JP2001293496A - Sludge volume reducing method and device for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the maintenance and control of a facility of a low construction cost easier and an amount of sludge smaller. SOLUTION: This sludge volume reducing device 2 alternately repeats the first treatment to decompose the organic matter of the sludge to be treated by microorganisms under aerobic conditions and to oxidize the nitrogen compounds of the sludge to be treated in a first sludge volume reducing tank 3 and the second treatment to promote the decomposition of the organic matter of the sludge to be treated by the microorganisms under anaerobic conditions and to decompose the nitrogen compounds oxidized by the first treatment in a second sludge volume reducing tank 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge reduction method capable of greatly reducing excess sludge generated in a wastewater treatment process by secondary treatment, and an apparatus therefor.

[0002]

2. Description of the Related Art In recent years, one of the major problems in human waste processing plants is the treatment of excess sludge generated from a septic tank. In other words, at a human waste treatment plant, purification of water contained in human waste, weight loss and dehydration of sludge generated in treated households,
Alternatively, incineration and the like are performed, but recently, due to the widespread use of the combined use septic tank for home use, the throughput of septic tank sludge has increased dramatically.

[0003] This is not limited to sludge generated from a household combined treatment and treatment septic tank, but also applies to surplus sludge generated from a collective treatment facility such as an agricultural settlement drainage facility or a final treatment plant for sewage.

For this reason, at present, surplus sludge is carried out to an off-site treatment facility where it is dealt with by incineration or landfill.

[0005] As a result, the sludge treatment cost occupies a large weight in the running costs related to wastewater treatment with the increase in the amount of sludge generated, and sludge treatment facilities are increased with the increase in surplus sludge. Due to the necessity, construction costs and maintenance costs have risen.

In response to this, Japanese Patent Laid-Open No. 60-1104 / 1985
No. 00, Japanese Patent Application Laid-Open No. Sho 60-129196 and Japanese Patent Application Laid-Open No. 2000-24697 previously filed by the applicant of the present application disclose sludge by repeating aerobic state and anaerobic state by intermittently ventilating sludge. Describes a technique for causing digestion to reduce sludge.

[0007]

As described above, in the conventional sludge reduction technology, the aerobic state and the anaerobic state are repeatedly performed in the state where the sludge is injected into the same sludge treatment tank to cause digestion. Even when agitation is performed, sludge is not sufficiently agitated near the wall of the sludge treatment tank, and sludge in such a position cannot be sufficiently aerobic and anaerobic, and can be digested sufficiently. Did not.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sludge reduction method and an apparatus thereof which are inexpensive construction costs, can be easily maintained, and can further reduce the amount of sludge.

[0009]

According to the present invention, there is provided a method for reducing sludge according to the present invention, comprising the steps of:
A first treatment for decomposing sludge to be treated by microorganisms under aerobic conditions in a first sludge reduction tank; and a second treatment for promoting decomposition of the sludge to be treated by microorganisms under anaerobic conditions in a second sludge reduction tank. Is alternately repeated.

According to a second aspect of the present invention, there is provided a method for reducing sludge according to the present invention, wherein microorganisms are decomposed by microorganisms under aerobic conditions in a first sludge reduction tank, and nitrogen compounds in the sludge are oxidized. A first treatment, and a second treatment for promoting decomposition of organic matter in the sludge to be treated by microorganisms under anaerobic conditions in a second sludge reduction tank and decomposing nitrogen compounds oxidized in the first treatment. And are alternately repeated.

A sludge reduction apparatus according to a third aspect of the present invention comprises a first sludge reduction tank for decomposing sludge with microorganisms under aerobic conditions, and a sludge reduction tank for sludge with microorganisms under anaerobic conditions. A second sludge reduction tank for promoting decomposition, a first sludge transfer means for transferring the sludge to be treated in the first sludge reduction tank to the second sludge reduction tank, and the second sludge reduction tank And a second sludge transfer means for transferring the sludge to the first sludge reduction tank.
In this case, preferably, a part of the side wall of the first sludge reduction tank and a part of the side wall of the second sludge reduction tank are integrally formed.

That is, in the sludge reduction method and the apparatus according to the first to third aspects, sludge is transferred between the first sludge reduction tank under aerobic conditions and the second sludge reduction tank under anaerobic conditions. Because of the circulation, the sludge can be sufficiently agitated and alternately turned into an aerobic state and an anaerobic state.This is a facility with low construction cost, easy to maintain and reduce the amount of sludge. Become.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Reference numeral 1 in FIG. 1 denotes a sludge storage tank such as a household sludge storage tank or a collective treatment facility such as an agricultural settlement drainage facility or a wastewater treatment plant, and a sludge reduction device 2 adjacent to the sludge storage tank 1. Are arranged.

The sludge reduction apparatus 2 comprises a first sludge reduction tank 3 for decomposing sludge by microorganisms under aerobic conditions, and a second sludge reduction tank 3 for promoting decomposition of organic matter of sludge by microorganisms under anaerobic conditions. Sludge weight loss tank 4 and the first sludge weight loss tank 3
First sludge transfer means (sludge transfer pipe 5) for transferring the sludge to be treated to the second sludge reduction tank 4;
The sludge to be treated in the sludge reduction tank 4 of the first sludge reduction tank 3
And a second sludge transfer means (sludge transfer pipe 6, anaerobic circulation pump 42).

The sludge reduction device 2 may be fixed, or may be a movable body that can be brought in and installed when necessary and withdrawn after completion.

At the bottom of the first sludge reduction tank 3, a plurality of biostone modules 32 are adhered, and a plurality of air diffusers 33 are arranged. Biostone module 32 is rich in aerobic microorganisms. In addition, the first sludge reduction tank 3 includes:
The air supply pipe 35 constituting the aeration means is inserted,
An aeration blower 36 is attached to one end of the air supply pipe 35, and diffusers 33, 33... Are attached to the other end of the air supply pipe 35 to diffuse sludge in the first sludge reduction tank 3. Air is expelled from 33, 33,.

On the other hand, the sludge reduction tank 4 has a hopper 41 with a steep bottom, so that sludge can easily accumulate at the bottom. An anaerobic circulation pump 42 is provided at the bottom of the hopper 41, an anaerobic stirring pump 43 is provided on the inner wall of the intermediate portion of the hopper 41, and a center well 44 is provided at the center of the sludge reduction tank 4. .

The bottom of the sludge storage tank 1 and the upper part of the first sludge reduction tank 3 can communicate with each other via a sludge introduction pipe 7. A sludge extraction pump 11 is mounted. In addition, sludge extraction pump 1
1 is for sucking activated sludge deposited at the bottom of the sludge storage tank 1, and may be inserted in the middle of the sludge input pipe 7.

On the side wall of the sludge reduction tank 4, one end of a sludge transfer pipe 5 is attached. The other end of the first treated sludge transfer pipe 5 is attached to the inner center well 44 via the side wall of the sludge reduction tank 3. The bottom of the sludge reduction tank 4 and the upper part of the sludge reduction tank 3 can communicate with each other via a treated sludge transfer pipe 6. The sludge reduction tank 4 side of the treated sludge transfer pipe 6 is connected to an anaerobic circulation pump 42. It is attached to.

Further, the sludge treatment tank 4 is closed at portions other than the sludge transfer pipes 5 and 6 to be treated, so that the inside can be made anaerobic.

On the other hand, a treated water return pump 34 is provided at an intermediate portion inside the first sludge reduction tank 3. One end of the treated water return pipe 8 is attached to the treated water return pump 34. The treated water return pipe 8 extends from the upper part of the sludge reduction tank 3, and the other end is connected to a disinfection tank (not shown).

Next, the operation of the present embodiment having the above configuration will be described.

First, the activated sludge accumulated in the sludge storage tank 1 is sucked by the sludge extraction pump 11 and transferred to the adjacent sludge treatment tank 3 through the sludge introduction pipe 7.

The sludge to be treated transferred to the sludge treatment tank 3 is
Are aerated by air discharged from the plurality of air diffusers 33, 33,. Thereby, under the aerobic condition, the organic matter of the sludge to be treated is decomposed by the microorganisms of the biostone modules 32, 32, and the nitrogen compounds of the sludge to be treated are oxidized. The sludge subjected to the first treatment as described above is transferred to the sludge treatment tank 4 via the treated sludge transfer pipe 5 and the center well 44. The sludge to be treated transferred to the sludge treatment tank 4 is forcibly shifted from the aerobic condition to the anaerobic condition, and accordingly, the microflora in the activated sludge changes state so as to conform to the condition (from aerobic to facultative anaerobic). Which is stirred by the anaerobic stirring pump 43 under anaerobic conditions to promote the decomposition of organic matter in the sludge to be treated by microorganisms and to decompose the nitrogen compound oxidized in the first treatment. I do. Thereafter, the sludge to be treated is transferred to the hopper 4
1 and is transferred to the sludge treatment tank 3 by the anaerobic circulation pump 42 via the sludge transfer pipe 6 to be treated.
The microorganism treatment is performed by the sludge treatment tank 3, and the same treatment is repeated thereafter. As a result, the decomposition of the untreated sludge proceeds,
In the middle part of the sludge treatment tank 3, clean treated water is obtained, and scum is generated above the treated water. The treated water in the middle part of the sludge treatment tank 3 contains harmful microorganisms such as Escherichia coli which has not been treated yet, and is returned to the disinfection tank via the treated water return pipe 8 by the treated water return pump 34. In the disinfection tank, chlorine is injected into the treated water for disinfection and sterilization. The harmless treated water is then used for flush toilets or discharged into public water bodies such as rivers and seas.

By the above-described operation, the method for reducing sludge of the present invention decomposes organic matter in the sludge to be treated by microorganisms under aerobic conditions in the first sludge reduction tank 3 and removes nitrogen compounds in the sludge to be treated. A first treatment for oxidation and a second treatment for oxidation.
In the sludge reduction tank 4 of the present invention, microorganisms are promoted under anaerobic conditions by organic substances in the sludge to be treated, and
And the second treatment for decomposing the nitrogen compound oxidized in the treatment are alternately repeated.

The measurement results in the sludge treatment tank are shown using the graphs of FIGS.

In this case, the sludge (MLSS concentration 2 to 30000)
mg / l, input amount 2.8m3) once or twice a month, change of MLSS concentration for one month, pH, ORP
The effect of sludge reduction is measured from the measurement results.

Each measurement is from October 13, 1999 to November 15, 1999.

From the graph of FIG. 2, sludge is reduced by almost 90% in almost one month.

From the graph of FIG. 3, under anaerobic conditions in the sludge reduction tank 4, ORP is started from the start of sludge introduction (redox unit, "+" indicates a saturated state, and "-" indicates a lack of oxygen). Represents an extreme "-", which indicates that the sludge is considerably reduced. Therefore, an increase in the amount of reducing substances promotes an oxidation reaction by aeration under aerobic conditions in the sludge reduction tank 3, thereby efficiently promoting sludge reduction.

According to such an embodiment, the sludge is circulated between the first sludge reduction tank 3 under aerobic conditions and the second sludge reduction tank 4 under anaerobic conditions. Can be alternately brought into an aerobic state and an anaerobic state by sufficiently stirring, and it is possible to maintain and manage the facility easily at a low construction cost and to further reduce the amount of sludge.

FIG. 4 is a schematic view showing a case where a modified example of the sludge reduction apparatus of FIG. 1 is applied to an observation sludge reduction system.

In FIG. 4, sewage from a wastewater treatment facility 51 is supplied to a sludge storage tank 61 via a sewage drainage pipe 52. The sludge storage tank 61 deposits and deposits sludge from the input wastewater, sucks activated sludge deposited in the sludge storage tank 61 by a sludge extraction pump, and sends the activated sludge to an adjacent sludge reduction device 70 via a sludge extraction pipe 62. Transfer. The sludge reduction device 70 is formed by integrally forming a part of the side wall of the sludge treatment tank 3 of FIG. 1 and a part of the side wall of the second sludge reduction tank 4. Do weight loss. The sludge reduced by the sludge reduction device 70 is dewatered by the dewatering device 71, carried out of the site as the dewatered sludge 81 by the truck 72, and disposed of by incineration or landfill.

According to such a modification, the same effect as that of the embodiment of the invention shown in FIG. 1 can be obtained, and a part of the side wall of the sludge treatment tank 3 and the side wall of the second sludge reduction tank 4 are formed. By integrally forming a part thereof, the weight and size of the device can be reduced, and the installation area can be relatively reduced.

[0035]

As described above, according to the present invention, it is possible to maintain and manage the facility easily at a low construction cost, and to further reduce the amount of sludge.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a sludge reduction device according to a first embodiment of the present invention.

FIG. 2 is a graph showing changes in MLSS concentration and pH in the sludge reduction device of FIG.

FIG. 3 is a graph showing a change in ORP in the sludge reduction device of FIG. 1;

FIG. 4 is a schematic diagram showing a case where a modified example of the sludge reduction apparatus of FIG. 1 is applied to an observation sludge reduction system.

[Explanation of symbols]

 2: Sludge weight reduction device 3: First sludge weight reduction tank 4: Second sludge weight reduction tank 5, 6: Sludge transfer pipe 41: Anaerobic circulation pump

Claims (4)

[Claims] A first treatment for decomposing sludge to be treated by microorganisms under aerobic conditions in a first sludge reduction tank;
And a second treatment for promoting the decomposition of the sludge to be treated by microorganisms under anaerobic conditions in a sludge reduction tank of the present invention. 2. A first treatment for decomposing organic matter in sludge to be treated by microorganisms under aerobic conditions in a first sludge reduction tank and oxidizing a nitrogen compound of the sludge to be treated, and a second sludge reduction tank. In the first step, microorganisms promote the decomposition of organic matter in the sludge to be treated under anaerobic conditions.
And a second treatment for decomposing the nitrogen compound oxidized by the treatment of the above. 3. A first sludge reduction tank for decomposing sludge by microorganisms under aerobic conditions, a second sludge reduction tank for promoting decomposition of sludge by microorganisms under anaerobic conditions, A first sludge transfer means for transferring the sludge to be treated in the first sludge reduction tank to the second sludge reduction tank; and a sludge to be treated in the second sludge reduction tank to the first sludge reduction tank. And a second sludge transfer means for transferring the sludge. 4. A sludge reduction apparatus according to claim 3, wherein a part of a side wall of said first sludge reduction tank and a part of a side wall of said second sludge reduction tank are integrally formed. .