JPH0975994A - Biological waste water treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biological waste water treating device which is equipped with a carrier outflow preventive device for separating carriers without using a screen and is capable of drastically lessening maintenance and inspection and improving treatment efficiency. SOLUTION: The suspending activated sludge and carriers 24 which are entrained in a nitrifying liquid and flowing out into an accepting vessel 48 from a nitrifying vessel 26 are lowered by a descending flow passage 54 and is admitted into a separating chamber 56. The carriers 24 are settled and separated from the suspending activated sludge by utilizing the difference in the sp. gr. between the suspending activated sludge and the carriers 24 in the separating chamber 24. The carriers 24 settling on the bottom of the separating chamber 56 returns to the nitrifying vessel 26 by riding the flow of a water feed pipe 58 which takes-in the lower liquid in the separating chamber 56 and feeding the water to the nitrifying vessel 26. At this time, the flow of the water feed pipe 58 is formed by an air lift and, therefore, the destruction of the carriers 24 does not arise. Besides, the suspending activated sludge is returned to a denitrifying vessel by a nitrifying liquid circulating path 16 for circulating the upper layer liquid of the separating chamber 56 to the denitrifying vessel and is sent to a sludge settling vessel via a trough 70 for allowing the overflow of the treated water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biological wastewater treatment system, and more particularly to a biological wastewater treatment system in which floating activated sludge and a carrier on which microorganisms are immobilized are allowed to coexist in a treatment tank. It relates to a wastewater treatment device.

[0002]

A nitrification / denitrification device is a typical example of a wastewater treatment device to which a biological wastewater treatment device is applied. This device is composed of a denitrification device and a nitrification device.In the denitrification device, the inflowing wastewater raw water and the nitrification liquid circulated from the nitrification device contact the floating activated sludge in an anaerobic state, Decomposition of organic substances and denitrification of nitric acid in nitrification liquid are performed. Then, the nitric acid in the nitrification liquid is reduced and released as nitrogen gas into the atmosphere to be removed.

On the other hand, in the nitrification device, the liquid sent from the denitrification device is brought into contact with the floating activated sludge in an aerobic state to nitrify the ammoniacal nitrogen in the wastewater into nitric acid. A part of the nitrification solution subjected to the nitrification treatment and a part of the floating activated sludge entrained in the nitrification solution are circulated to the denitrification device, and the rest are sent to the sludge settling tank as treated water. In the sludge settling tank, the floating activated sludge is settled and separated, and a part of the settled sludge is circulated to the denitrification device as return sludge, while the supernatant liquid is discharged to the outside of the system as treated water.

In this nitrification / denitrification device, nitrifying bacteria are less prone to breeding than denitrifying bacteria. Therefore, a carrier on which nitrifying bacteria are immobilized is put into a nitrification tank to increase the nitrification efficiency. In this case, it is necessary to provide a carrier flow-out prevention device so that the carrier introduced into the nitrification device will not flow away. Conventionally, as a carrier flow-out prevention device, an opening screen through which the carrier does not pass is provided at the drainage port of the nitrification device to separate the carrier from the suspended activated sludge discharged from the nitrification device along with the nitrification liquid. .

[0005]

However, in the case of the screen, there is a drawback that the solid content contained in the wastewater raw water or the fiber content such as hair adheres to the screen to cause clogging. If the screen is clogged, the discharge of the nitrification liquid from the nitrification device will deteriorate, and the water level of the nitrification device will rise, causing problems such as backflow of the liquid.Therefore, the screen must be cleaned frequently. There is.

The passage speed of the liquid passing through the screen is 60
By setting m / h or less (usually 100 m / h or more), the clogging of the screen can be somewhat reduced, but in this case, the screen area is enormous due to the balance with the inflow amount of the liquid flowing into the nitrification device. As a result, the equipment cost increases and maintenance of the screen becomes difficult.

The present invention has been made in view of the above circumstances, and is provided with a carrier outflow prevention device for separating carriers without using a screen, which greatly reduces maintenance and inspection and improves processing efficiency. An object of the present invention is to provide a biological wastewater treatment device that can be used.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention comprises a floating activated sludge in a treatment tank into which waste water flows.
A bioreactor for biologically treating the wastewater by coexisting with a carrier having a specific gravity larger than that of the floating activated sludge in which microorganisms are immobilized, and a carrier washout prevention device for preventing the washout of the carrier In biological wastewater treatment equipment,
The carrier flow-out prevention device is provided in the receiving tank for receiving the effluent flowing out from the bioreactor and the floating activated sludge flowing out in association with the effluent and the carrier, and the living organism provided in the receiving tank. A descending flow path that forms a descending flow in the effluent flowing out of the reactor and a communication path to the descending flow path, which is provided in the receiving tank, utilizes the difference in specific gravity between the suspended activated sludge and the carrier in the effluent. And a separation chamber for settling and separating the carrier from the suspended activated sludge, and a water inlet near the bottom of the separation chamber, and a water passage for taking the lower layer liquid of the separation chamber and sending it to the bioreactor. An air jetting means for forming a flow from the separation chamber to the bioreactor in the water supply path by an air lift power, and a discharge means provided at an upper portion of the separation chamber for discharging an upper layer liquid of the separation chamber, Consisting of the separation chamber With the carrier which settled to the bottom part placed on a flow of the water pass back to the bioreactor device, characterized in that the discharge from the receiving reservoir sedimentation difficult suspended activated sludge in the discharge means.

According to the present invention, the suspended activated sludge and the carrier that have flowed out from the bioreactor together with the effluent flow down into the separation chamber by the downflow passage. The descending flow path is descended to allow the floating activated sludge and the carrier to flow into the separation chamber, thereby giving a downward force that facilitates sedimentation to the carrier having a larger specific gravity than the floating activated sludge. In the separation chamber, the carrier is settled and separated from the floating activated sludge by utilizing the difference in specific gravity between the floating activated sludge and the carrier. The carrier settled at the bottom of the separation chamber returns to the bioreactor by taking the lower layer liquid of the separation chamber and riding on the flow of the water supply channel of the bioreactor. At this time, the carrier is not destroyed because the power source that forms the flow in the water passage is the air lift. On the other hand, the floating activated sludge, which is less likely to settle when the upper layer liquid in the separation chamber is discharged by the discharging means, is discharged together with the upper layer liquid.

As a result, the carrier can be prevented from flowing out from the bioreactor, and the carrier and the suspended activated sludge can be efficiently separated. In the above biological wastewater treatment apparatus, the ascending velocity of the ascending flow in the separation chamber generated by the discharging means is smaller than the sedimentation velocity at which the carrier sediments (calculated from Stokes' equation from the specific gravity and particle size of the carrier). Was set to be.
This facilitates the sedimentation of the carrier. Further, a plurality of straightening vanes are provided in the vertical direction in the separation chamber, the water intake is located below the straightening vane, and the discharge means is located above the straightening vane. As a result, uneven flow or turbulent flow does not occur in the separation chamber, so that the carrier is prevented from rising and the sedimentation can be promoted. Further, if a slanting plate that promotes the sedimentation of the carrier is provided in the separation chamber and the carrier is collected at the water intake by the slanting plate, the separation of the carrier and the suspended activated sludge becomes easier. Furthermore, if a deaerator is provided between the straightening vane and the discharge means, it is possible to prevent the floating activated sludge from staying on the liquid surface as scum due to bubbles or the like adhering to the floating activated sludge.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the biological wastewater treatment apparatus according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view illustrating a first embodiment of a biological wastewater treatment device of the present invention, which is an example of application as a nitrification device of a nitrification / denitrification device, in which nitrifying bacteria are fixed to the nitrification device. The solidified carrier is charged.

As shown in FIG. 1, a nitrification / denitrification apparatus 10
Is mainly a denitrification device 12 into which wastewater such as sewage containing organic matter and ammonia nitrogen components flows in,
The nitrification device 14 provided in the subsequent stage of the denitrification device 12, the nitrification liquid circulation path 16 for circulating a part of the nitrification liquid treated in the nitrification device 14 to the denitrification device 12, and the nitrification treatment in the nitrification device 14. Sludge settling tank 18 that sends the rest of the liquid as treated water
And a sludge return system path 20 for returning the sludge settled in the sludge settling tank 18 to the denitrification device 12 as return sludge.

The denitrification device 12 slowly removes the denitrification tank 22 in which floating activated sludge (not shown) is stored, and the waste water flowing into the denitrification tank 22 to make the denitrification tank 22 anaerobic. It is composed of a plurality of agitators 23, 23 that agitate and deaerate and efficiently contact waste water and floating activated sludge. The nitrification apparatus 14 includes a nitrification tank 26 in which a large number of carriers 24, 24 ... Immobilized with nitrifying bacteria and floating activated sludge coexist, and an inside of the nitrification tank 26 is aerobic and a denitrification tank is provided. Aeration device 28 for efficiently contacting the liquid flowing in from 22 with carrier 24 and suspended activated sludge, blower 30 for supplying compressed air to aeration device 28, and aeration device 2
Aeration amount adjusting valve 32 for adjusting the aeration amount of 8 and carrier 2
4 is composed of a carrier flow-out prevention device 34 for preventing the flow-out of the liquid from the nitrification tank 26. The liquid in the denitrification tank 22 overflows from the opening 38 formed in the upper part of the first partition wall 36 that partitions the denitrification tank 22 and the nitrification tank 26.

Further, the nitrification liquid circulation path 16 and the sludge return system path 2
Pumps 42, 44, and 46 are provided in the 0 and excess sludge removal system paths 40, respectively. Next, the carrier loss prevention device 34, which is an improved part of the present invention, will be described with reference to FIG. A receiving tank 48 is provided adjacent to the nitrification tank 26 on the rear side of the nitrification tank 26, and the nitrification solution nitrified in the nitrification tank 26 is located above the second partition wall 50 that partitions the nitrification tank 26 and the reception tank 48. Overflow from the overflow section 51 formed in the. The carrier 2 stored in the nitrification tank 26 by this overflow of the nitrification liquid.
Part 4 and part of the suspended activated sludge accompany the nitrification liquid and overflow into the receiving tank 48. On the side of the nitrification tank 26 in the receiving tank 48,
A partition plate 52, which is parallel to the second partition wall 50 and partitions the inside of the receiving tank 48 from the liquid surface to a substantially intermediate height in the vertical direction, is provided in the vertical direction, and the descending flow path 54 for descending the overflowed nitrification liquid.
Is formed. At the other end of the receiving tank 48 partitioned by the partition plate 52, the lower end of the partition plate 52 communicates with the descending flow path 54, and the specific gravity difference between the suspended activated sludge contained in the nitrification solution and the carrier 24 is set. A separation chamber 56 is formed for utilizing the carrier 24 to settle and separate it from the suspended activated sludge. In the separation chamber 56, a water supply pipe 58 for taking the lower layer liquid in the separation chamber 56 and supplying it to the nitrification tank 26 is provided. This water pipe 58
Is formed in the vicinity of the bottom of the separation chamber 56 by opening downward in the shape of a trumpet, and the water pipe 58 extending vertically from the water intake 60 to the liquid surface faces the nitrification tank 26 side above the liquid surface. Alternately, it extends obliquely downward to the liquid surface of the nitrification tank 26. Below the water intake 60 of the water supply pipe 58, the air jetting device 6 is provided.
2 is provided, the air ejection device 62 is the aeration device 28 described above.
Is connected to the blower 30 of FIG. As a result, compressed air is blown from the air ejection device 62 toward the water intake port, so that an upward flow is generated in the water supply pipe 58 by the air lift action, and the lower layer liquid in the separation chamber 56 is supplied to the nitrification tank 26. . Further, inclined plates 66, 66 are provided in the separation chamber 56 to promote the sedimentation of the carrier 24. The inclined plate 66 is formed so that the sedimented carrier 24 gathers at the water intake port 60 of the water supply pipe 58. On the other hand, separation room 5
An intake port 68 of the above-mentioned nitrification solution circulation path 16 for circulating the nitrification solution to the denitrification tank 22 is provided at the upper part of the unit 6. As a result, the upper layer liquid in the separation chamber 56 is taken from the water intake port 68 and circulated in the denitrification tank 22. Further, a trough 70 is formed on the outer edge of the upper part of the receiving tank 48, and a part of the upper layer liquid in the separation chamber 56 overflows into the trough 70 as treated water and sludge settling tank 18
Water is sent to

Next, the operation of the nitrification / denitrification apparatus to which the biological wastewater treatment apparatus of the present invention is applied as a nitrification apparatus will be described. Raw wastewater such as sewage flows into the denitrification tank 22 after solid components are removed by an unillustrated first settling tank or the like. In the denitrification tank 22, the floating activated sludge is contacted with the wastewater raw water and the nitrification solution circulated from the receiving tank 48 in an anaerobic state to decompose organic substances in the wastewater raw water and denitrify nitric acid in the nitrification solution. Is done. The nitrogen gas generated by the denitrification treatment is released to the atmosphere and removed. Next, the liquid in the denitrification tank 22 overflows the opening 38 in the upper part of the first partition wall 36 and flows into the nitrification tank 26. In the nitrification tank 26, air is aerated from the aeration device 28 into the nitrification tank 26 to form an aerobic state. In this state, the liquid from the denitrification tank 22 is brought into contact with the floating activated sludge and the carrier 24 to nitrify the ammonia nitrogen in the wastewater raw water. As a result, the ammonium nitrogen in the wastewater raw water is changed to nitrous acid and further to nitric acid.

Next, the nitrification solution nitrified in the nitrification tank 26 flows into the receiving tank 48 above the second partition wall 50 via the overflow section 51. A part of the carrier 24 and a part of the suspended activated sludge stored in the nitrification tank 26 are entrained in the overflow nitrification liquid. The nitrification liquid that has flowed into the receiving tank 48 has a descending flow path 54.
Is lowered and flows into the separation chamber 56. This descending channel 5
By lowering 4 to allow the floating activated sludge and the carrier 24 to flow into the separation chamber 56, a downward force that facilitates sedimentation is given to the carrier 24 having a larger specific gravity than the floating activated sludge. In the separation chamber 56, the carrier 24 is settled and separated from the floating activated sludge by utilizing the difference in specific gravity between the floating activated sludge and the carrier 24. Generally, the sedimentation velocity of the carrier 24 is 3000 m /
It is about a day, and the sedimentation rate of floating activated sludge depends on the particle size.
It is about 0 to 400 m / day. In the sedimentation separation of the carrier 24, the ascending velocity of the ascending flow in the separation chamber 56 generated by the circulation pump 42 of the nitrification liquid circulation path 16 is the sedimentation velocity at which the carrier 24 sediments (from Stokes' equation based on the specific gravity and particle size of the carrier). (Calculated in)). Furthermore,
Since the inclined plate 66 for promoting the sedimentation of the carrier 24 is provided in the separation chamber 56, and the carrier 24 is made to gather at the water intake port 58 of the water supply pipe by the inclined plate 66, the carrier 24 and the suspended activated sludge are separated. It can be performed more easily and reliably. The carrier 24 that has settled at the bottom of the separation chamber 56 is
Water pipe 5 for taking the lower layer liquid in 6 and sending it to the nitrification tank 26
The flow of No. 8 flows through the water supply pipe 58 and returns to the nitrification tank 26. At this time, since the flow in the water supply pipe 58 is formed by utilizing the air lift action of the air jetted into the water supply pipe 58, the carrier 24 is not destroyed. Further, since the water supply pipe 58 is turned to the nitrification tank 26 side above the liquid surface of the receiving tank 48 so as to extend obliquely downward to the liquid surface of the nitrification tank 26, the inside of the water supply pipe 58 is liquified by the air lift action. The carrier 24 that has risen to near the surface position flows down to the nitrification tank 26.

On the other hand, the floating activated sludge, which does not easily settle and floats in the separation chamber 56, is sent to the sludge settling tank 18 together with the treated water overflowing the trough 70, and the upper layer liquid in the separation chamber 56 is taken in. It is sent to the denitrification tank 22 by the nitrification liquid circulation path 16. As a result, the carrier 24 can be prevented from flowing out from the nitrification apparatus 14, and the carrier 24 and the suspended activated sludge can be efficiently separated. Therefore, unlike the conventional carrier flow-out prevention device, the screen does not become clogged, so that maintenance or inspection is not necessary or is significantly reduced. Also,
Since it is not necessary to reduce the flow rate of the nitrification liquid flowing out from the nitrification tank 26 in order to reduce clogging unlike the screen, the treatment efficiency is improved.

FIG. 3 is a sectional view for explaining a second embodiment of the biological wastewater treatment equipment of the present invention. In the second embodiment, a plurality of straightening vanes 72, 72 ... Are provided in the separation chamber 56 in the vertical direction, and a water intake port 60 of the water supply pipe 58 is provided.
Is arranged below the straightening vane 72, and the water intake port 68 of the nitrification liquid circulation path 16 is arranged above the straightening vane 72. Other configurations are the same as those of the first embodiment.

According to the second embodiment, since the flow straightening plate 72 is provided, uneven flow or turbulent flow does not occur in the separation chamber 56, so that it is possible to prevent the carrier 24 from rising up. The sedimentation can be promoted more. FIG. 4 is a sectional view illustrating a third embodiment of the biological wastewater treatment apparatus of the present invention. The third embodiment is configured such that a deaerator 74 is provided between the current plate 72 and the water intake 68 of the nitrification liquid circulation path 16. Other configurations are the same as those in the second embodiment. This is the nitrification tank 2
When the water depth of 6 is around 5 m, it does not matter much,
As the water depth becomes larger than 5 m, fine air bubbles (gas bubbles formed at deep water position become fine due to water pressure) due to gas components in the waste water adhere to the floating activated sludge, which causes the floating activated sludge to reach the liquid surface. Tends to rise. For this reason, the floating activated sludge in the nitrification liquid that has overflowed from the nitrification tank 26 to the receiving tank 48 floats on the liquid surface of the receiving tank 48, becomes a scum, and stays on the liquid surface. As a result, there are problems that the water quality in the receiving tank 48 is deteriorated and scum is mixed into the treated water sent to the sludge settling tank 18.

According to the third embodiment, since the deaerator 74 is provided between the straightening plate 72 and the water intake port 68, fine bubbles adhering to the suspended activated sludge are removed and scum is not generated. Can be prevented. The deaerator 74 referred to here is preferably an air diffuser that forms large bubbles. The floating activated sludge having fine air bubbles attached thereto comes into contact with the large air bubbles, so that the fine air bubbles are separated from the floating activated sludge, thereby preventing the generation of scum.

In the present embodiment, the receiving tank 48 is provided adjacent to the nitrification tank 26, but the nitrification tank 26 may be partitioned to form the receiving tank 48. In this case, since the volume of the nitrification tank 26 decreases, it is desirable to increase the sedimentation speed of the carrier 24 and reduce the volume occupied by the receiving tank 48 as much as possible. For this purpose, the specific gravity of the carrier 24 may be increased to the extent that the swirling operation due to aeration in the nitrification tank 26 is not hindered.

In addition, since the water temperature is high in summer and the nitrification performance of the suspended activated sludge is good, when the carrier 24 is put into the nitrification tank 26 only from the autumn to the spring, the receiving tank 48 is replaced with the carrier 2.
It may be used as the storage tank of No. 4. In this case, since the present invention is configured as described above, the carrier 24 can be easily transferred from the nitrification tank 26 to the receiving tank 48, which is convenient.

[0023]

As described above, according to the biological wastewater treatment apparatus of the present invention, it is possible to prevent the carrier from flowing out from the bioreactor and efficiently separate the carrier and the suspended activated sludge. Therefore, unlike the screen which is the carrier flow-out prevention device provided in the conventional biological wastewater treatment device, it does not cause clogging, so that maintenance and inspection is not necessary or is significantly reduced. Further, since it is not necessary to reduce the flow rate of the effluent flowing out of the processing tank in order to reduce the clogging unlike the screen, the processing efficiency is improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a nitrification / denitrification device to which a biological wastewater treatment device according to the present invention is applied as a nitrification device.

FIG. 2 is a sectional view for explaining the first embodiment of the biological wastewater treatment equipment of the present invention.

FIG. 3 is a sectional view illustrating a second embodiment of the biological wastewater treatment apparatus of the present invention.

FIG. 4 is a sectional view illustrating a third embodiment of the biological wastewater treatment apparatus of the present invention.

[Explanation of symbols]

 10 ... Nitrification / Denitrification Device 12 ... Denitrification Device 14 ... Nitrification Device 18 ... Sludge Settling Tank 22 ... Denitrification Tank 24 ... Carrier 26 ... Nitrification Tank 28 ... Aeration Device 34 ... Carrier Flow Prevention Device 52 ... Partition Plate 54 ... Downflow Channel 56 ... Separation chamber 58 ... Water pipe 62 ... Air jetting device 66 ... Inclined plate 70 ... Trough 72 ... Straightening plate 74 ... Degassing device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C02F 3/12 C02F 3/12 F

Claims (5)

[Claims] 1. An organism for biologically treating the wastewater by coexisting suspended activated sludge and a carrier in which microorganisms are immobilized and a specific gravity is larger than that of the suspended activated sludge in a treatment tank into which the wastewater flows. In a biological wastewater treatment apparatus comprising a reaction device and a carrier flow-out prevention device for preventing the flow-out of the carrier, the carrier flow-out prevention device is provided in the effluent and the effluent flowing out from the biological reaction device. A receiving tank for receiving the floating activated sludge and the carrier that are carried out together, a downward flow path provided in the receiving tank and forming a downward flow in the effluent flowing out from the bioreactor, and the downward flow A separation chamber that is provided in the receiving tank and communicates with a passage, and uses the difference in specific gravity between the floating activated sludge and the carrier in the effluent to separate the carrier from the floating activated sludge by sedimentation, and the vicinity of the bottom of the separation chamber Has a water intake in A water supply channel for taking the lower layer liquid of the separation chamber and sending it to the bioreactor, and an air jetting means for forming a flow from the separation chamber to the bioreactor in the water supply channel by air lift power, And a discharge unit that is provided at an upper portion of the separation chamber and discharges an upper layer liquid of the separation chamber. The carrier settled at the bottom of the separation chamber is put on the flow of the water supply path and returned to the biological reaction device. A biological wastewater treatment device, characterized in that the activated activated sludge, which is unlikely to settle, is discharged from the receiving tank by the discharging means. 2. The biological wastewater treatment apparatus according to claim 1, wherein the ascending speed of the ascending flow generated in the separation chamber by the discharging means is smaller than the sedimentation speed at which the carrier sediments. 3. A plurality of straightening vanes are provided in the separation chamber in the vertical direction, and the water intake is located below the straightening vane.
The biological wastewater treatment apparatus according to claim 1 or 2, wherein the discharge means is located above the straightening vane. 4. The inclined plate is provided in the vicinity of the bottom of the separation chamber to accelerate the sedimentation of the carrier, and the inclined plate collects the carrier at the water intake port. 2 or 3 biological wastewater treatment equipment. 5. The biological wastewater treatment system according to claim 3, further comprising a deaerator provided between the straightening vane and the discharge means.