Medicament addition amount adjustment method and medicament addition amount adjusting device

Abstract

To provide a medicament addition amount adjustment method that can maintain a mass ratio of a calcium component and a calcium insolubilization medicament in an appropriate range even when a concentration of the calcium component changes.SOLUTION: A medicament addition amount adjustment method for controlling an addition amount of a calcium insolubilization medicament for insolubilization of a calcium component contained in target water includes: a reaction step of insolubilization of a calcium component by addition of a calcium insolubilization medicament to target water; a precipitation separation step of precipitation separation of the target water after the reaction step; a turbidity measurement step of blending calcium insolubilization medicament to a part of a supernatant after the precipitation separation step and measuring its turbidity; and an addition amount control step of feedback controlling an addition amount of the calcium insolubilization medicament for addition in the reaction step based on the turbidity measured in the turbidity measurement step.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a chemical addition amount adjustment method and a chemical addition amount adjustment device for adjusting the addition amount of a calcium insolubilizing agent that insolubilizes calcium components contained in water to be treated.

Background Art

[0002] Since high-concentration calcium components are dissolved in the leachate of the final disposal site, scale may form on the pipes and equipment in the water treatment facility that treats the leachate, and inconvenient situations such as pipe blockage may occur. To prevent this, for example, as shown in Japanese Unexamined Patent Application Publication No. 2020-104042 (Patent Document 1), sodium carbonate, which is a calcium insolubilizing agent, is added to the leachate and precipitated and separated as calcium carbonate, so that a pretreatment for removing the calcium component in the leachate is performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When an operator measures the dissolved calcium concentration of leachate by manual analysis and sets the addition amount of sodium carbonate, an excessive amount of sodium carbonate beyond the theoretical required amount must be added to cope with changes in the dissolved calcium concentration of the leachate, resulting in a problem of increased chemical costs. Therefore, a method of measuring the dissolved calcium concentration using a commercially available ion electrode type calcium concentration meter has also been developed, but such a calcium concentration meter is affected by coexisting ions and it is difficult to obtain an accurate value. Moreover, since scale easily adheres to the electrode part immersed in the leachate, it may be difficult to accurately measure in real time when the concentration of calcium components in the water to be treated can vary.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for adjusting the dosage of a drug and a device for adjusting the dosage of a drug that can maintain the molar ratio of the calcium component to the calcium insolubilizing agent within an appropriate range even when the concentration of the calcium component can vary.

Means for Solving the Problems

[0006] The method for adjusting the dosage of a drug according to the present invention is characterized in that it is a method for adjusting the dosage of a calcium insolubilizing agent that insolubilizes the calcium component contained in the water to be treated, a reaction step of adding a calcium insolubilizing agent to the water to be treated to insolubilize the calcium component; a sedimentation separation step of sedimentation-separating the water to be treated after the reaction step; a turbidity measurement step of mixing a calcium insolubilizing agent with a part of the supernatant after the sedimentation separation step and measuring the turbidity; and an addition amount control step of feedback-controlling the addition amount of the calcium insolubilizing agent added in the reaction step based on the turbidity measured in the turbidity measurement step.

[0007] In the method for adjusting the dosage of a drug according to the present invention, it further includes a concentration calculation step of calculating the calcium concentration in the supernatant based on the turbidity measured in the turbidity measurement step, and it is preferable that the addition amount control step feedback-controls the addition amount of the calcium insolubilizing agent added in the reaction step based on the calcium concentration calculated in the concentration calculation step.

[0008] The drug dosage adjustment device according to the present invention is characterized in that it is a drug dosage adjustment device that adjusts the dosage of a calcium insolubilizing agent that insolubilizes the calcium component contained in the water to be treated, a reaction tank that adds a calcium insolubilizing agent to the water to be treated to insolubilize the calcium component; a sedimentation tank that aggregates and precipitates the calcium insoluble matter generated in the water to be treated; A measuring device that measures the turbidity by mixing a calcium insolubilizing agent with a part of the supernatant liquid in the precipitation tank, and a control device that calculates the calcium concentration in the supernatant liquid based on the turbidity measured by the measuring device and feedback-controls the addition amount of the calcium insolubilizing agent added to the reaction tank based on the calculated calcium concentration. The present invention is characterized in that it comprises these components.

[0009] In the chemical agent addition amount adjusting device according to the present invention, it is preferable that the measuring device is provided inside the precipitation tank.

[0010] In the chemical agent addition amount adjusting device according to the present invention, it is preferable that the measuring device includes a cylindrical member that is immersed in the liquid in the precipitation tank and can collect a certain amount of supernatant liquid.

[0011] In the chemical agent addition amount adjusting device according to the present invention, it is preferable that the measuring device is provided outside the precipitation tank.

[0012] In the chemical agent addition amount adjusting device according to the present invention, it is preferable that the measuring device includes a second reaction tank installed outside the precipitation tank and a transfer device that collects a certain amount of supernatant liquid from the precipitation tank and sends it to the second reaction tank.

Advantages of the Invention

[0013] According to the present invention, since the addition amount of the calcium insolubilizing agent added to the reaction tank is feedback-controlled based on the calcium remaining in the supernatant liquid of the precipitation tank, the amount of sodium carbonate added to precipitate calcium can be maintained more appropriately, and calcium can be removed more reliably. In addition, since it becomes easier to avoid the use of excessive sodium carbonate, it further contributes to reducing the operating cost of, for example, a calcium removal device equipped with the present invention.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0015] Embodiments of a chemical addition amount adjustment device and a chemical addition amount adjustment method according to the present invention will be described with reference to the drawings.

[0016] (First Embodiment) Hereinafter, as an example, a form in which a chemical addition amount adjustment device according to the present invention is applied to a calcium removal device 1 (hereinafter simply referred to as a removal device 1) that removes calcium components from leachate (an example of water to be treated) discharged from a final disposal site of waste will be used as an example to describe embodiments of the present invention.

[0017] 〔Configuration of Calcium Removal Device〕 The removal device 1 according to the present embodiment includes a sewage measuring tank 2, a reaction tank 3, a first preparation tank 4, a second preparation tank 5, and a control device 6 that performs arithmetic processing related to the control of the operations of the above components (FIGS. 1 and 2). Further, the removal device 1 includes a mixing tank 11, a sedimentation tank 12, and a neutralization tank 13 downstream of the reaction tank 3. Note that auxiliary devices such as stirring devices may be appropriately provided in each tank, but illustration and description are omitted for simplicity.

[0018] In the reaction tank 3, a calcium insolubilizing agent is added to the leachate to insolubilize the calcium component. In the removal device 1, the leachate flows into the reaction tank 3 through the sewage measuring tank 2, and in the reaction tank 3, it is mixed with an aqueous sodium carbonate solution (an example of a chemical solution) supplied from the first preparation tank 4 and an aqueous sodium hydroxide solution supplied from the second preparation tank 5. At this time, calcium ions Ca in the leachate 2+Calcium hydroxide and sodium carbonate Na₂CO₃ cause a reaction represented by the following formula (1), and calcium carbonate CaCO₃ precipitates. The aqueous sodium hydroxide solution serves to adjust the leachate to be basic so that the reaction of formula (1) proceeds easily. Ca 2+ + Na₂CO₃ → CaCO₃↓ + 2Na + (1)

[0019] For the leachate in which calcium carbonate precipitated by the reaction of formula (1) has precipitated, a flocculant is mixed in the mixing tank 11, and the aggregation of the calcium carbonate precipitate proceeds. Examples of such flocculants include, but are not limited to, ferric chloride, ferric polysulfate, and band sulfate. Also, a flocculation aid such as a polymer may be added in the mixing tank 11.

[0020] The sedimentation tank 12 aggregates and sediments the calcium carbonate precipitate generated in the leachate. The leachate containing the aggregated calcium carbonate precipitate is subjected to solid-liquid separation in the sedimentation tank 12, and the precipitated solid part (calcium carbonate precipitate) is discharged as sludge. On the other hand, the liquid part after the solid part is removed is mixed with an acid and neutralized in the neutralization tank 13, and then sent to a subsequent process (not shown).

[0021] The sewage measuring tank 2 is a tank that first receives the leachate flowing into the removal device 1, and has an electric conductivity meter 21 and a flow meter 22. The electric conductivity meter 21 is a device that measures the electric conductivity of the leachate flowing into the sewage measuring tank, and can be a known electric conductivity meter. Electric conductivity is a physical property value that correlates with the concentration of calcium in the leachate. The flow meter 22 is a device that measures the flow rate of the leachate flowing out of the sewage measuring tank 2 and flowing into the reaction tank 3, and can be a known flow meter. Both the electric conductivity meter 21 and the flow meter 22 are communicable with the control device 6, and the measured values of the electric conductivity and the flow rate are sent to the control device 6.

[0022] The reaction tank 3 has a pH meter 31. The pH meter 31 is a device that measures the pH of the liquid stored in the reaction tank 3 and can be a known pH meter. The measured pH value is used as an indicator for adjusting the leachate to be basic. The pH meter 31 is communicable with the control device 6, and the measured pH value is sent to the control device 6.

[0023] The first preparation tank 4 has a sodium carbonate supply unit 41, a water supply unit 42, a conductivity meter 43, and a liquid transfer pump 44. The aqueous sodium carbonate solution stored in the first preparation tank 4 is prepared in the first preparation tank 4 by dissolving the powdery sodium carbonate (an example of a calcium insolubilizing agent) supplied from the sodium carbonate supply unit 41 in the water supplied from the water supply unit 42. The sodium carbonate supply unit 41 is a known device capable of transporting powder and can be, for example, a screw conveyor. The water supply unit 42 supplies water for dissolving sodium carbonate and has a pipe connected to a water source such as city water or industrial water and a valve for controlling the supply and stop of water.

[0024] The conductivity meter 43 is a device that measures the conductivity of the aqueous sodium carbonate solution stored in the first preparation tank 4 and can be a known conductivity meter. Conductivity is a physical property value that correlates with the concentration of the aqueous sodium carbonate solution. The conductivity meter 43 is communicable with the control device 6, and the measured conductivity value is sent to the control device 6. The liquid transfer pump 44 is a pump provided in the pipe connecting the first preparation tank 4 and the reaction tank 3 and transfers the aqueous sodium carbonate solution from the first preparation tank 4 to the reaction tank 3. The liquid transfer pump 44 is communicable with the control device 6, and the operation and stop of the liquid transfer pump 44 are controlled by the control device 6.

[0025] The second preparation tank 5 has a sodium hydroxide supply section 51, a water supply section 52, and a liquid transfer pump 53. The aqueous sodium hydroxide solution stored in the second preparation tank 5 is prepared in the second preparation tank 5 by diluting the concentrated aqueous sodium hydroxide solution supplied from the sodium hydroxide supply section 51 with water supplied from the water supply section 52. The sodium hydroxide supply section 51 is a known device capable of transporting a liquid, and has an inlet for receiving the concentrated aqueous sodium hydroxide solution from a tank truck or the like, a pipe connecting the inlet and the second preparation tank 5, and a valve for controlling the supply and stop of the concentrated aqueous sodium hydroxide solution. The water supply section 52 supplies water for diluting the concentrated sodium hydroxide, and has a pipe connected to a water source such as city water or industrial water, and a valve for controlling the supply and stop of the water. Instead of the second preparation tank 5, a tank that only stores and supplies the aqueous sodium hydroxide solution (a tank that does not have a function of adjusting the concentration of the aqueous sodium hydroxide solution) may be provided. In this case, the aqueous sodium hydroxide solution having the concentration to be supplied to the reaction tank 3 is stored in the tank.

[0026] The liquid transfer pump 53 is a pump provided in the pipe connecting the second preparation tank 5 and the reaction tank 3, and transfers the aqueous sodium hydroxide solution from the second preparation tank 5 to the reaction tank 3. The liquid transfer pump 53 can communicate with the control device 6, and the operation and stop of the liquid transfer pump 53 are controlled by the control device 6.

[0027] The control device 6 is a device that controls the operations of the respective parts of the removal device 1 based on the measured values of the instruments provided in the respective parts of the removal device 1, and a known arithmetic device can be used. The control device 6 may have a storage device for storing various data, an input device used by the user, an output device for presenting information to the user, and the like. The control device 6 can communicate with at least the conductivity meter 21, the flow meter 22, the pH meter 31, the conductivity meter 43, the turbidity meter, the stirring device, the liquid transfer pumps 44 and 53, and P1 to P5 (FIG. 2).

[0028] 〔Configuration of Chemical Agent Addition Amount Adjusting Device〕 As shown in FIGS. 1 to 3, the chemical addition amount adjustment device 10 according to the present embodiment includes a reaction tank 3, a third preparation tank 14, a precipitation tank 12, a measuring device provided inside the precipitation tank 12, and a control device 6.

[0029] The measuring device adds and mixes a calcium insolubilizing agent to a part of the supernatant liquid in the precipitation tank 12 and measures the turbidity. The measuring device according to the present embodiment includes a cylindrical member 7 that is immersed in the liquid in the precipitation tank 12 and can collect a certain amount of supernatant liquid, and a turbidimeter 9 disposed inside the cylindrical member 7. A lid member 8 is provided at the lower end portion of the cylindrical member 7, and the lid member 8 can be opened and closed by a predetermined actuator (not shown) controlled by the control device 6. When the lid member 8 opens, the supernatant liquid in the precipitation tank 12 can flow into the inside of the cylindrical member 7, and when the lid member 8 closes, the supernatant liquid in the precipitation tank 12 cannot flow into the inside of the cylindrical member 7. Although not shown, for turbidity stabilization, the measuring device includes a stirring device for stirring the supernatant liquid in the cylindrical member 7.

[0030] The turbidimeter 9 is configured to calculate the concentration of the calcium component by measuring the turbidity by utilizing the fact that when the calcium component reacts with the calcium insolubilizing agent to form a calcium insoluble substance, the turbidity of the water to be treated increases. As the turbidimeter 9, for example, a surface scattering type turbidimeter that irradiates the liquid to be measured with measuring light and obtains the turbidity from the amount of scattered light scattered on the surface is preferably used.

[0031] The third preparation tank 14 is configured to be able to store a calcium insolubilizing agent at a predetermined concentration. The third preparation tank 14 has a liquid feed pump P1. The liquid feed pump P1 is a pump provided in a pipe connecting the third preparation tank 14 and the cylindrical member 7, and feeds the calcium insolubilizing agent from the third preparation tank 14 to the cylindrical member 7. The liquid feed pump P1 is communicable with the control device 6, and the operation and stop of the liquid feed pump P1 are controlled by the control device 6.

[0032] In addition to the above functions, the control device 6 calculates the calcium concentration in the supernatant liquid of the sedimentation tank 12 based on the turbidity measured by the turbidimeter 9 of the measuring device, and based on the calculated calcium concentration, feedback-controls the addition amount of the calcium insolubilizing agent added to the reaction tank 3.

[0033] In the chemical agent addition amount adjustment device according to the present embodiment, since the measuring device is configured to include a cylindrical member provided inside the sedimentation tank 12 and immersed in the liquid of the sedimentation tank 12 so as to be able to collect a certain amount of supernatant liquid, its configuration is simple, it is easy to handle, and the cost for installation is also low.

[0034] 〔Operation method of the removal device〕 Next, the operation method of the removal device 1 will be described. The operation method according to the present embodiment includes a first process group which is a group of processes directly related to the treatment of leachate for removing calcium, a second process group which is a group of processes for preparing an aqueous calcium carbonate solution and specifying its concentration, and a third process group which is a group of processes for validating and correcting the regression line (an example of a correlation) used in the first process group.

[0035] (1) First process group The first process group is a group of processes implemented in the normal operation of the removal device 1, which specifies the concentration of calcium in the leachate, and in view of the concentration, mixes an appropriate amount of aqueous calcium carbonate solution with the leachate to remove calcium in the leachate. The first process group includes a treated water measurement process, a control amount specification process, a reaction process, and a coagulation sedimentation process.

[0036] Note that the sewage measuring tank 2 and the control device 6 in the removal device 1 can be regarded as a calcium concentration measuring device for measuring the calcium concentration in the leachate. Therefore, the following embodiments are also embodiments of the operation method of the measuring device.

[0037] (1-1) Treated water measurement process The treated water measurement step is a step of measuring the electrical conductivity of the leachate. The treated water measurement step is realized by the control device 6 acquiring the measurement value of the electrical conductivity meter 21.

[0038] (1-2) Management quantity specification step The management quantity specification step is a step of specifying the concentration of the calcium component in the leachate (an example of the management quantity) from the electrical conductivity measured in the measurement step based on a regression line (correlation) prepared in advance. The regression line used here represents the correlation between the electrical conductivity of the leachate and the concentration of calcium in the leachate. For example, a plurality of points of leachate are prepared as samples, the electrical conductivity and the calcium concentration are measured for each sample, and a regression line is obtained by plotting the correspondence between the electrical conductivity and the calcium concentration. At this time, the calcium concentration can be measured by known methods such as a drop test or ICP emission spectrometry. The regression line prepared in advance is stored in the storage device of the control device 6.

[0039] (1-3) Reaction step The reaction step is a step of mixing an aqueous calcium carbonate solution in an amount determined based on the calcium concentration in the leachate specified in the management quantity specification step with the leachate. First, based on the calcium concentration in the leachate specified in the management quantity specification step and the measurement value of the flow meter 22, the amount of calcium flowing into the reaction tank 3 per unit time is specified. Next, the operation of the liquid feed pump 44 is controlled so that the ratio between the amount of calcium flowing into the reaction tank 3 per unit time and the amount of sodium carbonate flowing into the reaction tank 3 per unit time is within a predetermined range. Since the reaction used in the removal of calcium by the removal device 1 is a stoichiometric reaction between calcium ions and sodium carbonate (Equation (1)), the predetermined range referred to here is typically stoichiometric, but it may be appropriately determined according to the designation of the operator operating the removal device 1 or the like. In addition, in the control of the liquid feed pump 44, the concentration of the aqueous sodium carbonate solution specified in the second process group described later is taken into consideration.

[0040] (1-4) Coagulation and sedimentation step The coagulation precipitation process (an example of the sedimentation separation process) is a process of mixing leachate with a coagulant to precipitate calcium carbonate precipitate (an example of calcium-insoluble matter). A series of processes carried out in the mixing tank 11 and the precipitation tank 12 correspond to the coagulation precipitation process. Note that in the coagulation precipitation process, it is not prohibited to further mix chemicals such as coagulation aids.

[0041] (2) The second process group The second process group is a process group related to the preparation and concentration determination of an aqueous calcium carbonate solution. The second process group includes a chemical solution preparation process, a chemical solution measurement process, and a chemical solution concentration determination process.

[0042] (2-1) Chemical solution preparation process The chemical solution preparation process is a process of mixing sodium carbonate and water to prepare an aqueous sodium carbonate solution. Specifically, the chemical solution preparation process is implemented as a process of dissolving the sodium carbonate powder supplied from the sodium carbonate supply unit 41 in the water supplied from the water supply unit 42 in the first preparation tank 4. Since the sodium carbonate supplied here is in powder form, there may be cases where the intended amount of sodium carbonate powder is not introduced into the first preparation tank 4 due to adhesion inside the device of the sodium carbonate supply unit 41 or conveyance failures such as bridging. Therefore, the concentration of the aqueous sodium carbonate solution prepared in the first preparation tank 4 may vary.

[0043] (2-2) Chemical solution measurement process The chemical solution measurement process is a process of measuring the electrical conductivity of an aqueous sodium carbonate solution. The chemical solution measurement process is realized by the control device 6 acquiring the measurement value of the electrical conductivity meter 43.

[0044] (2-3) Chemical solution concentration determination process The chemical solution concentration determination process is a process of determining the concentration of an aqueous sodium carbonate solution based on the electrical conductivity measured in the chemical solution measurement process. The control device 6 stores in advance a regression line showing the correlation between the electrical conductivity and the concentration of the aqueous sodium carbonate solution, and uses the regression line to determine the concentration from the electrical conductivity.

[0045] (3) Third Project Group The third project group is a project group for verifying and correcting the validity of the regression line used in the first project group (management quantity determination project). While the first project group and the second project group are project groups carried out during the normal operation of the removal device 1, the third project group is a project group that is not normally carried out and is only carried out when predetermined conditions are met. Here, as an example, the case where the third project group includes a verification process and a correction process will be described.

[0046] The electrical conductivity of the leachate is a physical quantity that has a strong correlation with the concentration of calcium in the leachate. In this embodiment, this correlation is utilized to identify the calcium concentration in the leachate through the measurement of the electrical conductivity. However, this correlation may vary depending on the origin of the leachate. As factors that cause fluctuations in the correlation, there are various elements such as the quality and quantity of the waste treated at the final disposal site where the leachate was discharged, the location where the waste was landfilled, and the rainfall conditions (rainfall intensity, total rainfall amount, etc.) at the landfill site. Therefore, by verifying the regression line used in the management quantity determination project and correcting the regression line as necessary, the accuracy of the management quantity determination project is maintained.

[0047] (3-1) Verification Process The verification process is a process for verifying the validity of the regression line (correlation). In this embodiment, the verification process is carried out regularly. The interval for executing the verification process is not particularly limited and can be determined in consideration of the operating conditions of the removal device 1, weather conditions, etc. For example, it can be carried out once a month. When it is determined in the verification process that the regression line is valid, the third project group is terminated without performing the correction process, and the normal operation (the first project group and the second project group) is resumed. On the other hand, when it is determined in the verification process that the regression line is not valid, the correction process is performed.

[0048] The first example is a method for verifying the validity of a regression line based on the calcium concentration measured in the leachate water after the reaction process. For example, the leachate water collected in the neutralization tank 13 (which is the leachate water after the reaction process) is the supernatant after solid-liquid separation from calcium carbonate in the precipitation tank 12, so the calcium should have been removed. However, if there is a deviation in the regression line and the calcium concentration specified in the control quantity determination process is lower than the actual concentration, the amount of sodium carbonate input based on this concentration in the reaction process will be insufficient, and a part of the calcium in the leachate water will not precipitate and will remain in the liquid. Therefore, when this phenomenon occurs, the calcium concentration of the leachate water collected in the neutralization tank 13 will be higher than that of the leachate water collected in the neutralization tank 13 when the regression line is valid. Therefore, by measuring the calcium concentration in the leachate water collected in the neutralization tank 13 or the like, if the measured value is higher than a predetermined threshold value, it can be determined that the regression line is not valid. The calcium concentration can be measured by known methods such as chelate titration, drop test, ICP emission spectroscopy, etc.

[0049] The second example is a method for verifying the validity of a regression line by comparing the calcium concentration calculated from the regression line with the actually measured calcium concentration for a predetermined sample. For the same sample, by comparing the calculated value of the calcium concentration specified by performing the control quantity determination process with the actually measured value of the calcium concentration measured by known methods such as drop test or ICP emission spectroscopy, the validity of the regression line can be determined. For example, when the deviation between the calculated value and the actually measured value is higher than a predetermined threshold value, it can be determined that the regression line is not valid.

[0050] In any of the above examples, the measurement of the calcium concentration may be performed manually by an operator or automatically using a concentration measuring device (not shown) incorporated in the removal device 1. When the calcium concentration is measured manually, the measured value of the calcium concentration can be input into the control device 6. Also, instead of or in addition to the input of the calcium concentration, the result of manually judging the validity of the regression line may be input into the control device 6.

[0051] (3-2) Correction process The correction process is a process of correcting the regression line, and is performed when it is determined in the verification process as described above that the regression line is not appropriate. The method of correcting the regression line is not limited. For example, when it is determined in the verification process that the regression line is not appropriate, leachate is collected, and a set of the measured value of the electrical conductivity of the leachate and the measured value of the calcium concentration is added to the data set constituting the regression line. In this example, it is preferable to remove the set of the oldest measured values among the data sets constituting the regression line. In this example, a set of a predetermined number of measured values from the latest is used as the basis of the regression line, and a regression line that follows the behavior changing over time can be obtained.

[0052] Regarding the correction process, the measurement of the calcium concentration may be performed manually by an operator, or may be automatically performed using a concentration measuring device (not shown) incorporated in the removal device 1. Also here, when the measurement of the calcium concentration is performed manually, the measured value of the calcium concentration can be input to the control device 6. Further, instead of or in addition to the input of the calcium concentration, the result of manually correcting the regression line may be input to the control device 6.

[0053] 〔Operation method of chemical addition amount adjusting device〕 Next, the operation method of the chemical addition amount adjusting device will be described. The operation method of the chemical addition amount adjusting device includes a reaction step of adding a calcium insolubilizing agent to the water to be treated to insolubilize the calcium component, a coagulation sedimentation step (an example of sedimentation separation step) of coagulating and sedimenting (an example of sedimentation separation) the water to be treated after the reaction step, a turbidity measurement step of mixing a calcium insolubilizing agent with a part of the supernatant after the coagulation sedimentation step to measure the turbidity, a concentration calculation step of calculating the calcium concentration in the supernatant based on the turbidity measured in the turbidity measurement step, and an addition amount control step of feedback controlling the addition amount of the calcium insolubilizing agent added in the reaction step based on the calcium concentration calculated in the concentration calculation step.

[0054] The reaction process corresponds to the above (1-3) reaction process, and the aggregation precipitation process corresponds to the above (1-4) aggregation precipitation process. Also, the turbidity measurement process, the concentration calculation process, and the addition amount control process can be interpreted as processes that more specifically exemplify the above (3-1) verification process and (3-2) correction process.

[0055] In the turbidity measurement process, under the control of the control device 6, the lid member 8 of the cylindrical member 7 is opened, and the supernatant liquid in the precipitation tank 12 flows into the inside of the cylindrical member 7. After that, the lid member 8 is closed to sample the supernatant liquid into the cylindrical member 7. The sampling amount of the supernatant liquid is defined by the capacity of the cylindrical member 7, and a constant amount of supernatant liquid is always sampled. Next, under the control of the control device 6, a predetermined amount of calcium insolubilizing agent is fed from the third preparation tank 14 into the cylindrical member 7 through the liquid feed pump P1. At this time, the supernatant liquid in the cylindrical member 7 is stirred by a stirring device (not shown). And when calcium components remain in the supernatant liquid, if the calcium components react with the calcium insolubilizing agent to form calcium insoluble substances and the turbidity of the supernatant liquid increases, the turbidity of the supernatant liquid is measured by the turbidimeter 9.

[0056] Since there is a positive correlation between the turbidity and the calcium concentration, in the concentration calculation process, the control device 6 calculates the calcium concentration in the supernatant liquid based on the turbidity measured in the turbidity measurement process. Next, in the addition amount control process, the control device 6 performs feedback control on the addition amount of the calcium insolubilizing agent added in the reaction process based on the calcium concentration calculated in the concentration calculation process.

[0057] Since the supernatant liquid in the precipitation tank 12 is after being solid-liquid separated from the calcium insoluble substances, most of the calcium components should have been removed. However, when the calcium concentration in the supernatant liquid is measured and the measured value is higher than a predetermined threshold, the control device 6 determines that the addition amount of the calcium insolubilizing agent added in the reaction process is insufficient and controls the operation of the liquid feed pump 44 so that the addition amount of the calcium insolubilizing agent increases for feedback control, and / or performs feedback control to correct the regression line when it is determined that the regression line is not appropriate.

[0058] (Second Embodiment) Hereinafter, regarding the second embodiment of the chemical addition amount adjustment device according to the present invention, in the same manner as the above-described first embodiment, a form applied to a calcium removal device that removes calcium components from leachate discharged from a final waste disposal site will be described as an example. However, the configuration different from the above-described first embodiment will be mainly described, and the description of the common configuration will be omitted.

[0059] 〔Configuration of Chemical Addition Amount Adjustment Device〕 As shown in FIGS. 1, 2, and 4, the chemical addition amount adjustment device 10 according to the present embodiment includes a reaction tank 3, a third preparation tank 14, a fourth preparation tank 15, a sedimentation tank 12, a measuring device provided outside the sedimentation tank 12, and a control device 6.

[0060] The measuring device measures the turbidity by mixing a calcium insolubilizing agent with a part of the supernatant liquid in the sedimentation tank 12. The measuring device according to the present embodiment includes a second reaction tank 16 installed outside the sedimentation tank 12, a transfer device that collects a certain amount of supernatant liquid from the sedimentation tank 12 and sends it to the second reaction tank 16, a circulation flow path 18 that circulates the collected supernatant liquid, a turbidimeter 9 disposed in the circulation flow path 18, and a stirring device 17 that stirs the supernatant liquid in the second reaction tank 16.

[0061] The transfer device has a liquid feed pump P4. The liquid feed pump P4 is a pump provided in a pipe connecting the sedimentation tank 12 and the second reaction tank 16, and collects a certain amount of supernatant liquid from the sedimentation tank 12 and feeds it to the second reaction tank 16. The liquid feed pump P4 is communicable with the control device 6, and the operation and stop of the liquid feed pump P4 are controlled by the control device 6.

[0062] The third preparation tank 14 is configured to store a calcium insolubilizing agent at a predetermined concentration. The third preparation tank 14 has a liquid feed pump P2. The liquid feed pump P2 is a pump provided in a pipe connecting the third preparation tank 14 and the second reaction tank 16, and feeds the calcium insolubilizing agent from the third preparation tank 14 to the second reaction tank 16. The liquid feed pump P2 is communicable with the control device 6, and the operation and stop of the liquid feed pump P2 are controlled by the control device 6.

[0063] The fourth preparation tank 15 is configured to store an acidic solution for neutralization. The fourth preparation tank 15 has a liquid feed pump P3. The liquid feed pump P3 is a pump provided in a pipe connecting the fourth preparation tank 15 and the second reaction tank 16, and feeds the acidic solution from the fourth preparation tank 15 to the second reaction tank 16. The liquid feed pump P3 is communicable with the control device 6, and the operation and stop of the liquid feed pump P3 are controlled by the control device 6.

[0064] The circulation channel 18 is a channel for circulating the supernatant from the bottom to the top of the second reaction tank 16. The circulation channel 18 includes a liquid feed pump P5 and a turbidimeter 9. The liquid feed pump P5 is communicable with the control device 6, and the operation and stop of the liquid feed pump P5 are controlled by the control device 6.

[0065] In the chemical agent addition amount adjustment device according to the present embodiment, the measuring device is provided outside the sedimentation tank, and is configured to include a second reaction tank installed outside the sedimentation tank and a transfer device that collects a certain amount of supernatant from the sedimentation tank and sends it to the second reaction tank. Therefore, although the device configuration becomes somewhat complicated, since it can be completely separated from the sedimentation tank, the calcium concentration of the supernatant of the sedimentation tank can be measured more accurately.

[0066] 〔Operation method of chemical agent addition amount adjustment device〕 Next, the operation method of the chemical agent addition amount adjustment device according to the second embodiment will be described. The operation method of the chemical agent addition amount adjustment device includes, in the same manner as in the first embodiment, a reaction step of adding a calcium insolubilizing agent to the water to be treated to insolubilize the calcium component, a coagulation sedimentation step (an example of sedimentation separation step) of coagulating and sedimenting (an example of sedimentation separation) the water to be treated after the reaction step, a turbidity measurement step of mixing a calcium insolubilizing agent with a part of the supernatant after the coagulation sedimentation step to measure the turbidity, a concentration calculation step of calculating the calcium concentration in the supernatant based on the turbidity measured in the turbidity measurement step, and an addition amount control step of feedback controlling the addition amount of the calcium insolubilizing agent added in the reaction step based on the calcium concentration calculated in the concentration calculation step.

[0067] The reaction step corresponds to the above (1-3) reaction step, and the coagulation sedimentation step corresponds to the above (1-4) coagulation sedimentation step. Also, the turbidity measurement step, the concentration calculation step, and the addition amount control step may be interpreted as steps that more specifically illustrate the above (3-1) verification step and (3-2) correction step.

[0068] In the turbidity measurement step, the liquid feed pump is driven under the control of the control device 6 to allow a predetermined amount of the supernatant of the sedimentation tank 12 to flow into the second reaction tank 16 for sampling. Next, a predetermined amount of the calcium insolubilizing agent is fed from the third preparation tank 14 to the second reaction tank 16 through the liquid feed pump under the control of the control device 6. Then, the stirring device 17 is driven by the control device 6 to stir and mix the supernatant and the calcium insolubilizing agent. Further, the liquid feed pump of the circulation flow path 18 is driven by the control device 6 to circulate the mixed liquid of the supernatant and the calcium insolubilizing agent. When calcium components remain in the supernatant, the reaction between the calcium components and the calcium insolubilizing agent generates calcium insolubles, causing the turbidity of the supernatant to increase. Therefore, the turbidity of the supernatant is measured by the turbidity meter 9 of the circulation flow path 18.

[0069] In the concentration calculation step, the control device 6 calculates the calcium concentration in the supernatant based on the turbidity measured in the turbidity measurement step. Next, in the addition amount control step, the control device 6 performs feedback control on the addition amount of the calcium insolubilizing agent added in the reaction step based on the calcium concentration calculated in the concentration calculation step. Note that the concentration calculation step may be configured to be performed as needed. That is, the control device 6 may be configured to perform feedback control on the addition amount of the calcium insolubilizing agent added in the reaction step based on the turbidity measured in the turbidity measurement step without performing the concentration calculation step.

[0070] Since the supernatant of the sedimentation tank 12 is after solid-liquid separation from the calcium insoluble matter, most of the calcium component should have been removed. However, when the calcium concentration in the supernatant is measured and the measured value is higher than a predetermined threshold, the control device 6 determines that the addition amount of the calcium insolubilizing agent added in the reaction step is insufficient and controls the operation of the liquid feed pump 44 so that the addition amount of the calcium insolubilizing agent increases, and / or performs feedback control to correct the regression line on the grounds that the regression line is not appropriate. On the other hand, when the calcium concentration in the supernatant is measured and almost no calcium is detected, the control device 6 determines that the addition amount of the calcium insolubilizing agent added in the reaction step is excessive and controls the operation of the liquid feed pump 44 so as to reduce the addition amount of the calcium insolubilizing agent, and / or performs feedback control to correct the regression line on the grounds that the regression line is not appropriate.

[0071] Note that for the supernatant after the turbidity measurement step, the liquid feed pump P3 is driven under the control of the control device 6 to allow a predetermined amount of the acidic solution in the fourth preparation tank 15 to flow into the second reaction tank 16 for neutralization, and then it is sent to a subsequent process (not shown).

[0072] 〔Function and Effect〕 According to the above embodiment, since the correlation (regression line) is periodically verified and the correlation is corrected when it is determined that the correlation is not appropriate, the influence of the factors causing fluctuations in the correlation between the electrical conductivity of the leachate and the concentration of calcium is offset, and the accuracy of the calcium concentration specified in the management amount specifying step can be maintained. Therefore, since the amount of sodium carbonate added to precipitate calcium can be appropriately maintained, calcium can be surely removed. In addition, since it is easy to avoid the use of excessive sodium carbonate, it contributes to the reduction of the operating cost of the removal device 1.

[0073] According to the above embodiment, since the addition amount of the calcium insolubilizing agent added to the reaction tank is feedback-controlled based on the calcium concentration in the supernatant liquid of the precipitation tank 12, the amount of sodium carbonate added to precipitate calcium can be maintained more appropriately, and calcium can be removed more surely. In addition, since it becomes easier to avoid the use of excessive sodium carbonate, it further contributes to the reduction of the operating cost of the removal device 1.

[0074] 〔Other Embodiments〕 Finally, other embodiments of the operation method and the removal device according to the present invention will be described. Note that the configurations disclosed in the following respective embodiments can be applied in combination with the configurations disclosed in other embodiments as long as no contradiction occurs.

[0075] In the above embodiment, the configuration in which the control of the removal device 1 is performed using the regression line representing the correlation between the electrical conductivity of the leachate and the concentration of calcium in the leachate has been described as an example. However, the correlation between the electrical conductivity and the management amount used in the present invention is not limited to the form of a regression line. Such a correlation can be expressed, for example, in the form of a regression equation or a calibration curve. Further, as the correlation, a learned model generated by machine learning may be used.

[0076] In the above-described embodiment, the control of the removal device 1 is performed based on the idea of specifying the concentration of calcium from the measured value of the electrical conductivity of the leachate and adding sodium carbonate in an amount corresponding to the specified calcium concentration to the leachate. That is, the measured value of the conductivity meter 21 is reflected in the operating conditions of the liquid feed pump 44 through two-stage arithmetic processing. Here, as the correlation used in the control amount specifying step, if a correlation involving the amount of sodium carbonate to be added to the leachate to remove calcium in the leachate is used instead of the concentration of calcium in the leachate, the amount of sodium carbonate can be directly specified from the electrical conductivity using the correlation. Thus, the control amount specifying step is not limited to the mode of specifying the concentration of calcium in the leachate.

[0077] In the above-described embodiment, the configuration in which the chemical agent added to the leachate is sodium carbonate has been described as an example. However, in the present invention, the chemical agent added to the leachate is not limited as long as it can react with calcium in the leachate to remove it. For example, potassium carbonate may be used instead. Furthermore, any chemical agent that insolubilizes calcium may be used, not limited to the chemical agent that supplies carbonate ions.

[0078] In the above-described embodiment, the configuration in which sodium carbonate powder is dissolved in water in the first preparation tank 4 to prepare an aqueous sodium carbonate solution was described as an example, and it was explained that the concentration of the prepared aqueous sodium carbonate solution can vary due to the properties of the powder. However, in the present invention, even when the form of the drug is not a powder, the concentration of the drug solution may vary. For example, when the drug is a pellet, part of the drug mixed with the solvent may remain undissolved, which becomes a factor for the variation in the concentration of the drug solution. Also, when the drug is a liquid, part of the drug to be mixed with the solvent may adhere to the piping, which becomes a factor for the variation in the concentration of the drug solution. This problem is more likely to occur as the viscosity of the drug solution is higher. Thus, regardless of the form of the drug, the concentration of the drug solution may vary. Therefore, in the present invention, the form of the drug is not limited. However, since the variation in the concentration of the drug solution is relatively likely to occur when the drug is a solid, it can be said that the benefits of implementing the present invention are particularly great when the drug is a solid.

[0079] In the above-described embodiment, the configuration in which sodium carbonate powder is dissolved in water in the first preparation tank 4 to prepare an aqueous sodium carbonate solution was described as an example. However, in the present invention, the device used to adjust the drug solution is not limited to this configuration.

[0080] In the above-described embodiment, the configuration in which the concentration of the drug is specified based on the electrical conductivity was described as an example. However, in the present invention, the physical quantity measured and used as the basis for specifying the concentration of the drug is not limited to the electrical conductivity, and can be, for example, the absorbance by near-infrared spectroscopy.

[0081] In the above-described embodiment, the configuration for specifying the concentration of calcium in the leachate based on the electrical conductivity was described as an example. However, in the present invention, the measured value used as the basis for specifying the control amount of the water to be treated is not limited to the electrical conductivity. For example, it can be the absorbance by near-infrared spectroscopy, and the concentration of calcium specified by methods such as chelate titration, drop test, and ICP emission spectroscopic analysis. Further, the present invention is not limited to the configuration in which the measurement of the water to be treated is performed each time as in the above-described embodiment. For example, when the concentration of a specific component in the water to be treated is specified in advance, the amount of the chemical solution may be determined based on the concentration of the specific component and the concentration of the chemical agent in the chemical solution.

[0082] In the above-described embodiment, the configuration for measuring the electrical conductivity of the leachate in the sewage measuring tank 2 was described as an example. However, in the present invention, the location where the water to be treated measurement step is performed is not limited. For example, a method of measuring the measured value of the water to be treated before adding the chemical solution in a tank where the water to be treated and the chemical solution are mixed, and a method of measuring the measured value in a pipe through which the water to be treated flows are exemplified.

[0083] In the above-described embodiment, the water to be treated is the leachate, and the specific component is calcium, which was described as an example. However, in the present invention, neither the water to be treated nor the specific component to be removed is limited. That is, regarding the operation of the removal device that adds a chemical agent that reacts with the specific component to the water to be treated containing the specific component and removes the specific component by utilizing the reaction between the specific component and the chemical agent, the present invention can be applied in the same manner as in the above-described embodiment.

[0084] Regarding other configurations as well, it should be understood that all the embodiments disclosed in this specification are illustrative in all respects, and the scope of the present invention is not limited thereby. A person skilled in the art will easily understand that appropriate modifications can be made without departing from the spirit of the present invention. Therefore, another embodiment modified without departing from the spirit of the present invention is naturally included in the scope of the present invention.

Industrial Applicability

[0085] The present invention can be used, for example, in a calcium removal device for removing calcium from leachate discharged from a final disposal site of waste.

Explanation of Signs

[0086] 1: Calcium removal device 2: Sewage measuring tank 21: Electric conductivity meter 22: Flow meter 3: Reaction tank 31: pH meter 4: First preparation tank 41: Sodium carbonate supply section 42: Water supply section 43: Electric conductivity meter 44: Liquid transfer pump 5: Second preparation tank 51: Sodium hydroxide supply section 52: Water supply section 53: Liquid transfer pump 6: Control device 7: Cylindrical member 8: Cover member 9: Turbidity meter 10: Chemical agent addition amount adjustment device 11: Mixing tank 12: Sedimentation tank 13: Neutralization tank 14: Third preparation tank 15: Fourth preparation tank 16: Second reaction tank 17: Stirring device 18: Circulation flow path P1~P5: Liquid transfer pumps

Claims

1. A chemical agent addition amount adjustment method for adjusting the addition amount of a calcium insolubilizing agent that insolubilizes calcium components contained in water to be treated, comprising: a reaction step of adding a calcium insolubilizing agent to the water to be treated to insolubilize calcium components; a sedimentation separation step of sedimenting and separating the water to be treated after the reaction step; a turbidity measurement step of mixing a calcium insolubilizing agent with a part of the supernatant after the sedimentation separation step and measuring the turbidity; an addition amount control step of feedback controlling the addition amount of the calcium insolubilizing agent added in the reaction step based on the turbidity measured in the turbidity measurement step.

2. The chemical agent addition amount adjustment method according to claim 1, further comprising a concentration calculation step of calculating the calcium concentration in the supernatant based on the turbidity measured in the turbidity measurement step, wherein the addition amount control step feedback controls the addition amount of the calcium insolubilizing agent added in the reaction step based on the calcium concentration calculated in the concentration calculation step.

3. A chemical agent addition amount adjustment device for adjusting the addition amount of a calcium insolubilizing agent that insolubilizes calcium components contained in water to be treated, comprising: a reaction tank for adding a calcium insolubilizing agent to the water to be treated to insolubilize calcium components; a precipitation tank for sedimenting and separating calcium insolubles generated in the water to be treated; a measuring device for mixing a calcium insolubilizing agent with a part of the supernatant in the precipitation tank and measuring the turbidity; a control device for calculating the calcium concentration in the supernatant based on the turbidity measured by the measuring device and feedback controlling the addition amount of the calcium insolubilizing agent added to the reaction tank based on the calculated calcium concentration.

4. The chemical agent addition amount adjustment device according to claim 3, wherein the measuring device is provided inside the precipitation tank.

5. The chemical agent addition amount adjustment device according to claim 4, wherein the measuring device includes a cylindrical member immersed in the liquid of the precipitation tank and capable of collecting a certain amount of supernatant.

6. The chemical agent addition amount adjustment device according to claim 3, wherein the measuring device is provided outside the precipitation tank.

7. The chemical agent addition amount adjustment device according to claim 6, wherein the measuring device includes a second reaction tank installed outside the precipitation tank and a transfer device for collecting a certain amount of supernatant from the precipitation tank and sending it to the second reaction tank.

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