JPH0773709B2 - Control method of wastewater treatment in the oxidation ditch method - Google Patents

Description

The present invention relates to a method for controlling wastewater treatment in the oxidation ditch method.

[Conventional technology]

In the wastewater treatment by the oxidation ditch method, a horizontal rotary aeration rotor is installed in a ditch tank that has a circulation path for the wastewater so that the wastewater is aerated and flowed. The diameter and length of the aeration rotor are generally determined so as to supply the amount of oxygen required for purifying the sewage, and the aeration rotor is set to exhibit its performance at a predetermined rotation speed at a certain water immersion depth. The torque and horsepower are calculated with sufficient margin under the set conditions, and the motor and the speed reducer are provided.

Therefore, conventionally, the oxygen supply amount is adjusted or controlled by adjusting the number of rotations of the aeration rotor and the depth of water immersion (Japanese Patent Laid-Open No. 62-62160).
-294497, Japanese Patent Publication No. 63-14679, etc.).

(Problems to be Solved by the Invention) In such a conventional method, when the load is low, the required oxygen can be supplied, for example, by reducing the rotation speed of the aeration rotor. The flow velocity inside will also decrease. Therefore, in extreme cases, particles with large specific gravity and sludge may settle to the bottom of the tank. Especially when the amount of inflowing sewage is extremely small, such as at night, the aeration rotor may be stopped, but in such a case, there is a problem that sludge settles and accumulates on the bottom of the tank and stable treatment cannot be performed.

The present invention has been made in order to solve such a problem. Under the rated operating condition of the aeration rotor, the aeration rotor provided with the necessary oxygen supply amount and stirring power can be used to reduce the amount of inflowing wastewater. It is intended to provide a control method capable of ensuring a predetermined in-tank flow velocity by performing an operation in which the stirring power is not reduced even when the oxygen supply amount is reduced in accordance with the low load operation. is there.

[Means for Solving the Problems]

Next, the configuration of the present invention for achieving the above object will be described with reference to the drawings. In the invention of claim 1, the rotary aeration rotor 3 is used for aeration and flow of waste water. At the movable weir 7 where the treated water overflows
Is provided, and only when the preset load is small,
The rotation speed of the aeration rotor 3 is set lower than the rated value, the movable dam is raised above the rated value, and the water depth of the ditch tank 1 is increased.

Further, in the invention of claim 2, in the ditch tank 1 in which the rotary aeration rotor 3 aerates and flows the sewage, a movable weir 7 for overflowing the treated water is provided, and the circulation path 2 of the ditch tank 1 is provided. A liquid level gauge 9 for detecting the above-mentioned overflow water depth h ₁ is provided inside, and a water level signal from the liquid level gauge 9 is sent to the rotation control device 11 of the aeration rotor 3 and the drive control device 12 of the movable weir 7 to When the overflow water depth detected by the total 9 becomes less than a preset value, the rotation speed of the aeration rotor 3 is set lower than the rated value, and the movable dam 7 is raised above the rated value to increase the water depth of the ditch tank 1. It is characterized by doing.

[Action]

According to the first aspect of the present invention, when the preset time period when the load becomes small, the rotation speed of the aeration rotor 3 becomes lower than the rated speed and the movable weir 7 is moved only during that time period.
Will be pulled up and the water depth of the ditch tank will be kept high. Further, in the invention of claim 2, the overflow water depth from the movable weir is detected by the liquid level gauge 9, and the water level signal is sent to the rotation control device 11 of the aeration rotor and the drive control device 12 of the movable weir. . When the overflow water depth detected by the liquid level gauge 9 becomes lower than the preset value, the rotation speed of the aeration rotor becomes lower than the rated speed by both control devices 11 and 12, and the movable weir is above the rated value. It will be increased by a fixed amount.

Thereby, when the load becomes small, excessive aeration is suppressed and the flow in the ditch tank is maintained.

〔Example〕

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

In the figure, 1 is a ditch tank having a circulation path 2. In this ditch tank 1, a horizontal rotary aeration rotor 3 for performing aeration is provided across the circulation path 2 and driven by a motor 4, It is designed to aerate and flow water. Further, on the upstream side of the rotor 3, a side wall of the ditch tank 1 is cut down and a drainage port 5 of the treated water connected to the outflow passage 6 is provided. The drain port 5 is provided with a movable weir 7 which can be vertically moved and adjusted by a drive device 8. Further, a liquid level gauge 9 is provided in the circulation path 2,
This liquid level meter 9 is designed to measure the difference between the height of the movable weir 7 and the water depth in the ditch tank, that is, the height of the overflow water depth h ₁ , whereby the water depth of the ditch tank and the wastewater flow rate can be detected. it can.

One method of the present invention provides a specific time zone of the day, controls the rotation speed of the aeration rotor 3 which is steady during the time zone, and adjusts the height of the movable weir. That is, the daily inflow pattern of sewage volume or pollution load is investigated in advance,
On the other hand, a time zone with a low load (for example, nighttime) is set. And during that time, the aeration rotor 3
Rotation speed from rated (eg 60 rpm) to low speed (eg 2
0 rpm). This operation is performed by the motor 4 and the timer 10.
And may be combined, or may be a manual method. After the rotation of the aeration rotor 3 is lowered, the movable weir 7 is pulled up by a predetermined amount to increase the water depth of the ditch tank and increase the water immersion depth h ₂ of the aeration rotor 3. For example, the water immersion depth h ₂ of the aeration rotor 3 is increased from the rated value of 150 mm to 280 mm. The operation of the movable weir 7 can be performed in association with the timer 10 or manually as in the aeration rotor 3. Next, when the above specific time period has passed, the timer 10 or manually
The rotation speed of the aeration rotor 3 is returned to the rated value and the movable weir 7 is also lowered to the rated position.

The other method of the present invention is not the control by the time zone as described above, but the rotation speed and the movable weir of the aeration rotor 3 by the increase / decrease of the water level detected by the liquid level gauge 9 at the overflow water depth h ₁ from the movable weir 7. The height of 7 is controlled.

That is, as shown by the chain line in the figure, the rotation control device 11 for the motor 4 is provided, and the drive control device 12 connected to the drive device 8 for the movable weir 7 is provided. Rotation control device 1
Receives the water level signal from the liquid level gauge 9 and reduces the rotation speed of the motor 4 when the overflow water depth h ₁ becomes less than or equal to a preset value, and returns the motor 4 to the rated rotation when it exceeds the set value. To do so. Further, the drive control device 12 for the movable weir receives the water level signal from the liquid level gauge 9, raises the movable weir 7 by a predetermined amount when the water level signal falls below a preset value, and moves when the set value is exceeded. The cough 7 is lowered to the rated position.

In this way, regardless of the time period, when the inflow of dirty water decreases and becomes less than the predetermined value, the rotation speed of the aeration rotor 3 and the movable weir 7 can be raised at any time. When the predetermined value is reached, the rotation speed of the aeration rotor 3 can be returned to the rated value and the movable weir 7 can be returned to the rated position. As a result, the processing in the ditch tank can be automatically and stably performed.

〔The invention's effect〕

As described above, according to the present invention, during low load operation in which the amount of dirty water flowing into the ditch tank is small, the rotation speed of the aeration rotor can be reduced to supply oxygen according to the low load, and the movable weir can be raised. Therefore, it is possible to increase the submersion depth of the aeration rotor without lowering the stirring power, and therefore it is possible to prevent aeration suitable for low load and sedimentation and accumulation of sludge, and always perform stable and favorable wastewater treatment.

According to the method of claim 1, since the rotation control of the aeration rotor and the drive of the movable weir are controlled by setting the time zone, the facility cost becomes low and it is suitable for the operation of the small ditch tank.

Further, according to the method of claim 2, since the rotation control of the aeration rotor and the drive of the movable weir can be automatically performed by detecting the overflow water depth by the liquid level gauge, the control can be performed easily and reliably, and the sewage can be stabilized. Processing can be further improved.

[Brief description of drawings]

 The drawings are explanatory views showing an embodiment of the present invention. 1 ... Ditch tank, 2 ... Circulation path 3 ... Aeration rotor, 4 ... Motor 5 ... Drainage port, 6 ... Outflow path 7 ... Movable weir, 8 ... Drive device 9 ... Liquid level meter, 10 …… Timer 11 …… Rotation speed controller, 12 …… Drive controller

Claims (2)

[Claims] 1. A ditch tank in which a rotary aeration rotor performs aeration and flow of wastewater, and a movable weir for overflowing treated water is provided to rotate the aeration rotor only during a preset time period when the load is small. A method for controlling sewage treatment in the oxidation ditch method, which comprises lowering the number of rotations below the rated value, raising the movable dam above the rated value, and increasing the water depth of the ditch tank. 2. A ditch tank in which a rotary aeration rotor aerates and flows sewage, and a movable weir for overflowing the treated water is provided, and the overflow water depth is detected in the circulation path of the ditch tank. A level gauge is provided, and a water level signal from the level gauge is sent to the rotation controller of the aeration rotor and the drive controller of the movable weir, and the overflow water depth detected by the level gauge is
In the oxidation ditch method, when the rotation speed of the aeration rotor is lower than the rated value and the movable weir is raised from the rated value to increase the water depth of the ditch tank when the value becomes less than a preset value. Sewage treatment control method.