Field of the invention The invention relates to sheet membrane construction, and, more specifically, a Tollable membrane construction module to support biofilm for treating wastewater in a bioreactor.

Background Conventional wastewater treatment plants use an activated sludge process, which is based on the biological oxidation of organic materials. Such systems require extensive use of aerators and large treatment tanks, resulting in high costs. Other biological oxidation processes utilise the growth of biofilm on solid media or membranes in which a gas permeable membrane divides a treatment tank into a liquid compartment and a gas compartment with biofilm grown on the liquid side of the membrane. In such processes, the biofilm is provided with oxygen through an air permeable membrane. Disadvantages of the existing membrane based wastewater treatment plants include biofouling due to high biofilm growth density or low operating efficiency if biofilm membranes are spaced too far apart.

The applicant has determined that it would be advantageous to provide a sheet membrane construction module for a bioreactor with improved operational efficacy. The present invention, in its preferred embodiments, seeks to at least in part alleviate the above- identified problems.

Summary of the invention

According to an aspect of the present invention, there is provided a Tollable sheet membrane construction for a bioreactor, comprising: a sealed membrane layer defined by two adjacently located gas permeable, water repellent sheet membranes that are sealingly coupled to one another at or about their respective edges, the membrane layer comprising a top end and a bottom end between which locates two external-facing sheet membrane surfaces, wherein one or more internal air channels are defined between the top and bottom ends of the membrane layer; and a support layer operatively coupled to one of the two sheet membrane surfaces, the support layer comprising a plurality of elongated resilient ribs arranged in a lattice configuration with respect to said sheet membrane surface between a top end and a bottom end of the support layer so as to define one or more fluid permeable channels therebetween, wherein said sheet membrane surface is configured to retain a biofilm in an aqueous in use.

Preferably, the sealed membrane layer comprises a plurality of resilient support walls extending between the adjacent membranes internal of the layer so as to maintain air flow passageways within the air channel(s).

Preferably, the plurality of resilient support walls define corrugations forming separate air flow passageways within the air channel(s).

Preferably, the sheet membrane surface is pre-impregnated with biofilm material.

Preferably, the sheet membrane surface is configured with a fibrous texture to increase available surface area for biofilm growth. Preferably, the fibrous texture is formed by a thermally bonded layer of non-woven polypropylene.

Preferably, the support layer is coupled to the sheet membrane surface of the sealed membrane layer thermally or adhesively.

Preferably, the plurality of elongated resilient ribs is arranged in a diagonal lattice configuration with respect to the sheet membrane surface.

Preferably, the plurality of elongated resilient ribs are arranged in least two contiguous layers. Alternatively, resilient ribs are arranged in three contiguous layers. Preferably, each of the elongated resilient ribs is configured with a thickness of about 4 millimetres to about 10 millimetres.

Preferably, the support layer has a transverse width of about 6 millimetres when viewed from the top or bottom ends of the support layer.

Preferably, the two adjacently located air permeable, water repellent sheet membranes are sealingly coupled by ultrasonic or adhesive bonding.

Preferably, the sheet membranes are made from expanded polytetrafluoroethylene (PTFE) or polypropylene material.

Preferably, the plurality of elongated resilient ribs is made from polypropylene or polyethylene material.

According to another aspect of the present invention, there is provided a bioreactor for treating waste water, comprising a tank for holding waste water and a roll of sheet membrane construction as described.

Preferably, the sheet membrane construction is arranged as a rolled column in the tank such that substantially each support layer of the membrane construction at least partially in contact with any adjacent sealed membrane layers on each opposing side.

Preferably, the sheet membrane construction is arranged as a rolled column in the tank such that substantially each sealed membrane layer of the membrane construction at least partially in contact with any adjacent support layers on each opposing side.

According to another aspect of the present invention, there is provided a method of processing waste water in a bioreactor, comprising the steps of: (a) providing a bioreactor tank and providing therein a roll of sheet membrane construction as described, wherein the sheet membrane construction is arranged as a rolled column with each sheet layer of the roll at least in partial contact with its adjacent sheet layer; (b) flowing waste water into the bioreactor tank, wherein the waste water flows through the fluid permeable channels of the support layers of the sheet membrane construction; and (c) flowing oxygen containing gas into the bioreactor tank, wherein the gas flows through the internal air channels of the sealed membrane layer.

Brief description of the drawings

The invention will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:

Figure l is a schematic sectional view of a Tollable sheet membrane construction of an indeterminate length according to a preferred embodiment of the present invention;

Figure 2 is a schematic sectional view of a Tollable sheet membrane construction according to an alternative embodiment of the present invention;

Figure 3 is a schematic sectional view of two adjacently arranged sections of the Tollable sheet membrane of Figure 1 when in use;

Figure 4 is a schematic sectional view of two adjacently arranged sections of the Tollable sheet membrane of Figure 2 when in use;

Figure 5 is a schematic sectional view of three adjacently arranged sections of the Tollable sheet membrane of Figure 1 when in use;

Figure 6 is a schematic sectional view of three adjacently arranged sections of the Tollable sheet membrane of Figure 2 when in use;

Figure 7 is a schematic perspective view of a bioreactor tank and a roll of a sheet membrane construction in accordance with the preferred embodiment of the invention;

Figure 8 is a close up schematic view of the roll of sheet membrane construction when installed inside the bioreactor tank as seen in Figure 7; and

Figure 9 is a photograph showing a section of a roll of a sheet membrane construction in accordance with a preferred embodiments of the present invention.

It is to be appreciated that the schematic drawings are provided for illustrative purposes only and are not drawn to scale.

Detailed description of the embodiments

Preferred embodiments of the present invention relate to a sheet membrane construction, a bioreactor and a method of processing wastewater in a bioreactor. With reference to a sectional view of a sheet membrane construction 10 as seen in Figure 1, the sheet membrane construction 10 comprises, in combination, a sealed membrane layer 20 and an adjacently located support layer 30. The sheet membrane construction 10 is said to be a "construction" because it is constructed using two separate layers and 'Tollable" because the membrane construction 10 is configured to be sufficiently flexible so as to allow the membrane construction 10 to be rolled into a column with sections of membrane construction 10 folding over adjacent membrane construction 10 in a layered form. The dual layer configuration of the membrane construction 10 advantageously provides separate channels for gas and liquid flow, which discussed in detail below. It is to be appreciated that the Tollable sheet membrane construction 10 can be made according to any suitable lengths and/or widths, and their lengths have been shown as indeterminate in the schematic drawings.

The sealed membrane layer 20 comprises two sheet membranes 22, 24 adjacently aligned and sealingly coupled to one another at or about their respective edges. Specifically, the sheet membranes 22, 24 are sealingly coupled, with the sheet surfaces of the membranes 22, 24 facing one another, by any suitable manner, of which non-limiting examples include thermal bonding, chemical adhesion and mechanical fastening, so that a cavity defined between the sealed sheet membranes 22, 24 is substantially sealed from any liquid ingestion. The sheet membranes 22, 24 are constructed such that each membrane has the properties of being gas permeable and liquid impermeable (and in some configurations, water repellent). The sheet membranes 22, 24 can be constructed from suitable materials including expanded polytetrafluoroethylene or polypropylene material.

During use, the membrane layer 20 is arranged in an upright position, that is to say the transverse width of the membrane layer 20 is vertically oriented and that a length of the membrane layer 20 is rolled about a vertical axis to create a rolled column. In this configuration, the membrane layer 20 has a top end located substantially at or about a top side of the rolled column and a bottom end substantially located at or about a bottom side of the rolled column. Therefore, can be said that the membrane layer 20 comprises a top end and a bottom end between which locates to external-facing sheet membrane surfaces of the sheet membranes 22, 24. The sealed cavity defined by the sheet membranes 22, 24 allows free movement of gas through the membranes 22, 24 and into the cavity as well as through the membranes 22, 24 and out of the cavity, thereby forming air channels for gas flow. It is to be understood that gas can move freely between the top and bottom ends of the membrane layer 20 as well as between the cavity and its external environment, through the gas permeable membranes 22, 24.

In one embodiment, the sealed membrane layer 20 is further provided with structural elements 26 to keep the sheet membranes 22, 24 apart thereby preventing the membranes 22, 24 from collapsing in on itself causing the closure of airflow passageways within the air channels. Resilient support walls may be provided internal of the sealed membrane layer 20 to extend between the adjacent sheet membranes 22, 24, within the cavity, to maintain consistent airflow passageways. In some configurations, the structural elements 26 are provided in corrugated forms which, during use, define substantially discrete airflow passageways 28 of the sealed membrane layer 20. The structural elements 26 can be made from any suitable resilient material, including polypropylene or polyethylene materials.

In the preferred embodiment, the external-facing surfaces of the sheet membranes 22, 24 are provided with a fibrous texture to increase available surface area for biofilm 25 growth. In one configuration, a thin layer of non-woven polypropylene fibre is thermally bonded to one or both external-facing surfaces of sheet membranes 22, 24. The rough fibrous textured surface of the membranes 22, 24 provides means for biofilm 25 and organic matter to attach to the membranes 22, 24 when adjacent fluid permeable channels, which will be described in detail below.

The support layer 30 is configured to be a lattice structure having openings 38 which form channels therethrough to facilitate the flow of fluids in and out of the lattice structure. The terms "fluid" or "fluids" in the context of the present invention are used to mean liquid fluids with non-limiting examples including water, wastewater, chemical treatment solutions and sludge. Referring to Figure 1, the support layer 30 is arranged adjacent one of the two external-facing sheet membrane surfaces 27. In the preferred embodiment, support layer 30 comprises a plurality of elongated resilient ribs 36 arranged in a lattice structure 32 with respect to the sheet membrane surface 27. In one configuration, elongated resilient ribs 36 and/or the lattice structure 32 are operatively coupled to the sheet membrane surface 27 using any suitable coupling methods such as thermal bonding, chemical adhesion and mechanical fastening. In the preferred embodiment, each of the elongated resilient ribs is configured with a thickness of about 4 millimetres to about 10 millimetres, though other thickness dimensions may also be suitable depending on dimensional configurations of a given bioreactor plant design. In one configuration, the elongated resilient ribs 36 are made from polypropylene or polyethylene material, though other suitable materials may also be used.

The support layer 30 can be dimensioned to match that of the sheet membranes 22, 24 so that the combination of the sealed membrane layer 20 and support layer 30 forms a unified sheet membrane construction which is configurable in a rolled form. Specifically, the transverse width of support layer 30 substantially corresponds to the transverse width of the sealed membrane layer 20, and that the longitudinal length of the support layer 30 and the sealed membrane layer 20 are substantially the same. Further, when coupled to the sealed membrane layer 20 and oriented with its longitudinal length arranged horizontally, the support layer 30 has a top end and a bottom end between which locates the lattice structure 32. The top end of the support layer 30 is located adjacent the corresponding top end of the sealed membrane layer 20, and the bottom end of the support layer is located adjacent the corresponding bottom end of the sealed membrane layer 20. It can be said recesses and cavities formed by the openings throughout the lattice structure 32 define fluid permeable channels between the top and bottom ends of the support layer 30. It is to be understood that fluids can move freely between the top and bottom ends of the support layer 20 as well as between the cavities and openings of the lattice structure 32 and its external environment.

In one embodiment, the support layer 30 comprises a regular pattern of openings 38 and holes formed by the lattice structure 32. The elongated resilient ribs 36 may form the lattice structure 32 with longitudinal side ribs 34 and bridging ribs 36. With reference to Figure 2, support layer 30 comprises adjacent layers of longitudinal side ribs 34 joined by transverse bridging ribs 36 extending therebetween. In one configuration, the bridging ribs 36 are rooted in corresponding recesses located along the side ribs 34. The elongated resilient ribs 34, 36 of the support layer 30 can be joined together by any suitable means, including thermal bonding, chemical adhesion and mechanical fastening.

The membrane surface 27 facing the support layer 30 is suitable for hosting biofilm 25 to facilitate biological oxidation and the processing and treatment of wastewater and similar liquids. Biofilm 25 attached to and/or grown on the membrane surface 27 is provided with oxygen through the membrane surface 27 from airflow through the sealed membrane layer 20 as previously described and while being exposed to fluid flow through the support layer 30. This arrangement encourages optimal biofilm growth on the membrane surface 27. It will be appreciated that the support layer 30 and its resilient ribs 36 serve as spacing members to prevent the collapse of adjacent membrane layers on biofilm 25 attached or grown on the membrane surface 27, and to accommodate sufficient fluid flow volume through the fluid permeable channels 38 between the top and bottom ends of the support layer 30, preferably without causing congestion or blockage of the fluid permeable channels 38. In the preferred embodiment, the transverse width of the support layer 30 when viewed from the top end measures substantially about 6 millimetres. It is to be appreciated that in other embodiments, the support layer 30 may be configured with different dimensions in accordance with specific plant design or requirements.

Referring now to Figures 3 and 4, which show adjacent layers of the membrane construction 10 in accordance with a preferred embodiment and an alternative embodiment. As seen in Figure 3, a like second membrane construction 10B is positioned below a first membrane construction 10A with the support layer 30 of the first membrane construction 10A at least partially contacting or abutting an adjacently located sealed membrane layer 20 of the second membrane construction 10B. Effectively, the support layer 30 of the first membrane construction 10A provides a spacing structure between the sealed membrane layer 20 of the first membrane construction 10A and the sealed membrane layer 20 of the second membrane construction 10B so as to prevent the adjacently arranged sealed membrane layers 20 from collapsing in on one another and providing sufficient fluid permeable channels therebetween. The adjacent membrane constructions 10 A, 10B are preferably arranged in layers as described above when deployed in use in a vertical rolled form.

The layered arrangement as described above with reference to Figures 3 and 4 is similarly applied and shown in Figures 5 and 6, where three membrane construction layers are arranged adjacent one another typically when the membrane construction 10 is in a rolled form with overlapping adjacent membrane construction layers. In this arrangement, the membrane construction layers at least partially engage their adjacent like membrane construction layer(s) and the membrane construction 10 in this form alternates between a sealed membrane layer 20 and a support layer 30, which also means that air channels and fluid permeable channels are provided alternately across the sectional layers of a roll or layered arrangement of the membrane construction according to the present invention. Similarly, Figure 9 shows a photograph of the sheet membrane construction 10 in its alternating layers when arranged in a rolled form. It will be appreciated that membrane surfaces 27 which face the support layer 30 and are therefore exposed to fluid permeable channels are ideal for locating biofilm 25. In the preferred embodiment, each membrane surface 27 of the sealed membrane layer 20 that are adjacent a support layer 30 are configured for retaining biofilm 25.

Biofilm 25 can be introduced into the membrane construction 10 through a number of vectors, non-limiting examples include natural proliferation of bio-oxidation matter from substances that already exist in the treatment fluids such as wastewater and sludge or pre impregnating the membrane surfaces 27 with appropriate biofilm substance. Specifics of the biofilm substance is well known in the art and will not be described here in further detail.

In accordance with a preferred embodiment of the present invention, a bioreactor 50 comprises a bioreactor tank 52 within which locates sheet membrane construction 10 in a vertically oriented rolled form as seen in Figure 7 and 8. A close-up view of a top end section of a roll of the membrane construction 10 is provided in Figure 8. In one embodiment, the bio reactor tank 52 is provided with a cylindrical core 54 which defines an opening 56 and an attachment point for the Tollable sheet membrane construction 10. In use oxygen is provided in the tank 52 through the sealed membrane layers 20 of the sheet membrane construction 10 and wastewater flows through the fluid permeable channels defined by the support layers 30 of the sheet membrane construction 10. Advantageously, in this arrangement of alternating sealed membrane layers 20 and support layers 30, surface area for the growth, and hence density, of biofilm 25 is optimised while reducing the occurrence of bio fouling. Therefore, a bioreactor 50 embodying the membrane construction 10 of the present invention will likely provide improved bioprocessing efficiencies when treating wastewater.

In the description and drawings of this embodiment, the same reference numerals are used as have been used in respect of the first embodiment, to denote and refer to corresponding features.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.