EP2389238A1 - Cassette de membranes immergées et procédé de fonctionnement - Google Patents

Cassette de membranes immergées et procédé de fonctionnement

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Publication number
EP2389238A1
EP2389238A1 EP10731002A EP10731002A EP2389238A1 EP 2389238 A1 EP2389238 A1 EP 2389238A1 EP 10731002 A EP10731002 A EP 10731002A EP 10731002 A EP10731002 A EP 10731002A EP 2389238 A1 EP2389238 A1 EP 2389238A1
Authority
EP
European Patent Office
Prior art keywords
module
permeate
membrane
bubbles
header
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP10731002A
Other languages
German (de)
English (en)
Other versions
EP2389238A4 (fr
Inventor
Pierre Cote
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BL Technologies Inc
Original Assignee
BL Technologies Inc
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 BL Technologies Inc filed Critical BL Technologies Inc
Publication of EP2389238A1 publication Critical patent/EP2389238A1/fr
Publication of EP2389238A4 publication Critical patent/EP2389238A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
    • B01D63/02—Hollow fibre modules
    • B01D63/026—Wafer type modules or flat-surface type modules
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/145—Ultrafiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/147—Microfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
    • B01D63/02—Hollow fibre modules
    • B01D63/04—Hollow fibre modules comprising multiple hollow fibre assemblies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/02—Membrane cleaning or sterilisation ; Membrane regeneration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/02—Membrane cleaning or sterilisation ; Membrane regeneration
    • B01D65/06—Membrane cleaning or sterilisation ; Membrane regeneration with special washing compositions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/08—Prevention of membrane fouling or of concentration polarisation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2313/00—Details relating to membrane modules or apparatus
    • B01D2313/02—Specific tightening or locking mechanisms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2313/00—Details relating to membrane modules or apparatus
    • B01D2313/06—External membrane module supporting or fixing means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2313/00—Details relating to membrane modules or apparatus
    • B01D2313/16—Specific vents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2313/00—Details relating to membrane modules or apparatus
    • B01D2313/21—Specific headers, end caps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2313/00—Details relating to membrane modules or apparatus
    • B01D2313/26—Specific gas distributors or gas intakes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2315/00—Details relating to the membrane module operation
    • B01D2315/06—Submerged-type; Immersion type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
    • B01D2321/16—Use of chemical agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
    • B01D2321/18—Use of gases
    • B01D2321/185—Aeration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/02—Aerobic processes
    • C02F3/12—Activated sludge processes
    • C02F3/1236—Particular type of activated sludge installations
    • C02F3/1268—Membrane bioreactor systems
    • C02F3/1273—Submerged membrane bioreactors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/10—Biological treatment of water, waste water, or sewage

Definitions

  • This specification relates to immersed membrane systems, for example suction driven immersed microfiltration or ultrafiltration systems for producing usable water or treating wastewater, and methods of membrane system operation including methods to inhibit fouling such as aeration (or gas bubble scrubbing) methods and chemical cleaning methods.
  • aeration or gas bubble scrubbing
  • Immersed membrane systems may use hollow fiber ultrafiltration or microfiltration membranes immersed in a tank of water (including wastewater) to be treated.
  • Many hollow fibers may be mounted vertically between upper and lower potting heads to form a module.
  • the module is typically kept to a size that can be handled by a person.
  • modules are connected together into larger assemblies, sometimes called cassettes.
  • the configuration of the cassette and the arrangement of pipes around the cassettes can affect the cost of the installation, the ability to pack membrane area into a tank, the flow of fluids in the tank and the operational efficiency of the system.
  • US Patent 5,639,373 describes a module of immersed membranes.
  • the membranes are oriented vertically between solid upper and lower rectangular potting heads and tubular aerators are placed on the sides of the lower potting head.
  • the lower potting head of a module has a skirt extending below the potting head and tubes extending through the potting material. Air provided through a port in the side of the skirt flows though the tubes to create bubbles at the top of the lower potting head.
  • US Patent 6,245,239 describes a cyclic aeration system for submerged membrane modules.
  • a set of rectangular modules with membranes oriented vertically between solid upper and lower potting heads has a set of aerators below the modules. A flow of air to the aerators is switched on and off in repeated cycles.
  • Maintenance cleaning is used to sustain the operation of immersed membranes, for example ultrafiltration or microfiltration membranes in a membrane bioreactor.
  • maintenance cleaning involves frequent, for example 1-7 times per week, contact periods with cleaning chemical(s) to "condition" the fouling layer rather than attempt to remove it.
  • the active chemical in the cleaning solution is often chlorine, but other oxidants, bases or acids can also be used.
  • the efficiency of maintenance cleaning is related to the chlorine concentration and contact time. When NaOCI is used to supply chlorine, the concentration may be between 100- 500 mg/L. The contact time may be several minutes to one hour.
  • a module of vertically oriented membranes has an upper permeating header and a lower dead end header with integral air holes.
  • the headers are not fixed apart from each other in the module itself.
  • the module preferably has a square cross section in plan view, but with a permeate cap that provides a round permeate connection.
  • the modules are mounted in line on upper and lower beams to form a cassette.
  • the cassette is an elongated rectangular shape in plan view.
  • a skirt is formed under the modules or cassette to provide an open bottomed chamber under the lower headers in communication with the air holes. Adjustable side members between the beams allow for membrane slack adjustment and bottom beam levelling.
  • a permeate header is provided above and in line with the upper beam.
  • the cassette can be inserted from above into receivers mounted to the upper sides of the tank.
  • An aerator grid is provided separately.
  • the primary components of the aerator grid are flat assemblies of pipes and structural members that can be inserted vertically downwards into spaces between the cassettes. Air holes in the aerators can be located to provide bubbles both into the skirts and optionally also into the spaces between cassettes.
  • the top beam of each cassette is attached to the tank and bears the weight of the cassette.
  • the module may also be described as having membranes extending upwards from a potting head.
  • the potting head is located between two opposed walls of a skirt extending below the bottom of the potting head. There are passages for air to flow vertically through the potting head.
  • An aerator is provided on each side of the module. Each aerator has one or more holes and creates bubbles both between the wall of the skirt and outside of the skirt. Gas flow is provided at one time only or primarily to one of the aerators and at another time only or primarily to another of the aerators. Gas flows through the potting head to produce bubbles during both periods of time, optionally continuously.
  • An aeration method involves producing bubbles primarily or only to one side of the module, alternating from one side of the module to the other, while also producing bubbles within the module or between the membranes, optionally continuously.
  • One or more modules may be connected to a permeate header above the membrane surfaces of the modules.
  • the permeate header is in communication with an isolation valve to isolate the permeate header from other pipes in the permeate withdrawal system.
  • the permeate header is also in communication with a vent valve on the module side of the isolation valve operable to open the permeate header to atmosphere.
  • a chemical injection pipe allows a chemical to be injected into the permeate header.
  • the isolation valve is closed.
  • the water (mixed liquor in the case of a membrane bioreactor) level in the tank may be reduced.
  • a cleaning chemical is injected into the permeate header where it is mixed with water in the permeate header to a desired concentration.
  • a cleaning method involves flowing a chemical cleaning solution by force of gravity through a membrane module, optionally by injected a concentrated solution into a vented potion of a permeate withdrawal system located above the water level in a tank holding the module. By this method, only a small amount of chemical is used. The chemical may be evenly distributed among a number of modules without a high flow rate. The chemical remains at high concentration near the module, with little dilution into the water outside of the module.
  • Figure 1 is a cross section of a module.
  • Figure 2 is a side view of a cassette of modules in a tank, the tank shown in section.
  • Figure 3 is a side view of an aerator assembly.
  • Figure 4 is a schematic top view of a tank with cassettes and aerator assemblies installed.
  • Figure 5 shows a partial end view of cassettes in a tank with the lower parts of a set of modules as in Figure 1 in cross section and a schematic aeration system at one period of time.
  • Figure 6 shows a partial end view of cassettes in a tank with the lower parts of a set of modules as in Figure 1 in cross section and a schematic aeration system at another period of time.
  • Figure 7 is a longitudinal cross section of a part of the permeate header of figure 2.
  • Figure 8 is a cross section cut across the diameter of a part of the permeate header of Figure 2.
  • a module 10 has a lower potting head 12 and an upper potting head 14.
  • a large number of hollow fiber membranes 16 are potted in the potting heads 12, 14.
  • the potting heads 12, 14 are also sometimes called headers or tube sheets. Only a few of the membranes 16 are shown to simplify the drawing.
  • the membranes 16 are plugged at their lower ends in a block of potting resin within the lower potting head 12.
  • the membranes 16 pass through the upper potting head 14 so as to be open to a permeate collector cap 18 sealed to the upper surface of the upper potting head 14.
  • the cap 18 is connected to a permeate header 20 which is in turn connected to a source of suction operable to withdraw permeate through the membranes 16.
  • the potting heads 12, 14 may be attached to a frame 26 (only part shown) to space the potting heads 12, 14 and allow the module 10 to be lowered into a tank of liquid to be filtered.
  • the module 10 is intended to be immersed with the membranes 16 oriented vertically in an open tank.
  • the module 10 may be, for example, round or square with a diameter or width of between 100-200 mm or 100-150 mm.
  • Several modules 10 may be arranged side by side to create a rectangular assembly.
  • the height of the module 10 may be 1-2 m.
  • the total membrane surface area may be 15-25 square meters.
  • the lower potting head 12 has one or more, for example 1-10, holes 22 passing through it between the membranes 16. Each hole 22 may be 5-10 mm in diameter.
  • One or more of side walls of the lower potting head 12, parts of a frame 26 holding the module 10, and skirt walls 28, extend downwards at the sides of the lower potting head 12 to define the sides of an open bottom chamber 30 (sometimes called a skirt) below the lower potting head 12.
  • the lower potting head 12 or parts of a frame 26 holding the module 10 may define the top of the chamber 30 or additional top plates may be used. Extension tubes 24 may protrude from the holes 28 into the chamber 30. If several modules 10 are placed side by side to form a rectangular assembly, a skirt wall 28 may extend along the length of the entire assembly to form one long chamber 30 below several modules 10. Alternately, additional dividing walls may be placed between each pair of modules 10 to provide a separate chamber 30 below each module 10.
  • a set of modules 10 are held by their potting heads 12, 14 in a common frame 26 to form a cassette 60.
  • the modules 10 are placed as close together as possible in a row.
  • the frame 26 comprises horizontal beams 42 and vertical posts 44.
  • the permeate collection header 20 runs parallel to the frame 26 and is connected to the cap 18 of each module 10.
  • the permeate collection header 20 is also communicates with one or more larger permeate collection pipes 50 through one or more isolation valves 52.
  • one end of the permeate header 20 is capped and the other end of the permeate header 20 is attached to a shared permeate collection pipe 50 through an isolation valve 52 associated with only one permeate collection header 20.
  • the isolation valve 52 allows isolation of one or more beam- cassettes for maintenance without interruption of operation.
  • the permeate collection pipe 50 runs along the side of the tank 48 at a right angle to the permeate header 20 and is connected to the permeate headers of other sets of modules located in the tank 48 beside the set of modules 10 shown.
  • the permeate collection pipe 50 is also attached to a source of suction (not shown) operable to withdraw permeate from the modules 10.
  • the upper one of the beams 42 is normally immersed in water in the tank 48 while the permeate header 20 may be normally above or within the water.
  • Each cassette 60 is held in a pair of guides 46 connected to the tank 48.
  • the guides 46 of a pair face each other on opposite sides of the tank 48.
  • the cassette 60 slides vertically downwards into the guides 46.
  • An upper beam 42 of the cassette 60 bears on abutments of the guides 46 such that the weight (or buoyancy) of the cassette 60 as a whole is resisted via the upper beam 42.
  • the guides 46 may optionally restrain the lower beam 42 laterally or have no contact with the lower beam 42.
  • the distance between the top and bottom beams 42 is set by adjusting connections between the vertical posts 44 and the beams 42.
  • the upper beam 42 spans the width of the immersion tank 48 and is attached to the walls of the tank 48 on both sides via the guides. While the upper beam 42 (and the upper potting heads attached to it) is normally immersed, the attachment points to the guides 46 or between the guides 46 and the tank 48 can be above the water surface.
  • the vertical posts 44 are rigid structural pieces (pipe or beam) that connect the top and bottom beams 42 and maintain them at a fixed and adjustable distance. There are two vertical posts 44 per cassette 60, one at each end of the cassette 60. The distance between the top and bottom beams 42 should be slightly less than the length of the fibers between the potting heads 12, 14 to provide some hollow fibre slack. The amount of fiber slack can be adjusted for performance. Vertical posts 44 may be fixed into the bottom beam 42 (rotation allowed) but have an adjustable slide-type connection in the top beam 42 to make adjustments to the spacing of the beams 42. The vertical posts 44 and guides 46 maintain the bottom beam 42 in a fixed vertical position during operation when the bottom beam 42 becomes buoyant.
  • the vertical posts 44 can be used while the cassette 60 is in the tank 48 to change the position of the bottom beam 42 in order to adjust slack and ensure even air flow rate through the holes in the lower potting head.
  • the top beam 42 is roughly levelled by adjusting the attachment points to the tank 48 or guide 46.
  • the bottom beam 42 is pushed down until hollow fibres 16 are taut.
  • the vertical posts 44 are then moved back up by a distance that will provide the desired fibre slack.
  • the air flow is turned on at low value and the bubble pattern at the surface is observed.
  • the vertical posts can then be moved up and down until air flow is even, making sure that the required adjustment is split evenly between the two vertical posts 44 (one is moved up, the other is moved down) to avoid changing slack significantly.
  • the vertical posts 44 are then locked in place.
  • FIG. 3 shows a side view of an aerator assembly 70.
  • the aerator assembly 70 is separate from the cassettes 60.
  • An aerator assembly 70 is inserted between pairs of cassettes 60 and optionally beside outer cassettes.
  • Each aerator assembly 70 slides vertically into an aerator guide 72 attached to the tank 48 walls.
  • the aerator guide 72 may extend downwards into the tank 48 (rather than upwards as shown) like the guides 46 for the cassettes 60.
  • Each aerator assembly 70 consists of an aerator header 74, an aerator 32 and a number of down-pipes 76.
  • the aerator assembly 70 is generally planar.
  • Aerators 32 are also sometimes called air, gas or bubble spargers, or simply spargers.
  • An aerator header 74 runs between each pair of cassettes 60.
  • a down-pipe 76 is connected to the aerator header 74 on each side of it.
  • additional down-pipes 76 may be provided every 200-500 mm.
  • the down pipes 76 may be long enough to position the aerators 32 below the skirts of the cassettes 60 when installed.
  • the aerator assembly 70 described herein primarily occupies spaces in a tank 48 that would be required in any event for gaps for water flow between cassettes 60 and thereby facilitates a high tank intensity (square meters of membrane surface area per unit volume or surface area of a tank).
  • the tank 48 is typically rectangular in plan view. Cassettes 60 are laid across the tank width or length.
  • a useful feature of the beam - cassette structure described herein is that the length of the cassettes 60 may be made in increments of the width or diameter of the modules 10 such that the length of a cassette may be generally equal to, through slightly less than, the width or length of the tank 48.
  • custom-length cassettes can be built using a standardized size of module 10 merely by changing the length of the beams 28.
  • Cassettes 60 and aerator assemblies 70 may be placed side by side across the remaining dimension of the tank 48 to efficiently fill the tank area to a high tank intensity.
  • the permeate headers 20 are connected to a main permeate header 50 on one side of the tank 48.
  • the aeration assemblies 70 are connected in an alternating pattern to two separate aeration headers 34 on the other side of the tank 48, or to a single header if, optionally, air will be supplied to all cassettes 60 in the tank 48 at the same time.
  • the tank 48 may be 2-3m deep. In a membrane bioreactor application, the tank 48 also contains a layer of mixed liquor distribution pipes at the bottom (not shown) and a return activated sludge outlet or overflow (not shown). It is desirable that the membrane tank 48 be completely filled with cassettes 60 to ensure a uniform flow pattern in the tank 48.
  • a number of modules 10 may be immersed side by side in a tank (not shown in Figures 5 and 6) of water to be filtered, for example re-circulated mixed liquor in a wastewater treatment plant.
  • Each module 10 shown in Figures 5 and 6 may be part of a cassettes 60 extending in length perpendicular to the page.
  • a group of modules 10 are spaced apart, for example at 200-500 mm center to center, to provide gaps between them.
  • An aerator 32 is located between each spaced pair of modules 10, and optionally beside but outside of the modules 10 at the edges of the group of modules 10.
  • the aerators 32 may be pipes located 100-500 mm below the lower potting heads 12 with 5-15 mm air holes 40 every 50-100 mm on each side of the aerator 32.
  • the air holes 40 may be oriented radially pointing 30-60 degrees below horizontal.
  • the aerators 32 are attached to headers 34 connected through valves 36 to an air blower 38 or another source of a pressurized gas that will be used to make gas bubbles.
  • a process of membrane aeration is also sometimes called air, gas or bubble sparging, or simply bubbling.
  • the fraction of the bubble gas flow captured in the chambers 30 may be varied by the varying the design, position or location of the aerators 32, by varying the width of the gaps between the modules 10, or by varying the width of the bottom of the skirt walls 28.
  • the aerators 32 and lower potting heads 12 within a cassette 60 are preferably leveled to promote an even distribution of air flow from the air holes 40 of an aerator or from the holes 22 of the one or more lower potting heads 12 of a cassette 60.
  • the aerators 32 may be connected to the headers 34 such that each header 34 feeds gas to every second aerator 32.
  • the even numbered aerators 32 in a tank are numbered from left to right, the even numbered aerators 32 are attached to a first header 34a and the odd numbered aerators 32 are attached to a second header 34b.
  • the flow of gas from the blower 38 may be switched from first header 34a to second header 34b by closing valve 36a while opening valve 36b.
  • the flow of gas may be switched back to the first header 34a after a period of time by opening valve 36a while closing valve 36b.
  • the gas flow may be switched back and forth repeatedly while permeation and backwash or relaxation cycles of the filtration operation are on going.
  • Figure 6 shows the gas flow with valve 36a closed and valve 36b open while Figure 5 shows the gas flow with valve 36a open and valve 36b closed.
  • Dead end potting of the membranes 16 in the lower potting head is also helps inhibit fouling near the lower potting head 12 since transmembrane pressure decreases with distance from a permeating header due to head losses to permeate flow in the lumens in the membranes 16.
  • extension pipes 24 may be inserted into the bottom ends of the holes 22.
  • the extension pipes 24 protrude into the chamber 30, for example by 10-30 mm.
  • a gas pocket forms in the top of the chamber 30 that is always at least as thick as the length of protrusion of the extension pipes 24.
  • the gas pocket is usually thicker than that, with air overflowing into the extension pipes 25 and through the holes 22.
  • the additional gas pocket thickness provided by the extension pipes 24 allows gas to distribute across the chamber 30 more quickly as gas flow is switched from one aerator 32 to another and so promotes a more nearly even gas flow among holes 22 spaced across the width of a module 10.
  • the cleaning solution is preferably distributed evenly to all modules.
  • the concentration of cleaning solution should be high (though within the limit of the membrane material tolerance) and excess dilution into water in the tank outside of the modules is preferably avoided.
  • the cleaning solution is preferably delivered to the membrane surface and allowed to react there with minimal negative impact on biomass in the membrane tank.
  • Maintenance cleaning is preferably performed in a full or nearly full tank. Maintenance cleaning can be done in an empty tank to avoid dilution into the water in the tank, but in that case most of the solution is lost by permeation near the bottom of the hollow fibres where the static pressure of a cleaning solution inside the module is highest.
  • fouling near the bottom of the membranes is reduced both by the aeration method and dead end potting of the bottom of the fibres.
  • the permeate pumping system is often used to deliver maintenance cleaning solution to membrane modules.
  • a large amount of chlorine solution is needed just to fill the permeate piping network even before any cleaning solution is contacted with the membrane.
  • a large flow rate is needed to deliver the cleaning solution evenly to all modules to make use of the equalizing effect of pressure loss in the modules.
  • the combined impact of these constraints is that a large amount of low concentration chlorine solution permeates the membrane, dilution is excessive and a significant part of the biomass in the tank may be killed.
  • the permeate header 20 is connected to a vent pipe 54 with a vent valve 56. Opening the vent valve 56 exposes the inside of the permeate header 20 to atmospheric pressure.
  • a chemical injection tube 58 has a section running inside of the permeate header
  • Another section of the chemical injection tube 58 is located outside of the permeate header 20 and connected, typically through intermediate pipes and valves not shown, to a chemical pump 62 connected to a chemical tank 64.
  • the permeate header 20 is isolated from the permeate pumping network by closing isolation valve 52.
  • an isolation valve could be provided and closed further downstream in the permeate network so that multiple sets of modules 10 connected to permeate pipe 50, for example all of the modules 10 in a tank 48, can be maintenance cleaned at the same time. Closing the isolation valve 52 isolates a known volume of permeate in communication with one or more permeate headers 20.
  • An amount of concentrated chlorine or other cleaning chemical is injected in the permeate header 20 via the chemical injection tube 58.
  • the chemical cleaner flows out of the injection holes 60 and rapidly mixes into permeate in the permeate header 20 to the desired final concentration.
  • the chemical solution remains in the permeate header 20 at this stage although a small amount of permeate is displace into the membrane tank 48.
  • Membrane aeration is preferably turned off to minimize dispersion of the cleaning solution in the following steps.
  • the mixed liquor level in the tank 48 is optionally partially lowered to create or increase a potential driving force in a direction opposite to normal permeation.
  • This reverse-permeation driving force may be around one or more
  • the permeate header 20 should at least be completely above the water level before a flow of chemical solution from the permeate header is initiated.
  • the water level may be lower to 10 or 20 cm below the bottom of the upper header to encourage flow of cleaning chemical through the upper parts of the membranes.
  • the water level can be lowered by partially draining the tank 48 any time before opening the vent valve 56.
  • the water level can be lowered by shutting of flow of water into the tank while continuing to withdraw permeate before closing isolation valve 52.
  • vent valve 56 to connect the interior of the permeate header 20 to atmosphere. This allows the contents of the permeate header 20 to reverse-permeate by gravity.
  • the vent valve 56 or the extent to which it is opened, can be chosen so that the reverse-permeation (chemical discharge) time of the cleaning solution provides the desired contact time for the cleaning chemical.
  • a wait time of up to about 5 minutes may be provided after the reverse-permeation is substantially completed to allow time for the chemical cleaner to further react with foulants.
  • vent valve 56 is preferably located at a high point of the isolated area in or in communication with the isolated permeate header 20. Vent valve 56 can then be closed, membrane bubbles scouring resumed, and isolation valve 52 opened to put the modules 10 back into operation. Any air still trapped in the permeate header 20 may be removed through the ordinary air collector of the permeate system.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Organic Chemistry (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

Selon l'invention, un module de membranes verticales a un collecteur inférieur ayant des trous intégrés pour faire passer de l'air. Des modules sont montés en ligne sur des poutres supérieure et inférieure. Une jupe est formée sous la cassette. Des éléments latéraux ajustables entre les poutres permettent l'ajustement du jeu des membranes et le nivellement de la poutre du bas. Un ensemble aérateur plat peut être introduit dans les espaces entre les cassettes et fournit des bulles dans les jupes, les espaces entre les cassettes, ou les deux. Un procédé d'aération comprend la production de bulles principalement ou seulement sur un côté du module, alternant d'un côté du module à l'autre, tout en produisant également des bulles à l'intérieur du module ou entre les membranes, éventuellement en continu. Un procédé de nettoyage comprend la circulation d'une solution de nettoyage chimique par la force de la gravité dans un module membranaire, éventuellement par injection d'une solution concentrée dans une partie mise à l'air libre d'un système de soutirage de perméat situé au-dessus du niveau de l'eau dans une cuve contenant le module.
EP10731002.1A 2009-01-14 2010-01-14 Cassette de membranes immergées et procédé de fonctionnement Withdrawn EP2389238A4 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US14472309P 2009-01-14 2009-01-14
PCT/CA2010/000052 WO2010081228A1 (fr) 2009-01-14 2010-01-14 Cassette de membranes immergées et procédé de fonctionnement

Publications (2)

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EP2389238A1 true EP2389238A1 (fr) 2011-11-30
EP2389238A4 EP2389238A4 (fr) 2013-07-03

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EP (1) EP2389238A4 (fr)
KR (1) KR20110127123A (fr)
CN (1) CN102325583A (fr)
AU (1) AU2010205867A1 (fr)
BR (1) BRPI1004927A2 (fr)
WO (1) WO2010081228A1 (fr)

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Also Published As

Publication number Publication date
EP2389238A4 (fr) 2013-07-03
BRPI1004927A2 (pt) 2016-04-26
KR20110127123A (ko) 2011-11-24
CN102325583A (zh) 2012-01-18
AU2010205867A1 (en) 2011-07-21
WO2010081228A1 (fr) 2010-07-22

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