JPH0761475B2 - Sewage treatment control device in oxydation ditch tank - Google Patents

Description

The present invention relates to a control device for wastewater treatment in an oxidation ditch tank.

[Prior art] Oxidation ditch method (OD
Method has a long retention time of about 24 hours and a large buffering capacity, and is characterized by being strong against load fluctuations. It is an energy-saving type compared to the aeration method and the activated sludge method, and also in terms of operation management. Since it is easy, it is often used in small and medium-sized wastewater treatment plants.

[Problems to be solved by the invention]

By the way, load fluctuations in wastewater treatment include fluctuations in inflow water quantity and fluctuations in inflow water quality, and in many cases, an increase in water quantity and an increase in pollutant concentration coincide with each other. Although the OD method is strongly characterized by these load fluctuations, fluctuations in water quantity will directly affect the treatment capacity of the final settling basin. That is, the water area load and overflow load of the final settling basin are proportional to the amount of water flowing out of the ditch tank and flowing into the settling basin. Will get worse. In this way, in the OD method, the capacity of the final sedimentation tank is a major limiting factor for fluctuations in water load, and in particular, the sedimentation of flocs is inferior to other wastewater treatment methods. The load must be as small as 10 to 15 m ³ / m ³ · day, and more severe conditions are required for fluctuations in water load. Therefore, the OD method has a drawback that it is very weak against fluctuations in water load in the ditch tank.

The present invention eliminates such weak points in the OD method and enables the inflow water load to the sedimentation basin to be maintained as even as possible, further improving the buffer capacity of the ditch tank, stabilizing the treated water quality, and changing the load. It is intended to provide a strong wastewater treatment device to

[Means for solving problems]

Regarding the configuration of the present invention, FIG. 1 and FIG. 2 corresponding to the embodiment
Describing with reference to the drawings, the present invention relates to a sewage treatment apparatus using a ditch tank in which a rotary rotor aerates and flows sewage, on the outflow side of the ditch tank 1.
A means 18 for detecting the water level of the ditch tank 1 in association with the float 15 is provided while providing a drainage device 10 in which a drain 12 having a float 15 and a spout 13 for the outflow water is floatable vertically. Further, it is characterized in that means 19 for controlling the number of rotations of the rotor of the aeration device 3 is provided in correspondence with the detected water level.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIGS. 1 and 2, reference numeral 1 denotes a ditch tank having a circulation path 2, which is generally formed in a track type as shown. Then, the rotor rotation type aeration devices 3 and 3 are installed across the circulation path 2 by immersing the lower part in the drainage in the tank. The rotors of the aeration devices 3 and 3 are rotated by the drive devices 4 and 4, respectively, whereby the drainage in the tank flows in the direction shown by the arrow in FIG. An inflow pipe 5 is connected to one end side of the ditch tank 1 so that raw drainage is supplied from it, and an outflow pipe 7 communicating with a sedimentation tank 6 is provided at the other end side of the ditch tank 1. It is connected. Further, the bottom of the settling tank 6 and one end of the ditch tank 1 are connected by a return pipe 8 so that a part of the concentrated sludge separated and concentrated in the settling tank 6 is returned to one end of the ditch tank 1. ing. A movable outflow water extraction device 10 connected to the outflow pipe 7 is provided at one end of the ditch tank 1.

As shown in FIG. 2, the outflow water extraction device 10 includes an outflow pipe 7
An outer cylinder 11 having a locking step portion 11a on its inner surface is fixed to the end of the drain tube 12 having a lower stopper 12a capable of engaging the lower end with the locking step portion 11a. Is vertically and watertightly inserted, and an upper stopper 12b is projectingly provided on the upper part of the drainage pipe 12, and a funnel-shaped dovetail 13 is fixed to the upper end of the drainage pipe 12, and the upper part of the drainage pipe 12 is further fixed. The floats 15 and 15 whose upper ends are positioned higher than the dowel 13 are provided via brackets 14 and 14, respectively. And
A rope 16 is attached to the floats 15 and 15,
Is connected to a position detector 18 described later via a guide wheel 17.

The position detector 18 operates by pulling back the rope 16 that moves by the vertical movement of the float 15 associated with the height of the water level,
A water level signal in the ditch tank 1 is sent to the rotation speed control device 19. The rotation speed control device 19 receives the water level signal, determines the rotation speed of the rotor of the aeration device 3 to a preset rotation speed, and is the rotor drive device 4.
For example, the rotation speed of the variable drive device 4 such as a frequency conversion motor is controlled.

In the apparatus having the above-described configuration, the overflow water depth h (FIG. 2) of the float 15 is set so that the daily average sewage amount or a slightly larger amount of water flows out. As a result, the dirty water in the ditch tank 1 flows into the drain pipe 12 through the drinking port 13 and is taken out through the outflow pipe 7. When the amount of inflow water into the ditch tank 1 becomes larger than the daily average amount of wastewater, the water depth of the ditch tank 1 becomes deeper and the float 15 rises, but the lower stopper 12a of the drain 12 hits the locking step 11a of the outer cylinder 11. Until it touches, the overflow water depth h of the float 15 does not change,
The outflow amount of water from the ditch tank 1 is maintained constant. When the amount of inflow water into the ditch tank 1 becomes smaller than the daily average amount of wastewater, the water level of the ditch tank 1 lowers and the float 15 descends, reaching the position where the upper stopper 12b of the drain pipe contacts the upper end of the outer cylinder 11. Will be stopped. Therefore, when the amount of water is less than that, the float 15 has the same function as the conventional fixed weir.

Therefore, the standard water level of the ditch tank 1 is, for example, float.
Select in the middle of 15 lifting strokes,
Further, the aeration device 3 is installed in such a state that the water immersion depth and the rotation speed of the rotor are most effective at the reference water level. Therefore, if the water level in the ditch tank 1 rises, the inundation source of the rotor changes accordingly. That is, when the amount of dirty water increases and the float 15 rises, the water depth of the ditch tank 1 becomes deep and the water immersion depth of the rotor becomes large.
In this case, the oxygen supply amount increases as the submersion depth of the rotor increases, and the resistance from the water of the rotor increases, so the power also increases accordingly. On the contrary, when the amount of sewage decreases, the float 15 descends, and when the amount of daily sewage decreases, the upper stopper 12a comes into contact with the upper end of the outer cylinder 11 and is fixed. When the amount of water decreases in this way, the water immersion depth of the rotor decreases and the oxygen supply amount decreases.
Also, the power of the rotor is reduced.

FIG. 3 shows the change in the amount of sewage inflow with the change in the time of day, and the change in the amount of oxygen required for it. It is necessary to change the amount of oxygen supply according to the inflow of sewage. I understand that it will not happen.

The water level of the ditch tank 1 will increase or decrease from the set water level due to the increase or decrease of the inflow amount of sewage.
As mentioned above, the required oxygen supply amount will be adjusted to some extent by increasing or decreasing the inundation depth of the rotor.
In order to control this with higher accuracy, it becomes necessary to adjust the oxygen supply amount by changing the rotational speed of the rotor in response to fluctuations in the inflow water amount, that is, increase / decrease in the water level.
When the water level in the ditch tank 1 increases, the oxygen supply amount increases due to the water immersion depth of the rotor, although there is a tendency for over-aeration.
Although it does not have a significant effect on water quality and can be adjusted by controlling the inflow of wastewater, the inundation depth of the rotor becomes shallow when the water level decreases, resulting in insufficient oxygen supply. Will occur and the water quality will deteriorate.
A possible solution is to increase the rotation speed of the rotor.

From this point of view, the present invention controls the rotation speed of the rotor by the water level in order to further adjust the change in the oxygen supply amount due to the change in the rotor submersion depth due to the increase or decrease in the amount of dirty water to perform highly accurate oxygen supply control. I did it.

That is, the detection of the water level in the ditch tank 1 uses the elevation of the float 15 and transmits it to the position detector 18 by pulling back the rope 16 accompanying the elevation of the float 15. Then, a signal corresponding to the water level from the position detector 18 is sent to the rotation speed control device.
The rotation speed of the rotor drive device 4 is controlled by the operation. As a result, it is possible to increase the rotation speed of the rotor when the water level is lowered and decrease the rotation speed of the rotor when the water level is increased.
The control of the rotor rotational speed can be performed continuously or intermittently, and the rotor rotational speed can be controlled only when the water level is lowered.

〔The invention's effect〕

As described above, according to the present invention, on the outflow side of the ditch tank, the outflow water extraction device in which the discharge tube having the float and the outlet of the outflow water can be floated up and down by a predetermined amount is provided. Even if the amount of inflow water to the river fluctuates, the amount of outflow water can be kept almost constant, and therefore the treatment in the final settling basin can be maintained satisfactorily. Since the means for controlling the number of revolutions of the rotor of the aeration device according to the detected water level is provided, the aeration process for the water level of the ditch tank, that is, the increase or decrease of the load, is always performed effectively. In addition, it is possible to remarkably improve the resistance against the load fluctuation in the ditch tank and to improve the stability of the treated water quality, and many other excellent effects are exhibited.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing an embodiment of the device of the present invention.
FIG. 3 is a side sectional view showing a part of the outflow water extraction device, and FIG. 3 is a diagram showing a relationship between a change in daily sewage inflow amount in a ditch tank and a necessary oxygen amount. 1 ... Ditch tank, 2 ... Circulation path 3 ... Aeration device, 4 ... Drive device, 5 ... Inflow pipe, 6 ... Sedimentation tank, 7 ... Outflow pipe, 10 ... Outflow water removal device, 11 ... Outside Cylinder, 12 ... Drainage tube 13 ... Drinking mouth, 15 ... Float 18 ... Position detector, 19 ... Rotation speed control device

Claims (1)

[Claims] 1. In a pollution treatment device using a ditch tank for aeration and flow of sewage by means of a rotary rotor, a drain pipe having a float and a spout for the effluent is provided on the outflow side of the ditch tank up and down by a predetermined amount. And a means for detecting the water level in the ditch tank in relation to the float, and a means for controlling the rotation speed of the rotor of the aeration device in accordance with the detected water level. A sewage treatment control device in an oxidation ditch tank, characterized by being provided with.