JPH08243585A - Aerator - Google Patents

Abstract

PURPOSE: To provide an aerator exhibiting high oxygen dissolving efficiency and oxygen moving efficiency, excellent in durability and which is easily maintained and controlled. CONSTITUTION: An aerator 17 is formed with a suction pipe 21 vertically arranged at the definite depth of the water 16 to be treated, an air diffuser pipe 24 opened at the upper part in the suction pipe 21 and supplying air 23 and a pump 25 at the lower part of the suction pipe 21 and allowing the air 23 and water 16 to flow downward in the suction pipe 21. A tap 22 with the diameter gradually decreased downward is furnished at the upper end of the suction pipe 21, and a shaft 30 for driving the impeller of the pump 25 is extended upward through the inside of the suction pipe 21 and connected to a motor 31 above the water 16 surface.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an efficient aerator for use in water treatment such as sewage treatment and industrial wastewater treatment.

[0002]

2. Description of the Related Art Conventionally, an activated sludge method or the like has been performed in water treatment such as sewage treatment and industrial wastewater treatment. In the activated sludge method, generally, the water to be treated that has passed through the sand basin and the first sedimentation basin is introduced into the aeration tank, and aeration is performed with an aeration device such as a diffuser installed in the tank to agitate the activated sludge in the tank. By supplying oxygen while mixing, BOD and nitrogen content in the water to be treated are removed by the action of activated sludge. Then, a part of the activated sludge mixed water in the aeration tank is guided to the final settling basin to settle the activated sludge, and the supernatant water in the final settling basin is sent to a disinfection facility and discharged as treated water.

By the way, the conventional aeration tank has a depth of about 5 m, but when it is necessary to increase the capacity, it is unavoidable to deal with it by deepening the depth, and when deepening the depth, it dissolves oxygen. Due to the increase in the amount, what is called a deep layer aeration tank having a depth of 5 m or more, for example, a depth of 10 to 20 m, and an ultra deep layer aeration tank having a depth of about 100 m have come to be seen recently. In such a deep or super deep aeration tank, the conventional aeration device such as a diffuser plate does not have sufficient oxygen supply ability and stirring ability.
Various proposals have been made because the discharge pressure of the blower becomes very large and the power efficiency of the aerator becomes low.

For example, an aeration tank called a deep shaft as shown in FIGS. 3 and 4 is known. The deep shaft 1 is composed of a shaft 4 composed of a descending flow path 2 and an ascending flow path 3 and a head tank 5, and an activated sludge mixed liquid 6 in the deep shaft 1 is formed.
Descends through the descending passage 2 and inverts at the shaft bottom 4a,
A circulation flow that rises in the ascending passage 3 and returns to the descending passage 2 via the head tank 5 is formed. 7 is a raw water supply pipe, 8
Is a water supply pipe to the degassing equipment, and 9 is a sludge return pipe.

In the air-lift type deep shaft shown in FIG. 3, the upper end of the descending flow path 2 opens below the liquid surface of the activated sludge mixed liquid 6 and is connected to a compressor 10 as an air supply means. Are led to the middle of the descending flow path 2 and the ascending flow path 3, respectively. In such a configuration, air is blown into the ascending flow path 3 from the air diffusing pipe 10b to generate an ascending liquid flow in the ascending flow path 3 by the air lift action, and this ascending liquid flow and the descending flow caused thereby. With the descending liquid flow in the passage 2, a circulating liquid flow extending over the ascending flow path 3 and the descending flow path 2 is generated, and when the liquid circulation is stable, air for water treatment is supplied from the diffuser pipe 10a into the descending flow path 2. It is blowing.

In the pump type deep shaft shown in FIG. 4, the upper end 11 of the descending passage 2 is the head tank 5.
A circulation pump 13 is disposed in a pipe line 12 which is arranged so as to be positioned higher and which connects the upper end 11 and the inside of the head tank 5. Blower 14 as air supply means
The diffusing pipe 14 a connected to is led to the inside of the descending flow path 2. In such a configuration, the circulation pump 13 pumps up the activated sludge mixed liquid 6 in the head tank 5 to the upper end 11 of the descending flow path 2, and the circulating liquid flow is caused by the head difference between the upper end 11 and the head tank 5. When the liquid circulation is stable, air for water treatment is blown into the descending flow path 2 from the diffuser pipe 14a.

In both the air lift system and the pump system described above, the air blown into the descending passage 2 becomes air bubbles, is mixed with the activated sludge mixed liquid 6 descending in the descending passage 2, and is dragged to the shaft bottom 4a. Get caught.
The speed of the mixed liquid 6 in the descending flow path 2 is adjusted to 1 to 2 m / sec, which is sufficiently faster than the speed at which the bubbles float in the still water, so that the bubbles do not rise in the descending flow path 2 and Receives a large hydrostatic pressure in the shaft 4 depending on its depth, and oxygen in the air is quickly dissolved in the mixed liquid 6.

[0008]

However, even in such an aeration tank, depending on the case where a large number of diffuser plates are arranged for the purpose of supplying a large amount of air or depending on the shape of the reaction tank, a sufficient amount of air may be present in the descending passage. It may be difficult to secure the flow rate of the mixed solution. Further, although the dissolution efficiency can be increased as the depth of the diffused water is increased, a large amount of power is required to drive the compressor and the blower, which causes a problem that the oxygen transfer power efficiency is reduced.

For this reason, it is conceivable to install a pump device for causing the water to be treated to flow downward in the descending flow passage at the lower part of the descending flow passage, and to arrange an air diffuser at the upper part in the descending flow passage. In such a configuration, the motor that drives the pump device is located at the bottom of the tank and in the water to be treated, and its maintenance is not easy. Further, as the water depth becomes deeper, a larger water pressure is applied to the motor, so that there is a problem that water is flooded into the motor from the sliding portion, and the seal of the sliding portion is deteriorated more quickly.

The present invention solves the above problems, and can be used regardless of the shape of the reaction tank, can obtain high oxygen dissolution efficiency and oxygen transfer power efficiency, and has a large durability and easy maintenance. It is intended to provide.

[0011]

In order to solve the above-mentioned problems, the aeration apparatus of the present invention comprises a lead-in pipe arranged in the reaction tank in the vertical direction from below a certain depth to the bottom of the water to be treated. An air diffuser for opening the upper part of the intake pipe to supply oxygen-containing gas into the water to be treated, and an oxygen-containing gas supplied by the air diffuser and the water to be treated, which are installed at the lower part of the inlet pipe. And a pump means for causing the inside of the intake pipe to flow downward, wherein the intake pipe has a dovetail that gradually decreases in diameter downward and is formed at the upper end, and the pump means forms the oxygen-containing gas and the water to be treated in the intake pipe. It is characterized in that it has an impeller for making it flow downward, and a drive shaft for driving this impeller is inserted through the lead-in pipe and guided upward, and is connected to the drive means on the surface of the water to be treated.

[0012]

With the above structure, the water to be treated in the reaction tank flows downward in the intake pipe due to the pumping action of the pump means and the guiding action of the intake pipe, but at that time, the diameter of the drinking water is gradually reduced downward. A turbulent flow is generated by flowing from the inside into the lead-in pipe. Therefore, the oxygen-containing gas supplied from the air diffusing means in the upper part of the intake pipe is entrained in the water to be treated in a turbulent state and its bubbles are subdivided, and as the water depth increases while descending in the intake pipe. Since it is rapidly dissolved in the water to be treated, the amount of oxygen dissolved in the water to be treated and the power efficiency are large.

Further, since the driving means is installed on the water surface, it is possible to prevent water to be treated from entering the sliding portion and prevent the seal of the sliding portion from being deteriorated at an early stage, so that the durability of the driving means is improved. improves. When inspecting and repairing the drive means, the work of removing the drive means from the drive shaft can be easily performed outside the tank.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 1 and 2, 15 is a water depth of 20.
It is a reaction tank configured to store about m water to be treated. Water to be treated 16 mixed with activated sludge is stored inside the reaction tank 15, and an aeration device 17 is installed at a substantially central position in the horizontal direction of the tank 15 so as to be immersed in the water to be treated 16. Reference numeral 18 is a raw water supply pipe, 19 is a water supply pipe to the degassing equipment, and 20 is a sludge return pipe.

The aeration device 17 is provided with a lead-in pipe 21 which is vertically arranged from below a certain depth of the water 16 to be treated to at the bottom thereof, and the upper end of the lead-in pipe 21 is gradually reduced in diameter downward. 22 is formed. Aeration device 17
Is also supplied by the air diffuser 24 by opening an air diffuser such as an air diffuser 24 for supplying an oxygen-containing gas such as air 23 to the water 16 to be treated 16 to an upper part in the intake pipe 21, for example, about 5 m below the liquid surface. A pump device 25 for causing the air 23 and the water to be treated 16 to flow downward in the intake pipe 21 is provided at the lower portion of the intake pipe 21. The air diffuser 24 is connected to an air supply means such as a blower 26 outside the tank.

The pump device 25 has a closed structure as shown in the drawing, and has an inlet port 27 connected to the lower end of the lead-in pipe 21 and a discharge port 28 formed in a downward and radial circumferential shape. However, an impeller 29 is provided inside. A drive shaft 30 that drives the impeller 29 is inserted into the lead-in pipe 21 and guided upward, and is connected to a motor 31 on the surface of the water to be treated. By driving the impeller 29, the air 23 in the intake pipe 21 and the water 16 to be treated are introduced into the device 25 through the introduction port 27, are agitated and mixed, and are discharged to the outside of the device 25 through the discharge port 28.
With such introduction / discharge, air 23 in the intake pipe 21
And the water 16 to be treated flow downward at a flow rate of about 2 m / sec.

Reference numeral 32 is a vertical guide tube for guiding the taking-out and installation of the pump device 25 at the time of maintenance, and 33 is a guide for movably attaching the pump device 25 to the guide pipe 32.

The operation of the above configuration will be described below. In the reaction tank 15, raw water is supplied from the raw water supply pipe 18 and activated sludge is returned from the sludge return pipe 20,
The treated water 16 in the tank 15 is biologically treated by the activated sludge, and a part of the treated water 16 containing the activated sludge flows out of the tank 15 through the water supply pipe 19.

The water 16 to be treated in the reaction tank 15 is the intake pipe 2
1 is pulled downward into the pull-in pipe 21 by the pumping action of the pump device 25 installed in the lower part of 1 and the guide action of the pull-in pipe 21, and at that time, the pull-in pipe 21 is drawn from the dovetail 22 which gradually decreases in diameter downward. Turbulence is generated by flowing into the inside. The air 23 is supplied to the water 16 to be treated in such a turbulent state from the air diffusing pipe 24 in the upper part of the intake pipe 21.

The supplied air 23 is entrained in a turbulent flow, so that its bubbles are subdivided to increase the contact rate with the water 16 to be treated, and as the water depth increases as it descends in the intake pipe 21, Since the amount of dissolution increases, it dissolves quickly in the water 16 to be treated.

The water 16 to be treated and the air 23, which have flowed downward in the intake pipe 21 and reached the lower end thereof, flow into the interior thereof through the inlet 27 of the pump device 25 and are agitated and mixed by the impeller 29 while being discharged. It is radially discharged downward from the outlet 28.

At this time, the air 23 is mixed with the water 16 to be treated while the bubbles are further miniaturized by the impeller 29, and the contact rate with the water 16 to be treated is increased. Will be even bigger.

The water 16 to be treated, which is radially discharged downward from the discharge port 28, forms a circulating flow that rises near the side wall after reaching the bottom of the reaction tank 15. By forming such a circulation flow that circulates in the entire region in the tank, the contact rate between the air and the water 16 to be treated is increased, and the water 16 to be treated is
The amount of oxygen dissolved in is further increased.

As described above, the contact ratio between the air 23 and the water 16 to be treated is increased by making the bubbles of the air 23 fine and forming a circulating flow, and the water 16
Since the amount of air 23 dissolved in the water is increased, the treated water 16
The amount of oxygen dissolved therein is large, and the oxygen dissolution efficiency in the reaction tank 15 is high. Such an aeration device 17 is usually installed in a reaction tank having a water depth of 5 m or more, and the aeration pipe 2
No. 4 is opened under the water so that the blower power does not become excessively large. The power required for oxygen transfer in the reaction tank 15 is represented by the sum of pump power and blower power,
Since the oxygen transfer amount is increased more than the power increase, the oxygen transfer power efficiency is also improved.

Since the motor 31 is installed on the surface of the water, intrusion of water to be treated from the sliding portion and early deterioration of the seal of the sliding portion are prevented, whereby the durability of the motor 31 is improved. improves. At the time of inspection and repair, the motor 31 can be removed from the drive shaft 30 outside the tank, and maintenance is easy.

[0026]

As described above, according to the present invention, a turbulent flow is generated at the upper end of the intake pipe by the mouthpiece, and the oxygen-containing gas is dispersed in the turbulent water to be treated in the upper portion of the intake pipe. Then, the water to be treated was made to descend in the intake pipe. As a result, the oxygen-containing gas has a large contact rate with the water to be treated, and receives a large head to increase the amount of dissolution in the water to be treated, and the synergistic effect of these increases the oxygen dissolution efficiency and the oxygen transfer power efficiency. It will be expensive.

Further, since the drive shaft for driving the impeller is guided upward and connected to the drive means installed on the water surface, the impeller can secure a necessary flow velocity at the bottom of the tank, and the drive can be performed on the water surface. The life of the means can be extended and maintenance can be facilitated.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a reaction tank equipped with an aeration device according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of an essential part for explaining the operation of the aeration apparatus.

FIG. 3 is an explanatory view showing an example of a conventional super deep aeration tank.

FIG. 4 is an explanatory view showing another embodiment of the conventional super deep aeration tank.

[Explanation of symbols]

 15 Reaction tank 16 Treated water 17 Aeration device 21 Intake pipe 22 Dowel 23 Air 24 Air diffuser pipe 25 Pump device 26 Blower 29 Impeller 30 Drive shaft 31 Motor

Claims (1)

[Claims] 1. A lead-in pipe which is vertically arranged from below a certain depth to the bottom of the water to be treated inside the reaction vessel, and a dispersion pipe which is opened at an upper part of the lead-in pipe and supplies an oxygen-containing gas into the water to be treated. An air means, and a pump means installed at the lower part of the intake pipe for causing the oxygen-containing gas supplied by the air diffuser and the water to be treated to flow downward in the intake pipe,
The inlet pipe is formed at its upper end with a dowel that gradually reduces its diameter downward, and the pump means has an impeller for causing the oxygen-containing gas in the inlet pipe and the water to be treated to flow downward, and drives this impeller. An aerating device, characterized in that the drive shaft is inserted into the lead-in pipe and guided upward, and is connected to the drive means on the surface of the water to be treated.