JP4867180B2 - Immersion membrane separator and chemical cleaning method therefor - Google Patents

Description

  The present invention relates to an immersion type membrane separation apparatus used for various water treatments, particularly separation of activated sludge and membrane filtration of natural water such as river water, and a chemical cleaning method for the immersion type membrane separation apparatus.

  The submerged membrane separation device that places membrane modules in the water tank and filters the water to be treated in the water tank is widely used in various water treatment fields such as activated sludge separation and membrane water filtration of natural water such as river water. It has become. In such a submerged membrane separator, the driving pressure for membrane filtration is often generated by making negative pressure with a suction pump, but the method of using the difference in gravity by utilizing the water level of the water tank is also practical. It has become. Regarding the shape of the membrane module, a system in which a flat membrane or a hollow fiber membrane is arranged in the water tank in various forms is adopted. In addition, since the membrane is basically a solid-liquid separation operation, those having a pore size capable of separating the particles to be separated are used, such as microfiltration (MF) membrane, ultrafiltration (UF) membrane, nano A filtration (NF) membrane or the like is properly used according to the separation target.

  In addition, in order to suppress membrane fouling, an operation in which bubbles are diffused from below the membrane module and the membrane module is immersed continuously or intermittently under a gas-liquid two-phase flow has been put into practical use.

  However, if the film fouling cannot be recovered even when such a gas-liquid two-phase flow is applied, chemical cleaning of the film is required.

Conventionally, as a chemical cleaning method for a submerged membrane separator, a method in which a membrane module is placed in a water tank and a cleaning chemical is added to the water tank so that the membrane module is immersed in the water tank; A method in which the cleaning chemical flows backward from the secondary side of the membrane module to the primary side in a state where the membrane is immersed (Japanese Patent No. 3488535); or the membrane module is taken out of the water tank and transferred to a separate chemical cleaning tank In this tank, a chemical cleaning method is employed.
Japanese Patent No. 3488535

  However, the method of adding chemicals into the water tank not only requires a large amount of chemicals, but also has a problem that a large amount of cleaning waste liquid is generated. Further, in the method in which the cleaning chemical is caused to flow backward from the secondary side of the membrane module, there is a problem that a sufficient chemical cleaning effect cannot be expected because the chemical is diluted with the water to be treated stored in the water tank. This method also generates a large amount of cleaning waste liquid. In addition, the method of transferring to a separately provided chemical cleaning tank requires a special cleaning facility and also requires a process and means for transferring the membrane module, and is not suitable for a large-scale facility.

  The present invention solves the above-mentioned conventional problems, and can perform a chemical cleaning of a membrane module efficiently and with a simple method without requiring special equipment or work, and can reduce the amount of cleaning waste liquid. The purpose is to provide.

The submerged membrane separator of the present invention (Claim 1) is a submerged membrane separator in which a membrane module is disposed in a water tank, and the water to be treated in the water tank is subjected to membrane filtration with a suction pressure and / or gravity difference. A cleaning chemical injection means for injecting a cleaning chemical into the secondary side of the membrane and leaching out to the primary side, and a treated water discharge means for discharging the treated water in the water tank to the outside of the tank, the treated water when discharged to almost completely outside of the tank water to be treated by the discharge means, the treated water in the water tank is lowered and when the upper portion of the membrane of the membrane module is exposed on the water surface, the cleaning agent When the injection of cleaning chemical is started by the injection means and leached to the primary side, and the cleaning chemical leached to the primary side flows down the membrane surface, the water surface to be treated in the water tank descends, and the water to be treated in the water tank is almost Inject the cleaning chemical with the cleaning chemical completely discharged and leached to the primary side flowing down the membrane surface. Abolish a submerged membrane separator that is configured to so that the air diffuser means provided in the lower part of the membrane module in the water tank, said with the discharge of the water to be treated by the treatment water discharge means The present invention is characterized in that the bubble flow is supplied to the film surface by the air diffused by the air diffuser .

Submerged membrane separator in 請 Motomeko 2 Oite to claim 1, wherein the membrane module is characterized in that the film surface is arranged to be substantially the vertical direction.

The submerged membrane separator according to claim 3 is the submerged membrane separator according to claim 1 or 2 , wherein the cleaning chemical is sulfuric acid, hydrochloric acid, nitric acid, oxalic acid, citric acid, ascorbic acid, sodium hydroxide, sodium hypochlorite, peroxidation. 1 type or 2 or more types chosen from the group which consists of hydrogen, an enzyme, and surfactant are characterized by the above-mentioned.

The chemical cleaning method for the submerged membrane separation apparatus according to the present invention (Claim 4 ) is a submerged membrane in which a membrane module is placed in a water tank and the water to be treated in the water tank is subjected to membrane filtration with a suction pressure and / or a gravity difference. in chemical cleaning method of the separation apparatus, the treated water in the water tank when almost discharged completely outside the tank, the treated water in the water tank is lowered, on the upper part the water surface of the membrane of the membrane module When exposed, the injection of cleaning chemical to the secondary side of the membrane is started and leached to the primary side, and when the cleaning chemical leached to the primary side flows down the membrane surface, the water surface to be treated in the water tank It is a chemical cleaning method for a submerged membrane separator that descends, the treated water in the water tank is almost completely discharged, and the injection of the cleaning chemical is stopped while the cleaning chemical leached to the primary side flows down the membrane surface. Aeration means is provided at the lower part of the membrane module in the water tank, and the treated water in the water tank is stored in the tank. During the discharged outside, characterized that you feed the bubble flow to the film surface to air diffusion from the diverging air device.

Chemical cleaning method of the submerged membrane separator in 請 Motomeko 5, in claim 4, wherein the membrane module is characterized in that the film surface is arranged to be substantially the vertical direction.

The chemical cleaning method for the submerged membrane separation apparatus according to claim 6 is the method according to claim 4 or 5 , wherein the cleaning chemical is sulfuric acid, hydrochloric acid, nitric acid, oxalic acid, citric acid, ascorbic acid, sodium hydroxide, hypochlorous acid. It includes one or more selected from the group consisting of sodium, hydrogen peroxide, enzyme, and surfactant.

  According to the submerged membrane separation apparatus and the chemical cleaning method of the present invention, the membrane module can be efficiently cleaned with a simple method without requiring special equipment and work, and the amount of cleaning waste liquid Can also be greatly reduced.

  That is, in the present invention, the water to be treated in the water tank is discharged to the outside of the water tank, and when a part of the membrane of the membrane module is exposed on the water surface, injection of the cleaning chemical into the secondary side of the membrane is started. Therefore, the cleaning chemical supplied from the secondary side of the membrane and leached to the primary side is hardly diluted with the water to be treated in the water tank. That is, cleaning chemicals injected into the secondary side of the membrane preferentially leached from the membrane portion exposed on the water surface to the primary side of the membrane, so that most of the chemical leached on the membrane surface is in contact with the water to be treated. It is held on the film surface without flowing, and then flows down. For this reason, a high chemical cleaning effect can be obtained with a cleaning chemical having a sufficient concentration. Moreover, since the water to be treated discharged from the water tank is hardly mixed with chemicals, it does not become a cleaning waste liquid and can be treated again as water to be treated, and can also be discharged as it is depending on the water quality. .

  Further, when the chemical treatment is performed, the water to be treated in the water tank is discharged, and the physical action when the treated water surface descends from the membrane surface is given to the membrane surface leaching the chemical, the membrane surface Deposits are peeled off and a good cleaning effect is obtained.

  In the present invention, when the water to be treated in the water tank is discharged and a part of the membrane is exposed on the water surface, it is extremely important to start injecting the cleaning chemical into the secondary side of the membrane. In the method of Patent Document 1 described above, in which the cleaning chemical is injected from the secondary side of the membrane while the water to be treated is held in the water tank, the chemical leached to the primary side is diluted with the water to be treated, which is good. A chemical cleaning effect cannot be obtained, and a large amount of cleaning waste liquid is generated. On the other hand, prior to injecting the cleaning chemical into the secondary side of the membrane, if the water to be treated in the water tank is discharged and the entire membrane module is exposed to the atmosphere, it will be apparent from the results of Comparative Example 2 described later. As such, a sufficient cleaning effect cannot be obtained. This is because even if the deposit remains attached to the membrane surface, even if the cleaning chemical is injected into the secondary side of the membrane under the gas phase, the cleaning chemical does not leach evenly over the entire membrane surface. This is because the cleaning chemicals are leached non-uniformly only from the easily leaching part of the film, so that a sufficient cleaning effect cannot be obtained over the entire film surface.

In the present invention, the treatment water in the water tank is discharged, and when a part of the film is exposed on the water surface, the injection of the cleaning chemical into the secondary side of the film is, for example, described later. In the submerged membrane separation apparatus shown in FIG. 1, when the valve V ₆ is opened and the pump P is operated to inject the chemical solution in the chemical solution storage tank 5 into the secondary side of the membrane module 2, the valve V ₄ is opened in advance. as extracts the water to be treated in the water tank 1, when the water level in the water tank 1 reaches the film top of the membrane module 2, actuates the pump P, refers to the valve V ₆ is opened, therefore, When the chemical | medical solution inject | poured into the secondary side of the film | membrane leaches out to the primary side of a film | membrane, it points out that the film | membrane surface of the said leaching part exists above the to-be-processed water surface.

In the present invention, when discharging the water to be treated from the water tank, air is diffused from the air diffuser below the membrane module, and a bubble flow (gas-liquid two-phase flow) is imparted to the membrane surface. Ru it is possible to obtain a cleaning effect.

In addition, the membrane module is preferably arranged so that the membrane surface is in a substantially vertical direction, so that the cleaning chemical leached from the membrane surface is evenly applied to the membrane while flowing down the membrane surface. As a result, a high cleaning effect can be obtained. Also, when the water to be treated is discharged under the diffused air from the air diffuser, the surface of the water to be treated waved by the bubbling flow descends the film surface, and the bubble bursts at the gas-liquid interface or the gas-liquid interface. A high physical cleaning effect is obtained by applying a shearing force generated by rocking to the film surface, and the film surface deposit is efficiently peeled off by a synergistic effect with the chemical cleaning effect caused by the flow of cleaning chemicals. (Claims 2 and 5 ).

In the present invention, the chemicals used for washing are preferably sulfuric acid, hydrochloric acid, nitric acid, oxalic acid, citric acid, ascorbic acid, sodium hydroxide, sodium hypochlorite, hydrogen peroxide, enzyme, surfactant, etc. Terms 3 and 6 ).

  Embodiments of a submerged membrane separation apparatus and a chemical cleaning method thereof according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a system diagram showing an embodiment of a submerged membrane separation apparatus according to the present invention.

Reference numeral 1 denotes a water tank into which water to be treated is introduced, and the membrane module 2 is immersed in the tank. A diffuser tube 3 is provided below the membrane module 2 in the water tank 1. 4 filtered water (treated water) tank, 5 is a chemical storage tank, each symbol piping 11 to 18, P is a pump (suction and washing _{pump), V 1, V 2,} V 3, V 4, V 5 , _{V 6} represents the opening and closing valve.

  As described above, in such a submerged membrane separator, the driving pressure for membrane filtration is usually generated by making a negative pressure with a suction pump as shown in FIG. It may be due to the gravity difference. Moreover, it can also be set as both combined use.

  As for the shape of the membrane module, any method may be used as long as a flat membrane or a hollow fiber membrane is arranged in the water tank in various shapes. However, as described above, a method in which the membrane surface is installed vertically is preferable. Regarding the type of membrane, in order to perform the solid-liquid separation operation, those having a pore size capable of separating the particles to be separated are used, but MF membranes, UF membranes, NF membranes, etc. may be used properly according to the separation subject. it can.

  The membrane filtration operation and chemical cleaning operation in the submerged membrane separator shown in FIG. 1 will be described below.

<Membrane filtration operation>
The valves V ₁ , V ₂ , V ₃ are opened, the valves V ₄ , V ₅ , V ₆ are closed, the pump P is operated, and the water to be treated in the water tank 1 introduced from the pipe 11 is supplied by the suction pump P. The membrane is filtered by the membrane module 2 with the driving pressure, and the filtered water is stored in the filtered water tank 4 through the pipes 12 and 13.

  This membrane filtration operation is an intermittent operation in which the membrane filtration is stopped for a predetermined time, for example, 0.5 to 10 minutes, after performing the membrane filtration for a predetermined time, for example, 5 to 120 minutes by intermittently operating the suction pump P. It is good as driving. Further, during the membrane filtration stop period, air bubbles from the air diffuser 3 below the membrane module 2 may be brought into contact with the bubble surface to remove the membrane surface deposits.

Further, after such membrane filtration operation is performed for a predetermined time, for example, 0.5 to 24 hours, the pump P is stopped, the valve V _{1 is} closed, and the valve V _{4 is} opened to pipe the water to be treated in the water tank 1. once discharged from 17, then again the valve V ₄ is closed, the reservoir water to be treated in the water tank 1 is opened valves V _1, may be resumed membrane filtration operation. When discharging the water to be treated, a good physical cleaning effect can be obtained by performing air diffusion from the air diffusion tube 3 and bringing a bubble flow into contact with the membrane surface. In addition, the to-be-processed water discharged | emitted from the water tank 1 may return to a water tank again, and may be membrane-filtered, and may be discharged as it is depending on the water quality.

<Chemical cleaning operation>
After the membrane filtration operation as described above is performed for a predetermined period or when the suction pressure becomes higher than the predetermined pressure by continuing the membrane filtration operation, chemical cleaning is performed by the following operation.

First, the valves V ₁ , V ₃ , V ₅ are closed, the valve V ₄ is opened, and the aeration from the aeration pipe 3 is started, and the water to be treated in the water tank 1 is piped under the aeration from the aeration pipe 3 It is made to discharge outside the tank from 17. The discharged water to be treated may be subjected to membrane filtration again or discharged as described above. And when the to-be-processed water surface in the water tank 1 falls and a part (upper part) of the membrane of the membrane module 2 is exposed on the water surface, the valves V ₂ and V ₆ are opened and the pump P is operated. causes output immersed in the primary side of the chemical liquid in the chemical liquid storage tank 5 is injected into the secondary side of the membrane module 2 through a pipe 14,15,16,12.

  By discharging the water to be treated under the air diffused from below the membrane module 2 in this way, bubbles are ruptured at the gas-liquid interface or rocked at the gas-liquid interface on the vertically arranged membrane surface. The water surface to be treated in the water tank 1 is lowered while the contaminants attached to the film surface are peeled off by the shearing force generated by the above. Thereafter, the retained water amount in the water tank 1 is decreased by discharging the water to be treated to the lower end of the membrane module 2 or less.

  On the other hand, the chemical solution injected to the secondary side of the membrane module 2 fills the inside of the membrane and leaches to the primary side of the membrane, and the chemical solution leached to the primary side flows down the membrane surface arranged in a substantially vertical direction.

  When the membrane is arranged in a substantially vertical direction in this way, the chemical liquid that has leached to the primary side of the membrane flows down the membrane surface, so that the membrane surface is evenly wetted, as if the chemical solution was applied to the membrane surface. Thus, the entire film surface can be brought into contact with the chemical solution.

  Thus, when the chemical solution flows down the membrane surface, the treated water surface in the water tank is lowered, so the chemical solution is not diluted by the treated water, and the chemical solution is leached and applied evenly. The primary side of the film is sufficiently cleaned by the original cleaning effect of the chemical solution. In addition, when the chemical solution that has flowed down the membrane surface reaches the bottom of the water tank, the water to be treated in the water tank is completely discharged or only a small amount remains at the bottom of the membrane module. There is little or no cleaning waste liquid mixed in the water.

In this way, the water to be treated in the water tank 1 is almost completely discharged, the chemical is held inside the membrane of the membrane module 2, and the valve V ₆ is turned on while the chemical is leached to the primary side and flows down the membrane surface. By closing the pump P and holding it for a predetermined time, for example, 1 minute to 1 hour, the contaminants on the film surface are very easily peeled off due to the cleaning effect of the chemicals.

Thereafter, by operating the pump P and the valve V ₅ is opened, the filtered water in the filtered water tank 4, from the secondary side of the membrane module 2 through a pipe 17,15,16,12 by flow back to the primary side, The chemical cleaning is completed without leaving the chemical in the membrane module 2 and the water tank 1 by extruding the chemical in the membrane and discharging the extruded chemical from the pipe 17. In addition, the extrusion washing of the chemical solution is not limited to filtered water, and may be performed using fresh water from other systems, and depending on the water quality, it may be performed using treated water.

After such chemical cleaning, the valves V ₁ , V ₂ , V _{3 are} opened again, the valves V ₄ , V ₅ , V _{6 are} closed, the pump P is operated, and the above membrane filtration operation is resumed.

  In this chemical cleaning operation, two or more chemical solutions may be used, and the same operation may be repeated twice or more. Different chemical solutions are used for each chemical cleaning, for example, chemical cleaning with acid and chemical cleaning with alkali. You may make it carry out alternately.

  In the present invention, the chemicals used for cleaning are not particularly limited, and are appropriately selected according to the properties of the water to be treated, the operating conditions of the submerged membrane separator, and the contamination status of the membrane. In normal cases, sulfuric acid, hydrochloric acid , Nitric acid, oxalic acid, citric acid, ascorbic acid, sodium hydroxide, sodium hypochlorite, hydrogen peroxide, enzyme, surfactant, etc. are used to prepare a chemical solution. The chemical concentration of the chemical solution is also appropriately selected according to the type of chemical used and the properties of the water to be treated, the operating conditions of the submerged membrane separation apparatus, and the contamination status of the membrane. Two or more kinds of chemical solutions can be prepared using different chemicals, and chemical cleaning can be performed in multiple stages.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

<Immersion membrane separator configuration and operating conditions>
As shown in FIG. 1, the submerged membrane separation apparatus used in the following examples and comparative examples is composed of a screen-like membrane module made of polyethylene 0.1 μm microfiltration hollow fiber membrane manufactured by Mitsubishi Rayon, and a hollow fiber membrane membrane. It arrange | positions in a water tank so that a surface may become a perpendicular direction (a hollow fiber is a perpendicular direction), and the diffuser tube is arrange | positioned under this membrane module.

  For suction of the membrane filtrate, suction filtration (27 minutes filtration, 3 minutes stop) was performed intermittently at a rate of 2.0 m / d membrane filtration flux using a self-contained centrifugal pump. During the filtration stop period, bubbles were released from the diffuser tube arranged below the membrane module to expose the membrane module. Moreover, after continuing the filtration operation for 24 hours, the to-be-processed water in a water tank was discharged | emitted from the water tank, exposing a bubble to the membrane module from the diffuser pipe arrange | positioned under the membrane module. The discharged treated water was discharged out of the system.

  The filtration operation and the discharge of the water to be treated were repeated, and the suction pressure required for membrane filtration was recorded for a certain period. When the suction pressure reached 50 kPa, the filtration operation was stopped and each chemical was washed.

<Treatment water>
In the following examples and comparative examples, river water A with a relatively high concentration of organic matter is treated, and when the water quality changes due to fine weather and rain in May (absorbance at UV 260 nm as shown in Table 1) Water was passed for about one week until the suction pressure reached 50 kPa at the time (cell thickness 50 mm) changed from 0.06 to 0.09).

  Table 1 shows the filtration operation period and the quality of the water to be treated in Examples and Comparative Examples.

  The membrane module was replaced with a new one between the operation period of Example 2 and the operation period of Comparative Example 1.

<Example 1>
The filtration was stopped when the suction pressure reached 50 kPa in the above operation, and then the water to be treated was discharged. The surface of the water to be treated in the water tank gradually descended, and after 7 seconds, the surface of the water to be treated became lower than the upper part of the membrane surface of the membrane module, and a part of the membrane was exposed. At this time, injection of the chemical solution was started. That is, from the secondary side of the membrane, a mixed chemical solution containing NaOH: 5,000 mg / L and NaOCl: 500 mg-Cl ₂ / L is 1.0 m / d with respect to the membrane surface by changing the filtered water pump piping. It was made to flow backwards. Thereby, it was observed that a chemical | medical solution leached from the film | membrane surface exposed on the to-be-processed water surface.

  When the membrane of the membrane module was completely exposed, the injection of the chemical solution was stopped and kept in this state for 1 hour. During this time, the internal chemical solution slightly leached from the membrane surface exposed by the membrane module, and flowed down the membrane surface.

  Thereafter, the filtered water is washed back by flowing at 1.0 m / d for 1 minute from the secondary side of the membrane, and the chemical solution retained in the membrane is discharged to the primary side, and the washing waste water in the water tank is discharged. The chemical cleaning was finished.

  The water to be treated was again introduced into the water tank, the suction filtration was restarted by the above-described operation, the suction pressure immediately after the restart was measured, and the results are shown in Table 2.

  In addition, in the case of Comparative Example 1 which will be described later, the chemical cleaning drainage ratio is set to 1 when the chemical cleaning drainage amount (the sum of the chemical injection amount, the retained water amount in the water tank and the backwashing water amount by the filtered water after the chemical injection) is 1. The results are shown in Table 2.

<Example 2>
In Example 1, when injecting the chemical solution and discharging the water to be treated in the water tank, the bubbles are discharged from the air diffuser below the membrane module, and the bubbles are supplied to the membrane surface of the membrane module while being treated. The chemical cleaning was performed in the same manner except that the water was discharged out of the water tank. Then, suction filtration was restarted in the same manner, and the suction pressure and the chemical cleaning waste water ratio were examined. The results are shown in Table 2.

<Comparative example 1>
After the suction pressure reached 50 kPa in the above operation, the filtration was stopped, and then the mixed chemical solution containing NaOH: 5,000 mg / L and NaOCl: 500 mg-Cl ₂ / L was filtered from the secondary side of the membrane. By changing the water pump piping, it was made to flow backward for 60 seconds so that it might become 1.0 m / d with respect to the film surface.

  Thereafter, air bubbles were discharged from the air diffuser arranged below the membrane module, and the bubbles were supplied to the membrane surface of the membrane module, whereby the water to be treated in the water tank was gas-liquid mixed for 1 hour.

  Thereafter, the filtered water is washed back by flowing at a rate of 1.0 m / d from the secondary side of the membrane for 1 minute to discharge the chemical solution held inside the membrane to the primary side, and the water to be treated in the water tank (chemical cleaning) The waste water was discharged to finish the chemical cleaning.

  The water to be treated was again introduced into the water tank, the suction filtration was restarted by the above-described operation, the suction pressure immediately after the restart was measured, and the results are shown in Table 2. In addition, the amount of chemical cleaning wastewater was examined, and this wastewater amount was set to 1.

<Comparative example 2>
When the suction pressure reached 50 kPa in the above operation, the filtration was stopped, and then the entire amount of water to be treated in the water tank was discharged to expose the membrane module to the atmosphere. Thereafter, from the secondary side of the membrane, a mixed chemical solution containing NaOH: 5,000 mg / L and NaOCl: 500 mg-Cl ₂ / L is 1.0 m / d with respect to the membrane surface by changing the filtered water pump piping. After injecting back for 60 seconds, the injection of the chemical solution was stopped and kept in this state for 1 hour.

  Thereafter, the filtered water is washed back by flowing at 1.0 m / d for 1 minute from the secondary side of the membrane, and the chemical solution retained in the membrane is discharged to the primary side, and the washing waste water in the water tank is discharged. The chemical cleaning was finished.

  Thereafter, the suction filtration was resumed in the same manner as in Example 1 to examine the suction pressure and the chemical washing waste water ratio, and the results are shown in Table 2.

From Table 2, the following is clear.
・ There is a clear difference in the recovery rate of the suction pressure between Examples 1 and 2 and Comparative Example 1. In Examples 1 and 2, a significant improvement in the chemical cleaning effect and a large reduction in the amount of chemical cleaning wastewater were observed. It was.
In Comparative Example 2, the suction pressure was lower than that in Comparative Example 1, but did not reach Examples 1 and 2.
In Example 2 in which the chemical solution was discharged from the secondary side to the primary side at the same time as the treated water in the water tank was discharged while aerated from the air diffuser, the chemical solution was leached without aeration. Further, it was confirmed that the suction pressure was further reduced and the chemical cleaning effect was high.

  From the above results, it can be seen that according to the present invention, efficient chemical cleaning can be performed to obtain a high cleaning effect.

It is a systematic diagram which shows embodiment of the immersion type membrane separator of this invention.

DESCRIPTION OF SYMBOLS 1 Water tank 2 Membrane module 3 Aeration pipe 4 Filtration water tank 5 Chemical solution storage tank

Claims (6)

In the submerged membrane separation apparatus in which the membrane module is arranged in a water tank, and the water to be treated in the water tank is subjected to membrane filtration with a suction pressure and / or a gravity difference.
Cleaning chemical injection means for injecting cleaning chemical into the secondary side of the membrane and leaching out to the primary side;
Treated water discharge means for discharging the treated water in the water tank to the outside of the tank,
When discharged to almost completely outside of the tank water to be treated by該被treated water discharging means, the treated water in the water tank is lowered and when the upper portion of the membrane of the membrane module is exposed on the water surface When the cleaning chemical injection means starts injecting the cleaning chemical and leaches to the primary side, and the cleaning chemical leached to the primary side flows down the membrane surface, the water surface to be treated in the water tank descends and the water in the water tank treated water is almost completely discharged, a submerged membrane separator in which cleaning chemicals leached to the primary side has been configured to stop the injection of cleaning agent in a state of flowing down the film surface,
An air diffuser is provided at the lower part of the membrane module in the water tank, and a bubble flow is supplied to the membrane surface by the air diffused by the air diffuser together with the discharge of the water to be treated by the water to be treated discharged. An immersion type membrane separator characterized by being made . Oite to claim 1, wherein the membrane module is submerged membrane separator, wherein a film surface is arranged to be substantially the vertical direction. 3. The group according to claim 1 or 2 , wherein the cleaning chemical comprises sulfuric acid, hydrochloric acid, nitric acid, oxalic acid, citric acid, ascorbic acid, sodium hydroxide, sodium hypochlorite, hydrogen peroxide, an enzyme, and a surfactant. A submerged membrane separation apparatus comprising one or more selected from: In the chemical cleaning method of the submerged membrane separation apparatus, in which the membrane module is disposed in the water tank, and the water to be treated in the water tank is subjected to membrane filtration by suction pressure and / or gravity difference
When discharged to almost completely outside of the tank water to be treated in the water tank, the treated water in the water tank is lowered and when the upper portion of the membrane of the membrane module is exposed on the water surface, the membrane Injecting cleaning chemical into the secondary side of the water and leaching it to the primary side, when the cleaning chemical leached to the primary side flows down the membrane surface, the water surface to be treated in the water tank descends and the water to be treated in the water tank A chemical cleaning method for a submerged membrane separation device in which injection of cleaning chemical is stopped in a state where water is almost completely discharged and cleaning chemical leached to the primary side flows down the membrane surface,
Air diffuser is provided at the lower part of the membrane module in the water tank, and the air flow is supplied from the air diffuser to the membrane surface while discharging the water to be treated in the water tank to the outside. A chemical cleaning method for a submerged membrane separator. 5. The chemical cleaning method for a submerged membrane separator according to claim 4 , wherein the membrane module is arranged so that a membrane surface is in a substantially vertical direction. 6. The group according to claim 4 or 5 , wherein the cleaning chemical comprises sulfuric acid, hydrochloric acid, nitric acid, oxalic acid, citric acid, ascorbic acid, sodium hydroxide, sodium hypochlorite, hydrogen peroxide, an enzyme, and a surfactant. A chemical cleaning method for a submerged membrane separation apparatus, comprising one or more selected from the group consisting of:

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