Assembly for supporting hybrid biofilm

Abstract

A bioreactor has a biofilm that receives gas passing through a support membrane and another biofilm affixed to an inert support. The first biofilm is aerated through the membrane and provides nitrification. Another biofilm has an anoxic or anaerobic zone and provides denitrification. A module usable in a bioreactor has a cord encapsulated in at least one potting head. Optionally, some or all of the cords have a gas transfer membrane. The module may provide an inert support, an active gas transfer support, or a combination of two types of supports. Multiple modules may be assembled together into a cartridge that provides an inert support, an active support, or a combination. The module or cartridge may have aerators for mixing or biofilm control.

Description

Technical Field

[0001] The specification relates to wastewater treatment, membrane biofilm reactors, and supported biofilm devices and processes. Background Art

[0002] In a membrane biofilm reactor (MBfR), a membrane is used to support the biofilm and to deliver gas to the biofilm. Martin and Nerenberg recently reviewed membrane biofilm reactors in "Membrane biofilm reactors (MBfR) for water and wastewater treatment: principles, applications and recent developments" (Bioresour. Technol. 2012). Membrane aerated biofilm reactors (MABR) are a subset of MBfR in which oxygen-containing gases are used. Syron and Casey reviewed MABR in "Membrane aerated biofilm for high-rate biological treatment: performance evaluation, engineering principles, scale-up and development requirements" (Environmental Science and Technology, 42 (6): 1833-1844, 2008).

[0003] U.S. Patent No. 7169295 describes a membrane-supported biofilm reactor with a module having fine hollow fiber membranes. The membrane is made of dense wall polymethylpentene (PMP) for tow or forming a fabric. The membrane is potted in the manifold of the module to allow oxygen-containing gas to be supplied to the lumen of the hollow fibers. The reactor can be used to treat wastewater. Mechanical, chemical and biological methods are used to control the thickness of the biofilm. International Publication No. 2008 / 130885 describes a hybrid process with suspended biomass and membrane-supported biofilms. Summary of the invention

[0004] The specification describes a bioreactor with two types of dependent growth. One type of dependent growth is a biofilm that receives gas through a membrane. The other type of dependent growth is a biofilm that is nourished only by one or more fluids in which the biofilm is immersed or passes through. Biofilm support media that supply gas through the membrane to the biofilm are called active supports. Biofilm support media that do not supply gas through the membrane to the biofilm are called inert supports. These two types of supports are combined in the reactor, optionally in a box or within a module. One or both types of supports may be provided by grouped cords.

[0005] In the water treatment process described herein, the biofilm attached to the breathable membrane has an aerobic zone and is mainly used for nitrification. The biofilm receives oxygen through the membrane. Another biofilm attached to an inert support has an anoxic or anaerobic zone and is mainly used for denitrification and COD removal. Two types of biofilms can provide complete nitrogen removal, for example using a nitrification-denitrification biological pathway or a nitrification-denitrification pathway.

[0006] The specification also describes a module with inert cords, or a mixture of active and inert supports (e.g., cords potted in at least one potting head). The cords are preferably independent of each other, except in the potting head. The cords may be composed of one or more monofilament or multifilament yarns. Optionally, the module may have cords having one or more hollow fiber gas transfer membranes. The cords with gas transfer membranes may be connected to a gas source and provide active supports, or they may be used as inert supports without a gas source. Cords without gas transfer membranes may be used as inert supports. The module may have cords with or without gas transfer membranes or a combination of cords. Modules with cords with gas transfer membranes may be configured so that some of these cords can receive gas while others cannot. In use, the module may support an inert biofilm of the cords, or a mixture of inert and active biofilms.

[0007] The reactor has one or more modules with cords located in a tank suitable for containing water to be treated. Preferably, the reactor also has a gas delivery system connected to some but not all of the cords in the reactor. An alternative reactor has a gas delivery system connected to some or all of the cords in the reactor and the reactor also has inert supports, which may be provided in one or more modules or by another inert support system. The process for treating wastewater has the steps of supplying water to the tank and supplying gas to at least some of the cords in the reactor. In use, the biofilm covers the cords. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a schematic cross section of a cord.

[0009] Figure 2 is an isometric view of the cord.

[0010] Figures 3 to 5 is a schematic diagram of steps in a process for manufacturing a module comprising a plurality of cords.

[0011] Figure 6 is a schematic diagram of a module comprising a plurality of cords.

[0012] Figure 7 Yes Figure 6 Schematic diagram of the module reactor. DETAILED DESCRIPTION

[0013] Membrane-supported biofilm modules can be made in various configurations. For example, flat sheet modules are described in WO 01 / 66474A1. Modules using hollow fiber membranes in tow or woven into sheets are described in the background section of this article. Preferred modules use supports in the form of cords as described in WO 2014 / 130043. Modules using biofilm-supported membranes of other configurations and modules with inert supports of these or other configurations may be suitable for use in the devices and processes described herein.

[0014] Inert and active biofilm supports are combined in a single reactor. The reactor typically has a storage tank. The storage tank is suitable for receiving wastewater to be treated, accommodating wastewater when treating the wastewater, and discharging wastewater. For example, the reactor can be configured to be used for batch, piston flow or continuous stirring reaction conditions or combinations of conditions. Although supports of different structures can be mixed together, it is preferred to use supports with structures similar to both active and inert supports. This provides similar packing density for both active and inert supports, as well as similar performance in response to mixing and air scouring. Active and inert supports are preferably at least compatible, or can be made compatible. For example, the inert support can be a loose medium, such as a sponge or plastic beads of the type used in a moving bed bioreactor. However, since the loose medium may interfere with the operation of the membrane-supported biofilm, additional structures may be desired, for example, a screen to separate the loose medium from the membrane.

[0015] In a preferred module, the active support and optionally the inert support are such as Figure 1 and Figure 2 The cord 10 shown in . The cord 10 includes air-permeable hollow fibers 12. The hollow fibers 12 shown have a dense wall of an oxygen-permeable polymer such as silicone or polymethylpentene (PMP). The PMP fibers may have an outer diameter of less than 100 μm and a wall thickness of 15-20 μm. The hollow fibers 12 are distributed around the circumference of a core 14, which reinforces the cord 10 and supports the hollow fibers 12. For example, the core 14 may be a yarn made of a braided multifilament, a non-braided multifilament yarn, or a single monofilament yarn. The outer covering yarn 16 holds the hollow fibers 12 relative to the core 14 and protects the hollow fibers 12 from wear. Alternatively, the hollow fibers 12 may be wrapped around the core 14, and the wrapped yarn 16 may be omitted. In Figure 2 In the example of FIG. 1 , the hollow fibers 12 completely surround the core 14. Alternatively, as Figure 1 As in the example of , the hollow fibers 12 together cover only a portion of the circumference of the core 14 .

[0016] The cord 10 is flexible so that it can swing in response to agitation (set for mixing and biofilm control). The bare cord 10 has a diameter of about 1-2 mm. When the cord is covered with a biofilm, the diameter of the cord 10 increases by about 0.3 to 1.0 mm. The biofilm fills the gaps around the hollow fibers 12 and forms a film around the cord 10 to a certain extent. The cord 10 does not have a flat and smooth surface, but on the contrary, has an uneven surface, which provides a desired environment for biofilm anchoring and helps prevent complete separation of the biofilm during a flushing event. Alternatively, the cord can be made of another structure, such as a single hollow monofilament, or a plurality of hollow monofilaments, which are twisted, woven or otherwise formed into yarns or lines. In the case of an active support, a single hollow monofilament or other cords with hollow monofilaments (each hollow monofilament having a diameter greater than about 1 mm) are optionally made of silicone (PDMS).

[0017] The cord with the gas permeable membrane can be an active support or an inert support, depending on whether gas is supplied to it. Alternatively, an inert support can be made by eliminating the gas permeable hollow fibers or by replacing them with substantially impermeable hollow fibers or solid fibers. The alternative fibers may be cheaper than the gas permeable fibers, but using one type of cord can simplify manufacturing.

[0018] The relative surface areas for active and inert support configurations can be determined based on relevant parameters such as inflow characteristics, effluent concentration targets, nitrification and denitrification rates, retention time, temperature, etc. For specific situations, the relative surface areas can be estimated by modeling (e.g., using a wastewater treatment simulator such as GPS-X from Hydromantis Inc.) or by conducting pilot studies. The relative surface areas of active and inert supports can vary from 50:50 to 95:5.

[0019] A plurality of cords 10 (e.g., 100 or more) can be made into a module in the manner of making an immersed hollow fiber membrane filtration module. At least one end of each cord 10 is potted in a block of potting material, such as a thermoplastic or thermosetting resin. The solidified block of potting material may be referred to as a potting head. The potting head may be sealed to a disk to form a header. The ends of the hollow fibers 12 of at least the active cords 10 are connected to the interior of the header by, for example, cutting them open after potting. The other ends of the cords 10 may be potted in another potting head, which may or may not be part of the header, with the ends of the gas transfer membrane 14 open or closed. Alternatively, the other ends of the cords 10 may be closed separately, or returned and potted in the first potting head. The ports in the header allow gas to be optionally supplied to the lumen of the hollow fibers 12. Gas may be supplied to the hollow fibers 12 in a dead-end manner or together with exhaust gas through a second header. Alternatively, the ports of the header may be closed to produce an inertial support.

[0020] As an example, according to the ZeeWeed 500 sold by GE Water & Process Technologies TM The construction of the immersed membrane filtration unit, the cord 10 can be assembled into modules and boxes. It is preferred that the cords 10 are generally parallel in rows, and it is more preferred that the cords 10 are generally evenly spaced in the rows, and generally evenly spaced between the rows. In order to manufacture the module, multiple rows of cords 10 are stacked on top of each other to form bundles of adjacent rows spaced apart from each other, such as lines of hot melt adhesive. The bundle is potted. After the potting material is cured, the potting head is optionally cut to expose the open end of the hollow fiber 12 and optionally sealed to the header plate. Several such modules can be attached to a common frame to form a box. The ports in the header plate (if any) are optionally brought together to receive gas from a shared inlet. Various useful techniques that can be used or suitable for manufacturing modules are described in U.S. Patents 7169295, 7300571 and 7303676, U.S. Publication 2003 / 01737006A1 and International Publication No. WO 02 / 094421, all of which are incorporated herein by reference. Alternatively, other known techniques for manufacturing hollow fiber membrane modules may be applied.

[0021] refer to Figure 3 , a plurality of cords 10 or wavy cords 10 are shown arranged on a flat fixture or drum to provide rows of generally parallel segments of cords 10 in a sheet 38. The segments of cords 10 may be kept uniformly spaced from each other in the sheet 38 by, for example, a braided filament 40 or a strip of hot melt adhesive 42. Any open ends of the cords 10 may be sealed, for example by melting them along a sealing line 44 with an iron or heated cutter. Multiple sheets 38 may be stacked on top of each other, preferably with the ends of adjacent sheets 38 separated from each other, for example by hot melt adhesive 42 or by other spacers. The ends of the group of sheets 38 are dipped into a potting mold 46 filled with a potting resin 48. For example, the potting resin 48 may be formulated as a polyurethane resin, flowing around and sealing to the cords 10. Active and inert cords 10 may be mixed together. For example, some sheets 38 may have active cords 10 while other sheets 38 have inert cords 10 that are not manufactured using hollow fiber membranes.

[0022] refer to Figure 4 After the potting resin 48 is cured, the set of sheets 38 is removed from the potting mold 46. To optionally expose the open end of the hollow fiber 12, the potting resin 48 is cut through along the cutting line 50. The other end of the set of sheets 38 can be potted in the same manner. Optionally, the pieces of potting resin 48 can be cut to expose the open end of the hollow fiber 12.

[0023] refer to Figure 5, a header 60 is formed by sealing a mass of potting resin 48 to a header pan 52. For example, the header pan 52 may be made of molded plastic. The header pan 52 has an outlet 54. The mass of potting resin 48 may be held in the header pan 52 by an adhesive or gasket 56 between the perimeter of the potting resin 48 and the header pan 52. Optionally, a second potting material 58 may be poured over the potting resin 48. The second potting material 58 may further seal the cords 10 or the potting resin 48 to the header pan 52, or may gasket the cords 10 where they exit from the header 60. A similar header 60 may be made at the other end of the set of sheets 38.

[0024] refer to Figure 6 , the module 66 has two headers 60 with the cords 10 extending between them. The headers 60 are preferably aligned vertically and held apart by a frame 62. The length of the cords 10 between the opposing faces of the headers 60 may be slightly greater than the distance between the opposing faces of the headers 60. In this case, the cords 10 have some slack and can swing. The cords 10 are preferably not connected to each other between the headers 60. Although one cord 10 may contact another cord 10 when swinging, the movement of the cord 10 is otherwise independent of the other cords 10. Multiple modules 60 can be held in a common frame 62 to form a box. The frame 62 can also hold the aerator 68 near the bottom of the module 66. Modules 66 with inert supports can be made in the same manner and simply without gas. Alternatively, the module 66 of the inert support can be made by potting the cords 10 in the potting resin 48, but without opening the hollow fibers 12 (if any). Optionally, the potting resin 48 may be attached to the header tray 52 so that the inert modules 66 may be interchanged in the frame 62 with active modules 66 or modules with a mix of active and inert cords 10. In various alternatives, the modules 66 may have all inert cords 10, all active cords 10, or a mix of active and inert cords 10. For example, the inert cords 10 may be provided by cords 10 without hollow fibers 12, by cords 10 with hollow fibers 12 whose ends are closed, or by cords 10 with hollow fibers 12 that are not in communication with the header tray 52 to receive gas. In various alternatives, the cassette may have all modules 66 with active supports, all modules 66 with inert supports, one or more modules 66 with a combination of active and inert supports, or a mix of modules 66 with active supports and modules 66 with inert supports.

[0025] When used for wastewater treatment, the cord 10 is immersed in a bioreactor and a gas (usually air but may be oxygen, hydrogen, methane or another gas) is fed through the lumen of any hollow fibers 12 used as active supports. The biofilm forms on the outer surface of the cord 10 and anchors itself by filling the gaps between the filaments. The resulting membrane biofilm assembly has a generally circular cross-section.

[0026] Modules 66 of cords 10 can be arranged in a reactor by immersing them in an open tank. Gas injection can be provided at a low rate as bubbles generated below or near the bottom of the module 66 to renew the liquid around the cord 10. Gas injection at higher rates can be used to help control biofilm thickness, perhaps through the direct action of the bubbles (through bubble excitation or bubble pressure effects on the biofilm), or by swaying the cords 10 installed with slack in the water to create turbulence or contact between the cords 10. Optionally, the gas exhausted from the cord 10 can be recycled in the gas injection with or without re-pressurization.

[0027] refer to Figure 7 , two modules 66a and 66b are immersed in a sump 70. Modules 66a, 66b are made in the same way as the cord 10 with hollow fibers 12. The sump 70 is filled with water to be treated from an inlet 72. The treated water is removed through an outlet 74. Optionally, water can be recirculated from the outlet 74 to the inlet 72 to provide a water flow through the module 66, mix the sump 70 or maintain the desired conditions in the sump 70. Air or another gas is blown into or exhausted from the module 66a by a process gas blower 76. In the example shown, the gas is blown into the header 60, travels through the cord 10, and is exhausted from the other header 60. A throttle valve 78 can be used to increase the gas pressure in the cord 10. When it is needed to mix the sump 70 or control the thickness of the biofilm on the cord 10, the jet gas blower 80 blows air or recycled exhaust gas from the module 66a to the aerator 68. Module 66a provides an active support. Module 66b is not connected to process gas blower 76 and provides an inertial support. However, module 66b is connected to injection gas blower 80.

[0028] Optionally, the aerator 68 may include a supply tube 82 and a sensor 84. The sensor 84 collects gas exhausted from the supply tube in a pocket below the housing 86. As the gas accumulates, the pocket of gas grows larger, as shown in the first two compartments of the housing 86 starting from the left side of the housing 86. When the pocket of gas extends to the bottom of the J-tube, as in the third compartment of the housing 86, the gas is released through the J-tube (as shown in the last compartment of the housing 86). In this way, large bursts of bubbles are released periodically without the need to continuously pump large volumes of gas into the storage tank 70. Excessive flushing gas consumes energy and may interfere with the desired anoxic or anaerobic conditions in the storage tank 70. Periodic large bursts of bubbles can be used more effectively to renew the water around the cord 10 or remove biofilm from the cord 10 than the same amount of gas provided by a continuous stream of bubbles.

[0029] Active and inert supports can be combined at the reactor level by combining inert and active boxes in the reactor. Active and inert supports can alternatively be provided at the box level by combining active and inert modules in the box. Active and inert supports can alternatively be provided at the module level by combining active and inert cords in the module.

[0030] When the combination of supports occurs on a smaller scale, such as at or near the module level, the need for mixing to transport reactants from one type of support to another type of support is reduced. A preferred approach is to combine supports at the module level by having active and inert cords in the same module. For example, as described above, sheets of active cords may alternate with sheets of inert cords in a bundle assembly. When combined at the reactor level, it is easier to combine different types of supports. For example, a box of module 66 with active cords as described above may be used with a box of modules commonly used in IFAS reactors such as the Cleartec 66 sold by Jager. TM or Bioweb sold by Entex Technologies TM ) in an inert support assembly.

[0031] Wastewater treatment benefits from the use of different types of microorganisms. It is particularly important to achieve synergy by autotrophic and heterotrophic bacteria under fully aerobic and anoxic conditions. One application is nitrification by autotrophic bacteria under aerobic conditions, supplemented by denitrification by heterotrophic bacteria under anoxic conditions. Another application is the hydrolysis of complex organic molecules under anoxic / anaerobic conditions, supplemented by oxidation to CO2 and H2O by heterotrophic bacteria under aerobic conditions.

[0032] The mixture of active and inert biofilm supports allows these reactions (or others) to occur using fixed film supports located in the same tank. This can provide one or more benefits of a fixed film process relative to a suspended growth process, for example, i) biomass retention is substantially unaffected by the operation of the clarifier or the occurrence of shock loading events, ii) the reactor can be operated at a lower mass loading rate with reduced excess biomass production, iii) slurry retention time is independent of hydraulic retention time. In addition, pumping and mixing can be reduced relative to a suspended biomass reactor.

[0033] By providing separate aerobic and anoxic biofilms, the function of biofilm control (e.g., by air scouring) can be used to maintain a thin biofilm. This is contrary to using a single biofilm to provide nitrification (e.g., near the membrane surface) in the depths of the biofilm and denitrification in the outer anoxic layer. A single biofilm must be thick (i.e., greater than 500 microns) to provide both nitrification and denitrification. Therefore, a single biofilm method is faced with the difficulty of controlling biofilm thickness to have an appropriate amount of aerobic and anoxic biomass. Thick biofilms also create diffusion barriers for oxygen, nitrogen compounds, or COD, which slows down the process. Thin biofilms help provide relatively high aeration flux and reaction rate.

[0034] The active support provides a biofilm that is at least partially aerobic, and may be fully aerobic. However, the active support does not transfer a considerable amount of oxygen to a large amount of liquid in the reactor. A considerable amount of liquid in the reactor is under anoxic conditions. The biofilm on the inert support is at least partially anoxic. In a preferred reactor, the active support and the inert support are essentially similar, are arranged in similar (or identical) modules or boxes and use the same or similar mixing and flushing equipment. This provides a compact and simple reactor that can carry out multi-step biochemical reactions, such as nitrification-denitrification, without having to recycle wastewater between storage tanks or precipitate suspended biomass.

[0035] International Publication No. WO 2014 / 130043A1 (General Electric Company's membrane module for supporting biofilm) published on August 28, 2014 is incorporated herein by reference. International Publication No. WO 2014 / 130042A1 (General Electric Company's wastewater treatment using membrane aerated biofilm and anaerobic digester) published on August 28, 2014 is incorporated herein by reference. General Electric Company's International (WIPO) Application No. US2015 / 019943 (wastewater treatment using preliminary treatment and MBR or MABR-IFAS reactor) filed on March 11, 2015 is incorporated herein by reference.

[0036] This written description uses examples to disclose the invention and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art.

Claims

1. A module comprising: At least one potting head; and, A plurality of inert cords are potted in the at least one potting head, wherein the one or more inert cords include a core and a plurality of linear fibers covering at least a portion of the core, wherein the plurality of linear fibers are distributed around a circumference of the core.

2. The module according to claim 1, characterized in that The module does not include an active biofilm support.

3. The module according to claim 1 or claim 2, characterized in that: The module includes an aerator.

4. The module according to claim 1, characterized in that The linear fibers covering at least a portion of the core include hollow fibers.

5. The module according to claim 1, characterized in that It also includes an outer cover yarn that retains the linear fibers relative to the core.

6. A box comprising: frame; a first module comprising only an inert biofilm support, the first module being connected to the frame, wherein the inert biofilm support comprises a core and one or more fibers covering at least a portion of the core; and, A second module comprising only the gas transfer membrane biofilm support is connected to the frame.

7. The box according to claim 6, characterized in that The inert biofilm support comprises a cord.

8. The box according to claim 6 or 7, characterized in that The first module and the second module each include a header or potting head having a similar size and shape.

9. The box according to claim 6, characterized in that The first module is interchangeable with the second module in the frame.

10. The box according to claim 6, characterized in that The fibers covering at least a portion of the core include hollow fibers.

11. The box according to claim 6, characterized in that The inert biofilm support also includes an overwrap yarn that retains the fibers relative to the core.

12. A reactor comprising: a) Storage tanks; b) active biofilm support media in said storage tank; and, c) an inert biofilm support medium in the tank, wherein the inert biofilm support medium comprises a core and a plurality of linear fibers covering at least a portion of the core, wherein the plurality of linear fibers are distributed around a circumference of the core, Wherein, the active biofilm support medium and the inert biofilm support medium are arranged in different modules.

13. The reactor according to claim 12, characterized in that The inert biofilm support medium is a stationary medium.

14. The reactor according to claim 12, characterized in that The active support media includes a hollow fiber gas permeable membrane.

15. The reactor according to any one of claims 12 to 14, characterized in that The inert biofilm support media includes a plurality of cords.

16. The reactor according to claim 12, characterized in that The linear fibers covering at least a portion of the core include hollow fibers.

17. The reactor according to claim 12, characterized in that The inert biofilm support also includes an overwrap yarn that retains the linear fibers relative to the core.

18. A process for treating wastewater comprising the steps of: contacting the wastewater with an aerobic biofilm; and contacting the wastewater with an anoxic or anaerobic biofilm, wherein the anoxic or anaerobic biofilm is attached to an inert biofilm support, the support comprising a core and a plurality of linear fibers covering at least a portion of the core, wherein the plurality of linear fibers are distributed around a circumference of the core, wherein the aerobic biofilm and the anoxic or anaerobic biofilm are located in a common tank but attached to different supports, And wherein the different supports are arranged in different modules.

19. The process according to claim 18, characterized in that The process comprises the steps of maintaining the aerobic biofilm and the anoxic or anaerobic biofilm at a thickness of less than 0.5 mm.

20. A process according to claim 18 or claim 19, characterised in that The anoxic or anaerobic biofilms are dispersed among the aerobic biofilms.

21. The process of claim 18, wherein: The linear fibers covering at least a portion of the core include hollow fibers.

22. The process of claim 18, wherein: Also included is an outer covering yarn that holds the linear fibers relative to the core.

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