Water treatment apparatus and water treatment method

Abstract

The present invention provides a water treatment apparatus and water treatment method that can increase the operating rate of filtration operations while reducing costs and labor. [Solution] The water treatment device comprises a hollow fiber membrane module, a measuring 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 following steps: a water filling step, a depressurization step, a backwashing step, and a draining step, and an estimation unit that estimates the time required from the start to the end of the at least one step based on the pressure measurement results by the measuring unit.

Description

Technical Field

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

Background Art

[0002] Conventionally, water treatment apparatuses that filter raw water using a hollow fiber membrane module are known. In this water treatment apparatus, the amount of impurities adhering to the membrane surface of the hollow fiber membrane increases as the filtration time elapses, so it is necessary to periodically clean the module.

[0003] 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 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 Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem 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 proportion of the filtration time in the total operation time of the apparatus.

[0006] However, the time required to perform each cleaning process depends on various parameters such as the number of modules, pipe diameter and length, or water flow rate, and varies from site to site and equipment to equipment. Therefore, it is not possible to set a uniform time for all sites and equipment. For this reason, accurately determining the time required for each cleaning process requires measuring the process time at each site, which incurs significant costs and effort.

[0007] The present invention has been made in view of the above problems, and its purpose is to provide a water treatment apparatus and a water treatment method that can increase the operating rate of filtration operations while reducing costs and effort. [Means for solving the problem]

[0008] A water treatment apparatus according to one aspect of the present invention comprises a hollow fiber membrane module, a measuring 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 following steps: a water filling step, a depressurization step, a backwashing step, and a draining step, and an estimation unit that estimates the time required from the start to the end of the at least one step based on the results of the pressure measurement by the measuring unit.

[0009] This water treatment system estimates process time based on the time change of pressure on at least one of the primary and secondary sides of the hollow fiber membrane module, eliminating the need to measure process time on-site. This reduces the cost and effort required for measuring process time, and by setting each process time based on the estimated time, unnecessary process time can be reduced. Therefore, the operating rate of the filtration operation can be increased while keeping costs and effort down.

[0010] In the water treatment apparatus described above, the measuring unit may measure the pressure on the primary side 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 until the inflection point of the change in the pressure on the primary side is reached.

[0011] This configuration makes it easy to estimate the time required for the water filling process.

[0012] In the water treatment apparatus described above, the measuring unit may measure the pressure on the primary side 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 pressure on the primary side becomes constant.

[0013] This configuration makes it easy to estimate the time required for the drainage process.

[0014] In the water treatment apparatus described above, 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 draining process.

[0015] This configuration allows the bubbling process time to be adjusted to an appropriate duration, thereby reducing wasted time during hollow fiber membrane cleaning and increasing the operating efficiency of the filtration operation.

[0016] In the water treatment apparatus described above, the measuring 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.

[0017] This configuration makes it easy to estimate the time required for the backwashing process.

[0018] In the water treatment apparatus described above, the measuring 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 the maximum pressure.

[0019] This configuration makes it easy to estimate the time required for the backwashing process.

[0020] In the above water treatment apparatus, the estimating unit may estimate the length of time 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 cleaning time for the hollow fiber membrane can be reduced, and the operation rate of the filtration operation can be further increased.

[0022] In the above water treatment apparatus, the measuring unit may measure pressures on the primary side and the secondary side in the filtration step of the hollow fiber membrane module. The estimating unit may estimate the length of time of the filtration step based on a variation in transmembrane pressure difference 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, it is possible to achieve a balance between safe operation of the apparatus and the operation rate of the filtration operation.

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

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

[0026] In the above water treatment apparatus, the setting changing unit may change set times of a plurality of steps among the water filling step, the pressure releasing step, the backwashing step and the draining step based on the time estimated by the estimating unit.

[0027] A water treatment method according to another aspect of the present invention is a method of filtering raw water with a hollow fiber membrane module. This water treatment method comprises, in at least one step selected from a water filling step, a pressure release step, a backwashing step and a drainage step of the hollow fiber membrane module: measuring the pressure on at least one of the primary side and the secondary side of the hollow fiber membrane module at an interval of 3 seconds or less; estimating the time required from the start to the end of said at least one step based on the result of the pressure measurement on said at least one side; and changing the set time of said at least one step based on the estimated time of said at least one step.

[0028] According to this method, the step time is estimated based on the temporal change of pressure on at least one of the primary side and the secondary side of the hollow fiber membrane module, and the set step time is changed based on the estimated time. Therefore, it is not necessary to actually measure the step time on site before changing the set time. Accordingly, it is possible to reduce waste of step time while suppressing the cost and labor required for actual measurement of step time, and the operation rate of filtration operation can be increased. [Effects of the Invention]

[0029] As is clear from the above description, according to the present invention, it is possible to provide a water treatment device and a water treatment method that can increase the operation rate of filtration operation while suppressing cost and labor. [Brief Description of Drawings]

[0030] [Figure 1] It is a figure which shows typically the structure of the water treatment apparatus which concerns on Embodiment 1 of this invention. [Figure 2] It is a figure which shows the on / off state of a raw water pump and the open / closed state of a valve in each process of the water treatment method which concerns on Embodiment 1 of this invention. [Figure 3] It is a figure which shows the time change of the primary side pressure of the hollow fiber membrane module in the water filling process of Embodiment 1 of this invention. [Figure 4] It is a figure which shows the time change of the primary side pressure of the hollow fiber membrane module in the backwashing process of Embodiment 1 of this invention. [Figure 5] This figure shows the time change of the primary side pressure of the hollow fiber membrane module in the drainage process of Embodiment 1 of the present invention. [Figure 6] This figure shows the time change of the primary side pressure of the hollow fiber membrane module during the backwashing process in a modified embodiment 1 of the present invention. [Figure 7] This figure shows the time change of the primary side pressure of the hollow fiber membrane module during the backwashing process in a modified embodiment 2 of the present invention. [Figure 8] This figure shows the time change of the intermembrane differential pressure in a hollow fiber membrane module according to Embodiment 4 of the present invention. [Figure 9] This figure schematically shows the configuration of the water treatment apparatus in Embodiment 5 of the present invention. [Figure 10] This figure shows the on / off state of the pump and the open / closed state of the valve during the chemical immersion process in Embodiment 5 of the present invention. [Modes for carrying out the invention]

[0031] Embodiments of the present invention will be described in detail below 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 Figure 1. As shown in Figure 1, the water treatment apparatus 1 mainly comprises a hollow fiber membrane module 10, a raw water supply unit 20, a bubbling air supply unit 30, and a backwashing air supply unit 40.

[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 conduit 14 extending vertically inside the hollow fiber membrane bundle, and a diffuser 15. The hollow fiber membrane bundle, the fixing member 13, and the diffuser 15 are housed inside the housing 12. The space inside the housing 12 is divided into a raw water space S1 and a treated water space S2 by the fixing member 13. The hollow fiber membranes 11, the water conduit 14, and the diffuser 15 are housed in the raw water space S1.

[0034] As shown in Figure 1, the upper part of the housing 12 is provided with a treated water outlet 12A facing the treated water space S2, the side of the housing 12 (the part above the center in the longitudinal direction) is provided with an air vent 12B facing the raw water space S1, and the lower part of the housing 12 is provided with an air supply port 12C and a drain port 12D facing the raw water space S1. The ratio of the inner diameter of the housing 12 to the inner diameter of these pipe connection ports (outlet 12A, air vent 12B, air supply port 12C, and drain port 12D) is preferably 1.3 or more and 12 or less, preferably 2.5 or more and 12 or less, and more preferably 3.0 or more and 6.0 or less. Note that the inner diameter of the housing 12 referred to here is the inner diameter in a cross-section in a direction perpendicular 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 Figure 1, the upper end of the water conduit 14 is fixed to the fixing member 13 and its end face is closed, while the lower end protrudes below the lower part of the housing 12. A raw water inlet 14A and an air inlet 14B are provided at the lower end. The water conduit 14 also has numerous holes 14C formed inside it for ejecting at least one of raw water and air toward the raw water space S1.

[0036] The diffuser 15 is for dispersing air in the raw water space S1. The diffuser 15 has a disc shape that extends radially in the direction of the hollow fiber membrane bundle and is positioned below the lower end of the hollow fiber membrane 11. Multiple ventilation holes (not shown) are formed in the diffuser 15 at radial intervals. Air supplied into the housing 12 from the air supply port 12C is dispersed toward the hollow fiber membrane bundle through the ventilation holes in the diffuser 15.

[0037] As shown in Figure 1, the upstream end of the treated water piping 50 is connected to the outlet 12A of the housing 12. The downstream end of the treated water piping 50 is connected to the inlet of a treated water tank (not shown). The treated water piping 50 is equipped with a treated water valve 51 (on / off valve) and a flow meter 52 downstream of it. The diameter of the treated water piping 50 is smaller than the diameter of the housing 12.

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

[0040] As shown in Figure 1, the treated water piping 50 and the drainage piping 53 are connected to each other by a pressure relief pipe 57. One end of the pressure relief pipe 57 is connected to the portion of the treated water piping 50 upstream of the treated water valve 51, and the other end of the pressure relief pipe 57 is connected to the portion of the drainage piping 53 downstream of the connection point of the air vent pipe 55. A pressure relief valve 58 (on / off valve) is installed in the pressure relief pipe 57. The diameter of the pressure relief pipe 57 is smaller than the diameter of the housing 12.

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

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

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

[0044] The water treatment device 1 further includes a measuring unit 60 that measures the pressure on at least one of the primary and secondary sides of the hollow fiber membrane module 10 at intervals of 3 seconds or less (for example, at intervals of 2 seconds or less or 1 second or less) during at least one of the following processes: filling the hollow fiber membrane module 10 with water, depressurizing, backwashing, and draining. In this embodiment, the measuring unit 60 includes a primary side pressure sensor 61 that measures the pressure on the primary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less, and a secondary side pressure sensor 62 that measures the pressure on the secondary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less. As shown in Figure 1, the primary side pressure sensor 61 is installed in the portion of the raw water piping 21 between the raw water valve 23 and the raw water inlet 14A. The primary side pressure sensor 61 may also be installed in the portion of the water conduit 14 that extends from the housing 12 or in a position in the housing 12 facing the raw water space S1.

[0045] The secondary pressure sensor 62 is installed at the connection point between the treated water piping 50 and the air piping 41. In this embodiment, the primary pressure sensor 61 and the secondary pressure sensor 62 measure pressure at intervals of 0.1 seconds or less, and the measurement data is sent to the control unit 70 for storage. In other words, 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) may also be provided. The air vent pressure sensor is installed at the connection point 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 for storage. In other words, each measurement data is stored as logging data. However, as the number of pressure sensors increases, the analysis becomes more time-consuming and the cost increases, so it is desirable to omit the air vent pressure sensor and perform data analysis using data from the primary pressure sensor 61 and the secondary pressure sensor 62.

[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 following processes: the water filling process, the pressure depressurization process, the backwashing process, and the drainage process, based on the pressure measurement results from 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. Note that the estimation unit 71 and the setting change unit 72 may be implemented as functions of the control unit 70. The estimation of each process time by the estimation unit 71 will be described below.

[0048] Figure 2 shows each step of the water treatment method according to this embodiment, which is carried out using the water treatment apparatus 1 described above, and also shows the ON / OFF state of the raw water pump 22 and the open / closed state of each valve in each step. In Figure 2, circles indicate the ON state of the raw water pump 22 or the open state of the valve, and blank spaces indicate the OFF state of the raw water pump 22 or the closed state of the valve.

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

[0050] In the first water filling process, the primary pressure sensor 61 measures the pressure on the primary side of the hollow fiber membrane module 10 at intervals of 3 seconds or less, and the control unit 70 sequentially stores the measured pressure values. This provides data (Figure 3) showing the time change of the primary side pressure of the hollow fiber membrane module 10 during the first water filling process. In Figure 3, the horizontal axis represents time, and the vertical axis represents the primary side pressure of the hollow fiber membrane module 10. The secondary 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 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 Figure 3) to the inflection point of the primary side pressure change (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 begins 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.

[0052] Once the first water filling process is complete, the process moves to the filtration process. During the filtration process, the air vent valve 56 is closed and the treated water valve 51 is opened. Raw water permeates the membrane wall of the hollow fiber membrane 11 from the outer surface to the inner surface and flows into the treated water space S2 through the hollow portion of the membrane. Subsequently, the treated water flows out of the housing 12 through the outlet 12A and is collected in a treated water tank (not shown) through the treated water piping 50.

[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 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.

[0054] After the filtration process, a washing operation is performed to remove impurities that have adhered to the outer surface of the hollow fiber membrane 11 during filtration. The washing operation includes a backwash preparation process, a backwash process, an air venting process, a second water filling process, a diffuser bubbling process, a third water filling process, a water conduit bubbling process, a drainage process, and a pressure relief process.

[0055] First, during the backwash preparation process (pressure relief process), the raw water pump 22 is switched from on to off.

[0056] Next, in the backwashing process, the raw water valve 23 and the treated water valve 51 are closed, while the air valve 42 and the drain valve 54 are opened. That is, simultaneously with the opening of the air valve 42, the pressure of air pressurized by the compressor is instantaneously added to the treated water on the secondary side of the hollow fiber membrane module 10. As a result, the treated water on the secondary side of the hollow fiber membrane module 10 is pressurized by the air, and the treated water permeates the membrane wall from the inner surface to the outer surface of the hollow fiber membrane 11. This makes it easier for impurities attached to the outer surface of the hollow fiber membrane 11 to peel off. At this time, since the primary side pressure sensor 61 and the secondary side pressure sensor 62 measure the pressure at intervals of 3 seconds or less, it is possible to detect the pressure after the hollow fiber membrane 11 has been pressurized from the inside, but before the impurities on the membrane surface become easily peeled off.

[0057] In this way, during the backwashing process, the primary pressure sensor 61 measures the primary pressure of the hollow fiber membrane module 10 at intervals of 3 seconds or less. This provides logging data (Figure 4) showing the time change of the primary pressure of the hollow fiber membrane module 10 during the backwashing process. In Figure 4, the horizontal axis represents time, and the vertical axis represents the primary pressure of the hollow fiber membrane module 10. As shown in Figure 4, the primary pressure rises instantaneously after the start of the backwashing process to reach a maximum pressure, and then decreases to a constant level. This instantaneous rise in primary pressure can be seen from the subsequent rapid decrease 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, as the raw water is discharged into the drainage pipe 53, the primary pressure drops sharply, and thereafter the primary pressure gradually decreases. At this time, the gradual decrease in primary pressure is presumed to be due to the gradual decrease in the amount of water in the raw water space S1. Furthermore, it is presumed that when the pressure on the primary side becomes constant, it means 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 t0 in Figure 4) until the primary side pressure becomes constant (time t1 in the same figure). In order to estimate that the primary side pressure has become constant, it is necessary that the primary side pressure stabilizes at a constant value thereafter. 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 from time t1 onwards.

[0059] In addition, during 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 that in Figure 4 can be 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 pressure on the secondary side becomes constant.

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

[0061] Next, in the second water filling process, similar to the first water filling process, the raw water pump 22 is activated, and the raw water valve 23 and the air vent valve 56 are opened. 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 results of these pressure measurements.

[0062] Next, in the diffuser bubbling process, the raw water pump 22 is switched from on to off, the raw water valve 23 is closed, and the first air valve 32 is opened. The air vent valve 56 remains open. As a result, air is supplied into the housing 12 from the air supply port 12C, and this air is dispersed by the diffuser 15 toward the hollow fiber membrane bundle. This causes the hollow fiber membrane bundle to oscillate due to the bubbles, and impurities attached to the membrane surface are detached.

[0063] In the 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.

[0064] Next, in the third water filling process, similar to the first and second water filling processes, the raw water pump 22 is activated, and the raw water valve 23 and the air vent valve 56 are opened, respectively. This replenishes the raw water in the raw water space S1 that was reduced during the diffuser bubbling process. 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 results of these pressure measurements.

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

[0066] In 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.

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

[0068] During the drainage process, the primary pressure sensor 61 measures the primary pressure of the hollow fiber membrane module 10 at intervals of 3 seconds or less. This provides logging data (Figure 5) showing the time change of the primary pressure of the hollow fiber membrane module 10 during the drainage process. In Figure 5, the horizontal axis represents time, and the vertical axis represents the primary pressure of the hollow fiber membrane module 10. As shown in Figure 5, the primary pressure rises after a certain period of time has elapsed since the start of the drainage process, reaches a 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 t0 in Figure 5) until the primary side pressure becomes constant (time t1 in the same figure). In order to estimate that the primary side pressure has become constant, it is necessary that the primary side pressure stabilizes at a constant value thereafter. For this reason, the estimation unit 71 estimates the time required for the drainage process based on time t0 to time t1 by referring to measurement data from time t1 onwards.

[0070] Finally, in the depressurization process, the drain valve 54 remains open while the second air valve 33 is closed. This removes air from inside the housing 12 (raw water space S1). After the hollow fiber membrane module 10 is cleaned through the above process, the process returns to the first water filling process and the filtration operation resumes.

[0071] After the series of processes shown in Figure 2 (first water filling process to pressure relief process) are completed, the setting change unit 72 changes the setting times for the water filling process, backwashing process, and draining process based on the estimated times for these processes. Note that this change in setting times is not limited to being performed automatically by the setting change unit 72, but may also be changed manually by the user.

[0072] As described above, with the water treatment apparatus 1 according to this embodiment, the time for each process—the filling process, the backwashing process, and the draining process—is estimated based on the time change of the primary side pressure of the hollow fiber membrane module 10, so there is no need to actually measure each process time on site. Therefore, the cost and effort required for measuring process times can be reduced. In addition, by resetting each process time based on the estimated time, unnecessary process time can be reduced. Thus, the operating rate of the filtration operation can be increased while keeping costs and effort down.

[0073] Furthermore, in addition to the water filling process, backwashing process, and draining process, the pressure on the primary and secondary sides of the hollow fiber membrane module 10 may also be measured at intervals of 3 seconds or less during the backwash preparation process, air bleeding process, and pressure relief 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 backwash preparation, air bleeding, and pressure relief processes may be estimated based on the time from the start of the process until the pressure becomes zero. The set time for the process may then be changed based on this estimated time.

[0074] In the backwashing process, the secondary processing liquid may be pressurized using a 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 Figure 6. That is, the primary side pressure rises after the start of backwashing and becomes almost constant from time t1, which is after time has elapsed from 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 Figure 7) until the primary side pressure becomes constant (time t1 in the same figure).

[0075] Furthermore, there are no particular limitations on the frequency of automatically changing the setting time; for example, it could be once every hour, once a day, once a week, or once a month. This frequency is determined appropriately depending on the type of raw water (e.g., river water, wastewater, or sewage) and the season.

[0076] Furthermore, the set times for all processes—the filling process, the backwashing process, and the draining process—may be changed, but are not limited to this; the set times for only some of these processes may also be changed. The processes to which the set times are to be changed will be determined as appropriate according to the site conditions. For example, if the flow rate of the raw water pump 22 fluctuates significantly, or if it is difficult to visually confirm the status of filling through the raw water piping 21, changing the set time for the filling process is effective.

[0077] (Embodiment 2) Next, a 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 process differs from Embodiment 1. Below, only the differences from Embodiment 1 will be described.

[0078] In Embodiment 2, 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 pressure reaches its maximum pressure. That is, the time from time t0 to time t2 in the graph of Figure 4 is estimated as the time required for the backwashing process. This estimation method can be suitably used when the impurities adhering to the membrane surface are, for example, mainly inorganic components with good detachability. In other words, in the case of impurities with good detachability, they detach 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 pressure reaches its maximum value at time t2.

[0079] Similarly, when backwashing is performed using liquid instead of air, the process time can be estimated in the same manner as described above. Figure 7 is a graph showing the case where the treated water is circulated in advance by a pump before the start of backwashing, and the secondary side of the hollow fiber membrane 11 is suddenly pressurized at the start of the backwashing process. In Figure 7, 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 7, in this case as well, the primary side pressure rises instantaneously to the maximum pressure after a predetermined time has elapsed since the start of 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, that is, 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.

[0080] (Embodiment 3) Next, a 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 differs from Embodiment 1 in that the estimation unit 71 estimates the length of the bubbling process. Below, 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 Figure 2 is repeated, and the process time is estimated for the water filling step and draining step of each cycle. In this embodiment, the estimation unit 71 estimates the length of the bubbling step based on the estimated time of the water filling step or draining step.

[0082] Specifically, if the estimated time for the water filling process decreases when the above cycle is repeated, the amount of turbidity components accumulated in the housing 12 is increasing, and therefore the estimation unit 71 estimates that the time for the bubbling process is shorter than the desired time (insufficient bubbling). On the other hand, if the estimated time for the water filling process remains constant or increases when the above cycle is repeated, the amount of turbidity components accumulated in the housing 12 remains constant or decreases, and therefore the estimation unit 71 estimates that the time for the bubbling process is longer than the desired time.

[0083] Based on these estimation results, the bubbling process time can be adjusted to minimize the bubbling process time while suppressing the accumulation of turbidity components in the housing 12, thereby increasing the operating rate of the filtration operation. For example, such optimization of the bubbling time is effective when wastewater with a high SS (Suspended Solid) content is used as raw water. The estimated time of the drainage process may be used instead of the estimated time of the filling process. Furthermore, there are no particular limitations on the timing for determining the fluctuation trend of the estimated time of the filling or drainage process; for example, it may be every 10 cycles, once a day, or once a week.

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

[0085] Figure 8 is a graph showing the fluctuation of the intermembrane pressure differential in the hollow fiber membrane module 10 when the cycle consisting of the series of processes in Figure 2 is repeated. The intermembrane pressure differential 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 represents time, and the vertical axis represents the intermembrane pressure differential in the hollow fiber membrane module 10. Also, in Figure 8, for example, the time intervals t0 to t1, t1 to t2, and t2 to t3 each correspond to one cycle.

[0086] In Embodiment 4, the estimation unit 71 estimates the length of the filtration process based on fluctuations in the intermembrane pressure of the hollow fiber membrane module 10 during the filtration process. Specifically, the estimation unit 71 estimates that the filtration process is longer than the desired length if the intermembrane pressure at the start of the filtration process (for example, at times t0, t1, t2, and t3 in Figure 3) is on an upward trend during consecutive cycles. On the other hand, the estimation unit 71 estimates that the filtration process is shorter than the desired length if the intermembrane pressure at the start of the filtration process is constant or on a downward trend during consecutive cycles.

[0087] Based on such estimations, the filtration process time can be optimized to increase the operating efficiency of the filtration operation and the recovery rate of treated water while suppressing an excessive rise in the intermembrane pressure differential. For example, when groundwater or tap water is used as raw water, the operating efficiency 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 intermembrane pressure is not particularly limited; for example, it may be once every 10 cycles, or once a day or once a week.

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

[0089] First, the chemical immersion process of the hollow fiber membrane module 10 will be explained with reference to Figures 9 and 10. The chemical immersion process is a process of washing away fouling components that have entered the inside of 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 Figure 9, the chemical pump 81 is installed on the upstream end of the chemical piping 82, and the downstream end is connected to the portion of the raw water piping 21 downstream of the raw water valve 23.

[0090] Figure 10 shows the on / off states of the raw water pump 22 and the chemical pump 81, as well as the open / closed states of each valve, at each stage of the chemical immersion process. In Figure 10, circles indicate the pump being on or the valve being open, while blank spaces indicate the pump being off or the valve being closed.

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

[0092] Next, in the water filling process, the chemical pump 81 is stopped and the raw water pump 22 is activated. As a result, raw water is supplied to the raw water space S1 through the raw water piping 21 and the water conduit 14.

[0093] Next, in the immersion process, the raw water pump 22 is stopped and the raw water valve 23 is closed, and the system is left waiting for a predetermined time. This ensures that 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 process, the first air valve 32 is opened. As a result, the hollow fiber membrane 11 is bubbling and washed with raw water containing the chemical solution filling 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 out by the air and discharged outside the housing 12. In the subsequent depressurization 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 filling process, the raw water pump 22 is activated as described above, the drain valve 54 is closed, and the raw water valve 23 and the air vent valve 56 are opened. As a result, raw water is refilled into the raw water space S1.

[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 this air is dispersed upward toward the hollow fiber membrane 11 by the 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. Subsequently, in the depressurization process, only the second air valve 33 is closed, and the raw water space S1 is depressurized.

[0099] As described above, the chemical immersion process of the hollow fiber membrane module 10 is carried out. This chemical immersion process may be performed at a predetermined frequency when repeating the operation cycle shown in Figure 2, for example, once a day, once a week, or once a month. The cycle consisting of the last four steps (water filling to pressure release) in Figure 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 immersion process of the hollow fiber membrane module 10 based on the estimated time of the backwashing process. Specifically, the estimation unit 71 compares the estimated time of the backwashing process performed before and after the chemical immersion process, and if the estimated time tends to be constant or longer, it estimates that the chemical immersion process time (immersion process time in Figure 10) is shorter than the desired length. On the other hand, the estimation unit 71 compares the estimated time of the backwashing process performed before and after the chemical immersion process, and if the estimated time tends to be shorter, it estimates that the chemical immersion process time (immersion process time in Figure 10) is longer than the desired length. Based on such estimations, the chemical immersion process time can be optimized to increase the operating rate of the filtration operation and the recovery rate of treated water while ensuring the cleaning effect of chemical immersion.

[0101] In this embodiment, the case in which the chemical solution is injected from the primary side of the hollow fiber membrane module 10 has been described. However, the chemical solution may also be injected from the secondary side of the hollow fiber membrane module 10 and pushed out from the secondary side to the primary side. [Examples]

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

[0103] [Table 1]

[0104] Furthermore, permeate was used during backwashing, and each step in Table 2 below was performed in order. Then, as in the embodiment described above, the setting times for each step were changed based on the log data of the pressure measurement as shown in Table 2. As a result, while maintaining stable filtration operation, the operating rate of the filtration operation was improved by 2.5%.

[0105] [Table 2]

[0106] (Example 2) Industrial water was used as the raw water source and filtered using a water treatment apparatus configured as shown in Figure 9. Then, as in the above embodiment, the setting time for the chemical immersion process (immersion of a 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 trend of the estimated time of the backwashing process. In Table 3, the number of repetitions of the cycle consisting of processes No. 7 to 10 was set to 5 times. By shortening the time of the chemical immersion process, the operating rate of the filtration operation was improved.

[0107] [Table 3]

[0108] Furthermore, the chemical solution was injected from the secondary side of the hollow fiber membrane module, and the chemical immersion process was carried out by sequentially performing each step in Table 4. Then, as in the above embodiment, the setting time for the chemical immersion process was changed as shown in Table 4 based on the fluctuation trend of the estimated time of the backwash process. As a result, the time of the chemical immersion process was shortened, and the operating rate of the filtration operation was improved.

[0109] [Table 4]

[0110] The embodiments and examples disclosed herein should be understood in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0111] 1,1A Water Treatment System 10 Hollow fiber membrane modules 60 Measuring part 71 Estimation part 72 Settings Change Section

Claims

1. Hollow fiber membrane module and In at least one of the processes of filling the hollow fiber membrane module with water, depressurizing, backwashing, and draining, a measuring unit 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. A water treatment apparatus comprising: an estimation unit that estimates the time required from the start to the end of at least one process based on the results of pressure measurement by the measuring unit.

2. The measuring unit measures the pressure on the primary side at intervals of 3 seconds or less during the water filling process. The water treatment apparatus according to claim 1, wherein 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 inflection point of the change in pressure on the primary side.

3. The measuring unit measures the pressure on the primary side at intervals of 3 seconds or less during the drainage process. The water treatment apparatus according to claim 1 or 2, wherein the estimation unit estimates 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.

4. The water treatment apparatus according to claim 2 or 3, wherein the estimation unit estimates the length of the bubbling process of the hollow fiber membrane module based on the estimated time of the water filling process or the draining process.

5. The measuring unit measures the pressure on at least one side at intervals of 3 seconds or less during the backwashing process. The water treatment apparatus according to any one of claims 1 to 4, wherein the estimation unit estimates 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.

6. The measuring unit measures the pressure on at least one side at intervals of 3 seconds or less during the backwashing process. The water treatment apparatus according to any one of claims 1 to 4, wherein the estimation unit estimates 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.

7. The water treatment apparatus according to claim 5 or 6, wherein the estimation unit estimates the length of the chemical immersion process of the hollow fiber membrane module based on the estimated time of the backwashing process.

8. The measuring unit measures the pressure on the primary and secondary sides during the filtration process of the hollow fiber membrane module. The water treatment apparatus according to any one of claims 1 to 7, wherein the estimation unit estimates the length of the filtration process based on fluctuations in the intermembrane pressure of the hollow fiber membrane module during the filtration process.

9. The water treatment apparatus according to any one of claims 1 to 8, further comprising a setting change unit for changing the setting time of at least one process based on the estimated time by the estimation unit.

10. The water treatment apparatus according to claim 9, wherein the setting change unit changes the setting time of a plurality of processes among the water filling process, the pressure relief process, the backwashing process, and the draining process based on the estimated time by the estimation unit.

11. A water treatment method that filters raw water using a hollow fiber membrane module, In at least one of the processes of filling the hollow fiber membrane module with water, depressurizing, backwashing, and draining, the pressure on at least one of the primary and secondary sides of the hollow fiber membrane module is measured at intervals of 3 seconds or less. Based on the results of the pressure measurement on at least one side, estimate the time required from the start to the end of the at least one process, A water treatment method comprising changing the setting time of the at least one process based on the estimated time of the at least one process.

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