JP5951423B2 - Flocculant injection control method and flocculant injection control system - Google Patents

Description

  Embodiments of the present invention relate to a flocculant injection control method and a flocculant injection control system that control the injection amount of a flocculant in, for example, a water purification plant, a sewage treatment plant, and an industrial wastewater treatment facility.

  Conventionally, for example, in a water purification plant, a sewage treatment plant, or an industrial wastewater treatment facility, a flocculant is injected into the raw water to be treated to flock suspended matters contained in the raw water. As a result, the suspension in the raw water can be easily precipitated and filtered and removed. As the aggregating agent, for example, inorganic aggregating agents such as polyaluminum chloride (PAC) and aluminum sulfate (sulfur sulfate) are widely used. In addition, cationic or anionic organic polymer flocculants are also used.

  For example, in a water purification plant, an aluminum-based inorganic flocculant is added to raw water, and the suspension is flocculated and precipitated, and the turbidity at the outlet of the sedimentation basin is one of the management indexes of the treated water quality. Factors that influence the turbidity at the outlet of the precipitation basin include the raw water turbidity, the amount of flocculant injected, pH, water temperature, alkalinity, stirring strength in the mixing basin, the shape of the precipitation basin, and the residence time.

  Appropriate agglomeration conditions for keeping the sedimentation basin outlet turbidity at a good value (turbidity of about 0.5 degree) are constantly changing under the influence of the water quality fluctuation of the raw water. Here, the time until the injection result of the flocculant is reflected in the turbidity at the outlet of the settling basin is generally about 2 to 4 hours. For this reason, if the turbidity at the outlet of the sedimentation basin is measured and the injection amount of the flocculant is controlled based on the measurement result, the response will be delayed when the quality of the raw water changes.

  Therefore, feedforward control (hereinafter referred to as FF control) that calculates the injection rate of the flocculant from the turbidity of the raw water and the water temperature has been conventionally used. However, since the FF control creates an arithmetic expression of the FF control based on past experience and determines the injection amount of the flocculant based on the arithmetic expression, the FF control is affected by the past operation results used to create the arithmetic expression. . For example, if the past operation record is larger than the optimum injection amount, or if more injections were performed in consideration of safety, the target value for the injection rate of the flocculant is calculated to be larger. Tend to be. As a result, the coagulant is excessively injected, and the cost for using the coagulant is increased. Use of an excessive flocculant leads to an increase in excess sludge, which causes adverse effects such as an increase in sludge treatment cost and an increase in aluminum content preventing sludge reuse.

  As a coagulant injection control method other than the FF control described above, there is a method using a zeta potential. The zeta potential has heretofore been used as an index representing the quality of aggregation. Generally, the flocculant injected into the raw water is iron or an aluminum compound and has a positive charge. Since suspended substances that are removal objects existing in the raw water are negatively charged, a method of capturing the state of charge neutralization with a zeta potential is used.

  Here, the positively-charged flocculant electrostatically binds to the negatively-charged suspended matter, and micro flocs are formed. During this process, the zeta potential in the raw water changes from the minus side to the plus side. The micro flocs are attracted to each other by the attractive force between the molecules and gradually increase to form coarse flocs, which eventually settle. The quality of the aggregation is affected by the quality of the raw water and the stirring conditions, but in general, the agglomeration proceeds when the zeta potential when the aggregation proceeds is within a range of ± 15 to 20 mV.

  As a method of using this zeta potential, the mixed water after adding the flocculant is subjected to rough filtration, the zeta potential of the micro flocs that are still insufficiently aggregated in the filtrate is measured, and the flocculant conditions are set so that the micro flocs proceed to aggregate. There has been proposed a method for controlling (see, for example, Patent Document 1). It has also been proposed that the degree of floc formation is measured with a zeta potential and, for example, if the distribution of the zeta potential of the floc is -10 mV or more and the proportion of particles is 95% or more, it is determined that the state of aggregation is good ( For example, see Patent Document 2). Further, regarding the aggregation of the fouling factor substance in the membrane filtration method, when the zeta potential of the membrane surface is negative, the aggregation condition is controlled so that the zeta potential of the aggregation floc becomes, for example, −10 to 0 mV, A method of suppressing fouling formation by electrostatic repulsion between the surface and the aggregated floc has been proposed (see, for example, Patent Document 3).

  In addition to these, a flocculant injection control system to which feedback control (hereinafter referred to as FB control) that reflects the result after injection of the flocculant in the control using the flowing current value is also proposed (for example, Patent Document 4, Patent Document 4). 5). The flowing current is one of the methods used when measuring the zeta potential, and the flowing current is an index that can be converted into the zeta potential. In these methods, a flow ammeter is installed in the mixing basin, and the flow current value of the mixed water mixed with the flocculant is measured by the flow ammeter. A flow current as a control target value is calculated by performing a correction process for conductivity and pH on the measurement result, and the amount of the flocculant injected is controlled so as to be the target value.

JP 2000-300912 A JP 2002-66568 A JP 2009-248028 A JP 2001-327806 A JP 2002-239307 A

  In any of these flocculant injection control methods using the zeta potential, the zeta potential of the mixed water after the addition of the flocculant is measured, and the state after the aggregation has progressed to some extent is measured. However, in the mixed water after the addition of the flocculant, floc formation has already started, and flocs of different sizes are mixed there. In such a state, it is difficult to accurately measure the zeta potential that covers the characteristics of the whole raw water to be treated in the process of aggregation. For example, the zeta potential measured by electrophoresis is calculated from the speed at which particles move by applying a voltage to both ends of the measurement cell. It becomes difficult. For this reason, when trying to control the amount of flocculant injected using only the zeta potential value, the zeta potential used may not necessarily accurately reflect the state of aggregation actually occurring. The agent injection rate may not be appropriate.

  The problem to be solved by the present invention is to provide a coagulant injection control method and a coagulant injection control system capable of appropriately setting the coagulation conditions based on the coagulation characteristics of raw water to be treated.

The flocculant injection control method and the flocculant injection control system according to the embodiment of the present invention control the injection of the flocculant into the raw water to be processed, and the section of the zeta potential of the raw water divided in advance the distribution of the zeta potential representing the emerging frequency of the charge of each was measured, using data on the distribution of previously obtained the zeta potential of the flocculant, in response to the distribution of the zeta potential of the raw water, the section The injection rate of the flocculant necessary for shifting the distribution of the zeta potential to a range in which the agglomeration proceeds favorably is calculated.

  According to the above embodiment, by measuring the distribution of the zeta potential of the raw water to be treated, a flocculant can be added to grasp the agglomeration characteristics of the raw water to be treated and set the aggregation conditions appropriately. .

It is a figure which shows the structure of the coagulant | flocculant injection | pouring control system which concerns on the 1st Embodiment of this invention. It is a figure which shows the distribution characteristic of the zeta potential of the single component raw | natural water in embodiment of this invention. It is a figure which shows the distribution characteristic of the zeta potential of the multi-component raw water in the embodiment of the present invention. It is a figure which shows the structure of the coagulant | flocculant injection | pouring control system which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the coagulant | flocculant injection | pouring control system which concerns on the 3rd Embodiment of this invention. The zeta potential distribution diagram that changes depending on the raw water regulator in the third embodiment shows a case where the change is large. The zeta potential distribution diagram that changes depending on the raw water adjusting agent in the third embodiment shows a case where the change is small.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<First Embodiment>
FIG. 1 shows the configuration of a flocculant injection control system according to this embodiment. Although FIG. 1 is an example of a water purification plant, it is the same structure also in a sewage treatment plant.

  As shown in FIG. 1, a water purification plant or the like generally includes a landing well 60, a mixing basin 62, a flock formation pond 63, and a sedimentation basin 64. The raw water to be treated is taken into the landing well 60, sent from there to the mixing basin 62, and the flocculant is injected from the flocculant injection equipment 41. Then, the mixture is stirred by the rotation of the stirrer 67 and the mixing is promoted, and then sent to the flock formation pond 63. After the floc grows and grows in the floc formation pond 63, it is sent to the sedimentation basin 64, and after the floc is settled and removed in the sedimentation basin 64, it is transferred to the next process. Although the next process is not shown, in the case of a water purification plant, after passing through sand filtration, chlorine is added and then distributed to a water distribution pipe through a distribution reservoir. In addition, before passing through sand filtration, ozone treatment or biological activated carbon treatment may be appropriately performed.

  A water quality index measuring device 85 for measuring the quality index of the raw water is provided at the landing well 60 or its outlet. The water quality index measuring device 85 includes a plurality of measuring devices. That is, a zeta potential meter 51 as a zeta potential measuring means, and an alkalinity meter 52, a conductivity meter 53, a water temperature meter 54, a turbidity meter 55, and a pH meter 56 other than this are provided. The flow rate of raw water is measured by a flow meter 57.

  As shown in FIG. 1, the control device 10 includes a flocculant injection calculation means (hereinafter simply referred to as calculation means) 21, a process control means 22, and a flocculant information holding means 100. The calculating means 21 calculates the coagulant injection rate to be injected into the mixing basin 62 from the water quality measured by the water quality index measuring device 85 and the information held in the coagulant information holding means 100. The process control means 22 controls the flocculant injection equipment 41 based on the flocculant injection rate calculated by the calculation means 21. In the flocculant information holding unit 100, information on the zeta potential distribution of the solution containing the flocculant when the flocculant is diluted to an appropriate concentration is set as information on the flocculant currently used.

  In the above configuration, the zeta electrometer 51 measures the distribution of the zeta potential of the raw water to be treated. In recent years, a new measurement method has been proposed as a method for measuring the zeta potential, and computerization of analysis is progressing. For example, there are a microscope electrophoresis method, a laser Doppler method, an ultrasonic method, an electroosmosis method, a streaming potential method, and the like. Among these, electrophoresis using an image processing method can grasp the measurement result of the zeta potential as a distribution.

  FIG. 2 is a conceptual diagram showing the zeta potential distribution of a solution containing a uniform substance. In this figure, the horizontal axis represents the zeta potential, and the vertical axis represents the frequency (corresponding to the amount of charged substance). In FIG. 2, since a negatively charged substance (near -30 mv) is included, a peak exists on the negative side. However, raw water to be treated at a water purification plant, a sewage treatment plant, or an industrial wastewater treatment facility is a mixed raw water in which various substances coexist. Therefore, it does not become a single peak as shown in FIG. 2, but actually, as shown in FIG. 3, the zeta potential is measured as a distribution map in which peaks of various substances are combined. That is, there are positively charged substances and negatively charged substances in the raw water, and the charge intensity and the amount of substances that are charged by each substance are different. It becomes a distribution map.

  Here, when the aggregation characteristics of the raw water to be treated are expressed by a zeta potential, it can be expressed by an average value of the measured zeta potential. For example, an average value obtained by statistical processing based on a distribution diagram of zeta potential as shown in FIG. 3 is calculated. When this average value is used, even when the two types of raw water are compared, even if the zeta potential expressed by the average value is the same value, the zeta potential distribution (frequency value at each zeta potential) May be different. In this case, the coagulation operation is performed on the two types of raw water at the same coagulant injection rate, but the result of the coagulation operation is not always the same even if the average value of the zeta potential is the same. In other words, the zeta potential can capture more information about the aggregation characteristics of the raw water than the average of the distribution.

  Therefore, in the embodiment of the present invention, the characteristics of raw water are captured using the distribution of zeta potential as captured in FIG. 3, and the flocculant injection rate is determined according to the characteristics.

  Here, the components that are the source of turbidity in the raw water include inorganic particles such as metal ions, suspended colloids, and suspended particulate matter (SS), and plant organic matter such as algae. There are animal organic matter such as zooplankton and bacteria. These have different zeta potentials when present in water. For example, inorganic metal ions exhibit a positive zeta potential at a pH near neutral. Moreover, plant organic substance shows zeta potential of -30 to -20mV at pH 7-8 vicinity. Furthermore, animal organic substances also show a negative zeta potential. Therefore, it is possible to estimate what kind of substance is contained and how much by taking the measured zeta potential as a distribution and looking at the frequency of appearance of charge for each pre-segmented section of the zeta potential. .

  The measurement result of the distribution of zeta potential having such characteristics is input to the calculation means 21. Further, information on the coagulant currently used (injected into the raw water) is input from the coagulant information holding unit 100 to the calculation unit 21. As described above, this flocculant information is information on the zeta potential distribution of the solution containing the flocculant when the flocculant is diluted to an appropriate concentration. Here, since the injected flocculant becomes a solution containing a single substance, the peak of the distribution of the zeta potential of the flocculant becomes a peak as shown in FIG. For example, since an aluminum-based flocculant is positively charged, the zeta potential distribution appears on the positive side. Further, since the charge varies depending on the type of the flocculant, the place where the peak appears differs.

  The calculating means 21 calculates the injection rate of the flocculant injected into the raw water from the zeta potential distribution of the raw water to be treated and the zeta potential distribution of the flocculant itself. More specifically, the data relating to the distribution of the zeta potential of the flocculant itself set in the flocculant information holding means 100 is, for each section preset for the distribution of the zeta potential of the raw water, the zeta potential of that section, This is the data related to the injection rate of the flocculant necessary to set the value of the zeta potential at which aggregation proceeds favorably (in other words, to move to the range of the zeta potential at which aggregation proceeds favorably). Has been.

  This data is obtained in advance by experiments using raw water at the corresponding water purification plant. That is, the distribution of the zeta potential of the raw water is divided into a plurality of sections, and for each section, the coagulant injection rate necessary to move the zeta potential distribution of the section to the zeta potential range where the aggregation progresses well. It is obtained by experiment, and the obtained flocculant injection rate of each section is stored in the flocculant information holding means 100 for each section. In addition, since this data changes with kinds of flocculant, data will be utilized according to the flocculant currently used (inject | poured into raw | natural water).

  The computing means 21 divides the measured zeta potential distribution of the raw water into a plurality of sections described above in advance, and the flocculant necessary to move the distribution of each section to the zeta potential range where the aggregation proceeds well. The injection rate data is calculated using the corresponding section data set in the flocculant information holding means 100. That is, from the frequency in each section of the measured zeta potential distribution of the raw water and the data of the coagulant injection rate set for each section in the coagulant information holding means 100, the distribution of the section is improved in cohesion. The flocculant injection rate required to move to the range of the zeta potential to advance is calculated for each section. Then, the total value thereof is calculated as the required coagulant injection rate from the current distribution of zeta potential of the raw water.

  By using this method, it becomes possible to determine the flocculant injection rate from the zeta potential distribution of the raw water before the flocculant injection in an FF control manner. In addition, when water quality fluctuations occur in the raw water, the fluctuations appear quickly in the change in the zeta potential distribution, so by controlling the coagulant injection rate according to the change in the distribution, control according to the water quality fluctuations in the raw water It is possible to control the flocculant injection with good properties.

  Next, how to use other water quality indicators, alkalinity, conductivity, water temperature, turbidity, and pH will be described. Further, the alkalinity, conductivity, water temperature, turbidity, and pH, which are water quality indicators of the raw water, are input to the calculation means 21 described above. These data are used as correction means when calculating the flocculant injection rate from the zeta potential distribution of the raw water. For example, even if the distribution map of the zeta potential of the raw water is the same, the mobility of the zeta potential distribution with respect to the same coagulant injection rate is different if the water quality index is different. For this reason, the flocculant injection rate required to move the distribution of the zeta potential of the raw water to the range of the zeta potential where the aggregation proceeds well is different.

  Therefore, in order to correct this, data on alkalinity, conductivity, water temperature, turbidity, and pH is taken into the calculation means 21. The calculating means 21 corrects the coagulant injection rate calculated based on the distribution of the zeta potential of the raw water described above by using a correction coefficient stored in advance for each index. Thereby, a more appropriate flocculant injection rate can be calculated. In addition, although the data of alkalinity, electrical conductivity, water temperature, turbidity, and pH were shown as a water quality parameter | index of raw | natural water, all of these need not necessarily be used and any one or more may be used.

  The process control unit 22 receives the flocculant injection rate calculated by the calculation unit 21 and the raw water flow rate data measured by the flow meter 57. Based on these two data, the process control means 22 outputs the data of the coagulant injection amount to be injected into the mixing basin 62 to the coagulant injection equipment 41. In the flocculant injection facility 41, a predetermined flocculant injection amount is injected into the mixing basin 62.

  By controlling the flocculant injection, the zeta potential distribution of the raw water moves and concentrates in the range of the zeta potential where the aggregation proceeds well. That is, good agglomeration can be achieved by injecting an appropriate amount of aggregating agent.

  Thus, in the flocculant operation control method according to this embodiment, the zeta potential distribution of raw water is measured, and the data on the zeta potential distribution obtained in advance of the flocculant to be injected into the raw water is used. The injection rate of the flocculant corresponding to the distribution of the zeta potential is calculated, and the injection control of the flocculant into the raw water is executed according to the calculation result. In the above description, when all the function realizing means in the control device 10 are automatically controlled from the measurement of the distribution of the zeta potential of the raw water to the calculation of the injection rate of the coagulant and the injection control to the raw water based on the calculation result. However, the present invention is not limited to automatic control, and an operator may intervene in each of these stages.

  For example, the distribution of the measured zeta potential of the raw water can be displayed by the monitor device as the frequency in each preset section. The operator can easily grasp what state the quality of the raw water has changed if this monitor is monitored, so the operation of the injection amount of the flocculant corresponding to the change can be performed quickly. be able to. If the injection rate of the flocculant at that time is configured so that, for example, the calculation result by the calculation means 21 can be monitored, the operator can easily cope with it according to the monitor result.

  In recent years, there are cases where operations in water purification plants are entrusted to the private sector, and operators are not necessarily familiar with water quality. In such a case, it is desirable that such an operator can clearly determine the operation state of the plant (whether the flocculant injection state is good or bad). By using the control method described in the above embodiment, not only automatic operation but also an operator can easily intervene in the control operation, and more effective operation management is possible.

<Second Embodiment>
Next, a second embodiment shown in FIG. 4 will be described.

  In the second embodiment, the control device 10 is provided with data storage means 23 for storing the raw water zeta potential distribution data when the past flocculant injection control has been performed satisfactorily. Further, in order to detect that the flocculant injection control has been performed satisfactorily, a turbidimeter 71 is provided at the outlet of the sedimentation basin 64, and the sedimentation basin outlet turbidity, which is the measured value, is taken into the data storage means 23. Yes. For the same purpose, a floc image analysis device 72 for measuring the floc size is provided in the floc formation pond 63, and the floc size is taken into the data storage means 23. The turbidimeter 71 and the image analysis device 72 do not have special functions, and may be devices that are generally used.

  Further, the water quality index data including the zeta potential is input from the water quality index measuring device 85 to the calculation means 21 and is also taken into the data storage means 23. This is because the data storage means 23 stores the value of the water quality index when the past flocculant injection control has been performed satisfactorily. The calculation means 21 inputs the current zeta potential distribution of the raw water from the zeta potential meter 51 of the water quality indicator measuring device 85, and in the past zeta potential distribution corresponding to (similar to) the current zeta potential distribution of the raw water. The flocculant injection information is extracted from the data storage means 23. Then, the flocculant injection rate for the raw water to be processed is predicted from the extracted past flocculant injection information.

  Other configurations are the same as those of the first embodiment described with reference to FIG.

  In other words, in this embodiment, the control device 10 is configured so that the zeta potential distribution pattern of the raw water in the past, the coagulant injection rate injected into the raw water, and the sedimentation pond outlet turbidity in which the result of the aggregation appears. The data storage means 23 stores data on the degree and the size of the floc in the floc formation pond. Since the time for the treated water to reach the floc formation pond 63 and the sedimentation basin outlet 64 is different, when the data is stored, the data changed by the residence time is stored.

  In the above configuration, the data storage means 23 stores the zeta potential distribution information of the raw water, the water quality index at that time, and the coagulant injection rate implemented corresponding to these. Here, regarding the quality of the aggregation at the time of processing, the turbidity at the outlet of the sedimentation basin 64 and the information on the flock data analyzed in the flock formation basin 63 are used. In other words, the data storage means 23 is configured to store only the data when the aggregation is performed satisfactorily. Therefore, the information stored in the data storage unit 23 is only data when aggregation is performed well.

  The calculation means 21 refers to the flocculant injection rate from the data storage means 23 using the current raw water zeta potential distribution information and other water quality indicators based on past information stored in the data storage means 23. Is possible. Since the flocculant injection rate obtained here has a result of good aggregation, the value is used to achieve good aggregation.

  The calculating means 21 sends the flocculant injection rate extracted by referring to the data storage means 23 to the process control means 22. Then, the data on the amount of the flocculant injected is sent to the flocculant injection device 41, and a predetermined amount of the flocculant is injected into the mixing basin.

  In this way, the calculation means 21 of the present embodiment is based on the current raw water quality information including the zeta potential distribution of the raw water and the data of the past coagulant injection rate in which the aggregation was good. Since the coagulant injection rate suitable for the raw water is output, good coagulation can be performed with high accuracy.

  Also in this embodiment, if not only automatic control but also configured to be able to monitor the data of the past coagulant injection rate where the aggregation was good, the operator intervenes in the present coagulant injection control, It becomes possible to realize the flocculant injection control according to the control content in which past aggregation was good.

<Third Embodiment>
Next, a third embodiment shown in FIG. 5 will be described.

  In FIG. 5, in the third embodiment, a raw water adjusting agent injection facility 42 for injecting a raw water adjusting agent for adjusting the quality of raw water into the landing well 60 and this adjustment with respect to the first embodiment described above. This is a configuration in which a zeta potential meter 51 ′ for measuring the zeta potential after the raw water adjusting agent is injected by the agent injection facility 42 is separately provided. For this reason, the zeta potential meter 51 that measures the zeta potential distribution of the raw water before the injection of the raw water regulator just arrived at the landing well 60 is called the first zeta potential meter, and the zeta of the raw water after the raw water regulator is injected. The zeta electrometer 51 ′ that measures the potential distribution is referred to as a second zeta electrometer.

  As the raw water adjuster, acid / alkali, which is a commonly used pH adjuster, or soda ash or slaked lime for adjusting alkalinity is used.

  The second zeta electrometer 51 ′ may be one that uses the same device as the first zeta electrometer 51 and alternately measures with two sampling points. The sampling location of the second zeta electrometer 51 'is preferably collected from the raw water before the mixing basin 62, that is, before the flocculant is injected. The zeta potential distribution of the raw water measured by the second zeta electrometer 51 ′ is also input to the calculation means 21. Other configurations are the same as those of the first embodiment described with reference to FIG.

  As described above, the calculation means 21 has information on the distribution of the zeta potential of the raw water before the raw water adjusting agent is injected from the raw water adjusting agent injection facility 42 and the distribution of the zeta potential of the raw water after the raw water adjusting agent is injected. Information and information on the injection rate of the raw water adjusting agent are input.

  In the above configuration, when a raw water adjusting agent such as a pH adjusting agent or an alkalinity adjusting agent is injected into the raw water, information on changes in the zeta potential distribution before and after that is obtained. 6 and 7 show the change in the zeta potential distribution (shift) in the case of injecting the same raw water adjusting agent into raw water having the same original zeta potential but other water quality. Demonstrate the concept. 6 and 7 are simplified by using the zeta distribution of raw water when a single substance is included, but the same applies to the case where mixed raw water as shown in FIG. 3 is used.

  6 and 7 show that the zeta potential distribution after the raw water adjusting agent is injected is changed from the original zeta potential distribution. This indicates that the degree of influence on the distribution of the zeta potential varies depending on the aggregation characteristics of the raw water to be treated. That is, FIG. 6 shows a case where the influence of the zeta potential distribution due to the injection of the raw water adjusting agent is large, and FIG. 7 shows that the influence of the zeta potential distribution due to the injection of the raw water adjusting agent is small.

  In these figures, for easy understanding, the distribution of the zeta potential before and after the raw water adjusting agent is injected is greatly changed, but in actuality, either of FIGS. 6 and 7 is used. The zeta potential peaks before and after injection of the raw water regulator are in the same distribution section in each section of the measured zeta potential distribution described in the first embodiment.

  These pieces of information represent the agglomeration characteristics of the distribution of the zeta potential of the raw water to be treated, and the computing means 21 uses this information and the type of raw water regulator used and the information on the injection rate to use the zeta potential of the raw water. It is possible to correct the flocculant injection rate calculated from the distribution of.

  In other words, the calculation means 21 determines the flocculant set for each section according to the degree of change between the distribution of the zeta potential of the raw water before injection of the raw water regulator and the distribution of the zeta potential of the raw water after injection of the raw water regulator. The flocculant injection rate calculated using the injection rate is corrected. For example, in the example of FIG. 6, since the degree of the influence of the zeta potential distribution due to the injection of the raw water adjusting agent is large, it means that the change of the zeta potential distribution is likely to occur even when the flocculant is injected. . In the example of FIG. 7, the zeta potential distribution is relatively less affected by the injection of the raw water adjusting agent, which means that the change in the zeta potential distribution hardly occurs even when the flocculant is injected. Yes.

  In calculating the flocculant injection rate, as described in the first embodiment, the frequency in each section of the measured zeta potential distribution of raw water and the flocculant information holding means 100 are set for each section. From the data on the flocculant injection rate, calculate the flocculant injection rate required to move the distribution of the interval to the range of the zeta potential where the agglomeration progresses well, and calculate the total value of the raw water. It is calculated as the flocculant injection rate necessary for good aggregation.

  Therefore, in the present embodiment, the change in the zeta potential distribution before and after the injection of the raw water adjusting agent as shown in FIG. 6 or FIG. The flocculant injection rate into the raw water calculated using the data held in the agent information holding means 100 is corrected. For example, if the change in the zeta potential distribution before and after injection of the raw water regulator is classified as “large”, “medium”, or “small”, and the change is “large”, as described above, the injection of the flocculant This also means that a change in the zeta potential distribution is likely to occur, so that a correction coefficient that reduces the original flocculant injection rate is applied. When the change is “small”, it means that even if the flocculant is injected, the change in the distribution of the zeta potential hardly occurs. Therefore, a correction coefficient that increases the original flocculant injection rate is applied. On the other hand, when the change is “medium”, it means that the degree of change in the distribution of zeta potential is within the normal range with respect to the injection of the flocculant. To maintain.

  By performing such control, the flocculant can be injected at an injection rate more suitable for the properties of the raw water.

  It should be noted that the information related to the correction coefficient and the like described above may be stored in the data storage means 23, and may be cited as past data in the calculation of the future coagulant injection rate.

  Further, in this embodiment, the operator can intervene at each stage as well as the automatic control.

  Although several embodiments of the present invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 ... Control apparatus 21 ... Calculation means 22 ... Process control means 23 ... Data storage means 41 ... Coagulant injection equipment 42 ... Raw water regulator injection equipment 51 ... Zeta electrometer 52 ... alkalinity meter 53 ... conductivity meter 54 ... water temperature meter 55, 71 ... turbidity meter 56 ... pH meter 57 ... flow meter 60 ... landing well 62 ... Mixing basin 63 ... Flock formation pond 64 ... Sedimentation basin 72 ... Image analysis device 85 ... Water quality index measuring device 100 ... Flocculant information holding means

Claims (8)

A flocculant injection control method for controlling injection of a flocculant into raw water to be treated,
Measure the zeta potential distribution representing the frequency of charge appearance for each pre-segmented section of the raw water zeta potential ,
Using data on the distribution of previously obtained the zeta potential of the flocculant, in response to the distribution of the zeta potential of the raw water, the distribution of the zeta potential of the section, in order to shift to range agglomeration proceeds better A method for controlling the injection of a flocculant, comprising calculating a required injection rate of the flocculant. A flocculant injection control system for controlling the injection of flocculant into raw water to be treated,
Zeta potential measurement means for measuring the distribution of zeta potential representing the frequency of appearance of charge for each pre-segmented section of the zeta potential of the raw water;
A coagulant information holding means in which the data is stored about the distribution of previously obtained the zeta potential of the flocculant,
Using the data on the zeta potential distribution of the flocculant stored in the flocculant information holding means, the zeta potential distribution of the section corresponding to the measured zeta potential distribution is improved in agglomeration. A calculation means for calculating a flocculant injection rate necessary to shift to the advancing range ;
Corresponding to the distribution of the zeta potential of the raw water Based on the calculated flocculant injection rate, process control means for controlling a flocculant injection facility for injecting the flocculant,
A flocculant injection control system comprising: In the flocculant information holding means, the flocculant injection rate required to move the zeta potential of the section to the zeta potential range where the aggregation proceeds well for each preset section with respect to the zeta potential distribution of the raw water Data is stored,
The calculation means calculates a coagulant injection rate necessary for moving the measured zeta potential distribution of the raw water from the data set in the coagulant information holding means to a range of zeta potential where the aggregation proceeds well. The flocculant injection control system according to claim 2, wherein calculation is performed.   A water quality indicator measuring device that acquires a zeta potential and a water quality indicator of other raw water; and the calculation means calculates the flocculant calculated according to a correction coefficient for the flocculant injection rate set for each water quality indicator. The flocculant injection control system according to claim 2 or 3, wherein the injection rate is corrected.   The said water quality parameter | index measuring apparatus acquires the information of at least any one among the alkalinity, electrical conductivity, water temperature, turbidity, and pH in raw | natural water other than the said zeta potential, The said 4th characteristic is characterized by the above-mentioned. The described flocculant injection control system. In the past coagulant injection process, it has data storage means for holding the distribution information of the zeta potential of raw water and the actual value of the coagulant injection rate when coagulation has been performed satisfactorily. The flocculant injection information in the past zeta potential distribution corresponding to the current zeta potential distribution is extracted from the data storage means, and the flocculant injection rate for the current raw water to be processed is extracted from the extracted past flocculant injection information. coagulant injection control system according to any one of claims 2 to 5, characterized in that to predict.   The means for discriminating that the agglomeration has been satisfactorily obtained is characterized in that at least one of information on a floc image analysis device in a floc formation pond and turbidity at a sedimentation basin outlet is acquired. 6. The flocculant injection control system according to 6. A raw water adjusting agent injection facility for adjusting the quality of the raw water to be treated, and a post-injection zeta potential measuring means for measuring the distribution of the zeta potential after the raw water adjusting agent injection,
The calculation means calculates the calculated flocculant injection rate according to the degree of change between the distribution of the zeta potential of the raw water before the injection of the raw water regulator and the distribution of the zeta potential of the raw water after the injection of the regulator. coagulant injection control system according to any one of claims 2 to 7, characterized in that to correct.

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