JP2020059000A - Digestion tank with integrated solubilizer - Google Patents

Abstract

To provide a digestion tank integrated with a solubilizer that solubilizes sludge in the digestion tank to improve the efficiency of digestion of the sludge.SOLUTION: A digestion tank 2 provided with (i) a solubilization chamber 6 to which is supplied a sludge generated at a sewage treatment plant and with (ii) a digestion chamber 7 that digests the sludge supplied from the solubilization chamber 6, the solubilization chamber 6 being provided with a solubilizing device 8 positioned at the top of the digestion tank 2, a casing 9 that accommodates the solubilizing device 8, and an opening 14 positioned at the top of the casing 9, so as to improve the efficiency of digestion of the sludge and increase the amount of digestion gas generated.SELECTED DRAWING: Figure 2

Description

The present invention relates to a digestion tank having a sludge solubilization device built therein for improving digestion efficiency in digestion of sewage sludge.

  Conventionally, as a method of treating sludge generated in a sewage treatment facility, a treatment of decomposing organic substances by anaerobic bacteria in a digestion tank to reduce the volume is performed. Patent Document 1 discloses a technique for efficiently performing digestion treatment by solubilizing concentrated sludge by a sludge solubilizing device and supplying the solubilized sludge to a digestion tank.

Further, in Patent Document 2, an upper disc that rotates on top of a surplus sludge treatment tank and a fixed lower disc are arranged, the excess sludge is supplied between the upper disc and the lower disc, and the excess sludge is removed by rotation of the disc. A technique of using an excess sludge treatment device for grinding in an activated sludge method is disclosed.

JP, 2011-098249, A JP, 2004-249213, A

Excess sludge contains less easily decomposable organic matter than initial sludge (raw sludge), and therefore has poor methane fermentation characteristics. In addition, surplus sludge is mainly composed of hardly decomposable cellulose such as microbial cells and protein, and it takes a long time to decompose, so the energy recovery effect is lower than that of the first sludge. Furthermore, the excess sludge had poor digestion efficiency, and it took time to reduce the volume.
Although the digestion efficiency can be improved by performing solubilization with a solubilizer before performing the digestion treatment as in Patent Document 1, the power for supplying the solubilized sludge in addition to the solubilizer, It required a pipeline, and it was difficult to prepare all the equipment at some treatment plants.

In the surplus sludge treatment device of Patent Document 2, the surplus sludge ground between the discs is discharged to the lower part of the surplus sludge treatment tank when flowing out from between the discs. Therefore, the time for the excess sludge to be ground between the disks was short, and sufficient grinding could not be performed.

It is an object of the present invention to provide a solubilizer-integrated digestion tank that solubilizes excess sludge by performing solubilization treatment while temporarily storing excess sludge in the digestion tank.

In a digestion tank equipped with a solubilization chamber to which sludge generated in a sewage treatment plant is supplied and a digestion chamber to digest the sludge supplied from the solubilization chamber, the solubilization chamber is a solubilization device arranged above the digestion tank. By providing the casing for accommodating the solubilizer and the opening provided at the upper part of the casing, the digestion efficiency of sludge is improved and the amount of digested gas generated is increased.

Since the solubilization device is a rotary disk that works in conjunction with a motor, it can solubilize sludge by shearing force due to rotation and cavitation.

By providing the fixed disk facing the rotary disk in the solubilization chamber, sludge is crushed between the rotary disk and the fixed disk, and solubilization is promoted.

Since the fixed disk has a through hole penetrating the fixed disk, sludge circulates between the disks and is further solubilized.

By connecting a sludge supply pipe for supplying sludge to the through hole of the fixed disk, the sludge can be reliably supplied between the disks and solubilized.

By configuring the casing by the side wall and the upper wall of the digestion tank, the bottom plate protruding from the side wall, and the overflow weir standing upright from the bottom plate, it is possible to extend the time for the sludge to stay in the casing.

By providing a sludge supply pipe connected to the solubilization chamber to supply excess sludge and a pipe connected to the digestion chamber to supply initial sludge, only excess sludge with poor digestion efficiency can be efficiently supplied. It can be solubilized.

According to the present invention, a solubilization chamber is provided in the upper part of the digestion tank, and the sludge immediately after being supplied to the digestion tank is temporarily stored and solubilized. The amount of generation also increases.
By using the solubilizer, the sludge can be solubilized by the shearing force of the fluid and cavitation, and it is not necessary to use a large-scale solubilizer.
By disposing the fixed disc facing the rotating disc, sludge is crushed between the discs and solubilization is promoted.
By dividing the digestion tank into a solubilization chamber and a digestion chamber, excess sludge can be supplied to the solubilization chamber, first settled sludge can be supplied to the digestion chamber, and only excess sludge with poor digestion efficiency can be efficiently solubilized. You can

It is a flow chart of the sewage treatment plant according to the present invention. Similarly, it is sectional drawing of a digestion tank. Similarly, it is sectional drawing of a solubilization apparatus. It is sectional drawing of the solubilization apparatus which concerns on Example 1 of this invention. It is sectional drawing of the digestion tank which concerns on Example 2 of this invention.

FIG. 1 is a flow chart of a sewage treatment plant according to the present invention.
The inflow water that has flowed into the sewage treatment plant is first settled and separated in the settling tank 1, and the settled sludge is sent to the digestion tank 2 as the first settling sludge. First, the solid content and the liquid content having a low specific gravity are sent to the reaction tank 3 in the settling tank and aerated. Microorganisms propagate in the reaction tank 3 by aeration treatment, and they are sent to the final settling tank 4 as treated water. Gravity separation is performed in the final settling tank 4, and the settled sludge is sent to the digestion tank 2 as excess sludge. The supernatant water of the final settling tank 4 is subjected to advanced treatment as necessary and discharged into a river or the like. The initial sludge and excess sludge sent to the digestion tank 2 are digested. The digested sludge generated in the digestion tank 2 is sent to the dehydrator 5 to separate water and be treated. If necessary, sludge may be concentrated in each step.

FIG. 2 is a sectional view of the digestion tank according to the present invention.
FIG. 3 is a sectional view of a solubilizing device according to the present invention.
The digestion tank 2 of the present invention is provided with a solubilization chamber 6 in the upper part and a digestion chamber 7 in the lower part, and the solubilization chamber 6 houses a solubilization device 8.

The solubilization chamber 6 is formed by a casing 9 that surrounds the solubilization device 8. In FIG. 3, a part of the side wall 10 and the upper wall 11 of the digestion tank 2, a bottom plate 12 protruding from the side wall 10, and a bottom plate 12 are provided. The casing 9 is configured with the overflow weir 13 to be installed. The upper end of the overflow weir 13 extends to the vicinity of the upper wall 11 of the digestion tank 2, and the excess sludge flowing into the solubilization chamber 6 overflows into the digestion chamber 7 between the upper end of the overflow weir 13 and the upper wall 11. Has an opening 14 for

A sludge supply pipe 15 for supplying excess sludge is connected to the side wall 10 of the digestion tank 2 constituting the casing 9 or the upper wall 11 of the upper part of the solubilization chamber 6 to supply the excess sludge to the solubilization chamber 6. The excess sludge is temporarily stored in the solubilization chamber 6, and when the liquid level of the sludge exceeds the height of the overflow weir 13, it overflows from the opening 14 into the digestion chamber 7.
By providing a partition wall 16 protruding downward from the upper wall 11 in the solubilization chamber 6 and forming a flow path with the overflow weir 13, the retention time of sludge can be extended.

The sludge overflowed from the overflow weir 13 flows into the digestion chamber 7 below the digestion tank 2 and is subjected to digestion treatment.
A pipe 17 for supplying initial sludge is connected to the side wall 10 constituting the digestion chamber 7 or the upper wall 11 of the digestion chamber 7. Since the initial settled sludge has good digestion efficiency, it is not necessary to solubilize it in the solubilization chamber 6.
A digestion sludge discharge pipe 18 is provided below the digestion tank 2 to send the digestion sludge to the next step.

When the side wall 10 of the digestion tank 2 is not used as the casing 9, the solubilizing chamber 6 can be formed by surrounding the solubilizing device 8 with the casing 9 hanging from the upper wall 11. By providing the opening 14 on the upper portion of the casing 9, a part of the casing 9 having the opening 14 serves as the overflow weir 13.

Depending on the throughput of the solubilization device 8, the digestion tank 2 may be provided with a plurality of solubilization chambers 6 and a plurality of solubilization devices 8 may be arranged.

The solubilizing device 8 of the present invention crushes sludge to solubilize it, and includes a rotating disk 20 connected to a motor 19 and a fixed disk 21 fixed to the solubilizing chamber 6.
The rotating disk 20 is connected to the drive shaft 22 extending downward from the motor 19 mounted on the upper wall 11 and rotates in the solubilizing chamber 6. The fixed disk 21 is supported by a pedestal 23 provided upright on the bottom plate 12, and is installed in the vicinity of the lower part so as to face the rotary disk 20.
It is desirable that the rotating disk 20 and the fixed disk 21 have a gap of 5 mm to 30 mm.
The surfaces of the rotary disk 20 and the fixed disk 21 have smooth surfaces or fine irregularities.

The fixed disk 21 has a through hole 24 for sucking sludge in the center, and when the rotary disk 20 rotates, sludge is sucked from below the fixed disk 21 between the rotary disk 20 and the fixed disk 21, and the outer circumference of the rotary disk 20. Emitted from.
The sludge is crushed by the shearing force and cavitation caused by the rotation of the rotary disk 20, and the sludge is ground between the rotary disk 20 and the fixed disk 21. Therefore, the cell membrane of the microorganism in the sludge is destroyed and solubilized. The sludge discharged from between the discs stays in the solubilization chamber 6 and is agitated by the rotation of the rotary disc 20, so that the shearing force and the cavitation effect can be obtained around the rotary disc 20.

The sludge supplied to the solubilization chamber 6 stays while being solubilized by the solubilization device 8, and when the liquid level of the solubilization chamber 6 exceeds the overflow weir 13 by the supply of the sludge, the solubilized sludge is opened. Overflow into digestion room 7.

The rotating disk 20 and the fixed disk 21 may be installed vertically. In that case, the motor 19 is provided on the side wall 10 side, and the drive shaft 22 is horizontally installed to connect to the rotating disk 20.

Since the solubilization rate is high when the sludge concentration is high, sufficient solubilization can be achieved only by the shearing force and the cavitation effect due to the rotation of the rotary disk 20 without providing the fixed disk 21.

FIG. 4 is a cross-sectional view of the solubilization device according to the first embodiment of the present invention.
The rotary disk 20 and the fixed disk 21 are formed in a mortar shape by providing concave portions 25 on the surfaces facing each other.
The sludge supply pipe 15 is connected to the through hole 24 of the fixed disk 21 to supply the sludge between the disks. The fixed disk 21 is placed on the bottom plate 12, and the sludge supply pipe 15 penetrates the bottom plate 12 from the digestion chamber 7 and is connected to the through hole 24 of the fixed disk 21.
In Example 1, a solubilizer using a disk is used, but a known solubilizer such as a high-pressure jet or a heat solubilizer can be used.

FIG. 5: is sectional drawing of the digestion tank which concerns on Example 2 of this invention.
The solubilization chamber 6 may be provided outside the digestion tank 2, and the casing 9 is placed on the upper wall 11 of the digestion tank 2 as shown in FIG. 5 (a), or as shown in FIG. 5 (b). A casing 9 can be installed on the side wall 10 of the tank 2.
An opening 14 is provided above the casing 9, and the sludge overflowing from the opening 14 is supplied to the digestion chamber 7 of the digestion tank 2. The opening 14 of the casing 9 serves as an overflow weir 13.

Although excess sludge is supplied to the solubilization chamber 6 in the present embodiment, the sludge to be supplied to the solubilization chamber 6 is not limited to excess sludge, but mixed raw sludge in which excess sludge and first-sludge are mixed and digested. It is possible to supply and solubilize sludge that needs to be solubilized in sludge treatment, such as digested sludge circulated from the tank 2.

2 Digestion tank 6 Solubilization chamber 7 Digestion chamber 8 Solubilization device 9 Casing 10 Side wall 11 Upper wall 12 Bottom plate 13 Overflow weir 14 Opening 15 Sludge supply pipe 17 Piping 19 Motor 20 Rotating disk 21 Fixed disk 24 Through hole

Claims (7)

In a digestion tank (2) provided with a solubilization chamber (6) to which sludge generated in a sewage treatment plant is supplied, and a digestion chamber (7) for digesting the sludge supplied from the solubilization chamber (6),
The solubilization chamber (6) is
A solubilization device (8) arranged on the upper part of the digestion tank (2),
A casing (9) containing a solubilizer (8),
A digestion tank integrated with a solubilizing device, comprising: an opening (14) provided in an upper portion of a casing (9). The solubilizer (8) is
The solubilizer-integrated digestion tank according to claim 1, wherein the digestion tank is a rotating disk (20) that is interlocked with a motor (19). The digestion tank integrated with a solubilizer according to claim 2, wherein a fixed disk (21) facing the rotating disk (20) is provided in the solubilization chamber (6). The solubilizer-integrated digestion tank according to claim 3, wherein a through hole (24) is formed at a center of the fixed disk (21) so as to pass through the fixed disk (21). The digestion tank integrated with a solubilizer according to claim 4, wherein a sludge supply pipe (15) for supplying sludge is connected to the through hole (21) of the fixed disk (21). The casing (9) is
It is composed of a side wall (10) and an upper wall (11) of the digestion tank (2), a bottom plate (12) protruding from the side wall (10), and an overflow weir (13) standing from the bottom plate (12). The digestive tank integrated with a solubilizer according to any one of claims 1 to 5. A sludge supply pipe (15) which is connected to the solubilization chamber (6) and supplies excess sludge;
The solubilizer-integrated digestion system according to any one of claims 1 to 6, further comprising: a pipe (17) that is connected to the digestion chamber (7) and supplies the initial sludge. tank.

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