Membrane filtration facility operation support system, membrane filtration facility control device, membrane filtration facility control method, and computer program

Abstract

To provide a membrane filtration equipment controller which performs control reflecting information on the adhesion and peeling of foulant in membrane fouling during a filtration backwashing cycle.SOLUTION: The membrane filtration facility control device 40 according to the embodiment is a control device for controlling a membrane filtration facility that uses a separation membrane that separates a solid contained in a liquid from the liquid, and that performs a filtration step of filtering water to be treated with the separation membrane to obtain treated water, and a backwashing step of passing the treated water through the separation membrane in a direction opposite to a water passing direction in the filtration step to perform backwashing, the control device including a membrane filtration index calculation section 402 that calculates a membrane filtration index indicating information on adhesion and separation of foulant in membrane fouling of the separation membrane, using a membrane differential pressure that is a difference in pressure between a primary side and a secondary side of the separation membrane, and an operating condition control section 404 that controls the membrane filtration facility according to an operating condition calculated using the membrane filtration index.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a membrane filtration equipment operation support system, a membrane filtration equipment control device, a membrane filtration equipment control method, and a computer program. [Background technology]

[0002] In water treatment processes, solid-liquid separation techniques such as sedimentation and filtration, which separate solids and liquids, are frequently used. In particular, in the field of water purification, membrane separation processes using membranes are becoming increasingly popular due to their reliable removal of protozoa such as Cryptosporidium and bacteria. Membrane separation processes have advantages over other solid-liquid separation processes, such as space saving and stable treated water quality. However, membrane separation processes have disadvantages in terms of cost. In particular, the high initial costs and running costs associated with membrane separation processes pose a challenge to their widespread adoption. Therefore, there is a growing need for technologies that can reduce the running costs of membrane separation processes.

[0003] A characteristic phenomenon in membrane separation processes is membrane clogging (membrane fouling). Membrane fouling occurs when substances contained in raw water adhere to the membrane surface or inside the membrane. As membrane fouling progresses, the resistance to filtration by pressure or suction during membrane separation processes changes. In constant-flow filtration, the progression of membrane fouling increases the transmembrane pressure, which is the difference in pressure between the primary and secondary sides of the filtration membrane. To suppress membrane fouling, physical cleaning with air (aeration) and chemical cleaning with chemicals are required. Therefore, the running costs of membrane separation equipment include the electricity and chemical costs for physical and chemical cleaning. In other words, the electricity and chemical costs vary depending on the operation and control of the membrane separation equipment. However, with conventional control, the running costs of membrane separation equipment are sometimes not maximized based on the state of membrane fouling (clogging).

[0004] In membrane separation treatment processes, membrane fouling is reduced by physical cleaning such as air bubble cleaning, which diffuses air onto the membrane surface during operation, or backflow water cleaning, which passes cleaning water in the opposite direction to the filtered water every few tens of minutes to several hours. Generally, membrane fouling is referred to as reversible fouling when it is removed by physical cleaning, and irreversible fouling when it is not removed by physical cleaning.

[0005] Because the transmembrane pressure of a filtration membrane increases due to the accumulation (progression) of irreversible fouling, it is desirable to chemically clean the filtration membrane with acid, alkali, etc. once the transmembrane pressure reaches a certain value. Chemical cleaning is a heavy workload and cost burden, and repeated chemical cleaning can also lead to deterioration of the filtration membrane, so it is important to suppress irreversible fouling.

[0006] Conventionally, the frequency and intensity of physical cleaning of filtration membranes have been controlled to a fixed value that was adjusted in advance. However, such physical cleaning control of filtration membranes with a fixed frequency and intensity can result in excessive physical cleaning in order to suppress the rapid progression of irreversible fouling, which is not economical. In addition, the timing of chemical cleaning of filtration membranes is estimated by operators based on experience with increases in transmembrane pressure due to the progression of irreversible fouling, and management is dependent on the operators' know-how. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 11-319516 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-82027 [Patent Document 3] Japanese Patent Application Publication No. 2019-25437 Summary of the Invention [Problem to be solved by the invention]

[0008] Previously, a technology has been proposed that uses raw water quality measurements and operating conditions to predict the increase in transmembrane pressure across a filtration membrane due to irreversible fouling using a transmembrane pressure prediction model, and then appropriately controls the cleaning airflow rate based on this predicted transmembrane pressure. This technology can actively change the cleaning airflow rate as a control input to suppress the increase in transmembrane pressure, or can save energy when the increase in transmembrane pressure is small. However, this proposed technology does not explicitly state whether the predicted membrane resistance is due to changes in reversible fouling or irreversible fouling.

[0009] The target resistance is set based on the timing of chemical cleaning, which is usually performed every few months to several years, and it is reasonable to set it in response to changes in membrane resistance due to irreversible fouling. Therefore, it is equally reasonable to set the predicted resistance based on changes in membrane resistance due to irreversible fouling.

[0010] The embodiments of the present invention have been made in consideration of the above circumstances, and aim to provide a membrane filtration equipment operation support system, a membrane filtration equipment control device, a membrane filtration equipment control method, and a computer program that perform control that reflects information on the adhesion and detachment of foulants in membrane fouling during a filtration backwash cycle. [Means for solving the problem]

[0011] A membrane filtration equipment control device according to an embodiment is a control device that controls membrane filtration equipment that performs a filtration process in which treated water is filtered through a separation membrane using a separation membrane that separates solids contained in the liquid from the liquid to obtain treated water, and a backwashing process in which the treated water is passed through the separation membrane in a direction opposite to the water passing direction in the filtration process to perform backwashing.The control device includes: a membrane filtration index calculation unit that calculates a membrane filtration index that represents information on the adhesion and detachment of foulants in membrane fouling of the separation membrane using a membrane differential pressure, which is the difference in pressure between the primary and secondary sides of the separation membrane; and an operating condition control unit that controls the membrane filtration equipment according to the operating conditions calculated using the membrane filtration index. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of a process including a membrane filtration facility to which the membrane filtration facility control device of the first embodiment is applied. [Figure 2] FIG. 2 is a diagram schematically showing an example of the change over time between the actual value and the target value of the membrane resistance of the filtration membrane. [Figure 3] FIG. 3 is a time-series diagram showing an example of the membrane resistance of the filtration membrane measured during the filtration backwash cycle. [Figure 4] FIG. 4 is a diagram schematically illustrating an example of a process including a membrane filtration facility to which the membrane filtration facility control device of the second embodiment is applied. [Figure 5] FIG. 5 is a diagram schematically illustrating an example of a process including a membrane filtration facility to which the membrane filtration facility control device of the third embodiment is applied. [Figure 6] FIG. 6 shows an example of the results of a filtration experiment using raw water containing membrane foulant A and membrane foulant B. [Figure 7] FIG. 7 is a diagram schematically illustrating an example of a process including a membrane filtration facility to which the membrane filtration facility control device of the fourth embodiment is applied. [Figure 8] FIG. 8 is a diagram schematically illustrating an example of the configuration of a membrane filtration equipment operation support system including a membrane filtration equipment control device according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, a membrane filtration equipment operation support system, a membrane filtration equipment control device, a membrane filtration equipment control method, and a computer program according to embodiments will be described with reference to the drawings. FIG. 1 is a diagram schematically illustrating an example of membrane filtration equipment to which the membrane filtration equipment control device of the first embodiment is applied.

[0014] Membrane filtration is widely used as a water treatment method, and can be applied, for example, to processes for producing industrial water or tap water from surface water, groundwater, treated sewage water, etc., seawater desalination processes, wastewater treatment processes for sewage or industrial water, etc. In this embodiment, a case where membrane filtration is applied to a process for filtering surface water or groundwater will be described, but the device, method, and computer program may be applied to membrane filtration equipment in any process as long as similar measuring instruments and equipment can be installed.

[0015] The membrane filtration equipment includes a pretreatment section 10, a membrane immersion tank 20, a membrane filtration treatment water tank 30, a cleaning blower B1, a filtration pump P1, and a backwash pump P2. The pretreatment unit 10 includes, for example, a receiving well (not shown) into which the raw water to be treated flows, a mixing tank (not shown) into which the raw water supplied from the receiving well flows, and a chemical (at least one of chlorine, activated carbon, coagulant, and ozone) injector. In the mixing tank, for example, chemicals such as chlorine, activated carbon, and coagulant are injected into the raw water and stirred to coagulate and precipitate suspended solids contained in the raw water. The supernatant liquid of the raw water from which the suspended solids have settled is discharged from the pretreatment unit 10. The pretreated raw water (water to be treated) discharged from the pretreatment unit 10 flows into the membrane immersion tank 20.

[0016] The pretreatment unit 10 also includes a detector for detecting organic indicators (TOC (total organic carbon), Tu (turbidity), UV (ultraviolet light), and EEM (excitation-emission matrix)) and a detector for detecting hydrogen ion exponent (pH). Values ​​detected by the detectors are supplied to the membrane filtration equipment control device 40 as necessary.

[0017] The membrane immersion tank 20 is filled with the water to be treated that has flowed in from the pretreatment section 10, and is provided with a membrane filtration unit 201 including one or more membrane modules, and an aeration device 202. Each membrane module of the membrane filtration unit 201 includes a filtration membrane. Filtration membranes are separation membranes that separate solids contained in a liquid from the liquid and can be classified according to the pore size into large pore membranes (LP membranes), microfiltration membranes (MF membranes), ultrafiltration membranes (UF membranes), nanofiltration membranes (NF membranes), and reverse osmosis membranes (RO membranes). Filtration membranes are selected with a pore size that matches the characteristics of the raw water to be treated in the membrane filtration equipment. Regardless of the pore size of the filtration membrane, they all have in common the fact that they can be used to pass water by utilizing the water pressure difference between the primary and secondary sides of the membrane surface to perform filtration or backwashing operations. Therefore, filtration membranes of any pore size may be used in this embodiment.

[0018] For example, multiple membrane modules are stacked so that the water to be treated passes through multiple filtration membranes. In the example shown in Fig. 1, for example, multiple membrane modules are stacked vertically in the membrane immersion tank 20. At this time, the multiple filtration membranes are arranged with sufficient spacing so as not to block the flow path. The water to be treated that flows into the membrane immersion tank 20 passes through the filtration membranes and is filtered by the water pressure within the tank and the suction force of the filtration pump P1.

[0019] The air diffuser 202 is located below the multiple membrane modules. The air diffuser 202 is connected to the cleaning blower B1 and discharges air supplied from the cleaning blower B1 into the water to be treated in the membrane submerged tank 20. The air bubbles discharged from the air diffuser 202 come into contact with the filtration membranes of the multiple membrane modules as they rise from near the bottom to the top of the membrane submerged tank 20. The bubbles remove turbid matter adhering to the surfaces of the filtration membranes, cleaning the membrane modules. Generally, the cleaning airflow rate of the cleaning blower B1 is controlled to a constant value, but the increase in transmembrane pressure can be controlled by actively changing the cleaning airflow rate of the cleaning blower B1 as a control operation variable.

[0020] The membrane filtration treatment tank 30 receives the filtered water (membrane filtered water) sucked from the membrane immersion tank 20 by the filtration pump P1. When backwashing the filtration membrane, the water to be treated in the membrane filtration treatment tank 30 is sucked by the backwash pump P2 and supplied to the membrane immersion tank 20. When the filtration pump P1 supplies the membrane filtered water to the membrane immersion tank 20, the membrane filtered water passes through the filtration membrane in the opposite direction to the flow direction of the filtered water, thereby performing backwashing of the filtration membrane.

[0021] The membrane filtration equipment is also equipped with a flow meter F that measures the flow rate of membrane-filtered water flowing between the membrane immersion tank 20 and the membrane filtration treatment tank 30, a pressure meter P that monitors the state of the filtration membrane in the membrane immersion tank 20, a water level meter H that measures the water level in the membrane immersion tank 20, and a water thermometer T that measures the temperature of the water to be treated in the membrane immersion tank 20. The pressure meter P may also measure the pressure at which the filtration pump P1 draws membrane-filtered water from the membrane immersion tank 20 and the pressure at which the backwash pump P2 discharges membrane-filtered water to the membrane immersion tank 20. A pressure meter that measures the suction pressure of the filtration pump P1 and a pressure meter that measures the discharge pressure of the backwash pump P2 may also be installed to measure the respective pressures. Values ​​measured by these instruments are supplied to the membrane filtration equipment control device 40 as needed.

[0022] For the sake of explanation, Figure 1 shows an example in which there is one membrane filtration system and one chemical injection point in the pretreatment process, but the number of systems is not limited to the one shown. For example, the number of membrane filtration system systems may be two or more, there may be multiple chemical injection points, and the number of chemical injection points may differ from the number of membrane filtration system systems.

[0023] Furthermore, the type of membrane filtration device is not limited, and any type of membrane filtration device other than the tank immersion type shown in the figure may be used as long as it has a measuring instrument capable of measuring values ​​corresponding to the required physical quantities. Figure 1 shows a case of a dead-end filtration type in which all raw water in the membrane immersion tank 20 is obtained as filtrate, but a cross-flow type in which only a portion of the raw water is filtered may also be used. Similarly, when a casing-type filtration membrane is used, either a dead-end filtration type or a cross-flow type may be used.

[0024] In many membrane filtration facilities, backflow water cleaning (hereinafter referred to as backwashing) is performed every several tens of minutes to several hours, in which cleaning water is passed in the opposite direction to the filtered water. In this embodiment, a cycle of repeating filtration, backwashing, filtration, backwashing, ... is referred to as a filtration backwash cycle. A single filtration backwash cycle includes one filtration step and one backwashing step.

[0025] During a filtration backwash cycle, membrane fouling typically increases during the filtration operation and then decreases during the backwash operation. Reversible fouling corresponds to the increase in membrane resistance during filtration that is reduced by backwashing, while irreversible fouling corresponds to the increase in membrane resistance from the membrane resistance after backwashing in the previous filtration backwash cycle that is not removed by backwashing. When the membrane resistance of the filtration membrane reaches its upper limit (exceeds the threshold) due to irreversible fouling, chemical cleaning is required to remove the membrane fouling and reduce the membrane resistance again.

[0026] FIG. 2 is a diagram schematically showing an example of the change over time between the actual value and the target value of the membrane resistance of the filtration membrane. The target resistance value of the filtration membrane, which is set based on the timing of chemical cleaning, which is usually performed every few months to several years, is preferably set in response to changes in membrane resistance due to irreversible fouling. Therefore, it is preferable to calculate the predicted membrane resistance value taking into account changes in membrane resistance due to irreversible fouling. Based on the above considerations, the inventors of the present application have discovered information that is effective for predicting irreversible fouling by quantifying the accumulation, detachment, and remaining state of reversible fouling from changes in membrane resistance that occur during the filtration backwash cycle.

[0027] The membrane filtration equipment control device 40 of this embodiment optimally controls the operating conditions of the membrane filtration equipment using information (membrane filtration index) that is effective in predicting irreversible fouling. The membrane filtration equipment control device 40 is, for example, a computing device equipped with at least one processor and a memory that stores a program executed by the processor, and can realize various functions described below by software or a combination of software and hardware.

[0028] The membrane filtration equipment control device 40 includes a target membrane filtration index setting unit 401, a membrane filtration index calculation unit 402, an index calculation unit 403, an operating condition control unit 404, an operating condition constant control unit 405, and a subtraction unit A1.

[0029] The operating condition fixing control unit 405 controls the operations of the filtration pump P1, backwash pump P2, and cleaning blower B1, and the chlorine injection rate and activated carbon injection rate in the chemical injector, based on preset control conditions. That is, unlike the operating condition control unit 404 described later, the operating condition fixing control unit 405 controls the operating conditions without using feedback control utilizing a membrane filtration index.

[0030] The target membrane filtration index setting unit 401 sets a target value of an index (or a composite index) calculated by the index calculation unit 403 described later. The target value of the index is set, for example, taking into consideration the filtration membrane replacement schedule and the service life of the filtration membrane, and includes time-series information of the target value over the service life of the filtration membrane. The target value of the membrane filtration index may be set, for example, by a mathematical formula, or may be set as a table that associates the target value with the elapsed time since the start of use.

[0031] The membrane filtration index calculation unit 402 calculates the value of the transmembrane pressure difference during filtration (the difference in pressure between the primary and secondary sides of the filtration membrane) from the difference between the water level value measured by the water level gauge H installed in the membrane submerged tank 20 and the suction pressure value of the filtration pump measured by the pressure gauge P installed in the piping leading from the membrane submerged tank 20 to the membrane filtration treatment water tank 30. Similarly, the membrane filtration index calculation unit 402 calculates the value of the transmembrane pressure difference during backwashing from the difference between the water level value of the membrane submerged tank 20 and the discharge pressure value of the backwashing pump P2.

[0032] In the following, a case where the calculated transmembrane pressure value is converted into a transmembrane resistance value according to the following formula will be described, but it may also be expressed as a corrected transmembrane pressure value as will be described later. The membrane filtration index calculation unit 402 acquires the measurement value of the pressure gauge P and the measurement value of the water level gauge H. The membrane filtration index calculation unit 402 calculates the transmembrane pressure of the filtration membrane from the measurement value of the pressure gauge P and the measurement value of the water level gauge H. The transmembrane pressure of the filtration membrane is affected not only by membrane fouling, but also by the viscosity of the fluid (the water to be treated) and the filtration flow rate. In general, the transmembrane pressure is considered to follow the basic membrane filtration equation (1) below, and the transmembrane pressure ΔP can be expressed as the product of the viscosity μ, membrane resistance R, and transmembrane filtration flux J (membrane filtration flow rate divided by the membrane cross-sectional area). ΔP=μ·R·J (1)

[0033] The viscosity μ is largely dependent on the water temperature, and the viscosity μ may be expressed as a temperature correction factor (TCF). Conversely, when the behavior of transmembrane pressure is considered using the basic equation (1) of membrane filtration, the membrane resistance R, which indicates a value that changes substantially due to the membrane fouling phenomenon, can be expressed by the following equation (2). Note that, since the membrane resistance R may take an extremely small value depending on the unit system of physical quantities used, in such cases, the membrane filtration index calculation unit 402 may multiply the calculated value of membrane resistance R by a certain coefficient to make it approximately the same magnitude as other physical quantities.

number

[0034] The membrane resistance R can be used to express the adhesion and detachment state of membrane fouling in the membrane fouling phenomenon. Alternatively, instead of the membrane resistance R, the transmembrane pressure difference ΔP can be expressed as the viscosity μ T Alternatively, the corrected transmembrane pressure ΔP′ converted into the value of the constant flux J0 may be used. In this case, the corrected transmembrane pressure can be expressed by the following equation (3).

number

[0035] FIG. 3 is a time-series diagram showing an example of the membrane resistance of the filtration membrane measured during the filtration backwash cycle. The membrane filtration index calculation unit 402 can calculate the membrane filtration index for each cycle using the information of the filtration time, backwash time, start / end values ​​of membrane resistance during filtration, and start / end values ​​of membrane resistance during backwash for each cycle according to the following equations (4-1)-(4-5).

[0036] Membrane resistance change rate during filtration process: V R [n]=(R f [n]-R0[n]) / T (4-1) Membrane resistance change rate during backwashing process: V BWR [n]=(BWR f [n]-BWR0[n]) / T BW (4-2) Filtration process / backwashing process membrane resistance ratio: R Ratio[n]=R f [n] / BWR0[n] (4-3) Backwashing membrane resistance recovery rate: Recovery Rate[n]=(R f [n]-R0[n+1]) / (R f [n]-R0[n])×100 (4-4) Film resistance change ratio: R / R_initialratio[n]=R0[n] / R0[0] (4-5) R0: Initial value of membrane resistance during filtration process* R f : Final membrane resistance during filtration process* BWR0: Initial membrane resistance during backwashing process* BWR f: Final membrane resistance value during backwashing process* T: Filtration process time T BW :Backwash process time *n during addition represents the number of filtration and backwash cycles.

[0037] In the example of a typical experimental result shown in Figure 3, the membrane resistance R increases during the filtration process, and the membrane resistance BWR decreases during the backwashing process. Below, we will explain the physical interpretation of the membrane filtration index according to this typical experimental result.

[0038] Membrane resistance change rate during filtration process V R corresponds to the amount of foulants that adhered during the filtration process of the corresponding filtration backwash cycle. When filtering raw water with a high concentration of foulants, the membrane resistance change rate during the filtration process, V R On the other hand, when filtering raw water with a low concentration of foulants, the membrane resistance change rate V R The value of Foulants includes both those that contribute to reversible fouling and those that contribute to irreversible fouling.

[0039] Conventionally, the amount of foulants has been measured using water quality measurements such as turbidity, color, E260, and fluorescence intensity. While this method allows the amount of foulants to be measured in raw water before filtration, it is difficult to directly detect increases in substances that contribute to irreversible fouling, such as polysaccharides, which are difficult to measure using water quality measurements.

[0040] Membrane resistance change rate during backwashing process V BWR corresponds to the amount of foulants that peeled off from the filtration membrane during the backwashing process of the corresponding filtration backwashing cycle. When foulants peel off from the membrane during the backwashing process, the membrane resistance of the filtration membrane decreases, so the membrane resistance change rate during the backwashing process V BWR Typically, when there is a lot of reversible fouling during the filtration process, the membrane resistance change rate V BWR On the other hand, when the adhesion of reversible fouling during the filtration process is small, the absolute value of the membrane resistance change rate VBWR The absolute value of becomes smaller.

[0041] Within the scope of the experimental results, the membrane resistance ratio (R Ratio) for the filtration process / backwashing process often takes a value close to 1 in the initial stage of starting to use a new filtration membrane. This is thought to be because, if membrane resistance is solely due to the structure of the filtration membrane, the membrane resistance when filtering liquid is the same in both the filtration direction and the backwashing direction. As the membrane filtration equipment continued to operate, the membrane resistance ratio (R Ratio) for the filtration process / backwashing process sometimes increased and sometimes decreased. This was because the position and form of foulants adhering to the filtration membrane differed depending on the foulant characteristics and operating conditions, which had different effects on membrane resistance.

[0042] The backwash membrane resistance recovery rate indicates the percentage of foulants that have been removed from the filtration membrane by the backwashing process of the corresponding filtration backwash cycle. Even if membrane fouling occurs during the filtration process, if the foulants are removed by the backwashing process, the backwash membrane resistance recovery rate will be around 100%. If the impact of irreversible fouling that is not removed by the backwashing process is significant, the backwash membrane resistance recovery rate will decrease. Depending on the operating conditions, if more foulants than those attached in the previous filtration backwash cycle are removed, the recovery rate may exceed 100%.

[0043] The membrane resistance change ratio R / R_initialratio represents the ratio of the membrane resistance during filtration at the start of operation (when a new filtration membrane begins to be used) to the membrane resistance during filtration in the current filtration backwash cycle (the relevant filtration backwash cycle). This value corresponds to the degree to which irreversible fouling has progressed since the start of operation.

[0044] As described above, the membrane filtration index can represent the operational status of membrane filtration, which changes depending on the raw water conditions and operating conditions. By using the membrane filtration index, the membrane filtration equipment control device of this embodiment can obtain information on the adhesion and detachment of foulants in membrane fouling during the filtration backwash cycle, which has not been available in the past.

[0045] For example, as another method, a method of obtaining information equivalent to that of this embodiment can be considered, for example, by recording all calculated values ​​of membrane resistance measured during the filtration backwash cycle and constructing a machine learning model as time-series data. However, if only data analysis is performed without providing calculations based on such physical interpretations, it is unclear whether information on foulant adhesion and detachment in membrane fouling during the filtration backwash cycle can be obtained. In contrast, the membrane filtration index used in this embodiment is explicitly defined and utilized, so information on foulant adhesion and detachment in membrane fouling can be reliably obtained.

[0046] On the other hand, because the mechanism of membrane fouling is complex, changes and trends in the membrane filtration index that cannot be described in the physical interpretation of this embodiment may be observed depending on the material and pore size of the filtration membrane, the type of membrane module, and the type of raw water. However, even if the physical interpretation of the membrane filtration index has not been determined in advance, the membrane filtration index can be utilized by identifying the prediction model and control parameters described below depending on the individual device and conditions. In addition, by observing the operating status of the filtration membrane with reference to the output membrane filtration index, a physical interpretation can be given to unknown phenomena.

[0047] In addition, in equations (4-1)-(4-5), the average membrane resistance change rate V during the filtration process or backwash process R , V BWR is calculated, but the membrane resistance change rate V R , V BWR does not necessarily have to be the average change rate, and the membrane resistance change rate V R , V BWRThe time range for measuring may be set within the range of cycle times (filtration time and backwash time) T and Tbw.

[0048] In addition to the backwashing method used in this embodiment, backwashing by gas permeation through the membrane filtration can also be used. Furthermore, before and after backwashing, membrane filtration equipment may perform a process of draining water from the primary or secondary side of the membrane filtration, or an operation of cleaning the membrane surface by generating bubbles or a water flow on the membrane filtration surface. In this embodiment, for example, backwashing may be performed with both water and gas, or separate cleaning may be performed before and after backwashing. Other types of cleaning may also be applicable as long as the membrane filtration equipment has a process for periodically removing reversible fouling. Furthermore, the membrane filtration index calculation unit 402 does not necessarily need to calculate all of the contents of equations (4-1)-(4-5). Due to constraints such as the type of physical cleaning and the number and location of measuring instruments, some items may not be calculated. In such cases, the membrane resistance prediction and control described below can be performed using the items that can be calculated.

[0049] Although five types of membrane filtration indexes are listed in the formulas (4-1) to (4-5), the membrane filtration equipment control device 40 that performs control using membrane filtration indexes may also perform control using a composite index value calculated using multiple membrane filtration indexes. This makes it possible to construct index values ​​that contain more useful information for a plant that includes membrane filtration equipment.

[0050] The index calculation unit 403 calculates an index (control amount) using the multiple membrane filtration indices calculated by the membrane filtration index calculation unit 402. The index calculation unit 403 may, for example, calculate any one of the multiple membrane filtration indices as the index, or may calculate a composite index obtained by combining the multiple membrane filtration indices as the index.

[0051] The inventors of the present application have, for example, calculated the membrane resistance change rate V RWhen the manipulated variable is controlled using the index, it has been found through experimental verification that even if the membrane resistance increase rate during filtration is the same value, if the transmembrane pressure reduction effect in the backwashing process is different, the increase rate of irreversible fouling may be different. In contrast, in the membrane filtration equipment control device 40 of this embodiment, the index calculation unit 403 calculates, for example, the membrane resistance change rate V during the filtration process. R By using the backwash membrane resistance recovery rate and the backwash membrane resistance recovery rate, the composite index value is calculated as shown in the following formula (5), and the membrane resistance change rate during the filtration process V R It is possible to calculate a composite index that reflects not only the information on the membrane pressure difference reduction effect in the backwashing process but also the membrane pressure difference reduction effect in the backwashing process.

[0052] Composite Value[n] = a1×V R [n]+a2×Recovery Rate[n] (5) Composite Value[n]: Composite index value V R [n]: membrane resistance change rate during filtration process Recovery Rate[n]: Backwash recovery rate a1, a2: Coefficients for the composite index (including positive and negative information)

[0053] The formula used by the index calculation unit 403 to calculate the composite index is not limited to formula (5), and any formula configured by any combination of two or more membrane filtration indices can be used. The index calculation unit 403 may also calculate the composite index using a formula or flowchart other than a linear combination. The index calculation unit 403 may be omitted when calculation of the composite index is not necessary, such as when one of multiple membrane filtration indices is used as the index.

[0054] The operating condition control unit 404 performs feedback control using, for example, the index calculated by the index calculation unit 403 as a controlled variable and the operating condition set value as a manipulated variable, thereby controlling the index value to a constant. The operating condition control unit 404 receives as input the difference (output value of the subtraction unit A1) obtained by subtracting the index calculated by the index calculation unit 403 from the target value supplied from the target membrane filtration index setting unit 401. The operating condition control unit 404 calculates and outputs the operating condition set value so that the input value follows zero (so that the index follows the target value). As a result, the membrane filtration index measured during the filtration backwash cycle becomes constant, stabilizing the adhesion and detachment of foulants during the filtration backwash cycle and stabilizing the progression of irreversible fouling.

[0055] In this embodiment, for example, the operating condition control unit 404 performs feedback control using the membrane resistance change rate in the filtration process as a controlled variable and the coagulant injection amount as a manipulated variable. Through the feedback control, the operating condition control unit 404 can calculate the coagulant injection amount for controlling the increase in membrane resistance in the filtration process to a constant value.

[0056] In addition, a feedback control in which an index using a membrane filtration index is used as a control variable and an operating condition set value is used as a manipulated variable may be constructed in multiple ways corresponding to each manipulated variable, and different membrane filtration indexes (indexes) may be used to calculate each controlled variable. In addition, the operating condition set value may include a pretreatment condition set value including at least one of a coagulant injection amount, an activated carbon injection amount, a chlorine injection amount, etc., and a membrane filtration condition set value including at least one of a membrane filtration flux value, a cleaning air flow rate value, a filtration process time, a backwash process time, a backwash flux value, etc.

[0057] As described above, according to the membrane filtration equipment control device 40 of this embodiment, by controlling the operating condition setting values ​​using the membrane filtration index, which is an index that reflects the process of foulant adhesion and detachment in membrane fouling during the filtration backwash cycle, it is possible to control the membrane filtration equipment reflecting information on foulant adhesion and detachment in membrane fouling during the filtration backwash cycle, which was not previously available. Furthermore, since the membrane filtration equipment control device 40 of this embodiment performs control using explicitly defined indexes, it is possible to reliably obtain information on foulant adhesion and detachment in membrane fouling during the filtration backwash cycle.

[0058] That is, according to this embodiment, it is possible to provide a membrane filtration equipment control device 40, a membrane filtration equipment control method, and a computer program that perform control that reflects information on the adhesion and detachment of foulants in membrane fouling during a filtration backwash cycle.

[0059] Next, a membrane filtration equipment control device, a membrane filtration equipment control method, and a computer program according to a second embodiment will be described in detail with reference to the drawings. In the following description, the same components as those in the first embodiment will be denoted by the same reference numerals and will not be described again.

[0060] FIG. 4 is a diagram schematically illustrating an example of a process including a membrane filtration facility to which the membrane filtration facility control device of the second embodiment is applied. The membrane filtration equipment control device 40 of this embodiment differs from the first embodiment described above in that it optimally controls the control amounts of the filtration pump P1 and backwash pump P2 of the membrane filtration equipment using information on foulant adhesion and detachment during membrane fouling during the filtration backwash cycle and constraint values.

[0061] The membrane filtration equipment control device 40 of this embodiment includes a total filtered water volume constraint setting unit 400, a membrane filtration index calculation unit 402, an index calculation unit 403, an optimization calculation unit 407, an operating condition optimization control unit 408, an operating cost calculation unit (cost calculation unit) 406, and an operating condition constant control unit 405.

[0062] The operating condition fixing control unit 405 controls the operation of the cleaning blower B1 and the chlorine injection rate, activated carbon injection rate, and coagulant injection rate in the chemical injector based on preset control conditions. That is, unlike the operating condition optimization control unit 408 described later, the operating condition fixing control unit 405 controls the operating conditions without using optimal control utilizing a membrane filtration index.

[0063] The total filtered water volume constraint setting unit 400 sets a constraint value for the total filtered water volume. The total filtered water volume is, for example, a value obtained by subtracting the amount of backwash water consumed by backwashing from the amount of filtered water obtained by the filtration process. The constraint value for the total filtered water volume may be set to a minimum value and a maximum value for the total filtered water volume, or may be set to a value according to the season, outside temperature, or time of day.

[0064] The operating cost calculation unit 406 compiles the operating condition settings and outputs a cost function related to the operation of the membrane filtration equipment. The operating cost calculation unit 406 calculates the operating costs resulting from the settings of multiple manipulated variables. That is, the operating cost calculation unit 406 acquires operating conditions from the operating condition constant control unit 405 and the operating condition optimization control unit 408, and calculates the operating costs (cost function) including the operation of equipment such as the filtration pump P1, backwash pump P2, and cleaning blower B1, and chemical costs, based on the settings such as filtration time, backwash time, and chemical injection rate of coagulant, etc. The operating cost calculation unit 406 previously stores information (cost information) such as the cost required to operate equipment such as the filtration pump P1, backwash pump P2, and cleaning blower B1 per unit time, and the cost of chemicals per unit amount, and can calculate the operating costs using the operating conditions and cost information.

[0065] The membranous filtration index calculation unit 402 can calculate the membranous filtration index using the formulas (4-1)-(4-5) in the same manner as in the first embodiment. The index calculation unit 403 calculates the composite index in the same manner as in the first embodiment. Note that the index calculation unit 403 may be omitted when calculation of the composite index is not necessary, such as when one of the membrane filtration indices is used as the index.

[0066] The optimization calculation unit 407 calculates operating condition setting values ​​that minimize (or optimize) the operating cost (cost function) by setting a constraint value for the total filtered water volume and a penalty based on an index (or composite index). Various optimization problem solving methods can be used as algorithms used by the optimization calculation unit 407 for optimal control. For example, if the optimization problem is described as a linear optimization problem, the optimization calculation unit 407 can solve it using a method such as the simplex method or the interior point method. Even if the optimization problem is extended to a nonlinear one, the optimization calculation unit 407 can solve it using a metaheuristic method such as simulated annealing or particle swarm optimization.

[0067] In this embodiment, the optimization calculation unit 407 calculates the operating condition set values ​​of the filtration pump P1 and the backwash pump P2 based on the filtration time, backwash time, etc., for which the values ​​of the index (or composite index) and the total filtered water volume are within a predetermined set value range and which minimize the operating cost (cost function). Note that the operating condition set values ​​to which the optimization calculation unit 407 applies optimal control are not limited to the operating condition set values ​​of the filtration pump P1 and the backwash pump P2, and the operating condition set values ​​of any configuration may be optimally controlled.

[0068] The operating condition optimization control unit 408 controls the filtration pump P1 and the backwash pump P2 in accordance with the manipulated variable of the operating condition set value supplied from the optimization calculation unit 407. The membrane filtration index calculation unit 402 and the index calculation unit 403 have the same configuration as in the first embodiment described above, and therefore a description thereof will be omitted here.

[0069] For example, if a method is adopted in which the rate of membrane resistance change during filtration is calculated and the physical cleaning interval is adjusted according to a preset threshold, it is not possible to obtain information calculated using indicators other than the rate of membrane resistance change during filtration. Furthermore, when setting a threshold in advance, it is necessary to quantitatively understand the actual increase in membrane resistance and the effect of the physical cleaning interval on differential pressure recovery at the time of setting the threshold.

[0070] In contrast, the membrane filtration equipment control device 40 of this embodiment imposes constraints (penalties) on the membrane filtration index and the total filtered water volume, calculates the cost (cost function) resulting from the set values ​​of multiple manipulated variables, and controls the membrane filtration equipment to minimize the cost function. As described above, by setting an appropriate range for the total filtered water volume and performing feedback control of the membrane filtration index to minimize the cost, it becomes possible to respond to the actually occurring increase in membrane resistance and the differential pressure recovery between physical cleaning intervals by appropriately changing the target value.

[0071] That is, according to this embodiment, it is possible to provide a membrane filtration equipment control device, a membrane filtration equipment control method, and a computer program that perform control that reflects information on foulant adhesion and detachment in membrane fouling during a filtration backwash cycle.

[0072] Next, a membrane filtration equipment control device, a membrane filtration equipment control method, and a computer program according to a third embodiment will be described in detail with reference to the drawings. The membrane filtration equipment control device, membrane filtration equipment control method, and computer program of this embodiment differ from the first and second embodiments in that they control the membrane filtration treatment process using the results of transmembrane pressure prediction of the filtration membrane. Here, in order to effectively control the membrane filtration treatment process using the results of transmembrane pressure prediction of the filtration membrane, it is important to improve the accuracy of predicting the increase in transmembrane pressure due to the progression of irreversible fouling. Furthermore, because chemical cleaning of filtration membranes is often performed in cycles of several months to several years, it is necessary to predict the transmembrane pressure for several days to several weeks in advance in order to effectively perform physical cleaning. If the transmembrane pressure increase is predicted to be smaller than the actual increase, there is a risk that the physical cleaning of the filtration membrane will be insufficient and the chemical cleaning will be performed earlier. Conversely, if the transmembrane pressure increase is predicted to be larger than the actual increase, the physical cleaning of the filtration membrane will be excessive, increasing the running costs of the membrane filtration equipment.

[0073] Therefore, in this embodiment, a membrane filtration equipment control device, a membrane filtration equipment control method, and a computer program will be described, which include a prediction model that predicts the future progression of irreversible fouling using a membrane filtration index calculated from the membrane resistance value measured during a filtration backwash cycle. In the following description, components that overlap with the membrane filtration equipment control device 40 of the first and second embodiments will be assigned the same reference numerals, and descriptions thereof may be omitted.

[0074] FIG. 5 is a diagram schematically illustrating an example of a process including a membrane filtration facility to which the membrane filtration facility control device of the third embodiment is applied. The membrane filtration equipment control device 40 of this embodiment includes a membrane filtration index calculation unit 402, an operating condition control unit 404, an operating condition constant control unit 405, a water quality index measurement unit 409, a predicted resistance calculation unit 410, a target resistance setting unit 411, and a subtraction unit A2.

[0075] The operating condition fixing control unit 405 controls the operation of the filtration pump P1 and the backwash pump P2, and the chlorine injection rate, activated carbon injection rate, and coagulant injection rate in the chemical injector, based on preset control conditions. That is, unlike the operating condition control unit 404 described below, the operating condition fixing control unit 405 controls the operating conditions without using feedback control that utilizes a predicted value of membrane resistance.

[0076] The target resistance setting unit 411 sets time-series information on the target value of the membrane resistance. The target value of the membrane resistance is set, for example, taking into account the filtration membrane replacement schedule and the service life of the filtration membrane, and includes time-series information on the target value over the service life of the filtration membrane. The target value of the predicted membrane resistance may be set, for example, using a mathematical formula or as a table correlating the elapsed time from the start of use with the target value. The target value of the membrane resistance may be determined by calculating a target membrane resistance curve from the planned chemical cleaning period and the membrane resistance after chemical cleaning. In addition, in the case of membrane filtration equipment where the increase in membrane resistance is not significant, a constant membrane resistance target value may be set. In addition, in the case where periodic changes in membrane resistance are observed throughout the year, the average yearly membrane resistance change (e.g., average value or median value) may be calculated and used as the target.

[0077] The water quality index measurement unit 409 acquires detected values ​​of water quality indexes (including organic indexes and hydrogen ion index) from detectors for organic indexes (TOC (total organic carbon), Tu (turbidity), UV (ultraviolet light), and EEM (excitation-emission matrix)) and a hydrogen ion index (pH) detector installed in the pretreatment unit 10. The water quality index measurement unit 409 supplies the acquired detected values ​​of water quality indexes to the predicted resistance calculation unit 410. Note that the above water quality indexes are examples, and the water quality index may include at least one of the pH, turbidity, chromaticity, SS (suspended solids), SDI (silt density index), FI (fouling index), ultraviolet absorbance (E260), fluorescence intensity, zeta potential of suspended solids, and total organic carbon of the water to be treated in the pretreatment process.

[0078] The membranous filtration index calculation unit 402 can calculate the membranous filtration index using the formulas (4-1)-(4-5) in the same manner as in the first embodiment. The predicted resistance calculation unit 410 acquires the membrane filtration index calculated by the membrane filtration index calculation unit 402, the detected value of the water quality index, and the operating conditions set by the operating condition constant control unit 405 and the operating condition control unit 404. Note that the predicted resistance calculation unit 410 can adopt, as operating condition setting values ​​used to calculate the predicted value of membrane resistance, pretreatment condition setting values ​​including at least one of a pH adjuster injection rate, a chlorine injection rate, a coagulant injection rate, an ozone injection rate, and an activated carbon injection rate, and membrane filtration condition setting values ​​including at least one of a membrane filtration flux value, a cleaning airflow value, a filtration process time, a backwash process time, and a backwash flux value.

[0079] The predicted resistance calculation unit 410 can calculate a predicted value of membrane resistance due to irreversible fouling from the acquired value using the following equation (6). Note that equation (6) includes R, which represents membrane resistance due to irreversible fouling, and this represents the membrane resistance immediately after filtration begins during the filtration backwash cycle. Alternatively, R in equation (6) may be any value of membrane resistance that reflects the progression of fouling that is not removed by backwashing, and for example, the hourly average or daily average of the actually measured value may be used.

[0080]

number

[0081] The prediction model of the above formula (6) uses the value of the physical model coefficient A of the membrane filtration resistance as the explanatory variable x i and coefficient a i Linear regression of (Σa i x i The coefficient k represents the progression of blockage, with k = 1 corresponding to intermediate blockage, k = 1.5 corresponding to standard blockage, and k = 2.0 corresponding to complete blockage. After determining the value of k, the coefficient a is adjusted so that the change in membrane resistance matches the actual data. i By identifying the value of , in advance, it is possible to calculate a predicted value.

[0082] In this embodiment, the membrane filtration index calculated by the membrane filtration index calculation unit 402 is used as an explanatory variable x i That is, the membrane filtration index defined by the formulas (4-1) to (4-5) is calculated for each filtration backwash cycle, and the membrane resistance at a certain time after the calculation of the membrane filtration index can be calculated using the calculated value.

[0083] The data used to identify the parameters may be past performance values ​​of the membrane filtration equipment, or experimental data from a laboratory-scale membrane filtration equipment. Furthermore, the parameter identification method may be a least squares method, PLS (Partial Least Square) regression, ridge regression, lasso regression, or the like. Unknown variables may be updated online, such as by online least squares. Any method may be used to determine the unknown variables. When calculating the predicted membrane resistance value in the predicted resistance calculation unit 410, it is possible to arbitrarily determine how far into the future the predicted membrane resistance value should be calculated. Furthermore, it is also possible to arbitrarily determine how far back the membrane filtration index should be used in the prediction model in the predicted resistance calculation unit 410.

[0084] Furthermore, the predicted resistance calculation unit 410 can use various means other than linear regression to calculate the value of the physical model coefficient A. Specifically, it can use linear regression including quadratic or higher terms, or machine learning algorithms such as decision trees, k-nearest neighbors, support vector machines, and neural networks.

[0085] The predicted resistance calculation unit 410 may use a means for directly calculating a predicted value of membrane resistance change due to irreversible fouling from the membrane filtration index. Specifically, a learning model may be constructed using a machine learning algorithm such as multiple regression analysis, decision tree, k-nearest neighbor method, support vector machine, or neural network, with the membrane filtration index as the explanatory variable and the change in membrane resistance or the membrane resistance value after a certain time as the objective variable. Alternatively, the predicted resistance calculation unit 410 may calculate the change in membrane resistance using an ARIMA model with exogenous variables. The above calculations can be expressed by the following equation (7).

[0086]

number

[0087] The predicted resistance calculation unit 410 calculates the explanatory variable x by adding one or more of the following to the membrane filtration index: an operating condition index including at least one of a membrane filtration flux value, a cleaning air volume value, a filtration process time, a backwash process time, and a backwash flux value; a chemical injection index including at least one of a pH adjuster injection rate, a chlorine injection rate, an ozone injection rate, an activated carbon injection rate, and a coagulant injection rate used in the pretreatment; and a water quality index including at least one of pH, turbidity, color, SS (Suspended Solids), SDI (Silt Density Index), FI (Fouling Index), ultraviolet absorbance (E260), fluorescence intensity, zeta potential of suspended solids, and total organic carbon of the water to be treated in the pretreatment process. i It can be used as (t).

[0088] Explanatory variable x i When selecting (t), it is not always appropriate to use all factors, and depending on the characteristics of the membrane filtration equipment and the raw water conditions, some factors may not be appropriate to use as explanatory variables. Also, using a combination of factors may improve accuracy, but may also decrease it. Therefore, the explanatory variables x listed here i It is preferable to select any number of candidates for (t) that are appropriate depending on the situation and use them in equation (7).

[0089] By calculating the predicted value of the membrane resistance of the filtration membrane as described above, it is possible to improve the accuracy of the predicted value of membrane resistance compared to the value calculated based on water quality data measured online, operating condition settings, and water quality items measured in a preliminary survey. For example, when using a prediction model using water quality data measured online, it was difficult to accurately calculate the predicted value of membrane resistance when a phenomenon not anticipated at the time of constructing the prediction model occurred and irreversible fouling progressed. In contrast, in this embodiment, the state of membrane fouling is always calculated using the membrane filtration index, so that the predicted value can be calculated accurately even when an unexpected phenomenon occurs.

[0090] Furthermore, compared to a method that focuses only on irreversible fouling and predicts future irreversible fouling through time series analysis using its time series history, this embodiment also calculates the fouling state measured during the filtration backwash cycle, thereby enabling improved accuracy compared to a method that uses only the time series history of irreversible fouling.

[0091] Next, the advantages of this method will be explained using the results of experiments conducted by the inventors. FIG. 6 shows an example of the results of a filtration experiment using raw water containing membrane foulant A and membrane foulant B. In the early stages of the test, the progression speed of both irreversible fouling caused by membrane foulant A and irreversible fouling caused by membrane foulant B was slow. In contrast, it can be seen that in the final stages of the test, the progression speed of irreversible fouling caused by membrane foulant A increased. In these test results, the rate of membrane resistance change during filtration caused by membrane foulant A was greater than the rate of membrane resistance change during filtration caused by membrane foulant B, and this trend was consistent from the early stages to the end of the filtration test.

[0092] We considered applying a method to predict irreversible fouling to these experimental results. First, a method that uses only the time-series history of membrane resistance due to irreversible fouling is unable to make a sufficient prediction, because the initial irreversible fouling progression speed is sufficiently small for both membrane foulant A and membrane foulant B. Furthermore, even when making predictions based on water quality measurements, there are various types of foulants, including inorganic suspended matter, proteins, humic substances, and polysaccharides, and different instruments are used to measure each, making it difficult to measure everything comprehensively or to compare the degree of influence of each.

[0093] In contrast, the method for calculating the predicted membrane resistance using the membrane filtration index can find that for membrane foulant A, the rate of increase in membrane resistance during filtration is high from the early stages of the filtration test in the experimental results, so the predicted membrane resistance can be calculated taking into account the fact that the situation is such that irreversible fouling of membrane foulant A is likely to progress in the future. The subtraction unit A2 outputs the difference obtained by subtracting the predicted value of the membrane resistance calculated by the predicted resistance calculation unit 410 from the target value set by the target resistance setting unit 411.

[0094] The operating condition control unit 404 performs feedback control using the predicted membrane resistance calculated by the predicted resistance calculation unit 410 as the controlled variable and the operating condition set value as the manipulated variable, thereby controlling the predicted membrane resistance to a constant value. The output value of the subtraction unit A2 is input to the operating condition control unit 404. The operating condition control unit 404 calculates and outputs the operating condition set value so that the input value follows zero. As a result, the predicted membrane resistance becomes constant, which stabilizes the adhesion and detachment of foulants during the cycle at a predetermined time ahead, and makes it possible to stabilize the progression of irreversible fouling.

[0095] The operating condition control unit 404 can perform feedback control by setting the target value of membrane resistance in the part affected by irreversible fouling at a certain time as the target resistance and the operating condition setting value as the manipulated variable, so that the predicted resistance matches the target resistance. This controls the manipulated variable so that the membrane resistance matches the target value, preventing a sudden increase in membrane resistance and stabilizing the operation of the membrane filtration equipment.

[0096] In this embodiment, as an example, the operating condition control unit 404 performs feedback control using the operating conditions of the cleaning blower B1 as the manipulated variable. By using the cleaning air volume of the cleaning blower B1 as the manipulated variable, the operating condition control unit 404 can increase the cleaning air volume of the cleaning blower B1 when the predicted resistance is greater than the target resistance, and can reduce the cleaning air volume of the cleaning blower B1 when the predicted resistance is smaller than the target resistance.

[0097] The accuracy of the predicted resistance is important for optimizing the cleaning airflow rate of the cleaning blower B1. In this embodiment, the membrane filtration index calculated, for example, by equations (4-1)-(4-5) is used to calculate the predicted value, so that the predicted value of the membrane resistance value can be calculated with high accuracy. Therefore, the membrane filtration equipment control device 40 of this embodiment is expected to be effective in optimizing the cleaning airflow rate of the cleaning blower B1. Note that feedback control using the predicted value of the membrane resistance may be implemented in response to each of multiple operation amounts other than the cleaning airflow rate of the cleaning blower B1.

[0098] Because the susceptibility of membrane fouling to progression varies depending on seasonal fluctuations in raw water and the state of membrane fouling up to that point, if physical cleaning conditions (e.g., physical cleaning intervals and chemical addition amounts) were calculated simply based on indicators such as the rate of membrane resistance change during the filtration process, the physical cleaning intensity would be low when membrane fouling adhesion was low and high when adhesion was high. In contrast, the filtration equipment control device of this embodiment calculates a predicted membrane resistance using membrane filtration indicators calculated, for example, by equations (4-1)-(4-5), to stably operate the membrane filtration equipment during the interval until the next chemical cleaning. The physical cleaning intensity is then adjusted using the deviation between the predicted membrane resistance and the target value. This allows for control of the manipulated variable according to the operational status of the membrane filtration equipment, ensuring stable operation of the membrane filtration equipment.

[0099] That is, according to this embodiment, it is possible to provide a membrane filtration equipment control device, a membrane filtration equipment control method, and a computer program that perform control that reflects information on foulant adhesion and detachment in membrane fouling during a filtration backwash cycle.

[0100] Next, a membrane filtration equipment control device, a membrane filtration equipment control method, and a computer program according to a fourth embodiment will be described with reference to the drawings. The membrane filtration equipment control device 40 of this embodiment calculates the cost associated with chemical cleaning calculated from the predicted value of membrane resistance and the cost resulting from the set values ​​of multiple manipulated variables, and performs optimal control of the manipulated variables to minimize the sum of these cost functions. That is, the membrane filtration equipment control device of this embodiment combines the optimal control of the manipulated variables in the second embodiment with the control of the manipulated variables using the predicted value of membrane resistance in the third embodiment. In the following description, components that overlap with the membrane filtration equipment control device 40 of the first to third embodiments will be assigned the same reference numerals and may not be described again.

[0101] FIG. 7 is a diagram schematically illustrating an example of a process including a membrane filtration facility to which the membrane filtration facility control device of the fourth embodiment is applied. The membrane filtration equipment control device 40 of this embodiment includes a total filtered water volume constraint setting unit 400, a membrane filtration index calculation unit 402, an operating condition constant control unit 405, a water quality index measurement unit 409, a predicted resistance calculation unit 410, an operating cost calculation unit (cost calculation unit) 406, an optimization calculation unit 407, and an operating condition optimization control unit 408.

[0102] The operating condition fixing control unit 405 controls the operation of the cleaning blower B1 and the chlorine injection rate, activated carbon injection rate, and coagulant injection rate in the chemical injector based on preset control conditions. That is, unlike the operating condition optimization control unit 408 described later, the operating condition fixing control unit 405 controls the operating conditions without using optimal control utilizing a membrane filtration index.

[0103] The total filtered water volume constraint setting unit 400 sets a constraint value for the total filtered water volume. The total filtered water volume is, for example, a value obtained by subtracting the amount of backwash water consumed by backwashing from the amount of filtered water obtained by the filtration process. The constraint value for the total filtered water volume may be set to a minimum value and a maximum value for the total filtered water volume, or may be set to a value according to the season, outside temperature, or time of day.

[0104] The water quality index measurement unit 409 acquires detected values ​​of water quality indexes (including organic indexes and hydrogen ion index) from detectors for organic indexes (TOC (total organic carbon), Tu (turbidity), UV (ultraviolet light), and EEM (excitation-emission matrix)) and a hydrogen ion index (pH) detector installed in the pretreatment unit 10. The water quality index measurement unit 409 supplies the acquired detected values ​​of water quality indexes to the predicted resistance calculation unit 410. Note that the above water quality indexes are examples, and the water quality index may include at least one of the pH, turbidity, chromaticity, SS (suspended solids), SDI (silt density index), FI (fouling index), ultraviolet absorbance (E260), fluorescence intensity, zeta potential of suspended solids, and total organic carbon of the water to be treated in the pretreatment process.

[0105] The predicted resistance calculation unit 410 acquires the membrane filtration index calculated by the membrane filtration index calculation unit 402, the detected value of the water quality index, and the operating conditions set by the operating condition constant control unit 405 and the operating condition control unit 404. The predicted resistance calculation unit 410 can calculate the predicted value of the membrane resistance due to irreversible fouling from the acquired value using the above formula (6), as in the third embodiment.

[0106] The membranous filtration index calculation unit 402 can calculate the membranous filtration index using the formulas (4-1)-(4-5) in the same manner as in the first embodiment. The operating cost calculation unit 406 calculates the timing for chemical cleaning (e.g., filtration backwash cycle) from the predicted membrane resistance value calculated by the predicted resistance calculation unit 410, and calculates the chemical cleaning cost per unit time (e.g., per single filtration backwash cycle) from the timing for chemical cleaning. The operating cost calculation unit 406 also acquires set values ​​for operating conditions such as filtration time and backwash time used in the operating condition constant control unit 405, and calculates the operating costs of the filtration pump P1 and the backwash pump P2. The operating cost calculation unit 406 calculates the sum of the chemical cleaning cost and the operating cost as a cost function.

[0107] The optimization calculation unit 407 performs optimal control of the manipulated variables so as to minimize (or optimize) the cost function while satisfying the constraints on the total amount of filtered water. In this embodiment, the optimization calculation unit 407 aggregates the operating condition setting values ​​acquired from the operating condition constant control unit 405 and the operating condition optimization control unit 408 and the predicted membrane resistance value acquired from the predicted resistance calculation unit 410, and calculates a cost function related to the operation and long-term maintenance management of the membrane filtration equipment control device. The optimization calculation unit 407 optimizes the operating conditions of the filtration pump P1 and the backwash pump P2 so as to minimize the cost function while satisfying the constraints.

[0108] As in the second embodiment, the optimization calculation unit 407 can use various methods for solving optimization problems as algorithms for optimal control. For example, if the optimization problem is described as a linear optimization problem, the optimization calculation unit 407 can solve it using a method such as the simplex method or the interior point method. Furthermore, even if the optimization problem is expanded to a nonlinear one, the optimization calculation unit 407 can solve it using a metaheuristic method such as simulated annealing or particle swarm optimization.

[0109] The operating condition optimization control unit 408 controls the operations of the filtration pump P1 and the backwash pump P2 in accordance with the operating conditions calculated by the optimization calculation unit 407.

[0110] According to the present embodiment, it is possible to obtain the same effects as those of the first to third embodiments described above, and it is possible to provide a membrane filtration equipment control device, a membrane filtration equipment control method, and a computer program that perform control that reflects information on the adhesion and detachment of foulants in membrane fouling during a filtration backwash cycle.

[0111] Next, modifications of the membrane filtration equipment control device according to the first to fourth embodiments will be described. For example, the membrane filtration equipment control device according to the first to fourth embodiments may be installed in a membrane filtration equipment operation support system. FIG. 8 is a diagram schematically illustrating an example of the configuration of a membrane filtration equipment operation support system including a membrane filtration equipment control device according to one embodiment.

[0112] The membrane filtration equipment operation support system 100 includes a pretreatment equipment control panel 50, a membrane submerged tank control panel 60, a server 70, and a terminal device 90. The pretreatment equipment control panel 50, the membrane submerged tank control panel 60, the server 70, and the terminal device 90 are communicably connected via a network 80.

[0113] Values ​​detected by detectors for organic indicators (TOC (total organic carbon), Tu (turbidity), UV (ultraviolet light), EEM (excitation-emission matrix)) installed in the pretreatment unit 10 and values ​​measured by measuring instruments such as a pressure gauge, water level gauge, thermometer, and flow meter installed in the membrane filtration equipment can be supplied to the server 70, the pretreatment equipment control panel 50, and the membrane immersion tank control panel 60 via a network 80. The network 80 can be a LAN, a WAN, an intranet, the Internet, or a combination of these.

[0114] In this modification, the server 70, the pretreatment equipment control panel 50, and the membrane immersion tank control panel 60 are configured to share and execute the functions of the membrane filtration equipment control device 40 of the first to fourth embodiments described above.

[0115] The server 70 may be a single physical server device or a cloud server configured from multiple server devices. The server 70 includes at least one processor and a memory that stores a program executed by the processor, and can execute at least some of the functions of the membrane filtration equipment control device 40 of the first to fourth embodiments by software or a combination of software and hardware.

[0116] The pretreatment equipment control panel 50 and the membrane immersion tank control panel 60 each include a PLC (Programmable Logic Controller). The PLCs of the pretreatment equipment control panel 50 and the membrane immersion tank control panel 60 are configured to execute at least some of the functions of the membrane filtration equipment control device 40 of the first to fourth embodiments.

[0117] As an example, the server 70 may calculate predicted values ​​of the membrane filtration index and membrane resistance, and use the calculated values ​​to calculate appropriate operating conditions, and the pretreatment equipment control panel 50 and the membrane immersion tank control panel 60 may control the chemical injector, cleaning blower B1, filtration pump P1, and backwash pump P2 according to the operating conditions calculated by the server 70.

[0118] The server 70 includes a calculated value output unit (not shown) that generates display information displaying values ​​calculated by the server 70 and values ​​calculated by the pretreatment equipment control panel 50 and the membrane immersion tank control panel 60, and transmits the display information to the terminal device 90. The server 70 may also display the generated display information on paper media. By displaying calculated values ​​such as the membrane filtration index, predicted membrane resistance, and operating conditions on the display of the terminal device 90 or on a medium such as paper, it is possible to provide the operation manager with information useful for operating the membrane filtration equipment. For example, the operation manager can be supported by being presented with the calculated values ​​of the membrane filtration index, predicted membrane resistance, and recommended operating conditions calculated based on feedback control and optimal control algorithms.

[0119] The terminal device 90 may be a personal computer, a tablet terminal, a smartphone, etc., and the server 70, the pretreatment equipment control panel 50, and the membrane immersion tank control panel 60 may present calculated values ​​to multiple terminal devices 90.

[0120] The membrane filtration equipment operation support system 100 according to the above-described modified example can be applied even to facilities where it is difficult to automatically operate power equipment such as blowers and pumps due to restrictions associated with modifications or restrictions on the functions of the PLCs used, for example.

[0121] The division of functions of the membrane filtration equipment control device 40 among the server 70, pretreatment equipment control panel 50, and membrane submerged tank control panel 60 can be set appropriately depending on the facility, and in actual operation, for example, the cleaning air volume and filtration time may be directly controlled by signals from the PLC of the membrane submerged tank control panel 60, while the server 70 may calculate the membrane filtration index, calculate the predicted resistance, calculate the appropriate value for the coagulant injection amount, etc., and present the calculation results to the operation manager via the terminal device 90, etc. Furthermore, the calculation value output unit may be provided in either the pretreatment equipment control panel 50 or the membrane submerged tank control panel 60, or each of the server 70, pretreatment equipment control panel 50, and membrane submerged tank control panel 60 may have a calculation value output unit.

[0122] The membrane filtration equipment operation support system 100 calculates a membrane filtration index, which is an index reflecting the process of foulant adhesion and detachment during membrane fouling during the filtration backwash cycle, from the change in transmembrane pressure over time. The system predicts irreversible fouling (i.e., membrane resistance) using the membrane filtration index. The system also controls the cleaning airflow using the deviation between the predicted membrane resistance and the target resistance, and provides the calculated membrane resistance and the predicted membrane resistance to the operation manager. As with the first to fourth embodiments, the membrane filtration equipment operation support system 100 of this modification can accurately calculate the predicted resistance using information that has not been utilized until now, enabling more effective control. That is, a membrane filtration equipment operation support system, a membrane filtration equipment control device, a membrane filtration equipment control method, and a computer program can be provided that perform control reflecting information on foulant adhesion and detachment during membrane fouling during the filtration backwash cycle. Furthermore, the membrane filtration equipment operation support system 100 of this modified example can support the operation manager by providing the operation manager with the calculated values ​​of the membrane filtration index and the predicted resistance values.

[0123] The program according to this embodiment may be transferred in a state where it is stored in an electronic device, or in a state where it is not stored in an electronic device. In the latter case, the program may be transferred via a network, or in a state where it is stored in a storage medium. The storage medium is a non-transitory tangible medium. The storage medium is a computer-readable medium. The storage medium may be in any form, such as a CD-ROM or a memory card, as long as it is capable of storing the program and is computer-readable.

[0124] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0125] 10...Pretreatment unit, 20...Membrane immersion tank, 30...Membrane filtration treatment tank, 40...Membrane filtration equipment control device, 50...Pretreatment equipment control panel, 60...Membrane immersion tank control panel, 70...Server, 80...Network, 90...Terminal device, 100...Membrane filtration equipment operation support system, 201...Membrane filtration unit, 202...Aeration device, 400...Total filtered water volume constraint setting unit, 401...Target membrane filtration index setting unit, 402...Membrane filtration index calculation unit, 403...Index calculation unit, 404...Operating condition control unit, 405...Operating condition constant control unit, 406...Operating cost calculation unit (cost calculation unit), 407...Optimization calculation unit, 408...Operating condition optimization control unit, 409...Water quality index measurement unit, 410...Predicted resistance calculation unit, 411...Target resistance setting unit, A1...Subtraction unit, A2...Subtraction unit, B1...Cleaning blower, P1...Filtration pump, P2...Backwash pump

Claims

1. A control device for controlling membrane filtration equipment that performs a filtration process in which treated water is filtered through a separation membrane using a separation membrane that separates solids contained in the liquid from the liquid to obtain treated water, and a backwashing process in which the treated water is passed through the separation membrane in a direction opposite to the water passing direction in the filtration process to perform backflow water washing. a membrane filtration index calculation unit that calculates a membrane filtration index representing information on adhesion and detachment of foulants in membrane fouling of the separation membrane using a transmembrane pressure difference that is a difference in pressure between the primary side and the secondary side of the separation membrane; an operating condition control unit that controls the membrane filtration equipment according to operating conditions calculated using the membrane filtration index; A membrane filtration equipment control device equipped with the above.

2. The membrane filtration index includes at least one of a membrane resistance change rate during a filtration process, a membrane resistance change rate during a backwashing process, a membrane resistance ratio during a filtration process / backwashing process, a backwashing membrane resistance recovery rate, and a membrane resistance change ratio due to a change in the membrane differential pressure over time. The membrane filtration equipment control device according to claim 1.

3. The membrane filtration equipment control device according to claim 1 , wherein the operating condition control unit calculates the operating conditions so that the membrane filtration index follows a target value.

4. a cost calculation unit that calculates a cost function related to the operation of the membrane filtration equipment by aggregating the set values ​​of the operating conditions; The membrane filtration equipment control device according to claim 1 , further comprising: an optimization calculation unit that calculates the operating conditions so that the cost function becomes an optimal value using the membrane filtration index as a constraint condition.

5. A predicted resistance calculation unit is provided that calculates a predicted value of the membrane resistance of the separation membrane using the membrane filtration index, The membrane filtration equipment control device according to claim 1 , wherein the operating condition control unit controls the operating conditions so that the predicted value follows a target value.

6. A predicted resistance calculation unit is provided that calculates a predicted value of the membrane resistance of the separation membrane using the membrane filtration index, a cost calculation unit that calculates a filtration backwash cycle for performing the filtration process and the backwash process based on the predicted values, and calculates a cost function related to the operation of the membrane filtration equipment according to the filtration backwash cycle; The membrane filtration equipment control device according to claim 1 , further comprising: an optimization calculation unit that calculates the operating conditions so that the cost function becomes an optimal value using the membrane filtration index as a constraint condition.

7. The membrane filtration equipment includes a chemical injector that injects at least one chemical selected from the group consisting of a pH adjuster, chlorine, a coagulant, ozone, and activated carbon into the water to be treated, The predicted resistance calculation unit, in addition to the membrane filtration index, a water quality index including at least one value of pH, turbidity, color, E260, fluorescence intensity, zeta potential of suspended solids, or total organic carbon of the water to be treated; An operating condition index including at least one of a membrane filtration flux value, a cleaning air volume value, a filtration process time, a backwash process time, and a backwash flux value; a chemical injection index including at least one value of a pH adjuster injection rate, a chlorine injection rate, a coagulant injection rate, an ozone injection rate, and an activated carbon injection rate; The membrane filtration equipment control device according to claim 5 or 6, wherein the predicted resistance is calculated using at least one of the following:

8. The membrane filtration equipment includes a chemical injector that injects at least one chemical selected from the group consisting of a pH adjuster, chlorine, a coagulant, ozone, and activated carbon into the water to be treated, The operating conditions include at least one of a membrane filtration condition set value including a membrane filtration flux value, a cleaning air volume value, a filtration process time, a backwash process time, and a backwash flux value, and a pH adjuster injection rate, a chlorine injection rate, a coagulant injection rate, an ozone injection rate, and an activated carbon injection rate. The membrane filtration equipment control device according to claim 1, including at least one of the pretreatment condition set values ​​including at least one value.

9. A control method for controlling membrane filtration equipment that performs a filtration process in which treated water is filtered through a separation membrane using a separation membrane that separates solids contained in the liquid from the liquid to obtain treated water, and a backwashing process in which the treated water is passed through the separation membrane in a direction opposite to the water passing direction in the filtration process to perform backflow water washing. A membrane filtration index representing information on adhesion and detachment of foulants in membrane fouling of the separation membrane is calculated using a transmembrane pressure difference, which is the difference in pressure between the primary side and the secondary side of the separation membrane; A membrane filtration equipment control method, which controls the membrane filtration equipment according to operating conditions calculated using the membrane filtration index.

10. A computer program that causes a computer to execute the membrane filtration equipment control method according to claim 9.

11. An operation support system for membrane filtration equipment that performs a filtration process in which treated water is filtered through a separation membrane using a separation membrane that separates solids contained in the liquid from the liquid to obtain treated water, and a backwashing process in which the treated water is passed through the separation membrane in a direction opposite to the water passing direction in the filtration process to perform backflow water washing, a membrane filtration index calculation unit that calculates a membrane filtration index representing information on adhesion and detachment of foulants in membrane fouling of the separation membrane using a transmembrane pressure difference that is a difference in pressure between the primary side and the secondary side of the separation membrane; A membrane filtration equipment operation support system comprising: a calculated value output unit that generates and outputs display information including the value of the membrane filtration index.

Images