WO2013176145A1 - Cleaning method for separation membrane module - Google Patents

Cleaning method for separation membrane module Download PDF

Info

Publication number
WO2013176145A1
WO2013176145A1 PCT/JP2013/064115 JP2013064115W WO2013176145A1 WO 2013176145 A1 WO2013176145 A1 WO 2013176145A1 JP 2013064115 W JP2013064115 W JP 2013064115W WO 2013176145 A1 WO2013176145 A1 WO 2013176145A1
Authority
WO
WIPO (PCT)
Prior art keywords
membrane
separation membrane
water
backwash
membrane module
Prior art date
Application number
PCT/JP2013/064115
Other languages
French (fr)
Japanese (ja)
Inventor
亮太 高木
大久保 賢一
和希 羽川
Original Assignee
東レ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 東レ株式会社 filed Critical 東レ株式会社
Publication of WO2013176145A1 publication Critical patent/WO2013176145A1/en

Links

Images

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D65/00Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/02Membrane cleaning or sterilisation ; Membrane regeneration
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/44Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2321/00Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
    • B01D2321/04Backflushing
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2321/00Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
    • B01D2321/18Use of gases
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00Specific treatment goals
    • C02F2303/16Regeneration of sorbents, filters

Definitions

  • the present invention relates to a method for effectively cleaning a separation membrane module for stably operating the separation membrane module over 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.
  • 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.
  • 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.
  • 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 continuously or intermittently from the lower part of the raw water side of the membrane module, or the impurities accumulated on the separation membrane surface and the flow path between the separation membranes are peeled off by the shearing force of the bubbles, Or remove the raw water in the separation membrane module together with impurities removed and removed from the separation membrane surface by the backwashing or air washing (hereinafter referred to as “air washing” or “gas washing”) (hereinafter referred to as “air washing” or “gas washing”). , (Referred to as Patent Documents 1, 2, and 3).
  • 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.
  • 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.
  • 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).
  • Japanese Unexamined Patent Publication No. 11-342320 Japanese Patent No. 2118022 Japanese Patent No. 3948593 Japanese Laid-Open Patent Publication No. 2001-079366 Japanese Unexamined Patent Publication No. Hei 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 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. 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.
  • 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.
  • pressurized gas as a driving force
  • 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
  • FIG. 1 is an apparatus schematic flow diagram showing an example of a fresh water generator to which the cleaning method of the present invention is applied.
  • FIG. 2 is an apparatus schematic flow diagram showing another example of a fresh water generator to which the cleaning method of the present invention is applied.
  • FIG. 3 is an apparatus schematic flow diagram showing still another example of a fresh water generator to which the cleaning method of the present invention is applied.
  • FIG. 4 is an apparatus schematic flowchart showing still another example of a fresh water generator to which the cleaning method of the present invention is applied.
  • FIG. 5 is an apparatus schematic flowchart showing a fresh water generator used in a comparative example.
  • FIG. 6 is a diagram schematically showing the pressure applied to the inner surface of the separation membrane in the gas extrusion backwashing according to the present invention.
  • FIG. 7 is a diagram schematically showing the pressure applied to the inner surface of the separation membrane in the conventional backwashing.
  • FIG. 8 is a diagram schematically showing the pressure applied to the inner surface of the separation membrane in the conventional backwashing.
  • a fresh water generation apparatus that is a target of the cleaning method of the present invention supplies raw water via an external pressure separation membrane module 1 that performs membrane filtration of raw water, a raw water supply pipe 3, and a raw water valve 4.
  • Raw water supply pump 2 for supplying to the separation membrane module 1, an overflow valve 11 for extruding the gas in the separation membrane module 1, an overflow pipe 12, and membrane filtration for taking out membrane filtrate obtained by membrane filtration of the raw water Supply water pipe 5, backwash valve 6, membrane filtration water outflow pipe 9, backwash water pressurized water tank 7 for storing backwash water used for gas extrusion backwash, and pressurized gas that serves as driving force for gas extrusion backwash Pressurized 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, empty Air washing valve 1 for supplying gas for washing It consists of.
  • the external pressure type separation membrane module refers to a membrane module that performs membrane filtration in a direction from the outer surface of the separation membrane toward the inside of the separation membrane.
  • Each operation process includes, for example, a combination of start / stop of devices and opening / closing of valves as shown in Table 1.
  • 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.
  • the process proceeds to the membrane filtration step.
  • raw water is membrane filtered by the separation membrane module 1 by opening the backwash valve 6 and the membrane filtration water valve 8 and closing the overflow valve 11.
  • the obtained membrane filtered water is taken out through the membrane filtered water pipe 5, the backwash valve 6, the backwash water pressurized water tank 7, the membrane filtered water valve 8, and the membrane filtered water outflow pipe 9.
  • the time for the membrane filtration step 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.
  • 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.
  • gas cleaning empty cleaning
  • gas cleaning can be performed during the gas extrusion backwashing process and / or after the gas extrusion backwashing process.
  • the gas extrusion backwashing step is performed in Step 1 to Step3 and then the air washing step is performed in Step4 to Step5.
  • the embodiment of the present invention is not limited to this example.
  • Step 1 the overflow valve 11 and the drain valve 13 are opened, and the raw water on the primary side of the membrane in the separation membrane module 1 is discharged.
  • the membrane primary side of the separation membrane becomes a water level where at least a part is on the water surface. That is, the membrane primary side of the separation membrane is in a state where at least a part or all of the periphery is in a gas state, while the membrane secondary side is in a state where membrane filtrate is held.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • the membrane primary side of the separation membrane is the side where raw water to be filtered is supplied
  • the membrane secondary side of the separation membrane is 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.
  • the suspended substance is defined by turbidity, suspended solid amount or SS concentration (suspended substance 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
  • backwash drainage refers to the backwash water passing through the separation membrane from the membrane secondary side to the membrane primary side.
  • 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.
  • 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.
  • Step 2 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.
  • 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.
  • 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.
  • the backwash pump is selected to be several times the capacity of the raw water supply pump, and the backwash water is used.
  • 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.
  • 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.
  • the pressure of the pressurized gas is 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 obtained by the method described in JIS K3832 “Bubble Point Test Method for Microfiltration Membrane Element and Module”.
  • the pores of the separation membrane are filled with liquid (water in the case of a fresh water generator). This is the pressure at which one membrane surface is gradually pressurized with gas and liquid (water) is pushed out of the pores and the air begins to flow.
  • the pressurized gas source 15 for supplying a 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.
  • the membrane filtration water pipe 5 which is the membrane secondary side pipe
  • the membrane filtration water pipe 5 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • FIG. 6 is a diagram showing the pressure applied to the inner surface of the separation membrane at this time as a pressure distribution in the vertical direction of the surface of the separation membrane.
  • the inner surface of the separation membrane is defined as the surface where the water on the secondary side of the membrane is in contact with the separation membrane.
  • the vertical axis represents the vertical direction of the inner surface of the separation membrane
  • the subscript i represents the pressure at an arbitrary height (length Li of the separation membrane).
  • intersection of the vertical axis and the horizontal axis means the upper end of the inner surface of the separation membrane, and the arrow direction on the vertical axis means the length direction of the separation membrane whose longitudinal direction is substantially vertical.
  • the direction of the arrow represents the applied pressure in the backwash driving force, and the direction opposite to the arrow represents the magnitude of the loss pressure in the backwash driving force.
  • the inner surface of the separation membrane is backwashed pressure P 1 applied to the upper end of the separation membrane on the secondary side of the membrane, and the secondary side of the membrane is filled with water.
  • Water head pressure P 2 is applied toward the inner surface of the separation membrane.
  • the water head pressure P 2 gradually increases downward in the vertical direction.
  • the membrane primary side is not filled with water, there is no pressure applied from the membrane primary side toward the inner surface of the separation membrane.
  • a pressure loss P 3 is caused by the flow resistance. The pressure loss P 3 gradually increases downward in the vertical direction.
  • the backwash pressure P 1 applied to the secondary side of the membrane is due to the water pressure on the primary side of the membrane. It can be used as a driving force for backwashing without receiving resistance.
  • the separation membrane module longitudinal L i is arranged substantially vertically in the separation membrane, and, if the backwash water flows from the upper end of the separation membrane module and the separation membrane, membrane secondary side is filled with water Therefore, the water head pressure P 2 increases toward the lower end of the separation membrane. Therefore, the lower end portion of the separation membrane extending in the substantially vertical direction has a back head pressure P 1 applied to the upper end portion of the separation membrane to the head of the membrane secondary side.
  • the pressure applied with the pressure P 2 can be used as a driving force for gas extrusion 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.
  • FIG. 7 is a diagram showing the pressure applied to the inner surface of the separation membrane at this time.
  • the backwash pressure P 1 applied to the upper end portion of the separation membrane on the membrane secondary side, and the water head pressure P 2 from the membrane secondary side toward the inner surface of the separation membrane because the membrane secondary side is filled with water. It takes.
  • water head pressure P 4 is applied from the primary side of the membrane toward the inner surface of the separation membrane.
  • the water head pressure on the membrane secondary side and the water head pressure on the membrane primary side depend on the positional relationship between the membrane filtrate water pipe 5 and the overflow pipe 12 of the fresh water generator, but are substantially the same. Therefore, the membrane primary-side hydraulic head pressure P 4 and the membrane secondary-side hydraulic head pressure P 2 are offset through the inner surface of the separation membrane.
  • FIG. 8 shows the pressure applied to the inner surface of the separation membrane when the backwash wastewater is discharged from the separation membrane module in which the separation membrane is housed in the casing container in addition to the state at the time of backwashing shown in FIG. FIG.
  • the backwash wastewater that has passed from the membrane secondary side to the membrane primary side of the separation membrane flows due to the flow resistance that is generated when the separation membrane module flows to the backwash drainage port.
  • the pressure loss P 5 and the pressure loss P 6 due to the flow resistance generated when the backwash drainage passes through the backwash drain port and the overflow pipe of the separation membrane module are generated.
  • the head pressure P 4 due to the water filled on the primary side of the membrane and the backwash waste water are discharged from the separation membrane module 1 on the inner surface of the separation membrane, and are passed through the overflow valve 11 and the overflow pipe 12.
  • the flow resistances P 5 and P 6 caused by the outflow are 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.
  • the head pressure P 4 and the flow resistances P 5 and P 6 on the primary side of the membrane have an effect in the form of diminishing the driving force of backwashing, the driving force of backwashing that works effectively is reduced, As a result, the backwash effect is reduced.
  • the water head pressure P 4 applied to the primary side of the membrane and the water head pressure P 2 applied to the secondary side of the membrane are often substantially equal during backwashing.
  • the water head pressures P 4 and P 2 between the sandwiched membrane primary side and membrane secondary side are offset.
  • the backwash pressure P 1 at the upper end of the separation membrane becomes effective as it approaches the lower end of the separation membrane due to the flow resistance P 3 generated when the backwash water flows through the flow passage on the membrane secondary side of the separation membrane.
  • the driving force of the acting backwash is reduced.
  • the flow resistance P 5 that occurs when the backwash waste water flows out of the separation membrane module 1 close to the lower end of the separation membrane It becomes larger as it gets closer to the upper end of the separation membrane. Furthermore, in the case of a pressure-type separation membrane module in which the backwash drain of the separation membrane module 1 has a nozzle shape, when trying to discharge a large amount of backwash drainage in a short time, the nozzle shape and A large flow resistance P 6 is generated at the backwash drain, and the driving force for backwashing is reduced.
  • the driving force of backwashing is increased by the water head pressure P 4 on the membrane primary side compared with the gas extrusion backwashing in the present invention.
  • the flow resistance P 2 of the backwash water on the secondary side of the membrane and the flow resistances P 5 and P 6 of the backwash drainage on the primary side of the membrane are extended from the upper end to the lower end of the separation membrane. Since the degree of attenuation of the backwash driving force increases, sufficient backwashing effect cannot be obtained.
  • Step 1 of the gas extrusion backwashing step the water on the primary side of the separation membrane module 1 is discharged.
  • 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.
  • the entire separation membrane is above the water surface, there is no attenuation of the backwashing force due to the water head pressure on the membrane primary side and the backwashing driving force due to the back pressure due to the flow resistance, and the gas of the present invention. The effect of extrusion backwashing is maximized.
  • the separation membrane module 1 is a pressure type separation membrane module
  • 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 Flow resistance generated in the valve is applied as backwash back pressure, but backwash drainage flows out from the nozzle backwash drain even if the water level on the primary side of the membrane rises due to backwash drainage. Up to this point, the flow resistance does not occur. 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.
  • 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.
  • 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.
  • 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 or the like.
  • 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.
  • 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.
  • raw water may be supplied as described above, or the overflow valve 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.
  • 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.
  • 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
  • the separation membrane module can be gas-washed during gas extrusion counter-pressure cleaning 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.
  • the external pressure type separation membrane module As a form of the external pressure type separation membrane module to which the cleaning method of the present invention is applied, even in the case of a pressure type separation 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 water tank that is open to the atmosphere It may be a submerged membrane module soaked in the water. Since the submerged membrane module performs suction filtration, the pressure that can be used for membrane filtration is practically limited to about ⁇ 80 kPa.
  • the pressure that can be used for membrane filtration in a pressure-type separation membrane module is limited to the pressure resistance capability of the separation membrane module and / or the separation membrane, but in general, the pressure range that can be used for membrane filtration than the submerged membrane module Therefore, it is preferable because the membrane can be filtered with a high membrane filtration flux with a membrane filtration pressure higher than that of the submerged membrane module.
  • the submerged membrane module is preferable because the suspended matter indicated by turbidity and SS concentration (floating matter concentration) can be subjected to membrane filtration of raw water having a high concentration. 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.
  • 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 associated with the outflow of backwash wastewater is smaller than that of the pressure-type separation 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 pressure-type separation membrane module can enjoy the effect of the present invention more greatly from the viewpoint of outflow of the backwash waste water to the outside of the separation membrane module.
  • the separation membrane module there are a hollow fiber membrane module, a tubular membrane module, a spiral membrane module, a flat membrane module, etc., and any shape of the separation membrane module can be used to enjoy the effects of the present invention.
  • the hollow fiber membrane means a tubular separation membrane having a diameter of less than 2 mm
  • the tubular membrane means a tubular separation membrane having a diameter of 2 mm or more.
  • the flat membrane module there is a concern that the flat membrane may be peeled off from the support plate when strong backwashing is performed, and backwash water accumulates in the gap between the support plate and the flat membrane during backwashing.
  • the spiral membrane module has a shape in which a net-like spacer is incorporated as a channel material on the membrane primary side between the wound flat membrane and the membrane membrane.
  • hollow fiber membrane modules and tubular membrane modules can be used for strong backwashing, can secure sufficient flow paths between individual hollow fiber membranes / tubular membranes, and accept suspended substances of high concentration. From the point of view, it is preferable because the effects of the present invention can be sufficiently obtained. Moreover, the hollow fiber membrane module is more preferable from the point that the membrane area per unit volume can be taken larger than the tubular membrane module.
  • 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.
  • MF membrane microfiltration membrane
  • UF membrane ultrafiltration membrane
  • 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.
  • 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.
  • 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
  • the membrane pores on the surface of the separation membrane are fine and the surface of the separation membrane becomes smooth.
  • 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, ethylene-tetrafluoroethylene copolymer, polychlorotrifluorotrifluoro Ethylene, polytetrafluoroethylene, polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chlorotrifluoroethylene-ethylene copolymer, polyvinylidene fluoride (hereinafter sometimes referred to as “PVDF”), Polysulfone, polyethersulfone, cellulose acetate and the like can be used, and ceramic or the like can be used when an inorganic material is used.
  • PVDF polyvinylidene fluoride
  • an organic material containing fluorine or a material made of ceramic is preferable.
  • an organic material containing polyacrylonitrile or cellulose acetate, which is generally a hydrophilic material is preferred from the viewpoint of chemical cleaning recoverability.
  • 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.
  • the separation membrane module is arranged and installed in a substantially vertical direction. This is because separation membrane modules that are arranged and installed in a substantially vertical direction are more likely to discharge raw water on the primary side of the membrane and backwash drainage than separation membrane modules that are arranged and installed in a substantially horizontal direction. is there.
  • the longitudinal direction of the separation membrane module and hence the separation membrane is arranged in a substantially vertical direction. This is because when backwashing water flows from the upper end of the separation membrane module and the separation membrane on the membrane secondary side during gas extrusion backwashing, the membrane secondary side is filled with water, so the lower end of the separation membrane Because the head pressure increases, the pressure at the lower end of the separation membrane that extends in a substantially vertical direction is the backwash pressure applied to the upper end of the separation membrane plus the head pressure on the secondary side of the membrane as the driving force for backwashing. This is because it can. As a result, it is possible to apply a driving force for backwashing relatively uniformly from the upper end to the lower end in the substantially vertical direction of the separation membrane, and a high cleaning effect of the separation membrane can be obtained.
  • the control method for membrane filtration may be constant flow filtration or constant pressure filtration, but constant flow filtration is preferred from the viewpoint of obtaining a constant treated water amount or treated water flow rate.
  • 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.
  • 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 whole-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, the separation membrane module 1 uses one external pressure type 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.
  • HFU-2020 manufactured by Toray Industries, Inc.
  • Each operation process was configured by starting and stopping the equipment and opening and closing the valves as shown below.
  • 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.
  • 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.
  • the output of the raw water supply pump 2 is feedback-controlled by the output value of the membrane filtrate flow sensor (not shown), so that the membrane filtrate has a membrane filtration flux of 3 m 3 / (m 2 ⁇ d).
  • the flow rate was controlled at a constant flow rate.
  • Step 1 As a water level lowering step (Step 1) of the gas extrusion backwashing 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.
  • Step 2 the pressurized gas valve 17 is opened, pressurized air is supplied to the backwash water pressurized water tank 7, and pressure is 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.
  • Step 3 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 was pushed into the membrane secondary side of the separation membrane module 1 through the membrane filtration water pipe 5 and the backwash valve 6 to perform gas extrusion backwashing.
  • 100 L of water was used as backwashing water.
  • 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.
  • 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.
  • Step 4 of 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 raw water valve 4 is opened while the overflow valve 11 is open. Then, the raw water supply pump 2 was operated to supply the raw water to the separation membrane module 1, and the membrane primary side of the separation membrane module 1 was filled with the 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 (Step 5), 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.
  • the drain valve 13 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.
  • 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.
  • 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.
  • 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.
  • the average power consumption of this fresh water generator during the operation period was 0.035 kWh / m 3 , which was 1.06 as a ratio to the average power consumption of Example 1.
  • Example 4 3 is used to close the drain valve 13 during the gas extrusion backwashing step (Step 3) of the gas extrusion backwashing process, and permeate from the membrane secondary side of the separation membrane to the membrane primary side.
  • the backwash waste water generated in the separation membrane module 1 is accumulated on the primary side of the separation membrane module 1 so that the water filling step (Step 4) of the air washing process is omitted, and further in the gas extrusion backwashing step (Step 3).
  • the flush valve 18 is opened while the drain valve 13 is closed and air is introduced into the membrane primary side of the separation membrane module 1 to perform flushing. Went.
  • 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.
  • the average power consumption of this fresh water generator during the operation period was 0.033 kWh / m 3 , which was 1.03 as a ratio to the average power consumption of Example 1.
  • Step 5 Backwash drainage with the overflow valve 11 and the drain valve 13 open for the first 10 seconds of the gas extrusion backwashing step (Step 3) of the gas extrusion backwashing process using the fresh water generator having the equipment configuration shown in FIG. Is discharged outside the separation membrane module 1 through the drain valve 13 and the drain pipe 14, and then the gas extrusion back washing step is performed, and the drain valve 13 is closed after 10 seconds, and the back washing waste water is separated into the separation membrane module.
  • the water washing step (Step 4) of the air washing process is omitted, the drain valve 13 is closed, and the backwash waste water is accumulated on the membrane primary side in the separation membrane module 1.
  • the air washing valve 18 is opened and air is introduced into the membrane primary side of the separation membrane module 1 to perform air washing.
  • the pressurized gas valve 17 is used.
  • Backwash valve 6 Even after closing and stopping the gas extrusion backwashing, the air washing is continued with the air washing valve 18 opened, and after the air washing is performed for 30 seconds, the air washing valve 18 is closed to stop the air washing. The operation was performed in the same manner as in Example 1 except for the four points.
  • 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.
  • the average power consumption of this fresh water generator during the operation period was 0.032 kWh / m 3 , which was 1.00 as a ratio to the average power consumption of Example 1.
  • 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.
  • the average power consumption of this fresh water generator during the operation period was 0.038 kWh / m 3 , which was 1.18 as a ratio to the average power consumption of Example 1.
  • Comparative Example 2 5 using a fresh water generator having the equipment configuration shown in FIG. 5 and using one external pressure PVDF hollow fiber ultrafiltration membrane module HFU-2020 (manufactured by Toray Industries, Inc.) as the separation membrane module 1.
  • 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.
  • the output of the raw water supply pump 2 is feedback-controlled by the output value of the membrane filtrate flow sensor (not shown), so that the membrane filtrate has a membrane filtration flux of 3 m 3 / (m 2 ⁇ d).
  • the flow rate was controlled at a constant flow rate.
  • the backwashing valve 6 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.
  • 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.
  • 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.
  • the drain valve 13 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.
  • 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.
  • 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.
  • 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.
  • 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. .
  • 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.
  • the average power consumption of the fresh water generator during the operation period was 0.033 kWh / m 3 , which was 1.01 as a ratio to the average power consumption of Example 1.
  • 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.
  • the average power consumption of this fresh water generator during the operation period was 0.032 kWh / m 3 , which was 1.00 as a ratio to the average power consumption of Example 1.

Abstract

Provided is an efficient cleaning method for a separation membrane module with which the stable operation of the separation membrane module is made possible. In a cleaning method for an external pressure-type separation membrane module (1), at least a portion of a membrane primary side of a separation membrane is set at a water level that will be above water, pressurized gas is subsequently introduced to a membrane secondary side of the separation membrane and water on the membrane secondary side extrudes to the membrane primary side, thereby performing reverse-pressure cleaning.

Description

分離膜モジュールの洗浄方法Cleaning method for separation membrane module
 本発明は、分離膜モジュールを長期間にわたって安定に運転するための分離膜モジュールを効果的に洗浄する方法に関する。 The present invention relates to a method for effectively cleaning a separation membrane module for stably operating the separation membrane module over a long period of time.
 膜分離法は、省エネルギー・省スペースで、膜ろ過水の水質が優れていることに加え、運転維持管理が容易であること等の特長を有するため、様々な分野での使用が拡大している。例えば、精密ろ過膜や限外ろ過膜については、河川水や地下水や下水処理水から工業用水や水道水を製造する浄水プロセスへの適用や、海水淡水化逆浸透膜処理工程における前処理への適用、下水や工場排水の再利用逆浸透膜処理工程における前処理への適用が挙げられる。 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.
 原水を膜ろ過するにあたって、原水中の水分は分離膜を介して膜ろ過水として取り出され、不純物は分離膜表面上や分離膜の多孔質部内に残されるために、分離膜の目詰まりや分離膜間の流路閉塞が進行して、膜ろ過水量の低下あるいは膜ろ過差圧の上昇が問題となってくる。 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.
 そこで、定期的に分離膜の膜ろ過水側から原水側へ膜ろ過水を逆流させることによって分離膜表面に蓄積した不純物層を剥離、除去したり(以下、「逆洗」と称す)、分離膜モジュールの原水側下部から連続的、あるいは間欠的に気泡を導入させることによって分離膜を揺動させたり、気泡によるせん断力により分離膜表面や分離膜間の流路に蓄積した不純物を剥離、除去したり(以下、「空洗」または「気体洗浄」と称す)、分離膜モジュール内の原水を、前記逆洗や空洗によって分離膜表面から剥離、除去された不純物とともに排出したり(以下、「ドレン」と称す)する物理洗浄を実施している(例えば特許文献1、2、3参照)。 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 continuously or intermittently from the lower part of the raw water side of the membrane module, or the impurities accumulated on the separation membrane surface and the flow path between the separation membranes are peeled off by the shearing force of the bubbles, Or remove the raw water in the separation membrane module together with impurities removed and removed from the separation membrane surface by the backwashing or air washing (hereinafter referred to as “air washing” or “gas washing”) (hereinafter referred to as “air washing” or “gas washing”). , (Referred to as Patent Documents 1, 2, and 3).
 さらに洗浄効果を高めるため、例えば逆洗水に酸溶液、アルカリ溶液、酸化剤水溶液や洗浄剤を添加して、化学的に膜表面や膜細孔内に付着した物質を溶解もしくは分解除去する化学洗浄も併せて実施されている。 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.
 また、これらの物理洗浄や化学洗浄を組合わせた分離膜モジュールの洗浄方法として、逆洗水に次亜塩素酸ナトリウムを添加して逆洗を行うと同時に空洗を行ったり(例えば特許文献4参照)、ドレンを行って分離膜モジュール内の原水側の水を排出してから、逆洗排水をドレンしながら逆洗を行ったり(例えば特許文献5参照)、分離膜モジュールの原水側を水で満たした状態で、加圧気体を分離膜モジュールの膜ろ過水側に導入して、膜ろ過水側の滞留水を分離膜の膜ろ過水側から原水側へ通過させて分離膜表面に蓄積した不純物層を剥離、除去したり(例えば特許文献6参照)する洗浄が実施されている。 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).
 しかしながら、これらの方法をもってしても分離膜の洗浄は未だ不十分であり、さらに効果的な洗浄方法が求められている。 However, even with these methods, cleaning of the separation membrane is still insufficient, and a more effective cleaning method is required.
日本国特開平11-342320号公報Japanese Unexamined Patent Publication No. 11-342320 日本国特許第2118022号公報Japanese Patent No. 2118022 日本国特許第3948593号公報Japanese Patent No. 3948593 日本国特開2001-079366号公報Japanese Laid-Open Patent Publication No. 2001-079366 日本国特開平6-170364号公報Japanese Unexamined Patent Publication No. Hei 6-170364 日本国特許第3887072号公報Japanese Patent No. 3887072
 本発明の目的は、分離膜モジュールを安定に運転可能にするようにした分離膜モジュールの効果的な洗浄方法を提供することにある。 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.
 上記課題を解決する本発明の分離膜モジュールの洗浄方法は、次の特徴を有するものである。
(1)外圧式の分離膜モジュールの洗浄方法において、分離膜の膜一次側の少なくとも一部が水面上になる水位にした後に、分離膜の膜二次側に加圧気体を導入して膜二次側の水を膜一次側に押出すことによって気体押出し逆圧洗浄をすることを特徴とする分離膜モジュールの洗浄方法。
(2)外圧式の分離膜モジュールの洗浄方法において、分離膜の膜一次側がすべて水面上になるようにした後に、分離膜の膜二次側に加圧気体を導入して膜二次側の水を膜一次側に押出すことによって気体押出し逆圧洗浄をすることを特徴とする(1)に記載の分離膜モジュールの洗浄方法。
(3)分離膜の膜二次側に導入する加圧気体の圧力が、分離膜のバブルポイント未満であることを特徴とする(1)または(2)に記載の分離膜モジュールの洗浄方法。
(4)分離膜の膜二次側に加圧気体を導入して膜二次側の水を膜一次側に押出すことによって気体押出し逆圧洗浄をする際に、分離膜モジュールの下部に位置する排水弁を開くことにより、逆洗排水の一部またはすべてを膜モジュールの下部から排水させることを特徴とする、請求項(1)~(3)のいずれかに記載の分離膜モジュールの洗浄方法。
(5)分離膜の膜二次側に加圧気体を導入して膜二次側の水を膜一次側に押出すことによって気体押出し逆圧洗浄をする際に、分離膜モジュールの下部から排水される逆洗排水の流量よりも、分離膜の膜二次側から膜一次側へ押出す逆洗排水の流量を大きくすることにより、分離膜の膜一次側の水位を上げて、前記気体押出し逆圧洗浄中および/または気体押出し逆圧洗浄後に分離膜モジュールを空気洗浄することを特徴とする、(1)~(4)のいずれかに記載の分離膜モジュールの洗浄方法。
(6)分離膜モジュールが、ケーシング内に分離膜を収納した加圧型分離膜モジュールであることを特徴とする、(1)~(5)のいずれかに記載の分離膜モジュールの洗浄方法。
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 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. 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 separation membrane module cleaning 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 a drain valve that 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 method of cleaning a separation membrane module 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.
 本発明の分離膜モジュールの洗浄方法によれば、一旦分離膜モジュール内の水位を下げて、分離膜の膜一次側の少なくとも一部が水面上になるようにした後に、分離膜の膜二次側に加圧気体を導入して膜二次側の水を膜一次側に押出すことによって気体押出し逆圧洗浄(以下、「気体押出し逆洗」という。)を行う。ここで、加圧気体を駆動力にするために、従来のポンプを駆動力として水を加圧して行う逆洗よりも大きな圧力を分離膜の膜二次側にかけることができる上に、この気体押出し逆洗中における膜一次側、すなわち逆洗水の出口側には水圧がかからない状態となっているため、膜二次側に導入される加圧気体の圧力を最大限に気体押出し逆洗の駆動力として使用できるので、効果的に膜細孔内ならびに膜表面上に蓄積した不純物を剥離、除去することが可能である。さらに、膜一次側に水圧がかかる膜一次側周囲が液体の状態よりも膜表面に付着した物質が剥離しやすく、従来よりも効率的に洗浄をすることが可能である。また、ポンプを駆動力とした逆洗を行う従来の造水装置と比べて、本発明の洗浄方法を用いた造水装置は逆洗ポンプを省略することが可能である。 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.
図1は、本発明の洗浄方法が適用される造水装置の一例を示す装置概略フロー図である。FIG. 1 is an apparatus schematic flow diagram showing an example of a fresh water generator to which the cleaning method of the present invention is applied. 図2は、本発明の洗浄方法が適用される造水装置の他の例を示す装置概略フロー図である。FIG. 2 is an apparatus schematic flow diagram showing another example of a fresh water generator to which the cleaning method of the present invention is applied. 図3は、本発明の洗浄方法が適用される造水装置の更に他の例を示す装置概略フロー図である。FIG. 3 is an apparatus schematic flow diagram showing still another example of a fresh water generator to which the cleaning method of the present invention is applied. 図4は、本発明の洗浄方法が適用される造水装置の更に他の例を示す装置概略フロー図である。FIG. 4 is an apparatus schematic flowchart showing still another example of a fresh water generator to which the cleaning method of the present invention is applied. 図5は、比較例に使用した造水装置を示す装置概略フロー図である。FIG. 5 is an apparatus schematic flowchart showing a fresh water generator used in a comparative example. 図6は、本発明の気体押出し逆洗における分離膜内表面にかかる圧力を模式的に表した図である。FIG. 6 is a diagram schematically showing the pressure applied to the inner surface of the separation membrane in the gas extrusion backwashing according to the present invention. 図7は、従来の逆洗における分離膜内表面にかかる圧力を模式的に表した図である。FIG. 7 is a diagram schematically showing the pressure applied to the inner surface of the separation membrane in the conventional backwashing. 図8は、従来の逆洗における分離膜内表面にかかる圧力を模式的に表した図である。FIG. 8 is a diagram schematically showing the pressure applied to the inner surface of the separation membrane in the conventional backwashing.
 以下、図面に示す実施態様に基づいて本発明をさらに詳細に説明する。なお、本発明は以下の実施態様に限定されるものではない。 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.
 本発明の洗浄方法の対象となる造水装置は、例えば、図1に示すように、原水を膜ろ過する外圧式の分離膜モジュール1と、原水供給配管3、原水弁4を介して原水を分離膜モジュール1に供給する原水供給ポンプ2、分離膜モジュール1内の気体を押出すためのオーバーフロー弁11、オーバーフロー配管12、原水を膜ろ過して得られた膜ろ過水を取り出すための膜ろ過水配管5、逆洗弁6、膜ろ過水流出配管9、気体押出し逆洗に用いられる逆洗水を貯留する逆洗水加圧水槽7、気体押出し逆洗の駆動力となる加圧気体を供給する加圧気体源15、加圧気体配管16、加圧気体弁17、膜ろ過水弁8、分離膜モジュール1内の膜一次側の原水を排出するための排水弁13、排水配管14、空洗のための気体を供給するための空洗弁18から構成される。 For example, as shown in FIG. 1, a fresh water generation apparatus that is a target of the cleaning method of the present invention supplies raw water via an external pressure separation membrane module 1 that performs membrane filtration of raw water, a raw water supply pipe 3, and a raw water valve 4. Raw water supply pump 2 for supplying to the separation membrane module 1, an overflow valve 11 for extruding the gas in the separation membrane module 1, an overflow pipe 12, and membrane filtration for taking out membrane filtrate obtained by membrane filtration of the raw water Supply water pipe 5, backwash valve 6, membrane filtration water outflow pipe 9, backwash water pressurized water tank 7 for storing backwash water used for gas extrusion backwash, and pressurized gas that serves as driving force for gas extrusion backwash Pressurized 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, empty Air washing valve 1 for supplying gas for washing It consists of.
 ここで、外圧式の分離膜モジュールとは、分離膜の外表面から分離膜の内部に向かう方向に膜ろ過を行う形式の膜モジュールをいう。 Here, the external pressure type separation membrane module refers to a membrane module that performs membrane filtration in a direction from the outer surface of the separation membrane toward the inside of the separation membrane.
 上述の造水装置における基本的な運転工程である給水工程、膜ろ過工程、気体押出し逆洗工程、空洗工程および排水工程について説明する。各運転工程は、例えば、表1に示すような機器の発停と弁の開閉の組合わせによって構成される。 The water supply process, the membrane filtration process, the gas extrusion backwashing process, the air washing process, and the 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.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
 まず、分離膜モジュール1の膜一次側を原水で満たすための給水工程として、原水弁4、オーバーフロー弁11を開にして原水供給ポンプ2を稼動させて原水を分離膜モジュール1へと供給する。分離膜モジュール1の膜一次側が原水で満たされたら膜ろ過工程へと移行する。膜ろ過工程では、逆洗弁6、膜ろ過水弁8を開にして、オーバーフロー弁11を閉にすることで原水は分離膜モジュール1によって膜ろ過される。得られた膜ろ過水は、膜ろ過水配管5、逆洗弁6、逆洗水加圧水槽7、膜ろ過水弁8、膜ろ過水流出配管9を介して取り出される。膜ろ過工程の時間は、原水水質や膜ろ過流束に応じて適宜設定するのが好ましいが、所定の膜ろ過差圧に到達するまで膜ろ過を継続させてもよい。膜ろ過工程の後に、気体押出し逆洗工程を実施するために、原水供給ポンプ2を停止し、原水弁4、逆洗弁6、膜ろ過水弁8を閉にする。 First, as a water supply process 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, raw water is membrane filtered by the separation membrane module 1 by opening the backwash valve 6 and the membrane filtration water valve 8 and closing the overflow valve 11. The obtained membrane filtered water is taken out through the membrane filtered water pipe 5, the backwash valve 6, the backwash water pressurized water tank 7, the membrane filtered water valve 8, and the membrane filtered water outflow pipe 9. The time for the membrane filtration step 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.
 本発明の洗浄方法において、気体押出し逆洗工程の間および/または気体押出し逆洗工程の後に気体洗浄(空洗)を行うことができる。以下、気体押出し逆洗工程をStep1~Step3で行った後、空洗工程をStep4~Step5で行うものとして説明するが、本発明の実施形態はこの例に限定されるものではない。 In the cleaning method of the present invention, gas cleaning (empty cleaning) can be performed during the gas extrusion backwashing process and / or after the gas extrusion backwashing process. In the following description, it is assumed that the gas extrusion backwashing step is performed in Step 1 to Step3 and then the air washing step is performed in Step4 to Step5. However, the embodiment of the present invention is not limited to this example.
 気体押出し逆洗工程において、Step1ではオーバーフロー弁11、排水弁13を開にして分離膜モジュール1内の膜一次側の原水を排出する。この時、分離膜の膜一次側が少なくとも一部が水面上になる水位になる。すなわち、分離膜の膜一次側は少なくとも一部の周囲或いは全部の周囲が気体となった状態になり、一方、膜二次側には膜ろ過水が保持された状態になる。次いで、Step2では、加圧気体弁17を開にして加圧気体源15から逆洗水加圧水槽7に加圧気体を供給し、逆洗水加圧水槽7内の逆洗水に所定の圧力を印加する。さらに、Step3では、逆洗弁6を開にすることで、逆洗水加圧水槽7内で所定の圧力を印加された逆洗水が加圧気体に押出されて、膜ろ過水配管5、逆洗弁6を介して分離膜モジュール1の膜二次側へと押し込まれ、分離膜を透過して膜一次側へと流出する。分離膜を透過した逆洗排水は、その一部またはすべてが排水弁13から排水される。 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 primary side of the membrane in the separation membrane module 1 is discharged. At this time, the membrane primary side of the separation membrane becomes a water level where at least a part is on the water surface. That is, the membrane primary side of the separation membrane is in a state where at least a part or all of the periphery 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.
 空洗工程においては、Step4ではオーバーフロー弁11を開としたまま、逆洗弁6、排水弁13、加圧気体弁17を閉にして、原水弁4を開にして、原水供給ポンプ2を稼動させて原水を分離膜モジュール1へと供給して、分離膜モジュール1の膜一次側に水を張る。次いで、Step5ではオーバーフロー弁11を開としたまま、原水供給ポンプ2を停止、原水弁4を閉にして、空洗弁18を開にして分離膜モジュール1の膜一次側に気体を導入して、気泡によって分離膜を揺動させたり、気泡によるせん断力により分離膜表面や分離膜間の流路に蓄積した不純物を剥離、除去したりする空洗を行う。 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.
 排水工程においては、オーバーフロー弁11を開としたまま、空洗弁18を閉、排水弁13を開にして、分離膜モジュール1の膜一次側の水を、空洗によって分離膜表面や分離膜間の流路から剥離した不純物とともに分離膜モジュール1から排出する。 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.
 ここで、分離膜の膜一次側とはろ過対象となる原水が供給される側であり、分離膜の膜二次側とは原水を分離膜でろ過したろ過水側のことをいう。膜一次側には原水に含まれる懸濁物質が存在しているが、膜ろ過水には原水に含まれる懸濁物質は膜ろ過されて除去されているので、膜二次側には懸濁物質は存在していない。また、懸濁物質とは、濁度、浮遊物質量もしくはSS濃度(浮遊物質濃度)で定義されるものであり、一般的に精密ろ過膜および限外ろ過膜によって除去される物質である。 Here, the membrane primary side of the separation membrane is the side where raw water to be filtered is supplied, and the membrane secondary side of the separation membrane is 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 (suspended substance concentration), and is generally a substance removed by a microfiltration membrane and an ultrafiltration membrane.
 逆洗水とは逆洗に使用される水が膜二次側を流動する状態の水をいい、逆洗排水とは逆洗水が膜二次側から膜一次側へと分離膜を透過して、膜一次側の分離膜表面上へ至って、膜一次側を流動する状態の水をいう。また、分離膜表面は膜一次側の水と分離膜が接する面と定義する。なお、逆洗水としては、原水を分離膜でろ過したろ過水を使うことが一般的であるが、懸濁物質が除去された水であれば膜二次側を懸濁物質で汚染させることがないので逆洗水として使用することができる。 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.
 気体押出し逆洗では、予め加圧気体を膜二次側に導入して逆洗水に任意の逆洗圧を印加しておき(Step2)、その後に逆洗弁6を開とすることで、逆洗水に印加された逆洗圧が瞬時に開放されて分離膜に作用するため(Step3)、分離膜に任意の逆洗圧を印加することができる。 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.
 ところで、従来逆洗水をポンプの駆動力を用いて押し込んで逆洗を行うことが多いが、この場合には逆洗圧は逆洗用ポンプの駆動力の範囲内という制約下で逆洗水流量に依存して求められ、一般的には逆洗圧は逆洗水流量に比例する。また、膜ろ過工程時の膜ろ過圧も同様に膜ろ過水流量に比例する。従って、膜ろ過圧の数倍する逆洗圧を印加したい場合には、膜ろ過水流量の数倍になるよう逆洗水流量を調整する必要がある。しかしながら、膜ろ過水流量に対して逆洗水流量を数倍になるようにするためには、逆洗用ポンプを原水供給ポンプの数倍の能力となるように選定し、かつ、逆洗水ならびに逆洗排水が流下する膜ろ過水配管5、オーバーフロー配管12、逆洗弁6、オーバーフロー弁11の口径を逆洗水流量に見合うようにサイズアップしなければならないために、設備費、逆洗用ポンプの動力費が過剰にかかり、経済的でなくなる欠点がある。しかしながら、気体押し出し逆洗においては、逆洗圧は加圧気体に印加された圧力をもって任意に設定できるために、膜ろ過圧の数倍する逆洗圧であっても容易に印加することができ、高い逆洗圧によって強い洗浄効果を得ることができる。 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.
 本発明において、分離膜の膜二次側に導入する加圧気体の圧力としては、分離膜のバブルポイント未満であることが好ましい。加圧気体の圧力を分離膜のバブルポイント未満にすることにより、加圧気体が分離膜を透過することなく、逆洗水のみが分離膜を透過するので、分離膜の細孔内に気体を進入させて分離膜を乾燥させてしまうことなく逆洗をすることができる。バブルポイントは、JIS K3832「精密濾過膜エレメントおよびモジュールのバブルポイント試験方法」に記載された方法により求められ、分離膜の細孔内に液体(造水装置の場合は水)を充填し、その一方の膜面を気体で徐々に加圧していき、細孔内から液体(水)が押し出され、空気が流れ始めるときの圧力である。 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 obtained by the method described in JIS K3832 “Bubble Point Test Method for Microfiltration Membrane Element and Module”. The pores of the separation membrane are filled with liquid (water in the case of a fresh water generator). This is the pressure at which one membrane surface is gradually pressurized with gas and liquid (water) is pushed out of the pores and the air begins to flow.
 ここで、逆洗水に所定の圧力を印加する加圧気体を供給するための加圧気体源15としては、10kPa~1000kPa程度の圧力範囲の気体を供給できる手段であれば、いかなる手段を用いても構わない。一般的には、入手しやすく、維持管理が容易であるエアコンプレッサを用いることが好ましい。エアコンプレッサによって加圧された気体を一旦エアタンクに貯留し、エアタンクの後段に設置したレギュレータによってエアコンプレッサによって加圧された気体を任意の圧力に調圧した後に、加圧気体配管16、加圧気体弁17を介して、逆洗水加圧水槽7に供給することが、簡素な設備構成で容易に任意の圧力の加圧気体を供給できるので好ましい。 Here, as the pressurized gas source 15 for supplying a 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.
 さらに、本発明の気体押出し逆洗においては、加圧気体が逆洗水加圧水槽7などの膜二次側に供給されるため、膜二次側の管路である膜ろ過水配管5、逆洗水加圧水槽7、膜ろ過水流出配管9が加圧気体中の不純物によって汚染しないように、加圧気体源15から加圧気体弁17までの間に加圧気体中の不純物除去のためのフィルタを設置することが好ましい。加圧気体用フィルタとしては、エアコンプレッサ等の加圧気体源に由来するオイルミストを除去するためのオイルミストセパレータや、加圧気体中の微粒子等を除去するためのエアフィルタが挙げられる。また、加圧気体としては、本発明の主旨から特に限定されるものではないが、加圧気体を用いて水を押出すので、水への溶解度が小さい気体が好ましい。一般的には大気を圧縮した加圧空気を用いると、気体源の入手が容易であり、水への溶解度が小さく、かつ人体への有害性の面でも安全であるので好ましい。 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.
 逆洗水加圧水槽7としては、逆洗水となる水を貯留できて、加圧気体源15から供給される加圧気体の圧力への耐圧性を有していれば、本発明の主旨からどのような形状、材質であっても構わない。耐圧性を有する水槽を逆洗水加圧水槽7として膜ろ過水配管5の途中に設けても良いし、膜ろ過水配管5に逆洗水に必要な容積をもたせて逆洗水加圧水槽7として扱っても良い。 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.
 また、図4に示すように、膜ろ過工程において逆洗水加圧水槽7を満水にする際にだけ、逆洗弁6、逆洗水加圧水槽エア抜き弁19を開にして、逆洗水加圧水槽7に膜ろ過水を導き、逆洗水加圧水槽7が満水になれば逆洗弁6、逆洗水加圧水槽エア抜き弁19を閉にして、膜ろ過水を、膜ろ過水配管5、膜ろ過水弁8、膜ろ過水流出配管9を介して膜ろ過水を取り出すようにしても良い。 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.
 本発明において、Step3で気体押出し逆洗を行った際には、分離膜の膜二次側から膜一次側へ透過して流出した逆洗排水は、重力に従って分離膜モジュール1の下部へと分離膜表面を流下して排水弁13、排水配管14を介して排出される。図6は、この際の分離膜内表面にかかる圧力を、分離膜表面の鉛直方向における圧力分布として表わす図である。ここで、分離膜内表面とは膜二次側の水と分離膜が接する面と定義する。図中、縦軸は分離膜内表面の鉛直方向を表し、添え字iは任意の高さ(分離膜の長さLi)における圧力であることを表す。縦軸と横軸の交点は、分離膜内表面の上端部、縦軸の矢印方向は、長手方向を略鉛直にした分離膜の長さ方向を意味する。横軸は、矢印方向が逆洗駆動力における印加圧力、矢印の反対方向が逆洗駆動力における損失圧力の大きさを表す。 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 the drain valve 13 and drain pipe 14. FIG. 6 is a diagram showing the pressure applied to the inner surface of the separation membrane at this time as a pressure distribution in the vertical direction of the surface of the separation membrane. Here, the inner surface of the separation membrane is defined as the surface where the water on the secondary side of the membrane is in contact with the separation membrane. In the figure, the vertical axis represents the vertical direction of the inner surface of the separation membrane, and the subscript i represents the pressure at an arbitrary height (length Li of the separation membrane). The intersection of the vertical axis and the horizontal axis means the upper end of the inner surface of the separation membrane, and the arrow direction on the vertical axis means the length direction of the separation membrane whose longitudinal direction is substantially vertical. In the horizontal axis, the direction of the arrow represents the applied pressure in the backwash driving force, and the direction opposite to the arrow represents the magnitude of the loss pressure in the backwash driving force.
 図6において、分離膜内表面には膜二次側の分離膜の上端部に印加された逆洗圧力P1、および膜二次側には水が満たされているために膜二次側から分離膜内表面に向けて水頭圧P2がかかる。水頭圧P2は鉛直方向下向きに次第に大きくなる。一方、膜一次側には水が満たされていないことから、膜一次側から分離膜内表面に向けてかかる圧力は存在しない。ここで、気体押出し逆洗を行った際には、分離膜の膜二次側を分離膜の上端部から下端部に向けて逆洗水が流下するために、膜二次側で逆洗圧力の流動抵抗による圧力損失P3が生じる。圧力損失P3は鉛直方向下向きに次第に大きくなる。よって、分離膜内表面にかかる実効的な逆洗駆動力である逆洗実効圧PBは、式PB=P1+P2-P3で表される。上記の通り、膜一次側には水が満たされていないことから膜一次側に水圧による抵抗がなくなるために、膜二次側に印加されている逆洗圧力P1が膜一次側の水圧による抵抗を受けずに最大限に逆洗の駆動力として使用できる。さらに、分離膜の長手方向Liが略鉛直に配された分離膜モジュールで、かつ、分離膜モジュールならびに分離膜の上端部から逆洗水が流入する場合、膜二次側は水で満たされているために分離膜の下端ほど水頭圧P2が大きくなるため、略鉛直方向に伸びる分離膜の下端部には、分離膜の上端部にかかる逆洗圧力P1に膜二次側の水頭圧P2が加わった圧力が気体押出し逆洗の駆動力として使用できる。そのため、分離膜の略鉛直方向の上端から下端まで比較的均一に気体押出し逆洗の効果を与えることが可能となり、分離膜の洗浄の効果が高く得られる。 In FIG. 6, the inner surface of the separation membrane is backwashed pressure P 1 applied to the upper end of the separation membrane on the secondary side of the membrane, and the secondary side of the membrane is filled with water. Water head pressure P 2 is applied toward the inner surface of the separation membrane. The water head pressure P 2 gradually increases downward in the vertical direction. On the other hand, since the membrane primary side is not filled with water, there is no pressure applied from the membrane primary side toward the inner surface of the separation membrane. Here, when gas extrusion backwashing is performed, backwashing water flows down the membrane secondary side of the separation membrane from the upper end to the lower end of the separation membrane. A pressure loss P 3 is caused by the flow resistance. The pressure loss P 3 gradually increases downward in the vertical direction. Therefore, the backwash effective pressure P B which is an effective backwash driving force applied to the inner surface of the separation membrane is expressed by the formula P B = P 1 + P 2 −P 3 . As described above, 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 P 1 applied to the secondary side of the membrane is due to the water pressure on the primary side of the membrane. It can be used as a driving force for backwashing without receiving resistance. Furthermore, the separation membrane module longitudinal L i is arranged substantially vertically in the separation membrane, and, if the backwash water flows from the upper end of the separation membrane module and the separation membrane, membrane secondary side is filled with water Therefore, the water head pressure P 2 increases toward the lower end of the separation membrane. Therefore, the lower end portion of the separation membrane extending in the substantially vertical direction has a back head pressure P 1 applied to the upper end portion of the separation membrane to the head of the membrane secondary side. The pressure applied with the pressure P 2 can be used as a driving force for gas extrusion 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.
 また、分離膜表面上に付着、蓄積した不純物は、膜一次側に水圧による抵抗、膜一次側の水が分離膜モジュール外へ移送される際の流動抵抗がなくなるために、分離膜表面から剥離しやすく、剥離した不純物は重力に従って分離膜表面をしたたり落ちる逆洗排水に移送されて分離膜モジュール1の下部から排水弁13、排水配管14を介してそのまま排出される。 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.
 一方、従来の逆洗では、分離膜の膜一次側には原水ならびに逆洗排水が満たされた状態で実施されており、逆洗排水はオーバーフロー弁11、オーバーフロー配管12を介して分離膜モジュール1から排出される。図7は、この際の分離膜内表面にかかる圧力を表わす図である。膜二次側の分離膜の上端部に印加された逆洗圧力P1、膜二次側には水が満たされているために膜二次側から分離膜内表面に向けて水頭圧P2がかかる。一方、膜一次側にも水が満たされているために膜一次側から分離膜内表面に向けて水頭圧P4がかかる。なお、膜二次側の水頭圧と、膜一次側の水頭圧とは、造水装置の膜ろ過水配管5とオーバーフロー配管12との位置関係に左右されるが、略同等となる造水装置が多いので、分離膜内表面を介して膜一次側水頭圧P4と膜二次側水頭圧P2とは相殺された状態となる。ここで、気体押出し逆洗を行った際には、分離膜の膜二次側を分離膜の上端部から下端部に向けて逆洗水が流下するために、膜二次側で逆洗圧力の流動抵抗による圧力損失P3が生じる。よって、分離膜内表面にかかる実効的な逆洗駆動力である逆洗実効圧PBは、式PB=P1+P2-P3-P4=P1-P3で表される。 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. FIG. 7 is a diagram showing the pressure applied to the inner surface of the separation membrane at this time. The backwash pressure P 1 applied to the upper end portion of the separation membrane on the membrane secondary side, and the water head pressure P 2 from the membrane secondary side toward the inner surface of the separation membrane because the membrane secondary side is filled with water. It takes. On the other hand, since water is filled also on the primary side of the membrane, water head pressure P 4 is applied from the primary side of the membrane toward the inner surface of the separation membrane. The water head pressure on the membrane secondary side and the water head pressure on the membrane primary side depend on the positional relationship between the membrane filtrate water pipe 5 and the overflow pipe 12 of the fresh water generator, but are substantially the same. Therefore, the membrane primary-side hydraulic head pressure P 4 and the membrane secondary-side hydraulic head pressure P 2 are offset through the inner surface of the separation membrane. Here, when gas extrusion backwashing is performed, backwashing water flows down the membrane secondary side of the separation membrane from the upper end to the lower end of the separation membrane. A pressure loss P 3 is caused by the flow resistance. Therefore, the backwash effective pressure P B which is an effective backwash driving force applied to the inner surface of the separation membrane is expressed by the formula P B = P 1 + P 2 −P 3 −P 4 = P 1 −P 3 .
 また、図8は、図7で示した逆洗時の状態に加えて、ケーシング容器内に分離膜を収納した分離膜モジュール内から逆洗排水が排出される際に分離膜内表面にかかる圧力を表わす図である。図7で示した圧力に加えて、分離膜の膜二次側から膜一次側へと通過した逆洗排水が、分離膜モジュール内を逆洗排水口へと流動する際に発生する流動抵抗による圧力損失P5、さらに、逆洗排水が分離膜モジュールの逆洗排水口ならびにオーバーフロー配管を通過する際に発生する流動抵抗による圧力損失P6が生じる。よって、分離膜内表面にかかる実効的な逆洗駆動力である逆洗実効圧PBは、式PB=P1+P2-P3-P4-P5-P6=P1-P3-P5-P6で表される。 FIG. 8 shows the pressure applied to the inner surface of the separation membrane when the backwash wastewater is discharged from the separation membrane module in which the separation membrane is housed in the casing container in addition to the state at the time of backwashing shown in FIG. FIG. In addition to the pressure shown in FIG. 7, the backwash wastewater that has passed from the membrane secondary side to the membrane primary side of the separation membrane flows due to the flow resistance that is generated when the separation membrane module flows to the backwash drainage port. Further, the pressure loss P 5 and the pressure loss P 6 due to the flow resistance generated when the backwash drainage passes through the backwash drain port and the overflow pipe of the separation membrane module are generated. Therefore, the backwash effective pressure P B which is an effective backwash driving force applied to the inner surface of the separation membrane is expressed by the formula P B = P 1 + P 2 −P 3 −P 4 −P 5 −P 6 = P 1 −P 3 -P 5 -P 6
 このとき、逆洗にあたっては分離膜内表面に、膜一次側に満たされた水による水頭圧P4と、逆洗排水が分離膜モジュール1から排出されてオーバーフロー弁11、オーバーフロー配管12を介して流出する際に生ずる流動抵抗P5およびP6による背圧とが印加された状態になっている。このことによって、分離膜表面上に付着、蓄積した不純物が分離膜表面から剥離し難くなる。 At this time, in backwashing, the head pressure P 4 due to the water filled on the primary side of the membrane and the backwash waste water are discharged from the separation membrane module 1 on the inner surface of the separation membrane, and are passed through the overflow valve 11 and the overflow pipe 12. The flow resistances P 5 and P 6 caused by the outflow are 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.
 さらに、膜一次側の水頭圧P4と流動抵抗P5およびP6とが、逆洗の駆動力を減殺するかたちで影響を及ぼすために、有効に作用する逆洗の駆動力が減じられ、結果として逆洗効果が減じられる。ここで、膜一次側が水で満たされている場合、逆洗にあたっては膜一次側にかかる水頭圧P4と膜二次側にかかる水頭圧P2は略同等であることが多く、分離膜を挟んだ膜一次側と膜二次側との水頭圧P4およびP2が相殺された状態となる。また、分離膜の上端部での逆洗圧P1は、分離膜の膜二次側の流路を逆洗水が流動する際に生じる流動抵抗P3によって分離膜の下端に近づくにつれて有効に作用する逆洗の駆動力が減じられる。 Furthermore, since the head pressure P 4 and the flow resistances P 5 and P 6 on the primary side of the membrane have an effect in the form of diminishing the driving force of backwashing, the driving force of backwashing that works effectively is reduced, As a result, the backwash effect is reduced. Here, when the primary side of the membrane is filled with water, the water head pressure P 4 applied to the primary side of the membrane and the water head pressure P 2 applied to the secondary side of the membrane are often substantially equal during backwashing. The water head pressures P 4 and P 2 between the sandwiched membrane primary side and membrane secondary side are offset. Further, the backwash pressure P 1 at the upper end of the separation membrane becomes effective as it approaches the lower end of the separation membrane due to the flow resistance P 3 generated when the backwash water flows through the flow passage on the membrane secondary side of the separation membrane. The driving force of the acting backwash is reduced.
 分離膜モジュール1からの逆洗排水の出口が分離膜モジュール1の上方に位置している場合、逆洗排水が分離膜モジュール1から流出する際に生じる流動抵抗P5は分離膜の下端に近いほど大きくなり、分離膜の上端に近いほど小さくなる。さらに、分離膜モジュール1の逆洗排水口がノズル形状となっている加圧型分離膜モジュールにあっては、短時間で大流量の逆洗排水を流出させようとする場合には、ノズル形状となっている逆洗排水口で大きな流動抵抗P6が発生してしまい、逆洗の駆動力を減殺させる。 If backwash waste water outlet from the separation membrane module 1 is positioned above the separation membrane module 1, the flow resistance P 5 that occurs when the backwash waste water flows out of the separation membrane module 1 close to the lower end of the separation membrane It becomes larger as it gets closer to the upper end of the separation membrane. Furthermore, in the case of a pressure-type separation membrane module in which the backwash drain of the separation membrane module 1 has a nozzle shape, when trying to discharge a large amount of backwash drainage in a short time, the nozzle shape and A large flow resistance P 6 is generated at the backwash drain, and the driving force for backwashing is reduced.
 これらの作用から、分離膜の膜一次側に水が満たされた状態における逆洗にあたっては、本発明における気体押出し逆洗に比べると、膜一次側の水頭圧P4によって逆洗の駆動力が減殺された上に、膜二次側での逆洗水の流動抵抗P2と膜一次側での逆洗排水の流動抵抗P5およびP6とで分離膜の上端部から下端部へかけての逆洗の駆動力の減衰の度合いが大きくなることから、十分な逆洗の効果が得られない。 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 head pressure P 4 on the membrane primary side compared with the gas extrusion backwashing in the present invention. Moreover, the flow resistance P 2 of the backwash water on the secondary side of the membrane and the flow resistances P 5 and P 6 of the backwash drainage on the primary side of the membrane are extended from the upper end to the lower end of the separation membrane. Since the degree of attenuation of the backwash driving force increases, sufficient backwashing effect cannot be obtained.
 気体押出し逆洗工程のStep1では、分離膜モジュール1の膜一次側の水を排出するが、その際に分離膜モジュール1の膜一次側の水は残っていても構わないが、好ましくは分離膜の略鉛直方向の半分以上が、より好ましくは分離膜全体が水面よりも上になっていて、気体に触れるようにする。分離膜全体が水面よりも上になっている場合、上記した作用によって、膜一次側での水頭圧による背圧、流動抵抗による背圧による逆洗の駆動力の減衰がなく、本発明の気体押し出し逆洗の効果が最大となる。 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, there is no attenuation of the backwashing force due to the water head pressure on the membrane primary side and the backwashing driving force due to the back pressure due to the flow resistance, and the gas of the present invention. The effect of extrusion backwashing is maximized.
 しかしながら、分離膜の略鉛直方向の一部が水面よりも下になっている場合でも、分離膜モジュール1の膜一次側が水で満たされている場合に比べると、水面よりも下になっている部分については、水頭圧による背圧、流動抵抗による背圧が逆洗の駆動力を減衰させるとはいえ、本発明の気体押出し逆洗の効果を得ることができる。分離膜モジュール1の膜一次側の水が残っていて分離膜の略鉛直方向の一部が水面よりも下になっている場合、気体押出し逆洗にあたっては水面下の分離膜には、膜一次側の水位に依存する水頭圧が逆洗の背圧として印加される。また、分離膜モジュール1が加圧型分離膜モジュールである場合、逆洗排水が分離膜モジュールのノズル形状となっている逆洗排水口から流出する際には、逆洗排水口、オーバーフロー配管、オーバーフロー弁において発生する流動抵抗が逆洗の背圧として印加されるが、逆洗排水によって膜一次側の水位が上昇しても、ノズル形状となっている逆洗排水口から逆洗排水が流出するまでは前記流動抵抗は発生しない。よって、気体押出し逆洗を開始する時点での水位が低い方が、より逆洗の駆動力を減殺させる作用が小さくなるために、本発明の気体押出し逆洗の効果を高く得られるので好ましい。 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 the water head pressure and the back pressure by the 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 head 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 separation 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 Flow resistance generated in the valve is applied as backwash back pressure, but backwash drainage flows out from the nozzle backwash drain even if the water level on the primary side of the membrane rises due to backwash drainage. Up to this point, the flow resistance does not occur. 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.
 気体押出し逆洗工程のStep2では、逆洗水に薬液を添加した方が、分離膜表面や分離膜細孔内に付着、蓄積した不純物を薬液によって分解、溶解して除去する効果があるので好ましい。薬液を添加する手段としては図2に示すように、図1に示す造水装置に薬液貯槽21、薬液注入ポンプ22、薬液注入配管23を加えるとよい。また、添加する薬液としては、塩酸、硫酸、硝酸等の無機酸を用いるとアルミニウム、鉄、カルシウム等に対して洗浄効果が高くなるので好ましく、シュウ酸、クエン酸等の有機酸を用いるとアルミニウム、鉄、カルシウム、マンガン等に対して洗浄効果が高くなるので好ましい。次亜塩素酸ナトリウム、二酸化塩素、塩素、過酸化水素、オゾン等の酸化剤を用いると有機物に対して洗浄効果が高くなるので好ましく、特に次亜塩素酸ナトリウムは安価で、入手し易く、取扱いが容易であるのでより好ましい。薬液の注入方法としては、図2に示す造水装置における気体押出し逆洗工程のStep3において、加圧気体によって逆洗圧を印加された逆洗水が逆洗弁6、膜ろ過水配管5を介して分離膜モジュールに流入する際に、薬液貯槽21に貯留された薬液を、薬液注入ポンプ22を用いて薬液注入配管23を介して逆洗水に注入しても良いし、膜ろ過工程において、膜ろ過水が膜ろ過水配管5、逆洗弁6を介して、逆洗水加圧水槽7へと流入する際に、薬液貯槽21に貯留された薬液を、薬液注入ポンプ22を用いて薬液注入配管23を介して膜ろ過水に注入しても良い。 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 or the like. When an organic acid such as oxalic acid or citric acid is used, aluminum is preferable. , 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. 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.
 薬液を逆洗水に注入する場合、逆洗に使用される水量だけの逆洗水に薬液を注入すればよく、一般的には逆洗水が分離膜モジュールに移送されている工程中だけ薬液を注入するので、注入する薬液量を少なくすることができるので好ましい。一方、図4に示すような造水装置では、膜ろ過工程において膜ろ過水に薬液を注入して、あらかじめ薬液が注入された膜ろ過水を逆洗水加圧水槽7に貯留すると、あらかじめ所定の薬液濃度に調整した水を逆洗水として使用できるので、薬液注入ポンプ22の運用管理が容易になるので好ましい。 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.
 空洗工程のStep4における分離膜モジュール1の膜一次側を水で満たす手段としては、上記の通りで原水を供給してもよいし、オーバーフロー弁11、逆洗弁6、加圧気体弁17を開、膜ろ過水弁8、排水弁13を閉とした状態で逆洗を行い、逆洗水を分離膜モジュール1の膜二次側から膜一次側へと供給することで分離膜モジュール1の膜一次側を逆洗排水で満たしてもよいし、気体押出し逆洗工程において排水弁13から排水される逆洗排水の流量よりも、分離膜の膜二次側から膜一次側へ押出す逆洗排水の流量を大きくすることにより、分離膜の膜一次側の水位を上げて逆洗排水で満たしてもよいし、これらの手段を組み合わせてもよい。この時、分離膜モジュール1の原水側を満たすための原水あるいは逆洗水には酸化剤を添加した方が、分離膜表面や分離膜細孔内に付着、蓄積した不純物を酸化して分解除去する効果があるので好ましい。 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 valve 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
 また本発明において、気体押出し逆圧洗浄中および/または気体押出し逆圧洗浄後に分離膜モジュールを気体洗浄することができる。すなわち空洗工程中にも分離膜モジュール1の膜一次側に上記した手段で原水もしくは逆洗水を供給して、オーバーフロー弁11、オーバーフロー配管12を介して分離膜モジュール1から原水もしくは逆洗排水を流出させ続けた方が、空洗によって分離膜表面や分離膜間の流路から剥離した不純物が逐次、分離膜モジュール1の外へと移送されるので空洗の洗浄効果が高まって好ましい。 Further, in the present invention, the separation membrane module can be gas-washed during gas extrusion counter-pressure cleaning 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.
 空洗工程において分離膜モジュール1に導入する気体の加圧気体源15として、気体押出し逆洗工程において逆洗水に所定の圧力を印加するための加圧気体を供給するための加圧気体源15を共用しても構わないし、気体押出し逆洗用の加圧気体源15とは別にエアブロワを設置して用いても構わない。 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.
 本発明の洗浄方法を適用する外圧式の分離膜モジュールの形式としては、外圧式であれば圧力容器となるケーシング容器内に分離膜を収納した加圧型分離膜モジュールでも、大気開放された浸漬水槽に浸漬設置された浸漬型膜モジュールでも構わない。浸漬型膜モジュールは吸引ろ過を行うために、膜ろ過に使用できる圧力は現実的に-80kPa程度までに限定される。一方、加圧型分離膜モジュールでは膜ろ過に使用できる圧力は、分離膜モジュールおよび/または分離膜の耐圧能力に制限されるが、一般的には浸漬膜モジュールよりも膜ろ過に使用できる圧力の範囲が大きいために、浸漬膜モジュールよりも高い膜ろ過圧力を持って、高い膜ろ過流束で膜ろ過ができるので好ましい。 As a form of the external pressure type separation membrane module to which the cleaning method of the present invention is applied, even in the case of a pressure type separation 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 water tank that is open to the atmosphere It may be a submerged membrane module soaked in the water. 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 pressure-type separation membrane module is limited to the pressure resistance capability of the separation membrane module and / or the separation membrane, but in general, the pressure range that can be used for membrane filtration than the submerged membrane module Therefore, it is preferable because the membrane can be filtered with a high membrane filtration flux with a membrane filtration pressure higher than that of the submerged membrane module.
 他方で、浸漬型膜モジュールは濁度、SS濃度(浮遊物質濃度)で示される懸濁物質が高濃度の原水の膜ろ過が可能であるので好ましい。浸漬型膜モジュールにおいては、高濃度の懸濁物質が流入しても、逆洗や空洗などの物理洗浄によって浸漬型膜モジュール外に懸濁物質を排出しやすいためである。ここで、浸漬型膜モジュールは一般的にケーシング容器に分離膜が収納されておらず、逆洗排水が一箇所に集中するノズルを介して逆洗排水を流出させることなく、浸漬型膜モジュール外へと流出するので、加圧型分離膜モジュールと比べると逆洗排水の流出に伴う流動抵抗が小さくなり、逆洗駆動力を減衰させる背圧となりにくい利点を有する。つまり、分離膜モジュール外への逆洗排水の流出の観点から、加圧型分離膜モジュールの方が本発明の効果をより大きく享受できるといえる。 On the other hand, the submerged membrane module is preferable because the suspended matter indicated by turbidity and SS concentration (floating matter concentration) can be subjected to membrane filtration of raw water having a high concentration. 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 associated with the outflow of backwash wastewater is smaller than that of the pressure-type separation 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 pressure-type separation membrane module can enjoy the effect of the present invention more greatly from the viewpoint of outflow of the backwash waste water to the outside of the separation membrane module.
 分離膜モジュールの形状としては、中空糸膜モジュール、チューブラー膜モジュール、スパイラル膜モジュール、平膜モジュール等があるが、いずれの形状の分離膜モジュールを用いても本発明の効果を享受することができる。ここで、中空糸膜とは直径2mm未満の円管状の分離膜、チューブラー膜とは直径2mm以上の円管状の分離膜をいう。しかしながら、平膜モジュールは、強い強度の逆洗を行うと支持板から平膜が剥離する懸念がある点、逆洗時に支持板と平膜との隙間に逆洗水が溜まりこんで支持板から平膜が膨張する形に変形する点、さらにその際に並列に設置された平膜エレメント間で、それぞれ向かい合った平膜エレメントから膨張した平膜同士が接触して流路を塞いでしまう点、から本発明の効果が必ずしも十分には得られない場合がある。また、スパイラル膜モジュールは、巻き取られた平膜と平膜との間の膜一次側にネット状のスペーサーを流路材として組み込んだ形状のため、膜一次側の流路が狭くて膜モジュールの仕様として高い濃度の懸濁物質を受入れない点、膜一次側の流路が狭く、スペーサーを組み込んでいるために逆洗排水を重力による自然流下で排出し難い点、から本発明の効果が必ずしも十分には得られない場合がある。一方、中空糸膜モジュール、チューブラー膜モジュールは、強い逆洗に使用できる点、個々の中空糸膜・チューブラー膜の間の流路が十分に確保できる点、高い濃度の懸濁物質を受入れられる点、から本発明の効果を十分に得ることが出来るので好ましい。また、中空糸膜モジュールは、チューブラー膜モジュールよりも単位体積あたりの膜面積を大きく取れる点、からさらに好ましい。 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, etc., and any shape of the separation membrane module can be used to enjoy the effects of the present invention. it can. 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. However, in the flat membrane module, there is a concern that the flat membrane may be peeled off from the support plate when strong backwashing is performed, and backwash water accumulates in the gap between the support plate and the flat membrane during backwashing. The point that the flat membrane deforms into a shape that expands, and further, the flat membranes that have expanded from the opposing flat membrane elements contact each other between the flat membrane elements installed in parallel, and block the flow path. Therefore, the effects of the present invention may not always be sufficiently obtained. In addition, the spiral membrane module has a shape in which a net-like spacer is incorporated as a channel material on the membrane primary side between the wound flat membrane and the membrane membrane. The advantages of the present invention are that it does not accept suspended substances of high concentration as the specifications of the point, the flow path on the primary side of the membrane is narrow, and since the spacer is incorporated, it is difficult to discharge backwash wastewater under natural flow due to gravity. It may not always be sufficient. On the other hand, hollow fiber membrane modules and tubular membrane modules can be used for strong backwashing, can secure sufficient flow paths between individual hollow fiber membranes / tubular membranes, and accept suspended substances of high concentration. From the point of view, it is preferable because the effects of the present invention can be sufficiently obtained. Moreover, the hollow fiber membrane module is more preferable from the point that the membrane area per unit volume can be taken larger than the tubular membrane module.
 分離膜としては、本発明の主旨から多孔質であればどのようなものでも構わないが、一般的に除濁用途として用いられる精密ろ過膜(MF膜)および限外ろ過膜(UF膜)が好ましい。さらに、本発明の気体押出し逆洗にあっては、表面が平滑な性状を有し、さらに膜細孔が微細なUF膜を用いると、原水中の懸濁物質を分離膜の多孔部に流入させることなく分離膜表面で抑留することができるので、本発明の気体押出し逆洗によって分離膜の略鉛直方向の上端から下端までの分離膜表面に蓄積した懸濁物質を、効果的に剥離させることができるので好ましい。さらに、膜細孔が微細で、かつ分離膜表面が平滑なほど、分離膜表面上を下方に滴り落ちる逆洗排水によって分離膜表面から剥離させた懸濁物質を容易に移送できるので、懸濁物質を分離膜モジュール外に排出し易くなって好ましい。ここで、UF膜であっても膜表面から内部にかけての膜構造が均質な分離膜よりも、膜表面部が緻密で膜内部にかけて疎になっていく膜構造が不均質な分離膜の方が、一般的に分離膜表面の膜細孔が微細で分離膜表面が平滑となるために好ましい。 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.
 また、分離膜の素材としては、本発明の主旨から特に限定されるものではないが、有機素材を使用する場合、ポリエチレン、ポリプロピレン、ポリアクリロニトリル、エチレン-テトラフルオロエチレン共重合体、ポリクロロトリフルオロエチレン、ポリテトラフルオロエチレン、ポリビニルフルオライド、テトラフルオロエチレン-ヘキサフルオロプロピレン共重合体、およびクロロトリフルオロエチレン-エチレン共重合体、ポリフッ化ビニリデン(以下、「PVDF」と記すことがある。)、ポリスルホン、ポリエーテルスルホン、酢酸セルロース等が使用でき、無機素材を使用する場合はセラミック等が使用できる。この中でも膜強度や耐薬液性の観点からフッ素を含む有機素材やセラミックを素材とするものが好ましい。また、薬液洗浄回復性の観点から一般的に親水性素材とされるポリアクリロニトリルや酢酸セルロースを含む有機素材が好ましい。さらに、一般的に分離膜表面に付着、蓄積した懸濁物質は疎水性を示すことが多いため、分離膜表面での親水性が強い分離膜ほど分離膜表面に付着、蓄積した懸濁物質を剥離させ易くなるので好ましい。 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, ethylene-tetrafluoroethylene copolymer, polychlorotrifluorotrifluoro Ethylene, polytetrafluoroethylene, polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chlorotrifluoroethylene-ethylene copolymer, polyvinylidene fluoride (hereinafter sometimes referred to as “PVDF”), Polysulfone, polyethersulfone, cellulose acetate and the like can be used, and ceramic or the like can be used when an inorganic material is used. 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.
 また、分離膜モジュールは、略鉛直方向に配置、設置されるものが好ましい。略鉛直方向に配置、設置される分離膜モジュールでは、略水平方向に配置、設置される分離膜モジュールよりも、分離膜モジュール内の膜一次側の原水や、逆洗排水を排出し易いためである。 Moreover, it is preferable that the separation membrane module is arranged and installed in a substantially vertical direction. This is because separation membrane modules that are arranged and installed in a substantially vertical direction are more likely to discharge raw water on the primary side of the membrane and backwash drainage than separation membrane modules that are arranged and installed in a substantially horizontal direction. is there.
 また、本発明の主旨から、分離膜モジュールひいては分離膜の長手方向が、略鉛直方向に配されていることが好ましい。これは、気体押出し逆洗にあたって、分離膜モジュールならびに膜二次側の分離膜の上端部から逆洗水が流入する場合、膜二次側は水で満たされているために分離膜の下端ほど水頭圧が大きくなるため、略鉛直方向に伸びる分離膜の下端部には、分離膜の上端部にかかる逆洗圧に膜二次側の水頭圧が加わった圧力が逆洗の駆動力として使用できるためである。このことによって、分離膜の略鉛直方向の上端から下端まで比較的均一に逆洗の駆動力を与えることが可能となり、分離膜の洗浄の効果が高く得られる。 Further, from the gist of the present invention, it is preferable that the longitudinal direction of the separation membrane module and hence the separation membrane is arranged in a substantially vertical direction. This is because when backwashing water flows from the upper end of the separation membrane module and the separation membrane on the membrane secondary side during gas extrusion backwashing, the membrane secondary side is filled with water, so the lower end of the separation membrane Because the head pressure increases, the pressure at the lower end of the separation membrane that extends in a substantially vertical direction is the backwash pressure applied to the upper end of the separation membrane plus the head pressure on the secondary side of the membrane as the driving force for backwashing. This is because it can. As a result, it is possible to apply a driving force for backwashing relatively uniformly from the upper end to the lower end in the substantially vertical direction of the separation membrane, and a high cleaning effect of the separation membrane can be obtained.
 膜ろ過の制御方法としては、定流量ろ過であっても定圧ろ過であっても構わないが、一定の処理水量ないし処理水流量が得られる点から定流量ろ過が好ましい。一方、定圧ろ過は造水装置から流出する処理水流量が変動するものの、膜ろ過の制御は定流量ろ過よりも簡素にできるために好ましい。なお、定圧ろ過にあたっては、その後段に十分な緩衝能力を有する浄水池を設置している場合には、造水装置から流出する処理水流量の変動を浄水池で緩衝して、浄水池から一定の処理水量を供給することも可能である。 The control method for membrane filtration may be constant flow filtration or constant pressure filtration, but constant flow filtration is preferred 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.
 膜ろ過方式としては、全量ろ過であってもクロスフローろ過であっても構わないが、膜ろ過に要するエネルギー消費量が少ないという点から全量ろ過が好ましい。 The membrane filtration method may be whole-volume filtration or cross-flow filtration, but full-volume filtration is preferred from the viewpoint of low energy consumption required for membrane filtration.
(実施例1)
 図3に示す設備構成の造水装置を用いて、分離膜モジュール1に外圧式のPVDF製中空糸限外ろ過膜モジュールHFU-2020(東レ(株)製)を1本使用して、薬液貯槽21に次亜塩素酸ナトリウム水溶液を貯留して、河川水を膜ろ過流束3m3/(m2・d)で全量ろ過方式で定流量ろ過を行った。
Example 1
Using a fresh water generator having the equipment configuration shown in FIG. 3, the separation membrane module 1 uses one external pressure type 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.
 各運転工程は、以下に示す機器の発停と弁の開閉によって構成した。まず、給水工程として原水弁4、オーバーフロー弁11を開にして、原水供給ポンプ2を稼動させて原水を分離膜モジュール1へと供給して分離膜モジュール1の膜一次側を原水で満たした。次いで、膜ろ過工程として、逆洗弁6、膜ろ過水弁8を開にして、オーバーフロー弁11を閉にすることで原水は分離膜モジュール1によって膜ろ過されて、膜ろ過水配管5、逆洗弁6、逆洗水加圧水槽7、膜ろ過水弁8、膜ろ過水流出配管9を介して膜ろ過水が取り出される。この際、原水供給ポンプ2の出力を膜ろ過水流量センサ(図示せず)の出力値によるフィードバック制御することにより、膜ろ過流束3m3/(m2・d)となるように膜ろ過水流量を定流量制御した。膜ろ過工程を30分間継続した後、原水供給ポンプ2を停止して、原水弁4、逆洗弁6、膜ろ過水弁8を閉にした後、オーバーフロー弁11を開にした。 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 filtrate flow sensor (not shown), so that the membrane filtrate has a membrane filtration flux of 3 m 3 / (m 2 · d). The flow rate was controlled at a constant flow rate. 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.
 気体押出し逆洗工程の水位低下ステップ(Step1)として、排水弁13を開にして分離膜モジュール1内の膜一次側の水を全て分離膜モジュール外へ排出した。水位低下ステップは45秒間実施すれば、分離膜モジュール1内の膜一次側の水を全て排出することができた。なお、この時点では分離膜モジュール1内の膜一次側には水が無くなって周囲が空気となった状態となっているが、膜二次側には膜ろ過水が保持された状態となっている。次いで、逆洗準備ステップ(Step2)として、加圧気体弁17を開にして逆洗水加圧水槽7に加圧空気を供給して、逆洗水加圧水槽内7内の水に圧力を印加した。この加圧空気は、加圧気体源15としてエアコンプレッサを使用して圧縮した空気を、逆洗用加圧気体調圧弁31を用いて100kPaとなるように調整した。逆洗準備ステップは45秒実施すれば、逆洗水加圧水槽7内の圧力が100kPaで一定になった。次いで、気体押出し逆洗ステップ(Step3)として、加圧気体弁17を開にしたまま逆洗弁6を開にして、逆洗水加圧水槽7内で加圧空気によって100kPaに加圧された水を膜ろ過水配管5、逆洗弁6を介して分離膜モジュール1の膜二次側へと押し込み、気体押出し逆洗を行った。30秒間の気体押出し逆洗ステップにおいて、逆洗水として100Lの水を使用した。この気体押出し逆洗ステップ中に、薬液貯槽21に貯留した次亜塩素酸ナトリウム水溶液を、逆洗水として使用した100Lの水に対し塩素濃度5mg/Lとなるように薬液注入ポンプ22を用いて薬液注入配管23を介して逆洗水に注入した。この気体押出し逆洗ステップにあたっては、オーバーフロー弁11、排水弁13が開になっているので、分離膜を膜二次側から膜一次側へと透過した逆洗水は、逆洗排水として分離膜表面をつたって重力に従って分離膜モジュール1の下方へと流下して、排水弁13、排水配管14を介して分離膜モジュール1外へと流出した。 As a water level lowering step (Step 1) of the gas extrusion backwashing 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 (Step 2), the pressurized gas valve 17 is opened, pressurized air is supplied to the backwash water pressurized water tank 7, and pressure is 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 the gas extrusion backwashing step (Step 3), 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 Was pushed into the membrane secondary side of the separation membrane module 1 through the membrane filtration 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.
 空洗工程の水張りステップ(Step4)として、加圧気体弁17、逆洗弁6の順に弁を閉じて、排水弁13を閉にして、オーバーフロー弁11は開としたまま原水弁4も開にし、原水供給ポンプ2を稼動させて原水を分離膜モジュール1へと供給して分離膜モジュール1の膜一次側を原水で満たした。その後、原水供給ポンプ2を停止して原水弁4を閉にした。次いで、空洗ステップ(Step5)として、空洗弁18を開にして分離膜モジュール1の膜一次側に空気を空気流量100NL/minとなるように導入して空洗を30秒間行った。空気流量は、加圧気体源15としてエアコンプレッサを使用して圧縮した空気を、空洗用加圧気体調圧弁32、空洗用気体流量調整弁33を用いて100NL/minとなるように調整を行った。その後、空洗弁18を閉じた。 As the water filling step (Step 4) of 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 raw water valve 4 is opened while the overflow valve 11 is open. Then, the raw water supply pump 2 was operated to supply the raw water to the separation membrane module 1, and the membrane primary side of the separation membrane module 1 was filled with the 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 (Step 5), 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.
 排水工程として、オーバーフロー弁11を開としたまま、排水弁13を開にして、分離膜モジュール1内の膜一次側の水を、空洗工程によって分離膜表面や分離膜間の流路から剥離した不純物とともに分離膜モジュール1から排出した。次いで、給水工程に戻り、上記工程を繰り返した。 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.
 その結果、分離膜モジュール1の膜ろ過差圧は、運転開始直後の30kPaに対し、6ヶ月後も60kPaと安定運転を行うことができた。また、運転期間中の本造水装置の平均電力消費量は、0.033kWh/m3であった。 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 .
(実施例2)
 図4に示す設備構成の造水装置を用いて、逆洗水への次亜塩素酸ナトリウム水溶液の注入方法として、膜ろ過工程時において膜ろ過水に塩素濃度5mg/Lとなるように薬液貯槽21に貯留した次亜塩素酸ナトリウム水溶液を薬液注入ポンプ22を用いて薬液注入配管23を介して膜ろ過水に注入して、逆洗水加圧水槽7に塩素濃度5mg/Lの水を貯留して、これを逆洗水として使用することとした点以外は、実施例1と同様に運転を行った。
(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.
 その結果、分離膜モジュール1の膜ろ過差圧は、運転開始直後の30kPaに対し、6ヶ月後も60kPaと安定運転を行うことができた。また、運転期間中の本造水装置の平均電力消費量は、0.033kWh/m3であり、実施例1比で1.00であった。 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.
(実施例3)
 図3に示す設備構成の造水装置を用いて、気体押出し逆洗工程の気体押出し逆洗ステップ時に排水弁13を閉として、分離膜の膜二次側から膜一次側に透過して生じた逆洗排水を分離膜モジュール1内の膜一次側に溜め込んでいくようにして、空洗工程の水張りステップを省略した点以外は、実施例1と同様に運転を行った。
(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.
 その結果、分離膜モジュール1の膜ろ過差圧は、運転開始直後の30kPaに対し、6ヶ月後も70kPaと安定運転を行うことができた。また、運転期間中の本造水装置の平均電力消費量は、0.035kWh/m3であり、実施例1の平均電力消費量に対する比で1.06であった。 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 as a ratio to the average power consumption of Example 1.
(実施例4)
 図3に示す設備構成の造水装置を用いて、気体押出し逆洗工程の気体押出し逆洗ステップ(Step3)時に排水弁13を閉として、分離膜の膜二次側から膜一次側に透過して生じた逆洗排水を分離膜モジュール1内の膜一次側に溜め込んでいくようにして、空洗工程の水張りステップ(Step4)を省略した点、さらに気体押出し逆洗ステップ(Step3)の際に、排水弁13を閉としたまま空洗弁18を開にして分離膜モジュール1の膜一次側に空気を導入して空洗を行った点の2点以外は、実施例1と同様に運転を行った。
(Example 4)
3 is used to close the drain valve 13 during the gas extrusion backwashing step (Step 3) of the gas extrusion backwashing process, and permeate from the membrane secondary side of the separation membrane to the membrane primary side. The backwash waste water generated in the separation membrane module 1 is accumulated on the primary side of the separation membrane module 1 so that the water filling step (Step 4) of the air washing process is omitted, and further in the gas extrusion backwashing step (Step 3). In the same manner as in Example 1, except that the flush valve 18 is opened while the drain valve 13 is closed and air is introduced into the membrane primary side of the separation membrane module 1 to perform flushing. Went.
 その結果、分離膜モジュール1の膜ろ過差圧は、運転開始直後の30kPaに対し、6ヶ月後も65kPaと安定運転を行うことができた。また、運転期間中の本造水装置の平均電力消費量は、0.033kWh/m3であり、実施例1の平均電力消費量に対する比で1.03であった。 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 as a ratio to the average power consumption of Example 1.
(実施例5)
 図3に示す設備構成の造水装置を用いて、気体押出し逆洗工程の気体押出し逆洗ステップ(Step3)の最初の10秒間をオーバーフロー弁11、排水弁13を開としたまま、逆洗排水を分離膜モジュール1外に排水弁13、排水配管14を介して流出させた点、次いで、気体押出し逆洗ステップとなって10秒経過後に排水弁13を閉として、逆洗排水を分離膜モジュール1内の膜一次側に溜め込んでいくようにして、空洗工程の水張りステップ(Step4)を省略した点、排水弁13を閉として分離膜モジュール1内の膜一次側に逆洗排水を溜め込んでいくと同時に、空洗弁18を開にして分離膜モジュール1の膜一次側に空気を導入して空洗を行った点、気体押出し逆洗ステップを合計30秒間実施後に加圧気体弁17、逆洗弁6を閉にして気体押出し逆洗を停止させた後も、空洗弁18を開としたまま空洗を継続して、空洗を30秒間実施した後に空洗弁18を閉として空洗を停止させた点、の4点以外は、実施例1と同様に運転を行った。
(Example 5)
Backwash drainage with the overflow valve 11 and the drain valve 13 open for the first 10 seconds of the gas extrusion backwashing step (Step 3) of the gas extrusion backwashing process using the fresh water generator having the equipment configuration shown in FIG. Is discharged outside the separation membrane module 1 through the drain valve 13 and the drain pipe 14, and then the gas extrusion back washing step is performed, and the drain valve 13 is closed after 10 seconds, and the back washing waste water is separated into the separation membrane module. The water washing step (Step 4) of the air washing process is omitted, the drain valve 13 is closed, and the backwash waste water is accumulated on the membrane primary side in the separation membrane module 1. At the same time, the air washing valve 18 is opened and air is introduced into the membrane primary side of the separation membrane module 1 to perform air washing. After the gas extrusion back washing step is performed for a total of 30 seconds, the pressurized gas valve 17 is used. Backwash valve 6 Even after closing and stopping the gas extrusion backwashing, the air washing is continued with the air washing valve 18 opened, and after the air washing is performed for 30 seconds, the air washing valve 18 is closed to stop the air washing. The operation was performed in the same manner as in Example 1 except for the four points.
 その結果、分離膜モジュール1の膜ろ過差圧は、運転開始直後の30kPaに対し、6ヶ月後も61kPaと安定運転を行うことができた。また、運転期間中の本造水装置の平均電力消費量は、0.032kWh/m3であり、実施例1の平均電力消費量に対する比で1.00であった。 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 as a ratio to the average power consumption of Example 1.
(比較例1)
 図3に示す設備構成の造水装置を用いて、気体押出し逆洗工程の水位低下ステップ(Step1)および空洗工程の水張りステップ(Step4)を省略した点以外は、実施例1と同様に運転を行った。この逆洗工程における気体押出し逆洗ステップ(Step3)にあたっては、水位低下ステップを省略しているために分離膜モジュール1の膜一次側は水で満たされているので、分離膜を膜二次側から膜一次側へと透過した逆洗水は、逆洗排水として分離膜モジュール1の上方に設けられた逆洗排水口からオーバーフローして分離膜モジュール1外へと流出した。
(Comparative Example 1)
Operation was performed in the same manner as in Example 1 except that the water level lowering step (Step 1) of the gas extrusion backwashing process and the water filling step (Step4) of the air washing process were omitted using the fresh water generator having the equipment configuration shown in FIG. Went. In the gas extrusion backwashing step (Step 3) 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. The backwash water that permeated from the primary side to the membrane overflowed from the backwash drain provided above the separation membrane module 1 as backwash wastewater and flowed out of the separation membrane module 1.
 その結果、分離膜モジュール1の膜ろ過差圧は、運転開始直後の30kPaに対し、6ヶ月後には87kPaとなっていた。また、運転期間中の本造水装置の平均電力消費量は、0.038kWh/m3であり、実施例1の平均電力消費量に対する比で1.18であった。 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 as a ratio to the average power consumption of Example 1.
(比較例2)
 図5に示す設備構成の造水装置を用いて、分離膜モジュール1に外圧式のPVDF製中空糸限外ろ過膜モジュールHFU-2020(東レ(株)製)を1本使用して、薬液貯槽21に次亜塩素酸ナトリウム水溶液を貯留して、河川水を膜ろ過流束3m3/(m2・d)で全量ろ過方式で定流量ろ過を行った。
(Comparative Example 2)
5 using a fresh water generator having the equipment configuration shown in FIG. 5 and using one external pressure PVDF hollow fiber ultrafiltration membrane module HFU-2020 (manufactured by Toray Industries, Inc.) as the separation membrane module 1. 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.
 各運転工程は、以下に示す機器の発停と弁の開閉によって構成した。まず、給水工程として原水弁4、オーバーフロー弁11を開にして、原水供給ポンプ2を稼動させて原水を分離膜モジュール1へと供給して分離膜モジュール1の膜一次側を原水で満たした。次いで、膜ろ過工程として、膜ろ過水弁8を開にして、オーバーフロー弁11を閉にすることで原水は分離膜モジュール1によって膜ろ過されて、膜ろ過水配管5、膜ろ過水弁8を介して膜ろ過水が取り出され、逆洗水槽34に貯留される。逆洗水槽34からオーバーフローした膜ろ過水は、膜ろ過水流出配管9を介して装置外へと流出する。この際、原水供給ポンプ2の出力を膜ろ過水流量センサ(図示せず)の出力値によるフィードバック制御することにより、膜ろ過流束3m3/(m2・d)となるように膜ろ過水流量を定流量制御した。膜ろ過工程を30分間継続した後、原水供給ポンプ2を停止して、原水弁4、膜ろ過水弁8を閉にした後、オーバーフロー弁11を開にした。 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 filtrate flow sensor (not shown), so that the membrane filtrate has a membrane filtration flux of 3 m 3 / (m 2 · d). The flow rate was controlled at a constant flow rate. 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.
 逆洗工程として、逆洗弁6を開にして、逆洗ポンプ35を稼動させて逆洗水槽に貯留された膜ろ過水を逆洗水として、逆洗水配管36、逆洗弁6、膜ろ過水配管5を介して分離膜モジュール1の膜二次側へと押し込み、逆洗流束4m3/(m2・d)で30秒間の逆洗を行った。この逆洗工程中に薬液貯槽21に貯留した次亜塩素酸ナトリウム水溶液を、逆洗水に対して塩素濃度5mg/Lとなるように薬液注入ポンプ22を用いて薬液注入配管23を介して逆洗水に注入した。この逆洗工程にあたっては、分離膜モジュール1の膜一次側は水で満たされているので、分離膜を膜二次側から膜一次側へと透過した逆洗水は、逆洗排水として分離膜モジュール1の上方に設けられた逆洗排水口からオーバーフローして分離膜モジュール1外へと流出した。逆洗を30秒間実施した後、逆洗ポンプ35を停止させ、逆洗弁6を閉にした。 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.
 空洗工程として、オーバーフロー弁11は開としたまま空洗弁18を開にして、分離膜モジュール1の膜一次側に空気を空気流量100NL/minとなるように導入して空洗を30秒間行った。空気流量は、加圧気体源15としてエアコンプレッサを使用して圧縮した空気を、空洗用加圧気体調圧弁32、空洗用気体流量調整弁33を用いて100NL/minとなるように調整を行った。その後、空洗弁18を閉じた。 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.
 排水工程として、オーバーフロー弁11を開としたまま、排水弁13を開にして、分離膜モジュール1内の膜一次側の水を、空洗工程によって分離膜表面や分離膜間の流路から剥離した不純物とともに分離膜モジュール1から排出した。次いで、給水工程に戻り、上記工程を繰り返した。 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.
 その結果、分離膜モジュール1の膜ろ過差圧は、運転開始直後の30kPaに対し、6ヶ月後には95kPaとなっていた。また、運転期間中の本造水装置の平均電力消費量は、0.035kWh/m3であり、実施例1比で1.07であった。 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.
(比較例3)
 図5に示す設備構成の造水装置を用いて、膜ろ過工程が終了後に、オーバーフロー弁11を開としたまま排水弁13を開にして、分離膜モジュール1の膜一次側の水を排水した後に、逆洗工程として、逆洗弁6を開にして、逆洗ポンプを稼動させて逆洗水槽に貯留された膜ろ過水を逆洗水として、逆洗水配管36、逆洗弁6、膜ろ過水配管5を介して分離膜モジュール1の膜二次側へと押し込み、逆洗流束4m3/(m2・d)で30秒間の逆洗を行った点、この逆洗工程に次ぐ水張りステップとして逆洗弁6、排水弁13を閉、原水弁4を開にして原水供給ポンプ2を稼動させて原水を分離膜モジュール1へと供給して分離膜モジュール1の膜一次側を原水で満たしてから空洗工程を行った点以外は比較例2と同様に運転を行った。
(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.
 この逆洗工程にあたっては、オーバーフロー弁11、排水弁13が開になって分離膜モジュール1内の水は排出された状態になっているので、分離膜を膜二次側から膜一次側へと透過した逆洗水は、逆洗排水として分離膜表面をつたって重力に従って分離膜モジュール1の下方へと流下して、排水弁13、排水配管14を介して分離膜モジュール1外へと流出した。 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. .
 その結果、分離膜モジュール1の膜ろ過差圧は、運転開始直後の30kPaに対し、6ヶ月後には85kPaとなっていた。また、運転期間中の本造水装置の平均電力消費量は、0.033kWh/m3であり、実施例1の平均電力消費量に対する比で1.01であった。 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. In addition, the average power consumption of the fresh water generator during the operation period was 0.033 kWh / m 3 , which was 1.01 as a ratio to the average power consumption of Example 1.
(比較例4)
 図5に示す設備構成の造水装置を用いて、逆洗工程時に、空洗弁18を開にして、分離膜モジュールの膜一次側に空気を空気流量100NL/minとなるように導入して空洗を同時に行った点、空洗を同時に行った逆洗工程に引き続いて、排水工程を行い、次いで、給水工程に戻り、膜ろ過工程、逆洗工程、排水工程、給水工程を繰り返した点以外は比較例2と同様に運転を行った。
(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 Except that, the operation was performed in the same manner as in Comparative Example 2.
 その結果、分離膜モジュール1の膜ろ過差圧は、運転開始直後の30kPaに対し、6ヶ月後には85kPaとなっていた。また、運転期間中の本造水装置の平均電力消費量は、0.032kWh/m3であり、実施例1の平均電力消費量に対する比で1.00であった。 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 as a ratio to the average power consumption of Example 1.
 1:分離膜モジュール
 2:原水供給ポンプ
 3:原水供給配管
 4:原水弁
 5:膜ろ過水配管
 6:逆洗弁
 7:逆洗水加圧水槽
 8:膜ろ過水弁
 9:膜ろ過水流出配管
11:オーバーフロー弁
12:オーバーフロー配管
13:排水弁
14:排水配管
15:加圧気体源
16:加圧気体配管
17:加圧気体弁
18:空洗弁
19:逆洗水加圧水槽エア抜き弁
21:薬液貯槽
22:薬液注入ポンプ
23:薬液注入配管
31:逆洗用加圧気体調圧弁
32:空洗用加圧気体調圧弁
33:空洗用気体流量調整弁
34:逆洗水槽
35:逆洗ポンプ
36:逆洗水配管
1:逆洗圧力
2,i:膜二次側水頭圧
3,i:膜二次側逆洗水流動抵抗
4,i:膜一次側水頭圧
5,i:膜モジュール内膜二次側逆洗排水流動抵抗
6,i:膜モジュール出口ノズル部および出口側オーバーフロー配管部流動抵抗
B,i:逆洗実効圧
i:分離膜長(鉛直方向長さ)
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 pipe P 1 : Backwash pressure P 2, i : Membrane secondary side head pressure P 3, i : Membrane secondary side backwash water flow resistance P 4, i : Membrane primary side head pressure P 5, i: the membrane module in the membrane secondary backwash effluent flow resistance P 6, i: the membrane module outlet nozzle and the outlet side O Furo pipe section flow resistance P B, i: backwash effective pressure L i: the separation membrane length (vertical length)

Claims (6)

  1.  外圧式の分離膜モジュールの洗浄方法において、分離膜の膜一次側の少なくとも一部が水面上になる水位にした後に、分離膜の膜二次側に加圧気体を導入して膜二次側の水を膜一次側に押出すことによって気体押出し逆圧洗浄をすることを特徴とする分離膜モジュールの洗浄方法。 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.
  2.  外圧式の分離膜モジュールの洗浄方法において、分離膜の膜一次側がすべて水面上になるようにした後に、分離膜の膜二次側に加圧気体を導入して膜二次側の水を膜一次側に押出すことによって気体押出し逆圧洗浄をすることを特徴とする請求項1に記載の分離膜モジュールの洗浄方法。 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.
  3.  分離膜の膜二次側に導入する加圧気体の圧力が、分離膜のバブルポイント未満であることを特徴とする請求項1または2に記載の分離膜モジュールの洗浄方法。 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.
  4.  分離膜の膜二次側に加圧気体を導入して膜二次側の水を膜一次側に押出すことによって気体押出し逆圧洗浄をする際に、分離膜モジュールの下部に位置する排水弁を開くことにより、逆洗排水の一部またはすべてを膜モジュールの下部から排水させることを特徴とする、請求項1~3のいずれかに記載の分離膜モジュールの洗浄方法。 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 4. The method for cleaning a separation membrane module according to claim 1, wherein a part or all of the backwash drainage is drained from the lower part of the membrane module by opening the channel.
  5.  分離膜の膜二次側に加圧気体を導入して膜二次側の水を膜一次側に押出すことによって気体押出し逆圧洗浄をする際に、分離膜モジュールの下部から排水される逆洗排水の流量よりも、分離膜の膜二次側から膜一次側へ押出す逆洗排水の流量を大きくすることにより、分離膜の膜一次側の水位を上げて、前記気体押出し逆圧洗浄中および/または気体押出し逆圧洗浄後に分離膜モジュールを気体洗浄することを特徴とする、請求項1~4のいずれかに記載の分離膜モジュールの洗浄方法。 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.
  6.  分離膜モジュールが、ケーシング内に分離膜を収納した加圧型分離膜モジュールであることを特徴とする、請求項1~5のいずれかに記載の分離膜モジュールの洗浄方法。 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.
PCT/JP2013/064115 2012-05-21 2013-05-21 Cleaning method for separation membrane module WO2013176145A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2012-115694 2012-05-21
JP2012115694A JP2015155076A (en) 2012-05-21 2012-05-21 Separation film module cleaning method

Publications (1)

Publication Number Publication Date
WO2013176145A1 true WO2013176145A1 (en) 2013-11-28

Family

ID=49623833

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2013/064115 WO2013176145A1 (en) 2012-05-21 2013-05-21 Cleaning method for separation membrane module

Country Status (2)

Country Link
JP (1) JP2015155076A (en)
WO (1) WO2013176145A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103990383A (en) * 2014-03-20 2014-08-20 河海大学 Chemical cleaning method of external pressure membrane system
US9333464B1 (en) 2014-10-22 2016-05-10 Koch Membrane Systems, Inc. Membrane module system with bundle enclosures and pulsed aeration and method of operation
USD779631S1 (en) 2015-08-10 2017-02-21 Koch Membrane Systems, Inc. Gasification device
WO2017046214A1 (en) * 2015-09-18 2017-03-23 Basf Se Filtration system and method for backwashing a filtration system

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6653154B2 (en) * 2015-10-08 2020-02-26 株式会社クラレ Cleaning method and filtration device for hollow fiber membrane module
JP2018023965A (en) * 2016-08-03 2018-02-15 住友電気工業株式会社 Cleaning method for external pressure type filtration module and filtration device
CN106698593A (en) * 2016-09-13 2017-05-24 龙吉林 Method for refreshing water of water tank of water purifier
JP6866179B2 (en) * 2017-02-16 2021-04-28 株式会社清水合金製作所 Portable water treatment equipment and its operation method
JP6960791B2 (en) * 2017-07-19 2021-11-05 株式会社クラレ Cleaning method of hollow fiber membrane filtration device and hollow fiber membrane filtration device

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10323544A (en) * 1997-05-22 1998-12-08 Mizu:Kk Backwashing device for hollow yarn membrane filtration
JP2000237548A (en) * 1999-02-17 2000-09-05 Tokyo Denki Komusho Co Ltd Hollow fiber membrane type heat storage tank water purifying device
JP2003053160A (en) * 2001-08-14 2003-02-25 Mitsubishi Rayon Co Ltd Cleaning method for separating membrane and membrane filtrater
JP2007505727A (en) * 2003-09-19 2007-03-15 ユー・エス・フィルター・ウェイストウォーター・グループ・インコーポレイテッド Improved cleaning method for membrane modules
WO2011122289A1 (en) * 2010-03-30 2011-10-06 東レ株式会社 Method for cleaning separation membrane module, and method for fresh water generation

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10323544A (en) * 1997-05-22 1998-12-08 Mizu:Kk Backwashing device for hollow yarn membrane filtration
JP2000237548A (en) * 1999-02-17 2000-09-05 Tokyo Denki Komusho Co Ltd Hollow fiber membrane type heat storage tank water purifying device
JP2003053160A (en) * 2001-08-14 2003-02-25 Mitsubishi Rayon Co Ltd Cleaning method for separating membrane and membrane filtrater
JP2007505727A (en) * 2003-09-19 2007-03-15 ユー・エス・フィルター・ウェイストウォーター・グループ・インコーポレイテッド Improved cleaning method for membrane modules
WO2011122289A1 (en) * 2010-03-30 2011-10-06 東レ株式会社 Method for cleaning separation membrane module, and method for fresh water generation

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103990383A (en) * 2014-03-20 2014-08-20 河海大学 Chemical cleaning method of external pressure membrane system
CN103990383B (en) * 2014-03-20 2016-02-03 河海大学 A kind of external-compression type membranous system chemical cleaning method
US9333464B1 (en) 2014-10-22 2016-05-10 Koch Membrane Systems, Inc. Membrane module system with bundle enclosures and pulsed aeration and method of operation
US9956530B2 (en) 2014-10-22 2018-05-01 Koch Membrane Systems, Inc. Membrane module system with bundle enclosures and pulsed aeration and method of operation
US10702831B2 (en) 2014-10-22 2020-07-07 Koch Separation Solutions, Inc. Membrane module system with bundle enclosures and pulsed aeration and method of operation
USD779631S1 (en) 2015-08-10 2017-02-21 Koch Membrane Systems, Inc. Gasification device
USD779632S1 (en) 2015-08-10 2017-02-21 Koch Membrane Systems, Inc. Bundle body
WO2017046214A1 (en) * 2015-09-18 2017-03-23 Basf Se Filtration system and method for backwashing a filtration system

Also Published As

Publication number Publication date
JP2015155076A (en) 2015-08-27

Similar Documents

Publication Publication Date Title
WO2013176145A1 (en) Cleaning method for separation membrane module
JP5549589B2 (en) Fresh water system
JP5446416B2 (en) Separation membrane module for oil-containing wastewater treatment, oil-containing wastewater treatment method, and oil-containing wastewater treatment equipment
US20130015131A1 (en) Method for washing separation membrane module and method for generating fresh water
US20120125846A1 (en) Filtering method, and membrane-filtering apparatus
EP2703066A1 (en) Method for cleaning membrane module
WO2013111826A1 (en) Desalination method and desalination device
JP6492658B2 (en) Cleaning method for hollow fiber membrane module
CN106103349A (en) Method for treating water
JP4969580B2 (en) Operation method of membrane separator
JPWO2016199725A1 (en) Fresh water production apparatus and method for operating fresh water production apparatus
JP6191464B2 (en) Operation method of turbidity removal membrane module
JP5181987B2 (en) Cleaning method for submerged membrane module
JP4698274B2 (en) Filtration membrane cleaning method
JP2018023965A (en) Cleaning method for external pressure type filtration module and filtration device
JP2013202481A (en) Cleaning method of separation membrane module
JP2011110439A (en) Washing method of membrane module
JP2013212497A (en) Water treating method
JP7103526B2 (en) Cleaning trouble judgment method and cleaning trouble judgment program of water production equipment
WO2013047466A1 (en) Membrane module cleaning method
JP2008183513A (en) Water purifying apparatus
WO2011108589A1 (en) Method for washing porous membrane module, and fresh water generator
JP2006081979A (en) Membrane washing method
JP2009214062A (en) Operation method of immersion type membrane module
JP4943662B2 (en) Operation method of membrane separator

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 13793649

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 13793649

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: JP