JP2012223723A - Control device and control method of seawater desalination system - Google Patents

Abstract

【Task】
A seawater desalination system that can obtain fresh water stably and at low operating costs by controlling pretreatment so that fouling of the semipermeable membrane can be reduced according to the amount of fouling components contained in seawater or brine. Realize.
[Solution]
In order to solve the above-described problems, the present invention provides a semipermeable membrane treatment apparatus that desalinates seawater or brine with a semipermeable membrane, and is disposed upstream of the semipermeable membrane treatment apparatus and is supplied to the semipermeable membrane treatment apparatus. Pretreatment device for pretreating the seawater or brine to be treated, pretreatment water polysaccharide measurement means for measuring the concentration of polysaccharide contained in the treatment water treated by the pretreatment device, and measurement of the pretreatment water polysaccharide Control means for calculating an operation amount of the pretreatment device based on a pretreatment water polysaccharide concentration measurement value by means and a target signal given in advance and outputting a control signal to the pretreatment device. It is characterized by that.
[Selection] Figure 1

Description

  TECHNICAL FIELD The present invention relates to a control device for a seawater desalination system and a control method therefor, and more particularly to a control device for a seawater desalination system suitable for one using a semipermeable membrane to obtain fresh water from seawater or brine and the control method therefor. .

  In recent years, seawater desalination systems using semipermeable membranes, especially reverse osmosis membranes, fouling membranes (slightly soluble components in raw water, polymer solutes, colloids, micro solids, etc. are deposited on the membrane and permeate. Cases in which the phenomenon of lowering the flux) is a major problem have been reported.

  In order to remove fouling-causing components contained in seawater, so far, coagulation treatment, coagulation sedimentation treatment, sand filtration treatment, multimedia filter treatment, pressurized flotation separation treatment, precision membrane filtration treatment, ultramembrane filtration treatment, etc. Various pretreatment techniques have been applied. In particular, since the concentration of fouling components contained in seawater varies greatly depending on the season, time, and weather, the pretreatment operation control according to the fluctuations is necessary for fouling of the semipermeable membrane and reducing the environmental load. It has become important since.

  Among the pretreatments, in the case of agglomeration treatment using a flocculant or a coagulation precipitation treatment, the injection amount of the flocculant has been controlled by constant injection rate control or turbidity proportional control. In seawater desalination, SDI (Silt Density Index), which is an index of particulate matter, is widely used, and control based on this SDI value is also implemented.

  On the other hand, it has been reported that membrane fouling is caused not only by turbid particles but also by low molecular weight organic substances. For example, Non-Patent Document 1 describes that TEP (Transparent Exopolymer Particles) containing polysaccharides that are particularly sticky among organic substances greatly contribute to the generation of fouling.

  This TEP is usually formed by agglomeration of low-molecular-weight polysaccharides in seawater into particles or colloids, but phytoplankton is sheared by pretreatment such as ultrafiltration membranes, and is extracorporeal. It is also formed by agglomeration of the polysaccharide that flows out into In addition, changes in TEP concentration have a low correlation with changes in seawater turbidity. For example, when the seawater temperature is high and the amount of sunlight is high, the TEP concentration in the seawater increases regardless of the turbidity in the seawater.

  Therefore, with conventional injection rate constant control, turbidity proportional control, and flocculant injection control based on the SDI value, control according to changes in the concentration of polysaccharides contained in seawater is impossible, and the semipermeable membrane There are cases where fouling progresses quickly.

Takeuchi, “RO seawater desalination pretreatment and fouling”, Journal of the Seawater Society of Japan 63, p 367-371 (2009)

  In order to avoid the above-mentioned fouling of the semipermeable membrane from proceeding quickly, measures such as increasing the ratio in the case of constant injection rate control and increasing the offset value in the case of turbidity proportional control should be taken. However, in any case, the coagulant is excessively injected, and there is a problem that the chemical cost and the sludge disposal cost increase.

  In the treatment using the flocculant, the components in the seawater are flocculated and separated by precipitation, filtration or levitation. However, the flocculation requires the presence of turbidity as a core.

  In addition, when the raw seawater is low in turbidity, the growth of flocs is insufficient, and fouling-causing components such as polysaccharides and TEP are not sufficiently entrained in the flocs, making it difficult to separate from the seawater. there were.

  As a result, there is a problem in that the fouling component cannot be sufficiently removed by the pretreatment, and the fouling of the semipermeable membrane proceeds quickly.

  The present invention has been made in view of the above points, and the object of the present invention is to control the pretreatment so that the fouling of the semipermeable membrane can be reduced according to the amount of the fouling component contained in seawater or brine. Another object of the present invention is to provide a control device and a control method for a seawater desalination system that can operate at low cost and can stably obtain fresh water.

  In order to achieve the above object, the control device for the seawater desalination system of the present invention is disposed in a stage preceding the semipermeable membrane treatment device for desalinating seawater or brine with a semipermeable membrane, and the semipermeable membrane treatment device, A pretreatment device for pretreating seawater or brine supplied to the semipermeable membrane treatment device, and a pretreatment water polysaccharide measuring means for measuring the concentration of the polysaccharide contained in the treated water treated by the pretreatment device; , Based on a pretreatment water polysaccharide concentration measurement value by the pretreatment water polysaccharide measuring means and a target signal given in advance, an operation amount of the pretreatment device is calculated and a control signal is output to the pretreatment device And a control means for performing the above.

  Moreover, in order to achieve the above object, the control method of the seawater desalination system of the present invention desalinates the treated water obtained by treating seawater or brine with a pretreatment device with a semipermeable membrane of a semipermeable membrane treatment device. The concentration of the polysaccharide contained in the treated water of the pretreatment device is measured by the pretreatment water polysaccharide measuring means, the measured value of the polysaccharide concentration is compared with a target signal given in advance, and based on the comparison value The operation amount of the pre-processing device is calculated and controlled by the control means.

  According to the present invention, the pretreatment is controlled so as to reduce the fouling of the semipermeable membrane according to the amount of the fouling component contained in the seawater or brine, and the fresh water can be obtained stably at a low operating cost. effective.

1 is a flowchart showing Example 1 of a control device for a seawater desalination system according to the present invention. It is a flowchart for demonstrating the position of the evaluation parameter | index comparison means, evaluation parameter | index calculation means, and perturbation generation | occurrence | production means incorporated in Example 1 of the control apparatus of the seawater desalination system of this invention. It is a characteristic view which shows the relationship between the polysaccharide density | concentration in Example 1 of the control apparatus of the seawater desalination system of this invention, and the increase rate of semipermeable membrane filtration resistance. It is a flowchart which shows Example 2 of the control apparatus of the seawater desalination system of this invention. It is a flowchart which shows Example 3 of the control apparatus of the seawater desalination system of this invention. It is a flowchart which shows Example 4 of the control apparatus of the seawater desalination system of this invention.

  Hereinafter, the control apparatus of the seawater desalination system of this invention is demonstrated in detail based on various Examples. In addition, the same code | symbol has shown the equivalent throughout each Example.

  FIG. 1 shows a flow in Example 1 of a control device for a seawater desalination system of the present invention.

  As shown in the figure, the control device of the seawater desalination system in Example 1 is disposed in the front stage of the semipermeable membrane treatment device 12 that desalinates the seawater 1 with a semipermeable membrane, and the semipermeable membrane treatment device 12, A pretreatment device 10 for pretreating seawater 1 supplied to the semipermeable membrane treatment device 12, a pretreatment water polysaccharide measuring means 14 for measuring the concentration of polysaccharides contained in the treated water of the pretreatment device 10, Based on the polysaccharide concentration information 18 which is the pretreatment water polysaccharide concentration measurement value by the treatment water polysaccharide measuring means 14 and the target signal 22 given in advance, the operation amount of the pretreatment device 10 is calculated and the pretreatment device. A control unit 20 that outputs a control signal 24 is schematically configured. Further, the pretreatment device 10 includes a flocculant injection device 27 for injecting the flocculant and a solid material separation device 29 for separating the solid material.

  The pretreated water 16 flowing out from the pretreatment device 10 flows into the semipermeable membrane treatment device 12, and the concentration of the polysaccharide contained therein is measured by the pretreated water polysaccharide concentration measuring means 14. Although it is desirable that the pretreatment water polysaccharide concentration measuring means 14 can be measured online in real time, it may be offline in this embodiment.

  The polysaccharide concentration information 18 of the pretreated water 16 measured by the pretreated water polysaccharide concentration measuring means 14 is given to the control means 20 to which the target signal 22 is given in advance. The control means 20 calculates an operation amount of the preprocessing device 10 and outputs a preprocessing device control signal 24. Here, the target signal 22 may be a target concentration of the polysaccharide contained in the pretreated water 16 as a numerical value, or may be a stable operation period of the semipermeable membrane treatment apparatus 12. Alternatively, the target signal 22 may select the operating cost of the entire seawater desalination system or the environmental load of the entire seawater desalination system as an item of the operating condition search index.

  The semipermeable membrane processing apparatus 12 described above includes a pump, a power recovery device, and a pipe connecting them, in addition to the semipermeable membrane that forms a plurality of semipermeable membrane units in a plurality of stages. There are a reverse osmosis membrane and a forward osmosis membrane depending on the usage and material, but the semipermeable membrane of this embodiment may be any of them. Further, the pretreatment device 10 may be any of agglomeration treatment, agglomeration sedimentation treatment, sand filtration treatment, multimedia filter treatment, pressurized flotation separation treatment, precision membrane filtration treatment, and ultramembrane filtration treatment, or a combination thereof. good. However, the semipermeable membrane treatment device 12 is equipped with sand filtration, multimedia filter treatment, precision membrane filtration treatment, and ultrafiltration treatment for separating solid matter so as to suppress inflow of solid matter such as fine particles. Any solids separation device 29 is necessary.

  As shown in FIG. 2, the control unit 20 includes an evaluation index comparison unit 40, an evaluation index calculation unit 38, and a perturbation generation unit 36, which are used properly depending on the target signal 22. This will be described below.

  For example, when the target signal 22 is a polysaccharide concentration contained in the pretreated water 16, the evaluation signal comparing means 40 of the control means 20 compares the target signal 22 with the polysaccharide concentration information 18. When the polysaccharide concentration information 18 is larger than the target signal 22, the preprocessing device control signal 24 is output so that the preprocessing device 10 removes more polysaccharides. Conversely, when the polysaccharide concentration information 18 is smaller than the target signal 22, the preprocessing device control signal 24 is output so as to alleviate the removal of the polysaccharide in the preprocessing device 10.

  When the pretreatment device 10 is agglomeration treatment or agglomeration precipitation treatment, the pretreatment device control signal 24 is the amount of flocculant injected in the flocculant injection device 27, and when the polysaccharide concentration information 18 is larger than the target signal 22. Then, the injection amount of the flocculant in the flocculant injection device 27 is increased. When the pretreatment device 10 is any one of sand filtration processing, multimedia filter treatment, precision membrane filtration processing, and ultramembrane filtration processing, the pretreatment device control signal 24 becomes a cleaning start signal, and is more than the target signal 22. When the saccharide concentration information 18 is large, a trigger signal for physical backwashing using air or water is generated. When the pretreatment device 10 is a pressure levitation separation process, the pretreatment device control signal 24 is a pressure pressure or dissolved air amount, and when the polysaccharide concentration information 18 is larger than the target signal 22, the pressure is increased. Increase pressure or amount of dissolved air.

  For example, when the target signal 22 is the stable operation period of the semipermeable membrane treatment apparatus 12, the evaluation index calculation means 38 of the control means 20 is based on the polysaccharide concentration information 18 until the future chemical cleaning or replacement of the membrane. Is used as an evaluation index.

  First, the rate of increase in the membrane differential pressure of the semipermeable membrane or the rate of increase in filtration resistance due to fouling is calculated from the polysaccharide concentration information 18. As shown in FIG. 3, the higher the polysaccharide concentration, the greater the rate of increase in membrane differential pressure and filtration resistance, but the relationship becomes nonlinear (curved) as shown in FIG. 3, and the shape varies depending on the membrane and other conditions. .

  Since it is non-linear, the mathematical formula used in this calculation should be given in the form of a quadratic function, but it may be approximated by a linear function or another function. Alternatively, a table relating to the membrane differential pressure due to fouling and the rate of increase in filtration resistance may be generated in advance, the polysaccharide concentration information 18 may be applied, and values not in the table may be obtained by interpolation or extrapolation. .

  The membrane differential pressure or filtration resistance of the threshold value for chemical cleaning or replacement of the membrane is given in advance, and the difference from the current membrane differential pressure or filtration resistance of the semipermeable membrane is calculated at the above fouling increase rate. By dividing, the predicted value of the stable operation period of the semipermeable membrane treatment device 12 can be calculated. The predicted value of the stable operation period corresponds to a value when the current water quality (= concentration of polysaccharide given by the polysaccharide concentration information 18) continues in the future.

  Further, the evaluation index comparison unit 40 of the control unit 20 compares the predicted value of the stable operation period obtained by the above procedure with the stable operation period given as the target signal 22. When the predicted value of the stable operation period is smaller than the target signal 22, the pretreatment device control signal 24 is output so that the pretreatment device 10 removes more polysaccharides. Conversely, when the predicted value of the stable operation period is larger than the target signal 22, the pretreatment device control signal 24 is output so as to alleviate the removal of the polysaccharide in the pretreatment device 10.

  When the pretreatment device 10 is agglomeration treatment or agglomeration sedimentation treatment, the pretreatment device control signal 24 is the amount of the flocculant injected, and when the predicted value of the stable operation period is smaller than the target signal 22, Increase the dose of flocculant at 27. When the pretreatment device 10 is one of sand filtration processing, multimedia filter treatment, precision membrane filtration processing, and ultramembrane filtration processing, the pretreatment device control signal 24 becomes a cleaning start signal and is stable with respect to the target signal 22. When the predicted value of the operation period is small, a physical backwash trigger using air or water is generated. When the pretreatment device 10 is a pressurized flotation separation process, the pretreatment device control signal 24 is a pressurized pressure or a dissolved air amount, and when the predicted value of the stable operation period is smaller than the target signal 22, Increase pressure or dissolved air volume.

  For example, when the target signal 22 is the operating cost of the entire seawater desalination system, the control means 20 works to shift the operation to an operating condition that can reduce the operating cost. First, the evaluation index calculation means 38 of the control means 20 predicts and calculates the expected operating cost of the seawater desalination system as a whole based on the polysaccharide concentration information 18. First, from the polysaccharide concentration information 18, a predicted value of the membrane differential pressure increase rate of the semipermeable membrane or the filtration resistance increase rate due to fouling is calculated. The higher the polysaccharide concentration, the greater the rate of increase in membrane differential pressure and filtration resistance, but the relationship is generally non-linear (curved). Since it is non-linear, the mathematical formula used in this calculation should be given in the form of a quadratic function, but a linear function or another function may be used. Alternatively, a table relating to the membrane differential pressure due to fouling and the rate of increase in filtration resistance may be generated in advance, the polysaccharide concentration information 18 may be applied, and values not in the table may be obtained by interpolation or extrapolation. .

  The membrane differential pressure or filtration resistance of the threshold value for chemical cleaning or replacement of the membrane is given in advance, and the difference from the current membrane differential pressure or filtration resistance of the semipermeable membrane is calculated at the above fouling increase rate. By dividing, the predicted value of the stable operation period of the semipermeable membrane treatment device 12 can be calculated. The predicted value of the stable operation period corresponds to a value when the current water quality (= concentration of polysaccharide given by the polysaccharide concentration information 18) continues in the future.

  When a reverse osmosis membrane is used as the semipermeable membrane, the power of the high-pressure pump that pressurizes the semipermeable membrane occupies most of the power of the entire seawater desalination system. The power cost of the high-pressure pump can be calculated from the values of the membrane differential pressure and the filtration flow rate. The membrane differential pressure can be calculated from the predicted value of the membrane differential pressure increase rate or the filtration resistance increase rate and the current value of the membrane differential pressure. By using the filtration flow rate value and the power unit price (\ / kWh) In addition, it is possible to calculate a power cost prediction value for the entire stable operation period.

  Furthermore, the chemical cost prediction value can be calculated by integrating the current amount of the flocculant injected over the entire stable operation period and multiplying by the chemical unit price (\ / ton). After the stable operation period has elapsed, chemical cleaning or replacement of the membrane is required, and therefore chemical cleaning cost or membrane replacement cost is generated.

More power cost prediction value, chemical cost prediction value, chemical cleaning costs, or take the total film replacement cost, is divided by the total amount of fresh water 2 obtained in whole stable operation period, the freshwater 2 per 1 m ³ The operating cost can be determined.

  In addition, you may add the disposal cost of the sludge which generate | occur | produces by pre-processing, such as a flocculant injection | pouring, to the calculation content of the above-mentioned operation cost. In addition, if the number of possible chemical cleanings up to membrane replacement is known or can be assumed, the value obtained by dividing the membrane replacement cost by the number of possible chemical cleanings may be added to the chemical cleaning cost. .

  As a means for calculating the above operating cost, an evaluation index calculating means 38 is provided, and the operating cost is output from the evaluation index calculating means 38 as an evaluation index calculation value 44.

  Further, the perturbation generating means 36 of the control means 20 gives a one-way perturbation to the current operation condition output as the preprocessing device control signal 24. The frequency of the perturbation may be regular or irregular.

  For example, when the operation amount is the flocculant injection amount, the perturbation is one of the increase or decrease of the flocculant injection amount, and the width of the perturbation changes so as to affect the polysaccharide concentration information 18 of the pretreatment water 16. Good. As a result of this perturbation, the polysaccharide concentration given to the control means 20 as the polysaccharide concentration information 18 changes, and the operation cost can be calculated by the evaluation index calculation means 38. The evaluation index comparison means 40 of the control means 20 compares this value with the operating cost before perturbation, and determines the magnitude. If the operation cost after the perturbation is lower than the operation cost before the perturbation, the perturbation generating means 36 gives a further perturbation to the same side as the one where the perturbation was given earlier, and sets the manipulated variable 42 at the next time. Add perturbation until the operating cost starts to increase. If the operating cost reaches an increase, the operating condition is set to the previous condition, and the operation is continued until the next perturbation timing. As a result of giving perturbation first, if the operation cost after perturbation is higher than the operation cost before perturbation, the perturbation is given on the opposite side of the perturbation. If the operating cost is still high, the original operating condition is restored and the operation is continued until the next perturbation timing. By performing the above procedure, the seawater desalination system can be operated under conditions that can reduce the operating cost.

  When the pretreatment device 10 is any one of sand filtration processing, multimedia filter processing, precision membrane filtration processing, and ultramembrane filtration processing, the pretreatment device control signal 24 is a cleaning start signal. When the pretreatment device 10 is a pressure floating separation process, the pretreatment device control signal 24 is a pressure or a dissolved air amount.

For example, when the target signal 22 is the environmental load of the entire seawater desalination system, the control means 20 works to shift the operation to an operation condition that can reduce the environmental load. In this case, in the evaluation index calculation means 38 in the control means 20, instead of the power unit price (\ / kWh) described above, the environmental load power unit (kg-CO ₂ / kWh) and the chemical unit price (\ / ton) are set. Instead, environmental load chemical unit consumption (kg-CO ₂ / ton), instead of chemical cleaning cost, environmental load chemical cleaning basic unit (kg-CO ₂ / time), instead of membrane replacement cost, environmental load membrane replacement basic unit ( kg-CO ₂ / time), and an environmental load calculation value is output as the evaluation index 44.

  By repeating the perturbation and obtaining the manipulated variable 42 at the next time in the same procedure as in the case of the operation cost described above, the seawater desalination system can be operated under conditions that can reduce the environmental load.

  Thus, since the fouling of a semipermeable membrane used with a seawater desalination system and a performance fall can be suppressed by taking the structure of Example 1, fresh water can be supplied stably to a consumer. Moreover, the chemical cleaning frequency and replacement frequency of the semipermeable membrane can be reduced, and the cleaning chemicals and the membrane module to be discarded can be reduced. As a result, it is possible not only to reduce the amount of environmental loads and operating costs, but also to realize pre-processing that is not excessive or deficient according to the water quality fluctuations of seawater, so that chemical costs and sludge disposal costs can be reduced.

  FIG. 4 shows the flow in Example 2 of the control apparatus of the seawater desalination system of this invention.

  As shown in the figure, the configuration of the control device of the seawater desalination system in the second embodiment is substantially the same as that of the first embodiment shown in FIGS. Includes a process of injecting a flocculant, that is, a coagulation process or a coagulation precipitation process. And in Example 2, in addition to the structure of Example 1, the solid particle injection | pouring apparatus 26 which inject | pours a solid particle into the seawater 1 before inject | pouring a flocculant is provided. As solid fine particles, powdered activated carbon, zeolite powder, alumina powder, and magnetic particles are effective because they can also be expected to adsorb polysaccharides on their surfaces.

  The solid fine particle injection device 26 is composed of a solid fine particle tank and a solid fine particle injection pump (not shown). When injecting as a slurry, the solid fine particle injection device 26 is also provided with a liquid tank such as water for the future, a mixing tank, and a stirrer. . The solid particulate injection device 26 is given a solid particulate injection device control signal 28 from the control device 20 to adjust the injection amount of the solid particulates.

  In the pretreatment for injecting the flocculant, flocs are generated with turbidity as the core, and polysaccharides as fouling components are entrained in the flocs, and the flocs are precipitated, filtered, or separated from the seawater 1 by floating. Can be removed.

  However, when the turbidity of the seawater 1 is extremely low, the amount of polysaccharide taken into the floc is reduced due to poor floc generation, and as a result, the polysaccharide remains up to the semipermeable membrane treatment device 12, Increases the possibility of fouling.

  In such a case, if the solid fine particles are injected into the seawater 1 before the agglomeration treatment, the substance that becomes the core of the flocs increases, and the generation failure of flocs can be improved. As a result, the amount of polysaccharide incorporated into the floc increases, and fouling of the semipermeable membrane treatment apparatus 12 can be reduced. However, when solid particles are injected, the amount of sludge generated increases. Therefore, unless the injection amount of the solid fine particles is appropriately controlled, the sludge disposal cost also increases in addition to the increase in the chemical cost of the solid fine particles.

  In addition, since the solid fine particle injection water 3 after the solid fine particle injection needs to separate the turbidity before reaching the semipermeable membrane treatment apparatus 12, the turbid separation is performed when the injection amount of the solid fine particles is excessive. The operating cost of the device also increases. Depending on the properties of the powder, some organic substances can be removed and reused by washing with hot water, steam, heating, etc., but even in that case, regeneration costs are required, so the amount of solid particles injected is kept to a minimum. There is a need to.

  Therefore, the control means 20 calculates the operation amount of the solid particle injection device 26 in addition to the operation amount of the pretreatment device 10, and outputs the solid particle injection device control signal 28 together with the pretreatment device control signal 24. Here, the target signal 22 may be a target concentration of the polysaccharide contained in the pretreatment water 16 as a numerical value, or may be a stable operation period of the semipermeable membrane treatment device 12. Alternatively, the target signal 22 may select the operating cost of the entire seawater desalination system or the environmental load of the entire seawater desalination system as an item of the operating condition search index.

  For example, when the target signal 22 is a polysaccharide concentration contained in the pretreated water 16, the evaluation signal comparing means 40 of the control means 20 compares the target signal 22 with the polysaccharide concentration information 18.

  When the polysaccharide concentration information 18 is larger than the target signal 22, the pretreatment device control signal 24 and the solid particulate injection device control signal 28 are output so that more polysaccharide is removed by the pretreatment device 10. The Conversely, when the polysaccharide concentration information 18 is smaller than the target signal 22, the pretreatment device control signal 24 and the solid particulate injection device control signal 28 so as to alleviate the removal of the polysaccharide in the pretreatment device 10. Is output. When the pretreatment device 10 is agglomeration treatment or agglomeration precipitation treatment, the pretreatment device control signal 24 is an injection amount of a flocculant.

  When the polysaccharide concentration information 18 is larger than the target signal 22, it is necessary to remove more polysaccharides, so that an increase in the flocculant injection amount and an increase in the solid fine particle injection amount are performed. Conversely, when the polysaccharide concentration information 18 is smaller than the target signal 22, the polysaccharide has been removed excessively, so that the amount of flocculant injected and the amount of solid fine particles injected are reduced. become.

  Since there are multiple combinations of flocculant injection amount and solid fine particle injection amount to reduce or increase polysaccharides, the influence of the flocculant injection amount and solid fine particle injection amount on the removal of polysaccharides as a mathematical model in advance It is also possible to obtain the most appropriate operating condition by calculation according to the model. In order to focus on unique operating conditions, the formula model has a chemical unit price (\ / ton) for the flocculant and a chemical unit price (\ / ton) for the solid particulates, and performs calculations that minimize the total chemical cost. It is good to carry out.

Furthermore, it is desirable to consider the sludge disposal cost unit price (\ / ton) so that the disposal cost of sludge generated as a result of the injection of the flocculant and solid fine particles is included in the calculation. Alternatively, in order to focus on unique operating conditions, the mathematical model is equipped with an environmental impact chemical unit (kg-CO ₂ / ton) for flocculants and an environmental impact chemical unit (kg-CO ₂ / ton) for solid particles. It is preferable to perform an operation that minimizes the total environmental load.

Furthermore, it is desirable to consider the environmental load sludge disposal unit (kg-CO ₂ / ton) so that the environmental load caused by the disposal of sludge generated as a result of the injection of the flocculant and solid fine particles is included in the calculation.

  When the mathematical model is not used, the perturbation generator 36 can be used to obtain an appropriate combination of the flocculant injection amount and the solid fine particle injection amount in a feedback manner according to the following procedure.

  When the polysaccharide concentration information 18 is larger than the target signal 22, first, the amount of flocculant injected as the preprocessing device control signal 24 is given by the perturbation generating means 36 as perturbation in the increasing direction. The period for giving the perturbation may be regular or irregular, and the width of the perturbation may be a change that allows the polysaccharide concentration information 18 of the pretreatment water 16 to be affected. In the evaluation index calculation means 38, the product of the increase amount (ton) of the flocculant injection amount and the chemical unit price (\ / ton) of the flocculant at this time is divided by the polysaccharide concentration decrease amount (mg / L). The polysaccharide concentration reduction cost (¥ / (mg / L)) by the flocculant is obtained as the evaluation index calculation value 44. Here, the product of the increase in the flocculant injection amount (ton) and the chemical unit price of the flocculant (\ / ton) is the product of the increase in the flocculant injection amount (ton) and the sludge disposal cost unit cost (\ / ton) It is desirable to add the product of) and then divide by the decrease in polysaccharide concentration (mg / L).

  Next, the solid particle injection amount as the solid particle injection device control signal 28 is given by the perturbation generating means 36 as perturbation in the increasing direction. The period for giving the perturbation may be regular or irregular, and the width of the perturbation may be a change that allows the polysaccharide concentration information 18 of the pretreatment water 16 to be affected. The evaluation index calculation means 38 divides the product of the increase amount (ton) of the solid fine particle injection amount and the chemical unit price (\ / ton) of the solid fine particle at this time by the concentration decrease amount (mg / L) of the polysaccharide. Then, the polysaccharide concentration reduction cost (¥ / (mg / L)) by the solid fine particles is obtained as the evaluation index calculation value 44. Here, the product of the increase in the amount of solid particulate injection (ton) and the chemical unit price of solid particles (\ / ton), the increase in the amount of solid particulate injection (ton) and the unit cost of sludge disposal from solid particulates (\ / It is desirable to add the product of ton) and then divide by the decrease in polysaccharide concentration (mg / L).

  The evaluation index comparing means 40 compares the polysaccharide concentration reduction cost by the flocculant obtained by the above procedure with the polysaccharide concentration reduction cost by the solid fine particles. If the polysaccharide concentration reduction cost by the flocculant is smaller than the polysaccharide concentration reduction cost by the solid fine particles, the solid fine particle injection amount is returned to the value before the perturbation, and the value after the perturbation of the flocculant injection amount is The operation is continued using the operation amount 42. Conversely, if the polysaccharide concentration reduction cost by the flocculant is greater than the polysaccharide concentration reduction cost by the solid fine particles, the flocculant injection amount is returned to the value before the perturbation, and the value after the perturbation of the solid fine particle injection amount is The operation is continued using the operation amount 42 of the time.

By performing this procedure until the polysaccharide concentration information 18 is equal to or smaller than the target signal 22, an operation that satisfies the target signal 22 given as the concentration of the polysaccharide contained in the pretreated water 16 is performed. It can be realized at a lower cost. Alternatively, when the environmental load is more important than the operating cost, the evaluation index calculation means 38 calculates the chemical unit price (\ / ton) of the above flocculant as the environmental load chemical unit (kg-CO ₂ / kg) of the flocculant. ton), cost of reducing polysaccharide concentration by coagulant (\ / (mg / L)), environmental load of reducing polysaccharide concentration by coagulant (kg-CO ₂ / (mg / L)), disposal of coagulant-derived sludge Cost unit price (\ / ton), sludge disposal environmental load basic unit (kg-CO ₂ / ton) derived from flocculant, solid unit chemical unit price (\ / ton), solid particulate environmental load basic unit (kg -CO ₂ / ton), polysaccharide concentration reduction cost due to solid fine particles (\ / (mg / L)), polysaccharide concentration reduction environmental load due to solid fine particles (kg-CO ₂ / (mg / L)), solid fine particles By calculating the sludge disposal cost unit price (\ / ton) of origin as the sludge disposal environmental impact unit (kg-CO ₂ / ton) of solid particulates, the concentration of polysaccharides contained in the pretreated water 16 is calculated. Goal given as Operation that satisfies the 22, can be realized at lower environmental impact.

  For example, when the target signal 22 is the operating cost of the entire seawater desalination system, the control means 20 works to shift the operation to an operating condition that can reduce the operating cost. The operation cost based on the polysaccharide concentration information 18 at the present time can be calculated as the evaluation index calculation value 44 by the procedure of the evaluation index calculation means 38 described in the first embodiment. There are two factors that can be adjusted when reducing the operating cost, namely, the flocculant injection amount and the solid fine particle injection amount. In order to obtain an appropriate combination as the operation amount 42 at the next time, Perform the procedure.

  First, the perturbation generating means 36 gives a perturbation in one direction to increase or decrease the coagulant injection amount as the preprocessing device control signal 24. The period for giving the perturbation may be regular or irregular. The width of the perturbation may be a change such that an influence is recognized in the polysaccharide concentration information 18 of the pretreatment water 16.

  As a result of the perturbation, the polysaccharide concentration given to the control means 20 as the polysaccharide concentration information 18 changes, and the operation cost is calculated as the evaluation index calculation value 44 by taking the above-described procedure in the evaluation index calculation means 38. be able to.

  Next, the perfusion agent injection amount is returned to the value before the perturbation, and the perturbation generating means 36 gives a perturbation in one direction to increase or decrease the solid particle injection amount as the solid particle injection device control signal 28. The period for giving the perturbation may be regular or irregular. The width of the perturbation may be a change such that an influence is recognized in the polysaccharide concentration information 18 of the pretreatment water 16.

  As a result of the perturbation, the polysaccharide concentration given to the control means 20 as the polysaccharide concentration information 18 changes, and the operation cost is calculated as the evaluation index calculation value 44 by taking the above-described procedure in the evaluation index calculation means 38. be able to.

  The operation cost after perturbation obtained as described above is compared with the operation cost before perturbation by the evaluation index comparison means 40, and the magnitude is determined. If the operation cost after perturbation is lower than the operation cost before perturbation, the perturbation is given to the same side where the perturbation is given for both the flocculant injection amount and the solid particulate injection amount, and the operation cost increases. Add perturbation until it turns. When the operating cost increases, the operating condition is set as the previous condition, and it is output as the operation amount 42 at the next time, and the operation is continued until the next perturbation timing. As a result of giving perturbation first, if the operation cost after perturbation is higher than the operation cost before perturbation, the perturbation is given on the opposite side of the perturbation. If the operation cost is still high, the original operation condition is restored and the operation is continued until the next perturbation timing. By performing the above procedure, the seawater desalination system can be operated under conditions that can reduce the operating cost.

For example, when the target signal 22 is the environmental load of the entire seawater desalination system, the control means 20 works to shift the operation to an operation condition that can reduce the environmental load. In this case, in the evaluation index calculation means 38 in the control means 20, instead of the power unit price (\ / kWh) described above, the environmental load power unit (kg-CO ₂ / kWh) and the chemical unit price (\ / ton) are set. Instead, environmental load chemical unit consumption (kg-CO ₂ / ton), instead of chemical cleaning cost, environmental load chemical cleaning basic unit (kg-CO ₂ / time), instead of membrane replacement cost, environmental load membrane replacement basic unit ( (kg-CO ₂ / time) and repeat the calculation and perturbation in the same procedure as in the case of the above operating cost. As a result, the seawater desalination system can be operated under conditions that can reduce the environmental load.

  Thus, by taking the structure of Example 2, the same effect as Example 1 mentioned above can be acquired.

  FIG. 5 shows the flow in Example 3 of the control apparatus of the seawater desalination system of this invention.

  As shown in the figure, the configuration of the control apparatus for the seawater desalination system in the third embodiment is substantially the same as that of the first embodiment shown in FIGS. One is to use one of sand filtration, multimedia filter, and pressurized flotation separation.

  The pretreated water 16 flowing out from the pretreatment device 10 flows into the semipermeable membrane treatment device 12, and at the same time, the concentration of the polysaccharide contained therein is measured by the pretreatment water polysaccharide concentration measuring means 14, Turbidity is measured by the turbidity measuring device 30 and given to the control means 20 as turbidity information 32. The control means 20 is provided with a target signal 22 and a turbidity target value 34 in advance. Then, the control means 20 calculates an operation amount of the preprocessing device 10 and outputs a preprocessing device control signal 24. Here, the target signal 22 may be a target concentration of the polysaccharide contained in the pretreated water 16 as a numerical value, or may be a stable operation period of the semipermeable membrane treatment apparatus 12. Alternatively, the target signal 22 may select the operating cost of the entire seawater desalination system or the environmental load of the entire seawater desalination system as an item of the operating condition search index. The turbidity target value 34 is a turbidity target value of the pretreatment water 16 flowing into the semipermeable membrane treatment device 12.

  In the third embodiment, unlike the first and second embodiments, the turbidity of the pretreatment water 16 flowing into the semipermeable membrane treatment apparatus 12 is also taken into consideration.

  That is, as for the semipermeable membrane treatment apparatus 12, a hollow fiber membrane or a spiral membrane is often used in practice, and the pretreated water 16 flows in a narrow channel on the surface as a parallel flow. At that time, if turbidity is present, narrow channels are blocked and the performance of the semipermeable membrane is reduced. The presence of suspended or adhering turbidity on the surface of the semipermeable membrane as well as the blockage of the channel further deteriorates the performance of the semipermeable membrane. Therefore, it is desirable that not only polysaccharides but also turbidity be sufficiently removed from the pretreatment water 16 flowing into the semipermeable membrane treatment apparatus 12.

  When a precision membrane filtration process or an ultrafiltration process is used as the final solids separation device 29 of the pretreatment device 10, the turbidity is almost completely removed unless the membrane is damaged. However, when precipitation treatment, sand filtration treatment, multimedia filter treatment, or pressurized flotation separation treatment is used as the solid matter separation device 29, turbidity may remain in the pretreated water 16 depending on operating conditions, and a semipermeable membrane. There is a possibility of flowing into the processing device 12.

  In the case where the pretreatment device 10 is a coagulation precipitation process and the solid matter separation device 29 includes only the precipitation treatment, the evaluation index comparison means 40 of the control means 20 first determines the current turbidity given as the turbidity information 32. Compare with turbidity target value 34. When the current turbidity is higher than the turbidity target value 34, the agglomeration process is insufficient, and the injection amount of the aggregating agent output as the pretreatment device control signal 24 is increased. Conversely, when the current turbidity is lower than the turbidity target value 34, the agglomeration process is excessive, and the injection amount of the aggregating agent output as the pretreatment device control signal 24 is reduced. The flocculant injection amount obtained by this procedure will be referred to as a turbidity appropriate flocculant injection amount.

  The turbidity of the pretreatment water 16 flowing into the semipermeable membrane treatment device 12 can be suppressed to a value lower than the turbidity target value 34 by injecting a flocculant equal to or greater than the appropriate turbidity coagulant injection amount. At the same time, not only turbidity but also suppression of fouling by polysaccharides is necessary in the flocculant treatment.

  For example, when the target signal 22 is a polysaccharide concentration contained in the pretreated water 16, the evaluation signal comparing means 40 of the control means 20 compares the target signal 22 with the polysaccharide concentration information 18. When the polysaccharide concentration information 18 is larger than the target signal 22, the preprocessing device control signal 24 is output so that the preprocessing device 10 removes more polysaccharides.

  In the case of this Example 3, since the pretreatment device 10 is an agglomeration treatment or an aggregation precipitation treatment, when the polysaccharide concentration information 18 is larger than the target signal 22, the flocculant is injected as the pretreatment device control signal 24. Increase the amount. On the contrary, when the polysaccharide concentration information 18 is smaller than the target signal 22, the removal of the polysaccharide is excessive in the preprocessing device 10, but if the flocculant is reduced below the turbidity appropriate flocculant injection amount. Since the removal of turbidity becomes insufficient, the injection amount of the flocculant is controlled so that the turbidity appropriate flocculant injection amount is set to a lower limit.

  Even if the target signal 22 is not the concentration of the polysaccharide contained in the pretreated water 16 but the operating cost of the entire seawater desalination system or the environmental load of the entire seawater desalination system, the coagulant injection is similarly performed. By setting the lower limit of the amount to the value of the turbidity-appropriate coagulant injection amount, it is possible to suppress channel blockage due to turbidity and performance degradation of the semipermeable membrane.

  As described above, by adopting the configuration of the third embodiment, the same effects as those of the first embodiment or the second embodiment described above can be obtained.

  FIG. 6 shows the flow in Example 4 of the control apparatus of the seawater desalination system of this invention.

  As shown in the figure, the configuration of the control device for the seawater desalination system in Example 4 is substantially the same as that of Example 3 shown in FIG. A process for injecting the agent, that is, an agglomeration process or an agglomeration precipitation process is included, and a solid particle injection device 26 for injecting solid particles into the seawater 1 before injecting the aggregating agent is provided. As solid fine particles, powdered activated carbon, zeolite powder, alumina powder, and magnetic particles are effective because they can also be expected to adsorb polysaccharides on their surfaces.

  The solid fine particle injecting device 26 includes a solid fine particle tank and a solid fine particle injecting pump (not shown). When injecting as a slurry, the solid fine particle injecting device 26 also includes a liquid tank for mixing water, a mixing tank, and a stirrer. The solid particulate injection device 26 is given a solid particulate injection device control signal 28 from the control device 20 to adjust the injection amount of the solid particulates.

  In the pretreatment for injecting the flocculant, flocs are generated with turbidity as the core, and polysaccharides as fouling components are entrained in the flocs, and the flocs are precipitated, filtered, or separated from the seawater 1 by floating. Can be removed. However, when the turbidity of the seawater 1 is very low, the generation of flocs is poor and the amount of polysaccharides taken into the flocs decreases, resulting in the polysaccharide remaining up to the semipermeable membrane treatment device 12 and fouling. The possibility that a ring will occur increases.

  In such a case, if the solid fine particles are injected into the seawater 1 before the agglomeration treatment, the substance that becomes the core of the flocs increases, and the generation failure of flocs can be improved. As a result, the amount of polysaccharide incorporated into the floc increases, and fouling of the semipermeable membrane treatment apparatus 12 can be reduced. However, when solid particles are injected, the amount of sludge generated increases. Therefore, unless the injection amount of the solid fine particles is appropriately controlled, the sludge disposal cost also increases in addition to the increase in the chemical cost of the solid fine particles.

  In addition, since the solid fine particle injection water 3 after the solid fine particle injection needs to separate the turbidity before reaching the semipermeable membrane treatment device 12, when the injection amount of the solid fine particles is excessive, the turbidity separation device Operating costs also increase. Depending on the properties of the powder, some organic substances can be removed and reused by treatment such as hot water cleaning, steam cleaning, and heating. There is a need.

  The pretreated water 16 flowing out from the pretreatment device 10 flows into the semipermeable membrane treatment device 12, and the concentration of the polysaccharide contained therein is measured by the pretreatment water polysaccharide concentration measuring means 14 and polysaccharide information 18 is obtained. In addition, the turbidity is measured by the turbidity measuring device 30 and given to the control means 20 as turbidity information 32. Here, the polysaccharide and the turbidity may be measured at the same time or may be reversed.

  On the other hand, a target signal 22 and a turbidity target value 34 are given in advance to the control means 20, and the control means 20 calculates the operation amounts of the pretreatment device 10 and the solid particulate injection device 26 to control the pretreatment device. A signal 24 and a solid particulate injection device control signal 28 are output. Here, the target signal 22 may be a target concentration of the polysaccharide contained in the pretreated water 16 as a numerical value, or may be a stable operation period of the semipermeable membrane treatment apparatus 12. Alternatively, the target signal 22 may select the operating cost of the entire seawater desalination system or the environmental load of the entire seawater desalination system as an item of the operating condition search index. The turbidity target value 34 is a turbidity target value of the pretreatment water 16 flowing into the semipermeable membrane treatment device 12.

  In the fourth embodiment, unlike the second embodiment, the turbidity of the pretreated water 16 flowing into the semipermeable membrane treatment apparatus 12 is also taken into consideration. In practice, a hollow fiber membrane or a spiral membrane is often used for the semipermeable membrane treatment device 12, and the pretreated water 16 flows in a narrow channel on the surface as a parallel flow. At that time, if turbidity is present, narrow channels are blocked and the performance of the semipermeable membrane is reduced. The presence of suspended or adhering turbidity on the surface of the semipermeable membrane as well as the blockage of the channel further deteriorates the performance of the semipermeable membrane. Therefore, it is desirable that not only polysaccharides but also turbidity be sufficiently removed from the pretreatment water 16 flowing into the semipermeable membrane treatment apparatus 12.

  When a precision membrane filtration process or an ultrafiltration process is used as the final solids separation device 29 of the pretreatment device 10, the turbidity is almost completely removed unless the membrane is damaged. However, when precipitation treatment, sand filtration treatment, multimedia filter treatment, or pressurized flotation separation treatment is used as a solid matter separation device, turbidity may remain in the pretreated water 16 depending on operating conditions, and semipermeable membrane treatment. There is a possibility of flowing into the device 12. Therefore, it is necessary to control the injection rate of the flocculant so that the remaining turbidity can be appropriately removed.

  Therefore, the evaluation index comparison means 40 of the control means 20 first compares the current turbidity given as the turbidity information 32 with the turbidity target value 34. When the current turbidity is higher than the turbidity target value 34, the agglomeration process is insufficient, and the injection amount of the aggregating agent output as the pretreatment device control signal 24 is increased. Conversely, when the current turbidity is lower than the turbidity target value 34, the agglomeration process is excessive, and the injection amount of the aggregating agent output as the pretreatment device control signal 24 is reduced. The flocculant injection amount obtained by this procedure will be referred to as the turbidity appropriate flocculant injection amount.

  The turbidity of the pretreatment water 16 flowing into the semipermeable membrane treatment device 12 can be suppressed to a value lower than the turbidity target value 34 by injecting a flocculant equal to or greater than the turbidity appropriate flocculant injection amount. At the same time, not only turbidity but also suppression of fouling by polysaccharides is necessary in the aggregation treatment. For example, when the target signal 22 is a polysaccharide concentration contained in the pretreated water 16, the evaluation signal comparing means 40 of the control means 20 compares the target signal 22 with the polysaccharide concentration information 18. When the polysaccharide concentration information 18 is larger than the target signal 22, the pretreatment device 10 outputs a pretreatment device control signal 24 and a solid particulate injection device control signal 28 so as to remove more polysaccharides. . Conversely, when the polysaccharide concentration information 18 is smaller than the target signal 22, the pretreatment device control signal 24 and the solid particulate injection device control signal 28 are set so as to alleviate the removal of the polysaccharide in the pretreatment device 10. Is output. When the polysaccharide concentration information 18 is larger than the target signal 22, it is necessary to remove more polysaccharides, so that an increase in the flocculant injection amount and an increase in the solid fine particle injection amount are performed. Conversely, when the polysaccharide concentration information 18 is smaller than the target signal 22, the polysaccharide has been removed excessively, so that the amount of flocculant injected and the amount of solid fine particles injected are reduced. become. However, if the amount of flocculant is reduced below the appropriate turbidity coagulant injection amount, the removal of turbidity becomes insufficient. Control the injection volume.

  Since there are multiple combinations of the flocculant injection amount and solid fine particle injection amount to bring the polysaccharide to the desired concentration, the effects of the flocculant injection amount and solid fine particle injection amount on the removal of polysaccharides are provided in advance as a mathematical model. In addition, the most appropriate operating condition may be obtained by calculation according to the model. In order to focus on unique operating conditions, the formula model has a chemical unit price (\ / ton) for the flocculant and a chemical unit price (\ / ton) for the solid particulates, and performs calculations that minimize the total chemical cost. It is good to carry out.

Furthermore, it is desirable to consider the sludge disposal cost unit price (\ / ton) so that the disposal cost of sludge generated as a result of the injection of the flocculant and solid fine particles is included in the calculation. Alternatively, in order to focus on unique operating conditions, the mathematical model is equipped with an environmental impact chemical unit (kg-CO ₂ / ton) for flocculants and an environmental impact chemical unit (kg-CO ₂ / ton) for solid particles. It is preferable to perform an operation that minimizes the total environmental load. Furthermore, it is desirable to consider the environmental load sludge disposal unit (kg-CO ₂ / ton) so that the environmental load caused by the disposal of sludge generated as a result of the injection of the flocculant and solid fine particles is included in the calculation.

  Thus, the effect similar to each Example mentioned above can be acquired by taking the structure of Example 4. FIG.

  DESCRIPTION OF SYMBOLS 1 ... Seawater, 2 ... Fresh water, 3 ... Solid fine particle injection water, 10 ... Pretreatment apparatus, 12 ... Semipermeable membrane treatment apparatus, 14 ... Pretreatment water polysaccharide concentration measuring means, 16 ... Pretreatment water, 18 ... Polysaccharide Concentration information, 20 ... control means, 22 ... target signal, 24 ... pretreatment device control signal, 26 ... solid particulate injection device, 27 ... flocculant injection device, 28 ... solid particulate injection device control signal, 29 ... solid matter separation device , 30 ... Turbidity measuring device, 32 ... Turbidity information, 34 ... Turbidity target value, 36 ... Perturbation generating means, 38 ... Evaluation index calculating means, 40 ... Evaluation index comparing means, 42 ... Manipulation amount at next time, 44 ... Evaluation index calculated value.

Claims (13)

  A semipermeable membrane treatment device that desalinates seawater or brine with a semipermeable membrane, and a pretreatment device that is disposed upstream of the semipermeable membrane treatment device and pretreats seawater or brine supplied to the semipermeable membrane treatment device A pretreatment water polysaccharide measuring means for measuring the concentration of polysaccharide contained in the treated water treated by the pretreatment device, a pretreatment water polysaccharide concentration measurement value by the pretreatment water polysaccharide measurement means, and A control device for a seawater desalination system, comprising control means for calculating an operation amount of the pretreatment device based on a given target signal and outputting a control signal to the pretreatment device. . In the control apparatus of the seawater desalination system according to claim 1,
The said pre-processing apparatus is equipped with the coagulant | flocculant injection apparatus which inject | pours a coagulant | flocculant at least, and the solid substance separator which isolate | separates a solid substance from seawater or brackish water, The control apparatus of the seawater desalination system characterized by the above-mentioned. In the control apparatus of the seawater desalination system according to claim 2,
The apparatus for controlling a seawater desalination system, wherein the solid matter separation device is any one of sand filtration, multimedia filter, precision membrane filtration, and ultramembrane filtration. In the control apparatus of the seawater desalination system according to claim 1,
The control means includes a perturbation generating means for perturbing the manipulated variable of the preprocessing device periodically or irregularly, an evaluation index calculating means for calculating an operating cost or an environmental load as an evaluation index, and before and after the perturbation is given. A control device for a seawater desalination system, comprising: an evaluation index comparing means for comparing the magnitudes of the evaluation indices and outputting an operation amount at which the evaluation index becomes smaller as an operation amount at the next time. In the control apparatus of the seawater desalination system according to claim 1,
The turbidity measuring means for measuring the turbidity contained in the treated water of the pretreatment device using any one of sand filtration treatment, multimedia filter treatment, and pressurized flotation separation treatment as the pretreatment device, and the turbidity measurement Based on the turbidity measurement value by the means, the pretreatment water polysaccharide concentration measurement value by the pretreatment water polysaccharide measurement means, the pre-given target signal and the pre-given turbidity target value, the operation of the pretreatment device A control device for a seawater desalination system, comprising control means for calculating a quantity and outputting a control signal to the pretreatment device. In the control apparatus of the seawater desalination system according to claim 1,
A solid particulate injection device is provided in the preceding stage of the pretreatment device, and the pretreatment device and the solid particulates are based on a pretreatment water polysaccharide concentration measurement value by the pretreatment water polysaccharide measurement means and a predetermined target signal. A control device for a seawater desalination system, comprising control means for calculating an operation amount of an injection device and outputting a control signal to the pretreatment device and the solid particulate injection device. In the control apparatus of the seawater desalination system according to claim 5,
A solid particulate injection device is provided in the previous stage of the pretreatment device, the turbidity measurement value by the turbidity measurement means, the pretreatment water polysaccharide concentration measurement value by the pretreatment water polysaccharide measurement means, a target signal given in advance, and Control means for calculating an operation amount of the pretreatment device and the solid particulate injection device based on a turbidity target value given in advance and outputting a control signal to the pretreatment device and the solid particulate injection device A control device for a seawater desalination system. In the control apparatus of the seawater desalination system according to claim 6 or 7,
A control apparatus for a seawater desalination system, wherein at least one of powdered activated carbon, zeolite powder, alumina powder, and magnetic particles is used as the solid particulates of the solid particulate injection device.   In desalinating the treated water obtained by treating seawater or brine with a pretreatment device with the semipermeable membrane of the semipermeable membrane treatment device, the concentration of the polysaccharide contained in the treated water of the pretreatment device is measured by the pretreatment water polysaccharide measuring means. The measured value of the polysaccharide concentration is compared with a target signal given in advance, and the operation amount of the pretreatment device is calculated based on the comparison value and controlled by the control means. Control method of seawater desalination system. In the control method of the seawater desalination system according to claim 9,
The control means includes a perturbation generating means for perturbing the manipulated variable of the preprocessing device periodically or irregularly, an evaluation index calculating means for calculating an operating cost or an environmental load as an evaluation index, and before and after the perturbation is given. Evaluation index comparison means for comparing the magnitude of the evaluation index and outputting the operation amount at which the evaluation index becomes smaller as the operation amount at the next time;
The target signal is the concentration of polysaccharide contained in the treated water, the evaluation index comparing means compares the target signal with the polysaccharide concentration information in the pretreated water polysaccharide measuring means, and for the target signal When the polysaccharide concentration information is large, a preprocessing device control signal is output from the control means so as to remove the polysaccharide from the preprocessing device, and the polysaccharide concentration information is output with respect to the target signal. The control method of the seawater desalination system according to claim 1, wherein the control means outputs a pretreatment device control signal to the pretreatment device so as to alleviate the removal of polysaccharides. In the control method of the seawater desalination system according to claim 10,
When the pretreatment device is a coagulation treatment or a coagulation sedimentation treatment, the pretreatment device control signal is an injection amount of the coagulant, and when the polysaccharide concentration information is larger than the target signal, Increase the injection volume,
Alternatively, when the pretreatment device is one of sand filtration processing, multimedia filter processing, precision membrane filtration processing, and ultramembrane filtration processing, the pretreatment device control signal is a cleaning start signal, and the target signal When the polysaccharide concentration information is large, a trigger signal for backwashing using air or water is generated,
Alternatively, when the pretreatment device is a pressure levitation separation process, the pretreatment device control signal is a pressure or dissolved air amount, and when the polysaccharide concentration information is larger than the target signal, the pressure is increased. A method for controlling a seawater desalination system, characterized by increasing the pressure or the amount of dissolved air. In the control method of the seawater desalination system according to claim 9,
The control means includes a perturbation generating means for perturbing the manipulated variable of the preprocessing device periodically or irregularly, an evaluation index calculating means for calculating an operating cost or an environmental load as an evaluation index, and before and after the perturbation is given. Evaluation index comparison means for comparing the magnitude of the evaluation index and outputting the operation amount at which the evaluation index becomes smaller as the operation amount at the next time;
The target signal is a stable operation period of the semipermeable membrane treatment device, and the chemical evaluation or semi-permeable membrane chemical cleaning or replacement is performed based on the polysaccharide concentration information in the pretreatment water polysaccharide measurement means in the evaluation index calculation means. And the evaluation index comparison means compares the predicted value of the stable operation period with the stable operation period given as the target signal and compares the stable signal with the target signal. When the predicted value of the operation period is small, a preprocessing device control signal is output from the control means to remove the polysaccharide from the preprocessing device, and the stable operation period of the target signal is output. When the predicted value is large, the control means outputs a pretreatment device control signal so as to alleviate the removal of polysaccharides to the pretreatment device. Law. In the control method of the seawater desalination system according to claim 12,
When the pretreatment device is a coagulation treatment or a coagulation sedimentation treatment, the pretreatment device control signal is an injection amount of a coagulant, and when the predicted value of the stable operation period is smaller than the target signal, the aggregation Increase the dose of the agent,
Alternatively, when the pretreatment device is one of sand filtration processing, multimedia filter processing, precision membrane filtration processing, and ultramembrane filtration processing, the pretreatment device control signal is a cleaning start signal, and the target signal If the predicted value of the stable operation period is small, a trigger signal for backwashing using air or water is generated,
Alternatively, when the pretreatment device is a pressurized flotation separation process, the pretreatment device control signal is a pressurized pressure or an amount of dissolved air, and when the predicted value of the stable operation period is smaller than the target signal, A control method for a seawater desalination system, characterized by increasing a pressurized pressure or an amount of dissolved air.

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