JPH05169082A - Control unit for injection quantity of chemical - Google Patents

Abstract

PURPOSE:To make countermeasure against scum generation sure in the unit for sewage treatment by finding a chemical injection rate from the water temp. and pH value of an aeration tank to set the injection quantity according to the inflow water quantity and correcting the set value of the injection quantity by the weight of scum in a final settling basin. CONSTITUTION:The water temp. and pH value of an aeration tank 20 are detected by a water temp. meter 12 and a pH meter 11 respectively and sent the result to an injection rate setting arithmetic circuit 3 to calculate the injection rate. An injection quantity setting circuit 4 sets the injection quantity from the injection rate and a flow rate which is inputted from an inflow water flowmeter 10 to input it to an injection quantity correction circuit 5. The quantity correction circuit 5 corrects the set injection quantity by the scum weight of a final settling basin 21 which is input from a scum scale 15 to output it to PID 22. The PID 22 corrects the flow rate of the injected chemical which is output by an injection quantity flowmeter 13 to determine the operating speed of a chemical injection pump 14, causing the speed of the injection pump 14 to be controlled through a speed controller 23, permitting the injection quantity to be controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical injection amount control device used in a sewer water treatment plant.

[0002]

2. Description of the Related Art In the prior art, a sequential driving method using a timer or the like is performed instead of a continuous control method, and the driving judgment is made by an operator or by judging the amount of scum generated, Chemical injection was a constant injection method.

[0003]

Conventionally, since a quantitative batch injection method has resulted in waste of the amount of chemicals used and an operation method in which chemicals are injected after scum is generated, scum is used. There was a problem that the prevention of the transmission policy was delayed and the water mixed with the insufficiently treated scum leaked out.

[0004]

According to the present invention, a water thermometer for detecting the water temperature of an aeration tank, a PH meter for detecting a PH value of treated water in the aeration tank, and a weight of scum collected in a final settling tank are measured. With a scum scale to measure
An inflow rate flow meter that measures the flow rate of treated water flowing into the aeration tank, an injection rate setting calculation circuit that calculates the injection rate of the chemicals to be injected into the aeration tank from the water temperature and PH value, and an injection rate setting calculation circuit from this injection rate setting calculation circuit. The injection amount setting circuit that calculates the injection amount of the chemicals to be injected into the aeration tank from the output signal and the output signal of the flowmeter and the injection amount setting value output from this injection amount setting circuit is the output value of the scum scale. An injection amount correction circuit for correction and a PID for controlling the output of the injection amount correction circuit by adding the amount of chemical injection
A control circuit and a speed control device for controlling an operating speed of an infusion pump for injecting a chemical with an output value of the PID control circuit,
It is a chemical injection amount control device comprising.

[0005]

In the chemical injection amount control device according to the present invention,
The water temperature of the aeration tank is detected, the PH value of the treated water in the aeration tank is detected, the weight of the scum collected in the final settling tank is measured, and the flow rate of the treated water flowing into the aeration tank is measured to determine the water temperature and PH. Calculate the injection rate of the chemicals to be injected into the aeration tank from the values, calculate the injection rate of the chemicals to be injected into the aeration tank from the output signal from the injection rate setting calculation circuit and the output signal of the inflow rate flow meter, and set the injection rate setting circuit. The injection pump that corrects the set value of the injection amount output from the scum scale and controls the output of the injection amount correction circuit by adding the injection amount of the drug, and injects the drug with the output value of this PID control circuit. Control the driving speed of.

[0006]

EXAMPLE An example of the present invention will be described below. Figure 1
Is a water temperature gauge 12 that detects the water temperature of the aeration tank 20.
A pH meter 11 for detecting the pH value of the treated water in the aeration tank 20, a scum weight meter 15 for measuring the weight of scum collected in the final settling tank 21, and an aeration tank 20.
An inflow flowmeter 10 for measuring the flow rate of the treated water flowing into the
The injection rate setting calculation circuit 3 for calculating the injection rate of the chemical to be injected into the aeration tank 20 from the water temperature and the PH value, and the output signal from the injection rate setting calculation circuit 3 and the output signal of the inflow rate flowmeter 10 to the aeration tank 20. An injection amount setting circuit 4 for calculating the injection amount of the medicine to be injected, an injection amount correction circuit 5 for correcting the injection amount setting value output from the injection amount setting circuit 4 with the output value of the scum scale 15, and an injection amount correction PID control circuit 22 that controls the output of circuit 5 by adding the chemical injection amount
And a speed control device 23 for controlling the operating speed of the infusion pump 14 for injecting a drug with the output value of the PID control circuit 22, and for the purpose of suppressing scum levitation. Chemical injection (sulfuric acid band etc. as coagulant)
A control circuit determines the injection rate from the aeration tank temperature PH and the weight of scum generated, and starts injection control, a circuit that stops the control based on the weight of scum generated, the aeration tank temperature, and calculates the injection rate coefficient from the characteristic function obtained from the inflow. A correction value proportional to the amount of scum generated is added to the amount of chemical injection calculated by multiplication with the amount of water, and PID control is performed with the optimum amount of chemical injection as the target value.

That is, in order to prevent the waste of the amount of chemicals used, the batch control method is changed to the continuous control method, and the purpose is to measure the inflow water amount and grasp the environmental condition where scum is likely to occur in order to achieve the optimum continuous control method. The PH and temperature in the aeration tank are measured with a chemical injection rate of around 40 g / m ^3, which is a conventional method for quantitative chemical injection for a certain period of time.
In this control, the chemical injection rate is determined by factors such as the temperature of the inflowing sewage and PH to determine the optimum injection amount, and the chemical injection rate is determined by the factors of the inflowing sewage water temperature and PH for the following reasons. ..

[0008] That is, it is said that the cause of the scum is that the radiant bacteria abnormally proliferate in the aeration tank, and the main microorganism is Nocardia amaral (No.
cardia amaral), and temperature and PH are related to the environmental factors for growing this Nocardia, and FIGS. 2 and 3 show correlation diagrams showing the degree of growth. As shown in the figure, the growth amount of Nocardia is large near 24 to 30 ° C and 7.0 to 8.5 PH. Therefore, it is expected that the amount of scum generated in this vicinity will increase, and the chemical rate will also follow the correlation shown in FIGS.

Reference numeral 1 in FIG. 1 denotes a characteristic operation circuit of the PH meter, which shows a characteristic relationship as shown in FIG. PH value 6.5 to 8.
At 0 PH, the function output (PH) shows a variable value of 0.5 to 1.2.

Reference numeral 2 in FIG. 1 is a temperature characteristic calculation circuit, which shows a characteristic function as shown in FIG. At a temperature of 25 ℃ to 30 ℃,
The function output f (τ) shows a variable value of 0.5 to 1.2.

Reference numeral 3 in FIG. 1 is an injection rate setting arithmetic circuit.
It is a circuit that determines the injection rate of chemicals according to the water quality in the aeration tank.

Α _o = α (α _i f (PH) · fα ₂ · f
(Τ)), and the injection rate dimension is g / m ³ .

Here, α ₁ is 0.3 to 0.6 and α ₂ is 0.3
~ 0.6, α is usually 40 g / m ³ and injection rate α ₀ is 12 g / m ^3.
It takes a value of m ^{3 to} 57.6 g / m ³ .

In the injection amount setting circuit 4, the above injection rate is multiplied by the inflowing sewage amount to obtain a target amount of chemical liquid.

Next, in the injection amount correction circuit 5, the target injection amount setting value set by the injection amount setting circuit 4 is corrected by a signal from the scum weight scale 15 in proportion to the scum generation amount. .. In the calculation formula, α ₀ F + K · W.

Incidentally, K is a constant of 0.001 to 0.01, and W is a scum generation weight (g).

Then, the injection PID control of the medicine is performed by using the output signal of the injection amount correction circuit 5 as a target amount.

In the present control, when the scum is likely to occur, the signal determination circuits 6 and 7 and the operation determination circuit 8 issue an operation command for a circuit which is operated in advance.

The signal judging circuit 6 uses the PH in the aeration tank, and the signal judging circuit 7 uses the temperature judging circuit to judge the environmental conditions in which scum is likely to occur. Judgment is made by the judgment circuit 8 and an operation command is issued.

When the scum becomes less than the specified weight, the stop determination circuit 9 is used in consideration of the timing.

As the chemical used in this control, a sulfuric acid band which is often used as a coagulant is usually used. Since the sulfuric acid band itself is an acidic chemical, it should be acidified as shown in the PH value characteristic of FIG. Therefore, the generation of scum is suppressed. temperature
Since there is a factor that scum generation becomes high near 25 ° C, it is highly effective to suppress the scum generation by injecting a large amount of chemicals around this. Furthermore, by mounting a scum scale, chemical injection that correlates with the amount of scum generated can be injected. These factors measure the effective use of medicines.

[0022]

EFFECT OF THE INVENTION By incorporating the scum generation factor into the control arithmetic circuit, it is possible to optimally determine the chemical injection amount.

As a result, the effect of resource saving is great. In addition, since the start of injection is determined based on the amount of scum generated and the environmental condition in the aeration tank, it is possible to make a more standardized determination than the determination made by a conventional person, and prevent instability in plant operation.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a chemical injection amount control device showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of PH characteristics.

FIG. 3 is an explanatory diagram of temperature characteristics.

[Explanation of symbols]

 3 ... injection rate setting arithmetic circuit 4 ... injection amount setting circuit 5 ... injection amount correction circuit 11 ... PH meter 12 ... water thermometer 15 ... scum weight scale 14 ... injection pump 20 ... aeration tank 22 ... PID control circuit 23 ... speed control device

Claims (1)

[Claims] 1. A water thermometer for detecting a water temperature of an aeration tank, a PH meter for detecting a PH value of treated water in the aeration tank, and a scum scale for measuring the weight of scum collected in a final settling tank. An inflow rate flow meter for measuring the flow rate of treated water flowing into the aeration tank, an injection rate setting arithmetic circuit for calculating an injection rate of a chemical to be injected into the aeration tank from the water temperature and the PH value, and an injection rate setting The injection amount setting circuit for calculating the injection amount of the chemical to be injected into the aeration tank from the output signal from the arithmetic circuit and the output signal of the inflow amount flowmeter, and the injection amount setting value output from the injection amount setting circuit An injection amount correction circuit that corrects the output value of the scum scale, and a PID control circuit that controls the output of the injection amount correction circuit by adding the amount of chemical injection. And a speed control device for controlling the operating speed of an infusion pump for injecting the drug with the output value of the PID control circuit.