Method for predicting intermembrane differential pressure and water treatment apparatus

Abstract

The present invention provides a method for predicting the future increase in the intermembrane pressure differential of a hollow fiber membrane module, as well as a water treatment apparatus. [Solution] The intermembrane differential pressure prediction method is a method for predicting intermembrane differential pressure in a water treatment apparatus that filters raw water using a hollow fiber membrane module, and includes: when a backwashing process is performed multiple times in which treated water from 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, measuring the pressure on at least one side of the primary side and the secondary side at intervals of 3 seconds or less in each of the multiple backwashing processes; predicting the future increase in the intermembrane differential pressure 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 reporting the result of the prediction.

Description

Technical Field

[0001] The present invention relates to a transmembrane pressure difference prediction method and a water treatment apparatus. Background Art

[0002] Conventionally, water treatment apparatuses that filter raw water using a hollow fiber membrane module have been known. In such a water treatment apparatus, raw water is supplied into the 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 raises the transmembrane pressure difference, which is the difference between the pressure on the primary side (inner side) and the pressure on the secondary side (outer side) of the hollow fiber membrane module. Therefore, in the water treatment apparatus, generally, the transmembrane pressure difference is measured in units of minutes (for example, every 10 minutes) in the filtration step, and the transmembrane pressure difference 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 step, the pressures at the primary inlet, secondary outlet and primary outlet of a separation membrane module having a hollow fiber membrane are measured, and based on the measurement results, a membrane filtration pressure difference (corresponding to 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. It also describes that a clogged portion of the separation membrane module is specified based on calculation results such as the membrane filtration pressure difference.

[0004] Further, it is known that when an increase in transmembrane pressure difference is detected in a filtration step, the hollow fiber membrane module is washed on the assumption that the amount of impurities adhering to the hollow fiber membrane has increased and the permeation resistance of the hollow fiber membrane has increased. Prior Art Literature Patent Literature

[0005] Patent Document 1 Japanese Patent No. 6607319 Summary of the Invention [Problems that the invention aims to solve]

[0006] However, in the filtration process, raw water is not typically supplied to the hollow fiber membrane at a flow rate that maximizes the capacity of the hollow fiber membrane. Therefore, even if impurities adhere to a portion of the hollow fiber membrane, the raw water may still pass through the areas of the membrane that are free of impurities, and filtration may proceed normally. In this case, the intermembrane pressure difference will be measured at a level similar to that when no impurities adhere to the hollow fiber membrane. Consequently, with conventional technology, there is a risk that the increase in intermembrane pressure may not be detected until impurities adhere to a large portion of the hollow fiber membrane, causing filtration to cease.

[0007] The present invention has been made in view of the above problems, and its objective is to provide a method for predicting intermembrane differential pressure and a water treatment apparatus that can predict the future increase in intermembrane differential pressure of a hollow fiber membrane module. [Means for solving the problem]

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

[0009] A water treatment apparatus according to another aspect of the present invention is a water treatment apparatus that filters raw water using a hollow fiber membrane module, wherein a backwashing process is performed multiple times in which treated water from 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, and the apparatus is configured to include a measuring unit that measures the pressure on at least one side 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 the future increase in the intermembrane differential pressure 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 a notification unit that notifies the prediction results from the prediction unit.

[0010] In the above-described membrane differential pressure prediction method and water treatment apparatus, during 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 permeate through areas of the hollow fiber membrane where impurities are not attached, but also to collide with areas where impurities are attached. As a result, the pressure on the treated water can be changed according to the amount of impurities attached. Therefore, according to the above-described membrane differential pressure prediction method and water treatment apparatus, it is possible to measure the pressure on at least one side of the hollow fiber membrane module, either the primary or secondary side, according to the amount of impurities attached to the hollow fiber membrane.

[0011] Furthermore, in each of the multiple backwashing processes, the pressure on at least one side is measured at intervals of 3 seconds or less, which is shorter than the normal measurement interval for the intermembrane pressure differential in the filtration process. Therefore, it is possible to grasp the detailed temporal changes of the pressure on at least one side in each backwashing process, which is completed within a few minutes.

[0012] Therefore, by observing the differences in the detailed temporal progression between multiple backwashing processes, it is possible to understand the change in the amount of impurities adhering to the hollow fiber membrane in response to the change in pressure on at least one side. Thus, if it is determined that the amount of impurities adhering to the hollow fiber membrane is increasing, it is possible to predict that the intermembrane pressure will rise in the future, and the prediction can be reported.

[0013] In the above-described method for predicting the differential pressure between membranes, in each of the multiple backwashing steps, the pressure on the secondary side may be measured at least at the intervals described above, and the future increase in the differential pressure between membranes may be predicted based on the difference between the multiple backwashing steps at which the pressure on the secondary side, which increased instantaneously immediately after the start of the backwashing step, reaches its peak.

[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 degree to which the treated water permeates to the primary side. Therefore, the pressure on the secondary side increases instantaneously immediately after the start of the backwashing process. The resulting pressure on the secondary side during this increase will be higher as the amount of impurities adhering to the hollow fiber membrane increases and the permeation resistance of the hollow fiber membrane increases.

[0015] With this configuration, the pressure on the secondary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less during each of the multiple backwashing processes. Therefore, the point at which the secondary side pressure instantaneously increases immediately after the start of each backwashing process is detected. Consequently, the difference in this point between multiple backwashing processes allows for the determination of the amount of impurities adhering to the hollow fiber membrane and the change in the permeation resistance of the hollow fiber membrane. Therefore, when it is determined that the amount of impurities adhering to the hollow fiber membrane has increased and the permeation resistance of the hollow fiber membrane has also increased, it is possible to appropriately predict that the intermembrane differential pressure will rise.

[0016] In the above-described method for predicting the differential pressure between membranes, in each of the multiple backwashing steps, the pressure on the secondary side may be measured at the intervals described above, and the future increase in the differential pressure between membranes may be predicted based on the difference in the time between the multiple backwashing steps, from the start of the backwashing step until the pressure on the secondary side stabilizes at the pressure of the medium.

[0017] In the backwashing process, once the treated water from the secondary side has been pushed out to the primary side, the secondary side becomes filled with a pressurized medium, and the pressure on the secondary side stabilizes at the pressure of the medium. Here, the more impurities that adhere to the hollow fiber membrane and the greater the permeability resistance of the hollow fiber membrane, the longer it takes for all the treated water from the secondary side to be pushed out to the primary side. Therefore, the time from the start of the backwashing process until the pressure on the secondary side stabilizes at the pressure of the medium becomes longer as the amount of impurities that adhere to the hollow fiber membrane and the permeability resistance of the hollow fiber membrane increase.

[0018] With this configuration, the pressure on the secondary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less during each of the multiple backwashing processes. Therefore, the time from the start of each backwashing process until the secondary side pressure stabilizes at the pressure of the medium can be detected. Consequently, the difference in this time between multiple backwashing processes allows for the determination of the amount of impurities adhering to the hollow fiber membrane and the change in the permeation resistance of the hollow fiber membrane. Therefore, when it is determined that the amount of impurities adhering to the hollow fiber membrane is increasing and the permeation resistance of the hollow fiber membrane is also increasing, it is possible to appropriately predict that the intermembrane differential pressure will rise.

[0019] In the above-described method for predicting the differential pressure between membranes, in each of the multiple backwashing steps, the pressure on the primary side may be measured at the intervals described above, and the future increase in the differential pressure between membranes may be predicted based on the difference between the multiple backwashing steps at which the primary side pressure, which increased instantaneously immediately after the start of the backwashing step, reaches its peak.

[0020] When the backwashing process begins and the treated water from 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 permeability resistance of the hollow fiber membrane, the slower the rate at which the treated water from the secondary side is pushed out to the primary side becomes, and the lower the resulting pressure on the primary side becomes.

[0021] According to this configuration, in each of the plurality of backwashing steps, the pressure on the primary side of the hollow fiber membrane module is measured at an interval of 3 seconds or less, so that the reaching point of the instantaneously increasing pressure on the primary side immediately after the start of each backwashing step can be detected. Therefore, from the difference in this reaching point among the plurality of backwashing steps, the adhesion amount of impurities on the hollow fiber membrane and the change in permeation resistance of the hollow fiber membrane can be grasped. For this reason, when it is recognized that the adhesion amount of impurities on the hollow fiber membrane has increased and the permeation resistance of the hollow fiber membrane is increasing, an increase in transmembrane pressure difference can be appropriately predicted.

[0022] In the above prediction method, in each of the plurality of backwashing steps, at least the pressure on the primary side is measured at the interval, and a future increase in the transmembrane pressure difference may be predicted based on a difference among the plurality of backwashing steps in the time from the start of the backwashing step until the pressure on the primary side stabilizes at a predetermined end pressure indicating completion of pushing out the treated water on the secondary side.

[0023] Immediately after a backwashing step 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 larger the adhesion amount of impurities on the hollow fiber membrane and the higher 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 the time required to complete pushing out the treated water on the secondary side.

[0024] According to this configuration, in each of the plurality of backwashing steps, the pressure on the primary side of the hollow fiber membrane module is measured at an interval of 3 seconds or less, so that the time from the start of each backwashing step until the pressure on the primary side stabilizes at the aforementioned end pressure can be detected. Therefore, from the difference in this time among the plurality of backwashing steps, the adhesion amount of impurities on the hollow fiber membrane and the change in permeation resistance of the hollow fiber membrane can be grasped. For this reason, when it is recognized that the adhesion amount of impurities on the hollow fiber membrane has increased and the permeation resistance of the hollow fiber membrane is increasing, an increase in transmembrane pressure difference can be appropriately predicted.

[0025] In the prediction method described above, for the plurality of backwashing steps, regarding any one of the following time periods: the time from the start of the backwashing step to when the pressure on the primary side or the secondary side, which rises instantaneously immediately after the start of the backwashing step, reaches a reaching point; the time from when the pressure on the primary side or the secondary side, which rises instantaneously immediately after the start of the backwashing step, reaches said reaching point to when it stabilizes; and the time from the start of the backwashing step to when the pressure on the primary side or the secondary side stabilizes, an integrated value of the difference between the pressure on the secondary side and the pressure on the primary side within said any one time period is calculated, and a future increase in the transmembrane pressure difference may be predicted based on a difference between said integrated values among the plurality of backwashing steps.

[0026] The present inventors have found through test operations that, even when the difference between the pressure on the secondary side and the pressure on the primary side during the filtration step is substantially constant, the integrated value of said difference during the period from the start of the backwashing step to when the pressure on the primary side or the secondary side stabilizes differs significantly between cases where the adhesion amount of impurities on the hollow fiber membrane is greater than a predetermined amount and cases where it is less than said predetermined amount. Furthermore, the inventors have also found through additional test operations that the integrated values obtained during the period from the start of the backwashing step to when the pressure on the primary side or the secondary side, which rises instantaneously immediately after the start of the backwashing step, reaches a reaching point, and during the period from when the pressure on the primary side or the secondary side, which rises instantaneously immediately after the start of the backwashing step, reaches said reaching point to when it stabilizes, also differ significantly between cases where the adhesion amount of impurities on the hollow fiber membrane is greater than a predetermined amount and cases where it is less than said predetermined amount.

[0027] Therefore, according to the present configuration, a change in the adhesion amount of impurities on the hollow fiber membrane can be appropriately grasped based on the difference in the integrated values of the difference between the pressure on the secondary side and the pressure on the primary side within the above three time periods among the plurality of backwashing steps. For this reason, when it is grasped that the adhesion amount of impurities on 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 each of the multiple backwashing steps, the point at which the pressure on either the primary or secondary side reaches a peak, which rises instantaneously immediately after the start of the backwashing step, may be detected. Based on the difference between the pressure on the secondary side and the pressure on the primary side at the point in time when either pressure reaches the peak, and the difference between the multiple backwashing steps, the future rise in the intermembrane differential pressure may be predicted.

[0029] With this configuration, the pressure on at least one side of the hollow fiber membrane module, either the primary or secondary side, is measured at intervals of 3 seconds or less during multiple backwashing processes. Therefore, the peak pressure on either the primary or secondary side, which rises instantaneously immediately after the start of the backwashing process, can be detected. In other words, even if the impurities in the treated water are such that they peel off the surface of the hollow fiber membrane due to the force pushing the treated water from the secondary side to the primary side during the backwashing process, the pressure on either side before it drops due to the peeling off of the impurities can be appropriately detected.

[0030] 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, it is possible to appropriately grasp the change in the amount of impurities adhering to the hollow fiber membrane. Therefore, when it is determined 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 intermembrane pressure will rise.

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

[0032] A water treatment apparatus according to another aspect of the present invention is a water treatment apparatus that filters raw water using a hollow fiber membrane module, and is configured to include, when a filling process of filling the inside of the hollow fiber membrane module with raw water is performed multiple times, a measuring unit that measures the pressure on the primary side of the hollow fiber membrane module at intervals of 3 seconds or less in each of the multiple filling processes, a prediction unit that predicts the future rise in the intermembrane differential pressure of the hollow fiber membrane module based on the difference between the multiple filling processes in the measurement result of the primary side pressure, from the start of the filling process to reaching the inflection point of the change in the primary side pressure, and a notification unit that notifies the result of the prediction.

[0033] When the filling process begins and raw water flows into the hollow fiber membrane module, the primary pressure gradually increases due to hydrostatic pressure. Subsequently, as the inside of the hollow fiber membrane module approaches a full-water state, the primary pressure increases rapidly. Therefore, the time from the start of the filling process to reaching the inflection point of the primary pressure change becomes shorter when there is a large amount of impurity accumulated inside the hollow fiber membrane module and the effective volume inside the hollow fiber membrane module is small.

[0034] Furthermore, it is presumed that the greater the accumulation of impurities 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 membrane, which in turn suggests that the intermembrane pressure differential will increase in the future.

[0035] In the above-described membrane differential pressure prediction method and water treatment apparatus, the pressure on the primary side of the hollow fiber membrane module is measured during the filling process when raw water fills the inside of the hollow fiber membrane module. Therefore, the above-described membrane differential pressure prediction method and water treatment apparatus can measure the pressure on the primary side of the hollow fiber membrane module according to the amount of impurities accumulated inside the hollow fiber membrane module.

[0036] Furthermore, in the above-described membrane differential pressure prediction method and water treatment apparatus, the pressure on the primary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less, which is shorter than the normal measurement interval for the membrane differential pressure in the filtration process, during each of the multiple water filling processes. Therefore, it is possible to grasp the detailed temporal changes of the pressure on the primary side of the hollow fiber membrane module during each water filling process, which is completed within a few minutes.

[0037] Therefore, by examining the differences in this detailed temporal progression between multiple water filling processes, it is possible to understand the changes in the amount of impurities accumulated inside the hollow fiber membrane module in response to changes in the primary pressure of the hollow fiber membrane module.

[0038] Specifically, by observing the difference in time between multiple water-filling processes, from the start of each process to the inflection point of the primary side pressure change, it is possible to understand the amount of impurities accumulated inside the hollow fiber membrane module and the changes in its effective volume. Therefore, when it is determined 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 that the amount of impurities adhering to the hollow fiber membrane is increasing, that is, that the intermembrane pressure differential will rise in the future, and to report the prediction result.

[0039] A method for predicting intermembrane differential pressure according to another aspect of the present invention is a prediction method for a water treatment apparatus that filters raw water using a hollow fiber membrane module, and includes, when a drainage process is performed multiple times to drain drain water containing turbidity components detached from the hollow fiber membrane, measuring the pressure on the primary side of the hollow fiber membrane module at intervals of 3 seconds or less in each of the multiple drainage processes, predicting the future rise in intermembrane differential pressure of the hollow fiber membrane module based on the difference in the time from the start of the drainage process until the primary side pressure becomes constant between the multiple drainage processes, and reporting the result of the prediction.

[0040] A water treatment apparatus according to another aspect of the present invention is a water treatment apparatus that filters raw water using a hollow fiber membrane module, and is configured such that, when a drainage process is performed multiple times to drain drain water containing turbidity components detached from the hollow fiber membrane, each of the multiple drainage processes includes: a measuring unit that measures the pressure on the primary side of the hollow fiber membrane module at intervals of 3 seconds or less; a prediction unit that predicts the future rise in the intermembrane differential pressure of the hollow fiber membrane module based on the difference between the multiple drainage processes in the measurement result of the primary side pressure, from the start of the drainage process until the primary side pressure becomes constant; and a notification unit that notifies the result of the prediction.

[0041] During the drainage process, the primary pressure stabilizes once the drain water inside the hollow fiber membrane module has been completely discharged. Therefore, the time it takes for the primary pressure to become constant from the start of the drainage process is shorter when there is a large amount of impurity accumulated inside the hollow fiber membrane module and when the effective volume inside the hollow fiber membrane module is small.

[0042] Furthermore, it is presumed that the greater the accumulation of impurities 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 membrane, which in turn suggests that the intermembrane pressure differential will increase in the future.

[0043] In the above-described membrane differential pressure prediction method and water treatment apparatus, the pressure on the primary side of the hollow fiber membrane module is measured when the drain water inside the hollow fiber membrane module is discharged during the drainage process. Therefore, the above-described prediction method and water treatment apparatus can measure the pressure on the primary side of the hollow fiber membrane module according to the amount of impurities accumulated inside the hollow fiber membrane module.

[0044] Furthermore, in the above-described membrane differential pressure prediction method and water treatment apparatus, the pressure on the primary side inside the hollow fiber membrane module is measured at intervals of 3 seconds or less, which is shorter than the normal measurement interval for the membrane differential pressure in the filtration process, during each of the multiple wastewater treatment processes. Therefore, it is possible to grasp the detailed temporal changes of the pressure on the primary side of the hollow fiber membrane module during each wastewater treatment process, which is completed within a few minutes.

[0045] Therefore, by examining the differences in this detailed temporal progression between multiple drainage processes, it is possible to understand the changes in the amount of impurities accumulated inside the hollow fiber membrane module in response to changes in the primary pressure of the hollow fiber membrane module.

[0046] Specifically, by observing the difference in time between multiple drainage processes, from the start of a drainage process until the primary pressure becomes constant, it is possible to grasp the amount of impurities accumulated inside the hollow fiber membrane module and the changes in its effective volume. Therefore, if it is determined 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 that the amount of impurities adhering to the hollow fiber membrane is increasing, that is, that the intermembrane pressure differential will rise in the future, and to report the prediction result. [Effects of the Invention]

[0047] As is clear from the above description, the present invention provides a method for predicting intermembrane differential pressure and a water treatment apparatus that can predict the future increase in intermembrane differential pressure of a hollow fiber membrane module. [Brief explanation of the drawing]

[0048] [Figure 1] This figure schematically shows the configuration of a water treatment apparatus according to an embodiment of the present invention. [Figure 2] This figure shows the on / off state of the raw water pump and the open / closed state of the valves in each step of the water treatment method in the aforementioned water treatment apparatus. [Figure 3] This figure shows the time change of the secondary pressure of the hollow fiber membrane module during the backwashing process. [Figure 4] This figure shows the time change of the primary side pressure of the hollow fiber membrane module during the backwashing process. [Figure 5] This figure shows the time evolution of the primary and secondary pressures of the hollow fiber membrane module during the backwashing process when clogging of the hollow fiber membrane has not progressed. [Figure 6] This figure shows the time evolution of the primary and secondary pressures of a hollow fiber membrane module during the backwashing process when clogging of the hollow fiber membrane is progressing. [Figure 7] This figure shows the time change of the primary side pressure of the hollow fiber membrane module during the water filling process. [Figure 8] This figure shows the time change of the primary side pressure of the hollow fiber membrane module during the drainage process. [Modes for carrying out the invention]

[0049] (Embodiment) Embodiments of the present invention will be described in detail below with reference to the drawings.

[0050] First, the configuration of the water treatment apparatus 1 according to an embodiment of the present invention will be described with reference to Figure 1. As shown in Figure 1, the water treatment apparatus 1 mainly comprises a hollow fiber membrane module 10, a raw water supply unit 20, a bubbling air supply unit 30, and a backwashing 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 conduit 14 extending vertically inside the hollow fiber membrane bundle, and a diffuser 15. The hollow fiber membrane bundle, the fixing member 13, and the diffuser 15 are housed inside the housing 12. The space inside the housing 12 is divided into a raw water space S1 and a treated water space S2 by the fixing member 13. The hollow fiber membranes 11, the water conduit 14, and the diffuser 15 are housed in the raw water space S1.

[0052] As shown in Figure 1, an outlet 12A for treated water (filtered water) is provided at the top of the housing 12, facing the treated water space S2. An air vent 12B is provided on the side of the housing 12 (the part above the center in the longitudinal direction), facing the raw water space S1. An air supply port 12C and a drain port 12D are provided at the bottom of the housing 12, facing the raw water space S1. The ratio of the inner diameter of the housing 12 to the inner diameter of these pipe connection ports (outlet 12A, air vent 12B, air supply port 12C, and drain port 12D) is preferably 1.3 or more and 12 or less, preferably 2.5 or more and 12 or less, and more preferably 3.0 or more and 6.0 or less. Note that 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 Figure 1, the upper end of the water conduit 14 is fixed to the fixing member 13 and its end face is closed, while the lower end protrudes below 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 numerous holes 14C formed inside it for ejecting at least one of raw water and air toward the raw water space S1.

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

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

[0056] The upstream end of the drain pipe 53 is connected to the drain port 12D of the housing 12, and a drain valve 54 (on / off 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 section 55A, a second branch section 55B, and a connecting section 55C. One end of the connecting section 55C is connected to the air vent port 12B, and the other end is connected to the first branch section 55A and the second branch section 55B. The first branch section 55A is open to the atmosphere, and the second branch section 55B is connected to the portion of the drain pipe 53 downstream of the drain valve 54. An air vent valve 56 (on / off valve) is installed at the connecting section 55C. The diameter of the air vent pipe 55 is smaller than the diameter of the housing 12.

[0058] As shown in Figure 1, the treated water piping 50 and the drainage piping 53 are connected to each other by a pressure relief pipe 57. One end of the pressure relief pipe 57 is connected to the portion of the treated water piping 50 upstream of the treated water valve 51, and the other end of the pressure relief pipe 57 is connected to the portion of the drainage piping 53 downstream of the connection point of the air vent pipe 55. A pressure relief valve 58 (on / off valve) is installed in the pressure relief pipe 57. The diameter of the pressure relief pipe 57 is smaller than the diameter of the housing 12.

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

[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 branches at its 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 conduit 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 on / off 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 on 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 the portion of the treated water pipe 50 upstream of the connection point of the pressure relief 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 measuring unit 60 that measures the pressure on at least one of the primary and secondary sides 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. In this embodiment, the measuring unit 60 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] As shown in Figure 1, the primary pressure sensor 61 is installed in the portion of the raw water piping 21 between the raw water valve 23 and the raw water inlet 14A. Alternatively, the primary pressure sensor 61 may be installed in the portion of the water conduit 14 extending from the housing 12 or in a position within the housing 12 facing the raw water space S1.

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

[0065] In addition to the primary pressure sensor 61 and the secondary pressure sensor 62, an air vent pressure sensor may also be provided. The air vent pressure sensor is installed at the connection point 55C of the air vent piping 55. The air vent pressure sensor measures the pressure at intervals of 0.1 seconds to 3 seconds, and each measurement data is sent to the control unit 70 described later for storage. In other words, the measurement data from the air vent pressure sensor is stored as logging data indicating the primary side pressure of the hollow fiber membrane module 10. However, as the number of pressure sensors increases, the analysis becomes more time-consuming and the cost increases, so it is desirable to omit the air vent pressure sensor and perform data analysis using data from the primary pressure sensor 61 and the secondary pressure sensor 62.

[0066] The water treatment device 1 further comprises a control unit 70. The control unit 70 is composed of a microcomputer equipped with 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 that constitutes the filtration operation cycle according to the sequence information stored in the ROM, etc. When the execution of each process is started, the control unit 70 controls the drive of peripheral devices and the opening and closing of valves according to the process information stored in the ROM, etc.

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

[0068] Furthermore, the prediction unit 71 and the notification unit 72 do not necessarily have to be implemented as functions of the control unit 70. The control unit 70, the prediction unit 71, and the notification unit 72 may each be configured by separate microcomputers.

[0069] Figure 2 shows each step of the water treatment method carried out using the water treatment device 1 described above, as well as the ON / OFF state of the raw water pump 22 and the open / closed state of each valve in each step. In Figure 2, circles indicate the ON state of the raw water pump 22 or the open state of the valve, and blank spaces indicate the OFF state of the raw water pump 22 or the closed state of the valve.

[0070] First, in the first water filling process, the raw water pump 22 is activated, 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 to the raw water space S1 from the hole 14C.

[0071] Once the first water filling process is complete, the process moves to the filtration process. During the filtration process, the air vent valve 56 is closed and the treated water valve 51 is opened. Raw water permeates the membrane wall of the hollow fiber membrane 11 from the outer surface to the inner surface and flows into the treated water space S2 through the hollow portion of the membrane. Subsequently, the treated water flows out of the housing 12 through the outlet 12A and is collected in a 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 (pressure relief process), a backwash process, an air venting process, a second water filling process, a diffuser bubbling process, a third water filling process, a water conduit bubbling process, a drainage process, and a pressure relief process.

[0073] First, during the backwash preparation process (pressure relief 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, while the air valve 42 and the drain valve 54 are opened. That is, simultaneously with the opening of the air valve 42, the pressure of air pressurized by the compressor is instantaneously added 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 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. This makes it easier for impurities attached to the outer surface of the hollow fiber membrane 11 to peel off. At this time, since the primary side pressure sensor 61 and the secondary side pressure sensor 62 measure the pressure at intervals of 3 seconds or less, it is possible to detect the pressure after the hollow fiber membrane 11 has been pressurized from the inside, but before the impurities on the membrane surface become easily peeled off. Furthermore, the specified pressure is preferably 30kPa to 500kPa, more preferably 50kPa to 300kPa, and most preferably 50kPa to 200kPa.

[0075] During 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 (Figure 3) showing the time change of the secondary pressure of the hollow fiber membrane module 10 during the backwashing process. In Figure 3, the horizontal axis represents time, and the vertical axis represents the secondary pressure of the hollow fiber membrane module 10. Graph G31 in Figure 3 shows the time change of the secondary pressure of the hollow fiber membrane module 10 during the backwashing process immediately preceding the most recent backwashing process. Graph G32 in Figure 3 shows the time change of 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 of the secondary pressure during the backwashing process immediately preceding graph G32.

[0076] Immediately after the start of the backwashing process, the treated water on the secondary side is rapidly pushed into the primary side by pressurized air. 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 degree to which the treated water permeates to the primary side. Therefore, the pressure on the secondary side increases immediately after the start of the backwashing process. Then, as some of the impurities attached to the surface of the hollow fiber membrane 11 are detached or made more likely to detach due to the force of the treated water being pushed to the primary side, the pressure on the secondary side instantaneously decreases or is maintained. Subsequently, the pressure on the secondary side increases again due to pressurization by air. In this way, the pressure on the secondary side increases instantaneously immediately after the start of the backwashing process. The final pressure on the secondary side at this time of increase is higher the more impurities are attached to the hollow fiber membrane 11 and the greater the permeation resistance of the hollow fiber membrane 11.

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

[0078] Specifically, the prediction unit 71 predicts that if the secondary pressure reached immediately after the start of a backwashing process shows an upward trend between multiple backwashing processes, it indicates that the amount of impurities adhering to the hollow fiber membrane 11 is increasing and the permeation resistance of the hollow fiber membrane 11 is also increasing, and therefore predicts that the intermembrane differential pressure of the hollow fiber membrane module 10 will increase in the future.

[0079] In the example shown in Figure 3, the secondary pressure P32 immediately after the start of the most recent backwashing process is higher than the secondary pressure P31 immediately after the start of the backwashing process immediately preceding the most recent backwashing process. Therefore, the prediction unit 71 predicts that the intermembrane differential pressure of the hollow fiber membrane module 10 will increase in the future.

[0080] Furthermore, in the backwashing process, once the pushing of the treated water from the secondary side to the primary side is complete, the secondary side becomes filled with pressurized air, and the pressure on the secondary side stabilizes at the air pressure. Here, the greater the amount of impurities adhering 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 of the treated water from the secondary side to be pushed to the primary side. For this reason, the time from the start of the backwashing process until the pressure on the secondary side stabilizes at the air pressure becomes longer the greater the amount of impurities adhering to the hollow fiber membrane 11 and the greater the permeation resistance of the hollow fiber membrane 11.

[0081] Furthermore, "pressure stabilization" means, for example, that an increasing pressure reaches an inflection point where the slope of the pressure increase decreases, or that a decreasing pressure reaches an inflection point where the slope of the pressure decrease increases, or that an increasing or decreasing pressure continues to fluctuate within a predetermined allowable range for a predetermined period of time or longer.

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

[0083] Specifically, it is assumed that, between multiple backwashing processes, the time from the start of the backwashing process until the secondary pressure stabilizes at the air pressure shows an increasing trend. In this case, the prediction unit 71 predicts that the intermembrane differential pressure of the hollow fiber membrane module 10 will rise 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.

[0084] In the example shown in Figure 3, the time t32 from the start of the most recent backwashing process until the secondary pressure stabilizes at the air pressure is longer than the time t31 from the start of the backwashing process immediately preceding the most recent backwashing process until the secondary pressure stabilizes at the air pressure. Therefore, the prediction unit 71 predicts that the intermembrane differential pressure of the hollow fiber membrane module 10 will increase in the future.

[0085] Furthermore, during 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 (Figure 4) showing the time change of 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 at intervals of 3 seconds or less using the air vent pressure sensor. In this case, the prediction unit 71 may use data representing the average value of the primary side pressure indicated by the logging data received from the primary side pressure sensor 61 and the air vent pressure sensor as logging data representing the primary side pressure of the hollow fiber membrane module 10.

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

[0088] As shown in Figure 4, immediately after the backwashing process begins and the treated water from the secondary side is pushed out to the primary side, the primary side pressure instantaneously increases due to the pipe resistance generated when the raw water from the primary side flows into the drainage pipe 53, because the diameter of the drainage pipe 53 is smaller than that of the housing 12. At this time, the more impurities adhering 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 from the secondary side is pushed out to the primary side, and the lower the resulting pressure on the primary side.

[0089] Therefore, the prediction unit 71 may refer to the logging data stored in the control unit 70 and predict the future increase in the intermembrane differential pressure of the hollow fiber membrane module 10 based on the difference in the point at which the primary side pressure, which increased instantaneously immediately after the start of the backwashing process, reaches over multiple backwashing processes.

[0090] Specifically, assume that in multiple backwashing processes, the primary side's target pressure immediately after the start of the backwashing process shows a decreasing trend. In this case, the prediction unit 71 may predict that the intermembrane differential pressure of the hollow fiber membrane module 10 will increase in the future, as this indicates that the amount of impurities adhering to the hollow fiber membrane 11 is increasing and the permeation resistance of the hollow fiber membrane 11 is also increasing.

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

[0092] Furthermore, after the backwashing process is initiated and the treated water on the secondary side is pushed out to the primary side, the pressure on the primary side increases instantaneously. In such a situation, the greater the amount of impurities adhering 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 is pushed out to the primary side becomes, and the longer the time required to finish pushing out the treated water on the secondary side.

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

[0094] Specifically, in multiple backwashing processes, the time from the start of the backwashing process until the primary pressure stabilizes at the end pressure shows an increasing trend. In this case, the prediction unit 71 may predict that the intermembrane differential pressure of the hollow fiber membrane module 10 will rise in the future, as 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.

[0095] In the example shown in Figure 4, the time t42 from the start of the most recent backwashing process until the primary pressure stabilizes at the end pressure is longer than the time t41 from the start of the backwashing process immediately preceding the most recent backwashing process until the primary pressure stabilizes at the end pressure. Therefore, the prediction unit 71 predicts that the intermembrane differential pressure of the hollow fiber membrane module 10 will increase in the future.

[0096] Furthermore, the inventors conducted test runs and used logging data (Figures 5 and 6) obtained in each of the following backwashing processes: one 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 another when the amount of impurities adhering to the hollow fiber membrane 11 was greater than a predetermined amount (hereinafter referred to as the second backwashing process). The inventors then calculated the integral value of the difference between the secondary pressure and the primary pressure during the time from the start of the backwashing process until the primary pressure stabilized.

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

[0098] Next, the inventors used the logging data shown in Figure 5, acquired in the first backwashing process, to calculate the integral value of the difference between the secondary side pressure and the primary side pressure during the time t50 to t51 (hereinafter referred to as the target time), from the start time t50 of the first backwashing process to the time t51 when the primary side pressure stabilized. In Figure 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 enclosed by the dashed line representing the start time t50 of the first backwashing process, the dashed line representing the time t51 when the primary side pressure stabilized, graph G52, and graph G51.

[0099] Similarly, the inventors used the logging data shown in Figure 6, acquired in the second backwashing process, to calculate the integral value of the difference between the secondary pressure and the primary pressure during the target time t60 to t61, from the start of the second backwashing process t60 to the time when the primary pressure stabilized t61.

[0100] The inventors then compared the measurement results of the difference between the secondary pressure and the primary pressure in the filtration process performed after the first backwashing process, the measurement results of the same 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 pressure and the primary pressure during the filtration process is approximately constant, the integral value over the predetermined period differs significantly depending on whether the amount of impurities adhering to the hollow fiber membrane 11 is greater than or less than a predetermined amount.

[0101] This is presumed to be due to the fact that the time from the start of the backwashing process until the primary pressure, which increases instantaneously immediately after the start of the backwashing process, reaches its peak, and the time from when the primary pressure, which increases instantaneously immediately after the start of the backwashing process, reaches its peak until it stabilizes, becomes longer as the amount of impurities adhering to the hollow fiber membrane 11 increases.

[0102] Similarly, the inventors changed the target time from the start time t50 of the first backwashing process until the primary pressure, which increased instantaneously immediately after the start of the first backwashing process, reached the target point P51, and calculated the integral value. Furthermore, the inventors changed the target time from the start time t60 of the second backwashing process until the primary pressure, which increased instantaneously immediately after the start of the second backwashing process, reached the target point P61, and calculated the integral value. In this case as well, the inventors obtained the same findings as described above.

[0103] The inventors calculated the integral value by changing the target time to the time from when the primary pressure, which instantaneously increased immediately after the start of the first backwashing process, reaches the target point P51 until it stabilizes at time t51, and then by changing the target time to the time from when the primary pressure, which instantaneously increased immediately after the start of the second backwashing process, reaches the target point P61 until it stabilizes at time t61. In this case as well, the inventors obtained the same findings as described above.

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

[0105] The inventors calculated the integral value by changing the target time from the start time t50 of the first backwashing process to the time until the secondary pressure, which instantaneously increased immediately after the start of the backwashing process, reaches the target point P52, and by changing the target time from the start time t60 of the second backwashing process to the time until the secondary pressure, which instantaneously increased immediately after the start of the second backwashing process, reaches the target point P62. In this case as well, the inventors obtained the same findings as described above.

[0106] The inventors calculated the integral value by changing the target time to the time from when the secondary pressure, which instantaneously increased immediately after the start of the first backwashing process, reaches the target point P52 until it stabilizes at time t52, and then by changing the target time to the time from when the secondary pressure, which instantaneously increased immediately after the start of the second backwashing process, reaches the target point P62 until it stabilizes at time t62. In this case as well, the inventors obtained the same findings as described above.

[0107] Furthermore, the inventors have 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 target times becomes.

[0108] Therefore, based on the above findings obtained by the present inventors, the prediction unit 71 may calculate the integral value of the difference between the secondary pressure and the primary pressure at any one of the following times for multiple backwashing processes: the time from the start of the backwashing process until the primary or secondary pressure, which instantaneously increases immediately after the start of the backwashing process, reaches its target; the time from when the primary or secondary pressure, which instantaneously increases immediately after the start of the backwashing process, reaches its target until it stabilizes; and the time from the start of the backwashing process until the primary or secondary pressure stabilizes. The prediction unit 71 may then predict the future increase in the intermembrane differential pressure of the hollow fiber membrane module 10 based on the difference in the integral values ​​between the multiple backwashing processes.

[0109] Specifically, the integral value calculated during multiple backwashing processes shows an increasing trend. In this case, the prediction unit 71 may predict that the amount of impurities adhering to the hollow fiber membrane 11 is increasing, and that the permeation resistance of the hollow fiber membrane 11 will increase and the intermembrane differential pressure of the hollow fiber membrane module 10 will rise in the future.

[0110] Furthermore, as described above, immediately after the start of the backwashing process, the pressure on the secondary side increases instantaneously. At this time, the final pressure on the secondary side increases as the amount of impurities adhering to the hollow fiber membrane 11 increases. Also, 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 easily detached. Subsequently, when some of the fouling components adhering to the outer surface of the hollow fiber membrane 11 are detached, the pressure on the secondary side decreases instantaneously, but increases again due to pressurization with air. As a result, the speed at which the treated water is pushed to the primary side increases.

[0111] On the other hand, immediately after the treated water on the secondary side is pushed to the primary side, the pressure on the primary side instantaneously increases due to the pipe resistance generated when the raw water on the primary side flows into the drainage pipe 53. At this time, the more impurities that adhere to the hollow fiber membrane 11, the slower the speed at which the treated water on the secondary side is pushed to the primary side. Therefore, the resulting pressure on the primary side, which 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. Subsequently, as some of the impurities adhering to the outer surface of the hollow fiber membrane 11 are detached and the speed at which the treated water is pushed to the primary side increases, the speed at which the water on the primary side is discharged also increases, and the pressure on the primary side rapidly decreases.

[0112] In other words, just before the primary or secondary pressure, which increases instantaneously immediately after the start of the backwashing process, reaches its peak and some of the impurities attached to the outer surface of the hollow fiber membrane 11 are peeled off, the difference between the secondary pressure and the primary pressure becomes larger the more impurities are attached to the hollow fiber membrane 11.

[0113] Therefore, the prediction unit 71 may refer to the logging data stored in the control unit 70 and detect the point at which the pressure on either the primary or secondary side reaches its peak immediately after the start of the backwashing process for multiple backwashing processes. The prediction unit 71 may then predict the future increase in the intermembrane differential pressure of the hollow fiber membrane module 10 based on the difference between the secondary side pressure and the primary side pressure at the point at which either pressure reaches its peak, across the multiple backwashing processes.

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

[0115] In this case, for multiple backwashing processes, the pressure on at least one side of the hollow fiber membrane module 10, either the primary or secondary side, is measured at intervals of 3 seconds or less. Therefore, the point at which the pressure on either the primary or secondary side reaches a peak immediately after the start of the backwashing process can be detected. That is, even if the impurities are such that they peel off the surface of the hollow fiber membrane due to the force pushing the treated water from the secondary side to the primary side during the backwashing process, the pressure at any of the aforementioned points before it decreases due to the peeling off of the impurities can be appropriately detected. As a result, by using the difference between the pressure on the secondary side and the pressure on the primary side at the detection point, the change in the amount of impurities adhering to the hollow fiber membrane 11 can be appropriately grasped. For this reason, when the prediction unit 71 grasps that the amount of impurities adhering to the hollow fiber membrane 11 is increasing, it can appropriately predict that the permeation resistance of the hollow fiber membrane 11 will increase and the intermembrane differential pressure of the hollow fiber membrane module 10 will rise.

[0116] When the prediction unit 71 predicts a future increase in the intermembrane pressure differential 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 containing a message indicating that it has predicted a future increase in the intermembrane differential pressure of the hollow fiber membrane module 10 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 prediction result by the prediction unit 71 is not limited to the above message, but may also include logging data (Figure 3) used by the prediction unit 71 for the prediction.

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

[0119] Next, in the air bleeding process (pressure relief process), the air valve 42 and the drain valve 54 are closed, and the pressure relief 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 pressure relief pipe 57.

[0120] Next, in the second water filling process, similar to the first water filling process, the raw water pump 22 is activated, and the raw water valve 23 and the air vent valve 56 are opened, respectively.

[0121] Next, in the 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 vent valve 56 remains open. As a result, air is supplied into the housing 12 from the air supply port 12C, and this air is dispersed towards the hollow fiber membrane bundle by the diffuser 15. This causes the hollow fiber membrane bundle to oscillate due to the bubbles, and impurities attached to the membrane surface are detached.

[0122] Next, in the third water filling process, similar to the first and second water filling processes, the raw water pump 22 is activated, and the raw water valve 23 and the air vent valve 56 are opened, respectively. This replenishes the housing 12 with the raw water that was drained in the diffuser bubbling process.

[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. As a result, pressurized air from the compressor is supplied into the water conduit 14 from the air inlet 14B and supplied to the raw water space S1 through the hole 14C. This causes the hollow fiber membrane bundle to be bubble-cleaned.

[0124] Next, in the drainage process, the air vent valve 56 is closed and the drain valve 54 is opened. The second air valve 33 remains 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 process, the drain valve 54 remains open while the second air valve 33 is closed. This allows air to be removed from inside the housing 12 (raw water space S1). After the hollow fiber membrane module 10 has been physically cleaned through the above process, the process returns to the first water filling process and the filtration operation resumes.

[0126] Furthermore, the timing at which the prediction unit 71 predicts the increase in the intermembrane differential pressure of the hollow fiber membrane module 10 is not particularly limited. For example, it may be done each time the operation cycle shown in Figure 2 is performed, or every time the operation cycle shown in Figure 2 is repeated multiple times (for example, 10 times), or once a day, or once a week, or once a month. The frequency may be appropriately determined depending on the type of raw water (for example, river water, wastewater, or sewage) and the season.

[0127] Furthermore, in the backwashing process, the treated water on the secondary side may be pressurized with permeate pressurized to a predetermined pressure instead of air pressurized to a predetermined pressure. Chemicals may also be injected into the permeate.

[0128] As described above, in the water treatment apparatus 1 according to this embodiment, during 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 areas of the hollow fiber membrane 11 where no impurities are attached, but also to collide with areas where impurities are attached. As a result, the pressure applied to the treated water can be changed according to the amount of impurities attached. Therefore, it is possible to measure the pressure on at least one side of the hollow fiber membrane module 10, either the primary or secondary side, according to the amount of impurities attached to the hollow fiber membrane 11.

[0129] Furthermore, in each of the multiple backwashing processes, the pressure on at least one side of the hollow fiber membrane module 10, either the primary or secondary side, is measured at intervals of 3 seconds or less, which is shorter than the normal measurement interval for the intermembrane pressure differential in the filtration process. Therefore, the detailed temporal changes of the pressure on at least one side in each backwashing process, which is completed within a few minutes, can be grasped.

[0130] Therefore, by observing the differences in the detailed temporal progression between multiple backwashing processes, it is possible to understand the change in the amount of impurities adhering to the hollow fiber membrane 11 in response to the change in pressure on at least one side. Thus, if it is determined that the amount of impurities adhering to the hollow fiber membrane 11 is increasing, it is possible to predict that the intermembrane pressure will rise in the future, and the prediction result can be reported.

[0131] Furthermore, the timing at which the notification unit 72 notifies the prediction results from the prediction unit 71 is not particularly limited. The notification unit 72 may notify the prediction results each time the prediction unit 71 makes a prediction of a future increase in the intermembrane differential pressure, or it may notify the prediction results for a predetermined number of times at once each time the prediction unit 71 makes a prediction of a future increase in the intermembrane differential pressure a predetermined number of times.

[0132] (Deformed embodiment) The embodiments of the membrane differential pressure prediction method and water treatment apparatus according to the present invention have been described above, but the present invention is not limited thereto, and for example, the following modified embodiments can be adopted.

[0133] (1) In the above embodiment, the measurement unit 60 measures the pressure on the primary and secondary sides of the hollow fiber membrane module 10 in each of the multiple backwashing processes, and the prediction unit 71 predicts the future increase in the intermembrane differential pressure of the hollow fiber membrane module 10 based on the difference in the measurement results between the multiple backwashing processes. However, the embodiment is not limited to this, and 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 first water filling processes in the same manner as the backwashing process 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 in each of the multiple first water filling processes in the same manner as the backwashing process in the above embodiment. The prediction unit 71 may then predict the future increase in the intermembrane differential pressure of the hollow fiber membrane module 10 based on the difference in the measurement results between the multiple first water filling processes.

[0134] Specifically, during the first water filling process, the primary 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 (Figure 7) showing the time change in the pressure on the primary side of the hollow fiber membrane module 10 during the first water filling process. In the graph in Figure 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 Figure 7, when the first water filling process is started (time t70 in Figure 7) and raw water flows into the hollow fiber membrane module 10, the primary pressure gradually increases due to the hydrostatic pressure inside the hollow fiber membrane module 10. Subsequently, when the inside of the hollow fiber membrane module 10 approaches a full water state (time t71 in Figure 7), raw water flows into the air vent pipe 55. At this time, because the diameter of the air vent pipe 55 is smaller than the diameter of the housing 12, pipe resistance occurs, and the primary pressure increases rapidly. Therefore, the time t70~t71, indicated by the double arrows in Figure 7, from the start of the first water filling process to the inflection point of the primary pressure change, 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 presumed 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 membrane 11. In other words, it is presumed that the intermembrane pressure differential of the hollow fiber membrane module 10 will increase in the future.

[0137] Therefore, the prediction unit 71 may refer to the logging data (Figure 7) stored in the control unit 70 and predict the future increase in the intermembrane differential pressure of the hollow fiber membrane module 10 based on the difference between multiple first water filling processes in the time from the start of the first water filling process to reaching the inflection point of the primary side pressure change (t70~t71 in Figure 7).

[0138] Specifically, assume that, between multiple first water filling processes, the time from the start of the first water filling process to reaching the inflection point of the primary side pressure change (t70~t71 in Figure 7) shows a decreasing trend. In this case, the prediction unit 71 may predict that the intermembrane differential pressure of the hollow fiber membrane module 10 will increase in the future, as 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, the primary side pressure of the hollow fiber membrane module 10 is measured when raw water fills the inside of the hollow fiber membrane module 10 during the first water filling process. Therefore, in this modified embodiment, the primary side pressure of the hollow fiber membrane module 10 can be measured according to the amount of impurities accumulated inside the hollow fiber membrane module 10.

[0140] Furthermore, in this modified embodiment, 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 for the intermembrane pressure differential in the filtration process, during each of the multiple first water filling processes. Therefore, it is possible to grasp the detailed temporal changes of the pressure on the primary side of the hollow fiber membrane module 10 during each first water filling process, which is completed within a few minutes.

[0141] Therefore, by observing the differences in this detailed temporal progression between multiple first water filling processes, it is possible to understand the change in the amount of impurities accumulated 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 difference in time t70 to t71 (Figure 7) between multiple first water filling processes, from the start of the first water filling process t70 (Figure 7) to the point where the primary pressure change reaches an inflection point (Figure 7), allows us to understand the amount of impurities accumulated inside the hollow fiber membrane module 10 and the changes in its effective volume. Therefore, if it is determined 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 membrane 11 is increasing, that is, that the intermembrane pressure differential will rise in the future, and to report the prediction result.

[0143] (2) In the above modified embodiment, an example was described in which the measuring unit 60 measures the pressure on the primary side of the hollow fiber membrane module 10 in each of the multiple first water filling processes, and the prediction unit 71 predicts the future increase in the intermembrane differential pressure of the hollow fiber membrane module 10 based on the difference in the measurement results between the multiple first water filling processes. Similarly, the measuring 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 draining processes. Alternatively, the measuring 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 draining processes. Then, the prediction unit 71 may predict the future increase in the intermembrane differential pressure of the hollow fiber membrane module 10 based on the difference in the measurement results between the multiple draining processes.

[0144] Specifically, during the drainage process, the primary 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 (Figure 8) showing the time change in the pressure on the primary side of the hollow fiber membrane module 10 during the drainage process. In the graph in Figure 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 Figure 8, when the drainage process begins (time t80 in Figure 8), the drain water inside the hollow fiber membrane module 10 is discharged through the drainage pipe 53 (Figure 1). Subsequently, when the discharge of the drain water inside the hollow fiber membrane module 10 is completed (time t81 in Figure 8), the primary side pressure stabilizes at a predetermined drainage completion pressure of around 0 kPa, which indicates the end of drain water discharge. Therefore, the time t80~t81, indicated by the double arrows in Figure 8, from the start of the drainage process until the primary side pressure becomes constant, 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.

[0146] Furthermore, it is presumed 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 membrane 11. In other words, it is presumed that the intermembrane pressure differential of the hollow fiber membrane module 10 will increase in the future.

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

[0148] Specifically, assume that the time from the start of a drainage process until the primary pressure becomes constant (t80~t81 in Figure 8) shows a decreasing trend between multiple drainage processes. In this case, the prediction unit 71 may predict that the intermembrane differential pressure of the hollow fiber membrane module 10 will increase in the future, as 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 the drain water inside the hollow fiber membrane module 10 is discharged during the drainage process. Therefore, in this modified embodiment, the pressure on the primary side of the hollow fiber membrane module 10 can be measured according to the amount of impurities accumulated inside the hollow fiber membrane module 10.

[0150] Furthermore, in this modified embodiment, 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 for the intermembrane pressure differential in the filtration process, during each of the multiple drainage processes. Therefore, it is possible to grasp the detailed temporal changes of the pressure on the primary side of the hollow fiber membrane module 10 during each drainage process, which is completed within a few minutes.

[0151] Therefore, according to this modified embodiment, the difference in the detailed temporal progression between multiple drainage processes makes it possible to grasp the change in the amount of impurities accumulated 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.

[0152] Specifically, the difference in time t80 to t81 (Figure 8) between multiple drainage processes, from the start of the drainage process t80 (Figure 8) to the point t81 (Figure 8) when the primary pressure becomes constant, allows us to understand the amount of impurities accumulated inside the hollow fiber membrane module 10 and the changes in its effective volume. Therefore, if it is determined 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 membrane 11 is increasing, that is, that the intermembrane pressure differential will rise in the future, and to report the prediction result.

[0153] The embodiments and variations thereof disclosed herein should be understood in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

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

Claims

1. A method for predicting the intermembrane pressure differential in a water treatment apparatus that filters raw water using a hollow fiber membrane module, When a backwashing process is performed multiple times in which the 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, the pressure on at least one of the primary side and the secondary side is measured at intervals of 3 seconds or less during each of the multiple backwashing processes. Based on the difference in the measurement results of the pressure on at least one side between the multiple backwashing processes, predict the future increase in the intermembrane differential pressure of the hollow fiber membrane module. To report the results of the aforementioned prediction, A method for predicting the differential pressure between membranes, including the method described above.

2. In each of the aforementioned multiple backwashing steps, the pressure on the secondary side is measured at least at the aforementioned intervals. Based on the difference between the multiple backwashing processes at which the secondary pressure reaches a point that instantaneously increases immediately after the start of the backwashing process, the future increase in the intermembrane differential pressure is predicted. The method for predicting the differential pressure between membranes according to claim 1.

3. In each of the aforementioned multiple backwashing steps, the pressure on the secondary side is measured at least at the aforementioned intervals. Based on the difference in time between the multiple backwashing processes, from the start of the backwashing process until the pressure on the secondary side stabilizes at the pressure of the medium, the future increase in the intermembrane differential pressure is predicted. The method for predicting the differential pressure between membranes according to claim 1.

4. In each of the aforementioned multiple backwashing steps, the pressure on the primary side is measured at least at the aforementioned intervals. Based on the difference between the multiple backwashing processes at which the primary side pressure reaches a point that instantaneously increases immediately after the start of the backwashing process, the future increase in the intermembrane differential pressure is predicted. The method for predicting the differential pressure between membranes according to claim 1.

5. In each of the aforementioned multiple backwashing steps, the pressure on the primary side is measured at least at the aforementioned intervals. Based on the difference in time between the multiple backwashing processes, from the start of the backwashing process until the primary side pressure stabilizes at a predetermined termination pressure indicating the end of the secondary side treatment water discharge, the future increase in the intermembrane differential pressure is predicted. The method for predicting the differential pressure between membranes according to claim 1.

6. For each of the aforementioned multiple backwashing processes, the integral value of the difference between the pressure on the secondary side and the pressure on the primary side is calculated at any one of the following time points: the time from the start of the backwashing process until the pressure on the primary or secondary side, which rises instantaneously immediately after the start of the backwashing process, reaches its peak; the time from the start of the backwashing process until the pressure on the primary or secondary side stabilizes after reaching its peak; and the time from the start of the backwashing process until the pressure on the primary or secondary side stabilizes. Based on the difference in the integral value between the multiple backwashing steps, the future increase in the intermembrane differential pressure is predicted. The method for predicting the differential pressure between membranes according to claim 1.

7. For the aforementioned multiple backwashing steps, the point at which the pressure on either the primary side or the secondary side reaches a peak, which rises instantaneously immediately after the start of the backwashing step, Based on the difference between the secondary pressure and the primary pressure at the point when any of the aforementioned pressures reach the aforementioned target, and the difference between the multiple backwashing processes, the future increase in the intermembrane differential pressure is predicted. The method for predicting the differential pressure between membranes according to claim 1.

8. A method for predicting the intermembrane pressure differential in a water treatment apparatus that filters raw water using a hollow fiber membrane module, When the filling process of filling the hollow fiber membrane module with raw water is performed multiple times, the pressure on the primary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less during each of the multiple filling processes. Based on the difference between the multiple water-filling processes in the measurement results of the primary side pressure, from the start of the water-filling process to reaching the inflection point of the change in the primary side pressure, the future increase in the intermembrane differential pressure of the hollow fiber membrane module is predicted. To report the results of the aforementioned prediction, A method for predicting the differential pressure between membranes, including the method described above.

9. A method for predicting the intermembrane pressure differential in a water treatment apparatus that filters raw water using a hollow fiber membrane module, When a drainage process is performed multiple times to drain condensate containing turbidity components detached from the hollow fiber membrane, the pressure on the primary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less during each of the multiple drainage processes. Based on the measurement results of the primary side pressure, and the difference in the time from the start of the drainage process until the primary side pressure becomes constant between the multiple drainage processes, the future increase in the intermembrane differential pressure of the hollow fiber membrane module is predicted. To report the results of the aforementioned prediction, A method for predicting the differential pressure between membranes, including the method described above.

10. A water treatment device that filters raw water using a hollow fiber membrane module, When a backwashing process is performed multiple times in which the 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 measuring unit measures the pressure on at least one of the primary side and the secondary side at intervals of 3 seconds or less during each of the multiple backwashing processes, A prediction unit that predicts the future increase in the intermembrane differential pressure 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, A notification unit that notifies the prediction results from the prediction unit, A water treatment device equipped with the following features.

11. A water treatment device that filters raw water using a hollow fiber membrane module, When a filling process of filling the hollow fiber membrane module with raw water is performed multiple times, a measuring unit measures the pressure on the primary side of the hollow fiber membrane module at intervals of 3 seconds or less during each of the multiple filling processes, A prediction unit predicts the future increase in the intermembrane differential pressure of the hollow fiber membrane module based on the difference between multiple water-filling processes in the measurement results of the primary side pressure, specifically the time from the start of the water-filling process to the inflection point of the change in the primary side pressure. A notification unit that notifies the results of the aforementioned prediction, A water treatment device equipped with the following features.

12. A water treatment device that filters raw water using a hollow fiber membrane module, When a drainage process is performed multiple times to drain condensate containing turbidity components detached from the hollow fiber membrane, a measuring unit measures the pressure on the primary side of the hollow fiber membrane module at intervals of 3 seconds or less during each of the multiple drainage processes, A prediction unit predicts the future increase in the intermembrane differential pressure of the hollow fiber membrane module based on the difference between the multiple drainage processes in the time it takes for the primary side pressure to become constant from the start of the drainage process, as measured in the primary side pressure measurement results, A notification unit that notifies the results of the aforementioned prediction, A water treatment device equipped with the following features.

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