WO2021214600A1

WO2021214600A1 - Filtration capsule

Info

Publication number: WO2021214600A1
Application number: PCT/IB2021/053081
Authority: WO
Inventors: Omead SANEI; Ravi KOLAKALURI; Dian Zheng; Kannan DASHARATHI; Francis E. Porbeni
Original assignee: 3M Innovative Properties Company
Priority date: 2020-04-21
Filing date: 2021-04-14
Publication date: 2021-10-28

Abstract

A filtration capsule having an upper housing having an inlet and a lower housing having an outlet. The upper housing connected to the lower housing forming an internal chamber with the inlet and the outlet fluidly connected to the internal chamber. A filtration media positioned between the inlet and the outlet in the internal chamber, and a fluid distribution positioned in the internal chamber between the inlet and the filtration media. The fluid distribution insert having a hemispherical first surface, an opposing second surface, and a plurality of flow channels connecting the hemispherical first surface to the opposing second surface.

Description

FILTRATION CAPSULE

BACKGROUND

Often during the development of biopharmaceuticals, laboratory quantities of fluids must be sterilized. In biopharmaceutical laboratory screening, small amounts of solution containing recombinant proteins, monoclonal antibodies, or vaccines must be sterilized prior to further processing, analysis, and testing. Often there is a limited amount of the prototype solution to work with because the impact of various factors on the target molecule are being studied. As such, small-scale devices able to sterilize small amounts of solution are necessary.

SUMMARY

A sterilizing filtration device comprises a microporous media, often a membrane, with progressively smaller pores that does not allow the breakthrough of bacteria. Fluid that passes through these small pores is free of bacteria and therefore considered sterile.

Sterilizing membrane filtration devices come in various sizes often related to the development stage of the molecule. Laboratory devices typically have media effective filtration areas from about 5 to 17 cm². Scale-up or prototype devices typically have effective filtration areas from about 18 to 1200 cm². Commercial production devices typically have effective filtration areas of greater than 1200 cm². The effective filtration area can be determined, for example, by filtering a dye through the filter and determining the area stained by the dye or by using a CAD model of the filter and calculating the active area of the filter media that solution can pass through while ignoring peripheral areas that are blinded by being pinched to seal the media’s edges. It should be noted that other effective filtration areas can be provided depending on the needs of the customer.

The invention is particularly suited to laboratory scale devices, but can be used with other device sizes and effective filtration areas. While the invention is referred to as a sterilizing membrane filtration device, all aspects of this invention are equally applicable to other kinds of filtration and chromatography media such as (but not limited to) hydrogel functionalized nonwoven, nonwovens, other membranes, cellulose and diatomaceous earth based charged media, activated carbon, and functionalized membranes.

One issue for laboratory scale devices during use is tunneling. During early laboratory testing, the volume of available fluid is typically very low. Laboratory devices should desirably therefore have low head space upstream of the membrane or media to minimize fluid holdup volume losses. A small headspace coupled with an inlet axially aligned with the membrane or media can cause the feed solution to “tunnel” through the media disc’s center leading to premature localized clogging. This tunneling effect can be caused by poor upstream flow redistribution leading to saturation of the solute in the middle of the membrane or media. One possible solution is to increase the headspace which, when combined with membrane or media back pressure, leads to some flow redistribution away from the media’s center and better membrane or media utilization. However, this approach is often undesirable as it increases holdup volume.

Another issue for laboratory scale devices during use is holdup volume. Often there is a limited amount of the prototype solution to work with because the impact of various factors on the target molecule are being studied. If the laboratory device has a significant amount of holdup volume, significantly less filtered fluid is available to the researcher. As such, small-scale laboratory devices able to sterilize small amounts of solution are necessary.

Typically, the housings used for laboratory scale devices have a circular perimeter where the upper and lower housings are joined together, and the exterior surfaces of the upper and lower housings are often hemispherical in shape due to the device’s use as a pressure vessel. Filter housings with a hemispherical shape can have lower stress concentrations when pressurized. This provides an advantage when rated for a maximum operating pressure as a pressure vessel; however, the optimum shape for pressurized use also has a large holdup volume because the internal chamber where the filter media is located also hemispherical in shape.

In order to reduce the holdup volume and reduce tunneling, the inventive filtration device uses a fluid distribution insert located in the internal chamber of the device upstream from the media. The fluid distribution insert reduces holdup volume by physically taking up space in the internal chamber and is designed to distribute incoming fluid evenly over the media’s surface by use of a plurality of flow channels to eliminate tunneling.

Hence the invention resides in a filtration capsule having: an upper housing having an inlet; a lower housing having an outlet; the upper housing connected to the lower housing forming an internal chamber with the inlet and the outlet fluidly connected to the internal chamber; a media positioned between the inlet and the outlet in the internal chamber; a fluid distribution insert positioned in the internal chamber between the inlet and the media; the fluid distribution insert having a hemispherical first surface, an opposing second surface, and a plurality of flow channels connecting the hemispherical first surface to the opposing second surface.

In another embodiment, the invention resides in a filtration capsule having: an upper housing having an inner surface and an inlet; a lower housing having an outlet; the upper housing connected to the lower housing forming an internal chamber with the inlet and the outlet fluidly connected to the internal chamber; a media positioned between the inlet and the outlet in the internal chamber; a fluid distribution insert positioned in the internal chamber between the inlet and the media; the fluid distribution insert having a circular perimeter, a hemispherical first surface having a circular flange extending from the circular perimeter and ending in a step between a higher exterior surface of the circular flange and a lower exterior surface of the remaining portion of the hemispherical first surface; an opposing second surface to the hemispherical first surface, the second surface having a circular notch adjacent the circular perimeter, and a plurality of flow channels connecting the hemispherical first surface to the opposing second surface; an O-ring located in the circular notch in contact with the fluid distribution insert and an upper surface of the media; and the circular flange in contact with the inner surface of the upper housing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an assembly drawing of the one embodiment of the filter device.

FIG. 2 is a perspective view of the filter device of FIG. 1.

FIG. 3 is a cross sectional view of the filter device of FIG. 1 taken at 3-3 of FIG. 2.

FIG. 4 is a perspective view of one embodiment of a fluid distribution insert used in the filter device of FIG. 1.

FIG. 5 is a cross sectional view of the fluid distribution insert taken at 5-5 of FIG. 4.

FIG. 6 is a top view of the fluid distribution insert of FIG. 4.

FIG. 7 is a bottom view of the fluid distribution insert of FIG. 4.

DETAILED DESCRIPTION

Throughout this document, values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of “about 0.1% to about 5%” or “about 0.1% to 5%” should be interpreted to include not just about 0.1% to about 5%, but also the individual values (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. The statement “about X to Y” has the same meaning as “about X to about Y,” unless indicated otherwise. Likewise, the statement “about X, Y, or about Z” has the same meaning as “about X, about Y, or about Z,” unless indicated otherwise.

In this document, the terms “a,” “an,” or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. The statement “at least one of A and B” or “at least one of A or B” has the same meaning as “A, B, or A and B.” In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section.

The term “about” as used herein can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range, and includes the exact stated value or range.

The term “substantially” as used herein refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more, or 100%. The term “substantially free of’ as used herein can mean having none or having a trivial amount of, such that the amount of material present does not affect the material properties of the composition including the material, such that the composition is about 0 wt% to about 5 wt% of the material, or about 0 wt% to about 1 wt%, or about 5 wt% or less, or less than or equal to about 4.5 wt%, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.01, or about 0.001 wt% or less.

Filtration Device

Referring now to FIGS. 1, 2, and 3 a filtration device 8 is shown. The device has a housing 10 formed by joining an upper housing 12 to a lower housing 14. The housing has an inlet 16, an outlet 18, and an optional vent 20. The vent can assist in purging air from the device during use. Disposed between the inlet 16 and the outlet 18 is one or more media layers 22 in an internal chamber 24 such that fluid from the inlet 16 enters the internal chamber 24 and then passes through the media 22 and then out the outlet 18. The internal chamber 24 is in fluid communication with the inlet 16 and the vent 20 such that any air in the chamber 24 can be purged out the vent 20.

Typically, housings used for laboratory scale membrane filters have a circular perimeter 26 where the upper and lower housings are joined together, and the exterior surfaces of the upper and lower housings are often hemispherical in shape as shown. Filter housings with this shape can have lower stress concentrations when pressurized. This provides an advantage when rated for a maximum operating pressure as a pressure vessel. However, the optimum shape for pressurized use has a large holdup volume because the internal chamber 24 is often also hemispherical in shape as well.

It has been determined by Finite Element Analysis (FEA) using ABAQUS that the filtration device shown in the figures can have a maximum rated operating pressure rating of 65 psi with an added safety factor. Such results are not achievable without the use of a hemispherical housing shape. In order to reduce the holdup volume and reduce tunneling, the filtration device includes a fluid distribution insert 28 in the internal chamber 24 as seen in FIGS. 1 and 3. The fluid distribution insert reduces holdup volume by physically taking up space in the internal chamber 24 and it is designed to distribute incoming fluid evenly over the media’s surface by use of a plurality of flow channels 30.

The fluid distribution insert comprises a generally hemispherical first surface 32 in order to minimize the holdup volume in the generally hemispherical internal chamber 24, an opposing second surface 34 and the plurality of flow channels 30 connecting the first surface to the second surface. The flow channels can be slots, apertures, holes, a porous network such as that present in a sintered porous metal, or combinations of the preceding. In one embodiment, the plurality of flow channels comprise radially extending slots 38 in the hemispherical first surface 32 connected to a plurality of apertures 40 in the opposing second surface 34 along with an optional central post 41 for additional holdup volume reduction.

Referring now to FIGS. 4, 5, 6, and 7, one embodiment for the fluid distribution insert comprises a generally circular perimeter 36, the generally hemispherical first surface 32 having the plurality of radially extending slots 38 from the optional central post 41 to almost the circular perimeter 36 that divides the first surface into eight pie shaped segments 42 disposed between the eight radially extending slots. Disposed within each of the pie shaped segments 42 are two additional radially extending slots 38 that extend from near the apex to almost the circular perimeter bringing the total number of radially extending slots to 24. Some of the radial extending slots are fully contained within a pie shaped segment 42 and others are positioned between the pie shaped segments 42.

The number of radially extending slots and their design can be changed. For example, all of the radially extending slots could converge on the central post 41. Less, none, or more pie shaped segments 42 could be used than the eight depicted. One, none, two, or more radially extending slots 38 could be used within each of the pie shaped segments 42. The design shown in the figures can be easily made by injection molding and avoids having thin molded regions that could be difficult to form by extending all the radial slots to the center of the fluid distribution insert.

The radially extending slots 38 in combination with the optional central post 41 help to prevent fluid tunneling by moving fluid from the center of the filtration device to the outer periphery of the circular media 22 disposed beneath the fluid distribution insert 28. Fluid entering the fluid inlet 16 contacts the optional central post 41 which tends to redirect the fluid towards the radially extending slots 38 and the central post prevents the fluid from directly passing straight through the filtration device.

The radially extending slots 38 fluidly connect the hemispherical first surface 32 to the second surface 34 of the fluid distribution insert 28. The second surface 34 is generally circular in shape and has the plurality of apertures 40 located within it. The apertures 40 are arranged in a grid pattern along radially extending lines from a central longitudinal axis 44 of the fluid distribution insert and filtration capsule that extends along and though the central post 41.

As seen, the apertures have different shapes of square, rectangular, and pie shaped depending on where they are disposed on the second surface. The apertures can have other shapes as desired. The apertures also have different cross-sectional areas. The cross-sectional areas of the apertures are varied depending on whether the apertures are located beneath a radially extending slot in a pie shaped segment, beneath a radially extending slot that extends from the optional central post or are adjacent to and surrounding the central post. Since more fluid is likely to enter the radially extending slots that extend from the central post, the apertures beneath these slots are smaller to promote more fluid flow into the radially extending slots in the pie shaped segments. In turn the apertures beneath the radially extending slots in the pie shaped segments are larger to enhance fluid flow in these areas.

In the embodiment shown, ANSYS fluent computational fluid dynamics software has shown the pressure drop across the fluid distribution insert to be less than 0.110 psi at 400 mL/min. At more typical flowrates of 20 mL/min the pressure drop will be negligible. Filtration solutions containing dyes have shown a uniform dye staining of the filtration media using this pattern of apertures.

Alternative aperture patterns can be used. The apertures can be all the same size, or the apertures can vary in size. The apertures can be all the same shape, or they can vary in shape. The apertures can be arranged in a radial pattern as shown, in an XY grid pattern, or in a randomized pattern. Preferably at least one aperture is present in every radially extending slot. More preferably at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 or more apertures are present in each radially extending slot. In the radial extending slots in the pie shaped segments four square apertures are present. In the radially extending slots from the central post, fourteen rectangular apertures are present. In the circular area surrounding the central post seven triangular shaped apertures are present.

As best seen in FIG. 5, the second surface 34 of the fluid distribution insert 28 also has a circular perimeter notch 48 in addition to the apertures 40. The circular perimeter notch provides clearance and retains an O-ring 58 used to seal the media’s perimeter as best seen in FIG. 3. The hemispherical first surface 32 of the fluid distribution insert has a circular flange 50 where the radially extending slots 38 end before reaching the perimeter 36 of the fluid distribution insert. As best seen in FIG. 5, there is a step 52 between the higher exterior surface of the circular flange 50 and the lower exterior surface of the remaining portion of the hemispherical first surface 32. As best seen in the cross-section in FIG. 3, the circular flange 50 is in contact with an inner surface 54 of the upper housing while a first gap 56 is present between the inner surface 54 and the remainder of the hemispherical first surface 32. When the upper housing and lower housing are assembled with the media disposed beneath the fluid distribution insert, the inner surface 54 of the upper housing pushes down onto the circular flange 50, which in turn causes the fluid distribution insert 28 to slightly compress the O-ring 58 located in the circular perimeter notch 48 thereby sealing the perimeter of the media from leaking.

The first gap 56 between the hemispherical first surface and the interior surface of the upper housing allows for entrapped air to be readily exhausted through the vent 20 and allows for fluid to flow over the hemispherical first surface 32 into the radially extending slots 38. In various embodiments of the invention the first gap can be less than 0.40”, 0.30”, 0.20”, 0.10”, 0.090”, 0.080”, 0.070”, 0.060”, 0.050”, 0.040”, 0.030”, 0.020”, 0.010” and greater than 0.001” inches. In one embodiment, the first gap was about 0.030 inches.

As best seen in FIG. 3, the circular flange 50 above the circular perimeter notch 48 is supported upon a circular boss 60 of the lower housing 14 thereby supporting the fluid distribution insert 28 within the housing. The media 22 is disposed beneath the second surface 34 of the fluid distribution insert and a second gap 62 is present between the upper surface of the media and the second surface of the fluid distribution insert. The second gap is height is controlled by a depth of the circular perimeter notch in combination with the thickness of the O-ring selected and the compression when the housings are assembled. This allows for full utilization of the media’s surface area as the solid circular rings 64 in the second surface 34 as shown in FIGS. 6 and 7 are not in contact with the media. Surface contact of the insert with the media could blind some of the media’s surface area and reduce capacity and throughput. In various embodiments of the invention the second gap can be greater then 0.001”, 0.005”, 0.010”, 0.015”, 0.020”, 0.030”, 0.040”, 0.050”, 0.060”, 0.070”, 0.080”, 0.090”, 0.10”, 0.20”, 0.30” and less than 0.40” inch. In one embodiment, the second gap was about 0.010 to about 0.020 inch.

Since the filtration device is designed to operate at pressures up to 65 psi, the filtration device has circular hemispherical upper and lower housings to reduce the stress concentrations. An optional knurled surface can be provided on the circular perimeter to enhance grip on the housing.

The upper housing 12 is a generally hemispherical injection molded part having an outer surface 64, an inner surface 54, and a nominal wall thickness 66. The wall thickness in one embodiment is nominally 1/8 inch. The inside of the upper housing is the substantially hemispherical internal chamber 24. The vent 20 and the fluid inlet 16 are molded into the upper housing and are in fluid communication with the internal chamber 24. Various known fitting can be used on these connections such as a barbed fitting, Luer lock connectors, and flange fittings. A Luer lock connector is used for the vent while a flange fitting is used for the inlet. A radially extending upper flange 68 forms a lower surface of the upper housing and a circular thermoplastic welding flange 70 extends longitudinally from the radially extending upper flange 68.

The lower housing 14 is a generally hemispherical injection molded part having an outer surface 72, an inner surface 74, and a nominal wall thickness 76. In one embodiment, the wall thickness is nominally 1/8 inch. The inside of the lower housing has a lower chamber 78 with a plurality of radial extending fins 80 as best seen in FIG. 1. The radial extending fins 80 rise longitudinally from the substantially hemispherical inner surface 74 of the lower housing and end radially from the longitudinal axis 46 while leaving a central bore 82 as seen in the cross-section in FIG. 3. The radially extending fins 80 form a support surface 84 for the media 22 without unduly blinding off large portions of the media’s second surface. The fluid outlet 18 is molded into the lower housing and is in fluid communication with the central bore 82 and the internal chamber 24. Various known fitting can be used on this connection such as a barbed fitting, Luer lock connectors, and flange fittings. A radially extending lower flange 86 forms an upper surface of the lower housing 12. The exterior perimeter of the radially extending lower flange 86 is optionally knurled for additional grip while handling the filtration capsule. A circular groove extends 88 longitudinally into the radially extending lower flange 86. The circular groove 88 and welding flange 70 can be used to attach and seal the two houses pieces to each other.

The filtration capsule is assembled by placing the die cut circular media layer(s) 22 onto the radially extending fins 80 within the area defined by the circular boss 60 in the lower housing 14The O- ring 58 is inserted on top of the media adjacent to the circular boss and then the fluid distribution insert 28 is placed over the media and the O-ring in located in the circular notch 48. The upper housing 12 is then positioned with the circular thermoplastic welding flange deposed 70 into the circular groove 88. A fixturing jig in an ultrasonic welder then compresses the upper and lower housing together while applying sufficient energy to thermo-plastically weld the assembly.

As used herein upper housing is a relative term for convenience. In a like manner, lower housing is a relative term for convenience. First housing portion can be used instead for the upper housing and second housing portion can be used instead for the lower housing. Throughout the specification for any element referenced where the term “upper” appears “first” can be substituted and where the term “lower” appears “second” can be substituted.

Suitable media membranes or use with the device are known and can include PES membranes or media available from 3M Corporation, Pall Corporation, or Sartorius. In general, the media is die cut to a suitable diameter and one or more media layers having the correct membrane pore size rating for the desired application are used. In one embodiment, one prefilter layer of a 0.6 pm membrane and one layer of a sterilizing grade 0.2 pm membrane was used as the filtration media for the fluid to pass though.

The filtration housing is preferably injection molded from a suitable material. Desirably this material is readily ultrasonically welded such that the upper housing and lower housing can be joined in a fluid tight manner. Suitable materials for the housing include thermoplastics such as Acetal (POM), Acrylic (PMMA), Acrylonitrile Butadiene Styrene (ABS), Polycarbonate (PC), Polyphenylene Oxide (PPO), Polyphenylene Sulphide (PPS), and Polypropylene (PP). In one embodiment, the housings were molded from polypropylene.

The fluid distribution insert is preferably made from a fluid impermeable material to reduce holdup volume and is preferably injection molded from a suitable material. Suitable materials for the fluid distribution insert include thermoplastics such as Acetal (POM), Acrylic (PMMA), Acrylonitrile Butadiene Styrene (ABS), Polycarbonate (PC), Polyethylene (LD/HDPE), Polyphenylene Oxide (PPO), Polyphenylene Sulphide (PPS), Polypropylene (PP), and porous sintered metals. In one embodiment, the housings were molded from polypropylene.

Alternatively, other means of fastening the upper housing to the lower housing can be used such as a liquid tight, threaded connection as used for example on common water pipe. The upper and lower housings could be made of suitable materials for the threaded connection such as plastic or metal.

Alternatively, the housings and fluid distribution inset can be 3D printed using a three- dimensional printer. In this case, the housings can be bonded together using adhesives such as epoxy or acrylic to form liquid tight seal.

Claims

What is claimed is:

1. A filtration capsule comprising: an upper housing having an inlet; a lower housing having an outlet; the upper housing connected to the lower housing forming an internal chamber with the inlet and the outlet fluidly connected to the internal chamber; a media positioned between the inlet and the outlet in the internal chamber; a fluid distribution insert positioned in the internal chamber between the inlet and the media; the fluid distribution insert having a hemispherical first surface, an opposing second surface, and a plurality of flow channels connecting the hemispherical first surface to the opposing second surface.

2. The filtration capsule of claim 1 comprising a vent in the upper housing fluidly connected to the internal chamber.

3. The filtration capsule of claim 1 comprising a first gap between the hemispherical first surface and an inner surface of the upper housing and wherein the first gap is less than 0.40 and greater than 0.001 inches.

4. The filtration capsule of claim 3 wherein the first gap is from 0.020 to 0.040 inches.

5. The filtration capsule of any preceding claim comprising a second gap between an upper surface of the media and the second surface of the fluid distribution inset and wherein the first gap is greater than 0.001 and less than 0.40 inches.

6. The filtration capsule of claim 5 wherein the second gap is from 0.010 to 0.020 inches.

7. The filtration capsule of any preceding claim 1 wherein the plurality of flow channels comprise radially extending slots in the hemispherical first surface.

8. The filtration capsule of any preceding claim wherein the opposing second surface comprises a plurality of apertures.

9. The filtration capsule of claim 8 wherein the plurality of apertures vary in size.

10. The filtration capsule of any preceding claim wherein the fluid distribution insert comprises a circular perimeter and a circular notch in the second surface adjacent the circular perimeter.

11. The filtration capsule of claim 10 comprising an O-ring located in the circular notch.

12. The filtration capsule of any proceeding claim wherein the hemispherical first surface comprises a circular flange extending from a circular perimeter and ending in a step between a higher exterior surface of the circular flange and a lower exterior surface of the remaining portion of the hemispherical first surface.

13. The filtration capsule of any proceeding claim wherein the fluid distribution insert comprises a central post extending from the second surface.

14. The filtration capsule of claim 12 wherein a plurality of apertures are located in the second surface in a circular pattern around the central post.

15. The filtration capsule of any proceeding claim wherein the lower housing comprises a lower chamber with a plurality of radially extending fins and a central bore.

16. A filtration capsule comprising: an upper housing having an inner surface and an inlet; a lower housing having an outlet; the upper housing connected to the lower housing forming an internal chamber with the inlet and the outlet fluidly connected to the internal chamber; a media positioned between the inlet and the outlet in the internal chamber; a fluid distribution insert positioned in the internal chamber between the inlet and the media; the fluid distribution insert comprising; a circular perimeter, a hemispherical first surface having a circular flange extending from the circular perimeter and ending in a step between a higher exterior surface of the circular flange and a lower exterior surface of the remaining portion of the hemispherical first surface, an opposing second surface to the hemispherical first surface, the second surface having a circular notch adjacent the circular perimeter, and a plurality of flow channels connecting the hemispherical first surface to the opposing second surface; an O-ring located in the circular notch in contact with the fluid distribution insert and an upper surface of the media; and the circular flange in contact with the inner surface of the upper housing.

17. The filtration capsule of claim 16 comprising a first gap between the inner surface and the hemispherical first surface and a second gap between the second surface of the fluid distribution insert and the upper surface of the media.

18. The filtration capsule of any claim 16 wherein the lower housing comprises a lower chamber with a plurality of radially extending fins forming a support surface for the media.

19. The filtration capsule of claim 18 wherein the radially extending fins form a central bore in the lower chamber in fluid communication with the outlet.

20. The filtration capsule of claim 16 wherein the hemispherical first surface comprises a plurality of slots and the second surface comprises a plurality of apertures.