JP2003334592A - Sewage treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently reduce the volume of sludge in a sedimentation tank into which sewage flows in. <P>SOLUTION: The sedimentation tank 1 into which sewage flows in, a digestion tank 10 for digesting sludge 9 drawn out of the sedimentation tank and a reaction tank 3 for biologically treating the supernatant liquid 2 in the sedimentation tank and the liquid 12 taken out of the digestion tank 10 are provided. An immersion type membrane filter device 5 for filtering the treated liquid 4 of the reaction tank 3 and an excess sludge draw-out passage 7 are provided to the reaction tank. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a sewage treatment apparatus.

[0002]

2. Description of the Related Art As a conventional sewage treatment apparatus, for example, FIG.
As shown in FIG. 1, a first settling tank 1 into which sewage flows, a main reaction tank 30 for biologically treating the supernatant 2 of the first settling tank 1, and a final settling tank 31 into which treated water of the main reaction tank 30 flows. Provided,
Part of the excess sludge extracted from the final settling tank 31 is returned to the main reaction tank 30, and the remaining excess sludge is sent to the disposal facility 8 for disposal, and the supernatant of the final settling tank 31 is sent to the sterilization facility 6. Some are configured to be sent and released.

In this sewage treatment apparatus, in order to reduce the volume of the sludge (first settling sludge) 9 first settled in the settling tank 1, a sub-process for biologically treating organic matter in the sludge first drawn out of the settling tank 1. The membrane tank 5 is provided with the reaction tank 32 and the submerged membrane filter 5 for filtering the treatment liquid 33 in the side reaction tank 32.
The filtrate filtered in step 1 is biologically treated in the main reaction tank 30 together with the supernatant 2 of the precipitation tank 1, and the fermented sludge drawn from the sub-reaction tank 32 is discarded together with the excess sludge drawn from the final precipitation tank 31. Is configured as follows.

[0004]

The sewage treatment apparatus described above is
Although the sludge 9 extracted from the settling tank 1 is biologically treated in the sub-reaction tank 32, the treatment liquid 33 in the sub-reaction tank 32 is filtered by the membrane filtration device 5, and only the filtrate is filtered into the main reaction tank 3
At 0, the biological treatment is carried out again, and the fermented sludge drawn from the side reaction tank 32 is discarded together with the excess sludge drawn from the final settling tank 31. There is a drawback that the volume cannot be reduced well.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to efficiently reduce the volume of sludge in a sedimentation tank into which sewage flows.

[0006]

According to a first aspect of the present invention, there is provided a settling tank into which sewage flows, a digestion tank for digesting sludge drawn from the settling tank, and a supernatant of the settling tank. A reaction tank for biologically treating the solution in the tank taken out from the digestion tank is provided, and the reaction tank is provided with a submerged membrane filtration device for filtering the treatment solution and a path for extracting excess sludge. is there.

[Operation and effect] By digesting the sludge drawn from the settling tank into which the sewage flows, in the digestion tank, it is possible to efficiently perform digestion treatment as sludge water having a higher concentration,
Moreover, it is decomposed into highly biodegradable organic substances with smaller molecular weight that are easily bioprocessed in the reaction tank, and the in-tank liquid that has become easier to bioprocess is taken out without solid-liquid separation, together with the supernatant of the precipitation tank. By supplying it to the reaction tank, biological treatment can be efficiently carried out in a state where the microorganisms are rich in nutrients, and the treated liquid is filtered by the immersion type membrane filtration device, and excess sludge can be withdrawn from the reaction tank through the withdrawal path. Therefore, more advanced activated sludge treatment can be performed, and as a result, sludge in the sedimentation tank into which sewage flows can be efficiently reduced in volume by biological treatment in the reaction tank.

According to a second aspect of the present invention, the reaction tank is composed of a denitrification tank and a nitrification tank, and the supernatant liquid of the precipitation tank and the tank liquid taken out from the digestion tank are The nitrification tank is made to flow through the denitrification tank, and a part of the treatment liquid in the nitrification tank is returned to the denitrification tank for circulation, and the nitrification tank is provided with the membrane filtration device and the extraction path. There is a point.

[Operation and effect] The reaction tank is composed of a denitrification tank and a nitrification tank, and the supernatant liquid of the precipitation tank and the tank liquid taken out from the digestion tank are circulated between the denitrification tank and the nitrification tank. Since the nitrification denitrification process is performed by this method, the sludge in the sedimentation tank into which the sewage flows can be finally efficiently decomposed in the reaction tank to reduce the volume, and the treatment liquid in the nitrification tank is filtered by the immersion type membrane filtration device. Then, since the excess sludge is drawn out from the nitrification tank, the sludge concentration in the nitrification tank becomes high, the activated sludge treatment becomes possible, and the biological treatment can be carried out by a smaller equipment as a whole.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the parts indicated by the same reference numerals as those in the conventional example indicate the same or corresponding parts.

FIG. 1 shows a sewage treatment apparatus according to the present invention,
A first settling tank 1 into which sewage flows, a reaction tank 3 for biologically treating a supernatant 2 of the first settling tank 1, an immersion type membrane filtration device 5 for filtering a treatment liquid 4 in the reaction tank 3, and a membrane filtration device 5 A sterilization tank 6 for sterilizing the filtrate filtered in step 1 and a withdrawal path 7 for withdrawing excess sludge from the reaction tank 3 are provided, and organic substances contained in the supernatant 2 of the precipitation tank 1 are first decomposed and removed in the reaction tank 3. Then, the filtrate filtered by the membrane filtration device 5 is sterilized in the sterilization tank 6 and discharged, and the excess sludge extracted from the reaction tank 3 is sent to the disposal facility 8 for disposal.

Then, a digestion tank 10 for extracting and digesting the first settled sludge 9 that has been settled and separated in the first settling tank 1 is provided, and while stirring the first settled sludge 9 in the digestion tank 10 with a stirring device 11, a reaction tank 3 is decomposed into an organic substance having a small molecular weight which is easily bioprocessed, and the decomposed liquid (tank liquid) 12 is taken out and biologically treated in the reaction tank 3 together with the supernatant liquid 2 of the first settling tank 1, and the first settling sludge 9 The volume can be reduced.

The digestion tank 10 has a reaction tank 3 in which the initial sludge 9 is digested by microorganisms in an aerobic atmosphere.
It is designed so that it can be decomposed into relatively low molecular weight organic substances that are easily decomposed by microorganisms inside.

The reaction tank 3 includes a denitrification tank 13 and a nitrification tank 14.
First, the supernatant liquid 2 of the precipitation tank 1 and the in-tank liquid 12 taken out from the digestion tank 10 are passed through the denitrification tank 13 and the nitrification tank 1
4 and a part of the treatment liquid 4 in the nitrification tank 14 is returned to the denitrification tank 13 and circulated, and the membrane filtration device 5 is immersed in the nitrification tank 14 for installation.
A drainage path 7 for excess sludge is provided at the bottom of No. 4.

In the membrane filtration device 5, a plurality of flat plate-shaped membrane cartridges 16 are mounted in the case 15, and an air diffuser 17 is provided in the lower part thereof so that air supplied from a blower 18 is supplied from the air diffuser 17 to the air blower 18. Aeration is performed to aerobically process the treatment liquid 4 in the nitrification tank 14 in an oxygen-rich environment, and the suction pump 19 is driven to suction-filter the treatment liquid 4 in the nitrification tank 14 to sterilize the filtered water. It is taken out to the tank 6.

The air diffused from the air diffuser 17 causes an upward flow of a gas-liquid mixed phase in the treatment liquid 4 by an air lift action, and this upward flow acts as a sweep flow on the membrane surface of the membrane cartridge 16. In this way, the adhesion of sludge to the membrane surface can be suppressed.

The withdrawal path 7 is configured to withdraw excess sludge with a sludge pump 20 and send it to a disposal facility 8 equipped with a sludge dehydrator, a sludge dryer, an incinerator, and the like.

[Other Embodiments] 1. The sewage treatment apparatus according to the present invention may be provided with a digestion tank for digesting sludge drawn out from the settling tank in an anaerobic environment. 2. The sewage treatment apparatus according to the present invention is configured such that the supernatant liquid of the precipitation tank and the in-tank liquid taken out from the digestion tank are biologically treated in a reaction tank configured to alternately perform nitrification treatment and denitrification treatment. It may be.

[0019]

EXAMPLE The amount of sludge generated when treated by the sewage treatment apparatus according to the present invention was compared with the amount of sludge generated when treated by the conventional sewage treatment apparatus shown in FIG. Sludge generation amount (k
g) is usually expressed per SS amount (kg) in the inflowing sewage, and in the conventional sewage treatment, the value as shown in [Table 1] is obtained as the amount of sludge generated by each method (sewerage facilities (Planning and design guidelines and commentary: Japan Sewer Association).

[Table 1]

When treated with the conventional sewage treatment apparatus shown in FIG. 2, it has been reported that the amount of sludge generated is similar to that of the standard activated sludge method, and it is an effective method for reducing the volume of sludge. I can not say.

Therefore, using the sewage treatment apparatus according to the present invention, the digestion tank is operated under aerobic conditions under the experimental conditions of an experimental water amount of 50 m ³ / day, a reaction tank residence time of 6 hours, and a digestion tank residence time of 48 hours. In this case, the sludge generation rate was 0.5 (sludge generation rate (kg) / SS amount (kg)), and a sludge volume reduction rate of about 50% was obtained compared to the standard activated sludge method.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a sewage treatment device.

FIG. 2 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

1 settling tank 2 supernatant 3 reaction tanks 4 processing liquid 5 Membrane filtration device 7 Withdrawal path 9 sludge 10 digestive tank 12 Tank liquid 13 denitrification tank 14 Nitrification tank

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hideki Iwabe             3 1-3 Nihombashi Muromachi, Chuo-ku, Tokyo             Kubota Tokyo Head Office F-term (reference) 4D006 GA07 HA41 JA31Z JA71                       KA01 KA31 KA44 KB22 KB23                 4D040 BB54 BB57 BB65                 4D059 AA04 AA05 BA01 BB01 BD00                       BE00 BJ00 CA28

Claims (2)

[Claims] 1. A reaction for biologically treating a sedimentation tank into which sewage flows, a digestion tank for digesting sludge drawn from the sedimentation tank, a supernatant of the sedimentation tank, and an in-tank liquid removed from the digestion tank. A sewage treatment apparatus, which is provided with a tank, and wherein the reaction tank is provided with an immersion type membrane filtration device for filtering the treatment liquid and a withdrawal path for excess sludge. 2. The reaction tank is composed of a denitrification tank and a nitrification tank, and the supernatant liquid of the precipitation tank and the in-tank liquid taken out from the digestion tank are caused to flow into the nitrification tank through the denitrification tank. At the same time, a part of the treatment liquid in the nitrification tank is returned to the denitrification tank for circulation, and the nitrification tank is provided with the membrane filtration device and the extraction passage. apparatus.