JPH07171591A - Aeration device and operation thereof - Google Patents

Abstract

PURPOSE:To enable both of aerobic stirring and anaerobic stirring without lowering stirring efficiency by forming a distributing plate preventing surface waves generated on the surface of the water and selecting the normal and reverse rotations of an aerator. CONSTITUTION:At the time of aeration, the screw 23 of an aerator 2 is normally rotated to perform aeration and an ascending stream is generated to generate a circulating stream in an aeration tank. The ascending stream is diffused in the direction opposite to the aerator 2 along the surface of the water by the distributing plate 3 disposed at the upper water surface position of the aerator 2. Therefore, air bubbles discharged into sewage are circulated within the tank while carried by stirring streams and the generation of surface waves is prevented and aerating stirring efficiency is enhanced. At the time of anaerobic operation, the screw 23 is reversely rotated to generate a descending stream to perform only the stirring of sewage in the tank. By this constitution, both of aerobic stirring and anaerobic stirring can be performed without lowering stirring efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a self-priming aerator capable of forward and reverse rotation and a rectifying plate to selectively perform aerobic and anaerobic agitation by controlling the operation of the aerator for efficient sewage treatment. The present invention relates to an aeration device adapted to carry out the above process and its operating method.

[0002]

2. Description of the Related Art When treating sewage, it is well known that alternating aerobic (aeration) stirring and anaerobic stirring in an aeration tank is effective for nitrifying and denitrifying. However, conventionally, the agitator or aerator installed in the aeration tank has the same screw rotation direction during aerobic and anaerobic operation.

[0003]

When the screw rotates in the same direction in both aerobic and anaerobic operation, and generally during aerobic operation, the agitated water flow of the sewage is downward due to the screw. The air bubbles caused by aeration are mixed with the downward flow of water by the rotation of the screw, but buoyancy acts on the air bubbles, resulting in an air lift force of 0.3 m / sec. The air lift force of this bubble is in opposition to the direction of the thrust force (downward water flow) and weakens the downward water flow velocity. Therefore, it is necessary to obtain a downward flow velocity that overcomes this air lift force.
The aerator is agitated to obtain a flow rate of ~ 2 m / sec. For this reason, not only a large loss of output occurs, but also in the deep aeration tank, it is not possible to sufficiently perform aeration with stirring up to the bottom of the tank.

Further, if the rotation of the screw is set in the direction in which the upward flow is generated, a wave (surface wave) is generated on the water surface above the aerator.
Occurs, the resistance of this surface wave is also added, and the stirring effect deteriorates.

According to the present invention, the aerator is installed at a predetermined position, the rotation direction of the screw is controlled, and a straightening plate is used to reduce agitation efficiency without agitation.
Anaerobic, aiming to carry out both stirring.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and includes an aerator which has a required size and capacity and which is provided vertically along one inner surface of one side of an aeration tank.
It is arranged above this aerator and consists of a straightening plate that prevents surface waves generated on the water surface by the rotation of the screw, making it possible to select forward and reverse rotation of the aerator, and to raise it by the screw during aeration operation. The point is that a countercurrent is generated.

[0007]

When the self-priming aerator is rotated in the normal direction, it is aerated and an upward flow is generated to generate a circulating water flow in the tank. An upflow is diffused along the water surface toward the side opposite to the aerator by a straightening plate provided above the water surface of the aerator. For this reason, the bubbles released into the dirty water ride on the stirring water flow and circulate in the tank, and the generation of surface waves is prevented in advance.
Aeration and stirring efficiency is improved. Furthermore, during the aeration operation, since the stirring is performed so that an upward flow in the same direction as the air lift force due to the bubbles is generated, the loss due to the air lift force of the bubbles is eliminated, and the loss of power can be prevented.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The aeration apparatus of the present invention and its operating method will be described below with reference to the illustrated embodiments. In the figure, 1 is a rectangle,
Aeration tank with other desired shape, size and depth,
An aerator 2 is arranged substantially vertically along the inner surface of one side of the aeration tank 1. When only one aerator 2 is used, it is arranged in the rectangular aeration tank at approximately the center of the inner surface on one side, as shown in the figure, and the upward rotation is generated by the rotation of the screw. In the air operation, the screw position is set to a predetermined depth below the surface of the water so that the bubbles can be accumulated in the dirty water as long as possible.

Further, one or more aerators 2 are used in a large aerator tank so that uniform agitation can be efficiently performed, and the number of the aerators installed is determined, and the aerators can be rotated in the normal and reverse directions. 2 is used so that aerobic stirring and anaerobic stirring can be selected.

The aerator 2 has a screw 23 fixed to the lower end of a hollow shaft 22 of a required length which is driven by a motor 21. When the screw 23 is rotated in the normal direction, the agitated wastewater causes an upward flow. In addition, the screw shape is appropriately determined so that a downward flow is generated at the time of reverse rotation, and at the time of normal rotation, the negative pressure generated in the screw end water region sucks in from the intake port above the water surface of the hollow shaft, It is made to flow down in the shaft and to be aerated by discharging air into the water from the discharge port at the end of the screw. In this case, self-priming is performed only with negative pressure in water, but it is also possible to supply pressurized air.

A rectifying plate 3 is arranged above the aerator 2 at the water surface. As shown in detail in FIGS. 1 and 3, the flow straightening plate 3 smoothly turns the upward flow, which is a mixture of a large number of bubbles generated by the rotation of the screw, into a horizontal flow near the water surface of the tank. As shown in the figure, it is bent into a concave arc shape so that the inner wall side end is deep and the tip is separated from the tank wall in the horizontal vicinity, and the upward flow naturally becomes a horizontal flow and diffuses throughout the tank. It is a guide.

The size of the current plate 3 is not limited as long as it achieves the above object, but in the illustrated embodiment, the length is larger than the width.

Therefore, in order to perform aerobic agitation with the aeration device configured as described above, the aerator is driven so as to rotate the screw forward. As a result, in the case shown in FIG. 1, a negative pressure is generated by the screw thrust in the upper water area at the screw end, and the sewage is agitated, and an upward flow is generated according to the shape of the screw blades, and it is submerged in water. The bubbles that are sucked and discharged are mixed. Then, the upward flow is strengthened by the air lift force and the screw thrust and rises, and when it collides with the upper straightening plate, it naturally changes its flow direction horizontally along the curved surface of this plate and spreads in all directions. To be done. Then, when it reaches the side wall surface of the anti-aeration tank, as shown in the figure, the flow direction of water next turns downward from horizontal and becomes a downward flow, and further reaches the aerator lower position along the tank bottom,
In this way, the upper and lower parts of the tank circulate. In this downward flow area, large air bubbles are released into the atmosphere when flowing down horizontally, but fine air bubbles are mixed in water and circulated in the downward flow and circulating flow throughout the tank, resulting in a deep tank bottom. However, sufficient agitation and aeration are performed.

Further, in the case of anaerobic stirring, if the screw is controlled so as to rotate in the reverse direction, it will not be sucked in, so only the sewage will be stirred, and a downward flow will be generated by the screw thrust, and the flow that has reached the tank bottom will be The flow is redirected along the bottom, then upwards along the side wall of the anti-aerator and then horizontal at the surface of the water, reaching the upper part of the aerator, thus only circulating wastewater.

[0015]

According to the present invention, an aerator which is vertically provided along the inner surface of one side of the aeration tank having a required size and capacity, and the rotation of the screw which is arranged above the aerator. It consists of a straightening plate that prevents surface waves generated on the water surface by making it possible to select forward or reverse rotation of the aerator, and at the time of aeration operation, the screw generates an upward flow, so the same aerator Both aerobic and anaerobic, both agitation can be performed, surface wave generation is suppressed, power loss is minimized,
Moreover, there is an advantage that uniform agitation and aeration can be performed in a deep tank.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an aeration apparatus of the present invention, showing aerobically stirring.

FIG. 2 is a cross-sectional view showing the state during anaerobic stirring.

FIG. 3 is a plan view of the same.

FIG. 4 is an explanatory diagram of an embodiment that does not use a current plate.

[Explanation of symbols]

 1 aeration tank 2 aerator 23 screw 3 straightening plate

Claims (2)

[Claims] 1. An aerator having a required size and capacity provided vertically along one inner surface of an aeration tank, and an aerator disposed above the aerator and generated on the water surface by the rotation of a screw. An aeration device comprising a rectifying plate for preventing surface waves, which allows the forward and reverse rotation of the aerator to be selected, and an upward flow is generated by a screw during aeration operation. 2. An aerator capable of rotating in the normal and reverse directions on an inner surface of one side of the aeration tank and a rectifying plate at a water surface position above the aerator, and when the aeration is performed, the aerator is normally rotated to generate by rotation of a screw. While sucking air by the negative pressure of the screw end water area to aerate by aerating the upward flowing water generated by the screw,
The function of the rectifying plate prevents the generation of surface waves and efficiently uses the circulating water flow to aerate and agitate the entire tank, and during anaerobic operation, the aerator is rotated forward to generate a downward water flow. The method of operating an aeration device is characterized in that only the waste water in the tank is stirred.