JP5571424B2 - Method and apparatus for controlling the injection rate of flocculant in real time - Google Patents

Description

  The present invention relates to a method and an apparatus for controlling the injection rate of a coagulant in real time in a coagulation process of raw water to be treated in a water purification plant or a water treatment facility.

In water purification plants that employ a rapid filtration system, generally a flocculant is injected and a rapid agitation is carried out, a floc formation pond in which agglomerates (floc) generated in the admixture are grown, and a grown floc It is composed of a sedimentation basin for removing sediments and a filtration basin for removing particles and flocs that did not settle.
The important point of the water purification process by the rapid filtration method is to control the injection rate of the flocculant to an appropriate value according to the raw water quality and to form a floc with good sedimentation.

When flocculation is performed at an inappropriate injection rate, the loss of flocs from the sedimentation basin and the failure of flocculation increase the loss head of the filtration basin, the frequency of backwashing, and the flow of fine particles from the filtration basin. Problems occur.
As one of these problems, there is a problem that non-ferrous heavy metals, light metals, etc. exceeding the standard values stipulated by the ministerial ordinance flow out of the filter basin.
For example, with respect to aluminum, the standard value for aluminum and its compounds is 0.2 mg / L or less as a standard that does not hinder the use of tap water as domestic water or that may cause damage to water facilities. It has been established.
In recent years, scientific data showing the relationship between aluminum intake and Alzheimer's syndrome have also been published.

  Therefore, in the agglomeration process of the raw water to be treated at the water purification plant or the water treatment facility, it is indispensable to perform the agglomeration treatment at an appropriate injection rate.

However, the appropriate flocculant injection rate varies depending on the raw water turbidity, alkalinity, pH, water temperature, etc., and differs depending on the river surface water. Therefore, the flocculant injection rate is uniquely determined based only on the raw water turbidity. It cannot be determined.
For this reason, conventionally, in water purification plants, the following methods are used to determine the agglomeration status and to determine or control the coagulant injection rate.

(1) Jar test Collect a certain amount of raw water to be processed in several beakers, change the injection rate step by step for each beaker, cause agglomeration reaction by rapid stirring and slow stirring, for a predetermined time The flocculation agent injection rate is determined by determining the supernatant water turbidity or the sedimentation state of flocs after only allowing to stand.
Although these operations are generally performed by manual analysis, as described in Patent Document 1, from the sampling of raw water, the flocculant is injected, the rotation speed and rotation time of the stirrer are set, and the supernatant water is suspended. An automatic jar tester that automatically measures the degree is also put into practical use.

(2) Injection rate formula Feed-forward control is performed based on an injection rate formula that expresses the relationship with the appropriate flocculant injection rate, using the water quality such as turbidity, pH, alkalinity, and water temperature of the raw water as parameters. The injection rate formula is determined by an empirical method based on the jar test and sedimentation water turbidity of the facility. There are examples of development of this method, such as incorporating feedback control based on the measured value of sediment water turbidity, and using fuzzy or neuro control to bring the result of jar test by the operator closer to the actual operation of the facility. .

(3) Aggregation sensor As in the method described in Patent Document 2, the flow of the fluid to be measured is irradiated with a light beam, and the average particle size and number concentration of flocs are obtained from the average value and standard deviation of the amount of transmitted light. At the same time, the flocculant injection rate is controlled so that the average particle size becomes an appropriate value.

Such a determination method of agglomeration status by the above method or a determination method of the coagulant injection rate has the following problems.
The method using the jar test of (1) requires a skilled operator, and further has a problem that the result tends to vary depending on the operator. In addition, since it takes a long time of about 30 minutes to determine the agglomeration status and the appropriate coagulant injection rate, it is difficult to perform frequent jar tests, and the reflection to the coagulant injection rate of the implementation facility is delayed. There is.
With an auto jar tester that automates the jar test work, the operator's work is greatly reduced, but it still takes about 30 minutes to obtain a measurement result, and the problem of a large time lag cannot be solved.

  In the method of (2) using the injection rate formula, the injection rate formula differs depending on the raw water. Therefore, the injection rate formula must be managed for each water treatment plant, and there is no guarantee that the injection rate formula can be used permanently. In other words, the relationship between the water quality and the optimal coagulant injection rate may be disrupted when a dam is formed upstream from the intake, riverbank construction is performed, or due to heavy rain, etc. There is a problem that there is no universality in time.

The method using the aggregation sensor of (3) can automatically manage the flocculant injection rate in real time so as to obtain an appropriate floc particle size, and the problem of the operator and time lag of (1), (2 ) To solve the problem of universality. However, the appropriate floc particle size differs depending on the raw water quality, and in order to automatically control the flocculant injection rate, a database must be created in advance regarding the relationship between raw water turbidity and optimum floc particle size. I must. In other words, there is a problem that data from the aggregation sensor must be acquired throughout the four seasons, and it takes time until the official operation.
In addition, there are similar problems with coagulation precipitation in industrial water, sewage and factory wastewater.

Japanese Patent Application Laid-Open No. 2-114178 Japanese Patent No. 3205450 JP 2009-672 A

  In view of the above problems, an object of the present invention is to provide a method and apparatus capable of controlling universally regardless of time and place and controlling the injection rate of the flocculant in real time. .

In order to achieve the above object, the present invention provides a method for controlling the injection rate of the flocculant in the flocculation process of the raw water to be treated.
This method is independent of the water quality measurement step for measuring the quality of raw water, the injection rate calculation step for calculating the basic flocculant injection rate from the obtained water quality measurement value, and the water quality measurement step. Agglomeration start time measurement step for measuring the time until the agglomeration of particles in raw water starts by injecting the agent, and recommended agglomeration agent injection rate from the measured value of the agglomeration start time A correction value calculating step of calculating a correction value from the difference between the agent injection rate determination step, the basic flocculant injection rate, and the recommended flocculant injection rate, and the basic flocculant injection rate based on the correction value. And an injection rate correction step of correcting.

  Further, the flocculant injection rate control method of the present invention is characterized in that the water quality measurement step measures turbidity or fine particles of raw water.

  The flocculant injection rate control method according to the present invention is the agglomeration start time when the flocculant injected into the raw water is supplied at the basic flocculant injection rate in the agglomeration start time measurement step. Is measured.

  Further, the flocculant injection rate control method of the present invention is the agglomeration start time measurement step, wherein each agglomerate is supplied when the flocculant is supplied at different flocculant injection rates to the raw water divided into a plurality of parts. It is characterized by measuring the start time.

  In the flocculant injection rate control method of the present invention, the recommended flocculant injection rate is determined based on the measured value of the agglomeration start time and a fitting line determined in advance.

  Further, the flocculant injection rate control method of the present invention is such that the fitting line collects a predetermined amount of raw water in a plurality of test water tanks, and sets different flocculant injection rates in advance for the sample water. A flocculant injection step for injecting the flocculant in step, agglomeration start time measuring step for measuring the agglomeration start time until the agglomeration of particles in each sample water starts after the flocculant injection, A fitting line calculation step for calculating a correlation between the agglomeration start time and the flocculant injection rate as a fitting line based on the agglomeration start time measured for each sample water and each of the flocculant injection rates. It is calculated.

Moreover, according to another aspect of the present invention, there is provided an apparatus for controlling the injection rate of the flocculant in the flocculation process of the raw water to be treated.
This apparatus includes a water quality measuring means for measuring the quality of raw water, a coagulation analysis means for injecting a flocculant into raw water and measuring agglomeration start time, a water quality measurement value from the water quality measuring means and the agglomeration analysis means And an information processing means connected so as to receive a measurement value of the agglomeration start time.
Further, the information processing means calculates a basic flocculant injection rate from the water quality measurement value, determines a recommended flocculant injection rate from the measurement value of the agglomeration start time, the basic flocculant injection rate, A correction value is calculated from the difference from the recommended flocculant injection rate, and the basic flocculant injection rate is corrected based on the correction value.

  According to the control method and the apparatus of the present invention, the control method depends on the conventional injection rate, and furthermore, the injection rate can be controlled in real time in order to correct the basic flocculant injection rate.

  In addition, according to the control method of the present invention, it is possible to make up for the disadvantage of lack of local and temporal universality of control, which was a drawback of the injection rate type.

  Furthermore, according to the control method according to the present invention, it is possible to eliminate the drawback that the control cycle of the flocculant injection rate cannot be made in units of several minutes due to batch measurement, which was a disadvantage of the conventional apparatus. it can.

It is the schematic which shows one Embodiment of the coagulant | flocculant injection rate control apparatus of this invention. It is the schematic which shows the relationship between the water quality measurement means, the aggregation analysis means, and the built-in sequencer in one Embodiment of the coagulant injection rate control apparatus of this invention. It is a graph explaining agglomeration start time. It is a graph which shows the fitting line calculated by the aggregation analysis means. It is a graph which shows the relationship between the raw | natural water turbidity calculated by the conventional injection | pouring rate type | formula, and a basic flocculant injection | pouring rate. In the method for determining the injection rate of the flocculant of the present invention, the basic flocculant injection rate calculated by the conventional method, the recommended flocculant injection rate obtained from the measured value of the agglomeration start time, the basic flocculant injection rate, and the recommendation It is a graph which shows the relationship with correction value (DELTA) p which is the difference of the coagulant injection rate. It is a graph which shows the relationship between the correction | amendment injection rate computed by the injection rate determination method of the coagulant | flocculant of this invention, and the basic | foundation flocculant injection rate computed by the conventional system. It is a flowchart of the operation | movement method of the apparatus which controls the injection | pouring rate of the coagulant | flocculant which concerns on embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In general, as shown in FIG. 1, a water treatment plant has a landing well 10 for storing water from a river, a quick mixing basin 20 for injecting and mixing a flocculant into raw water for treatment, and a raw material for treatment by slow stirring. It comprises a floc formation pond 30 for forming flocs in water, a sedimentation basin 40 for precipitating suspended solids and flocs, and a filtration basin 50 for filtering treated water. In the coagulation sedimentation process, fine particles are agglomerated and grow as flocs from the rapid stirring in the mixing basin 20 after the flocculant injection to the slow stirring in the flock formation pond 30. At this time, agglomeration is basically started in the mixing basin 20, and it is important that the agglomeration start time of the fine particles is approximately the same as the residence time of the mixing basin 20. In this situation, the treatment after the mixing basin 20 is carried out satisfactorily. As a result, flocs having high sedimentation properties are formed, and the sedimentation turbidity can be reduced.

Here, in this invention, the coagulant | flocculant injection rate control apparatus 60 is installed in a water purification plant or a water intake facility. The flocculant injection rate control device 60 includes a water quality measurement unit 1, a coagulation analysis unit 2, and a built-in sequencer 3. The water quality measuring means 1 and the agglomeration analyzing means 2 of the flocculant injection rate control device 60 are connected so that a part of raw water can be collected from the piping from the landing well 10 to the mixing basin 20.
Further, the water quality measuring means 1 and the coagulation analyzing means 2 may be installed in the water intake facility, and a part of the raw water may be collected from a pipe from the water intake to the landing well 10.

  FIG. 2 shows in more detail the relationship among the water quality measurement means 1, the aggregation analysis means 2, and the built-in sequencer 3 in the coagulant injection rate control device 60 of the present invention. As shown in FIG. 2, the flocculant injection rate control device 60 of the present invention includes a water quality measuring unit 1 that measures the quality of raw water that is the water to be treated, and a coagulation analyzing unit that measures the agglomeration start time of the raw water. 2 and a built-in sequencer 3 that calculates the injection rate of the flocculant from the water quality measurement value from the water quality measurement means 1 and the measurement value of the agglomeration start time from the aggregation analysis means 2.

  The water quality measuring means 1 collects a part of the raw water supplied from the intake port to the mixing pond and measures the quality of the raw water. Water quality measurements are used to derive the base flocculant injection rate. As the quality of raw water, water quality such as turbidity, number of fine particles, pH, alkalinity, and water temperature can be treated as parameters. As a means for measuring turbidity, for example, a light beam from a light source such as a transmitted light method, a scattered light method, a surface scattered light method, or a transmitted-scattered light method is applied to a sample, and the turbidity is measured using a photoelectric conversion device. A device capable of measuring the degree can be used. When measuring the number of fine particles in the raw water, a light blocking fine particle counter or the like can be used as the fine particle measuring device. In addition, a device that has been conventionally used for measuring the quality of raw water can be applied. The raw water quality information measured by the water quality measuring means 1 is sent to the built-in sequencer 3. The water quality information from the water quality measuring means 1 sent to the built-in sequencer 3 is used in the built-in sequencer 3 to derive the basic flocculant injection rate based on the injection rate equation. The water quality measuring means 1 measures the water quality in real time and sends information to the built-in sequencer 3.

  The agglomeration analyzing means 2 is also supplied with a part of the raw water supplied from the intake port to the mixing pond, and measures the agglomeration start time of the raw water independently of the water quality measuring means 1. The agglomeration start time is used to derive a correction value for the base flocculant injection rate. The pipe for supplying the raw water to the aggregation analysis means 2 can be connected to the pipe for supplying the raw water to the water quality measuring means 1 or may be independent. As the agglutination analysis means 2, for example, an apparatus described in Japanese Patent Application Laid-Open No. 2009-672 can be used. Japanese Patent Application Laid-Open No. 2009-672 includes a test water tank for containing a predetermined amount of raw water, a feed water pump, a feed water / drain valve for raw water and washing water, a stirrer, a flocculant injection part, and a floc particle size. And a detector for measuring the number of particles are disclosed. According to this agglutination analyzer, it is possible to measure the time (aggregation start time) from when the aggregating agent is injected into the test water tank until the aggregating agent is dispersed by stirring and particle agglomeration starts. . Further, the flocculant injection rate can also be determined according to the difference between the agglomeration start time and a preset target agglomeration time (agglomeration start time measurement method).

  Here, the agglomeration start time measured by the agglutination analysis means 2 is the injection of the aggregating agent at a certain injection rate with respect to the raw water collected into the agglutination analysis means 2, and the aggregating agent is dispersed by stirring. It measures the time at which particle agglomeration begins. Agglomeration is measured by a fine particle count method or a fluctuation analysis method using a detector in the agglutination analysis means as described in JP-A-2009-672.

  In the case of the fine particle counting method, the detector measures the number of particles and the particle size in the sample, and the time for increasing the number of particles having a certain particle size (starting time for increasing the number of particles) or the particle having a certain particle size decreases. The average value of either or both of the times (particle number reduction time) is set as the agglomeration start time. At this time, the detector can measure the increase / decrease in the number of particles for each certain particle size range, and the particle size of interest can be appropriately selected. For example, when measuring the time for increasing the number of particles in a certain particle size range, 3 to 7 μm is selected as the particle size, and the increase in the number of particles in that range is measured.

  On the other hand, in the case of the fluctuation analysis method, the detector irradiates the sample water flowing in the detector with a light beam from at least one place, forward scattered light, side scattered light, back scattered light, and transmission. At least one of the lights is received by a photoelectric converter, and the average particle diameter and the number of particles contained in the sample water are determined from the average value and standard deviation of the converted electric signal. At this time, the time when the average particle diameter starts to increase is taken as the floc growth start time, and when the point at which the number of particles counted as floc begins to increase is measured as the floc increase start time, at least one time or both The result of calculating the time is used as the agglomeration start time.

  In FIG. 3, the graph of the measurement result of the agglomeration start time by a fluctuation | variation analysis method is shown. As shown in FIG. 3, when the flocculant is injected into the sample and stirred, the measured average particle size increases with time. At this time, the agglomeration start time is, for example, as shown in FIG. 3, the time at the point where the inclination when the average rate of increase in the average particle size of the flocs reaches the time axis intersects with the time axis be able to. Or, when the formation of floc reaches the maximum, that is, when the average particle size or the number of particles reaches the maximum value, for example, a value that becomes a constant ratio selected from 10% to 50% is agglomerated It is also possible to set an agglomeration start time, more preferably 15-30% when the maximum value is reached, and most preferably, the time point when the agglomeration start time exceeds the 20% value when the maximum value is reached. Can be set.

  In this way, information on the agglomeration start time measured by the aggregation analysis means 2 is sent to the built-in sequencer 3. The aggregation analysis means 2 sends update information to the built-in sequencer 3 every 10 to 15 minutes. This information is used in the built-in sequencer 3 to derive a correction value for the basic flocculant injection rate.

  According to the aggregation analysis means 2 described above, since the raw water to be actually processed is used as a sample and the agglomeration start time is used as a parameter, the influence of the aggregation inhibitor not considered in the conventional injection rate formula is reflected, and the most appropriate A simple flocculant injection rate can be calculated. Further, compared with the jar test, since the step of slow stirring to standing is not required, the flocculant injection rate can be automatically determined in about 10 to 15 minutes. Therefore, the operation by a skilled operator is not required, and it is possible to realize the flocculant injection rate control with a smaller time lag than the jar test. Furthermore, unlike the agglomeration sensor, it is not necessary to create a database of raw water turbidity and appropriate floc particle size, so the agglomeration agent injection rate control system by the agglomeration analyzer is put into actual operation in a relatively short period after the installation There is a feature that can be.

  The aggregation analysis means 2 can also divide the collected raw water into a plurality of sections, inject a flocculant into each section at a different flocculant injection rate, and measure each agglomeration start time. Thereby, the fitting line which shows the relationship between the coagulant | flocculant injection rate and agglomeration start time can be created about the raw | natural water under process.

  FIG. 4 is a graph showing an example of the fitting line produced by the above process. FIG. 4 shows the fitting line created by measuring and plotting the agglomeration start time when the flocculant was injected at different flocculant injection rates for the raw water divided into four sections A to D. . By creating such a fitting line, it is also possible to calculate an appropriate flocculant injection rate from the target agglomeration time of each implementation facility.

次に注入率式で扱われる定数を決定する。式（１）を採用する場合、降雨時や低水温期など、様々な条件における原水に対して、ジャーテストで求めた適正注入率Ｐ_ｎと、原水濁度の測定値Ｔ_Ｂｎとを１組として、複数組のデータを式（１）に代入し、最小二乗法で解析することで定数を決定する。このとき、定数は最小二乗法による解析時に発散しないような値を初期値として代入する必要がある。また、実際の浄水場の運用データの中で、目標となる沈殿水濁度の範囲（例えば０．５〜１度）に収まった時のみのデータを抜き取って、浄水場の実際の注入率Ｐ_ｎ、その時の原水濁度をＴ_Ｂｎとして、解析することもできる。以上のようにして、定数を決めた後、方程式に定数を代入すると、注入率式が完成する。
また、基礎凝集剤注入率の算出式は、本装置設置前に浄水場が運用していた注入率式を使用してもよい。 The built-in sequencer 3 receives the measurement value information from the water quality measuring means 1 and calculates a basic flocculant injection rate based on a preset injection rate equation. The formula for calculating the basic flocculant injection rate (injection rate equation) can be determined by those skilled in the art based on the jar test, the sedimentation water turbidity of the facility, and the like. Specifically, the shape of the injection rate formula, such as linear or non-linear, and the water quality item as a variable used in the formula are determined. Usually, the equation (1) is used, and the variable can be the raw water turbidity.

Next, the constant handled by the injection rate equation is determined. When formula (1) is adopted, one set of the appropriate injection rate P _n obtained by the jar test and the measured value T _Bn of the raw water turbidity for raw water under various conditions such as rain or low water temperature As described above, a plurality of sets of data are substituted into the equation (1), and the constant is determined by analyzing the least square method. At this time, it is necessary to substitute a constant value that does not diverge at the time of analysis by the least square method as an initial value. In addition, from the actual operation data of the water purification plant, data is extracted only when it falls within the target turbidity range (for example, 0.5 to 1 degree), and the actual injection rate P of the water purification plant is extracted. _n , The raw water turbidity at that time can be analyzed as _TBn . After determining the constant as described above, substituting the constant into the equation completes the injection rate equation.
Moreover, the calculation formula of the basic flocculant injection rate may use the injection rate formula operated by the water purification plant before the installation of the present apparatus.

The built-in sequencer 3 receives information on the agglomeration start time from the agglutination analysis means 2, determines a recommended flocculant injection rate from the information on the agglomeration start time, and determines a basic flocculant injection rate and a recommended flocculant injection rate. The correction value is calculated from the difference between. The injection rate is finally calculated by correcting the basic flocculant injection rate with this correction value. The basic flocculant injection rate is updated in real time, and the correction value of the injection rate is periodically updated (about 10 to 15 minutes) and reflected in the flocculant injection rate.
The built-in sequencer 3 controls the injection rate of the flocculant by outputting the corrected injection rate to a flocculant injection pump or the like. The built-in sequencer 3 may be integrated with the water quality measurement unit 1 or the aggregation analysis unit 2 or may be independent.

  According to the above configuration, first, the raw water taken is introduced from the landing well 10 to the mixing basin 20, while a part of the raw water is supplied to the water quality measuring means 1 and the aggregation analysis means 2 of the flocculant injection rate control device 60. And introduced. The quality of raw water is measured by the water quality measuring means 1 and the measurement information is transmitted to the built-in sequencer 3. The built-in sequencer 3 calculates the basic flocculant injection rate based on the information sent from the water quality measuring means 1 and the injection rate equation. In addition, the agglomeration start time of raw water at a predetermined flocculant injection rate is measured by the aggregation analysis means 2, and the measurement information is transmitted to the built-in sequencer 3. Here, the predetermined flocculant injection rate is a predetermined fixed value or a basic flocculant injection rate (variation value) obtained by the basic injection rate equation. When the predetermined flocculant injection rate is treated as a variable value, the result of actually measuring the agglomeration start time at the basic flocculant injection rate may be the agglomeration start time at the predetermined flocculant injection rate. The agglomeration start time at a predetermined flocculant injection rate may be obtained from the fitting line indicating the relationship between the aggregating agent injection rate and the agglomeration start time and a predetermined flocculant injection rate.

The built-in sequencer 3 calculates a correction value for the coagulant injection rate from the information sent from the coagulation analysis means 2, and the basic coagulant injection rate is periodically corrected by this correction value.
In this way, by correcting the basic flocculant injection rate using the correction value calculated based on the agglomeration start time, there is a disadvantage that there is no locational and temporal universality of control by the injection rate formula. In addition, it is possible to shorten the control period of the agglomeration start time measurement method of the aggregation analyzer. Hereinafter, a method for calculating the flocculant injection rate will be described in more detail.

ここで、Ｃ、Ａ_０、ｂ_０は定数、Ｔ_Ｂは原水濁度である。なお、水温区分によって、各係数を変更したり、式（１）に水温の項を追加したりする例もある。
このとき、原水濁度や水温は、凝集剤注入点よりも前段階で採水した試料水に対して、秒単位以下の周期で測定が可能であるから、式（１）等の注入率式による制御は、連続的なフィードフォワード制御となる。先に述べたように、この注入率式は、場所的、時間的普遍性がなく、浄水場によって式の構造自体が異なっていたり、同じ河川から取水する浄水場であっても場所によって異なる係数を用いたりする場合が多い。また、雨の降り始めや降り終わり、季節等によって、複数の式を用いる場合もある。 The injection rate equation (basic injection rate equation) for deriving the injection rate p from the measured value of the general water quality measuring unit 1 is, for example, the equation (1) using the turbidity measured by the water quality measuring unit 1 as a parameter. It is expressed in

_{Here, C,} A _{0, b} 0 is a constant, _{T B} is the raw water turbidity. Note that there are examples in which each coefficient is changed depending on the water temperature classification, or a term of water temperature is added to the equation (1).
At this time, the raw water turbidity and the water temperature can be measured with a cycle of seconds or less with respect to the sample water collected before the flocculant injection point. The control by is continuous feedforward control. As mentioned earlier, this injection rate formula is not universal in terms of location and time, and the structure of the formula itself varies depending on the water treatment plant, or even if it is a water purification plant that draws water from the same river, Is often used. In addition, a plurality of formulas may be used depending on the start or end of rain, the season, and the like.

In the present invention, the recommended flocculant injection rate is determined. The recommended flocculant injection rate is determined based on the measured value of the agglomeration start time and the fitting line determined in advance.
A correction value is calculated from the difference between the recommended coagulant injection rate and the basic coagulant injection rate.

If the correction value is applied to equation (1), equation (2) is obtained.

Here, the correction value Δp is the recommended coagulant injection rate p _A obtained from the agglomeration start time appropriate value and the basic coagulant injection rate p obtained based on the raw water quality at the same time as the collected raw water. The difference value from _E0 .
The recommended flocculant injection rate p _A is updated every time the agglomeration start time is measured, and the previous value is maintained until the next update. Therefore, Δp is also updated every time the agglomeration start time is measured.

p_iは補正された注入率であり、集塊化開始時間測定時をi=0とし、基礎凝集剤注入率p_Eiが更新されるたびにiが増加するものとする。 Next, the basic flocculant injection rate is corrected based on the correction value Δp.

p _i is a corrected injection rate, i = 0 when the agglomeration start time is measured, and i increases every time the basic flocculant injection rate p _Ei is updated.

FIG. 8 is a flowchart of the operation method of the apparatus for controlling the injection rate of the flocculant according to the embodiment of the present invention.
Hereinafter, the operation of the apparatus for controlling the flocculant according to the embodiment of the present invention will be described using the flowchart shown in FIG.
First, in the control device according to the embodiment of the present invention, the water quality measuring unit 1 measures the quality of raw water (S801). Specifically, the water quality measuring means 1 measures the turbidity or fine particles of raw water.
Next, the internal sequencer 3 receives the water quality measurement value from the water quality measurement means 1. The internal sequencer 3 calculates the basic flocculant injection rate from the water quality measurement value (step S802).
The agglutination analysis means 2 measures the time until the agglomeration of particles in the raw water starts after injecting the flocculant into the raw water independently of the above-described step S801 for measuring the quality of the raw water (step S803).

  Next, the internal sequencer 3 determines a fitting line (step S804). Here, in the step of determining the fitting line (S804), a predetermined amount of raw water is sampled in a plurality of test water tanks, and the flocculant is injected at different flocculant injection rates set in advance for the sample water. And a step of measuring the agglomeration start time for each sample water until the agglomeration of particles in each sample water starts after the injection of the flocculant, the agglomeration start time measured for each sample water, It comprises a step of calculating the correlation between the agglomeration start time and the flocculant injection rate as a fitting line based on each flocculant injection rate.

  Subsequently, the internal sequencer 3 obtains a recommended flocculant injection rate from the measured values of the fitting line and the agglomeration start time (step S805). Next, the internal sequencer 3 calculates a correction value from the difference between the recommended flocculant injection rate and the basic flocculant injection rate (step S806). Finally, the internal sequencer 3 corrects the basic flocculant injection rate based on the calculated correction value (step S807).

Next, an embodiment in which the injection rate is calculated using the agglomeration start time at a predetermined flocculant injection rate will be described below.
The control device according to the present invention has the function of inputting the turbidity output (analog signal) from the raw water turbidimeter as shown in FIG. 1 in addition to the function of the device described in JP-A-2009-672. The built-in sequencer 3 makes it possible to calculate the basic flocculant injection rate using the conventional injection rate equation, and calculate the final injection rate by calculating the correction value.

Fig. 5 shows the change in raw water turbidity for river surface water and the basic flocculant injection rate calculated by the conventional injection rate formula. The period when the change in raw water quality was relatively large was extracted. Yes.
Here, the basic flocculant injection rate is obtained by substituting the measured value of the raw water turbidity and the coefficients C = 10, A ₀ = 5, b ₀ = 0.5 into the equation (1).

FIG. 4 shows fitting lines calculated from the relationship between the agglomeration start times T _{SA to} T _SD measured at four water tanks at different flocculant injection rates and the four flocculant injection rates. Yes. Here, the appropriate value of the agglomeration start time is determined based on the residence time of the mixing pond . The recommended flocculant injection rate is calculated from the relationship between the appropriate value of the agglomeration start time and the fitting line.

FIG. 6 shows the relationship between the basic coagulant injection rate, the recommended coagulant injection rate, and the correction value Δp, which is the difference between the basic coagulant injection rate and the recommended coagulant injection rate. Here, the basic flocculant injection rate is calculated at a cycle of 1 minute, but the calculation cycle of the recommended flocculant injection rate is set to be calculated at a cycle of 15 minutes. Accordingly, the previous value is held until the latest value is updated. As a result, the update period of Δp is 15 minutes.

FIG. 7 shows the result of adding the basic flocculant injection rate and the corrected injection rate obtained by the present invention, that is, the basic flocculant injection rate and Δp.
When the turbidity increased, the corrected injection rate obtained by the present invention was higher than that of the basic flocculant obtained by the conventional method. On the other hand, when the turbidity was stable, the corrected injection rate obtained by the present invention was lower than the basic flocculant obtained by the conventional method.
In particular, when the turbidity is stable, the basic flocculant obtained by the conventional method has been found to be excessive injection from the measurement result of aluminum in the filtered water. Compared to a few years ago when the coefficient of the injection rate equation was determined, it is expected that the coefficient of the injection rate equation has shifted.

Next, over the course of a month, the conventional injection rate equation was compared with the method of the present invention.
The average monthly injection rate was 25 mg / L for the conventional method. On the other hand, in the case of the method of the present invention, it was 22 mg / L.
Therefore, using the control method of the present invention, the monthly average injection rate could be reduced by 3 mg / L. Thus, the use amount of the flocculant can be reduced by optimizing the flocculant injection rate according to the present invention.

  By using the flocculant control method and apparatus according to the present invention, the amount of flocculant used can be set to an optimum value. As a result, it is possible to prevent non-ferrous heavy metals, light metals, and the like that exceed the reference values stipulated by the ministerial ordinance from flowing out of the filter basin.

  Further, in the method of the present invention, the recommended flocculant injection rate calculated by the agglomeration start time measurement method and the basic flocculant injection depending on the amount of algae and other aggregation-inhibiting substances that do not appear in the conventional injection rate formula The correction value is introduced from the difference from the rate, and the injection rate increases. Therefore, safer injection rate control is possible.

  Furthermore, although the method of JP2009-672A can manage an appropriate injection rate, there is a problem that a data update cycle is long (10 to 15 minutes). According to this method, the injection rate can be controlled with a shorter cycle (1 minute in this embodiment) by the conventional injection rate equation.

  In the present embodiment, only the raw water turbidity is used as a parameter in the conventional injection rate formula and the corrected injection rate formula of the present invention, but other water qualities such as water temperature and chromaticity are used as parameters. Is also possible. At that time, in addition to the method of inputting the water quality as an analog signal, other communication methods such as RS485 may be used. The raw water turbidity and other water qualities can also be incorporated into a coagulation analyzer.

In this example, the injection rate is calculated by the sequencer built in the agglutination analyzer, but a personal computer or the like is connected to the upper side of the agglutination analyzer, and the injection rate is calculated by the conventional injection rate formula on the personal computer. In addition, the correction injection rate of the present invention may be calculated.

DESCRIPTION OF SYMBOLS 1 Water quality measurement means 2 Aggregation analysis means 3 Built-in sequencer 10 Landing well 20 Rapid mixing basin 30 Flock formation basin 40 Sedimentation basin 50 Filtration basin 60 Flocculant injection rate control device

Claims (3)

A water quality measurement process for measuring the quality of raw water;
An injection rate calculation step for calculating a basic flocculant injection rate from the obtained water quality measurement value,
Independent of the water quality measurement step, agglomeration start time measurement step for measuring the time until the agglomeration of particles in the raw water starts by injecting a flocculant into the raw water,
Calculating the correlation between the measurement value of the agglomeration start time and the flocculant injection rate as a fitting line;
It is a recommended flocculant injection rate determination step for substituting an appropriate value for the agglomeration start time of the actual facility into the fitting line and determining a recommended flocculant injection rate, and the recommended flocculant injection rate is updated to the latest value. A recommended coagulant injection rate determination step that keeps the previous value until,
A correction value calculating step of calculating a correction value from the difference between the basic flocculant injection rate and the recommended flocculant injection rate;
Based on said correction value, look including the infusion rate correction step of correcting the basic coagulant injection rate,
In the step of calculating the correlation between the measurement value of the agglomeration start time and the flocculant injection rate as a fitting line, the fitting line is:
A predetermined amount of raw water is collected in a plurality of test water tanks, and a flocculant injecting step for injecting the flocculant into the sample water at different preset flocculant injection rates,
Agglomeration start time measuring step for measuring the agglomeration start time until the agglomeration of particles in each sample water starts after the injection of the flocculant;
A fitting line calculation step of calculating a correlation between the agglomeration start time and the flocculant injection rate as a fitting line based on the agglomeration start time measured for each sample water and the respective flocculant injection rate; A method of controlling the injection rate of the flocculant in the flocculation process of the raw water to be treated , calculated by :   The method according to claim 1, wherein the water quality measurement step measures turbidity or fine particles of raw water. Water quality measuring means for measuring the quality of raw water;
Agglutination analysis means for injecting a flocculant into raw water and measuring the agglomeration start time;
And an information processing means connected to receive the water quality measurement value from the water quality measurement means and the measurement value of the agglomeration start time from the coagulation analysis means. Here, the information processing means calculates a basic flocculant injection rate from the water quality measurement value , collects a predetermined amount of raw water into a plurality of test water tanks, and supplies the sample water to the sample water. On the other hand, the flocculant injection process in which the flocculant is injected at different preset flocculant injection rates, and the agglomeration start time until the agglomeration of particles in each sample water starts after the flocculant injection, for each sample water Based on the agglomeration start time measuring step to be measured, the agglomeration start time measured for each sample water, and the respective flocculant injection rate, the agglomeration start time and the flocculant injection rate Calculate correlation as fitting line The fitting line is calculated by the fitting line calculation step, the appropriate agglomeration start time value of the implementation facility is substituted into the fitting line, the recommended flocculant injection rate is determined, and the recommended flocculant injection rate is updated to the latest value. The previous value is held until updated, and a correction value is calculated from the difference between the basic flocculant injection rate and the recommended flocculant injection rate, and the basic flocculant injection rate is corrected based on the correction value. ,apparatus.

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