JP2015155076A - Separation film module cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an effective cleaning method for a separation film module that makes it possible to stably operate a separation film module.

SOLUTION: According to the present invention, in an external pressure-type separation film module 1 cleaning method, a water level is set so that a film primary side of the separation film is at least partially over a water surface, and then, a pressurized gas is introduced to a film secondary side of the separation film to push out water on the film secondary side to the film primary side for back pressure cleaning.

COPYRIGHT: (C)2015,JPO&INPIT

Description

  The present invention relates to a method for effectively cleaning a separation membrane module for stably operating the separation membrane module for a long period of time.

  The membrane separation method has features such as energy saving, space saving, excellent quality of membrane filtrate water, and easy operation and maintenance, so it is widely used in various fields. . For example, microfiltration membranes and ultrafiltration membranes can be applied to water purification processes that produce industrial water and tap water from river water, groundwater and sewage treated water, and to pretreatment in seawater desalination reverse osmosis membrane treatment processes. Application and application to pretreatment in the reverse osmosis membrane treatment process of sewage and industrial wastewater.

  When the raw water is subjected to membrane filtration, the water in the raw water is taken out as membrane filtered water through the separation membrane, and impurities are left on the surface of the separation membrane or in the porous part of the separation membrane. The blockage of the flow path between the membranes proceeds, and a decrease in the amount of membrane filtration water or an increase in the membrane filtration differential pressure becomes a problem.

  Therefore, the impurity layer accumulated on the surface of the separation membrane is peeled off and removed by periodically flowing back the membrane filtration water from the membrane filtration water side to the raw water side of the separation membrane (hereinafter referred to as “backwashing”) or separation. The separation membrane is swung by introducing bubbles from the bottom of the membrane module continuously or intermittently, and the impurities accumulated on the separation membrane surface and the flow path between the separation membranes are peeled off and removed by the shearing force of the bubbles. (Hereinafter referred to as “air washing” or “gas washing”), the raw water in the separation membrane module is discharged together with impurities removed and removed from the surface of the separation membrane by the back washing or air washing (hereinafter referred to as “drain”). (Refer to Patent Documents 1, 2, and 3).

  In order to further enhance the cleaning effect, for example, an acid solution, an alkaline solution, an aqueous oxidizing agent solution or a cleaning agent is added to the backwash water to chemically dissolve or decompose and remove substances adhered to the membrane surface or membrane pores. Cleaning is also performed.

  In addition, as a method of cleaning a separation membrane module in which these physical cleaning and chemical cleaning are combined, sodium hypochlorite is added to backwash water and backwashing is performed simultaneously with empty cleaning (for example, Patent Document 4). Drain) and drain the water on the raw water side in the separation membrane module, and then backwash while draining the backwash drainage (see, for example, Patent Document 5), or water the raw water side of the separation membrane module. In a state filled with, introduce pressurized gas to the membrane filtration water side of the separation membrane module and pass the accumulated water on the membrane filtration water side from the membrane filtration water side of the separation membrane to the raw water side and accumulate on the separation membrane surface Cleaning is performed to remove or remove the impurity layer (see, for example, Patent Document 6).

  However, even with these methods, cleaning of the separation membrane is still insufficient, and a more effective cleaning method is required.

JP 11-342320 A JP 2007-289940 A JP-A-10-309567 JP 2001-079366 A JP-A-6-170364 Japanese Patent No. 3887072

  An object of the present invention is to provide an effective cleaning method for a separation membrane module that enables the separation membrane module to be stably operated.

  The separation membrane module cleaning method of the present invention that solves the above problems has the following characteristics.

(1) In the cleaning method of the external pressure type separation membrane module, after making the water level so that at least part of the membrane primary side of the separation membrane is on the water surface, a pressurized gas is introduced into the membrane secondary side of the separation membrane. A method for cleaning a separation membrane module, wherein gas extrusion and back pressure cleaning are performed by extruding water on the secondary side to the primary side of the membrane.

(2) In the cleaning method of the external pressure type separation membrane module, after all the membrane primary side of the separation membrane is on the water surface, a pressurized gas is introduced into the membrane secondary side of the separation membrane to The method for cleaning a separation membrane module according to (1), wherein gas extrusion and reverse pressure cleaning are performed by extruding water to the primary side of the membrane.

(3) The method for cleaning a separation membrane module according to (1) or (2), wherein the pressure of the pressurized gas introduced to the membrane secondary side of the separation membrane is less than the bubble point of the separation membrane.

(4) When performing gas extrusion back pressure cleaning by introducing pressurized gas into the membrane secondary side of the separation membrane and extruding water on the membrane secondary side to the membrane primary side, it is located at the bottom of the separation membrane module The cleaning of the separation membrane module according to any one of claims (1) to (3), wherein a part or all of the backwash drainage is drained from a lower part of the membrane module by opening the drain valve Method.

(5) Drainage from the lower part of the separation membrane module during gas extrusion back pressure cleaning by introducing pressurized gas into the membrane secondary side of the separation membrane and extruding water on the membrane secondary side to the membrane primary side By increasing the flow rate of the backwash waste water that is extruded from the membrane secondary side of the separation membrane to the primary side of the membrane, the water level on the primary side of the separation membrane is raised and the gas extrusion is performed. The method for cleaning a separation membrane module according to any one of (1) to (4), wherein the separation membrane module is air-washed during back-pressure washing and / or after gas extrusion back-pressure washing.

(6) The separation membrane module cleaning method according to any one of (1) to (5), wherein the separation membrane module is a pressure type separation membrane module in which the separation membrane is housed in a casing.

  According to the method for cleaning a separation membrane module of the present invention, the water level in the separation membrane module is once lowered so that at least part of the membrane primary side of the separation membrane is on the water surface, and then the membrane secondary of the separation membrane. Gas extrusion back pressure washing (hereinafter referred to as “gas extrusion back washing”) is performed by introducing pressurized gas to the side and extruding water on the membrane secondary side to the membrane primary side. Here, in order to use the pressurized gas as a driving force, it is possible to apply a larger pressure to the membrane secondary side of the separation membrane than backwashing which is performed by pressurizing water using a conventional pump as a driving force. Since the water pressure is not applied to the membrane primary side during gas extrusion backwashing, that is, the backwash water outlet side, the pressure of the pressurized gas introduced to the membrane secondary side is maximized. Therefore, the impurities accumulated in the membrane pores and on the membrane surface can be effectively peeled off and removed. Furthermore, the substance adhering to the membrane surface is more likely to be peeled off than the liquid primary side where the water pressure is applied to the membrane primary side, and cleaning can be performed more efficiently than in the past. Moreover, compared with the conventional fresh water generator which performs the backwashing which used the pump as the driving force, the fresh water generator using the washing | cleaning method of this invention can abbreviate | omit a backwash pump.

It is an apparatus general | schematic flowchart which shows an example of the desalinator to which the washing | cleaning method of this invention is applied. It is an apparatus general | schematic flowchart which shows the other example of the fresh water generator to which the washing | cleaning method of this invention is applied. It is an apparatus general | schematic flowchart which shows the further another example of the fresh water generator with which the washing | cleaning method of this invention is applied. It is an apparatus general | schematic flowchart which shows the further another example of the fresh water generator with which the washing | cleaning method of this invention is applied. It is an apparatus general | schematic flowchart which shows the fresh water generator used for the comparative example.

  Hereinafter, the present invention will be described in more detail based on embodiments shown in the drawings. In addition, this invention is not limited to the following embodiments.

  As shown in FIG. 1, for example, the fresh water generation apparatus targeted by the present invention separates raw water through an external pressure type separation membrane module 1 for membrane filtration of raw water, a raw water supply pipe 3, and a raw water valve 4. 1. Raw water supply pump 2 for supplying to 1, an overflow valve 11 for extruding gas in the separation membrane module 1, an overflow pipe 12, and a membrane filtrate pipe 5 for taking out membrane filtrate obtained by membrane filtration of raw water , Backwash valve 6, membrane filtered water outflow pipe 9, backwash water pressurizing water tank 7 for storing backwash water used for gas extrusion backwash, pressurization for supplying pressurized gas as driving force for gas extrusion backwash Gas source 15, pressurized gas pipe 16, pressurized gas valve 17, membrane filtration water valve 8, drain valve 13 for draining the raw water on the membrane primary side in the separation membrane module 1, drain pipe 14, for air washing It consists of an air flush valve 18 for supplying the gas of That.

  A water supply process, a membrane filtration process, a gas extrusion backwash process, an air wash process, and a drainage process, which are basic operation processes in the above-described fresh water generator, will be described. Each operation process includes, for example, a combination of start / stop of devices and opening / closing of valves as shown in Table 1.

  First, as a water supply step for filling the membrane primary side of the separation membrane module 1 with raw water, the raw water valve 4 and the overflow valve 11 are opened and the raw water supply pump 2 is operated to supply the raw water to the separation membrane module 1. When the membrane primary side of the separation membrane module 1 is filled with raw water, the process proceeds to the membrane filtration step. In the membrane filtration step, the backwash valve 6 and the membrane filtration water valve 8 are opened, and the overflow valve 11 is closed, so that the raw water is membrane filtered by the separation membrane module 1, and the membrane filtration water pipe 5 and the backwash valve are collected. 6. Membrane filtrate is taken out through the backwash water pressurized water tank 7, the membrane filtration water valve 8, and the membrane filtration water outflow pipe 9. The membrane filtration process time is preferably set as appropriate according to the raw water quality and the membrane filtration flux, but the membrane filtration may be continued until a predetermined membrane filtration differential pressure is reached. After the membrane filtration step, the raw water supply pump 2 is stopped and the raw water valve 4, the backwash valve 6, and the membrane filtration water valve 8 are closed in order to carry out the gas extrusion backwashing step.

  In the present invention, gas cleaning (empty cleaning) can be performed during the gas extrusion backwashing process and / or after the gas extrusion backwashing process. Hereinafter, after performing a gas extrusion backwashing process by Step1-Step3, it demonstrates as what performs an air-washing process by Step4-Step5, However, Embodiment of this invention is not limited to this example.

  In the gas extrusion back washing process, in Step 1, the overflow valve 11 and the drain valve 13 are opened, and the raw water on the membrane primary side in the separation membrane module 1 is discharged. At this time, the membrane primary side of the separation membrane is in a state where at least a part of the membrane or the whole of the membrane is in a gas state, while the membrane secondary side is in a state where membrane filtrate is held. Next, in Step 2, the pressurized gas valve 17 is opened to supply pressurized gas from the pressurized gas source 15 to the backwash water pressurized water tank 7, and a predetermined pressure is applied to the backwash water in the backwash water pressurized water tank 7. Apply. Further, in Step 3, by opening the backwash valve 6, backwash water to which a predetermined pressure is applied in the backwash water pressurized water tank 7 is extruded into pressurized gas, and the membrane filtrate water pipe 5, It is pushed into the membrane secondary side of the separation membrane module 1 through the flush valve 6, passes through the separation membrane, and flows out to the membrane primary side. Part or all of the backwash drainage that has permeated the separation membrane is drained from the drain valve 13.

  In the air washing process, in Step 4, with the overflow valve 11 open, the backwash valve 6, the drain valve 13 and the pressurized gas valve 17 are closed, the raw water valve 4 is opened, and the raw water supply pump 2 is operated. The raw water is supplied to the separation membrane module 1 and water is applied to the primary side of the separation membrane module 1. Next, in Step 5, with the overflow valve 11 open, the raw water supply pump 2 is stopped, the raw water valve 4 is closed, the flush valve 18 is opened, and gas is introduced to the membrane primary side of the separation membrane module 1. The separation membrane is oscillated by bubbles, or the impurities accumulated on the separation membrane surface and the flow path between the separation membranes are removed and removed by shearing force of the bubbles.

  In the drainage process, the flush valve 18 is closed and the drain valve 13 is opened while the overflow valve 11 is kept open, and the water on the primary side of the separation membrane module 1 is removed by flushing the surface of the separation membrane and the separation membrane. It is discharged from the separation membrane module 1 together with the impurities separated from the flow path between them.

  Here, the membrane primary side of the separation membrane is the side to which raw water to be filtered is supplied, and the membrane secondary side of the separation membrane means the filtered water side obtained by filtering the raw water through the separation membrane. Suspended substances contained in the raw water are present on the primary side of the membrane, but the suspended substances contained in the raw water are removed by membrane filtration in the membrane filtered water, so that they are suspended on the secondary side of the membrane. There is no substance. The suspended substance is defined by turbidity, suspended solid amount or SS concentration, and is generally a substance removed by a microfiltration membrane and an ultrafiltration membrane.

  Backwash water refers to water in which the water used for backwash flows on the membrane secondary side, and backwash drainage refers to the backwash water passing through the separation membrane from the membrane secondary side to the membrane primary side. Thus, it means water in a state where it reaches the surface of the separation membrane on the primary side of the membrane and flows on the primary side of the membrane. The surface of the separation membrane is defined as the surface where the water on the primary side of the membrane is in contact with the separation membrane. As backwash water, it is common to use filtered water obtained by filtering raw water with a separation membrane. However, if the suspended solids are removed, the secondary side of the membrane is contaminated with suspended substances. Since there is no, it can be used as backwash water.

  In gas extrusion backwashing, by introducing a pressurized gas into the membrane secondary side in advance and applying an arbitrary backwashing pressure to the backwashing water (Step 2), and then opening the backwashing valve 6, Since the backwash pressure applied to the backwash water is instantaneously released and acts on the separation membrane (Step 3), an arbitrary backwash pressure can be applied to the separation membrane.

  By the way, conventional backwash water is often pushed back by using the driving force of the pump, and in this case, the backwashing pressure is within the range of the driving force of the backwash pump. The backwash pressure is generally proportional to the backwash water flow rate. Similarly, the membrane filtration pressure during the membrane filtration step is proportional to the membrane filtrate flow rate. Therefore, when it is desired to apply a backwash pressure that is several times the membrane filtration pressure, it is necessary to adjust the backwash water flow rate to be several times the membrane filtrate water flow rate. However, in order to make the backwash water flow several times higher than the membrane filtrate water flow, the backwash pump is selected to be several times the capacity of the raw water supply pump, and the backwash water is used. In addition, since the diameters of the membrane filtrate water pipe 5, the overflow pipe 12, the backwash valve 6, and the overflow valve 11 through which the backwash drainage flows down must be increased to match the backwash water flow rate, the equipment cost, backwash There is a disadvantage that the power cost of the industrial pump is excessive and not economical. However, in gas extrusion backwashing, the backwashing pressure can be set arbitrarily with the pressure applied to the pressurized gas, so even a backwashing pressure that is several times the membrane filtration pressure can be easily applied. A strong cleaning effect can be obtained by a high backwashing pressure.

  In the present invention, the pressure of the pressurized gas introduced to the membrane secondary side of the separation membrane is preferably less than the bubble point of the separation membrane. By making the pressure of the pressurized gas less than the bubble point of the separation membrane, only the backwash water permeates the separation membrane without allowing the pressurized gas to permeate the separation membrane. Backwashing can be performed without allowing the separation membrane to enter and drying the separation membrane. The bubble point is determined by the method described in JIS K3832 “Bubble Point Test Method for Microfiltration Membrane Elements and Modules”, and a liquid (water in the case of a fresh water generator) is filled in the pores of the separation membrane. This is the pressure at which one membrane surface is gradually pressurized with gas and water is pushed out of the pores and the air begins to flow.

  Here, as the pressurized gas source 15 for supplying the pressurized gas for applying a predetermined pressure to the backwash water, any means can be used as long as it can supply a gas in a pressure range of about 10 kPa to 1000 kPa. It doesn't matter. In general, it is preferable to use an air compressor that is easily available and easy to maintain. The gas pressurized by the air compressor is temporarily stored in the air tank, and after adjusting the gas pressurized by the air compressor to an arbitrary pressure by a regulator installed at the subsequent stage of the air tank, the pressurized gas piping 16 and the pressurized gas Supplying to the backwash water pressurized water tank 7 through the valve 17 is preferable because pressurized gas of any pressure can be easily supplied with a simple equipment configuration.

  Furthermore, in the gas extrusion backwashing of the present invention, since the pressurized gas is supplied to the membrane secondary side such as the backwash water pressurized water tank 7, the membrane filtration water pipe 5, which is the membrane secondary side pipe, For removing impurities in the pressurized gas between the pressurized gas source 15 and the pressurized gas valve 17 so that the washing water pressurized water tank 7 and the membrane filtered water outflow pipe 9 are not contaminated by the impurities in the pressurized gas. It is preferable to install a filter. Examples of the pressurized gas filter include an oil mist separator for removing oil mist derived from a pressurized gas source such as an air compressor, and an air filter for removing fine particles in the pressurized gas. Further, the pressurized gas is not particularly limited from the gist of the present invention, but a gas having a low solubility in water is preferable because water is extruded using the pressurized gas. In general, it is preferable to use pressurized air obtained by compressing the atmosphere because it is easy to obtain a gas source, has low solubility in water, and is safe in terms of harmfulness to the human body.

  From the gist of the present invention, the backwashing water pressurized water tank 7 can store water to be backwashed water and has pressure resistance to the pressure of the pressurized gas supplied from the pressurized gas source 15. Any shape and material may be used. A water tank having pressure resistance may be provided in the middle of the membrane filtration water pipe 5 as the backwash water pressurized water tank 7, or the membrane filtration water pipe 5 is provided with a volume necessary for backwash water to serve as the backwash water pressurized water tank 7. May be handled.

  In addition, as shown in FIG. 4, only when the backwash water pressurized water tank 7 is filled in the membrane filtration step, the backwash valve 6 and the backwash water pressurized water tank air vent valve 19 are opened, and the backwash water pressurized water is opened. Membrane filtrate is led to the tank 7, and when the backwash water pressurized water tank 7 becomes full, the backwash valve 6 and the backwash water pressurized water tank air vent valve 19 are closed, so that the membrane filtrate is supplied to the membrane filtrate water pipe 5, Membrane filtrate may be taken out via the membrane filtrate valve 8 and the membrane filtrate outlet pipe 9.

  In the present invention, when gas extrusion backwashing is performed at Step 3, the backwash drainage that permeates and flows out from the membrane secondary side of the separation membrane to the lower side of the separation membrane module 1 according to gravity. It flows down the membrane surface and is discharged through drain valve 13 and drain valve 14. At this time, since the primary side of the membrane is not filled with water, there is no resistance due to water pressure on the primary side of the membrane, so the backwash pressure applied to the secondary side of the membrane receives resistance due to the water pressure on the primary side of the membrane. It can be used as a driving force for backwashing to the maximum. Furthermore, in the case of a separation membrane module in which the longitudinal direction of the separation membrane is arranged substantially vertically, and backwash water flows from the upper end of the separation membrane module and the separation membrane, the membrane secondary side is filled with water. Therefore, since the water pressure increases toward the lower end of the separation membrane, the pressure obtained by adding the water pressure on the secondary side to the backwash pressure applied to the upper end portion of the separation membrane is gas-extruded at the lower end portion of the separation membrane extending in the substantially vertical direction. It can be used as a driving force for backwashing. Therefore, it becomes possible to give the effect of gas extrusion and backwashing relatively uniformly from the upper end to the lower end of the substantially vertical direction of the separation membrane, and the effect of washing the separation membrane is high.

  Impurities that have adhered and accumulated on the surface of the separation membrane are separated from the surface of the separation membrane because there is no resistance due to water pressure on the primary side of the membrane and no flow resistance when water on the primary side of the membrane is transferred out of the separation membrane module. The separated impurities are transferred to the backwash drainage that drops or falls on the surface of the separation membrane according to gravity, and is discharged as it is from the lower part of the separation membrane module 1 through the drain valve 13 and the drain pipe 14.

  On the other hand, in the conventional backwash, the membrane primary side of the separation membrane is filled with raw water and backwash wastewater, and the backwash wastewater is separated from the separation membrane module 1 via the overflow valve 11 and the overflow pipe 12. Discharged from. For this reason, in backwashing, when the water pressure by the water filled on the primary side of the membrane and the backwash wastewater is discharged from the separation membrane module 1 and flows out through the overflow valve 11 and the overflow pipe 12 on the surface of the separation membrane. The back pressure due to the generated flow resistance is applied. This makes it difficult for impurities attached and accumulated on the surface of the separation membrane to be separated from the surface of the separation membrane.

  Furthermore, since the water pressure and flow resistance on the primary side of the membrane contribute in the form of reducing the driving force for backwashing, the driving force for effective backwashing is reduced, and as a result, the backwashing effect is reduced. Here, when the primary side of the membrane is filled with water, the water pressure applied to the primary side of the membrane and the secondary side of the membrane during backwashing is often substantially the same, and the primary side of the membrane and the secondary side of the membrane sandwiching the separation membrane The water pressure with the side is offset. In addition, the backwash pressure at the upper end of the separation membrane is such that the backwash works effectively as it approaches the lower end of the separation membrane due to the flow resistance generated when the backwash water flows through the flow path on the membrane secondary side of the separation membrane. The driving force is reduced.

  When the outlet of the backwash wastewater from the separation membrane module 1 is located above the separation membrane module 1, the flow resistance generated when the backwash wastewater flows out of the separation membrane module 1 increases as it approaches the lower end of the separation membrane. Thus, the closer to the upper end of the separation membrane, the smaller. Furthermore, in the case of a pressurized membrane module in which the backwash drain of the separation membrane module 1 has a nozzle shape, when a large flow of backwash drainage is to be discharged in a short time, the nozzle shape is obtained. A large flow resistance is generated at the backwash drain, which reduces the driving force of backwash.

  From these actions, in the backwashing in the state where the membrane primary side of the separation membrane is filled with water, the driving force of backwashing is increased by the water pressure and flow resistance of the membrane primary side compared with the gas extrusion backwashing in the present invention. In addition to the flow resistance of the backwash water on the secondary side of the membrane and the flow resistance of backwash drainage on the primary side of the membrane, the driving force of backwashing from the upper end to the lower end of the separation membrane is reduced. Since the degree of attenuation becomes large, a sufficient backwashing effect cannot be obtained.

  In Step 1 of the gas extrusion backwashing step, the water on the primary side of the separation membrane module 1 is discharged. At this time, the water on the primary side of the separation membrane module 1 may remain, but preferably the separation membrane. More than half of the substantially vertical direction is more preferably, the entire separation membrane is above the water surface so as to come into contact with the gas. When the entire separation membrane is above the water surface, the above-described action prevents back pressure due to water pressure on the primary side of the membrane, and backwash driving force due to flow resistance does not attenuate. The effect of backwashing is maximized.

  However, even when a part of the substantially vertical direction of the separation membrane is below the water surface, it is below the water surface as compared with the case where the membrane primary side of the separation membrane module 1 is filled with water. Regarding the portion, the back pressure by water pressure and the back pressure by flow resistance attenuate the driving force of backwashing, but the effect of gas extrusion backwashing of the present invention can be obtained. When water on the membrane primary side of the separation membrane module 1 remains and a part of the separation membrane in a substantially vertical direction is below the water surface, the membrane primary is included in the separation membrane below the water surface during gas extrusion backwashing. The water pressure depending on the water level on the side is applied as the backwash back pressure. Further, when the separation membrane module 1 is a pressure type membrane module, when the backwash drainage flows out from the backwash drainage port having the nozzle shape of the separation membrane module, the backwash drainage port, the overflow pipe, the overflow valve The flow resistance generated in the backwash is applied as backwash back pressure, but even if the water level on the primary side of the membrane rises due to backwash drainage, the backwash drainage flows out from the nozzle backwash drainage outlet. Does not generate the flow resistance. Therefore, it is preferable that the water level at the time of starting the gas extrusion backwashing is lower because the effect of reducing the driving force of the backwashing is reduced, so that the effect of the gas extrusion backwashing of the present invention can be enhanced.

  In Step 2 of the gas extrusion backwashing step, it is preferable to add a chemical to the backwashing water because it has an effect of decomposing, dissolving, and removing the adhered and accumulated impurities on the separation membrane surface and separation membrane pores. . As a means for adding the chemical solution, as shown in FIG. 2, a chemical solution storage tank 21, a chemical solution injection pump 22, and a chemical solution injection pipe 23 may be added to the desalination apparatus shown in FIG. 1. In addition, as the chemical solution to be added, it is preferable to use an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid or the like because the cleaning effect is enhanced with respect to aluminum, iron, calcium, etc., and when an organic acid such as oxalic acid or citric acid is used, aluminum , Iron, calcium, manganese, etc., because the cleaning effect is high. It is preferable to use an oxidizing agent such as sodium hypochlorite, chlorine dioxide, chlorine, hydrogen peroxide, ozone, etc., because it has a high cleaning effect on organic matter. Especially, sodium hypochlorite is inexpensive, easily available, and handled. Is more preferable because it is easy. As a method for injecting the chemical solution, in Step 3 of the gas extrusion backwashing process in the fresh water generator shown in FIG. 2, the backwash water applied with the backwash pressure by the pressurized gas is connected to the backwash valve 6 and the membrane filtrate water pipe 5. When flowing into the separation membrane module, the chemical solution stored in the chemical solution storage tank 21 may be injected into the backwash water through the chemical solution injection pipe 23 using the chemical solution injection pump 22, or in the membrane filtration step. When the membrane filtrate flows into the backwash water pressurized water tank 7 through the membrane filtrate pipe 5 and the backwash valve 6, the chemical liquid stored in the chemical liquid storage tank 21 is treated with the chemical liquid injection pump 22. You may inject | pour into membrane filtration water via the injection piping 23. FIG.

  When injecting chemical liquid into backwash water, it is only necessary to inject the chemical liquid into backwash water for the amount of water used for backwashing. Generally, chemical liquid is used only during the process in which the backwash water is transferred to the separation membrane module. Is preferable since the amount of the chemical solution to be injected can be reduced. On the other hand, in a fresh water generator as shown in FIG. 4, when a medicinal solution is injected into the membranous filtrate in the membranous filtration step and the membranous filtered water into which the medicinal solution has been injected in advance is stored in the backwash water pressurized water tank 7, Since the water adjusted to the chemical concentration can be used as the backwash water, it is preferable because the operation management of the chemical injection pump 22 becomes easy.

  As means for filling the membrane primary side of the separation membrane module 1 with water in Step 4 of the air washing step, raw water may be supplied as described above, or the overflow pipe 11, the backwash valve 6, and the pressurized gas valve 17 may be provided. Back-washing is performed with the membrane filtration water valve 8 and the drain valve 13 closed, and backwash water is supplied from the membrane secondary side of the separation membrane module 1 to the membrane primary side. The primary side of the membrane may be filled with backwash drainage, or the reverse of extruding from the membrane secondary side of the separation membrane to the membrane primary side rather than the flow rate of backwash drainage drained from the drain valve 13 in the gas extrusion backwash process. By increasing the flow rate of the washing waste water, the water level on the primary side of the separation membrane may be raised and filled with back washing waste water, or these means may be combined. At this time, if the oxidant is added to the raw water or backwash water to fill the raw water side of the separation membrane module 1, the impurities attached and accumulated in the separation membrane surface and the separation membrane pores are oxidized and decomposed and removed. It is preferable because of the effect of

  In the present invention, the separation membrane module can be gas-washed during and / or after gas extrusion counter-pressure cleaning. That is, raw water or backwash water is supplied to the primary side of the separation membrane module 1 by the above-described means even during the air washing step, and the raw water or backwash drainage from the separation membrane module 1 through the overflow valve 11 and the overflow pipe 12. It is preferable to continue to flow out because the impurities separated from the separation membrane surface and the flow path between the separation membranes are successively transferred to the outside of the separation membrane module 1 by the washing, so that the washing effect of the washing is increased.

  Pressurized gas source for supplying a pressurized gas for applying a predetermined pressure to the backwash water in the gas extrusion backwashing process as the pressurized gas source 15 of the gas introduced into the separation membrane module 1 in the air washing process 15 may be shared, or an air blower may be installed and used separately from the pressurized gas source 15 for gas extrusion backwashing.

  Here, the external pressure type separation membrane module refers to a membrane module of a type that performs membrane filtration in a direction from the outer surface of the separation membrane toward the inside of the separation membrane.

  In addition, as a form of the separation membrane module, a pressurized membrane module in which a separation membrane is housed in a casing container that is a pressure vessel if it is an external pressure type, an immersion type membrane module that is immersed in an immersion water tank that is open to the atmosphere, or I do not care. Since the submerged membrane module performs suction filtration, the pressure that can be used for membrane filtration is practically limited to about −80 kPa. On the other hand, the pressure that can be used for membrane filtration in a pressurized membrane module is limited to the pressure resistance capability of the separation membrane module and / or the separation membrane, but generally the range of pressure that can be used for membrane filtration is higher than that of the submerged membrane module. Since it is large, membrane filtration can be performed with a high membrane filtration flux with a higher membrane filtration pressure than the submerged membrane module, which is preferable.

  On the other hand, the submerged membrane module is preferable because the suspended matter indicated by turbidity and SS concentration can be subjected to membrane filtration of high concentration raw water. This is because in the submerged membrane module, even if a high concentration suspended substance flows in, the suspended substance is easily discharged out of the submerged membrane module by physical washing such as back washing or empty washing. Here, the submerged membrane module generally does not contain the separation membrane in the casing container, and the backwash wastewater does not flow out through the nozzle where the backwash wastewater is concentrated in one place. Therefore, the flow resistance accompanying the outflow of the backwash drainage is smaller than that of the pressurized membrane module, and there is an advantage that the back pressure is less likely to attenuate the backwash driving force. That is, it can be said that the pressurized membrane module can enjoy the effect of the present invention more greatly from the viewpoint of outflow of the backwash drainage to the outside of the separation membrane module.

  As the shape of the separation membrane module, there are a hollow fiber membrane module, a tubular membrane module, a spiral membrane module, a flat membrane module and the like, but the effect of the present invention is not changed even if any shape of the separation membrane module is used. Here, the hollow fiber membrane means a tubular separation membrane having a diameter of less than 2 mm, and the tubular membrane means a tubular separation membrane having a diameter of 2 mm or more.

  The separation membrane may be any porous membrane as long as it is porous from the gist of the present invention, but a microfiltration membrane (MF membrane) and an ultrafiltration membrane (UF membrane) generally used for turbidity are used. preferable. Furthermore, in the gas extrusion backwashing of the present invention, when a UF membrane having a smooth surface and fine membrane pores is used, suspended substances in raw water flow into the porous portion of the separation membrane. Therefore, the suspended matter accumulated on the separation membrane surface from the upper end to the lower end in the substantially vertical direction of the separation membrane can be effectively separated by the gas extrusion backwashing of the present invention. This is preferable. Furthermore, the finer the pores of the membrane and the smoother the surface of the separation membrane, the easier it is to transfer suspended substances separated from the surface of the separation membrane by backwash drainage that drops down on the surface of the separation membrane. It is preferable because the substance can be easily discharged out of the separation membrane module. Here, even in the case of a UF membrane, a separation membrane having a non-homogeneous membrane structure in which the membrane surface portion is dense and becomes sparse toward the inside of the membrane is better than a separation membrane having a homogeneous membrane structure from the membrane surface to the inside. Generally, it is preferable because the membrane pores on the surface of the separation membrane are fine and the surface of the separation membrane becomes smooth.

  Further, the material of the separation membrane is not particularly limited from the gist of the present invention, but when an organic material is used, polyethylene, polypropylene, polyacrylonitrile, an ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene are used. Ethylene, polytetrafluoroethylene, polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chlorotrifluoroethylene-ethylene copolymer, polyvinylidene fluoride, polysulfone, polyethersulfone, cellulose acetate, etc. can be used. Ceramics can be used when using inorganic materials. Among these, from the viewpoint of film strength and chemical resistance, an organic material containing fluorine or a material made of ceramic is preferable. In addition, an organic material containing polyacrylonitrile or cellulose acetate, which is generally a hydrophilic material, is preferred from the viewpoint of chemical cleaning recoverability. In addition, suspended substances that adhere and accumulate on the surface of the separation membrane generally exhibit hydrophobicity. Therefore, the more strongly the separation membrane on the surface of the separation membrane, the more the suspended matter that has adhered and accumulated on the surface of the separation membrane. Since it becomes easy to peel, it is preferable.

  As a control method for membrane filtration, either constant flow filtration or constant pressure filtration may be used, but constant flow filtration is preferable from the viewpoint of obtaining a constant treated water amount or treated water flow rate. On the other hand, constant pressure filtration is preferable because control of membrane filtration can be made simpler than constant flow filtration, although the flow rate of treated water flowing out from the water generator varies. In the case of constant pressure filtration, if a water purification pond with sufficient buffering capacity is installed in the subsequent stage, fluctuations in the flow rate of the treated water flowing out from the water generator will be buffered in the water purification pond and fixed from the water purification pond. It is also possible to supply the amount of treated water.

  The membrane filtration method may be total-volume filtration or cross-flow filtration, but full-volume filtration is preferred from the viewpoint of low energy consumption required for membrane filtration.

Example 1
Using a fresh water generator having the equipment configuration shown in FIG. 3, one separation membrane module 1 using an external pressure PVDF hollow fiber ultrafiltration membrane module HFU-2020 (manufactured by Toray Industries, Inc.) is used as a chemical storage tank. A sodium hypochlorite aqueous solution was stored in No. 21, and the river water was subjected to constant flow filtration with a membrane filtration flux of 3 m ³ / (m ² · d) by a total filtration method.

Each operation process was configured by starting and stopping the equipment and opening and closing the valves as shown below. First, as a water supply process, the raw water valve 4 and the overflow valve 11 were opened, the raw water supply pump 2 was operated, and raw water was supplied to the separation membrane module 1 to fill the membrane primary side of the separation membrane module 1 with raw water. Next, as a membrane filtration step, the backwash valve 6 and the membrane filtration water valve 8 are opened, and the overflow valve 11 is closed, so that the raw water is membrane-filtered by the separation membrane module 1, and the membrane filtration water pipe 5 and reverse Membrane filtrate is taken out through the flush valve 6, the backwash water pressurized water tank 7, the membrane filtrate water valve 8, and the membrane filtrate drain pipe 9. At this time, the output of the raw water supply pump 2 is feedback-controlled by the output value of the membrane filtration water flow sensor, so that the membrane filtration water flow is controlled at a constant flow rate so that the membrane filtration flux is 3 m ³ / (m ² · d). did. After the membrane filtration process was continued for 30 minutes, the raw water supply pump 2 was stopped, the raw water valve 4, the backwash valve 6, and the membrane filtration water valve 8 were closed, and then the overflow valve 11 was opened.

  As a water level lowering step in the gas extrusion back washing process, the drain valve 13 was opened and all the water on the membrane primary side in the separation membrane module 1 was discharged out of the separation membrane module. If the water level lowering step was carried out for 45 seconds, all the water on the primary side of the membrane in the separation membrane module 1 could be discharged. At this time, the membrane primary side in the separation membrane module 1 is in a state where there is no water and the surroundings become air, but the membrane secondary side is in a state where membrane filtered water is retained. Yes. Next, as a backwash preparation step, the pressurized gas valve 17 was opened, pressurized air was supplied to the backwash water pressurized water tank 7, and pressure was applied to the water in the backwash water pressurized water tank 7. The compressed air was adjusted so that the air compressed by using an air compressor as the pressurized gas source 15 was 100 kPa using the pressurized gas pressure regulating valve 31 for backwashing. If the backwash preparation step was performed for 45 seconds, the pressure in the backwash water pressurized water tank 7 became constant at 100 kPa. Next, as a gas extrusion backwashing step, the backwashing valve 6 is opened while the pressurized gas valve 17 is opened, and the water pressurized to 100 kPa with pressurized air in the backwashing water pressurized water tank 7 is subjected to membrane filtration. It pushed into the membrane secondary side of the separation membrane module 1 through the water pipe 5 and the backwash valve 6 to perform gas extrusion backwashing. In the gas extrusion backwashing step for 30 seconds, 100 L of water was used as backwashing water. During this gas extrusion backwashing step, the aqueous solution of sodium hypochlorite stored in the chemical solution storage tank 21 is used with a chemical solution injection pump 22 so that the chlorine concentration becomes 5 mg / L with respect to 100 L of water used as backwashing water. The solution was injected into the backwash water through the chemical solution injection pipe 23. In this gas extrusion backwashing step, since the overflow valve 11 and the drainage valve 13 are open, the backwash water that has permeated the separation membrane from the membrane secondary side to the membrane primary side is used as backwash wastewater. The surface passed through the separation membrane module 1 according to gravity and flowed out of the separation membrane module 1 via the drain valve 13 and the drain pipe 14.

  As a water filling step in the air washing process, the pressurized gas valve 17 and the backwash valve 6 are closed in this order, the drain valve 13 is closed, the overflow valve 11 is kept open, the raw water valve 4 is also opened, and raw water supply is performed. The pump 2 was operated to supply raw water to the separation membrane module 1 and the membrane primary side of the separation membrane module 1 was filled with raw water. Thereafter, the raw water supply pump 2 was stopped and the raw water valve 4 was closed. Next, as an air washing step, the air washing valve 18 was opened and air was introduced into the membrane primary side of the separation membrane module 1 at an air flow rate of 100 NL / min and air washing was performed for 30 seconds. The air flow rate is adjusted so that air compressed using an air compressor as the pressurized gas source 15 becomes 100 NL / min using the pressurized gas pressure regulating valve 32 for washing and the gas flow regulating valve 33 for washing. went. Thereafter, the flush valve 18 was closed.

  As a drainage process, the drain valve 13 is opened while the overflow valve 11 is kept open, and the water on the primary side of the membrane in the separation membrane module 1 is separated from the separation membrane surface and the flow path between the separation membranes by an air washing step. It was discharged from the separation membrane module 1 together with the impurities. Subsequently, it returned to the water supply process and the said process was repeated.

As a result, the membrane filtration differential pressure of the separation membrane module 1 was stable at 60 kPa after 6 months with respect to 30 kPa immediately after the start of operation. Moreover, the average power consumption of this fresh water generator during the operation period was 0.033 kWh / m ³ .

(Example 2)
As a method of injecting the sodium hypochlorite aqueous solution into the backwash water using the fresh water generator having the equipment configuration shown in FIG. 4, the chemical liquid storage tank has a chlorine concentration of 5 mg / L in the membrane filtrate during the membrane filtration step. The sodium hypochlorite aqueous solution stored in 21 is injected into the membrane filtrate through the chemical injection pipe 23 using the chemical injection pump 22, and water with a chlorine concentration of 5 mg / L is stored in the backwash water pressurized water tank 7. The operation was performed in the same manner as in Example 1 except that this was used as backwash water.

As a result, the membrane filtration differential pressure of the separation membrane module 1 was stable at 60 kPa after 6 months with respect to 30 kPa immediately after the start of operation. Moreover, the average power consumption of this fresh water generator during the operation period was 0.033 kWh / m ³ , which was 1.00 compared to Example 1.

(Example 3)
Using the desalination apparatus having the equipment configuration shown in FIG. 3, the drain valve 13 was closed during the gas extrusion backwashing step in the gas extrusion backwashing process, and the permeation occurred from the membrane secondary side of the separation membrane to the membrane primary side. The operation was performed in the same manner as in Example 1 except that the backwash waste water was collected on the primary side of the membrane in the separation membrane module 1 and the water filling step of the air washing step was omitted.

  As a result, the membrane filtration differential pressure of the separation membrane module 1 was stable at 70 kPa after 6 months, compared to 30 kPa immediately after the start of operation. Moreover, the average power consumption of this fresh water generator during the operation period was 0.035 kWh / m 3, which was 1.06 compared with Example 1.

Example 4
Using the desalination apparatus having the equipment configuration shown in FIG. 3, the drain valve 13 was closed during the gas extrusion backwashing step in the gas extrusion backwashing process, and the permeation occurred from the membrane secondary side of the separation membrane to the membrane primary side. The backwash drainage is accumulated on the primary side of the membrane in the separation membrane module 1 so that the water filling step of the air washing process is omitted, and the drain valve 13 is kept closed during the gas extrusion backwashing step. The operation was performed in the same manner as in Example 1 except that the air washing valve 18 was opened and air was introduced into the membrane primary side of the separation membrane module 1 to perform air washing.

As a result, the membrane filtration differential pressure of the separation membrane module 1 was stable at 65 kPa after 6 months with respect to 30 kPa immediately after the start of operation. Moreover, the average power consumption of this fresh water generator during the operation period was 0.033 kWh / m ³ , which was 1.03 compared with Example 1.

(Example 5)
Using the fresh water generator of the equipment configuration shown in FIG. 3, the backwash wastewater is separated from the backwash drainage with the overflow valve 11 and the drainage valve 13 open for the first 10 seconds of the gas extrusion backwash step of the gas extrusion backwash step. The point where it was discharged outside the module 1 through the drain valve 13 and the drain pipe 14, and then the gas extrusion back washing step, the drain valve 13 was closed after 10 seconds, and the back washing waste water was separated into the separation membrane module 1. The water filling step of the air washing process is omitted by storing the water on the primary side of the membrane, the drain valve 13 is closed and the backwash waste water is stored on the primary side of the membrane in the separation membrane module 1 and at the same time The valve 18 was opened and air was introduced into the membrane primary side of the separation membrane module 1 to perform air washing. After the gas extrusion back washing step was performed for a total of 30 seconds, the pressurized gas valve 17 and the back washing valve 6 were closed. Stop gas extrusion backwashing After the rinsing, the rinsing was continued with the rinsing valve 18 kept open, and after rinsing for 30 seconds, the rinsing valve 18 was closed and the rinsing was stopped. The operation was performed in the same manner as in Example 1.

As a result, the membrane filtration differential pressure of the separation membrane module 1 was stable at 61 kPa after 6 months with respect to 30 kPa immediately after the start of operation. Moreover, the average power consumption of this fresh water generator during the operation period was 0.032 kWh / m ³ , which was 1.00 compared to Example 1.

(Comparative Example 1)
Operation was performed in the same manner as in Example 1 except that the water level lowering step in the gas extrusion backwashing step and the water filling step in the air washing step were omitted using the fresh water generator having the equipment configuration shown in FIG. In the gas extrusion backwashing step in this backwashing process, since the water level lowering step is omitted, the membrane primary side of the separation membrane module 1 is filled with water, so the separation membrane is moved from the membrane secondary side to the membrane primary side. The backwash water that permeated to the side overflowed from the backwash drain provided above the separation membrane module 1 as backwash wastewater and flowed out of the separation membrane module 1.

As a result, the membrane filtration differential pressure of the separation membrane module 1 was 87 kPa after 6 months, compared to 30 kPa immediately after the start of operation. Moreover, the average power consumption of this fresh water generator during the operation period was 0.038 kWh / m ³ , which was 1.18 compared with Example 1.

(Comparative Example 2)
A water storage device having the equipment configuration shown in FIG. 5 is used, and the separation membrane module 1 uses one external pressure PVDF hollow fiber ultrafiltration membrane module HFU-2020 (manufactured by Toray Industries, Inc.), A sodium hypochlorite aqueous solution was stored in No. 21, and the river water was subjected to constant flow filtration with a membrane filtration flux of 3 m ³ / (m ² · d) by a total filtration method.

Each operation process was configured by starting and stopping the equipment and opening and closing the valves as shown below. First, as a water supply process, the raw water valve 4 and the overflow valve 11 were opened, the raw water supply pump 2 was operated, and raw water was supplied to the separation membrane module 1 to fill the membrane primary side of the separation membrane module 1 with raw water. Next, as a membrane filtration step, the raw water is subjected to membrane filtration by the separation membrane module 1 by opening the membrane filtration water valve 8 and closing the overflow valve 11, and the membrane filtration water pipe 5 and the membrane filtration water valve 8 are connected. Membrane filtered water is taken out and stored in the backwash water tank 34. The membrane filtrate overflowed from the backwash water tank 34 flows out of the apparatus through the membrane filtrate outlet pipe 9. At this time, the output of the raw water supply pump 2 is feedback-controlled by the output value of the membrane filtration water flow sensor, so that the membrane filtration water flow is controlled at a constant flow rate so that the membrane filtration flux is 3 m ³ / (m ² · d). did. After the membrane filtration process was continued for 30 minutes, the raw water supply pump 2 was stopped, the raw water valve 4 and the membrane filtration water valve 8 were closed, and then the overflow valve 11 was opened.

As the backwashing process, the backwashing valve 6 is opened, the backwashing pump 35 is operated, and the membrane filtrate stored in the backwashing water tank is used as backwashing water, and the backwashing water pipe 36, the backwashing valve 6, the membrane It was pushed into the membrane secondary side of the separation membrane module 1 through the filtrate pipe 5 and backwashed for 30 seconds with a backwash flow rate of 4 m ³ / (m ² · d). The sodium hypochlorite aqueous solution stored in the chemical solution storage tank 21 during the backwashing process is reversely passed through the chemical solution injection pipe 23 using the chemical solution injection pump 22 so that the chlorine concentration becomes 5 mg / L with respect to the backwash water. It was poured into the washing water. In this backwashing process, since the membrane primary side of the separation membrane module 1 is filled with water, the backwash water that has permeated the separation membrane from the membrane secondary side to the membrane primary side is used as backwash wastewater. It overflowed from the backwash drain provided above the module 1 and flowed out of the separation membrane module 1. After backwashing for 30 seconds, the backwash pump 35 was stopped and the backwash valve 6 was closed.

  As the air washing step, the air washing valve 18 is opened while the overflow valve 11 is kept open, and air is introduced into the membrane primary side of the separation membrane module 1 at an air flow rate of 100 NL / min, and air washing is performed for 30 seconds. went. The air flow rate is adjusted so that air compressed using an air compressor as the pressurized gas source 15 becomes 100 NL / min using the pressurized gas pressure regulating valve 32 for washing and the gas flow regulating valve 33 for washing. went. Thereafter, the flush valve 18 was closed.

  As a drainage process, the drain valve 13 is opened while the overflow valve 11 is kept open, and the water on the primary side of the membrane in the separation membrane module 1 is separated from the separation membrane surface and the flow path between the separation membranes by an air washing step. It was discharged from the separation membrane module 1 together with the impurities. Subsequently, it returned to the water supply process and the said process was repeated.

As a result, the membrane filtration differential pressure of the separation membrane module 1 was 95 kPa after 6 months, compared to 30 kPa immediately after the start of operation. Moreover, the average power consumption of this fresh water generator during the operation period was 0.035 kWh / m ³ , which was 1.07 compared with Example 1.

(Comparative Example 3)
After the membrane filtration step was completed, the drainage valve 13 was opened while the overflow valve 11 was open, and the water on the primary side of the separation membrane module 1 was drained using the fresh water generator having the equipment configuration shown in FIG. Later, as the backwashing process, the backwashing valve 6 is opened, the backwashing pump is operated, and the membrane filtrate stored in the backwashing water tank is used as backwashing water. In this backwashing step, the membrane was pushed into the membrane secondary side of the separation membrane module 1 through the membrane filtration water pipe 5 and backwashed with a backwash flow rate of 4 m ³ / (m ² · d) for 30 seconds. As the next water filling step, the backwash valve 6 and the drain valve 13 are closed, the raw water valve 4 is opened and the raw water supply pump 2 is operated to supply the raw water to the separation membrane module 1 so that the membrane primary side of the separation membrane module 1 is The operation was performed in the same manner as in Comparative Example 2 except that the air washing step was performed after filling with raw water.

  In this backwashing process, the overflow valve 11 and the drain valve 13 are opened and the water in the separation membrane module 1 is discharged, so the separation membrane is moved from the membrane secondary side to the membrane primary side. The permeated backwash water flows through the separation membrane surface as backwash drainage, flows down to the separation membrane module 1 according to gravity, and flows out of the separation membrane module 1 through the drain valve 13 and the drain pipe 14. .

As a result, the membrane filtration differential pressure of the separation membrane module 1 was 85 kPa after 6 months, compared to 30 kPa immediately after the start of operation. Moreover, the average power consumption of this fresh water generator during the operation period was 0.033 kWh / m ³ , which was 1.01 compared to Example 1.

(Comparative Example 4)
Using the fresh water generator having the equipment configuration shown in FIG. 5, during the backwashing process, the air washing valve 18 is opened and air is introduced to the primary side of the separation membrane module so that the air flow rate becomes 100 NL / min. The point of performing the flushing at the same time, following the backwashing process of performing the flushing at the same time, performing the drainage process, then returning to the water supply process and repeating the membrane filtration process, the backwash process, the drainage process, and the water supply process The operation was performed in the same manner as in Comparative Example 2 except that.

As a result, the membrane filtration differential pressure of the separation membrane module 1 was 85 kPa after 6 months, compared to 30 kPa immediately after the start of operation. Moreover, the average power consumption of this fresh water generator during the operation period was 0.032 kWh / m ³ , which was 1.00 compared to Example 1.

1: Separation membrane module 2: Raw water supply pump 3: Raw water supply piping 4: Raw water valve 5: Membrane filtration water piping 6: Backwash valve 7: Backwash water pressurized water tank 8: Membrane filtration water valve 9: Membrane filtration water outflow piping 11: Overflow valve 12: Overflow pipe 13: Drain valve 14: Drain pipe 15: Pressurized gas source 16: Pressurized gas pipe 17: Pressurized gas valve 18: Empty flush valve 19: Backwash water pressurized water tank air vent valve 21 : Chemical liquid storage tank 22: Chemical liquid injection pump 23: Chemical liquid injection pipe 31: Pressurized gas pressure regulating valve for backwashing 32: Pressurized gas pressure regulating valve for air washing 33: Gas flow adjusting valve for air washing 34: Backwash water tank 35: Backwashing pump 36: Backwash water piping

Claims (6)

  In the cleaning method of the external pressure type separation membrane module, after the water level is reached such that at least a part of the membrane primary side of the separation membrane is on the water surface, a pressurized gas is introduced into the membrane secondary side of the separation membrane to A method for cleaning a separation membrane module, comprising performing gas extrusion counter-pressure cleaning by extruding water in the primary side of the membrane.   In the cleaning method of the external pressure type separation membrane module, after making the membrane primary side of the separation membrane all over the water surface, a pressurized gas is introduced into the membrane secondary side of the separation membrane to form water on the membrane secondary side. 2. The method for cleaning a separation membrane module according to claim 1, wherein the pressure extrusion backwashing is performed by extruding to the primary side.   The method of cleaning a separation membrane module according to claim 1 or 2, wherein the pressure of the pressurized gas introduced to the membrane secondary side of the separation membrane is less than the bubble point of the separation membrane.   Drain valve located at the bottom of the separation membrane module when performing gas extrusion back pressure cleaning by introducing pressurized gas into the membrane secondary side of the separation membrane and extruding water on the membrane secondary side to the membrane primary side The method for cleaning a separation membrane module according to any one of claims 1 to 3, wherein a part or all of the backwash drainage is drained from a lower part of the membrane module by opening.   When the pressure extrusion is introduced into the membrane secondary side of the separation membrane and the water on the membrane secondary side is extruded to the membrane primary side for gas extrusion back pressure cleaning, the reverse drainage from the lower part of the separation membrane module By increasing the flow rate of the backwash wastewater that is pushed out from the membrane secondary side of the separation membrane to the membrane primary side rather than the flow rate of the wash drainage, the water level on the primary side of the separation membrane is raised and the gas extrusion back pressure washing is performed. The method for cleaning a separation membrane module according to any one of claims 1 to 4, wherein the separation membrane module is gas-washed in the middle and / or after gas extrusion back pressure washing.   The method of cleaning a separation membrane module according to any one of claims 1 to 5, wherein the separation membrane module is a pressure type separation membrane module in which the separation membrane is housed in a casing.

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