JPH06320187A - Aerating and stirring method in oxidation ditch - Google Patents

Abstract

PURPOSE:To improve efficiency in treatment by controlling energy loss, and obtaining a greater stirring force taking into consideration the characteristic of screw type aeration devices. CONSTITUTION:A plurality of screw type aeration devices 2 and 3 are arranged in a cross section of circulating water passage 1S of oxidation ditch in such a manner that the adjacent aeration devices rotate in the directions opposite each other. By this method, the currents produced between the aerating devices 2 and 3 in the circulating water passage 1S meet each other in the same direction to mutually accelerate their velocities so as to impart a greater stirring and mixing action to the inside of the water passage 1S. In this way the aeration can be effected evenly and efficiently over the entire area of the water passage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aeration stirring method in an oxidation ditch, which suppresses energy loss and gives a larger stirring and mixing action.

[0002]

2. Description of the Related Art An oxidation ditch method is one of the methods for treating sewage. In this system, a plurality of screw type aerators are installed in an aeration tank equipped with a circulating water channel, and desired treatment is performed by stirring and aerating sewage.

[0003]

In this oxidation ditch method, a plurality of screw type aerators are used so that substantially uniform agitation can be performed over the entire width of the water channel. However, this aeration device uses a screw that can obtain a desired aeration and stirring performance only when rotating in one direction. For this reason, when a plurality of units are installed in the cross section of the water channel, all of them have the same rotation direction, which causes the flows of the two to be opposite to each other between the aeration devices, resulting in collision energy loss. As a result, the stirring flow rate is further reduced, and there is a disadvantage that dirty sand and activated sludge having a high specific gravity tend to settle at the bottom of the screw.

In view of the characteristics of the screw type aerator, the present invention aims to suppress energy loss, obtain a larger stirring force, and sufficiently stir and mix the entire tank to improve the treatment effect.

[0005]

The present invention has been made to achieve the above object, and a plurality of screw type aerators are provided in one section of the circulation channel of the oxidation ditch.
Moreover, the aeration devices adjacent to each other are arranged so that their rotation directions are different from each other, and the water flows generated between the aeration devices in the circulating water channel are set in the same direction to accelerate the flow velocities thereof to give a greater stirring and mixing action in the water channel. The point is to do so.

[0006]

A plurality of screw type aerators are arranged such that a right-turning screw and a left-turning screw are alternately arranged on one cross section of the circulation channel of the oxidation ditch. As a result, the rotation directions of the screws of the adjacent aerators become opposite to each other, the agitation flow speeds are accelerated with the flow generated between the aerators in the same direction, and energy loss is suppressed, resulting in greater agitation in the aeration tank circulation channel. A mixing action can be given, sedimentation of activated sludge and sedimentation can be prevented, and uniform aeration treatment can be efficiently performed over the entire water channel.

[0007]

EXAMPLES The aeration stirring method in the oxidation ditch of the present invention will be described below with reference to the illustrated examples.
In FIG. 1, reference numeral 1 denotes an aeration tank provided with a circulating water channel for performing activated sludge treatment. The aeration tank 1 may have various shapes such as a circular shape in addition to the oval shape shown in FIG. Then, a plurality of screw type aerators 2, 3 are installed at a predetermined interval so that substantially uniform agitation can be performed on one cross section of the circulating water channel 1S of the aeration tank 1. The arrangement interval of the aeration device is appropriately determined according to the stirring ability of the aeration device.

The screw type aeration devices 2 and 3 are arranged so that their rotation directions are different from each other, the screw 21 provided in the aeration device 2 is for turning right, and the screw 31 of the aeration device 3 is for turning left, respectively. The aeration devices 2 and 3 are arranged so that those having different turning directions are alternately arranged. And the screws 21, 31 of each aeration device
The shape of is not particularly limited, but it is assumed to have a required capacity having a stirring flow for pushing water forward of the screw by the rotation of the motor and an action of sucking air and aerating.

The aeration devices 2 and 3 have the same shape, and are provided with a motor, a hollow shaft rotatably driven by the motor, and a screw for turning to the right or turning to the left at the end of the hollow shaft. The air is sucked from the hollow shaft by using the negative pressure generated in the screw tip water area by driving, and discharged and stirred into water and into the screw tip water area that is stirred by the screw.
The desired aeration is performed.

The aeration devices 2 and 3 installed in one section of the circulating water channel 1S are one for right turn and one for left turn in the embodiment of FIGS. 1 to 3. The number of units used is not limited, as it is appropriately selected and used depending on the width, the agitation capacity of the aerator, and the like. However, the aeration devices adjacent to each other are arranged such that their turning directions are opposite to each other.

Therefore, in the apparatus constructed as described above, the screw type aeration apparatus 2, 3 installed in the circulating water channel 1S.
Is operated, the screws 21 and 31 provided at the tip of each aeration device rotate to generate a stirring flow in the water channel and generate a negative pressure at the tip of the screw. Therefore, the air on the water surface is sucked from the upper opening of the hollow shaft, guided to the tip of the screw, and sheared by the screw edge to be atomized. FIG. 2 shows the state around the screw at this time as seen from the upstream side of the screw, and since the flow between the screw 21 and the screw 31 is both downward, the water flow is accelerated. A flow is generated as if going into the bottom of the water channel as indicated by the mark a1.
On the other hand, the one shown in FIG. 3 shows the flow when two conventional aerators are installed, and there is an upward flow and a downward flow between the two screws as shown by b. Since the water flows cancel each other, energy loss occurs and the flow velocity decreases. Therefore, as shown in FIG. 4, accumulation of dirt and sludge occurs in the lower part C of the screw of the aerator.
However, in the case of the present invention, since the flow of a2 in FIG. 2 is generated in the lower part of the screw, the flow velocity in the lower part of the screw is high and the accumulation of dirt and the like can be prevented.

When a plurality of screw type aerators are installed in the cross section of the water channel 1S, it is preferable to install two screw aerators as a set as much as possible and arrange them so that the flow between the screws is downward as shown in FIG. preferable. At this time, since the accelerated downward flow a1 collides with the bottom surface and flows toward the side wall, the flow velocity at the bottom portion increases, and as described above, the deposition is less likely to occur. When three or more aerators are required due to the water channel width, the right-handed screw and the left-handed screw are arranged alternately, but the order of arrangement is not particularly limited.

[0013]

According to the present invention, in the aeration tank forming the circulating water channel, a plurality of screw type aerating devices are installed in one cross section of the circulating water channel, and the aerating devices adjacent to each other are screw type with different rotating directions. Since it is an aeration device, the flow between the aeration devices is in the same direction and they can accelerate each other to generate a large flow velocity, which causes sewage sand and activated sludge with a large specific gravity to accumulate at the bottom of the aeration tank and decompose anaerobically. And an obstacle such as deterioration of water quality can be prevented, and uniform agitation can be achieved over the entire water channel.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of an aeration stirring method in an oxidation ditch of the present invention.

FIG. 2 is an explanatory view showing a stirring water flow according to the present invention.

FIG. 3 is an explanatory view showing a stirring water flow of a known example.

FIG. 4 is an explanatory diagram showing a state of sand settling in the aeration tank.

[Explanation of symbols]

 1 Aeration tank 1S Circulating water channel 2,3 Screw type aeration device 21,31 Screw

Claims (1)

[Claims] 1. A plurality of screw type aerators are disposed in one cross section of the circulation water channel of the oxidation ditch, and the aerators adjacent to each other are arranged so that the rotation directions thereof are different from each other, and the aeration apparatuses are disposed between the aeration apparatuses in the circulation channel. An aeration stirring method in an oxidation ditch, characterized in that the generated water flows are directed in the same direction and the flow velocities are mutually accelerated so as to give a larger stirring and mixing action in the water channel.