JP2013188710A - Membrane filtration apparatus and water production apparatus, and cleaning method of membrane filtration apparatus - Google Patents

Abstract

A membrane filtration device capable of eliminating clogging of a membrane module in a short time with high reliability is provided.
SOLUTION: A membrane filtration device 5 that filters insoluble components in raw water from raw water A by a membrane module 11 and eliminates clogging of the membrane module 11 that accompanies filtration, comprising a water feed pump 13, a washing water pump 21 , A drain pipe 23, pressure difference detection means 17, 19, and a controller 28. The washing water is sent to the membrane module 11 by the washing water pump 21 so as to circulate from the secondary side to the primary side, and the sent washing water is discharged through the drain pipe 23 connected to the primary side of the membrane module 11. Pressure difference detecting means 17 and 19 detect the pressure difference between the primary side and the secondary side of the membrane module 11 during filtration. The flow rate of the washing water is controlled by the controller 28 so that the detected pressure difference is kept constant, and the membrane module 11 exceeds the pressure difference between the primary side and the secondary side of the membrane module 11 during filtration. It is characterized by being controlled to be in a range less than the withstand voltage.
[Selection] Figure 1

Description

  Embodiments of the present invention relate to, for example, a membrane filtration device used for water treatment, a water producing device, and a cleaning method for eliminating clogging of a membrane module of the membrane filtration device.

  In the water treatment field, raw water such as brackish water, seawater, groundwater, landfill leachate, industrial wastewater containing solutes such as ions and salts is filtered to produce domestic water, industrial water, agricultural water, etc. A desalinator using an osmotic membrane module is known.

  The reverse osmosis membrane of the reverse osmosis membrane module has a characteristic that water in raw water can permeate but solutes other than water such as ions and salts in raw water cannot permeate. Using this characteristic, water and solute can be separated by applying a pressure equal to or higher than the osmotic pressure according to the concentration of the solute to the raw water and filtering the raw water through a reverse osmosis membrane.

  For example, a desalination apparatus (also referred to as a membrane filtration system) for producing seawater by filtering, for example, seawater using a reverse osmosis membrane module is used in the seawater taken before desalting the seawater through the reverse osmosis membrane module. Pretreatment is performed to remove insoluble components contained in. Insoluble components are, for example, turbidity, dissolved organic matter, microorganisms, highly viscous organic matter released by microorganisms, inorganic ions, and the like contained in seawater.

  The device responsible for the pretreatment is called a membrane filtration device. By the pretreatment by this apparatus, the contamination of the reverse osmosis membrane is reduced, and the frequency of cleaning the reverse osmosis membrane with chemicals can be reduced. Accordingly, it is possible to operate the fresh water generator continuously for a long period of time.

  A microfiltration (MF) or ultrafiltration (UF) membrane is used as a filtration membrane of a membrane module that performs filtration in the membrane filtration apparatus that performs this pretreatment. Since the membrane module filters the insoluble component, the filtered insoluble component gradually accumulates as a fouling factor substance, thereby clogging the filtration membrane of the membrane module.

  When this clogging progresses, the pressure difference between the inflow side (primary side) of the raw water to the membrane module and the side (secondary side) from which the water filtered by the membrane module flows out gradually increases. Accordingly, the permeation flow rate (flux; abbreviated as “Flux”) of the membrane module is reduced, or the output of the raw water pump that supplies raw water to the membrane module is increased.

  In order to eliminate such clogging of the filtration membrane, the membrane filtration apparatus performs fouling factor substances consisting of insoluble components adhering to the filtration membrane of the membrane module after the filtration operation for a certain period of time. It is comprised so that can be removed. For this reason, the membrane filtration apparatus is generally operated by alternately repeating the raw water filtration operation and the cleaning operation for eliminating clogging of the filtration membrane.

  The membrane module is cleaned through a reverse cleaning process, a water removal process, and a water supply process.

  In the reverse cleaning step, on the contrary to the time of filtration, cleaning water is circulated from the secondary side to the primary side of the membrane module. In this case, a constant flow of washing water is passed for a certain period of time. For example, a manufacturer of a membrane module recommends a reverse cleaning process in which cleaning water having an amount of 1 to several times the raw water flow rate during filtration is passed through the membrane module for a certain period of time. As the washing water, filtered water filtered by the membrane module, demineralized water (concentrated water) obtained by the reverse osmosis membrane module, or the like is used.

  In the water discarding process, the cleaning water collected on the primary side of the reversely cleaned membrane module is drained out of the membrane module.

  In the water supply process, the primary side of the membrane module is washed away with running water. Specifically, the raw water is discharged from the primary side while supplying the raw water from the primary side to the filtration membrane of the membrane module.

  By the way, the quality of raw water, such as seawater, varies depending on the day and place. When the quality of the seawater is poor, the concentration of insoluble components in the seawater is high, so the amount of fouling factor substances attached to the filtration membrane increases with the filtration through the membrane module. Conversely, when the quality of the seawater is good, the concentration of insoluble components in the seawater is low, so the amount of fouling factor substances attached to the filtration membrane is reduced by filtration through the membrane module.

  As described above, there is a variation in the amount of the fouling factor adhering to the filtration membrane of the membrane module. For this reason, as described above, when washing water with a constant flow rate is allowed to flow through the membrane module for a certain period of time and the filtration membrane of this membrane module is backwashed, the washing pressure at that time is that of the fouling factor substance to the filtration membrane. It varies according to the amount of adhesion. In addition, the cleaning pressure gradually decreases as the clogging progresses with cleaning.

  Thus, when the washing pressure varies in the reverse washing of the filtration membrane, it may be difficult to eliminate clogging with sufficient reliability.

  That is, when the cleaning pressure is reduced as the clogging is resolved in the reverse cleaning, the cleaning pressure applied to a part of the pores at which clogging has not been eliminated also decreases. This makes it difficult to eliminate clogging of some of the pores. Such a phenomenon is considered to occur when washing water concentrates on the pores that have been clogged.

  In addition, as described above, when the cleaning pressure decreases with the progress of back cleaning, a relatively long time may be required until clogging is sufficiently eliminated. For this reason, if the backwashing time is constant as described above, backwashing may end before clogging is sufficiently eliminated.

JP 2002-282855 A JP-A-2004-25018 JP 2001-252536 A

  An embodiment is to provide a membrane filtration device, a water producing device, and a cleaning method for a membrane filtration device that can eliminate clogging of a membrane module in a short time with high reliability.

  In order to solve the above problems, the membrane filtration device of the embodiment is a membrane filtration device that filters insoluble components in raw water from raw water with a membrane module, and eliminates clogging of the membrane module accompanying filtration, A water pump, a washing water pump, a drain pipe, a pressure difference detecting means, and a controller are provided. The washing water is sent to the membrane module by a washing water pump so as to flow from the secondary side to the primary side, and the sent washing water is discharged through a drain pipe connected to the primary side of the membrane module. A pressure difference detecting means detects a pressure difference between the primary side and the secondary side of the membrane module during filtration. The flow rate of washing water is controlled by the controller so that the detected pressure difference is kept constant, and this pressure difference is greater than the pressure difference between the primary and secondary sides of the membrane module during filtration and the pressure resistance of the membrane module It is characterized by controlling so as to be less than the range.

It is a schematic block diagram of the membrane filtration apparatus which concerns on 1st Embodiment shown with a reverse osmosis membrane module etc. It is a schematic block diagram of the membrane filtration apparatus which concerns on 2nd Embodiment shown with a reverse osmosis membrane module etc. It is a schematic block diagram of the membrane filtration apparatus which concerns on 3rd Embodiment shown with a reverse osmosis membrane module etc. It is a schematic block diagram which expands and shows a part of membrane filtration apparatus of FIG. It is a perspective view which shows the turning water flow formation member with which the membrane filtration apparatus of FIG. 3 is provided. It is a schematic block diagram of the membrane filtration apparatus which concerns on 4th Embodiment shown with a reverse osmosis membrane module etc. It is a schematic block diagram which expands and shows a part of membrane filtration apparatus of FIG. It is a perspective view which shows the injection member with which the membrane filtration apparatus of FIG. 6 is provided.

  Hereinafter, the membrane filtration device 5 according to the first embodiment, a cleaning method for the device, and the like will be described in detail with reference to FIG.

  A fresh water generator denoted by reference numeral 1 in FIG. 1 is composed of a system that desalinates raw water A, for example, seawater to produce product water C and the like. This fresh water generator 1 includes a raw water pump 2, a raw water tank 3, an injection device 4, a membrane filtration device 5, a high-pressure pump 6, a reverse osmosis membrane module 7, a power recovery pump 8, and a power recovery device. 9 is provided.

  The raw water pump 2 and the raw water tank 3 are facilities for supplying the raw water A to the membrane filtration device 5. The raw water pump 2 supplies the pumped raw water A to the raw water tank 3.

  The injection device 4 is disposed with respect to the raw water tank 3 and supplies the aggregate to the raw water tank 3 as necessary. The aggregating material is supplied to reduce the pressure difference between the raw water inlet and the filtrate outlet of the membrane filtration device 5. With this supply, the raw water in the raw water tank 3 is preferably stirred with a stirrer (not shown). Note that the injection device 4 and the stirrer can be omitted.

  The high-pressure pump 6 and the reverse osmosis membrane module 7 are facilities for desalting the filtrate G flowing out from the membrane filtration device 5.

  The high-pressure pump 6 supplies the filtered water G to the reverse osmosis membrane module 7 at a high pressure. The reverse osmosis membrane module 7 further filters the filtered water G and separates it into production water C that has been desalinated by desalting and water (concentrated water) B that has been concentrated to increase the salt concentration.

  The reverse osmosis membrane module 7 is preferably provided in a plurality of stages. In the case of periodically removing dirt adhered to a reverse osmosis membrane (not shown) included in the reverse osmosis membrane module 7, the reverse cleaning membrane is cleaned using a chemical.

  The power recovery pump 8 and the power recovery device 9 recover the high-pressure energy of the condensed water B, and assist the supply of the filtrate G discharged from the membrane filtration device 5 to the reverse osmosis membrane module 7. It is. Part of the high-pressure energy that the condensed water B has is recovered by the power recovery device 9. The power recovery pump 8 is driven using the recovered energy. Thereby, the filtrate water that has flowed out of the membrane filtration device 5 is supplied to the reverse osmosis membrane module 7 via the bypass pipe 10 that bypasses the high-pressure pump 6.

  Next, the membrane filtration device 5 disposed in the front stage of the reverse osmosis membrane module 7 will be described. The membrane filtration device 5 includes, for example, a membrane module 11, a water pump 13, a first pressure gauge 15, a second pressure gauge 17, a filtrate water tank 19, a washing water pump 21, a drain pipe 23, and a third. A pressure gauge 25, a return pipe 26, a flow meter 27, a controller 28, and a plurality of valves are provided.

  At least one, preferably a plurality of membrane modules 11, for example, two in FIG. 1 are prepared. Each membrane module 11 is formed by arranging a vertical container 11a and a filtration membrane 11b in the container 11a.

  An ME membrane or a UF membrane is used as the filtration membrane 11b. These ME membranes and UF membranes are made of aggregates of hollow fiber membranes, for example. Specifically, for example, several dozen to several hundred hollow fiber membranes having a diameter of about 1 mm are bundled. The filtration membrane 11b is built in the container 11a such that the direction in which the hollow fiber membrane extends coincides with the longitudinal direction of the container 11a, that is, the vertical direction.

  The container 11a has a raw water inlet (not shown) at its lower end. The raw water A is introduced into the container 11a from the raw water inlet so as to fill the space between the inner surface of the container 11a and the filtration membrane 11b. The container 11a has a filtered water outlet (not shown) at its upper end. The filtrate water outlet communicates with the inside of the hollow fiber membrane.

  Furthermore, the container 11a has a washing water outlet. A pipe connected to a later-described valve 38 is connected to the washing water outlet. For convenience of drawing, the washing water outlet is depicted in FIG. 1 as being disposed on the side surface of the container 11a, but this washing water outlet can also be disposed at the lower end of the container 11a.

  The raw water inlet of the container 11 a is connected to the raw water tank 3 through the raw water pipe 12. Since the two membrane modules 11 are prepared as described above, the raw water piping 12 is branched in conformity with the membrane modules 11, and the ends of the piping are connected to the raw water inlets of the membrane modules 11, respectively.

  A water supply pump 13, a first on-off valve 31, a second on-off valve 32, a first pressure gauge 15, and the like are attached to the raw water pipe 12.

  The water pump 13 can adjust the rotation speed. The first on-off valve 31 is disposed in a raw water suction pipe portion that connects the raw water tank 3 and the suction port of the water pump 13 in the raw water pipe 12. The second on-off valve 32 is disposed in a piping part connecting the discharge port of the water pump 13 and the raw water inlet of each membrane module 11 in the raw water pipe 12. In order to measure the primary pressure of the membrane module 11, that is, the pressure of the raw water A supplied to the membrane module 11, the first pressure gauge 15 is connected to the discharge port of the water pump 13 and the second in the raw water pipe 12. It is disposed in a piping part connected to the on-off valve 32.

  Two pipe ends branched from the filtrate pipe 33 are connected to the filtrate outlet of each membrane module 11. The filtrate water pipe 33 guides the filtrate water G flowing out from the membrane module 11 to the filtrate water tank 19.

A third on-off valve 35 is attached to each end of the filtered water pipe 33. At the same time, a fourth open / close valve 36 is attached to a portion of the filtrate water pipe 33 downstream of the third open / close valve 35. Further, the second pressure gauge 17 is attached to the filtrate water pipe 33. Specifically, the second pressure gauge 17 is disposed at, for example, a downstream portion of the third on-off valve 35 and an upstream portion of the fourth on-off valve 36. The second pressure gauge 17 measures the pressure on the secondary side of the membrane module 11, that is, the pressure of the filtrate water flowing through the filtrate water pipe 33. The washing water pump 21 can adjust the rotation speed. The washing water pump 21 is communicated with the secondary side of the membrane module 11 through the washing water pipe 22. For this purpose, for example, one end of the cleaning water pipe 22 is connected to the filtrate water tank 19. At the same time, the other end of the washing water pipe 22 is located upstream of the fourth on-off valve 36 of the filtrate water pipe 33, specifically, downstream of the third on-off valve 35 and upstream of the fourth on-off valve 36. It is connected to the side part. The other end of the cleaning water pipe 22 can be directly connected to the upper end portion of the container 11a of the membrane module 11 instead of the filtrate water pipe 33.

  A cleaning water pump 21 and a fifth on-off valve 37 are attached to the cleaning water pipe 22. The suction port of the washing water pump 21 communicates with the filtrate water tank 19. The fifth on-off valve 37 is disposed on the discharge side of the cleaning water pump 21.

  One end of the drain pipe 23 is connected to the washing water outlet of the membrane module 11. The other end (tip) of the drainage pipe 23 is disposed outside the membrane filtration device 5 and is open. The drainage pipe 23 discharges the discharged water from the primary side of the membrane module 11 to the outside of the membrane filtration device 5.

  A fifth on-off valve 38, a drain valve 39, a third pressure gauge 25, and monitoring means such as a flow meter 27 are attached to the drain pipe 23, respectively.

  The fifth on-off valve 38 is disposed at a portion of the drainage pipe 23 on the membrane module 11 side. The drain valve 39 is disposed at the tip side portion of the drain pipe 23. For example, a flow control valve is used as the drain valve 39. In the case where the return pipe 26 described later is omitted, an open / close valve can be used as the drain valve 39.

  The third pressure gauge 25 and the flow meter 27 are disposed on the downstream side of the fifth on-off valve 38 of the drainage pipe 23 and on the upstream side of the drainage valve 39.

  The third pressure gauge 25 measures the pressure of the water flowing through the drainage pipe 23, that is, the discharged water from the primary side of the membrane module 11.

  The flow meter 27 measures the amount of drainage flowing through the drainage pipe 23, converts the measured value into an electrical signal as information for monitoring the cleaning state of the membrane module 11, and outputs the electrical signal.

  The return pipe 26 communicates the drain pipe 23 and the suction port of the water pump 13. Specifically, one end of the return pipe 26 is connected to a pipe portion (raw water suction pipe portion) between the water supply pump 13 and the first on-off valve 31 in the raw water pipe. At the same time, the other end of the return pipe 26 is connected to a pipe portion between the third pressure gauge 25 and the drain valve 39 in the drain pipe 23. A seventh on-off valve 40 is attached in the middle of the return pipe 26.

  Each of the valves described above is a valve that is operated using a fluid such as electricity, air, or hydraulic pressure. Furthermore, each meter (a pressure gauge and a flow meter) changes the measured value into an electric signal having a value corresponding to the magnitude and outputs it.

  The controller 28 controls the overall operation of the fresh water generator 1. This control includes control for alternately performing the filtration of the raw water A and the cleaning for eliminating the clogging of the filtration membrane with respect to the membrane filtration device 5. In the membrane filtration device 5, the operation of each pump, the opening / closing of each on-off valve, the adjustment of the opening degree of the drain valve, etc. are controlled by the controller 28 based on the signal output from each instrument in real time and supplied to the controller 28. Be controlled.

  Next, the filtration operation of the membrane filtration device 5 will be described. In this operation, all of the first on-off valve 31, the second on-off valve 32, the third on-off valve 35, and the fourth on-off valve 36 are opened. The other on-off valves, that is, the fifth on-off valve 37, the sixth on-off valve 38, the drain valve 39, and the seventh on-off valve 40 are all closed. At the same time, the water pump 13 is operated, and the washing water pump 21 is stopped.

  Thereby, the raw water A stored in the raw water tank 3 is supplied from the primary side to the membrane module 11 via the raw water pipe 12, and the supplied raw water A is a hollow fiber forming the filtration membrane 11b of the membrane module 11. It is filtered through a membrane and flows out as secondary water G to the secondary side of the membrane module 11. Therefore, insoluble components in the raw water A are attached to the outer surface or pores of the hollow fiber membrane.

  On the other hand, the filtered water that has permeated the filtration membrane 11 b and flowed out to the secondary side of the membrane module 11 flows out of the membrane module 11. This filtrate G is stored in the filtrate tank 19 via the filtrate pipe 33.

  The filtrate G stored in the filtrate tank 19 by such filtration operation is used for fresh water generation. That is, the filtrate G is sent to the reverse osmosis membrane module 7 at a high pressure by the operation of the high pressure pump 6 of the fresh water generator 1. Thereby, the filtered water G is separated into product water C and condensed water B by the reverse osmosis membrane of the reverse osmosis membrane module 7.

  According to the filtration operation described above, the fouling factor substance composed of insoluble components is gradually deposited on the filtration membrane 11b of the membrane module 11, and the filtration membrane 11b is clogged.

  The degree of clogging can be known by a clogging determination unit included in the controller 28. That is, the clogging determination unit obtains a difference between the primary pressure value of the filtration membrane 11 b measured by the first pressure gauge 15 and the secondary pressure value of the filtration membrane 11 b measured by the second pressure gauge 17. . At the same time, the clogging determination unit compares a clogging determination threshold set in advance with the value of the difference. Then, when the difference value exceeds the threshold value, it is determined that the clogging has progressed to a predetermined state.

  Therefore, the first pressure gauge 15, the second pressure gauge 17, and the clogging determination unit of the controller 28 perform the first measurement for detecting the pressure difference between the primary side and the secondary side of the membrane module 11 during the filtration operation. It has a means. Note that the clogging determination unit can be provided separately from the controller 28, whereby the first measuring means can be provided independently of the controller 28.

  When the clogging progresses to a predetermined state, the difference value exceeds an allowable value defined by the pressure resistance of the filtration membrane 11b. Alternatively, the water pump 13 cannot secure the amount of water necessary for fresh water generation. In these cases, under the control of the controller 28, the filtration operation of the membrane filtration device 5 is stopped, and then the operation proceeds to a washing operation for eliminating clogging of the filtration membrane 11b of the membrane filtration device 5.

  As described above, the washing operation is performed by obtaining the back washing process, the water discharging process, and the water supply process. In the reverse cleaning process, the first on-off valve 31, the second on-off valve 32, the fourth on-off valve 36, and the seventh on-off valve 40 are all closed. The other on-off valves, that is, the third on-off valve 35, the fifth on-off valve 37, the sixth on-off valve 38, and the drain valve 39 are all opened. In this cleaning process, the cleaning water pump 21 is operated and the water pump 13 is maintained in a stopped state.

  For this reason, the filtrate G stored in the filtrate tank 19 is supplied as wash water from the secondary side to the filtration membrane 11b of the membrane module 11 via the wash water pipe 22 and the filtrate water pipe 33. .

  In this case, the controller 28 controls the number of rotations of the washing water pump 21 so that the pressure difference between the primary side and the secondary side of the membrane module 11 during filtration is greater than the pressure difference of the membrane module 11. The flow rate of the cleaning water sent to the secondary side of the membrane module 11 is controlled. In addition, the primary side and the secondary side of the filtration membrane 11b in such a reverse cleaning process are not based on the flow of the cleaning water, but are based on the flow of water in the filtering operation state.

  As described above, the flow rate of the cleaning water flowing through the filtration membrane 11b from the secondary side to the primary side is controlled by changing the rotation speed of the cleaning water pump 21 in real time. Thereby, the fouling factor substance adhering to the pores and the membrane surface of the filtration membrane 11b is pushed out to the primary side of the membrane module 11 by the washing water flowing through the filtration membrane 11b. The extruded substance is discharged from the inside of the container 11a of the membrane module 11 to the outside of the membrane filtration device 5 through the drain pipe 23.

  In such a reverse cleaning process, the amount of cleaning water flowing through the drain pipe 23 is monitored by a flow meter 27. The controller 28 ends the back washing process based on the signal output from the flow meter 27 in real time.

  For this purpose, the controller 28 has a flow rate determination unit in which, for example, a predetermined drainage flow rate value is set in advance as a threshold value as a reverse cleaning end determination unit for determining the end time of the reverse cleaning process. The flow rate determination unit compares the measurement value of the flow meter 27 input thereto with a threshold value, and determines that it is time to end the reverse cleaning when the measurement value (drainage flow rate) exceeds the threshold value. .

  That is, at the beginning of the reverse cleaning, the filtration membrane 11b is clogged with the fouling factor substance so that the pressure difference between the primary side and the secondary side is kept constant across the filtration membrane 11b. The amount of washing water required is small. However, as the clogging of the filtration membrane 11b progresses due to the reverse cleaning, the amount of cleaning water necessary to ensure the constant pressure difference gradually increases. As a result, the flow rate when clogging is resolved is set in advance as a threshold value, and the backwashing is completed by comparing whether or not the drainage flow rate measured reaches this set flow rate (threshold value). It is possible to determine when to perform.

  In addition, the threshold value in a flow volume determination part is determined as follows. For example, the pressure difference between the primary side and the secondary side at the boundary of the filtration membrane 11b and the washing water in a state where the fouling factor substance is not attached to the filtration membrane 11b or the initial adsorption of the filtration membrane 11b is completed. Find the relationship with the flow rate. And it can determine suitably from the set differential pressure | voltage at the time of backwashing with reference to the calculated | required relationship. In this case, pure water or the like may be used as the water for backwashing that passes through the membrane module 11.

  The flow meter 27 and the flow rate determination unit (backwashing end determination unit) constitute backwashing end determination means for determining the end timing of the backwashing process. Based on the determination result of the determination means, the controller 28 controls to end the cleaning process. Note that the backwashing end determination unit can be provided separately from the controller 28, whereby backwashing end determination means can be provided independently from the controller 28.

  As described above, in the reverse cleaning process, the controller 28 adjusts the rotation speed of the cleaning water pump 21 so that the pressure difference between the primary side and the secondary side of the filtration membrane 11b is kept constant. The flow rate of the washing water sent to the secondary side of the module 11 is controlled. In this case, the water flow pressure at the time of backwashing is maintained in a range that is equal to or greater than the pressure difference between the primary side and the secondary side of the membrane module 11 during filtration and less than the pressure resistance of the membrane module 11 as described above.

  The supply flow rate of the cleaning water at the time of such reverse cleaning is controlled by the controller 28 based on the measured values of the second pressure gauge 17 and the third pressure gauge 25.

  That is, the controller 28 has a pressure difference determination unit. The pressure difference determination unit firstly determines the pressure value on the secondary side of the filtration membrane 11b measured by the second pressure gauge 17 and the pressure value on the primary side of the filtration membrane 11b at the time of cleaning measured by the third pressure gauge 25. From these, the difference is obtained. Next, the pressure difference determination unit compares a pressure range defined by a preset first threshold for pressure determination and a second threshold having a higher set pressure value with the difference value. By this comparison, when the difference value is out of the pressure range, it is determined that the pressure difference during cleaning is not constant, and when the difference value is within the pressure range, the pressure difference during cleaning is constant. It is determined that

  Accordingly, the second pressure gauge 17, the third pressure gauge 25, and the pressure difference determination unit of the controller 28 are more accurately connected to the primary side of the membrane module 11 and the second side in the reverse cleaning process when the cleaning water pump 21 is operated. Second measuring means for detecting a pressure difference with the secondary side is provided. And based on the output of this 2nd measurement means, the controller 28 adjusts the rotation speed of the washing water pump 21 as mentioned above, and controls the flow volume of washing water. Note that the pressure difference determination unit can be provided separately from the controller 28, whereby the second measuring means can be provided independently of the controller 28.

  In the state where the washing water pump 21 is stopped and the back washing process is finished, the fouling factor substance separated from the filtration membrane 11b by the back washing stays on the primary side of the filtration membrane 11b in the container 11a of the membrane module 11. ing.

  Therefore, after the cleaning process, the controller 28 performs a water removal process. In this step, the membrane module 11 is drained through the drain pipe 23. By this drainage, the fouling factor substance is discharged out of the membrane module 11.

  Next, the controller 28 performs a water supply process. In this case, the first on-off valve 31, the second on-off valve 32, the sixth on-off valve 38, and the drain valve 39 are all opened, and other valves, that is, the third on-off valve 35, the fourth on-off valve 36, Both the fifth on-off valve 37 and the seventh on-off valve 40 are closed. At the same time, the state where the washing water pump 21 is stopped is maintained, and the water pump 13 is operated.

  Thus, the raw water A is supplied to the filtration membrane 11b from its primary side. Along with such water supply, the fouling factor substances remaining on the inner surface of the container 11 a and the filtration membrane 11 b are washed away with running water and further discharged through the drainage pipe 23.

  In this water supply process, in the first embodiment, it is possible to add a part of the discharged water from the membrane module 11 to the raw water A to increase the amount of water washed away to the filtration membrane 11b. In this case, the seventh open / close valve 40 is opened by the controller 28 and, preferably, the drain valve 39 is controlled so that the opening degree of the drain valve 39 is reduced to some extent. At the same time, the controller 28 increases the rotation speed of the water pump 13.

  Thereby, the amount of water sprayed upward with respect to the hollow fiber membrane which makes the filtration membrane 11b increases. For this reason, there exists an advantage that the washing-out effect of the fouling factor substance which entered the bundle of hollow fiber membranes becomes high.

  The clogging of the filtration membrane 11b can be eliminated by the cleaning operation described above. In this case, the reverse cleaning of the filtration membrane 11b is performed by controlling the flow rate of the washing water as described above to keep the pressure difference between the primary side and the secondary side of the filtration membrane 11b constant.

  Thereby, the fluctuation | variation of the washing | cleaning pressure required for the back washing | cleaning of the filtration membrane 11b is suppressed. For this reason, it is possible to eliminate clogging of almost all pores of the filtration membrane 11b in a short time and with sufficient reliability.

  That is, even if the clogging is resolved in the reverse cleaning, the cleaning pressure applied to some of the pores in which the clogging has not been resolved does not decrease, so that the filtration membrane 11b can be stably backwashed. It is.

  In this case, even if the cleaning water concentrates on the pores with which clogging has been eliminated, a constant washing pressure can be applied to the pores with which clogging has not been eliminated. . Therefore, it is possible to eliminate clogging of pores that have not been clogged.

  In addition, since the cleaning pressure does not decrease until the reverse cleaning is completed, it is possible to shorten the time required to sufficiently eliminate clogging.

  As described above, the membrane filtration device 5 having the above configuration can eliminate clogging of the filtration membrane 11b with high reliability in a short time regardless of the state of the fouling factor substance attached to the filtration membrane 11b. Is possible. Accordingly, the power cost of the washing water pump 21 can be reduced.

  Further, as described above, the amount of drainage flowing through the drainage pipe 23 is measured by the flow meter 27 in the back washing process. Based on this, it is possible for the controller 28 to monitor the state of fouling factor substances adhering to the filtration membrane 11b. Then, when the amount of drainage measured by the flow meter 27 becomes equal to or larger than a predetermined amount per unit time, the back washing process is ended by the controller 28.

  For this reason, it is possible to eliminate clogging of the filtration membrane 11b without excess or deficiency by back-washing the filtration membrane 11b regardless of the difference in the fouling factor substance adhering state to the filtration membrane 11b due to the water quality fluctuation of the raw water A. Is possible.

  In addition, as described above, the backwashing state is monitored and backwashing is stopped at an appropriate time. Therefore, the filtration membrane 11a is not excessively backwashed, and the filtration membrane 11b is minimally washed. It is possible to back-wash sufficiently.

  Along with this, it is possible to suppress wasteful consumption of the cleaning water (filtered water) used for the reverse cleaning, and it is possible to suppress a substantial reduction in processing capacity in the membrane filtration device 5. Further, as the back washing process for performing the back washing of the filtration membrane 11b is completed in the minimum necessary time as described above, the time occupied in the back washing process in each process executed by the membrane filtration device 5 The ratio is shortened. Therefore, the ability to process the raw water A in the membrane filtration device 5 also increases.

  In the first embodiment, water derived from filtered water, for example, condensed water B can be used as the washing water.

  FIG. 2 shows a second embodiment. The second embodiment is different from the first embodiment in the configuration described below, and the other configurations are the same as those in the first embodiment. For this reason, about the structure which show | plays the same or same function as 1st Embodiment, the code | symbol same as 1st Embodiment is attached | subjected and the description is abbreviate | omitted.

  In the second embodiment, a constant capacity pump is used as the washing water pump 21. Furthermore, in the second embodiment, a flow rate adjustment valve 29 is attached to the cleaning water pipe 22. The flow rate control valve 29 is disposed, for example, in a piping portion between the discharge port of the cleaning water pump 21 and the fifth on-off valve 37, but is disposed anywhere on the discharge side of the cleaning water pump 21. It may be provided. Therefore, in the configuration of the second embodiment in which a part of the filtrate water pipe 33 is used as the wash water pipe, the flow rate control valve 29 is disposed in a pipe portion of the filtrate water pipe 33 through which the wash water flows. It is also possible.

  The membrane filtration device 11 of the second embodiment has a second pressure gauge in order to maintain a constant pressure difference between the primary side and the secondary side of the filtration membrane 11b when the filtration membrane 11b is back-washed. The controller 28 adjusts the opening degree of the flow rate adjusting valve 29 instead of adjusting the rotational speed of the washing water pump 21 based on the output signals of the first pressure gauge 17 and the third pressure gauge 25. Thereby, the flow volume of the washing water sent to the membrane module 11 is controlled so that the pressure difference between the primary side and the secondary side of the filtration membrane 11b can be kept constant.

  In the second embodiment, the fifth on-off valve 37 can be omitted. In this case, when the fifth on-off valve 37 needs to be closed, the flow rate adjustment valve 29 may be fully closed under the control of the controller 28 so that water cannot flow through the flow rate adjustment valve 29.

  Furthermore, in 2nd Embodiment, it replaces with the flowmeter demonstrated in 1st Embodiment, and the water quality sensor 30 is used as a monitoring means. The water quality sensor 30 is attached to a piping part upstream of the drain valve 39 of the drain pipe 23. The water quality sensor 30 measures the concentration of the fouling factor substance contained in the waste water flowing through the drain pipe 23.

  Accordingly, the controller 28 has a water quality determination unit in which, for example, a predetermined concentration of the fouling factor substance in the drainage is set as a threshold value as the reverse cleaning end determination unit.

  The water quality determination unit compares the measurement result (concentration) input from the water quality sensor 30 with a threshold value in real time, and when the concentration falls below the set threshold value, the time to end the reverse cleaning is reached. It is determined that Therefore, the water quality sensor 30 and the reverse cleaning end determination unit constitute reverse cleaning end determination means for determining the end timing of the reverse cleaning step. Based on the determination result of the reverse cleaning end determination means, the controller 28 controls to end the reverse cleaning process.

  Since the filtration membrane 11b is clogged with the fouling factor substance at the beginning of the reverse cleaning for the filtration membrane 11b, the concentration of the fouling factor substance in the drainage through the drainage pipe 23 is high. However, this concentration gradually decreases as the clogging of the filtration membrane 11b progresses by backwashing.

  Therefore, by setting in advance as a threshold the concentration of the fouling factor substance when clogging has been resolved, and comparing whether the concentration of the fouling factor substance in the wastewater has reached this concentration, It is possible to determine when to finish the reverse cleaning. In this case, the fouling factor substance in the wastewater may be turbid or dissolved organic matter, but can be appropriately selected depending on the properties of the wastewater to be treated.

  The membrane filtration device 5 according to the second embodiment is the same as the first embodiment except for the configuration described above. Therefore, also in the second embodiment, the problem can be solved for the same reason as already explained in the first embodiment, and the clogging of the membrane module 11 can be solved with high reliability in a short time. It is.

  The water quality sensor 30 can be applied in place of the flowmeter in the first embodiment and the embodiments described below.

  3 to 5 show a third embodiment. The third embodiment is different from the first embodiment in the configuration described below, and the other configurations are the same as those in the first embodiment. For this reason, about the structure which show | plays the same or same function as 1st Embodiment, the code | symbol same as 1st Embodiment is attached | subjected and the description is abbreviate | omitted.

  The membrane filtration device 5 according to the third embodiment includes gas supply means 45 that inserts gas into the raw water A fed to the primary side of the membrane module 11. The gas supply means 45 includes, for example, a gas introduction pipe 46 and an opening / closing valve 47 attached to the gas introduction pipe 46.

  The gas introduction pipe 46 is branched upward from the raw water suction pipe portion of the raw water pipe 12 and its upper end is open. The on-off valve 47 is preferably an electromagnetic type that is controlled to open and close by the controller 28, for example, but may be a valve that is manually opened and closed. The on-off valve 47 is opened in the water supply process during the cleaning operation, and is kept closed except for this process.

  When the on-off valve 47 is opened in the water supply process, air is taken into the raw water A that is sent to the primary side of the filtration membrane 11b to wash away the filtration membrane 11b. Thus, the filtration membrane 11b is washed with the raw water A mixed with air.

  Thereby, the fouling factor substance remaining in the bundle of hollow fiber membranes forming the filtration membrane 11b can be efficiently removed by the scrubbing effect caused by bubbles. Therefore, when the membrane filtration device 5 moves to the next filtration operation after the washing operation, an increase in the differential pressure between the primary side and the secondary side of the filtration membrane 11b is suppressed, and thus stable filtration operation can be continued. It becomes.

  Furthermore, the membrane filtration device 5 according to the third embodiment includes a swirling water flow forming member 51 as a vibration means for shaking the hollow fiber membrane of the filtration membrane 11b. As shown in FIG. 4, the swirling water flow forming member 51 is built in a pipe portion between the second on-off valve 32 and the inlet of the membrane module 11 in the raw water pipe 12. Note that the swirling water flow forming member 51 may be disposed at the inlet of the membrane module 11 at a downstream side of the second on-off valve 32 instead of such a piping part.

  As shown in FIG. 5, the swirling water flow forming member 51 is formed of a plate material twisted by 180 degrees, for example. A swirling water flow forming member formed by twisting a plate material by 180 degrees or more can also be used. The swirling water flow forming member 51 is fixed in contact with the inner surface of the raw water pipe 12 and forms a water passage that is twisted between the swirling water flow forming member 51 and the inner surface of the raw water pipe 12.

  In the water supply process during the filtration operation and the washing operation, the raw water fed by the water pump 13 through the raw water pipe 12 and into the membrane module 11 is swirled on the primary side of the filtration membrane 11b by the swirling water flow forming member 51. . Thereby, the raw water A supplied upward into the membrane module 11 can be swung along the bundle of hollow fiber membranes forming the filtration membrane 11b. An image of such a swirling flow is indicated by an arrow in FIG.

  The swirled raw water A flows out to the secondary side of the filtration membrane 11b through the filtration membrane 11b while shaking the bundle of hollow fiber membranes. Thereby, the fouling factor substance remaining in the bundle of hollow fiber membranes forming the filtration membrane 11b is more efficiently removed.

  Therefore, it is possible to greatly reduce the fouling factor substances remaining in the bundle of hollow fiber membranes after the cleaning operation. Along with this, when the membrane filtration device 5 moves to the next filtration operation after the washing operation, an increase in the differential pressure between the primary side and the secondary side of the filtration membrane 11b is suppressed, and thus the stable filtration operation is continued. Is possible.

  As described above, in the membrane filtration device 5 according to the third embodiment, the water contained in the swirling water flow while swirling the raw fiber for washing and shaking the hollow fiber bundle of the filtration membrane 11b in the water supply process. The scrubbing effect is obtained, and the filtration membrane 11b is washed on its primary side. For this reason, the cleaning effect is high. However, one of the vibrating means for shaking the bundle of hollow fiber bundles of the filtration membrane 11b and the gas supplying means for mixing the gas into the washing water may be omitted.

  The membrane filtration device 5 according to the third embodiment is the same as the first embodiment except for the configuration described above. Therefore, also in the third embodiment, the above-described problem can be solved for the reason already described in the first embodiment, and the clogging of the membrane module 11 can be solved with high reliability in a short time.

  In addition, in 3rd Embodiment, although the hollow fiber membrane of the filtration membrane 11b is shaken also at the time of filtration, this does not give a problem to the filterability of the filtration membrane 11b. Moreover, in 3rd Embodiment, while forming separately the flow path for water flow for washing | cleaning so that the hollow fiber membrane of the filtration membrane 11b may not be shaken at the time of filtration, this flow path and the hollow fiber membrane of the filtration membrane 11b at the time of water supply There may be provided means for selecting one of the flow paths for swirling the raw water for washing so as to shake the water. With this selection of the selection means, it is possible to supply the raw water to the filtration membrane 11b through a flow path that does not rotate during filtration, and to supply the raw water to the filtration membrane 11b while turning during supply.

  6 to 8 show a fourth embodiment. The fourth embodiment is different from the first embodiment in the configuration described below, and the other configurations are the same as those in the first embodiment. For this reason, about the structure which show | plays the same or same function as 1st Embodiment, the code | symbol same as 1st Embodiment is attached | subjected and the description is abbreviate | omitted.

  The membrane filtration device 5 according to the fourth embodiment includes gas supply means 45 that inserts gas into the raw water A fed to the primary side of the membrane module 11. For example, the gas supply means 45 includes a gas introduction pipe 46, an on-off valve 47, and a gas tank 48.

  The gas introduction pipe 46 is branched upward from the raw water suction pipe portion of the raw water pipe 12. The on-off valve 47 is attached to an intermediate portion of the gas introduction pipe 46. The gas tank 48 is connected to the tip of the gas introduction pipe 46. The gas stored in the gas tank 48 is preferably a gas having a cleaning effect such as carbon dioxide. The on-off valve 47 is preferably an electromagnetic type that is controlled to open and close by the controller 28, for example, but may be a valve that is manually opened and closed. The on-off valve 47 is opened in the water supply process during the cleaning operation, and is kept closed except for this process.

  When the on-off valve 47 is opened in the water supply process, the gas flowing out from the gas tank 48 is taken into the raw water A that is sent to the primary side of the filtration membrane 11b to wash away the filtration membrane 11b. Thus, the filtration membrane 11b is washed with the raw water A mixed with the gas.

  Thereby, the fouling factor substance remaining in the bundle of hollow fiber membranes forming the filtration membrane 11b can be efficiently removed by the scrubbing effect caused by the gas bubbles. Therefore, when the membrane filtration device 5 moves to the next filtration operation after the washing operation, an increase in the differential pressure between the primary side and the secondary side of the filtration membrane 11b is suppressed, and thus stable filtration operation can be continued. It becomes.

  Furthermore, the membrane filtration device 5 according to the fourth embodiment includes an injection member 55 as a vibration means for shaking the hollow fiber membrane of the filtration membrane 11b. As shown in FIG. 8, the injection member 55 uses an injection tube provided with nozzle holes 56 at regular intervals along the longitudinal direction. The injection member 55 is disposed in the container 11a of the membrane module 11 along the vertical (vertical) direction, and the nozzle hole 56 is formed on the bundle of hollow fiber membranes forming the filtration membrane 11b from the side direction. Opposite.

  In the water supply process in the filtration operation and the washing operation, the raw water fed by the water pump 13 through the raw water pipe 12 and into the membrane module 11 passes through the nozzle hole 56 of the injection member 55 into the bundle of hollow fiber membranes. The bundle is injected so as to intersect with the extending direction. Preferably, it is injected so as to be orthogonal.

  An image of such a swirl flow is shown by arrows in FIGS. The raw water A thus sprayed onto the bundle of hollow fiber membranes flows out to the secondary side of the filtration membrane 11b through the filtration membrane 11b while shaking the bundle of hollow fiber membranes.

  Thereby, the fouling factor substance remaining in the bundle of hollow fiber membranes forming the filtration membrane 11b is more efficiently removed, and the fouling factor substance remaining in the bundle of hollow fiber membranes after the cleaning operation is removed. It can be greatly reduced. Therefore, when the membrane filtration device 5 moves to the next filtration operation after the washing operation, an increase in the differential pressure between the primary side and the secondary side of the filtration membrane 11b is suppressed, and thus stable filtration operation can be continued. It becomes.

  As described above, the membrane filtration device 5 according to the fourth embodiment injects the raw water for washing into the hollow fiber bundle of the filtration membrane 11b from the lateral direction in the water supply process, and shakes the bundle. Since the scrubbing effect due to the bubbles contained in the water flow is obtained and the filtration membrane 11b is washed on its primary side, the washing effect is high. However, one of the vibrating means for shaking the bundle of hollow fiber bundles of the filtration membrane 11b and the gas supplying means for mixing the gas into the washing water may be omitted.

  The membrane filtration device 5 according to the fourth embodiment is the same as the first embodiment except for the configuration described above. Therefore, also in this 4th Embodiment, the said subject can be solved for the reason already demonstrated in 1st Embodiment, and it is possible to eliminate clogging of the membrane module 11 with high reliability in a short time.

  In addition, in 4th Embodiment, although the hollow fiber membrane of the filtration membrane 11b is shaken also at the time of filtration, this does not give a problem to the filterability of the filtration membrane 11b. Moreover, in 4th Embodiment, while forming the flow path which does not spray raw water from the horizontal direction with respect to the filtration membrane 11b separately so that the hollow fiber membrane of the filtration membrane 11b may not shake at the time of filtration, You may provide the means to select either a path | route and the flow path which sprays raw | natural water from a horizontal direction with respect to the filtration membrane 11b so that the hollow fiber membrane of the filtration membrane 11b may be shaken at the time of water supply. With this selection of the selection means, it is possible to supply the raw water to the filtration membrane 11b through a flow path that does not shake during filtration, and to supply to the filtration membrane 11b through a flow passage that fluctuates during water supply. is there.

  In each of the above-described embodiments, the water discarded from the membrane module 11 is discharged through the cleaning water pipe 23 in the water discarding step. However, a waste water pipe for guiding the discarded water may be provided separately from the cleaning water pipe. It is preferable to connect the upper end of the drainage pipe to the bottom of the container 11b of the membrane module 11. Thereby, it is possible to drain water from the container 11b without using a drain pump.

  In this case, a part of the waste water pipe can also serve as a part of the raw water pipe 12. That is, the upstream side open / close valve and the downstream side open / close valve are respectively attached to the waste water pipe whose upper end is connected to the bottom surface of the container 11b based on the flow direction of the waste water passing through the waste water pipe. Further, the raw water pipe 12 is connected to a piping portion between the on-off valves, and the raw water valve is attached to the raw water pipe 12.

  With this piping configuration, at the time of filtration, both the raw water valve and the upstream on-off valve disposed closer to the container 11b than the downstream on-off valve are opened, and the water supply pump 13 is operated with the downstream on-off valve closed. By doing this, raw water can be sent into the membrane module 11. Moreover, at the time of water removal, while closing a raw | natural water valve and opening an upstream on-off valve and a downstream on-off valve, the water in the container 11b can be discharged | emitted through a waste water piping, without using a pump.

  Further, when a drain pipe for guiding water discarded from the membrane module 11 is provided separately from the washing water pipe, the drain pipe can be provided separately from the raw water pipe 12. That is, the 2nd on-off valve (raw water valve) 32 is attached in the middle of raw water piping 12, and the upper end part of this raw water piping 12 is connected to container 11b. A drain valve is attached in the middle of a drain pipe prepared separately from the raw water pipe 12, and the upper end of the drain pipe is connected to the bottom surface of the container 11 b of the membrane module 11. This piping configuration has the advantage that the number of valves used is small.

  With this piping configuration, during filtration, raw water can be fed into the membrane module 11 by opening the second on-off valve 32 and operating the water feed pump 13 with the drain valve closed. Moreover, at the time of wastewater, while closing the 2nd on-off valve 32 and opening a wastewater valve, the water in the container 11b can be discharged | emitted through a wastewater piping, without using a pump.

  Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope of the invention, and also included in the invention described in the claims and the equivalent scope thereof.

  DESCRIPTION OF SYMBOLS 1 ... Fresh water generator, 5 ... Membrane filtration apparatus, 6 ... High pressure pump, 7 ... Reverse osmosis membrane module, 11 ... Membrane module, 11a ... Container of membrane module, 11b ... Filtration membrane of membrane module, 12 ... Raw water piping, 13 ... water pump, 15 ... first pressure gauge (first measuring means), 17 ... second pressure gauge (first measuring means and second measuring means), 19 ... filtrate water tank, 21 ... wash water pump, 22 ... wash Water piping, 23 ... Drain piping, 25 ... Third pressure gauge (second measuring means), 26 ... Return piping, 27 ... Flow meter (monitoring means), 28 ... Controller, 29 ... Flow control valve, 30 ... Water quality sensor ( Monitoring means), 33 ... Filtration water piping, 39 ... Drain valve, 45 ... Gas introduction means, 46 ... Gas introduction pipe, 47 ... Open / close valve, 48 ... Gas tank, 51 ... Swirling water flow forming member (vibration means), 55 ... Injection member (vibration means), 56 ... injection hole, A ... Water, B ... condensed water, C ... product water, G ... filtered water

Claims (15)

A membrane module for filtering insoluble components in raw water;
A water pump that feeds raw water to be distributed from the primary side to the secondary side of the membrane module;
First measuring means for detecting a pressure difference between the primary side and the secondary side of the membrane module when performing the filtration;
A filtered water tank to which filtered water that has passed through the membrane module is supplied;
A wash water pump for sending filtered water stored in this filtrate water tank or water derived from this water as wash water so as to be circulated from the secondary side to the primary side to the membrane module;
A drainage pipe for guiding the drainage water from the primary side of the membrane module during operation of the washing water pump;
Second measuring means for detecting a pressure difference between a primary side and a secondary side of the membrane module during operation of the washing water pump;
The pressure difference detected by the second measuring means is kept constant, and the pressure difference is greater than the pressure difference between the primary side and the secondary side of the membrane module during filtration and less than the pressure resistance of the membrane module. A controller for controlling the flow rate of the wash water sent to the secondary side of the membrane module,
The membrane filtration apparatus characterized by comprising.   The apparatus further comprises monitoring means for monitoring the cleaning state of the membrane module, and the controller determines the completion of cleaning of the membrane module from the output of the monitoring means and stops the supply of cleaning water to the membrane module. The membrane filtration device according to claim 1.   The monitoring means is a flow meter that measures the flow rate of drainage flowing through the drainage pipe, the controller has a reverse cleaning end determination unit in which a flow rate threshold is set, and the drainage flow rate of the reverse cleaning end determination unit The membrane filtration device according to claim 2, wherein the controller stops the washing water pump when a threshold value is exceeded.   The monitoring means is a water quality sensor for measuring a concentration of a fouling factor substance contained in drainage flowing through the drainage pipe, and the controller has a backwashing end determination unit in which a concentration threshold is set, and the fouling The membrane filtration device according to claim 2, wherein the cleaning water pump is stopped when a concentration of a ring factor substance exceeds a threshold value of the reverse cleaning end determination unit.   The controller adjusts the number of rotations of the washing water pump based on the output of the second measuring means to control the flow rate of the washing water sent to the membrane module. The membrane filtration apparatus as described in any one of these.   A flow rate adjusting valve is provided in a piping system for guiding the cleaning water to the membrane module, and the controller adjusts the opening of the flow rate adjusting valve based on the output of the second measuring means, and is sent to the membrane module. The membrane filtration device according to any one of claims 1 to 4, wherein the flow rate of water is controlled.   The membrane module according to any one of claims 1 to 6, further comprising a vibration means that has a plurality of hollow fiber membranes in which filtration membranes of the membrane module are bundled, and shakes the filtration membrane. The membrane filtration apparatus described.   8. The membrane filtration device according to claim 7, wherein the vibrating means is a swirling water flow forming member that swirls raw water sent into the membrane module.   The vibration means is an injection member that is disposed in the membrane module and injects raw water sent into the membrane module into the bundle of hollow fiber membranes so as to cross the direction in which the bundle extends. 8. The membrane filtration device according to claim 7,   The membrane filtration device according to any one of claims 1 to 9, further comprising gas supply means for introducing a gas into the raw water fed to a primary side of the membrane module.   11. The membrane according to claim 10, wherein the gas supply unit includes a gas introduction pipe that communicates with a suction port of the water pump and is opened to the atmosphere, and an on-off valve attached to the introduction pipe. Filtration device.   The gas supply means has a gas introduction pipe communicated with a suction port of the water pump, a gas tank connected to the introduction pipe, and an on-off valve attached to the gas introduction pipe. Item 11. The membrane filtration device according to Item 10.   The apparatus further comprises a raw water pipe for guiding the raw water discharged from the water pump to the primary side of the membrane module, a return pipe for connecting the drain pipe, and an on-off valve attached to the return pipe. The membrane filtration device according to any one of Items 1 to 12. A membrane filtration device according to any one of claims 1 to 13,
A reverse cleaning membrane module having a reverse cleaning membrane;
A high-pressure pump for pumping filtrate in the filtrate tank provided in the membrane filtration device to the reverse cleaning membrane module;
A fresh water generator characterized by comprising: In the cleaning method of the membrane filtration device that eliminates clogging of the membrane module that filters insoluble components in the raw water sent by the water pump, by supplying cleaning water from the secondary side to the membrane module,
While sending the washing water using a washing water pump so as to circulate from the secondary side of the membrane module to the primary side, the sent washing water is discharged from the primary side of the membrane module,
Detecting the pressure difference between the primary side and the secondary side of the membrane module when performing the filtration,
While maintaining this pressure difference constant, the pressure difference of the membrane module is such that the pressure difference is greater than the pressure difference between the primary side and the secondary side of the membrane module during filtration and less than the pressure resistance of the membrane module. A method for cleaning a membrane filtration device comprising controlling a flow rate of cleaning water sent to a secondary side.

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