JPH0585238B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of operating an aeration device for crushing floating scum and preventing scum from accumulating.

[Conventional technology]

Equipment for agitating and aerating the wastewater is installed in building pits and pump wells where wastewater is temporarily stored in the underground layers of buildings and pumped up and drained while being aerated. This aeration equipment operates continuously regardless of the water level.

[Problem to be solved by the invention]

These aeration devices use a screw driven by a motor to agitate the wastewater, and use the negative pressure generated at the tip of the screw to aerate the wastewater. Scum is also allowed to flow in from the inlet to be crushed.
However, there is a limit to the suction power of surface water into the aerator casing required for scum breaking. For this reason, the inner wall of the pit is used to generate a swirling flow within the pit to guide the scum to the vicinity of the scum suction port. Square ponds with special shapes, such as pump wells, have the disadvantage that the corners become blind spots where scum accumulates and grows.

Furthermore, it is difficult to install an aeration device near the suction port of the sewage pump because air may enter the sewage pump and cause cavitation.

[Means to solve the problem]

Ventilation is controlled according to the level of the sewage water or the operation of the sewage pump, and the sewage is stirred while crushing floating scum.

Restricting this ventilation increases the rate at which scum is sucked into the aerator, increasing scum crushing capacity.

〔Example〕

The method of operating the aeration system of the present invention will be explained below based on the illustrated embodiment.

In the figure, 1 is a tank such as a building pit or a pump well that temporarily stores wastewater for treatment (hereinafter referred to as a sewage treatment tank), and an aeration device 2 is installed directly at the bottom of this sewage treatment tank 1, or a mount 3 is installed. Installed via.

This aeration device 2 can adopt various types of mechanisms, but in the illustrated embodiment, as shown in FIG. 23 and rectifier tube 28
It's getting more and more familiar.

The underwater motor 21 is driven by a hydraulic, electric or other power source, and a similarly hollow stirring blade shaft 25 is directly connected and fixed to a hollow motor shaft 24 of the underwater motor 21. The stirring blade 22 is formed by integrally providing a stirring blade base body 26 having a spiral shape or other shape suitable for aeration around the outer periphery of a hollow shaft 25.

The motor shaft 24 of the underwater motor 21 is hollow with a ventilation hole 27 having a required cross-sectional area, so that the inside of the motor shaft can be ventilated.
A ventilation pipe 23 is connected to the opposite output side of the underwater motor shaft 24, that is, the side opposite to the stirring blade, and the tip of the ventilation pipe 23 is arranged so as to be always above the water surface. The stirring blade shaft is electrically connected to the ventilation hole 27, and the inside of the stirring blade shaft can be ventilated from the inside of this motor shaft. Further, the stirring blade 22
is stored in the rectifier tube 28 (draft tube),
The rectifier tube 28 has a suction port 29 whose upper end is widened into a flap shape, and an air outlet 30 that opens in the long axis direction of the stirring blade.
The waste water is sucked into the straightening tube 28, stirred by the blades, and discharged into the waste water again from the outlet. When inhaling scum, the scum is crushed and discharged.

Further, a ventilation control valve 31 is provided above the water surface of the ventilation pipe 23, and this valve 3
The opening/closing operation of 1 is performed by a water level detection signal from a water level gauge or by a timer.

4 is a sewage pump, and 41 indicates a suction port of this pump. The pump 4 is stopped in response to a water level detection signal from a timer 5 or a water level gauge.

The rotation of the underwater motor is directly transmitted to the stirring blade 22 by driving the aeration device. Motor power is transmitted to the water by rotation of the stirring blade 22 and converted into velocity energy and pressure energy. In this device, when the ventilation valve is fully open, stirring force is generated due to an increase in velocity energy, and negative pressure is generated at the tip of the blade due to an increase in pressure energy. This negative pressure sucks the air supplied through the vent pipe through the hollow stirring blade shaft and the underwater motor shaft, atomizes it with the blades, and stirs and releases it into the water. As mentioned above, the water mixed with microbubbles is also stirred by the blades, thereby performing aeration. At this time, the sewage is sucked in through the suction port 29 of the straightening tube 28 and discharged from the outlet, and the sewage circulates within the tank.

As the ventilation valve is closed, the negative pressure at the tip of the stirring blade begins to suck in not only air but also water behind the screw. As a result, as the ventilation is reduced, the suction force from the suction port 29 also increases, and reaches its peak when the ventilation is stopped. In order for this device to crush scum, it is necessary to suck the scum through the suction port 29, so an improvement in the suction force means an improvement in the scum crushing ability. When comparing the surface water suction limit depth (vortex generation limit water depth) from the suction port 29, it has been confirmed through experiments that when ventilation is stopped, it is possible to suction to a depth approximately 1.5 times that of the one specified for ventilation. Furthermore, since the radial water flow associated with the floating of air bubbles is eliminated, the flow condition changes and blind spots are eliminated.

Next, a method of operating the present aeration device will be described using an example.

As shown in the flowchart in Figure 2, when the water level meter detects the maximum operating water level Hmax, the sewage pump 4
Start driving. After the sewage pump 4 is operated for a predetermined time T seconds using a timer, the ventilation control valve control 31 is throttled or closed. This predetermined time T seconds is set using the following formula.

T=Hmax-Hv/V Hmax: Maximum water level for pump operation Hv: Water level at which the aeration device starts scum crushing V: Average value of the water level drop rate by the sewage pump Also, the scum crushing water level Hv set after the sewage pump is turned on It is also possible to close the valve by detecting the water level.

When the water level gauge detects that the minimum operating water level Hmin has been reached, the ventilation valve is opened and the drainage pump is also stopped. While this ventilation control valve is closed, the force for sucking in scum from the suction port 29 of the rectifier cylinder 28 increases, a large amount of scum is sucked in, and the scum crushing ability increases. Next, sewage is introduced and the above operation is repeated in sequence.

〔Effect of the invention〕

The first aspect of the present invention controls ventilation according to the water level of wastewater, performs aeration and agitation of wastewater above a set water level, and limits the amount of ventilation below the set water level,
Since the sewage is stirred while crushing the floating scum, it is possible to selectively aerate the sewage and crush the scum depending on the water level, which has the advantage of effectively and efficiently aerating the sewage. .

The second invention has the effect of minimizing cavitation caused by air entering the sewage pump and increasing the scum crushing ability by limiting the operation of the sewage pump and the amount of ventilation.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the method of operating the aeration device of the present invention, FIG. 2 is a flowchart, and FIG. 3 is a sectional view of the aeration device. 1 is a sewage treatment tank, 2 is an aeration device, 23 is a ventilation pipe, 31 is a ventilation valve, and 4 is a sewage pump.

Claims (1)

[Scope of Claims] 1. In an apparatus for stirring and aerating wastewater while aerating it, the amount of aeration is limited at a water level at which scum is absorbed into the apparatus and crushing begins, and the aeration is stopped at the lowest operational water level. A method of operating an aeration device characterized by canceling a quantity restriction. 2. An aeration device that aerates sewage by stirring and aerating the sewage, the aeration device being characterized in that after starting the operation of the sewage pump, the aeration amount is limited, and at the same time when the sewage pump is stopped, the aeration amount restriction is canceled. How to drive.