JPH0252522B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a control device for floc formation in a floc formation pond (mixing pond) of a water purification plant.

[Background of the Invention] In water purification plants, turbid substances in raw water are flocculated into flocs, and the flocs are allowed to settle. For this reason, it is essential to monitor the flocs in the floc formation pond (mixing pond).

Conventionally, in order to appropriately control the amount of coagulant injected, a method has been known in which the turbidity, particle size and surface area of raw water suspension are measured and the coagulant is injected (Japanese Patent Publication No. 59-29281). However, the quality of floc formation is not determined only by the surface area of the flocculant and raw water suspension, but is also affected by temperature and stirring, so even if conventional techniques are applied, it may not be possible to form a floc properly. Ta. For example, if the temperature is low or the stirring is not proper, flocculation cannot be achieved properly. For this reason, there was a problem in that the suspended particles that did not become flocs did not settle in the settling basin and clogged the basin.

Traditionally, water treatment plant maintenance managers have to check whether the amount of flocculant injected is appropriate or not.
It was visually monitored several times a day. Because it relies on visual inspection, it is not possible to measure the density of flocs even though it is possible to qualitatively determine the size of flocs. For this reason, it was not possible to know whether or not good flocs were formed that were easy to settle in the sedimentation basin.

On the other hand, recently, industrial television cameras (ITVs) have been used to monitor flocks in floc formation ponds, and photoelectric conversion devices have been used to change the shape of flocs, as described in Japanese Patent Application Laid-Open No. 1432926/1983. A method has also been devised to extract the corresponding electrical signals and monitor the shape and size of the flock.

However, a large particle size of the flocs does not necessarily mean that it is good, and even if the particle size and shape of the flocs are recognized based on known techniques, it is not possible to optimally form the flocs. That is, even if the particle size of flocs is large, if the density is low, the sedimentation speed in the sedimentation basin will be slow, and furthermore, micro flocs will be left behind during the sedimentation process, and the micro flocs will flow into the filter basin and become a load. On the other hand, even if the density of flocs is high, if the particle size is small, the flocs will be difficult to settle in the sedimentation basin, which will still cause a load on the filtration basin. As described above, there is a drawback that it is not possible to form flocs satisfactorily by simply knowing the particle size of the flocs based on known techniques.

[Object of the Invention] The object of the present invention is to provide a floc formation control device that can form flocs with good sedimentation properties at a minimum flocculant injection rate when forming flocs in a flocculation pond (mixing pond) of a water treatment plant. It is about providing.

[Summary of the Invention] Although methods for determining the particle size by image processing flocs are known, there has been no concept of measuring the density of flocs.

The present invention applies turbidity measurement technology and image processing technology to measure the floc density, calculates the floc density based on these measured values, and controls the floc formation status based on this calculated density value to obtain a good floc formation condition. It is characterized by forming flocs.

An outline of this will be explained below. The particle size of the flocs is determined using an industrial television camera and image processing, and the volume V of the flocs is calculated. Meanwhile, the turbidity of the raw water is measured using a turbidity meter. Since turbidity has a correlation with the weight of suspended matter, the weight M of the floc can be determined from the turbidity. Therefore, the floc density ρ can be calculated as M/V.

If the floc density ρ is small, this indicates that too much flocculant is being injected, so the flocculant injection rate is reduced. Conversely, if the density ρ of the flocs is large, this indicates a lack of flocculant, so the flocculant injection rate is increased. In this way, the flocculant injection rate and paddle rotation speed are controlled so that an optimal floc is formed.

[Embodiments of the Invention] FIG. 1 shows embodiments of the present invention. In FIG. 11, a turbidity meter 11 measures the turbidity of the landing well 10.
This turbidity measurement value Tu is calculated by the floc weight calculation device 23.
It is input to 0. The floc weight calculation device 230 calculates the total weight M of the inflowing suspended solids from the measured turbidity value Tu. The total weight signal M is sent to the flock density calculation device 2.
20 is input.

The rapid mixing pond 20 is provided with an agitator 21 . A flocculant is injected into the rapid mixing pond 20 from a flocculant injector 22 . The floc formation pond 30 is provided with three stirring paddles 31A, 31B, 31C.
31C are stirring motors 32A, 32B,
Rotationally driven by 32C. Stirring paddle 3
Between 1A, 31B, 31C are rectifying walls 33A, 33
It is divided by B.

The fine flocs flowing into the floc formation basin 30 from the rapid mixing basin 20 sequentially flow down the floc formation basin 30 and are sequentially stirred by stirring paddles 31A, 31B, and 31C. While the minute flocs flow down in the floc formation pond 30, they collide and coalesce to form a large floc 34. In this manner, the particle size of the flocs gradually increases while passing through the floc formation pond 30.

An imaging device 100 for converting the luminance signal of the image of the flock 34 into an electrical signal is disposed in the flock formation pond 30. The imaging device 100 includes an industrial television camera ITV. Image processing device 11
0 performs image processing of the flock 34 based on the electric signal obtained by the imaging device 100, and calculates the particle size arrangement and particle size distribution Fd. The calculation device 210 calculates the total floc volume Vt from the particle size distribution Fd calculated by the image processing device 110. Flock volume calculation device 2
The total floc volume Vt calculated in step 10 is input to the floc density calculation device 220.

The floc density calculating device 220 calculates the average floc density ρ from the total weight M of the inflowing suspended solids and the total floc volume Vt using the following equation.

ρ=M/Vt (1) The flocculant injection calculation device 200 receives the signal of the floc density ρ calculated by the floc density calculation device 220 and calculates the flocculant injection amount A. The flocculant injection machine 22 receives the signal of the flocculant injection amount A and operates the flocculant injection amount.

Flock 3 formed in the floc formation pond 30
4 flows into the sedimentation tank 40 and is settled and removed. The supernatant water from which the flocs 34 have been removed flows into a filter pond 50. In the filter basin 50, remaining minute flocs that were not removed in the settling basin 40 are filtered and removed. The water that has passed through the pond 50 is supplied to consumers via a drainage pond (not shown), a reservoir (not shown), and the like.

FIG. 2 shows an imaging device 100 and an image processing device 110.
A detailed diagram of an example is shown. . The ITV 130 fixed in the airtight container 120 has an observation window 121 made of a transparent material such as glass using a close-up lens 131.
The floc 3 in the floc formation pond 30 through
Enlarge and recognize the image of 4. Wiper drive device 12
The wiper 122 driven by the wiper 122 is operated periodically to remove dirt from the surfaces of the observation window 121 and the back screen 124.
The back screen 124 is provided to accurately recognize flock groups with high contrast.
It is installed in front of 21. back screen 12
4 is preferably a dark color in order to accurately recognize white flocks with high contrast. The light-shielding cover 142 is provided to darken the surroundings where the ITV 130 is arranged and to maintain a constant illuminance only by the lamp 140. By providing the light-shielding cover 142, the image of the flock group is not affected by changes in surrounding illuminance. A plurality of lamps 140 are installed, and irradiate the flocks 34 from multiple sides. In addition, in FIG. 2, an illuminance controller 141 is provided to keep the illuminance constant even without providing the light shielding cover 142, and the illuminance is controlled to be constant at appropriate times according to changes in the surrounding illuminance. As the lamp 140, an instantaneous light emitting stroboscope or the like may be used in order to accurately recognize the floc regardless of its movement. Jiyama board 125A, 125B, 125C
are provided in the floc formation pond 30 so as to suppress the movement of water as much as possible and so as not to block the illumination. Therefore, an image of a group of flocs in a flowing state can be recognized with high accuracy.

Brightness information of the flock image captured by the ITV 130 is transmitted to the image recognition device 150 via the ITV controller 132. The ITV controller 132 also has the function of providing the ITV 130 with a timing signal that determines the timing for extracting luminance information. The image recognition control device 160 controls the number of times the image recognition device 150 performs flock recognition. Monitoring the floc formation status using these devices is easy because it rarely changes rapidly in a short period of time.
It is carried out about once every 10 minutes to an hour.

Next, the image information of the flock group is sent to the image recognition device 1.
The signal processing operation in 50 will be explained.

FIG. 3 shows the image plane of the flocks recognized by ITV 130. Since the flock group is white, the brightness level is high. On the other hand, since the background backscreen 124 is black, the brightness level of the water is low. Since the flock group is a grayscale image, the boundary between the flock 34 and water is not clear in reality, but
In FIG. 3, only the outline of the flock group is shown for simplicity.

FIG. 4 shows the distribution of brightness levels scanned by line AA' on the screen of FIG. 3. For example, the brightness level is
Displayed in 256 levels, the brightness is lower towards the top of the vertical axis.
The brightness increases toward the bottom. Since the flock 34 is white, the brightness is high. That is, the portion where the luminance level becomes a valley in the downward direction represents a flock.

In the brightness distribution of FIG. 4, binarization processing is performed based on the brightness threshold specified by the BB' line. A pixel at a luminance level higher than the threshold value is set to "1" (flock), while a pixel at a luminance level below a predetermined value is set to "0" (water). Figure 5 is similar to Figure 3.
It is a diagram obtained by binarization processing using the AA′ line.

Next, the number of pixels (Ni, i
= 1, 2, . . . n), the particle diameter of each floc (Di, i = 1, 2, . . . n) is calculated using the following formula.

Di=√4 (2) The calculated particle size signal is output from the image recognition device 150. Next, referring to FIG. 1, the procedure for calculating the density from the grain size of the flocs will be explained. The flock density calculation device 210 calculates the volume of the flock (Vi, i=1, 2, . . . n) from the flock signal Di output from the image recognition device 150 using the following equation.

Vi=4πDi ³ /3 (3) The total volume of the flock, Vt, is calculated using the following formula.

Vt= _o 〓 ⁱ⁼ Vi (4) On the other hand, the floc weight calculation device 230 calculates the total weight M of turbidity from the turbidity measurement value Tu obtained from the turbidity meter 11 using the following formula. Here, k is a constant.

M=k・Tu ......(5) The floc density calculation device 220 calculates the total volume of flocs output by the floc volume calculation device 210.
The average floc density ρ is calculated from Vt and the total suspended solid weight M output from the floc weight calculating device 230 using the above-mentioned equation (1).

ρ=M/Vt……(1) The density of flocs is lower as the floc particle size becomes larger, and conversely, as the particle size is smaller, it is higher (change range of density=
1.002 to 1.050), but floc formation pond 3
Since most of the grown flocs occupy the last pond at 0, the average density of the grown flocs should be used as an approximation for calculation.

The flocculant injection amount calculation device 200 receives the signal of the floc density ρ calculated by the floc density calculation device 220, converts it as shown in FIG. 6, and calculates the flocculant injection amount A.
Calculate. That is, if the density ρ of the flocs becomes low, the amount of flocculant injected is excessive, so the flocculant injector 22 is operated to reduce the amount A of flocculant injected.
Conversely, if the floc density ρ increases, the amount of coagulant injected is insufficient, so the flocculant injector 22 is operated to increase the amount A of coagulant injected.

[Effects of the Invention] According to the present invention, since the density of flocs is constantly measured and the amount of flocculant injected is controlled, flocs with excellent sedimentation properties can be formed with the minimum amount of flocculant to be injected. Therefore, it is possible to maintain a low load on the sedimentation basin and over pond, and as a result, it is possible to save energy and labor in water purification plant maintenance and management, and to improve reliability.

[Brief explanation of the drawing]

1 and 2 are configuration diagrams showing one embodiment of the present invention, and FIGS. 3 to 6 are diagrams for explaining the operation of the present invention. [Brief explanation of symbols], 10...Water landing well, 11
...Turbidity meter, 20...Rapid mixing pond, 22...Flocculant injection machine, 30...Floc formation pond, 31A, 3
1B, 31C... Stirring paddle, 32A, 32
B, 32C... Stirring motor, 100... Imaging device, 110... Image processing device, 200... Floe density calculation device, 210... Floe volume calculation device, 220... Coagulant injection amount calculation device, 230...
...Flock weight calculation device.

Claims (1)

[Scope of Claims] 1. In a water purification plant, a means for measuring turbidity in raw water, a means for controlling the amount of flocculant to be injected, an imaging means for converting brightness information of an image of a group of flocs in a floc-forming pond into an electrical signal, and an image processing means that calculates the particle size and volume of the floc group based on the electrical signal obtained from the imaging means; and a density of the floc group from the measured value of the turbidity and the floc volume value obtained by the image processing means. 1. A floc formation control device comprising floc density calculation means for calculating the density, and flocculant injection amount control means for controlling the flocculant injection amount based on the calculated density value. 2. In claim 1, when the floc density decreases, the flocculant injection amount control means decreases the flocculant injection amount, and when the floc density increases, the flocculant injection amount control means decreases the flocculant injection amount. A floc formation control device characterized by increasing the amount of injection.