AERATED BIOFILM REACTOR HOLLOW FIBRE MEMBRANE

Abstract

The present invention is concerned with a hollow fibre membrane for use in a Membrane Supported Biofilm Reactor (MSBR) or the like, the hollow fibre membrane comprising a substantially cylindrical sidewall defining an internal lumen from which gas can permeate through the sidewall, and characterised in that at least a part of an outer surface of the fibre membrane is engineered to define at least one biofilm retaining region which acts to retain a quantity of biofilm therein, in particular when the fibre membrane is subjected to a high sheer biofilm control event, such as experienced during a reactor cleaning cycle, for removing excess biofilm in order to prevent clogging of the reactor.

Claims

1. An aerated biofilm reactor fibre membrane comprising a substantially cylindrical sidewall defining an internal lumen from which gas can permeate through the sidewall, wherein at least a part of an outer surface of the fibre membrane is engineered to define at least one biofilm retaining region.

2. The fibre membrane according to claim 1, wherein the outer surface of the fibre membrane defines an array of the engineered biofilm retaining regions.

3. The fibre membrane according to claim 1, wherein the engineered biofilm retaining region of the outer surface comprises one or more concave regions.

4. The fibre membrane according to claim 1, wherein the engineered biofilm retaining region of the outer surface comprises one or more substantially radially extending protrusions.

5. The fibre membrane according to claim 1, wherein the engineered biofilm retaining region of the outer surface comprises one or more substantially longitudinally extending corrugations.

6. The fibre membrane according to claim 1, wherein the outer surface of the fibre membrane is multilateral.

7. The fibre membrane according to claim 1, wherein an inner surface of the fibre membrane, which defines the lumen, is shaped to optimise gas transfer through the sidewall.

8. The fibre membrane according to claim 1, wherein the fibre membrane is formed as a polymer extrusion.

9. The fibre membrane according to claim 1, wherein the fibre membrane comprises an open end opposed the close end and through which gas may be supplied to the lumen.

10. The fibre membrane according to claim 1, wherein the fibre membrane has an external diameter in the range of between 0.2 mm to 5 mm, more preferably between 0.35 mm and 0.9 mm, and most preferably 0.5 mm.

11. The fibre membrane according to claim 1, wherein the fibre membrane comprises a gas permeable polymer.

12. The fibre membrane according to claim 1, wherein the fibre membrane comprises polydimethyl siloxane (PDMS).

13. A membrane aerated biofilm reactor comprising a plurality of hollow fibre membranes according to claim 1.

14. The membrane aerated biofilm reactor according to claim 13, comprising means for supplying a gas to the lumen of one or more of the fibre membranes.

15. The membrane aerated biofilm reactor according to claim 14, wherein at least an open end of each fibre membrane is captured in an anchor.

16. The membrane aerated biofilm reactor according to claim 14, wherein the fibre membranes are arranged in groups.

17. An aerated biofilm reactor fibre membrane, the fibre membrane comprising: a substantially cylindrical sidewall defining an internal lumen from which gas can permeate through the sidewall, the lumen including an inner surface; an outer surface, at least a part of the outer surface of the fibre membrane being engineered to define an array of engineered biofilm retaining regions; a closed end; and an open end opposite the closed end, the open end being configured to allow a gas to pass through the open end into the internal lumen.

18. The aerated biofilm reactor fibre membrane of claim 17, wherein the inner surface of the lumen is shaped to optimise gas transfer through the sidewall.

19. The aerated biofilm reactor fibre membrane of claim 17, wherein the array of engineered biofilm retaining includes at least one of: at least one concave region; at least one substantially radially extending protrusion; and at least one substantially longitudinally extending corrugation.

20. A membrane aerated biofilm reactor, the reactor comprising: a plurality of hollow fibre membranes, each fibre membrane comprising: a substantially cylindrical sidewall defining an internal lumen from which gas can permeate through the sidewall, the lumen including an inner surface; an outer surface, at least a part of the outer surface of the fibre membrane being engineered to define an array of engineered biofilm retaining regions, the array of engineered biofilm retaining regions including at least one of: at least one concave region; at least one substantially radially extending protrusion; and at least one substantially longitudinally extending corrugation; a closed end; and an open end opposite the closed end, the open end being captured in an anchor and being configured to allow a gas to pass through the open end into the internal lumen, each fibre membrane being composed of a gas permeable polymer and formed as a polymer extrusion; the plurality of fibre membranes being arranged in a plurality of groups; each fibre membrane having an external diameter in the range of between 0.35 mm and 0.9 mm; and a means for supplying a gas to the internal lumen of each of the plurality of fibre membranes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 illustrates a cross section of an conventional prior art hollow fibre for use in a membrane aerated biofilm reactor;

[0035] FIG. 2 illustrates a cross section of an aerated biofilm reactor membrane fibre according to a preferred embodiment of the present invention;

[0036] FIG. 3 illustrates a cross section of an alternative aerated biofilm reactor membrane fibre according to a preferred embodiment of the present invention;

[0037] FIG. 4 illustrates a cross section of another alternative aerated biofilm reactor membrane fibre according to a preferred embodiment of the present invention;

[0038] FIG. 5 illustrates a cross section of another alternative aerated biofilm reactor membrane fibre according to a preferred embodiment of the present invention

[0039] FIG. 6 illustrates a cross section of another alternative aerated biofilm reactor membrane fibre according to a preferred embodiment of the present invention

[0040] FIG. 7 illustrates a cross section of another alternative aerated biofilm reactor membrane fibre according to a preferred embodiment of the present invention; and

[0041] FIG. 8 illustrates a cross section of another alternative aerated biofilm reactor membrane fibre according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0042] Referring now to FIG. 1 there is shown a cross-section of a conventional prior art hollow fibre F for use in a membrane aerated biofilm reactor (not shown). The hollow fibre F is substantially cylindrical in cross-section and defines an interior lumen L through which gas such as oxygen, air, oxygen enriched air, hydrogen or any other suitable gas, may be supplied, and which then permeates through the sidewall of the hollow fibre F in order to, in use, oxygenate a biofilm colonising the outer surface of the hollow fibre F. It can be seen that the outer surface of the hollow fibre F is a substantially smooth and continuous surface.

[0043] Turning then to FIG. 2 there is illustrated a cross-section of a fibre membrane for use in a membrane aerated biofilm reactor (not shown), the fibre membrane being generally indicated as 10. The fibre membrane 10 comprises a substantially cylindrical side wall 12 which is annular in form, and thus defines an interior lumen 14 which extends longitudinally of the fibre membrane 10. In use a gas such as oxygen or the like is pumped into the lumen 14 and, by providing the sidewall 12 as a gas permeable material, the gas can permeate through the sidewall 12 to be supplied to a biofilm (not shown) colonizing an outer surface 16 of the fibre membrane 10. Unlike prior art hollow fibres, the fibre membrane 10 of the present invention defines one or more, and preferably a plurality of, engineered biofilm retaining regions 18 which, as described in detail hereinafter, act to retain a quantity of biofilm therein, in particular when the fibre membrane 10 is subjected to a high sheer biofilm control event, such as experienced during a reactor cleaning cycle, for removing excess biofilm in order to prevent clogging of the reactor. As a result, once such an event has been completed, the biofilm held in the retaining regions 18 ensure expedient regrowth of the biofilm to full operational levels, thus significantly reducing the lead time between such a cleaning event and a return to full operation of the reactor. Conventionally this would be a significantly longer period in order to facilitate reseeding of the biofilm and regrowth on the outer surface of the fibre to an operational level.

[0044] Unlike prior art fibres, in the FIG. 2 embodiment the outer surface 16 is multilateral, and includes four concave sides 20, each of which defines a single biofilm retaining region 18. It can be seen that the inner surface 22 of the sidewall 12 is also multilateral, corresponding in number of sides to that of the outer surface 16, although each of the sides are relatively flat as opposed to the concave sides 20 of the outer surface 16. It will however be appreciated that the shape of both the outer surface 16 and inner surface 22 may be varied as required. For example it may be preferable that the outer surface 16 and inner surface 22 are substantially parallel in order to provide the side wall 12 with a substantially uniform thickness, thereby ensuring an equal transfer of gas at all points around the side wall 12, in order to establish an equal growth rate of biofilm about the outer surface 16. Equally however it will understood that it may be desirable to encourage regions of increased or decreased biofilm thickness on the outer surface 16, by suitably altering the gas permeability of that region of the sidewall 12, for example by varying the thickness of the sidewall 12 at localised regions. The fibre membrane 12 preferably has a external diameter in the range of between 0.2 mm to 5 mm, more preferably between 0.35 mm and 0.9 mm, and most preferably 0.5 mm, which diameter is measured at the radially outmost extremity of the fibre membrane 12.

[0045] The fibre membrane 12 is preferably produced by extruding a polymer through a suitably shaped die (not shown) to provide the desired external and internal profiles to the fibre membrane 10. It will however be immediately understood that any other suitable method of manufacturing the fibre membrane 10 may be employed, and the material or combination of materials selected to form the fibre membrane 10 may be varied. The fibre membrane 12 is preferably comprised of silicone (polydimethyl siloxane (PDMS)) Or a modified version of PDMS, although other suitable materials may be employed.

[0046] Referring to FIGS. 3 to 8 there are illustrated alternative embodiments of a fibre membrane according to the present invention and for use in a MABR, each variant providing an alternative sidewall profile, as dictated by the shape of an outer surface and/or an inner surface of the respective fibre membrane.

[0047] In particular, referring to FIG. 3 there is illustrated a fibre membrane 110 similar in cross-section to the fibre membrane 10 of the first embodiment. However, an outer surface 116 and an inner surface 122 are substantially parallel with one another, thus providing the side wall 112 with a substantially uniform thickness.

[0048] FIG. 4 illustrates a fibre membrane 210 having a multilateral outer surface 216 and a substantially circular inner surface 222 defining an interior lumen 214.

[0049] The cross-section illustrated in FIG. 5 is similar to that shown in FIG. 4, illustrating a fibre membrane 310 having a multilateral outer surface 316 comprising four concave sides 320 which each define a biofilm retaining region 318, separated from one another by a more pronounced or sharp apex. An inner surface 322 is substantially circular in cross-section.

[0050] The cross-section of illustrated in FIG. 6 illustrates a fibre membrane 410 which is again multi-lateral in form, defining six concave sides 420 and a substantially circular inner surface 422.

[0051] Turning to FIG. 7, there is illustrated a fibre membrane 510 having an outer surface 516 from which protrude a plurality of substantially radially extending projections 524 between adjacent pairs of which are thus defined a biofilm retaining region 518 in the form of a concave corrugation 520, each of which extends substantially longitudinally of the fibre membrane 510.

[0052] FIG. 8 illustrates a further alternative fibre membrane 610 which comprises a side wall 612 having a substantially circular outer surface 616 and a substantially circular inner surface 622. However the side wall 612 is further provided with a circular array of substantially radially extending protrusions 624 between adjacent pairs of which are thus defined biofilm retaining regions 618 which extend substantially longitudinally of the fibre membrane 610.

[0053] In each of the above fibre membranes at least one, and preferably an array of, biofilm retaining regions are defined about an outer surface of the fibre membrane, such that during a high sheer event such as a biofilm purge in order to prevent clogging of a reactor, some level of biofilm is retained in the retaining regions on the outer surface of each fibres membrane, in order to facilitate a speedy regrowth of the biofilm following the high shear event, in order to allow the reactor to be fully operational in a reduced period of time.