JPH11216487A - Method for controlling aerator of oxidation ditch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method for controlling the aerator of an oxidation ditch by which the overloading of the aerator is automatically avoided without stopping the operation of the aerator when the aerator is overloaded due to any causes, and the aerator is continuously operated. SOLUTION: A detector 8 to detect the torque exerted on the aerator 3 of an oxidation ditch, a controller 6 to compute the signal from the detector 8 and an inverter 7 to change the rotating speed of the aerator 3 under the command from the controller 6 are installed. When the overload of the torque on the aerator 3 is detected by the signal from the detector 8, a command to reduce the speed of the aerator is imparted to the inverter 7 from the controller 6 to operate the aerator 3 at a reduced speed, and the overload is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sewage treatment plant,
In particular, the present invention relates to a method for controlling an aerator in an oxidation ditch.

[0002]

2. Description of the Related Art FIG. 2 is a schematic plan view of a known oxidation ditch for treating sewage by an oxidation ditch method. In the oxidation ditch, a bulkhead 2 is installed along a longitudinal direction at a central portion of the endless waterway 1,
A vertical aerator 3 close to the partition 2 at the curved portion of the water channel 1
Is installed, and the waterway 1
Mixing and stirring with activated sludge and aeration treatment are performed while recirculating the sewage flowing into the water channel formed by the tank wall and the partition wall 2 along the rotation direction of the aerator, and purified water is provided in the water channel 1. This is a sewage treatment facility that is discharged from the overflow weir 4 to the sedimentation tank.

[0003] In order to obtain good treated water quality with the above facilities, it is necessary to appropriately maintain and control dissolved oxygen in the mixture in the ditch. For this purpose, as shown in FIG. 3, a DO sensor 5 for detecting the amount of dissolved oxygen is installed in the water channel 1, and when a detection signal from the DO sensor is input to an automatic DO controller 6 ', the controller 6' 5 calculates the deviation between the dissolved oxygen amount and the control set value, and inputs the optimum rotation speed command signal of the aerator to the inverter 7, thereby controlling the rotation speed of the aerator drive motor and automatically controlling the dissolved oxygen amount. doing.

When the aerator is operated by controlling the rotation speed, for example, the water level in the water channel 1 rises,
When the immersion depth of the aerator becomes deep and the torque applied to the aerator becomes overloaded due to this,
The operation of the aerator is stopped in order to protect the aerator, such as to prevent burnout of the motor. However, if the aerator is out of operation for a long time without an operator, the sewage treatment by the oxidation ditch is interrupted even though the aerator is not malfunctioning, which may hinder the operation of the entire sewage treatment facility. .

[0005]

SUMMARY OF THE INVENTION According to the present invention, when an overload is applied to an aerator for any reason, the aerator can be automatically prevented from being overloaded without stopping the operation of the aerator, and the operation can be continued. It aims at a control method that can be performed.

[0006]

Means for Solving the Problems A detector 8 for detecting a torque applied to the aerator 3 of the oxidation ditch, a control device 6 for arithmetically processing a signal from the detector 8, and a command from the control device 6 When the signal from the detector 8 detects that the torque applied to the aerator 3 has become overloaded, the control device 6 sends the signal to the inverter 7.
The deceleration command of the aerator is given to the aerator 3 so that the aerator 3 is decelerated to avoid an overload state.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for controlling an aerator 3 according to the present invention will be described with reference to FIG. A DO sensor 5 for detecting the dissolved oxygen content of the mixed liquid in the ditch is installed in the non-terminal waterway 1 for performing the oxidation ditch, and a detection signal from the sensor 5 is automatically detected.
Input to the control device 6 having the O control function,
Means for automatically controlling the dissolved oxygen amount by controlling the rotation speed of the aerator drive motor by inputting the optimum rotation speed command signal of the aerator to the inverter 7 after being processed by the control device 6 is the same as the conventional method.

According to the present invention, during the automatic control operation of the aerator, a large amount of inflowing sewage temporarily flows in, and when the water level in the tank 1 rises and the aerator 3 is overloaded, the torque applied to the aerator is reduced. A torque detector 8 for detection is provided, and a detection signal from the torque detector 8 is input to the control device 6. Note that some of the torque detectors detect a current value of the aerator driving motor.

When it is detected that the torque detection signal inputted to the control device 6 is equal to or more than a set value, a timer is operated to issue a minimum permissible rotation speed command signal of the aerator for a predetermined time (30 minutes to 1 hour). 7, the aerator is switched to the low-speed rotation operation during that time. The permissible minimum rotation speed of the aerator is
This is the minimum speed at which the sludge does not settle to the bottom of the tank. Then, after a predetermined time has elapsed, the normal oxidation ditch operation is switched again.

Next, the operation of the present invention will be described.
During the normal operation of the oxidation ditch, the detection signal from the DO sensor 5 is subjected to arithmetic processing by the control device 6 and the optimum rotation speed command signal of the aerator is input to the inverter 7.
The operation of the inverter 7 controls the rotation speed of the motor of the aerator, and controls the aerator so that the dissolved oxygen amount of the mixed liquid in the ditch becomes an optimum value. During the above normal operation,
For some reason, the water level in the tank 1 rises, the immersion depth of the aerator increases, and the torque applied to the aerator gradually increases. The torque is detected by the torque detector 8,
When the torque detection signal is input to the control device 6 and the detection signal reaches the allowable maximum set value, the timer is activated by a command from the control device 6 and the aerator 3 is switched from the normal operation to the timer operation.

When the operation is switched to the timer operation, the inverter 7 reduces the rotation speed of the aerator until the sludge can maintain a circulating flow that does not deposit on the bottom of the tank for a timer set time (about 30 minutes to 1 hour). The deceleration speed command signal is input to the aerator to reduce the rotation speed of the aerator, and the aerator is prevented from being overloaded. Therefore, the efficiency of the aeration treatment is reduced during the timer operation, but the inflow sewage is circulating in the tank 1 so as not to deposit sludge. Then, when the timer set time elapses, the operation is switched to the normal operation. If the water level in the tank 1 drops during the timer operation, the normal oxidation ditch operation is restarted.

[0011]

According to the present invention, when the oxidation ditch is operated, when the aerator falls into an overload state for any reason, the rotation speed of the aerator is temporarily stopped without sludge deposition without stopping the operation of the aerator. If the operation is continued at a reduced speed to the extent that the aerator is not out of order, the normal rotation speed is restored and the aeration process is restarted, so that the disadvantage of stopping the operation of the aerator can be eliminated.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one embodiment of a method for controlling an aerator according to the present invention.

FIG. 2 is a schematic explanatory view of a known oxidation ditch.

FIG. 3 is an explanatory diagram of control means of a known aerator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-terminal waterway 2 Partition wall 2 'Rectifier wall 3 Vertical aerator 4 Overflow weir 5 DO sensor 6 Control device 7 Inverter 8 Torque detector

Claims (2)

[Claims] 1. A detector (8) for detecting a torque applied to an aerator of an oxidation ditch tank, a control device (6) for arithmetically processing a signal from the detector, and a control device (6). An inverter (7) for changing the rotation speed of the aerator (3) according to a command is provided, and when a signal from the detector (8) detects that the torque applied to the aerator (3) is in an overload state, control is performed. A method for controlling an aerator for oxidation ditch, characterized in that a deceleration command of an aerator is given from a device (6) to an inverter (7) to decelerate the aerator (3) to avoid an overload condition. 2. The aerator for oxidation ditch according to claim 1, wherein the deceleration operation of the aerator is operated by a timer for a predetermined time, and after a predetermined time has elapsed, the operation is switched to a normal oxidation ditch operation. Control method.