Membrane filtration system, membrane filtration method, flocculant addition device, and control device for flocculant addition device

Abstract

To provide a membrane filtration system capable of suppressing membrane fouling and ensuring stable operation even when properties of treated water fluctuate in membrane filtration treatment using a filtration membrane.SOLUTION: A membrane filtration system 1 comprises: a main membrane filtration unit 10 that filters treated water using a main filtration membrane; a sub-membrane filtration unit 12 that filters branched treated water branched from the treated water in the main membrane filtration unit 10 using a sub filtration membrane; main coagulant adding means that adds a main coagulant to the treated water in the main membrane filtration unit 10; sub-filtration resistance detection means that detects filtration resistance values of the sub filtration membrane; and output means that performs predetermined output based on the filtration resistance values detected by the sub-filtration resistance detection means.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a membrane filtration system that performs membrane filtration of water to be treated using a filtration membrane such as a turbidity removing membrane, a membrane filtration method, a flocculant addition device used in the membrane filtration system, and a control device for the flocculant addition device. [Background technology]

[0002] The recent rise in water demand has led to an increasing demand for the recovery and reuse of wastewater. One method for recovering and reusing wastewater involves membrane filtration of biologically treated water or solid-liquid separated water containing suspended solids, using a filtration membrane such as a turbidity-removing membrane, after biological treatment, coagulation, and solid-liquid separation. In this method, fluctuations in the properties of the water to be treated can make the biological treatment, coagulation, and solid-liquid separation unstable, leading to membrane fouling (blockage) during membrane filtration.

[0003] In order to perform control linked to fluctuations in the properties of the water to be treated, a method is known in which the coagulation conditions are changed depending on the turbidity, chromaticity, ultraviolet absorbance, etc. of the water to be treated (see, for example, Patent Document 1).

[0004] When control linked to fluctuations in the properties of the water to be treated is performed using turbidity, color, ultraviolet absorbance, etc., if membrane fouling is caused by water quality factors (such as alkalinity) that cannot be detected by these methods, membrane fouling may occur even if control linked to fluctuations in the properties of the water to be treated is performed.In addition, increasing the number of water quality measurement devices to respond to various water quality fluctuations is economically inefficient. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-223846 Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to provide a membrane filtration system, a membrane filtration method, a coagulant addition device used in the membrane filtration system, and a control device for the coagulant addition device that can suppress membrane fouling and operate stably even if the properties of the water to be treated fluctuate in a membrane filtration process using a filtration membrane. [Means for solving the problem]

[0007] The present invention comprises a main membrane filtration device that filters water to be treated using a main filtration membrane, a sub-membrane filtration device that filters branched water to be treated that is branched from the water to be treated of the main membrane filtration device using a sub-filtration membrane, a main flocculant adding means that adds a main flocculant to the water to be treated of the main membrane filtration device, a sub-filtration resistance detecting means that detects the filtration resistance value of the sub-filtration membrane, and an output means that performs a predetermined output based on the filtration resistance value detected by the sub-filtration resistance detecting means. A control means for controlling the conditions of the main flocculant addition means based on the filtration resistance value detected by the sub-filtration resistance detection means; and a recording unit for storing data on the filtration resistance value detected by the sub-filtration resistance detection means. Equipped with The data stored in the recording unit is used as training data. It is a membrane filtration system.

[0008] In the membrane filtration system, the sub-membrane filtration device is preferably a device for filtering branched treated water branched from the treated water to which the main flocculant has been added by the main flocculant adding means.

[0009] It is preferable that the membrane filtration system further comprises a sub-flocculant addition means for adding a sub-flocculant to the branched treated water of the sub-membrane filtration device, and that the sub-membrane filtration device is a device for filtering the branched treated water that is branched from the treated water before the main flocculant is added and has had the sub-flocculant added by the sub-flocculant addition means.

[0010] In the membrane filtration system, it is preferable that water is passed through the sub-membrane filtration device at a higher flux than that of the main membrane filtration device.

[0013] The present invention includes a main membrane filtration process of filtering water to be treated using a main filtration membrane, a sub-membrane filtration process of filtering branched water to be treated branched from the water to be treated in the main membrane filtration process using a sub-filtration membrane, a main flocculant addition process of adding a main flocculant to the water to be treated in the main membrane filtration process, a sub-filtration resistance detection process of detecting a filtration resistance value of the sub-filtration membrane, and an output process of performing a predetermined output based on the filtration resistance value detected in the sub-filtration resistance detection process. The conditions of the main flocculant addition step are controlled based on the filtration resistance value detected in the sub-filtration resistance detection step, and the data of the filtration resistance value detected in the sub-filtration resistance detection step is used as training data. , a membrane filtration method.

[0014] In the sub-membrane filtration step of the membrane filtration method, it is preferable to filter branched water to be treated that is branched from the water to be treated to which the main flocculant has been added in the main flocculant adding step.

[0015] It is preferable that the membrane filtration method further includes a sub-flocculant addition step of adding a sub-flocculant to the branched treated water in the sub-membrane filtration step, and that in the sub-membrane filtration step, the branched treated water that is branched from the treated water before the addition of the main flocculant and to which the sub-flocculant has been added in the sub-flocculant addition step is filtered.

[0016] In the membrane filtration method, it is preferable that water is passed through the sub-membrane filtration step at a higher flux than that in the main membrane filtration step.

[0019] The present invention is a flocculant addition device that adds a main flocculant to water to be treated in a main membrane filtration device that filters water to be treated using a main filtration membrane, and includes: a sub-membrane filtration device that filters branched water to be treated that is branched from the water to be treated in the main membrane filtration device using a sub-filtration membrane; a main flocculant addition means that adds a main flocculant to the water to be treated in the main membrane filtration device; a sub-filtration resistance detection means that detects the filtration resistance value of the sub-filtration membrane; and a control means that controls the conditions of the main flocculant addition means based on the filtration resistance value detected by the sub-filtration resistance detection means. a recording unit for storing data of the filtering resistance value detected by the sub-filtering resistance detecting means; Equipped with The data stored in the recording unit is used as training data. This is a flocculant addition device.

[0020] In the flocculant addition device, the sub-membrane filtration device is preferably a device for filtering branched water to be treated that is branched from the water to be treated to which the main flocculant has been added by the main flocculant addition means.

[0021] It is preferable that the coagulant addition device further comprises a sub-coagulant addition means for adding a sub-coagulant to the branched treated water of the sub-membrane filtration device, and that the sub-membrane filtration device is a device for filtering branched treated water that is branched from the treated water before the main coagulant is added and has had the sub-coagulant added by the sub-coagulant addition means.

[0022] In the coagulant addition device, it is preferable that water is passed through the sub-membrane filtration device at a higher flux than that of the main membrane filtration device.

[0024] The present invention provides a control device for a coagulant addition device that controls the addition of a main coagulant to water to be treated in a main membrane filtration device that filters water to be treated using a main filtration membrane, the coagulant addition device comprising: a sub-membrane filtration device that filters branched water to be treated branched from the water to be treated in the main membrane filtration device using a sub-filtration membrane; a main coagulant addition means that adds a main coagulant to the water to be treated in the main membrane filtration device; and a sub-filtration resistance detection means that detects the filtration resistance value of the sub-filtration membrane, and a control means that controls the conditions of the main coagulant addition means based on the filtration resistance value detected by the sub-filtration resistance detection means. a recording unit for storing data on the filtering resistance value detected by the sub-filtering resistance detecting means; Equipped with The data stored in the recording unit is used as training data. This is a control device for a flocculant addition device.

[0025] In the control device of the coagulant addition device, it is preferable that the sub-membrane filtration device is a device that filters branched treated water branched from the treated water to which the main coagulant has been added by the main coagulant addition means.

[0026] In the control device of the coagulant addition device, it is preferable that the coagulant addition device further includes a sub-coagulant addition means for adding a sub-coagulant to the branched treated water of the sub-membrane filtration device, and that the sub-membrane filtration device is a device for filtering branched treated water that is branched from the treated water before the main coagulant is added and has had the sub-coagulant added by the sub-coagulant addition means.

[0027] In the control device of the coagulant addition device, it is preferable that water is passed through the sub-membrane filtration device at a higher flux than that of the main membrane filtration device. [Effects of the Invention]

[0029] The present invention provides a membrane filtration system, a membrane filtration method, a coagulant addition device used in the membrane filtration system, and a control device for the coagulant addition device that can suppress membrane fouling and operate stably even if the properties of the water to be treated fluctuate in a membrane filtration process using a filtration membrane. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a schematic configuration diagram illustrating an example of a membrane filtration system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic configuration diagram showing another example of a membrane filtration system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present invention. The embodiment is an example of implementing the present invention, and the present invention is not limited to the embodiment.

[0032] <Membrane filtration method and membrane filtration system> An example of a membrane filtration system according to an embodiment of the present invention is outlined in FIG. 1, and its configuration will be described.

[0033] The membrane filtration system 1 includes a main membrane filtration device 10 that filters water to be treated using a main filtration membrane, a sub-membrane filtration device 12 that filters branched water to be treated branched from the water to be treated in the main membrane filtration device 10 using a sub-filtration membrane, a main flocculant addition device 20 as main flocculant addition means that adds a main flocculant to the water to be treated in the main membrane filtration device 10, a sub-filtration resistance detection device 14 as sub-filtration resistance detection means for detecting the filtration resistance value of the sub-filtration membrane, and an output unit 16 as output means that produces a predetermined output based on the filtration resistance value detected by the sub-filtration resistance detection device 14. The membrane filtration system 1 may also include a control device 18 as control means. The membrane filtration system 1 may include a treated water tank 22 for storing treated water obtained in the main membrane filtration device 10, a main backwash piping 30 as a main backwashing means for backwashing the main filtration membrane of the main membrane filtration device 10 and backwashing with the addition of chemicals, and a sub-backwash piping 36 as a sub-backwashing means for backwashing the sub-filtration membrane of the sub-membrane filtration device 12 and backwashing with the addition of chemicals.

[0034] In the membrane filtration system 1 of Fig. 1, a main treated water pipe 24 is connected to the treated water inlet of the main membrane filtration device 10. The main treated water outlet and the inlet of the treated water tank 22 are connected by a main treated water pipe 26, and the main treated water outlet of the treated water tank 22 is connected to a main treated water pipe 28. The main backwash liquid outlet of the treated water tank 22 and the main backwash liquid inlet on the secondary side of the main membrane filtration device 10 are connected by a main backwash pipe 30. The main backwash effluent outlet on the primary side of the main membrane filtration device 10 is connected to a main backwash effluent pipe 32. The outlet of the main flocculant addition device 20 and the main treated water pipe 24 are connected by a main flocculant addition pipe 42.

[0035] A sub-branch treated water pipe 34, which branches off from the main treated water pipe 24 downstream of the connection point of the main coagulant addition pipe 42, is connected to the branch treated water inlet of the sub-membrane filtration device 12, and a sub-treated water pipe 40 is connected to the sub-treated water outlet. The sub-backwash liquid outlet of the treated water tank 22 and the sub-backwash liquid inlet on the secondary side of the sub-membrane filtration device 12 are connected by a sub-backwash piping 36. A sub-backwash effluent outlet on the primary side of the sub-membrane filtration device 12 is connected to a sub-backwash effluent pipe 38. A sub-filtration resistance detection device 14 is installed on the secondary side of the sub-membrane filtration device 12.

[0036] The output unit 16 and the sub-filtration resistance detection device 14, the output unit 16 and the control device 18, the sub-filtration resistance detection device 14 and the control device 18, and the control device 18 and the main coagulant addition device 20 may be communicatively connected via wired or wireless electrical connections. The membrane filtration system 1 may further include a communication device as a communication means. The communication device is connected to the control device 18, for example, to a server via the Internet. The server is provided with at least a recording unit or a calculation unit. The recording unit stores data such as the filtration resistance value measured by the sub-filtration resistance detection device 14. The calculation unit performs calculations using data such as the filtration resistance value measured by the sub-filtration resistance detection device 14, and outputs an alarm or the execution of main coagulant addition by the main coagulant addition device 20. The data stored in the recording unit may also be used to calculate and store or output the coagulant addition history, amount of coagulant used, and coagulant cost. The output may be sent back to the control device 18 via the Internet, where it may issue an alarm to the output unit 16, execute coagulant addition, or change the coagulant addition conditions.

[0037] The membrane filtration method and the operation of the membrane filtration system 1 according to this embodiment will be described.

[0038] The water to be treated is sent to the main membrane filtration device 10 through the main water to be treated pipe 24. Here, in the main water to be treated pipe 24, a main flocculant is added to the water to be treated from the main flocculant addition device 20 through the main flocculant addition pipe 42 (main flocculant addition process). In the main membrane filtration device 10, membrane filtration of the water to be treated is performed using the main filtration membrane (main membrane filtration process). The obtained main treated water is sent to the treated water tank 22 through the main treated water pipe 26 as needed and stored therein. The main treated water stored in the treated water tank 22 is discharged through the main treated water pipe 28.

[0039] Meanwhile, branched treated water branched from the treated water to which the main flocculant has been added by the main flocculant addition device 20 is sent to the sub-membrane filtration device 12 through the sub-branched treated water piping 34. In the sub-membrane filtration device 12, membrane filtration of the branched treated water is performed using a sub-filtration membrane (sub-membrane filtration step). The obtained sub-treated water is discharged through the sub-treated water piping 40.

[0040] The main membrane filtration device 10 and the sub-membrane filtration device 12 repeatedly perform a membrane filtration process and a cleaning process. The cleaning process can be classified into two types: a backwashing process in which treated water is passed from the secondary side of the filtration membrane to the primary side, and a chemical-addition backwashing process in which chemicals such as acids, alkalis, and oxidizing agents are added during the backwashing process. At least one of these cleaning processes may be performed.

[0041] In the sub-membrane filtration device 12, the sub-filtration resistance value may be measured by the sub-filtration resistance detection device 14 during the filtration process.

[0042] In the membrane filtration system 1, the main membrane filtration device 10 is cleaned, for example, periodically, when the main membrane filtration device 10 is continuously operated. The cleaning of the main filtration membrane is performed, for example, by backflowing at least a portion of the main treated water from the treated water tank 22 as main backwash water from the secondary side to the primary side of the main membrane filtration device 10 through the main backwash piping 30 (main backwash process). The main backwash effluent is discharged from the primary side of the main membrane filtration device 10 through the main backwash effluent piping 32.

[0043] If the fouling of the main filtration membrane is not resolved even after performing this main backwash, chemical-added backwashing is performed using a main chemical-added backwash solution prepared by adding a chemical to the main backwash water (main chemical-added backwashing process). In the main chemical-added backwashing process, for example, the main chemical-added backwash solution, in which a chemical has been added to at least a portion of the main treated water, is backflowed from the secondary side to the primary side of the main membrane filtration device 10 through the main backwash piping 30 (main chemical-added backwashing process). The main chemical-added backwashing effluent is discharged from the primary side of the main membrane filtration device 10 through the main backwash effluent piping 32. In the main chemical-added backwashing process, an immersion process may be performed in which the main filtration membrane is immersed in the main chemical-added backwashing solution for a predetermined time. Furthermore, in the main chemical-added backwashing process, the main chemical-added backwashing effluent discharged from the primary side of the main membrane filtration device 10 may be circulated to the secondary side of the main membrane filtration device 10.

[0044] As described above, fluctuations in the properties of the water to be treated, etc., can cause the upstream biological treatment, coagulation, and solid-liquid separation processes to become unstable, which can lead to membrane fouling (blockage) in the membrane filtration process. In the membrane filtration system 1, in addition to the main membrane filtration process using the main membrane filtration device 10, a sub-membrane filtration process using a sub-membrane filtration device 12 equipped with sub-filtration resistance detection means for detecting the filtration resistance value of the sub-filtration membrane is provided, and based on the filtration resistance value in the sub-membrane filtration process detected by the sub-filtration resistance detection device 14, which is the sub-filtration resistance detection means, an output according to the state of membrane filtration in the sub-membrane filtration device 12 is issued, for example, an alarm or other output is issued when the filtration resistance value exceeds a predetermined threshold.

[0045] For example, it is preferable that the filtration resistance value of the sub-membrane filtration device 12 is recorded, and when a predetermined condition is met, the amount of coagulant added to the main membrane filtration device 10, etc. is controlled.

[0046] In the membrane filtration system 1 of FIG. 1, for example, at least one of the following controls (1) to (3) using the sub-filtration resistance value may be performed.

[0047] (1) For example, when the rate of increase in the sub-filtration resistance value during the filtration process of the sub-membrane filtration device 12 exceeds a predetermined value, the amount of main coagulant added by the main coagulant addition device 20 in the main membrane filtration device 10 is increased.

[0048] (2) For example, when the "sub-filtration resistance value after cleaning" vs. "slope of the filtration volume of the sub-membrane filtration device" in the sub-membrane filtration device 12 becomes equal to or greater than a predetermined value, the amount of main coagulant added by the main coagulant addition device 20 in the main membrane filtration device 10 is increased.

[0049] (3) For example, while changing the amount of main coagulant added in the main membrane filtration device 10, the “sub-filtration resistance value after cleaning” versus the “slope of the filtration volume of the sub-membrane filtration device” is calculated, and the amount of main coagulant added by the main coagulant addition device 20 in the main membrane filtration device 10 is controlled to find the condition under which the slope becomes small or to approach that condition.

[0050] This allows early detection of fouling of the sub-filtration membrane in the sub-membrane filtration device 12. If fouling of the sub-filtration membrane is detected, the coagulant addition conditions in the main membrane filtration device 10 can be changed, thereby suppressing membrane fouling even if the properties of the water to be treated fluctuate, enabling stable operation of the main membrane filtration device 10. By providing the sub-membrane filtration device 12 separately from the main membrane filtration device 10, the coagulant addition conditions can be changed without stopping the main membrane filtration device 10, and the main membrane filtration process can be continued. This allows the operating time of the main membrane filtration device 10 to be maximized.

[0051] Another example of a membrane filtration system according to an embodiment of the present invention is shown in Figure 2. The membrane filtration system 3 shown in Figure 2 includes a main membrane filtration unit 10 that filters water to be treated using a main filtration membrane, a sub-membrane filtration unit 12 that filters branched water branched from the water to be treated in the main membrane filtration unit 10 using a sub-filtration membrane, a main flocculant addition device 20 as a main flocculant addition means for adding a main flocculant to the water to be treated in the main membrane filtration unit 10, a sub-flocculant addition device 46 as a sub-flocculant addition means for adding a sub-flocculant to the water to be treated in the sub-membrane filtration unit 12, a sub-filtration resistance detection device 14 as a sub-filtration resistance detection means for detecting the filtration resistance value of the sub-filtration membrane, and an output unit 16 as an output means for providing a predetermined output based on the filtration resistance value detected by the sub-filtration resistance detection device 14. The membrane filtration system 1 may also include a control device 18 as a control means. The membrane filtration system 1 may include a treated water tank 22 for storing treated water obtained in the main membrane filtration device 10, a main backwash piping 30 as a main backwashing means for backwashing the main filtration membrane of the main membrane filtration device 10 and backwashing with the addition of chemicals, and a sub-backwash piping 36 as a sub-backwashing means for backwashing the sub-filtration membrane of the sub-membrane filtration device 12 and backwashing with the addition of chemicals.

[0052] In the membrane filtration system 3 of Fig. 2, a main treated water pipe 24 is connected to the treated water inlet of the main membrane filtration device 10. The main treated water outlet and the inlet of the treated water tank 22 are connected by a main treated water pipe 26, and the treated water outlet of the treated water tank 22 is connected to a main treated water pipe 28. The main backwash liquid outlet of the treated water tank 22 and the main backwash liquid inlet on the secondary side of the main membrane filtration device 10 are connected by a main backwash pipe 30. The main backwash effluent outlet on the primary side of the main membrane filtration device 10 is connected to a main backwash effluent pipe 32. The outlet of the main flocculant addition device 20 and the main treated water pipe 24 are connected by a main flocculant addition pipe 42.

[0053] A sub-branch treated water pipe 34, which branches off from the upstream side of the connection point of the main flocculant addition pipe 42 in the main treated water pipe 24, is connected to the branch treated water inlet of the sub-membrane filtration device 12, and a sub-treated water pipe 40 is connected to the sub-treated water outlet. A sub-backwash liquid outlet of the treated water tank 22 is connected to the sub-backwash liquid inlet on the secondary side of the sub-membrane filtration device 12 by a sub-backwash piping 36. A sub-backwash effluent outlet on the primary side of the sub-membrane filtration device 12 is connected to a sub-backwash effluent pipe 38. A sub-filtration resistance detection device 14 is installed on the secondary side of the sub-membrane filtration device 12. The outlet of the sub-flocculant addition device 46 is connected to the sub-branch treated water pipe 34 by a sub-flocculant addition pipe 44.

[0054] The output unit 16 and the sub-filtration resistance detection device 14, the output unit 16 and the control device 18, the sub-filtration resistance detection device 14 and the control device 18, the control device 18 and the main flocculant addition device 20, and the control device 18 and the sub-flocculant addition device 46 may be connected to each other via wired or wireless electrical connections or the like. The membrane filtration system 1 may further include a communication device as a communication means. The communication device is connected to the control device 18, for example, to a server via the Internet. The server is provided with at least a recording unit or a computing unit. The recording unit stores data such as the filtration resistance value measured by the sub-filtration resistance detection device 14. The computing unit performs calculations using data such as the filtration resistance value measured by the sub-filtration resistance detection device 14, and may output an alarm or the execution of flocculant addition by the main flocculant addition device 20 or the sub-flocculant addition device 46. The data stored in the recording unit may also be used to calculate the execution history of flocculant addition by the main flocculant addition device 20 or the sub-flocculant addition device 46, the amount of flocculant used, the flocculant cost, etc., and store or output the data. The output is then sent back via the Internet to the control device 18, which may issue an alarm to the output unit 16, execute flocculant addition by the main flocculant addition device 20 or the sub-flocculant addition device 46, or change the flocculant addition conditions. The data recorded in the recording unit may be used as training data for AI (machine learning, deep learning, etc.). For example, a model may be created using the filtration resistance values ​​measured by the sub-filtration resistance detection device 14 for the flocculation conditions and water quality recorded in the recording unit as training data, and the model may be used to present or control flocculation conditions that will lower the filtration resistance value for future water quality. Furthermore, for example, the accuracy of outputs such as alarms and flocculant addition performed after calculations may be verified by jar tests or equipment maintenance, and the results may be labeled with the correctness of the calculations. This data may then be used as training data to adjust the model and improve the accuracy of alarms and flocculant addition.

[0055] The water to be treated is sent to the main membrane filtration device 10 through the main water to be treated pipe 24. Here, in the main water to be treated pipe 24, a main flocculant is added to the water to be treated from the main flocculant addition device 20 through the main flocculant addition pipe 42 (main flocculant addition process). In the main membrane filtration device 10, membrane filtration of the water to be treated is performed using the main filtration membrane (main membrane filtration process). The obtained main treated water is sent to the treated water tank 22 through the main treated water pipe 26 as needed and stored therein. The main treated water stored in the treated water tank 22 is discharged through the main treated water pipe 28.

[0056] Meanwhile, branched treated water branched from the treated water before the main flocculant is added by the main flocculant addition device 20 is sent to the sub-membrane filtration device 12 through the sub-branched treated water piping 34. Here, in the sub-branched treated water piping 34, a sub-flocculant is added from the sub-flocculant addition device 46 to the branched treated water through the sub-flocculant addition piping 44 (sub-flocculant addition step). In the sub-membrane filtration device 12, membrane filtration of the branched treated water is performed using a sub-filtration membrane (sub-membrane filtration step). The obtained sub-treated water is discharged through the sub-treated water piping 40.

[0057] The main membrane filtration device 10 and the sub-membrane filtration device 12 repeatedly perform a membrane filtration process and a cleaning process. The cleaning process is performed in the same manner as in the membrane filtration system 1 of FIG.

[0058] In the sub-membrane filtration device 12, the sub-filtration resistance value may be measured by the sub-filtration resistance detection device 14 during the filtration process.

[0059] In the membrane filtration system 3, in addition to the main membrane filtration process using the main membrane filtration device 10, a sub-membrane filtration process using a sub-membrane filtration device 12 equipped with a sub-filtration resistance detection means for detecting the filtration resistance value of the sub-filtration membrane is provided, and based on the filtration resistance value in the sub-membrane filtration process detected by the sub-filtration resistance detection device 14, which is the sub-filtration resistance detection means, an output according to the membrane filtration status in the sub-membrane filtration device 12 is issued, for example, an alarm or the like is output when the filtration resistance value exceeds a predetermined threshold.

[0060] For example, it is preferable that the filtration resistance value of the sub-membrane filtration device 12 is recorded, and when certain conditions are met, the amount of coagulant added to at least the main membrane filtration device 10 out of the main membrane filtration device 10 and the sub-membrane filtration device 12 is controlled.

[0061] In the membrane filtration system 3 of FIG. 2, for example, at least one of the following controls (1) to (3) using the sub-filtration resistance value may be performed.

[0062] (1) For example, when the rate of increase in the sub-filtration resistance value during the membrane filtration process of the sub-membrane filtration device 12 exceeds a predetermined value, the amount of main coagulant added by the main coagulant addition device 20 in the main membrane filtration device 10 and the amount of sub-coagulant added by the sub-coagulant addition device 46 in the sub-membrane filtration device 12 are increased.

[0063] (2) For example, when the "sub-filtration resistance value after cleaning" vs. "slope of the filtration amount of the sub-membrane filtration device" in the sub-membrane filtration device 12 becomes equal to or greater than a predetermined value, the amount of main coagulant added by the main coagulant addition device 20 in the main membrane filtration device 10 and the amount of sub-coagulant added by the sub-coagulant addition device 46 in the sub-membrane filtration device 12 are increased.

[0064] (3) For example, while changing the amount of sub-flocculant added in the sub-membrane filtration device 12, the “sub-filtration resistance value after cleaning” versus the “slope of the filtration volume of the sub-membrane filtration device” is calculated, and the amount of main flocculant added by the main flocculant addition device 20 is controlled to find the condition under which the slope becomes small or to approach that condition.

[0065] This allows early detection of fouling of the sub-filtration membrane in the sub-membrane filtration device 12. If fouling of the sub-filtration membrane is detected, the coagulant addition conditions in the main membrane filtration device 10 can be changed, thereby suppressing membrane fouling even if the properties of the water to be treated fluctuate, enabling stable operation of the main membrane filtration device 10. By providing the sub-membrane filtration device 12 separately from the main membrane filtration device 10, the coagulant addition conditions can be changed without stopping the main membrane filtration device 10, and the main membrane filtration process can be continued. This allows the operating time of the main membrane filtration device 10 to be maximized.

[0066] The sub-filtration membrane in the sub-membrane filtration device 12 has, for example, the same membrane material, shape, and pore size as the main filtration membrane in the main membrane filtration device 10, but has a smaller membrane area than the main filtration membrane. If fouling is detected by the sub-membrane filtration device 12, which is smaller than the main membrane filtration device 10, fouling in the main membrane filtration device 10 can be predicted at an early stage.

[0067] It is preferable to pass water through the sub-membrane filtration device 12 (sub-membrane filtration step) at a higher flux than through the main membrane filtration device 10 (main membrane filtration step). This allows for earlier detection of fouling of the sub-filtration membrane in the sub-membrane filtration device 12. If fouling of the sub-filtration membrane is detected, changing the conditions for adding the coagulant in the main membrane filtration device 10 will make it possible to suppress membrane fouling even if the properties of the water to be treated fluctuate, enabling stable operation of the main membrane filtration device 10.

[0068] The flux in the sub-membrane filtration apparatus 12 (sub-membrane filtration step) is, for example, 2 to 10 times, and preferably 4 to 6 times, the flux in the main membrane filtration apparatus 10 (main membrane filtration step). If the flux in the sub-membrane filtration apparatus 12 is less than 2 times the flux in the main membrane filtration apparatus 10, it may not be possible to detect the occurrence of fouling in the sub-filtration membrane at an early stage, whereas if it exceeds 10 times, the occurrence of fouling may be overestimated, resulting in a decrease in prediction accuracy.

[0069] Furthermore, for example, the conditions for adding the main flocculant in the main membrane filtration device 10 and the conditions for adding the sub-flocculant in the sub-membrane filtration device 12 may be controlled based on the filtration resistance value in the sub-membrane filtration device 12 detected by the sub-filtration resistance detection device 14. For example, the conditions for adding the flocculant in the main membrane filtration step, such as the type of flocculant and the amount added, may be controlled based on the tendency of the resistance increase in the sub-membrane filtration device 12. These controls may be performed manually or automatically.

[0070] The sub-filtration resistance detection device 14 is not particularly limited as long as it can detect the filtration resistance value in the sub-membrane filtration device 12, and examples thereof include pressure measurement means such as a pressure gauge, and flow rate measurement means such as a flow meter. The sub-filtration resistance detection device 14 preferably includes both pressure measurement means such as a pressure gauge and flow rate measurement means such as a flow meter. When the temperature dependency of the water to be treated is taken into consideration, it is preferable to further include a thermometer as temperature measurement means.

[0071] The control device 18 may store data measured on the pressure, flow rate, etc. when the branched treated water is passed through the sub-membrane filtration device 12, calculate data on the increase in filtration resistance, and based on this, automatically control the conditions for adding the main coagulant by the main coagulant addition device 20 in the main membrane filtration device 10 (e.g., the type of main coagulant, the amount added, etc.) and the conditions for adding the sub-coagulant by the sub-coagulant addition device 46 in the sub-membrane filtration device 12 (e.g., the type of sub-coagulant, the amount added, etc.).

[0072] The output from the output unit 16 may include visually and audiovisually perceptible alarms such as a display or sound indicating the status of membrane filtration in the sub-membrane filtration device 12, as well as the display of a response method for dealing with the status of membrane filtration, improvement suggestions, etc. The output unit 16 may be, for example, any device capable of displaying and outputting information, and may include, for example, a display device such as a liquid crystal display or an organic EL display, or an audio output device such as a speaker. For example, alarms may be issued by displaying the alarm on a touch panel on a control panel, notifying an operator via internet communication, or notifying a monitoring room, etc.

[0073] The output unit 16 may output an alarm or the like when the filtration resistance value in the sub-membrane filtration device 12 exceeds, for example, a predetermined threshold. The alarm threshold may be set to one value in advance, or may be changed in stages or proportionally.

[0074] The control device 18 is composed of, for example, a microcomputer and electronic circuits, which include a calculation means such as a CPU that operates a program, and storage means such as a ROM and RAM that store the program and calculation results. The control device 18 has a function of controlling the conditions for main coagulant addition by the main coagulant addition device 20 in the main membrane filtration device 10 and the conditions for sub-coagulant addition by the sub-coagulant addition device 46 in the sub-membrane filtration device 12, based on, for example, the filtration resistance value detected by the sub-filtration resistance detection means. The control device 18 has a function of controlling the amount of coagulant added to the water to be treated, for example, by adjusting the on / off and flow rate of the pump used to add coagulant in the main coagulant addition device 20 or the sub-coagulant addition device 46, the opening and closing of the valve, etc.

[0075] The water to be treated is water containing, for example, suspended solids, organic matter, inorganic matter such as metal particles, and the like, and is not particularly limited, and examples include biologically treated water obtained by biologically treating wastewater containing organic matter discharged from semiconductor manufacturing factories, food factories, etc. (biological treatment process), solid-liquid separation treated water obtained by coagulation and solid-liquid separation treatment (coagulation / solid-liquid separation treatment process), solid-liquid separation treated water obtained by biologically treating the biologically treated water and then coagulating and solid-liquid separation treatment, etc. Water that has been treated through other processes before or after the biological treatment process or coagulation / solid-liquid separation treatment process may also be water that has been treated.

[0076] The biological treatment is not particularly limited as long as it uses microorganisms to treat the water to be treated. The coagulation and solid-liquid separation treatment is not particularly limited as long as it uses a coagulant such as an inorganic coagulant, e.g., polyaluminum chloride, or a polymer coagulant to perform coagulation and solid-liquid separation of the water to be treated.

[0077] The membrane filtration system and membrane filtration method according to this embodiment are preferably applied when the properties of the water to be treated are such that the content of organic matter as measured by TOC varies within a range of 1 to 50 mg / L, or the content of inorganic matter such as metal particles (e.g., iron, aluminum, manganese) and dissolved metals as measured by ICP analysis varies within a range of 0.01 to 20 mg / L.

[0078] The main filtration membrane and the sub-filtration membrane are, for example, turbidity removal membranes such as ultrafiltration membranes (UF membranes) or microfiltration membranes (MF membranes), etc. The shape of the membranes is, for example, a hollow fiber membrane.

[0079] Chemicals used in chemical backwashing include acids, oxidizing agents, alkalis, etc. The acid is not particularly limited, but examples include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as oxalic acid and citric acid, and it is preferable to use organic acids such as oxalic acid and citric acid from the viewpoint of recovery after chemical backwashing.

[0080] The oxidizing agent used in the chemical backwashing is not particularly limited, but examples thereof include chlorine-based oxidizing agents such as sodium hypochlorite.

[0081] The alkali used for chemical backwashing is not particularly limited, but it is preferable to use relatively inexpensive alkalis such as sodium hydroxide and sodium hypochlorite.

[0082] In the backwashing with chemical addition, chemicals other than acids, alkalis and oxidizing agents, for example, membrane cleaning agents such as surfactants, may be used as needed.

[0083] <Flocculant Addition Device> A flocculant addition device according to an embodiment of the present invention is a flocculant addition device that adds a main flocculant to water to be treated in a main membrane filtration device 10 that filters the water using a main filtration membrane, as shown in Figures 1 and 2. The flocculant addition device includes a sub-membrane filtration device 12 that filters branched water to be treated that is branched from the water to be treated in the main membrane filtration device 10 using a sub-filtration membrane, a main flocculant addition device 20 as main flocculant addition means that adds the main flocculant to the water to be treated in the main membrane filtration device 10, a sub-filtration resistance detection device 14 as sub-filtration resistance detection means for detecting the filtration resistance value of the sub-filtration membrane, and a control device 18 as control means that controls the conditions of the main flocculant addition device 20 based on the filtration resistance value detected by the sub-filtration resistance detection device 14.

[0084] In the flocculant addition device shown in FIG. 1, the sub-membrane filtration device 12 is a device that filters branched water to be treated that is branched from the water to be treated to which the main flocculant has been added by the main flocculant addition device 20.

[0085] The flocculant addition device shown in Figure 2 further includes a sub-flocculant addition device 46 as a sub-flocculant addition means for adding a sub-flocculant to the branched treated water of the sub-membrane filtration device 12, and the sub-membrane filtration device 12 is a device that filters the branched treated water that is branched from the treated water before the main flocculant is added and to which the sub-flocculant has been added by the sub-flocculant addition device 46.

[0086] It is preferable that the sub-membrane filtration device 12 in the coagulant addition device passes water at a higher flux than the main membrane filtration device 10 .

[0087] <Control device for flocculant addition device> A control device for a coagulant addition device according to an embodiment of the present invention is a control device for a coagulant addition device that controls the addition of a main coagulant to water to be treated in a main membrane filtration device 10 that filters the water to be treated using a main filtration membrane. The coagulant addition device includes a sub-membrane filtration device 12 that filters branched water to be treated branched from the water to be treated in the main membrane filtration device 10 using a sub-filtration membrane, a main coagulant addition device 20 as main coagulant addition means that adds a main coagulant to the water to be treated in the main membrane filtration device 10, and a sub-filtration resistance detection device 14 as sub-filtration resistance detection means for detecting the filtration resistance value of the sub-filtration membrane. The control device for the coagulant addition device includes a control device 18 as control means that controls the conditions of the main coagulant addition device 20 based on the filtration resistance value detected by the sub-filtration resistance detection device 14.

[0088] In the flocculant addition device in the control device for the flocculant addition device shown in Figure 1, the sub-membrane filtration device 12 is a device that filters branched treated water branched from the treated water to which the main flocculant has been added by the main flocculant addition device 20.

[0089] The flocculant addition device in the control device for the flocculant addition device shown in Figure 2 further includes a sub-flocculant addition device 46 as a sub-flocculant addition means for adding a sub-flocculant to the branched treated water of the sub-membrane filtration device 12, and the sub-membrane filtration device 12 is a device that filters the branched treated water that is branched from the treated water before the main flocculant is added and to which the sub-flocculant has been added by the sub-flocculant addition device 46.

[0090] In the flocculant addition device in the control device for the flocculant addition device, it is preferable to pass water through the sub-membrane filtration device 12 at a higher flux than through the main membrane filtration device 10. [Explanation of symbols]

[0091] 1,3 Membrane filtration system, 10 Main membrane filtration device, 12 Sub-membrane filtration device, 14 Sub-filtration resistance detection device, 16 Output unit, 18 Control device, 20 Main coagulant addition device, 22 Treatment water tank, 24 Main treated water piping, 26, 28 Main treated water piping, 30 Main backwash piping, 32 Main backwash drainage piping, 34 Sub-branch treated water piping, 36 Sub-backwash piping, 38 Sub-backwash drainage piping, 40 Sub-treated water piping, 42 Main coagulant addition piping, 44 Sub-coagulant addition piping, 46 Sub-coagulant addition device.

Claims

1. A main membrane filtration device that filters the water to be treated using a main filtration membrane; A sub-membrane filtration device that filters a branched treated water branched from the treated water of the main membrane filtration device using a sub-filtration membrane; A main flocculant adding means for adding a main flocculant to the water to be treated in the main membrane filtration device; A sub-filtration resistance detection means for detecting a filtration resistance value of the sub-filtration membrane; an output means for outputting a predetermined output based on the filtering resistance value detected by the sub filtering resistance detection means; A control means for controlling the conditions of the main flocculant adding means based on the filtration resistance value detected by the sub filtration resistance detecting means; A recording unit in which data of the filtering resistance value detected by the sub filtering resistance detection means is stored; Equipped with A membrane filtration system characterized in that the data stored in the recording unit is used as teaching data.

2. 2. The membrane filtration system of claim 1, A membrane filtration system characterized in that the sub-membrane filtration device is a device for filtering branched treated water branched off from the treated water to which the main flocculant has been added by the main flocculant adding means.

3. 2. The membrane filtration system of claim 1, The sub-membrane filtration apparatus further includes a sub-flocculant adding means for adding a sub-flocculant to the branched treated water of the sub-membrane filtration apparatus, The sub-membrane filtration device is a membrane filtration system characterized in that it is a device that filters branched treated water that is branched off from the treated water before the main coagulant is added and to which the sub-coagulant has been added by the sub-coagulant adding means.

4. The membrane filtration system according to any one of claims 1 to 3, A membrane filtration system, characterized in that the sub-membrane filtration device passes water at a higher flux than the main membrane filtration device.

5. a main membrane filtration process for filtering the water to be treated using a main filtration membrane; a sub-membrane filtration process for filtering a branched water to be treated that is branched from the water to be treated in the main membrane filtration process using a sub-filtration membrane; a main flocculant addition step of adding a main flocculant to the water to be treated in the main membrane filtration step; A sub-filtration resistance detection step for detecting a filtration resistance value of the sub-filtration membrane; an output step of performing a predetermined output based on the filtering resistance value detected by the sub filtering resistance detection step; Including, Controlling conditions of the main flocculant addition step based on the filtration resistance value detected by the sub-filtration resistance detection step; A membrane filtration method, characterized in that data on the filtration resistance value detected in the sub-filtration resistance detection process is used as teaching data.

6. A flocculant addition device that adds a main flocculant to the water to be treated in a main membrane filtration device that filters the water to be treated using a main filtration membrane, A sub-membrane filtration device that filters a branched treated water branched from the treated water of the main membrane filtration device using a sub-filtration membrane; A main flocculant adding means for adding a main flocculant to the water to be treated in the main membrane filtration device; A sub-filtration resistance detection means for detecting a filtration resistance value of the sub-filtration membrane; A control means for controlling the conditions of the main flocculant adding means based on the filtration resistance value detected by the sub filtration resistance detecting means; A recording unit in which data of the filtering resistance value detected by the sub filtering resistance detection means is stored; Equipped with A flocculant addition device, characterized in that the data stored in the recording unit is used as teaching data.

7. The flocculant addition device according to claim 6, A coagulant addition device, characterized in that in the sub-membrane filtration device, water is passed through at a higher flux than in the main membrane filtration device.

8. A control device for a flocculant addition device that controls addition of a main flocculant to water to be treated in a main membrane filtration device that filters the water to be treated using a main filtration membrane, The coagulant addition device includes a sub-membrane filtration device that uses a sub-filtration membrane to filter branched treated water branched from the treated water of the main membrane filtration device, a main coagulant addition means that adds a main coagulant to the treated water of the main membrane filtration device, and a sub-filtration resistance detection means that detects the filtration resistance value of the sub-filtration membrane, A control means for controlling the conditions of the main flocculant adding means based on the filtration resistance value detected by the sub filtration resistance detecting means; A recording unit in which data of the filtering resistance value detected by the sub filtering resistance detection means is stored; Equipped with A control device for a flocculant addition device, characterized in that the data stored in the recording unit is used as teaching data.

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