Wastewater treatment apparatus, wastewater treatment method, and control program for wastewater treatment apparatus

Abstract

To provide: a wastewater treatment apparatus, in wastewater treatment that involves supply of hydrated lime slurry, that can prevent pipe clogging caused by hydrated lime slurry and appropriately control supply of the hydrated lime slurry even in a range of neutral pH value; a wastewater treatment method; and a control program for the wastewater treatment apparatus.SOLUTION: The invention relates to a wastewater treatment apparatus that comprises: reaction means that performs a reaction by supplying hydrated lime slurry; slurry supply means including a flowmeter and an on-off valve; calculation means that calculates a needed supply amount of the slurry based on a flow rate of treated water and a concentration of reaction target components to be reacted with hydrated lime; and control means that performs on-off control of the on-off valve so that a supply accumulated value of the slurry exceeds the needed supply amount. A wastewater treatment method and a control program relating to the apparatus are also provided.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wastewater treatment apparatus, a wastewater treatment method, and a control program for a wastewater treatment apparatus. In particular, the present invention relates to a wastewater treatment apparatus, a wastewater treatment method, and a control program for a wastewater treatment apparatus involving the supply of slaked lime slurry.

Background Art

[0002] Various treatment means related to wastewater treatment are known, and the treatment means are selected according to the component to be removed in the wastewater. For example, as an example of the treatment means, there is one that adds various treatment agents according to the component to be removed in the wastewater.

[0003] For example, Patent Document 1 describes adding a calcium compound for treating fluoride ion-containing wastewater. Patent Document 1 also describes using slaked lime (Ca(OH)2) as the calcium compound and adding the calcium compound by operating a valve linked to a pH meter through a pipe so that the pH value in the reaction tank satisfies a specific range.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Generally, when slaked lime is used as an additive in wastewater treatment, it is known to use it in a slurry state because it is difficult to handle in a powder state and because a small amount of high-concentration calcium ions or hydroxide ions can be added. However, in the supply of slaked lime slurry, due to the properties of the slurry, it is prone to solidifying or adhering (hereinafter, this phenomenon will be collectively referred to as "adhesion") inside the pipes, which poses a risk of pipe blockage. On the other hand, while Patent Document 1 describes operating a valve installed in the piping based on pH when supplying slaked lime, it does not specifically disclose anything regarding avoiding the risk of pipe blockage.

[0006] Furthermore, Patent Document 1 shows that the supply of slaked lime is controlled based on pH. However, in wastewater treatment where slaked lime is supplied, there is also a known method in which slaked lime and acid are supplied to the same reaction tank and treated in the pH neutral range. In such treatment, slaked lime is consumed in order to maintain the pH in the neutral range. Therefore, if the supply of slaked lime is controlled based on pH, it becomes difficult to distinguish between the amount of slaked lime required for the reaction with the treatment target in wastewater treatment and the amount of slaked lime required for pH adjustment, which can lead to an oversupply of slaked lime. Consequently, with pH-based supply control, it is difficult to appropriately control the amount of slaked lime supplied across all wastewater treatments that use slaked lime as an additive, and in particular, there is a need for slaked lime supply control that functions appropriately in the pH neutral range.

[0007] The object of the present invention is to provide a wastewater treatment apparatus, a wastewater treatment method, and a control program for the wastewater treatment apparatus that can suppress pipe blockage by slaked lime slurry in wastewater treatment involving the supply of slaked lime slurry, and that can appropriately control the supply of slaked lime slurry even in the pH neutral range. [Means for solving the problem]

[0008] As a result of diligent research into the above-mentioned problems, the inventors of the present invention have found that in wastewater treatment involving the supply of slaked lime slurry, by calculating the required amount of slaked lime slurry and controlling the ON / OFF state of the on / off valve based on the calculated amount of slaked lime slurry and the cumulative supply amount of slaked lime slurry, it is possible to suppress the slaked lime slurry from adhering to the pipes and causing pipe blockage, as well as to suppress the oversupply of slaked lime slurry, thereby completing the present invention. In other words, the present invention relates to the following wastewater treatment apparatus, wastewater treatment method, and control program for the wastewater treatment apparatus.

[0009] The wastewater treatment apparatus of the present invention, which solves the above problems, is characterized by comprising: a reaction means for supplying slaked lime slurry to water to be treated and allowing the reaction to proceed; a slaked lime slurry supply means equipped with a flow meter and an on / off valve for measuring the flow rate of the slaked lime slurry; a calculation means for calculating the required amount of slaked lime slurry to be supplied based on the flow rate of the water to be treated and the concentration of the components to be reacted with slaked lime; and a control means for controlling the ON / OFF state of the on / off valve so that the cumulative value of the slaked lime slurry supplied by the supply means is equal to or greater than the required amount determined by the calculation means. According to the wastewater treatment apparatus of the present invention, the supply control of slaked lime slurry is performed by supplying the slurry based on ON / OFF control of an on / off valve, and by controlling the supply using the calculated required amount of slaked lime slurry and the cumulative supply value of slaked lime slurry. This suppresses slurry adhesion in the piping when slaked lime slurry is supplied, enables slaked lime slurry supply control without pH control, and prevents excessive supply of slaked lime slurry. As a result, in the reaction (wastewater treatment) in which slaked lime slurry is supplied to the water to be treated, pipe blockage by slaked lime slurry is suppressed, and the supply control of slaked lime slurry can be appropriately performed even in the pH neutral range.

[0010] Furthermore, in one embodiment of the wastewater treatment apparatus of the present invention, the reaction means is equipped with a reaction tank, the batch time in the reaction means is set to 1 minute or more and 10 minutes or less, and the opening and closing times of the on / off valve by the control means are set to 3 seconds or more per batch time. This feature allows for batch-type reactions using slaked lime slurry, increasing the contact efficiency between slaked lime and the reaction target components, thereby improving reaction efficiency (treatment efficiency). However, if the batch time is too long, the contact efficiency between slaked lime and the reaction target components decreases, while if the batch time is too short, controlling the operation of the on-off valves provided as supply means becomes difficult. Furthermore, if the opening and closing times of the on-off valves for supplying the slaked lime slurry are both too short, the operability of the opening and closing operations decreases. Therefore, by setting upper and lower limits for the batch time, as well as a lower limit for the opening and closing time of the on-off valves, it becomes possible to suppress pipe blockage by slaked lime slurry and appropriately control the supply of slaked lime slurry in the pH neutral range, thereby enabling efficient and effective wastewater treatment.

[0011] The wastewater treatment method of the present invention, which solves the above problems, is characterized by comprising: a reaction step of supplying slaked lime slurry to the water to be treated and allowing the reaction to proceed; a slaked lime slurry supply step equipped with a flow meter and an on / off valve for measuring the flow rate of the slaked lime slurry; a calculation step of calculating the required amount of slaked lime slurry to be supplied based on the flow rate of the water to be treated and the concentration of the components to be reacted with slaked lime; and a control step of controlling the ON / OFF state of the on / off valve so that the cumulative value of the slaked lime slurry supplied in the supply step is equal to or greater than the required amount determined in the calculation step. According to the wastewater treatment method of the present invention, the steps related to the supply control of slaked lime slurry include supplying slaked lime slurry based on ON / OFF control of an on / off valve, and control using the calculated required supply amount of slaked lime slurry and the cumulative supply value of slaked lime slurry. By performing these steps, it is possible to suppress slurry adhesion in the piping when slaked lime slurry is supplied, enable slaked lime slurry supply control without pH control, and prevent excessive supply of slaked lime slurry. As a result, in the reaction (wastewater treatment) in which slaked lime slurry is supplied to the water to be treated, pipe blockage by slaked lime slurry is suppressed, and the supply control of slaked lime slurry can be appropriately performed even in the pH neutral range.

[0012] The present invention provides a control program for a wastewater treatment apparatus that solves the above problems, comprising: a reaction means for supplying slaked lime slurry to water to be treated and allowing the reaction to proceed; and a slaked lime slurry supply means equipped with a flow meter and an on / off valve for measuring the flow rate of the slaked lime slurry, the control program for a wastewater treatment apparatus that has the following features: a calculation function for calculating the required amount of slaked lime slurry to be supplied based on the flow rate of the water to be treated and the concentration of the components to be reacted with slaked lime; and a control function for controlling the ON / OFF state of the on / off valve so that the cumulative value of the slaked lime slurry supplied by the supply means is equal to or greater than the required amount calculated by the calculation function. According to the control program for the wastewater treatment apparatus of the present invention, in a wastewater treatment apparatus that involves supplying slaked lime slurry via an on-off valve, the supply control of slaked lime slurry is performed by calculating the required supply amount of slaked lime slurry and controlling the ON / OFF of the on-off valve using the calculated required supply amount of slaked lime slurry and the cumulative supply value of slaked lime slurry. This suppresses slurry adhesion in the piping when slaked lime slurry is supplied and enables automatic control of the supply control of slaked lime slurry without pH control. As a result, in the reaction (wastewater treatment) in which slaked lime slurry is supplied to the water to be treated, pipe blockage by slaked lime slurry is suppressed and optimization of the supply control of slaked lime slurry is made easier even in the pH neutral range. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a wastewater treatment apparatus, a wastewater treatment method, and a control program for the wastewater treatment apparatus that can suppress pipe blockage by slaked lime slurry in wastewater treatment involving the supply of slaked lime slurry, and that can appropriately control the supply of slaked lime slurry even in the pH neutral range. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram illustrating a wastewater treatment apparatus according to an embodiment of the present invention. [Figure 2] A flowchart illustrating an example of the control steps in a wastewater treatment apparatus according to an embodiment of the present invention. [Figure 3]It is a diagram schematically showing an example of supply control of slaked lime slurry in a wastewater treatment apparatus according to an embodiment of the present invention. [Figure 4] It is a schematic explanatory view showing another aspect of the wastewater treatment apparatus according to an embodiment of the present invention. [Embodiments for Carrying Out the Invention]

[0015] The wastewater treatment apparatus, wastewater treatment method, and control program for the wastewater treatment apparatus of the present invention are used for wastewater treatment involving the supply of slaked lime slurry. In particular, the wastewater treatment apparatus, wastewater treatment method, and control program for the wastewater treatment apparatus of the present invention are suitably used for so-called batch-type wastewater treatment in which slaked lime slurry is supplied to a predetermined amount of wastewater stored in a reaction tank.

[0016] The wastewater W in the present invention may be any as long as it contains a reaction target component that reacts with slaked lime in the wastewater W, and is not particularly limited. Here, examples of the reaction target component with slaked lime include fluoride, which is a component to be removed from the wastewater W, and hydrogen ions that cause pH adjustment (neutralization) by reaction with slaked lime. Hereinafter, the "reaction target component with slaked lime" may be simply referred to as the "reaction target component".

[0017] Hereinafter, embodiments of the wastewater treatment apparatus, wastewater treatment method, and control program for the wastewater treatment apparatus according to the present invention will be described in detail while referring to the drawings. Note that the wastewater treatment method and control program for the wastewater treatment apparatus of the present invention shall be replaced by the following description of the structure and operation of the wastewater treatment apparatus. Also, the structure of the wastewater treatment apparatus described in the embodiments is merely an example for explaining the wastewater treatment apparatus according to the present invention, and is not limited thereto.

[0018] [Embodiment] (Wastewater Treatment Apparatus) FIG. 1 is a schematic explanatory view of a wastewater treatment apparatus 10 according to an embodiment of the present invention. As shown in Figure 1, the wastewater treatment apparatus 10 according to this embodiment comprises a reaction tank 1 to which the water to be treated W is supplied, a supply means 2 for supplying slaked lime slurry S to the reaction tank 1, a calculation means 3 for calculating the required supply amount of slaked lime slurry S, and a control means 4 for controlling the supply of slaked lime slurry S. In Figure 1, the dashed-dotted arrows indicate that a controllable or inputtable connection is indicated.

[0019] In the wastewater treatment apparatus 10 of this embodiment, slaked lime slurry S is supplied to the water to be treated W in the reaction tank 1 via the supply means 2, and the reaction proceeds. The reaction that proceeds in the reaction tank 1 is a reaction between slaked lime and the component to be reacted with slaked lime. In this embodiment, the component to be removed in the water to be treated W (fluorine) is taken as an example of the component to be reacted with slaked lime, and the following explanation will be given.

[0020] The reaction tank 1 in this embodiment is for supplying slaked lime slurry S to the water to be treated W and carrying out a reaction step to allow the reaction to proceed. The reaction tank 1 can be any tank capable of storing the water to be treated W, and is not particularly limited in terms of its structure or material. Furthermore, the reaction tank 1 is connected to a line L1 for supplying the water to be treated W and a line L2 for discharging the treated water W1 after its reaction with the slaked lime slurry S. Here, line L1 is equipped with a flow meter 11 for measuring the supply flow rate of the water to be treated W, which will be used as one of the calculation parameters in the calculation means 3 described later. Furthermore, a supply means 2, which will be described later, is connected to the reaction tank 1, and the slaked lime slurry S is supplied to the water to be treated W via the supply means 2.

[0021] In this embodiment, the reaction tank 1 is a reaction tank commonly used in so-called batch-type wastewater treatment. By carrying out the reaction using slaked lime slurry S in a batch manner, the contact efficiency between slaked lime and the components to be reacted with slaked lime can be increased, thereby improving the reaction efficiency (treatment efficiency). In this case, if the batch time is too long, the contact efficiency between the slaked lime and the components to be reacted with the slaked lime decreases, while if the batch time is too short, it becomes difficult to control the operation of the on-off valve 24, which is provided as the supply means 2 described later. Therefore, by setting upper and lower limits on the batch time in the reaction tank 1 of this embodiment, it becomes possible to perform efficient and effective wastewater treatment. In this embodiment, the lower limit of the batch time is set to 1 minute or more. On the other hand, the upper limit of the batch time in this embodiment is set to 10 minutes or less. This, in conjunction with appropriate supply control of the slaked lime slurry S, enables efficient and effective wastewater treatment.

[0022] The reaction tank 1 may be equipped with means to improve the treatment efficiency of the water to be treated W by increasing the reaction efficiency between the reactant component (fluorine) contained in the water to be treated W and the slaked lime slurry S. For example, this could include providing a stirring mechanism (not shown) inside the reaction tank 1.

[0023] Supply means 2 is for performing a supply step of supplying slaked lime slurry S to reaction tank 1. As shown in Figure 1, the supply means 2 of this embodiment includes a storage tank 21 for storing slaked lime slurry S, a pipe 22 for transferring the slaked lime slurry S from the storage tank 21 to the reaction tank 1, and a flow meter 23 and an on-off valve 24 provided on the pipe 22 for measuring the flow rate of the slaked lime slurry S. Furthermore, it is preferable to provide a branch passage 25 in the pipe 22 and connect this branch passage 25 to the storage tank 21 to form a circulation path for the slaked lime slurry S. This makes it possible to suppress solidification of the slaked lime slurry S by preventing it from accumulating in the pipe 22 even when the slaked lime slurry S is not being supplied to the reaction tank 1.

[0024] The on-off valve 24 in the supply means 2 of this embodiment is provided on the piping 22 and can be controlled ON / OFF, and the structure of the valve is not particularly limited. A specific example of the on-off valve 24 in this embodiment is a solenoid valve that can be switched between an opening of 0% and an opening of 100%, but is not limited to this. Another example of the on-off valve 24 is a control valve that can adjust the opening in steps or freely, and can control only two openings: an opening of 0% and a predetermined opening.

[0025] Furthermore, the supply means 2 may include a concentration meter (not shown) for measuring the concentration of the slaked lime slurry S, which will be used as one of the calculation parameters in the calculation means 3 described later. Furthermore, as a supply means 2, a stirring mechanism may be provided in the storage tank 21 (not shown). This suppresses a decrease in the dispersibility (concentration fluctuation) of the slaked lime slurry S in the storage tank 21, and makes it possible to stably supply the slaked lime slurry S.

[0026] The calculation means 3 is for calculating the required amount of slaked lime slurry S to be supplied for the reaction with the reactant component (fluorine) in the water to be treated W, and in this embodiment, it is for calculating the required amount of slaked lime slurry S to be supplied to the reaction tank 1. Here, "the required amount of slaked lime slurry S to be supplied" refers to the amount of slaked lime slurry S required to obtain the desired result from the reaction in reaction tank 1. More specifically, for example, if the reaction target component is a component to be removed from the treated water W, such as fluorine, the required amount of slaked lime slurry S to be supplied refers to the amount of slaked lime slurry S required to remove fluorine from the treated water W. As another example, if the reaction target component is hydrogen ions, the required amount of slaked lime slurry S to be supplied refers to the amount of slaked lime slurry S required to adjust the pH of the treated water W to a predetermined pH.

[0027] The calculation means 3 in this embodiment only needs to be capable of calculating the required supply amount of slaked lime slurry S using the flow rate of the water to be treated W supplied to the reaction tank 1 and the concentration of the reaction target component (fluorine) in the water to be treated W as calculation parameters. For example, it may include manual operation by an operator, but it may also include using a computing device that has data input / output functions for acquiring information and executes the program necessary for calculation using a processor such as a CPU.

[0028] The calculation parameters used in the calculation means 3, namely the flow rate of the water to be treated W supplied to the reaction tank 1 and the concentration of the reaction target component (fluorine) in the water to be treated W, may be the results measured by each measurement means, or they may be set values ​​input by the operator. As an example of acquiring calculation parameters, for instance, as shown in Figure 1, a flow meter 11 on the line L1 supplying the water to be treated W to the reaction tank 1 is connected to the calculation means 3 in an input / output manner, and data related to the flow rate of the water to be treated W is directly input to the calculation means 3. Alternatively, a concentration measuring means 12 is provided to measure the concentration of the reaction target component in the water to be treated W, and this concentration measuring means 12 is connected to the calculation means 3 in an input / output manner, and data related to the concentration of the reaction target component is directly input to the calculation means 3. In this embodiment, the concentration measuring means 12 can be any device capable of measuring the concentration of the reaction target component, and a fluorine concentration meter can be used. If the reaction target component is hydrogen ions, a pH meter can be used as the concentration measuring means 12. In addition, as shown in Figure 1, the concentration measuring means 12 may be installed on the line L1, or it may be installed inside the reaction tank 1. Furthermore, the measurement by the concentration measuring means 12 may involve continuously measuring the concentration of the reaction target component in real time, or, if there is little fluctuation in the discharge status of the treated water W, performing periodic sampling and concentration measurements of the reaction target component at regular intervals (e.g., once to several times per day), and inputting these measurement results into the calculation means 3.

[0029] An example of calculation in calculation means 3 will be explained. Here, we will explain using the case where fluorine is used as the reactant component. First, calculate the required amount of slaked lime (a) [kg / h] to be supplied to reaction vessel 1. The required amount of slaked lime (a) is calculated using the following formula 1.

number

[0030] Next, using the value of the required supply amount (a) of slaked lime obtained by Equation 1, we calculate the required flow rate (i) of the slaked lime slurry [m³ 3 Calculate / h. The required flow rate (i) of the slaked lime slurry is calculated using the following equation 2.

number

[0031] Then, using the required flow rate (i) of the slaked lime slurry obtained in Equation 2, the integrated value of the required flow rate (j) of the slaked lime slurry [m³] is calculated. 3 The following is calculated. This integrated value (j) of the required flow rate of the slaked lime slurry corresponds to the required amount of slaked lime slurry to be supplied to reaction tank 1. The required flow rate (j) of the slaked lime slurry is calculated using the following equation 3.

number

[0032] The calculation means 3 of this embodiment may include a display means for displaying each calculation parameter in the above-described equations 1 to 3, and an input means for the display means. For example, a display may be provided as the display means, and equations 1 to 3 may be displayed on this display. For some or all of the calculation parameters in each displayed equation, measurement results from each measurement means may be automatically input, or the operator may be able to input them externally. This makes it easier for the operator to understand the situation regarding the supply control of slaked lime slurry S and to take appropriate action.

[0033] Based on the above-mentioned equations 1 to 3, the integrated required flow rate of the slaked lime slurry (the required supply amount of slaked lime slurry) is calculated, and the supply of the slaked lime slurry S is controlled by the control means 4.

[0034] The control means 4 is for performing control steps to control the supply of slaked lime slurry S to the reaction tank 1. As shown in Figure 1, the control means 4 is connected to the controllable on-off valve 24, and is also connected in such a way that it can receive the measurement results from the flow meter 23 and the calculation results from the calculation means 3 as information related to the control.

[0035] The control means 4 can be any device capable of ON / OFF control of the connected on / off valve 24 as the control target, as well as acquiring and calculating information related to the control. In this embodiment, the control means 4 may include, for example, manual operation by an operator, but it is preferable to use a computing device that has data input / output functions for acquiring information and executes a program for performing calculations and sending control signals related to the control using a processor such as a CPU, thereby enabling automatic control. This makes it easier to optimize the supply control of slaked lime slurry S to the water to be treated W. The computing device as the control means 4 may be used in conjunction with the computing device as the calculation means 3, or it may be provided as a separate unit. Furthermore, similar to the calculation means 3, it may also include a display means for displaying the control parameters (see equations 4 and 5) described later, and an input means for the display means.

[0036] (Supply control of slaked lime slurry) Below, an example of a preferred control step for supplying slaked lime slurry S to the treated water W in the wastewater treatment device 10 of this embodiment will be described by illustration. Note that the explanation and flowchart for each control step are merely illustrative examples of the embodiment and are not limited thereto.

[0037] Figure 2 shows a flowchart of the control steps by the control means 4 in the wastewater treatment device 10 of this embodiment. In the following explanation of the control by the control means 4, the explanation will be based on the processing process within one batch time.

[0038] First, the water to be treated W is supplied to the reaction tank 1. At this time, information regarding the flow rate of the water to be treated W (b) and the concentration of the components to be reacted with slaked lime (c) is input to the calculation means 3. Then, in calculation means 3, based on equations 1 to 3 described above, the required supply amount of slaked lime slurry is calculated as the integrated value (j) of the required flow rate of slaked lime slurry.

[0039] Here, the control means 4 needs to control the supply means 2 so as to satisfy the required flow rate (j) of the slaked lime slurry, which is the required amount of slaked lime slurry to be supplied to the reaction vessel 1. Therefore, the control means 4 sets the target supply value (P) of the slaked lime slurry supplied from the supply means 2, based on the required flow rate (i) of the slaked lime slurry determined by the calculation means 3, as one of the control parameters. 3 The target value (P) for supplying slaked lime slurry is determined by the following formula 4.

number

[0040] After setting the supply target value (P) based on Equation 4, the control means 4 opens the on / off valve 24. At this time, the flow rate (k) of the slaked lime slurry measured by the flow meter 23 is (m³) 3 Using [ / h], the cumulative supply value of the slaked lime slurry supplied from supply means 2 is defined as the cumulative flow rate of the slaked lime slurry (l) [m 3 The following is calculated and used as one of the control parameters. The integrated flow rate (l) of the slaked lime slurry is calculated using equation 5 below.

number

[0041] The control means 4 closes the on-off valve 24 and resets the integrated flow rate value (l) of the slaked lime slurry when the integrated flow rate value (l) obtained by equation 5 exceeds the supply target value (P). Then, after a predetermined batch time T1 has elapsed, the next batch process is started.

[0042] Figure 3 is a schematic graph showing an example of the supply control of slaked lime slurry in the wastewater treatment device 10 of this embodiment. Here, Figure 3 shows a wastewater treatment process in which a slaked lime slurry S is supplied to the water to be treated W supplied to the reaction tank 1, and the treatment is repeated multiple times with a batch time of T1 [s]. Furthermore, Figure 3 is a graph with time on the horizontal axis, showing the opening and closing operation of the on-off valve 24, the required supply amount of slaked lime slurry determined by the calculation means 3 (integrated required flow rate of slaked lime slurry (j)), and the integrated supply value of slaked lime slurry supplied by the control means 4 (integrated flow rate of slaked lime slurry (l)) over time.

[0043] As shown in Figure 3, in the first batch processing, the cumulative required flow rate (j) of the slaked lime slurry increases over time. At this time, the height of the cumulative required flow rate (j) of the slaked lime slurry after the first batch time T1 corresponds to the supply target value (P) used by the control means 4. Then, in the batch processing at the next batch time T1, the on-off valve 24 is opened until the integrated flow rate (l) of the slaked lime slurry reaches the supply target value (P). When the integrated flow rate (l) of the slaked lime slurry exceeds the supply target value (P), the on-off valve 24 is closed and the integrated flow rate (l) of the slaked lime slurry is reset. After a predetermined batch time T1 has elapsed, the control means 4 sets the supply target value (P) and controls the ON / OFF state of the on / off valve 24 based on the required flow rate (j) of the slaked lime slurry, and the batch processing of the water to be treated W is repeated.

[0044] In this case, if the opening and closing times of the on-off valve 24 for supplying the slaked lime slurry S are too short, the operability of the opening and closing operation will decrease. Therefore, it is preferable to set a lower limit for the opening and closing times of the on-off valve 24. For example, in this embodiment, the lower limits for the opening and closing times of the on-off valve 24 are set to 3 seconds or more per batch time. This, combined with appropriate supply control of the slaked lime slurry S, enables efficient and effective wastewater treatment. While there are no particular upper limits on the opening and closing times of the on-off valve 24, in order to stably perform wastewater treatment by the reaction means (reaction tank 1), it is preferable from the viewpoint of increasing pseudo-continuity to shorten the batch time in the reaction tank 1 and to operate the on-off valve 24 to supply the slaked lime slurry S in short spans.

[0045] By repeating the above-described supply control and processing process for slaked lime slurry, it is possible to suppress slurry adhesion within the piping 21 during the supply of slaked lime slurry S, enable supply control of slaked lime slurry S without pH control, and prevent excessive supply of slaked lime slurry S. Furthermore, it is preferable to create a control program for the supply control and processing process of the slaked lime slurry described above, and to execute the functions related to each means via a processor such as a CPU in the calculation means 3 and the control means 4. This enables automatic control of the supply control of the slaked lime slurry and facilitates the optimization of the supply control of the slaked lime slurry.

[0046] As described above, the wastewater treatment device 10 of this embodiment controls the supply of slaked lime slurry S by controlling the supply of slaked lime slurry based on ON / OFF control of an on / off valve, and by controlling the supply using the calculated required amount of slaked lime slurry and the cumulative value of the supplied slaked lime slurry. This suppresses slurry adhesion in the piping when slaked lime slurry is supplied, enables slaked lime slurry supply control without pH control, and prevents excessive supply of slaked lime slurry. As a result, in the reaction (wastewater treatment) in which slaked lime slurry is supplied to the water to be treated, pipe blockage by slaked lime slurry is suppressed, and the supply of slaked lime slurry can be appropriately controlled even in the pH neutral range.

[0047] The embodiments described above are merely examples of a wastewater treatment apparatus, a wastewater treatment method, and a control program for the wastewater treatment apparatus. The wastewater treatment apparatus, wastewater treatment method, and control program for the wastewater treatment apparatus according to the present invention are not limited to the embodiments described above, and the wastewater treatment apparatus, wastewater treatment method, and control program for the wastewater treatment apparatus according to the embodiments described above may be modified without changing the gist of the invention.

[0048] In this embodiment, the wastewater treatment apparatus and wastewater treatment method may also involve providing further treatment equipment downstream of the reaction tank 1 to perform wastewater treatment. In particular, if the component to be reacted with the slaked lime contained in the water to be treated W is a component to be removed, such as fluorine, it is preferable to provide various treatment equipment for fluorine removal and perform wastewater treatment.

[0049] Figure 4 is a schematic diagram illustrating another embodiment of the wastewater treatment device of this embodiment. As shown in Figure 4, an example of the wastewater treatment apparatus 10' in this embodiment is one that includes a conditioning tank 5 and a coagulation and sedimentation tank 6 downstream of the reaction tank 1. The adjustment tank 5 is used to perform necessary pretreatment on the treated water W1 discharged from the reaction tank 1 before supplying it to the coagulation and sedimentation tank 6. For example, it is used to add additives such as coagulants (such as aluminum sulfate) to the treated water W1 supplied via line L2. Furthermore, the coagulation and sedimentation tank 6 is used to perform solid-liquid separation treatment on the treated water W2 supplied from the adjustment tank 5, and a known coagulation and sedimentation tank can be used. For example, treated water W2 is supplied into the tank via line L3, and in this tank, calcium fluoride, which is a reaction product produced by the reaction of slaked lime and fluorine in the reaction tank 1, is precipitated and separated into treated water W3 and solid components, which are then discharged out of the system via lines L4 and L5, respectively. This, along with the proper control of the supply of slaked lime slurry, makes it possible to improve the wastewater treatment capacity for the treated water W. [Industrial applicability]

[0050] The wastewater treatment apparatus, wastewater treatment method, and control program for the wastewater treatment apparatus of the present invention are suitably used in wastewater treatment involving the supply of slaked lime slurry. [Explanation of Symbols]

[0051] 10,10′ Wastewater treatment device, 1 reaction tank, 11 flow meter, 12 concentration measuring means, 2 supply means, 21 storage tank, 22 piping, 23 flow meter, 24 on / off valve, 25 branch line, 3 calculation means, 4 control means, 5 adjustment tank, 6 coagulation and sedimentation tank, L1~L5 lines, S slaked lime slurry, W treated water, W1,W2,W3 treated water

Claims

1. A reaction means for supplying slaked lime slurry to the water to be treated and allowing the reaction to proceed, A means for supplying slaked lime slurry, comprising a flow meter for measuring the flow rate of slaked lime slurry and an on / off valve, A calculation means for calculating the required supply amount of slaked lime slurry based on the flow rate of the water to be treated and the concentration of the components to be reacted with slaked lime, The system includes a control means that controls the ON / OFF state of the on / off valve so that the cumulative supply value of slaked lime slurry by the supply means is equal to or greater than the required supply amount determined by the calculation means. The wastewater treatment apparatus is characterized in that the control means opens the on-off valve at predetermined intervals, and the opening time and closing time of the on-off valve are each set to be at least a predetermined time.

2. The reaction means comprises a reaction vessel, The batch time in the reaction means is set to be 1 minute or more and 10 minutes or less. The opening and closing times of the on / off valve by the control means are set to 3 seconds or less per batch time. The wastewater treatment apparatus according to claim 1, characterized in that it is as described above.

3. A reaction step involves supplying slaked lime slurry to the water to be treated and allowing the reaction to proceed, A supply station for slaked lime slurry, equipped with a flow meter and an on / off valve for measuring the flow rate of the slaked lime slurry. Top, Based on the flow rate of the water to be treated and the concentration of the components to be reacted with slaked lime, the required supply of slaked lime slurry is determined. A calculation step to calculate the supply amount, The cumulative supply value of slaked lime slurry in the supply step is the same as the value obtained in the calculation step. The system includes a control step of controlling the ON / OFF state of the on / off valve so that the supply amount is greater than or equal to the required amount. picture, The wastewater treatment method is characterized in that the control step involves opening the on-off valve at predetermined intervals, and the opening time and closing time of the on-off valve are each set to be at least a predetermined time.

4. A reaction means for supplying slaked lime slurry to the water to be treated and allowing the reaction to proceed, A supply means for slaked lime slurry, comprising a flow meter for measuring the flow rate of slaked lime slurry and an on / off valve. A control program for a wastewater treatment apparatus comprising the following: Based on the flow rate of the water to be treated and the concentration of the components to be reacted with slaked lime, the required supply of slaked lime slurry is determined. A calculation function that calculates the amount to be supplied, The cumulative value of the slaked lime slurry supplied by the supply means is equal to the required supply amount determined by the calculation function. The control function that controls the ON / OFF state of the on / off valve is executed as described above. The control function is characterized by opening the on / off valve at predetermined intervals, and by setting the opening time and closing time of the on / off valve to be at least predetermined. This is a control program for a wastewater treatment apparatus.

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