JP2012101171A - Coagulant injection control system - Google Patents

Abstract

Provided is a flocculant injection control system which can further reduce the time delay of feedback correction and can be applied even when raw water is highly turbid, and which can calculate an appropriate amount of flocculant injection.
At least turbidity of raw water is measured in a flocculant injection control system of a water purification plant including a floc formation pond that injects a flocculant into raw water to form a floc, a sedimentation basin that separates and removes the floc, and a filtration basin. Raw water sensor, sampling section for collecting flocculant injection water in which flocculant is injected into raw water, aluminum measuring device for measuring the concentration of aluminum contained in the collected flocculant injection water, and turbidity of the raw water sensor An injection rate calculation function that calculates the basic coagulant injection rate using the measured value, a first correction value calculation function that calculates a correction value for the coagulant injection rate from the measured value of the aluminum concentration and its target value, and an operation As a sum of the basic flocculant injection rate and the first correction value, an injection rate correction function for determining the flocculant injection rate is provided.
[Selection] Figure 1

Description

  The present invention relates to a monitoring control system for a water purification treatment facility, and more particularly to a flocculant injection control system for controlling the injection amount of a flocculant.

  In the water purification plant, a flocculant is injected into the raw water taken to agglomerate turbid components in the raw water to form flocs, and a coagulation sedimentation process is performed in which the generated flocs are settled and separated in a sedimentation basin. The treated water from which flocs have been settled and separated is introduced into a filtration basin, which is the next water purification facility, and filtered.

  In this coagulation sedimentation treatment, the coagulant injection rate determined according to the raw water quality is important. When surface water such as rivers and lakes is used as raw water, the quality of raw water fluctuates due to factors such as weather conditions and seasons.Therefore, in order to obtain clean water below the set turbidity, an appropriate flocculant injection rate or flocculation There is a need for a flocculant injection control method that can determine the amount of agent injection.

  In the flocculant injection control method, the flocculant injection rate is calculated according to a preset flocculant injection model formula from the measurement results of turbidity, alkalinity, pH, etc. of the raw water quality, and the flocculant injection rate is determined based on this flocculant injection rate. There is a feed-forward control that injects the agent. However, the feedforward control causes the coagulant injection amount to be inadequate and cause cohesion failure when the raw water quality fluctuates and cannot be matched with the coagulant injection model formula created in the past. As a result, the turbidity at the sedimentation basin outlet becomes high, and precipitation-treated water having a high turbidity is introduced into the filtration basin, which increases the frequency of backwashing of the filtration basin.

  In contrast to feedforward control, there is feedback control that corrects the flocculant injection amount based on the measurement result of turbidity at the sedimentation tank outlet. According to the feedback control, even if the raw water quality changes, if the effect is measured as a change in turbidity at the outlet of the settling basin, feedback will work and the coagulant injection amount can be corrected. However, it takes about 3 to 4 hours until the result of injecting the flocculant into the raw water becomes turbidity at the sedimentation tank outlet, and a time delay occurs in correcting the flocculant injection amount. Because of this time delay, it is difficult to cope with a sudden change in raw water quality.

  Since feedforward control and feedback control have their respective disadvantages, combining each control method, first calculate the basic flocculant injection rate from the raw water quality, and correct the calculated value using the turbidity at the sedimentation tank outlet There is feed-forward feedback control. The feedforward feedback control can maintain the coagulant injection amount appropriately because the feedback works even when the coherent injection model equation is not consistent with the Ford forward control. However, since the time delay, which is a problem of feedback control, has not been solved, it is still difficult to cope with unsteady times when the raw water quality changes rapidly.

  In order to reduce the time delay of feedback correction, the following techniques have been proposed.

  For example, Patent Document 1 automatically supplies raw water to a plurality of stirring tanks and injects a flocculant, and automatically agglomerates from ultraviolet absorbance data that is an index of the obtained floc particle size and the amount of soluble organic matter. An apparatus and method for controlling the amount of agent injected is disclosed.

  Patent Document 2 discloses a coagulant injection control method in which a sample collected from a mixing pond is introduced into an aggregation monitoring device, the turbidity or chromaticity of a treatment liquid is measured, and the measurement value is calculated to control the coagulant injection pump. Is disclosed.

  In Patent Document 3, a flow current value is measured by a flow ammeter, and this is corrected by the alkalinity and electrical conductivity of raw water, and the flocculant injection facility is controlled using the corrected flow current value. An agent injection control device is disclosed.

  Patent Document 4 discloses a water to be treated in which a flocculant is added in a flocculant injection control system in a water treatment facility in which an aluminum-based flocculant is added to water to be treated to agglomerate suspended solids and precipitate. The dissolved aluminum ion concentration was measured with a dissolved aluminum ion concentration measuring device, and the flocculant injection rate was calculated with the flocculant injection rate calculation device from this measurement result. Based on the flocculant injection rate calculation result, the flocculant injection device Discloses a technique for injecting a flocculant into water to be treated.

Japanese Patent No. 3205450 JP-A-5-146608 JP 2004-223357 A JP 2008-161809 A

  In the technique described in Patent Document 1, turbidity and turbidity unevenness and size are used for controlling the amount of flocculant injected. The turbidity and the ubiquity and size of the turbidity are data on the raw water into which the flocculant has been injected (hereinafter referred to as “flocculating agent injected water”). It is also affected. For this reason, there is a drawback that the correction accuracy of the flocculant injection amount is lower than in the case of using the data at the sedimentation tank outlet.

  In the technique described in Patent Document 2, flocculant injection water is introduced into a coagulation monitoring device, flocs are grown, filtered, and turbidity or chromaticity is measured. For this reason, although the feedback correction can be performed more quickly than using the turbidity at the sedimentation tank outlet described above, the coagulation monitoring device requires the same operation as that of the actual plant, so that a time delay still occurs in the correction. In addition, since the aggregation monitoring device that executes these series of operations is different in scale and configuration from the actual plant, there is a drawback that the correction accuracy of the coagulant injection amount is lowered.

  In the technique described in Patent Document 3, flocculant injection water is introduced into a flow current meter, and the flow current is measured. At this time, when the raw water has a high turbidity, it is difficult to measure the flowing current. Therefore, when the turbidity is high, the correction accuracy of the flocculant injection amount is low.

  In the technique described in Patent Document 4, flocculant injection water is introduced into an on-line type ion chromatography, and the dissolved aluminum concentration (concentration of aluminum ions contained in the flocculant injection water) is measured. Since the dissolved aluminum concentration is generally determined by the water temperature and pH, it is difficult to use it as an index for judging the quality of aggregation.

  The object of the present invention is to cope with the above-mentioned problems, further reduce the time delay of feedback correction, and can be applied even when raw water is highly turbid, and can calculate an appropriate amount of flocculant injected. It is to provide an injection control system.

  In order to achieve the above-described object, the present inventors have arrived at an invention of a flocculant injection control system having the following characteristics.

  In the present invention, at least turbidity of raw water is measured in a floc formation pond that injects a flocculant into raw water to form a floc, and a flocculant injection control system of a water purification plant that includes a sedimentation basin and a filtration basin that separates and removes the floc. Raw water sensor, sampling section for collecting flocculant injection water in which flocculant is injected into raw water, aluminum measuring device for measuring the concentration of aluminum contained in the collected flocculant injection water, and turbidity of the raw water sensor An injection rate calculation function that calculates the basic coagulant injection rate using the measured value, a first correction value calculation function that calculates a correction value for the coagulant injection rate from the measured value of the aluminum concentration and its target value, and an operation An injection rate correction function for determining the flocculant injection rate is provided as the sum of the basic flocculant injection rate and the first correction value.

  Further, when measuring the aluminum contained in the collected flocculant injection water, a floc having a predetermined particle size contained in the flocculant injection water is used.

  Further, flocs having a particle diameter of 50 μm or less and having a particle diameter within a predetermined range are used separately.

  In addition, a second sedimentation water sensor that measures water quality including at least turbidity of the sedimentation water and a second correction value that calculates the second correction value of the flocculant injection rate using the measured value and the target value of the sedimentation water turbidity. A correction value calculation function, and the injection rate correction function determines the coagulant injection rate as the sum of the basic coagulant injection rate, the first correction value, and the second correction value.

  In addition, it comprises a third correction value calculation function for calculating the third correction value of the flocculant injection rate using the measured value of the filtered water of the filtration pond, the measured value of the water quality measurement means and the target value of the filtered water, The injection rate correction function determines the coagulant injection rate as the sum of the calculated basic coagulant injection rate, the first correction value, the second correction value, and the third correction value.

  In addition to turbidity, one or more of alkalinity, water temperature, pH, and ultraviolet absorbance are input as water quality items to be measured by the raw water sensor, and the input value is reflected in the calculation of the first correction value.

  In addition, a water intake sensor for detecting turbidity is provided at the water intake for taking the raw water, and the output of the water intake sensor is reflected in the calculation of the basic coagulant injection rate.

  Moreover, the basic flocculant injection rate of the flocculant is calculated using the measured value at the water intake point and the amount of change per unit time.

  In addition, a correction value weight calculation function for calculating a weight coefficient when adding the correction value of the flocculant injection rate using the measured value of the raw water sensor and the amount of change per unit time is provided.

  In addition, the weighting factor given to the first correction value and the second correction value of the flocculant injection rate has a relationship that when one weighting factor is increased, the other weighting factor is decreased.

  Further, when the time change rate of the turbidity measured by the raw water sensor is large, the first correction value is obtained. When the time change rate of the turbidity measured by the raw water sensor is small, the second correction value is obtained. The relationship greatly affects the output.

  In addition, the first correction value of the flocculant injection rate is the target value of the aluminum residual rate calculated from the target value of the turbidity measured by the raw water sensor and the sedimentation water turbidity, and the measured value of the aluminum concentration. Based on the aluminum residual rate obtained by dividing by (concentration conversion), the aluminum residual rate is determined so as to approach the target value of the aluminum residual rate.

  According to the present invention, since the flocculant injection water is collected at an earlier stage than the conventional sedimentation basin outlet, the time delay in correcting the flocculant injection rate can be shortened.

  As other effects in the embodiment, the main component of the flocculant (polyaluminum chloride, sulfuric acid band) is aluminum, and it is possible to directly determine the excess or deficiency of the flocculant by measuring the aluminum concentration of the classified water. It becomes possible.

  Further, as another effect in the embodiment, the robustness of the control is improved by performing correction based on the precipitation-treated water turbidity.

The block diagram of the coagulant | flocculant injection | pouring control system by Example 1 of this invention. 1 is a configuration diagram of a floc classifier using a metal rotary filter in Embodiment 1. FIG. The block diagram of the aluminum measuring device in Example 1. FIG. 1 is a configuration diagram of management means in Embodiment 1. FIG. The figure explaining the relationship between precipitation processing water turbidity and aluminum residual rate. FIG. 6 is a diagram illustrating a processing flow of a first correction value calculation function in the first embodiment. FIG. 5 is a diagram illustrating a processing flow of an injection rate correction function according to the first embodiment. FIG. 10 is a diagram illustrating a processing flow of a second correction value calculation function in the second embodiment. The block diagram of the coagulant | flocculant injection | pouring control system in Example 7. FIG. View for explaining the relationship of the weight w ₁ of the change rate and the correction value. The figure explaining the time change example of raw water turbidity. The figure explaining the time passage example of a raw water turbidity change rate. The block diagram of the coagulant | flocculant injection | pouring control system in Example 9. FIG.

  Hereinafter, an embodiment of a flocculant injection control system according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing an embodiment of a flocculant injection control system according to the present invention.

  First, the water purification treatment facility 100 which is a control target of the flocculant injection control system 10 includes a landing well 110, a mixing basin 120, a flock formation basin 130, a sedimentation basin 140, a filtration basin 150, a water purification basin 160, and a chemical injection facility 170. Consists of In the purified water treatment facility 100, the raw water W1 taken from a water source such as a river or groundwater is purified, and the finally obtained filtered water is sent from the purified water reservoir 160 as clean water. For this purpose, the raw water W1 is first introduced into the landing well 110, and then introduced into the mixing basin 120, the flock formation basin 130, the sedimentation basin 140, the filtration basin 150, and the clean water basin 160 in order.

  On the other hand, the flocculant injection control system 10 according to the first embodiment includes a raw water sensor 210, an aluminum measuring device 220, a precipitation treated water sensor 230, and a floc classifying device 300 in the water purification treatment facility 100 as shown in FIG. These various measuring devices are installed, and various quantities obtained from these are used for the following control.

  The flocculant injection control system 10 according to the first embodiment includes a water purification treatment facility control unit 400, a network 500, and a management unit 600, and is installed in the water purification treatment facility 100 based on the various measurement quantities described above. The injection amount of the flocculant injected by the chemical injection equipment 170 (hereinafter referred to as “the flocculant injection amount”) is determined.

  In the flocculant injection control system 10, the raw water sensor 210, the aluminum measuring device 220, and the floc classifying device 300 are provided in the water purification treatment facility 100. The water purification treatment facility control means 400, the network 500, and the management means 600 may be provided inside the water purification treatment facility 100 or outside the water purification treatment facility 100. In this embodiment, it is provided outside the water purification treatment facility 100. The water purification treatment facility control means 400 and the management means 600 are connected via a network 500, and the water purification treatment facility 100 and the water purification treatment facility control means 400 are connected via a communication line (not shown) to transmit and receive data.

  Hereinafter, the process of processing the raw water W1 will be described. First, the raw water W1 is introduced into the landing well 110 after sand having a large particle size is settled and removed, and the amount and quality of water are measured by the raw water W1 sensor 210.

  In the mixing basin 120, the flocculant is injected into the raw water W1 from the chemical injection facility 170 and rapidly stirred. Due to the rapid stirring, the turbid components in the raw water W1 aggregate and become floc. Thereafter, the raw water W <b> 1 into which the flocculant is injected, that is, the flocculant injected water W <b> 2 is introduced into the flock formation pond 130. The chemical injection facility 170 is controlled by the water purification treatment facility control means 400, injects a coagulant into the raw water W1, and measures process data such as the injection amount of the coagulant.

  In the floc formation pond 130, the flocculant injection water W2 is gently stirred, and the growth of floc is promoted. The flocculant injection water W <b> 2 that has been gently stirred is introduced into the sedimentation basin 140.

  In the sedimentation basin 140, the flocs of the flocculant injection water W2 after the slow stirring are settled and separated. The settling water W3 is introduced into the filtration basin 150.

  In the filtration basin 150, the sedimentation water W3 is filtered, and in the sedimentation basin 140, fine flocs that have not been separated by sedimentation are removed. The filtered treated water W3, that is, the filtered water W4, is introduced into the water purification basin 160. The filtered water W4 is supplied to customers as clean water W5 from the water purification tank 160.

  In the present invention, in the mixing basin 120, a part of the flocculant injection water W2 is collected through a water supply means (not shown) such as a pump and introduced into the floc classifier 300. The place for collecting the flocculant injection water W2 may be anywhere between the mixing basin 120 for injecting the flocculant into the raw water W1 and the outlet of the settling basin 140. It is good to collect water between.

  In the floc classifying apparatus 300, the floc contained in the flocculant injection water W2 is classified, and waste water W6 and classified treated water W7 are obtained. The role of the floc classifier 300 is to quickly grasp the content ratio state of small flocs having poor sedimentation that affects the turbidity of the sedimentation water W3.

  In general, the particle size of flocs varies from 1 to 100 μm, but a floc having poor sedimentation is a small floc having a particle size of 50 μm or less, particularly 15 μm or less. Therefore, classification by the floc classifying apparatus 300 separates small flocs having a particle diameter of 50 μm or less, desirably 5 to 15 μm or less, determined from a range of 5 to 15 μm. Here, as the floc classifying apparatus 300, for example, a metal or ceramic filter (filter opening: 5 to 15 μm) is used. When classifying flocs contained in the flocculant injection water W2, In addition, a hydrocyclone, a sedimentation separator, a floating separator, and the like may be used, and the means for classifying flocs in the flocculant injection water W2 is not particularly limited.

  As an example of this embodiment, FIG. 2 shows a configuration of a flock classifying apparatus 300 using a metal rotary filter. The flock classifying apparatus 300 includes a filtration tank 310, a rotary filter 320, a motor 330 for driving the rotary filter, and a pump 340 for obtaining classified water.

  In the filtration tank 310, the flocculant injection water W2 is classified by the rotary filter 320. At this time, the filter aperture of the rotary filter 320 is preferably 5 to 15 μm as described above. When the classification is performed, the classified treatment water W7 has a small floc content ratio and the drainage W6 has a small floc content ratio compared to the flocculant injection water W2. Here, the drainage W6 may be drained by a normal drainage facility or may be returned to the flock formation pond 130. The obtained classified treated water W7 is introduced into the aluminum measuring device 220.

  In the aluminum measuring device 220, the aluminum concentration of the classified treated water W7 is measured. Methods for measuring the aluminum concentration of the classified water W7 include atomic absorption spectrophotometry, ICP emission spectroscopic analysis, ICP mass spectrometry and spectrophotometry, but as a means for continuously measuring the aluminum concentration at low cost, Absorptiometry is desirable.

As an absorptiometric method, there is a method using eriochrome cyanine red (C ₂₃ H ₁₅ Na ₃ O ₉ S, hereinafter referred to as ECR) as a color reagent. In this method, soluble aluminum causes a color reaction with an ECR reagent in the region of pH 4.6 to 5.6 to form a complex, and its absorbance is determined and quantified. At this time, the quantification range of the aluminum concentration is preferably 0 to 0.5 mg / L, and the addition amount of the ECR reagent and the like are adjusted so that a linear relationship is obtained between the absorbance and the aluminum concentration within this range.

  In the case of an absorptiometric method using an ECR reagent, since the waste water W8 is a weakly acidic liquid having a pH of about 5, the waste water W8 is neutralized or diluted and drained by a normal drainage facility. Moreover, since the aluminum contained in the floc in the classified water W7 is insoluble, an acid is previously injected to adjust the pH of the classified water W7 to 3 to 4, thereby dissolving the insoluble aluminum.

  As an example of this embodiment, FIG. 3 is a diagram illustrating a configuration of the aluminum measuring device 220. The aluminum measuring device 220 includes a pump 221, a reagent tank 222, a stirring tank 223, an absorbance measuring device 224, a waste liquid tank 225, and an electromagnetic valve 226.

  In FIG. 3, the pump 221 continuously supplies the classified water and the reagent at a constant flow rate, and stirs and mixes in the first stirring tank 223a and the second stirring tank 223b. Specifically, the sample water (classified water) W7 and the ECR reagent solution in the tank 222a are sent to the first stirring tank 223a via the sample water pump 221a and the ECR solution pump 21b, respectively, and mixed and stirred. The mixed solution a is mixed and stirred in the buffer solution in the buffer solution tank 222b sent from the buffer solution pump 221c and the second stirring tank 223b.

  Thereafter, the mixed solution b is sent to the absorbance measuring device 224 via the electromagnetic valve 226 and the aluminum concentration is measured. The pure water in the pure water tank 222c is sent from the pure water pump 221d to the electromagnetic valve 226, and the mixed liquid and pure water are switched to the absorbance measuring device 224 and supplied.

  In the apparatus shown in FIG. 3, the ECR solution supplied from the tank 222a forms a complex with the soluble aluminum of the classified water W7, and also serves to dissolve insoluble aluminum. The buffer solution supplied from the tank 222b has a role of 4.6 to 5.6 which is a pH range in which soluble aluminum undergoes a color reaction with the ECR reagent to form a complex. In addition, it is important that the buffer solution is in a predetermined pH range, but it is desirable that the buffer solution is not subject to the PRTR target substance in order to cope with the environment. For example, an acetate buffer solution may be used.

  The mixed solution b in which aluminum is dissolved and adjusted to a predetermined pH range as described above is supplied to the absorbance measurement device 224, and the absorbance is measured.

  The measured absorbance is converted into an aluminum concentration from the relationship between the absorbance and the aluminum concentration determined in advance by basic experiments. This conversion may be performed by a computer such as a personal computer (not shown), or may be stored as an aluminum concentration conversion function 652 in the memory 650 of the management means 600 shown in FIG. It is not limited. In the present embodiment, the aluminum concentration conversion function 652 stored in the memory 650 is used.

  In addition, it is desirable not to change the operating conditions of the floc classifier 300 and the aluminum measuring device 220 once determined.

  The flocculant injection control system 10 in FIG. 1 obtains water quality data from the raw water sensor 210, the aluminum measuring device 220, and the precipitation treated water sensor 230 as described above. In addition, process data such as the amount of water and the amount of flocculant injected is obtained from the raw water sensor 210 and the chemical injection facility 170. These water quality data and process data D1 are transmitted to the water purification facility control means 400 via a communication line.

  In the present invention, as water quality data, turbidity and alkalinity are measured by the raw water sensor 210, the aluminum concentration is measured by the aluminum measuring device 220, and the precipitation treated water turbidity is measured by the precipitation treated water sensor 230.

  The purified water treatment facility control means 400 controls each process of the purified water treatment facility 100 such as controlling the chemical injection facility 170, the flock classifying device 300, and the aluminum measuring device 220. In addition, the water purification treatment facility control unit 400 transmits / receives measured water quality data, process data D1, and control data D2 described later to / from the management unit 600 via the network 500.

  The management means 600 includes a computer such as a personal computer and software executed by the computer. The management means 600 receives the water quality data and the process data D1 from the water purification treatment facility control means 400 via the network 500, and calculates the coagulant injection amount using the received water quality data and process data. This coagulant injection amount is transmitted as control data D2 to the water purification facility control means 400 via the network 500.

  Here, the management means 100 will be described in detail with reference to FIG. FIG. 4 is a configuration diagram of the management unit 600 in the present embodiment. The management unit 600 includes a CPU 610, a network interface (hereinafter referred to as “IF”) 620, and a memory 650.

  The CPU 610 executes this program to operate each function described above.

  The IF 620 is an interface with the network 500 and serves to communicate information with the water treatment facility control means 400 connected to the network 500.

  In the memory 650, the management means 600 has a data collection function 651, an aluminum concentration conversion function 652, an injection rate calculation function 653, a first correction value calculation function 654, a second correction value calculation function 656, and an injection rate correction function 655. A program for storing the program is stored. The memory 650 temporarily stores water quality data and process data D1.

  As described above, the data collection function 651 collects process data and water quality data D1 via the water purification facility control unit 400, and the process data and water quality data D1 are temporarily stored in the memory 650.

The aluminum concentration conversion function 652 calculates the residual aluminum concentration C _Al from the absorbance. The residual aluminum concentration C _Al is temporarily stored in the memory 650.

The injection rate calculation function 653 calculates the basic flocculant injection rate F ₀ according to the equation (1) using the water quality data (turbidity Tu ₀ and alkalinity AL _{0 of the} raw water W1) measured by the raw water sensor 210. To do.
[Equation 1]
F ₀ = a ₁ · Tu ₀ ^a2 + a ₃ · AL ₀ ^a4 (1)
Here, a ₁ , a ₂ , a ₃ , and a ₄ are coefficients, which are determined in advance in a basic test and stored in the memory 650. For example, when a ₁ = 5.5, a ₂ = 0.4, a ₃ = −0.55, and a ₄ = 0.04, the raw water W1 turbidity Tu ₀ is 100 degrees and the alkalinity AL ₀ is 35 mg / If L, the basic flocculant injection rate F ₀ is given by the following equation (2).
[Equation 2]
F ₀ = 5.5 · Tu ₀ ^0.4 + (− 0.55) · AL ₀ ^0.04 = 34 mg / L (2)
The basic coagulant injection rate _{F 0,} the raw W1 water quality, water volume, and varies depending on the purification plant specifications, is preferably in the range of at least 5 to 100 mg / L.

Further, the formula for calculating the basic coagulant injection rate F ₀ is not limited to (1). The raw water sensor 210 may measure other water quality data, for example, the water temperature T ₀ , pH, or ultraviolet absorbance E ₂₆₀ , and calculate the basic flocculant injection rate F ₀ according to an equation that takes them into account.

The basic flocculant injection rate F ₀ calculated in this way is temporarily stored in the memory 650.

FIG. 5 is a diagram showing the relationship between the turbidity (horizontal axis) of the precipitated treated water W3 and the aluminum residual rate (vertical axis). Here, the aluminum residual rate is a ratio obtained by dividing the aluminum concentration by the coagulant injection rate (aluminum concentration in the injected PAC). According to the figure, the aluminum residual rate tends to increase as the turbidity of the precipitated treated water W3 increases (horizontal axis). Also, the increasing rate is large enough turbidity Tu ₀ of the raw water W1 is small. From this relationship, for example, the target value DV _Al of the aluminum residual rate is calculated from the raw water W1 turbidity Tu ₀ and the target value DV _Tu of the clarified treated water W3 stored in the memory 650 in advance according to the equation (3). To do.
[Equation 3]
DV _Al = b ₁ · Tu ₀ ^b2 · DV _Tu ^b3 (3)
Here, b ₁ , b ₂ , and b ₃ are coefficients, which are determined in advance in a basic test and stored in the memory 650. The target value DV _Al of the aluminum residual rate is temporarily stored in the memory 650.

A target value DV _Al aluminum residual rate was calculated from the above equation (3), actually calculating the first correction value Q ₁ from the difference between the aluminum residual percentage R _Al computed from the residual aluminum concentration measured. Here, the coagulant injection rate F ₁ when calculating the aluminum residual rate R _Al is the current time t in consideration of the time delay τ until water is measured as the residual aluminum concentration after sampling from the sampling location. From this, the flocculant injection rate F ₁ (t−τ) before the time delay τ is used.

  The time delay τ is determined in advance in a basic test and stored in the memory 650.

  FIG. 6 shows a processing flow of the first correction value calculation function 654 in the first embodiment.

The first correction value calculation function 654 functions for each feedback control period Δt ₁ stored in the memory 650 in advance, and calculates the first correction value Q ₁ .

In step S11, the raw water W1 turbidity Tu ₀ and the target value DV _Tu of the sedimentation water turbidity are acquired. Here, the raw water W1 turbidity Tu ₀ is the water quality data measured by the raw water sensor 210, and the target value DV _Tu of the sedimentation water turbidity is a target value stored in the memory 650 in advance.

In step S12, the residual aluminum concentration C _Al is acquired from the aluminum concentration conversion function 652 in FIG. The residual aluminum concentration C _Al is a value measured by the aluminum measuring device 220.

In step S13, the flocculant injection rate F ₁ (t−τ) before the time delay τ from the current time t is acquired. Here, τ is a time delay until water is measured as a residual aluminum concentration after sampling from the sampling location.

In step S14, an aluminum residual rate R _Al is calculated according to the equation (4).
[Equation 4]
R _Al = C _Al / F ₁ (t−τ) × 100 (4)
In step S15, in accordance with equation (3), calculates a target value _{DV Al} aluminum residual rate.

In step S16, (5) in accordance with equation calculates a deviation [Delta] R _Al of the aluminum residual percentage _{R Al.}
[Equation 5]
ΔR _Al (t) = R _Al −DV _Al (5)
In step S17, in accordance with equation (6), calculates a first correction value _{Q 1.}
[Equation 6]
Q ₁ = c ₁ · ΔR _Al (t) + c ₂ · ∫ ₀ ^t ΔR _Al (s) ds (6)
Here, c ₁ and c ₂ are coefficients, which are adjusted in advance so that the first correction value Q ₁ does not vibrate and can quickly reach an appropriate value, and are stored in the memory 650. The first correction value Q ₁ calculated in this way is temporarily stored in the memory 650.

  FIG. 7 shows a processing flow of the injection rate correction function 655 (FIG. 4) in the first embodiment.

In step S21, it acquires a basic coagulant injection rate _{F 0} from the injection rate calculation function 653. The basic flocculant injection rate F ₀ is obtained by the equation (1) and stored in the injection rate calculation function 653.

In step S22, it acquires the first correction value _{Q 1} from the first correction value calculation function 654. The first correction value Q ₁ is obtained by the equation (6) and stored in the first correction value calculation function 654.

In step S23, in accordance with equation (7), calculates the coagulant injection rate _{F 1.}
[Equation 7]
F ₁ = F ₀ + Q ₁ (7)
The flocculant injection rate F ₁ is temporarily stored in the memory 650.

  In step S24, the amount of raw water W1 is acquired. The amount of raw water W1 is data measured by the raw water sensor 210.

In step S25, the coagulant injection amount is calculated. Coagulant injection amount is determined by multiplying the amount of water in the raw water W1 to (7) of the coagulant injection rate F _1.

  The calculated flocculant injection amount is input to the chemical injection facility 170 via the water purification facility control means 400 as control data D2. The chemical injection facility 170 injects the flocculant into the raw water W1 according to the amount of the flocculant injected.

In the present invention, since water is collected at an early stage of the process of the water purification treatment facility 100 (before the flock formation pond 130), the time delay in correcting the flocculant injection rate can be shortened. Further, the first correction value to Q ₁ coagulant injection rate, since the decision based on the indication that the raw water W1 turbidity and sedimentation treated water W3 turbidity and high correlation is aluminum residual rate, the coagulant injection amount It can be optimized.

Example 2, the memory 650 of the management unit 600 of the first embodiment, the second correction which calculates a second correction value _{Q 2} from the target value _{DV Tu} precipitation treated water W3 turbidity and sedimentation treated water W3 turbidity Tu _s This is a case where a value calculation function 656 is provided. That is, in the first embodiment, the flocculant injection amount is corrected and controlled from the viewpoint of the raw water W1, but in the second embodiment, the flocculant injection amount is further corrected and controlled from the viewpoint of the precipitation treated water W3.

The second correction value calculation function 656 functions for each feedback control period Δt ₂ stored in the memory 650 in advance, and calculates the second correction value Q ₂ .

  FIG. 8 shows a processing flow of the second correction value calculation function 656 in the second embodiment.

In step S31, the sedimentation water turbidity Tu _s and the target value DV _Tu of the sedimentation water turbidity are acquired. The sedimentation treatment water turbidity Tu _s is data measured by the sedimentation treatment water sensor 230, and the precipitation treatment water turbidity target value DV _Tu is a target value stored in the memory 650 in advance.

In step S32, the deviation ΔTu _s of the sedimentation water turbidity is calculated according to the equation (8).
[Equation 8]
ΔTu _s (t) = Tu _s −DV _Tu (8)
In step S33, in accordance with equation (9), calculates the second correction value _{Q 2.}
[Equation 9]
Q ₂ = d ₁ · ΔTu _s (t) + d ₂ · ∫ ₀ ^t ΔTu _s (s) ds (9)
Here, d ₁ and d ₂ are coefficients, and are adjusted in advance so that the second correction value Q ₂ does not vibrate and can quickly reach an appropriate value, and is stored in the memory 650. Second correction value Q ₂ are temporarily stored in memory 650 within.

In Example 2, the second correction value Q ₂ is obtained by injection rate calculation function 655, in accordance with (10), calculates the coagulant injection rate F _1.
[Equation 10]
F ₁ = F ₀ + Q ₁ + Q ₂ (10)
The flocculant injection rate F ₁ is temporarily stored in the memory 650.

According to Example 2, the robustness of the control is improved by performing the correction by the turbidity Tu _s of the precipitation treated water W3, and the precipitation treated water turbidity Tu _s is set to the preset precipitation treated water turbidity. The target value DV _Tu can be stably maintained.

The third embodiment is a case where the alkalinity AL ₀ measured by the raw water sensor 210 is considered in the formula for calculating the target value DV _Al of the aluminum residual rate of the first correction value calculation function 654.

In the present embodiment, when the alkalinity AL ₀ is considered, the target value DV _Al of the aluminum residual rate is calculated according to the equation (11).
[Equation 11]
DV _Al = b ₁ · Tu ₀ ^b2 · DV _Tu ^b3 · AL ₀ ^b4 ··· (11)
Here, b ₁ , b ₂ , b ₃ , and b ₄ are coefficients, which are determined in advance in a basic test and stored in the memory 650.

Note that the arithmetic expression of the target value DV _Al of the aluminum residual rate considering the alkalinity AL ₀ is not limited to the expression (11), and may be expressed as the expression (12).
[Equation 12]
DV _Al = b ₁ · Tu ₀ ^b2 · DV _Tu ^b3 + b ₅ · AL ₀ ^b4 ··· (12)
Here, b ₅ is a coefficient, which is determined in advance in a basic test and stored in the memory 650.

According to the third embodiment, by taking into account the alkalinity AL ₀ to arithmetic expression of the target value DV _Al aluminum residual rate, it is possible to calculate the target value DV _Al aluminum residual rate more accurately.

The fourth embodiment is a case where the water temperature T ₀ measured by the raw water sensor 210 is taken into account in the equation for calculating the target value DV _Al of the aluminum residual rate of the first correction value calculation function 654.

When the water temperature T ₀ is taken into account, the target value DV _Al of the aluminum residual rate is calculated according to the equation (13).
[Equation 13]
DV _Al = k ₀ · exp (−K / T ₀ ) · Tu ₀ ^b2 · DV _Tu ^b3 (13)
Here, b ₂ , b ₃ , k ₀ , and K are coefficients, which are determined in advance in a basic test and stored in the memory 650.

The calculation formula of the target value DV _Al of the aluminum residual rate considering the water temperature T ₀ is not limited to the Arrhenius type of the equation (13), and may be expressed by a power of the water temperature T ₀ , for example.

According to the fourth embodiment, by considering the temperature T ₀ in the arithmetic expression of the target value DV _Al aluminum residual rate, it is possible to calculate the target value DV _Al aluminum residual rate more accurately.

The fifth embodiment is a case where the pH measured by the raw water sensor 210 is taken into account in the equation for calculating the target value DV _Al of the aluminum residual rate of the first correction value calculation function 654.

In consideration of pH, (14) in accordance with equation calculates a target value _{DV Al} aluminum residual rate.
[Formula 14]
DV _Al = b ₁ · Tu ₀ ^b2 · DV _Tu ^b3 + b ₆ · pH ^b7 (14)
Here, b ₁ , b ₂ , b ₃ , b ₆ , and b ₇ are coefficients, which are determined in advance in a basic test and stored in the memory 650.

The calculation formula of the target value DV _Al aluminum residual percentage considering the pH, (14) is not limited to type, for example, it may be combined into a single function, as (11).

According to the fifth embodiment, by taking into account the pH to arithmetic expression of the target value DV _Al aluminum residual rate, it is possible to calculate the target value DV _Al aluminum residual rate more accurately.

Example 6 is a case where the ultraviolet light absorbance E ₂₆₀ measured by the raw water sensor 210 is taken into account in the equation for calculating the target value DV _Al of the aluminum residual rate of the first correction value calculation function 654.

When the ultraviolet absorbance E ₂₆₀ is considered, the target value DV _Al of the aluminum residual rate is calculated according to the equation (15).
[Equation 15]
DV _Al = b ₁ · Tu ₀ ^b2 · DV _Tu ^b3 + b ₈ · E ₂₆₀ ^b9 (15)
Here, b ₁ , b ₂ , b ₃ , b ₈ and b ₉ are coefficients, which are determined in advance in a basic test and stored in the memory 650.

Note that the calculation formula of the target value DV _Al of the aluminum residual rate considering the ultraviolet absorbance E ₂₆₀ is not limited to the formula (15), and for example, it may be combined into one function like the formula (11). Good.

According to the sixth embodiment, by taking into account the UV absorbance E ₂₆₀ to the arithmetic expression of the target value DV _Al aluminum residual rate, it is possible to calculate the target value DV _Al aluminum residual rate more accurately.

FIG. 9 shows a configuration diagram of the flocculant injection control system in the seventh embodiment. In Example 7, a water intake sensor 240 is installed at a water intake 180 before the water receiving well 110, and turbidity at the water intake (hereinafter referred to as "water intake turbidity") is measured by the water intake sensor 240. In this case, the basic coagulant injection rate F ₀ is calculated from the intake port turbidity and the water quality data measured from the raw water sensor 210.

The intake port turbidity Tu ₂ measured by the intake port sensor 240 is temporarily stored in the memory 650.

From the water quality data measured by the raw water sensor 210 and the intake port turbidity Tu ₂ measured by the intake port sensor 240, the basic coagulant injection rate F ₀ is calculated according to the equation (16).
[Equation 16]
^{_{F 0 = a 1 · Tu 0}} a2 + a 3 · AL 0 a4 + a 5 · (Tu 2 -Tu 2 (t-Δt a)) ·· (16)
Here, a ₁ , a ₂ , a ₃ , a ₄ , and a ₅ are coefficients, which are determined in advance in a basic test and stored in the memory 650. Tu ₂ (t−Δt ₃ ) is the intake port turbidity Tu ₂ before Δt ₃ from the current time t.

Incidentally, the formula for calculating the basic coagulant injection rate F ₀ is not limited to the equation (16). In addition, other water quality data such as the water temperature T ₀ , pH, or ultraviolet absorbance E ₂₆₀ may be measured by the raw water sensor 210, and the basic flocculant injection rate F ₀ may be calculated according to an equation that takes them into account.

The basic flocculant injection rate F ₀ is temporarily stored in the memory 650.

According to Example 7, by taking into account the intake turbidity Tu ₂ in the formula for calculating the basic flocculant injection rate F ₀ in Example 1, it is quicker with respect to a rapid change in turbidity than in Example 1. It is possible to correct the flocculant injection rate.

Further, in the equation (16), the intake port turbidity Tu ₂ is taken into consideration, but the water quality of the water other than the intake port turbidity Tu ₂ can be measured by the intake port sensor 240, and the basic flocculant injection is performed using those water qualities. The rate F ₀ may be calculated. For example, the basic coagulant injection rate F ₀ is calculated according to the equation (17) considering the alkalinity AL ₂ measured by the water intake sensor.
[Equation 17]
F ₀ = a ₁ · Tu ₀ ^a2 + a ₃ · AL ₀ ^a4 + a ₅ · (Tu ₂ −Tu ₂ (t−Δt _a )) + a ₆ • (AL ₂ −AL ₂ (t−Δt ₃ ))... (17)
Here, a ₆ are coefficients, determined in advance by basic tests, are stored in the memory 650 within. AL ₂ (t−Δt ₃ ) is an alkalinity AL ₂ that is Δt ₃ before the current time t.

In the eighth embodiment, the correction value weight calculation function 657 is stored in the memory 650 of the management unit 600 according to the second embodiment. Correction value weight calculator function 657 is responsible for determining the weight of a plurality of correction values from the rate of change R _Tu0 raw water turbidity Tu _0.

First, according to (18), calculates a change rate _{R Tu0} of the raw water W1 turbidity Tu _0.
[Equation 18]
R _Tu0 = (Tu ₀ -Tu ₀ (t−Δt ₄ )) / Tu ₀ (18)
Here, Tu ₀ (t−Δt ₄ is the raw water W1 turbidity Tu ₀ before Δt ₄ from the current time t.

Next, a weight w ₁ to be multiplied by the first correction value Q ₁ using the aluminum residual rate R _Al as an index is calculated according to the equation (19).
[Equation 19]
w ₁ = e ₁ · | R _Tu0 | (19)
Here, e ₁ is a coefficient, which is determined in advance in a basic test and stored in the memory 650. Further, the equation for calculating the weight w ₁ to be multiplied by the first correction value Q ₁ is not limited to the equation (19).

Finally, according to the equation (20), the weight w ₂ to be multiplied by the second correction value Q ₂ using the turbidity Tu _s of the precipitation treated water W3 as an index is calculated.
[Equation 20]
w ₂ = 1−w ₁ (20)
FIG. 10 a shows the relationship between the change rate (horizontal axis) and the correction value weight w ₁ (vertical axis). In short, the weight w _{1 of the} correction value is increased as the absolute value of the change rate is larger. In addition, FIG. 10 b shows how the turbidity (vertical axis) of the raw water W1 decreases and stabilizes after greatly increasing with time (horizontal axis). Moreover, FIG. 10c has shown a mode that the turbidity change rate (vertical axis) of the raw | natural water W1 at the time of FIG. 10b fluctuates with time passage (horizontal axis).

In the eighth embodiment, the injection rate correction function 655 acquires the correction value weights w ₁ and w ₂ calculated by the correction value weight calculation function 657, and calculates the coagulant injection rate F ₁ according to the equation (21).
[Equation 21]
F ₁ = F ₀ + w ₁ · Q ₁ + w ₂ · Q ₂ (21)
According to the equations (19), (20), and (21), in the transient phenomenon of FIG. 10 (when the turbidity (vertical axis) of the raw water W1 suddenly increases), the flocculant injection rate F ₁ In addition, the first correction value Q ₁ using the aluminum residual ratio R _Al as an index becomes dominant, and after stabilization, the second correction value Q ₂ using the turbidity Tu _s of the precipitated treated water W3 as an index becomes dominant.

According to Example 8 enhanced, as the change rate R _Tu0 of the raw water W1 turbidity Tu ₀ is large, the effect of the first correction value Q ₁ in which the aluminum concentration as an index is large, the same robustness as in Example 1 In addition, the precipitation-treated water turbidity Tu _s can be stably maintained at a preset target value DV _Tu of the precipitation-treated water turbidity.

In Example 8, but calculating the weight of the correction value from the change rate _{R Tu0} of the raw water W1 turbidity Tu _0, may be water other than raw water W1 turbidity Tu ₀ measured by the raw water sensor 210. Examples of the water quality other than the raw water W1 turbidity Tu ₀ include alkalinity AL ₀ , water temperature T ₀ , pH, ultraviolet absorbance E _{260 and the} like. You may calculate the weight of a correction value with those magnitude | sizes or a change rate. Further, the water quality for calculating the weight of the correction value is not limited to one type, and a plurality of water qualities measured by the raw water sensor 210 may be combined.

  Moreover, in Example 8, the water quality data of the raw water sensor 210 is used, but when there is a water intake sensor 240 as in Example 7, it is measured by the water intake sensor 240 instead of the water quality data of the raw water sensor 210. The weight of the correction value may be calculated using the water quality data.

In FIG. 11, the block diagram of the coagulant | flocculant injection | pouring control system in Example 9 is shown. In Example 9, a filtrate water sensor 250 is installed at the outlet of the filtration basin 160, the filtrate water turbidity Tu ₃ is measured from the filtrate water sensor 250, and the third correction value Q _{3 is} calculated from the measured filtrate water turbidity Tu ₃ . This is a case where

  In the ninth embodiment, a third correction value calculation function 658 is stored in the memory 650 of the management unit 600 of the first embodiment.

The processing flow of the third correction value calculation function 658 is the same as the processing flow of the second correction value calculation function, but the target of the filtered water turbidity stored in the memory 650 in advance, not the sedimentation water turbidity Tu _s. The calculation of the third correction value Q ₃ is different from the value DV _Tu3 and the filtered water turbidity Tu ₃ .

According to Example 9, in injection rate correction function 655 of the first embodiment, the process is added to obtain a third correction value Q ₃ calculated by the third correction value calculation function 658, in accordance with (22), aggregating agents calculates the infusion rate _{F 1.}
[Equation 22]
F ₁ = F ₀ + Q ₁ + Q ₂ + Q ₃ (22)
According to Example 9, the robustness of the control is further improved as compared with Example 1 by adding correction based on the filtered water turbidity Tu ₃ , and the precipitation treated water turbidity Tu _s is set to a preset precipitation. It can be stably maintained at the target value DV _Tu of the treated water turbidity.

DESCRIPTION OF SYMBOLS 10 ... Flocculant injection | pouring control system 100 ... Water purification treatment facility 110 ... Landing well 120 ... Mixing basin 130 ... Flock formation basin 140 ... Sedimentation basin 150 ... Filtration basin 160 ... Water purification basin 170 ... Chemical injection facility 180 ... Water intake sensor 210 ... Raw water Sensor 220 ... Aluminum measuring device 221 ... Pump 222 ... Tank 223 ... Stirring tank 224 ... Absorbance measuring device 225 ... Waste liquid tank 226 ... Solenoid valve 230 ... Precipitation water sensor 240 ... Intake sensor 250 ... Filtration water sensor 300 ... Flock classifier 310 ... Filtration tank 320 ... Rotary filter 330 ... Motor 340 ... Pump 400 ... Water purification facility control means 500 ... Network 600 ... Management means 610 ... CPU
620 ... Network interface 650 ... Memory 651 ... Data collection function 652 ... Aluminum concentration conversion function 653 ... Injection rate calculation function 654 ... First correction value calculation function 655 ... Injection rate correction function 656 ... Second correction value calculation function 657 ... Correction value Weight calculation function 658 ... third correction value calculation function

Claims (12)

In a flocculant injection control system of a water purification plant comprising a floc formation pond for injecting flocculant into raw water to form flocs, and a settling basin and a filtration basin for separating and removing flocs,
A raw water sensor that measures at least the turbidity of the raw water;
A sampling unit for collecting flocculant injection water obtained by injecting flocculant into raw water;
An aluminum measuring device for measuring the concentration of aluminum contained in the collected flocculant injection water;
An injection rate calculation function that calculates the basic flocculant injection rate using the measured value of the turbidity of the raw water sensor,
A first correction value calculation function for calculating a correction value of the coagulant injection rate from the measured value of the aluminum concentration and its target value;
As a sum of the calculated basic flocculant injection rate and the first correction value, an injection rate correction function for determining the flocculant injection rate,
A flocculant injection control system comprising: The flocculant injection control system according to claim 1,
A flocculant injection control system using flocs having a predetermined particle size contained in the flocculant injection water when measuring aluminum contained in the collected flocculant injection water. The flocculant injection control system according to claim 2,
The flocculant injection control system characterized in that flocs having a particle diameter of 50 μm or less and having a particle diameter in a predetermined range are used separately as the flocs of the predetermined particle diameter. The flocculant injection control system according to claim 1,
Precipitation treated water sensor that measures water quality including at least turbidity of the clarified treated water, and a second correction value that calculates a second correction value of the coagulant injection rate using this measured value and the target value of the clarified turbidity A coagulant injection control system, wherein the injection rate correction function determines a coagulant injection rate as a sum of the basic coagulant injection rate and the first correction value and the second correction value. . The flocculant injection control system according to claim 4,
The water quality measuring means of the filtered water of the filtration pond, and a third correction value calculating function for calculating a third correction value of the coagulant injection rate using the measured value of the water quality measuring means and the target value of the filtered water, The injection rate correction function determines the flocculant injection rate as the sum of the calculated basic flocculant injection rate, the first correction value, the second correction value, and the third correction value. The flocculant injection control system according to claim 1,
In addition to turbidity, one or more of alkalinity, water temperature, pH, and UV absorbance are input as water quality items to be measured by the raw water sensor, and the input value is reflected in the calculation of the first correction value. Flocculant injection control system. The flocculant injection control system according to claim 1,
A flocculant injection control system comprising a water intake sensor for detecting turbidity at a water intake for taking in the raw water, and reflecting the output of the water intake sensor in the calculation of the basic flocculant injection rate. The flocculant injection control system according to claim 7,
A flocculant injection control system that calculates a basic flocculant injection rate of a flocculant using a measured value at a water intake point and a change amount per unit time. The flocculant injection control system according to claim 4,
Flocculant injection control characterized by having a correction value weight calculation function for calculating a weight coefficient when adding a correction value for the flocculant injection rate using the measured value of the raw water sensor and the amount of change per unit time system. The flocculant injection control system according to claim 9,
The weighting coefficient given to the first correction value and the second correction value of the flocculant injection rate is such that when one weighting factor is increased, the other weighting factor is decreased. Control system. The flocculant injection control system according to claim 9,
The first correction value is output when the time change rate of turbidity measured by the raw water sensor is large, and the second correction value is output when the time change rate of turbidity measured by the raw water sensor is small. A flocculant injection control system characterized by having a relationship that greatly affects The flocculant injection control system according to claim 1,
The first correction value of the flocculant injection rate is obtained by calculating the aluminum residual rate target value calculated from the turbidity measured by the raw water sensor and the target value of the precipitation-treated water turbidity, and the aluminum concentration measurement value as the flocculant injection rate (aluminum concentration A coagulant injection control system characterized in that the aluminum residual rate is determined so as to approach the target value of the aluminum residual rate based on the aluminum residual rate obtained by dividing by (conversion).

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