JP7670540B2 - Water treatment device and water treatment method - Google Patents

Description

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

Conventionally, water treatment devices are known that use hollow fiber membrane modules to filter raw water. In these water treatment devices, the amount of impurities adhering to the membrane surface of the hollow fiber membrane increases over the course of filtration time, so the modules need to be cleaned periodically.

This type of technology is described, for example, in Patent Document 1. In Patent Document 1, after a filtration operation is performed for a certain period of time in an external pressure filtration type hollow fiber membrane module, the filtration operation is switched to a cleaning operation. In the cleaning operation, an operation sequence program is executed to perform a chemical injection process, a pressurization process, a water filling process, a gas cleaning process, and a drainage process in that order, thereby cleaning the hollow fiber membrane.

Patent No. 6653154

In order to increase the recovery rate of treated water (filtered water) in the above water treatment equipment, it is necessary to increase the operating rate of the filtration operation. And to increase the operating rate of the filtration operation, it is necessary to shorten the cleaning time of the hollow fiber membrane module as much as possible and ensure that the proportion of filtration time in the total operating time of the equipment is long.

However, the time required to perform each cleaning process depends on various parameters, such as the number of modules, pipe diameter, pipe length, and water flow rate, and varies depending on the site and equipment, so it is not possible to set a uniform time for all sites and equipment. For this reason, in order to accurately grasp the time required for the cleaning process, it is necessary to actually measure the process time at each site, which requires a great deal of cost and effort.

The present invention was made in consideration of the above problems, and its purpose is to provide a water treatment device and a water treatment method that can increase the operating rate of filtration operation while reducing costs and labor.

A water treatment device according to one aspect of the present invention includes a hollow fiber membrane module, a measurement unit that measures the pressure on at least one of the primary and secondary sides of the hollow fiber membrane module at intervals of 3 seconds or less during at least one of the filling process, depressurization process, backwash process, and drainage process of the hollow fiber membrane module, and an estimation unit that estimates the time required from the start to the end of at least one of the processes based on the results of the pressure measurement by the measurement unit.

With this water treatment device, the process time is estimated based on the change in pressure over time on at least one of the primary and secondary sides of the hollow fiber membrane module, so there is no need to actually measure the process time on-site. This reduces the cost and effort required to actually measure the process time, and by setting each process time based on the estimated time, it is possible to reduce excess process time. This makes it possible to increase the operating rate of the filtration operation while reducing costs and effort.

In the water treatment device, the measurement unit may measure the primary side pressure at intervals of 3 seconds or less during the water filling process. The estimation unit may estimate the time required for the water filling process based on the time from the start of the water filling process to the time when the change in the primary side pressure reaches an inflection point.

This configuration makes it easy to estimate the time required for the water filling process.

In the water treatment device, the measurement unit may measure the primary side pressure at intervals of 3 seconds or less during the drainage process. The estimation unit may estimate the time required for the drainage process based on the time from the start of the drainage process until the primary side pressure becomes constant.

This configuration makes it easy to estimate the time required for the drainage process.

In the water treatment device, the estimation unit may estimate the length of the bubbling process of the hollow fiber membrane module based on the estimated time of the water filling process or the drainage process.

This configuration allows the time for the bubbling process to be changed to an appropriate time, reducing the waste of time spent cleaning the hollow fiber membrane and further increasing the operating rate of the filtration operation.

In the water treatment device, the measurement unit may measure the pressure on at least one side during the backwashing process at intervals of 3 seconds or less. The estimation unit may estimate the time required for the backwashing process based on the time from the start of the backwashing process until the pressure on at least one side becomes constant.

This configuration makes it easy to estimate the time required for the backwash process.

In the water treatment device, the measurement unit may measure the pressure on at least one side during the backwashing process at intervals of 3 seconds or less. The estimation unit may estimate the time required for the backwashing process based on the time from the start of the backwashing process until the pressure on at least one side reaches a maximum pressure.

This configuration makes it easy to estimate the time required for the backwash process.

In the water treatment device, the estimation unit may estimate the length of time for the chemical solution immersion process of the hollow fiber membrane module based on the estimated time for the backwash process.

This configuration allows the time for the chemical immersion process to be changed to an appropriate time, reducing the waste of time spent cleaning the hollow fiber membrane and further increasing the operating rate of the filtration operation.

In the water treatment device, the measurement unit may measure the pressure on the primary side and the secondary side during the filtration process of the hollow fiber membrane module. The estimation unit may estimate the length of the filtration process based on the fluctuation of the transmembrane pressure difference of the hollow fiber membrane module during the filtration process.

With this configuration, the time for the filtration process can be changed to an appropriate time, allowing a balance to be achieved between safe operation of the device and the operating rate of the filtration operation.

The water treatment device may further include a setting change unit that changes the set time of at least one of the processes based on the time estimated by the estimation unit.

With this configuration, the process time can be changed automatically, which improves efficiency compared to when an operator changes the time manually.

In the water treatment device, the setting change unit may change the set times of multiple processes among the filling process, the depressurization process, the backwash process, and the drainage process based on the time estimated by the estimation unit.

A water treatment method according to another aspect of the present invention is a method for filtering raw water using a hollow fiber membrane module. This water treatment method includes measuring the pressure on at least one of the primary and secondary sides of the hollow fiber membrane module at intervals of 3 seconds or less in at least one of the filling process, depressurizing process, backwashing process, and drainage process of the hollow fiber membrane module, estimating the time required from the start to the end of the at least one process based on the result of the pressure measurement on the at least one side, and changing the set time of the at least one process based on the estimated time of the at least one process.

According to this method, the process time is estimated based on the change in pressure over time on at least one of the primary and secondary sides of the hollow fiber membrane module, and the process set time is changed based on the estimated time, so there is no need to actually measure the process time on-site and then change the set time. Therefore, it is possible to reduce wasted process time while suppressing the cost and effort required for measuring the actual process time, and to increase the operating rate of the filtration operation.

As is clear from the above explanation, the present invention can provide a water treatment device and a water treatment method that can increase the operating rate of filtration operation while reducing costs and labor.

1 is a diagram illustrating a schematic configuration of a water treatment device according to a first embodiment of the present invention. FIG. 2 is a diagram showing the on/off state of a raw water pump and the open/closed state of a valve in each process of a water treatment method 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 water filling 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. 2 is a diagram showing the change over time in the primary side pressure of the hollow fiber membrane module in the drainage step according to the first embodiment of the present invention. FIG. 11 is a diagram showing the change over time in the primary side pressure of the hollow fiber membrane module in the backwashing process of the modified example of the first embodiment of the present invention. FIG. 13 is a diagram showing the change over time in the primary side pressure of the hollow fiber membrane module in the backwashing process of the modified example of the second embodiment of the present invention. FIG. 11 is a graph showing the change over time in the transmembrane pressure difference of a hollow fiber membrane module in embodiment 4 of the present invention. FIG. 13 is a diagram illustrating a schematic configuration of a water treatment device according to a fifth embodiment of the present invention. FIG. 13 is a diagram showing the on/off state of a pump and the open/closed state of a valve in a chemical immersion step according to the fifth 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 a treated water outlet 12A facing the treated water space S2, the side part of the housing 12 (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 positioned 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 measuring unit 60 that measures the pressure on at least one of the primary and secondary sides of the hollow fiber membrane module 10 at intervals of 3 seconds or less (for example, at intervals of 2 seconds or less or 1 second or less) in at least one of the filling process, depressurizing process, backwash process, and drainage process of the hollow fiber membrane module 10. The measuring unit 60 in this embodiment includes a primary side pressure sensor 61 that measures the pressure on the primary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less, and a secondary side pressure sensor 62 that measures the pressure on the secondary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less. As shown in FIG. 1, the primary side pressure sensor 61 is installed in a portion of the raw water piping 21 between the raw water valve 23 and the raw water inlet 14A. The primary side pressure sensor 61 may be installed in a portion of the water conduit 14 extending 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. 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 (not shown) 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 seconds or more and 3 seconds or less, and each measurement data is sent to the control unit 70 and stored. In other words, each measurement data is stored as logging data. 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 data from the primary pressure sensor 61 and the secondary pressure sensor 62.

The water treatment device 1 further includes an estimation unit 71 that estimates the time required from start to finish of at least one of the filling process, depressurization process, backwash process, and drainage process based on the results of pressure measurement by the measurement unit 60, and a setting change unit 72 that changes the set time of the at least one process based on the time estimated by the estimation unit 71. The estimation unit 71 and the setting change unit 72 may be realized as one function of the control unit 70. The estimation of each process time by the estimation unit 71 is described below.

Figure 2 shows each process of the water treatment method according to this embodiment, which is carried out using the water treatment device 1, and also shows the on/off state of the raw water pump 22 and the open/closed state of each valve in each process. 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.

In the first water filling process, the primary side pressure sensor 61 measures the pressure on the primary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less, and the control unit 70 stores the measured pressure values sequentially. This provides data (Figure 3) showing the change over time in the primary side pressure of the hollow fiber membrane module 10 during the first water filling process. In Figure 3, the horizontal axis indicates time, and the vertical axis indicates the primary side pressure of the hollow fiber membrane module 10. The secondary side pressure sensor 62 also measures the pressure on the secondary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less, and the control unit 70 stores the measured pressure values sequentially.

The estimation unit 71 estimates the time required from the start to the end of the first water filling process based on the stored pressure measurement data. Specifically, the estimation unit 71 estimates the time required for the first water filling process based on the time from the start of the first water filling process (time t0 in FIG. 3) to the inflection point of the change in the primary side pressure (time t1 in the same figure, the time when the pressure starts to rise sharply). This time t1 corresponds to the timing when the raw water in the housing 12 starts to flow into the air vent pipe 55. In other words, it corresponds to the timing when the raw water space S1 of the housing 12 is filled with raw water.

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.

In the filtration process, the primary pressure sensor 61 measures the pressure on the primary side of the hollow fiber membrane module 10, and the secondary pressure sensor 62 measures the pressure on the secondary side of the hollow fiber membrane module 10. The interval between these pressure measurements may be 3 seconds or less, as in the first water filling process, but is not limited to this and may be longer than 3 seconds.

After the filtration process, a cleaning operation is carried out to remove impurities that have adhered to the outer surface of the hollow fiber membrane 11 during filtration. The cleaning operation includes a backwash preparation process, a backwash process, an air bleed 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 treated water valve 51 are closed, and the air valve 42 and 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, 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 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.

In this way, in the backwashing process, the primary pressure sensor 61 measures the primary pressure of the hollow fiber membrane module 10 at intervals of 3 seconds or less. This provides logging data (FIG. 4) showing the time change in the primary pressure of the hollow fiber membrane module 10 during the backwashing process. In FIG. 4, the horizontal axis indicates time, and the vertical axis indicates the primary pressure of the hollow fiber membrane module 10. As shown in FIG. 4, the primary pressure rises instantaneously after the start of the backwashing process to reach the maximum pressure, and then drops and becomes constant. This instantaneous rise in the primary pressure can be seen from the subsequent sudden reduction in pressure, and is presumed to be due to a large amount of pressurized treated water beginning to permeate the hollow fiber membrane 11. Then, the primary pressure drops suddenly as the raw water is discharged to the drainage pipe 53, and then the primary pressure gradually drops. It is presumed that the gradual drop in the primary pressure at this time is due to the gradual decrease in the amount of water in the raw water space S1. It is assumed that when the primary pressure becomes constant, all of the treated water in the raw water space S1 has been discharged from the housing 12.

The estimation unit 71 estimates the time required for the backwashing process based on the pressure measurement data stored in the control unit 70. Specifically, the estimation unit 71 estimates the time required for the backwashing process based on the time from the start of the backwashing process (time t0 in FIG. 4) until the primary side pressure becomes constant (time t1 in FIG. 4). Note that, in order to estimate that the primary side pressure has become constant, it is necessary to detect that the primary side pressure has subsequently stabilized at a constant value. For this reason, the estimation unit 71 estimates the time required for the backwashing process based on time t0 to time t1 by referring to measurement data after time t1.

In addition, during the backwashing process, the secondary pressure sensor 62 may also measure the secondary pressure of the hollow fiber membrane module 10 at intervals of 3 seconds or less. In this case, pressure logging data similar to that shown in FIG. 4 is obtained. The estimation unit 71 may then estimate the time required for the backwashing process based on the time from the start of the backwashing process until the secondary pressure becomes constant.

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. Then, as in the first filling process, the pressure on the primary side of the hollow fiber membrane module 10 is measured at intervals of 3 seconds or less, and the time required from the start to the end of the second filling process is estimated based on the results of the pressure measurements.

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.

Even during the air diffuser bubbling process, the primary pressure sensor 61 measures the pressure on the primary side of the hollow fiber membrane module 10, and the secondary pressure sensor 62 measures the pressure on the secondary side of the hollow fiber membrane module 10. The interval between these pressure measurements may be 3 seconds or less, but is not limited to this, and may be longer than 3 seconds.

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 replenishes the raw water in the raw water space S1 that was lost in the air diffuser bubbling process. Then, as in the first and second filling processes, the pressure on the primary side of the hollow fiber membrane module 10 is measured at intervals of 3 seconds or less, and the time required from the start to the end of the third filling process is estimated based on the results of the pressure measurements.

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 bubble-cleaned.

Even during the water conduit bubbling process, the primary pressure sensor 61 measures the pressure on the primary side of the hollow fiber membrane module 10, and the secondary pressure sensor 62 measures the pressure on the secondary side of the hollow fiber membrane module 10. The interval between these pressure measurements may be 3 seconds or less, but is not limited to this, and may be longer than 3 seconds.

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.

During the drainage process, the primary side pressure sensor 61 measures the primary side pressure of the hollow fiber membrane module 10 at intervals of 3 seconds or less. This provides logging data (Figure 5) that shows the change over time in the primary side pressure of the hollow fiber membrane module 10 during the drainage process. In Figure 5, the horizontal axis indicates time, and the vertical axis indicates the primary side pressure of the hollow fiber membrane module 10. As shown in Figure 5, the primary side pressure rises after a certain time has elapsed from the start of the drainage process, reaches a maximum pressure, then drops, and then remains constant.

The estimation unit 71 estimates the time required from the start to the end of the drainage process based on the stored pressure measurement data. Specifically, the estimation unit 71 estimates the time required for the drainage process based on the time from the start of the drainage process (time t0 in FIG. 5) until the primary side pressure becomes constant (time t1 in the same figure). Note that, in order to estimate that the primary side pressure has become constant, it is necessary to detect that the primary side pressure has subsequently stabilized at a constant value. For this reason, the estimation unit 71 estimates the time required for the drainage process from time t0 based on time t1 by referring to measurement data after time t1.

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 cleaned through the above process, the process returns to the first water filling process and filtration operation is resumed.

After the series of processes in FIG. 2 (from the first water filling process to the depressurization process) is completed, the setting change unit 72 changes the set times for the water filling process, backwash process, and drainage process based on the estimated times for these processes. Note that this change in set times is not limited to being performed automatically by the setting change unit 72, but may also be changed manually by the user.

As described above, according to the water treatment device 1 of this embodiment, the process times for the filling process, backwash process, and drainage process are estimated based on the change over time in the primary side pressure of the hollow fiber membrane module 10, so there is no need to actually measure the process times on-site. This makes it possible to reduce the cost and effort required for actually measuring the process times. In addition, by resetting the process times for each process based on the estimated times, it is possible to reduce unnecessary process times. Therefore, it is possible to increase the operating rate of the filtration operation while reducing costs and effort.

In addition to the filling process, backwash process, and drainage process, the pressure on the primary side and secondary side of the hollow fiber membrane module 10 may be measured at intervals of 3 seconds or less in the backwash preparation process, air venting process, and depressurization process, and the time required from start to finish of the process may be estimated based on the measurement results. Specifically, the time required for each process may be estimated based on the time from the start of each of the backwash preparation process, air venting process, and depressurization processes until the pressure becomes zero. The set time for the process may then be changed based on this estimated time.

In the backwashing process, the secondary treatment liquid may be pressurized using liquid instead of air. In this case, the primary side pressure of the hollow fiber membrane module 10 in the backwashing process changes over time as shown in FIG. 6. That is, the primary side pressure rises after the start of the backwashing process and becomes almost constant after time t1, which is the time that has passed since the start time t0. The estimation unit 71 then estimates the time required for the backwashing process based on the time from the start of the backwashing process (time t0 in FIG. 7) until the primary side pressure becomes constant (time t1 in the same figure).

Furthermore, the frequency of automatically changing the set time is not particularly limited, and may be, for example, once an hour, once a day, once a week, or once a month. This frequency is appropriately determined depending on the type of raw water (e.g., river water, wastewater, or sewage), the season, etc.

The set times may be changed for all of the filling, backwashing, and draining processes, but this is not limited to this, and the set times may be changed for only some of the processes. The processes for which the set times are changed are appropriately determined according to the situation at the site. For example, when there is a large fluctuation in the flow rate of the raw water pump 22 or when it is difficult to visually check the filling status through the raw water piping 21, it is effective to change the set time for the filling process.

(Embodiment 2)
Next, a water treatment device and a water treatment 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 the estimation of the process time in the backwash process. Only the differences from the first embodiment will be described below.

In the second embodiment, the estimation unit 71 estimates the time required for the backwashing process based on the time from the start of the backwashing process until the primary side pressure reaches the maximum pressure. That is, the time from time t0 to time t2 in the graph of FIG. 4 is estimated as the time required for the backwashing process. This estimation method can be suitably used when the impurities attached to the membrane surface are, for example, mainly inorganic components that have good peelability. In other words, in the case of impurities that have good peelability, they peel off from the membrane surface at the same time that the backwash water begins to permeate the hollow fiber membrane 11, so it can be inferred that the backwashing is effectively completed when the primary side pressure reaches time t2, which indicates its maximum value.

In addition, when backwashing is performed using liquid instead of air, the process time can be estimated in the same manner as above. Figure 7 is a graph showing the case where the treated water is circulated by a pump before the start of the backwashing, and the secondary side of the hollow fiber membrane 11 is pressurized all at once at the same time as the start of the backwashing process. The horizontal axis of Figure 7 indicates time, and the vertical axis indicates the primary side pressure of the hollow fiber membrane module 10. As shown in Figure 7, in this case too, the primary side pressure rises instantaneously to the maximum pressure a predetermined time after the start of the backwashing (time t2). Then, the primary side pressure gradually decreases and stabilizes at a constant pressure (time t1). The time until this maximum pressure is reached, i.e., the time from time t0 to time t2 in the graph of Figure 7, can be estimated as the time required for the backwashing process.

(Embodiment 3)
Next, a water treatment device and a water treatment method according to a third embodiment of the present invention will be described. The third embodiment is basically the same as the first embodiment, but differs from the first embodiment in that the estimation unit 71 estimates the length of the bubbling process. Only the differences from the first embodiment will be described below.

The cycle consisting of the series of steps in FIG. 2 (first water filling step to depressurization step) is repeated, and the process time is estimated for the water filling step and the drainage step of each cycle. In this embodiment, the estimation unit 71 estimates the length of the bubbling step based on the estimated time for the water filling step or the drainage step.

Specifically, if the estimated time for the water filling process tends to decrease when the above cycle is repeated, the amount of turbid components accumulated in the housing 12 tends to increase, and the estimation unit 71 estimates that the time for the bubbling process is short relative to the desired length of time (insufficient bubbling). On the other hand, if the estimated time for the water filling process is constant or tends to increase when the above cycle is repeated, the amount of turbid components accumulated in the housing 12 tends to be constant or tends to decrease, and the estimation unit 71 estimates that the time for the bubbling process is long or too long relative to the desired length of time.

By adjusting the time of the bubbling process based on such an estimation result, it is possible to shorten the time of the bubbling process as much as possible while suppressing the accumulation of turbid components in the housing 12, thereby increasing the operating rate of the filtration operation. For example, when wastewater containing a large amount of SS (Suspended Solid) components is used as the raw water, such optimization of the bubbling time is effective. Note that the estimated time of the drainage process may be used instead of the estimated time of the filling process. Furthermore, the timing for determining the trend of fluctuation in the estimated time of the filling process or drainage process is not particularly limited, and may be, for example, every 10 cycles, once a day, or once a week.

(Embodiment 4)
Next, a water treatment device and a water treatment method according to a fourth embodiment of the present invention will be described. The fourth embodiment is basically the same as the first embodiment, but differs from the first embodiment in that the estimation unit 71 estimates the length of the filtration process. Only the differences from the first embodiment will be described below.

Figure 8 is a graph showing the fluctuation of the transmembrane pressure difference of the hollow fiber membrane module 10 when a cycle consisting of a series of steps in Figure 2 is repeated. The transmembrane pressure difference is the difference between the primary side pressure and the secondary side pressure of the hollow fiber membrane module 10. In Figure 8, the horizontal axis shows time, and the vertical axis shows the transmembrane pressure difference of the hollow fiber membrane module 10. In Figure 8, for example, the periods between times t0 and t1, t1 and t2, and t2 and t3 each correspond to one cycle.

The estimation unit 71 in the fourth embodiment estimates the length of the filtration process based on the fluctuation of the transmembrane pressure difference of the hollow fiber membrane module 10 during the filtration process. Specifically, the estimation unit 71 estimates that the filtration process time is longer than the desired length if the transmembrane pressure difference at the start of the filtration process (e.g., times t0, t1, t2, and t3 in FIG. 3) tends to increase between successive cycles. On the other hand, the estimation unit 71 estimates that the filtration process time is shorter than the desired length if the transmembrane pressure difference at the start of the filtration process is constant or tends to decrease between successive cycles.

Based on such an estimation, the filtration process time can be optimized to increase the operating rate of the filtration operation and the recovery rate of treated water while suppressing an excessive increase in the transmembrane pressure difference. For example, when groundwater or tap water is used as the raw water, the operating rate and water recovery rate can be increased by extending the filtration process time beyond the standard 30 minutes. The period for estimating the fluctuation trend of the initial value of the transmembrane pressure difference is not particularly limited, and may be, for example, once every 10 cycles, or once a day or once a week.

(Embodiment 5)
Next, a water treatment device and a water treatment method according to a fifth embodiment of the present invention will be described. The fifth embodiment is basically the same as the first embodiment, but differs from the first embodiment in that the estimation unit 71 estimates the length of time for the chemical solution immersion step of the hollow fiber membrane module 10. Only the differences from the first embodiment will be described below.

First, the chemical immersion process of the hollow fiber membrane module 10 will be described with reference to Figs. 9 and 10. The chemical immersion process is a process of washing away fouling components that have penetrated into the hollow fiber membrane 11 with chemicals. The water treatment device 1A according to embodiment 5 further includes a chemical supply unit 80 in addition to the configuration of embodiment 1. The chemical supply unit 80 includes a chemical pump 81 and a chemical piping 82. As shown in Fig. 9, the chemical piping 82 has the chemical pump 81 installed on the upstream end side and has a downstream end connected to a portion of the raw water piping 21 downstream of the raw water valve 23.

Figure 10 shows the on/off state of the raw water pump 22 and the chemical pump 81 and the open/closed state of each valve at each stage of chemical immersion. In Figure 10, circles indicate the pump is on or the valve is open, and blank spaces indicate the pump is off or the valve is closed.

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, the chemical immersion process of the hollow fiber membrane module 10 is carried out. This chemical immersion process may be carried out 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. 10 (filling with water to releasing pressure) is repeated a predetermined number of times until the chemical solution in the housing 12 is sufficiently discharged.

In this embodiment, the estimation unit 71 estimates the length of the chemical immersion process of the hollow fiber membrane module 10 based on the estimated time of the backwash process. Specifically, the estimation unit 71 compares the estimated times of the backwash processes performed before and after the chemical immersion process, and if the estimated times are constant or tend to be longer, estimates that the time of the chemical immersion process (the time of the immersion process in FIG. 10) is shorter than the desired time length. On the other hand, the estimation unit 71 compares the estimated times of the backwash processes performed before and after the chemical immersion process, and if the estimated times tend to be shorter, estimates that the time of the chemical immersion process (the time of the immersion process in FIG. 10) is longer than the desired time length. Based on such estimation, the time of the chemical immersion process can be optimized so as to increase the operating rate of the filtration operation and the recovery rate of the treated water while ensuring the cleaning effect of the chemical immersion.

In this embodiment, the case where the chemical solution is injected from the primary side of the hollow fiber membrane module 10 has been described, but the chemical solution may be injected from the secondary side of the hollow fiber membrane module 10 and then pushed from the secondary side to the primary side.

Example 1
Iron chloride simulated water was used as raw water and filtered using a water treatment device having the configuration of Fig. 1. Specifically, each process in Table 1 below was carried out in order, and then the set times of the processes were changed based on the log data of the pressure measurement as in the above embodiment, as shown in Table 1. As a result, it was possible to improve the operating rate of the filtration operation by 3.6% while maintaining a stable filtration operation.

In addition, permeate was used during backwashing, and each process in Table 2 below was carried out in order. Then, as in the above embodiment, the process setting times were changed as shown in Table 2 based on the pressure measurement log data. As a result, it was possible to improve the filtration operation operating rate by 2.5% while maintaining stable filtration operation.

Example 2
Industrial water was used as raw water, and filtered using a water treatment device having the configuration of Fig. 9. As in the above embodiment, the set time for the chemical immersion step (immersing the hollow fiber membrane in water with a sodium hypochlorite concentration of 100 mg/l) was changed as shown in Table 3 based on the fluctuation tendency of the estimated time for the backwashing step. In Table 3, the cycle consisting of steps No. 7 to 10 was repeated five times. By shortening the time for the chemical immersion step, the operating rate of the filtration operation could be improved.

The chemical solution was injected from the secondary side of the hollow fiber membrane module, and the chemical solution immersion process was carried out by carrying out each process in order in Table 4. As in the above embodiment, the set time for the chemical solution immersion process was changed as shown in Table 4 based on the fluctuation trend of the estimated time for the backwash process. This made it possible to shorten the time for the chemical solution immersion process and improve the operating rate of the filtration operation.

The embodiments and examples 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.

REFERENCE SIGNS LIST 1, 1A Water treatment device 10 Hollow fiber membrane module 60 Measurement unit 71 Estimation unit 72 Setting change unit

Claims (11)

A hollow fiber membrane module;
a measuring unit that measures the pressure on at least one of the primary side and the secondary side of the hollow fiber membrane module at intervals of 3 seconds or less in at least one of a water filling process, a pressure release process, a backwash process, and a drainage process of the hollow fiber membrane module;
an estimation unit that estimates a time required from a start to an end of the at least one process based on a result of the pressure measurement by the measurement unit,
The measurement unit measures the primary side pressure at intervals of 3 seconds or less during the water filling process,
The estimation unit estimates the time required for the water filling process based on the time from the start of the water filling process to the time when the change in the primary side pressure reaches an inflection point. A hollow fiber membrane module;
a measuring unit that measures the pressure on at least one of the primary side and the secondary side of the hollow fiber membrane module at intervals of 3 seconds or less in at least one of a water filling process, a pressure release process, a backwash process, and a drainage process of the hollow fiber membrane module;
an estimation unit that estimates a time required from a start to an end of the at least one process based on a result of the pressure measurement by the measurement unit,
The measurement unit measures the primary side pressure at intervals of 3 seconds or less during the drainage process,
The estimation unit estimates a time required for the drainage process based on a time from a start of the drainage process until the pressure on the primary side becomes constant. The water treatment device according to claim 1 , wherein the estimation unit estimates whether a bubbling step of the hollow fiber membrane module is longer or shorter than a predetermined time based on an estimated time of the water filling step or the water discharge step. A hollow fiber membrane module;
a measuring unit that measures the pressure on at least one of the primary side and the secondary side of the hollow fiber membrane module at intervals of 3 seconds or less in at least one of a water filling process, a pressure release process, a backwash process, and a drainage process of the hollow fiber membrane module;
an estimation unit that estimates a time required from a start to an end of the at least one process based on a result of the pressure measurement by the measurement unit,
The measurement unit measures the pressure on the at least one side at intervals of 3 seconds or less during the backwashing process,
The estimation unit estimates a time required for the backwashing process based on a time from the start of the backwashing process until the pressure on the at least one side becomes constant. A hollow fiber membrane module;
a measuring unit that measures the pressure on at least one of the primary side and the secondary side of the hollow fiber membrane module at intervals of 3 seconds or less in at least one of a water filling process, a pressure release process, a backwash process, and a drainage process of the hollow fiber membrane module;
an estimation unit that estimates a time required from a start to an end of the at least one process based on a result of the pressure measurement by the measurement unit,
The measurement unit measures the pressure on the at least one side at intervals of 3 seconds or less during the backwashing process,
The estimation unit estimates a time required for the backwashing process based on a time from a start of the backwashing process to a time when the pressure on the at least one side reaches a maximum pressure. The water treatment device according to claim 4 or 5 , wherein the estimation unit estimates whether a time for the chemical solution immersion step of the hollow fiber membrane module is excessive or insufficient , based on an estimated time for the backwashing step. The measurement unit measures the pressure on the primary side and the secondary side in a filtration process of the hollow fiber membrane module,
The water treatment device according to claim 1 , wherein the estimation unit estimates whether the time for the filtration step is excessive or insufficient based on a fluctuation in a transmembrane pressure difference of the hollow fiber membrane module during the filtration step. The water treatment device according to claim 1 , further comprising a setting change unit that changes a set time of the at least one process based on the time estimated by the estimation unit. The water treatment device according to claim 8 , wherein the setting change unit changes set times of a plurality of steps among the filling step, the depressurization step, the backwashing step, and the drainage step, based on the times estimated by the estimation unit. A water treatment method for filtering raw water using a hollow fiber membrane module, comprising:
measuring the pressure on at least the primary side of the primary side and the secondary side of the hollow fiber membrane module at intervals of 3 seconds or less during at least the water filling process among the water filling process, the pressure release process, the backwash process, and the water discharge process of the hollow fiber membrane module;
Based on the measurement result of the time from the start of the water filling process to the inflection point of the pressure change on the front primary side, estimating the time required from the start to the end of the water filling process;
and changing a set time for the water-filling process based on an estimated time for the water- filling process. A water treatment method for filtering raw water using a hollow fiber membrane module, comprising:
measuring the pressure on at least the primary side of the primary side and the secondary side of the hollow fiber membrane module at intervals of 3 seconds or less during at least the drainage process of the hollow fiber membrane module among the filling process, the depressurization process, the backwash process, and the drainage process;
estimating a time required from the start to the end of the drainage process based on a measurement result of a time from the start of the drainage process until the pressure on the primary side becomes constant;
and changing a set time of the drainage process based on the estimated time of the drainage process.

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