JP2002143895A - Decomposition method for excess sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a decomposition method for excess sludge mainly composed of lower microorganisms, such as bacteria which entirely eliminates the discharge of the excess sludge by decomposing the excess sludge by the food chain of higher microorganisms, such as Protozoa and Metazoa. SOLUTION: The excess sludge 11 mainly composed of the lower microorganisms generated and propagated by biological treatment of sewage 2 is introduced to contact aerators 15A and 15B provided with contact materials 18 and air diffusion pipes 5 for ejecting air bubbles where the higher microorganisms, such as the Protozoa and Metazoa, living in the contact materials 18 of the contact aerators 15A and 15B prey on the sludge and the sludge is decomposed by the food chain. The treated water thereof is introduced to a settling tank 16 from which the supernatant 8 is drained. The residues 20, such as the settled microorganisms, is returned to the contact aerator 15A and the sludge is repetitively treated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for decomposing excess sludge mainly composed of low-grade microorganisms such as bacteria by a food chain of higher-grade microorganisms such as protozoa and metazoa.

[0002]

2. Description of the Related Art An activated sludge treatment method for purifying organic substances contained in sewage by microorganisms has been generally performed.
In this method, it is necessary to settle the treated sewage in a settling tank, drain the supernatant, and then treat the settled excess sludge.

Conventionally, as a method of treating excess sludge, the sludge is concentrated in a sludge concentration tank or the like, then dewatered by a dehydrator, and then landfilled or incinerated. However, this disposal method is laborious and expensive, and has the problems of landfill sites and the emission of large amounts of carbon dioxide.

As a method for treating excess sludge, which has recently attracted attention, low-grade microorganisms such as bacteria, which are the main components of sludge, are taken out, oxidized by ozone oxidation or chemicals to solubilize the microorganisms, and converted into microorganisms again as organic matter. There is a method of performing processing. There is also a method in which the low-grade microorganisms taken out are ground by a mill, solubilized, and treated with microorganisms. However, the method of taking out and treating these low-grade microorganisms has a problem that it is troublesome and costly.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and decomposes excess sludge mainly composed of low-grade microorganisms such as bacteria by the food chain of higher-grade microorganisms such as metazoans to greatly reduce the discharge. An object of the present invention is to provide a method of decomposing excess sludge that has been reduced.

[0006]

According to a first aspect of the present invention, there is provided a method for decomposing excess sludge, comprising the steps of: treating excess sludge mainly composed of low-grade microorganisms such as bacteria generated and grown by biologically treating sewage with a contact material; And a contact aeration tank provided with aeration means for ejecting air bubbles into the water, and food that feeds on lower-grade microorganisms of excess sludge by high-grade microorganisms such as protozoa and metazoans living in the contact material of the contact aeration tank. The sludge is decomposed by a chain, the treated water is guided to a sedimentation tank, the supernatant is drained, and residues such as microorganisms precipitated here are returned to the contact aeration tank and repeatedly treated. Things.

According to a second aspect of the present invention, in the method for decomposing excess sludge, the contact material is formed of a cord-like core material having a large number of protrusions attached to the surface, and the contact material is spirally wound on the surface. It is characterized in that higher-grade microorganisms such as protozoa and metazoans are attached and propagated.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIG.
This will be described in detail with reference to FIG. In the figure, 1 is an adjustment tank,
The sewage 2 that has flowed in here is stored. An aeration tank 3 is provided adjacent to the adjustment tank 1, and sewage 2 is sent from the adjustment tank 1 by a pump 4. On the bottom side of the aeration tank 3, there is provided an air diffuser 5 for ejecting bubbles into the wastewater 2.

A settling tank 6 is provided adjacent to the aeration tank 3, and the supernatant 8 is drained to an adjacent disinfecting tank 10, and a part of the settled excess sludge 11 is returned to the aeration tank 3. ing. In the disinfecting tank 10, the supernatant 8 is supplied to the disinfecting solution supply device 12.
The treated water 9 sterilized by adding an antiseptic solution is drained to the outside. The apparatus up to this point is the same as the conventional activated sludge treatment apparatus.

In the present invention, most of the excess sludge 11 settled in the settling tank 6 is sent to a sludge storage tank 13 and the excess sludge 11 stored therein is supplied to a sludge treatment device 14. This sludge treatment apparatus 14 is provided with two contact aeration tanks 15A and 15B, and further provided with a settling tank 16 adjacent thereto.

In the contact aeration tanks 15A and 15B, a diffuser tube 5 for ejecting air bubbles into water is provided on the bottom side, and a large number of flexible cord-like core members are provided in the tank. A large number of contact members 18 having projections attached and spirally wound around the projections are supported by a support frame 19. High-grade microorganisms such as protozoa and metazoans adhere to the surface of the contact material 18 and inhabit. The settling tank 16 is provided with a residue return pipe 21 for returning the residue 20 to the first-stage contact aeration tank 15.

A method of treating the excess sludge 11 generated by biologically treating the sewage 2 with the above-described apparatus will be described. First, sewage 2 such as sewage or factory wastewater is led to the regulating tank 1 and stored therein. The sewage 2 stored here is supplied to an adjacent aeration tank 3 by a pump 4. The aeration tank 3 is provided with an air diffuser 5 for blowing air bubbles into the sewage 2 from which air is blown into the sewage 2, and the sewage 2 is convectively flowing, as shown in FIG. Organic matter contained in the sewage 2 is decomposed into carbon dioxide and water by bacteria. The decomposed water and the bacteria grown using the organic matter as nutrients are sent to the adjacent settling tank 6.

In the sedimentation tank 6, the supernatant 8 and the excess sludge 11 mainly composed of low-grade microorganisms generated and grown by biological treatment of the wastewater 2 are separated. The supernatant liquid 8 is sent to a disinfecting tank 10, where the disinfecting liquid is added from a disinfecting liquid supply device 12 to sterilize, and the sterilized treated water 9 is drained to the outside.

A part of the excess sludge 11 mainly composed of low-grade microorganisms settled in the sedimentation tank 6 is returned to the aeration tank 3 by a sludge return pipe 7 and reused for biological treatment of the wastewater 2. The remaining excess sludge 11 is sent to a sludge storage tank 13 where it is stored. The surplus sludge 11 is sent from the sludge storage tank 13 by the pump 4 to the first-stage contact aeration tank 15A of the sludge treatment device 14.

In the contact aeration tanks 15A and 15B, a large number of contact members 18 are supported by a support frame 19.
Higher-grade microorganisms such as protozoa such as Paramecium and Vinebug and metazoans such as rotifer adhere to the surface of No. 8 and inhabit. Further, a diffuser 5 is provided on the bottom side of the contact aeration tanks 15A and 15B, from which bubbles are blown out into the excess sludge 11, and the excess sludge 11 adheres to the contact material 18 while convectively flowing. Higher-grade microorganisms such as protozoa and metazoans prey on lower-grade microorganisms such as bacteria contained in the excess sludge 11 and are decomposed into carbon dioxide and water.

In the first-stage contact aeration tank 15A, first, as shown in FIG. 2, bacteria which are the main components of the excess sludge 11 are preyed on by protozoa such as paramecium and vorticella. Preyed by animals. High-grade microorganisms such as protozoa and metazoans that have multiplied,
The low-grade microorganisms that have not been decomposed are supplied to a second-stage contact aeration tank 15B provided adjacently. The contact material 18 of the contact aeration tank 15B is inhabited by high-grade microorganisms such as protozoa and metazoa, earthworms, and daphnia.

In the contact aeration tank 15B of the second stage, the contact material 18
Undegraded low-grade microorganisms are eaten by protozoa that inhabit and inhabit, and protozoa that have proliferated are eaten by metazoans, and protozoa that have proliferated are preyed on by earthworms and daphnia, repeating the food chain. The surplus sludge 11 is gradually decomposed into water.

The decomposed water and high-grade microorganisms such as undegraded protozoa and metazoan are sent to a sedimentation tank 16, and the supernatant liquid 8 separated here is drained to the outside, and For high-grade microorganisms such as animals and metazoans, return pipe 2
1 returns to the first stage contact aeration tank 15A.

High-grade microorganisms such as protozoa and metazoans returned to the first-stage contact aeration tank 15A adhere to the contact material 18 and inhabit, and the balance between the amount of predation and the amount of inflowing bacteria (the amount of surplus sludge input) is described below. By repeating the same food chain, surplus sludge 11 can be decomposed into water and treated. Therefore, compared with the conventional method in which the surplus sludge 11 is disposed of by landfill or incineration, the present invention only requires the addition of a simple sludge treatment device 14 to substantially completely disassemble the surplus sludge 11 and greatly increase the treatment cost. Can be reduced.

A decomposition treatment experiment was performed using the sludge treatment apparatus 14 of the present invention. When excess sludge 11 containing 31,000 mg / L of suspended solids (SS) was decomposed,
Reduced to 18,000 mg / L per day, 10 per day
% Or more. From the fifth day, surplus sludge 11 was continuously supplied to the contact aeration tank 15A while being supplied every day. From the tenth day, the treatment reached a substantially constant state, and the supplied surplus sludge 11 was almost completely treated. Was decomposed into water. Contact aeration tank 1
Earthworms inhabited the contact material 18 of 5B. In other words, the presence of the earthworm, a high-grade microorganism, is evidence that the food chain is in operation.

In the above description, the case where two contact aeration tanks 15A and 15B are provided in the sludge treatment device 14 is shown, but a structure in which one or three or more contact aeration tanks are provided may be used.

[0022]

As described above, claim 1 according to the present invention.
According to the method for decomposing excess sludge described, the excess sludge mainly composed of low-grade microorganisms such as bacteria generated and grown by biological treatment of wastewater is provided with a contact material and aeration means for blowing bubbles into water. It is led to the contact aeration tank, and higher-grade microorganisms such as protozoa and metazoans living in the contact material of this contact aeration tank prey on lower-grade microorganisms such as bacteria, decompose sludge by a food chain, and dispose of this treated water. By guiding the supernatant to a sedimentation tank and draining the supernatant, and returning the residue such as microorganisms precipitated here to the contact aeration tank and repeating the treatment, the excess sludge can be almost completely decomposed and treated. The cost can be significantly reduced as compared with the method for disposing of excess sludge.

Further, in the method for decomposing excess sludge according to the second aspect of the present invention, a large number of projections are attached to the surface of a cord-like core material, and the contact material obtained by spirally winding the projections into a contact aeration tank. By providing this, the surface can be a habitat for high-grade microorganisms such as protozoa and metazoans and can be inhabited in large quantities, and the food chain can be effectively continued to accelerate the decomposition of excess sludge.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an apparatus for decomposing excess sludge according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a state of a food chain.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Adjustment tank 2 Sewage 3 Aeration tank 4 Pump 5 Aeration tube 6 Settling tank 7 Sludge return pipe 8 Supernatant 9 Treatment water 10 Disinfection tank 11 Excess sludge 12 Disinfectant supply device 13 Sludge storage tank 14 Sludge treatment device 15A Contact aeration tank 16 Settling tank 18 Contact material 19 Support frame 20 Residue 21 Residue return pipe

Claims (2)

[Claims] 1. Excess sludge mainly composed of low-grade microorganisms such as bacteria generated and grown by biological treatment of sewage is led to a contact aeration tank provided with a contact material and aeration means for blowing air bubbles into water. Protozoa living in the contact material of the contact aeration tank,
The sludge is decomposed by a food chain that preyes on lower-grade microorganisms of surplus sludge by higher-grade microorganisms such as metazoans, the treated water is guided to a sedimentation tank, and the supernatant is drained, and the residue of microorganisms and the like precipitated here. Is returned to the contact aeration tank and is repeatedly treated. 2. A contact material is formed of a cord-like core material having a large number of projections attached to a surface thereof, which is spirally wound to adhere and propagate high-grade microorganisms such as protozoa and metazoans on the surface. 2. The method for decomposing excess sludge according to claim 1, wherein: