Transmembrane pressure prediction method and water treatment device

Abstract

To provide a transmembrane pressure difference prediction method and a water treatment apparatus capable of predicting a future increase in a transmembrane pressure difference of a hollow fiber membrane module.SOLUTION: A transmembrane pressure difference prediction method for predicting a transmembrane pressure difference in a water treatment apparatus that filters raw water by use of a hollow fiber membrane module, includes: measuring, at intervals of 3 seconds or less, a pressure on at least one side of a primary side and a secondary side in each of a plurality of times of a backwash step when the backwash step of pushing treated water on the secondary side of the hollow fiber membrane module to the primary side of the hollow fiber membrane module by a pressurized medium is performed a plurality of times; predicting a future increase in a transmembrane pressure difference in the hollow fiber membrane on the basis of a difference among the plurality of times of the backwash step as a measurement result of the pressure on the at least one side; and reporting a result of the prediction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for predicting a transmembrane pressure difference and a water treatment device. [Background technology]

[0002] Conventionally, water treatment devices that use a hollow fiber membrane module to filter raw water are known. In the water treatment device, raw water is supplied to the inside of a hollow fiber membrane module, and the raw water is permeated through the hollow fiber membrane, thereby discharging treated water from which impurities have been removed to the outside of the hollow fiber membrane module. When filtration is performed for a certain period of time, impurities adhere to the hollow fiber membrane. This increases the permeation resistance of the hollow fiber membrane, and the transmembrane pressure, which is the difference between the pressure on the primary side (internal side) and the pressure on the secondary side (external side) of the hollow fiber membrane module, increases. Therefore, in the water treatment device, the transmembrane pressure is generally measured every minute (e.g., every 10 minutes) in the filtration process, and the transmembrane pressure is used as a performance index of the hollow fiber membrane module.

[0003] For example, Patent Document 1 describes that at the start of a filtration process, the pressures at the primary inlet, secondary outlet, and primary outlet of a separation membrane module having hollow fiber membranes are measured, and that a membrane filtration differential pressure (corresponding to a transmembrane pressure difference) which is the difference between the pressure on the primary side and the pressure on the secondary side of the separation membrane module is calculated based on the measurement results.Then, it describes that the location of a blockage in the separation membrane module is identified based on the calculation results of the membrane filtration differential pressure, etc.

[0004] It is also known that when an increase in the transmembrane pressure difference is detected during the filtration process, it is assumed that the amount of impurities adhering to the hollow fiber membranes has increased and the permeation resistance of the hollow fiber membranes has increased, and therefore the hollow fiber membrane module is cleaned. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6607319 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the filtration process, raw water is not usually supplied to the hollow fiber membrane at a flow rate that maximizes the capacity of the hollow fiber membrane. Therefore, even if impurities are attached to a part of the hollow fiber membrane, the raw water may pass through the part of the hollow fiber membrane where the impurities are not attached, and filtration may be performed normally. In this case, the transmembrane pressure is measured at the same level as when no impurities are attached to the hollow fiber membrane. Therefore, in the conventional technology, there is a risk that an increase in the transmembrane pressure cannot be detected until impurities are attached to most of the hollow fiber membrane and filtration is no longer performed normally.

[0007] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a method for predicting a transmembrane pressure difference, and a water treatment device, which are capable of predicting a future increase in the transmembrane pressure difference of a hollow fiber membrane module. [Means for solving the problem]

[0008] A method for predicting a transmembrane pressure difference according to one aspect of the present invention is a method for predicting a transmembrane pressure difference in a water treatment device that filters raw water using a hollow fiber membrane module, and includes, when a backwashing process in which treated water on the secondary side of the hollow fiber membrane module is pushed to the primary side of the hollow fiber membrane module by a pressurized medium is performed multiple times, measuring the pressure of at least one of the primary side and the secondary side at intervals of 3 seconds or less in each of the multiple backwashing processes, predicting a future increase in the transmembrane pressure difference of the hollow fiber membrane module based on the difference in the measurement results of the pressure on the at least one side between the multiple backwashing processes, and reporting the result of the prediction.

[0009] A water treatment device according to another aspect of the present invention is a water treatment device that filters raw water using a hollow fiber membrane module, and is configured to include, when a backwashing process in which treated water on the secondary side of the hollow fiber membrane module is pushed to the primary side of the hollow fiber membrane module by a pressurized medium is performed multiple times, a measurement unit that measures the pressure of at least one of the primary side and the secondary side at intervals of 3 seconds or less in each of the multiple backwashing processes, a prediction unit that predicts a future increase in the transmembrane pressure difference of the hollow fiber membrane module based on the difference in the measurement results of the pressure on at least one side between the multiple backwashing processes, and an alarm unit that alarms the prediction result by the prediction unit.

[0010] In the above-mentioned method for predicting a transmembrane pressure difference and the above-mentioned water treatment device, in the backwashing process, the treated water on the secondary side is pushed to the primary side by a pressurized medium. This allows the treated water to not only pass through the parts of the hollow fiber membrane where impurities are not attached, but also collide with the parts where impurities are attached. As a result, the pressure applied to the treated water can be changed according to the amount of attached impurities. Therefore, according to the above-mentioned method for predicting a transmembrane pressure difference and the above-mentioned water treatment device, it is possible to measure the pressure on at least one of the primary side and the secondary side of the hollow fiber membrane module according to the amount of attached impurities on the hollow fiber membrane.

[0011] Moreover, in each of the multiple backwashing processes, the pressure on the at least one side is measured at intervals of 3 seconds or less, which is shorter than the usual measurement interval of the transmembrane pressure in the filtration process, so that the detailed time transition of the pressure on the at least one side in each backwashing process, which is completed within a few minutes, can be grasped.

[0012] Therefore, from the difference in the detailed time transition between multiple backwash processes, it is possible to grasp the change in the amount of impurities adhering to the hollow fiber membrane in response to the change in the pressure on at least one side. Therefore, when it is grasped that the amount of impurities adhering to the hollow fiber membrane is increasing, it is possible to predict that the transmembrane pressure difference will increase in the future, and the prediction result can be notified.

[0013] In the above-mentioned method for predicting transmembrane pressure, in each of the multiple backwashing processes, at least the secondary side pressure is measured at the intervals, and a future increase in the transmembrane pressure is predicted based on the difference between the multiple backwashing processes in the point at which the secondary side pressure, which instantaneously increases immediately after the start of the backwashing process, reaches.

[0014] Immediately after the start of the backwashing process, the treated water on the secondary side is pushed by the pressurized medium and flows into the primary side. At this time, the permeation of the treated water through the hollow fiber membrane becomes the rate-limiting step, and the degree to which the treated water is pressurized by the medium is greater than the permeation of the treated water to the primary side. Therefore, the pressure on the secondary side increases instantaneously immediately after the start of the backwashing process. The reached pressure on the secondary side during this increase becomes higher the greater the amount of impurities attached to the hollow fiber membrane and the greater the permeation resistance of the hollow fiber membrane.

[0015] According to this configuration, the secondary pressure of the hollow fiber membrane module is measured at intervals of 3 seconds or less in each of the multiple backwashing processes, so that it is possible to detect the point at which the secondary pressure, which increases instantaneously immediately after the start of each backwashing process, reaches. Therefore, it is possible to grasp the change in the amount of impurities adhering to the hollow fiber membrane and the permeation resistance of the hollow fiber membrane from the difference in the arrival point between the multiple backwashing processes. Therefore, when it is grasped that the amount of impurities adhering to the hollow fiber membrane is increasing and the permeation resistance of the hollow fiber membrane is increasing, it is possible to appropriately predict the increase in the transmembrane pressure difference.

[0016] In the above-mentioned method for predicting transmembrane pressure, in each of the multiple backwashing processes, at least the secondary side pressure is measured at the intervals, and a future increase in the transmembrane pressure is predicted based on the difference between the multiple backwashing processes in the time from the start of the backwashing process until the secondary side pressure stabilizes at the pressure of the medium.

[0017] In the backwashing process, when the pushing of the treated water on the secondary side to the primary side is completed, the secondary side is filled with a pressurized medium, and the pressure on the secondary side is stabilized at the pressure of the medium. Here, the greater the amount of impurities attached to the hollow fiber membrane and the greater the permeation resistance of the hollow fiber membrane, the longer the time required for all the treated water on the secondary side to be pushed to the primary side. Therefore, the greater the amount of impurities attached to the hollow fiber membrane and the greater the permeation resistance of the hollow fiber membrane, the longer the time from the start of the backwashing process until the pressure on the secondary side is stabilized at the pressure of the medium.

[0018] According to this configuration, the pressure on the secondary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less in each of the multiple backwashing processes, so that it is possible to detect the time from the start of each backwashing process until the pressure on the secondary side stabilizes at the pressure of the medium. Therefore, from the difference in this time between the multiple backwashing processes, it is possible to grasp the change in the amount of impurities attached to the hollow fiber membrane and the permeation resistance of the hollow fiber membrane. Therefore, when it is grasped that the amount of impurities attached to the hollow fiber membrane is increasing and the permeation resistance of the hollow fiber membrane is increasing, it is possible to appropriately predict the increase in the transmembrane pressure difference.

[0019] In the above-mentioned method for predicting transmembrane pressure, in each of the multiple backwashing processes, at least the primary side pressure is measured at the intervals, and a future increase in the transmembrane pressure is predicted based on the difference between the multiple backwashing processes in the point at which the primary side pressure, which instantaneously increases immediately after the start of the backwashing process, reaches.

[0020] Immediately after the backwash process is started and the treated water on the secondary side is pushed out to the primary side, the pressure on the primary side increases instantaneously. At this time, the greater the amount of impurities adhering to the hollow fiber membrane and the greater the permeation resistance of the hollow fiber membrane, the slower the speed at which the treated water on the secondary side is pushed out to the primary side, and the lower the ultimate pressure on the primary side.

[0021] According to this configuration, the pressure on the primary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less in each of the multiple backwashing processes, so that it is possible to detect the point at which the pressure on the primary side increases instantaneously immediately after the start of each backwashing process. Therefore, it is possible to grasp the change in the amount of impurities attached to the hollow fiber membrane and the permeation resistance of the hollow fiber membrane from the difference in the pressure point between the multiple backwashing processes. Therefore, when it is grasped that the amount of impurities attached to the hollow fiber membrane is increasing and the permeation resistance of the hollow fiber membrane is increasing, it is possible to appropriately predict the increase in the transmembrane pressure difference.

[0022] In the above prediction method, in each of the multiple backwashing processes, at least the pressure on the primary side is measured at the intervals, and a future increase in the transmembrane pressure is predicted based on the difference between the multiple backwashing processes in the time from the start of the backwashing process to the time when the pressure on the primary side stabilizes at a predetermined end pressure indicating the end of the pushing of treated water to the secondary side.

[0023] Immediately after the backwash process is started and the treated water on the secondary side is pushed out to the primary side, the pressure on the primary side increases instantaneously. Thereafter, the greater the amount of impurities adhering to the hollow fiber membrane and the greater the permeation resistance of the hollow fiber membrane, the slower the speed at which the treated water is pushed out to the primary side, and the longer it takes to finish pushing out the treated water on the secondary side.

[0024] According to this configuration, the pressure on the primary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less in each of the multiple backwashing processes, so that it is possible to detect the time from the start of each backwashing process until the pressure on the primary side stabilizes at the end pressure. Therefore, from the difference in this time between the multiple backwashing processes, it is possible to grasp the change in the amount of impurities attached to the hollow fiber membrane and the permeation resistance of the hollow fiber membrane. Therefore, when it is grasped that the amount of impurities attached to the hollow fiber membrane is increasing and the permeation resistance of the hollow fiber membrane is increasing, it is possible to appropriately predict the increase in the transmembrane pressure difference.

[0025] In the above prediction method, for the multiple backwashing processes, an integral value of the difference between the secondary side pressure and the primary side pressure at any one of the following times may be calculated: the time from the start of the backwashing process to when the primary side or secondary side pressure, which instantaneously increased immediately after the start of the backwashing process, reaches its target point; the time from when the primary side or secondary side pressure, which instantaneously increased immediately after the start of the backwashing process, reaches its target point and stabilizes; and the time from when the backwashing process starts to when the primary side or secondary side pressure stabilizes. The future increase in the transmembrane pressure may be predicted based on the difference in the integral values ​​between the multiple backwashing processes.

[0026] The inventor found that, through test runs, even if the difference between the secondary side pressure and the primary side pressure during the filtration process is approximately constant, the integral value of the difference from the start of the backwashing process until the primary side or secondary side pressure stabilizes is significantly different between cases where the amount of impurities adhering to the hollow fiber membrane is more than a predetermined amount and cases where it is less than a predetermined amount. The inventor also conducted further test runs and found that the integral value of the time from the start of the backwashing process until the pressure on the primary side or secondary side, which has risen instantaneously immediately after the start of the backwashing process, reaches a target point, and the integral value of the time from the start of the backwashing process until the pressure on the primary side or secondary side, which has risen instantaneously immediately after the start of the backwashing process, reaches the target point and stabilizes is also significantly different between cases where the amount of impurities adhering to the hollow fiber membrane is more than a predetermined amount and cases where it is less than a predetermined amount.

[0027] Therefore, according to this configuration, the change in the amount of impurities adhering to the hollow fiber membrane can be appropriately grasped by the difference between the integral value of the difference between the secondary side pressure and the primary side pressure at the above three times during multiple backwashing processes. Therefore, when it is grasped that the amount of impurities adhering to the hollow fiber membrane is increasing, it is possible to appropriately predict that the permeation resistance of the hollow fiber membrane will increase and the transmembrane pressure difference will rise.

[0028] For the multiple backwashing processes, the end point of the pressure of either the primary side or the secondary side that instantaneously rose immediately after the start of the backwashing process is detected, and a future increase in the transmembrane pressure is predicted based on the difference between the secondary side pressure and the primary side pressure at the point when either pressure reaches the end point, between the multiple backwashing processes.

[0029] According to this configuration, since the pressure of at least one of the primary side and the secondary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less for multiple backwashing processes, the arrival point of either the primary side or the secondary side pressure that instantaneously rises immediately after the start of the backwashing process can be detected. That is, even if the treated water contains impurities that peel off from the hollow fiber membrane surface due to the force of the treated water being pushed from the secondary side to the primary side in the backwashing process, the pressure of either of the above before it drops due to the impurities peeling off can be appropriately detected.

[0030] As a result, by using the difference between the pressure difference on the secondary side and the pressure difference on the primary side at the time of detection, it is possible to appropriately grasp the change in the amount of impurities adhering to the hollow fiber membrane. Therefore, when it is grasped that the amount of impurities adhering to the hollow fiber membrane is increasing, it is possible to appropriately predict that the permeation resistance of the hollow fiber membrane will increase and the transmembrane pressure difference will rise.

[0031] A method for predicting a transmembrane pressure difference according to another aspect of the present invention is a prediction method in a water treatment device that filters raw water using a hollow fiber membrane module, and includes, when a filling process of filling raw water into the hollow fiber membrane module is performed multiple times, measuring the primary side pressure of the hollow fiber membrane module at intervals of 3 seconds or less in each of the multiple filling processes, predicting a future increase in the transmembrane pressure difference of the hollow fiber membrane module based on the difference in the time from the start of the filling process to reaching an inflection point of the change in the primary side pressure in the measurement results of the primary side pressure between the multiple filling processes, and reporting the result of the prediction.

[0032] A water treatment device according to another aspect of the present invention is a water treatment device that filters raw water using a hollow fiber membrane module, and is configured to include: a measurement unit that measures the primary side pressure of the hollow fiber membrane module at intervals of 3 seconds or less during each of the multiple filling steps when a filling process of filling raw water into the inside of the hollow fiber membrane module is performed multiple times; a prediction unit that predicts a future increase in the transmembrane pressure difference of the hollow fiber membrane module based on the difference between the time from the start of the filling process to the time when the inflection point of the change in the primary side pressure is reached in the measurement results of the primary side pressure between the multiple filling steps; and an alarm unit that alarms the result of the prediction.

[0033] When the water filling process is started and raw water flows into the hollow fiber membrane module, the pressure on the primary side gradually increases due to the hydraulic head pressure. After that, when the inside of the hollow fiber membrane module approaches a full water state, the pressure on the primary side increases rapidly. Therefore, the time from the start of the water filling process to the inflection point of the change in the primary side pressure is shorter the more the amount of impurities accumulated inside the hollow fiber membrane module and the smaller the effective volume inside the hollow fiber membrane module is.

[0034] Furthermore, it is presumed that the greater the amount of impurities accumulated inside the hollow fiber membrane module and the smaller the effective volume inside the hollow fiber membrane module, the greater the amount of impurities adhering to the hollow fiber membranes, i.e., the greater the likelihood of the transmembrane pressure difference increasing in the future.

[0035] In the above-mentioned method for predicting a transmembrane pressure difference and the above-mentioned water treatment device, the pressure on the primary side of the hollow fiber membrane module is measured when the inside of the hollow fiber membrane module is filled with raw water in the water filling step. Therefore, in the above-mentioned method for predicting a transmembrane pressure difference and the above-mentioned water treatment device, it is possible to measure the pressure on the primary side of the hollow fiber membrane module according to the amount of accumulated impurities inside the hollow fiber membrane module.

[0036] Moreover, in the above-mentioned method for predicting transmembrane pressure and the above-mentioned water treatment device, the pressure on the primary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less in each of the multiple water-filling processes, which is shorter than the usual measurement interval of the transmembrane pressure in the filtration process. Therefore, it is possible to grasp the detailed temporal transition of the pressure on the primary side of the hollow fiber membrane module in each water-filling process, which is completed within a few minutes.

[0037] Therefore, from the difference in this detailed time progression between multiple water filling processes, it is possible to grasp the change in the amount of accumulated impurities inside the hollow fiber membrane module in response to the change in pressure on the primary side of the hollow fiber membrane module.

[0038] Specifically, the change in the amount of impurities accumulated inside the hollow fiber membrane module and the effective volume can be grasped from the difference in time between the start of the water-filling process and the time when the inflection point of the change in the primary pressure is reached between multiple water-filling processes. Therefore, when it is grasped that the amount of impurities accumulated inside the hollow fiber membrane module is increasing and the effective volume inside the hollow fiber membrane module is decreasing, it is possible to appropriately predict the situation in which the amount of impurities adhering to the hollow fiber membrane is increasing, that is, the situation in which the transmembrane pressure difference will increase in the future, and the prediction result can be notified.

[0039] A method for predicting a transmembrane pressure difference according to another aspect of the present invention is a prediction method in a water treatment device that filters raw water using a hollow fiber membrane module, and includes, when a drainage process for discharging drain water containing turbid components peeled off from the hollow fiber membranes is performed multiple times, measuring the primary side pressure of the hollow fiber membrane module at intervals of 3 seconds or less in each of the multiple drainage processes, predicting a future increase in the transmembrane pressure difference of the hollow fiber membrane module based on the difference in the time from the start of the drainage process to when the primary side pressure becomes constant, between the multiple drainage processes, in the measurement results of the primary side pressure, and reporting the result of the prediction.

[0040] A water treatment device according to another aspect of the present invention is a water treatment device that filters raw water using a hollow fiber membrane module, and is configured to include, when a drainage process for draining drain water containing turbid components peeled off from the hollow fiber membranes is performed multiple times, a measurement unit that measures the primary side pressure of the hollow fiber membrane module at intervals of 3 seconds or less in each of the multiple drainage processes, a prediction unit that predicts a future increase in the transmembrane pressure difference of the hollow fiber membrane module based on the difference in the time from the start of the drainage process to when the primary side pressure becomes constant, between the multiple drainage processes, in the measurement results of the primary side pressure, and an alarm unit that alarms the result of the prediction.

[0041] When the drainage process is completed, the pressure on the primary side stabilizes. Therefore, the time from the start of the drainage process until the pressure on the primary side becomes constant becomes shorter as the amount of impurities accumulated inside the hollow fiber membrane module increases and the effective volume inside the hollow fiber membrane module becomes smaller.

[0042] Furthermore, it is presumed that the greater the amount of impurities accumulated inside the hollow fiber membrane module and the smaller the effective volume inside the hollow fiber membrane module, the greater the amount of impurities adhering to the hollow fiber membranes, i.e., the greater the likelihood of the transmembrane pressure difference increasing in the future.

[0043] In the above-mentioned method for predicting transmembrane pressure and the above-mentioned water treatment device, the pressure on the primary side of the hollow fiber membrane module is measured when drain water inside the hollow fiber membrane module is discharged in the drainage step. Therefore, in the above-mentioned prediction method and the above-mentioned water treatment device, it is possible to measure the pressure on the primary side of the hollow fiber membrane module according to the amount of accumulated impurities inside the hollow fiber membrane module.

[0044] Moreover, in the above-mentioned method for predicting transmembrane pressure and the above-mentioned water treatment device, the pressure on the primary side inside the hollow fiber membrane module is measured at intervals of 3 seconds or less in each of the multiple drainage processes, which is shorter than the usual measurement interval of the transmembrane pressure in the filtration process. Therefore, it is possible to grasp the detailed temporal transition of the pressure on the primary side of the hollow fiber membrane module in each drainage process, which is completed within a few minutes.

[0045] Therefore, from the difference in this detailed time progression between multiple drainage processes, it is possible to grasp the change in the amount of accumulated impurities inside the hollow fiber membrane module in response to the change in pressure on the primary side of the hollow fiber membrane module.

[0046] Specifically, the change in the amount of impurities accumulated inside the hollow fiber membrane module and the effective volume can be grasped from the difference in time from the start of the drainage process until the pressure on the primary side becomes constant between multiple drainage processes. Therefore, when it is grasped that the amount of impurities accumulated inside the hollow fiber membrane module is increasing and the effective volume inside the hollow fiber membrane module is decreasing, it is possible to appropriately predict the situation in which the amount of impurities adhering to the hollow fiber membrane is increasing, that is, the situation in which the transmembrane pressure difference will increase in the future, and the prediction result can be notified. Effect of the Invention

[0047] As is clear from the above description, the present invention can provide a method for predicting a transmembrane pressure difference and a water treatment apparatus capable of predicting a future increase in the transmembrane pressure difference of a hollow fiber membrane module. [Brief description of the drawings]

[0048] [Figure 1] 1 is a diagram illustrating a schematic configuration of a water treatment device according to an embodiment of the present invention. [Diagram 2] 3 is a diagram showing the on / off state of a raw water pump and the open / closed state of valves in each step of a water treatment method in the water treatment device. FIG. [Diagram 3] FIG. 13 is a graph showing the change over time in the secondary side pressure of the hollow fiber membrane module in the backwashing process. [Figure 4] FIG. 13 is a graph showing the change over time in the primary side pressure of a hollow fiber membrane module in a backwashing process. [Diagram 5] FIG. 13 is a diagram showing the time changes in the primary side pressure and secondary side pressure of a hollow fiber membrane module in a backwashing process when clogging of the hollow fiber membranes is not progressing. [Figure 6] FIG. 13 is a diagram showing the time changes in the primary side pressure and secondary side pressure of a hollow fiber membrane module in a backwashing process when clogging of the hollow fiber membranes is progressing. [Figure 7] FIG. 13 is a graph showing the change over time in the primary side pressure of a hollow fiber membrane module in a water filling process. [Figure 8] FIG. 13 is a graph showing the change over time in the primary side pressure of the hollow fiber membrane module in the drainage process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] (Embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0050] First, the configuration of a water treatment device 1 according to an embodiment of the present invention will be described with reference to Fig. 1. As shown in Fig. 1, the water treatment device 1 mainly includes a hollow fiber membrane module 10, a raw water supply unit 20, a bubbling air supply unit 30, and a backwash air supply unit 40.

[0051] The hollow fiber membrane module 10 includes a hollow fiber membrane bundle having a plurality of hollow fiber membranes 11 whose upper ends are fixed to a fixing member 13, a housing 12, a water guide pipe 14 extending vertically inside the hollow fiber membrane bundle, and an air diffuser plate 15. The hollow fiber membrane bundle, the fixing member 13, and the air diffuser plate 15 are accommodated in the housing 12. The space within the housing 12 is divided by the fixing member 13 into a raw water space S1 and a treated water space S2. The hollow fiber membranes 11, the water guide pipe 14, and the air diffuser plate 15 are accommodated in the raw water space S1.

[0052] As shown in FIG. 1, an outlet 12A for treated water (filtrate water) is provided at the top of the housing 12 so as to face the treated water space S2. An air vent 12B is provided at the side of the housing 12 (above the center in the longitudinal direction) so as to face the raw water space S1. An air supply port 12C and a drain port 12D are provided at the bottom of the housing 12 so as to face the raw water space S1. The ratio of the inner diameter of the housing 12 to the inner diameters of these piping connection ports (the outlet 12A, the air vent 12B, the air supply port 12C, and the drain port 12D) is 1.3 to 12, preferably 2.5 to 12, and more preferably 3.0 to 6.0. The inner diameter of the housing 12 referred to here is the inner diameter in a cross section perpendicular to the longitudinal direction of the housing 12.

[0053] The water conduit 14 is for supplying raw water and air to the raw water space S1. As shown in Fig. 1, the upper end of the water conduit 14 is fixed to the fixing member 13 and the end face is closed, and the lower end protrudes downward from the lower part of the housing 12. A raw water inlet 14A and an air inlet 14B are provided at the lower end. The water conduit 14 also has a number of holes 14C for spraying at least one of raw water and air from the inside of the water conduit 14 toward the raw water space S1.

[0054] The air diffuser 15 is for dispersing air in the raw water space S1. The air diffuser 15 has a disk shape that expands in the radial direction of the hollow fiber membrane bundle, and is installed below the lower end of the hollow fiber membrane 11. The air diffuser 15 has a plurality of air holes (not shown) formed at intervals in the radial direction. Air supplied from the air supply port 12C into the housing 12 is dispersed toward the hollow fiber membrane bundle through the air holes of the air diffuser 15.

[0055] 1, the upstream end of a treated water pipe 50 is connected to the outlet 12A of the housing 12. The downstream end of the treated water pipe 50 is connected to the inlet of a treated water tank (not shown). A treated water valve 51 (on / off valve) and a flow meter 52 downstream of the valve are installed in the treated water pipe 50. The diameter of the treated water pipe 50 is smaller than the diameter of the housing 12.

[0056] The upstream end of a drain pipe 53 is connected to the drain port 12D of the housing 12, and a drain valve 54 (opening and closing valve) is installed in the drain pipe 53. The diameter of the drain pipe 53 is smaller than the diameter of the housing 12.

[0057] One end of the air vent pipe 55 is connected to the air vent port 12B of the housing 12. The other end of the air vent pipe 55 branches into two. That is, the air vent pipe 55 includes a first branch portion 55A, a second branch portion 55B, and a connection portion 55C. One end of the connection portion 55C is connected to the air vent port 12B, and the other end is connected to the first branch portion 55A and the second branch portion 55B. The first branch portion 55A is open to the atmosphere, and the second branch portion 55B is connected to a portion of the drain pipe 53 that is downstream of the drain valve 54. An air vent valve 56 (opening and closing valve) is installed in the connection portion 55C. The diameter of the air vent pipe 55 is smaller than the diameter of the housing 12.

[0058] 1, the treated water pipe 50 and the drainage pipe 53 are connected to each other by a depressurization pipe 57. One end of the depressurization pipe 57 is connected to a portion of the treated water pipe 50 that is upstream of the treated water valve 51, and the other end of the depressurization pipe 57 is connected to a portion of the drainage pipe 53 that is downstream of the connection portion of the air vent pipe 55. A depressurization valve 58 (opening / closing valve) is installed in the depressurization pipe 57. The diameter of the depressurization pipe 57 is smaller than the diameter of the housing 12.

[0059] The raw water supply unit 20 includes a raw water piping 21, and a raw water pump 22 and a raw water valve 23 installed in the raw water piping 21. The raw water piping 21 has an upstream end connected to an outlet of a raw water tank (not shown) and a downstream end connected to a raw water inlet 14A of the water conveyance pipe 14. The diameter of the raw water piping 21 is smaller than the diameter of the housing 12. The raw water valve 23 is an opening / closing valve, and is installed in the raw water piping 21 downstream of the raw water pump 22.

[0060] The bubbling air supply unit 30 includes an air pipe 31, a first air valve 32, a second air valve 33, and a flow meter 34. The air pipe 31 is branched at the downstream end, and each branch is connected to the air supply port 12C of the housing 12 and the air inlet 14B of the water guide pipe 14, respectively. The diameter of the air pipe 31 is smaller than the diameter of the housing 12. The first air valve 32 and the second air valve 33 are open / close valves, and are installed at each branch of the air pipe 31, respectively. The upstream end of the air pipe 31 is connected to an air compressor (not shown).

[0061] The backwash air supply unit 40 includes an air pipe 41 and an air valve 42 (on-off valve) installed in the air pipe 41. The upstream end of the air pipe 41 is connected to an air compressor (not shown), and the downstream end is connected to a portion of the treated water pipe 50 that is upstream of the connection portion of the depressurization pipe 57. The diameter of the air pipe 41 is smaller than the diameter of the housing 12.

[0062] The water treatment device 1 further includes a measurement unit 60 that measures the pressure on at least one of the primary side and secondary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less (for example, at intervals of 2 seconds or less or 1 second or less) during the backwashing process of the hollow fiber membrane module 10. The measurement unit 60 in this embodiment includes a primary side pressure sensor 61 that measures the pressure on the primary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less, and a secondary side pressure sensor 62 that measures the pressure on the secondary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less.

[0063] 1, the primary pressure sensor 61 is installed in a portion of the raw water piping 21 between the raw water valve 23 and the raw water inlet 14A. The primary pressure sensor 61 may be installed in a portion of the water conduit 14 extending from the housing 12 or in a position of the housing 12 facing the raw water space S1.

[0064] The secondary pressure sensor 62 is installed at the connection between the treated water pipe 50 and the air pipe 41. In this embodiment, the primary pressure sensor 61 and the secondary pressure sensor 62 perform pressure measurement at intervals of 0.1 seconds or less, and the measurement data is sent to and stored in the control unit 70 described below. In other words, each measurement data is stored as logging data.

[0065] In addition to the primary side pressure sensor 61 and the secondary side pressure sensor 62, an air vent pressure sensor may be provided. The air vent pressure sensor is installed at the connection part 55C of the air vent pipe 55. The air vent pressure sensor measures the pressure at intervals of 0.1 seconds or more and 3 seconds or less, and each measurement data is sent to and stored in the control part 70 described below. In other words, the measurement data of the air vent pressure sensor is stored as logging data indicating the pressure on the primary side of the hollow fiber membrane module 10. However, since there are problems such that the more pressure sensors there are, the more time and effort it takes to analyze and the higher the cost, it is preferable to omit the air vent pressure sensor and analyze the data using the data from the primary side pressure sensor 61 and the secondary side pressure sensor 62.

[0066] The water treatment device 1 further includes a control unit 70. The control unit 70 is configured by a microcomputer including a CPU, RAM, ROM, etc. The control unit 70 controls the execution of the filtration operation. Specifically, the control unit 70 sequentially executes each process constituting the filtration operation cycle according to sequence information stored in the ROM or the like. When the control unit 70 starts the execution of each process, it controls the drive of peripheral devices and the opening and closing of valves according to the process to be executed according to the process information stored in the ROM or the like.

[0067] The functions of the control unit 70 include a prediction unit 71 and a notification unit 72. The prediction unit 71 predicts an increase in the transmembrane pressure difference of the hollow fiber membrane module 10 based on the result of pressure measurement by the measurement unit 60. The transmembrane pressure difference of the hollow fiber membrane module 10 is the differential pressure between the secondary side pressure and the primary side pressure of the hollow fiber membrane module 10, and is obtained by subtracting the primary side pressure from the secondary side pressure. The notification unit 72 notifies the result of the evaluation by the prediction unit 71.

[0068] The prediction unit 71 and the notification unit 72 do not have to be realized as a function of the control unit 70. The control unit 70, the prediction unit 71, and the notification unit 72 may each be configured by an individual microcomputer.

[0069] 2 shows each step of the water treatment method carried out using the water treatment device 1, and also shows the on / off state of the raw water pump 22 and the open / closed state of each valve in each step. A circle in Fig. 2 indicates the on state of the raw water pump 22 or the open state of the valve, and a blank space indicates the off state of the raw water pump 22 or the closed state of the valve.

[0070] First, in the first filling step, the raw water pump 22 is operated, and the raw water valve 23 and the air vent valve 56 are opened. As a result, raw water is supplied into the water conduit 14 through the raw water piping 21, and raw water is supplied into the raw water space S1 through the hole 14C.

[0071] After the first water filling step is completed, the process moves to the filtration step. In the filtration step, the air vent valve 56 is closed and the treated water valve 51 is opened. The raw water permeates the membrane wall from the outer surface to the inner surface of the hollow fiber membrane 11 and flows into the treated water space S2 through the hollow part of the membrane. The treated water then flows out of the housing 12 through the outlet 12A and is collected in the treated water tank (not shown) through the treated water piping 50.

[0072] After the filtration process, physical cleaning is performed to remove impurities that have adhered to the outer surface of the hollow fiber membrane 11 during filtration. The physical cleaning includes a backwash preparation process (depressurization process), a backwash process, an air venting process, a second water filling process, an air diffuser bubbling process, a third water filling process, a water pipe bubbling process, a drainage process, and a depressurization process.

[0073] First, in the backwash preparation process (depressurization process), the raw water pump 22 is switched from on to off.

[0074] Next, in the backwashing process, the raw water valve 23 and the treated water valve 51 are closed, and the air valve 42 and the drain valve 54 are opened. That is, at the same time as the air valve 42 is opened, the pressure of the air pressurized by the compressor is instantaneously applied to the treated water on the secondary side of the hollow fiber membrane module 10. As a result, the treated water on the secondary side of the hollow fiber membrane module 10 is pressurized by the air (medium) pressurized to a predetermined pressure, and the treated water permeates the membrane wall from the inner surface to the outer surface of the hollow fiber membrane 11. As a result, the impurities attached to the outer surface of the hollow fiber membrane 11 become easy to peel off. At this time, the primary side pressure sensor 61 and the secondary side pressure sensor 62 measure the pressure at intervals of 3 seconds or less, so that it is possible to detect the pressure after the hollow fiber membrane 11 is pressurized from the inner surface and before the impurities on the membrane surface become easy to peel off. The above-mentioned predetermined pressure is preferably 30 kPa to 500 kPa, more preferably 50 kPa to 300 kPa, and most preferably 50 kPa to 200 kPa.

[0075] In the backwashing process, the secondary pressure sensor 62 measures the pressure on the secondary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less. This provides logging data (FIG. 3) showing the time change in the secondary pressure of the hollow fiber membrane module 10 during the backwashing process. In FIG. 3, the horizontal axis shows time, and the vertical axis shows the secondary pressure of the hollow fiber membrane module 10. Graph G31 in FIG. 3 shows the time change in the secondary pressure of the hollow fiber membrane module 10 during the backwashing process immediately before the most recent backwashing process. Graph G32 in FIG. 3 shows the time change in the secondary pressure of the hollow fiber membrane module 10 during the most recent backwashing process. In other words, graph G31 shows the time change in the secondary pressure during the backwashing process one cycle before graph G32.

[0076] Immediately after the start of the backwashing process, the treated water on the secondary side is suddenly pushed by the pressurized air and flows into the primary side. At this time, the permeation of the treated water through the hollow fiber membrane 11 becomes the rate-limiting step, and the degree to which the treated water is pressurized by the air is greater than the permeation of the treated water to the primary side. For this reason, the pressure on the secondary side increases immediately after the start of the backwashing process. Then, some of the impurities attached to the surface of the hollow fiber membrane 11 peel off or become easily peeled off due to the force of the treated water being pushed out to the primary side, and the pressure on the secondary side is instantaneously reduced or maintained. After that, the pressure on the secondary side increases again due to pressurization by the air. In this way, the pressure on the secondary side increases instantaneously immediately after the start of the backwashing process. The higher the amount of impurities attached to the hollow fiber membrane 11 and the larger the permeation resistance of the hollow fiber membrane 11, the higher the reached pressure on the secondary side during this increase.

[0077] The prediction unit 71 refers to the logging data stored in the control unit 70 and predicts a future increase in the transmembrane pressure difference of the hollow fiber membrane module 10 based on the difference between multiple backwashing processes in the arrival point of the secondary side pressure that instantaneously increased immediately after the start of the backwashing process. The multiple backwashing processes may be, for example, the most recent backwashing process and the backwashing process performed immediately before the most recent backwashing process, or the most recent backwashing process and multiple backwashing processes performed before the most recent backwashing process.

[0078] Specifically, if the secondary side attained pressure immediately after the start of the backwashing process between multiple backwashing processes shows an increasing tendency, the prediction unit 71 predicts that the transmembrane pressure difference of the hollow fiber membrane module 10 will increase in the future, because the amount of impurities adhering to the hollow fiber membrane 11 is increasing and the permeation resistance of the hollow fiber membrane 11 is increasing.

[0079] In the example of Fig. 3, the secondary side ultimate pressure P32 immediately after the start of the most recent backwashing step is higher than the secondary side ultimate pressure P31 immediately after the start of the backwashing step immediately preceding the most recent backwashing step. Therefore, the prediction unit 71 predicts that the transmembrane pressure of the hollow fiber membrane module 10 will increase in the future.

[0080] In the backwashing process, when the pushing of the treated water on the secondary side to the primary side is completed, the secondary side is filled with pressurized air, and the pressure on the secondary side is stabilized by the air pressure. Here, the greater the amount of impurities attached to the hollow fiber membrane 11 and the greater the permeation resistance of the hollow fiber membrane 11, the longer the time required for all the treated water on the secondary side to be pushed to the primary side. Therefore, the greater the amount of impurities attached to the hollow fiber membrane 11 and the greater the permeation resistance of the hollow fiber membrane 11, the longer the time from the start of the backwashing process until the pressure on the secondary side is stabilized by the air pressure.

[0081] In addition, pressure stabilization refers to, for example, when an increasing pressure reaches an inflection point where the slope of the pressure increase decreases, when a decreasing pressure reaches an inflection point where the slope of the pressure decrease increases, or when an increasing or decreasing pressure continues to fluctuate within a predetermined tolerance range for a predetermined period of time or more.

[0082] For this reason, the prediction unit 71 may refer to the logging data stored in the control unit 70 and predict a future increase in the transmembrane pressure difference of the hollow fiber membrane module 10 based on the difference in the time from the start of the backwashing process until the secondary side pressure stabilizes at the air pressure over multiple backwashing processes.

[0083] Specifically, it is assumed that the time from the start of the backwashing process until the secondary pressure stabilizes at the air pressure shows an increasing tendency between multiple backwashing processes. In this case, the prediction unit 71 predicts that the transmembrane pressure of the hollow fiber membrane module 10 will increase in the future because the amount of impurities adhering to the hollow fiber membranes 11 is increasing and the permeation resistance of the hollow fiber membranes 11 is increasing.

[0084] 3, the time t32 from the start of the most recent backwashing step to when the secondary pressure stabilizes at the air pressure is longer than the time t31 from the start of the backwashing step immediately preceding the most recent backwashing step to when the secondary pressure stabilizes at the air pressure. Therefore, the prediction unit 71 predicts that the transmembrane pressure of the hollow fiber membrane module 10 will increase in the future.

[0085] In the backwashing process, the primary pressure sensor 61 measures the primary pressure of the hollow fiber membrane module 10 at intervals of 3 seconds or less. This provides logging data (FIG. 4) that shows the change over time in the primary pressure of the hollow fiber membrane module 10 during the backwashing process.

[0086] As described above, the primary side pressure of the hollow fiber membrane module 10 is measured by the air vent port pressure sensor at intervals of 3 seconds or less. In this case, the prediction unit 71 may use data indicating an average value of the primary side pressure indicated by the logging data received from each of the primary side pressure sensor 61 and the air vent port pressure sensor as logging data indicating the primary side pressure of the hollow fiber membrane module 10.

[0087] In Fig. 4, the horizontal axis represents time, and the vertical axis represents the primary pressure of the hollow fiber membrane module 10. Graph G41 in Fig. 4 represents the change over time in the primary pressure of the hollow fiber membrane module 10 during the backwashing step immediately preceding the most recent backwashing step. Graph G42 in Fig. 4 represents the change over time in the primary pressure of the hollow fiber membrane module 10 during the most recent backwashing step.

[0088] 4, immediately after the backwash process is started and the treated water on the secondary side is pushed out to the primary side, the diameter of the drain pipe 53 is smaller than the housing 12, so that the pressure on the primary side increases instantaneously due to the pipeline resistance generated when the raw water on the primary side flows into the drain pipe 53. At this time, the greater the amount of impurities attached to the hollow fiber membrane 11 and the greater the permeation resistance of the hollow fiber membrane 11, the slower the speed at which the treated water on the secondary side is pushed out to the primary side, and the lower the ultimate pressure on the primary side.

[0089] For this reason, the prediction unit 71 may refer to the logging data stored in the control unit 70 and predict the future increase in the transmembrane pressure difference of the hollow fiber membrane module 10 based on the difference in the reach of the primary side pressure that instantaneously increases immediately after the start of the backwashing process over multiple backwashing processes.

[0090] Specifically, in the case where the primary side ultimate pressure immediately after the start of the backwashing process shows a decreasing tendency in multiple backwashing processes, the prediction unit 71 may predict that the transmembrane pressure of the hollow fiber membrane module 10 will increase in the future because the amount of impurities adhering to the hollow fiber membranes 11 is increasing and the permeation resistance of the hollow fiber membranes 11 is increasing.

[0091] In the example of Fig. 4, the primary side ultimate pressure P42 immediately after the start of the most recent backwashing step is lower than the primary side ultimate pressure P41 immediately after the start of the backwashing step immediately preceding the most recent backwashing step. Therefore, the prediction unit 71 predicts that the transmembrane pressure of the hollow fiber membrane module 10 will increase in the future.

[0092] In addition, after the backwash process is started and the pressure on the primary side increases instantaneously immediately after the secondary side treated water is pushed to the primary side, the speed at which the treated water is pushed to the primary side becomes slower the greater the amount of impurities attached to the hollow fiber membrane 11 and the greater the permeation resistance of the hollow fiber membrane 11, and the longer it takes to complete the pushing of the treated water to the secondary side.

[0093] For this reason, the prediction unit 71 may refer to the logging data stored in the control unit 70 and predict the future increase in the transmembrane pressure difference of the hollow fiber membrane module 10 based on the difference between multiple backwashing processes in the time from the start of the backwashing process to the time when the pressure on the primary side stabilizes at a predetermined end pressure (e.g., 0 kPa), which indicates the end of the pushing of treated water to the secondary side.

[0094] Specifically, it is assumed that the time from the start of the backwashing process until the pressure on the primary side stabilizes at the end pressure shows an increasing tendency in multiple backwashing processes. In this case, the prediction unit 71 may predict that the transmembrane pressure of the hollow fiber membrane module 10 will increase in the future because the amount of impurities adhering to the hollow fiber membranes 11 is increasing and the permeation resistance of the hollow fiber membranes 11 is increasing.

[0095] 4, the time t42 from the start of the most recent backwashing step to the time the primary pressure stabilizes at the end pressure is longer than the time t41 from the start of the backwashing step immediately preceding the most recent backwashing step to the time the primary pressure stabilizes at the end pressure. Therefore, the prediction unit 71 predicts that the transmembrane pressure of the hollow fiber membrane module 10 will increase in the future.

[0096] In addition, the inventor conducted a test run and, using the logging data (Figures 5 and 6) obtained in each of a backwashing process when the amount of impurities adhering to the hollow fiber membrane 11 was less than a predetermined amount (hereinafter referred to as the first backwashing process) and a backwashing process when the amount of impurities adhering to the hollow fiber membrane 11 was more than a predetermined amount (hereinafter referred to as the second backwashing process), calculated the integral value of the difference between the secondary side pressure and the primary side pressure from the start of the backwashing process to the time when the primary side pressure stabilized.

[0097] In Figures 5 and 6, the horizontal axis represents time, and the vertical axis represents the pressure on the primary side and secondary side of the hollow fiber membrane module 10. Graph G51 in Figure 5 represents the change over time in the primary side pressure of the hollow fiber membrane module 10 in the first backwashing process. Graph G52 in Figure 5 represents the change over time in the secondary side pressure of the hollow fiber membrane module 10 in the first backwashing process. Graph G61 in Figure 6 represents the change over time in the primary side pressure of the hollow fiber membrane module 10 in the second backwashing process. Graph G62 in Figure 6 represents the change over time in the secondary side pressure of the hollow fiber membrane module 10 in the second backwashing process.

[0098] Next, the inventors calculated the integral value of the difference between the secondary side pressure and the primary side pressure during the time t50 to t51 (hereinafter, the target time) from the start time t50 of the first backwashing process to the time t51 when the primary side pressure stabilizes, using the logging data shown in Fig. 5 obtained during the first backwashing process. Note that in Fig. 5, the integral value of the difference between the secondary side pressure and the primary side pressure during the target time t50 to t51 corresponds to the area of ​​the region surrounded by the dashed line indicating the start time t50 of the first backwashing process, the dashed line indicating the time t51 when the primary side pressure stabilizes, the graph G52, and the graph G51.

[0099] Similarly, using the logging data shown in Figure 6 obtained in the second backwashing process, the inventors set the time t60 to t61 from the start time t60 of the second backwashing process to the time t61 at which the primary side pressure stabilizes as the target time, and calculated the integral value of the difference between the secondary side pressure and the primary side pressure during the target time t60 to t61.

[0100] The inventors compared the measurement results of the difference between the secondary side pressure and the primary side pressure in the filtration process performed after the first backwashing process with the measurement results of the difference in the filtration process performed after the second backwashing process, and the calculation results of the integral value. As a result, the inventors found that even if the difference between the secondary side pressure and the primary side pressure during the filtration process is approximately constant when the amount of impurities adhering to the hollow fiber membrane 11 is greater than a predetermined amount and when it is less than a predetermined amount, the integral value during the predetermined period significantly differs between when the amount of impurities adhering to the hollow fiber membrane 11 is greater than a predetermined amount and when it is less than a predetermined amount.

[0101] This is presumably due to the fact that the time from the start of the backwashing process until the primary side pressure, which instantaneously increases immediately after the start of the backwashing process, reaches its target point, and the time from when the primary side pressure, which instantaneously increases immediately after the start of the backwashing process, reaches its target point until it stabilizes, become longer the greater the amount of impurities adhering to the hollow fiber membrane 11.

[0102] In the same manner, the inventor changed the target time to the time from the start time t50 of the first backwashing process until the pressure on the primary side, which increases instantaneously immediately after the start of the first backwashing process, reaches the end point P51, and calculated the integral value. The inventor also changed the target time to the time from the start time t60 of the second backwashing process until the pressure on the primary side, which increases instantaneously immediately after the start of the second backwashing process, reaches the end point P61, and calculated the integral value. In this case, the inventor also obtained the same findings as above.

[0103] The inventor changed the target time to the time from when the pressure on the primary side, which increases instantaneously immediately after the start of the first backwashing process, reaches the point P51 until the point t51 at which the pressure stabilizes, and calculated the integral value, and changed the target time to the time from when the pressure on the primary side, which increases instantaneously immediately after the start of the second backwashing process, reaches the point P61 until the point t61 at which the pressure stabilizes, and calculated the integral value. In this case, the inventor also obtained the same findings as above.

[0104] Furthermore, the inventor changed the target time to the time from the start time t50 of the first backwashing process to the time t52 when the secondary pressure stabilizes, and calculated the integral value, and changed the target time to the time from the start time t60 of the second backwashing process to the time t62 when the secondary pressure stabilizes, and calculated the integral value. In this case, the inventor also obtained the same findings as above.

[0105] The inventor changed the target time to the time from the start time t50 of the first backwashing process until the secondary side pressure, which increases instantaneously immediately after the start of the backwashing process, reaches the point P52, and calculated the integral value, and changed the target time to the time from the start time t60 of the second backwashing process until the secondary side pressure, which increases instantaneously immediately after the start of the second backwashing process, reaches the point P62, and calculated the integral value. In this case, the inventor also obtained the same findings as above.

[0106] The inventor changed the target time to the time from when the secondary side pressure, which increases instantaneously immediately after the start of the first backwashing process, reaches the point P52 until the point t52 at which the pressure stabilizes, and calculated the integral value, and changed the target time to the time from when the secondary side pressure, which increases instantaneously immediately after the start of the second backwashing process, reaches the point P62 until the point t62 at which the pressure stabilizes, and calculated the integral value. In this case, the inventor also obtained the same findings as above.

[0107] The present inventors have also found that the greater the amount of impurities adhering to the hollow fiber membrane 11, the larger the integral value at each of the above-mentioned target times becomes.

[0108] Therefore, based on the above knowledge obtained by the present inventor, the prediction unit 71 may calculate, for multiple backwashing processes, an integral value of the difference between the secondary side pressure and the primary side pressure at any one of the following times: a time from the start of the backwashing process until the primary side or secondary side pressure, which increases instantaneously immediately after the start of the backwashing process, reaches a target point; a time from the start of the backwashing process until the primary side or secondary side pressure, which increases instantaneously immediately after the start of the backwashing process, reaches a target point and stabilizes; and a time from the start of the backwashing process until the primary side or secondary side pressure stabilizes. Then, the prediction unit 71 may predict a future increase in the transmembrane pressure of the hollow fiber membrane module 10 based on the difference in the integral value between the multiple backwashing processes.

[0109] Specifically, it is assumed that the integral value calculated in multiple backwashing processes shows an increasing tendency. In this case, since the amount of impurities adhering to the hollow fiber membranes 11 is increasing, the prediction unit 71 may predict that the permeation resistance of the hollow fiber membranes 11 will increase and the transmembrane pressure difference of the hollow fiber membrane module 10 will increase in the future.

[0110] As described above, immediately after the start of the backwashing process, the pressure on the secondary side increases instantaneously. At this time, the ultimate pressure on the secondary side increases as the amount of impurities adhering to the hollow fiber membrane 11 increases. As the pressure on the secondary side increases, the permeation rate of the treated water increases, and the fouling components adhering to the outer surface of the hollow fiber membrane 11 become more likely to peel off. Thereafter, when some of the fouling components adhering to the outer surface of the hollow fiber membrane 11 are peeled off, the pressure on the secondary side decreases instantaneously, but increases again due to pressurization by air. This increases the speed at which the treated water is pushed out to the primary side.

[0111] On the other hand, immediately after the secondary-side treated water is pushed out to the primary side, the pressure on the primary side increases instantaneously due to the pipeline resistance that occurs when the primary-side raw water flows into the drainage pipe 53. At this time, the greater the amount of impurities adhering to the hollow fiber membrane 11, the slower the speed at which the secondary-side treated water is pushed out to the primary side. For this reason, the primary-side ultimate pressure that instantaneously increases immediately after the start of the backwashing process becomes lower as the amount of impurities adhering to the hollow fiber membrane 11 increases. After that, when some of the impurities adhering to the outer surface of the hollow fiber membrane 11 are peeled off and the speed at which the treated water is pushed out to the primary side increases, the speed at which the primary-side water is discharged also increases, and the pressure on the primary side drops rapidly.

[0112] In other words, when the pressure on the primary or secondary side, which increases instantaneously immediately after the start of the backwash process, reaches a target point and just before some of the impurities adhering to the outer surface of the hollow fiber membrane 11 are peeled off, the difference between the pressure on the secondary side and the pressure on the primary side becomes larger the greater the amount of impurities adhering to the hollow fiber membrane 11.

[0113] For this reason, the prediction unit 71 may refer to the logging data stored in the control unit 70 and detect the arrival point of either the primary side or secondary side pressure that instantaneously increases immediately after the start of the backwashing process for multiple backwashing processes. The prediction unit 71 may then predict a future increase in the transmembrane pressure of the hollow fiber membrane module 10 based on the difference between the secondary side pressure and the primary side pressure at the time when either of the pressures reaches its arrival point, between the multiple backwashing processes.

[0114] Specifically, it is assumed that the difference between the secondary side pressure and the primary side pressure at the time when any of the pressures that instantaneously increased immediately after the start of the backwashing process reaches a target point during multiple backwashing processes shows an upward trend. In this case, since the amount of impurities adhering to the hollow fiber membranes 11 is increasing, the prediction unit 71 may predict that the permeation resistance of the hollow fiber membranes 11 will increase and the transmembrane pressure difference of the hollow fiber membrane module 10 will increase in the future.

[0115] In this case, since the pressure of at least one of the primary side and the secondary side of the hollow fiber membrane module 10 is measured at intervals of 3 seconds or less for multiple backwashing processes, the arrival point of either the primary side or the secondary side pressure that instantaneously increased immediately after the start of the backwashing process can be detected. That is, even if the impurities are such that they peel off from the hollow fiber membrane surface due to the force of the treated water being pushed from the secondary side to the primary side in the backwashing process, the pressure of either of the above before it decreases due to the impurities peeling off can be properly detected. As a result, by using the difference between the pressure on the secondary side and the pressure on the primary side at the time of detection, the change in the amount of impurities attached to the hollow fiber membrane 11 can be properly grasped. Therefore, when the prediction unit 71 grasps that the amount of impurities attached to the hollow fiber membrane 11 is increasing, it can properly predict that the permeation resistance of the hollow fiber membrane 11 will increase and the transmembrane pressure difference of the hollow fiber membrane module 10 will increase.

[0116] When the prediction unit 71 predicts a future increase in the transmembrane pressure difference of the hollow fiber membrane module 10, the notification unit 72 notifies the result of the prediction by the prediction unit 71.

[0117] Specifically, the notification unit 72 uses a communication device (not shown) provided in the water treatment device 1 to send an email including a message indicating that a future increase in the transmembrane pressure difference of the hollow fiber membrane module 10 has been predicted to an information processing device such as a personal computer, tablet terminal, or smartphone owned by the administrator of the water treatment device 1. The result of the prediction by the prediction unit 71 is not limited to the above message, and may include logging data (FIG. 3) used by the prediction unit 71 for the prediction.

[0118] The water treatment device 1 may also be provided with an audio output device such as a speaker, and the notification unit 72 may output a sound indicating that it has predicted a future increase in the transmembrane pressure difference of the hollow fiber membrane module 10 from the audio output device. The water treatment device 1 may also be provided with a display device such as a liquid crystal display, and the notification unit 72 may display the above message and the logging data (FIG. 3) used by the prediction unit 71 for the prediction on the display device. Alternatively, the notification unit 72 may combine two or more of these communication devices, audio output devices, and display devices, and cause the two or more devices to notify the results of the prediction by the prediction unit 71.

[0119] Next, in the air release step (depressurization step), the air valve 42 and the drain valve 54 are closed, and the depressurization valve 58 is opened. As a result, the air accumulated on the secondary side of the hollow fiber membrane module 10 is discharged through the depressurization pipe 57.

[0120] Next, in the second water filling step, similarly to the first water filling step, the raw water pump 22 is operated, and the raw water valve 23 and the air vent valve 56 are each opened.

[0121] Next, in the air diffuser bubbling process, the raw water pump 22 is switched from on to off, the raw water valve 23 is closed, and the first air valve 32 is opened. The air bleed valve 56 is kept open. As a result, air is supplied from the air supply port 12C into the housing 12, and the air is dispersed toward the hollow fiber membrane bundle by the air diffuser 15. As a result, the hollow fiber membrane bundle is rocked by the air bubbles, and impurities attached to the membrane surface are peeled off.

[0122] Next, in the third water filling step, as in the first and second water filling steps, the raw water pump 22 is operated, and the raw water valve 23 and the air vent valve 56 are opened. This causes the raw water drained in the air diffuser bubbling step to be replenished into the housing 12.

[0123] Next, in the water conduit bubbling process, the raw water pump 22 is switched from on to off, the raw water valve 23 is closed, and the second air valve 33 is opened. This causes compressed air from the compressor to be supplied into the water conduit 14 from the air inlet 14B and into the raw water space S1 through the hole 14C. This causes the hollow fiber membrane bundle to be bubbling washed.

[0124] Next, in the drainage process, the air vent valve 56 is closed and the drainage valve 54 is opened. The second air valve 33 is maintained open. As a result, the raw water in the raw water space S1 is pushed by the air and discharged outside the housing 12 through the drain port 12D.

[0125] Finally, in the depressurization step, the second air valve 33 is closed while the drain valve 54 is left open. This allows air to be removed from inside the housing 12 (the raw water space S1). After the hollow fiber membrane module 10 is physically cleaned by the above process, the process returns to the first water filling step, and the filtration operation is resumed.

[0126] The timing at which the prediction unit 71 predicts the increase in the transmembrane pressure difference of the hollow fiber membrane module 10 is not particularly limited, and may be, for example, every time the operation cycle of Fig. 2 is performed, or every time the operation cycle of Fig. 2 is repeated a number of times (e.g., 10 times), or once a day, once a week, or once a month. This frequency may be appropriately determined depending on the type of raw water (e.g., river water, wastewater, or sewage), the season, etc.

[0127] In the backwashing process, the treated water on the secondary side may be pressurized by a permeated liquid pressurized to a predetermined pressure instead of air pressurized to a predetermined pressure. A chemical may be injected into the permeated liquid.

[0128] As described above, in the water treatment device 1 according to this embodiment, in the backwashing process of the hollow fiber membrane module 10, the treated water on the secondary side is pushed to the primary side by pressurized air. This allows the treated water to not only pass through the parts of the hollow fiber membrane 11 where impurities are not attached, but also collide with the parts where impurities are attached. As a result, the pressure applied to the treated water can be changed according to the amount of attached impurities. Therefore, the pressure on at least one of the primary side and the secondary side of the hollow fiber membrane module 10 according to the amount of attached impurities on the hollow fiber membrane 11 can be measured.

[0129] Moreover, in each of the multiple backwashing processes, the pressure on at least one of the primary side and secondary side of the hollow fiber membrane module 10 is measured at intervals of 3 seconds or less, which is shorter than the usual measurement interval of the transmembrane pressure difference in the filtration process. Therefore, it is possible to grasp the detailed time transition of the pressure on at least one of the sides in each backwashing process, which is completed within a few minutes.

[0130] Therefore, from the difference in the detailed time transition between multiple backwashing processes, it is possible to grasp the change in the amount of impurities adhering to the hollow fiber membrane 11 in response to the change in the pressure on at least one side. Therefore, when it is grasped that the amount of impurities adhering to the hollow fiber membrane 11 is increasing, it is possible to predict that the transmembrane pressure difference will increase in the future, and the prediction result can be notified.

[0131] There is no particular limitation on the timing at which the notification unit 72 notifies the prediction result by the prediction unit 71. The notification unit 72 may notify the prediction result every time the prediction unit 71 predicts a future increase in the transmembrane pressure, or may notify a predetermined number of prediction results collectively every time the prediction unit 71 predicts a future increase in the transmembrane pressure a predetermined number of times.

[0132] (Modified embodiment) Although the embodiments of the transmembrane pressure prediction method and the water treatment device according to the present invention have been described above, the present invention is not limited thereto, and for example, modified embodiments such as those described below can be adopted.

[0133] (1) In the above embodiment, the measurement unit 60 measures the pressures on the primary side and the secondary side of the hollow fiber membrane module 10 in each of the multiple backwashing steps, and the prediction unit 71 predicts a future increase in the transmembrane pressure of the hollow fiber membrane module 10 based on the difference in the measurement results between the multiple backwashing steps. However, the present invention is not limited to this, and the measurement unit 60 may measure the pressure on the primary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less in each of the multiple first water-filling steps, similar to the backwashing step in the above embodiment. Alternatively, the measurement unit 60 may measure the pressure on the primary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less only in each of the multiple first water-filling steps, similar to the backwashing step in the above embodiment. Then, the prediction unit 71 may predict a future increase in the transmembrane pressure of the hollow fiber membrane module 10 based on the difference in the measurement results between the multiple first water-filling steps.

[0134] Specifically, in the first water filling step, the primary side pressure sensor 61 measures the pressure on the primary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less. This provides logging data (FIG. 7) that shows the change over time in the pressure on the primary side of the hollow fiber membrane module 10 during the first water filling step. In the graph of FIG. 7, the horizontal axis represents time, and the vertical axis represents the pressure on the primary side of the hollow fiber membrane module 10.

[0135] As shown in FIG. 7, when the first water-filling step is started (time t70 in FIG. 7) and raw water flows into the hollow fiber membrane module 10, the pressure on the primary side gradually increases due to the hydraulic head pressure inside the hollow fiber membrane module 10. After that, when the inside of the hollow fiber membrane module 10 approaches a full water state (time t71 in FIG. 7), raw water flows into the air vent pipe 55. At that time, since the diameter of the air vent pipe 55 is smaller than the diameter of the housing 12, pipe resistance occurs, and the pressure on the primary side increases rapidly. Therefore, the time t70 to t71 from the start of the first water-filling step to the inflection point of the change in the primary side pressure, indicated by the double arrow in FIG. 7, becomes shorter as the amount of impurities accumulated inside the hollow fiber membrane module 10 increases and the effective volume inside the hollow fiber membrane module 10 decreases.

[0136] Furthermore, it is estimated that the greater the amount of impurities accumulated inside the hollow fiber membrane module 10 and the smaller the effective volume inside the hollow fiber membrane module 10, the greater the amount of impurities adhering to the hollow fiber membranes 11, i.e., the greater the situation in which the transmembrane pressure difference of the hollow fiber membrane module 10 will increase in the future.

[0137] For this reason, the prediction unit 71 may refer to the logging data (Figure 7) stored in the control unit 70 and predict a future increase in the transmembrane pressure difference of the hollow fiber membrane module 10 based on the difference in the time from the start of the first water-filling step to the time when the change in the primary side pressure reaches an inflection point (t70 to t71 in Figure 7) between multiple first water-filling steps.

[0138] Specifically, it is assumed that the time from the start of the first water-filling step to the inflection point of the change in the primary side pressure (t70 to t71 in FIG. 7) shows a decreasing trend among multiple first water-filling steps. In this case, the prediction unit 71 may predict that the transmembrane pressure of the hollow fiber membrane module 10 will increase in the future, since the amount of impurities accumulated inside the hollow fiber membrane module 10 is increasing and the effective volume inside the hollow fiber membrane module 10 is decreasing.

[0139] As described above, in this modified embodiment, in the first water filling step, the pressure on the primary side of the hollow fiber membrane module 10 is measured when the raw water is filled into the hollow fiber membrane module 10. Therefore, in this modified embodiment, the pressure on the primary side of the hollow fiber membrane module 10 according to the amount of accumulated impurities inside the hollow fiber membrane module 10 can be measured.

[0140] Moreover, in this modified embodiment, in each of the multiple first water-filling steps, the pressure on the primary side of the hollow fiber membrane module 10 is measured at intervals of 3 seconds or less, which is shorter than the normal measurement interval of the transmembrane pressure difference in the filtration step. This makes it possible to grasp the detailed temporal transition of the pressure on the primary side of the hollow fiber membrane module 10 in each first water-filling step, which is completed within a few minutes.

[0141] Therefore, from the difference in this detailed time progression between multiple first water filling processes, it is possible to grasp the change in the amount of accumulated impurities inside the hollow fiber membrane module 10 in response to the change in the primary side pressure of the hollow fiber membrane module 10.

[0142] Specifically, the change in the amount of impurities accumulated and the effective volume inside the hollow fiber membrane module 10 can be grasped from the difference between the time t70 to t71 (FIG. 7) from the start time t70 (FIG. 7) of the first water-filling step to the time t71 (FIG. 7) at which the inflection point of the change in the primary side pressure is reached during multiple first water-filling steps. Therefore, when it is grasped that the amount of impurities accumulated inside the hollow fiber membrane module 10 is increasing and the effective volume inside the hollow fiber membrane module 10 is decreasing, it is possible to appropriately predict that the amount of impurities adhering to the hollow fiber membranes 11 is increasing, that is, that the transmembrane pressure difference will increase in the future, and the prediction result can be notified.

[0143] (2) In the above modified embodiment, the measurement unit 60 measures the pressure on the primary side of the hollow fiber membrane module 10 in each of the multiple first water filling steps, and the prediction unit 71 predicts a future increase in the transmembrane pressure of the hollow fiber membrane module 10 based on the difference in the measurement results between the multiple first water filling steps. In the same manner, the measurement unit 60 may also measure the pressure on the primary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less in each of the multiple drainage steps. Alternatively, the measurement unit 60 may measure the pressure on the primary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less only in each of the multiple drainage steps. Then, the prediction unit 71 may predict a future increase in the transmembrane pressure of the hollow fiber membrane module 10 based on the difference in the measurement results between the multiple drainage steps.

[0144] Specifically, in the water discharge process, the primary side pressure sensor 61 measures the pressure on the primary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less. This provides logging data (FIG. 8) that shows the change over time in the pressure on the primary side of the hollow fiber membrane module 10 during the water discharge process. In the graph of FIG. 8, the horizontal axis represents time, and the vertical axis represents the pressure on the primary side of the hollow fiber membrane module 10.

[0145] As shown in Fig. 8, when the drainage process is started (time t80 in Fig. 8), the drain water inside the hollow fiber membrane module 10 is discharged through the drainage pipe 53 (Fig. 1). Thereafter, when the drainage of the drain water inside the hollow fiber membrane module 10 is completed (time t81 in Fig. 8), the pressure on the primary side stabilizes at a predetermined drainage completion pressure near 0 KPa, which indicates the completion of the drainage of the drain water. Therefore, the time t80 to t81 from the start of the drainage process until the pressure on the primary side becomes constant, as indicated by the double-headed arrow in Fig. 8, becomes shorter the greater the amount of accumulated impurities inside the hollow fiber membrane module 10 and the smaller the effective volume inside the hollow fiber membrane module 10.

[0146] Furthermore, it is estimated that the greater the amount of impurities accumulated inside the hollow fiber membrane module 10 and the smaller the effective volume inside the hollow fiber membrane module 10, the greater the amount of impurities adhering to the hollow fiber membranes 11, i.e., the greater the situation in which the transmembrane pressure difference of the hollow fiber membrane module 10 will increase in the future.

[0147] For this reason, the prediction unit 71 may refer to the logging data (FIG. 8) stored in the control unit 70 and predict the future increase in the transmembrane pressure difference of the hollow fiber membrane module 10 based on the difference in the time from the start of the drainage process to the time when the primary side pressure becomes constant (t80 to t81 in FIG. 8) between multiple drainage processes.

[0148] Specifically, the time from the start of the drainage process to when the pressure on the primary side becomes constant (t80 to t81 in FIG. 8) shows a decreasing trend among multiple drainage processes. In this case, the prediction unit 71 may predict that the transmembrane pressure of the hollow fiber membrane module 10 will increase in the future, since the amount of impurities accumulated inside the hollow fiber membrane module 10 is increasing and the effective volume inside the hollow fiber membrane module 10 is decreasing.

[0149] As described above, in this modified embodiment, the pressure on the primary side of the hollow fiber membrane module 10 is measured when drain water is discharged from inside the hollow fiber membrane module 10 in the drainage step. Therefore, in this modified embodiment, the pressure on the primary side of the hollow fiber membrane module 10 according to the amount of accumulated impurities inside the hollow fiber membrane module 10 can be measured.

[0150] Moreover, in this modified embodiment, in each of the multiple drainage steps, the pressure on the primary side of the hollow fiber membrane module 10 is measured at intervals of 3 seconds or less, which is shorter than the usual measurement interval of the transmembrane pressure difference in the filtration step. This makes it possible to grasp the detailed temporal transition of the pressure on the primary side of the hollow fiber membrane module 10 in each drainage step, which is completed within a few minutes.

[0151] Therefore, according to this modified embodiment, the change in the amount of accumulated impurities inside the hollow fiber membrane module 10 in response to the change in the pressure on the primary side of the hollow fiber membrane module 10 can be understood from the difference in this detailed time progression between multiple drainage processes.

[0152] Specifically, the change in the amount of impurities accumulated and the effective volume inside the hollow fiber membrane module 10 can be grasped from the difference between the time t80 to t81 (FIG. 8) from the start time t80 (FIG. 8) of the drainage process to the time t81 (FIG. 8) when the pressure on the primary side becomes constant, between multiple drainage processes. Therefore, when it is grasped that the amount of impurities accumulated inside the hollow fiber membrane module 10 is increasing and the effective volume inside the hollow fiber membrane module 10 is decreasing, it is possible to appropriately predict the amount of impurities adhering to the hollow fiber membranes 11 is increasing, that is, the transmembrane pressure difference will increase in the future, and the prediction result can be notified.

[0153] The disclosed embodiments and their modified embodiments are illustrative in all respects and should not be construed as limiting. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0154] 1: Water treatment equipment 10: Hollow fiber membrane module 11: Hollow fiber membrane 60: Measuring part 71: Prediction Department 72: Information Department

Claims

1. A method for predicting a transmembrane pressure difference in a water treatment device that filters raw water using a hollow fiber membrane module, comprising: When a backwashing process in which treated water on the secondary side of the hollow fiber membrane module is pushed to the primary side of the hollow fiber membrane module by a pressurized medium is performed multiple times, measuring the pressure on at least one of the primary side and the secondary side at intervals of 3 seconds or less in each of the multiple backwashing processes; predicting a future increase in transmembrane pressure of the hollow fiber membrane module based on a difference in the measurement results of the pressure on at least one side during the multiple backwashing processes; notifying the result of the prediction; and Including, In each of the plurality of backwashing steps, at least the pressure on the secondary side is measured at the intervals; A future increase in the transmembrane pressure is predicted based on a difference between the multiple backwashing processes in the point at which the pressure on the secondary side increases and then decreases as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process. Transmembrane pressure prediction method.

2. A method for predicting a transmembrane pressure difference in a water treatment device that filters raw water using a hollow fiber membrane module, comprising: When a backwashing process in which treated water on the secondary side of the hollow fiber membrane module is pushed to the primary side of the hollow fiber membrane module by a pressurized medium is performed multiple times, measuring the pressure on at least one of the primary side and the secondary side at intervals of 3 seconds or less in each of the multiple backwashing processes; predicting a future increase in transmembrane pressure of the hollow fiber membrane module based on a difference in the measurement results of the pressure on at least one side during the multiple backwashing processes; notifying the result of the prediction; and Including, In each of the plurality of backwashing steps, at least the pressure on the secondary side is measured at the intervals; A future increase in the transmembrane pressure is predicted based on a difference between the start of the backwashing process and the time when the pressure on the secondary side, which is increasing to the pressure of the medium after the secondary side treated water is pushed out to the primary side immediately after the start of the backwashing process and then starts to decrease, reaches an inflection point at which the slope of the increase in pressure decreases, between the multiple backwashing processes. Transmembrane pressure prediction method.

3. A method for predicting a transmembrane pressure difference in a water treatment device that filters raw water using a hollow fiber membrane module, comprising: When a backwashing process in which treated water on the secondary side of the hollow fiber membrane module is pushed to the primary side of the hollow fiber membrane module by a pressurized medium is performed multiple times, measuring the pressure on at least one of the primary side and the secondary side at intervals of 3 seconds or less in each of the multiple backwashing processes; predicting a future increase in transmembrane pressure of the hollow fiber membrane module based on a difference in the measurement results of the pressure on at least one side during the multiple backwashing processes; notifying the result of the prediction; and Including, In each of the plurality of backwashing steps, at least the pressure on the primary side is measured at the intervals; A future increase in the transmembrane pressure is predicted based on a difference between the multiple backwashing processes in the point at which the pressure on the primary side increases and then decreases as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process. Transmembrane pressure prediction method.

4. A method for predicting a transmembrane pressure difference in a water treatment device that filters raw water using a hollow fiber membrane module, comprising: When a backwashing process in which treated water on the secondary side of the hollow fiber membrane module is pushed to the primary side of the hollow fiber membrane module by a pressurized medium is performed multiple times, measuring the pressure on at least one of the primary side and the secondary side at intervals of 3 seconds or less in each of the multiple backwashing processes; predicting a future increase in transmembrane pressure of the hollow fiber membrane module based on a difference in the measurement results of the pressure on at least one side during the multiple backwashing processes; notifying the result of the prediction; and Including, In each of the plurality of backwashing steps, at least the pressure on the primary side is measured at the intervals; A future increase in the transmembrane pressure is predicted based on a difference between the start of the backwashing process and the time when the primary side pressure, which is decreasing to a predetermined end pressure indicating the end of the pushing out of the secondary side treated water after increasing and then decreasing due to the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process, reaches an inflection point where the slope of the pressure decrease increases, between the multiple backwashing processes. Transmembrane pressure prediction method.

5. A method for predicting a transmembrane pressure difference in a water treatment device that filters raw water using a hollow fiber membrane module, comprising: When a backwashing process in which treated water on the secondary side of the hollow fiber membrane module is pushed to the primary side of the hollow fiber membrane module by a pressurized medium is performed multiple times, measuring the pressure on at least one of the primary side and the secondary side at intervals of 3 seconds or less in each of the multiple backwashing processes; predicting a future increase in transmembrane pressure of the hollow fiber membrane module based on a difference in the measurement results of the pressure on at least one side during the multiple backwashing processes; notifying the result of the prediction; and Including, Regarding the multiple backwashing steps, A time from the start of the backwashing process to a first time point when the pressure on the primary side or the secondary side increases and then decreases as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process; The time from the first point in time to a second point in time at which the pressure on the secondary side, which is increasing to the pressure of the medium after the secondary side treated water is pushed out to the primary side immediately after the start of the backwashing process and then starts to decrease, reaches an inflection point at which the slope of the increase in pressure decreases; A time from the first point in time to a third point in time at which the pressure on the primary side, which increases and then starts to decrease as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process, decreases to a predetermined end pressure, and then reaches an inflection point at which the slope of the decrease in pressure increases; and Calculate an integral value of the difference between the secondary side pressure and the primary side pressure at any one of the times from the start of the backwashing process to the second time point or the third time point; predicting a future increase in the transmembrane pressure based on a difference in the integral value between the multiple backwash steps; Transmembrane pressure prediction method.

6. A method for predicting a transmembrane pressure difference in a water treatment device that filters raw water using a hollow fiber membrane module, comprising: When a backwashing process in which treated water on the secondary side of the hollow fiber membrane module is pushed to the primary side of the hollow fiber membrane module by a pressurized medium is performed multiple times, measuring the pressure on at least one of the primary side and the secondary side at intervals of 3 seconds or less in each of the multiple backwashing processes; predicting a future increase in transmembrane pressure of the hollow fiber membrane module based on a difference in the measurement results of the pressure on at least one side during the multiple backwashing processes; notifying the result of the prediction; and Including, For the multiple backwashing processes, a point is detected at which the pressure of either the primary side or the secondary side increases and then decreases as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process; predicting a future increase in the transmembrane pressure based on a difference between the pressure on the secondary side and the pressure on the primary side at a time when either one of the pressures reaches the target point during the multiple backwashing steps; Transmembrane pressure prediction method.

7. When a water-filling process of filling raw water into the hollow fiber membrane module is performed multiple times, measuring the pressure on the primary side of the hollow fiber membrane module at the intervals during each of the multiple water-filling processes; predicting a future increase in transmembrane pressure of the hollow fiber membrane module based on a difference in the time from the start of the water-filling process to the time when the change in the primary side pressure reaches an inflection point between the multiple water-filling processes in the measurement result of the primary side pressure; notifying the result of the prediction; and Further comprising: The method for predicting a transmembrane pressure according to any one of claims 1 to 6.

8. When a drainage process for draining drain water containing turbid components peeled off from the hollow fiber membrane is performed multiple times, measuring the pressure on the primary side of the hollow fiber membrane module at the intervals during each of the multiple drainage processes; predicting a future increase in transmembrane pressure of the hollow fiber membrane module based on a difference in the time from the start of the drainage process until the pressure on the primary side becomes constant between the multiple drainage processes in the measurement results of the primary side pressure; notifying the result of the prediction; and Further comprising: The method for predicting a transmembrane pressure according to any one of claims 1 to 6.

9. A water treatment device that filters raw water using a hollow fiber membrane module, a measuring unit that measures the pressure of at least one of the primary side and the secondary side at intervals of 3 seconds or less in each of the multiple backwashing processes when a backwashing process is performed multiple times in which treated water on the secondary side of the hollow fiber membrane module is pushed to the primary side of the hollow fiber membrane module by a pressurized medium; a prediction unit that predicts a future increase in transmembrane pressure difference of the hollow fiber membrane module based on a difference in the measurement results of the pressure on at least one side between the multiple backwashing processes; a notification unit that notifies a prediction result by the prediction unit; Equipped with A first configuration in which the measurement unit measures at least the pressure on the secondary side at the intervals in each of the multiple backwashing processes, and the prediction unit predicts a future increase in the transmembrane pressure based on a difference between the multiple backwashing processes in a point at which the secondary side pressure increases and then decreases as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process; A second configuration in which the measurement unit measures at least the pressure on the secondary side at the intervals in each of the multiple backwashing processes, and the prediction unit predicts a future increase in the transmembrane pressure based on the difference between the start of the backwashing process and the time when the secondary side pressure, which is increasing to the pressure of the medium after increasing and then decreasing due to the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process, reaches an inflection point where the slope of the pressure increase decreases, between the multiple backwashing processes; A third configuration in which the measurement unit measures at least the pressure on the primary side at the intervals in each of the multiple backwashing processes, and the prediction unit predicts a future increase in the transmembrane pressure based on a difference between the multiple backwashing processes in a point at which the primary side pressure increases and then decreases as the secondary side treated water is pushed out to the primary side immediately after the start of the backwashing process; A fourth configuration in which the measurement unit measures at least the pressure on the primary side at the intervals during each of the multiple backwashing processes, and the prediction unit predicts a future increase in the transmembrane pressure based on the difference between the time from the start of the backwashing process to the time when the primary side pressure, which is decreasing to a predetermined end pressure indicating the end of the pushing out of the secondary side treated water after increasing and then decreasing due to the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process, reaches an inflection point where the slope of the pressure decrease increases, during the multiple backwashing processes; The prediction unit predicts, for the multiple backwashing processes, a time from a start point of the backwashing process to a first point at which the pressure on the primary side or the secondary side increases and then decreases as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process, a time from the first point to a second point at which the pressure on the secondary side, which is increasing to the pressure of the medium after increasing and then decreasing as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process, reaches an inflection point at which the slope of the increase in pressure decreases, and a time from the start of the backwashing process to a third time point at which the pressure on the primary side, which is decreasing to a predetermined end pressure after increasing and then decreasing due to the secondary side treated water being pushed to the primary side immediately after the start of the backwashing process, reaches an inflection point at which the slope of the pressure decrease increases, and a time from the start of the backwashing process to the second time point or the third time point is calculated, and a future increase in the transmembrane pressure is predicted based on the difference in the integral value between the multiple backwashing processes; The prediction unit detects a point at which the pressure of either the primary side or the secondary side increases and then decreases as the treated water on the secondary side is pushed to the primary side immediately after the start of the backwashing process, and predicts a future increase in the transmembrane pressure based on a difference between the pressure on the secondary side and the pressure on the primary side at the time when either pressure reaches the point, between the multiple backwashing processes; and A water treatment device having any one of the configurations above.

10. The measuring unit further measures the pressure on the primary side of the hollow fiber membrane module at the intervals during each of the multiple water filling steps when a water filling step of filling raw water into the hollow fiber membrane module is performed multiple times, The prediction unit further predicts a future increase in transmembrane pressure of the hollow fiber membrane module based on a difference between a plurality of the water-filling steps in a time from the start of the water-filling step to an inflection point of the change in the primary side pressure in the measurement result of the primary side pressure. The water treatment device according to claim 9.

11. The measuring unit further measures the pressure on the primary side of the hollow fiber membrane module at the intervals during each of a plurality of drainage processes in a case where a drainage process for draining drain water containing turbid components peeled off from the hollow fiber membrane is performed multiple times, the prediction unit further predicts a future increase in the transmembrane pressure of the hollow fiber membrane module based on a difference between the times from the start of the drainage process until the primary side pressure becomes constant, between the multiple drainage processes, in the measurement results of the primary side pressure. The water treatment device according to claim 9.

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