JPS5854879B2 - How to improve an aeration tank - Google Patents

Description

[Detailed Description of the Invention] This invention is a method for improving an aeration tank in an existing sewage purification facility by modifying the aeration tank to improve the sewage purification ability and to eliminate the need for a final settling tank. It is related to.

FIG. 1 shows an example of a known aeration device used in a typical sewage purification facility to aerate sewage.

This aeration device has an aeration tank 1 for storing wastewater to be treated, and an aeration pipe 2 arranged along the bottom surface of the aeration tank 1. From the aeration pipe 2, the liquid in the aeration tank 1 is Air sent from the air supply pipe 3 is blown into it.

Due to this exposure, the BOD contained in the wastewater is biochemically oxidized by the action of activated sludge, and the wastewater that has been treated for a certain period of time is sent to the final settling tank to separate the coexisting activated sludge by sedimentation. It will be done.

This type of aeration device is difficult to obtain the desired aeration effect due to the low oxygen content of the air and the insufficient contact between the air and the liquid.
The disadvantage is that it requires a large amount of air and a long processing time.

In addition, the blown air violently agitates the liquid in the aeration tank 1, so no matter where in the aeration tank 1 the liquid is taken out, it contains a large amount of activated sludge, so the activated sludge is settled in the final settling tank. It can only be released after separation.

In order to separate the activated sludge by sedimentation, the liquid must be stored for a long residence time, so it is necessary to prepare a large volume final sedimentation tank, and the activated sludge that has settled will be deficient in oxygen. This brings with it problems such as corruption.

This invention improves the aeration tank of existing sewage purification facilities so that the liquid in the aeration tank can be effectively aerated, and activated sludge can also be sedimented and separated in the aeration tank. The purpose is to provide a method to do so.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows an aeration device that is an improved version of the existing aeration device shown in FIG. 1 in accordance with the method of the present invention.

In FIG. 2, the existing elements including the aeration tank 1 and the aeration pipe 2 remain as they are, and a weir 11 and an oxygen supply mechanism 12 are newly added thereto.

The oxygen supply mechanism 12 has a duct 4 arranged so as to extend along the liquid level in the aeration tank 1 regulated by the weir 11 and to be partially located below the liquid level. 4 is provided with a plurality of bubblers 5 and settlers 6.

As shown in detail in FIG. 3, a number of intake ports 41 are formed in the duct 4 at a portion located below the liquid surface, and the liquid flows into the duct 4 through the intake ports 41. ing.

The interior of the duct 4 is divided into upper and lower chambers 43 by a partition wall 42.
．． 44, and the intake port 41 communicates the lower chamber 44 with the outside.

Each of the bubblers 5 provided in the duct 4 includes a cylindrical outer cylinder 51 that vertically extends through the duct 4 and is arranged approximately vertically, an inner cylinder 52 and a gas supply pipe that are inserted concentrically into the outer cylinder 51. 53.

The outer cylinder 51 forms an annular chamber 55 between it and the inner cylinder 52, which is closed by a plate 54 having the same height as the partition wall 42.
0) The upper end communicates with the lower chamber 44 of the duct 4 via an inlet 56 formed in the outer cylinder 51.

This chamber 55 also communicates with the inside of the inner cylinder 52 via a communication port 57 formed at the lower end of the inner cylinder 52.

Further, the upper end of the inner cylinder 52 opens into the chamber 43 above the duct 4.

This allows the passage from the intake port 41 to the upper chamber 43 through the chamber 44, inlet 56, chamber 55, communication port 57 and inner cylinder 52.
A flow path connected to is formed.

Further, at the bottom of the inner cylinder 52, a diffuser pipe 58 connected to the gas supply pipe 53 is arranged.

This diffuser pipe 58 supplies high concentration oxygen gas (this means a gas containing oxygen at a higher concentration than the oxygen of air) supplied from a supply source via the gas supply pipe 53 to the inner cylinder 52.
It is used to blow fine bubbles into the liquid present in the liquid.

On the other hand, the settler 6 is pipe-shaped with a conical part 61 at the upper end, and the conical part 61 communicates with the upper chamber 43 through an opening 45 formed in the partition wall 42, and the settler 6 is provided at the lower end. It communicates with the inside of the aeration tank 1 via a directional pipe 62.

In the aeration device modified in this way, the aeration tank 1
A part of the liquid inside is taken into the chamber 44 below the duct 4 through the intake port 41, and then from the inlet port 56 to the chamber 55.
Then, it enters the inner cylinder 52 through the communication port 57.

The high concentration oxygen gas blown from the diffuser pipe 58 is dispersed in the form of small bubbles in the liquid existing in the inner cylinder 52, and is effectively absorbed therein, while at the same time imparting upwelling force to the liquid. give.

Due to this upwelling force, the liquid rises within the inner cylinder 52, overflows its upper end, and flows into the chamber 43 above the duct 4.

This liquid then flows along the length of the duct 4 on the partition wall 42 and flows into the settler 6 through the opening 45.

During this time, the bubbles contained in the liquid are separated, and then the liquid is returned to the aeration tank 1 through the directing tube 62.

That is, the liquid in the aeration tank 1 enters from the intake port 41,
After passing through the above-mentioned flow path, from the directional pipe 62 to the aeration tank 1.
While returning to the interior, the oxygen gas blown from the diffuser pipe 58 is absorbed.

Therefore, when this liquid is mixed with the liquid in the aeration tank 1, it supplies oxygen to the activated sludge it contains, promoting the biological oxidation of BOD substances.

A similar action is also performed in all the bubblers 5 and settlers 6 provided in the common duct 4.

The gas separated from the liquid may be released into the atmosphere as it is, but it is preferable that a part or most of it be mixed with the high concentration oxygen gas supplied to the gas supply pipe 53 and reused.

Through the above operations, the liquid in the aeration tank 1 can be effectively aerated only by the oxygen supply mechanism 12, or the flow rate or water quality of the inflowing sewage may suddenly change and the quality of the outflowing water may change. If there is a possibility that the temperature may decrease, air is blown into the liquid in the aeration tank 1 from the aeration pipe 2, as in conventional aeration devices.

This provides a large amount of oxygen to the liquid, so the quality of the effluent does not deteriorate.

Furthermore, air is supplied from the diffuser pipe 2 even when air is supplied to the oxygen supply mechanism 12 due to a failure of the high concentration oxygen gas supply mechanism or the like.

In any case, when air is supplied from the aeration pipe 2, the liquid is stirred in the aeration tank 1, so the effluent is introduced into the final settling tank and the activated sludge is separated by sedimentation as in the conventional method. It is necessary to do this.

As described above, the improved aeration device according to the present invention effectively brings highly concentrated oxygen gas into contact with the liquid, causes the liquid to absorb oxygen, and returns this oxygen-rich liquid to the aeration tank. This provides oxygen supply, so
Sedimentation separation in a final settling tank is usually not required since it can be efficiently vented and the effluent flowing over the weir contains little activated sludge.

In addition, the existing air diffuser pipes can be used effectively in times of abnormality.

Furthermore, construction work for improvement is easy and cost-effective.

Note that the oxygen supply mechanism 12 is not limited to the one shown in the figure, and the oxygen supply mechanism 12 is not limited to the one shown in the figure. Any form can be used as long as it has the function of returning the gas into the aeration tank 1.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing a conventional ventilation device, FIG. 2 is a vertical sectional view of a ventilation device improved according to the present invention,
3 is a partially cutaway side view showing the oxygen supply mechanism used in the aeration device of FIG. 2. FIG. 1...Aeration tank, 2...Aeration pipe, 3.
...Air supply pipe, 4...Duct, 5...
...Bubbler, 6...Settler 41...
...Intake, 42...Bulkhead, 43°44.
... Chamber, 51 ... Outer cylinder, 52 ...
- Inner cylinder, 58... Diffuser pipe, 62... Directional tube.

Claims (1)

[Claims] 1. A part of the liquid in the aeration tank is taken out and introduced into a bubbler into an existing aeration device equipped with an aeration tank and a means for blowing air into the liquid contained therein, and the bubbler By blowing high-concentration oxygen gas into the liquid from the bottom of the bubbler, the oxygen is dissolved in the liquid and an upwelling force is applied.Then, this liquid is led into the settler from the top of the bubbler to remove the oxygen contained in the liquid. 1. A method for improving an aeration tank, comprising: adding an oxygen supply mechanism for separating air bubbles and returning the bubbles to the aeration tank; and a weir for regulating the height of the liquid level in the aeration tank.