JP2013248607A - Membrane separator apparatus and membrane separation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane separator apparatus and a membrane separation method which can eliminate membrane clogging during an emergency period when clogging has developed and a transmembrane pressure difference increases.SOLUTION: A membrane separator apparatus 10 is configured such that raw water is made to flow into a tubular membrane 2 constituting a tube form, with the inside of a tube as a flow passage, and while a membrane surface is being cleaned, treated water is solid-liquid separated from raw water. During an emergency period when the pressure difference between an upper stream side and a lower stream side of a tubular membrane 2 exceeds a prescribed value P, churn flow is caused in the flow passage inside the cylinder of the tubular membrane 2 so that air bubbles having a shape like a collapsed longitudinal bullet are generated. Large and small various air bubbles are then forced to flow up in the tubular membrane 2 while keeping strong contact with the membrane surface.

Description

  The present invention relates to a membrane separation apparatus and a membrane separation method for performing solid-liquid separation of raw water and treated water using a filtration membrane.

  In recent years, membrane separation methods have received much attention in water treatment. In this membrane separation method, solid-liquid separation of conventional water treatment is performed with a membrane. By performing solid-liquid separation with a membrane, the treated water becomes clear and a sedimentation basin is not required, so that advantages such as the entire apparatus being compact can be obtained.

  However, in the membrane separation method, there is a problem that the clogging of the membrane proceeds and the amount of filtered water decreases when the operation time elapses. Therefore, membrane cleaning by gas-liquid two-phase flow is widely performed.

  As a method for cleaning a membrane by a gas-liquid two-phase flow, for example, in the cleaning of a membrane separation apparatus including a filtration membrane for separating treated raw water into sludge solids and treated water, the membrane on the upstream side and the downstream side of the membrane There is known a membrane surface cleaning method by gas-liquid two-phase flow in which the differential pressure is monitored with a pressure sensor and the amount of aeration air supplied to the diffuser is increased when the membrane differential pressure rises above a predetermined value (for example, , See Patent Document 1).

JP 2005-144291 A

  By the way, even when the membrane surface cleaning is performed as described above, there is a case where the membrane surface clogging progresses for some reason and the membrane differential pressure may increase, and sufficient filtration performance cannot be obtained. There's a problem. Therefore, it is desired to develop a cleaning method capable of eliminating the clogging of the membrane at the unsteady time when the membrane differential pressure increases due to the progress of such clogging.

  The present invention has been made in view of such circumstances, and provides a membrane separation apparatus and a membrane separation method capable of eliminating clogging of a membrane at the unsteady time when clogging progresses and a membrane differential pressure increases. The purpose is to provide.

  In order to solve the above-mentioned problems, the membrane separation apparatus according to the present invention is configured to flow into the tubular membrane having a tubular shape, using the inside of the tube as a flow path, to feed the raw water, wash the membrane surface, and simultaneously fix the raw water and the treated water. A membrane separation device for liquid separation, a differential pressure detecting means for detecting a differential pressure between the upstream side and the downstream side of the membrane, and an air for adjusting the ratio of the raw water gas by supplying air to the raw water flowing into the membrane Control for controlling the amount of air supplied by the air supply means so that a churn flow is generated in the flow path when the differential pressure detected by the supply means and the differential pressure detection means exceeds a preset value P Means.

  Further, the membrane separation method according to the present invention is a membrane separation in which raw water is introduced into a tubular membrane having a tubular shape, and the membrane surface is washed, and at the same time, the membrane surface is separated into raw water and treated water. A method for detecting a differential pressure between the upstream side and the downstream side of the membrane, an air supply step for adjusting the ratio of the raw water gas by supplying air to the raw water flowing into the membrane, Control for controlling the churn flow to be generated in the flow path by increasing the air supply amount in the air supply process when the differential pressure detected in the pressure detection process exceeds a preset value P. A process.

  According to such a membrane separation device and a membrane separation method, when the differential pressure between the upstream side and the downstream side of the tubular membrane exceeds the set value P, the churn flow is caused in the flow path formed in the tube of the tubular membrane. Will occur. When the churn flow is generated, bubbles having a shape in which the vertically long bullet-shaped bubbles are broken are generated, and various large and small bubbles are lifted up inside the tubular membrane while strongly contacting the membrane surface. Thereby, at the time of the non-stationary state where the film differential pressure increases due to the progress of clogging, it is possible to reinforce the cleaning power and eliminate clogging of the film.

  In addition, when the differential pressure detected by the differential pressure detection unit exceeds the set value P, the control unit supplies the air by the air supply unit so that the ratio of the raw water gas becomes 0.77 to 0.89. It is preferred to control the amount. In this case, when the differential pressure exceeds the set value P, a churn flow can be more suitably generated in the flow path. Therefore, the clogging of the film can be more reliably resolved by enhancing the cleaning power at the non-steady time.

  Here, the flow rate adjusting means for adjusting the flow rate of the raw water flowing into the membrane is provided, and the control means is the amount of the raw water flowing into the membrane when the differential pressure detected by the differential pressure detecting means exceeds the set value P. It is preferable to control the flow rate adjusting means so as to increase the flow rate. In this case, the membrane differential pressure rises due to the progress of clogging, and the amount of raw water flowing into the tubular membrane tube is controlled to increase in the non-steady state when the set value P is exceeded. Since the inside of the tubular membrane is raised while contacting the surface, the cleaning power can be further enhanced.

  Further, the control means supplies air by the air supply means so that the ratio of the raw water gas is 0.4 to 0.76 when the differential pressure detected by the differential pressure detection means is equal to or less than the set value P. It is preferred to control the amount. In this case, a vertically long bullet-shaped bubble is generated in the flow path in the tube of the tubular membrane, and the bubble rises in contact with the membrane surface so that it is pressed against the membrane surface, and a slight gap between the bubble and the membrane surface It is presumed that a strong shear force is generated when the raw water moves downward at a high flow rate in the opposite direction to the bubbles. Thereby, at the time of the steady state where the differential pressure of the membrane is equal to or less than the set value P, the cleaning power that suppresses the occurrence of clogging of the membrane is exhibited, and the running cost can be suppressed by reducing the gas ratio from the non-steady state. it can.

  According to the present invention, the clogging of the film can be eliminated by enhancing the cleaning power at the non-steady time when the clogging progresses and the film differential pressure increases.

It is a schematic block diagram which shows the water treatment apparatus provided with the membrane separation apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the relationship between the gas ratio (0.1-0.6) of the flow path of a tubular membrane, and bubble shape. It is a figure which shows the relationship between the gas ratio (0.70-0.75) of the flow path of a tubular membrane, and bubble shape. It is a figure which shows the relationship between the gas ratio (0.76-0.8) of the flow path of a tubular membrane, and bubble shape. It is a figure which shows the relationship between the gas ratio (0.88-0.91) of the flow path of a tubular membrane, and bubble shape. It is a flowchart which shows the operation | movement of the membrane separator in FIG. It is a schematic block diagram which shows the water treatment apparatus provided with the membrane separator which concerns on 2nd Embodiment of this invention.

  Hereinafter, preferred embodiments of a membrane separation apparatus and a membrane separation method according to the present invention will be described with reference to FIGS. Note that, in each drawing, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic configuration diagram showing a water treatment apparatus provided with a membrane separation apparatus according to the first embodiment of the present invention, and FIGS. 2 to 5 show the relationship between the gas ratio of the flow path of the tubular membrane and the bubble shape. FIG. 6 and FIG. 6 are flowcharts showing the operation of the membrane separation apparatus.

  As shown in FIG. 1, a water treatment apparatus 100 includes a tank 1 for introducing raw water, and a membrane separation apparatus provided outside the tank 1 and having an internal pressure tubular membrane (tubular membrane) 2 having a cylindrical shape. 10. The raw water is not particularly limited, and examples thereof include river water, raw water used for citation, sludge, and drainage.

  Raw water is introduced into the tank 1 through the line L1. A diffuser pipe (not shown) is provided in the lower part of the tank 1, and by performing aeration with this diffuser pipe, for example, biological treatment (sludge activation process) is performed on the raw water introduced into the tank 1, and organic matter Disassemble.

  The membrane separation device 10 includes the above-described tubular membrane 2, a circulation pump (flow rate adjusting means) 4 for supplying raw water from the tank 1 to the tubular membrane 2 and returning the raw water from the tubular membrane 2 to the tank 1. A blower (air supply means) 3 for supplying air to the raw water from 1, a suction pump 5 for sucking treated water from the tubular membrane 2, a pressure sensor 6 for detecting the pressure on the downstream side of the tubular membrane 2, A pressure sensor 7 for detecting the pressure on the upstream side of the tubular membrane 2 and a controller (differential pressure detection means; control means) 8 for controlling the operation of the blower 3 and the circulation pump 4 are provided.

  The tubular membrane 2 is a separation membrane for solid-liquid separation of raw water in the tank 1 outside the tank 1. The tubular membrane 2 of the present embodiment is, for example, a straw-like membrane having an inner diameter of several millimeters, and may be used in a normal membrane separation method. Polyolefin resins such as chlorinated polyethylene, polyfluorinated Examples thereof include a porous film formed from vinylidene resin, polytetrafluoroethylene resin, polypropylene, polyethylene, polystyrene, polyacrylonitrile, cellulose acetate, polysulfone, polyethersulfone, ceramic and the like.

  The tubular membrane 2 is placed vertically so as to extend in the vertical direction. In order to avoid complication of the drawing, only one tubular membrane 2 is shown in the drawing, but actually, for example, about 100 tubular membranes 2 are bundled together. The tank 1 is connected to the inlet at the lower end of each tubular membrane 2 through a line L2. The line L <b> 2 includes the circulation pump 4, and the raw water from the tank 1 is introduced into the tube of the tubular membrane 2 by driving the circulation pump 4.

  In addition, the outlet at the upper end of each tubular membrane 2 and the upper portion of the tank 1 are connected by a line L3 for returning the raw water solid-liquid separated on the membrane surface of the tubular membrane 2 into the tank 1. Yes.

  In addition, on the outer peripheral side of the tubular membrane 2, a line provided with the suction pump 5 so as to take out treated water solid-liquid separated from raw water on the membrane surface of the tubular membrane 2 to the outside of the tubular membrane 2. L4 is provided. Then, by driving the suction pump 5, the raw water from the tank 1 flows into the tube of the tubular membrane 2 in cooperation with the circulation pump 4 and is fixed from the inside to the outside of the tubular membrane 2. A flow in which the treated water separated from the liquid is led out through the flow line L4 is formed, and a so-called internal pressure type tubular membrane 2 is formed.

  The blower 3 is for supplying air to the raw water from the tank 1 flowing into the tubular membrane 2, and is connected in the middle of the line L2. By controlling the amount of air supplied by the blower 3, the gas ratio of the raw water flowing through the line L2 can be adjusted.

  The pressure sensor 7 is for detecting the pressure of the raw water passing through the upstream side of the tubular membrane 2 and is provided downstream of the connection position with the blower 3 in the line L2.

  The pressure sensor 6 is for detecting the pressure of the treated water passing through the downstream side of the tubular membrane 2, and is provided in the line L4.

  The controller 8 detects a differential pressure between the pressure on the upstream side of the tubular membrane 2 detected by the pressure sensor 7 and the pressure on the downstream side of the tubular membrane 2 detected by the pressure sensor 6. The controller 8 outputs a control signal to the blower 3 and the circulation pump 4 according to the detected differential pressure, and controls the operation of the blower 3 and the circulation pump 4.

  According to the water treatment apparatus 100 having such a configuration, raw water is introduced into the tank 1 through the line L1, and, for example, organic components in the raw water are decomposed by activated sludge (aerobic treatment). In this way, the raw water in the tank 1 is drawn out of the tank 1 through the line L2, supplied to the tubes of the numerous tubular membranes 2 constituting the tubular membrane unit, and moves (increases) in the tubes. In addition, the tubular membrane 2 separates the raw water and the treated water from each other.

  At this time, that is, at the same time as the raw water moves in the tube of the tubular membrane 2 and is solid-liquid separated, the membrane surface of the tubular membrane 2 is subjected to a shearing force due to the raw water, and the membrane surface is washed. The The treated water separated by the tubular membrane 2 is taken out through the line L4, and the raw water separated by the tubular membrane 2 and moving in the cylinder is returned to the tank 1 through the line L3.

  Thus, the shearing force by the raw water acts on the membrane surface of the tubular membrane 2, and the membrane surface of the tubular membrane 2 is washed, but the flow path 2a in the cylinder of the tubular membrane 2 (FIGS. 2 to 2) It has been confirmed by the present inventors that the cleaning effect varies depending on the gas ratio of the raw water flowing through (5). Here, the blower 3 provided in the upstream line L2 of the tubular membrane 2 is controlled so that the gas ratio of the sludge flowing through the flow path 2a in the cylinder of the tubular membrane 2 is 0.1, 0.2, While changing to 0.4, 0.6, 0.7 to 0.8, and 0.88 to 0.91, the shape of bubbles was observed, and the cleaning effect of the membrane surface of the tubular membrane 2 was confirmed. 2-5 is a figure which shows the relationship between the gas ratio in the flow path 2a, and bubble shape.

  As shown in FIG. 2A and FIG. 2B, when the gas ratio is 0.1 to 0.2, a bubble flow is formed in which small bubbles rise in the flow path 2a. In addition, as shown in FIGS. 2 (c), 2 (d), 3 (a) to (f), and 4 (a), when the gas ratio is 0.4 to 0.76, In the path 2a, a slug flow is generated in which a vertically elongated bullet-shaped bubble A is generated. When this slag flow is generated, the bubble A rises while being pressed against the membrane surface, and as the bubble A rises, sludge is bubbled through a slight gap between the bubble A and the membrane surface. It is estimated that a strong shearing force is generated by moving downward in the direction opposite to A. Clogging can be suppressed by this slag flow.

  Moreover, as shown in FIGS. 4B to 4E, when the gas ratio is 0.77 to 0.8, the lower end of the bubble is collapsed, and various large and small bubbles are generated from the slag flow. Transition to mixed churn flow. Moreover, as shown to Fig.5 (a) and (b), when a gas ratio is 0.88-0.89, the churn flow in which various small and large bubbles are mixed generate | occur | produces. When this churn flow is generated, a vertically long bullet-shaped bubble A is generated, and bubbles inside the tubular membrane 2 rise while the large and small bubbles are in strong contact with the membrane surface. Become. By this churn flow, the cleaning power can be further strengthened and clogging can be eliminated.

  Further, as shown in FIGS. 5C and 5D, when the gas ratio is 0.90 to 0.91, the flow of bubbles completely disappears, and the center of the flow path 2a becomes almost gas, and the cleaning effect is obtained. An annular flow that cannot be expected occurs.

  Based on such a relationship of the cleaning power depending on the gas ratio, the membrane separation apparatus 10 of the present embodiment performs the following processing. FIG. 6 is a flowchart showing the processing operation of the membrane separation apparatus 10 by the controller 8. First, the clogging of the membrane surface of the tubular membrane 2 has not progressed, the differential pressure between the upstream side and the downstream side of the tubular membrane 2 has not increased, and the differential pressure is set to a preset value P In the following steady state, steady operation is performed (S1). At this time, the blower 3 is controlled so that the ratio of the gas flowing into the tubular membrane 2 is 0.4 to 0.76, and cleaning with the slag flow is performed, and at the same time, the solid water is separated from the treated water.

  Then, the differential pressure between the upstream side and the downstream side of the tubular membrane 2 is detected by the pressure sensors 6 and 7 (S2). The process of S2 corresponds to a differential pressure detection process.

  Next, it is determined whether or not the differential pressure detected in S2 is larger than a preset value P (S3). Here, when the membrane surface of the tubular membrane 2 is not clogged and the pressure difference between the upstream side and the downstream side of the tubular membrane 2 is equal to or less than the set value P, the process proceeds to S2. Repeated detection of return differential pressure. On the other hand, when the clogging of the membrane surface of the tubular membrane 2 proceeds, the differential pressure between the upstream side and the downstream side of the tubular membrane 2 increases, and it is determined that the differential pressure is unsteady when the differential pressure is larger than the set value P. To S4.

  In S4, the circulation amount and gas ratio of the raw water are increased. That is, the circulation pump 4 and the blower 3 are controlled to increase the amount of raw water flowing into the tubular membrane 2, and the ratio of the raw water gas flowing into the tubular membrane 2 is 0.77 to 0.89. The amount of air supplied by the blower 3 is controlled so that a churn flow is generated. In this way, a churn flow is generated in the flow path 2a (see FIGS. 4 (b) to (e), FIGS. 5 (a) and 5 (b)), and a vertically long bullet-shaped bubble A is generated. Then, the inside of the tubular membrane 2 is raised while strongly contacting various large and small bubbles with the membrane surface. As a result, the detergency is strengthened from the slag flow at the normal time, and clogging is eliminated. The process of S4 corresponds to an air supply process, a flow rate adjustment process, and a control process.

  Next, similarly to S2, a differential pressure between the upstream side and the downstream side of the tubular membrane 2 is detected (S5), and it is determined whether or not the detected differential pressure is equal to or less than a preset value P. (S6). In this case, the clogging of the membrane surface of the tubular membrane 2 has not been eliminated, and the differential pressure between the upstream side and the downstream side of the tubular membrane 2 has been increased and is not at or below the set value P. Returning to S5, the detection of the differential pressure is repeated. On the other hand, when the clogging of the membrane surface of the tubular membrane 2 is eliminated and the differential pressure between the upstream side and the downstream side of the tubular membrane 2 decreases and is equal to or less than the set value P, the process proceeds to S7. .

  In S7, the circulation pump 4 and the blower 3 are controlled to return the circulation amount and gas ratio of the raw water to the initial state, and the ratio of the raw water gas flowing into the tubular membrane 2 becomes 0.4 to 0.76. The amount of air supplied by the blower 3 is controlled so that a slag flow is generated.

  As described above, according to the membrane separation device 10 of the first embodiment, when the differential pressure between the upstream side and the downstream side of the tubular membrane 2 exceeds the set value P, the tubular membrane 2 is placed in the cylinder. A churn flow is generated in the formed flow path, creating bubbles that are shaped like a vertically elongated bullet-like bubble collapsed, and the bubbles inside the tubular membrane 2 rise while the large and small bubbles are in strong contact with the membrane surface. Therefore, when the membrane differential pressure increases due to the progress of clogging, the cleaning power can be strengthened to eliminate the clogging of the membrane.

  In addition, when the differential pressure exceeds the set value P, the controller 8 controls the amount of air supplied by the blower 3 so that the ratio of the raw water gas is 0.77 to 0.89. Thus, the churn flow can be generated more suitably. Therefore, the clogging of the film can be more reliably resolved by enhancing the cleaning power at the non-steady time.

  Moreover, the circulation pump 4 which adjusts the flow volume of the raw | natural water which flows into the tubular membrane 2 is provided, and the controller 8 is the quantity of the raw | natural water which flows into the tubular membrane 2 in the case of the unsteady time when a differential pressure exceeds the setting value P. Since the circulation pump 4 is controlled so as to increase the amount of raw water flowing into the cylinder of the tubular membrane 2 at the non-steady time when the membrane differential pressure increases due to the progress of clogging, more raw water is The inside of the tubular membrane 2 is raised while contacting the membrane surface, and the cleaning power can be further enhanced.

  Further, the controller 8 controls the amount of air supplied by the blower 3 so that the ratio of the raw water gas is 0.4 to 0.76 in the steady state where the differential pressure is equal to or less than the set value P. In the tube of the tubular membrane 2, a vertically long bullet-shaped bubble A is generated and rises in contact so that the bubble A is pressed against the membrane surface, and a slight gap is formed between the bubble A and the membrane surface. It is presumed that a strong shearing force is generated when the raw water moves downward at a high flow rate opposite to the bubbles A. As a result, at the time of steady state where the differential pressure of the membrane does not increase, the cleaning power that suppresses the occurrence of clogging of the tubular membrane 2 is exhibited and the running cost is suppressed by reducing the gas ratio from the unsteady state. Can do.

  Next, the membrane separation apparatus 20 of 2nd Embodiment is demonstrated, referring FIG. The membrane separator 20 of the second embodiment is different from the membrane separator 10 of the first embodiment in that two blowers connected to the line L2 and supplying air to the raw water passing through the line L2 are used instead of the blower 3. 13a and 13b are connected in parallel, and instead of the circulation pump 4, two circulation pumps 14a and 14b provided in parallel with each other are connected to the line L2.

  The blower 13a and the circulation pump 14a always operate, and the blower 13b and the circulation pump 14b receive a control signal from the controller 8 so that the differential pressure between the upstream side and the downstream side of the tubular membrane 2 is the set value P. It works only when it exceeds.

  About the operation | movement of the membrane separator 20, the processing content of S1, S4, and S7 shown in FIG. 6 differs from 1st Embodiment, and other points are the same as that of 1st Embodiment. In the second embodiment, in S1, only the blower 13a and the circulation pump 14a operate, and the blower 13b and the circulation pump 14b are stopped. At this time, the gas ratio of the raw water flowing into the tubular membrane 2 is 0.4 to 0.76.

  In S4, the circulating pump 14b and the blower 13b that have been stopped are operated to increase the amount of raw water flowing into the tubular membrane 2, and the ratio of the raw water gas flowing into the tubular membrane 2 is 0.77 to The amount of air supplied by the blower 13b is controlled to be 0.89.

  In S7, the circulation pump 14b and the blower 13b are stopped so that only the circulation pump 14a and the blower 13a operate. Thus, the amount of raw water flowing into the tubular membrane 2 is returned, and the amount of air supplied to the raw water is controlled so that the ratio of the raw water gas flowing into the tubular membrane 2 is 0.4 to 0.76. .

  As described above, according to the membrane separation device 20 of the second embodiment, when the differential pressure between the upstream side and the downstream side of the tubular membrane 2 exceeds the set value P, the ratio of the raw water gas is 0.77 to 0.89. Since the ratio of the raw water gas is controlled to be 0.4 to 0.76 when the differential pressure is equal to or less than the set value P, the same effect as in the first embodiment is obtained. can get.

  As described above, the present invention has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment. For example, in the above embodiment, the circulation pump 4 is disposed on the upstream side of the tubular membrane 2. Although provided in the line L2, it may be provided in the line L3 on the downstream side of the tubular membrane 2.

  Moreover, in the said embodiment, as especially preferable, when the differential pressure | voltage of the upstream and downstream of the tubular membrane 2 exceeds preset value P, both the amount of raw | natural water and a gas ratio are increased, and differential pressure is set value. In the case of P or less, both the amount of raw water and the gas ratio are restored to the original, but not limited to this, when the differential pressure exceeds the set value P, only the gas ratio is increased and the differential pressure is set to the set value. In the case of P or less, only the gas ratio may be restored.

  Moreover, in the said embodiment, although the membrane separation apparatus 10 and 20 applied to the water treatment apparatus 100 of a tank outside type was demonstrated as being especially preferable, it is not restricted to this, It applies to a submerged type (integrated type, tank separate type). It may be a membrane separation device.

  DESCRIPTION OF SYMBOLS 1 ... Tank, 2 ... Tubular membrane (tubular membrane), 2a ... Flow path, 3, 13a, 13b ... Blower, 4, 14a, 14b ... Circulation pump, 5 ... Suction pump, 6, 7 ... Pressure sensor, 8 ... Controller, 10, 20 ... Membrane separator, A ... Bubble.

Claims (5)

A membrane separation device for solid-liquid separation into the raw water and treated water at the same time as washing the membrane surface by flowing the raw water into the tubular membrane that forms a cylinder, using the inside of the cylinder as a flow path,
Differential pressure detecting means for detecting a differential pressure between the upstream side and the downstream side of the membrane;
Air supply means for adjusting the ratio of the raw water gas by supplying air to the raw water flowing into the membrane;
Control means for controlling the amount of air supplied by the air supply means so that a churn flow is generated in the flow path when the differential pressure detected by the differential pressure detection means exceeds a preset value P. When,
A membrane separation apparatus. The control means uses the air supply means so that when the differential pressure detected by the differential pressure detection means exceeds the set value P, the ratio of the raw water gas becomes 0.77 to 0.89. Control air supply,
The membrane separator according to claim 1. A flow rate adjusting means for adjusting the flow rate of the raw water flowing into the membrane;
The control means controls the flow rate adjusting means so as to increase the amount of the raw water flowing into the membrane when the differential pressure detected by the differential pressure detection means exceeds the set value P.
The membrane separator according to claim 1 or 2. When the differential pressure detected by the differential pressure detection means is equal to or less than the set value P, the control means uses the air supply means so that the ratio of the raw water gas is 0.4 to 0.76. Control air supply,
The membrane separation apparatus as described in any one of Claims 1-3. A membrane separation method for solid-liquid separation into the raw water and treated water at the same time as washing the membrane surface by flowing raw water into the tubular membrane that forms a cylinder, using the inside of the cylinder as a flow path,
A differential pressure detection step of detecting a differential pressure between the upstream side and the downstream side of the membrane;
An air supply step of adjusting the ratio of the gas of the raw water by supplying air to the raw water flowing into the membrane;
When the differential pressure detected in the differential pressure detection step exceeds a preset set value P, the amount of air supplied in the air supply step is increased so that a churn flow is generated in the flow path. A control process to control,
A membrane separation method.

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