Patent Document

RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Patent Application PCT/EP2014/068068 filed on Aug. 26, 2014 claiming priority from German patent application DE 10 2013 218 208.2 filed on Sep. 11, 2013, both of which are incorporated in their entirety by this reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a membrane filter for filtering a liquid to be filtered, the membrane filter comprising including at least one membrane carrier at which membranes are attached which membranes facilitates filtering a liquid permeate from the liquid and wherein the membrane carrier includes a permeate collecting cavity at which the membranes are connected with an open permeate side, and a permeate outlet for letting the permeate out of the permeate collecting cavity; a gas distribution system arranged below the at least one membrane carrier and including at least one downward open and upward closed tub which includes a wall with downward open vertical slots for distributing a gas into the liquid; and at least one gas inlet into the gas distribution system. 
         [0003]    The invention also relates to a method for filtering a liquid in a membrane filter including at least one membrane carrier, at least one gas inlet, and a gas distribution system with at least one downward open and upward closed tub which includes a wall with downward open slots, wherein a gas flows through the at least one gas inlet into the at least one tub the gas fills the at least one tub and the slots up to a portion of a height of the slots with a gas cushion, the gas flows out the gas cushion through the slots in a laterally outward direction from the at least one tub and thus flows at several locations below the at least one membrane carrier into the liquid, the gas generates a liquid flow at a phase boundary below the gas cushion during a lateral flow of the gas through the slots wherein the liquid flow is parallel to the lateral gas flow, the gas rises in the membrane filter, and thus generates an upward movement of the liquid in the membrane filter. 
       BACKGROUND OF THE INVENTION 
       [0004]    Membrane filters of this general type that are known in the art are configured for filtering waste water that is heavily loaded with solids like they can be found for example in biologic waste water treatment plant in membrane bioreactors (MBR). The membrane filter can either be submerged in the tanks of the waste water treatment plant or can be provided with inlet and outlet conduits and can be set up on dry land integrated in a pipe. The driving force for the filtration is implements in most cases through a vacuum applied on the permeate side but can also be implemented for the dry set up variant by a low feed side (raw water side) positive pressure. 
         [0005]    The membranes that are fixated in the membrane carrier can be in particular hollow fiber membranes which have a diameter of less than 5 mm but they can also be flat membranes. Thus a portion of the membrane filter is designated as the membrane carrier in which portion the membranes are fixated. Hollow fiber membranes are typically attached at least on a bottom in a membrane carrier, typically additionally also on top in a second membrane carrier. Also membrane filters with flat membranes include membrane carriers at which the flat membranes are attached. The flat membranes themselves have a permeability of microfiltration membranes or ultra-filtration membrane. Using membranes for reverse osmosis or nano filtration is possible. Typically hollow fiber membranes in a diameter range of 0.5-3 mm are being used. 
         [0006]    In order to prevent a blocking of the membrane filters by filtered materials the membrane filter is flushed continuously or in periodic internals. Typically used physical flushing methods for the membrane filter use a permeate side back flushing of the membranes with liquid or gas combined with a gas bubble flushing on an outside of the membranes. Rising gas bubbles typically also generate an upward flow of the liquid to be filtered which is designated as mammoth pumping effect. A shear force of the 2 face flow including gas and liquid generates a high level of turbulence which removes coatings from the membranes and flushes them out. In membrane bioreactors air is typically used as a gas. 
         [0007]    A membrane filter of this type is known from JP 10 06 63834. Thus plural membrane carriers with membranes attached therein which are not specified in more detail are arranged above a gas distribution system which includes plural downward open and upward closed tubs which have walls with downward open vertical slots for distributing the gas into the liquid. 
         [0008]    In the known membrane filter the tub has the shape of a downward open cuboid or half cylinder with slots that are laterally arranged in the wall, extend vertically and are open in a downward direction. The known membrane filter has plural gas inlets into the gas distribution system which respectively connect to an interior of the tubs from above through a sealing of the tubs. 
         [0009]    Through the gas inlets a gas flows from above into the tubs and fills the tubs up to a portion of the height of the tubs with a gas cushion. Thus also the slots fill up to an identical level with gas since the slots are open in outward direction the gas flows out of the gas cushion through the gas filled portion of the slots laterally out of the tub and thus flows at several locations below the membranes into the liquid to be filtered. In order to be able to compensate variations in the gas volume the slots are typically sized for normal operations so that they are only partially filled with gas. The filling level of the tub with gas and thus also the filling level of the slots is a function of the gas volume flow that flows into the gas distribution system. For higher gas volume flows the gas backs up in the tub to a higher level and thus a larger portion of the slots is filled with gas, this means the flow through cross section for the gas increases and a higher volume of gas flows through the slots. Up to a complete back up of the tub the gas flows out of the slots evenly. Only when the gas volume becomes large enough so that the tub flows over the additional gas volume exits from the tub in an uncontrolled manner. 
         [0010]    After the gas flows out of the slots the gas subsequently rises in the membrane filter and thus generates an upward movement of the liquid through the membrane filter according to the mammoth pumping principle. The high shear force effect of the 2 face flow including the rising liquid and the gas thus flushes the membranes, wherein coatings and deposits are removed and carried out of the filter. 
         [0011]    During lateral flow through the slots the gas generates a liquid flow that is oriented parallel to the lateral gas flow at a face boundary below the gas cushion wherein the liquid flow impacts the portion of the wall between the slots that protrudes on a bottom out of the gas cushion. This flow typically flushes in hair or fibrous compounds in membrane bioreactors, in particular in applications for municipal waste water processing. 
         [0012]    In the membrane filter described in JP 10 06 6834 sections of the wall between the slots protruding from a bottom of the gas cushion act like a comb or rake upon hair and fibrous compounds included in the liquid to be filtered wherein the hair and fibrous compounds easily lodge in the slots. When the hair is carrier for example by the flow with one end into one slot and with another end into an adjacent slot the hair is retained at flow leading edges of the wall between the slots which can lead to a blocking of the slots. Thus the gas volume flowing through these slots is obstructed up to a complete blockage. As a consequence insufficient gassing and flushing is provided for a membrane portions that are arranged there above which creates a risk of blocking these portions. 
       BRIEF SUMMARY OF THE INVENTION 
       [0013]    Thus it is an object of the invention to provide a membrane filter with reduced blocking propensity. 
         [0014]    Improving upon known membrane filers it is proposed according to the invention that the at least one tub includes an inner edge respectively between adjacent slots in at least one vertical sectional view orthogonal to the wall which inner edge at least in a portion of a lower half of the slots has an angle relative to horizontal of less than 60° in any point. This configuration can either be implemented by a greater slant angle or rounding this inner edge. This creates a flow impact portion at lower inner edges of the wall for the liquid flowing below the gas cushion wherein hair and fibrous compounds are stripped off by the liquid flow in the flow impact portion which reduces the blocking propensity of the slots and of the membrane portion arranged there above. 
         [0015]    In an advantageously embodiment of the membrane filter according to the invention the gas distribution system is configured at a bottom side of the at least one membrane carrier. In this case the membrane carrier and the gas distribution system are one component. Thus the gas is distributed into the liquid to be filtered directly at a bottom side of the membrane carrier, thus at locations where it exits from the gas distribution system. Thus the gas bubbles flow around the membrane carrier and the membranes attach therein directly at their intended locations. The configuration of the gas distribution system at the bottom side of the membrane carrier helps to prevent potential deviating gas flows. 
         [0016]    Due to the small blow in depth an energy requirement for the gas loading is reduced compared to systems with a gas distribution system that is separately installed below the membrane carrier. The low production costs presents another advantage since the membrane filter has one less component due to the configuration of the gas distribution system at a base of the membrane carrier. 
         [0017]    In order to provide a stripping of hair and fibrous compounds at the rounded or slanted inner edge of the tub a horizontal extension of this inner edge of approximately of 10-15 mm is required. In the simplest case this requirement causes a configuration of the tub that is configured accordingly thick. 
         [0018]    In the membrane filter according to the invention the gassing system can be installed in an alternative as a separate component below the membrane carrier and offset therefrom. The gas distribution system in this case can be configured as a separate component. However the offset between the gas distribution system and the membrane carrier also has a disadvantage. In the liquid filled flow portion between the gas distribution system and the membrane carrier the gas bubbles can be deflected by transversal flows in the bio reactor or other flows and may not impact the membrane carrier at the provided location which does not assure an even gassing of the membranes any more. Furthermore the energy requirement for the gassing increases due to the greater blow in depth. For a blow in depth of 2 meters 20 cm additional blow in depth already would require 10% more energy. 
         [0019]    In the configuration of the membrane filter it is advantageous that the at least one tub includes at least one vertical rib that extends from the wall inward between adjacent slots wherein an extension of the vertical rib decreases in downward direction going into the at least one tube. When the gas distribution system and also the tub is configured as an injection molded component the thicker wall has the disadvantage of material accumulations. Figuratively speaking the ribs are the only portion of the thickened wall which is maintained while the other portions of the thicker wall remain cut off so that only one wall in the otherwise typical thinner wall thickness of the component remains. The ribs prevent material accumulations in the component and facilitate producing it as an injection molded component. In this case the ribs form the portion of the wall between respectively adjacent slots where hair and fibrous compounds can be stripped off in an outward direction. The vertical sectional view which includes an inner edge which at least in a portion of a lower half of the slots has an angle relative to horizontal of less than 60° in each point extends in this case longitudinally through the ribs. 
         [0020]    Since the ribs are a left over of the thickened wall of the tub they require the same horizontal extension of approximately 10-15 mm. Thus, there are limits for the configuration of the tub. Thus tubs with a total width under 3% cannot be configured with useful flow dynamic properties since the remaining open flow cross section between the ribs in an interior of the tub is typically too small to let the entire gas volume glow through. 
         [0021]    In a membrane filter according to the invention the tub of the gas distribution system can have different plan forms from circular over rectangular and polygonal to completely free shapes. When the gas distribution system and thus also the tub are configured at a bottom side of the membrane carrier the tub as a matter of consequence reflects some of the geometric details and dimensions of the membrane carrier. 
         [0022]    In an advantageous embodiment of the membrane filter according to the invention the gas distribution system includes downward open gas conduction channels which adjoin at least a portion of the slots on an outside for further conduction and distribution of the gas away from the at least one tub. Thus it is an advantage of the gas distribution channels to also facilitate significantly smaller components for the gas distribution system. 
         [0023]    Thus the membrane carrier of a membrane filter according to the invention can include for example an anchor at which plural fingers are arranged at which membranes are attached on top. When the tub is configured for example according to the invention below, the gas conduction channels are formed on a bottom side of the fingers and facilitate conducting the gas into portions of the membrane filter that are further remote from the tub. 
         [0024]    The gas conducting channels of a membrane filter according to the invention have a base which either extends horizontally or has a slope relative to horizontal so that the end of the gas conducting channels is arranged above the position of the their beginnings adjoining the slots. Through the sloped base forwarding the gas in the gas conduction channels is accelerated and a blocking risk of the gas conduction channels is reduced. 
         [0025]    In another advantageous embodiment of a membrane filter according to the invention the gas conduction channels adjoin the slots with a vertical upward offset. Thus the interaction between the slots and the adjoin gas conduction channels is significantly reduced which provides a more even flow through of the slots without and with the connected gas conduction channels. Additionally gas conduction channels that are further offset upward and adjoin the slots can help implement a configuration of the components that more favorable from an injection molded point of view since material accumulations in the component are avoided. 
         [0026]    In another advantageous embodiment of the membrane filter according to the invention the slots become wider in downward direction, this has the advantage that the cross sectional surface of the slots increases over proportionally for an increasing volume flow and a gas cushion in the tub that backs up further downward. Thus the gas pressure in the gas inlet only increases minimally which improves the self-regulation of the even flow through of the slots and thus the evenness of the gassing. The slots that become wider in downward direction thus form a variable “throttle” for the gas volume flowing through the slots for different gas volume flows. Through the cross sectional shape of the throttle the volume dependent filling level in the slots can be influenced. 
         [0027]    In another advantageous embodiment of the membrane filter according to the invention the slots have cross sectional surfaces with different sizes. This because different geometric configuration of the tub, in particular also when gas conduction channels are connected at some of the slots which shall facilitate flushing differently sized membrane surfaces with the gas volume flowing through the different slots it is advantageous to adapt the gas volume flowing through the slots through the geometric configuration of the slots to adapt to different required gas volumes. Thus in slots to which a gas conducting channel adjoins which transports the gas into portions of the membrane filter which are arranged further outward and away from the tub larger cross sectional surfaces of the slots are implemented in that the slots have a greater width. 
         [0028]    In another advantageous embodiment of the membrane according to the invention the at least one gas inlet laterally adjoins the at least one tub. This is part advantageous when the gas distribution system is configured at a bottom side of the membrane carrier. In this case the gas distribution is provided at the level of the slots which helps to prevent vertical flows of the gas and thus a sloshing of the gas cushion out of the tube. 
         [0029]    In case of a gas distribution system that is separated from the membrane carrier the gas inlet can be alternatively also provided from above through the base of the tub that is arranged on top. Alternatively a gas inlet that is separate from the tub and the gas distribution system can provide that the gas flows into the tub for example from a separate tube that is positioned below the tub. 
         [0030]    Improving upon the known method it is provided according to the invention that the liquid flow generated below the gas cushion flows respectively between adjacent slots in at least one vertical sectional view orthogonal to the wall against an inner edge of the at least one tub which inner edge at least in a portion of a lower half of the slots has an angle relative to horizontal of less than 60°. Thus hair and fibrous compounds at the inner edge are stripped off and blocking the slots and the membrane portions arranged there above is substantially avoided. Thus the blocking propensity of the membrane filter is reduced overall. 
         [0031]    In another advantageous embodiment of the method according to the invention the gas flows after flowing through some of the slots through gas conducing channels in to portions of the membrane filter that are moved further outward from the at least one tub. This facilitates an overall even distribution of the gas over the entire cross section of the membrane filter. In another advantageous embodiment of the method according to the invention the gas flows from a gas distribution system formed at a bottom side of the at least one membrane carrier and flows around the at least one membrane carrier after flowing into the liquid. This has the advantage that the gas before reaching the membrane carrier does not have to flow through any additional flow portion in which it can be prevented from reaching its destination at the membrane carrier. 
         [0032]    In order to perform a method according to the invention the membrane filter can be submerged in the liquid. The membrane filter is then surrounded by the liquid to be filtered and the mammoth pumping effect of the gas that is introduced into the base element and which rises in the membrane filter the liquid to be filtered is suctioned from below into the base element and flows through the filter unit together with the gas before both flow out on top of the filter unit. 
         [0033]    When performing the method according to the invention the liquid to be filtered can be supplied to the base element by a first liquid conductor and can be let out from the filter unit by a second liquid conductor, wherein the second liquid conductor is connected to a tube above the membranes which envelops the membranes and adjoins the base element on top. This variant of operations of a filter unit according to the invention is also designated as dry set up operations. 
         [0034]    When implementing larger filter units plural membrane filters according to the invention can be mounted parallel adjacent to each other on a common frame. Thus the permeate outlets of the individual membrane filters are connected with tubular conduits which are used for running the generated permeate out of the membrane filters. Also the gas inlets are connected with the tubular conduits which are used for feeding the gas into the membrane filters. Thus the gas feed conductors can be individually configured with throttles to even the air supply to the individual membrane filters. Thus it is advantage to position the throttles in the gas supply lines above the liquid surface in order to preclude flooding the throttle cross sections also when the filter is switched off and thus to preclude a clogging of the throttles with solid components of the liquid. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    The invention is subsequently described based on embodiments with reference to drawing figures, wherein: 
           [0036]      FIGS. 1A-1E  illustrate a first embodiment of the membrane filter according to the invention (total sectional view, partial sectional views and views of the base element); 
           [0037]      FIGS. 2A-2C  illustrate flow conditions in the first membrane filter: 
           [0038]      FIG. 3  illustrates the first membrane filter in submerged operations: 
           [0039]      FIG. 4  illustrates the first membrane filter in dry set up operations: 
           [0040]      FIGS. 5A-5I  illustrate details of the second embodiment of the membrane filter according to the invention. 
           [0041]      FIGS. 6A-6C  illustrate partial views and sectional views of the gas distribution system of the second membrane filter: 
           [0042]      FIGS. 7A-7D  illustrate additional membrane filters according to the invention: 
           [0043]      FIG. 8A  illustrates a view and a sectional view of a tub of a seventh membrane filters according to the invention; 
           [0044]      FIG. 8B  illustrates a view and a sectional view of a tub of an eighth membrane filter according to the invention; 
           [0045]      FIGS. 9A and 9B  illustrate a view and a sectional view of a base element of a ninth membrane filters according to the invention; 
           [0046]      FIG. 10A-10C  illustrate a view and sectional views of a gas distribution system of a tenth membrane filter according to the invention; and 
           [0047]      FIGS. 11A and 11B  illustrates variants of a gas distribution system of additional membrane filters according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0048]    The drawing figures are not to scale. All non stated details of subsequently described membrane filters according to the invention are identical with embodiments of previously described membrane filters according to the invention. 
         [0049]      FIGS. 1A-1E  illustrate sectional views and views of a first membrane filter  1  according to the invention. This membrane filter includes a base element  2  with a shell  3  and a membrane carrier  4  arranged therein in which hollow fiber membrane  5  are arranged on top. A cylindrical tube  6  adjoins the shell  3  of the base element  2  on top of the base element  2 . 
         [0050]    The hollow fiber membranes  5  are fabric reinforced and have an external diameter of 2.5 mm. They are individually closed at an upper end  7 . The tube  6  extends beyond the upper end  7  by a length of 8 cm to 10 cm. The hollow fiber membranes  5  are cast in in a sealing manner in the membrane carrier  4  by a resin layer  9 , wherein lumens of the hollow fiber membrane  5  remain open. 
         [0051]    The membrane filter  1  has a height  10  of 200 cm the base element  2  has a height  11  of 12 cm and the membrane carrier  4  has a height  12  of 11 cm. The base element  2  and the tube  6  both have an external diameter of 75 mm. The tube  6  has an internal diameter of 68 mm. The base element  2  furthermore includes a gas inlet  13  and a permeate outlet  14 . 
         [0052]    The membrane carrier  4  is connected with the shell  3  through an anchor location  15 . The base element  2  includes a flow cavity  16  between the shell  3  and the main membrane carrier  4  wherein the flow cavity is configured as an annular gap with a width of 9 mm, envelops the membrane carrier  4  and is only interrupted by the anchor location  15 . The flow cavity  16  is adjacent in each horizontal sectional view to the shell  3  and also to the membrane carrier  4 . 
         [0053]    The flow cavity  16  is limited in vertical direction by the overlap portion of the height  11  of the base element  2  and the height  12  of the membrane carrier  4 . The base element  2  is open in downward direction and capable of flow through. The flow cavity  16  includes an outlet  17  on top into the tube  6 . 
         [0054]    The gas inlet  13  is connected with a gas distribution system  18  configured on a bottom side of the membrane carrier  4  wherein the gas distribution system includes a tub  19  that is open in downward direction and closed in upward direction, wherein the tub includes a wall  20  with downward open vertical slots  21 . The tub  19  includes an inner edge  22  respectively in a center between adjacent slots  21  in a sectional view that is vertical and orthogonal to the wall  20 , wherein the inner edge  22  is a slanted edge over an entire height of the slots  21  wherein an angle  24  of the slanted edge  22  is 40° relative to horizontal. Alternatively the inner edge  22  in a portion of a lower half  23  of the slots  21  can have an angle  24  relative to horizontal that is less than 60° in any point. 
         [0055]    The base element  2  furthermore includes a permeate collecting cavity  25  into which the lumens of the hollow fiber membrane lead. The permeate collecting cavity  25  is connected with the permeate outlet  14  of the base element  2 . 
         [0056]      FIG. 1D  illustrates a top view of the base element  2  with the hollow fiber membranes  5  without the tube  6 . The number of the illustrated hollow fiber membranes  5  does not correspond to an actual number of the actual hollow fiber membranes  5 .  FIG. 1E  illustrates a view of the base element  2  from below. The number of slots  21  is 6. The slots are evenly distributed over a circumference of the top  19  in the wall  20  of the top  19 . 
         [0057]    The permeate outlet  14  and the gas inlet  13  are arranged in a radially outward extension of the anchor location  15 . 
         [0058]      FIGS. 2A-2C  illustrate the flow conditions in the base element  2  and in the lower portion of the tube  6  of the first membrane filter  1  during filtering operations. 
         [0059]    Thus,  FIG. 2A  illustrates a first vertical sectional view of the lower portion of the membrane filter  1 , wherein the sectional view also extends through the anchoring location  15 . 
         [0060]    A gas  26  is introduced into the base element  2  and the flow cavity  16  through the gas inlet  13  during operations of the membrane filter  1  thus the gas  26  flows through the gas inlet  13  initially into the tub  19 . The gas  26  fills the tub  19  up to a portion of the height of the slots  21  and forms a gas cushion  27  in the tub,  19 . The gas  26  also fills the slots  21  up to the level of the gas cushion  27  and eventually flows laterally through the portion of the slots  21  that are filled with the gas  26  out of the tube  19  or out of the gas cushion  27  and thus into a liquid  28  that is to be filtered. 
         [0061]    Besides the flow cavity  16  the membrane carrier  4  closes the base element  2  completely for the flow through of the liquid  28  and of the gas  26 , this means besides the flow cavity  16  there are no additional pass through openings for the gas  26  and the liquid  28  in the base element  2 . 
         [0062]    Above the base element  2  there are no additional installations in the tube  6  besides the hollow fiber membranes  5 . Therefore the hollow fiber membranes  5  float freely in the liquid  28  without impediment and are only fixated at their bases. Thus also hair, fibrous compounds or other contaminants from the liquid  28  cannot be lodged in this portion. 
         [0063]    During lateral flow through the slots  21  the gas  26  generates a radially outward oriented liquid flow that is parallel to the lateral gas flow at a face boundary surface below the gas cushion  27 . The liquid flows between respective adjacent slots  21  against and inner edge  22  of the wall  20  which has an angle relative to horizontal of less than 60° in each point in the portion of the slots. At this slanted inner edge hair and fibrous compounds included in the liquid  28  to be filtered are stripped off through the outward oriented gas flow and liquid flow which reduces a risk of these contaminants lodging in the membrane filter  1 . 
         [0064]    After flowing through the slots  21  the gas  26  rises through its buoyancy in the membrane filter  1  and generates an upward flow of the liquid  28 . This liquid flow is suctioned into the membrane filter only from below. The gas  26  and the liquid  28  flow through the flow cavity  16  of the base element  2  and jointly flow through the outlet  17  into the tube  6  and above at the tube  6  out of the membrane filter  1 . 
         [0065]    The strong shear force effect of the two phase flow including the liquid  28  and the gas  26  which rises through the mammoth pumping effect in the membrane filter  1 . The membrane carrier  4  is flushed on the outside in the flow cavity  16  of the base element  2  and the hollow fiber membranes  5  are flushed on the outside in the tube  6  and thus coatings and deposits are flushed off from the surfaces of the membrane carrier  4  and of the hollow fiber membranes  5  and are carried out the membrane filter  1 . 
         [0066]    Between the outside of the hollow fiber membranes  5  and their lumens there is a pressure differential based on which a liquid permeate  29  is filtered out the liquid  28  and flows into the lumens of the hollow fiber membranes  5 . The permeate  29  is collected from the lumens of the hollow fiber membranes  5  and then flows through the permeate outlet  14  out of the membrane filter  1 . 
         [0067]    Through the anchor location  15  the gas  26  is supplied and the permeate  29  that is filtered in the membrane filter  1  is drained. 
         [0068]    The gas inlet  13  is flow connected with the flow cavity  16  within the base element  2 , so that the base element  2  is flowable from the gas inlet  13  through the tub  19 , through the slots  21  and through the flow cavity  16  to the outlet  17 . 
         [0069]      FIG. 2B  illustrates an additional sectional view of the lower portion of the membrane filter  1  which sectional view however is turned by 90°. Thus the anchor location  15  is not sectioned but 2 of the slots  21 . The lateral outflow of the gas  26  through the slots  21  from the tub  19  or from the gas cushion  27  are visible. Additionally this sectional view shows the permeate collecting cavity  25  but does not show the permeate outlet  14 . 
         [0070]      FIG. 2C  illustrates another sectional view of the lower portion of the first membrane filter  1  which in this case only sections the shell  3  and otherwise extends through the flow cavity  16  so that the outside of the membrane carrier  4  becomes visible. Thus the lateral outflow of the gas  26  from the slots  21  is visible. 
         [0071]      FIG. 3  illustrates the first membrane filter  2  is submerged operations. Thus gas bubbles in the liquid  28  are not illustrated. Thus the membrane filter  1  is submerged in a tank with the liquid  28  to be filtered so that a liquid overhang  30  of 15 cm remains above the membrane filter  1  to the surface of the liquid  28 . Through a gas feed conductor  31  the gas  26  is run from above the surface of the liquid  28  to the gas inlet  13 . A throttle  32  is installed in the gas feed conduit  31 . The throttle is illustrated at this location in an exemplary manner and is only required when plural membrane filters  1  are operated in parallel and supplied with gas  26  simultaneously. The throttles  32  in the gas feed conduits  31  are used for balancing volumes of gas  26  flowing into the individual membrane filters  1 . The throttle  32  is arranged above the surface of the liquid to be filtered. Through a permeate conductor  33  the permeate  24  generated in the membrane filter  1  is drained by the permeate outlet  14 . 
         [0072]      FIG. 4  illustrates the first membrane filter  1  according to the invention in dry set up operation. Gas bubbles in the liquid  28  to be filtered are thus not illustrated. The liquid  28  is supplied to the membrane filter  1  through a first liquid conduit  34 . A permeate  29  if filtered from the liquid  28  and drains through the permeate outlet  14 . Through the gas inlet  13  the gas  26  is supplied. Through a second liquid conduit  35  the gas  26  and the liquid  28  minus the permeate  29  are drained. The second liquid conduit  35  is connected at a top of the tube  6  wherein the tube extends beyond the hollow fiber membranes  5 . 
         [0073]      FIGS. 5A-5G  illustrate views and various sectional views of a second membrane filter  36  according to the invention. 
         [0074]      FIG. 5A  illustrates a longitudinal sectional view of the second membrane filter  36 . The second membrane filter  36  includes a base element  39  that is open in downward direction towards a liquid  37  to be filtered and that is flowable by a gas  38  and a liquid  37  wherein the base element includes a tubular shelf  40  and precisely one membrane carrier  41  arranged therein, wherein the membrane carrier  41  is connected with the shell  40  through  2  anchor locations  42 . Hollow fiber membranes  43  are attached on top in the membrane carrier  41  wherein the hollow fiber membranes respectively include a lumen into which a liquid permeate  44  from the liquid  37  is filterable. Additionally the membrane filter  36  includes a circumferentially closed tube  45  which envelops the hollow fiber membranes  43  and adjoins the shell  40  or the base element  49  at a top and a gas inlet  46  for letting the gas  38  into the base element  39 . The base element  39  includes a permeate collecting cavity  47  which is connected with the lumens of the hollow fiber membranes  43  collecting the permeate  44  from the hollow fiber membranes  43  and a permeate outlet  48  for draining the permeate  44  from the permeate collecting cavity  47 . 
         [0075]    The base element  31  has a height  49  of 12 cm and the membrane filter  36  has a height  50  of 212 cm. The hollow fiber membranes  43  are encased at a bottom in the membrane carrier  41  by a resin layer  51  against the liquid  37  to be filtered in a sealing manner, wherein the lumens of the hollow fiber membranes  43  remain open. The number of the illustrated hollow fiber membranes  43  does not correspond to the actual number of the hollow fiber membranes  43 . The hollow fiber membranes  43  are individually closed on top and flowed freely on top in the liquid  37  to be filtered besides the lower fixation. The hollow fiber membranes  43  are completely enclosed by the tube  45 . The tube  45  protrudes by 10 cm above the upper ends  52  of the hollow fiber membranes  43 . 
         [0076]      FIG. 5B  illustrates a top view of the base element  39  of the second membrane filter  36  and  FIG. 5C  illustrates a perspective view with a cut up shell  40 . Between the shell  40  and the membrane carrier  41  the base element  39  includes a downward open flow cavity  53  for flowing the liquid  37  to be filtered wherein the flow cavity includes an outlet  54  on top for letting the liquid  37  to be filtered out into the tube  45 . 
         [0077]    The flow cavity  53  has bulges  55  that protruded into the membrane carrier  41  up to an anchor  56  of the membrane carrier  41 . Thus  6  fingers  57  are formed at the membrane carrier  41  wherein the  6  fingers are connected by the anchor  56  of the membrane carrier  41 . The  2  anchors  42 , are arranged in an extension of the anchor  56 , wherein the gas inlet  46  runs through one anchor location and the permeate outlet  48  runs through the other anchor location. The two anchor locations  42  are the only connections of the membrane carrier  41  with the shell  40 . Outfitting the membrane carrier  41  with the hollow fiber membranes  43  is performed in the second membrane filter  36  only in the portion of the fingers  57 , wherein the portion between the fingers above the anchor  56  remains recessed for production reasons. The hollow fiber membranes  43  of the second membrane filter  36  are fabric reinforced and have an outer diameter of 2.5 mm. 
         [0078]    In the portion of the anchor  56  there is a horizontal section in the base element  39  in which the flow cavity  53  forms two continuous flow channels  58  which have a uniform width  59  of 6 mm in the annular gap in the outer portion of the fingers  57 . Also between the fingers  57  the flow channel  58  has the same width  59  of six mm. Since the edges of the fingers  57  are rounded for hydrodynamic reasons the  2  flow channels  58  have a slightly greater width than 6 mm at the edges of the fingers  57 . Overall the  2  flow channels  58  have a uniform width of 6 mm on more than 80% of their length. 
         [0079]    The flow cavity  53  in each horizontal section is adjacent to the shell  40  and also adjacent to the membrane carrier  41  and is only interrupted by the two anchor locations. The membrane carrier  41  closes the base element  39  completely besides the flow path  53 , this means the base element  39  has no additional flow through channels besides the flow cavity  53  for the liquid  37  to be filtered for the gas  38 . 
         [0080]    The diameter  60  of the base element  39  of the second membrane filter  36  is approximately 208 mm. 
         [0081]      FIG. 5D  illustrates a sectional view of the base element  39  of the second membrane filter  36  so that the anchor  56  is cut precisely in the flow cavity  53  between two fingers  57 . Within the anchor  56  there is a portion of the permeate collecting cavity  47 . The flow cavity  53  is defined in vertical direction by the overlap portion of the height  49  of the base element  39  and a height  61  of the membrane carrier  41 . At the bottom side of the membrane carrier  41  a gas distribution system  62  is formed whose height remains unconsidered when defining the flow cavity  53 . The flow cavity  53  terminates on top in the outlet  54 . 
         [0082]    As evident from  FIGS. 5D and 5   e  the fingers  57  are provided with a bevel on a bottom in both horizontal direction wherein the membrane carrier  41  has a horizontal cross sectional surface that decreases in the downward direction. Thus hair and fibrous compounds included in the liquid  57  to be filtered so not adhere to the fingers  57  but are stripped off along the bevel of the fingers  57  into the flow cavity  53 , flushed through the flow cavity  53  and subsequently move into the portion of the hollow fiber membranes  43  in the tube  45 . Since no other installations are provided in this portion besides the hollow fiber membranes  43  that are individually closed on top and at which hair or fibrous compounds can adhere and additionally since the hollow fiber membranes  43  are individually closed on top hair and fibrous compounds can be flushed freely in upward direction out of the membrane filter  36 . 
         [0083]      FIG. 5F  illustrates a perspective view of the base element  39  of the second membrane filter  36  at a slant angle from below and  FIG. 5G  illustrates a half of the base element  39  with a cut up shell  40 . 
         [0084]    In the second membrane filter  36  the base element  39  includes the gas inlet  46 . The gas inlet  46  is connected with a gas distribution system  62  formed at a bottom side of the membrane carrier  41  wherein the gas distribution system  62  includes a downward open and upward closed tube  63  which includes a wall  64  with downward open vertical slots  65  for distributing the gas  38  into the liquid  37  to be filtered. The width of the tub  63  corresponds to the width of the anchor  56  and is formed at its lower side. The gas inlet  46  adjoins laterally directly at the tub  63 . 
         [0085]    At each second slot  65  a gas conducting channel  66  is externally connected to the tub  63  wherein the gas conducting channel is configured at a bottom side of the finger  57  for conducting the gas  38  away from the tub in a direction towards the shell  40 . The other slot  65  at which no gas conducting channel  66  are connected respectively open between two fingers  57  or for the outer fingers  57  between the fingers  57  and the shell  40  on an outside of the anchor  56 . Thus the tub  63  has a wall  64  on each of its  2  longitudinal sides wherein the wall  64  respectively includes 13 slots  65 . The slot  65  become wider in downward direction in order to also be able to compensate larger variations in the amount of gas that is being supplied. 
         [0086]    The width of the slots  65  and thus also their cross sectional surface have different sizes. Thus the volume of the gas  38  is adapted to the surface of the hollow fiber membranes  43  flowing through the slots  65 . Accordingly the slots  65  include wider slots  65  below the longer fingers  67  in a center of the base element  39  then the outer slots  65  below the shorter fingers  57 . The narrowest slots  65  are the slots that open between the fingers  57 . Through the configuration of the gas distribution system  62  with slot  65  and gas conduction channels  66  the gas  38  flows around the membrane carrier  41  after flowing in the liquid  37  to be filtered. 
         [0087]    The base element  39  is flowable from the gas inlet  46  through the wall  63  through the slots  65  and through the flow cavity  53  to the outlet  54 . The membrane carrier  41  closes the base element  39  besides the flow cavity  53  not only for the flow through of the liquid  37  to be filtered but also for the flow through of the gas  38 . 
         [0088]      FIG. 5H  illustrates only one of the fingers  57  of the second membrane filter  36 . Thus the anchor  56  is visible in a sectional view as well as the tub  63  formed on its bottom side. Furthermore gas conducting channels  66  are visible on a bottom side of the finger  57 , wherein the gas conducting channels  66  extend on both sides of the tub  63 . 
         [0089]      FIG. 5I  shows a sectional view of the gas conducting channel  66  in the base element  39  of the second membrane filter  36 . Thus it is evident that the gas conducting channel  66  adjoin the slots  65  vertically offset in upward direction. 
         [0090]      FIGS. 6A-6C  illustrate views and sectional views of elements of the tub  63  of the second membrane filter  36 . 
         [0091]    The tub  63  includes vertical ribs  67  respectively extending in a center between adjacent slots  65  orthogonal to the wall  64 . Each rib  67  includes a taper at a bottom which runs towards the wall  64  and thus forms a slanted or rounded inner edge  68  of the tub  63 . 
         [0092]    Geometrically speaking the tub  63  includes an inner edge  68  respectively extending between adjacent slots  65  in a vertical sectional view wherein the vertical sectional view in this case extends orthogonal to the wall  64  through the rib  67  wherein the inner edge at least in a portion of a lower half  69  of the slot  65  includes in every point an angle  70  relative to horizontal of less than 60° at a level of the half  69  of the slots  65  of 58°. 
         [0093]    The non illustrated filtration operations of the second membrane filter  56  differs from filtrations operations of the first membrane filter  1  as follows. 
         [0094]    The gas  38  flows through the gas inlet  46  into the tub  63  and fills the tub  63  and the slots  65  up to a portion of the height of the slot  65  with a gas cushion. From the gas cushion the gas  38  flows through the slot  65  in laterally outward direction from the tub  63  and thus at plural locations below the membrane carrier  41  into the liquid  37  to be filtered. Thus the gas  38  flows out of the slot  65  into bulges  55  of the flow cavity  53  respectively between two fingers  57  and on the other hand side out of the slot  65  below the finger  57  into the gas conduction channel  66 . Through the gas conduction channel  66  the gas  38  flows in outward direction further away from the tub  63  into the outer portion of the membrane filter  36 . 
         [0095]    During lateral flow through the slots  65  a liquid flow that is oriented parallel to the lateral gas flow is generated at the face boundary below the gas cushion wherein the liquid flow flows against the inner edge  68  of the rib  67 . Based on the angle  70  of the inner edge  68  of the tub  63  which is arranged between two slots  65  hair and fibrous compounds can be stripped off when the inner edge  68  is exposed to a flow which significantly reduces a clogging propensity of the membrane filter  36 . 
         [0096]    After the gas enters the liquid  37  to be filtered the membrane carrier  41  is flowed by the gas  38  and the liquid  37  before the mix from gas  38  and liquid  37  flows around the hollow fibers membranes  43  attached at a top in the membrane carrier  41 . Due to the high shear force of the two phase flow the hollow fiber membranes and the membrane carrier  41  are flushed on an outside. 
         [0097]    The base element  39  is flowed by the gas  38  starting from the gas inlet  46  through the tub  63  through the slot  65  and through the flow cavity  53  to the outlet  54 . Since the flow cavity  53  is always arranged between the shell  40  and the membrane carrier  41  and furthermore protrudes through the bulges  55  also into the inner portion of the membrane filter  36  this generates even gassing of the membrane filter  36  over the entire cross section while avoiding a flow through of small parallel connected flow cavities. Thus over all the blocking propensity of the membrane filter  36  is reduced compared to what is known in the art. 
         [0098]    Also the second membrane filter  36  can be set up for submerged operations or dry operations. 
         [0099]      FIG. 7A-7D  illustrate additional variants of membrane filters according to the invention with a base element and a head element. 
         [0100]      FIG. 7A  illustrates a third membrane filter  71  according to the invention. This membrane filter differs from a first membrane filter  1  in that a base element  72  is adjoined on top by a closed tube  73  which envelops the hollow fiber membrane  74  and which adjoins at a head element ( 75 ) on top. The head element  75  includes a shell  76  and a membrane carrier  77 , included therein wherein the membrane carrier  77  is connected with the shell  76  only through an anchor location  78 . In the head element  75  the hollow fiber membrane  74  are encased and attached on top by a resin layer  79  in a sealing manner relative to the liquid to be filtered with their lumens in an open manner. 
         [0101]    The head element  75  includes a permeate collecting cavity  80  which is flow connected with the lumens of the hollow fiber membranes  74  for collecting the permeate and a permeate outlet  81  for draining the permeate. Furthermore the head element  75  includes a second flow cavity  82  for flowing the gas and the liquid to be filtered and flowing out of the head element  75 . The third membrane filter  71  can be used in submerged operations and in dry set up operations. 
         [0102]      FIG. 7B  illustrates a fourth membrane filter  83  according to the invention. The fourth membrane filter differs from the third membrane filter  71  in that a tube  84  which adjoins at a base element  85  on top is adjoined on top initially by a tube insert  86  with openings  87  for lateral outflowing of a portion of the gas and of the liquid to be filtered from the tube  84 . The tube insert  86  and the tube  84  are made for the fourth membrane filter  83  form one piece. A head element  88  adjoins on top to the tube insert  86  wherein the head element  88  has the same details as the head element  75  of the third membrane filter  71 . The base element  85  forms another difference to the third membrane filter  71  wherein the base element  85  does not have any permeate collecting cavity, this means the hollow fiber membranes  39  are closed at a bottom and encased with resin in the base element  85  and fixated. The permeate generated in the hollow fiber membranes  39  only flows into the permeate collecting cavity  90  of the head element  88 , is collected therein and flows through a permeate outlet  91  from the fourth membrane filter  83 . This fourth membrane filter  83  can only be used in submerged operations due to the openings  87  in the tubular insert  86 . 
         [0103]      FIG. 7C  illustrates a fifth membrane filter  92  according to the invention. The fifth membrane filter differs from the third membrane filter  71  in that the tube  93  is not run to the head element  94  but terminates even earlier with a tubular expansion  95  on top. Thus the head element  93  is not connected with the tube  93  and is accordingly not configured flowable for the liquid to be filtered and the gas. Therefore it only includes one membrane carrier  96  with hollow fiber membranes  98  that are resin connected and open towards a permeate collecting cavity  97  and a permeate outlet  99  adjoining the permeate collecting cavity  97  for collecting and draining a portion of the permeate generated from the hollow fiber membranes  98 . The other portion of the permeate is drained from a base element  100  that is identical to the base element of the third membrane filter  71 . Also the fifth membrane filter  92  can only be used in submerged operation due to the open configuration between the tube  93  and the head element  94 . 
         [0104]      FIG. 7D  illustrates a sixth membrane filter  101  according to the invention. The sixth membrane filter  101  respectively includes a base element  102  and a head element  103  which are identical to the respective elements of the fourth membrane filter  83  and which are connected through a continuously closed tube  104 . The sixth membrane filter  101  according to the invention is configured for dry operations. Thus a first liquid conduit  105  is connected to the base element  102  for letting the liquid to be filtered flow from below into the base element  102 . Furthermore a second liquid conduit  106  adjoins the head element  103  for letting out the liquid and the gas from the sixth membrane filter  101 . 
         [0105]      FIGS. 8A and 8B  illustrate separate tubs  2  additional membrane filters according to the invention. 
         [0106]      FIG. 8A  illustrates a tub  107  of a seventh membrane filter according to the invention which is otherwise not further illustrated and includes a gas inlet  108  which laterally joins the tub  107  for flowing a gas into the tub  107 . The tube  107  includes a wall  109  vertical slots  110  for flowing the gas out of the tub  107 .  FIG. 8A  furthermore illustrates a sectional view through the tub  107  which sectional view is arranged on the left side centrally between 2 slots  110  and on the right side exactly through one of the slots  110 . The wall  109  in the portion of the slots  110  and also in the portion between 2 slots  110  has a uniform thickness  111  of 15 mm on top. In the vertical sectional view of the tub  107  illustrated on the left side between 2 slots  110  the tub includes an inner edge  112  which includes an angle relative to horizontal of less than 60° in any point in the portion in the lower half of the slots  110  for stripping hair and fibrous compounds included in the liquid to be filtered. 
         [0107]      FIG. 8B  illustrates a tub  113  of an eighth membrane filter according to the invention which differs from the tub  107  only in that only ribs  114  are left over from the thick wall  109  of the tub  107 . The ribs  114  are respectively centrally arranged between adjacent slots  115  and have an extension  116  into the tub  113  which decreases in downward direction. The extension  116  of the ribs  114  corresponds to the thickness  111  of the wall  109  of the tub  107  of the seventh membrane filter. In the illustrated sectional view through the rib  114  the rib  114  and thus also the tub  113  have an inner edge  117  which in each point of a lower half of the slots  115  have an angle relative to horizontal that is less than 60 degrees for stripping hair and fibrous compounds included in the liquid to be filtered, thus the rib  114  in the eighth embodiment of the membrane filter according to the invention performs the function of the thick wall  109  of the seventh membrane filter according to the invention. The thickness  118  of the wall  119  of the eighth membrane filter according to the invention is thus significantly reduced which avoids material accumulations that are disadvantageous for configuring the tub  113  as an injected molded component. 
         [0108]    In alternative embodiment of the eighth embodiment the ribs of the opposite sides of the tub can also be arranged offset relative to one another so that also narrower tubs are implementable. This however has negative effects for longer tubs with respect to their pressure drop and thus with respect to an even longitudinal flow through of the gas. 
         [0109]      FIGS. 9A and 9B  illustrate a view and a sectional view of a base element  120  of a ninth membrane filter according to the invention. This embodiment includes a rectangular membrane carrier  121  at which membranes  122  are encased and attached in a resin layer  123  which facilitate filtering a liquid permeate from a liquid to be filtered. The membrane carrier  121  furthermore includes a permeate collecting cavity  124  at which the membranes  122  are connected in an open manner at the permeate side and a permeate outlet  125  for draining the permeate from the permeate collecting cavity  124 . Below the membrane carrier  121  a gas distribution system  126  is arranged which is in this case configured at a bottom side of the membrane carrier  121 . Thus the membrane carrier  121  and the gas distribution system  126  are one component. The gas distribution system  126  includes a downward open tub  127  that is closed on top into which a gas inlet  128  leads on the side. The tub  127  furthermore includes a wall  129  with downward open vertical slots  130  for distributing the gas into the liquid to be filtered. The wall  129  respectively includes a vertical rib  131  between adjacent slots  130  wherein the vertical rib extends orthogonal to the wall  129  and wherein an extension of the rib into the tub  127  decreases in downward direction. Thus the rib  131  in an orthogonal sectional view relative to the wall includes an inner edge  132  of the wall which has an angle relative to horizontal of less than 60 degrees in any portion of a lower half of the slots for stripping hair and fibrous compounds included in the liquid to be filtered. 
         [0110]      FIGS. 10A-10C  illustrate a separate gas distribution system of a tenth membrane filter membrane filter according to the invention. The gas distribution system  133  includes a circular tub  134  which is open in downward direction and closed on top. The tub  134  includes a wall  135  with downward open vertical slots  136  for flowing a gas out of the tub  134 . The gas distribution system  122  furthermore more includes downward open gas conducting channels  137  which adjoin each second slot  136  on an outside with a vertical upward offset. The gas conducting channels  137  include a base  139  on top which rises in upward direction starting from the connection at the tub  134 . The gas distribution system  133  additionally includes a gas inlet  139  which connects to the tub  134  from above. 
         [0111]      FIG. 10C  illustrates a sectional view through the wall  135  of the tub  134 . In this sectional view the tub  134  includes an inner edge  140  that is beveled at a bottom which has an angle of 40 degrees relative to horizontal in the portion of the height of the slots  136 . 
         [0112]      FIGS. 11A and 11B  illustrate gas distribution systems of two additional membrane filters according to the invention.  FIG. 11A  illustrates a sectional view of a gas distribution system  141  of an eleventh membrane filter according to the invention. This gas distribution system includes a downward open circular tub  142  that is closed on top. The tub  142  includes a wall  143  with downward open vertical slots  144  for flowing a gas out of the tub  142 . In a sectional view between adjacent slots  144  the tub  142  has an inner edge  145  which has an angle relative to horizontal of 40 degrees in a portion of a height of the slots  144 . The gas distribution system  141  includes a gas inlet  146  which connects to the top  142  from above. 
         [0113]      FIG. 11B  illustrates a gas distribution system  147  of a twelfth membrane filter according to the invention which differs from the eleventh membrane filter only in that the gas inlet  149  is not connected with a tub  148  but arranged below the tub  148  as a tubular spout for letting a gas into the tub  148 . 
       REFERENCE NUMERALS AND DESIGNATIONS 
       [0000]    
       
         
           
               1  membrane filter 
               2  base element 
               3  shell 
               4  membrane carrier 
               5  hollow fiber membrane 
               6  tube 
               7  upper end 
               8  length 
               9  resin layer 
               10  height membrane filter 
               11  height base element 
               12  height membrane carrier 
               13  gas inlet 
               14  permeate outlet 
               15  anchor location 
               16  flow portion 
               17  outlet 
               18  gas distribution system 
               19  tub 
               20  wall 
               21  vertical slot 
               22  inner edge 
               23  lower half 
               24  angle 
               25  permeate collecting cavity 
               26  gas 
               27  gas cushion 
               28  liquid to be filtered 
               29  permeate 
               30  surface 
               31  gas feed conduit 
               32  throttle 
               33  permeate conduit 
               34  first liquid conductor 
               35  second liquid conductor 
               36  membrane filter 
               37  liquid to be filtered 
               38  gas 
               39  base element 
               40  jacket 
               41  membrane carrier 
               42  anchor location 
               43  hollow fiber membrane 
               44  permeate 
               45  tube 
               46  gas inlet 
               47  permeate collecting cavity 
               48  permeate outlet 
               49  height base element 
               50  height membrane filter 
               51  resin layer 
               52  upper end 
               53  flow cavity 
               54  outlet 
               55  bulge 
               56  anchor 
               57  finger 
               58  flow channel 
               59  width 
               60  diameter 
               61  height of membrane carrier 
               62  gas distribution system 
               63  tub 
               64  wall 
               65  vertical slot 
               66  gas conducting channel 
               67  rib 
               68  inner edge 
               69  lower half 
               70  angle 
               71  membrane filter 
               72  base element 
               73  shell 
               74  hollow fiber membrane 
               75  head element 
               76  shell 
               77  membrane carrier 
               78  anchor location 
               79  resin layer 
               80  permeate collecting cavity 
               81  permeate outlet 
               82  flow cavity 
               83  membrane filter 
               84  tube 
               85  base element 
               86  tube insert 
               87  opening 
               88  head element 
               89  hollow fiber membrane 
               90  permeate collecting cavity 
               91  permeate outlet 
               92  membrane filter 
               93  tube 
               94  head element 
               95  tube expansion 
               96  membrane carrier 
               97  permeate collecting cavity 
               98  hollow fiber membrane 
               99  permeate outlet 
               100  base element 
               101  membrane filter 
               102  base element 
               103  head element 
               104  tube 
               105  first liquid conductor 
               106  second liquid conductor 
               107  tub 
               108  gas inlet 
               109  wall 
               110  slot 
               111  thickness 
               112  inner edge 
               113  tub 
               114  rib 
               115  slot 
               116  extension 
               117  inner edge 
               118  thickness 
               119  wall 
               120  base element 
               121  membrane carrier 
               122  membrane 
               123  resin layer 
               124  permeate collecting cavity 
               125  permeate outlet 
               126  gas distribution system 
               127  tub 
               128  gas inlet 
               129  wall 
               130  slot 
               131  rib 
               132  inner edge 
               133  gas distribution system 
               134  tub 
               135  wall 
               136  slot 
               137  gas conducing channel 
               138  base 
               139  gas inlet 
               140  inner edge 
               141  gas distribution system 
               142  tub 
               143  wall 
               144  slot 
               145  inner edge 
               146  gas inlet 
               147  gas distribution system 
               148  tub 
               149  gas inlet

Technology Category: 7