 1.2 times the amount of surplus sludge generated due to organic waste water is stirred by a rotary blade and formed on a screen arranged around the rotary blade. The excess sludge volume reduction rate was low because the material was sheared and crushed by passing through the through hole.
In Comparative Example 3, surplus sludge having a volume larger than 3.8 times the amount of surplus sludge generated due to organic wastewater is stirred by a rotary blade and formed on a screen arranged around the rotary blade. Since the material was sheared and crushed by passing through the formed through hole, the quality of the treated water deteriorated.

It is a schematic diagram which shows one embodiment of the excess sludge volume reduction apparatus which concerns on this invention. It is a schematic block diagram of the sludge crusher in the example of this embodiment. It is the figure which expanded the sludge crusher front-end | tip of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surplus sludge volume reduction apparatus 10 Biological treatment tank 40 Sludge crusher 44 Rotating shaft 45 Rotary blade 46 Screen 46a Through-hole 48 Drive means 50 Crushing sludge return pipe

Claims (2)

Biological treatment of organic wastewater in a biological treatment tank, crushing at least part of excess sludge generated by the biological treatment, returning the crushed excess sludge to the biological treatment tank and biological again In the excess sludge volume reduction method to be processed,
The excess sludge of 1.2 to 3.8 times the volume of surplus sludge generated due to organic wastewater is stirred by a rotary blade, and the penetration formed in a screen arranged around the rotary blade A surplus sludge volume reduction method characterized by shearing and crushing by passing through a hole. A biological treatment tank that biologically treats organic wastewater, a sludge crusher that crushes at least part of excess sludge generated in the biological treatment tank, and surplus sludge crushed by the sludge crusher is returned to the biological treatment tank. In the surplus sludge volume reducing device comprising a crushed sludge return pipe,
A sludge crusher is attached to a rotating shaft, a rotating blade for stirring excess sludge, a screen disposed in the vicinity of the rotating blade and having a large number of through holes, and a driving means for rotationally driving the rotating shaft. An excess sludge volume reduction device characterized by comprising:

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