JPH0817893B2 - Coagulant injection controller for water purification plants - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial field of application) The present invention provides a coagulation of a water purification plant equipped with an injection amount adjusting means for adjusting an injection amount of a coagulant to be injected into raw water of a water purification plant. The present invention relates to a drug injection control device.

(Prior Art) Generally, in a water purification plant, since the particle size of suspended particles in the raw water is small, a flocculant is injected to form a floc and precipitate. Therefore, in water purification plants, it is important to form good flocs, maintain good precipitation efficiency, and obtain a good supernatant liquid. Therefore, the injection amount of coagulant is controlled so that good flocs can be obtained. There is a need to. FIG. 2 shows a conventional flocculant injection control device for a water purification plant. In FIG. 2, the flow rate of the raw water 1 flowing into the landing well 20 is detected by the flow meter 2. Then, the turbidity (concentration of suspended matter) of the raw water 1 flowing into the landing well 20 is detected by the turbidity meter 31. Based on the flow rate of the raw water 1 detected by the flow meter 2 and the turbidity detected by the turbidity meter 31, the amount of suspended matter contained in the raw water 1 flowing into the landing well 3 is calculated by the calculator 33. To be done. The calculated amount of suspended matter is multiplied by a predetermined ratio (coagulant injection rate), and the target value of the coagulant injection amount is output from the target injection amount calculator 35.

On the other hand, the coagulant 10 is transferred by the pump 11 and
It is injected into the mixing pond 21 through 12 and the flow control valve 13.
Then, the injection amount of the coagulant 10 at this time is controlled as follows. That is, the controller 9 outputs an operation signal such that the deviation between the flow rate of the coagulant detected by the flow meter 12 and the target value of the coagulant injection amount calculated by the target injection amount calculator 35 becomes zero. . Based on this operation signal, the valve opening of the flow rate adjusting valve 13 is adjusted by an actuator (not shown), so that the flow rate of the coagulant is controlled to a target value. Then, the injection amount of the coagulant 10 thus controlled is injected into the raw water 1 in the mixing basin 21, and the raw water 1 is agitated by the agitator 22. The agitated treated water is sent to the floc formation pond 23 and the flocculator 24
Form a floc. The flocs formed are settled in settling basin 25. The treated water in which the flocs are precipitated is sent to the filter basin 26 and filtered. The filtered treated water is sent to and stored in the water purification pond 27.

(Problems to be Solved by the Invention) The turbidity meter 31 used in such a conventional flocculant injection control device is affected by the particle size of the turbidity and the coloring of the solution.
Absorbance method (A), scattered light measurement method (S), fluorometer method (T), and macroscopic turbidimetric method (V) when changing the particle size of the turbidity without changing the concentration of the turbid mass The change in the turbidity indication measured by the is shown in FIG. It can be seen that the turbidity indication greatly changes depending on the particle size.

On the other hand, the turbidity of raw water has a particle size distribution, but the particle size distribution changes significantly during rainfall. Therefore, even if the particle size distribution of the turbidity of the raw water changes to the smaller side or to the larger side, the turbidity indicator measured by the turbidimeter does not show the correct value of the turbid mass. Further, as shown in FIG. 4, if the particle size distribution of suspended matter in the raw water changes, the optimum injection rate of the coagulant also changes. That is, the larger the particle size, the smaller the optimum injection rate of the aggregating agent, and conversely, the smaller the particle size, the larger the optimum injection rate of the aggregating agent. Furthermore, even if the turbid mass in the raw water changes, the optimum injection rate of the coagulant changes as shown in FIG. That is, the optimum injection rate decreases as the turbid mass increases, but the optimum injection rate becomes almost constant when the turbid mass exceeds a certain value.

Therefore, as in the conventional flocculant injection control device, the turbid mass contained in the raw water 1 is calculated by the calculator 33 based on the turbidity of the raw water 1 and the detected value of the flow rate, and the calculated turbid mass and a predetermined value are calculated. The product of the ratio (coagulant injection rate) (target value of coagulant injection amount) is calculated by the target injection amount calculator 35,
The control device that controls the coagulant injection amount based on the calculated target value of the coagulant injection amount can perform appropriate coagulant injection when the particle size distribution of suspended matter changes, such as during rainfall. No
An excess or deficiency of the coagulant occurs. If the flocculant is insufficient, the flocs do not grow sufficiently even if they are agitated by the flocculator 24 in the floc formation pond 23, causing sedimentation failure in the sedimentation pond 25, causing a load on the filtration pond 26, and a purification water pond 27.
There was a problem that the turbidity of the treated water increased, and conversely, when the coagulant was too much, the coagulant was wasted.

The present invention has been made in view of the above problems, and even if the particle size distribution of suspended matter changes, such as during rainfall, the coagulant is injected just enough to obtain good treated water. An object of the present invention is to provide a coagulant injection control device for a water purification plant.

[Structure of Invention]

(Means for Solving the Problem) The present invention relates to a coagulant injection control device for a water purification plant, which comprises an injection amount adjusting means for adjusting the injection amount of the coagulant injected into the raw water of the water purification plant. Flow rate detector that detects the flow rate of raw water, image capturing means that captures an image of turbidity in raw water, and the image captured by this image capturing means is analyzed to determine the particle size and particle area of the turbidity. Measure
Image processing means for obtaining the total particle size distribution and particle volume of suspended matter contained in raw water, and the total amount of particle size distribution and particle volume obtained by this image processing means, as well as the detection value of the flow rate detector. Based on this, an optimum injection amount of the coagulant is calculated, and an arithmetic means for transmitting this to the injection amount adjusting means as an injection amount target value is provided.

(Operation) According to the coagulant injection control device for a water purification plant according to the present invention configured as described above, based on the particle size distribution and the total amount of the particle volume obtained by the image processing means, and the detection value of the flow rate detector. The optimum injection amount of the coagulant is calculated by the calculating means, and the injection amount of the coagulant is adjusted by the injection amount adjusting means based on the calculated optimum injection amount.
Therefore, even if the particle size distribution of suspended matter changes, such as during rainfall, the coagulant can be injected without excess or deficiency, and good treated water can be obtained.

(Example) FIG. 1 shows an example of a flocculant injection control device (hereinafter, referred to as a control device) for a water purification plant according to the present invention. The control device of this embodiment includes a landing well 20, a mixing pond 21, an agitator 22, a floc formation pond 23, a flocculator 24, a settling pond 25, and a filtration pond 2.
6, which is used in a water purification plant having a water purification pond 27, a flow meter 2, a sampling pump 3, a diluting device 5, an image capturing device 6, an image processing device 7, an arithmetic device 8, A controller 9, a pump 11, a flow meter 12, and a flow rate adjusting valve 13 are provided. In addition, the arithmetic unit 8 is an optimum injection rate arithmetic unit 8a,
It has an inflow turbid mass calculation unit 8b and an optimum injection amount calculation unit 8c. It should be noted that the description other than the sampling pump 3, the diluting device 5, the image capturing device 6, the image processing device 7, and the arithmetic device 8 has already been described in the section of the related art, and thus the description thereof is omitted.

The sampling pump 3 samples the raw water 1 from the landing well 3. The diluting device 5 dilutes the sampled raw water 1 with the diluting water 4 at a predetermined dilution rate K. This dilution ratio K is normally set automatically according to the total amount V of the particle volume of suspended matter in the sampled raw water, which is the output of the image processing device 7 described later, but can also be set manually. It is possible. The image capturing device 6 passes the raw water diluted by the diluting device 5 through a flow-type thin cell (not shown) and irradiates the raw water with a strobe light source (not shown) to remove turbidity in the raw water. Enlarge and capture a still image. The image processing device 7 analyzes the image captured by the image capturing device 6 to measure the particle size and the particle area of the turbidity, and determines the particle size distribution and the particle volume of the turbidity contained in the diluted raw water. Obtain the total amount V. The optimum injection rate calculation unit 8a of the calculation device 8 calculates the optimum injection rate α of the coagulant 10 based on the particle size distribution obtained by the image processing apparatus 7, the total amount V of the particle volume, and the dilution rate K. . The inflow turbid mass calculation unit 8b calculates the total volume V of the particle volume and the dilution ratio K,
And the flow rate Q _{i of the} raw water 1 detected by the flow meter 2
Based on, the inflow turbid mass M contained in the inflowing raw water 1
Is calculated. The optimum injection amount calculator 8c calculates the optimum injection amount Q _m of the coagulant from the optimum injection rate α and the inflow turbid mass M.

Next, operation of the embodiment will be described. The flow rate of the raw water 1 flowing into the landing well 20 is detected by the flow meter 2. The raw water 1 flowing into the landing well 20 is sampled by the sampling pump 3. Raw water 1 sampled is diluted device 5
Is diluted with dilution water 4. The diluted raw water 1 is
It is sent to the image capturing device 6, passed through a flow-type thin cell, irradiated with strobe light, and a still image of the turbidity in the raw water 1 is enlarged and captured. The image captured by the image capturing device 6 is sent to the image processing device 7 for processing, and the particle size and particle area of the suspended particles in the screen are measured. Then, based on the measured particle size and particle area, the image processing apparatus 7 obtains the particle size distribution of the turbid particles in the screen and the total amount V _{i of the} particle volume. Note that in the above measurement, one sample may include a large error in the measured value, so several images are continuously captured, the above-described processing is performed, and the averaging processing is performed. That is, the average value V of the total amount of particle volumes is n when the number of samples is n. Becomes

Based on the particle size distribution and the total amount V of the particle volume obtained by the image processing device 7 and the dilution ratio K,
Aggregation based on the preset relationship between the particle size distribution and the optimum injection rate (see FIG. 4), and the relationship between the turbid mass (proportional to the product of V and K) and the optimum injection rate (see FIG. 5). The optimum injection rate α of the agent 10 is calculated by the optimum injection rate calculation unit 8a. In addition, the flow rate Q of the raw water 1 detected by the flow meter 2
_The inflow turbid mass M is calculated by the inflow turbid mass calculator 8b using the following equation (2) based on _i , the total amount V of the particle volume obtained by the image processing device 7, and the dilution ratio K. .

M = K × V × Q _i × ρ (2) Here, ρ represents the specific gravity of the suspended matter. The product of the inflow turbid mass M and the optimum injection rate α is calculated by the optimum injection amount calculation unit 8c,
The product (α · M) becomes the optimum injection amount Q _{m of the} coagulant. That is, Q _m = α · M (3)

The controller 9 outputs an operation signal for the valve opening of the flow rate adjusting valve 13 so that the deviation between the optimum injection amount Q _m and the actual injection amount of the coagulant 10 detected by the flow meter 12 becomes zero. It Based on this operation signal, the valve opening of the flow rate adjusting valve 9 is operated by an actuator (not shown), and the injection amount of the coagulant 10 injected into the mixing basin 21 becomes optimum.

As described above, according to the present embodiment, even when the particle size distribution of the turbidity of the raw water changes due to rainfall or the like, the particle size distribution of the raw water and the inflow turbid mass can be accurately measured by the image processing device 7, so that the coagulant is prevented It can be injected without deficiency, which makes it possible to always obtain good treated water and prevent the coagulant from being wasted.

〔The invention's effect〕

According to the present invention, it is possible to inject the coagulant without excess or deficiency even if the particle size distribution of the suspended matter varies as in the case of rainfall, which makes it possible to obtain good treated water and waste the coagulant. Can also be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a flocculant injection control device for a water purification plant according to the present invention, FIG. 2 is a block diagram showing a conventional flocculant injection control device for a water purification plant, and FIG. A graph showing changes in the turbidity indication measured by the absorbance method, the scattered light measuring method, the fluorometer method, and the naked eye turbidimetric method, respectively, when the particle size of the turbidity is changed without changing the concentration, respectively. FIG. 5 is a graph showing the relationship between the particle meter and the optimum injection rate, and FIG. 5 is a graph showing the relationship between the turbid mass and the optimum injection rate. 1 ... Raw water, 2 ... Flow meter, 3 ... Sampling pump, 4 ... Diluting water, 5 ... Diluting device, 6 ... Image capturing device, 7 ... Image processing device, 8 ... Computing device, 8a: Optimum injection rate calculation unit, 8b: Inflow turbid mass calculation unit, 8c: Optimal injection amount calculation unit, 9 ... Controller, 10 ... Flocculant, 11 ... Transfer pump, 12 ... Flowmeter , 13 …… Flow control valve, 20 …… Water well, 21 …… Mixing pond, 22 …… Stirrer, 23 …… Floc formation pond, 24 …… Flocculator, 25 …… Sedimentation pond, 26 …… Filtration pond , 27 …… Purification pond.

Claims (1)

[Claims] 1. A coagulant injection control device for a water purification plant, comprising an injection amount adjusting means for adjusting an injection amount of a coagulant injected into the raw water of the water purification plant, wherein the flow rate of the raw water flowing into the water purification plant is detected. A flow rate detector, an image capturing means for capturing an image of the turbidity in the raw water, and an image captured by the image capturing means is analyzed to measure the particle diameter and particle area of the turbidity, and Based on the image processing means for determining the particle size distribution and the total amount of the particle volume of the suspended matter contained therein, and the total amount of the particle size distribution and the particle volume determined by this image processing means, and the detection value of the flow rate detector. A coagulant injection control device for a water purification plant, comprising: an arithmetic means for calculating an optimum injection amount of the coagulant and sending it to the injection amount adjusting means as an injection amount target value.