JP2000051883A - Method for treating activated sludge of drainage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce excess sludge discharged from a sewage treatment plant and others remarkably and to enable stable bio-treatment in a bio-reaction tank by a method in which sludge discharged from the bio-reaction tank with treated water is separated into solid and liquid, and the separated sludge is crushed and returned to the bio-reaction tank. SOLUTION: Drainage charged into an apparatus is introduced from a drainage pit 1 into a bio-reaction tank 3 through a drainage pump 2. The bio-reaction tank 3 is equipped with an aerator 4 for aerating the drainage, the introduced drainage is aerated, agitated to activate microorganisms in activated sludge, organic substances in the drainage is subjected to aerobic fermentation and anaerobic fermentation, the sludge is separated from treated water. Part or the whole separated sludge, after being crushed through a sludge pump 6 and a mechanical crusher 7, is returned to the bio-reaction tank 3. In this way, the decomposition of the sludge in the bio-reaction tank 3 is promoted to reduce excess sludge so that bio-treatment in the bio-reaction tank 3 can be performed stably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating activated sludge of sewage, and more particularly to a method for separating sewage sludge flowing out of a biological reaction tank together with treated water into solid and liquid and returning the sludge to the biological reaction tank. The present invention relates to an activated sludge treatment method for sewage, in which excess sludge discharged from a treatment plant or the like is reduced and biological treatment in a biological reaction tank can be performed stably.

[0002]

2. Description of the Related Art Conventionally, in a sewage treatment plant or the like, an activated sludge treatment method in which organic wastewater such as sewage is biologically treated with activated sludge in a biological reaction tank such as an aeration tank. In this activated sludge treatment method for wastewater, after solid-liquid separation of the sludge flowing out together with the treated water from the biological reaction tank, part or all of the separated sludge is returned to the biological reaction tank as it is, thereby reducing the sewage. Surplus sludge discharged from a treatment plant or the like is reduced, and biological treatment in a biological reaction tank can be stably performed.

[0003]

By the way, in the conventional activated sludge treatment method for wastewater, the sludge flowing out of the biological reaction tank together with the treated water is separated into solid and liquid, and the separated sludge is returned to the biological reaction tank as it is. However, the separated sludge has a mixture of fine particles that are soluble in sewage and large particles that are not easily dissolved in sewage. Even if it is returned to the tank, those with a large particle size that does not dissolve in the wastewater do not contribute to biological treatment and flow out of the biological reaction tank again without being decomposed together with the treated water, and eventually as excess sludge It will be discarded. Since excess sludge has a high moisture content (sludge concentration is about 1%), it cannot be directly incinerated or dumped in landfills. They are dumped in landfills, which is not only expensive to treat, but also due to the recent rise in environmental protection and lack of landfills,
The processing itself is becoming difficult.

[0004] In view of the problem of the treatment of excess sludge of the conventional method for treating activated sludge, the present invention remarkably reduces excess sludge discharged from a sewage treatment plant and the like, and reduces biological treatment in a biological reaction tank. An object of the present invention is to provide a method for treating activated sludge of sewage, which can be performed stably.

[0005]

In order to achieve the above object, the method for treating activated sludge of sewage of the present invention is characterized in that activated sludge of sewage for purifying sewage by returning sludge discharged from a biological reaction tank to a biological reaction tank. The treatment method is characterized in that the sludge flowing out of the biological reaction tank together with the treated water is subjected to solid-liquid separation, and then the separated sludge is crushed and returned to the biological reaction tank.

In this method for treating activated sludge, the sludge flowing out of a biological reaction tank is separated into solid and liquid, and then the separated sludge is crushed, so that the sludge having a large particle size that is not easily dissolved in the sludge in the sludge. Since the waste is reduced to a soluble fine particle size and then returned to the biological reaction tank, the decomposition of sludge in the biological reaction tank is promoted, and surplus sludge discharged from sewage treatment plants is significantly reduced. Alternatively, excess sludge can be prevented from being generated, and the biological treatment in the biological reaction tank can be stably performed.

[0007] In this case, the sludge can be crushed by a crusher such as a mechanical crusher or an ultrasonic crusher.

Thus, the sludge can be crushed reliably.

Further, the sludge can be crushed by existing equipment such as a sewage pump and an aerator.

As a result, the construction cost of the equipment can be reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for treating activated sludge of wastewater of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of an activated sludge treatment facility installed in a sewage treatment plant or the like for implementing the activated sludge treatment method of the present invention.

The sewage flowing into the activated sludge treatment facility is:
The sewage pit 1 is introduced into a biological reaction tank 3 such as an aeration tank via a sewage pump 2.

An aerator 4 for aerating sewage is installed in the biological reaction tank 3, and the sewage introduced into the biological treatment tank 3 is aerated and agitated to remove microorganisms in the activated sludge. (Bacteria) are activated to treat organic matter in wastewater by repeating aerobic fermentation and anaerobic fermentation.

The treated water containing the sludge biologically treated in the biological treatment tank 3 is introduced into the sedimentation tank 5 and separated from the treated water by solid-liquid separation by gravity sedimentation or the like. The supernatant water is discharged to rivers and the like after sterilization.

On the other hand, part or all of the separated sludge is returned to the biological reaction tank 3 by the return sludge pump 6 via the return sludge pipe 8.

Incidentally, the separated sludge is in a mixed state of fine particles having a fine particle size soluble in sewage and large particles which are not easily dissolved in sewage. Even if it is returned to the wastewater, those having a large particle size that does not dissolve in the sewage do not contribute to biological treatment and flow out again from the biological reaction tank 3 together with the treated water without being decomposed, and eventually as excess sludge. It will be discarded.

For this reason, a mechanical crusher 7 is interposed in the return sludge pipe 8 so that the sludge is crushed and then returned to the biological reaction tank 3. As described above, the sludge having a large particle size that is not easily dissolved in the sludge is converted into a fine particle having a soluble size, and then returned to the biological reaction tank 3.
The decomposition of sludge in the above is promoted, the excess sludge to be discharged can be remarkably reduced or surplus sludge is not generated, and the biological treatment in the biological reaction tank 3 can be stably performed.

In this embodiment, the sludge is crushed by the mechanical crusher 7 interposed in the return sludge pipe 8, but the crushing method of the sludge is not limited to this. In addition to the method of crushing by the pressure difference and the impact force generated when air is released to the atmosphere, an ultrasonic crusher that crushes sludge by the impact force during cavitation generated by high frequency of about 20 kHz can be used.

In any of the mechanical crushing method and the ultrasonic crushing method, a large particle size that is not easily dissolved in the sludge in the sludge is converted into a fine particle size that is soluble. And the cell wall of sludge mainly composed of bacteria can be destroyed, so that intracellular substances can be solubilized. Also, these crushing methods
Unlike chemical solution decomposition using acid or alkali or oxidative decomposition using ozone, no chemical solution or ozone remains in the treated water, so that the secondary treatment of the treated water becomes unnecessary, and furthermore, it is necessary for the sewage treatment. Since the amount of microorganisms to be removed does not decrease, the biological treatment in the biological reaction tank 3 can be stably performed.

As described above, the separated sludge is converted into a fine one having a soluble fine particle diameter, and then returned to the biological reaction tank 3, where biological treatment is performed. Usually, the sludge has an organic matter content of about 70%. In addition, since the sludge conversion rate of organic matter by the oxidation ditch method or the long-time aeration method is about 70%, in this activated sludge treatment method, the sludge concentration in the biological reaction tank 3 is 49%. The amount of sludge generated at the time of the increase and the amount of sludge to be decomposed are equalized, so that the activated sludge treatment method apparently does not generate excess sludge.

In the above embodiment, a mechanical crusher 7 is interposed in the return sludge pipe 8 to crush the sludge.
However, as in the second embodiment of the activated sludge treatment facility installed in a sewage treatment plant or the like that performs the activated sludge treatment method of the present invention shown in FIG. When the sludge is connected to the pit 1 and introduced into the biological reaction tank 3 via the sewage pump 2 from the sewage pit 1 together with the sewage, the sludge is crushed by the sewage pump 2 or the present invention shown in FIG. Of activated sludge treatment equipment installed in a sewage treatment plant or the like that implements the activated sludge treatment method for sewage in Japan
As in the embodiment, the return sludge pipe 8 is connected to a position near the aerator 4 in the biological reaction tank 3, and the sludge is crushed by the aerator 4 when the sludge is introduced into the biological reaction tank 3. be able to.

[0023]

According to the activated sludge treatment method of the present invention, the sludge flowing out of the biological reaction tank is subjected to solid-liquid separation.
By crushing the separated sludge, the sludge with a large particle size that is not easily dissolved in the sewage is converted into a fine particle size that is soluble, and then returned to the biological reaction tank. Decomposition of sludge in the reaction tank is promoted, surplus sludge discharged from sewage treatment plants and the like can be significantly reduced or surplus sludge is not generated, and biological treatment in the biological reaction tank can be stably performed. Thus, problems associated with the treatment of excess sludge can be eliminated at a glance.

Further, by crushing the sludge using a crusher such as a mechanical crusher or an ultrasonic crusher, the sludge can be reliably crushed.

[0025] In addition, since the sludge is crushed by existing equipment such as a sewage pump and an aerator, the construction cost of the equipment can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment of an activated sludge treatment facility installed in a sewage treatment plant or the like for implementing the activated sludge treatment method of the present invention.

FIG. 2 is an explanatory view of a second embodiment of the activated sludge treatment facility installed in a sewage treatment plant or the like for implementing the activated sludge treatment method for wastewater of the present invention.

FIG. 3 is an explanatory view of a third embodiment of an activated sludge treatment facility installed in a sewage treatment plant or the like for implementing the activated sludge treatment method of the present invention.

[Explanation of symbols]

 Reference Signs List 1 sewage pit 2 sewage pump 3 biological reaction tank 4 aerator 5 sedimentation tank 6 return sludge pump 7 mechanical crusher 8 return sludge piping

Claims (3)

[Claims] 1. An activated sludge treatment method for sewage in which sludge flowing out of a biological reaction tank is returned to a biological reaction tank to purify sewage. A method for treating activated sludge in sewage, wherein the crushed sludge is returned to a biological reaction tank after crushing. 2. The activated sludge treatment method according to claim 1, wherein the sludge is crushed by a crusher such as a mechanical crusher or an ultrasonic crusher. 3. The activated sludge treatment method according to claim 1, wherein the sludge is crushed by an existing facility such as a sewage pump and an aerator.