JP2002005814A - Method for evaluating state of clean water floc formation, and system for controlling injection of flocculant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for evaluating the floc grain diameter distribution, capable of covering tens of microns or smaller for judging the propriety of floc flocculation in a clean water treating process. SOLUTION: The method for evaluating the floc grain diameter distribution includes a process 200 to measure intensity of transmitted a light through flocculation water in a flocculation reaction tank 30, a process 300 for registering and make reference to the time series of the intensity of the transmitted light in the representative state of floc formation as a template 390, and a process 400 for evaluating the ratio of flocculation failure flocs by collation computations between the continuously measured time series of the intensity of the transmitted light and a template. By grasping the ratio of the flocculation failure flocs, it is possible to appropriately operate the injection of a flocculant and to stabilize the quality of treated water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flocculant injection control in a water purification treatment process, and more particularly to a method for online evaluation of a floc formation state serving as a criterion for determining a flocculant injection amount.

[0002]

2. Description of the Related Art As a method for judging the quality of coagulation and sedimentation treatment, which is a main step of a water purification treatment process, a method of evaluating the state of floc formation using process measurement data has been used. As a conventional method, a method of measuring the transmitted light intensity of the coagulated water in the coagulation reaction tank and a method of performing image processing on a floc image are representative. In the former method, for example, “online continuous measurement of floc formation state using ultraviolet / near-infrared light absorption” (Otoki et al., Proceedings of the 43rd National Waterworks Research Conference, 1992), and JP-A-7-204412 As shown in the above, attention is paid to the fact that the temporal fluctuation width of the transmitted light intensity of the flocculated water (dispersion with respect to the moving average value in a predetermined time; referred to as fluctuation) has a correlation with the average particle size of the flocculated particles. In addition, the average diameter of the flock can be evaluated.

[0003] In the latter method, as disclosed in Japanese Patent Application No. 2-290801 or the like, a portion where floc is present in an image of flocculated water imaged by an ITV camera is compared with other background portions. By using the fact that the brightness is high, only the flocks can be identified. The diameter of each floc can be evaluated based on the identification result and the imaging area of each pixel determined by the imaging conditions.

Since the above transmitted light intensity measurement method can be implemented by a relatively simple laser device, it is practically useful, but it is difficult to evaluate the distribution of the floc diameter, which should have variation, and it is difficult to evaluate the average diameter information. Stay only. On the other hand, the image processing method can measure the distribution of the floc diameter. However, since only flocs having a diameter of several tens to 100 μm or more are generally targeted, there are cases where flocs having a small diameter cannot be measured due to poor coagulation.

[0005]

In the above prior art,
It has been difficult to continuously measure the floc diameter distribution formed in the coagulation reaction tank in the water purification process in a range covering a particle size of several tens of μm or less. Of course, even if the average diameter of the floc and the distribution of the floc particle size of 100 μm or more can be grasped, it can be an effective means for judging whether or not the aggregation is good.
However, considering that flocs that directly affect the treated water quality are minute flocs that are difficult to settle and separate in the sedimentation basin following the flocculation reaction tank, the floc particle size distribution of several tens of μm or less cannot be measured. In the method, it is difficult to provide information for accurately evaluating the deterioration of treated water quality due to poor coagulation.

An object of the present invention is to provide a floc formation state evaluation method capable of grasping the floc particle size distribution in a range including even minute flocs so that deterioration of treated water quality due to poor coagulation flocs can be evaluated. Another object is to provide a coagulant injection control method that satisfies a predetermined treatment water quality based on the evaluation of the floc formation state.

[0007]

In order to achieve the above object, the present invention provides a method for evaluating the state of floc formation based on optical measuring means in a flocculation reaction tank of a water purification plant. A transmitted light intensity measurement step of measuring transmitted light intensity over time, and a state in which floc formation is favorable,
A template reference step in which the time-series measurement values in the transmitted light intensity measurement step in a defective state can be registered and referenced as a template, and the time-series data in the transmitted light intensity measurement step and the template registered in the template reference step And a floc formation evaluation step of evaluating the ratio of the formation failure flocs in the flocs corresponding to the time-series data by a collation operation with the time series data.

Further, the floc formation evaluation step approximates and develops the time-series data from the transmitted light intensity measuring step into a linear sum of the template data registered in the template reference step, and based on the expansion coefficient, detects the formation failure floc. It is characterized by including a calculation step of estimating the ratio.

According to the present invention, in a flocculant injection control system for determining an injection amount of a flocculant into a water purification process based on a process measurement value, a ratio of defective flocs is estimated by the floc formation state evaluation method. The floc formation state evaluation system to be output, and the injection amount of the flocculant is determined based on the deviation between the target value of the percentage of defective floc formation and the estimated value of the percentage of defective floc output from the floc formation state evaluation system. And a coagulant injection control logic.

[0010] According to the present invention, the floc formation state evaluation method can evaluate the floc particle size distribution in the flocculation reaction tank in the water purification treatment process over a wide range by processing the measurement values from the simple optical measuring means. As a result, it is possible to obtain information directly reflected in the quality of the treated water, such as the percentage of flocs whose formation is poor. Further, by performing the coagulant injection control based on the acquired information, it is possible to stabilize the quality of the treated water.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method for evaluating the quality of floc formation that directly affects the quality of treated water during coagulation and sedimentation in a water purification process. The water purification process referred to here means that the suspended solids in the raw water are flocculated by flocculation by injecting a flocculant, such as the rapid filtration method that is the most widely used current treatment method, and then turbid by solid-liquid separation in a sedimentation tank. Refers to the process of doing

One of the main manipulated variables in the water treatment process is the coagulant injection volume. In general, the injection amount is determined by using an injection model formula with the raw water quality as an explanatory variable and making corrections as necessary. As a method of correcting the injection amount, a method of feeding back a deviation between a target value and an actually measured value of turbidity of a supernatant liquid of a sedimentation basin (referred to as sediment turbidity at a water purification plant site) is widely used. In addition, a driver evaluates the state of floc formation in the agglutination reaction tank by visual observation and corrects it empirically. Desirable floc formation is a state in which a strong floc having a large floc diameter and a high density is formed, so that sedimentation in the sedimentation basin is rapid and no floc remains in the supernatant liquid.

The method according to the present invention provides a means for estimating the distribution of the floc diameter in a wider range and optimizes the correction of the flocculant injection. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the overall configuration of a coagulant injection control system according to one embodiment of the present invention. The flocculant injection control system 600 determines the flocculant injection control logic 550 based on the percentage of flocs having good flocculation (or the percentage of flocks having poor flocculation) evaluated by the floc formation state evaluation system 500.
Determine the coagulant injection amount internally. The operation units of these processes are constructed as software on a computer system. In addition, various water quality sensors 4 necessary for coagulant injection control
5. Data from the water quality sensor 60 and output signals to the coagulant injection device 40 are input and output via a computer network (not shown) in the water purification plant.

Next, the general flow of the operation of the coagulant injection control system 600 will be described. The water quality data measured by the water quality sensor 45 that measures the quality of the raw water flowing into the water purification process is transmitted to the coagulant injection control system 600 at regular intervals. The water quality items here are turbidity, alkalinity, p
H, water temperature, etc. These water quality data are sent to the coagulant injection control logic 550, and the coagulant injection amount is first determined feed-forward. In addition, the data of the transmitted light intensity of the coagulated water measured by the transmitted light intensity measuring device 50 installed in the coagulation reaction tank 30 is also sent to the flocculant injection control system 600, and then sent to the floc formation state evaluation system 500. ,
Used for estimating good floc rate.

The deviation between the target good floc rate input from the keyboard 601 and the good floc rate estimated by the floc formation state evaluation system 500 is input to the coagulant injection control logic 550, and is fed forward from raw water quality. A correction amount for the determined coagulant injection amount is set.

The set coagulant injection amount (or injection rate with respect to the raw water flow rate) is transmitted to the coagulant injection device 40, and the coagulant in the coagulant tank 25 is injected into the coagulation reaction tank 30. The injected coagulant coagulates with the turbidity in the raw water to form flocs. The deviation between the sediment turbidity measured by the water quality sensor 60 at the sedimentation tank outlet and the target turbidity is also reflected in the coagulant injection control logic 550, and the correction amount of the coagulant injection is determined in a feedback manner.

By the above operation, more appropriate combination of the injection amount correction with a small time delay based on the evaluation of the floc formation state in the agglutination reaction tank 30 and the injection amount correction based on the measured value of the treated water quality is used. Achieve coagulant injection control.

The floc formation state evaluation system 500 includes a transmitted light intensity measurement step 200, a template reference step 300,
It is composed of a software module group for realizing the floc formation evaluation step 400 and a template DB 390.

In the transmitted light intensity measurement step 200, a signal of a measurement instruction is output to the transmitted light intensity measurement 50, and time-series measured values are obtained. A time series measurement value in a typical floc formation state, such as a state where floc formation is very good without agglomeration failure and a state where floc diameter is small and coagulation is not very good, is registered as a template in the template DB 390. . In the template reference step 300, registration in the template DB 390 and template data reference processing for the floc formation evaluation step 400 described later are performed.

In the floc formation evaluation step 400, a matching operation is performed between the time-series data of the transmitted light intensity at each time point acquired in the transmitted light intensity measurement step 200 and the template registered in the template DB 390, and the floc particle at each time point is calculated. Estimate the diameter distribution. Based on the estimation result, the ratio of the floc having poor coagulation and the ratio of the floc having good coagulation are obtained and output to the coagulant injection control logic 550.

The above is an outline of the configuration and operation of the coagulant injection control system 600 according to the present embodiment. According to this embodiment, time-series data of transmitted light intensity in a typical floc formation state is prepared as a template, and collation with continuous time-series data is performed to evaluate the floc formation state. Hereinafter, details of each component will be described in order.

FIG. 2 shows the structure of a transmitted light intensity measuring device 50 for measuring the transmitted light intensity of the coagulated water in the agglutination reaction tank 30, and near-infrared wavelength light radiation capable of being immersed in the agglutination reaction tank. It consists of a detector and a light receiver. That is, the emitter 51 and the detector 52 face each other with the flocculated water
Is fixed, and the whole can be immersed in the agglutination reaction tank 30.

Light having a predetermined intensity is emitted from the emitter 51. The wavelength of the emitted light is preferably in the visible to near-infrared region, and an element such as a light emitting diode (LED) can be used. Some of the emitted light is reflected, absorbed, and scattered by the flocs in the flocculated water, but the remaining light is transmitted and received by the detector 52. As the detector 52, a photoelectric element can be used. The intensity received here, that is, the transmitted light intensity is converted into an electric signal and transmitted to the floc formation state evaluation system 500. The timing and cycle of the measurement are performed according to an instruction from the transmitted light intensity measurement step 200.

Next, the detailed operation of each component of the floc formation state evaluation system 500 will be described. FIG. 3 is a flowchart showing the processing of the transmitted light intensity measurement step 200. In this step, the measurement by the transmitted light intensity measuring device 50 installed in the agglutination reaction tank 30 is controlled.

In a first measurement condition setting step 210, measurement conditions input from the operator via the keyboard 601 are set. The measurement conditions here refer to the timing, cycle, time series length, and the like measured by the transmitted light intensity measurement device 50 as described above. In the next light emission synchronization step 220, the emitter 5 is driven in accordance with the timing set in the measurement condition setting step 210.
Outputs a trigger to emit light from 1.

In the measurement light emitting step 230, light for measurement is emitted from the emitter 51 with a predetermined output. In the next transmitted light receiving step 240, of the light emitted from the emitter 51, the light passing through the optical path in the condensed water to the detector 52 is received by the detector 52. In the last received signal output step 250,
The signal photoelectrically converted by the detector 52 is output and stored as data usable by the floc formation state evaluation system 500. The above processing is repeated at a set cycle to obtain time-series data of transmitted light intensity. The data obtained here is registered in the template DB 390 as a template or used for evaluating the floc formation state at that time.

FIG. 4 shows a flowchart of the template reference process. In the template reference step 300, template registration and template reference at the time of evaluation of the floc formation state are performed. In the registration condition setting step 310, conditions for registering the template are set. The registration conditions include the number of time-series data steps constituting the template, the time interval between steps, and the like.

In a registration start instruction step 320, an instruction to start registration is received from the driver via the keyboard 601, and measurement of transmitted light intensity for registration is started. In the measurement step 330, measurement is performed under the set conditions. The measurement here can be performed in the same procedure as that described in the transmitted light intensity measurement step 200.

When the required number of data steps has been measured, a registration end confirmation step 340 presents a registration end confirmation prompt. After confirming the end of registration and inputting the template name, the corresponding floc particle size distribution data name, etc., the registration is completed. In the final measurement time series data output step 350, the time series data and additional information such as the template name are output to the template DB 390 and stored.

FIG. 5 is an explanatory diagram of a template registered in the template DB. In this example, two templates named “good flocculation floc” and “good flocculation floc” are registered as typical floc formation states. Each time series of the transmitted light intensity has a fluctuation component of a different amplitude. It is known that there is a correlation between the amplitude (variance or standard deviation) with respect to the average value of the time series data and the average floc diameter.

Conventionally, the state of floc formation is evaluated based on the average diameter of the flocs based on this correlation. In the method according to the present embodiment, the ratio of good flocs and poor flocs to all flocs is evaluated. In addition, when the floc particle size distribution for “cohesive good flocs” and “cohesive poor flocs” is registered together with the template,
It is possible to estimate not only the ratio of the “good flocculation floc” and the “floc poor floc” at that time, but also the particle size distribution of the mixed floc mixed with them. In the example of FIG. 5, two typical floc formation states are provided, but three or more floc formation states can be used as necessary.

FIG. 6 is a flowchart showing the process of the floc formation evaluation process. In step 400, the floc formation state evaluation as described above is performed by comparing the time-series data of the transmitted light intensity with the template in the template DB 390. In the first measurement time series reading step 410, the time series data input via the transmitted light intensity measurement step 200 is read and used for subsequent calculations. In the template reading step 420, all templates registered in the template DB 390 are read, and can be used for the subsequent calculations as before.

In the template matching step 430, a collation operation between the time series data and the template data is performed.
It is determined which template the current time-series data is closest to. The collation operation here includes, for example, (1) comparison of autocorrelation coefficient patterns, (2) comparison of power spectra decomposed into frequency components, and (3) variance (or standard deviation).
And (4) a method of comparing the two based on the magnitude of the cross-correlation coefficient. For (1) and (2), it is determined that the template with the highest pattern similarity, (3) is the template with the closest value itself, and (4) is the template with the largest correlation coefficient is close to the current floc formation state. . This result is output to the CRT 602 and can be displayed as driving guidance. If such guidance is not required, the template matching step 430
May be skipped without performing.

In the next linear sum development step 440, processing is performed to develop the current transmitted light intensity time series data into a linear sum of the time series data of a plurality of templates. This is based on the assumption that the transmitted light intensity in the case where flocs having different formation states are mixed is the transmission light intensity in each formation state superimposed at the respective existing ratios. If the transmitted light intensity measurement contains noise or the assumption of the tatami mat is not strictly established, it is difficult to completely expand the linear sum. Become.

FIG. 7 is a flowchart showing an example of the calculation method. This example describes a case where two representative floc aggregation states are “good aggregation floc” and “incomplete aggregation floc”. The mixed floc transmitted light intensity Lgp is calculated as the linear sum of the flocculated good floc transmitted light intensity Lg and the flocculated defective floc transmitted light intensity Lp while changing the defective coagulated floc rate α at a predetermined width, and Calculate correlation coefficients and errors.

In the poor flocculation rate determining step 450, the current poor flocking rate α is determined based on a preset criterion.

For example, when the correlation coefficient between Lgp and L is used as a criterion, 0 ≦≦
It suffices to select α that maximizes the correlation coefficient in the range of α ≦ 1. The flocculation failure floc rate α or the flocculation good floc rate (1-α) determined here is determined by the flocculant injection control logic 5
Sent to 50, depending on the deviation from the target floc rate,
The coagulant injection amount is corrected.

When the template DB390 has registered therein each template, that is, floc diameter distribution data corresponding to a representative floc formation state, the floc rate of each formation state (in this example, α and 1−α ), The particle size distribution of the mixed floc at the present time can be estimated. According to this, even a particle size distribution of several tens of μm or less can be estimated. It should be noted that the control target may be set as the target floc particle size distribution instead of the above-described floc rate, and the coagulant injection correction may be performed.

The above is the floc formation state evaluation system 500
Is an embodiment of a flocculant injection control system 600 including By performing the coagulant injection control that reflects the ratio of flocs with poor coagulation, stable water purification can be achieved.

[0041]

According to the present invention, it is possible to evaluate the floc particle size distribution in the flocculation reaction tank in the water purification treatment process in a wide range by processing the measurement values from the simple optical measuring means. There is an effect that information directly reflected in the quality of treated water, such as the ratio of defective flocks, can be obtained. Further, by performing the coagulant injection control based on the acquired information, the quality of the treated water can be stabilized.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a floc formation state evaluation system according to the present invention.

FIG. 2 is an explanatory view of a transmitted light intensity measuring device for measuring transmitted light intensity of coagulated water.

FIG. 3 is a flowchart illustrating a transmitted light intensity measurement process.

FIG. 4 is a flowchart illustrating processing of a template reference step.

FIG. 5 is an explanatory diagram of a template of time-series data of transmitted light intensity.

FIG. 6 is a flowchart illustrating processing of a floc formation evaluation step.

FIG. 7 is a flowchart illustrating an example of a process of a linear sum expansion process.

[Explanation of symbols]

25 ... flocculant tank, 30 ... flocculation reaction tank, 40 ... flocculant injection device, 45 ... water quality sensor, 50 ... transmitted light intensity measurement device, 60 ... water quality sensor, 200 ... transmitted light intensity measurement process, 300 ... template reference process , 390: template DB, 400: floc formation evaluation process, 500: floc formation state evaluation system, 550
... flocculant injection control logic, 600 ... flocculant injection control system, 601 ... keyboard, 602 ... CRT.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) G01N 21/59 G01N 21/59 C 33/18 33/18 A (72) Inventor Naoki Hara Hitachi City, Ibaraki Prefecture 5-2-1 Omika-cho Hitachi Ltd. Omika Works F-term (reference) 2G059 AA05 BB06 CC19 CC20 DD05 EE01 FF07 FF08 GG02 HH01 HH02 KK01 MM01 MM03 MM05 MM10 PP04 4D062 BA19 BA32 BB05 CA14 EA03

Claims (4)

[Claims] 1. A method for evaluating the state of floc formation based on optical measurement means in an agglutination reaction tank of a water purification plant, wherein a transmitted light intensity measuring step of measuring a transmitted light intensity of the agglutination water of the agglutination reaction tank over time, A template reference step in which a time series measurement value in the transmitted light intensity measurement step in a good state of floc formation and in a poor state is registered and referenced as a template, and the time series data and the template in the transmitted light intensity measurement step A floc formation evaluation step for evaluating a ratio of defective flocks formed in the flocs corresponding to the time-series data by a collation operation with the template registered in the reference step. . 2. The floc formation evaluation step according to claim 1, wherein the time series data obtained by the transmitted light intensity measurement step is approximately developed into a linear sum of template data registered in the template reference step, and based on a development coefficient. A method for evaluating the formation state of purified water flocs, comprising a calculating step of estimating the ratio of poorly formed flocs. 3. A flocculant injection control system for determining an injection amount of a flocculant into a water purification treatment process based on a process measurement value, wherein the ratio of defective flocs formed by the floc formation state evaluation method according to claim 1 or 2. A floc formation state evaluation system for estimating and outputting a flocculant injection based on a deviation between a target value of a poorly formed floc rate and an estimated value of a poorly formed floc rate output from the floc formation state evaluation system. A coagulant injection control system comprising coagulant injection control logic for determining an amount. 4. The method according to claim 3, wherein the means for realizing the transmitted light intensity measuring step comprises a near-infrared wavelength light emitter and a light receiver capable of being immersed in the agglutination reaction tank. A unique coagulant injection control system.