JP5876719B2 - Control method and control device for rapid stirring intensity - Google Patents

Description

  The present invention relates to a rapid stirring intensity control method for controlling the rapid stirring intensity of agglomeration and floc forming processes in water purification plants and water treatment facilities, and a control apparatus therefor.

  In general, a water purification plant that employs a rapid filtration method is a mixing pond in which a flocculant is injected into raw water and rapidly stirred, a floc formation pond that grows aggregates (micro flocs) generated in the mixing pond, and a floc A sedimentation basin that precipitates and removes flocs grown in the formation basin; and a filtration basin that removes particles and flocs that have not settled in the sedimentation basin.

  The important point of the water purification process by the rapid filtration method is to control the flocculant injection rate to an appropriate value according to the quality of the raw water and to form a floc with good sedimentation. When water treatment is performed with an inappropriate flocculant injection rate, the loss of head of the filter basin, the frequency of backwashing increase, and the fine particles from the filter basin are increased due to carryover of floc from the sedimentation basin and poor flocculation. Problems such as outflow occur. However, the appropriate flocculant injection rate varies depending on factors such as raw water turbidity, alkalinity, pH, and water temperature, and differs for each river surface water. It cannot be determined uniquely. For this reason, in water treatment plants that employ a rapid filtration method, the flocculation condition is determined and the appropriate flocculant injection rate is determined by methods such as jar test, injection rate formulas with various water qualities as parameters, and floc particle size control. Or control.

Stirring is as important as the control of the flocculant injection rate in the water purification process by rapid filtration. That is, in a water purification plant that employs a rapid filtration method, it is important that the flocculant diffuses quickly throughout the tank in the mixing pond. For this reason, in the mixing pond, mechanical stirring by a flash mixer or water flow stirring using energy of water flow is performed. In general, rapid stirring intensity at this time (G _R value) is set to about 150s ^-1, rapid stirring intensity examples changed little depending on the season and water. On the other hand, in the flock formation pond, a mechanical stirring method using a paddle or a stirring method using vertical or horizontal bypass is employed. In floc formation ponds, flocs grow while repeating collision coalescence and destruction. Therefore, it is important to gradually reduce the stirring strength (tapered flocculation) as it goes to the subsequent tank.

Proper G _R values in the mixing basin is dependent coagulant, generally requires a high G _R value the higher the molecular weight of the flocculant. For example, G _R value of about 150s ^-1 is the proper value in the aluminum sulfate is flocculant and has been used for a long time. However, according to the results of the jar test using a kaolin aqueous suspension (artificial raw water), the proper value of _{G R} values in the polyaluminum chloride (PAC) is 450s ^-1, of _{G R} values in polysilica iron (PSI) The appropriate value is reported to be even higher. However, in actual water purification plants, based on the idea that flocculants may be promptly even spreading, example to increase or decrease the G _R value even in the case of using the PAC is small, aggregation of the lack of G _R value This is compensated by an increase in the drug injection rate.

  On the other hand, the amount of the flocculant used at the water purification plant after the Ministry of Health, Labor and Welfare requested that the turbidity at the outlet of the filtration basin be maintained at 0.1 degrees or less, triggered by the outflow accident of Cryptosporidium that occurred in 1996 Is growing. This is because it is necessary to reduce the turbidity of the precipitated water in order to reduce the turbidity of the filtered water. To that end, it is easy to increase the flocculant injection rate. is there. However, due to the revision of water quality standards in 2003, aluminum has been standardized, and it has become necessary to keep the aluminum concentration in purified water below 0.2 mg / L. For this reason, especially in water treatment plants that use a flocculant containing aluminum, it is necessary to manage the pH to suppress aluminum leakage and to control the amount of flocculant while maintaining the turbidity of filtrate water at a low value. It has become a major issue in recent water purification treatment.

In order to suppress the amount of flocculant while maintaining the turbidity of the filtered water to a low value, which is one of the effective means to properly control the G _R value in the mixing basin, as described above, G _R value of mixing basin in actual water treatment plants are operated fixed. Why control of G _R value is not performed, there is a following problem.

(1) Actual raw water Unlike artificial raw water, because of the different possibilities proper G _R value by raw water quality, requires jar tests to determine the proper G _R value for each water treatment plant operator The judgment results will vary.
(2) Apart from performing a jar test for determination of G _R value and jar test for determination of the coagulant injection rate is a significant burden for the operator.

JP-A-63-278509 JP-A-5-240767 JP 2009-672 A

Thus, in the conventional water treatment plant, despite the existence of proper G _R value according to the aggregating agent used as raw water quality, G _R value is operated at a constant value, coagulant injection rate Corresponding to changes in water quality, etc., only by increasing or decreasing. For this reason, conventional water treatment plants are often operated and managed with an excessive flocculant injection rate, which increases the cost of chemicals and generated soil, and when using flocculants containing aluminum. May cause an increase in the quality of purified water aluminum. There are similar problems with coagulation sedimentation in industrial water, sewage and factory wastewater.

  In addition, in the water purification plant where the mechanical flocculator is employed in the flock formation pond, an inverter for changing the rotational speed is usually installed. For this reason, the technique of patent document 1 and patent document 2 is proposed regarding the stirring control of a flocculator. Specifically, the technique described in Patent Document 1 is based on the time from immediately after the start of slow stirring in the next step until the floc particle size does not change after injecting a flocculant into raw water and performing rapid stirring. Thus, the rotational speed of the flocculator is determined. The technique described in Patent Document 2 analyzes the floc particle size based on image information, and controls the rotation speed of the flocculator using various feature values related to floc as management indices.

Patent Documents 1 and 2 described technique is not intended to control the G _R value of mixing basin, and so indirectly determine G _R value of mixing basin though based on the rotation speed of the determined flocculator However, there are the following problems. That is, in the technique described in Patent Document 1, the time from when the flocculant is injected to when the rotation speed of the flocculator is determined, the process proceeds to slow stirring through the rapid stirring and the time until the floc particle size does not change is changed. Since it is necessary, it takes about 30 minutes as a whole when the measurement tank is washed after the measurement is completed and the next raw water sampling step is included. However, it is desirable to control the rotational speed of the flocculator within at least 15 minutes in order to respond to changes in the raw water quality. Moreover, since the technique of patent document 2 determines stirring intensity | strength based on the information of the floc particle size in the floc formation pond of implementation, there exists a delay time of about 30 minutes from the mixing pond in the front | former stage of a flock formation pond. . Therefore, G _R value of mixing basin which is determined using the Patent Document 2 described technique is not intended to reflect the current state of raw water quality, the problem becomes a value based on past raw water quality There is.

  As described above, various techniques for controlling the rotational speed of flocculators have been devised, but all have problems of measurement time and delay time, and are difficult to apply to rapid stirring control. Therefore, it has been expected to provide a technology capable of automatically controlling the rapid stirring strength to an appropriate value according to the quality of raw water and the type of flocculant.

  The present invention has been made in view of the above problems, and its purpose is to control the rapid stirring speed capable of automatically controlling the rapid stirring strength to an appropriate value according to the raw water quality and the type of the flocculant, and its It is to provide a control device.

In order to solve the above problems and achieve the object, the method for controlling the rapid stirring strength according to the present invention is to stir the raw water into which the flocculant has been injected with a plurality of stirring strengths, and after adding the flocculant, the average floc Based on the measurement step of measuring the time until the particle size reaches the maximum floc particle size for each of a plurality of stirring strengths, and the relationship between the maximum floc particle size and the stirring strength measured in the measurement step, the maximum floc particle size A proper stirring strength calculation step for calculating the stirring strength to obtain the proper stirring strength, a time from the injection of the flocculant measured in the measurement step until the average floc particle size reaches the maximum floc particle size, and the stirring strength based on the relationship between, calculate the time from the injection of coagulant during stirring at the proper agitation intensity to an average floc diameter is maximum floc diameter as a proper agitation time Calculating the stirring strength of the stirring means for rapidly stirring the raw water injected with the flocculant in the mixing basin using the appropriate stirring time calculating step, the appropriate stirring strength and the appropriate stirring time, and the calculated stirring strength And a control step for controlling the stirring means so as to rapidly stir the raw water.

  In the method for controlling the rapid stirring intensity according to the present invention, in the above invention, the control step calculates a product of the appropriate stirring intensity and the appropriate stirring time, and calculates the mixing pond capacity and the amount of treated water per unit time. The step of calculating the residence time of the raw water in the mixing basin and calculating the stirring intensity of the stirring means from the product and the residence time is included.

  The rapid stirring intensity control method according to the present invention is the above-described invention, wherein the stirring means is a flash mixer, and the control step controls the stirring intensity of the flash mixer by controlling the rotation speed of the flash mixer. Including the step of:

  In the method for controlling the rapid stirring intensity according to the present invention, the control step includes the step of calculating the rotation speed of the flash mixer corresponding to the stirring intensity using the mixing pond capacity, the total area of the stirring blades, and the water temperature. It is characterized by including.

  The method for controlling the rapid stirring strength according to the present invention is the above-described method, wherein the measuring step injects a flocculant into the same volume of raw water stored in a plurality of test water tanks, A step of stirring.

In order to solve the above-described problems and achieve the object, the rapid stirring strength control device according to the present invention stirs raw water into which a flocculant has been injected with a plurality of stirring strengths, and after adding the flocculant, the average floc Based on the relationship between the time until the particle diameter reaches the maximum floc particle diameter and the measurement means for measuring the maximum floc particle diameter for each of a plurality of stirring strengths, and the maximum floc particle diameter measured by the measuring means and the stirring strength And an appropriate stirring intensity calculating means for calculating the stirring intensity at which the maximum floc particle diameter is obtained as an appropriate stirring intensity, and from the injection of the flocculant measured by the measuring means until the average floc particle diameter reaches the maximum floc particle diameter. based on the relationship between the time and the intensity of stirring of the time from the injection of coagulant during stirring at the proper agitation intensity to an average floc diameter is maximum floc particle size and appropriate stirring time Using the proper stirring time calculating means to calculate, the appropriate stirring strength and the appropriate stirring time, the stirring strength of the stirring means for rapidly stirring the raw water into which the flocculant is injected in the mixing pond is calculated, and the calculated stirring is performed. And control means for controlling the stirring means so as to rapidly stir the raw water with strength.

  According to the rapid stirring speed control method and control apparatus according to the present invention, the rapid stirring strength can be automatically controlled to an appropriate value according to the quality of raw water and the type of flocculant.

FIG. 1 is a schematic diagram showing a configuration of a rapid stirring intensity control system according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining the configuration of the test water tank shown in FIG. 1. FIG. 3 is a flowchart showing a flow of rapid stirring intensity control processing according to an embodiment of the present invention. FIG. 4 is a diagram showing the change over time of the average particle size of floc. FIG. 5 is a diagram showing changes in the temporal change profile of the average particle diameter of flocs accompanying changes in the stirring intensity. FIG. 6 is a diagram illustrating an example of the agglomeration start time function and the maximum floc particle size arrival time function. FIG. 7 is a diagram illustrating an example of the maximum floc particle size function. FIG. 8 is a diagram showing a change in turbidity of the precipitated treated water when the number of revolutions of the flash mixer is controlled by the number of revolutions calculated according to the present invention. FIG. 9 is a diagram showing a change in turbidity of the precipitated treated water when the water treatment is performed by reducing the flocculant injection rate of the series in which the rapid stirring control is performed by 3 mg / L. FIG. 10 is a diagram showing the change over time of the flocculant injection rate.

  Hereinafter, the configuration and operation of a rapid stirring intensity control system according to an embodiment of the present invention will be described with reference to the drawings.

[Control system for rapid stirring intensity]
First, with reference to FIG. 1 and FIG. 2, the structure of the control system of the rapid stirring intensity which is one Embodiment of this invention is demonstrated.

  FIG. 1 is a schematic diagram showing a configuration of a rapid stirring intensity control system according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining the configuration of the test water tanks 1a to 1d shown in FIG. The rapid stirring intensity control system according to an embodiment of the present invention calculates and controls the rotational speed of a flash mixer that rapidly stirs raw water into which a flocculant has been injected in a mixing pond. However, the controlled object of the present invention is not limited to the flash mixer, and any stirring means other than the flash mixer can be controlled as long as it controls the rapid stirring intensity in the mixing pond.

  As shown in FIG. 1, the control system of the rapid stirring intensity which is one embodiment of the present invention includes a plurality (four in this embodiment) of test water tanks 1a to 1d. The test water tanks 1a to 1d are constituted by the same water tank, and store the sample water W or washing water which is raw water therein. As shown in FIG. 2, a drain pipe 31 is provided at a predetermined height position of the test water tanks 1 a to 1 d, and the sample water W or the cleaning water that has reached the predetermined height position is outside the tank via the drain pipe 31. It is configured to be discharged. The drain pipe 31 is provided with a flow rate switch 32 for detecting the flow of the sample water W or the washing water in the drain pipe 31, and the sample water W or the washing water has reached a predetermined height position in the test water tanks 1a to 1d. It is configured so that it can be detected.

  Water supply / drainage valves 2a-2e are provided at the bottoms of the test water tanks 1a-1d and the water level adjustment tank 14, and a water supply pipe 11 and a drainage pipe 12 are connected to the water supply / drainage valves 2a-2e. In the test water tanks 1a to 1d, stirrers 3a to 3d for stirring the test water W into which the flocculant has been injected are provided. A tap water supply system and a raw water supply system are connected to the water pipe 11. The tap water supply system includes a tap water inlet valve 6, a water supply pump 7, a filter 8, and a filter inlet valve 9, and supplies tap water as cleaning water to a water pipe 11. The filter 8 is for removing fine particles contained in tap water.

  The raw water supply system includes a raw water inlet valve 4, a raw water drain valve 5, a feed water pump 7, and a raw water water supply valve 10, and supplies raw water as sample water W to a water supply pipe 11. The washing water or sample water W supplied to the water supply pipe 11 is supplied to the test water tanks 1a to 1d and the water level adjusting tank 14 via the water supply / drain valves 2a to 2e. The drain pipe 12 is for discharging the sample water W or the washing water in the test water tanks 1a to 1d and the water level adjusting tank 14 to the outside, and is a drain valve for controlling the discharge of the sample water W or the washing water to the outside. 13 is provided.

  The water level adjusting tank 14 is divided into two regions by an overflow wall 14a having a height lower than the height position of the drain pipe 31 provided in the test water tanks 1a to 1d. A water supply / drainage valve 2e is provided on the bottom surface of one region partitioned by the overflow wall 14a, and a water supply pipe 11 and a drainage pipe 12 are connected to the water supply / drainage valve 2e. A drain pipe 15 is connected to the bottom surface of the other region partitioned by the overflow wall 14a.

  The flocculant storage tank 16 stores the flocculant injected into the sample water W in the test water tanks 1a to 1d. The syringe pump 17 pumps the flocculant in the flocculant storage tank 16 into the test water tanks 1a to 1d. The valve 18 controls switching of the supply of the flocculant into the test water tanks 1a to 1d.

  The detectors 19 a to 19 d measure the average particle diameter and the average number of flocs formed in the test water tanks 1 a to 1 d and send the measured values to the control device 22. Specifically, the detectors 19a to 19d are included in the sample water W and a light beam irradiation unit configured by any one of a laser, an LED, and a lamp for irradiating the sample water W with the light beam. A photoelectric converter that receives at least one of forward-scattered light, side-scattered light, back-scattered light, or transmitted light emitted from a particle and converts the light into an electric signal; and an average value and a standard deviation of the electric signal; To an electronic circuit for measuring the average particle size and the average particle number of floc. See Japanese Patent No. 2824164 for the method of measuring the average particle size and the average number of flocs.

  The central monitoring device 20 is configured by an information processing device such as a personal computer or a workstation, and the central monitoring device 20 is used to perform monitoring control of water purification treatment of raw water at the water purification plant. The POD 21 is used to input measurement result display and device setting conditions. The control device 22 is configured by an information processing device such as a microcomputer or a personal computer, or a sequencer, and controls the operation of the entire rapid stirring intensity control system.

[Rapid stirring intensity control process]
In the rapid stirring intensity control system having such a configuration, the controller 22 calculates and controls the rotation speed of the flash mixer by executing the following rapid stirring intensity control process. Hereinafter, with reference to the flowchart shown in FIG. 3, the operation of the control device 22 when executing this control process will be described.

  FIG. 3 is a flowchart showing a flow of rapid stirring intensity control processing according to an embodiment of the present invention. The flowchart shown in FIG. 3 starts when the operator instructs the control device 22 to execute the rapid stirring intensity control process, and the rapid stirring intensity control process proceeds to step S1.

  In the process of step S1, after the control device 22 stops the agitators 3a to 3d and the water supply pump 7, the tap water inlet valve 6, the filter inlet valve 9, and the raw water supply valve 10 are closed, and the water supply / drainage valve 2a. The sample water W remaining in the test water tanks 1a to 1d and the water level adjusting tank 14 is discharged to the outside through the drain pipe 12 by opening the ~ 2e and the drain valve 13 (test water draining process). Moreover, the control apparatus 22 discharge | releases raw | natural water outside by making the raw | natural water inlet valve 4 and the raw | natural water wastewater valve 5 into a closed state and an open state, respectively. Thereby, the process of step S1 is completed and this control process progresses to the process of step S2.

  In the process of step S2, the control device 22 opens the tap water inlet valve 6 and the filter inlet valve 9 and closes the drain valve 13, and then drives the water supply pump 7 to drive the water supply pipe 7 through the water pipe 11. Tap water as cleaning water is supplied into the test water tanks 1a to 1d and the water level adjustment tank 14 (cleaning water feeding process). In addition, wash water gradually accumulates in the test water tanks 1 a to 1 d, and when the surface level of the wash water reaches the height position of the drain pipe 31, excess wash water is discharged to the outside through the drain pipe 31. . At this time, the agitators 3a to 3d may be driven. By driving the stirrers 3a to 3d, the test water tanks 1a to 1d are washed to a predetermined level even when raw water with high turbidity and chromaticity remains in the test water tanks 1a to 1d. It can suppress that the raw | natural water which remained in the water tanks 1a-1d affects the process mentioned later. Thereby, the process of step S2 is completed and this control process progresses to the process of step S3.

  In the process of step S3, the control device 22 outputs a signal instructing zero point calibration to the detectors 19a to 19d. In the detectors 19a to 19d that have received the signals, the photoelectric converters constituting the detectors are detected. The level of the electric signal to be output is detected and the detected value is stored (zero water measurement step). By storing the level of the electrical signal output from the photoelectric converter, it is possible to determine the contamination of the optical system, the deterioration of the filter, and the like, and it is possible to correct the amount of light in the processing described later. Thereby, the process of step S3 is completed and this control process progresses to the process of step S4.

  In the process of step S4, after the control device 22 stops the water supply pump 7, the drain valve 13 is opened, and the tap water inlet valve 6 and the filter inlet valve 9 are closed, whereby the test water tanks 1a to 1a. 1d and the washing water in the water level adjustment tank 14 are discharged to the outside (washing water draining step). Thereby, the process of step S4 is completed, and the control process proceeds to the process of step S5.

  In the process of step S5, the control device 22 opens the raw water inlet valve 4 and the raw water water supply valve 10 and closes the raw water drain valve 5 and the drain valve 13 and then operates the water supply pump 7, The test water W is supplied into the test water tanks 1a to 1d and the water level adjusting tank 14 through the water supply pipe 11 (raw water supply process). Thereby, the process of step S5 is completed, and the control process proceeds to the process of step S6.

  In the process of step S6, the control device 22 detects that the flow switch 32 has been switched from the off state to the on state, whereby the water level of the test water W in the test water tanks 1a to 1d has reached a predetermined height. Detect that. When it is detected that the water level of the test water W has reached a predetermined height, the control device 22 stops the feed water pump 7 and then closes the raw water feed valve 10 and the raw water inlet valve 4 to close the raw water drain valve. 5 is opened. Thereby, the test water W in the test water tanks 1 a to 1 d is discharged to the outside through the drain pipe 15 of the water level adjustment tank 14 until the water level becomes the same height as the overflow wall 14 a of the water level adjustment tank 14. As a result, the water levels of the test water W in the test water tanks 1a to 1d are all adjusted to the same height as the overflow wall 14a, and the test water W having the same capacity is stored in the test water tanks 1a to 1d (water level adjusting step). ). In addition, you may enable it to change the capacity | capacitance of the test water W stored in the test water tanks 1a-1d by changing the height of the overflow wall 12 provided in the water level adjustment tank 14. FIG. Thereby, the process of step S6 is completed and this control process progresses to the process of step S7.

  In the process of step S7, the control device 22 stirs the test water W in the test water tanks 1a to 1d by operating the stirrers 3a to 3d. At this time, the control device 22 changes the stirring strength of the test water tanks 1a to 1d from each other by changing the rotation speed of the stirrers 3d to 3d or the area of the stirring blades for each test water tank. Next, the control device 22 measures the number of particles, turbidity, water temperature, chromaticity, E260, and the like of the sample water W using the detectors 19a to 19d, and sets the flocculant injection rate based on the measured values. (Coagulant injection rate setting step). In addition, the control apparatus 22 may acquire the information regarding the present value of the coagulant injection rate in the water purification plant from the central monitoring apparatus 20, and may set the coagulant injection rate based on the acquired information. Thereby, the process of step S7 is completed, and the control process proceeds to the process of step S8.

  In the process of step S8, the control device 22 supplies the predetermined amount of the flocculant set in the flocculant injection rate setting step from the flocculant storage tank 16 to each test water tank by driving the syringe pump 17 (flocculation). Agent injection step). At this time, the injection of the flocculant into the test water tanks 1 a to 1 d is sequentially performed by switching the valve 18. Thereby, the process of step S8 is completed, and the control process proceeds to the process of step S9.

In the process of step S9, the control device 22 measures and stores, as the agglomeration start time, the time when the average particle size of floc in the test water tanks 1a to 1d starts to increase based on the output signals of the detectors 19a to 19d. (Agglomeration start time measurement step). Specifically, as shown in FIG. 4, when the flocculant is injected into the test water W (time = T1), the flocculant is dispersed by stirring, and particle agglomeration starts (time T = T2). . Then, the average particle diameter of the flocs reaches the maximum value R _{max at} time T = T3 by repeating the collision coalescence, and then decreases with time. Therefore, the control device 22 measures and stores the time T = T2 at which particle agglomeration starts as the agglomeration start time. Thereby, the process of step S9 is completed and this control process progresses to the process of step S10.

In the process of step S10, the measurement control unit 22, based on the output signal of the detector 19 a to 19 d, a maximum value _{R max} of the average grain size of the flocs measured every test aquarium 1a~1d the maximum floc particle size And memorize (maximum floc particle size measurement step). Thereby, the process of step S10 is completed, and the control process proceeds to the process of step S11.

In step S11, the control unit 22, based on the output signal of the detector 19 a to 19 d, the time average particle size of the flocs reached the maximum floc particle size _{R max} (time T = T3 shown in FIG. 4) It is measured and stored as the maximum floc particle diameter arrival time (maximum floc particle diameter arrival time measurement step). Since the agglomeration start time, the maximum floc particle size, and the maximum floc particle size arrival time vary depending on the stirring strength, as shown in FIG. 5, the profile of the average particle size of floc in the test water tanks 1a to 1d Are different profiles L1 to L4. Thereby, the process of step S11 is completed and this control process progresses to the process of step S12.

  In the process of step S12, the control device 22 collects a function indicating the relationship between the stirring intensity and the agglomeration start time using the data of the agglomeration start time of each test water tank stored in the process of step S9. Calculated as agglomeration start time function (agglomeration start time function calculation step). The agglomeration start time function is represented by a curve L5 as shown in FIG. 6, for example. Plots P1 to P4 on the curve L5 indicate the stirring intensity and the agglomeration start time in each test water tank. Thereby, the process of step S12 is completed and this control process progresses to the process of step S13.

  In the process of step S13, the control device 22 uses the data of the maximum floc particle diameter of each test water tank stored in the process of step S10 to calculate a function indicating the relationship between the stirring strength and the maximum floc particle diameter. It calculates as a diameter function (maximum floc particle size function calculation process). Note that the maximum floc particle size function is represented by a curve L7 as shown in FIG. 7, for example. The plot on the curve L7 shows the stirring intensity and the maximum floc particle diameter in each test water tank. Thereby, the process of step S13 is completed and this control process progresses to the process of step S14.

  In the process of step S14, the control device 22 uses the data of the maximum floc particle diameter arrival time of each test water tank stored in the process of step S11 to indicate the relationship between the stirring intensity and the maximum floc particle diameter arrival time. Is calculated as a maximum floc particle size arrival time function (maximum flock particle size arrival time function calculation step). The maximum floc particle size arrival time function is represented by a curve L6 as shown in FIG. 6, for example. Plots P5 to P8 on the curve L6 indicate the stirring strength and the maximum floc particle size arrival time in each test water tank. Thereby, the process of step S14 is completed, and the control process proceeds to the process of step S15.

In the process of step S15, the control device 22 uses the maximum flock particle size function calculated by the process of step S13 to change the stirring intensity at which the maximum flock particle diameter _Rmax is obtained as shown in FIG. Calculated as _r value (appropriate stirring intensity calculating step). Thereby, the process of step S15 is completed, and the control process proceeds to the process of step S16.

In the process of step S16, the control device 22 uses the agglomeration start time function calculated by the process of step S12, as shown in FIG. 6, the proper stirring intensity G _r value calculated by the process of step S15. The agglomeration start time is calculated as an appropriate stirring time _Tr value (appropriate stirring time calculating step). The control device 22 uses the maximum flock particle size arrival time function calculated by the process of step S14 instead of the agglomeration start time function to appropriately set the maximum flock particle size arrival time at the appropriate stirring strength G _r value. You may calculate as stirring time _Tr value. Thereby, the process of step S16 is completed and this control process progresses to the process of step S17.

In the process of step S17, the control device 22 calculates the product G _r T _r value of the appropriate stirring intensity G _r value calculated by the process of step S15 and the appropriate stirring time T _r value calculated by the process of step S16. (Appropriate G _r T _r value calculation step). Thereby, the process of step S17 is completed and this control process progresses to the process of step S18.

In the process of step S18, the control device 22 uses raw water in the mixing pond from the capacity of the mixing pond in the water purification plant that is input in advance as a set value and the treated water amount per unit time of the water purification plant obtained from the central monitoring device 20. calculating the residence time as mixing basin dwell time T _R values (mixing basin retention time calculation step). Thereby, the process of step S18 is completed, and the control process proceeds to the process of step S19.

In the process of step S19, the control unit 22, the equation (1) indicating the mixing basin dwell time T _R value calculated by the processing of the G _r T _r value and step S18 which is calculated by the processing in step S17 in the following by substituting for, to calculate an appropriate rapid agitation intensity G _R value (proper water treatment plant rapid stirring intensity calculation step). Note that Equation (1), if the test water W and the same quality in the raw water and test water tank 1a~1d water treatment plant, the proper _G R _{T R} value based on the idea that equals _G r _{T r} value However, it may be changed to an equation corrected by coefficients α and β as shown in the following equation (2) according to the actual situation. Thereby, the process of step S19 is completed, and the control process proceeds to the process of step S20.

In the process of step S20, the control device 22 uses the following equation (5) obtained from the equation for calculating the G value in equation (3) below and the equation for calculating the average peripheral speed of the stirring blades in equation (4) below. the rapidly stirring intensity G _R value calculated by the processing in step S19, the capacity of the mixing basin of a water purification plant, the total area of the stirring blade, the rotation of the stirring blade radius, viscosity of the raw water depends on the water temperature of the raw water, and raw water By substituting the density, an appropriate rotational speed of the flash mixer is calculated (hereinafter referred to as an appropriate rotational speed calculating step). And the control apparatus 22 memorize | stores the data of the calculated appropriate rotation speed with the measured value obtained at each process. The appropriate rotation speed is output to a rotation speed control device such as an inverter of a flash mixer as a communication signal or an analog signal as necessary. In addition, you may correct | amend the suitable rotation speed of a flash mixer according to the operation performance of an implementation installation. Thereby, the process of step S20 is completed and this control process returns to the process of step S1.

Here, ρ in Formula (3) is the density of water (kg / m ³ ), C is the stirring coefficient (1.5 is adopted), A is the total area of the stirring blade (m ² ), and v is the stirring blade. Average speed (m / s), μ is a viscosity coefficient (kg / (m · s)), and V indicates a mixing pond capacity (m ³ ). Moreover, r in Formula (4) has shown the radius of the stirring blade, and n has shown the rotation speed (rpm) of the stirring blade.

  As is apparent from the above description, according to the rapid stirring intensity control system according to an embodiment of the present invention, the control device 22 stirs the raw water into which the flocculant has been injected with a plurality of stirring intensities. The time from the injection of particles to the start of agglomeration of particles in raw water and the maximum floc particle size are measured for each of several stirring strengths, and the maximum floc particle size is determined based on the relationship between the maximum floc particle size and the stirring strength. Is calculated as the appropriate stirring strength, and based on the relationship between the stirring strength and the time from the injection of the flocculant to the start of agglomeration of particles in the raw water, Calculate the time from the injection of the flocculant to the start of agglomeration of particles in the raw water as the appropriate stirring time, and use the appropriate stirring strength and the appropriate stirring time to calculate the stirring strength of the flash mixer. The raw water is rapidly To control the flash mixer to stir. Thereby, the rapid stirring intensity | strength of a flash mixer can be automatically controlled to an appropriate value according to the raw | natural water quality and the kind of flocculant.

  In addition, although this invention is similar to the technique of patent document 3, the technique of patent document 3 is for calculating an appropriate coagulant | flocculant injection rate, and calculating the appropriate rapid stirring intensity | strength. Is not. In the present invention, the agglomeration start time, the maximum floc particle size, and the maximum floc particle size arrival time are measured for each stirring strength by adopting different stirring strengths in each test water tank. In the technique described in Document 3, the maximum floc particle size and the maximum floc particle size arrival time are not measured, and the agglomeration start time is measured for each different flocculant injection rate, not for each different stirring intensity.

〔Example〕
In an actual water purification plant, an inverter is connected to a flash mixer, and the results of a control experiment according to the present invention are shown below. FIG. 8 is a diagram showing a change in precipitation-treated water turbidity when the rotation speed of the flash mixer is controlled by the rotation speed calculated according to the present invention. As shown in FIG. 8, according to the rapid stirring control according to the present invention (rotational speed control of the flash mixer), the turbidity of the precipitated treated water is compared with the case where the rapid stirring control according to the present invention is not performed (prior art). The degree could be reduced. FIG. 9 is a diagram showing a change in turbidity of the precipitated treated water when the water treatment is performed by reducing the flocculant injection rate of the series in which the rapid stirring control is performed by 3 mg / L. It can be confirmed that the system in which the rapid stirring control was performed can maintain the same water quality as the conventional injection rate series (without rapid stirring control), although the flocculant injection rate was decreased as shown in FIG. It was. As described above, according to the present invention, it is possible to optimize the rapid stirring strength of the water purification plant, that is, the rotational speed of the flash mixer, and as a result, improve the precipitated water quality and agglomerate while maintaining the precipitated water quality. The amount of agent used was reduced.

  Although the embodiment to which the invention made by the present inventor is applied has been described above, the present invention is not limited by the description and the drawings that form a part of the disclosure of the present invention according to this embodiment. That is, other embodiments, examples, operational techniques, and the like made by those skilled in the art based on this embodiment are all included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1a-1d Test water tank 2a-2e Water supply / drainage valve 3a-3d Stirrer 4 Raw water inlet valve 5 Raw water discard valve 6 Tap water inlet valve 7 Water supply pump 8 Filter 9 Filter inlet valve 10 Raw water supply valve 11 Water supply pipe 12, 15 Drain pipe 14 Water level adjustment tank 14a Overflow wall 16 Coagulant storage tank 17 Syringe pump 18 Valve 19a-19d Detector 20 Central monitoring device 21 POD
22 Control device 31 Drain pipe 32 Flow switch

Claims (6)

A measurement step of stirring the raw water into which the flocculant has been injected with a plurality of stirring strengths and measuring the time from the injection of the flocculant until the average floc particle size reaches the maximum floc particle size for each of the plurality of stirring strengths;
Based on the relationship between the maximum flock particle size and the stirring strength measured in the measurement step, an appropriate stirring strength calculation step for calculating the stirring strength at which the maximum flock particle size is obtained as the appropriate stirring strength;
Based on the relationship between the stirring strength and the time from the injection of the flocculant measured in the measurement step until the average floc particle size reaches the maximum floc particle size, the flocculant when stirring at the appropriate stirring strength A proper stirring time calculating step for calculating the time from the injection until the average floc particle size reaches the maximum floc particle size as the appropriate stirring time;
Using the appropriate stirring intensity and the appropriate stirring time, calculate the stirring strength of the stirring means for rapidly stirring the raw water injected with the flocculant in the mixing pond, and rapidly stir the raw water with the calculated stirring strength A control step for controlling the stirring means;
A control method of rapid stirring intensity, comprising:   The control step calculates the product of the appropriate stirring intensity and the appropriate stirring time, calculates the residence time of raw water in the mixing basin from the volume of the mixing basin and the amount of treated water per unit time, and the product and the stagnation The method for controlling the rapid stirring intensity according to claim 1, further comprising a step of calculating the stirring intensity of the stirring means from time.   The said stirring means is a flash mixer, and the said control step includes the step which controls the stirring intensity | strength of this flash mixer by controlling the rotation speed of this flash mixer. Method for controlling the rapid stirring intensity.   The said control step includes the step of calculating the rotation speed of the flash mixer corresponding to the said stirring intensity | strength using the capacity | capacitance of a mixing basin, the total area of a stirring blade, and water temperature. Among them, the rapid stirring intensity control method according to any one of the above. Said measuring step is to inject the coagulant to the raw water of the same volume, which is stored in a plurality of test aquarium, according to claim 1-4, characterized in that it comprises a step of stirring the raw water at different agitation intensities for each test aquarium Among them, the rapid stirring intensity control method according to any one of the above. The raw water into which the flocculant has been injected is stirred at multiple stirring strengths, and the time from when the flocculant is injected until the average floc particle size reaches the maximum floc particle size and the maximum floc particle size are measured for each of the multiple stirring strengths. Measuring means to
Based on the relationship between the maximum flock particle size measured by the measuring unit and the stirring strength, appropriate stirring strength calculating means for calculating the stirring strength at which the maximum flock particle size is obtained as the appropriate stirring strength;
Based on the relationship between the stirring intensity and the time from the injection of the flocculant measured by the measuring means until the average floc particle diameter reaches the maximum floc particle diameter, the flocculant when stirred at the appropriate stirring intensity An appropriate stirring time calculating means for calculating the time from the injection until the average floc particle size reaches the maximum floc particle size as the appropriate stirring time;
Using the appropriate stirring intensity and the appropriate stirring time, calculate the stirring strength of the stirring means for rapidly stirring the raw water injected with the flocculant in the mixing pond, and rapidly stir the raw water with the calculated stirring strength Control means for controlling the stirring means;
A control device for rapid stirring intensity, comprising:

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