JPH02284605A - Paddle control device in flocculation basin - Google Patents

Abstract

PURPOSE:To control the floc formation and to improve the control accuracy by finding the average particle diameter and the number of flocs in the rear part of a flocculation basin and using these values as the factors of feedback control to control the number of revolution of paddle. CONSTITUTION:When the paddles 4 agitating the water to be treated added with flocculant in the flocculation basin 3 are controlled, an image treatment part 12 finds the average particle diameter and the number of flocs according to the image informations sent from the camera 11 in water to be treated provided in the rear part of the flocculation basin 3. A number-of-revolution control part 13 controls the number of revolution of paddles 4 based on the average particle diameter and the number of flocs, increasing the number of revolution when the average particle diameter is smaller than a threshold value and the number is smaller than a threshold value, and decreasing the number of revolution when the average diameter is larger than the threshold value and the number is larger than the threshold value. As a result, the control accuracy is improved compared with the feedback control based on the turbidimetry of the effluent flow from a settling basin.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Application Field The present invention relates to floc formation control for coagulating turbid components in treated water, and in particular to a paddle control device that controls paddles for stirring treated water using a feedback control system. Regarding.

B1 Summary of the Invention The present invention installs a treated water camera at the rear of a floc formation pond, determines the average particle size and number of flocs in the treated water based on image information from the treated water camera, and measures the flocs. By controlling the rotation speed of the paddle based on the average particle size and number of particles, the paddle control delay time is shortened,
This is designed to improve control accuracy.

C. Conventional technology In general, in water treatment plants, raw water taken from rivers, lakes and marshes is treated with a flocculant (polycalcium chloride) in a flocculation pond.
PΔC), sulfuric acid band, etc.) to aggregate turbid components (clay, algae, etc.) and remove them in a settling tank.

Conventionally, when controlling floc/liquid formation, new water treatment plants conducted floc formation using a jar test (indoor experiment).
A control equation between raw water turbidity and flocculant injection rate or ALT ratio (AL"/turbidity) is determined and used on an actual scale based on parameters such as OCT values. On the other hand, in existing water treatment plants, The accumulated data is used to control floc formation.

In such floc formation control, in order to improve efficiency, a correction term (such as raw water temperature or PI3) is provided in the injection method, etc., and control is performed. Also, this control
Since it is a word control system, it cannot cope with rapid changes in the turbidity of raw water, and there is a risk that the δ passage in the subsequent stage will become a heavy load. For this reason, aspects have also been constructed in which a feedback control system is incorporated.

FIG. 10 shows an example of paddle-type floc formation control employed in medium-sized or larger water purification plants.

First, raw water is taken into the receiving well 1, and a flocculant is introduced into the mixing pond 2. Then, in the floc formation pond 3, the paddle 4 is rotated by the rotation speed controller 10 to agitate the treated water, thereby flocculating the suspended matter components (forming flocs). Thereafter, the flocs are settled in a settling tank 5.

Turbidity meters 6 and 7 are attached to the landing well 1 and the settling pond 5. The flocculant injection controller 8 calculates the amount of flocculant to be injected based on the measured turbidity of raw water, etc., and controls the injection of the flocculant into the mixing pond 2 .

D1 Problems to be Solved by the Invention However, in the conventional floc formation control, the turbidity meter 7 causes precipitation/II! Feedback control is performed based on the turbidity measured at the exit of 5, so the delay time is 2.
Since it lasted about 3 hours, there was a problem that the control accuracy deteriorated.

Moreover, since the turbidity meter 6.7 is a light application device such as a scattered light type or a near-infrared light type, it measures all substances that scatter and absorb light, such as chromaticity and algae.

For this reason, a control system using a turbidity meter has a problem in that it has a factor that increases error fluctuations and is inferior in reliability.

In view of these problems, it is an object of the present invention to improve the feedback control system and improve control accuracy in floc formation control.

E1 Means for Solving the Problems In order to achieve the above object, the present invention provides a paddle control device for controlling a paddle that stirs treated water into which a coagulant has been introduced in a floc formation pond, which includes the following means. It is to be established.

■ Treated water camera installed at the rear of the floc formation pond.

■ An image processing unit that calculates the average particle size and number of flocs and rocks in the treated water based on image information from the treated water camera.

■ The rotation speed of the paddle is controlled based on the average particle size and number of flocs, and when the average particle size is smaller than the threshold and the number is less than the threshold, the rotation speed is increased and the average A rotation speed control unit that lowers the rotation speed when the particle size is smaller than a threshold value and the number of particles is larger than the threshold value.

The particle size of the flocs formed in the F9 action floc formation pond is related to the turbidity, as will be described later. In other words, it can be seen that the larger the particle size of the floc, the lower the turbidity.

If the stirring force in the flocculation pond is too small, flocs will not be sufficiently formed and the particle size of the flocs will remain small. On the other hand, if the stirring force is too large, the formed flocs will be destroyed and the particle size of the flocs will become smaller.

When the particle size of the flocs is small, whether the stirring force is too large or too small can be determined based on the number of flocs. In other words, if the number of flocs is small, the flocs are not sufficiently formed, and the stirring force is small. z can be determined. If there are a large number of flocs, it can be determined that although flocs are formed, the particle size is small, that is, the stirring force is too large and destroys the flocs.

In the paddle control device according to the present invention, treated water is photographed by a treated water photographing device installed at the rear of the floc formation pond.

Then, the image processing unit determines the average particle size and number of flocs in the treated water.

Furthermore, based on the average particle size and number of flocs,
Based on the above discrimination criteria, determine whether the stirring force is appropriate, and if it is not appropriate, determine whether it is too large or too small l7;
Controls the number of rotations of the paddle.

G. Example The present invention will be explained in detail below.

G l Overview of the floc measurement system according to the example 1st
The figure shows an example of paddle-type floc formation control used in medium-sized or larger water treatment plants.

■ is the landing well, 2 is the mixing pond where the flocculant is immersed in the treated water, 3
is the floc formation t1. l! , 5 is the precipitation 1i to precipitate the flocs? It is IJl.

A turbidity meter 6 for measuring raw water turbidity is attached to the landing well l. A turbidity meter 7 is attached to the sedimentation tank 5 to measure the turbidity of the outflow. The flocculant injection controller 8 controls the flocculant injection.

In the flocculation pond 3, paddles 4 (1) for stirring the treated water are installed. 9 is a motor for rotating the paddles, and a rotation speed controller 10 is for controlling the motor 9.

At the last stage of the floc formation pond 3, an underwater camera 11 with a cleaning mechanism is attached for photographing the treated water. In order to obtain a completely still image of the flowing floes, a fully interlaced camera with an electronic shutter mode is used as the underwater camera 11.

The image processing device 12 processes the image from the underwater camera 11 and determines the floc formation state! This will create data showing the island. The host computer 13 performs statistical processing of data from the image processing device 12 and controls the present floc measurement system.

G.2 Operating Principle of Embodiment The following formula can be cited as a coagulant injection method that allows feedback control.

D=A-TB'+B, -(1) where D is the flocculant injection rate, TB is the raw water turbidity, B is the feedback correction value, and A and n are coefficients.

In addition to equation (1), factors that determine the optimal conditions for floc formation, that is, the maximum growth floc particle size, include GC
There is a T value. The GCT value is the stirring intensity (G value), the concentration of suspended solids in raw water (C value), and the stirring time (T value). These factors also serve as design guidelines for floc formation ponds.

G, 2. I Field experiment summary of GCT value This GC
A field experiment conducted to verify the validity of the T value will be explained.

This experiment was conducted using the floc measurement system shown in FIG.

A still image taken by an underwater camera 11 is processed by an image processing device 12 to extract feature quantities, and a host computer 13
Statistical processing of the feature values is performed using The total floc volume ratio (FV value), etc. were measured.

Then, these screen factors (average particle size, number of flocs/
Consistency was analyzed using stepwise regression analysis based on the following factors: screen, FV value), injection factors (turbidity, ALT ratio), hydraulic factors (stirring intensity, stirring time), water quality factors (PH1 water temperature, conductivity), etc.

In other words, explanatory variables x1~ with high correlation with objective variable Y
Extract and delete the relationship of X (variable increase/decrease, increase method),
The standard partial regression coefficients β1 to β are applied to equation (2) as a linear combination equation. was determined by least squares approximation.

Y=β. +βIXI+β, X, ten...+βnXn+ε
(2) In this equation (2), the average particle diameter of the floc is taken as the objective variable Y, and the explanatory variables β1 to β. Taking injection factors, hydraulic factors, and water quality factors,
Analysis was carried out.

As a result, formula (3) was obtained.

()oy average particle size) = β. +β1×(number of flocks/
screen) +4. X (FV value) + β3X (water intake ff1)
+Lx (GT value) +βaX, (water level It was found that all the variables were functions of the GCT value.This revealed that the average floc particle diameter obtained by image measurement was the floc formation factor.

G.2.2 Optimal floc formation control conditions for floc formation The following three points can be cited as optimal floc formation control conditions.

■ Keep the turbidity of the sedimentation tank at a low and stable level.

■ Reduce the amount of coagulant injection.

■ Maintaining maximum growth floc diameter.

Condition (2) is especially important in the water purification process. This is because when the effluent turbidity increases, the burden on the filter pond at the later stage increases.

When flocs are formed with a stable injection rate formula, the occurrence of fine flocs is considered to be the cause of the increase in the turbidity of the outflow from the sedimentation basin.

Figure 2 shows the floc average particle size distribution. In the figure, Xl represents the normal average particle size, X represents the geometric average particle size, (a) represents the normal probability density distribution, and (b) represents the lognormal probability density distribution. For a normal probability density distribution, the normal mean particle size is 1.54
88, the standard deviation is 0.771291, and for the lognormal probability density distribution, the geometric mean particle size is 1.35858,
The standard deviation is 0.232319. In addition, the threshold value is 34, T, F is 8549, T, Vl; 12.25643
, the FV value was 0.334305, and the number of measurement screens was 11. As can be seen from this figure, the particle size distribution of flocs always has dispersion, and as the average particle size of flocs increases, the proportion of fine flocs inevitably decreases. do. Therefore, the average particle diameter of the flocs can be taken as the representative diameter of the flocs.

G, 2.3 Relationship between average floc particle size and number of flocs/screen with respect to effluent turbidity Figure 3 shows the relationship between the geometric average particle size of flocs and sedimentation basin effluent turbidity. As can be seen from this figure, the smaller the floc geometric mean particle size, the higher the outflow turbidity, and the larger the floc geometric mean particle size, the lower the outflow turbidity.

Furthermore, Fig. 4 shows the relationship between the number of flocs/screen and the turbidity of the sedimentation basin outflow. As can be seen from this figure, as the number of flocs/screen increases, the effluent turbidity increases, and as the number of flocs/screen decreases, the turbidity of the effluent decreases (becomes less than 800). It does not change.

In this way, there is a strong alternating relationship between the average floc particle size and the number of flocs/screen, and it can be seen that the effluent turbidity decreases when the average floc particle size is large and the number of flocs/screen is small. .

GJ Variation factors for the average particle diameter of the flocs and the number of flocs/screen according to this embodiment include the following.

■ Concentration of flocculant injection rate ■ Change in intake water pellet concentration ■ Change in paddle rotation speed ■ Change in water intake As mentioned above, the growth of flocs depends on the stirring intensity of the paddle (
G value), stirring time (T value) and raw water turbidity concentration (C value). FIG. 5 shows the influence of GCT value on floc growth. In the figure, the horizontal axis shows raw water turbidity, and the vertical axis shows stirring time. OCT is constant (e.g. about 1,000,000), e.g. stirring intensity G-20
, the raw water turbidity c=io, the time required for floc formation T=5000 (seconds).

Among these GCT values, the ones suitable for control are:
It is only the stirring intensity (G value) of the paddle.

In this example, the average particle diameter of the flocs and the number of flocs/screen are used as feedback control factors (7. The number of rotations of the paddle is controlled.

The relationship between the geometric mean particle size of flocs and the number of flocs/screen with respect to the turbidity of the sedimentation basin is summarized in FIG. 6.

When the goal is to maintain the sedimentation tank outflow turbidity below the managed outflow turbidity of the water purification plant (0.5 mm), it is sufficient if the average floc particle size is 12.5 mm or more and the number of flocs/screen is 940 or less.

Based on these values, a threshold HD 8117 is set for the average particle diameter HD of the flocs, and a threshold CSIT is set for the number of flocs/screen C.

Furthermore, in floc formation, if the stirring force is small, the degree of collision and mixing will be impaired, the collision probability will be reduced, and flocs will not be sufficiently formed. On the other hand, if the stirring force is large, the formed flocs will be re-dissociated and destroyed. Therefore, if the stirring force is too high or too low, the particle size of the flocs will become small.

FIG. 7 shows the paddle control procedure.

The image processing device 12 takes in an image from the underwater camera 11 (step ■) and performs binarization processing (step ■).

Next, the image is inverted (step (2)) and subjected to processing such as area 7 dead area conversion, and characteristics m such as the particle size and number of flocs are extracted (step (2)).

After the feature m has been extracted a predetermined number of times (step ■), statistical processing is performed by the host computer 13 (
In step (2), the geometric mean particle diameter HD of the flocs, the number of flocs/screen C, etc. are determined.

Then, the number of rotations of the paddle is controlled based on the judgment criteria listed in Table 1 (step ■).

Table 1 If condition (■) in the table applies, it is determined that the flocs have not grown, and the paddle rotation speed is increased.

If condition (2) is met, it is determined that the stirring force is too high and the flocs are being destroyed, and the paddle rotation speed is reduced. If condition 1 (■) is met, it is determined that a moderate amount of flocs is formed, and the current state is maintained at f(
Hold f.

In addition, in the case of condition ■■, conditions are further divided according to the difference between the threshold value and the control factor, and the change in paddle rotation speed ■ is determined in stages according to the difference between the two. You can also do it.

As mentioned above, floc formation/Il! 3 is equipped with a plurality of paddles 4, and the stirring methods include a control method that keeps all paddle rotation speeds constant, and a tapered flocculation control method that lowers the rotation speed toward the later stages (
(Refer to Japanese Patent Laid-Open No. 111110/1983). In the latter method, a high probability of collision is maintained by a strong stirring force in the first stage, and the stirring force is weakened in the latter stage to avoid re-dissociation and destruction of the flocs.

FIG. 8 shows the control range of the paddle rotation speed in the former control method, and FIGS. 9(a), (b), and (c) show the control range of the paddle rotation speed in the latter control method. In the figure, R is the steady rotation speed, R+n l n is the minimum rotation speed, R
+1llllK is the maximum rotation speed. In the latter control method, for example, the ratio of R1 is 5:3: middle: rear:
It is 1.

This embodiment can be applied to any control method, and the rotation speed of each paddle may be controlled within the control range based on the control criteria described above.

As described in detail of the H invention, the paddle control device according to the present invention includes:
The average particle size and number of flocs at the rear of the floc formation pond are determined, and floc formation is controlled by controlling the paddle rotation speed using these as feed paddle control factors. Therefore, compared to feedback control based on sedimentation tank outflow turbidity, there is an advantage that the delay time can be reduced to about 1/3 and control accuracy can be improved.

Since the configuration is such that the paddle rotation speed is controlled based on the average $Iγ diameter of roughly 70 pieces and the number of paddles, there is an advantage that it is possible to accurately determine whether the paddle rotation speed is too high or too low, and to perform appropriate control.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing paddle-type feedback formation control according to an embodiment of the present invention, FIG. 2 is a distribution diagram of the average floc particle size, and FIG. 3 is a diagram showing the geometric average particle size of the flocs and the effluent turbidity of the sediment. Figure 4 is a diagram showing the relationship between the number of flocs/screen and sedimentation tank outflow of 138 degrees, Figure 5 is a diagram showing the influence of GCT value on floc growth, and Figure 6 is a diagram showing the influence of sedimentation tank outflow turbidity. Figure 7 is a flowchart showing the paddle control procedure, Figures 8 and 9 (a) (+))
(C) is an explanatory diagram showing the control range of the rotation speed of the paddle, the first
FIG. 0 is a block diagram showing conventional paddle type feedback formation control. 3...Floc formation pond, 4...Paddle, 10...Rotation speed controller, 11...Underwater camera, 12...Image processing device, 13...Host controller. Fig. 2 Floc particle size distribution measurement diagram Volume histogram Fig. 4 Relationship between number of flocs/screen and sedimentation tank effluent turbidity Number of flocs/screen (solid) Fig. 3 Geometric mean particle size of flocs Relationship between diameter and sedimentation tank outflow turbidity Figure 5 Relationship between raw water turbidity and floc formation time (pieces) Flock geometric mean particle size (mm) Figure 8 Paddle rotational speed control range Figure 7 Paddle control flow Figure 9 Paddle rotational speed control range

Claims (1)

[Claims] (1) A device that controls the paddle that stirs the treated water containing a coagulant in the floc formation pond, including a treated water camera installed at the rear of the floc formation pond, and image information from this treated water camera. an image processing unit that calculates the average particle size and number of flocs in treated water based on the average particle size and number of flocs; and an image processing unit that controls the rotation speed of the paddle based on the average particle size and number of flocs, and the A rotation speed controller is provided that increases the rotation speed when the particles are smaller and the number is less than the threshold value, and lowers the rotation speed when the average particle size is smaller than the threshold value and the number is greater than the threshold value. A paddle control device for a flocculation pond, characterized by: