System and method for supplying a submerged membrane unit

Abstract

In an immersed membrane system, an influent flows into an open membrane tank. The membrane tank may have a plurality of horizontally spaced immersed membrane units. The immersed membrane unit may have a flat membrane element in a membrane shell. One or more pipes are disposed in the tank for directing the flow of the influent to the immersed membrane unit. In some examples, the influent is divided into substreams, which are optionally supplied to the corresponding immersed membrane units in substantially equal amounts, optionally in a single-pass flow through baffles. During operation of the membrane tank, the influent is directed through the bottom of the membrane tank and is divided into a plurality of portions. Each of the plurality of portions is directly supplied to the bottom of the corresponding immersed membrane unit located in the tank. The influent may be a mixed liquor in a membrane bioreactor (MBR).

Description

Technical Field

[0001] The present invention relates to an immersed membrane filter and a method for operating the same. Background Art

[0002] Membranes are usually in the form of flat sheets, tubes or hollow fibers. In immersed membrane units, multiple membrane elements are assembled together into modules or boxes and immersed in an open tank. The permeate is drawn from the module by suction generated by gravity or by an osmotic pump connected to the inner surface of the membrane. Typical applications include filtering surface water to produce drinking water, treating wastewater in membrane bioreactors (MBRs) or treating secondary effluent in tertiary filtration applications. In these applications, the membranes usually have pores in the microfiltration or ultrafiltration range.

[0003] Some examples of immersed hollow fiber membrane units are described in U.S. Patent 5,639,373. In these hollow fiber membrane units, the hollow fiber membranes extend between upper and lower end sleeves. In other examples, only one end sleeve and / or membrane extends horizontally. Some examples of immersed flat sheet membrane units are described in U.S. Patent 6,287,467. In a flat sheet membrane unit, pairs of flat sheet membranes are assembled together above a frame or spacer to form an element. Many of these elements are placed in parallel in a box. The box may have a membrane shell, or shield, which forms a vertically oriented tube around the element. An aerator unit may be attached to the box. In some cases, a diffuser box below the box contains an aerator unit in a vertically oriented tube. The aerator produces bubbles that scour the surface of the membrane and also produces air lift that circulates water upward through the membrane. A similar structure is provided with a flat ceramic membrane. An alternative flat-plate immersed membrane unit having assembled corrugated membrane sheets without internal frames or spacers is described in U.S. Publication No. 2017 / 0095773, which is incorporated herein by reference.

[0004] In a membrane filtration system, one or more immersed membrane units are typically placed in an open (i.e., with a free water surface) membrane tank. In a membrane bioreactor (MBR), the membrane filtration system can function like a secondary clarifier in an activated sludge process. In this case, water is treated in a treatment tank upstream of the membrane tank to produce a mixed liquor that flows into the membrane tank. The permeate is discharged through the membrane unit, leaving the activated sludge in the membrane tank. The activated sludge is discharged from the membrane tank and divided into waste activated sludge (WAS) and returned activated sludge (RAS). RAS returns to the treatment tank and becomes part of the activated sludge. The influent (raw wastewater) flow rate (Q) is roughly balanced by the sum of the permeate flow rate and the WAS flow rate. The RAS flow rate is typically in the range of 2Q to 5Q. Summary of the invention

[0005] This summary is intended to introduce the reader to the invention and the detailed description that follows but does not limit or define the claimed invention.

[0006] In an immersed membrane system, the influent flows into an open membrane tank, the permeate is removed by the membrane, and the concentrate flows out of the membrane tank. The inventors have observed that, although each membrane unit is flushed equally with bubbles, the contamination rate may be different between membrane units in different parts of the tank. For example, in a system in which the membrane units are distributed in a straight line along a narrow tank, the tank is supplied with the influent from one end, and the most downstream membrane unit is the most polluted. This may be caused at least in part by the solid (or other pollutant) concentration gradient generated along the length of the tank. However, the membrane units are usually connected to a common permeate and return pipe and run with the same permeation and cleaning protocol. As a result, the upstream membrane unit does not operate effectively, or the downstream membrane unit is over-polluted. However, this configuration is used in a variety of immersed membrane devices including membrane bioreactors (MBRs), one of the reasons being that it helps to create a large system with multiple parallel membrane tanks. Therefore, there is already a large installation bottom of an immersed membrane system with a narrow tank.

[0007] The specification describes a membrane tank having an opening to one or more immersed membrane units. Each membrane unit may have one or more boxes or other structures containing a filter membrane. Optionally, the membrane units are spaced apart along the length of the tank. Optionally, the immersed membrane unit may have a flat membrane element that may be located within a membrane shell. An inlet is provided at one end of the tank, optionally near the bottom of the tank. One or more conduits are provided to connect the inlet to the one or more immersed membrane units. In some examples, the conduit has multiple openings that are respectively connected to different membrane units. Optionally, the openings have different sizes that can be selected to help equalize the flow of the mixed liquor to the different membrane units. Optionally, the conduit may have a horizontally extending baffle below the membrane unit. In some cases, the membrane tank is part of a membrane bioreactor.

[0008] This specification also illustrates the operation process of the membrane tank of the opening of the immersed membrane filtration system, such as MBR. In this process, the flow of the influent into the membrane tank is directed to the bottom of one or more immersed membrane units. Optionally, the flow of the mixed liquor can be divided into multiple parts. In some cases, the flow error of each of the multiple parts is less than 10% of the average flow of the multiple parts. Optionally, the influent is further directed upward through the immersed membrane unit. In some cases, a single pass or vertical piston flow state can be provided by the membrane unit. For example, the influent can be a mixed liquor in the MBR or a secondary effluent in a three-stage filtration.

[0009] As a result of the membrane tank and method described herein, the influent is usually supplied directly to one or more immersed membrane units. This helps prevent the influent, such as the influent supplied to the downstream membrane unit, from being pre-concentrated by other membrane units. Optionally, the system can also be constructed so that the flow rate of the influent through various immersed membrane units is approximately equal. Optionally, providing the influent of its original concentration to different immersed membrane units at approximately equal flow rates can make the productivity of the entire system higher and / or easier to operate. In addition, the influent is forced to pass through the membrane unit upward. The upward flow of the influent through the membrane unit can help force adjacent membranes to separate from each other, inhibit the dehydration or retention of sludge in the membrane unit, and / or disperse fresh influent into the entire membrane unit. In this way, the influent flowing into the immersed membrane tank can be used to help prevent pollution or silting in the membrane unit and / or reduce the frequency of membrane cleaning. In the case of MBR, some of the energy involved in the recirculating RAS can be recovered in the form of liquid velocity or impulse. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic diagram of a membrane bioreactor.

[0011] Figure 2 is shown with one side of the pipe removed Figure 1 Schematic side view of the membrane tank of a membrane bioreactor.

[0012] Figure 3 The front of the box is removed Figure 2 Schematic end view of a membrane tank.

[0013] Figure 4 An edge view of the membrane is shown.

[0014] Figure 5 Shown include Figure 4 Front view of the membrane assembly with the diaphragm in FIG.

[0015] Figure 6 is a schematic perspective view of a cut-away assembly showing the feed and permeate flow directions.

[0016] Figure 7 Shows three stacked together Figure 5 A front view of the component.

[0017] Figure 8 It contains several Figure 5 An isometric view of the block of components.

[0018] Fig. 9 yes Figure 8 An enlarged view of a portion of the block.

[0019] Fig.10 yes Figure 8 An enlarged view of a cross-section of the block.

[0020] Fig.11 It has three stacked Figure 8 An isometric view of a box of blocks.

[0021] Fig.12 is an isometric view of another pipe.

[0022] Fig.13 yes Fig.12 The top of the pipe Fig.11 Isometric view of the parts of the two boxes in Figure 1.

[0023] Fig.14 These are seven pipes installed on top of another pipe in the tank. Fig.11 An isometric, fragmentary cutaway view of the parts of the box in Figure 1. DETAILED DESCRIPTION

[0024] Figure 1 A membrane bioreactor (MBR) 100 using an activated sludge process is shown. Wastewater 102, such as industrial wastewater or municipal sewage, is collected and passed through a coarse screen 104 and an optional fine screen 106. For example, the fine screen 106 may have openings of 2-5 mm and may be located in the MBR 100. Figure 1 The screened wastewater 102 flows through a primary treatment unit 108 such as a clarifier or a rotary belt filter. The primary treatment unit 108 produces a primary sludge 110 and a primary effluent 112.

[0025] The primary effluent 112 flows to one or more treatment tanks 114. In some examples, there is one aerobic treatment tank 114. In other examples, there may be a series of two or more treatment tanks 114, containing aerobic, anoxic, and / or anaerobic treatment zones. Microorganisms in the treatment tanks 114 digest the primary effluent 112 and produce a mixed liquor 116. The mixed liquor 116 is conveyed to the membrane tank 70. In the example shown, the mixed liquor 116 is pumped to the membrane tank 70. In other examples, the mixed liquor flows to the membrane tank 70 by gravity.

[0026] The membrane tank 70 includes one or more pipes 80 and one or more membrane units 120. The one or more pipes 80 extend from the inlet 86 of the membrane tank 70 to the bottom of the membrane unit 120. The pipes 80 provide pressurization for the mixed liquor 116 to flow through the membrane tank 70 to reach the one or more membrane units 120. Then, the mixed liquor 116 flows upward through the membrane unit 120 and enters the membrane tank 70 outside the membrane unit 120. The permeate pump 122 extracts permeate from the mixed liquor 116 as the mixed liquor 116 passes through the membrane unit 120. Therefore, the mixed liquor 116 is concentrated in the membrane unit and leaves the membrane unit as activated sludge 126. The activated sludge 126 is taken out of the membrane tank 70, for example, by a pump or gravity, and is divided into waste activated sludge (WAS) 128 and returned (or recovered) activated sludge (RAS) 130.

[0027] exist Figure 1 In the MBR 100, the membrane tank 70 is part of the MBR 100. The flow rate of the wastewater 102 entering the MBR 100 is generally referred to as Q. For example, the flow rate of the RAS 130 can be in the range of 1Q to 5Q. For example, the flow rate of the mixed liquor 116 can be 2Q to 6Q. Therefore, a large amount of energy is applied to the recirculating RAS in the MBR 100. This causes the mixed liquor 116 to flow into the membrane tank 70 with a significant flow rate and / or energy. However, in some cases, the membrane tank 70 can be part of another filtration system such as a surface or groundwater filtration system intended to produce drinking water or industrial process water or a tertiary filtration system intended to purify wastewater that has been treated by another process.

[0028] exist Figure 2 Side view and Figure 3 The membrane tank 70 is shown in an end view of FIG. The length of the membrane tank 70 may be more than 2 times or more than 4 times the width of the membrane tank 70. The spacing between the walls of the membrane tank 70 and the front, side and rear of the membrane unit 120 may be closer than in the example shown.

[0029] In the example shown, the duct 80 is partially formed by the bottom of the membrane tank 70. A side wall 82 extends upward from the bottom of the membrane tank 70 to the bottom of the membrane element 120. The duct 80 extends along the length of the tank 70 below the membrane element 120. The downstream end of the duct 80 is closed by an end wall 84. The top of the duct 80 is formed by a plate 88. The plate 88 is discontinuous, providing a gap 89 that is approximately equal in length and width to the horizontal dimension of the membrane element 120.

[0030] The conduit 80 optionally has a baffle 90. In the example shown, the baffle 90 extends downward from the plate 88 so that water flowing through the baffle 90 can be dispersed over the entire area of ​​the gap 89 before entering the membrane unit 120. The area of ​​the gap 89 can be at least 80% of the horizontal cross-sectional area of ​​the membrane unit 120 above it. The baffle 90 also extends horizontally at least partially, optionally entirely, below the bottom of the box 50. The horizontal extension of the baffle 90 defines an opening 92. Optionally, the openings 92 have different sizes relative to each other to help provide a selected division of the total influent mixed liquor flowing into the membrane unit 120. The horizontal extension of the baffle 90 above the bottom of substantially all (i.e., more than 80% or more than 90%) of the membrane unit 120 or above the bottom but moving from below to the top of the conduit 80 tends to produce a selected distribution of the influent flow between the membrane units 120 over a wider range of influent flow rates. Without being limited by theory, this may be due in part to the small area of ​​opening 92 relative to gap 89 (ie, less than 50%) or because opening 92 faces the incoming flow upstream of gap 89 .

[0031] In the example shown, the height of the opening 92 associated with the first (upstream) baffle 90 is defined by the vertical distance between the first baffle 90 and the plate 88. The height of the opening 92 associated with the intermediate baffle 90 is defined by the vertical distance between the intermediate baffle 90 and the first baffle 90. The baffle 90 of the most downstream membrane unit 120 is set by a portion of the bottom of the tank 70 and the end 84 of the pipe 80. The opening 92 of the most downstream membrane unit 120 is defined between the intermediate baffle 90 and the bottom of the tank 70. Alternatively, a separate pipe 80 can be provided for each membrane unit 120, but it is expected that this will require additional materials and manufacturing and may increase the overall head loss of the pipe 80. In the example shown, the portion of the pipe 80 between the opening 92 and the gap 89 provides a path for the mixed liquor to flow from the pipe 80 to the bottom of the membrane unit 120.

[0032] The membrane unit 120 optionally includes a membrane shell, or a shield, which is a structure that provides a vertically extending conduit containing the membrane itself. The membrane shell can be a separate structure, or it can be formed integrally with the other parts of the membrane unit 120. The membrane unit 120 optionally includes an aerator 132 that produces bubbles when air from a blower 134 is provided. In some cases, for example, the aerator 132 is integrated with the membrane unit 120 and is located in the membrane box. In other cases, the aerator can be placed below the membrane unit 120, optionally in a shield or an aeration box, which provides a vertically extending conduit connecting the pipeline 80 to the membrane unit 120. If the membrane is in the membrane shell, the membrane is preferably arranged to provide a vertical channel for liquid to flow upward through the membrane through the membrane unit. For example, the membrane can be a flat membrane or a flat ceramic membrane.

[0033] In some examples, the connection between the pipeline 80 and the mixed liquor inlet 86 and the connection between the pipeline 80 and the bottom of the membrane unit 120 are usually fluid-tight. In addition to the connection with the inlet 86 and the membrane unit 120, the pipeline 80 is usually a closed plenum. If used, the membrane and the aeration box are usually closed pipes. In this way, the influent of the membrane tank 70 is usually directly provided to the membrane unit 120. The previously concentrated influent in the membrane tank 70 is basically not mixed with the influent supplied to the membrane unit through the pipeline 80. However, since these are large civil engineering projects, it is not expected that a perfect fluid-tight connection or a completely closed pipeline or membrane shell. For example, the connection between the curved sheet metal flange of the pipeline 80 and the concrete wall or bottom of the membrane tank 70 or the frame of the box 50 may leak to some extent, and the pipeline 80 itself may be made of multiple parts that are not connected together by a perfect fluid-tight connector. However, relative to a completely closed system, the use of an open membrane tank 70 and an immersed membrane unit 120 allows a large system to be constructed more economically.

[0034] Although in the open membrane tank 70 which is generally used as a stirred reactor, Figure 2 and Figure 3 The membrane unit 120 in the example can be operated in a flow regime more like a single-pass cross-flow. Preferably, at least 90% or at least 95% of the influent entering the membrane tank 70 is directed to the membrane unit 120 through the pipe 80, and less than 10% or less than 5% of the influent flowing upward through the membrane unit 120 is the influent from the membrane tank 70 outside the pipe 80, opposite to the influent from the inlet 86 to the membrane tank 70. Optionally, the pipe 80 and its connections to and from are sufficiently closed and tight so that the total suspended solids (TSS) concentration of the influent at the bottom of the membrane unit 120 is less than 5% or less than 3% higher than the TSS concentration of the influent. Thus, the concentration of the influent reaching the membrane unit 120 in different parts of the membrane tank 70 is also approximately equal. The pipe 80 can also help provide a substantially uniform flow distribution to the membrane units 120 in different parts of the membrane tank 70. In examples where the membrane unit 120 includes a membrane housing (and, if the aerator 132 is below the membrane unit, an aerator box), the concentration of water leaving the membrane unit 120 is also approximately equal. Figure 1 In the MBR 100 of FIG. 1 , the total suspended solids (TSS) concentration of the water (centrate) at the top of the membrane unit 120 as a whole shall not be less than 5% of the TSS concentration of the activated sludge 126 in the membrane tank 70. In the case of the MBR 100, in which the solids content of the mixed liquor 116 and the activated sludge 126 is high, reducing the difference in solids concentration between the membrane units 120 can reduce the frequency of membrane cleaning and can increase the average flux of the membrane units 120.

[0035] The influent (i.e., mixed liquor 116) flows upward from the pipe 80 through the membrane shell of the membrane unit 120 at an average velocity, which is mainly determined by the influent flow rate and the open horizontal cross-sectional area of ​​the membrane shell of the membrane unit. The ability to achieve a significant concentration of influent in a single pass through the membrane unit 120 (which helps to avoid excessive RAS recycling rates or above 6Q) is largely determined by the packing density (packing density) (occupancy) of the membrane unit 120 relative to their horizontal cross-sectional area. The high occupancy of a planar form (i.e., flat sheet or flat ceramic) membrane can be achieved by close spacing and / or stacking of multiple sheets. For example, the unobstructed vertical space between the membranes (i.e., face-to-face separation) can be less than 5 mm, less than 3 mm, or less than 2 mm. The membrane unit 120 can be made of more than 2 or 3 components stacked vertically.

[0036] In a test using four membrane units 120 in an MBR, Fig.11 Each of the four membrane units in the form of box 50 shown has a face-to-face spacing between membrane sheets of 1.5 mm, and a RAS recirculation rate of 2.78Q produces an average (upward) liquid velocity in box 50 of 0.023 m / s. Increasing the RAS recirculation rate to 5Q and 5.6Q produces average (upward) liquid velocities of 0.035 and 0.046 m / s, respectively. The calculation of the average liquid velocity takes into account the horizontal area of ​​the clear space in the box (i.e., the cumulative area of ​​multiple 1.5 mm wide vertically extending gaps between individual membranes) and the inflow rate into the bottom of each box, but no adjustment is made for the air bubbles provided in the box. When operating at a velocity of 0.023 m / s, there was a 20% difference between the maximum and minimum mixed liquor suspended solids (MLSS) concentrations in the water collected at the top of the four boxes (i.e., a difference of approximately 10% from the average), and two of the four boxes had higher fouling rates than the other two boxes. When running at 0.046 m / s, there was only a 10% difference between the maximum and minimum mixed liquor suspended solids (MLSS) concentrations in the water collected at the top of the four boxes (i.e., a difference of about 5% from the average), and all four boxes had similar low fouling rates. Running at a velocity of 0.035 m / s also produced sustainable operation with similar low fouling rates in all four boxes. Without being limited by theory, the relatively poor results at the lowest velocity may be due to the low velocity itself, the four boxes (using Figure 2 and Figure 3 The uneven distribution of the total inflow flow between the baffle designs (not shown) and the varying opening sizes, or a combination of both.

[0037] Optionally, the average liquid velocity in the membrane unit is above 0.025 m / s or above 0.03 m / s. By modifying one or more parameters (e.g., RAS recirculation rate), a higher average liquid velocity of up to 0.05 m / s, up to 0.7 m / s or up to 0.1 m / s can be obtained. These speeds are much lower than the speeds commonly used for cross-flow filtration in conventional sealed systems (i.e., plate-and-frame systems, inner / outer hollow fiber systems, or tubular membrane systems), which are generally about 0.2 m / s when filtering a generally clean influent and above 1.0 m / s when filtering a mixed liquor. Without being limited by theory, because lower speeds are involved, the shear force of the liquid flowing through the membrane surface in the systems and processes described herein may not be effective, as is required in typical cross-flow filtration systems to consider fluid shear. However, providing fresh mixed liquor through multiple boxes at a generally consistent fluid velocity seems to advantageously provide consistent conditions between boxes, thereby avoiding a system determined by one or more boxes having a cleaning and operating protocol that is contaminated faster than other boxes. In addition, forced flow of liquid can provide one or more effects, such as forcing membrane separation or forcing an initial accumulation of solids to flow out from between the membranes, which is independent of shear forces but still uses the energy of the flowing influent to help avoid scaling or fouling in a manner that is not provided by bubbles caused by flow of liquid through the box (i.e., air lift).

[0038] Figures 4 to 11 Examples of cassettes 50 or portions thereof are illustrated. Cassettes 50 may be used individually or in groups of multiple cassettes 50 to provide membrane unit 120.

[0039] Figure 4 An example of a diaphragm 10, or referred to as an element, is shown. The diaphragm 10 is composed of two substrate sheets 12 formed and bonded together to provide an internal channel 14. The outer side of the substrate sheet 12 is coated with a porous separation layer 16. The separation layer 16 can be made by casting a membrane coating above the substrate sheet 12 and then curing the coating in a quenching bath. This usually produces pores according to the non-solvent induced phase separation (NIPS) method within the ultrafiltration or microfiltration range. The central sheet 18 between the two substrate sheets 12 is optional, but can be added to provide a more rigid diaphragm 10 if necessary. In other examples, the element can be made of two flat membranes attached together on a frame or spacer, for example in the manner of a Kubota or Microdyn Nadir element. In other examples, the element can be made of plate-like ceramics.

[0040] Figure 5 A membrane assembly 20 is shown. The assembly 20 has one or more membrane sheets 10. The edges of the membrane sheets 10 that are open to the internal passage 14 (i.e., Figure 1The edge shown in (shown in) is encapsulated in the manifold 22, or called an end sleeve or permeate collector. When in use, the manifold 22 is oriented approximately vertically and the internal channel 14 is approximately horizontal. For example, suction applied to the permeate port 24 of the manifold 22 by a pump or a siphon will cause permeate 26 to be produced in the internal channel 14 and flow through the manifold 22. Optionally, the permeate can be drawn out from one or both ends of the membrane 10. The assembly 20 typically has a plurality of parallel membranes 10. Adjacent membranes 10 are separated by vertical gaps of approximately equal width (e.g., a width between 1.5 mm and 4 mm). In one example, the assembly 20 is approximately 1900 mm wide, approximately 800 mm high, and approximately 60 mm thick, and includes 16 membranes 10 spaced approximately equally apart in thickness. In this example, the manifold 22 and the outer membrane 10 form a membrane shell. In other examples, the assembly can be surrounded by a separate membrane shell.

[0041] When used in a membrane bioreactor (MBR) or filtration apparatus, air bubbles 28 provided from below the module 20 assist the flow of filtered liquid 30 upward through the module 20 , including through the gaps between adjacent membrane sheets 10 .

[0042] Figure 6 A schematic diagram of the assembly 20 is shown cut away to further illustrate the flow of the liquid 30 through the assembly 20. The undulating shape of the diaphragm 10 creates turbulence in the liquid 30 as it rises. The diaphragm 10 may vibrate as the liquid 30 and the gas bubbles 28 move between them. In addition to aiding the flow of the liquid, the gas bubbles 28 may also provide some direct flushing of the diaphragm 10.

[0043] Figure 7 A stack 32 of three modules 20 is shown. The modules 20 are stacked vertically on top of each other. The permeate port 24 of the lower module fits into a socket (not visible) in the header 22 of the upper module. The socket in the lowermost module 20 is plugged. The permeate port 24 of the uppermost module can be connected to a permeate drain and used to drain permeate from all three modules 20. The stack 32 can also be made of two, four, or other numbers of modules 20. Because the headers 22 of adjacent modules are vertically aligned and continuous, the feed liquid can flow vertically through the entire stack 32 without being hindered by the headers 22.

[0044] Figure 8A block 40 is shown containing a plurality of assemblies 20 in a frame 42. The assemblies 20 are placed side by side in the frame 42. The assemblies 20 can slide vertically into or out of the frame 42. When in the frame 42, in the example shown, the headers 22 of the assemblies 20 fit into corresponding slots provided by plastic moldings 44 attached to the frame 42. The frame 42 is preferably made of stainless steel, but other materials may also be used. Side panels 45 cover the sides of the frame parallel to the assemblies 20. The headers 22 each include a plurality of assemblies 20, and adjacent headers 22 are in contact or close to contact with each other, for example, less than 10 mm apart or less than 5 mm apart. The side panels 45 and the headers 22 thus form an integral membrane shell defining a vertically extending fluid channel through the block 40.

[0045] Fig. 9 An enlarged view of the top of block 40 is shown. Edge 46 of the top of block 40 and a similar edge ( Fig. 9 The permeate 24 of the assembly 20 protrudes above the edge 46 to allow for the upper or lower block 40 to be supported and to allow the blocks 40 in the stack to be fastened together. Figure 7 The components 20 in the stack described herein are connected by penetration.

[0046] Fig.10 An enlarged view of a horizontal cross section of a portion of the block 40 is shown. The header 22 contains a permeate chamber 23 defined by the header 22, the edges of the membranes 10, and the sealing resin 27 between the membranes 10. The permeate chamber 23 is in fluid communication with the permeate port 24 and the spigot. To hold the assembly 20 in the frame 42, bolts 48 pass through the frame 42 and are threaded into nuts 25 adhered to the header 22, or as shown, are integrally molded with the plastic molded header 22.

[0047] Fig.11 A box 50 consisting of three blocks 40 stacked vertically one above the other is shown. Optionally, the box 50 is made with one, two, four or other number of blocks 40. The permeate port 24 of the upper block 40 is optionally connected to the permeate header 54 by a connecting pipe 52 as shown. The frame 42 of the block 40 is connected to each other by a support 58, which is a threaded rod with a nut at its end in the example shown. The support 58 also attaches the upper block 40 to a box frame 56 that can be used to hang the box 50 in the tank. An air supply pipe 60 brings air to the bottom of the box to supply a set of aerators (not visible) below the lowest block 40. The moldings 44 and side panels 45 of the vertically adjacent blocks 40 form a continuous vertically extending channel for fluid to flow through the box 50. The box 50 thus has an integrated membrane shell as a whole. Alternatively, a separate membrane box can be provided.

[0048] The box 50 can be lowered into the membrane tank 70 by a motorized lift or crane attached to the box frame 56, or raised outside the membrane tank 70. The box frame 56 can rest on the ledge of the membrane tank 70. In the example shown, the box 50 has 84 modules 20. The packing density by volume is 450-500m 2 / m 3 The packing density based on the occupied space is about 850m 2 / m 3 In one example, each assembly 20 is approximately 7-10 cm wide. The assemblies 20 may be arranged in a vertical stack of 1 to 5 assemblies 20 high in the box 50. Each stack of assemblies 20 in the box 50 has an aerator approximately 3-6 cm wide below the lowest assembly 20 in the stack.

[0049] Additional information describing suitable membrane sheets, assemblies, blocks and boxes can be found in the following: U.S. Publication No. US2017 / 0095773: Operating method of a membrane filter disclosed by Fibracast Ltd. on April 6, 2017; International Publication No. WO 2013 / 056373: Coating device and method for coating formed sheet membrane elements disclosed by Fibracast Ltd. on April 25, 2013; and International Publication No. WO 2011 / 130853: Formed sheet membrane elements and filtration systems disclosed by Fibracast Ltd. on October 27, 2011, which are incorporated herein by reference.

[0050] Fig.12 and Fig.13 Two views of another pipe 80 are shown. In this example, the pipe 80 directs the influent to two membrane units 120, each having one cassette 50. The baffle 90 is made of a horizontal plate connected to a vertical plate located below the plate 88. The opening 92 of the upstream baffle is defined in area by the width of the pipe 80 multiplied by the displacement of the horizontal plate 94 below the top of the pipe 80. The opening 92 of the downstream baffle is defined in area by the width of the pipe 80 multiplied by the displacement of the horizontal plate 94 above the bottom of the membrane tank 70.

[0051] Fig.14 A further conduit 80 is shown extending below three membrane units 120. The first membrane unit 120 has three cassettes 50. The second and third membrane units 120 have two cassettes 50, respectively.

[0052] Another example of a pipeline intended to use 5 membrane units of equal size in a row extending downstream from the inlet is modeled as used in MBR using computational fluid dynamics. Pipe 80 is generally as shown in FIG. Fig.12 and Fig.13The configuration shown, but with more baffles 90 and openings 92. The area of ​​each intermediate opening 92 is defined by the width of the duct 80 multiplied by the area of ​​the displacement of the horizontal plate 94 of the current baffle below the horizontal plate 94 of the upstream baffle 90.

[0053] Table 1 shows the average velocity of the mixed liquid passing through the openings in the above modeling example with the same opening size. As shown in Table 1, under the same opening size, the velocities of the mixed liquid passing through different openings are similar but not completely the same.

[0054] Table 1

[0055]

[0056]

[0057] Table 2 shows the average velocity of the opening in the above-mentioned modeling example with the opening size of adjustment (non-equal). As shown in Table 2, the fluid velocity through the opening can be made substantially equal by adjusting the baffle and / or the opening. Further adjustment can make the average liquid velocity through the membrane unit substantially equal. Alternatively, the liquid velocity flowing through each membrane unit can be controlled to be less than 10% of the average velocity through all membrane units under a selected inflow flow (e.g., average or peak design flow). It is expected that substantially equal velocity, because the membrane unit with a significantly lower than average velocity will be exposed to a more concentrated mixed liquor at the top of the membrane unit and / or will be cleaned inefficiently by the moving liquid.

[0058] Table 2

[0059] <![CDATA[Adjusted opening size (m 2 )]]> Average speed through the opening (m / s) 0.34 0.25 0.38 0.25 0.42 0.26 0.38 0.26 0.37 0.27

[0060] like Fig.11 As shown, the experimental MBR had a single membrane tank with two cassettes. The tank was significantly larger than the cassettes. The return activated sludge (RAS) recirculation rate was 4Q. Initially, the membrane tank was operated without piping. Later, as Fig.12 and Fig.13 As shown, the membrane tank was operated using tubing 80. Without increasing the transmembrane pressure (TMP), which was 2 psi when operated with and without tubing, the permeate production more than doubled when the tubing was added.

Claims

1. A method for operating an immersed membrane system, comprising the following steps: Providing a membrane tank having a plurality of immersed membrane units; supplying an influent to the membrane tank; dividing the influent in the membrane tank into a plurality of portions by flowing the influent into a conduit, wherein the conduit includes at least one baffle, the baffle: (a) extending downwardly from the membrane element, and (b) extending horizontally at: (i) below at least a portion of the membrane element; and (ii) above a bottom of the conduit, the horizontal extension defining an opening facing the influent; and Each of the plurality of portions of the influent is directed to a bottom of a different membrane unit among the plurality of submerged membrane units through the conduit.

2. The method according to claim 1, wherein: The submerged membrane system is a part of the membrane bioreactor operated with a return activated sludge flow rate of at least the flow rate of wastewater entering the membrane bioreactor.

3. The method according to claim 2, wherein: The submerged membrane system is a portion of the membrane bioreactor operated with a return activated sludge flow rate of at least twice the flow rate of wastewater entering the membrane bioreactor.

4. The method of claim 1 or 2, further comprising directing the portions of the influent upwardly through the plurality of submerged membrane elements.

5. The method according to claim 1 or 2, wherein: The membrane tank is elongated and / or the membrane units are spaced apart along the length of the membrane tank.

6. The method according to claim 1 or 2, wherein: At least 90% of the influent supplied to the membrane tank flows directly into the bottom of the submerged membrane unit.

7. The method according to claim 1 or 2, wherein: The flow rate error of each of the plurality of sections is less than 10% of an average flow rate of the plurality of sections.

8. The method of claim 1 or 2, wherein each of the plurality of portions exits the conduit through a separate opening.

9. The method according to claim 1 or 2, wherein: The influent flows through the membrane units in a single pass.

10. The method according to claim 1 or 2, wherein: The upward velocity of the influent in the membrane unit is above 0.025 m / s.

11. The method according to claim 1 or 2, wherein: Adjacent baffles extend horizontally at different positions from the bottom of the duct.

12. A membrane filtration system comprising: a membrane tank having an inlet; a plurality of submerged membrane units spaced apart within the membrane tank; as well as A conduit in the membrane tank extending from the inlet to a plurality of openings corresponding to the plurality of submerged membrane units, wherein each opening corresponds to a different membrane unit, wherein the one conduit includes at least one baffle that: (a) extends downward from the membrane unit and (b) extends horizontally at the following locations: (i) below at least a portion of the membrane unit above the at least one baffle; and (ii) above the bottom of the conduit.

13. The system according to claim 12, wherein: Each of the plurality of membrane units has a cassette of one or more flat sheet or plate ceramic membrane elements within a membrane housing which creates a vertically oriented flow path through the cassette.

14. The system according to claim 12 or 13, wherein: The length of the membrane tank is at least twice the width of the membrane tank.

15. The system according to claim 12 or 13, wherein: The at least one baffle moves vertically below the top of the duct.

16. The system according to claim 12 or 13, wherein: Each of the at least one baffle forms an opening facing the inlet.

17. The system according to claim 12 or 13, wherein: The openings are of unequal sizes.

18. The system according to claim 12 or 13, wherein: The area of ​​the opening is less than 50% of the horizontal cross-sectional area of ​​the membrane unit.

19. The system according to claim 12 or 13, wherein: Adjacent baffles extend horizontally at different positions from the bottom of the duct.

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