JPS631885B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to control of injection of flocculant in water treatment.

Conventionally, there has been a device of this type as shown in FIG. Figure 1 shows a conventional example using a feedback injection control device. In the figure, 1 is a rapid stirring tank that injects a flocculant into raw water, 2 is a settling tank that includes a flocculator that mixes the raw water turbidity and the flocculant, and 3 is the above-mentioned sedimentation tank. 4 is a flocculant flow meter; 5 is a flocculant injection operator for controlling the flocculant flow rate; 6 is a controller for controlling the flocculant flow rate; An injection amount calculator that calculates the injection amount from the raw water flow rate by the raw water flow meter 3 and the injection rate determined by the ratio calculator 9; 8 is a treated water turbidity meter that measures the treated water turbidity, which is a control amount; 10 is a settling basin This is a treatment water setting turbidity calculator that calculates a desired treatment water turbidity setting value from the sedimentation tank outlet turbidity setting value set by the outlet turbidity setting device 11.

In the configuration shown in FIG. 1, when the operator sets the set value of the turbidity at the outlet of the settling tank 2 using the setting device 11,
The signal is sent to the treated water setting turbidity calculator 10, and the set value of the treated water turbidity to be controlled by feedback control is calculated using a predetermined functional formula. The calculated treated water turbidity set value is sent to the ratio calculator 9, where it is compared with the treated water turbidity value measured by the treated water turbidity meter 8, and the flocculant injection rate (ratio) is determined according to the deviation between the two. is calculated and sent to the injection amount calculator 7. The injection amount calculation unit 7 calculates the amount of flocculant injection based on the injection rate determined by the ratio calculation unit 9 and the raw water flow rate determined by the raw water flow meter 3. Then, this injection amount is sent to the injection amount controller 6, and an appropriate amount of coagulant is injected into the rapid stirring pond 1 by this controller, the feedback signal of the flocculant flow meter 4, and the operation device 5, and the raw water is It is becoming mixed with Furthermore, after this, the raw water forms flocs in a flocculator, and the flocs are settled in a sedimentation basin behind the flocculator to reach the desired outlet turbidity before entering the next filter basin.

Because the conventional flocculant injection control device is configured as described above, the raw water flow rate signal is not input to the treated water turbidity calculator, and therefore, when the raw water flow rate changes, the settling tank 2 outlet turbidity and It has the disadvantage that it cannot follow changes in the functional expression of treated water turbidity, and can only be used when the raw water flow rate is always constant.

The present invention was made in order to eliminate the drawbacks of the conventional ones as described above, and by sending changes in the raw water flow rate to a treated water setting turbidity calculator, the treated water turbidity setting value according to the raw water flow rate can be determined. It is an object of the present invention to provide a flocculant injection control device that can calculate and thereby control the turbidity at the outlet of a sedimentation tank.

Hereinafter, one embodiment of the present invention will be described with reference to FIG. 2, in which the same parts as in FIG. 1 are denoted by the same reference numerals.
In FIG. 2, the raw water flow rate measured by the raw water flow meter 3 is inputted to the treated water setting turbidity calculator 12 according to the present invention together with the set value of the sedimentation tank outlet turbidity set by the sedimentation tank outlet turbidity setting device 11. ing. Others are the same as before.

Therefore, in the configuration shown in FIG. 2, when the operator sets the set value of the settling tank outlet turbidity using the setting device 11, the signal is sent to the treated water setting turbidity calculator 10, where the predetermined value is calculated. The set turbidity of the treated water is determined by the calculated function formula (residence time differs depending on the raw water flow rate, so the functional formula differs depending on the raw water flow rate), the raw water flow rate measured by the raw water flow meter 3, and the set value by the setting device 11. calculated.

The subsequent operation is the same as before, and the calculated treated water turbidity set value is sent to the ratio calculator 9, where it is compared with the treated water turbidity value measured by the treated water turbidity meter 8, and the difference between the two is The flocculant injection rate (ratio) is calculated according to the above and sent to the injection amount calculator 7. The amount of flocculant to be injected is calculated from the injection rate by the injection amount calculator 9 and the raw water flow rate by the raw water flow meter 3. Then, this injection amount is sent to the injection amount controller 6, and an appropriate amount of coagulant is injected into the rapid stirring pond 1 by this controller, the feedback signal of the flocculant flow meter 4, and the operation device 5, and the raw water is It is becoming mixed with Furthermore, after this, the raw water forms flocs in a flocculator, and the flocs are settled in a sedimentation basin behind the flocculator to reach the desired outlet turbidity before entering the next filter basin.

In the above embodiment, feedback control has been described, but it goes without saying that the same effect can be achieved when the feedback control is combined with the feedback control.

As described above, according to the present invention, since the raw water flow rate signal is input to the treated water setting turbidity calculator, the sedimentation tank outlet turbidity can be easily controlled to the set value even if the raw water flow rate changes, and stable turbidity can be maintained. of water.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional flocculant injection control device, and FIG. 2 is a block diagram showing a flocculant injection control device according to an embodiment of the present invention. 1... Rapid stirring pond, 2... Sedimentation tank, 3... Raw water flow meter, 4... Coagulant flow meter, 5... Coagulant injection operator, 6... Injection amount controller, 7... Injection amount Computing unit, 8...Treatment water turbidity meter, 9...Ratio computing unit, 1
0, 12... Treated water setting turbidity calculator, 11... Sedimentation tank outlet turbidity setting device. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A raw water flow meter that measures the flow rate of raw water to remove suspended matter, a treated water turbidity meter that measures the turbidity of treated water,
a setting device for setting the turbidity at the outlet of the settling tank; a computing device for calculating the turbidity setting value of the treated water based on the setting value by the setting device and the raw water flow rate; A ratio calculator that calculates the flocculant injection ratio from the set value by the calculator, an injection amount calculator that calculates the flocculant injection amount based on the ratio by the ratio calculator and the raw water flow rate, and an injection amount that controls the flocculant injection amount. A flocculant injection control device for water treatment, comprising a controller, a flocculant injection operator, and a flocculant flowmeter.