JPH07144195A - Chlorine injection control system - Google Patents

Abstract

PURPOSE:To be most preferable from a broad view point and to prevent deterioration of water quality by decreasing a phenomenon of an excessive injection of chlorine or a short injection, in a chlorine injection control system at a sewerage treating plate. CONSTITUTION:Turbidity TB of treating water flowing in a chlorine mixing pool, water temp. TP of the mixing pool, residual chlorine DC of discharging water from the mixture pool and a manual analysis estimated value of the treating water are defined as input variables, and the chlorine injection quality is performed with fuzzy interference by a fuzzy interference means 7 and a chlorine injection objective value is obtained with a ratio against a discharge flow rate, a chlorine injection machine 10 is controlled by a deviation from an actual chlorine injection quality.

Description

Detailed Description of the Invention

[0001]

[Industrial application] The present invention relates to a chlorine injection control system optimized by introducing fuzzy reasoning into chlorine injection control of a sewage treatment plant by a control device such as a process control.

[0002]

2. Description of the Related Art In the current chlorine injection control, it is assumed that the quality of treated water in a sewage treatment plant is almost constant.
A chlorine injection control method is generally used in which chlorine is injected at a fixed ratio to the amount of treated water.

[0003]

When the sewage treatment plant is conceptually expressed from a qualitative viewpoint, the influent sewage is treated by various processes such as a sedimentation basin; a first sedimentation basin, an aeration tank, and a final sedimentation basin. This is a series of processes in which the resulting treated water is further sterilized and then discharged as discharged water.

In the case of discharge, there are standards for discharged water quality such as total amount regulation, and residual chlorine is also specified.

Generally, it is said that biochemical treatment such as a sewage treatment plant has redundancy with respect to reaction response to follow a sudden change. The treated water is affected to some extent by qualitative and quantitative fluctuations of inflowing sewage such as time of day.

Therefore, the quantitative control system in which chlorine is injected at a constant ratio to the amount of treated water has the following problems.

(1) It is not a control considering the quality of treated water.

(2) It is not a control that considers the residual chlorine content of discharged water, which is one of the evaluation factors for chlorine injection.

(3) Since the main control is quantitative control and qualitative factors are not taken into consideration, it is not macro-optimal control and
There is a possibility that the chemical consumption due to over-injection and the electric power consumption of the injecting pump increase, resulting in high cost and deterioration of discharged water quality due to small injection.

The present invention has been made in view of the above problems, is macroscopically optimal, and enables stable chlorine injection control that reduces over-injection and low-injection, and can reduce the quality of discharged water during low-injection. The purpose is to provide a chlorine injection control method for prevention.

[0011]

The present invention relates to a chlorine injection control system for a sewage treatment plant, which introduces treated water flowing from a treatment process into a chlorine mixing tank to inject chlorine to prevent deterioration of water quality. Turbidity signal of treated water flowing into the pond,
Fuzzy inference means for calculating the chlorine injection amount of the output variable by fuzzy inference using the water temperature signal of the mixing pond, the residual chlorine signal of the discharged water discharged from the mixing pond and the manual analysis evaluation value of the treated water as input variables, and the chlorine injection amount. And a ratio adjusting means for calculating the chlorine injection amount target value by calculation based on the injection ratio by inputting the discharge flow rate signal of the discharged water, and the deviation between the injection amount target value and the actual chlorine injection amount injected into the mixing pond. And PI adjusting means for controlling the chlorine injector.

[0012]

[Function] Qualitative factors such as turbidity of treated water, water temperature of mixing pond, residual chlorine of discharged water, and manual analysis evaluation value of treated water are incorporated into fuzzy inference means to infer and calculate chlorine injection amount based on fuzzy rules. . The ratio adjustment means calculates this inferred value based on the discharge flow rate and the set injection rate to calculate the chlorine injection target value. Also, by the PI adjusting means,
The target value is compared with the actual amount of chlorine injected into the chlorine mixing pond, and the chlorine injector is controlled according to the deviation.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. 1, which is a system configuration diagram. 1 is a chlorine mixing pond. A turbidimeter 2 detects the turbidity TB of the inflowing treated water. Three
Detects the water temperature TP of the chlorine mixing pond with a thermometer. A flow meter 4 detects the discharge flow rate Q of the chlorine mixing pond. A residual chlorine meter 5 detects residual chlorine DC in the discharged water. 6
Is a chlorine injection amount detector. Reference numeral 7 is a fuzzy inference means, which infers the chlorine injection amount RT by the detection element and the hand analysis evaluation value of the treated water. 8 is a ratio adjusting means,
The chemical injection ratio to the discharge flow rate Q is set,
The chlorine injection amount RT and the discharge flow rate Q are input and the chlorine injection amount target value RTM is calculated. Reference numeral 9 is a PI adjusting means, which inputs the chlorine injection target value RTM and the actual actual chlorine injection amount RTJ and sends an injection command of a deviation output to the chlorine injector 10.

Next, the operation of the embodiment will be described.

Inflow to chlorine mixing pond 1 Turbidity signal TB detected by turbidity meter 2 provided in treated water, water temperature signal TP detected by thermometer 3 provided in chlorine mixing pond 1, chlorine mixing pond 1 The residual chlorine signal DC detected by the residual chlorine meter 5 provided in the discharge channel of the above is input to the fuzzy inference means 7. At the same time, the manual analysis evaluation value BH obtained by evaluating the values obtained by manually analyzing the components of the treated water, such as the organic substances and ammonia, is input to the fuzzy inference means 7. This evaluation value is used for correction when the water quality of treated water cannot be specified only by turbidity.

In the fuzzy inference means 7, FIG. 2 shows the hand analysis evaluation value BH which is the input variable, the turbidity signal TB, the water temperature signal TP, the residual chlorine amount signal DC and the chlorine injection amount signal RT which is the output variable. Like H (High), M
A fuzzy function having three stages of (medium) and L (Low) is defined, and a rule matrix for inference is defined as shown in Table 1.

[0017]

[Table 1]

That is, the following IF-THEN rules IF TB = H and and DC = L THEN RT = H IF TB = H and TP = H and DC = L THEN RT = M IF TB = M and TP = L and DC = L THEN RT = M IF BH = H and TB = M and and DC = L THEN RT = M IF TB = L and TP = L and DC = L THEN RT = L IF BH = L and TB = L and TP = M and DC = L THEN RT = M IF BH = H and TB = M and DC = L THEN RT = H IF BH = L and TB = M and DC = H THEN RT = L Inferred.

The inferred chlorine injection amount RT is input to the ratio adjusting means 8 and the flow meter 4 provided in the discharge channel.
The discharge flow rate Q detected in step 3 is input, calculation is performed based on the injection ratio of the chlorine injection amount to the preset discharge flow rate, and the chlorine injection target value RTM is calculated. This target value R
TM is input to the PI adjusting means 9, and the actual chlorine injection amount RTJ detected by the chlorine injection amount detector 6 and input is compared, and an injection command, which is a deviation output thereof, is given to the chlorine injection device 10, and the actual injection chlorine is supplied. Control is performed so that the amount RTJ matches the target value RTM.

[0020]

INDUSTRIAL APPLICABILITY The present invention employs fuzzy control in consideration of qualitative factors such as turbidity of treated water, water temperature of mixing pond, residual chlorine of discharged water, and manual analysis evaluation value of treated water.
Macroscopically optimum chlorine injection control became possible, problems of over-injection and low-injection could be reduced, and stable chlorine injection was achieved. In addition, the cost of chemicals is low and the power consumption of infusion pump is energy saving. In addition, it is possible to prevent the quality of discharged water from deteriorating when a small amount of water is injected. Furthermore, since fuzzy reasoning is used, flexible algorithm configuration is possible, and there are many excellent effects such as easy change and modification of rules.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an embodiment of the present invention.

FIG. 2 is a membership function of input / output variables.

[Explanation of symbols]

 1 ... Chlorine mixing pond 2 ... Turbidity meter 3 ... Thermometer 4 ... Flowmeter 5 ... Residual chlorine meter 6 ... Chlorine injection amount meter 7 ... Fuzzy inference means 8 ... Ratio adjusting means 9 ... PI adjusting means 10 ... Chlorine injector TB ... Turbidity signal TP ... Water temperature signal DC ... Residual chlorine signal BH ... Hand analysis evaluation value RT ... Chlorine injection amount signal RTM ... Chlorine injection amount target value RTJ ... Actual chlorine injection amount Q ... Discharge flow rate

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Claims (1)

[Claims] 1. A chlorination control system for a sewage treatment plant, which introduces treated water flowing from a treatment process to a chlorine mixing tank to inject chlorine to prevent deterioration of water quality. A fuzzy inference means for calculating the chlorine injection amount of the output variable by fuzzy inference using the temperature signal, the water temperature signal of the admixture pond, the residual chlorine signal of the discharged water discharged from the admixture pond and the manual analysis evaluation value of the treated water as an input variable; Ratio adjusting means for inputting the chlorine injection amount and the discharge flow rate signal of the discharged water and calculating a chlorine injection target value by calculation based on the injection ratio, the injection amount target value and the actual chlorine injection amount to be injected into the mixing pond A chlorine injection control system characterized by having a PI adjusting means for controlling the chlorine injection machine according to the deviation from the above.