JPH0523689A - Aerator - Google Patents

Abstract

PURPOSE:To improve efficiency in dissolving oxygen and to increase the dissolved oxygen concn. by vertically providing a partition plate in a deep aeration tank >=10m deep to form an upward passage and a downward passage, furnishing an upper diffuser and a lower diffuser and further providing a passage for a gas staying in the top cavity to the upper diffuser. CONSTITUTION:A water A to be treated contg. org. matter such as sewage and night soil supplied to an aeration tank 1 is air-lifted by a concd. oxygne D introduced from a lower diffuser 6, circulated through the upward passage 3 and downward passage 4 of the tank 1 and aerobically oxidized. An appropriate amt. of return sludge G from a settling tank 40 is introduced through a sludge inlet pipe 33, and the fine bubble regenerated at the shallow part deposits on activated sludge which is thereby floated. The gas E staying in the top cavity of the tank 1 is introduced by a circualting blower 11 from the upper diffuser 5 through a passage 10 to promote the settling of the activated aludge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aeration treatment apparatus for aerobically treating sewage, night soil and organic matter-containing wastewater in various industries.

[0002]

2. Description of the Related Art As an apparatus for aerobically treating organic matter-containing wastewater, an apparatus for treating water to be treated with activated sludge in an aerobic aeration tank is widely used. In the conventional processing device,
An air diffuser for aerating with air using an aeration tank with a water depth of 10 m or less, typically 4 to 6 m, an oxygen aerator for aerating with high-concentration oxygen instead of air in the device, and a water depth of 10 m There is a deep layer aeration device that performs aeration with air using the above deep layer aeration tank.

[0003]

DISCLOSURE OF THE INVENTION In the above conventional aerobic treatment apparatus, in the air diffusion treatment apparatus, the oxygen partial pressure is low and the gas-liquid contact time is short, so the dissolved oxygen concentration per unit volume is low, The installed area of the treatment equipment becomes too large and the activated sludge concentration (hereinafter ML) is related to the treatment efficiency of wastewater.
It is called SS. There is a limit to maintaining high concentration of) and improving the treatment efficiency. Further, in the oxygen aeration device, the oxygen partial pressure is high, and therefore the dissolved oxygen concentration can be increased, so that the ML
Although SS can be maintained at a high concentration and the installation area of the processing apparatus can be reduced, there is a problem that the oxygen dissolution efficiency is low because the gas-liquid contact time is short.

Further, in the deep aeration apparatus, the oxygen dissolution capacity can be increased by water pressure and the installation area of the processing apparatus can be reduced, but the dissolved concentration of unnecessary carbon dioxide gas and nitrogen in the air is also increased. Of the activated sludge due to the adhesion of fine bubbles generated by re-foaming in the shallow layer to the activated sludge, which lowers the treatment efficiency and deteriorates the sedimentation property in the subsequent settling tank. Due to fear, there is a problem that a vacuum deaeration tank must be installed between the aeration tank and the precipitation tank.

The present invention has been made in view of the above problems of the prior art, and aims to improve the oxygen dissolution efficiency and the dissolved oxygen concentration by making the most of the advantages of the oxygen aeration apparatus and the deep layer aeration apparatus. It is an object of the present invention to provide an aeration treatment device capable of maintaining a high concentration of water and further improving the treatment efficiency, narrowing the installation area of the treatment device, and preventing the floating sludge of activated sludge due to the generation of fine bubbles. I am trying.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aeration treatment apparatus for treating water to be treated aerobically, which is provided with a feed port for treated water and a discharge port for treated water, and has a closed structure. In a deep aeration tank having a water depth of 10 m or more, a partition plate having communication ports vertically to circulate and circulate the treated water is vertically installed to form an ascending flow path and a descending flow path, and an upper layer portion of the ascending flow path. An upper diffuser for agitation and a lower diffuser for supplying high-concentration oxygen are provided in the lower layer, and gas staying in the top void in the aeration tank is circulated to the upper diffuser. It is an aeration processing device characterized by having a flow path attached.

[0007]

[Operation] High-concentration oxygen produced by the oxygen generator is introduced into the water to be treated supplied to the aeration tank from the lower diffuser, and gas remaining in the top void in the aeration tank is passed through the gas circulation channel. When introduced from the upper diffuser, the water to be treated is aerobically treated while circulating and circulating over the ascending and descending passages of the aeration tank due to the airlift effect. Most of the high-concentration oxygen introduced from the lower diffuser in the above is dissolved in the water to be treated and used in the bio-oxidation reaction, but nitrogen and some oxygen once dissolved in the deep layer are recovered in the shallow layer. The gas is bubbled and stays in the top void in the aeration tank together with the undissolved gas for recycling.

Further, since the re-foamed nitrogen and the like tend to become fine bubbles and adhere to the activated sludge to cause a floating action, the adhered bubbles are aggregated and separated by being agitated by the gas circulated from the upper diffuser. Therefore, the sedimentation of the activated sludge is promoted. Incidentally, if the dissolution efficiency is increased, the PH value is inevitably lowered due to the dissolution of carbon dioxide gas, but the carbon dioxide gas can also be purged by stirring the gas. The water to be treated is aerobically treated for a certain retention time, but because of the high oxygen partial pressure due to the deep layer and high concentration oxygen, the dissolved oxygen concentration is also kept high and can be treated efficiently.

In the treated water treated in the aeration tank, the activated sludge is settled and separated in the subsequent settling tank and discharged as clear water. Further, part of the activated sludge that has been separated by settling is circulated to the aeration tank as return sludge, and the remaining part is supplied to an appropriate sludge treatment device as excess sludge for treatment.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the drawings showing an embodiment. FIG. 1 is a system diagram of one embodiment, and FIG. 2 is a system diagram of another embodiment in which a plurality of aeration tanks are connected in series. Reference numeral 20 denotes an aeration processing apparatus, which is provided with a single tank aeration tank 1 in FIG. 1. However, as shown in FIG. Aeration tank 1a, 1b, 1
It is preferable to provide c in series, and it is also preferable to provide the deaeration tank 14 at the final stage in order to sufficiently remove the bubbles adhered to the activated sludge and reduce the power.

The aeration tank 1 has a supply port 7 for the treated water A and an outlet 8 for the treated water B, and is a vertically structured tank having a watertight depth of 10 m or more. The inside of the tank 1 is the treated water. In order that A circulates and flows, communication ports 12a and 12b are provided at the top and bottom, the partition plate 2 is vertically installed, and the ascending flow path 3 and the descending flow path 4 are formed.
An upper diffuser 5 for stirring and an lower diffuser 6 for supplying high-concentration oxygen D are provided in the upper layer portion of the ascending flow path 3, and further in the aeration tank 1. Gas E staying in the top void 9
A gas circulation flow path 10 for circulating the gas to the upper diffuser 5 using a circulation blower 11 is additionally provided.

The water depth in the aeration tank 1 may be 10 m or more, but it is preferably 10 to 20 m from the viewpoint of aeration power and equipment costs. Further, a sludge supply pipe 33 for supplying the returned sludge G from the subsequent settling tank 40 is connected to the aeration treatment device 20,
Further, a gas discharge port 13 for discharging the surplus gas F from the top void 9
It is equipped with. The pressure in the aeration tank 1 is usually atmospheric pressure, but it is preferable to equip the gas outlet 13 with a pressure control valve when pressure is applied.

The upper diffuser 5 and the lower diffuser 6 are preferably arranged at a water depth of 4 to 6 m in the upper diffuser 5, and in the lower diffuser 6, the aeration tank. 1 is preferably provided near the bottom. In the above, the reason why the lower diffuser 6 is provided in the ascending flow path 3 is that if it is provided in the descending flow path 4, the reverse flow of the water A to be treated occurs when the gas diffusion from the upper diffuser 5 is stopped. Immediately before that, a stopped state occurs, and at this time, a temporary gas ejection phenomenon occurs, which may hinder the operation of the device.

Reference numeral 30 denotes a PSA type oxygen generator,
It may be another device such as a cryogenic separation type. The PSA-type oxygen generator 30 comprises an air compressor 22 and an air C in an adsorption tower 21 having three or four molecular sieves packed therein.
A generally used apparatus for producing high concentration oxygen D by introducing oxygen and cyclically repeating pressurization and depressurization to adsorb and desorb oxygen is applied. Further, the concentration of the high-concentration oxygen D produced is preferably 70 vol% or more in order to reduce unnecessary dissolution of nitrogen.

Reference numeral 40 denotes a settling tank 40 for obtaining the clear water by settling and separating the activated sludge in the treated water B. The inside of the tank is slowly stirred to promote coagulation, or the settled activated sludge is discharged to the sludge outlet 32.
A sludge introducing pipe 33 which is equipped with a sludge scraper 31 for collecting the sludge and circulates a part of the sludge as return sludge G to the aeration tank 1.
The remaining sludge is discharged as excess sludge H to a not-shown sludge treatment device in the subsequent stage. Further, an outlet 34 for the clear water J, which has been solid-liquid separated, is provided at the upper part.

The operation of the aeration treatment apparatus 20 of the present invention having the above structure will be described in detail below. In FIG. 1, treated water A containing organic matter such as sewage and night soil supplied to the aeration tank 1
Is aerobically circulated through the ascending passage 3 and the descending passage 4 of the aeration tank 1 due to the air lift effect of the high concentration oxygen D produced by the oxygen generator 30 introduced from the lower diffuser 6. Is biooxidized. In the above treatment, the sludge G returned from the settling tank 40 is the sludge introducing pipe 33.
However, since the dissolved oxygen concentration becomes extremely high due to the effect of the high concentration oxygen D and deep layer aeration, the MLS is mixed.
S is also maintained at a concentration of about 2 to 4 times that of a normal activated sludge device, and the treatment efficiency can be improved.

Further, in the above, nitrogen and a part of oxygen once dissolved in the deep layer are re-foamed in the shallow layer to generate fine bubbles, which adhere to the activated sludge and cause a floating action.
By introducing the gas E retained in the top void 9 of the aeration tank 1 from the upper diffuser 5 by the circulation blower 11 through the gas circulation flow path 10, the adhered bubbles are aggregated and separated, so that the sedimentation property of the activated sludge is increased. It can be accelerated and purged of dissolved carbon dioxide can be carried out to prevent a decrease in PH value. Further, by circulating the gas E, effective use of oxygen is achieved, and the gas A has an oxygen concentration similar to that of the atmosphere, and is discharged as excess gas F from the gas outlet 13. It should be noted that the discharging may be performed after processing by a post-processing device (not shown).

In FIG. 2, an aeration tank 1a having the same shape,
Three tanks 1b and 1c are connected in series via a partition wall 16, and a deaeration tank 14 is provided at the final stage to aerate the gas E by a degassing diffuser 15. This is because the treatment efficiency is improved and the oxygen utilization efficiency is also improved by advancing the treatment in three tanks by shortening the residence time in one tank rather than increasing the capacity of the single tank. Further, by providing the deaeration tank 14, it is not necessary to continuously perform the gas aeration from the upper air diffuser 5, and the power can be reduced by the intermittent aeration, and the precipitation tank 40 at the subsequent stage can be used. Sedimentation and separation of is performed well.

The treated water B which has been aerobically treated in the aeration tank 1 for a certain retention time is introduced into the precipitation tank 40. Treated water B
The activated sludge therein is slowly stirred by the sludge scraper 31 to coagulate and settle, and is collected and discharged to the sludge discharge port 32.
In the above, an aggregating agent may be added as necessary to promote aggregation. A part of the activated sludge discharged is returned to the aeration tank 1 as return sludge G, but the rest is excess sludge H.
Is discharged to the outside of the system and dehydrated by a sludge treatment device such as a belt press dehydrator in the subsequent stage. The supernatant water from which the activated sludge has been separated is discharged to the outside of the system as the clear water J and discharged as it is, or after being subjected to post-treatment with a sterilizer or the like and then discharged.

[0020]

According to the present invention having the above-described structure and operation, the following effects can be obtained. B) Aeration of high-concentration oxygen under the deep layer greatly improves the oxygen dissolution efficiency and maintains a high dissolved oxygen concentration. B) The activated sludge concentration can be maintained at a high concentration and the treatment efficiency can be improved. C) The installation area of the processing device can be reduced. D) It is possible to prevent floating of activated sludge in an aeration tank and sedimentation failure in a sedimentation tank due to generation of fine bubbles.

[Brief description of drawings]

FIG. 1 is a system diagram of one embodiment.

FIG. 2 is a system diagram of another embodiment.

[Explanation of symbols]

20: Aeration treatment device, 30: Oxygen generator, 40: Precipitation tank, 1, 1a, 1b, 1c: Aeration tank, 2: Partition plate, 3:
Upflow channel, 4: Downflow channel, 5: Upper diffuser, 6: Lower diffuser, 7: Treated water supply port, 8: Treated water discharge port, 9: Top void, 10: Circulation channel, 11: Circulating blower, 12a:
Lower communication port, 12b: Upper communication port, 13: Gas discharge port,
14: Deaeration tank, 15: Diffuser for deaeration, 16: Partition wall, 2
1: Adsorption tower, 22: Air compressor, 31: Sludge attractor, 3
2: Sludge discharge port, 33: Sludge introduction pipe, 34: Clear water discharge port. A: water to be treated, B: treated water, C: air, D: high concentration oxygen, E: gas, F: surplus gas, G: returned sludge, H: surplus sludge, J: clear water.

Claims (1)

Claim: What is claimed is: 1. An aeration treatment device for treating water to be treated aerobically, comprising an inlet for treated water and an outlet for treated water, and has a closed structure and a water depth of 10 m or more. In the deep aeration tank, partition plates having upper and lower communication ports are vertically installed so as to circulate and circulate the water to be treated to form an ascending flow path and a descending flow path. An upper diffuser and a lower diffuser for supplying high-concentration oxygen are arranged in the lower layer, and a gas circulation flow path for circulating the gas staying in the top void in the aeration tank to the upper diffuser is attached. An aeration treatment device characterized by the above.