Membrane separation apparatus and water treatment method

Abstract

To provide a membrane separation device which is multistaged with multiple membrane modules juxtaposed in a vertical direction, and which can adequately restrict deposition of organic matters and the like on membrane surfaces up to an upper stage membrane module.SOLUTION: In a membrane separation device, two or more membrane modules 22 are juxtaposed in a vertical direction in a membrane separation unit 23, and an air diffuser 110 is disposed below the lowest membrane module 22 in the membrane separation unit. The outer peripheral parts of the membrane modules 22 comprise cover plates 52. In addition, a coupling auxiliary plate 53 is provided at a coupling part of the membrane modules that are juxtaposed in the vertical direction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention is a membrane separation device and water treatment methods Regarding. [Background technology]

[0002] Industrial and domestic wastewater are treated to remove organic matter and other substances before being reused as industrial water or discharged into rivers, etc. One method of treating industrial wastewater is the activated sludge method, which involves aeration to allow aerobic microorganisms to decompose organic matter and other substances.

[0003] A membrane bioreactor (MBR) method is known, which combines activated sludge treatment with membrane filtration using a membrane module. In MBR treatment, as membrane filtration continues, organic matter and other substances may accumulate on the surface of the separation membrane, which can lead to a decrease in filtration flow rate and an increase in the differential pressure between membranes. Therefore, in MBR treatment, an aeration device is generally installed below the membrane module, and the impact of bubbles generated by the aeration device when they come into contact with the membrane surface, or the water flow associated with the generation of bubbles, vibrates the membrane itself, thereby suppressing the accumulation of organic matter and other substances on the membrane surface.

[0004] Various methods have been investigated for solid-liquid separation of activated sludge using membrane modules equipped with separation membranes such as microfiltration membranes and ultrafiltration membranes. As a membrane separation device, a multi-stage membrane separation device is known in which multiple membrane modules are arranged vertically above an aeration device (Patent Documents 1 and 2).

[0005] Multistage membrane separation systems are proposed for applications requiring a large membrane area and deep water, such as large-scale sewage treatment plants. Using a multistage membrane separation system leads to a reduction in the installation area of ​​the membrane modules. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2014 / 104135 [Patent Document 2] International Publication No. 2021 / 015156 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, with conventional membrane separation devices such as those described in Patent Document 1, it is difficult to sufficiently suppress the accumulation of organic matter and other substances on the membrane surface of the upper membrane module.

[0008] In membrane separation devices like the one described in Patent Document 2, bubbles diffused from the lower aeration device may not be collected by the aeration device between membrane modules, making it difficult to suppress the accumulation of organic matter on the membrane surface. While increasing the amount of aeration diffused from the aeration device can suppress the accumulation of organic matter, it reduces energy efficiency and increases costs.

[0009] The present invention aims to provide a membrane separation device that is energy-efficient and low-cost, in which multiple membrane modules are arranged in a multi-stage configuration in the vertical direction, and which can sufficiently suppress the deposition of organic matter and other substances on the membrane surface up to the upper membrane modules. [Means for solving the problem]

[0010] The present invention has the following aspects. [1] A membrane separation apparatus comprising a membrane separation section in which two or more membrane modules are arranged in a vertical direction, an aeration device positioned below the lowest membrane module of the membrane separation section, and a gas supply device that supplies gas to the aeration device, wherein the membrane separation section and the aeration device are immersed in water to be treated, and the outer periphery of the membrane module is provided with a cover plate. [2] The membrane separation apparatus according to [1], wherein a connecting auxiliary plate is installed at the connecting portion between the membrane modules which are arranged in a vertical direction. [3] The membrane separation apparatus according to [1] or [2], wherein the membrane separation unit and the aeration device are immersed in sludge-containing treated water containing activated sludge. [Effects of the Invention]

[0011] According to the present invention, a multi-stage membrane separation device can be provided in which a plurality of membrane modules are arranged side by side in the vertical direction, deposition of organic substances and the like on the membrane surface is sufficiently suppressed up to the upper membrane module, and energy is saved and the cost is low.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic diagram showing an example of a water treatment device. [Figure 2] It is a perspective view showing an example of the membrane separation part of the present invention. [Figure 3] It is a perspective view of membrane modules arranged side by side in the vertical direction. [Figure 4] It is a perspective view of the state where the membrane modules arranged side by side in the vertical direction are separated. [Figure 5] It is a front view showing an example of an air diffuser and a header. [Figure 6] It is a longitudinal sectional view of the header of FIG. 5. [Figure 7] It is a plan view of the air diffuser of FIG. 5. [Figure 8] It is a sectional view taken along line I-I of the air diffuser of FIG. 7. [Figure 9] It is a sectional view for explaining the operating mechanism of the air diffuser. [Figure 10] It is a sectional view for explaining the operating mechanism of the air diffuser. [Figure 11] It is a sectional view for explaining the operating mechanism of the air diffuser. [Figure 12] It is a sectional view for explaining the operating mechanism of the air diffuser. [Figure 13] It is a sectional view for explaining the operating mechanism of the header. [Figure 14] [[ID=5I]]It is a sectional view for explaining the operating mechanism of the header.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. Note that the dimensions and other details shown in the following description are examples only, and the present invention is not necessarily limited to them. It can be implemented with appropriate modifications without altering the essence of the invention.

[0014] [Water treatment equipment] As shown in Figure 1, the water treatment device 1000 comprises an activated sludge treatment tank 11, a membrane separation tank 21 located downstream of the activated sludge treatment tank 11, and a treated water tank 41 located downstream of the membrane separation tank 21. Furthermore, although not shown in the figure, the water treatment device 1000 also comprises a flow rate adjustment tank for adjusting the flow rate of raw water flowing into the activated sludge treatment tank 11, an extraction pump for extracting excess sludge from the membrane separation tank 21, a liquid supply means for supplying chemicals and dilution water to the membrane separation tank 21, and a discharge means for discharging treated water from the treated water tank 41 to factories, rivers, etc.

[0015] The activated sludge treatment tank 11 is filled with activated sludge in order to perform activated sludge treatment. The activated sludge treatment tank 11 is connected to a first channel 12 and a second channel 13. The first channel 12 is a channel through which raw water discharged from factories, homes, etc., flows into the activated sludge treatment tank 11. The second channel 13 is a channel through which sludge-containing treated water (water to be treated) discharged from the activated sludge treatment tank 11 flows into the membrane separation tank 21.

[0016] An aeration device 14 is installed inside the activated sludge treatment tank 11 to maintain aerobic conditions inside the tank. The aeration device 14 comprises an aeration pipe 14a that aerates the activated sludge treatment tank 11, an inlet pipe 14b that supplies gas to the aeration pipe 14a, and a blower 14c that delivers the gas. The aeration pipe 14a is not particularly limited as long as it can discharge the gas supplied from the blower 14c upward, for example, a perforated pipe or a membrane type.

[0017] The membrane separation tank 21 stores sludge-containing treated water, including activated sludge and biologically treated water, which is sent from the activated sludge treatment tank 11. The membrane separation tank 21 is equipped with a membrane separation activated sludge apparatus 100 (hereinafter sometimes referred to as "MBR apparatus 100") to which one embodiment of the membrane separation apparatus of the present invention is applied. The MBR apparatus 100 will be described later.

[0018] A sludge return means 30 is connected to the membrane separation tank 21 and the activated sludge treatment tank 11. The sludge return means 30 returns a portion of the sludge-containing treated water from the membrane separation tank 21 to the activated sludge treatment tank 11. The sludge return means 30 is equipped with a fourth flow path 31. The fourth flow path 31 is a flow path that discharges a portion of the sludge-containing treated water from the membrane separation tank 21 and flows it into the activated sludge treatment tank 11. A pump 31a is installed in the fourth flow path 31. This allows a portion of the sludge-containing treated water in the membrane separation tank 21 to be returned from the membrane separation tank 21 to the activated sludge treatment tank 11.

[0019] The treatment tank 41 stores the treated water after membrane separation of the sludge-containing treated water.

[0020] [Membrane separation equipment] The MBR device 100 comprises a membrane separation unit 23 in which two or more membrane modules 22 are arranged vertically, an aeration device 110 positioned below the lowest membrane module 22 of the membrane separation unit 23, and a gas supply device 150 that supplies gas to the aeration device 110. Within the membrane separation tank 21, both the membrane separation unit 23 and the aeration device 110 are positioned immersed in the sludge-containing treated water (water to be treated).

[0021] (Membrane separation section) In this example, the membrane separation section 23 is formed by two membrane modules 22 arranged side by side in the vertical direction. The number of membrane modules 22 arranged side by side in the vertical direction in the membrane separation section 23 can be appropriately set according to the size of the membrane separation tank 21, and can be, for example, 2 to 5.

[0022] The membrane module 22 separates treated water containing activated sludge via membrane separation. As shown in Figure 2, the membrane module 22 is equipped with a separation membrane 51, which separates the treated water containing sludge into biologically treated water and activated sludge through solid-liquid separation (membrane separation). In this example, the separation membrane of the membrane module 22 has a rectangular shape in plan view. However, the shape of the separation membrane in plan view is not limited to a rectangular shape.

[0023] The separation membrane 51 is not particularly limited as long as it has separation ability, and examples include hollow fiber membranes, flat membranes, tubular membranes, and monolithic membranes. Among these, hollow fiber membranes are preferred because they have a high volume packing efficiency. For example, by aligning multiple hollow fiber membranes to form a sheet, a separation membrane with a rectangular shape in plan view can be obtained.

[0024] When a hollow fiber membrane is used as the separation membrane 51, examples of materials for the membrane include cellulose, polyolefin, polysulfone, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE). Among these, PVDF and PTFE are preferred as materials for the hollow fiber membrane due to their strong chemical resistance and resistance to pH changes. When using a monolithic membrane as the separation membrane, it is preferable to use a ceramic membrane.

[0025] The average pore size of the micropores formed in the separation membrane 51 is generally about 0.001 to 0.1 μm for membranes called ultraseparation membranes and about 0.1 to 1 μm for membranes called precision separation membranes. In this embodiment, it is preferable to use a separation membrane in which the average pore size is within the above range.

[0026] A third channel 33 is connected to the membrane module 22. The third channel 33 is a channel that discharges the treated water that has permeated through the separation membrane 51 from the membrane separation tank 21 and flows into the treated water tank 41. A pump 33a is installed in the third channel 33. This allows the treated water that has permeated through the separation membrane of the membrane module 22 to be discharged from the membrane separation tank 21.

[0027] In the membrane separation section 23 of the MBR apparatus 100, multiple membrane modules 22 are arranged in a line perpendicular to the planar direction of the separation membrane 51 of the membrane module 22, even in the horizontal direction. The vertical positions of the first row of membrane modules 22 from the bottom in the membrane separation section 23 coincide with each other. The vertical positions of the second row of membrane modules 22 from the bottom in the membrane separation section 23 also coincide with each other. The planar ends of the multiple membrane modules 22 arranged horizontally are fixed by frames 50. The number of membrane modules 22 arranged horizontally can be appropriately set according to the size of the membrane separation tank 21, and can be, for example, 2 to 5,000.

[0028] As shown in Figure 3, the outer periphery of the membrane modules 22, which are arranged in a vertical direction, is provided with a cover plate 52 that surrounds the outer periphery of the membrane modules 22. The cover plate may surround only a part of the outer periphery, or it may surround the entire outer periphery as shown in Figure 3.

[0029] The material of the cover plate 52 is not particularly limited, and examples include metals such as stainless steel (SUS304 series, SUS316 series). Alternatively, it may be polyethylene, polypropylene, acrylonitrile-styrene (AS) resin, acrylonitrile-butadiene-styrene (ABS) resin, acrylic resin (polymethyl methacrylate (PMMA), etc.), polyvinyl chloride resin (PVC), polyacetal resin (POM), polyamide resin (PA), polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polycarbonate resin (PC), modified polyphenylene ether resin (PPE), polyphenylene sulfide resin (PPS), polyetheretherketone resin (PEEK), polysulfone resin (PSf), polyethersulfone resin (PES), etc. The material of the cover plate 52 can be selected according to the size, weight, and required strength of the membrane module 22.

[0030] The cover plates 52 installed on the outer periphery of the membrane module 22 may be installed one per surface of the outer periphery, or multiple covers may be installed on a single surface depending on the size of the membrane module 22. Cover plates 52 may also be installed in the spaces between membrane modules 22 that are arranged in a vertical direction.

[0031] As shown in Figure 3, it is preferable that connecting auxiliary plates 53 are installed at the connecting portions of membrane modules 22 arranged vertically, to suppress sliding of the membrane modules 22 in the liquid being processed. This is because even if there are manufacturing errors in the dimensions of each module membrane 22, the connecting auxiliary plates can suppress sliding due to those manufacturing errors. In this example, connecting auxiliary plates 53 are provided on the upper part of the frames 50 arranged on both sides of each separation membrane 51 of the first-stage membrane module 22, so as to rise upward, thereby suppressing sliding of the second-stage membrane module 22, which is positioned between the two connecting auxiliary plates 53, relative to the first-stage membrane module 22. The connecting auxiliary plates 53 that suppress sliding of the membrane modules 22 also serve to align the membrane modules 22 when they are arranged vertically, and the vertical movement of the membrane modules 22 after placement is not fixed. Therefore, as shown in Figure 4, the placement and separation of the membrane modules 22 becomes easier. Furthermore, by providing connecting auxiliary plates 53 at the lower part of the frame 50 positioned on both sides of each separation membrane 51 of the second-stage membrane module 22, sliding between the first-stage membrane module 22 and the second-stage membrane module 22 in the liquid being processed may be suppressed.

[0032] The material of the connecting auxiliary plate 53 may be, for example, a metal such as stainless steel (SUS304 series, SUS316 series). To ensure sufficient strength to prevent bending or damage when in contact with the membrane module 22, it may also be an L-angle member.

[0033] (aeration device) The aeration device 110 is a siphon-type aeration device, that is, an aeration device equipped with a siphon-type diffuser tube. In the present invention, it is preferable to equip the device with a siphon-type diffuser tube because it is energy-saving and low-cost, and it is easy to suppress the accumulation of organic matter and the like on the membrane surface of the membrane module 22. An aeration device equipped with a known diffuser tube other than a siphon diffuser tube is also acceptable, as long as it does not impair the effects of the present invention.

[0034] Below the membrane module 22 of the membrane separation section 23, a plurality of aeration devices 110 are arranged in a row in a direction perpendicular to the plane direction of the separation membrane of the membrane module 22 in the horizontal direction. In a plan view, each aeration device 110 has its aeration holes 126 of a siphon-type aeration pipe 120 (described later) located between adjacent membrane modules 22, and is positioned so that the length direction of the aeration holes 126 (the length direction of the aeration device 110) coincides with the plane direction of the membrane module 22.

[0035] The number of aeration devices 110 arranged horizontally can be appropriately set according to the size of the membrane separation tank 21 and the number of membrane modules 22 arranged horizontally, for example, from 2 to 5000.

[0036] As shown in Figure 5, the aeration device 110 comprises a horizontal pipe 116 extending horizontally, three distribution units 118 spaced apart along the length of the horizontal pipe 116 to distribute gas from the horizontal pipe 116, and six siphon-type aeration pipes 120 arranged in a line horizontally.

[0037] Each distribution section 118 is connected to the horizontal pipe 116 via a connecting pipe section 119 and is provided to extend downward from the horizontal pipe 116. The six siphon-type diffusers 120 are provided below the horizontal pipe 116, aligned along the length of the horizontal pipe 116, with two siphon-type diffusers 120 located on either side of each distribution section 118.

[0038] The siphon-type diffuser 120 is a box-shaped housing made by combining multiple plate-like members. As shown in Figures 5 and 7-9, the siphon-type diffuser 120 comprises an upper plate portion 120A, two side plate portions 120B, two side plate portions 120C, a bottom plate portion 120D, a first partition wall 122, and a second partition wall 124.

[0039] The two side plates 120B and 120C that form each siphon-type diffuser pipe 120 are rectangular in shape, with side plate 120B being wider than side plate 120C. As shown in Figures 7 and 8, the two side plates 120B and 120C that form each siphon-type diffuser pipe 120 are arranged so as to extend downward from the lower surface of the upper plate 120A, with the faces of side plate 120B facing each other and the faces of side plate 120C facing each other. The two side plates 120B and 120C form a rectangular tube with a rectangular cross-section. In each siphon-type diffuser pipe 120, the surface direction of side plate 120B is parallel to the length direction of the horizontal pipe 116.

[0040] In the diffuser 110, the upper plate portion 120A of the six siphon-type diffuser pipes 120 is integrally formed from a single flat plate, and the side plate portions 118B on both sides of the six siphon-type diffuser pipes 120 are each integrally formed from a single flat plate. The six siphon-type diffuser pipes 120 are connected such that the surfaces of the side plate portions 120C of adjacent siphon-type diffuser pipes 120 face each other.

[0041] As shown in Figure 7, in a plan view, rectangular diffuser holes 126 are formed along the side plate portion 120B on the side of each upper plate portion 120A that is furthest from the horizontal pipe 116. As shown in Figure 9, the bottom plate portion 120D is provided so as to extend inward from the portion near the lower end of the side plate portion 120B on the side where the diffuser holes 126 are formed. The length of the bottom plate portion 120D in the planar direction from the side plate portion 120C is shorter than that of the upper plate portion 120A. The bottom plate portion 120D blocks approximately half of the lower opening of the rectangular tube formed by the two side plate portions 120B and the two side plate portions 120C, and the portion of the opening that is not blocked by the bottom plate portion 120D becomes the treated water inlet 127. In this way, the siphon-type diffuser pipe 120 has a treated water inlet 127 formed at the bottom opening.

[0042] The first partition wall 122 has a rectangular shape when viewed from the front, and is provided so as to extend downward from the upper plate portion 120A with its faces facing the side plate portion 120B across the air diffuser hole 126. The lower end 122a of the first partition wall 122 is spaced apart from the bottom plate portion 120D. The treated water inlet 127 is located below the lower end 122a of the first partition wall 122.

[0043] The second partition wall 124 is provided so as to extend upward from the end of the first partition wall 122 located on the opposite side of the air diffuser 126 in the bottom plate portion 120D. The first partition wall 122 and the second partition wall 124 have opposing faces to each other. The upper end 124a of the second partition wall 124 is spaced apart from the top plate portion 120A. The upper end 124a of the second partition wall 124 is located above the lower end 122a of the first partition wall 122.

[0044] A siphon chamber 128 is formed inside the siphon-type diffuser pipe 120. The siphon chamber 128 is a section for storing gas. The siphon chamber 128 refers to the space within the siphon-type diffuser pipe 120 that is located on the treated water inlet 127 side of the first partition wall 122, with a height from the upper end 124a of the second partition wall 124 to the lower end 122a of the first partition wall 122. The siphon chamber 128 is divided into a first siphon chamber 128A and a second siphon chamber 128B by the second partition wall 124.

[0045] The upper part of the first siphon chamber 128A and the upper part of the second siphon chamber 128B are connected by a connecting section 125. The section from the second siphon chamber 128B to the diffuser hole 126 within the siphon diffuser pipe 120 is the path 123. In the siphon diffuser pipe 120, the treated water inlet 127 side is considered the "upstream" and the diffuser hole 126 side is considered the "downstream" when considering the flow of treated water from the treated water inlet 127 to the diffuser hole 126.

[0046] The material of the siphon-type diffuser 120 is not particularly limited and includes, for example, polyethylene, polypropylene, acrylonitrile-styrene (AS) resin, acrylonitrile-butadiene-styrene (ABS) resin, acrylic resin (polymethyl methacrylate (PMMA), etc.), polyvinyl chloride resin (PVC), polyacetal resin (POM), polyamide resin (PA), polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polycarbonate resin (PC), modified polyphenylene ether resin (PPE), polyphenylene sulfide resin (PPS), polyetheretherketone resin (PEEK), polysulfone resin (PSf), polyethersulfone resin (PES), etc. The material of the siphon-type diffuser 120 may be one type or a combination of two or more types. It may also be made of metal such as stainless steel (SUS304 series, SUS316 series).

[0047] The shape of the horizontal tube 116 is not particularly limited and can be cylindrical, polygonal, or the like. For example, if the cross-sectional shape of the horizontal tube 116 is circular, the inner diameter of the horizontal tube 116 is preferably 10 mm or more.

[0048] The cross-sectional area of ​​the horizontal pipe 116 is 100 mm². 2 The above is preferable, 300mm 2 Above 2000mm 2 The following are more preferable: If the flow path cross-sectional area of ​​the horizontal pipe 116 is greater than or equal to the lower limit of the range, the horizontal pipe 116 is less likely to become clogged with sludge. If the flow path cross-sectional area of ​​the horizontal pipe 116 is less than or equal to the upper limit of the range, the aeration device 110 becomes more compact. Note that the flow path cross-sectional area of ​​the horizontal pipe 116 is the minimum area of ​​the flow path cross-section when the horizontal pipe 116 is cut in a direction perpendicular to the length direction of the horizontal pipe 116 (vertical direction).

[0049] The horizontal pipe 116 is not particularly limited and can be made of resin, metal, or other materials. Examples of resins that make up resin pipes and tubes include polyvinyl chloride, polyethylene, polypropylene, PTFE, PVDF, fluororesins such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), nylon, and polyurethane. Examples of metals that make up metal pipes include stainless steel (SUS304 series, SUS316 series). The material of the horizontal pipe 116 may be one type or a combination of two or more types.

[0050] As shown in Figures 7 and 8, the distribution section 118 in this example is a cylindrical portion formed by two opposing side plates 120C on the two adjacent siphon-type diffusers 120, two side plates 130 connected to the ends of the two side plates 120C, and a top plate 132 that covers the upper open end of the rectangular tube formed by the two side plates 120C and the two side plates 130. The distribution section 118 in this example shares the side plates 120C with the two adjacent siphon-type diffusers 120. Furthermore, the pair of side plates 130 and top plate 132 that form the distribution section 118 are integrated with the adjacent siphon-type diffusers 120.

[0051] An opening 118a is formed on the side opposite to the horizontal pipe 116 of the distribution part 118. The opening 118a consists of an open end at the lower end of the distribution part 118 and a notch 134 formed at the lower end of a side plate part 120C that is shared with the siphon air diffuser pipe 120 in the distribution part 118. The opening 118a of the distribution part 118 functions as a gas supply port for supplying gas to the siphon air diffuser pipe 120.

[0052] The material of the distribution part 118 is not particularly limited, and for example, the same materials as those mentioned for the siphon air diffuser pipe 120 can be mentioned. The material of the distribution part 118 may be one type, or may be a combination of two or more types.

[0053] The cross-sectional area of the flow path of the distribution part 118 is preferably 300 mm 2 or more, more preferably 500 mm[[ID=1十三]] 2 or more. On the other hand, it is preferably 3000 mm 2 or less. If the cross-sectional area of the flow path of the distribution part 118 is not less than the lower limit value of the above range, the inside of the distribution part 118 is less likely to be blocked by sludge. If the cross-sectional area of the flow path of the distribution part 118 is not more than the upper limit value of the above range, the air diffuser device 110 becomes compact. Note that the cross-sectional area of the flow path of the distribution part 118 is the minimum value of the area of the flow path cross-section when the distribution part 118 is cut in a direction (horizontal direction) perpendicular to the length direction of the flow path inside the distribution part 118.

[0054] The horizontal pipe 116 and the distribution part 118 are connected via a connecting pipe part 119 whose cross-sectional area of the flow path is smaller than that of the distribution part 118 so that the flow path inside the horizontal pipe 116 and the flow path inside the distribution part 118 are connected. The shape of the connecting pipe part 119 is not particularly limited, and examples include a cylindrical shape and a polygonal cylindrical shape.

[0055] The cross-sectional area of the flow path of the connecting pipe part 119 is preferably 20 mm 2 or more, more preferably 28 mm 2 or more, even more preferably 35 mm 2 or more, particularly preferably 40 mm 2 or more. On the other hand, it is preferably 350 mm 2 or less, preferably 200 mm 2The following is more preferable: 100 mm 2 The following is even more preferable: 60 mm 2 The following are particularly preferable: If the flow path cross-sectional area of ​​the connecting pipe section 119 is greater than or equal to the lower limit of the range, the inside of the connecting pipe section 119 is less likely to be blocked by sludge. If the flow path cross-sectional area of ​​the connecting pipe section 119 is less than or equal to the upper limit of the range, the gas is more easily distributed evenly to each siphon-type diffuser pipe 120. The flow path cross-sectional area of ​​the connecting pipe section 119 is the minimum area of ​​the flow path cross-section when the connecting pipe section 119 is cut in a direction perpendicular to the length direction of the flow path inside the connecting pipe section 119. At least a portion of the flow path cross-sectional area of ​​the connecting pipe section 119 is 20 mm². 2 More than 350mm 2 The following is preferable:

[0056] The material of the connecting pipe section 119 is not particularly limited, and for example, the same material as that used for the horizontal pipe 116 can be used. The material of the connecting pipe section 119 may be one type, or a combination of two or more types.

[0057] In the aeration device 110, the alternatingly arranged siphon-type diffuser pipes 120 and each distribution unit 118 are integrated into one unit. This configuration of the aeration device 110 eliminates the need for vertical alignment of the opening 118a of the distribution unit 118 and the vertical alignment of each siphon-type diffuser pipe 120, making it easy to evenly diffuse air from each siphon-type diffuser pipe 120. Furthermore, it simplifies the assembly of the aeration device 110 and reduces the number of parts, resulting in cost advantages.

[0058] In the diffuser 110, each siphon-type diffuser pipe 120 is located below the horizontal pipe 116. Because the horizontal pipe 116 is positioned above each siphon-type diffuser pipe 120, gas can be supplied evenly from the opening 118a of each distribution section 118 to each siphon-type diffuser pipe 120, thus enabling even diffusion from each siphon-type diffuser pipe 120. Furthermore, compared to a diffuser where a component is located above the horizontal pipe, the height of the MBR device 100 can be reduced, making the MBR device 100 more compact.

[0059] The aeration device 110 is preferably positioned so that, when the membrane separation tank 21 is viewed from above, the space between adjacent separation membranes in the membrane module 22 and the aeration holes 126 of each siphon-type aeration pipe 120 overlap. Alternatively, the aeration device 110 may be positioned so that, when the membrane separation tank 21 is viewed from above, the aeration holes 126 of each siphon-type aeration pipe 120 intersect with the membrane module 22.

[0060] (Header) The MBR apparatus 100 in this example further includes a header 200. The header 200 is positioned within the membrane separation tank 21, together with the membrane separation unit 23 and the aeration device 110, and is immersed in the sludge-containing treated water (water to be treated). As shown in Figures 5 and 6, the header 200 includes a gas storage section 210, an air supply section 212, and an air delivery section 214.

[0061] The gas storage section 210 is a part for storing gas and comprises a cylindrical body 216 and an upper plate 218 provided to close the upper open end of the body 216. The lower end of the body 216 in the gas storage section 210 is open. That is, the gas storage section 210 has a water inlet 210a formed at its lower part. The shape of the gas storage section 210 is not particularly limited and can be cylindrical, polygonal, or the like.

[0062] When the gas storage section 210 is cut horizontally, the cross-sectional area of ​​the gas storage portion is 10,000 mm². 2 The above is preferable, and 20,000 mm 2 The above is more preferable, while 1,000,000 mm 2 The following are preferable: If the cross-sectional area of ​​the gas storage section 210 is greater than or equal to the lower limit of the range, the gas storage section 210 is less likely to be clogged with sludge. If the cross-sectional area of ​​the gas storage section 210 is less than or equal to the upper limit of the range, the aeration device 110 can be made more compact.

[0063] In the header 200, the air supply section 212 and the air supply section 214 are provided on the upper plate section 218 of the gas storage section 210. Thus, the air supply section 212 and the air supply section 214 are located on the upper part of the gas storage section 210. In the header 200, the air supply section 212 is located on the side of the gas storage section 210 that is further from the diffuser 110 than the air supply section 214. This results in a simpler layout and a more compact MBR device 100.

[0064] The air supply section 212 is cylindrical and is installed so as to penetrate the upper plate section 218 of the gas storage section 210. The air supply section 212 is connected to the blower 152 of the gas supply device 150 shown in Figure 1 via piping 154. As a result, the gas sent from the blower 152 through piping 154 is fed into the gas storage section 210 from the air supply section 212.

[0065] The shape of the air intake section 212 is not particularly limited and can be cylindrical, polygonal, or the like. The flow path cross-sectional area of ​​the air intake section 212 is 2000 mm². 2 The above is preferable, 3000mm 2 The above is more preferable, while 8000mm 2 The following are preferable: If the flow path cross-sectional area of ​​the air supply unit 212 is greater than or equal to the lower limit of the range, the air supply unit 212 is less likely to be blocked by sludge. If the flow path cross-sectional area of ​​the air supply unit 212 is less than or equal to the upper limit of the range, the air diffuser 110 will be more compact. Note that the flow path cross-sectional area of ​​the air supply unit 212 is the minimum area of ​​the flow path cross-section when the air supply unit 212 is cut in a direction perpendicular to the length of the flow path within the air supply unit 212.

[0066] The air supply section 214 is the part from which the gas in the gas storage section 210 is discharged, and is provided in a cylindrical shape so as to protrude upward from the upper plate section 218 of the gas storage section 210. The air supply section 214 of the header 200 is connected to the horizontal pipe 116 of the diffuser 110 via the connecting pipe 220. As a result, the gas stored in the gas storage section 210 is sent from the air supply section 214 to the horizontal pipe 116 of the diffuser 110.

[0067] The shape of the air supply section 214 is not particularly limited and can be cylindrical, polygonal, or the like. The flow path cross-sectional area of ​​the air supply section 214 is 100 mm². 2 The above is preferable, 300mm 2 The above is preferable, while 2000mm 2 The following are preferable: If the flow path cross-sectional area of ​​the air supply unit 214 is greater than or equal to the lower limit of the range, the air supply unit 214 is less likely to be blocked by sludge. If the flow path cross-sectional area of ​​the air supply unit 214 is less than or equal to the upper limit of the range, the diffuser 110 will be more compact. Note that the flow path cross-sectional area of ​​the air supply unit 214 is the minimum area of ​​the flow path cross-section when the air supply unit 214 is cut in a direction perpendicular to the length of the flow path within the air supply unit 214.

[0068] In the header 200, the air inlet 214a of the air supply unit 214, which opens into the gas storage unit 210, is located above the air inlet 212a of the air supply unit 212, which opens into the gas storage unit 210. In this invention, the positional relationship in the height direction between the air inlet opening in the gas storage unit of the air supply unit and the air inlet opening in the gas storage unit of the air supply unit is based on the upper end of the air inlet or air supply opening if the air inlet of the air supply unit or the air inlet of the air supply unit does not open downwards. If there are multiple air inlets in the gas storage unit that open into the gas storage unit of the air supply unit, the uppermost air inlet is used as the reference.

[0069] By positioning the air inlet 214a of the air supply unit 214 above the air inlet 212a of the air supply unit 212, sludge is less likely to enter the horizontal pipe 116 of the diffuser 110 from the gas storage unit 210, thereby preventing the horizontal pipe 116 and the connecting pipe section 119 from becoming clogged with sludge.

[0070] The height difference h1 between the air outlet 214a of the air supply unit 214 and the air inlet 212a of the air supply unit 212 is preferably 50 mm or more, and more preferably 100 mm or more. On the other hand, it is preferably 500 mm or less, and more preferably 300 mm or less. If the difference h1 is above the lower limit of the above range, it is easier to suppress sludge from entering the diffuser 110 from the header 200. If the difference h1 is below the upper limit of the above range, the diffuser 110 can be made more compact.

[0071] The air inlet 212a of the air supply section 212 in the header 200 is located above the opening 118a of the distribution section 118 in the diffuser 110. In the present invention, when the diffuser is equipped with a distribution section that extends downward from a horizontal pipe, it is preferable that the height of the air inlet of the air supply section of the header is the same as or higher than the height of the opening of the distribution section. This makes it easier to obtain a sufficient effect in suppressing the intrusion of sludge from the header into the diffuser, as the rise of the water level in the gas storage section stops when it reaches the air inlet of the air supply section when the operation is stopped. In the present invention, the height relationship between the air inlet opening in the gas storage section of the air supply section and the opening of the distribution section is based on the upper end of the air inlet or opening if the air inlet of the air supply section or the opening of the distribution section does not open downward. If there are multiple air inlets opening into the gas storage section of the air supply section in the gas storage section, the uppermost air inlet is used as the reference.

[0072] The height difference h2 between the air inlet 212a of the air supply unit 212 and the opening 118a of the distribution unit 118 is preferably 5 mm or more, and more preferably 10 mm or more. On the other hand, it is preferably 200 mm or less, and more preferably 180 mm or less. If the difference h2 is above the lower limit of the above range, it is easier to suppress sludge from entering the diffuser 110 from the header 200. If the difference h2 is below the upper limit of the above range, the diffuser 110 can be made more compact.

[0073] The air inlet 212a of the air supply section 212 in the header 200 is located below the lower end 119a of the connecting pipe section 119 of the air diffuser 110. Thus, in the present invention, when an air diffuser is provided in which the horizontal pipe and the distribution section are connected by a connecting pipe section having a smaller flow path cross-sectional area than the distribution section, it is preferable that the air inlet of the air supply section of the header is located above the lower end of the connecting pipe section. This makes it easier to suppress sludge buildup in the connecting pipe section.

[0074] The height difference h3 between the air inlet 212a of the air supply section 212 and the lower end 119a of the connecting pipe section 119 is preferably 50 mm or more, and more preferably 100 mm or more. On the other hand, 180 mm or less is preferable. If the difference h3 is above the lower limit of the above range, it is easier to suppress clogging of the connecting pipe section 119 with sludge. If the difference h3 is below the upper limit of the above range, the aeration device 110 can be made more compact.

[0075] The connecting pipe 220 that connects the air supply section 214 and the horizontal pipe 116 is preferably flexible. This allows the vibrations of the diffuser 110 and header 200 to be absorbed and mitigated by the connecting pipe 220, thus reducing the likelihood of damage to the diffuser 110 and header 200. Note that "the connecting pipe is flexible" means that the minimum bending radius is 1000 mm or less.

[0076] The material of the flexible connecting pipe 220 can be any material within the range that allows the connecting pipe 220 to be flexible, such as PVC hose, silicone hose, or fluorine hose. The material of the connecting pipe 220 may be one type or two or more types.

[0077] The cross-sectional area of ​​the connecting pipe 220 is 100 mm². 2 The above is preferable, 300mm 2 The above is more preferable. On the other hand, 2000mm 2 The following are preferable: If the flow path cross-sectional area of ​​the connecting pipe 220 is greater than or equal to the lower limit of the range, the connecting pipe 220 is less likely to be blocked by sludge. If the flow path cross-sectional area of ​​the connecting pipe 220 is less than or equal to the upper limit of the range, the aeration device 110 will be more compact. Note that the flow path cross-sectional area of ​​the connecting pipe 220 is the minimum area of ​​the flow path cross-section when the connecting pipe 220 is cut in a direction perpendicular to the length direction of the flow path within the connecting pipe 220.

[0078] The operating mechanism of the MBR device 100 will be described below. Before operation begins, as shown in Figure 9, the siphon chamber 128, connecting section 125, and path 123 within the siphon-type diffuser pipe 120 of the diffuser 110 are filled with sludge-containing treated water B (water to be treated).

[0079] Air is supplied from the blower 152 of the gas supply device 150 through the piping 154, and as shown in Figure 13, gas A is sent from the air supply section 212 into the gas storage section 210 of the header 200. For example, air can be used as gas A. In the header 200, gas A is temporarily stored in the gas storage section 210, pushing down the water level S1, while a portion of gas A is sent from the air supply section 214 through the connecting pipe 220 to the horizontal pipe 116 of the diffuser 110.

[0080] The gas sent to the horizontal pipe 116 is distributed to each distribution section 118 and sent through the opening 118a of the distribution section 118 to each siphon-type diffuser pipe 120 of the diffuser device 110 from the treated water inlet 127. When gas A is continuously supplied to the siphon-type diffuser pipe 120 of the diffuser device 110 in this way, as shown in Figure 10, the sludge-containing treated water B in the siphon chamber 128 is pushed out from the diffuser holes 126 and the treated water inlet 127, and the liquid level S2 in the siphon chamber 128 gradually drops.

[0081] As gas A is continuously supplied, and the liquid level S2 falls below the lower end 122a of the first partition wall 122, as shown in Figure 11, gas A moves into the path 123 due to the difference in height between the two gas-liquid interfaces, the path 123 and the first siphon chamber 128A, and is released all at once from the diffuser holes 126 to form bubbles 400. The bubbles 400 released from the diffuser holes 126 rise inside the cover plate 52 surrounding the membrane module 22 of the membrane separation unit 23, causing the separation membrane 51 to vibrate either by contact with the membrane surface of the separation membrane 51 or by the water flow associated with the generation of bubbles 400. Because the cover plate 52 is provided, the bubbles 400 also sufficiently act on the upper membrane module 22, so the accumulation of organic matter on the surface of the separation membrane 51 is sufficiently suppressed without having to increase the amount of diffused gas excessively. As aeration occurs through the aeration holes 126, the sludge-containing treated water B flows in from the treated water inlet 127, as shown in Figure 12, causing the liquid level S2 to rise to near the upper end 124a of the second partition wall 124. Then, the conditions from Figure 10 to Figure 12 are repeated, resulting in intermittent aeration from the aeration device 110.

[0082] When operation is stopped, gas A in the gas storage section 210 flows back from the air supply section 212 due to the lack of airtightness near the blower 152, causing the water level S1 in the gas storage section 210 to rise to the air inlet 212a of the air supply section 212, as shown in Figure 14. In the header 200, the air inlet 214a of the air supply section 214 is located above the air inlet 212a of the air supply section 212, so even when operation is stopped, the air inlet 214a of the air supply section 214 remains away from the water level S1. Therefore, even if operation is repeatedly stopped and restarted, the intrusion of sludge from the air supply section 214 into the diffuser 110 is suppressed. As a result, clogging of the horizontal pipe 116 and other components with dried sludge is suppressed.

[0083] [Water treatment methods] The following describes a water treatment method using the water treatment apparatus 1000 described above. The water treatment method of this embodiment includes an activated sludge treatment step in which raw water is treated with activated sludge, and a membrane separation step in which the sludge-containing treated water obtained in the activated sludge treatment step is separated by membrane.

[0084] (Activated sludge treatment process) In the water treatment method using the water treatment device 1000, wastewater (raw water) such as industrial wastewater and domestic wastewater discharged from factories and homes is introduced into the activated sludge treatment tank 11 through the first channel 12, where it is treated with activated sludge to produce biologically treated water. The treated water containing sludge after treatment (water to be treated) is introduced into the membrane separation tank 21 through the second channel 13.

[0085] (Membrane separation process) In the membrane separation tank 21, the membrane module 22 of the MBR device 100 performs membrane separation treatment on the sludge-containing treated water (water to be treated), which includes activated sludge and biologically treated water. During the membrane separation treatment, aeration is performed by the aeration device 110.

[0086] A portion of the sludge-containing treated water B is returned from the membrane separation tank 21 to the activated sludge treatment tank 11 by the sludge return means 30. After membrane separation of the sludge-containing treated water B by the membrane module 22, the treated water is sent to the treated water tank 41 through the third channel 33 for storage. The treated water stored in the treated water tank 41 can be reused as industrial water or discharged into rivers, etc.

[0087] Furthermore, the water treatment method may involve using a water treatment apparatus in which an MBR device 100 is installed inside the activated sludge treatment tank 11, and performing the activated sludge treatment process and the membrane separation process simultaneously.

[0088] As described above, in the present invention, an aeration device is positioned below the lowest membrane module of a multi-stage membrane separation unit in which two or more membrane modules are arranged vertically, and a cover plate is further positioned around the outer periphery of the membrane module. As a result, the accumulation of organic matter and other substances on the membrane surface of the lower membrane module is suppressed by the bubbles dispersed from the aeration device. Furthermore, the accumulation of organic matter and other substances on the membrane surface of the upper membrane module is also suppressed. Furthermore, if connecting auxiliary plates are installed between membrane modules that are arranged vertically, it becomes possible to suppress sliding of the connecting parts of the membrane separation section immersed in the liquid being treated. In addition, the separation of the membrane separation section within the immersion tank becomes easier, and construction work such as transportation and installation using cranes becomes easier. Furthermore, in this invention, since water treatment is performed using only the bubbles diffused from the lowest aeration device, even a device equipped with a multi-stage membrane separation section is energy-efficient and low-cost. [Explanation of symbols]

[0089] 22... Membrane module, 23... Membrane separation section, 51... Separation membrane, 52... Cover plate, 53... Connecting auxiliary plate, 100... Membrane separation activated sludge device, 110... Aeration device, 116... Horizontal pipe, 118... Distribution section, 118a... Opening, 119... Connecting pipe section, 120... Siphon type aeration pipe, 150... Gas supply device, 152... Blower, 200... Header, 210... Gas storage section, 210a... Inlet for treated water, 212... Air supply section, 212a... Air supply port, 214... Air supply section, 214a... Air supply port, 216... Body section, 218... Top plate section, 220... Connecting pipe.

Claims

1. The system comprises a membrane separation unit in which two or more membrane modules are arranged vertically, an aeration device positioned below the lowest membrane module of the membrane separation unit, and a gas supply device that supplies gas to the aeration device, wherein the membrane separation unit and the aeration device are immersed in the water to be treated, and the outer periphery of the membrane module is provided with a cover plate. At the connecting portions of the membrane modules, which are arranged in a vertical direction, connecting auxiliary plates are provided so as to rise vertically from the top or bottom of the membrane modules, with their planes facing each other. A membrane separation device in which the membrane modules, each provided with the aforementioned connecting auxiliary plates, are arranged vertically in a manner in which their vertical movement is not fixed, such that they fit between the connecting auxiliary plates with their planes facing each other.

2. The membrane separation apparatus according to claim 1, wherein the membrane module comprises a separation membrane, and the separation membrane is in the form of a sheet comprising a plurality of hollow fiber membranes.

3. The membrane separation apparatus according to claim 2, wherein the aeration devices are arranged on the lower side of the membrane module in a direction perpendicular to the plane direction of the sheet-like separation membrane in the horizontal direction.

4. The membrane separation apparatus according to any one of claims 1 to 3, wherein the membrane separation unit and the aeration device are immersed in sludge-containing treated water containing activated sludge.

5. A water treatment method using the membrane separation apparatus described in claim 4.

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