JPH05177193A - Aeration method and device therefor - Google Patents

Abstract

PURPOSE:To agitate uniformly even in the bottom section of a deep tank, supply air or oxygen of desired amount and carry out aeration efficiently. CONSTITUTION:A self-suction aeration machine 4 for generating water flow by the rotation of a screw 41 and sucking air by the negative pressure generated at the end of the screw 41, a cylindrical body 2 provided below the aeration machine 4 and an agitator 3 forming downward flow in the cylindrical body 2 are installed in an aeration tank 1. Circulating flow generated in the aeration tank 1 by driving aeration machine 4 and the agitator 3, and the foams blown into water in the shallow position of the water are transferred to the bottom section of the tank 1 by the downward flow in the cylindrical body 2 and jetted as upward flow in the outer peripheral section of the cylindrical body 2 to carry out the agitation and aeration covering whole the inside of tank 1 uniformly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for aerating efficiently by uniformly agitating even at the bottom of a deep tank having a depth of 10 m or more and supplying a required amount of air or oxygen. Is.

[0002]

2. Description of the Related Art In the treatment of sewage, there is an aeration method in which air is supplied into a tank and sewage is agitated as a method of decomposing and treating organic matter in sewage. Conventionally, there is one disclosed in Japanese Examined Patent Publication No. 55-29756 for aeration by agitating the sewage in a deep tank and further agitating the tank. This consists of arranging a cylinder in the tank, and installing a screw in this cylinder to generate a downward flow while blowing air into the sewage in the cylinder, and after reaching the bottom of the tank, the outer periphery of the cylinder is raised. This is a method of circulating in the tank as a countercurrent.

[0003]

When a downward flow is generated by a stirrer in a cylinder installed in the tank to stir sewage in the cylinder and air is blown down to the bottom of the tank, 10
In a tank of about several meters, the entire circulation flow in the tank is generated, and required agitation and aeration can be performed. However, when aeration is performed in the downward flow of sewage, a certain amount of upward flow is generated in the cylinder due to the bubbles rising in the cylinder in a part of the downward flow of the stirrer.
Due to the air lift force of the bubbles, the generated upward flow is generally about 0.3 m / S. Therefore, in a deep tank of 10 m or more, the downward flow of water and air did not reach the bottom of the tank due to the upward flow due to the air lift force, and uniform stirring and aeration in the tank were not possible.

In the present invention, the aerator is further equipped with a screw for stirring to generate a strong water flow to generate a circulating flow throughout the tank even in a deep tank of 10 m or more to stably supply oxygen and perform mixing and stirring. The purpose is to perform desired stirring and aeration evenly to the bottom of the tank.

[0005]

The present invention has been made to achieve the above object, and a self-priming aerator for generating a water flow by swirling a screw and sucking at a negative pressure generated at the tip of the screw. , A cylinder provided in the lower direction of the aerator and a stirrer that forms a downward flow in the cylinder are provided in the aeration tank, and the aerator / agitator is driven to circulate in the aeration tank. The flow of air is generated and the bubbles blown into the water at a shallow depth are transferred to the bottom of the tank by the downward flow of the cylinder, and are jetted as an upward flow at the outer circumference of the cylinder to agitate the entire tank. The point is to perform aeration uniformly.

[0006]

[Operation] When a self-priming aerator is installed near the water surface and air is blown into the water for aeration, the air bubbles generated by the aeration act as an air lift force, which cancels the flowing water velocity toward the bottom, and It becomes an upward flow and begins to rise.
For this reason, in a deep tank of 10 m or more, water flow and air bubbles do not reach the bottom of the tank, and aeration and stirring inside the tank cannot be performed. However, by installing an aerator near the water surface and installing a stirring blade below this as in the present invention, the aerator / agitator is operated so that the downward flow is 1 m / sec or more in the cylinder (draft tube). By doing so, even in a deep tank, it is not canceled by the air lift force due to this bubble, bubble-like air or oxygen blown from the water surface can be transferred to the bottom of the tank, and this bubble is raised again from the bottom of the tank to recycle wastewater in the tank. Uniform aeration can be performed by stirring and mixing.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The aeration method and apparatus of the present invention will be described below with reference to the illustrated embodiments. In the figure, 1 is a rectangular aeration tank having a required volume and a depth of 10 m or more. At the center of the aeration tank 1, the agitator and a self-priming aerator agitate the whole sewage in the tank. A cylindrical body 2 (draft tube) is arranged vertically so as to generate a circulating water flow between the upper part and the lower part of the tank, and the upper and lower ends of the cylindrical body 2 are for circulating sewage from the water surface and the bottom of the tank. Make an appropriate space.

The aerator 4 is installed in the upper position of the cylindrical body 2 and the agitator 3 is installed in the lower position thereof, but the cylindrical body 2 is not limited to the cylindrical shape, and may be a rectangular cylindrical shape. The aerator 4 is installed so that its screw 41 is near the water surface, and the screw 41 is fixed to the lower end of a hollow shaft 43 driven by a motor 42. The rotation of this screw 41 causes the screw 41 to move in the cylinder and The negative pressure generated in the tip water area sucks air from the upper end of the hollow shaft and discharges it into the water as fine bubbles.

The agitator 3 is a screw 41 of the aerator 4.
It is installed at a lower position and the stirring screw 32 is rotated by the submersible motor 31, and the downward flow velocity of water generated by the stirring screw reaches the bottom of the cylinder at the bottom of the cylinder sufficiently. The upward flow of 0.3 m / sec caused by the air lift force is set to 1.0 m / sec, which is more than the cancellation.

The stirrer 3 is installed in water as a whole as shown in FIG. 1, or as shown in FIG.
1 is installed in the center of the cylindrical body 2 above the water surface, and a screw 33 is fixed to the lower end of a relatively long shaft 32 so that a downward flow of 1.0 m / sec or more is generated. The flow is made to reach the bottom of the tank. Then, one or two or more aerators 4 are installed in the cylindrical body with the agitator 3 sandwiched therebetween, at a position slightly displaced from the center thereof. The structure and the installation position of the aerator 4 from the water surface are the same as those in the embodiment of FIG.

Further, FIG. 3 shows an embodiment in which the agitator 3 and the aerator 4 are integrated, and a hollow shaft 51 which is arranged at the center of the cylindrical body 2 is driven by a motor 50 installed above the water surface. At the lower end of this hollow shaft 51, a screw 3a for stirring is attached.
The aeration screws 4a are provided at positions higher than the above, and the intake air amount control valve 6 is provided at the upper end of the hollow shaft, whereby agitation and aeration are performed by the same motor.

In the embodiment shown in FIG. 1, both the raw water A and the returned sludge B are made to flow in from the upper part of the cylindrical body 2, the aeration tank mixed liquid C is made to overflow from the upper side surface of the tank 1, and sent to a separate settling basin. Here, solid-liquid separation is performed into sludge and supernatant water.
The position C from which this mixed liquid is taken out is not limited as shown in the figure as long as it is a position where the inflowing raw water is not short-circuited, and it may be anywhere.

Since the specific gravity of the raw water and the returned sludge is heavier than the mixed liquid (circulating water) in which air bubbles are mixed by aeration, the effect of promoting air bubbles downward in the cylindrical body by flowing into the upper part of the aeration position is obtained. Is obtained.

Next, the aeration operation in the above device will be described. At the start of operation of the aeration tank, first, only the stirrer 3 is operated to stir the dirty water in the cylindrical body 2 to generate a downward flow, and after reaching the tank bottom, the outer peripheral portion of the cylindrical body is directed upward. A circulating water flow is generated in the tank between the upper part and the bottom part through the cylindrical body. The downward flow velocity, for example, 1 m /, above which the flow velocity of this circulating water flow is not canceled by the air lift force of the bubbles.
When the number of seconds is exceeded, the aerator 4 is operated.

Further, the larger the amount of aeration and the larger the diameter of the bubbles, the greater the buoyancy that tends to rise inside the cylinder. Therefore, an aerator that can form the finest bubbles as possible is used, and the aeration amount is limited at the start of aeration. However, it is desirable to gradually increase. The aeration amount is controlled by controlling the rotation speed when there is one aerator as shown in FIG. 1, and by controlling the number when a plurality of aerators is provided as shown in FIG. When attached, it can be performed by controlling the valve opening.

In the present invention, the smaller the diameter of the cylindrical body, the lower the flow velocity of 1 m / sec or more can be obtained with an agitator having a smaller power, but the plane area in the cylinder with respect to the plane cross-sectional area of the aeration tank becomes smaller, The effect of raising the liquid mixture on the outside is reduced. Therefore, when installing the aeration apparatus of the present invention, it is considered whether to install a plurality of the aeration apparatus of the present invention or to install one large-diameter cylindrical body in consideration of the diameter of the cylindrical body with respect to the plane cross section of the aeration tank. There is a need.

[0017]

According to the present invention, a cylindrical body, a stirrer and a self-priming aerator are provided, and bubbles blown into a shallow water depth are placed on the downward flow of the cylindrical body generated by the stirrer to provide a deep tank aeration tank. By moving to the bottom, the bubbles receive high water pressure in the deep tank to increase the oxygen partial pressure in the bubbles, and the contact time of the bubbles can be lengthened, so the oxygen utilization efficiency is extremely high and space-saving deep tank aeration is possible. Aeration can be economically performed in the tank, and since the drive device is installed on the surface of the water, maintenance is easy.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the second embodiment.

FIG. 3 is an explanatory diagram showing the third embodiment.

FIG. 4 is an explanatory diagram of a known example.

[Explanation of symbols]

 1 Aeration tank 2 Cylindrical body 3 Stirrer 4 Aeration machine 5 Valve

Claims (2)

[Claims] 1. A self-priming aerator that generates a water flow by swirling a screw and inhales with a negative pressure generated at the tip of the screw, a cylinder provided in the lower direction of the aerator, and a cylinder inside the cylinder. A stirrer that forms a downward flow is installed in the aeration tank, and this aerator / stirrer is driven to generate a circulating flow in the aeration tank and bubbles blown into the water at a shallow water depth are placed inside the cylinder. The aeration method is characterized in that it is transferred to the bottom of the tank by the downward flow of the air, and is jetted as an upward flow at the outer peripheral portion of the cylindrical body to uniformly stir and aerate the entire inside of the tank. 2. A self-priming aerator that generates a water flow by swirling a screw and inhales by a negative pressure generated at the tip of the screw, a cylinder body provided in the lower direction of the aerator, and a cylinder body inside the cylinder body. An aeration device, characterized in that a stirrer that forms a downward flow is provided in the aeration tank.