JP2019136665A - Water processing system - Google Patents

Abstract

To provide reduction of the amount of sludge derived from a flocculation agent associated with excessive input of chemicals while performing wastewater treatment that complies with wastewater standards in wastewater fluorine treatment.SOLUTION: An aluminum injection rate calculation unit 208 calculates an aluminum injection rate based on a predetermined adsorption isotherm in a fluorine treatment tank 100 and a fluorine concentration Cof waste water, an aluminum injection rate correction unit 209 calculates a corrected aluminum injection rate by correcting the aluminum injection rate calculated by the aluminum injection rate calculation unit 208, with a correction coefficient based on the history of the fluorine concentration Cof the treated water, and a chemical input amount calculation unit 210 calculates an amount of aluminum salt to be input into waste water.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a water treatment system. In particular, the present invention relates to a water treatment system for treating fluorine contained in waste water from a plant.

With increasing global environmental awareness, various environmental regulations have been established for exhaust gas, drainage, waste, etc. discharged from plants in each country and region. For this reason, the plant is provided with an environmental protection device for removing regulated substances contained in exhaust gas, waste water, waste, and the like below a predetermined value. In the case of an environmental protection device for a power plant, a denitration device, an electrostatic precipitator, and a desulfurization device are sequentially arranged in the exhaust gas flow path, and nitrogen oxide (NO _x ), soot dust, sulfur oxide (SO _x ) is removed. The wet lime gypsum method, which is one of the typical systems of desulfurization equipment, absorbs SO ₂ by causing gas-liquid contact between exhaust gas and limestone slurry and reacting calcium (Ca) and sulfurous acid gas (SO ₂ ). Also collect gypsum as a by-product. The desulfurization effluent discharged by this method contains regulated substances such as fluorine, nitrogen, and heavy metals, and effluent treatment conforming to these effluent standards is performed and discharged to the environment.

  In order to perform wastewater treatment, a treatment tank for each regulated substance is generally provided, and the regulated substance is removed from the wastewater by injecting a treatment chemical corresponding to the regulated substance. Since the concentration of the regulated substance contained in the wastewater varies and the effect of the treatment chemical varies depending on the properties of the wastewater, the appropriate amount of the treatment chemical to be introduced into the treatment tank varies. For this reason, there have been proposals related to automatic control of the injection amount of treatment chemicals.

  Patent Document 1 relates to a treatment apparatus for fluorine-containing wastewater. It is disclosed that the addition amount of aluminum salt and neutralizing agent used for the fluorine treatment is controlled according to the flow rate of raw water, the fluorine concentration, and the pH in the reaction vessel. Although the control of the chemical solution input amount is based on feedback control, the feed forward control, the feed forward control, and the combined use of feedback control are also mentioned.

  Patent Document 2 injects a flocculant into raw water, agglomerates turbid components in the raw water to form flocs, and obtains clean water below a set turbidity in a flocculent sedimentation process in which flocs settle and separate in a sedimentation basin. A flocculant injection control is disclosed. In performing correction by feedback control with respect to feedforward control, it is disclosed that a time delay of correction, which is a problem of feedback control, is reduced by applying an improved turbidity measurement method.

  Patent Document 3 discloses that a water quality prediction unit that predicts the quality of wastewater using plant operation information is provided, and the water treatment operation conditions are feedforward controlled based on the predicted water quality.

JP 60-197293 A JP 2011-5463 A International Publication No. 2017/022113

  When changing the coal type or power generation load at a thermal power plant, the concentration of components in the desulfurization effluent varies greatly. In order to properly treat fluorine in wastewater, it is common practice to analyze the fluorine concentration in power plant wastewater (desulfurization wastewater and other wastewater) by hand analysis and change the amount of drug injection using the results. ing. The fluorine concentration in the wastewater is monitored by a fluorine meter, but the measured value of the fluorine meter is greatly influenced by interfering substances that cause the measured value to fluctuate in addition to the fluorine concentration. There is currently no accuracy to measure and determine the amount of chemicals to be injected. For this reason, water quality analysis and operation adjustment when the component concentration fluctuates are burdens on the operator. In addition, the effect of the amount of treatment chemical injection such as a flocculant varies depending on the drainage properties. For this reason, when a chemical | drug | medicine is inject | poured more than a theoretical injection amount so that insufficient injection | pouring will not arise, the amount of sludge derived from a coagulant | flocculant will become incidentally large.

  Patent Document 1 is directed to fluorine treatment, but there is no specific description on how to calculate and control the amount of chemical solution input from the measured value.

  Neither Patent Document 2 nor Patent Document 3 discloses a specific treatment of fluorine treatment. In Patent Document 2, the feedback control is used together to correct the inappropriateness of the feedforward control due to the water quality fluctuation. However, there is a time delay between the injection of the chemical and the actual change appearing in the sensor measurement. Inevitable, there is a risk that the greater the response delay, the greater the swing of the control.

  In the present invention, the feed amount of the fluorine treatment chemical (aluminum salt) is optimized by feedforward control or feedback control according to the change in the concentration of waste water or treated water, and the amount of sludge derived from the flocculant is reduced The problem is to adjust the value.

  A water treatment system according to an embodiment of the present invention is a water treatment system for treating wastewater containing fluorine, and the treated water and fluorine in which fluorine contained in the wastewater is reduced by introducing an aluminum salt into the wastewater. A fluorine treatment tank that separates the sludge containing aluminum hydroxide that adsorbs aluminum, and a control unit that controls the amount of aluminum salt thrown into the wastewater. The control unit includes a processor and a memory. Executes a control program read into the memory, and the control program has an aluminum injection rate calculation unit, an aluminum injection rate correction unit, and a chemical injection amount calculation unit, and the aluminum injection rate calculation unit has a predetermined fluorine treatment. The aluminum injection rate is calculated based on the adsorption isotherm in the tank and the fluorine concentration in the waste water. The aluminum injection rate correction unit calculates the aluminum injection rate calculated by the aluminum injection rate calculation unit. Calculates a correction aluminum infusion rate corrected by the correction coefficient based on a history of the fluorine concentration in the treated water, the agent charged amount calculating unit, based on the correction aluminum infusion rate, to calculate the dosage of aluminum salt to be introduced into the waste water.

  Other problems and novel features will become apparent from the description of the present specification and the accompanying drawings.

  In wastewater fluorine treatment, wastewater treatment that conforms to wastewater standards is performed, while excessive input of chemicals is suppressed, and the amount of sludge derived from the coagulant is reduced.

It is a structural example of a fluorine treatment tank. It is a figure explaining a fluorine processing model. It is Freundlich's adsorption isotherm calculated so as to match the actual measurement value. It is an adsorption isotherm of Langmuir obtained so as to match the measured value. It is a simulation of the drainage fluorine concentration C ₀ of the actual plant. It is a figure explaining the correction method of a control model. It is a figure which shows the control result (simulation) by Example 1. FIG. It is a graph which shows the correlation with the aluminum injection rate in an actual plant, and the amount of fluorine removed. It is a graph which shows the correlation with the aluminum injection rate in an actual plant, and the amount of fluorine removed. It is a figure which shows the control result (simulation) by Example 2. FIG. It is a figure which shows the control result (simulation) by Example 2. FIG. It is a summary of the control result (simulation) by Example 2. FIG.

FIG. 1 shows a configuration example of the fluorine treatment tank 100. The fluorine treatment tank 100 has a reaction tank 101, a coagulation tank 102, and a precipitation tank 103, and the waste water passes through these tanks sequentially, so that the treated water with reduced fluorine content and the hydroxylated water adsorbed and precipitated. Separated into sludge containing aluminum (Al (OH) ₂ ). The reaction tank 101 is charged with a chemical 111 and a neutralizing agent 112 for treating fluorine. As the drug 111, PAC (polyaluminum chloride) or an aluminum salt such as a sulfate band is used. After adding the aluminum salt, the pH of the reaction vessel 101 is adjusted by introducing a neutralizing agent 112 in order to adjust the pH to an optimum value for aggregation. As the neutralizing agent 112, for example, hydrochloric acid, sulfuric acid, caustic soda, or the like is used. In the agglomeration tank 102, an agglomeration aid 113 for facilitating precipitation of aluminum hydroxide generated by the introduction of the chemical is introduced, and solid-liquid separation is performed in the precipitation tank 103. In general, the fluorine treatment is performed in two stages. In this case, the concentration of fluorine in the waste water is reduced to the target value by passing the treated water from the fluorine treatment tank 100 through a fluorine treatment tank (not shown) in the next stage.

  A control unit 200 is provided for the fluorine treatment tank 100 in order to control the input amount of a medicine or the like. The control unit 200 has a function of controlling the input amounts of the drug 111, the neutralizing agent 112, and the coagulation aid 113. Here, control of the input amount of the drug (aluminum salt) 111 will be described. The other input amounts are also controlled, for example, the neutralizing agent 112 may control the input amount based on the pH of the reaction tank 101, and the aggregation aid 113 may control the input amount according to the input amount of the aluminum salt.

The control unit 200 includes a processor 201, a memory 202, a water quality database 203, a process database 204, an interface 205, and a bus 206 for connecting them. The processor 201 executes a control program loaded in the memory 202 and realizes a function of calculating the dose of the medicine 111. The control program includes a data collection unit 207, an aluminum injection rate calculation unit 208, an aluminum injection rate correction unit 209, and a medicine input amount calculation unit 210. The functions performed by the control unit 200 are realized by a control program loaded in the memory 202. The The data collection unit 207 collects the fluorine concentration C ₀ of the wastewater by the fluorine concentration sensor 104 and the fluorine concentration C ₁ of the treated water by the fluorine concentration sensor 105 via the interface 205. The collected fluorine concentration is stored in the water quality database 203, and is appropriately called to the memory 202 and used for calculating the aluminum injection rate. It is assumed that the water quality database 203 collects not only the fluorine concentration but also the amount of waste water and treated water and other water quality data. The aluminum injection rate calculation unit 208 calculates the aluminum injection rate based on the fluorine concentration C ₀ (Example 1) of the wastewater stored in the water quality database 203 or the fluorine concentration C ₁ (Example 2) of the treated water. The aluminum injection rate correction unit 209 performs predetermined correction on the aluminum injection rate calculated by the aluminum injection rate calculation unit 208 as necessary, and stores the determined aluminum injection rate in the process database 204. The contents of processing in the aluminum injection rate calculation unit 208 and the aluminum injection rate correction unit 209 will be described later. The drug input amount calculation unit 210 calculates the input amount of the drug 111 based on the information on the aluminum injection rate stored in the process database 204 and the amount of wastewater stored in the water quality database 203. The control unit 200 controls the input amount of the drug 111 by a control command S ₁ issued through the interface 205 so that the input amount of the drug 111 becomes the calculated input amount.

In Example 1, the amount of aluminum salt introduced into the fluorination tank is feedforward controlled to optimize the amount of aluminum salt introduced. A fluorine treatment model in Example 1 will be described. FIG. 2A is a diagram for explaining a fluorine treatment model (adsorption isotherm) in the fluorine treatment tank 100. Drainage fluorine concentration C ₀ [mg / l], the fluorine concentration C ₁ of the treated water [mg / l], when the drug amount of fluorine is removed by (aluminum salts) F [mg / l], (Equation 1) A relationship is established.

  The fluorine treatment tank 100 utilizes the phenomenon of adsorption of fluorine on aluminum hydroxide, and in the precipitation tank, fluorine adsorbed on aluminum hydroxide and fluorine dissolved in the treated water as a supernatant are in an equilibrium state. It can be said. There are several known adsorption isotherms that show the correlation between the concentration and absorption when a solute in a solution is adsorbed to a solid at a certain temperature. Here, (1) Freundlich adsorption isotherm An example of applying the equation and (2) Langmuir adsorption isotherm is shown. Freundlich's adsorption isotherm is known to empirically match the actual adsorption isotherm in the industrial field. When the aluminum injection rate (equivalent to the aluminum concentration in the treated water) is A [mg / l], the adsorption amount V is expressed by (Expression 2). Note that a and n are constants.

  By substituting (Equation 2) into (Equation 1), (Equation 3) is obtained.

  Although Freundlich's adsorption isotherm is an unsaturated adsorption isotherm, the adsorption amount is considered to be saturated in practice when the fluorine concentration of the treated water increases. For this reason, the Langmuir adsorption isotherm suitable for the saturated adsorption isotherm may be used. In this case, the adsorption amount V is expressed by (Equation 4). Here, a is a Langmuir constant and b is a saturated adsorption amount.

  By substituting (Equation 4) into (Equation 1), (Equation 5) is obtained.

The relationship between the fluorine concentration C ₁ of the treated water in the fluorine treatment tank 100 and the adsorption amount V is measured, and the coefficients a and n of (Equation 2) or the coefficients a and b of (Equation 4) are adjusted so as to match the measured values. Determine. FIG. 2B is a Freundlich adsorption isotherm in which the coefficients a and n are determined so as to match the actual measurement values, and FIG. 2C is a Langmuir adsorption isotherm in which the coefficients a and b are determined so as to match the same actual measurement values. . The actual measurement and the expected value from the adsorption isotherm are in good agreement, and in both cases, the error can be suppressed to within 20% (excluding abnormal values in the actual measurement). Which adsorption isotherm is to be used may be selected based on actual plant measurements.

Thus, the coefficient is calculated from the actual measurement value of the actual plant to be controlled to obtain the adsorption isotherm, and the treated water fluorine concentration C ₁ is set to the target fluorine concentration (fixed value) of the fluorine treatment tank 100. For example, in Japan, it relates fluorine, effluent standards in waters 15 [mg / l], rivers, because it is defined as 8 [mg / l] except in waters, such as lakes, the treated water fluorine concentration C ₁ May be determined based on these regulation values. By applying (Equation 3) or (Equation 5) based on the adsorption isotherm with the calculated coefficient and the fluorine concentration C _{0 of the} wastewater, the required aluminum concentration and the required amount of aluminum salt input can be calculated based on this. Can be calculated.

  However, in the case of such feedforward control, if the deviation between the drainage property when the adsorption isotherm coefficient is obtained and the drainage property during actual operation becomes large, a deviation from the control target occurs. Examples of factors that cause deviations in drainage properties include switching of coal types. In the case of a coal-fired boiler, the amount of fluorine contained in coal varies greatly depending on the production area and the like, and therefore, the amount of fluorine contained in wastewater varies greatly by switching the type of coal used by the boiler. In addition, since various substances are dissolved in the waste water, and some substances inhibit the adsorption of fluorine, changes in the water supply also affect the effect of feedforward control.

FIG. 3 is a simulation of fluctuations in the wastewater fluorine concentration C ₀ that can occur in the actual plant based on the actual measurement values in the actual plant. As described above, the wastewater fluorine concentration C ₀ varies due to the change of the coal type and various factors, and there is a possibility that the aluminum salt is insufficient or excessive when the charging is performed based on a predetermined model. Therefore, in this embodiment, the amount of aluminum salt charged is determined by a corrected aluminum injection rate A ′ (= αA) obtained by multiplying an aluminum injection rate A [mg / l] obtained by an adsorption isotherm by a correction coefficient α. An example of how to determine the correction coefficient α will be described with reference to FIG. In this example, the value of the correction coefficient α is controlled based on the treated water fluorine concentration C ₁ .

The target value of the treated water fluorine concentration is C _1T, and C _{1L to} C _1H (C _1L <C _1T <C _1H ) is defined as the dead zone. For example, it may be set as ± 20% of the target value C _1T . If this dead zone is exceeded on the low concentration side, it is judged that fluorine removal has been performed excessively and α is decreased, and if the dead zone is exceeded on the high concentration side, it is judged that fluorine removal is insufficient. To increase α. In the example of FIG. 4, the treated water fluorine concentration C ₁ was lower than C _1L at time 401, thereby reducing α from 1.0 to 0.9, and the treated water fluorine concentration C ₁ was higher than C _1H at time points 402 and 403. Thus, α is increased from 0.9 to 1.0 and α is increased from 1.0 to 1.1, respectively.

FIG. 5 shows a simulation result on how the treated water fluorine concentration C ₁ varies when the wastewater fluorine concentration C ₀ varies as shown in FIG. 3. The solid line is the result when the amount of aluminum salt charged is corrected by the correction coefficient α in FIG. 4, and the dotted line is the result when no correction is performed. In this way, by performing correction based on the history of the treated water fluorine concentration C ₁ , it is possible to prevent the chemical input amount from continuing for a long period of time while being excessive, or to continue for a long time while being too small. The fluctuation range of the density C ₁ can be further reduced. That is, it is possible to optimize the input amount of the aluminum salt.

The correspondence relationship between the control program shown in FIG. 1 and the processing in the first embodiment will be described. The aluminum injection rate calculation unit 208 calculates the aluminum injection rate A based on the adsorption isotherm in the fluorine treatment tank and the fluorine concentration C _{0 of the} waste water. The aluminum injection rate correction unit 209 calculates a corrected aluminum injection rate A ′ obtained by correcting the calculated aluminum injection rate A with a correction coefficient α based on the history of the fluorine concentration of the treated water. Although the method of reflecting the history of the fluorine concentration of the treated water using the dead zone has been described, the method is not limited to this method. For example, depending on how the drainage water quality fluctuates, it may be desirable that the standard can be adjusted flexibly as appropriate, rather than changing the correction coefficient based on a predetermined standard. Specifically, the aluminum concentration rate may be adjusted according to the adjusted reference by adjusting the fluorine concentration range to be a dead zone or the amount of change of the correction coefficient once in accordance with the history of the fluorine concentration of the treated water. Based on the corrected aluminum injection rate A ′, the chemical input amount calculation unit 210 calculates the input amount of the aluminum salt to be supplied to the waste water.

  In the case of the feedforward control of the present embodiment, it is desirable that the drain side fluorine concentration sensor 104 (see FIG. 1) continuously monitors the drain to calculate the aluminum injection rate by relatively high frequency. Since the side fluorine concentration sensor 105 takes several hours to appear as the fluorine concentration of the treated water, it is sufficient to monitor it at a lower frequency than the fluorine concentration sensor 104. For this reason, FIG. 1 shows an example in which the concentration sensor is connected to the control unit 200 online to control, but the fluorine concentration of the treated water is measured with higher accuracy and is transmitted to the control unit 200 offline. You may make it do.

  In Example 2, the amount of aluminum salt introduced into the fluorine treatment tank is controlled by feedback control. For the calculation of the initial input amount for this purpose, the following empirical formula (Formula 6) is used.

This empirical formula is derived from operation data in the actual plant. As shown in FIG. 6, from the actual plant operation data, the aluminum injection rate A [mg / l] and the amount of fluorine F [mg / l] removed by the chemical (aluminum salt) (fluorine concentration C ₀ [mg of waste water] / l] is equal to the difference between the fluorine concentration C ₁ [mg / l] of the treated water (see (Equation 1)) and has a positive correlation. FIG. 7 is a logarithmic display of the fluorine concentration C ₁ [mg / l] of the treated water limited to a predetermined range from the data of FIG. 6, and in this example, the correlation equation of (Equation 6) is a = 7.8 , N = 1.3.

In Example 2, Figure 8 shows the drainage fluorine concentration C ₀ [mg / l] treated water fluorine concentration C ₁ [mg / l] Simulation results of the variation in the case where variation occurs in shown in FIG. In the second embodiment, the initial control value is determined based on (Equation 6), and thereafter, the aluminum injection rate A is corrected from the deviation from the target treated water concentration. In FIG. 8, the target treated water concentration is 5 [mg / l], and the control method is also simple P control. In this example, the average treated water concentration is 5.2 [mg / l], and the maximum value is 13.9 [mg / l]. In the case of feedback control, in order to suppress the control delay with respect to the fluctuation of the wastewater fluorine concentration, it can be expected that the fluctuation range is reduced by shortening the control delay amount. Although P control is applied this time, feedback control using PI control and PID control may be performed. However, since the delay time until the fluctuation of the wastewater fluorine concentration C ₀ [mg / l] is reflected in the treated water fluorine concentration C ₁ [mg / l] is unavoidable, the treated water fluorine concentration C caused by the control delay is unavoidable. The fluctuation of ₁ [mg / l] is essential in feedback control.

Therefore, in this embodiment, the target value of the treated water fluorine concentration is changed according to the history of the treated water fluorine concentration C ₁ . Furthermore, the output sensitivity with respect to the shift width may be increased (that is, the amount of aluminum salt to be increased or decreased with respect to the predetermined shift width is increased). In the example of FIG. 9, the target value of the treated water fluorine concentration is 8 [mg / l], and the treated water fluorine concentration C ₁ is in the range of 50% to 200% (4 to 16 [mg / l]) (dead zone). If it exceeds the target value, the target value and the output sensitivity are changed. At this time, the average treated water concentration was 5.9 [mg / l], and the maximum value was 14.8 [mg / l].

  FIG. 10 summarizes the simulation results. Cases 1 and 2 are not corrected, and only the setting of the target value is different. When the target value is set to 6 [mg / l], the maximum value exceeds the Japanese drainage standard of 15 [mg / l]. Thus, in performing feedback control, by correcting the target value and the output sensitivity according to the history of the treated water fluorine concentration, it is possible to increase the average treated water concentration while suppressing an increase in the maximum value. It is possible. Thereby, it turns out that the amount of aluminum supplied excessively in order to satisfy the treated water standard is reduced.

  The correspondence relationship between the control program shown in FIG. 1 and the processing in the second embodiment will be described. The aluminum injection rate calculation unit 208 calculates the initial input amount of the aluminum salt by the initial input amount calculation formula (Equation 6) of the fluorine treatment tank, and thereafter, based on the deviation amount between the fluorine concentration of the treated water and the target fluorine concentration. Calculate the aluminum injection rate. The feedback control method may be any of P control, PI control, and PID control. Based on the calculated aluminum injection rate A, the chemical input amount calculation unit 210 calculates the input amount of the aluminum salt to be supplied to the waste water. The aluminum injection rate correction unit 209 changes the target fluorine concentration value of the treated water based on the history of the fluorine concentration of the treated water. Furthermore, the output sensitivity for the amount of deviation between the fluorine concentration of the treated water and the target fluorine concentration may be increased based on the history of the fluorine concentration of the treated water.

100: Fluorine treatment tank, 101: Reaction tank, 102: Coagulation tank, 103: Precipitation tank, 104, 105: Fluorine concentration sensor, 111: Chemical agent, 112: Neutralizing agent, 113: Coagulation aid, 200: Control unit, 201: processor, 202: memory, 203: water quality database, 204: process database, 205: interface, 206: bus.

Claims (9)

A water treatment system for treating wastewater containing fluorine,
Fluorine treatment tank that separates into a treated water in which fluorine contained in the wastewater is reduced and sludge containing aluminum hydroxide that has adsorbed fluorine by introducing an aluminum salt into the wastewater;
A control unit for controlling the amount of the aluminum salt charged into the waste water,
The control unit includes a processor and a memory, and the processor executes a control program read into the memory,
The control program includes an aluminum injection rate calculation unit, an aluminum injection rate correction unit, and a medicine input amount calculation unit,
The aluminum injection rate calculation unit calculates an aluminum injection rate based on a predetermined adsorption isotherm in the fluorine treatment tank and the fluorine concentration of the waste water,
The aluminum injection rate correction unit calculates a corrected aluminum injection rate obtained by correcting the aluminum injection rate calculated by the aluminum injection rate calculation unit with a correction coefficient based on a history of fluorine concentration of the treated water,
The said chemical | medical agent input amount calculation part is a water treatment system which calculates the injection amount of the aluminum salt thrown into the said waste_water | drain based on the said correction | amendment aluminum injection rate. In claim 1,
The adsorption isotherm is a Freundlich adsorption isotherm or a Langmuir adsorption isotherm. In claim 1,
The aluminum injection rate correction unit defines a fluorine concentration range that is a dead zone with respect to a target fluorine concentration of the treated water, and if the fluorine concentration of the treated water is a fluorine concentration range that is the dead zone, the value of the correction coefficient is set. A water treatment system for maintaining and changing the value of the correction coefficient when the fluorine concentration of the treated water exceeds a fluorine concentration range as the dead zone. In claim 3,
A water treatment system capable of adjusting a change amount of the correction coefficient when the fluorine concentration range as the dead zone or the fluorine concentration of the treated water exceeds the fluorine concentration range as the dead zone. In claim 3,
The water treatment system in which the measurement frequency of the fluorine concentration of the treated water is lower than the measurement frequency of the fluorine concentration of the waste water. A water treatment system for treating wastewater containing fluorine,
Fluorine treatment tank that separates into a treated water in which fluorine contained in the wastewater is reduced and sludge containing aluminum hydroxide that has adsorbed fluorine by introducing an aluminum salt into the wastewater;
A control unit for controlling the amount of the aluminum salt charged into the waste water,
The control unit includes a processor and a memory, and the processor executes a control program read into the memory,
The control program includes an aluminum injection rate calculation unit, an aluminum injection rate correction unit, and a medicine input amount calculation unit,
The aluminum injection rate calculation unit calculates an initial charging amount of the aluminum salt by a predetermined formula for calculating an initial charging amount of the fluorine treatment tank, and thereafter a fluorine concentration of the treated water and a target fluorine concentration of the treated water. Calculate the aluminum injection rate based on the amount of deviation from
The drug input amount calculation unit calculates the input amount of aluminum salt to be injected into the waste water based on the aluminum injection rate calculated by the aluminum injection rate calculation unit,
The said aluminum injection rate correction | amendment part is a water treatment system which changes the value of the target fluorine concentration of the said treated water based on the log | history of the fluorine concentration of the said treated water. In claim 6,
The aluminum injection rate correction unit is a water treatment system that further increases output sensitivity with respect to a deviation amount between a fluorine concentration of the treated water and a target fluorine concentration of the treated water based on a history of fluorine concentration of the treated water. In claim 6,
The aluminum injection rate calculation unit is a water treatment system that performs P control, PI control, or PID control on the aluminum injection rate. In claim 6,
The aluminum injection rate correction unit defines a fluorine concentration range that is a dead zone with respect to the target fluorine concentration of the treated water, and if the fluorine concentration of the treated water is a fluorine concentration range that is the dead zone, the target fluorine of the treated water A water treatment system that maintains the concentration value and changes the target fluorine concentration value of the treated water when the treated water fluorine concentration exceeds a fluorine concentration range that is the dead zone.

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