JPH11244893A - Operation method of organic sewage treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently clean sewage and treat excess sludge at the time of treating the org. sewage by a membrane-separation activated-sludge process. SOLUTION: Org. sewage is introduced into a denitrification tank 1, a liq 9 in the denitrification tank is made to overflow into nitrification tanks 2 and 3, solid is separated from the liq. therein by membrane separators 5 and 7, the clean treated water is discharged, and the liqs. 10 and 11 concentrated thereby in the nitrification tanks are temporally transferred to a sludge storage tank 4 by pumps 6 and 8 then, returned to the denitrification tank 1 from the sludge storage tank 4 by overflowing. By passing the sludge storage tank 4, the dissolved oxygen is consumed to improve the denitrification efficiency, the oxidized nitrogen concn. in decreased as well biological dephosphorization is caused and the phosphorus removal rate is improved. Further, excess sludge high in the sludge concn. can be extracted from the sludge storage tank 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating an organic sewage treatment apparatus for treating organic sewage containing nitrogen by membrane separation activated sludge.

[0002]

2. Description of the Related Art As a method for treating organic wastewater, there is a method called membrane separation activated sludge treatment in which an activated sludge method and a membrane separation method are used in combination.

[0003] The membrane separation method is carried out, for example, in a processing tank in which a membrane separation apparatus as shown in FIG. 3 is installed as shown in FIG. The membrane separation device 21 has a plurality of flat membrane cartridges 22 and a diffuser 23 that blows out aerated air that also serves as a membrane surface cleaning from below the cartridges 22 in a case 24. The membrane cartridge 22 has a filter membrane 22B disposed on each of the front and back surfaces of the filter plate 22A, and a permeate liquid that communicates with the permeate flow path formed between the filter plate 22A and the filter membrane 22B and inside the filter plate 22A. The outlet 22C is formed in the filter plate 22A, and the permeate outlet 22C of each membrane cartridge 22 is provided.
A water collecting pipe 26 communicating with the case 2 through a tube 25 is connected to the case 2
4 attached. Further, a permeated liquid outlet pipe 27 communicating with the water collecting pipe 26 is provided.

[0004] A case where an organic wastewater containing nitrogen is subjected to membrane separation activated sludge treatment will be described. As shown in FIG. 5, a membrane separation device (as a membrane) is provided inside a nitrification tank 29 disposed downstream of a denitrification tank 28. Immersed). Then, in the flow of sequentially introducing the pretreated wastewater into the denitrification tank 28 and the nitrification tank 29 and circulating and returning a part of the nitrification tank internal liquid 30 to the denitrification tank 28, the BOD component and the nitrogen content in the wastewater are activated sludge. , And the nitrification tank solution 30 is gravity filtered by a membrane separator using the head of the solution as a driving pressure (suction filtration using a suction pump is also possible), and the clear treated water that has passed through the membrane surface is removed from the tank. Derived to At this time, in the nitrification tank 29, oxygen is supplied by the aerated air ejected from the above-mentioned air diffuser, and the membrane surface of the membrane separator is washed by the bubbles and the rising water flow generated by the bubbles. To prevent the entire membrane separation device from stopping due to a decrease in the temperature.

[0005] Such a membrane separation activated sludge treatment has begun to spread widely because the treated water quality is stable and the maintenance is easy. However, regarding the membrane separation apparatus, although the membrane surface is cleaned with aerated air, the membrane surface is unavoidably gradually contaminated. Therefore, the membrane surface is periodically cleaned by a method such as backwashing.

In particular, in gravity filtration, if the air level is stopped by using the liquid level as a control element and the amount of filtration is small, a trouble may occur in the liquid level meter or the like, or a trouble may occur in the air diffuser itself. When this occurs, solid-liquid separation will be performed in the absence of the membrane surface cleaning fluid, and sludge will accumulate on the membrane surface, making filtration impossible, and in such cases,
The operation of the entire membrane separation apparatus must be stopped, and the membrane cartridge must be taken out of the tank and washed, or washed by physical means in the tank.

At least once a year, the membrane cartridge is taken out of the tank and inspected, or the liquid in the tank is drained and inspected once a year, even if the filtration cannot be performed as described above. In such a case, a similar nitrification tank 29 'is installed in parallel with the nitrification tank 29 as shown in FIG. (29a, 29a 'are membrane separation devices)

[0008]

When the nitrification tanks 29 and 29 'are installed in parallel as described above,
As shown in the figure, a pump device 28a is installed in the denitrification tank 28, and the liquid 31 in the denitrification tank is transferred to the nitrification tank 29 through the distribution tank 28 'by the pump device 28a.
Is often returned cyclically on overflow. However, in this method, when the excess sludge is to be extracted using the pump device 28a, the liquid 31 in the denitrification tank is extracted, and the sludge concentration is reduced.

As shown in FIG. 6, the nitrification tanks 29, 29 '
Pump devices 29b and 29b 'are installed in the tank.
When the liquid 30 ′ is circulated back to the denitrification tank 28 and the liquid 31 in the denitrification tank is caused to flow into the nitrification tanks 29 and 29 ′ by overflow, the liquid 3 in the nitrification tank concentrated by solid-liquid separation is obtained.
0,30 'is extracted as surplus sludge, and the sludge concentration increases. However, in this case, the nitrification tank 29, 2
In order to equalize the sludge withdrawal amount at 9 ', not only each pump device 29b, 29b' and its spare device, but also a metering device (not shown) corresponding to each pump device must be operated. It is complicated.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide an operation method of an organic sewage treatment apparatus capable of efficiently purifying organic sewage and treating excess sludge.

[0011]

According to a first aspect of the present invention, there is provided a method of operating an organic wastewater treatment apparatus, comprising: a denitrification tank and a nitrification tank for treating organic wastewater containing nitrogen with activated sludge;
An operation method of an organic sewage treatment device having a membrane separation device that performs solid-liquid separation by being immersed and installed inside a nitrification tank,
The organic wastewater is introduced into the denitrification tank, and the liquid in the denitrification tank is caused to flow into the nitrification tank by overflow, and the liquid in the nitrification tank is separated into solid and liquid by a membrane separation device to derive clear treated water. The concentrated liquid in the nitrification tank is once transferred to a sludge storage tank by a pump device, and is returned from the sludge storage tank to the denitrification tank by overflow.

According to a second aspect of the present invention, there is provided an operation method of the organic wastewater treatment apparatus, wherein the liquid in the denitrification tank is caused to flow into a nitrification tank provided in parallel. According to a third aspect of the present invention, there is provided an operation method of the organic sewage treatment apparatus, wherein the organic sewage is introduced into a denitrification tank provided in parallel, and then introduced into a nitrification tank provided in series with each denitrification tank. .

According to the method for operating the organic wastewater treatment apparatus according to the first aspect of the present invention, the organic wastewater flows into the denitrification tank and the nitrification tank in order, and is returned to the denitrification tank via the sludge storage tank. It is nitrified and denitrified, separated into solid and liquid, and discharged as clear treated water.

This flow generally corresponds to the nitrification liquid circulation method,
In general, in the nitrification liquid circulation method, when the amount of circulating liquid increases, dissolved oxygen brought into the denitrification tank by the liquid in the nitrification tank (nitrification liquid) reacts with the hydrogen donor in the wastewater, and the denitrification rate tends to decrease. Although there is a drawback, in the above flow, the dissolved oxygen in the liquid in the nitrification tank is completely consumed in the sludge storage tank, does not inhibit the denitrification reaction, and the amount of circulating liquid can be increased. Nitrogen efficiency is improved.

In addition, since denitrification occurs partially in the sludge storage tank and the concentration of oxidized nitrogen is reduced, phosphorus is discharged from the denitrification tank and biological dephosphorization in which phosphorus is excessively taken up in the nitrification tank. And the phosphorus removal rate is improved.

Since the sludge in the sludge storage tank has the same high concentration as that of the nitrification tank, the subsequent treatment is easy when the sludge is extracted as surplus sludge. According to the configuration of the second aspect, when performing maintenance on the membrane separation device, it is only necessary to stop the operation of only the nitrification tank provided with the membrane separation device, and it is possible to avoid the entire stoppage of the facility.

In addition, since the liquid in the nitrification tank is simply transferred to the sludge storage tank, the sludge is automatically equalized, and a conventional method for equalizing the sludge withdrawal amount of each nitrification tank. No management is required.

According to the third aspect of the present invention, when the maintenance of the membrane separation apparatus is performed, only the operation of the nitrification tank provided with the membrane separation apparatus may be stopped, and the entire stoppage of the facility can be avoided.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, an organic wastewater treatment apparatus for treating organic wastewater containing nitrogen with activated sludge has a denitrification tank 1 and nitrification tanks 2 and 3 arranged in parallel. A sludge storage tank 4 is provided at the subsequent stage.

Although not shown in detail, the denitrification tank 1 includes:
A sewage introduction pipe is opened at an upper part, a stirring means for stirring the liquid in the tank is installed therein, and an overflow channel to the nitrification tanks 2 and 3 is provided.

In the nitrification tank 2, an overflow channel from the denitrification tank 1 is opened, and a membrane separation device 5 for performing solid-liquid separation is immersed and installed therein. A transfer path is provided to reach the sludge storage tank 4.

Similarly, in the nitrification tank 3, an overflow channel from the denitrification tank 1 is opened, and a membrane separation device 7 for performing solid-liquid separation is immersed therein, and an in-tank type or out-of-tank type pump device is provided. A transfer path leading to the sludge storage tank 4 with the intermediary 8 interposed therebetween is provided.

Each of the membrane separators 5 and 7 has the same configuration as that described above with reference to FIG. 2, and is provided with an air diffuser below the membrane cartridge to communicate with the permeate outlet pipe. doing.

The other end of the transfer pipe from the nitrification tanks 2 and 3 communicates with the sludge storage tank 4, and a stirring means and an aeration means for stirring the liquid in the tank are installed inside the sludge storage tank 4. A channel is provided, and sludge extraction means is provided at the bottom.

The operation of the above organic wastewater treatment apparatus will be described. The pretreated organic sewage is continuously introduced into the denitrification tank 1 and the liquid 9 in the denitrification tank flows into the nitrification tanks 2 and 3 by overflow, and the liquid in the nitrification tank is solid-liquid by the membrane separation devices 5 and 7. Separated and treated water is led out, and the concentrated liquids 10 and 11 in the nitrification tank are transferred to the sludge storage tank 4 by the pump devices 6 and 8, and the tank upper liquid 12 of the sludge storage tank 4 is removed by overflow. Return to Nitrification tank 1.

As a result, the organic wastewater sequentially flows into the denitrification tank 1 and the nitrification tanks 2 and 3, and in the flow circulated back to the denitrification tank 1 through the sludge storage tank 4, the BOD component and the nitrogen component become activated sludge. It is decomposed and removed by the action, and solid-liquid separated in the nitrification tanks 2 and 3 to obtain clear treated water.

At this time, since the liquids 10 and 11 in the nitrification tank pass through the sludge storage tank 4, the dissolved oxygen in the liquids 10 and 11 in the nitrification tank is completely consumed.
Since it does not react with the hydrogen donor in the sewage, the denitrification efficiency is improved.

Also, denitrification occurs partially in the sludge storage tank 4,
Since the nitrogen oxide concentration is reduced, biological dephosphorization occurs and the phosphorus removal rate is improved. The sludge in the sludge storage tank 4 is appropriately extracted as excess sludge, but the extracted excess sludge has a high sludge concentration, so that subsequent processing such as dehydration is easy.

Periodically or appropriately, for example, in the nitrification tank 2, maintenance of the membrane separation device 5 is performed such that the membrane cartridge is taken out of the tank or the liquid in the nitrification tank is drained. The liquid 9 is allowed to flow only into the nitrification tank 3, and conversely, during maintenance of the membrane separation device 7, the liquid 9 in the denitrification tank is caused to flow only into the nitrification tank 2, thereby avoiding the entire stoppage of the facility.

As shown in FIG. 2, in an apparatus provided with a denitrification tank 1 and a nitrification tank 2 and a denitrification tank 1 'and a nitrification tank 3 in parallel, only the nitrification tank 2 is operated during maintenance of the membrane separation apparatus 5. It is only necessary to stop the operation, and conversely, stop the operation of only the nitrification tank 3 during the maintenance of the membrane separation device 7. At that time, it is not always necessary to stop the operation of the denitrification tank 1 or the denitrification tank 1 ′, and it is sufficient that the denitrification tank 1 or the denitrification tank 1 ′ flows into the operating nitrification tank 2 or nitrification tank 3.

The denitrification tanks 1, 1 ', the nitrification tanks 2, 3,
The sludge storage tank 4 and the membrane separation devices 5 and 6 are not limited to the above-described configurations. For example, the membrane separation devices 5 and 6 may be changed to another type of external pressure type membrane separation device having a tubular membrane or the like. Is also possible.

[0032]

As described above, according to the present invention, when the organic wastewater containing nitrogen is subjected to the membrane separation activated sludge treatment, the wastewater is sequentially flown into the denitrification tank and the nitrification tank, and is then passed through the sludge storage tank. By circulating and returning to the nitrification tank, dissolved oxygen in the liquid in the nitrification tank is completely consumed in the sludge storage tank, and the denitrification efficiency is improved. Since the nitrogen concentration is reduced, biological dephosphorization occurs, and the phosphorus removal rate is improved. At this time, the liquid was sent by overflow from the denitrification tank to the nitrification tank and from the sludge storage tank to the denitrification tank, and the liquid was pumped from the nitrification tank to the sludge storage tank, so that excess sludge with a high sludge concentration in the sludge storage tank was used. Can be pulled out, and the subsequent processing becomes easy. In addition, since fresh sludge concentrate is always transferred to the sludge storage tank, generation of offensive odor and fly due to insufficient stirring and aeration is completely eliminated.

In a processing apparatus in which a nitrification tank is provided in parallel, or a denitrification tank and a nitrification tank are arranged in series with each other and in parallel with each other, a nitrification tank and a denitration tank for maintenance are required during maintenance of a membrane separation device or the like. It is only necessary to stop the operation of the nitrification tank alone, and it is possible to avoid a complete stoppage of the facility.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an organic sewage treatment apparatus operated in a first embodiment of the present invention and a processing flow thereof.

FIG. 2 is an explanatory diagram showing a schematic configuration of an organic sewage treatment apparatus operated in a second embodiment of the present invention and a processing flow thereof.

FIG. 3 is a perspective view showing the overall configuration of a conventional membrane separation device installed in each of the organic wastewater treatment devices described above.

FIG. 4 is an explanatory view showing a state where the above-mentioned membrane separation device is installed in a processing tank.

FIG. 5 is an explanatory diagram showing a schematic configuration of an organic sewage treatment apparatus operated by a conventional method and a processing flow thereof.

FIG. 6 is an explanatory diagram showing a schematic configuration of another organic sewage treatment apparatus operated by a conventional method and a processing flow thereof.

[Explanation of symbols]

 5,7 Membrane separation device 6,8 Pump device 9,9 'Liquid in denitrification tank 10,11 Liquid in nitrification tank 12 Liquid in upper part of tank

Continued on the front page (72) Inventor Hidehiko Sakai 3-3-1, Nihonbashi Muromachi, Chuo-ku, Tokyo Kubota Tokyo Head Office

Claims (3)

[Claims] 1. An organic wastewater treatment system comprising: a denitrification tank and a nitrification tank for treating nitrogen-containing organic wastewater with activated sludge; and a membrane separation device immersed in the nitrification tank for solid-liquid separation. An operation method of the apparatus, wherein the organic wastewater is introduced into a denitrification tank, and the liquid in the denitrification tank is caused to flow into the nitrification tank by overflow, and the liquid in the nitrification tank is separated into solid and liquid by a membrane separation device to obtain a clear liquid. An organic sewage treatment apparatus characterized in that the treated water is led out, and the liquid in the nitrification tank concentrated thereby is once transferred to a sludge storage tank by a pump device and returned to the denitrification tank by overflow from the sludge storage tank. how to drive. 2. The method according to claim 1, wherein the liquid in the denitrification tank flows into a nitrification tank provided in parallel. 3. The organic sewage treatment apparatus according to claim 1, wherein the organic sewage flows into a denitrification tank provided in parallel, and then is introduced into a nitrification tank provided in series with each denitrification tank. how to drive.