JPH06327907A - Flocculation controller - Google Patents

Abstract

PURPOSE:To efficiently flocculate and to appropriately keep the turbidity of the effluent from a settling basin by using this flocculation controller. CONSTITUTION:A controller 10B for controlling the injection of a flocculant based on the change in the floc characteristic in a flocculating basin 4, the measured quality of raw water by a water quality meter 1 and the turbidity of the effluent from a settling basin 6 and a controller 18 for controlling the speed of revolution of agitator paddles 4A, 4B and 4C are provided.

Description

Detailed Description of the Invention

[0001]

This invention relates to a purification plant, a sewage treatment plant,
The present invention relates to a floc formation control device that controls a coagulant injection rate and a stirring strength in a coagulation process of suspended solids in an industrial wastewater treatment plant or the like.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a conventional floc formation control device disclosed in, for example, Japanese Patent Laid-Open No. 1-266813. In the figure, 1 is a water quality meter for measuring the quality of raw water,
2 is a rapid mixing tank for stirring and mixing the raw water and the coagulant injected based on the command of the coagulant injection rate control means 10 by a stirrer 4, and 4 is three stirring motors 5A from the mixing water of the mixing pond 2. 5B and 5C are activated to stir paddle 4
A floc formation pond for rotating A, 4B, 4C to form flocs, and 6 is a sedimentation pond for precipitating the flocs formed in the floc formation pond 4. Reference numeral 7 is an image pickup device for photographing the flock in the floc formation pond 4, 8 is an image processing device for calculating a floc characteristic amount from the image of the flock of the image pickup device 7, and the command of the coagulant injection rate control means 10 is water quality. It is determined by the water quality measurement value of the raw water of 1 in total, the floc characteristic amount, and the outflow turbidity of the sedimentation tank of the water quality meter 9 provided in the sedimentation tank 6.

Next, the operation will be described. In the rapid mixing basin 2, the raw water whose water quality is measured by the water quality meter 1 and the coagulant injected based on the command from the coagulant injection rate control means 10 are stirred by the stirrer 3 to make mixed water.
Microflocs of suspended matter are formed in this mixed water. The mixed water stirred and mixed in the rapid mixing basin 2 flows into the floc formation basin 4 together with the micro flocs, and the three flocculation basins 4 are rotated by three stirring motors 5A, 5B and 5C. 4C, and while the microflock groups flowing into the flock formation pond 4 pass through them, they collide with each other or come into contact with each other to aggregate and grow into large flocs. The grown flocs are settled down in the settling tank 6, and the supernatant liquid flows into the filter tank. In addition, the floc is imaged by the camera 7 provided near the exit of the floc formation pond 4, the image processing device 8 recognizes the image, the floc characteristic amount is obtained, and the characteristic amount is measured by the water quality meter 1. The coagulant injection rate C is calculated by the coagulant injection rate control means 10 in comparison with the water quality value. This coagulant injection rate C is expressed by the following equation using a linear regression equation.

C = ΣAiXi (1)

Here, X1 is the raw water temperature, X2 is the raw water alkalinity, X3 is the raw water turbidity, X4 is the raw water pH, X5 is the treatment flow rate, X6 is the floc number concentration, X7 is the floc particle size, and X8 is the floc. Brightness, X9 is the amount of flock formation, X1
0 is a floc density, and A1 to A10 are coefficients obtained by statistically analyzing long-term data. Also,
The coagulant injection rate C of the equation (1) is corrected to increase by ΔC when the turbidity of the sedimentation basin measured by the water quality meter 9 exceeds a certain set value, and the floc particle size X7 is lower than a certain set value. Also in this case, the coagulant injection rate C is corrected to increase by ΔC.

The floc formation control device disclosed in the above-mentioned Japanese Patent Laid-Open No. 1-266813 relates to the control of the coagulant injection rate, and the operation factor for the floc formation control is the stirring paddle 4A of the floc formation pond. 4B, 4
Controlling the rotational speed of C is also a problem. As a conventional technique relating to this, as disclosed in, for example, Japanese Patent Laid-Open No. 4-35702, the stirring paddles 4A, 4B, 4 of the floc formation pond based on the floc characteristic amount obtained from the image processing device 8.
The maximum flock particle size achievable at the number of revolutions of C was calculated using an arithmetic expression, and the maximum flock particle size was compared with the actually measured flock particle size, and from the fine flock amount obtained by image processing, Calculate the predicted runoff turbidity of the settling basin from the calculation formula and compare this predicted runoff turbidity with the set value of runoff turbidity at the outlet of the settling basin, and further set the set inflow rate of raw water (processed water quantity) and its The paddle rotation speed is controlled by comparing with the measured flow rate and judging from these results whether to increase or decrease the rotation speed of the paddle or maintain the current state.

[0007]

As described above, in the conventional floc formation control device, the actual operation data is included in the formula for calculating the coagulant injection rate and the formula for controlling the rotation speed of the stirring paddle in the floc formation pond. Since many coefficients that were statistically obtained are included in the original, it is difficult to correct if these coefficients do not match the actual phenomenon for some reason,
In addition, when the raw water quality changes suddenly during rainfall and when the raw water quality during stable weather is stable, the above-mentioned coefficient values for each condition are different, so flocs should be formed reliably and runoff of the sedimentation basin There was a problem that the turbidity could not always be maintained properly.

The present invention has been made in order to solve such problems, and the coagulant injection rate and the coagulant injection rate for good floc formation so that the outflow turbidity in the sedimentation tank can be appropriately maintained. An object of the present invention is to obtain a floc formation control device capable of controlling the rotation speed of the stirring paddle in the floc formation pond.

[0009]

In the flock formation control device according to the present invention, the floc characteristic amount measuring means is provided with a flock characteristic amount change tendency calculating means, and the coagulant injection rate is calculated based on the change in the flock characteristic amount. To correct.

At least one of the average particle size of flocs and the average number of flocs is used as the above-mentioned floc characteristic amount.

Further, a feedforward injection rate calculation means is provided in the raw water quality measuring means, and the coagulant injection rate corrected based on the change in the floc characteristic amount is determined based on the change amount of the raw water quality measured value. .

The amount of change in the raw water turbidity is used as the amount of change in the water quality measurement value of the raw water.

Further, the stirring paddles of the floc formation pond are provided with a stirring paddle control means for controlling the respective paddles, and the required retention time of the mixed water in the floc formation pond calculated by the required retention calculation means based on the raw water quality measurement value. The agitation strength of the floc formation pond is controlled based on the residence time calculated from the inflow amount of raw water and the change in the floc characteristic amount.

The measured water quality of the raw water is used as the raw water turbidity.

[0015]

As described above, in the floc formation control device according to the present invention, the change in the outflow turbidity of the sedimentation basin can be predicted by the change in the floc characteristic amount. Therefore, the present floc formation state is judged from the change in the floc characteristic amount. The coagulant injection rate can be determined by

Further, since the rotation speed of the stirring paddle of the floc formation pond can be controlled by changing the floc characteristic amount, the coagulant can be injected based on the measured water quality of the raw water and the floc formation state, and the sedimentation of the sedimentation pond High efficiency can be maintained.

[0017]

【Example】

Example 1. FIG. 1 is a block diagram showing an embodiment of the present invention. 1-9, 4A, 4B, 4C, 5A, 5
B and 5C are the same as those of the conventional device, and the coagulant injection rate control means 10A calculates the injection rate of the coagulant based on the water quality of the raw water of the water quality meter 1 (hereinafter referred to as F).
(Abbreviated as F) injection rate calculation means 11, flock characteristic amount change tendency calculation means 12 for calculating a change in the flock characteristic amount from the image processing device 8, the FF injection rate calculation means 11 and flock characteristic amount change tendency calculation means 12 It is composed of an FF injection rate correction calculation means 13 for calculating a correction amount of the coagulant injection rate and a coagulant injection rate target value setting means 14 for controlling the coagulant injection rate to a target value by the correction calculation means 13. There is.

The operation of each part other than the coagulant injection rate control means 10A is the same as the operation of the conventional apparatus. Here, the operation of this embodiment will be described in the case where the floc characteristic amount is the floc average particle size. The flock image obtained by the imaging device 7 provided near the exit of the flock formation pond 4 is image-recognized by the image processing device 8 to calculate the flock average particle size, and the obtained flock average particle size is used as the flock characteristic amount. It is input to the change tendency calculation means 12. In the floc characteristic amount change tendency calculating means 12, the change ΔD of the present floc average particle diameter is calculated from the time series data of the floc average particle diameter inputted in the past.
Is calculated by the following formula.

The _{ΔD = (Σ a Di-Σ} b Di) / I (2)

Here, the subscript i means time, and Di indicates the average particle size of floc at time i. And Σ _a is i =
The addition from n−I to n−1 is performed, and Σ _b is i = n−1.
Add from -I to n-1. Further, n represents the current time, and I represents the number of times the moving average of the floc average particle size is obtained. If ΔD> 0, the average particle size of floc is large, and if ΔD <0, it is small. The measurement cycle of the average particle size of flock is usually about 15 to 60 minutes, and I is 2 to
It is about 5. In the FF injection rate calculation means 11, the water quality meter 1
4 factors of raw water quality, water temperature θ, alkalinity A
FF injection rate C is calculated by the following formula from L and raw water turbidity TUin, PH.

C = b1TUin + b2θ + b3AL + b4PH (3)

Here, b1 to b4 are coefficients obtained by multiple regression from long-term data. Further, in the FF injection rate correction calculation means 13, the C calculated by the equation (3) and the sedimentation tank outflow turbidity TUout obtained by the water quality meter 9 and (2)
Based on ΔD calculated by the formula, correction is made by the following formula.

When ΔD ≧ 0 and TUout ≦ TUout * Cp = C−ΔC When ΔD ≧ 0 and TUout ≧ TUout * Cp = C (4) When ΔD ≦ 0 and TUout ≦ TUout * Cp = C ΔD ≦ 0 And when TUout ≧ TUout *, Cp = C + ΔC

Here, TUout * is a target value of turbidity of the outflow of the sedimentation tank, and ΔC is a correction amount of the injection rate. As shown in FIG. 2, when the floc average particle size increases, the sedimentation basin outflow turbidity TUout decreases with time delay, and conversely, when the floc average particle size decreases, the sedimentation pond turbidity turbidity decreases. It has been empirically found that the degree TUout rises with a time delay. In other words, the change in sediment turbidity turbidity can be predicted from the change in floc average particle size. However, the relationship between the average particle size of flocs and the turbidity of the sedimentation basin is as follows: raw water quality, raw water inflow, coagulant injection rate,
It is easily affected by the paddle agitation strength, etc., and if it is affected by these, it is not stable and the dispersion becomes large. Therefore,
From equation (4), when the outflow turbidity of the sedimentation tank is lower than the target value and the floc average particle size is large, the injection rate is corrected so as to decrease the injection rate, and conversely the outflow turbidity of the sedimentation tank is targeted. When it is larger than the value and the floc average particle size is smaller, the injection rate is corrected so as to increase the injection rate. In the FF injection rate correction calculation means 13,
The coagulant injection rate Cp corrected by the equation (4) is input to the coagulant injection rate target value setting means 14, and the coagulant is injected into the rapid mixing pond 2 so that the injection rate of Cp is obtained.

In addition, although four factors were taken into consideration as raw water quality in equation (3), if all of these factors cannot be measured at all times, the accuracy may drop slightly, but the raw water turbidity of the first term on the right side of equation (3) Only the second term on the right side may be omitted considering only the term of degree. In addition, the coagulant injection rate C is not only viewed as a change in the floc characteristic amount, but feedback correction by the sedimentation tank outflow turbidity is performed so as to increase the injection rate when the sedimentation tank outflow turbidity is higher than the target value. May be added.

Further, here, the description has been made by taking the floc average particle size as the floc characteristic amount by way of example, but instead of the flock average particle size, the average number of flock particles or both of the flock average particle size and the flock average particle number are used for injection. The rate may be corrected. When using the average number of flocs,
The injection rate in the FF injection rate correction calculation means 13 is corrected by the following equation.

When ΔN ≧ 0 and TUout ≦ TUout * Cp = C ΔN ≧ 0 and TUout ≧ TUout * Cp = C + ΔC (5) When ΔN ≦ 0 and TUout ≦ TUout * Cp = C−ΔC ΔN ≦ 0 And when TUout ≧ TUout *, Cp = C

Here, ΔN represents the change in the average number of flocs, and the above equation is calculated by replacing Di in the equation (2) with Ni.

Up to this point, the injection rate correction amount ΔC has been described as a fixed value, but the ratio of the change ΔTUOUT of the sedimentation basin turbidity to the changes ΔD and ΔN of the floc characteristic amount, ΔTUO.
Since UT / ΔD and ΔTUOUT / ΔN are easily affected by changes in raw water quality, if the injection rate correction amount ΔC can be set based on the amount of change in raw water quality, flocs can be formed more stably and sedimentation can be improved. The pond runoff turbidity can also be maintained near the target value. Changes in raw water quality, especially changes in turbidity of the raw water, compared to other factors are ΔD / ΔTUOUTΔN / Δ
Since the effect on TUOUT is large, even if the injection rate correction amount ΔC is set only for the change amount of the raw water turbidity, the same effect as above can be obtained.

Although the camera 7 is provided on the exit side of the floc formation pond 4, it may be provided on the side of the sedimentation pond close to the exit of the floc formation pond. In the above configuration, the water quality meter 1 constitutes the raw water quality measuring means in the claims, and the image pickup device 7
Represents a flock image pickup means, and the image processing device 8 constitutes a flock characteristic amount measuring means.

Example 2. In the first embodiment, the case where the coagulant injection rate is corrected based on the change in the floc characteristic amount has been described, but in the present embodiment, as shown in FIG. 4, the required residence time of the mixed water in the floc formation pond 4 is changed. Necessary residence time calculation means 15 which is set based on the raw water quality measurement value of the water quality meter 1, and the stirring paddles 4A, 4B, 4C based on the required residence time and the change in the floc characteristic amount and the residence time calculated from the inflow of raw water. Since the stirring paddle control means 16 for controlling the number of rotations of Flock formation was provided so as to control both the coagulant injection rate and the stirring strength of the floc formation pond 4 which are the operating factors for floc formation, the first embodiment is described. A higher-performance flock formation control device can be provided.

In order to perform floc formation satisfactorily and efficiently, appropriate flocculant injection is performed, and at the outlet of the floc formation pond 4 under the present flocculant injection conditions, an appropriate floc average particle size is obtained. It is necessary to control the rotation speed of the stirring paddles 4A, 4B, and 4C so that The floc growth rate in the floc formation pond 4 is determined by the value of (stirring strength Gx inflowing turbidity concentration Tux stirring time T into the floc formation pond 4) under the given coagulant injection conditions, and is also produced. The maximum floc diameter is determined by the stirring strength G. Stirring strength G is stirring paddle 4
It can be controlled by the number of revolutions of A, 4B, and 4C, the stirring time T is considered to be the average residence time in the floc formation pond 4 of the mixed water, and the turbidity concentration Tu is determined by the turbidity concentration in the raw water and the coagulant injection amount. The raw water turbidity TUin
However, there is not much difference. In the stirring paddle control means 16,
From the formula (6), the change ΔD of the average particle size of the flocs, the turbidity TUout of the settling basin, the required residence time TL, and the measured inflow amount Q of raw water were used to calculate the stirring paddles 4A, 4B, and 4C rotation speed R, and these values were calculated. Based on the stirring motors 5A, 5B, 5
Operate C to control the rotation speed of the stirring paddles 4A, 4B, 4C.

When ΔD <0 and TUout> TUout * and T <TL R = R * + ΔR ΔD <0 and TUout> TUout * and T> TL R = R * −ΔR ΔD> 0 and TUout ≦ TUout * In case of R = R * + ΔR In other cases R = R * (6)

Here, R * is the current rotation speed of the stirring paddle, and ΔR is the correction amount of the rotation speed of the stirring paddle. T is the average residence time of the mixed water, which is the effective volume U of the floc formation pond 4.
Is divided by the inflow amount of raw water measured by the flow meter 17. Further, the required residence time TL is calculated by the required residence time calculation means 15 by the four-factor water temperature of raw water quality, raw water turbidity,
It is calculated from alkalinity, PH and coagulant injection rate.

Stirring paddles 4A, 4B, 4 according to formula (6)
If the turbidity TUOUT of the sedimentation basin is expected to be higher than the target value TOUT * due to the change ΔD of the average particle size of the floc, the rotation speed of C is corrected. By 4 in and out
Judgment is made as to whether a sufficiently large average floc particle size cannot be obtained or whether the stirring strength (rotation speed) is too high and the flock particle size has been destroyed.
The rotation speed is increased when it is caused by the floc growth rate, and conversely, the rotation speed is decreased when it is caused by the floc destruction. On the contrary, when it is expected that the outflow turbidity TOUT of the sedimentation basin becomes lower than the target value TOUT * from the change ΔD of the floc average particle diameter, it is considered that the floc average particle diameter is too large. The rotation speed of the stirring paddle is reduced so that the particle size is slightly reduced. Then, under the conditions other than the above, the rotation speed of the stirring paddle is kept as it is.

The rotation speeds of the stirring paddles 4A, 4B, and 4C are set to the upper and lower limits based on the operational experience of the agglomeration process. Therefore, within this range, the rotation speed of the stirring paddles should be controlled by the equation (6). To do. Also, stirring paddle 4
The rotational speeds of A, 4B, and 4C are generally tapered flocculation, and the rotational speeds are lowered from the inlet side to the outlet side of the floc formation pond 4, and the ratio of the rotational speeds is the same as that of the flocculation process. It is set based on operational experience. Depending on operational experience, the rotation speeds of the stirring paddles 4A and 4C in the front and rear stages may be kept constant and only the rotation speed of the stirring paddles 4B in the middle stage may be controlled. In the above configuration, the stirring paddle control means 16 constitutes means for controlling the stirring strength of the floc formation pond in claim 5.

[0037]

As described above, according to the flock formation control device of the first aspect of the present invention, the raw water quality measuring means for measuring the water quality of the raw water and the raw water and the coagulant are mixed by stirring. From the image signal of the mixed water, a floc formation pond that forms flocs of suspended substances from the mixed water, a sedimentation pond that precipitates the flocs, a floc imaging unit that captures an image of the floc, and an image signal of the floc imaging unit Flock characteristic amount measuring means for measuring the floc characteristic amount, sedimentation tank outflow turbidity measuring means for measuring the outflow turbidity of the sedimentation tank, the floc characteristic amount, the sedimentation tank outflow turbidity and the raw water quality measuring means And a controller for correcting the coagulant injection rate based on the change in the floc characteristic amount. Further, according to the flock formation control device of the second aspect of the present invention, the flock characteristic amount uses at least one of the average particle size of the flock and the average number of the flock. According to the floc formation control device according to the above, the correction of the coagulant injection rate based on the change in the floc characteristic amount is determined based on the amount of change in the water quality measurement value by the raw water quality measuring means. According to the flock formation control device of the fourth aspect of the invention, since the amount of change in the quality of the raw water is the amount of change in the turbidity of the raw water, proper flock formation can be performed, and the turbidity of the sedimentation basin can be properly adjusted. Can be managed.

According to a fifth aspect of the flock formation control device of the present invention, in the flock formation control device of the first aspect, further, means for controlling agitation of the flock formation pond and the flock formation pond are provided. A means for setting the required retention time of the mixed water based on the water quality measurement value of the raw water, the required retention time of the mixed water, the retention time calculated from the inflow amount of the raw water, and the change of the floc characteristic amount, from the flock formation pond. And a means for controlling the agitation intensity of the raw water. Further, according to the floc formation control device of the sixth aspect of the present invention, the water quality measurement value of the raw water is obtained based on the raw water turbidity. The effect can be produced more efficiently.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between changes in the average particle size of flocs and changes in the turbidity of the sedimentation basin according to the present invention.

FIG. 3 is a diagram showing the relationship between changes in the average number of flocs and changes in the turbidity of sedimentation basin according to the present invention.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIG. 5 is a block diagram of a conventional flock formation control device.

[Explanation of symbols]

 1 Water quality meter 2 Rapid mixing pond 3 Stirrer 4 Flock formation pond 4A, 4B, 4C Stirring paddle 5A, 5B, 5C Stirring motor 6 Sedimentation tank 7 Imager 8 Image processing device 9 Water quality meter 10, 10A, 10B Coagulant injection rate Control means 18 Stirring paddle rotation speed control means

Claims (6)

[Claims] 1. A raw water quality measuring means for measuring the quality of raw water, a floc pond for mixing the raw water and a flocculant by stirring to obtain mixed water, and forming flocs of suspended substances from the mixed water. A sedimentation basin for sedimenting the flocs, a floc imaging means for capturing an image of the flocs, a floc characteristic amount measuring means for measuring the floc characteristic amount from an image signal of the floc imaging means, and an outflow turbidity of the sedimentation reservoir. Sedimentation tank outflow turbidity measuring means to measure, coagulant injection rate control means for controlling the injection rate of the coagulant from the floc characteristic amount, the sedimentation tank outflow turbidity and the measured value of the raw water quality measuring means, A control device that corrects the coagulant injection rate based on a change in the floc characteristic amount, and a flock formation control device. 2. The flock formation control device according to claim 1, wherein at least one of a flock average particle size and a flock average number is used as the flock characteristic amount. 3. The flock formation according to claim 1, wherein the correction of the coagulant injection rate based on the change of the floc characteristic amount is determined based on the change amount of the water quality measured value by the raw water quality measuring means. Control device. 4. The flock formation control device according to claim 3, wherein the change amount of the raw water quality is a change amount of the raw water turbidity. 5. A means for controlling the agitation of the floc formation pond, a means for setting a required retention time of the mixed water in the flock formation pond based on a water quality measurement value of raw water, and a required retention time of the mixed water. The flock formation control device according to claim 1, further comprising: a unit that controls a stirring intensity of a floc formation pond based on a change in the residence time calculated from the inflow amount of the raw water and the flock characteristic amount. 6. The floc formation control device according to claim 5, wherein the water quality measurement value of the raw water is obtained based on the turbidity of the raw water.