Water treatment equipment and water treatment method

Abstract

To provide a water treatment equipment and a water treatment method capable of increasing an operation rate of a filtration operation while suppressing a cost and labor.SOLUTION: There is provided a water treatment equipment including: a measuring unit that measures a pressure on at least one of a primary side and a secondary side of a hollow fiber membrane module at intervals of 3 seconds or less; and an estimating unit that estimates the time required from a start to an end of the at least one step based on a result of the pressure measurement by the measuring unit, and is provided a water treatment method including a hollow fiber membrane module, a water filling step, a depressurization step, a backwashing step and drainage step of the hollow fiber membrane module.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a water treatment apparatus and a water treatment method.

Background Art

[0002] Conventionally, a water treatment apparatus that filters raw water using a hollow fiber membrane module has been known. In this water treatment apparatus, since the amount of impurities adhering to the membrane surface of the hollow fiber membrane increases with the passage of the filtration time, it is necessary to periodically clean the module.

[0003] This type of technology is described in, for example, Patent Document 1. In Patent Document 1, after a filtration operation is performed for a certain period of time in an outside pressure filtration type hollow fiber membrane module, the operation is switched from the filtration operation to a cleaning operation. In the cleaning operation, by executing an operation sequence program, a chemical solution injection step, a pressurization step, a water filling step, a gas cleaning step, and a drainage step are sequentially performed, and the hollow fiber membrane is cleaned.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to increase the recovery rate of treated water (filtered water) in the above water treatment apparatus, it is necessary to increase the operation rate of the filtration operation. And in order to increase the operation 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 a long ratio of the filtration time in the entire operation time of the apparatus.

[0006] However, the time required for each cleaning process depends on various parameters such as, for example, the number of modules, the pipe diameter, the pipe length, or the water flow rate, and varies from site to site and from apparatus to apparatus. Therefore, it cannot be uniformly set for all sites and apparatuses. For this reason, in order to accurately grasp the time of the cleaning process, it is necessary to actually measure the process time at each site, which requires a great deal of cost and labor.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a water treatment apparatus and a water treatment method capable of increasing the operation rate of a filtration operation while suppressing cost and labor.

Means for Solving the Problems

[0008] A water treatment apparatus according to an aspect of the present invention includes a hollow fiber membrane module, and a measurement 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 backwashing process, and a drainage process of the hollow fiber membrane module, and an estimation unit that estimates the time required from the start to the end of the at least one process based on the result of the pressure measurement by the measurement unit.

[0009] According to this water treatment apparatus, since the process time is estimated based on the time change of the pressure on at least one of the primary side and the secondary side of the hollow fiber membrane module, it is not necessary to actually measure the process time at the site. For this reason, the cost and labor required for actually measuring the process time can be suppressed, and by setting each process time based on the estimated time, extra process time can be reduced. Therefore, it is possible to increase the operation rate of the filtration operation while suppressing cost and labor.

[0010] In the above water treatment apparatus, the measurement unit may measure the pressure on the primary side at intervals of 3 seconds or less in 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 until reaching the inflection point of the change in the pressure on the primary side.

[0011] According to this configuration, the time required for the water filling process can be easily estimated.

[0012] In the above water treatment apparatus, the measurement unit may measure the pressure on the primary side at intervals of 3 seconds or less in 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 pressure on the primary side becomes constant.

[0013] According to this configuration, the time required for the drainage process can be easily estimated.

[0014] In the above water treatment apparatus, the estimation unit may estimate the length of the bubbling process time of the hollow fiber membrane module based on the estimated time of the water filling process or the drainage process.

[0015] According to this configuration, since the time of the bubbling process can be changed to an appropriate time, waste of the cleaning time of the hollow fiber membrane can be reduced, and the operation rate of the filtration operation can be further increased.

[0016] In the above water treatment apparatus, the measurement unit may measure the pressure on at least one side at intervals of 3 seconds or less in the backwashing process. 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.

[0017] According to this configuration, the time required for the backwashing process can be easily estimated.

[0018] In the above water treatment apparatus, the measurement unit may measure the pressure on at least one side at intervals of 3 seconds or less in the backwashing process. 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 the maximum pressure.

[0019] According to this configuration, the time required for the backwashing process can be easily estimated.

[0020] In the water treatment apparatus, the estimation unit may estimate the length of the chemical solution immersion step of the hollow fiber membrane module based on the estimated time of the backwashing step.

[0021] According to this configuration, since the time of the chemical solution immersion step can be changed to an appropriate time, waste of the cleaning time of the hollow fiber membrane can be reduced, and the operation rate of the filtration operation can be further increased.

[0022] In the water treatment apparatus, the measurement unit may measure the pressures on the primary side and the secondary side in the filtration step of the hollow fiber membrane module. The estimation unit may estimate the length of the filtration step based on the fluctuation of the transmembrane differential pressure of the hollow fiber membrane module in the filtration step.

[0023] According to this configuration, by changing the time of the filtration step to an appropriate time, a balance can be achieved between the safe operation of the apparatus and the operation rate of the filtration operation.

[0024] The water treatment apparatus may further include a setting change unit that changes the set time of the at least one step based on the estimated time by the estimation unit.

[0025] According to this configuration, since the set time of the step can be automatically changed, efficiency can be improved as compared with the case where an operator manually changes the set time.

[0026] In the water treatment apparatus, the setting change unit may change the set times of a plurality of steps among the water filling step, the pressure release step, the backwashing step, and the drainage step based on the estimated time by the estimation unit.

[0027] The water treatment method according to another aspect of the present invention is a method of filtering raw water using a hollow fiber membrane module. This water treatment method measures the pressure on at least one side 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 the water filling step, pressure release step, backwashing step, and drainage step of the hollow fiber membrane module, estimates the time required from the start to the end of the at least one step based on the result of the pressure measurement on the at least one side, and changes the set time of the at least one step based on the estimated time of the at least one step.

[0028] According to this method, since the process time is estimated based on the time change of the pressure on at least one side of the primary side and the secondary side of the hollow fiber membrane module, and the set time of the process is changed based on the estimated time, there is no need to actually measure the process time on site and then change the set time. Therefore, it is possible to reduce the waste of the process time while suppressing the cost and labor required for actually measuring the process time, and to increase the operation rate of the filtration operation.

Effect of the Invention

[0029] As is clear from the above description, according to the present invention, it is possible to provide a water treatment apparatus and a water treatment method capable of increasing the operation rate of the filtration operation while suppressing cost and labor.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0032] (Embodiment 1) First, the configuration of the water treatment apparatus 1 according to Embodiment 1 of the present invention will be described with reference to FIG. 1. As shown in FIG. 1, the water treatment apparatus 1 mainly includes a hollow fiber membrane module 10, a raw water supply unit 20, a bubbling air supply unit 30, and a backwashing air supply unit 40.

[0033] The hollow fiber membrane module 10 includes a hollow fiber membrane bundle having a plurality of hollow fiber membranes 11 whose upper ends are fixed to a fixing member 13, a housing 12, a water guide pipe 14 extending vertically inside the hollow fiber membrane bundle, and a diffuser plate 15. Inside the housing 12, the hollow fiber membrane bundle, the fixing member 13, and the diffuser plate 15 are accommodated. The space inside the housing 12 is partitioned into a raw water space S1 and a treated water space S2 by the fixing member 13. The hollow fiber membranes 11, the water guide pipe 14, and the diffuser plate 15 are accommodated in the raw water space S1.

[0034] As shown in Fig. 1, at the upper part of the housing 12, a treated water outlet 12A facing the treated water space S2 is provided. At the side part of the housing 12 (the part above the center in the longitudinal direction), an air vent 12B facing the raw water space S1 is provided. At the lower part of the housing 12, an air supply port 12C and a drain port 12D facing the raw water space S1 are provided. The ratio of the inner diameter of the housing 12 to the inner diameters of these pipe connection ports (the outlet 12A, the air vent 12B, the air supply port 12C, and the drain port 12D) is 1.3 or more and 12 or less, preferably 2.5 or more and 12 or less, and more preferably 3.0 or more and 6.0 or less. Here, the inner diameter of the housing 12 refers to the inner diameter in the cross section in the direction orthogonal to the longitudinal direction of the housing 12.

[0035] 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 with its end face blocked, and the lower end protrudes below the lower part of the housing 12. A raw water inlet 14A and an air inlet 14B are respectively provided at the lower end. Further, a number of holes 14C for jetting at least one of raw water and air from the inside of the water conduit 14 toward the raw water space S1 are formed in the water conduit 14.

[0036] The air diffuser plate 15 is for dispersing air in the raw water space S1. The air diffuser plate 15 has a disk shape spreading in the radial direction of the hollow fiber membrane bundle and is disposed below the lower end of the hollow fiber membrane 11. A plurality of vent holes (not shown) are formed in the air diffuser plate 15 at intervals in the radial direction. The air supplied into the housing 12 from the air supply port 12C is dispersed toward the hollow fiber membrane bundle through the vent holes of the air diffuser plate 15.

[0037] 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 on the downstream side thereof are respectively installed in the treated water pipe 50. The diameter of the treated water pipe 50 is smaller than the diameter of the housing 12.

[0038] The upstream end of the drain pipe 53 is connected to the drain port 12D of the housing 12, and a drain valve 54 (on-off valve) is installed in the drain pipe 53. The diameter of the drain pipe 53 is smaller than the diameter of the housing 12.

[0039] One end of the air vent pipe 55 is connected to the air vent port 12B of the housing 12. The other end side of the air vent pipe 55 branches into two. That is, the air vent pipe 55 includes a first branch portion 55A, a second branch portion 55B, and a connection portion 55C. One end of the connection portion 55C is connected to the air vent port 12B, and the other end is connected to the first branch portion 55A and the second branch portion 55B. The first branch portion 55A is open to the atmosphere, and the second branch portion 55B is connected to a portion of the drain pipe 53 downstream of the drain valve 54. An air vent valve 56 (on-off valve) is installed in the connection portion 55C. The diameter of the air vent pipe 55 is smaller than the diameter of the housing 12.

[0040] As shown in FIG. 1, the treated water pipe 50 and the drain pipe 53 are connected to each other by a pressure relief pipe 57. One end of the pressure relief 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 pressure relief pipe 57 is connected to a portion of the drain pipe 53 downstream of the connection portion of the air vent pipe 55. A pressure relief valve 58 (on-off valve) is installed in the pressure relief pipe 57. The diameter of the pressure relief pipe 57 is smaller than the diameter of the housing 12.

[0041] The raw water supply unit 20 includes a raw water pipe 21, a raw water pump 22 and a raw water valve 23 installed in the raw water pipe 21. The upstream end of the raw water pipe 21 is connected to the outlet of a raw water tank (not shown), and the downstream end is connected to the raw water inlet 14A of the water guide pipe 14. The diameter of the raw water pipe 21 is smaller than the diameter of the housing 12. The raw water valve 23 is an on-off valve and is installed downstream of the raw water pump 22 in the raw water pipe 21.

[0042] 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 downstream end side of the air pipe 31 is branched, and each branched portion is connected to the air supply port 12C of the housing 12 and the air inlet 14B of the water conduit 14, respectively. The diameter of the air pipe 31 is smaller than the diameter of the housing 12. The first air valve 32 and the second air valve 33 are on-off valves and are respectively installed at each branched portion of the air pipe 31. The upstream end of the air pipe 31 is connected to an air compressor (not shown).

[0043] The backwashing air supply unit 40 includes an air pipe 41 and an air valve 42 (on-off valve) installed on the air pipe 41. The upstream end of the air pipe 41 is connected to an air compressor (not shown), and the downstream end is connected to a portion of the treated water pipe 50 that is upstream of the connection portion of the pressure relief pipe 57. The diameter of the air pipe 41 is smaller than the diameter of the housing 12.

[0044] The water treatment apparatus 1 further includes a measuring unit 60 that measures the pressure on at least one of the primary side and the secondary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less (for example, intervals of 2 seconds or less or 1 second or less) in at least one of the water filling process, the pressure relief process, the backwashing process, and the drainage process of the hollow fiber membrane module 10. The measuring unit 60 in the present 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 pipe 21 between the raw water valve 23 and the raw water inlet 14A. Note that the primary side pressure sensor 61 may be installed at a position extending from the housing 12 in the water conduit 14 or facing the raw water space S1 in the housing 12.

[0045] The secondary pressure sensor 62 is installed at the connection part between the treated water pipe 50 and the air pipe 41. The primary pressure sensor 61 and the secondary pressure sensor 62 in this embodiment perform pressure measurement at intervals of 0.1 second or less, and the measurement data is sent to the control unit 70 and stored. That is, each measurement data is stored as logging data.

[0046] In addition to the primary pressure sensor 61 and the secondary pressure sensor 62, an air vent pressure sensor (not shown in the figure) may be provided. The air vent pressure sensor is installed at the connection part 55C in the air vent pipe 55. The air vent pressure sensor performs pressure measurement at intervals of 0.1 second or more and 3 seconds or less, and each measurement data is sent to the control unit 70 and stored. That is, each measurement data is stored as logging data. However, since the more the number of pressure sensors increases, the more troublesome the analysis becomes and the cost increases, it is desirable to omit the air vent pressure sensor and perform data analysis using the data from the primary pressure sensor 61 and the secondary pressure sensor 62.

[0047] The water treatment apparatus 1 further includes an estimation unit 71 that estimates the time required from the start to the end of at least one of the water filling process, the pressure release process, the backwashing process, and the drainage process based on the result of the 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 estimated time by the estimation unit 71. Note that the estimation unit 71 and the setting change unit 72 may be realized as a function of the control unit 70. Hereinafter, the estimation of each process time by the estimation unit 71 will be described.

[0048] FIG. 2 shows each process of the water treatment method according to the present embodiment implemented using the water treatment apparatus 1, and shows the on / off state of the raw water pump 22 and the open / closed state of each valve in each process. The circles in FIG. 2 indicate the on state of the raw water pump 22 or the open state of the valve, and the blanks indicate the off state of the raw water pump 22 or the closed state of the valve.

[0049] First, in the first water filling step, the raw water pump 22 operates, and the raw water valve 23 and the air vent valve 56 are each opened. As a result, raw water is supplied into the water conduit 14 through the raw water pipe 21, and the raw water is supplied from the hole 14C to the raw water space S1.

[0050] In the first water filling step, the primary side pressure sensor 61 measures the pressure on the primary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less, and the control unit 70 sequentially stores the measured pressure values. As a result, data (Figure 3) indicating the time change of the pressure on the primary side of the hollow fiber membrane module 10 during the first water filling step is obtained. In Figure 3, the horizontal axis represents time, and the vertical axis represents the pressure on the primary side of the hollow fiber membrane module 10. Note that 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 sequentially stores the measured pressure values.

[0051] The estimation unit 71 estimates the time required from the start to the end of the first water filling step based on the stored pressure measurement data. Specifically, the estimation unit 71 estimates the time required for the first water filling step based on the time from the start of the first water filling step (time point t0 in Figure 3) to the inflection point of the change in the primary side pressure (time point t1 in the same figure, the time point when the pressure starts to rise rapidly). This time point t1 corresponds to the timing when the raw water in the housing 12 starts to flow into the air vent pipe 55. That is, it corresponds to the timing when the raw water space S1 of the housing 12 is filled with raw water.

[0052] When the first water filling step ends, the process proceeds 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. Thereafter, the treated water flows out of the housing 12 through the outlet 12A and is collected in a treated water tank (not shown) through the treated water pipe 50.

[0053] 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 of this pressure measurement may be 3 seconds or less, but is not limited thereto, and may be longer than 3 seconds, similar to the first water filling process.

[0054] After the filtration process, a cleaning operation is performed to remove impurities adhering to the outer surface of the hollow fiber 11 during filtration. The cleaning operation includes a reverse washing preparation process, a reverse washing process, an air venting process, a second water filling process, a diffuser plate bubbling process, a third water filling process, a water conduit bubbling process, a drainage process, and a pressure release process.

[0055] First, in the reverse washing preparation process (pressure release process), the raw water pump 22 is switched from on to off.

[0056] Next, in the reverse washing 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, simultaneously with the opening of the air valve 42, 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 11. Thereby, the impurities adhering to the outer surface of the hollow fiber 11 are in a state where they are easily peeled off. At this time, since the primary pressure sensor 61 and the secondary pressure sensor 62 perform pressure measurement at intervals of 3 seconds or less, it is possible to detect the pressure in the state before the hollow fiber 11 is pressurized from the inner surface and before the impurities on the membrane surface are in a state where they are easily peeled off.

[0057] Thus, in the backwashing process, the primary pressure sensor 61 measures the pressure on the primary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less. As a result, logging data (Figure 4) showing the time change of the primary side pressure of the hollow fiber membrane module 10 during the backwashing process is obtained. In Figure 4, the horizontal axis represents time, and the vertical axis represents the primary side pressure of the hollow fiber membrane module 10. As shown in Figure 4, the primary side pressure instantaneously rises after the start of the backwashing process to reach the maximum pressure, and then decreases to become constant. This instantaneous rise in the primary side pressure can also be seen from the fact that a rapid pressure reduction occurs thereafter, and it is presumed to be due to a large amount of pressurized treated water starting to permeate through the hollow fiber 11. Then, as the raw water is discharged into the drain pipe 53 of the raw water, the primary side pressure rapidly decreases, and thereafter, the primary side pressure gradually decreases. It is presumed that the reason for the gradual decrease in the primary side pressure at this time is due to the gradual decrease in the amount of water in the raw water space S1. And when the pressure on the primary side becomes constant, it is presumed that all the treated water in the raw water space S1 has been discharged from the housing 12.

[0058] 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 point t0 in Figure 4) until the pressure on the primary side becomes constant (time point t1 in the same figure). Note that in order to estimate that the pressure on the primary side has become constant, it is necessary to detect that the primary side pressure stabilizes at a constant value thereafter. For this reason, the estimation unit 71 refers to the measurement data after the time point t1 to estimate the time required for the backwashing process based on the time from the time point t0 to the time point t1.

[0059] In addition, in the backwashing process, the secondary pressure sensor 62 may also measure the pressure on the secondary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less. In this case, pressure logging data similar to Figure 4 is obtained. And the estimation unit 71 may estimate the time required for the backwashing process based on the time from the start of the backwashing process until the pressure on the secondary side becomes constant.

[0060] Next, in the air bleeding process (pressure bleeding process), the air valve 42 and the drain valve 54 are closed, and the pressure bleeding valve 58 is opened. As a result, the air accumulated on the secondary side of the hollow fiber membrane module 10 is discharged through the pressure bleeding pipe 57.

[0061] Next, in the second water filling process, similar to the first water filling process, the raw water pump 22 operates, and the raw water valve 23 and the air bleeding valve 56 are opened respectively. Then, similar to the first water 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 water filling process is estimated based on the result of the pressure measurement.

[0062] 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. Note that the air bleeding valve 56 remains open. As a result, air is 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. Thereby, the hollow fiber membrane bundle swings due to the bubbles, and the impurities attached to the membrane surface are peeled off.

[0063] Also in the air diffuser bubbling process, the primary side pressure sensor 61 measures the pressure on the primary side of the hollow fiber membrane module 10, and the secondary side pressure sensor 62 measures the pressure on the secondary side of the hollow fiber membrane module 10. The interval of this pressure measurement may be 3 seconds or less, but is not limited thereto, and may be longer than 3 seconds.

[0064] Next, in the third water filling process, similar to the first and second water filling processes, the raw water pump 22 operates, and the raw water valve 23 and the air bleeding valve 56 are opened respectively. As a result, the raw water in the raw water space S1 reduced in the air diffuser bubbling process is replenished. Then, similar to the first and second water 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 water filling process is estimated based on the result of the pressure measurement.

[0065] Next, in the aqueduct bubbling process, the raw water pump 22 is switched from on to off, the raw water valve 23 is closed, and the second air valve 33 is opened. As a result, the pressurized air from the compressor is supplied into the aqueduct 14 from the air inlet 14B and supplied to the raw water space S1 through the hole 14C. Thereby, the hollow fiber membrane bundle is bubbling-cleaned.

[0066] Also in the aqueduct bubbling process, the primary side pressure sensor 61 measures the pressure on the primary side of the hollow fiber membrane module 10, and the secondary side pressure sensor 62 measures the pressure on the secondary side of the hollow fiber membrane module 10. The interval of this pressure measurement may be 3 seconds or less, but is not limited thereto, and may be longer than 3 seconds.

[0067] Next, in the drainage process, the air vent valve 56 is closed and the drain valve 54 is opened. Note that the second air valve 33 remains open. As a result, the raw water in the raw water space S1 is pushed by the air and discharged outside the housing 12 from the drain port 12D.

[0068] In the drainage 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. Thereby, logging data (Figure 5) showing the time change of the primary side pressure of the hollow fiber membrane module 10 during the drainage process is obtained. In Figure 5, the horizontal axis represents time, and the vertical axis represents 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 since the start of the drainage process, reaches the maximum pressure, then decreases, and then becomes constant.

[0069] 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 point t0 in FIG. 5) to when the pressure on the primary side becomes constant (time point t1 in the same figure). Note that in order to estimate that the pressure on the primary side has become constant, it is necessary to detect that the primary side pressure subsequently stabilizes at a constant value. For this reason, the estimation unit 71 estimates the time required for the drainage process based on time points t0 to t1 by referring to the measurement data after time point t1.

[0070] Finally, in the pressure release process, the second air valve 33 is closed while the drain valve 54 remains open. Thereby, the air in the housing 12 (raw water space S1) is removed. After the hollow fiber membrane module 10 is cleaned by the above process, it returns to the first water filling process and the filtration operation is restarted.

[0071] After the series of processes (first water filling process to pressure release process) in FIG. 2 are completed, the setting change unit 72 changes the set times of these processes based on the estimated times of the water filling process, backwashing process, and drainage process. Note that the change of this set time is not limited to being automatically performed by the setting change unit 72, and the user may change it manually.

[0072] As described above, according to the water treatment apparatus 1 according to the present embodiment, since the time of each process of the water filling process, backwashing process, and drainage process is estimated based on the time change of the pressure on the primary side of the hollow fiber membrane module 10, it is not necessary to actually measure the time of each process on site. Therefore, the cost and labor required for actually measuring the process time can be suppressed. In addition, by resetting the time of each process based on the estimated time, the extra process time can be reduced. Therefore, the operation rate of the filtration operation can be increased while suppressing cost and labor.

[0073] In addition to the water filling process, backwashing process, and drainage process, the pressures on the primary side and secondary side of the hollow fiber membrane module 10 may also be measured at intervals of 3 seconds or less in the backwashing preparation process, air venting process, and pressure release process, and the time required from the start to the end of the process may be estimated based on the measurement results. Specifically, the time required for each of these backwashing preparation process, air venting process, and pressure release process may be estimated based on the time from the start of the process until the pressure becomes zero. Then, based on this estimated time, the set time for the process may be changed.

[0074] In the backwashing process, instead of air, a liquid may be used to pressurize the processing liquid on the secondary side. In this case, the primary side pressure of the hollow fiber membrane module 10 in the backwashing process changes as shown in FIG. 6 over time. That is, the primary side pressure rises after the start of backwashing and becomes substantially constant after time t1 has elapsed from the start time t0. Then, 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. 7) until the pressure on the primary side becomes constant (time t1 in the same figure).

[0075] Also, the frequency of automatically changing the set time is not particularly limited. For example, it may be once an hour, once a day, once a week, or once a month. This frequency is appropriately determined according to the type of raw water (for example, river water, wastewater, or sewage) and seasons, etc.

[0076] Also, the set times for all of the water filling process, backwashing process, and drainage process may be changed, but it is not limited thereto, and the set time may be changed only for some of the processes. The processes for which the set time is to be changed are appropriately determined according to the site conditions. For example, when the flow rate fluctuation of the raw water pump 22 is large or when it is difficult to visually confirm the water filling situation by the raw water pipe 21, it is effective to change the set time for the water filling process.

[0077] (Embodiment 2) Next, the water treatment apparatus and water treatment method according to Embodiment 2 of the present invention will be described. Embodiment 2 is basically the same as Embodiment 1, but the estimation of the process time in the backwashing step is different from that in Embodiment 1. Hereinafter, only the differences from Embodiment 1 will be described.

[0078] In Embodiment 2, the estimation unit 71 estimates the time required for the backwashing step based on the time from the start of the backwashing step until the pressure on the primary side reaches the maximum pressure. That is, the time from time point t0 to time point t2 in the graph of FIG. 4 is estimated as the time required for the backwashing step. This estimation method can be preferably used when the impurities adhering to the membrane surface are, for example, those with good peelability mainly composed of inorganic components. That is, in the case of impurities with good peelability, when the backwash water starts to permeate through the hollow fiber membrane 11, they are peeled off from the membrane surface at the same time. Therefore, it can be inferred that the backwashing has virtually ended when the primary side pressure reaches the maximum value at time point t2.

[0079] Also, when backwashing with a liquid instead of air, the process time can be estimated in the same manner as above. FIG. 7 is a graph when the treated water is circulated in advance 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 step. The horizontal axis of FIG. 7 represents time, and the vertical axis represents the primary side pressure of the hollow fiber membrane module 10. As shown in FIG. 7, also in this case, the primary side pressure instantaneously rises to the maximum pressure after a lapse of a predetermined time after the start of the backwashing (time point t2). Then, thereafter, the primary side pressure gradually decreases and stabilizes at a certain pressure (time point t1). The time until this maximum pressure is reached, that is, the time from time point t0 to time point t2 in the graph of FIG. 7, can be estimated as the time required for the backwashing step.

[0080] (Embodiment 3) Next, the water treatment apparatus and water treatment method according to Embodiment 3 of the present invention will be described. Embodiment 3 is basically the same as Embodiment 1, but is different from Embodiment 1 in that the estimation unit 71 estimates the length of the bubbling step. Hereinafter, only the differences from Embodiment 1 will be described.

[0081] The cycle consisting of a series of steps (first water filling step to pressure release step) in FIG. 2 is repeated, and the process time is estimated in the water filling step and the drainage step of each cycle. The estimation unit 71 in the present embodiment estimates the length of the bubbling step based on the estimated time of the water filling step or the drainage step.

[0082] Specifically, when the estimated time of the water filling step shows a decreasing trend when the above cycle is repeated, since the accumulation amount of the turbidity component in the housing 12 tends to increase, the estimation unit 71 estimates that the time of the bubbling step is short with respect to the desired time length (insufficient bubbling). On the other hand, when the estimated time of the water filling step shows a constant or increasing trend when the above cycle is repeated, since the accumulation amount of the turbidity component in the housing 12 tends to be constant or decreasing, the estimation unit 71 estimates that the time of the bubbling step is long or too long with respect to the desired time length.

[0083] Based on such an estimation result, by adjusting the time of the bubbling step, it is possible to suppress the accumulation of the turbidity component in the housing 12 while shortening the time of the bubbling step as much as possible, and to increase the operation rate of the filtration operation. For example, when drainage water with a large amount of SS (Suspended Solid) component is used as raw water, such optimization of the bubbling time is effective. Note that the estimated time of the drainage step may be used instead of the estimated time of the water filling step. Also, the timing for determining the fluctuation trend of the estimated time of the water filling step or the drainage step is not particularly limited, and may be, for example, every 10 cycles, once a day, or once a week.

[0084] (Embodiment 4) Next, a water treatment apparatus and a water treatment method according to Embodiment 4 of the present invention will be described. Embodiment 4 is basically the same as Embodiment 1, but is different from Embodiment 1 in that the estimation unit 71 estimates the length of the filtration step. Hereinafter, only the differences from Embodiment 1 will be described.

[0085] FIG. 8 is a graph showing the variation of the transmembrane pressure difference of the hollow fiber membrane module 10 when a cycle consisting of a series of steps in FIG. 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 FIG. 8, the horizontal axis represents time, and the vertical axis represents the transmembrane pressure difference of the hollow fiber membrane module 10. Also in FIG. 8, for example, the periods between time points t0 to t1, t1 to t2, and t2 to t3 each correspond to one cycle.

[0086] The estimation unit 71 in Embodiment 4 estimates the length of time of the filtration process based on the variation of the transmembrane pressure difference of the hollow fiber membrane module 10 in the filtration process. Specifically, when the transmembrane pressure difference at the start time of the filtration process (for example, time points t0, t1, t2, and t3 in FIG. 3) shows an upward trend between consecutive cycles, the estimation unit 71 estimates that the time of the filtration process is longer than the desired length. On the other hand, when the transmembrane pressure difference at the start time of the filtration process is constant or shows a downward trend between consecutive cycles, the estimation unit 71 estimates that the time of the filtration process is shorter than the desired length.

[0087] Based on such an estimation, it is possible to optimize the time of the filtration process so as to increase the operation rate of the filtration operation and the recovery rate of the 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 operation rate and the water recovery rate can be increased by extending the time of the filtration process longer than the standard 30 minutes. Note that the period for estimating the variation 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.

[0088] (Embodiment 5) Next, a water treatment apparatus and a water treatment method according to Embodiment 5 of the present invention will be described. Embodiment 5 is basically the same as Embodiment 1, but is different from Embodiment 1 in that the estimation unit 71 estimates the length of time of the chemical immersion process of the hollow fiber membrane module 10. Hereinafter, only the differences from Embodiment 1 will be described.

[0089] First, the chemical solution immersion process of the hollow fiber membrane module 10 will be described with reference to FIGS. 9 and 10. The chemical solution immersion process is a process of flushing out fouling components that have entered the inside of the hollow fiber membrane 11 with a chemical. The water treatment apparatus 1A according to Embodiment 5 further includes a chemical solution supply unit 80 in addition to the configuration of Embodiment 1. The chemical solution supply unit 80 includes a chemical solution pump 81 and a chemical solution pipe 82. As shown in FIG. 9, the chemical solution pipe 82 has the chemical solution pump 81 installed on the upstream end side, and the downstream end is connected to a portion of the raw water pipe 21 that is downstream of the raw water valve 23.

[0090] FIG. 10 shows the on / off states of the raw water pump 22 and the chemical solution pump 81 and the open / closed states of the respective valves in each step of the chemical solution immersion. In FIG. 10, the filled circles indicate the on state of the pump or the open state of the valve, and the blanks indicate the off state of the pump or the closed state of the valve.

[0091] First, in the chemical solution injection step, the chemical solution pump 81 operates, and the raw water valve 23 and the air vent valve 56 are each opened. Thereby, the chemical solution is supplied to the raw water space S1 of the housing 12. The type of the chemical solution is not particularly limited, and for example, in addition to acids such as sulfuric acid, nitric acid, or hydrochloric acid, oxidizing agents, alkaline agents, surfactants, chelating agents, or combinations thereof can be used.

[0092] Next, in the water filling step, the chemical solution pump 81 is stopped, and the raw water pump 22 operates. Thereby, the raw water is supplied to the raw water space S1 through the raw water pipe 21 and the water conduit 14.

[0093] Next, in the immersion step, the raw water pump 22 is stopped, the raw water valve 23 is closed, and the system waits for a predetermined time. Thereby, the hollow fiber membrane 11 is held in the raw water containing the chemical solution for a predetermined time.

[0094] Next, in the air bubbling step, the first air valve 32 is opened. Thereby, the hollow fiber membrane 11 is bubble-cleaned in a state where the raw water containing the chemical solution fills the raw water space S1.

[0095] Next, in the drainage process, the air vent valve 56 and the first air valve 32 are closed, while the drain valve 54 and the second air valve 33 are opened. As a result, the raw water containing the chemical solution and impurities is pushed by the air and discharged outside the housing 12. In the subsequent pressure relief process, the drain valve 54 remains open while the second air valve 33 is closed, and the inside of the housing 12 (raw water space S1) is depressurized.

[0096] Next, in the water filling process, as described above, the raw water pump 22 operates, the drain valve 54 is closed, and the raw water valve 23 and the air vent valve 56 are opened. As a result, the raw water space S1 is refilled with raw water again.

[0097] 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. As a result, air is supplied into the housing 12, and the air is dispersed upward toward the hollow fiber membrane 11 by the air diffuser plate 15.

[0098] Next, in the drainage process, the air vent valve 56 and the first air valve 32 are closed, while the drain valve 54 and the second air valve 33 are opened. As a result, the water in the raw water space S1 is pushed out of the housing 12 by the air. Then, in the pressure relief process, only the second air valve 33 is closed, and the inside of the raw water space S1 is depressurized.

[0099] In the above manner, the chemical solution immersion process of the hollow fiber membrane module 10 is carried out. This chemical solution immersion process may be carried out at a predetermined frequency, for example, once a day, once a week, or once a month, when repeating the operation cycle of FIG. 2. Note that the cycle consisting of the last four processes (water filling to pressure relief) in FIG. 10 is repeated a predetermined number of times until the chemical solution in the housing 12 is sufficiently discharged.

[0100] In this embodiment, the estimation unit 71 estimates the length of the chemical solution immersion process time 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 solution immersion process. When the estimated time is constant or tends to be long, the estimation unit 71 estimates that the time of the chemical solution immersion process (the immersion process time in FIG. 10) is short compared to the desired time length. On the other hand, when the estimated time of the backwash process performed before and after the chemical solution immersion process is compared and the estimated time tends to be short, the estimation unit 71 estimates that the time of the chemical solution immersion process (the immersion process time in FIG. 10) is long compared to the desired time length. Based on such estimation, it is possible to optimize the time of the chemical solution immersion process so as to increase the operation rate of the filtration operation and the recovery rate of the treated water while ensuring the cleaning effect by the chemical solution immersion.

[0101] In addition, 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. However, the chemical solution may be injected from the secondary side of the hollow fiber membrane module 10 and the chemical solution may be pushed out from the secondary side to the primary side.

Example

[0102] (Example 1) Simulated iron chloride water was used as raw water and filtered using the water treatment apparatus having the configuration shown in FIG. 1. Specifically, each step in Table 1 below was performed in order, and then the set time of the step was changed as shown in Table 1 based on the log data of the pressure measurement as in the above embodiment. As a result, while maintaining a stable filtration operation, the operation rate of the filtration operation could be improved by 3.6%.

[0103]

Table 1

[0104] Also, permeate was used during backwashing, and each step in Table 2 below was performed in order. Then, the set time of the step was changed as shown in Table 2 based on the log data of the pressure measurement as in the above embodiment. As a result, while maintaining a stable filtration operation, the operation rate of the filtration operation could be improved by 2.5%.

[0105]

Table 2

[0106] (Example 2) Industrial water was used as raw water and filtered using a water treatment apparatus having the configuration shown in FIG. 9. Then, as in the above embodiment, the set time of 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 variation trend of the estimated time of the backwashing step. In Table 3, the number of repetitions of the cycle consisting of steps No. 7 to 10 was set to 5 times. By shortening the time of the chemical immersion step, the operation rate of the filtration operation could be improved.

[0107]

Table 3

[0108] Also, the chemical immersion step was carried out by injecting the chemical solution from the secondary side of the hollow fiber membrane module and carrying out each step in Table 4 in order. Then, as in the above embodiment, the set time of the chemical immersion step was changed as shown in Table 4 based on the variation trend of the estimated time of the backwashing step. As a result, the time of the chemical immersion step could be shortened and the operation rate of the filtration operation could be improved.

[0109]

Table 4

[0110] The embodiments and examples disclosed this time should be construed as illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of claims rather than the above description, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims be included.

Explanation of Reference Numerals

[0111] 1, 1A Water treatment apparatus 10 Hollow fiber membrane module 60 Measuring unit 71 Estimation unit 72 Setting change unit

Claims

1. a hollow fiber membrane module; a measuring unit that measures the pressure on at least one of the primary side and secondary side of the hollow fiber membrane module at intervals of 3 seconds or less during at least one of a water filling process, a depressurization process, a backwashing process, a drainage process, a backwash preparation process, an air venting process, an air diffuser bubbling process, and a water conduit bubbling process of the hollow fiber membrane module; an estimation unit that estimates a time required from the start to the end of the at least one process based on a result of the pressure measurement by the measurement unit; a setting change unit that automatically changes a set time of the at least one process based on the time estimated by the estimation unit.

2. A water treatment device as described in claim 1, wherein the setting change unit changes the setting time once per hour, once per day, once per week, or once per month.

3. The estimation unit estimates the time required from the start to the end of the water filling process based on the result of pressure measurement on the primary side of the hollow fiber membrane module, The water treatment device according to claim 1 , wherein the setting change unit changes the set time of the water filling step among the at least one step based on the time estimated by the estimation unit.

4. The estimation unit estimates the time required from the start to the end of the drainage process based on the result of pressure measurement on the primary side of the hollow fiber membrane module, The water treatment device according to claim 1 , wherein the setting change unit changes the set time of the drainage process of the at least one process based on the time estimated by the estimation unit.

5. The estimation unit estimates the time required from the start to the end of all processes, including the water filling process, the depressurization process, the backwash preparation process, the backwash process, the air bleeding process, the drainage process, the air diffuser bubbling process, and the water conduit bubbling process, 5. The water treatment device according to claim 1, wherein the setting change unit automatically changes the set times of all the processes based on the times estimated by the estimation unit.

6. The measuring unit includes a primary side pressure sensor that measures the pressure on the primary side of the hollow fiber membrane module at intervals of 0.1 seconds or less, and a secondary side pressure sensor that measures the pressure on the secondary side of the hollow fiber membrane module at intervals of 0.1 seconds or less, The water treatment device according to any one of claims 1 to 5, further comprising a control unit that stores measurement data from the primary pressure sensor and the secondary pressure sensor as logging data.

7. The hollow fiber membrane module includes an air vent pipe connected to a housing in which a hollow fiber membrane bundle is accommodated, the measuring unit includes an air vent port pressure sensor installed in the air vent pipe, the air vent pressure sensor measures pressure at intervals of 0.1 seconds or more and 3 seconds or less; The water treatment device according to claim 6 , wherein the control unit stores measurement data obtained by the air vent port pressure sensor as logging data.

8. The hollow fiber membrane module comprises a housing in which a hollow fiber membrane bundle is housed, The water treatment device according to any one of claims 1 to 6, wherein the ratio of the inner diameter of the housing to the inner diameter of the piping connection port provided in the housing is 1.3 or more and 12 or less, 2.5 or more and 12 or less, or 3.0 or more and 6.0 or less.

9. A water treatment method for filtering raw water using a hollow fiber membrane module, comprising: measuring the pressure on at least one of the primary side and secondary side of the hollow fiber membrane module at intervals of 3 seconds or less in at least one of the water filling step, the pressure release step, the backwashing step, the drainage step, the backwash preparation step, the air venting step, the air diffuser bubbling step, and the water conduit bubbling step of the hollow fiber membrane module; estimating a time required from the start to the end of the at least one process based on the results of the pressure measurement on the at least one side; automatically changing a set time of the at least one process by a setting change unit based on an estimated time of the at least one process.

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