JP7628465B2 - Cleaning evaluation method - Google Patents

Description

The present invention relates to a cleaning evaluation method and a water treatment device.

Conventionally, in water treatment equipment that uses a hollow fiber membrane module to filter raw water, methods have been proposed for cleaning the hollow fiber membrane module to remove impurities that adhere to the membrane surface during filtration. For example, Patent Document 1 proposes that chemical cleaning and physical cleaning can be efficiently performed by adding a chemical solution to the secondary side of the hollow fiber membrane module and performing backwashing, which pushes the treated water from the secondary side together with the chemical solution to the primary side.

Patent No. 6653154

However, if the hollow fiber membrane is excessively dirty, such as when clogging of the hollow fiber membrane progresses or when there is an excessive amount of fouling components attached to the hollow fiber membrane, there is a risk that sufficient effects will not be obtained even if physical cleaning or chemical cleaning is performed efficiently using the method described in Patent Document 1. For this reason, it is important to properly evaluate the effects of the physical cleaning or chemical cleaning performed and to appropriately adjust the cleaning conditions based on the results of this evaluation.

As a method of the above evaluation, for example, a portion of the hollow fiber membranes may be collected from the hollow fiber membrane module after cleaning, and the cleaning effect of the collected hollow fiber membranes may be evaluated. However, this evaluation method requires the effort of going to the installation site of the hollow fiber membrane module and collecting a portion of the hollow fiber membranes from the hollow fiber membrane module. In addition, because only a portion of the hollow fiber membranes collected from the hollow fiber membrane module can be evaluated, there is also the problem that the cleaning effect of the entire hollow fiber membrane module cannot be properly understood.

It is also possible to evaluate the effectiveness of physical or chemical cleaning by measuring the transmembrane pressure difference of the hollow fiber membrane module before and after cleaning and comparing the results of the measurements. However, in the filtration process, the transmembrane pressure difference of the hollow fiber membrane module is usually measured every minute (e.g., every 10 minutes), so there is a risk that the effectiveness of the cleaning will not be evaluated appropriately.

The present invention was made in consideration of the above problems, and its purpose is to provide a cleaning evaluation method and water treatment device that can appropriately grasp the effects of physical cleaning or chemical cleaning of hollow fiber membrane modules while minimizing the effort.

A cleaning evaluation method according to one aspect of the present invention is a cleaning evaluation method for evaluating the cleaning effect of a hollow fiber membrane module in a water treatment device that filters raw water using the hollow fiber membrane module, and includes measuring the pressure of at least one of the primary side and secondary side of the hollow fiber membrane module at intervals of 3 seconds or less during a backwashing process of the hollow fiber membrane module, evaluating the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on the measurement result of the pressure of the at least one side, and notifying the result of the evaluation.

According to this configuration, in the backwash process of the hollow fiber membrane module, the pressure of at least one of the primary and secondary sides of the hollow fiber membrane module is measured at intervals of 3 seconds or less, which is shorter than the usual measurement interval of the transmembrane pressure difference in the filtration process. This makes it possible to grasp the detailed time progression of the pressure on at least one of the sides in the backwash process, which is completed within a few minutes. Therefore, by using this detailed time progression, the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module can be appropriately evaluated.

In addition, with this configuration, the evaluation results of the effects of physical cleaning or chemical cleaning are reported. Therefore, the effects of physical cleaning or chemical cleaning of the hollow fiber membrane module can be understood without the need to go to the installation site of the hollow fiber membrane module and take some of the hollow fiber membranes from the hollow fiber membrane module.

In the cleaning evaluation method, the backwashing process may push the treated water on the secondary side to the primary side by a pressurized medium. In the cleaning evaluation method, the effect of the physical cleaning may be evaluated based on the difference between the multiple backwashing processes in the point where the pressure on the secondary side, which increases instantaneously immediately after the start of the backwashing process, reaches.

Immediately after the start of the backwash process, the treated water on the secondary side is suddenly 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 treated water is pressurized to a greater extent by the medium than it is permeating to the primary side. For this reason, the pressure on the secondary side increases instantaneously immediately after the start of the backwash process, and the reached pressure on the secondary side during this increase becomes higher the more the hollow fiber membrane becomes clogged and the greater the permeation resistance of the hollow fiber membrane becomes.

Therefore, with this configuration, the amount of change in the permeation resistance of the hollow fiber membrane can be grasped from the difference in the secondary side attained pressure immediately after the start of the backwashing process between multiple backwashing processes. Then, based on the grasped amount of change in permeation resistance, the effect of physical cleaning on the recovery of clogged hollow fiber membranes can be appropriately evaluated.

In the cleaning evaluation method, in the backwashing process, the treated water on the secondary side may be pushed to the primary side by a pressurized medium. In the cleaning evaluation method, the effect of the physical cleaning may be evaluated based on the difference between the backwashing processes in the time from the start of the backwashing process until the pressure on the secondary side stabilizes at the pressure of the medium.

In the backwash process, when the pushing of the treated water from the secondary side to the primary side is completed, the secondary side becomes filled with the pressurized medium, and the pressure on the secondary side stabilizes at the pressure of the medium. Here, the more the hollow fiber membrane becomes clogged and the greater the permeation resistance of the hollow fiber membrane, the longer the time it takes for all the treated water on the secondary side to be pushed to the primary side. Therefore, the more the clogging of the hollow fiber membrane progresses and the greater the permeation resistance of the hollow fiber membrane, the longer the time it takes from the start of the backwash process to the pressure on the secondary side stabilizes at the pressure of the medium.

Therefore, with this configuration, the amount of change in the permeation resistance of the hollow fiber membrane can be grasped from the difference in time between multiple backwashing processes from the start of the backwashing process until the secondary pressure stabilizes at the pressure of the medium. Then, based on the grasped amount of change in permeation resistance, the effect of physical cleaning in recovering from clogging of the hollow fiber membrane can be appropriately evaluated.

In the cleaning evaluation method, the backwashing process may push the treated water on the secondary side to the primary side by a pressurized medium. In the cleaning evaluation method, the effect of the physical cleaning may be evaluated based on the difference between the multiple backwashing processes in the point where the pressure on the primary side, which increases instantaneously immediately after the start of the backwashing process, reaches.

Immediately after the backwash process begins and the treated water on the secondary side is pushed out to the primary side, the pressure on the primary side increases instantaneously. At this time, the less clogging there is in the hollow fiber membrane and the smaller the permeation resistance of the hollow fiber membrane, the faster the treated water on the secondary side is pushed out to the primary side, and the higher the pressure reached on the primary side.

Therefore, with this configuration, the amount of change in the permeation resistance of the hollow fiber membrane can be grasped from the difference in the reached pressure on the primary side immediately after the start of the backwashing process between multiple backwashing processes. Then, based on the grasped amount of change in permeation resistance, the effect of physical cleaning on the recovery of clogged hollow fiber membranes can be appropriately evaluated.

In the cleaning evaluation method, the backwashing process may push the treated water on the secondary side to the primary side by a pressurized medium. In the cleaning evaluation method, the effect of the physical cleaning may be evaluated based on the difference between the backwashing processes in the time from the start of the backwashing process to the time when the pressure on the primary side stabilizes at a predetermined end pressure indicating the end of the pushing of the treated water on the secondary side.

Immediately after the backwash process begins 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 more the hollow fiber membrane becomes clogged and the greater the permeation resistance of the hollow fiber membrane, the slower the rate at which the treated water is pushed out to the primary side becomes, and the longer it takes to finish pushing the treated water out to the secondary side.

Therefore, with this configuration, the amount of change in the permeation resistance of the hollow fiber membrane can be grasped from the difference in time between multiple backwashing processes from the start of the backwashing process until the primary side pressure stabilizes at the end pressure. Then, based on the grasped amount of change in permeation resistance, the effect of physical cleaning in recovering from clogging of the hollow fiber membrane can be appropriately evaluated.

In the cleaning evaluation method, in the backwashing process, the treated water on the secondary side may be pushed to the primary side by a pressurized medium. In the cleaning evaluation method, for a plurality of the backwashing processes, an integral value of the difference between the pressure on the secondary side and the pressure on the primary side at any one of the following times may be calculated: a time from the start of the backwashing process until the pressure on the primary side or the secondary side, which increases instantaneously immediately after the start of the backwashing process, reaches a target point; a time from the start of the backwashing process until the pressure on the primary side or the secondary side, which increases instantaneously immediately after the start of the backwashing process, reaches the target point and stabilizes; and a time from the start of the backwashing process until the pressure on the primary side or the secondary side stabilizes. Then, the effect of the physical cleaning may be evaluated based on the difference in the integral value between the plurality of backwashing processes.

The inventor found through test runs that even if the difference between the secondary side pressure and the primary side pressure during the filtration process is approximately constant, the integral value of the difference between the primary side pressure and the secondary side pressure during the time from the start of the backwash process until the primary side or secondary side pressure stabilizes is significantly different when the degree of clogging of the hollow fiber membrane is greater than or less than a predetermined degree. The inventor also conducted further test runs and found that the integral value of the time from the start of the backwash process until the primary side or secondary side pressure, which increases instantaneously immediately after the start of the backwash process, reaches its target point, and the integral value of the time from the time the primary side or secondary side pressure, which increases instantaneously immediately after the start of the backwash process, reaches its target point until it stabilizes, are also significantly different when the degree of clogging of the hollow fiber membrane is greater than or less than a predetermined degree.

Therefore, with this configuration, the degree of clogging of the hollow fiber membrane can be appropriately grasped by the difference between the integral value of the difference between the secondary side pressure and the primary side pressure at the above three times among multiple backwashing processes. Then, based on the grasped degree of clogging of the hollow fiber membrane, the effect of physical cleaning on recovery from clogging of the hollow fiber membrane can be appropriately evaluated.

In the cleaning evaluation method, in the backwashing process, the treated water on the secondary side may be pushed to the primary side by a pressurized medium. In the cleaning evaluation method, for a plurality of the backwashing processes, the reaching point of the pressure of either the primary side or the secondary side that instantaneously increases immediately after the start of the backwashing process may be detected. Then, the effect of the physical cleaning may be evaluated based on the difference between the pressure on the secondary side and the pressure on the primary side at the time when either of the pressures reaches the reaching point, between the plurality of backwashing processes.

According to this configuration, since the pressure of at least one of the primary and secondary sides of the hollow fiber membrane module is measured at intervals of 3 seconds or less for multiple backwashing processes, the arrival point of either the primary or secondary side pressure that instantaneously increases immediately after the start of the backwashing process can be detected. That is, even if the fouling components in the backwashing process are such that they peel off from the hollow fiber membrane surface due to the force of the treated water being pushed from the secondary side to the primary side, it is possible to properly detect either of the pressures before they decrease due to the peeling off of the fouling components. As a result, by using the difference between the pressure on the secondary side and the pressure on the primary side at the time of detection, the degree of clogging of the hollow fiber membrane after physical cleaning can be properly grasped. Then, based on the degree of clogging of the hollow fiber membrane that has been grasped, the effect of physical cleaning on the recovery of the clogging of the hollow fiber membrane can be properly evaluated.

In the above cleaning evaluation method, the chemical cleaning may dissolve fouling components attached to the hollow fiber membrane by immersion in the chemical solution. Then, in the backwashing process, the treated water on the secondary side may be pushed to the primary side by a pressurized medium. Then, the effect of the chemical cleaning may be evaluated based on the difference between the backwashing process before and after the chemical cleaning in the point where the pressure on the secondary side, which increases instantaneously immediately after the start of the backwashing process, reaches.

Immediately after the start of the backwash process, the treated water on the secondary side is suddenly 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 treated water is pressurized to a greater extent by the medium than it is permeated to the primary side. For this reason, the pressure on the secondary side increases instantaneously immediately after the start of the backwash process, and the reached pressure on the secondary side during this increase becomes higher the more fouling components adhered to the hollow fiber membrane and the greater the permeation resistance of the hollow fiber membrane.

Therefore, with this configuration, the amount of change in the permeation resistance of the hollow fiber membrane can be grasped from the difference in the secondary side attained pressure immediately after the start of the backwashing process between before and after the chemical cleaning. Then, based on the grasped amount of change in permeation resistance, the effect of dissolving the fouling components adhering to the hollow fiber membrane by the chemical cleaning can be appropriately evaluated.

In the above cleaning evaluation method, the chemical cleaning may dissolve fouling components attached to the hollow fiber membrane by immersion in the chemical solution. Then, in the backwashing process, the treated water on the secondary side may be pushed to the primary side by a pressurized medium. Then, the effect of the chemical cleaning may be evaluated based on the difference in the time from the start of the backwashing process until the pressure on the secondary side stabilizes at the pressure of the medium, between the backwashing processes before and after the chemical cleaning.

In the backwash process, when the pushing of the treated water from the secondary side to the primary side is completed, the secondary side becomes filled with the pressurized medium, and the pressure on the secondary side stabilizes at the pressure of the medium. Here, the more fouling components attached to the hollow fiber membrane and the greater the permeation resistance of the hollow fiber membrane, the longer the time required for all the treated water on the secondary side to be pushed to the primary side. Therefore, the more fouling components attached to the hollow fiber membrane and the greater the permeation resistance of the hollow fiber membrane, the longer the time from the start of the backwash process until the pressure on the secondary side stabilizes at the pressure of the medium.

Therefore, according to this configuration, the change in the permeation resistance of the hollow fiber membrane can be grasped from the difference in time between the start of the backwashing process before and after the chemical cleaning process until the secondary side pressure stabilizes at the pressure of the medium. Then, based on the grasped change in permeation resistance, the effect of dissolving the fouling components attached to the hollow fiber membrane by the chemical cleaning can be appropriately evaluated.

In the above cleaning evaluation method, the chemical cleaning may dissolve fouling components attached to the hollow fiber membrane by immersion in the chemical solution. Then, in the backwashing process, the treated water on the secondary side may be pushed to the primary side by a pressurized medium. Then, the effect of the chemical cleaning may be evaluated based on the difference between the backwashing process before and after the chemical cleaning in the point where the pressure on the primary side, which increases instantaneously immediately after the start of the backwashing process, reaches.

Immediately after the backwash process begins and the treated water on the secondary side is pushed out to the primary side, the pressure on the primary side increases instantaneously. At this time, the fewer the fouling components adhering to the hollow fiber membrane and the smaller the permeation resistance of the hollow fiber membrane, the faster the treated water on the secondary side is pushed out to the primary side, and the higher the pressure reached on the primary side.

Therefore, with this configuration, the amount of change in the permeation resistance of the hollow fiber membrane can be grasped from the difference in the reached pressure on the primary side immediately after the start of the backwashing process between before and after the chemical cleaning. Then, based on the grasped amount of change in permeation resistance, the effect of dissolving the fouling components adhering to the hollow fiber membrane by the chemical cleaning can be appropriately evaluated.

In the above cleaning evaluation method, the chemical cleaning may dissolve fouling components attached to the hollow fiber membrane by immersion in the chemical solution. Then, in the backwashing process, the treated water on the secondary side may be pushed to the primary side by a pressurized medium. Then, the effect of the chemical cleaning may be evaluated based on the difference between the backwashing process before and after the chemical cleaning in the time from the start of the backwashing process until the pressure on the primary side stabilizes at a predetermined end pressure indicating the end of the pushing of the treated water on the secondary side.

Immediately after the backwash process begins 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 more fouling components that have adhered to the hollow fiber membrane and the greater the permeation resistance of the hollow fiber membrane, the slower the rate at which the treated water is pushed out to the primary side, and the longer it takes to finish pushing the treated water out to the secondary side.

Therefore, according to this configuration, the change in the permeation resistance of the hollow fiber membrane can be grasped from the difference in time between the start of the backwashing process before and after the chemical cleaning process until the primary side pressure stabilizes at the end pressure. Then, based on the grasped change in the magnitude of the permeation resistance, the effect of dissolving the fouling components attached to the hollow fiber membrane by the chemical cleaning can be appropriately evaluated.

In the above cleaning evaluation method, the chemical cleaning may dissolve fouling components attached to the hollow fiber membrane by immersion in a chemical solution, and the backwashing process may push the treated water on the secondary side to the primary side by a pressurized medium. In the above cleaning evaluation method, for the backwashing process before and after the chemical cleaning, the integral value of the difference between the pressure on the secondary side and the pressure on the primary side during any one of the following periods may be calculated: the time from the start of the backwashing process until the pressure on the primary side or the secondary side, which increases instantaneously immediately after the start of the backwashing process, reaches a target point; the time from the start of the backwashing process until the pressure on the primary side or the secondary side, which increases instantaneously immediately after the start of the backwashing process, reaches the target point and stabilizes; and the time from the start of the backwashing process until the pressure on the primary side or the secondary side stabilizes. Then, the effect of the chemical cleaning may be evaluated based on the difference in the integral value between the backwashing process before and after the chemical cleaning.

The inventor found through test runs that even if the difference between the secondary side pressure and the primary side pressure during the filtration process is approximately constant, the integral value of the difference between the primary side pressure and the secondary side pressure during the time from the start of the backwash process until the primary side or secondary side pressure stabilizes is significantly different when the degree of clogging of the hollow fiber membrane is greater than or less than a predetermined degree. The inventor also conducted further test runs and found that the integral value of the time from the start of the backwash process until the primary side or secondary side pressure, which increases instantaneously immediately after the start of the backwash process, reaches its target point, and the integral value of the time from the time the primary side or secondary side pressure, which increases instantaneously immediately after the start of the backwash process, reaches its target point until it stabilizes, are also significantly different when the degree of clogging of the hollow fiber membrane is greater than or less than a predetermined degree.

Therefore, with this configuration, the degree of clogging of the hollow fiber membrane can be properly grasped by the difference between the integral value of the difference between the secondary side pressure and the primary side pressure at the above three times during the backwash process before and after the chemical cleaning. Then, based on the grasped degree of clogging of the hollow fiber membrane, the effect of chemical cleaning on the recovery of the clogged hollow fiber membrane can be properly evaluated.

In the above cleaning evaluation method, the chemical cleaning may dissolve fouling components attached to the hollow fiber membrane by immersion in a chemical solution, and the backwashing process may push the treated water on the secondary side to the primary side by a pressurized medium. In the above cleaning evaluation method, the backwashing process before and after the chemical cleaning may detect the point at which either the pressure on the primary side or the pressure on the secondary side, which increases instantaneously immediately after the start of the backwashing process, reaches. The effect of the chemical cleaning may be evaluated based on the difference between the pressure on the secondary side and the pressure on the primary side at the point at which either pressure reaches the point, between the backwashing process before and after the chemical cleaning.

According to this configuration, the pressure of at least one of the primary and secondary sides of the hollow fiber membrane module is measured at intervals of 3 seconds or less during the backwash process before and after the chemical cleaning, so that the arrival point of either the primary or secondary side pressure, which instantaneously increased immediately after the start of the backwash process, can be detected. That is, even if the treated water is a fouling component that peels off from the hollow fiber membrane surface due to the force of the treated water being pushed from the secondary side to the primary side during the backwash process, the pressure of either of the above before it decreases due to the fouling component peeling off can be properly detected. As a result, by using the difference between the pressure on the secondary side and the pressure on the primary side at the time of detection, the degree of clogging of the hollow fiber membrane after chemical cleaning can be properly grasped. Then, based on the degree of clogging of the hollow fiber membrane that has been grasped, the effect of the chemical cleaning on the recovery of the clogging of the hollow fiber membrane can be properly evaluated.

A water treatment device according to another aspect of the present invention is a water treatment device that filters raw water using a hollow fiber membrane module. This device is configured to include a measurement unit that measures the pressure of at least one of the primary side and secondary side of the hollow fiber membrane module at intervals of 3 seconds or less during the backwashing process of the hollow fiber membrane module, an evaluation unit that evaluates the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on the measurement result of the pressure of the at least one side, and a notification unit that notifies the evaluation result by the evaluation unit.

This configuration can achieve the same effects as the cleaning evaluation method described above.

As is clear from the above explanation, the present invention can provide a cleaning evaluation method and water treatment device that can appropriately grasp the effects of physical cleaning or chemical cleaning of hollow fiber membrane modules while minimizing the labor required.

1 is a diagram illustrating a schematic configuration of a water treatment device according to a first embodiment of the present invention. FIG. 4 is a diagram showing the on/off state of a raw water pump and the open/closed state of a valve in each step of the cleaning evaluation method according to the first embodiment of the present invention. FIG. 2 is a diagram showing the change over time in the secondary side pressure of the hollow fiber membrane module in the backwashing step according to the first embodiment of the present invention. FIG. 2 is a diagram showing the change over time in the primary side pressure of the hollow fiber membrane module in the backwashing step according to the first embodiment of the present invention. FIG. 13 is a diagram showing the time changes in the primary side pressure and secondary side pressure of a hollow fiber membrane module in a backwashing process when clogging of the hollow fiber membranes is not progressing. FIG. 13 is a diagram showing the time changes in the primary side pressure and secondary side pressure of a hollow fiber membrane module in a backwashing process when clogging of the hollow fiber membranes is progressing. FIG. 10 is a diagram illustrating a schematic configuration of a water treatment device according to a second embodiment of the present invention. 13A and 13B are diagrams illustrating the on/off state of a pump and the open/closed state of a valve in chemical cleaning according to a second embodiment of the present invention.

The following describes in detail an embodiment of the present invention with reference to the drawings.

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

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

As shown in FIG. 1, the upper part of the housing 12 is provided with an outlet 12A for treated water (filtered water) facing the treated water space S2, the side part of the housing 12 (part above the center in the longitudinal direction) is provided with an air vent 12B facing the raw water space S1, and the lower part of the housing 12 is provided with an air supply port 12C and a drain port 12D facing the raw water space S1. The ratio of the inner diameter of the housing 12 to the inner diameters of these piping connection ports (outlet 12A, air vent 12B, air supply port 12C, and drain port 12D) is 1.3 to 12, preferably 2.5 to 12, and more preferably 3.0 to 6.0. The inner diameter of the housing 12 referred to here is the inner diameter in a cross section perpendicular to the longitudinal direction of the housing 12.

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

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

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

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

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

As shown in FIG. 1, the treated water pipe 50 and the drain pipe 53 are connected to each other by a depressurization pipe 57. One end of the depressurization pipe 57 is connected to a portion of the treated water pipe 50 upstream of the treated water valve 51, and the other end of the depressurization pipe 57 is connected to a portion of the drain pipe 53 downstream of the connection portion of the air bleed pipe 55. A depressurization valve 58 (opening and closing valve) is installed in the depressurization pipe 57. The diameter of the depressurization pipe 57 is smaller than the diameter of the housing 12.

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 in the raw water pipe 21. The raw water pipe 21 has an upstream end connected to the outlet of a raw water tank (not shown) and a downstream end connected to a 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 opening/closing valve, and is installed in the raw water pipe 21 downstream of the raw water pump 22.

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

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

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

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

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

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

The water treatment device 1 further includes a control unit 70. The control unit 70 is configured by 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 sequence information stored in the ROM, etc. When the control unit 70 starts the execution of each process, it controls the drive of peripheral devices and the opening and closing of valves according to the process being executed, according to the process information stored in the ROM, etc.

The control unit 70 includes an evaluation unit 71 and a notification unit 72. The evaluation unit 71 is configured by a microcomputer equipped with a CPU, RAM, ROM, etc. The evaluation unit 71 evaluates the effect of physical cleaning of the hollow fiber membrane module 10 based on the results of pressure measurement by the measurement unit 60. The notification unit 72 is configured by a microcomputer equipped with a CPU, RAM, ROM, etc. The notification unit 72 notifies the results of the evaluation by the evaluation unit 71.

In addition, two or more of the control unit 70, the evaluation unit 71, and the notification unit 72 may be configured by the same microcomputer. In other words, the evaluation unit 71 and the notification unit 72 may be realized as one function of the control unit 70. Alternatively, the control unit 70, the evaluation unit 71, and the notification unit 72 may each be configured by an individual microcomputer.

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

First, in the first filling step, the raw water pump 22 is operated, and the raw water valve 23 and the air vent valve 56 are opened. This causes raw water to be supplied into the water conduit 14 through the raw water piping 21, and raw water is supplied into the raw water space S1 through the hole 14C.

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

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

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

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

During the backwash process, the secondary pressure sensor 62 measures the secondary pressure of the hollow fiber membrane module 10 at intervals of 3 seconds or less. This provides logging data (Figure 3) that shows the time change in the secondary pressure of the hollow fiber membrane module 10 during the backwash process. In Figure 3, the horizontal axis shows time, and the vertical axis shows the secondary pressure of the hollow fiber membrane module 10. Graph G31 in Figure 3 shows the time change in the secondary pressure of the hollow fiber membrane module 10 during the backwash process immediately before the most recent backwash process. Graph G32 in Figure 3 shows the time change in the secondary pressure of the hollow fiber membrane module 10 during the most recent backwash process.

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

The evaluation unit 71 refers to the logging data stored in the control unit 70 and evaluates the effect of physical cleaning based on the difference between multiple backwash processes in the point at which the secondary side pressure, which increases instantaneously immediately after the start of the backwash process, reaches. The multiple backwash processes may be, for example, the most recent backwash process and the backwash process performed immediately before the most recent backwash process, or the most recent backwash process and multiple backwash processes performed before the most recent backwash process.

Specifically, if the secondary side achieved pressure immediately after the start of a backwashing process shows an upward trend between multiple backwashing processes, the evaluation unit 71 evaluates that the clogging of the hollow fiber membrane 11 is progressing, i.e., the effect of physical cleaning is insufficient. On the other hand, if the secondary side achieved pressure immediately after the start of a backwashing process shows a downward trend between multiple backwashing processes, the evaluation unit 71 evaluates that the clogging of the hollow fiber membrane 11 is recovering, i.e., the effect of physical cleaning is sufficient.

In the example of FIG. 3, the secondary side reached pressure P32 immediately after the start of the most recent backwashing process is higher than the secondary side reached pressure P31 immediately after the start of the backwashing process immediately preceding the most recent backwashing process. For this reason, the evaluation unit 71 evaluates that the effect of physical cleaning is insufficient.

In addition, in the backwash process, when the pushing of the treated water from the secondary side to the primary side is completed, the secondary side becomes filled with pressurized air, and the pressure on the secondary side stabilizes at the air pressure. Here, the more the hollow fiber membrane 11 becomes clogged and the greater the permeation resistance of the hollow fiber membrane 11, the longer it takes for all the treated water on the secondary side to be pushed to the primary side. Therefore, the more the clogging of the hollow fiber membrane 11 progresses and the greater the permeation resistance of the hollow fiber membrane 11, the longer the time from the start of the backwash process until the pressure on the secondary side stabilizes at the air pressure.

The pressure stabilizing means, for example, that the rising pressure reaches an inflection point where the slope of the pressure increase decreases, that the decreasing pressure reaches an inflection point where the slope of the pressure decrease increases, or that the rising or decreasing pressure continues to fluctuate within a predetermined tolerance range for a predetermined period of time or more.

For this reason, the evaluation unit 71 may refer to the logging data stored in the control unit 70 and evaluate the effect of physical cleaning based on the difference in the time from the start of the backwash process until the secondary pressure stabilizes at the air pressure in multiple backwash processes.

Specifically, if the time from the start of a backwashing process until the pressure on the secondary side stabilizes at air pressure shows an increasing trend among multiple backwashing processes, the evaluation unit 71 may evaluate the situation as a situation in which clogging of the hollow fiber membrane 11 is progressing, i.e., the effect of physical cleaning is insufficient. On the other hand, if the time from the start of a backwashing process until the pressure on the secondary side stabilizes at air pressure shows a decreasing trend among multiple backwashing processes, the evaluation unit 71 may evaluate the situation as a situation in which clogging of the hollow fiber membrane 11 is recovering, i.e., the effect of physical cleaning is sufficient.

In the example of FIG. 3, the time t32 from the start of the most recent backwashing process until the secondary pressure stabilizes at 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 air pressure. For this reason, the evaluation unit 71 evaluates that the effect of physical cleaning is insufficient.

In addition, during the backwash 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) that shows the change over time in the primary pressure of the hollow fiber membrane module 10 during the backwash process.

As described above, when 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, the evaluation unit 71 may use data indicating the average value of the primary side pressure indicated by the logging data received from each of the primary side pressure sensor 61 and the air vent pressure sensor as logging data indicating the primary side pressure of the hollow fiber membrane module 10.

In Figure 4, the horizontal axis indicates time, and the vertical axis indicates the primary side pressure of the hollow fiber membrane module 10. Graph G41 in Figure 4 shows the change over time in the primary side pressure of the hollow fiber membrane module 10 during the backwash step immediately preceding the most recent backwash step. Graph G42 in Figure 4 shows the change over time in the primary side pressure of the hollow fiber membrane module 10 during the most recent backwash step.

As shown in FIG. 4, immediately after the backwash process is started and the treated water on the secondary side is pushed out to the primary side, the diameter of the drain pipe 53 is smaller than the housing 12, so the pressure on the primary side increases instantaneously due to the pipeline resistance that occurs when the raw water on the primary side flows into the drain pipe 53. At this time, the less the hollow fiber membrane 11 is clogged and the smaller the permeation resistance of the hollow fiber membrane 11, the faster the treated water on the secondary side is pushed out to the primary side, and the higher the pressure reached on the primary side.

For this reason, the evaluation unit 71 may refer to the logging data stored in the control unit 70 and evaluate the effect of physical cleaning based on the difference in the reach of the primary side pressure that instantaneously increases immediately after the start of the backwash process among multiple backwash processes.

Specifically, in multiple backwashing processes, if the achieved pressure on the primary side immediately after the start of the backwashing process shows an upward trend, the evaluation unit 71 may evaluate the situation as a situation in which the clogging of the hollow fiber membrane 11 has been recovered, that is, the effect of physical cleaning is sufficient. On the other hand, in multiple backwashing processes, if the achieved pressure on the primary side immediately after the start of the backwashing process shows a downward trend, the evaluation unit 71 may evaluate the situation as a situation in which the clogging of the hollow fiber membrane 11 is progressing, that is, the effect of physical cleaning is insufficient.

In the example of FIG. 4, the primary side achieved pressure P42 immediately after the start of the most recent backwashing process is lower than the primary side achieved pressure P41 immediately after the start of the backwashing process immediately preceding the most recent backwashing process. For this reason, the evaluation unit 71 evaluates that the effect of physical cleaning is insufficient.

In addition, after the backwash process is started and the pressure on the primary side increases instantaneously immediately after the treated water on the secondary side is pushed to the primary side, the more the hollow fiber membrane 11 becomes clogged and the greater the permeation resistance of the hollow fiber membrane 11, the slower the rate at which the treated water is pushed to the primary side becomes, and the longer it takes to finish pushing the treated water to the secondary side.

For this reason, the evaluation unit 71 may refer to the logging data stored in the control unit 70 and evaluate the effect of physical cleaning based on the difference between multiple backwash processes in the time from the start of the backwash process until the pressure on the primary side stabilizes at a predetermined end pressure (e.g., 0 kPa), which indicates the end of the pushing of treated water from the secondary side.

Specifically, if the time from the start of the backwash process until the pressure on the primary side stabilizes at the end pressure shows an increasing trend in multiple backwash processes, the evaluation unit 71 may evaluate the situation as the clogging of the hollow fiber membrane 11 progresses and the permeation resistance of the hollow fiber membrane 11 increases, that is, the effect of physical cleaning is insufficient. On the other hand, if the time from the start of the backwash process until the pressure on the primary side stabilizes at the end pressure shows a decreasing trend in multiple backwash processes, the evaluation unit 71 may evaluate the situation as the clogging of the hollow fiber membrane 11 recovers and the permeation resistance of the hollow fiber membrane 11 decreases, that is, the effect of physical cleaning is sufficient.

In the example of FIG. 4, the time t42 from the start of the most recent backwash process until the primary side pressure stabilizes at the end pressure is longer than the time t41 from the start of the backwash process immediately preceding the most recent backwash process until the primary side pressure stabilizes at the end pressure. For this reason, the evaluation unit 71 evaluates that the effect of physical cleaning is insufficient.

The inventor also performed a test run and, using the logging data (Figures 5 and 6) acquired during the backwashing process when the degree of clogging of the hollow fiber membrane 11 was low (hereinafter referred to as the first backwashing process) and during the backwashing process when the degree of clogging of the hollow fiber membrane 11 was high (hereinafter referred to as the second backwashing process), calculated the integral value of the difference between the secondary side pressure and the primary side pressure from the start of the backwashing process to the time when the primary side pressure stabilizes.

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

Next, the inventors used the logging data shown in Figure 5 obtained during 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, the target time) from the start time t50 of the first backwashing process to the time t51 when the primary side pressure stabilizes. Note that 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 of the region surrounded by the dashed dotted line indicating the start time t50 of the first backwashing process, the dashed dotted line indicating the time t51 when the primary side pressure stabilizes, graph G52, and graph G51.

Similarly, the inventor used the logging data shown in Figure 6 obtained during the second backwashing process to calculate the integral value of the difference between the secondary side pressure and the primary side pressure during the target time t60 to t61, which is the time from t60 when the second backwashing process starts to t61 when the primary side pressure stabilizes.

The inventor then compared the measurement results of the difference between the secondary side pressure and the primary side pressure in the filtration process performed after the first backwashing process with the measurement results of the difference in the filtration process performed after the second backwashing process, and the calculation results of the integral value. As a result, the inventor found that even if the difference between the secondary side pressure and the primary side pressure during the filtration process is approximately constant when the degree of clogging of the hollow fiber membrane 11 is large and small, the integral value over the specified period significantly differs between when the degree of clogging of the hollow fiber membrane 11 is large and small.

This is presumably because the greater the degree of clogging of the hollow fiber membrane 11, the longer the time it takes for the pressure on the primary side, which increases instantaneously from the start of the backwashing process, to reach its target point, and the time it takes for the pressure on the primary side, which increases instantaneously from the start of the backwashing process, to reach its target point and stabilize.

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

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

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

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

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

The inventors also discovered that the greater the degree of clogging of the hollow fiber membrane 11, the larger the integral value at each of the above target times.

Based on the above findings obtained by the inventor, the evaluation unit 71 may calculate, for multiple backwashing processes, an integral value of the difference between the secondary side pressure and the primary side pressure at any one of the following times: the time from the start of the backwashing process until the pressure on the primary side or secondary side, which increases instantaneously immediately after the start of the backwashing process, reaches its target point; the time from the start of the backwashing process until the pressure on the primary side or secondary side, which increases instantaneously immediately after the start of the backwashing process, reaches its target point and stabilizes; and the time from the start of the backwashing process until the pressure on the primary side or secondary side stabilizes. The evaluation unit 71 may then evaluate the effect of physical cleaning based on the difference in the integral values between the multiple backwashing processes.

Specifically, when the integral value calculated in multiple backwashing processes shows an increasing trend, the evaluation unit 71 may evaluate the situation as a situation in which the degree of clogging of the hollow fiber membrane 11 is increasing, that is, the effect of physical cleaning is insufficient. On the other hand, when the integral value calculated in multiple backwashing processes shows a decreasing trend, the evaluation unit 71 may evaluate the situation as a situation in which the degree of clogging of the hollow fiber membrane 11 is decreasing, that is, the effect of physical cleaning is sufficient.

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

On the other hand, immediately after the treated water on the secondary side is pushed out to the primary side, the pressure on the primary side increases instantaneously due to the pipeline resistance that occurs when the raw water on the primary side flows into the drainage pipe 53. At this time, the more the hollow fiber membrane 11 becomes clogged and the greater the permeation resistance of the hollow fiber membrane 11, the slower the speed at which the treated water on the secondary side is pushed out to the primary side. Therefore, the reached pressure on the primary side, which instantaneously increased immediately after the start of the backwash process, becomes lower the more the hollow fiber membrane 11 becomes clogged and the greater the permeation resistance of the hollow fiber membrane 11. After that, when some of the fouling components attached to the outer surface of the hollow fiber membrane 11 are peeled off and the speed at which the treated water is pushed out to the primary side increases, the speed at which the water on the primary side is discharged also increases, and the pressure on the primary side drops rapidly.

In other words, the pressure on the primary or secondary side, which increases instantaneously immediately after the start of the backwash process, reaches a target point, and just before some of the fouling components adhering to the outer surface of the hollow fiber membrane 11 are peeled off, the difference between the pressure on the secondary side and the pressure on the primary side becomes larger the more the hollow fiber membrane 11 becomes clogged and the greater the permeation resistance of the hollow fiber membrane 11 becomes.

For this reason, the evaluation unit 71 may refer to the logging data stored in the control unit 70 and detect the reaching point of either the primary side or the secondary side pressure that instantaneously increases immediately after the start of the backwash process for multiple backwash processes. The evaluation unit 71 may then evaluate the effect of physical cleaning based on the difference between the secondary side pressure and the primary side pressure at the time when either of the pressures reaches the reaching point, between the multiple backwash processes.

Specifically, if the difference between the pressure on the secondary side and the pressure on the primary side at the time when any of the pressures that instantaneously increased immediately after the start of the backwashing process reaches a target point during multiple backwashing processes shows an upward trend, the evaluation unit 71 may evaluate the situation as the clogging of the hollow fiber membrane 11 has progressed and the permeation resistance of the hollow fiber membrane 11 has increased, that is, the effect of physical cleaning is insufficient. On the other hand, if the difference between the pressure on the secondary side and the pressure on the primary side at the time when any of the pressures that instantaneously increased immediately after the start of the backwashing process reaches a target point during multiple backwashing processes shows a downward trend, the evaluation unit 71 may evaluate the situation as the clogging of the hollow fiber membrane 11 has recovered and the permeation resistance of the hollow fiber membrane 11 has decreased, that is, the effect of physical cleaning is sufficient.

In this case, since the pressure of at least one of the primary and secondary sides of the hollow fiber membrane module 10 is measured at intervals of 3 seconds or less for multiple backwashing processes, the arrival point of either the primary or secondary side pressure that instantaneously increased immediately after the start of the backwashing process can be detected. That is, even if the treated water is a fouling component that peels off from the hollow fiber membrane surface due to the force of the treated water being pushed from the secondary side to the primary side in the backwashing process, the pressure of either of the above before it decreases due to the peeling off of the fouling component can be properly detected. As a result, by using the difference between the pressure on the secondary side and the pressure on the primary side at the time of detection, the degree of progress of clogging of the hollow fiber membrane 11 after physical cleaning can be properly grasped. Then, based on the grasped degree of progress of clogging of the hollow fiber membrane 11, the effect of physical cleaning on recovery from clogging of the hollow fiber membrane 11 can be properly evaluated.

When the evaluation unit 71 evaluates the effect of physical cleaning, the notification unit 72 notifies the result of the evaluation by the evaluation unit 71.

Specifically, the notification unit 72 uses a communication device (not shown) provided in the water treatment device 1 to send an e-mail including a message indicating whether the effect of the physical cleaning is sufficient or insufficient to an information processing device such as a personal computer, tablet terminal, or smartphone owned by the administrator of the water treatment device 1. The result of the evaluation by the evaluation unit 71 is not limited to the above message, and may also include the logging data (FIG. 3) used by the evaluation unit 71 for the evaluation.

The water treatment device 1 may also be provided with an audio output device such as a speaker, and the notification unit 72 may cause the audio output device to output a sound indicating whether the effect of the physical cleaning is sufficient or insufficient. The water treatment device 1 may also be provided with a display device such as a liquid crystal display, and the notification unit 72 may display the above message and the logging data (Figure 3) used by the evaluation unit 71 for the evaluation on the display device. Alternatively, the notification unit 72 may combine two or more of these communication devices, audio output devices, and display devices, and cause the two or more devices to notify the results of the evaluation by the evaluation unit 71.

Next, in the air release process (depressurization process), the air valve 42 and the drain valve 54 are closed and the depressurization valve 58 is opened. This allows the air that has accumulated on the secondary side of the hollow fiber membrane module 10 to be discharged through the depressurization pipe 57.

Next, in the second filling process, as in the first filling process, the raw water pump 22 is operated and the raw water valve 23 and the air vent valve 56 are opened.

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

Next, in the third filling process, as in the first and second filling processes, the raw water pump 22 is operated and the raw water valve 23 and the air bleed valve 56 are opened. This causes the amount of raw water drained in the air diffuser bubbling process to be replenished into the housing 12.

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

Next, in the drainage process, the air vent valve 56 is closed and the drainage valve 54 is opened. The second air valve 33 is kept open. This causes the raw water in the raw water space S1 to be pushed by the air and discharged outside the housing 12 through the drain port 12D.

Finally, in the depressurization process, the second air valve 33 is closed while the drain valve 54 is left open. This allows air to be removed from inside the housing 12 (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 filtration operation is resumed.

The timing at which the evaluation unit 71 evaluates the effect of physical cleaning is not particularly limited, and may be, for example, every time the operation cycle of FIG. 2 is performed, or every time the operation cycle of FIG. 2 is repeated multiple times (e.g., 10 times), or once a day, once a week, or once a month. This frequency may be appropriately determined depending on the type of raw water (e.g., river water, wastewater, or sewage), the season, etc.

In addition, in the backwash process, the secondary treated water may be pressurized with a permeate liquid pressurized to a predetermined pressure instead of air pressurized to a predetermined pressure. In addition, a chemical may be injected into the permeate liquid.

In addition, if the evaluation unit 71 evaluates that the effect of physical cleaning is insufficient, the effect of physical cleaning can be improved, for example, by increasing the secondary air pressure during the backwashing process and/or increasing the amount of air inflow during the bubbling process. In addition, in the backwashing process using the permeated liquid, the effect of physical cleaning can be improved by adjusting the flow rate and flow velocity of the permeated liquid. In addition, the effect of physical cleaning can be improved by adjusting the time of the backwashing process and/or the bubbling process.

As described above, according to the water treatment device 1 of this embodiment, in the backwash process of the hollow fiber membrane module 10, the pressure of at least one of the primary side and secondary side of the hollow fiber membrane module 10 is measured at intervals of 3 seconds or less, which is shorter than the usual measurement interval of the transmembrane pressure difference in the filtration process. Therefore, it is possible to grasp the detailed time progression of the pressure on at least one of the sides in the backwash process, which is completed within a few minutes. Therefore, by using this detailed time progression, the effect of physical cleaning of the hollow fiber membrane module 10 can be appropriately evaluated.

In addition, according to the water treatment device 1 of this embodiment, the notification unit 72 notifies the evaluation result of the effect of physical cleaning. Therefore, the effect of physical cleaning of the hollow fiber membrane module 10 can be grasped without going to the installation site of the hollow fiber membrane module 10 and taking the time to collect some of the hollow fiber membranes 11 from the hollow fiber membrane module 10.

(Embodiment 2)
Next, a water treatment device 1A and a cleaning evaluation method according to a second embodiment of the present invention will be described. The second embodiment is basically the same as the first embodiment, but differs from the first embodiment in that an evaluation unit 71 evaluates the effect of chemical cleaning, and a notification unit 72 notifies the evaluation result of the effect of chemical cleaning. Only the differences from the first embodiment will be described below.

First, chemical cleaning of the hollow fiber membrane module 10 will be described with reference to Figures 5 and 6. In chemical cleaning, fouling components attached to the hollow fiber membrane 11 are dissolved by immersion in a chemical solution. As shown in Figure 5, the water treatment device 1A according to the second embodiment further includes a chemical supply unit 80 in addition to the configuration of the first embodiment. The chemical supply unit 80 includes a chemical pump 81 and a chemical piping 82. The chemical piping 82 has the chemical pump 81 installed on the upstream end thereof and has a downstream end connected to a portion of the raw water piping 21 downstream of the raw water valve 23.

As shown in FIG. 6, chemical cleaning includes a chemical injection process, a water filling process, an immersion process, an air bubbling process, a drainage process, and a depressurization process. FIG. 6 shows the on/off state of the raw water pump 22 and the chemical pump 81 and the open/closed state of each valve during each process of chemical cleaning. In FIG. 6, circles indicate the on state of the pump or the open state of the valve, and blank spaces indicate the off state of the pump or the closed state of the valve.

First, in the chemical injection process, the chemical pump 81 is operated and the raw water valve 23 and the air bleed valve 56 are each opened. This causes the chemical to be supplied to the raw water space S1 of the housing 12. The type of chemical is not particularly limited, but examples include acids such as sulfuric acid, nitric acid, and hydrochloric acid, as well as oxidizing agents, alkaline agents, surfactants, chelating agents, or combinations of these.

Next, in the water filling process, the chemical pump 81 is stopped and the raw water pump 22 is operated. This causes raw water to be supplied to the raw water space S1 through the raw water piping 21 and the water conduit 14.

Next, in the immersion process, the raw water pump 22 is stopped and the raw water valve 23 is closed, and the process waits for a predetermined time. This allows the hollow fiber membrane 11 to be held in the raw water containing the chemical solution for a predetermined time.

Next, in the air bubbling process, the first air valve 32 is opened. This causes the hollow fiber membrane 11 to be bubble-cleaned while the raw water space S1 is filled with raw water containing the chemical solution.

Next, in the drainage process, the air vent valve 56 and the first air valve 32 are closed, and the drainage valve 54 and the second air valve 33 are opened. This causes the raw water containing the chemicals and impurities to be pushed by the air and discharged outside the housing 12. In the subsequent depressurization process, the second air valve 33 is closed while the drainage valve 54 remains open, and the inside of the housing 12 (raw water space S1) is depressurized.

Next, in the water filling process, the raw water pump 22 is operated, the drain valve 54 is closed, and the raw water valve 23 and the air vent valve 56 are opened, as described above. This causes the raw water space S1 to be filled with raw water again.

Next, in the air bubbling process, the raw water pump 22 is stopped, the raw water valve 23 is closed, and the first air valve 32 is opened. This causes air to be supplied into the housing 12, and the air is dispersed upward toward the hollow fiber membrane 11 by the air diffuser 15.

Next, in the drain process, the air vent valve 56 and the first air valve 32 are closed, and the drain valve 54 and the second air valve 33 are opened. This causes the water in the raw water space S1 to be pushed out of the housing 12 by the air. Then, in the depressurization process, only the second air valve 33 is closed, and the raw water space S1 is depressurized.

In this manner, chemical cleaning of the hollow fiber membrane module 10 is performed. This chemical cleaning may be performed at a predetermined frequency when repeating the operation cycle of FIG. 2, for example, once a day, once a week, or once a month. The cycle consisting of the last four steps in FIG. 6 (filling with water to releasing pressure) is repeated a predetermined number of times until the chemical solution in the housing 12 is sufficiently discharged.

The evaluation unit 71 in this embodiment evaluates the effect of chemical cleaning of the hollow fiber membrane module 10 based on the results of pressure measurement by the measurement unit 60 before and after chemical cleaning. Specifically, the evaluation unit 71 refers to the logging data stored in the control unit 70, and evaluates the effect of chemical cleaning based on the difference between the backwashing process before and after the chemical cleaning in the point where the secondary side pressure reaches, which increases instantaneously immediately after the start of the backwashing process.

In more detail, if the secondary side reached pressure immediately after the start of the backwashing process performed after the chemical cleaning is higher than the secondary side reached pressure immediately after the start of the backwashing process performed before the chemical cleaning, the evaluation unit 71 evaluates that the clogging of the hollow fiber membrane 11 is progressing, that is, the effect of the chemical cleaning is insufficient. If the secondary side reached pressure immediately after the start of the backwashing process performed after the chemical cleaning is lower than the secondary side reached pressure immediately after the start of the backwashing process performed before the chemical cleaning, the evaluation unit 71 evaluates that the clogging of the hollow fiber membrane 11 is recovered, that is, the effect of the chemical cleaning is sufficient.

The evaluation unit 71 may also refer to the logging data stored in the control unit 70 and evaluate the effect of the chemical cleaning based on the difference in the time from the start of the backwash process until the secondary side pressure stabilizes at the air pressure between the backwash processes before and after the chemical cleaning.

Specifically, the time from the start of the backwash process after chemical cleaning until the pressure on the secondary side stabilizes at air pressure is increased compared to the time from the start of the backwash process before chemical cleaning until the pressure on the secondary side stabilizes at air pressure. In this case, the evaluation unit 71 may evaluate the situation as one in which clogging of the hollow fiber membrane 11 is progressing, in other words, the effect of chemical cleaning is insufficient.

On the other hand, the time from the start of the backwash process after chemical cleaning until the pressure on the secondary side stabilizes at air pressure is assumed to be shorter than the time from the start of the backwash process before chemical cleaning until the pressure on the secondary side stabilizes at air pressure. In this case, the evaluation unit 71 may evaluate the situation as being where clogging of the hollow fiber membrane 11 has been repaired, that is, the effect of physical cleaning is sufficient.

The evaluation unit 71 may also refer to the logging data stored in the control unit 70 and evaluate the effect of the chemical cleaning based on the difference in the reach of the primary side pressure that instantaneously increases immediately after the start of the backwashing process before and after the backwashing process.

Specifically, the pressure reached on the primary side immediately after the start of the backwashing process after chemical cleaning is higher than the pressure reached on the primary side immediately after the start of the backwashing process before chemical cleaning. In this case, the evaluation unit 71 may evaluate the situation as being in a state where clogging of the hollow fiber membrane 11 has been repaired, in other words, the effect of chemical cleaning is sufficient.

On the other hand, suppose that the pressure reached on the primary side immediately after the start of the backwashing process after chemical cleaning is lower than the pressure reached on the primary side immediately after the start of the backwashing process before chemical cleaning. In this case, the evaluation unit 71 may evaluate that clogging of the hollow fiber membrane 11 is progressing, that is, that the effect of chemical cleaning is insufficient.

The evaluation unit 71 may also refer to the logging data stored in the control unit 70 and evaluate the effect of chemical cleaning based on the difference in the time from the start of the backwash process until the pressure on the primary side stabilizes at a predetermined end pressure indicating the end of the pushing of treated water from the secondary side during the backwash process before and after the chemical cleaning.

Specifically, the time from the start of the backwash process after chemical cleaning until the pressure on the primary side stabilizes at the end pressure is increased compared to the time from the start of the backwash process before chemical cleaning until the pressure on the primary side stabilizes at the end pressure. In this case, the evaluation unit 71 may evaluate the situation as one in which clogging of the hollow fiber membrane 11 progresses and the permeation resistance of the hollow fiber membrane 11 increases, in other words, the effect of chemical cleaning is insufficient.

On the other hand, the time from the start of the backwash process after chemical cleaning until the pressure on the primary side reaches the end pressure is assumed to be shorter than the time from the start of the backwash process before chemical cleaning until the pressure on the primary side stabilizes at the end pressure. In this case, the evaluation unit 71 may evaluate the situation as being where the clogging of the hollow fiber membrane 11 has been repaired and the permeation resistance of the hollow fiber membrane 11 has been reduced, in other words, the effect of the chemical cleaning is sufficient.

The evaluation unit 71 may also refer to the logging data stored in the control unit 70 and calculate, for the backwashing process before and after the chemical cleaning, an integral value of the difference between the secondary side pressure and the primary side pressure at any one of the following times: the time from the start of the backwashing process until the pressure on the primary side or secondary side, which increases instantaneously immediately after the start of the backwashing process, reaches its target point; the time from the start of the backwashing process until the pressure on the primary side or secondary side, which increases instantaneously immediately after the start of the backwashing process, reaches its target point and stabilizes; and the time from the start of the backwashing process until the pressure on the primary side or secondary side stabilizes.The evaluation unit 71 may then evaluate the effect of the chemical cleaning based on the difference in the integral value between the backwashing processes before and after the chemical cleaning.

Specifically, when the integral value calculated in the backwash process before and after the chemical cleaning shows an increasing trend, the evaluation unit 71 may evaluate the situation as a situation in which the degree of clogging of the hollow fiber membrane 11 is increasing, that is, the effect of the chemical cleaning is insufficient. On the other hand, when the integral value calculated in the backwash process before and after the chemical cleaning shows a decreasing trend, the evaluation unit 71 may evaluate the situation as a situation in which the degree of clogging of the hollow fiber membrane 11 is decreasing, that is, the effect of the chemical cleaning is sufficient.

The evaluation unit 71 may also refer to the logging data stored in the control unit 70 and detect the peak pressure of either the primary side or the secondary side that instantaneously increases immediately after the start of the backwashing process before and after the chemical cleaning. The evaluation unit 71 may then evaluate the effect of the chemical cleaning based on the difference between the secondary side pressure and the primary side pressure at the point when either of the pressures reaches the peak pressure, between multiple backwashing processes.

Specifically, if the difference between the pressure on the secondary side and the pressure on the primary side at the time when any of the pressures that instantaneously increased immediately after the start of the backwashing process during the backwashing process before and after the chemical cleaning shows an upward trend, the evaluation unit 71 may evaluate the situation as the clogging of the hollow fiber membrane 11 has progressed and the permeation resistance of the hollow fiber membrane 11 has increased, that is, the effect of the chemical cleaning is insufficient. On the other hand, if the difference between the pressure on the secondary side and the pressure on the primary side at the time when any of the pressures that instantaneously increased immediately after the start of the backwashing process during the backwashing process before and after the chemical cleaning shows a downward trend, the evaluation unit 71 may evaluate the situation as the clogging of the hollow fiber membrane 11 has recovered and the permeation resistance of the hollow fiber membrane 11 has decreased, that is, the effect of the chemical cleaning is sufficient.

When the evaluation unit 71 evaluates the effect of the chemical cleaning, the notification unit 72 notifies the evaluation result of the effect of the chemical cleaning in the same manner as when the evaluation result of the effect of the physical cleaning is notified.

The timing at which the evaluation unit 71 evaluates the effect of the chemical cleaning is not particularly limited, and may be, for example, every time the chemical cleaning of FIG. 6 is performed, or every time the chemical cleaning of FIG. 6 is performed multiple times (for example, twice), or once a week, or once a month. This frequency may be appropriately determined depending on the type of raw water (for example, river water, wastewater, or sewage), the season, etc.

In addition, in the chemical injection process, instead of injecting the chemical from the primary side of the hollow fiber membrane module 10, the chemical may be injected from the secondary side of the hollow fiber membrane module 10 and the chemical may be pushed out from the secondary side to the primary side.

The logging data used by the evaluation unit 71 to evaluate the effect of chemical cleaning is not limited to the logging data received during one backwash process before and after chemical cleaning. For example, it may be the average value of the logging data received during a predetermined number of backwash processes or a predetermined number of days before and after chemical cleaning.

In addition, if the evaluation unit 71 evaluates that the effect of the chemical cleaning is insufficient, the effect of the chemical cleaning can be improved by increasing the concentration of the chemical during chemical cleaning or by extending the time for which the hollow fiber membrane 11 is immersed in the chemical solution. The effect of the chemical cleaning can also be improved by adjusting the temperature of the chemical solution, the presence or absence of bubbling during immersion in the chemical solution, the presence or absence of circulation of the chemical solution, etc. In addition, if the evaluation unit 71 evaluates that the effect of the chemical cleaning is insufficient, the effect of physical cleaning can be improved by extending the time for changing the type of chemical solution.

As described above, according to the water treatment device 1A of this embodiment, the effect of chemical cleaning of the hollow fiber membrane module 10 can be appropriately evaluated based on the detailed time transition of the primary side pressure or secondary side pressure measured in the backwash process before and after the chemical cleaning. Furthermore, according to the water treatment device 1A of this embodiment, the notification unit 72 notifies the evaluation result of the effect of chemical cleaning. Therefore, the effect of chemical cleaning of the hollow fiber membrane module 10 can be grasped without going to the installation site of the hollow fiber membrane module 10 and taking the time to collect some of the hollow fiber membranes 11 from the hollow fiber membrane module 10.

The timing at which the notification unit 72 notifies the evaluation result by the evaluation unit 71 is not particularly limited. The notification unit 72 may notify the evaluation result each time the evaluation unit 71 performs an evaluation, or may notify a predetermined number of evaluation results collectively each time the evaluation unit 71 performs a predetermined number of evaluations.

The embodiments disclosed herein are illustrative in all respects and should not be construed as limiting. The scope of the present invention is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope of the claims.

1, 1A: Water treatment device 10: Hollow fiber membrane module 11: Hollow fiber membrane 60: Measuring unit 71: Evaluation unit 72: Notification unit

Claims (12)

A cleaning evaluation method for evaluating a cleaning effect of a hollow fiber membrane module in a water treatment device that filters raw water using the hollow fiber membrane module, comprising:
In the backwashing step of the hollow fiber membrane module, a pressure on at least one of a primary side and a secondary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less;
Evaluating the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on the measurement result of the pressure on at least one side;
notifying the result of the evaluation; and
Including,
In the backwashing step, the treated water from the secondary side is pushed to the primary side by a pressurized medium,
The effect of the physical cleaning is evaluated based on a difference between the plurality of backwashing processes in a point at which the pressure on the secondary side increases and then decreases as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process.
Cleaning evaluation method. A cleaning evaluation method for evaluating a cleaning effect of a hollow fiber membrane module in a water treatment device that filters raw water using the hollow fiber membrane module, comprising:
In the backwashing step of the hollow fiber membrane module, a pressure on at least one of a primary side and a secondary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less;
Evaluating the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on the measurement result of the pressure on at least one side;
notifying the result of the evaluation; and
Including,
In the backwashing step, the treated water from the secondary side is pushed to the primary side by a pressurized medium,
The effect of the physical cleaning is evaluated based on a difference between the plurality of backwashing processes in the time from the start of the backwashing process to the time when the pressure on the secondary side, which is increasing to the pressure of the medium after the secondary side treated water is pushed out to the primary side immediately after the start of the backwashing process and then starts to decrease, reaches an inflection point at which the slope of the pressure increase decreases .
Cleaning evaluation method. A cleaning evaluation method for evaluating a cleaning effect of a hollow fiber membrane module in a water treatment device that filters raw water using the hollow fiber membrane module, comprising:
In the backwashing step of the hollow fiber membrane module, a pressure on at least one of a primary side and a secondary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less;
Evaluating the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on the measurement result of the pressure on at least one side;
notifying the result of the evaluation; and
Including,
In the backwashing step, the treated water from the secondary side is pushed to the primary side by a pressurized medium,
The effect of the physical cleaning is evaluated based on a difference between a plurality of backwashing processes in a point at which the pressure on the primary side increases and then decreases as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process.
Cleaning evaluation method. A cleaning evaluation method for evaluating a cleaning effect of a hollow fiber membrane module in a water treatment device that filters raw water using the hollow fiber membrane module, comprising:
In the backwashing step of the hollow fiber membrane module, measuring the pressure of at least one of the primary side and the secondary side of the hollow fiber membrane module at intervals of 3 seconds or less;
Evaluating the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on the measurement result of the pressure on at least one side;
notifying the result of the evaluation; and
Including,
In the backwashing step, the treated water from the secondary side is pushed to the primary side by a pressurized medium,
The effect of the physical cleaning is evaluated based on a difference between a start point of the backwashing process and a time point at which the pressure on the primary side, which is decreasing to a predetermined end pressure indicating the end of the pushing out of the treated water on the secondary side after the start of the backwashing process and then starts to decrease due to the treated water on the secondary side being pushed out to the primary side, reaches an inflection point at which the slope of the decrease in pressure increases.
Cleaning evaluation method. A cleaning evaluation method for evaluating a cleaning effect of a hollow fiber membrane module in a water treatment device that filters raw water using the hollow fiber membrane module, comprising:
In the backwashing process of the hollow fiber membrane module, measuring the pressure on the primary side and the secondary side of the hollow fiber membrane module at intervals of 3 seconds or less;
Evaluating the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on a measurement result of the pressure on at least one of the primary side and the secondary side;
notifying the result of the evaluation; and
Including,
In the backwashing step, the treated water from the secondary side is pushed to the primary side by a pressurized medium,
For the plurality of backwashing steps,
A time from the start of the backwashing process to a first time point when the pressure on the primary side or the secondary side increases and then decreases as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process;
The time from the first point in time to a second point in time at which the pressure on the secondary side, which is increasing to the pressure of the medium after the secondary side treated water is pushed out to the primary side immediately after the start of the backwashing process and then starts to decrease, reaches an inflection point at which the slope of the pressure increase decreases ;
A time from the first time point to a third time point at which the pressure on the primary side, which increases and then starts to decrease as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process, decreases to a predetermined end pressure, and then reaches an inflection point at which the slope of the decrease in pressure increases; and
Calculate an integral value of the difference between the secondary side pressure and the primary side pressure at any one of the times from the start of the backwashing process to the second time point or the third time point ;
Evaluating the effect of the physical cleaning based on a difference in the integrated value between the plurality of backwashing processes.
Cleaning evaluation method. A cleaning evaluation method for evaluating a cleaning effect of a hollow fiber membrane module in a water treatment device that filters raw water using the hollow fiber membrane module, comprising:
In the backwashing process of the hollow fiber membrane module, measuring the pressure on the primary side and the secondary side of the hollow fiber membrane module at intervals of 3 seconds or less;
Evaluating the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on a measurement result of the pressure on at least one of the primary side and the secondary side;
notifying the result of the evaluation; and
Including,
In the backwashing step, the treated water from the secondary side is pushed to the primary side by a pressurized medium,
For the plurality of backwashing processes, a point at which the pressure of either the primary side or the secondary side increases and then decreases as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process is detected;
Evaluating the effect of the physical cleaning based on a difference between the pressure on the secondary side and the pressure on the primary side at a time when any one of the pressures reaches the target point, among the plurality of backwashing processes.
Cleaning evaluation method. A cleaning evaluation method for evaluating a cleaning effect of a hollow fiber membrane module in a water treatment device that filters raw water using the hollow fiber membrane module, comprising:
In the backwashing step of the hollow fiber membrane module, measuring the pressure of at least one of the primary side and the secondary side of the hollow fiber membrane module at intervals of 3 seconds or less;
Evaluating the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on the measurement result of the pressure on at least one side;
notifying the result of the evaluation; and
Including,
In the chemical cleaning, the fouling components adhering to the hollow fiber membrane are dissolved by immersion in the chemical solution,
In the backwashing step, the treated water from the secondary side is pushed to the primary side by a pressurized medium,
The effect of the chemical cleaning is evaluated based on the difference between the backwashing process before and after the chemical cleaning in the point at which the pressure on the secondary side increases and then decreases as a result of the treated water on the secondary side being pushed out to the primary side immediately after the start of the backwashing process.
Cleaning evaluation method. A cleaning evaluation method for evaluating a cleaning effect of a hollow fiber membrane module in a water treatment device that filters raw water using the hollow fiber membrane module, comprising:
In the backwashing step of the hollow fiber membrane module, a pressure on at least one of a primary side and a secondary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less;
Evaluating the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on the measurement result of the pressure on at least one side;
notifying the result of the evaluation; and
Including,
In the chemical cleaning, the fouling components adhering to the hollow fiber membrane are dissolved by immersion in the chemical solution,
In the backwashing step, the treated water from the secondary side is pushed to the primary side by a pressurized medium,
The effect of the chemical cleaning is evaluated based on the difference between the time from the start of the backwashing process to the time when the pressure on the secondary side, which is increasing to the pressure of the medium after the secondary side treated water is pushed out to the primary side immediately after the start of the backwashing process, increases and then decreases, and then reaches an inflection point at which the slope of the pressure increase decreases , between the backwashing processes before and after the chemical cleaning.
Cleaning evaluation method. A cleaning evaluation method for evaluating a cleaning effect of a hollow fiber membrane module in a water treatment device that filters raw water using the hollow fiber membrane module, comprising:
In the backwashing step of the hollow fiber membrane module, a pressure on at least one of a primary side and a secondary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less;
Evaluating the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on the measurement result of the pressure on at least one side;
notifying the result of the evaluation; and
Including,
In the chemical cleaning, the fouling components adhering to the hollow fiber membrane are dissolved by immersion in the chemical solution,
In the backwashing step, the treated water from the secondary side is pushed to the primary side by a pressurized medium,
The effect of the chemical cleaning is evaluated based on the difference between the backwashing process before and after the chemical cleaning in the point at which the pressure on the primary side increases and then decreases as a result of the treated water on the secondary side being pushed out to the primary side immediately after the start of the backwashing process.
Cleaning evaluation method. A cleaning evaluation method for evaluating a cleaning effect of a hollow fiber membrane module in a water treatment device that filters raw water using the hollow fiber membrane module, comprising:
In the backwashing step of the hollow fiber membrane module, a pressure on at least one of a primary side and a secondary side of the hollow fiber membrane module is measured at intervals of 3 seconds or less;
Evaluating the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on the measurement result of the pressure on at least one side;
notifying the result of the evaluation; and
Including,
In the chemical cleaning, the fouling components adhering to the hollow fiber membrane are dissolved by immersion in the chemical solution,
In the backwashing step, the treated water from the secondary side is pushed to the primary side by a pressurized medium,
The effect of the chemical cleaning is evaluated based on the difference between the time from the start of the backwashing process to the time when the pressure on the primary side, which is decreasing to a predetermined end pressure indicating the end of the pushing out of the treated water on the secondary side, reaches an inflection point where the slope of the pressure decrease increases, after the pressure increases and then decreases as a result of the treated water on the secondary side being pushed out to the primary side immediately after the start of the backwashing process, between the backwashing process before and after the chemical cleaning.
Cleaning evaluation method. A cleaning evaluation method for evaluating a cleaning effect of a hollow fiber membrane module in a water treatment device that filters raw water using the hollow fiber membrane module, comprising:
In the backwashing process of the hollow fiber membrane module, measuring the pressure on the primary side and the secondary side of the hollow fiber membrane module at intervals of 3 seconds or less;
Evaluating the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on a measurement result of the pressure on at least one of the primary side and the secondary side;
notifying the result of the evaluation; and
Including,
In the chemical cleaning, the fouling components adhering to the hollow fiber membrane are dissolved by immersion in the chemical solution,
In the backwashing step, the treated water from the secondary side is pushed to the primary side by a pressurized medium,
Regarding the backwashing process before and after the chemical cleaning,
A time from the start of the backwashing process to a first time point when the pressure on the primary side or the secondary side increases and then decreases as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process;
The time from the first point in time to a second point in time at which the pressure on the secondary side, which is increasing to the pressure of the medium after the secondary side treated water is pushed out to the primary side immediately after the start of the backwashing process and then starts to decrease, reaches an inflection point at which the slope of the increase in pressure decreases ;
A time from the first point in time to a third point in time at which the pressure on the primary side, which increases and then starts to decrease as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process, decreases to a predetermined end pressure, and then reaches an inflection point at which the slope of the decrease in pressure increases; and
Calculate an integral value of the difference between the secondary side pressure and the primary side pressure at any one of the times from the start of the backwashing process to the second time point or the third time point ;
Evaluating the effect of the chemical cleaning based on a difference in the integrated value between the backwashing process before and after the chemical cleaning.
Cleaning evaluation method. A cleaning evaluation method for evaluating a cleaning effect of a hollow fiber membrane module in a water treatment device that filters raw water using the hollow fiber membrane module, comprising:
In the backwashing process of the hollow fiber membrane module, measuring the pressure on the primary side and the secondary side of the hollow fiber membrane module at intervals of 3 seconds or less;
Evaluating the effect of physical cleaning or chemical cleaning of the hollow fiber membrane module based on a measurement result of the pressure on at least one of the primary side and the secondary side;
notifying the result of the evaluation; and
Including,
In the chemical cleaning, the fouling components adhering to the hollow fiber membrane are dissolved by immersion in the chemical solution,
In the backwashing step, the treated water from the secondary side is pushed to the primary side by a pressurized medium,
With respect to the backwashing process before and after the chemical cleaning, a point at which the pressure of either the primary side or the secondary side increases and then decreases is detected as a result of the secondary side treated water being pushed out to the primary side immediately after the start of the backwashing process;
Evaluating the effect of the chemical cleaning based on a difference between the pressure on the secondary side and the pressure on the primary side at a time when any one of the pressures reaches the target point, among the plurality of backwashing processes.
Cleaning evaluation method.

Images