JPH06226011A - Flocculant injection control method in water treating flocculation process and flocculant injection control device - Google Patents

Abstract

PURPOSE:To give a water treating facility proper operation control by correcting the injected quantity of a flocculant injected into raw water to be treated according to the detected ratio of the injection of powder active carbon into the raw water. CONSTITUTION:An automatic water quality measuring instrument 11 for measuring the turbidity of raw water in a water level adjusting well 10, an image pickup unit 300 for monitoring the formation of flocs in a floc formation basin 30, an active carbon injection device 60 for injecting powder active carbon into the raw water, an active carbon injection ratio arithmetic unit 200 for calculating the injection ratio of active carbon, an arithmetic unit 400 for calculating the ratio of active carbon in a turbid substance in the raw water from raw water turbidity and the active carbon injected quantity, an image processor 80 for processing an image signal from the image pickup unit to calculate the average floc diameter, etc., and a flocculant injection ratio arithmetic unit 100 for determining the flocculant injection ratio based on the turbidity of raw water or the formed floc particle diameter observed are provided. And the flocculant injection rate arithmetic unit 100 properly corrects the quantity of the flocculant injected into a rapid mixing basin 20 according to the value of the ratio of the active carbon influencing the sedimentation velocity of the turbid substance in the raw water.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a water purification plant, a sewage treatment plant,
The present invention relates to a coagulant injection control method and apparatus in a coagulation process of a water treatment facility such as industrial wastewater treatment, and more particularly, to a coagulant injection control method and apparatus in a water treatment coagulation process utilizing powdered activated carbon treatment.

[0002]

2. Description of the Related Art In a coagulation process in a water treatment facility such as a water purification plant, a coagulant such as an aluminum salt is added to raw water taken from rivers and lakes to coagulate suspended substances in the liquid. Aggregate (hereinafter called floc)
And is removed by sedimentation.

By the way, in recent years, the pollution of water intake sources and the enrichment of nutrients have progressed, and the removal of fine impurities such as off-flavor and chromaticity that cannot be removed by sedimentation separation by a conventional coagulation process has become a problem. As a removal method, for example, adsorption removal by activated carbon has become widespread. In the powdered activated carbon treatment method of this activated carbon use method, powdered activated carbon is injected into a landing well that has introduced the raw water taken in, the impurities are adsorbed, and then the powdered activated carbon is settled as a suspended substance by a coagulation process. Therefore, the adsorbed components such as off-flavor and chromaticity are removed together with the powdered activated carbon. With this method of injecting powdered activated carbon into raw water, the required amount of injection can be adjusted freely and no new facility is required. However, since the injected activated carbon is disposable, in reality, in the summer For example, the temporary use is carried out as necessary only during the period when the mixing of impurities becomes a problem.

A water purification facility utilizing such properties of powdered activated carbon and a method for controlling powdered activated carbon injection are already known, for example, from Japanese Patent Laid-Open No. 57-65378.
That is, according to the method for controlling the injection of powdered activated carbon according to this conventional technique, it is necessary to remove the harmful substance trihalomethane produced by the reaction of the humic substance with chlorine which is the bactericidal agent and at the same time prevent the deterioration of the sterilization process due to the chlorine adsorption of the activated carbon. The powdered activated carbon is injected into the raw water after a lapse of a predetermined time from the injection of chlorine.

In addition, in a water treatment apparatus using such powdered activated carbon, a powdered activated carbon injection control device for automatically controlling the powdered activated carbon injection amount is disclosed in, for example, Japanese Patent Laid-Open No. 4-1872.
No. 87 publication. According to the powder activated carbon injection control device according to this conventional technique, in the water treatment device,
Predict the floc where raw water containing coagulant and powdered activated carbon settles in a sedimentation basin by image processing, and obtain the particle size distribution, average particle size, and amount of pulverized coal per unit volume of pulverized coal in treated water. The outflow turbidity is calculated, and the injection amount of the activated carbon powder is automatically controlled while comparing the predicted outflow turbidity with the set outflow turbidity.

As described above, various methods have been already known as methods for controlling the injection amount of powdered activated carbon in the coagulation process of powdered activated carbon treatment in which powdered activated carbon that is a suspended matter is artificially injected into raw water.

On the other hand, in the coagulation process of the powdered activated carbon treatment in which the powdered activated carbon, which is a suspended matter, is artificially injected into the raw water, as a method for determining the injection rate of the coagulant to be injected into the raw water, like the above-mentioned powdered activated carbon. Are known, for example, by a jar test or by a coagulant injection model based on automatic measurement data of intake water quality. The former is a method of determining the coagulant injection rate each time by a batch test by a jar test, and the latter is a method of determining turbidity and p
Automatic measurement data of water quality such as H, alkalinity and water temperature
Is a feedforward control that determines the coagulant injection rate by a coagulant injection model formula based on

Further, as a method of controlling the injection of a flocculant in the flocculation process of flocculating suspensions in raw water regardless of the flocculation process of powdered activated carbon treatment in which powdered activated carbon is injected, for example, JP-A-4-83504 discloses a method. A method has been proposed in which the floc formation state is measured by image processing and the coagulant is injected and controlled based on the measurement result.

[0009]

By the way, when a suspended substance in raw water from a river or the like is compared with powdered activated carbon, the suspended substance in raw water is more likely to agglomerate when it contains powdered activated carbon and settles down. Form flock that is easy to do. Therefore, flocs containing powdered activated carbon have good sedimentability even if they are small,
The coagulant injection rate should be small when the amount of powdered activated carbon in the suspension is large, and conversely, it should be large when the amount of powdered activated carbon in the suspension is small.

FIG. 6 shows the relationship between the ratio of activated carbon in the raw water turbidity and the floc sedimentation rate. That is, if the sizes of the flocs are the same, it is understood that the flocs containing a large amount of powdered activated carbon have a better sedimentation property. Moreover, the pH range at the time of flocculation also differs between the suspended substance in the raw water and the powdered activated carbon. As described above, in the coagulation process in the water treatment plant in which the powdered activated carbon is artificially injected, the case where only the suspended solids of the raw water for intake are aggregated and the case where the suspended solids containing the powdered activated carbon are aggregated are considered. Flocculant needs to be injected.

Here, in the determination of the coagulant injection amount by the batch test by the jar test according to the above-mentioned conventional technique, the turbidity, pH, alkalinity, water temperature, etc. of the sampled raw water are judged to determine the floc formation state. Although the quality of the sedimentation state is comprehensively judged, the floc formation state and the sedimentation state are visually empirically determined, so continuous and quantitative monitoring of the coagulant injection amount cannot be performed. Therefore, for example, when the intake water quality changes abruptly, such as during rainfall, there is a problem that it is impossible to properly follow the change in the intake water quality.

On the other hand, in feedforward control by automatic measurement data, for example, even if flocculation reaction in a sedimentation basin does not proceed favorably and floc formation is defective, it is not detected from that method. The coagulation effect of the actual plant cannot be reflected in the coagulant injection. Therefore, in actual operation management, even if there is no powder activated carbon injection, there is a tendency to inject the coagulant excessively from the safety side, and in particular, when the powder activated carbon is injected, the excessive coagulant injection becomes remarkable. There was a problem that the water quality would deteriorate.

As described above, when flocculating suspended solids, flocs which are more likely to flocculate and settle more easily are formed when powdered activated carbon is contained. But,
Turbulence, p
Factors related to aggregation are complicatedly intertwined, such as H, alkalinity, electric and electric power, water temperature, inflow rate, and the phenomenon has not been clarified yet. The turbidity of the river is
When it rains, an increase of several tens to several hundreds of times the normal amount occurs in a short time. As described above, even if the powdered activated carbon is injected into the raw water whose water quality changes from time to time, it does not always have a favorable effect on the agglomeration, but on the contrary, the balance of the agglomeration may be disturbed and the agglomeration may be poor. Therefore, unless the actual coagulation effect is reflected in the injection operation, economical and stable operation cannot be achieved by proper injection of the coagulant.

On the other hand, in Japanese Patent Laid-Open No. 2-197928, which is the above-mentioned conventional technique, the flock formation is image-processed and measured, the flock formation is quantitatively measured, and the measurement result is fed back to the coagulant injection. Is proposed. Therefore, in this method, it is possible to control the coagulant injection that reflects the coagulation effect, however, the property change of flocs due to the presence or absence of powdered activated carbon injection is not taken into consideration, and therefore activated carbon is injected into the raw water during activated carbon injection. Since the turbidity in the added liquid is treated as the raw water turbidity to calculate the coagulant injection rate, the coagulant is injected at a higher level than the proper injection rate. In addition, even though the properties of black floc containing powdered activated carbon have changed, such as the color becoming blacker than the floc formed by river turbidity, activated carbon is injected by the above-mentioned conventional method. Since the image processing is performed by the floc extraction logic in the case where the floc extraction is not performed, the floc recognition accuracy may be deteriorated and appropriate coagulant injection control cannot be performed.

Therefore, in view of the above problems in the prior art, the present invention appropriately follows a change in the quality of raw water whose water quality changes at any time in a water treatment plant in which powdered activated carbon is artificially injected, and The injection is controlled to a proper injection amount throughout the year without overdoing,
It is an object of the present invention to provide a flocculant injection control method and device for a water treatment device capable of forming flocs with good sedimentation.

[0016]

SUMMARY OF THE INVENTION The present invention relates to the quality of raw water in which flocs are to be formed by injecting a flocculant in the flocculation process of water treatment, in particular, the flocculation tendency of a suspended substance in raw water is a powder into raw water. It was made paying attention to the difference depending on the activated carbon injection.

That is, in the method and apparatus for controlling coagulant injection in a water treatment apparatus proposed by the present invention, the coagulant injection rate into raw water reflects the amount of activated carbon injected and varies depending on whether powdered activated carbon is injected or not. To control. Therefore, the coagulant injection control method proposed by the present invention is
A water treatment apparatus for injecting powdered activated carbon and a flocculant into treated raw water containing suspended substances and impurities, and precipitating and removing the suspended substances and the injected powdered activated carbon adsorbing impurities as flocs. In the coagulation process, the turbidity of the treated raw water is automatically measured, and the amount of the coagulant injected into the treated raw water is automatically determined based on the automatically measured turbidity of the treated raw water. Furthermore, the method is a coagulant injection control method for detecting injection of powdered activated carbon into raw water, and correcting the injection amount of coagulant injected into the treated raw water by the detected injection of powdered activated carbon.

Further, another coagulant injection control method proposed by the present invention is to inject powdered activated carbon and a coagulant into treated raw water in which suspension substances and impurities are mixed, and In the flocculation process of a water treatment device that precipitates and removes the injected powder activated carbon that has adsorbed impurities as flocs, the diameter of the flocs formed is monitored, and the flocs are injected into the raw water while comparing this with the target floc diameter. In the coagulant injection control method for automatically determining the agent injection amount,
Further, it is a coagulant injection control method for detecting injection of powdered activated carbon into raw water and correcting the target floc diameter for determining the coagulant injection amount by the detected injection of powdered activated carbon.

On the other hand, what is proposed by the present invention as a coagulant injection control device is to inject powdered activated carbon and a coagulant into treated raw water in which suspended substances and impurities are mixed, and the suspended substance, and In a coagulation process of a water treatment device that precipitates and removes the injected powder activated carbon that has adsorbed impurities as flocs, a turbidity measuring unit that automatically measures the turbidity of the raw water to be treated, and a process that is automatically measured by the turbidity measuring unit. A coagulant injection control device comprising a coagulant injection means for automatically determining the coagulant injection amount to be injected into the treated raw water based on the turbidity of the raw water. A coagulant for detecting activated carbon injection detecting means is provided, and the coagulant injection amount injected into the treated raw water by the coagulant injection control means is corrected by the powdered activated carbon injection detected by the activated carbon injection detecting means. An insertion controlling device.

Furthermore, according to the present invention, powdered activated carbon and a flocculant are injected into the treated raw water containing suspended substances and impurities, and the suspended substances and the injected powdered activated carbon in which impurities are adsorbed. In the flocculation process of a water treatment device that precipitates and removes flocs as flocs, the floc diameter monitoring means that monitors the diameter of the flocs that are formed and the coagulant injection amount that is injected into the raw water while comparing this to the target floc diameter A coagulant injection control device comprising automatically determining coagulant injection means, further comprising powder activated carbon injection detection means for detecting injection of powdered activated carbon into raw water, wherein the coagulant injection means A flocculant injection control device has been proposed in which the target floc diameter used for determining the injection amount is corrected by the detection output of the powder activated carbon injection detection means.

[0021]

That is, according to the method and apparatus for controlling coagulant injection in the coagulation process of water treatment proposed by the present invention, coagulation is performed while considering that the tendency of floc formation of suspended solids in raw water differs depending on powder activated carbon injection. By controlling the agent injection, when the ratio of powdered activated carbon to the turbidity is high, the coagulant injection amount is set to a small amount, without excessive injection even if the raw water turbidity due to the powdered activated carbon injection is high, It is always possible to determine the proper coagulant injection rate.

Further, by applying the coagulant injection control method and apparatus of the present invention to the coagulation process of water treatment for controlling the coagulant injection while monitoring the floc particle size which changes by the powder activated carbon injection by image processing measurement, A coagulant injection control method and apparatus in a coagulation process of water treatment, which enables more appropriate coagulant injection, reflecting an actual floc formation situation becomes possible.

[0023]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. First, FIG. 2 shows an overall outline of a water treatment facility that employs coagulant injection control in the coagulation process according to the present invention. In this figure, raw water taken from a river or lake is guided to a landing well 10 via a sand basin (not shown). Water quality information such as turbidity of raw water, water temperature, pH, alkalinity, and electrical conductivity is displayed before the landing well 10 is shown upstream of the landing well 10, for example, an automatic water quality measuring instrument. It is automatically measured by 12.

In this landing well 10, powdery activated carbon is injected into the raw water by the activated carbon injection device 60 as needed in order to remove the offensive odor and chromaticity of the raw water. Powdered activated carbon is
It is a porous carbonaceous substance that adsorbs minute impurities contained in gas and liquid and performs water purification treatment, and has a normal agglomeration such as off-flavor, chromaticity, anionic surfactant, phenols and other organic substances. Adsorbs and removes substances that cannot be removed by precipitation. This powdered activated carbon is injected in the summer and in dry season.
It is often injected in the short term when the water quality deteriorates. The activated carbon injection device 60 for injecting powdered activated carbon injects the activated carbon injection amount C calculated by multiplying the activated carbon injection rate C set by the activated carbon injection rate calculation device 200 by the inflow rate of raw water. In addition, the quality of the raw water accumulated in the landing well 10 is
The water quality is automatically measured by the water quality automatic measuring instrument 11 shown by the reference numeral 11.

Subsequently, the taken raw water is guided from the landing well 10 to the rapid mixing basin 20. Among impurities contained in raw water, turbidity, coloring components, colloidal components such as viruses, bacteria, and algae are usually charged with a negative charge, and these colloidal particles repel each other and do not bond, As it is, it cannot be separated and removed from the raw water by precipitation or filtration. Therefore, rapid mixing pond 20
Now inject a flocculant that produces particles of positive charge opposite the colloidal particles. This aggregating agent serves to neutralize the negative charge of the colloidal particles, thereby eliminating the repulsion between the colloidal particles and establishing a bondable state. An aluminum salt is generally used as the aggregating agent.

That is, in the quick mixing pond 20, the coagulant is injected by the coagulant injection device 70, and for example, the agitation device 21 having fins for agitation attached to the tip of the rotating shaft of the electric motor rapidly agitates for about several minutes. To do. As a result, microflock having a particle size of about 10 μm is formed. Although not shown, an alkaline agent such as sodium hydroxide may be injected to promote the formation of flocs. In that case, in addition to the coagulant injecting device 70, an aggregating accelerator injecting device is further added. Will be provided.

By the way, since the particles of the above colloidal component are small and are unlikely to settle if they remain as microflocs, in the next floc formation pond 30, microflocks grow into large flocks. That is, in this flock formation pond 30, the paddle 31 in the pond is kept for about 30 minutes.
The particles are rotated by a slow agitation so that the micro-flocs grow in contact with each other and have a particle size of 1
The size of the floc is about 100 μm. Thereafter, the grown flocs settle in the settling tank 40, and the supernatant thereof is further filtered in the downstream filter tank 50.

Here, in the flock formation pond 30,
An imaging device 300 is installed, and with this, an image of a floc group flowing in water is taken. In this example,
Although the imaging device 300 has been described as being installed in the flock formation pond 30, the present invention is not limited to this.
For example, it may be installed in the rapid mixing tank 20 or the settling tank 40.

The flock video signal photographed by the image pickup device 300 is subjected to so-called image processing after being digitally converted by the image processing device 80 in the figure. Although details of the image processing device 80 will be described later, the amount of flock formation such as the number, area, volume, and average particle size of flock is calculated from the flock video signal using an image processing method.

On the other hand, the arithmetic unit 400 calculates the ratio R of the powdered activated carbon to the raw water turbidity Tu automatically measured by the water quality automatic measuring device 11. An example of this calculation formula is shown in (Equation 1) below.

[Equation 1] R = C / Tu Incidentally, the raw water turbidity may be measured by the automatic water quality measuring device 12 installed before the inflow of the landing well 10, and the calculation formula of the ratio R of the powdered activated carbon at this time is as follows. It is represented by (Equation 2).

## EQU2 ## R = C / (Tu + C) where C is the activated carbon injection amount.

Further, the coagulant injection rate calculation device 100 described above is used.
Then, the flock formation amount from the image processing device 80,
The coagulant injection rate A into the raw water is calculated based on the turbidity and the ratio R of the activated carbon from the arithmetic device 400. And
The activated carbon injection device 60 uses the calculated coagulant injection rate A
Then, the coagulant is injected into the raw water in the rapid mixing tank 20 based on the injection amount obtained by multiplying the raw water inflow rate.

FIG. 3 shows an embodiment of the image processing apparatus 80 described above. In this figure, the image processing apparatus 80 is C
PU (central processing unit) 501, main memory 502, storage device 503, communication interface 504, system bus 5
05, an image processing unit 506. CPU 501
Executes a program stored in the main memory 502 and controls the entire image processing apparatus 80. Storage device 503
Stores a program for controlling the image processing apparatus 80 and the image processing result. This control program is transferred to the main memory 502 by the microprogram of the CPU 501 when the image processing apparatus 80 is initially started.

On the other hand, the communication interface 504 has a data transmission / reception function with other computers, measuring devices, etc.
The PU 501, via this communication interface 504,
The image measurement information is transmitted to the coagulant injection rate calculation device 100 and the image pickup device 300 is controlled. The image processing device unit 506 includes an image processing processor 508, an image memory 507, and a video interface 509. The image memory 507 has, for example, 256 pixels in the vertical direction and 256 pixels in the horizontal direction and a luminance gradation of 256 (8 bits).
Grayscale image memory of 256 pixels in the vertical direction and 25 pixels in the horizontal direction
A plurality of binary memories each having 6 pixels and having a luminance gradation of 2 (1 bit) are arranged. Further, the image processor 508 is a plurality of LSIs for performing high-speed grayscale image processing calculation, binarization processing, shape feature amount extraction, and the like on the grayscale image and the binary image in the image memory 507. It consists of Further, the video interface 509 has a plurality of inputs and outputs, and an A / D converter is arranged at the input and a D / A converter is arranged at the output.
Converts analog video signals to digital signals.

As described above, inside the image processing apparatus 80, signal processing is performed by digital signals. First, the imaging device 300 (see FIG. 2) arranged in the flock formation pond 30.
Video signal from the video interface 509.
Is converted into a digital signal by the digital camera, and is stored in one grayscale image memory in the image memory 507 in real time. The image processing processor 508 performs various image processing on the image stored in the grayscale image memory. The CPU 8 controls the timing of image processing. On the other hand, in the monitor television 510 connected to the video interface 509, the image stored in the image memory 507 and the video signal of the imaging device 300 are displayed on the display screen.

Next, the image processing flow in the image processing apparatus 80 will be described in detail with reference to FIG.
First, when the processing time preset in the timer is reached, the following processing is executed (step 601). This frequency is, for example, about once per minute to one hour.

In this process, first, the number of repetitions N
Is set to "0 (zero)" (step 602), and thereafter, the number of repetitions N is incremented by 1 (step 603). Then, the flock video signal is transferred to the image memory 50.
It is stored in the grayscale image memory in 7 (step 604).
Next, the grayscale image memory in the image memory 507 is pre-processed so that the flocs are easily extracted so that flocs can be easily extracted (step 605). The binarization processing is executed and stored in the binary image memory (step 606). Where 2
The binarization is to convert the flock pixels to “1” and all the background pixels to “0” for the flock image stored in the grayscale image memory with a predetermined brightness as a threshold. The threshold value is calculated from the brightness of the flock portion. The calculation formula is shown in (Equation 3) below.

## EQU00003 ## L = a.F + b where L: threshold value, F: brightness of the flock portion, and a, b: constants. In the above (Equation 3), the threshold value is calculated from the brightness of the floc portion, but it may be calculated by feeding back the background brightness, the number of flocs described below, the average diameter of the flocs, and the like.

Subsequently, after performing a labeling process (step 607) for assigning numbers to the flocs stored in the binary image memory, the area Si (i) of each floc is calculated.
= 1 to the number of flocs) is calculated (step 608).
Since the actual area of one pixel is known in advance from the enlargement ratio of the image, the area Si of the flock is calculated by multiplying the total number of pixels forming the floc by the actual area of one pixel. Next, the diameter di of the floc is calculated by the following (Equation 4) (step 609).

[Equation 4] di = √4Si / π Further, the volume Vi is calculated by the following (Equation 5) from the diameter di obtained above (step 610).

[Number 5] ^{Vi = π (di) 3/} 6

The above calculation is repeated until the number of repetitions N (see step 603) exceeds a preset value M (step 611). When N = M, the process proceeds to the next step (step 612), where
The particle size distribution is calculated by classifying the floc particle size. The classification width may be about 0.1 mm, but this width may be set arbitrarily. From this particle size distribution, the average diameter D of flocs is determined by a known method known from Japanese Patent Application No. 61-82952.
Is calculated (step 613).

Next, FIG. 1 attached herewith shows a processing flow in the coagulant injection rate computing device 100, which is a feature of the present invention. In this processing flow, first, whether or not the turbidity Tu measured by the automatic water quality measuring device 11 or 12 exists, whether or not h, the upper and lower limits of the data, and the state of fluctuation, the data is normal. It is determined (step 101). As a result, if there is a measurement error in the turbidity Tu (in the figure, "data abnormality"
If it is determined that the coagulant injection rate A is the previously calculated value (step 112).

On the other hand, when the turbidity Tu is judged to be normal, next, there is the data of the average floc diameter D from the image processing device 80, or the upper and lower limits of the data, From the state of fluctuation, it is judged whether or not the data is abnormal (step 102). As a result of this determination, when it is determined that the turbidity Tu and the average floc diameter D are measured “normally”, the process proceeds to the next step, where the activated carbon injection device 60 puts the raw water in the landing well 10 into the raw water. It is determined whether or not the powder activated carbon injection operation is being performed (step 10).
3).

When it is judged that activated carbon has been injected, the activated carbon ratio R calculated from the turbidity Tu and the activated carbon injection amount C from the arithmetic unit 400 is read (step 104). Then, based on these measurement information, raw water turbidity Tu, activated carbon ratio R, and floc average diameter target value Do
The target floc average diameter target value Do is calculated from the relationship (the details will be described later) (step 105). Further, in the next step (step 106), the coagulant injection rate A is calculated from the deviation between the measured floc average target value Do and the measured value D.

On the other hand, as a result of determining in step 103 above whether or not the activated carbon injector 60 is injecting,
When it is judged that activated carbon has not been injected, raw water turbidity Tu
And the floc average diameter target value Do, the activated carbon ratio R
= 0.0, the target floc average diameter target value Do
Is calculated (step 105). After that, the coagulant injection rate A is calculated based on the calculated floc average particle size target value Do (step 106), and the process ends.

As described above, according to the present invention, in the coagulation process of water treatment, particularly in this embodiment, the powder activated carbon injection device 60 for injecting the powder activated carbon into the raw water in the landing well 10 is determined. By doing so, it is determined whether or not the powdered activated carbon is injected into the raw water, and the coagulant injection is optimally controlled in consideration of the changes in the raw water quality and the changes in the flocs formed depending on whether or not the powdered activated carbon is injected. That is, as described above, the suspended substance in the raw water forms flocs more easily aggregated and settled when the powdered activated carbon is contained. Therefore, flocs containing powdered activated carbon have good sedimentability even if they are small.

An example of the relationship between the raw water turbidity Tu, the activated carbon ratio R, and the floc mean particle size target value Do is shown in the graph of FIG. In this figure, the horizontal axis is the landing well 1
The raw water turbidity Tu of 0 is shown, and the vertical axis shows the target value (average value) of the formed floc particle size. Further, the three curves in the graph have different values of the activated carbon ratio R injected into the raw water (R = 0.0, R = 0.5, R = 0.
The characteristic in 8) is shown.

When the powdered activated carbon is injected, the automatic measuring device 11 installed in the landing well 10 measures the value of the activated carbon powder and the suspended matter such as the river together with the turbidity T.
Measure as u. The average target value of the floc particle size represents the size of flocs that tend to settle, and the characteristic curve that rises to the right of this graph shows that when the turbidity of raw water is high, a large amount of coagulant is injected to produce colloidal particles. It is shown that the target value of the average particle size of flocs becomes larger as the turbidity becomes higher, because the impurities cannot be removed unless the amount of flocs forming the aggregates by neutralizing the charges is increased. Further, when the activated carbon is not injected, the target value of the average particle size of flocs can be calculated from the curve of R = 0.0 in the graph.

Then, for example, the floc mean particle size target value Do at the raw water turbidity Tu is the value of the ratio R of activated carbon injected by the injection of activated carbon, that is, in the raw water (R = 0.
0, R = 0.5, R = 0.8). That is,
The floc mean particle size target value Do is smaller when the activated carbon is injected into the raw water (R = 0.5) than when the activated carbon is not injected into the raw water (R = 0.0).
When the amount of activated carbon injected into the raw water is large (R = 0.
It can be seen that in 8), the floc mean particle size target value Do becomes smaller.

FIG. 6 shows an example of the relationship between the ratio R of activated carbon in the particles forming flocs and the sedimentation rate. As is clear from the characteristic curve shown in this graph, for flocs with the same particle size, the larger the ratio R of activated carbon in the particles constituting the flocs, the higher the floc sedimentation rate,
That is, it indicates that flocs are likely to settle.

Based on this, returning to FIG. 5 again and adding the explanation, it means that the floc mean particle size target value Do may be set smaller than in the case without activated carbon. . On the other hand, the ratio of the activated carbon in the particles forming the floc can be expressed by the ratio R of the activated carbon in the raw water turbidity. Therefore, as the activated carbon ratio R increases to 0.5 and 0.8, it is calculated from the turbidity Tu. The target flock average particle diameter Do becomes smaller. In other words, it means that even if the amount of the coagulant injected into the raw water is reduced, it is possible to sufficiently remove sediment by turbidity, which is smaller than the calculated small floc average particle size target value Do. The coagulant may be injected.

In the above embodiment, the control of the coagulant injection amount at the time of activated carbon injection is fed back while observing the flocs actually formed in the floc formation pond, so that the average particle size target value becomes small. By performing the correction as described above, the control is properly performed. However, for example, in the above embodiment, when the image measurement data from the image processing device 80 is abnormal, or means for monitoring the flock formed (for example, an imaging device).
It is possible to calculate the coagulant injection amount and control it to an appropriate value without using the floc average particle size target value even in a water treatment facility that is not equipped with the method. To do.

That is, in FIG. 1 described above, the judgment step 1 is made based on the presence of data of the floc average particle size D from the image processing apparatus 80, the upper and lower limits of the data and the fluctuation state thereof.
If 02 determines that the image data is abnormal, the processing flow moves to the processing flow on the right side of the drawing. In addition, in the water treatment facility not equipped with the floc monitoring means, only the following treatments need be performed. First, it is determined whether the activated carbon injection device 60 is in the process of injecting powdered activated carbon (step 108),
When it is determined that activated carbon has been injected (“present”), the arithmetic device 400 reads the activated carbon ratio R calculated from the turbidity Tu and the activated carbon injection amount C (step 109).

Subsequently, the arithmetic unit 400 performs turbidity correction from the read activated carbon ratio R and raw water turbidity Tu (step 110). In this turbidity correction, first, the turbidity correction value Tu
x is calculated by the following (Equation 6).

## EQU00006 ## Tux = Tu-c.Tu.R where c is a constant. Next, based on the calculated turbidity correction value Tux, the coagulant injection rate A is calculated by the following (Equation 7) (step 111).

## EQU7 ## A = d√Tux + e where d and e are constants. In addition, in the calculation of the coagulant injection rate A in this (Equation 7), in addition to the turbidity of the raw water, the raw water temperature, the raw water pH, the raw water alkalinity, the sedimentation turbidity, etc. You may use the calculation formula which made the grade etc. the variable. In addition, when it is determined in the above step 108 that the powdered activated carbon has not been injected, the measured turbidity Tu is used as it is without performing the turbidity correction in the processing flow, and aggregation is performed by the following (Equation 8). The agent injection rate A is calculated (step 111).

## EQU8 ## A = d√Tu + e

FIG. 7 shows raw water turbidity Tu, activated carbon ratio R,
An example of the relationship of the turbidity correction value Tux is shown in the graph. As is clear from this graph, when the powdered activated carbon was injected, the automatic measuring device 11 installed in the landing well 10 showed a value obtained by combining the injected activated carbon powder and suspended substances such as rivers as described above. Is measured as turbidity Tu. By the way, as recognized by the inventors of the present invention, even if the turbidity Tu is high, if the ratio of the powdered activated carbon to the raw water turbidity Tu, that is, the activated carbon ratio R is high, the flocs formed are small. However, since the sedimentation property is good, a sufficient effect can be obtained even if the coagulant is injected in a small amount. This was confirmed experimentally, and the ratio R of a plurality of activated carbons (R = 0.0,
An example of the turbidity correction value Tux obtained for R = 0.5 and R = 0.8) is shown as a plurality of characteristic curves on the graph.

That is, the ratio of the activated carbon in the particles forming the floc is the ratio R of the activated carbon in the raw water suspension.
Therefore, as the ratio R of activated carbon increases to 0.5 and 0.8, the turbidity correction value T calculated from the turbidity Tu
ux becomes smaller. In this way, when the image measurement data is abnormal, or even in a water treatment facility that does not have a means for monitoring flocs, the required coagulant injection amount is calculated based on the activated carbon injection and is appropriate. It is possible to control the value.

[0054]

As is apparent from the above detailed description of the present invention, according to the present invention, in a water treatment plant in which powdered activated carbon is artificially injected, the amount of coagulant injected into raw water is injected. Is effective for removing fine impurities that cannot be removed by sedimentation separation mixed in raw water, but on the other hand, while considering the injection of powdered activated carbon that affects the floc formation property of suspended matter in raw water, the flocculant By controlling the injection, the ratio of activated carbon in the turbidity of the raw water is calculated, and when the ratio of activated carbon is high, the coagulant injection amount can be reduced and proper operation can be performed. , The appropriate coagulant injection rate can be determined throughout the year, and at the same time, it is possible to economically operate the facility by improving water quality and avoiding unnecessary coagulant injection Exhibit.

Further, the coagulant injection control method and apparatus of the present invention can be applied to the coagulation process of water treatment in which the flocculant injection is controlled while the floc particle size is monitored by image processing measurement. Thereby, it becomes possible to obtain a coagulation process of water treatment capable of more appropriate coagulant injection that reflects the actual floc formation situation.

[Brief description of drawings]

FIG. 1 is a flowchart showing a calculation process of a coagulant injection rate in a coagulant injection control device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing the overall configuration of a water treatment facility to which the coagulant injection control method and device of the present invention are applied.

FIG. 3 is a circuit configuration diagram showing an embodiment of an image processing device of the coagulant injection control device.

FIG. 4 is a flowchart showing an image processing procedure of the image processing apparatus.

FIG. 5 is a graph showing the relationship between the raw water turbidity Tu and the target value of the floc average particle size.

FIG. 6 is a graph showing the relationship between the activated carbon ratio R and the floc sedimentation rate.

FIG. 7: Raw water turbidity Tu, activated carbon ratio R, turbidity correction value Tu
It is a graph showing the relationship with x.

[Explanation of Codes] 10 Water Well 11 Automatic Water Quality Measuring Instrument 12 Automatic Water Quality Measuring Instrument 20 Rapid Mixing Pond 21 Stirrer 30 Flock Forming Pond 40 Sedimentation Tank 50 Filtration Tank 60 Activated Carbon Injection Device 70 Coagulant Injection Device 80 Image Processing Device 100 Coagulation Agent injection rate calculation device 200 Activated carbon injection rate calculation device 300 Imaging device 400 Calculation device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikio Yoda 52-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Omika factory

Claims (14)

[Claims] 1. A powdered activated carbon and a coagulant are injected into treated raw water in which suspended substances and impurities are mixed, and the suspended powder and the injected powdered activated carbon adsorbed with impurities are precipitated as flocs. In the coagulation process of the water treatment device for removal, the turbidity of the treated raw water is automatically measured, and the coagulant injection amount to be injected into the treated raw water is automatically determined based on the automatically measured turbidity of the treated raw water. An injection control method,
Further, a method for controlling coagulant injection, characterized by detecting the injection of powdered activated carbon into raw water and correcting the injection amount of the coagulant injected into the treated raw water by the detected injection of powdered activated carbon. 2. The coagulant injection control method according to claim 1, further comprising detecting an amount of powdered activated carbon injected into raw water,
A coagulant injection characterized by calculating a ratio R of the powdered activated carbon to the raw water turbidity Tu, and correcting the coagulant injection amount injected into the treated raw water based on the calculated ratio R of the powdered activated carbon. Control method. 3. The coagulant injection control method according to claim 1, further comprising detecting an amount of powdered activated carbon injected into raw water,
The ratio R of the powdered activated carbon to the raw water turbidity Tu is calculated, and based on the calculated ratio R of the powdered activated carbon, the coagulant injection amount to be injected into the treated raw water so that the floc diameter to be formed changes. A method for controlling coagulant injection, which comprises: 4. A powdered activated carbon and a coagulant are injected into treated raw water in which suspended substances and impurities are mixed, and the suspended powder and the injected powdered activated carbon adsorbed with impurities are precipitated as flocs. In the coagulant injection control method that monitors the diameter of the flocs formed in the coagulation process of the water treatment device to be removed and automatically determines the coagulant injection amount to be injected into the raw water while comparing this with the target floc diameter. A coagulant injection control method further comprising detecting the powder activated carbon injection into raw water and correcting the target floc diameter for determining the coagulant injection amount by the detected powder activated carbon injection. 5. The coagulant injection control method according to claim 4, further comprising detecting an amount of powdered activated carbon injected into raw water,
A coagulant injection characterized by calculating a ratio R of the powdered activated carbon to the raw water turbidity Tu, and correcting the coagulant injection amount injected into the treated raw water based on the calculated ratio R of the powdered activated carbon. Control method. 6. The coagulant injection control method according to claim 5, wherein the target floc diameter to be formed is changed based on the calculated ratio R of the powdered activated carbon and the coagulant injection is performed. A method for controlling coagulant injection, which comprises correcting the amount. 7. A powdered activated carbon and a coagulant are injected into treated raw water containing a suspended substance and impurities, and the suspended powder and the injected powdered activated carbon adsorbed with impurities are precipitated as flocs. In the coagulation process of the water treatment device for removal, a turbidity measuring means for automatically measuring the turbidity of the treated raw water, and a coagulant injected into the treated raw water based on the turbidity of the treated raw water automatically measured by the turbidity measuring means. A coagulant injection control device comprising a coagulant injection means for automatically determining an injection amount, further comprising an activated carbon injection detection means for detecting injection of powdered activated carbon into raw water, wherein the coagulant injection control means is provided. The coagulant injection control device is characterized in that the coagulant injection amount injected into the treated raw water is corrected by the powder activated carbon injection detected by the activated carbon injection detection means. 8. The coagulant injection control device according to claim 7, further comprising a powder activated carbon injection amount detecting means for detecting an injection amount of the powder activated carbon into the raw water, and a ratio R of the powder activated carbon in the raw water turbidity Tu. And a powdered activated carbon ratio calculating means for calculating, wherein the coagulant injecting means corrects the coagulant injection amount injected into the treated raw water based on the calculated ratio R of the powdered activated carbon. Flocculant injection control device. 9. A powdered activated carbon and a flocculant are injected into treated raw water in which suspended substances and impurities are mixed, and the suspended powder and the injected powdered activated carbon adsorbed with impurities are precipitated as flocs. In the flocculation process of the water treatment device to be removed, a floc diameter monitoring means for monitoring the diameter of the flocs formed and a flocculation agent for automatically determining the coagulant injection amount to be injected into the raw water while comparing this with the target floc diameter. A coagulant injection control device comprising a chemical agent injection means, further comprising a powdered activated carbon injection detection means for detecting injection of powdered activated carbon into the raw water, for determining the coagulant injection amount in the coagulant injection means. A flocculant injection control device, characterized in that the target floc diameter used for is corrected by the detection output of the powder activated carbon injection detection means. 10. The coagulant injection control device according to claim 9, further comprising turbidity measuring means for automatically measuring the turbidity of the treated raw water. 11. The coagulant injection control device according to claim 10, wherein the powdered activated carbon injection detection means detects the powdered activated carbon injection amount into raw water, and the coagulant injection means is the turbidity measurement means. The powdered activated carbon ratio calculating means for calculating the ratio R of the powdered activated carbon to the raw water turbidity Tu measured by the above is provided, and the ratio R of the powdered activated carbon calculated by the powder activated carbon ratio calculating means is used in the treated raw water. A coagulant injection control device for correcting the coagulant injection amount to be injected. 12. The flocculant injection control device according to claim 9, wherein the flock diameter monitoring means includes an imaging device arranged in a floc formation pond and an image processing device for processing an image signal from the imaging device. A flocculant injection control device characterized by containing. 13. The coagulant injection control according to claim 12, wherein the image processing device has a function of calculating an average measurement value of flocs formed in the floc formation pond. apparatus. 14. The coagulant injection control device according to claim 13, further comprising turbidity measuring means for automatically measuring the turbidity of the raw treated water, wherein the coagulant injecting means is such that the image processing device has a floc average. If the measured value cannot be calculated,
The coagulant injection amount is determined based on the raw water turbidity Tu measured by the turbidity measuring device, and the determined coagulant injection amount is corrected by the detection output of the powder activated carbon injection detecting device. Coagulant injection control device.