Membrane separation equipment used for membrane bioreactor and water treatment facility comprising membrane separation equipment

Abstract

To provide membrane separation equipment comprising membrane elements and enabling prevention of the damage of the membrane elements by using an existing apparatus.SOLUTION: Membrane separation equipment 100 includes a plurality of membrane elements 20, air diffusers 42, and a dividing device 30. The membrane element 20 includes: a filter plate 21; and a separation membrane 22 on a surface of the filter plate 21. The air diffuser 42 diffuses air into the plurality of membrane elements 20 from below the plurality of membrane elements 20. The dividing device 30 is detachably disposed below the plurality of membrane elements 20 and above the air diffusers 42. The dividing device 30 includes a plurality of long cutters 32 each including a cutting edge 32b facing downward. The plurality of membrane elements 20 are arranged in parallel at predetermined intervals in a thickness direction of the membrane element. The plurality of cutters 32 are arranged in parallel at intervals corresponding to predetermined intervals of the membrane elements in a thickness direction of the cutters 32. Each of the cutters 32 is continuously arranged below the membrane elements 20.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a membrane separation device used in membrane bioreactor activated sludge treatment and a water treatment facility equipped with the membrane separation device. [Background technology]

[0002] Conventionally, this type of membrane separation device has multiple membrane elements, each equipped with a separation membrane, arranged side by side. Wastewater flows into the membrane elements from below and upward between the membrane elements. The wastewater is separated into permeate and activated sludge as it passes through the separation membrane. The wastewater contains fine "screen residue" such as hair and paper fragments. The fine screen residue can become entangled and enlarge. As the enlarged screen residue clumps flow between the membrane elements along with the wastewater, they can become caught on the lower end of the membrane element and become trapped within the membrane separation device. When the trapped screen residue accumulates and grows larger, it can reach the separation membrane, causing contact and potentially damaging the separation membrane. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-168546 Summary of the Invention [Problem to be solved by the invention]

[0004] In response to this, for example, the membrane separation apparatus described in Patent Document 1 is provided with a screened residue contact suppression member below the membrane element. The membrane separation apparatus described in Patent Document 1 prevents contact between the screened residue and the separation membrane due to the screened residue being accumulated by hooking the clumps of screened residue onto the screened residue contact suppression member. Thus, the membrane separation apparatus described in Patent Document 1 prevents damage to the separation membrane due to the screened residue being accumulated.

[0005] However, in the membrane separation apparatus described in Patent Document 1, the screened residue caught on the screened residue contact suppression member continues to accumulate for a long period of time, causing the accumulated screened residue to swell and eventually reach the separation membrane of the membrane element. This can cause contact between the screened residue and the separation membrane, potentially damaging the separation membrane. Furthermore, in the membrane separation apparatus described in Patent Document 1, the overall length of the membrane element is increased by providing the screened residue contact suppression member, which can make it impossible to repurpose an existing membrane separation apparatus as is.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide a membrane separation device that can prevent damage to membrane elements (separation membranes) by utilizing an existing device. [Means for solving the problem]

[0007] According to one aspect of the present invention, a membrane separation device includes a plurality of membrane elements that filter water to be treated; an air diffuser provided below the membrane element; a separating device that is detachably provided below the membrane element and above the air diffuser; Equipped with The membrane element comprises: A filter plate extending in the vertical and width directions; a separation membrane provided on the surface of the filter plate; and The plurality of membrane elements are arranged in parallel at predetermined intervals in the thickness direction of the membrane elements, The air diffuser diffuses air from below the plurality of membrane elements, The cutting device has a plurality of elongated cutters with cutting edges facing downward, The plurality of cutters are arranged in parallel at intervals corresponding to the predetermined intervals in the thickness direction of the cutter, and the respective cutters are arranged in series below the membrane element.

[0008] According to this, the membrane separation apparatus uses the cutting edges of the multiple cutters of the cutting device to cut the clumps of screened residue below the membrane elements. That is, the clumps of screened residue are cut into multiple pieces. The pieces of screened residue flow upward or downward through the flow passages between the membrane elements and pass above the membrane elements. Therefore, the membrane separation apparatus can prevent the clumps of screened residue from accumulating at the lower ends of the membrane elements and can suppress the accumulated screened residue from contacting the separation membranes of the membrane elements. Furthermore, because the cutting device is configured to be detachable, the membrane separation apparatus can be configured as the membrane separation apparatus by simply modifying an existing apparatus by adding the cutting device.

[0009] In the membrane separation device according to the second invention, the longitudinal direction of the cutter is the same as the width direction of the membrane element.

[0010] According to this, the membrane separation device is disposed so that the cutter covers the lower end of the membrane element, and therefore the membrane separation device prevents the screened residue from remaining at the lower end of the membrane element.

[0011] In the membrane separation device according to the third invention, the plurality of cutters are provided with the cutting edge at each of both lower ends in the thickness direction of the cutter.

[0012] This increases the contact area between the cutting edges of the cutters and the screened residue, allowing the screened residue clumps to be broken into smaller pieces by both cutting edges, thereby effectively preventing the screened residue from accumulating at the lower end of the membrane element.

[0013] In the membrane separation device according to the fourth invention, the plurality of cutters have a thickness thinner than the thickness of the membrane element.

[0014] This allows the membrane separation device to reduce the width of the gap between the cutter and the membrane element, thereby preventing the screen residue from clogging and accumulating in the gap, and also allows the membrane separation device to be made lighter.

[0015] In the membrane separation device according to the fifth aspect of the present invention, the plurality of cutters include cutters made of resin.

[0016] This allows the membrane separation device to reduce the manufacturing cost of the separating device, and therefore the membrane separation device can inexpensively prevent the screened residue from remaining at the lower end of the membrane element.

[0017] In the membrane separation device according to the sixth aspect of the present invention, the plurality of cutters include composite cutters, The composite cutter comprises: A resin cutter body, a metal blade portion provided on the cutter body and having the cutting edge; It has the following characteristics.

[0018] This allows the membrane separation device to reduce manufacturing costs for the cutting device. Furthermore, the membrane separation device has a metal blade, which makes it easy to cut up clumps of screened residue. Therefore, the membrane separation device can effectively and inexpensively prevent the screened residue from accumulating at the lower end of the membrane element.

[0019] In the membrane separation device according to the seventh invention, the plurality of cutters have cutting edges that are inclined in the vertical direction.

[0020] According to this, the screened residue that comes into contact with the cutting edge moves diagonally upward along the cutting edge while receiving the acting force from the cutting edge. As a result, the clump of screened residue moves in the longitudinal direction of the cutting edge while remaining in contact with the cutting edge, making the clump of screened residue more likely to break up. Therefore, the membrane separation device effectively prevents the screened residue from accumulating at the lower end of the membrane element.

[0021] The water treatment facility according to the eighth invention includes a treatment tank having one or more of the membrane separation devices; a supply line that supplies the water to be treated to the treatment tank; a pre-filtration device provided in the supply line; a return line for returning the water to be treated in the treatment tank from the treatment tank to the pre-filtration device; Equipped with The pre-filtration device filters the water to be treated.

[0022] In this way, the water to be treated in the treatment tank is returned to the pre-filtration tank through the return line, and the screened residue contained in the water to be treated returned to the pre-filtration device is captured by the pre-filtration device. As a result, the amount of screened residue in the treatment tank is reduced, and the water treatment facility can suppress the retention of screened residue in the membrane separation device. [Effects of the Invention]

[0023] According to the present invention, the membrane separation device can utilize an existing device and prevent damage to the membrane elements. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a diagram showing an example of a water treatment facility equipped with a membrane separation device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an exploded perspective view showing the configuration of the membrane separation device. [Figure 3] FIG. 3 is a longitudinal cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. 4 is a vertical cross-sectional view of a membrane separation device according to a second embodiment of the present invention. [Figure 5] FIG. 10 is a vertical cross-sectional view of a membrane separation device according to a third embodiment of the present invention. [Figure 6] FIG. 10 is a longitudinal sectional view of a membrane separation device according to a fourth embodiment of the present invention. [Figure 7A] FIG. 10 is a perspective view of a dividing device for a membrane separation apparatus according to a fifth embodiment of the present invention. [Figure 7B] FIG. 7B is a longitudinal cross-sectional view taken along line BB in FIG. 7A. DETAILED DESCRIPTION OF THE INVENTION

[0025] A membrane separation apparatus 100 according to an embodiment of the present invention will be described below with reference to the drawings. In the drawings, identical or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated. In the following description, terms indicating positions or directions, such as "upper," "lower," "horizontal," and "vertical," may also be used. These terms are used for convenience to facilitate understanding of the embodiment, and are not limited to positions or directions when actually implemented.

[0026] <Embodiment 1> [Water treatment facility 1] Referring to FIG. 1, an example of a water treatment facility 1 including a membrane separation device 100 according to a first embodiment of the present invention will be described. FIG. 1 is a diagram illustrating an example of a water treatment facility 1 including a membrane separation device 100. As shown in FIG. 1, the water treatment facility 1 includes a treatment tank 6, a pre-filtration tank 7 (an example of a pre-filtration device), a supply line 81, a sludge transport line 82, and a return line 83. The supply line 81 supplies wastewater (an example of water to be treated) to the treatment tank 6 (arrow D1 in the figure). In the treatment tank 6, the wastewater is biologically treated by activated sludge (hereinafter, sometimes simply referred to as "sludge") to produce treated water. The sludge transport line 82 uses a pump 82p to suck up sludge that has settled in the treatment tank 6 together with the wastewater (arrow D2 in the figure), and transports the sludge in the treatment tank 6 to an outside of the water treatment facility 1 (for example, a sludge dehydrator) (arrow D3 in the figure). The return line 83 branches off from the branch point 82b of the sludge transport line 82 and returns the sludge that has settled in the treatment tank 6 to the pre-filtration tank 7 together with the wastewater.

[0027] The treatment tank 6 includes an aerobic tank 61 and an anoxic tank 62. The aerobic tank 61 includes one or more membrane separation devices 100 and a drainage line 12. The anoxic tank 62 includes an agitator 62b. In the aerobic tank 61, the wastewater is treated while maintained in an aerobic state. Specifically, in the aerobic tank 61, the microorganisms in the activated sludge are in a favorable state, and the nitrification reaction mainly proceeds as wastewater treatment. As will be described in more detail below, the membrane separation device 100 in the aerobic tank 61 separates the permeate from the wastewater via a membrane. The drainage line 12 discharges the membrane-separated permeate outside the water treatment facility 1 (for example, to a disinfection tank, etc.).

[0028] The wastewater contains "screen residue S" such as hair and paper fragments. As will be described in more detail below, the membrane separation device 100 has a membrane unit 10, a cutter unit 30 (an example of a dividing device), and an air diffuser unit 40 (an example of an air diffuser). Within the membrane separation device 100, an upward flow F1 is generated by the air diffuser unit 40. The screen residue S in the wastewater is divided by the cutter unit 30 as it rises due to the upward flow F1. The upward flow F1 reverses near the water surface, becoming a downward flow (not shown) that flows downward outside the membrane separation device 100. Therefore, the wastewater (and screen residue S) circulates vertically within the treatment tank 6.

[0029] The anoxic tank 62 is a tank maintained in an anaerobic state and treats the wastewater to be treated in the treatment tank 6 before the aerobic tank 61. Specifically, in the anoxic tank 62, the microorganisms in the activated sludge are in an anaerobic state and denitrification reactions mainly occur as wastewater treatment. The agitator 62s agitates the activated sludge and wastewater in the anoxic tank 62, mixing the activated sludge and wastewater, thereby accelerating wastewater treatment.

[0030] The pre-filtration tank 7 is provided midway along the supply line 81, i.e., upstream of the treatment tank 6. The pre-filtration tank 7 has a filter screen 71 (an example of a pre-filtration device) that captures residue S in the supplied wastewater. The return line 83 returns the wastewater from a branch point 82b in the sludge transport line 82 to the upstream side 72 of the filter screen 71 in the pre-filtration tank 7 (arrow D4 in the figure). The returned wastewater contains screen residue S, including screen residue S separated by the separation device. Therefore, the filter screen 71 also captures the screen residue S in the returned wastewater.

[0031] The supply line 81 supplies the filtered wastewater from the downstream side 73 of the filter screen 71 in the pre-filtration tank 7 to the treatment tank 6. Fine residue S that could not be captured by the filter screen 71 remains in the filtered wastewater. The fine residue S may become entangled and enlarged in the treatment tank, resulting in clumps Sm of the enlarged residue S (hereinafter referred to as "clumped residue Sm") remaining in the membrane separation device 100. The present invention prevents the retention of such enlarged clumped residue Sm in the membrane separation device 100.

[0032] The sludge transport line 82 has a first valve section 82v. The return line 83 has a second valve section 83v. When the first valve section 82v is open and the second valve section 83v is closed, the wastewater returned from the treatment tank 6 passes through the branch section 82b and is transported to the outside of the water treatment facility 1 through the sludge transport line 82 (arrow D3 in the figure). When the first valve section 82v is closed and the second valve section 83v is open, the wastewater removed from the treatment tank 6 is returned from the branch section 82b through the return line 83 to the pre-filtration tank 7 (arrow D4 in the figure). In other words, the water treatment facility 1 is configured to be able to select whether to discharge the wastewater to the outside of the water treatment facility 1 or to return it to the pre-filtration tank 7.

[0033] [Regarding the membrane separation device 100] Next, the configuration of the membrane separation device 100 will be described with reference to Fig. 2. Fig. 2 is an exploded perspective view showing the configuration of the membrane separation device 100. As shown in Fig. 2, the membrane separation device 100 includes a membrane unit 10, a cutter unit 30 (an example of a cutting device), and an aeration unit 40.

[0034] The membrane unit 10 has a plurality of membrane elements 20, a membrane case 11, and a drain line 12. The plurality of membrane elements 20 are detachably supported by the membrane case 11 at support portions (not shown) provided on the inner surface of the membrane case 11, and are arranged in parallel inside the membrane case 11. The plurality of membrane elements 20 are provided with separation membranes 22 on the surfaces of filter plates 21 that extend in the up-down direction D5 and the width direction D6. In the example shown, the membrane element 20 has separation membranes 22 on both sides of the filter plates 21.

[0035] The separation membrane 22 filters the wastewater by allowing it to pass through. The membrane element 20 has a plurality of water passages (not shown) formed in the filter plate 21. The wastewater that has permeated the separation membrane 22 passes through the water passages of the filter plate 21 as permeated water and is guided to the drain pipe 13 of the drain line 12. The permeated water guided to the drain pipe 13 is collected in the collecting pipe 14 of the drain line 12 and is drained through the drain line 12 to the outside of the facility. A gap G1 is formed between adjacent drain pipes 13.

[0036] The cutter unit 30 has a cutter case 31 which is a rectangular frame body, and a plurality of elongated cutters 32. The cutter unit 30 is disposed below the membrane unit 10 (a plurality of membrane elements 20) and above the air diffusion unit 40 (aeration device 42). The plurality of cutters 32 are supported by the cutter case 31 at support portions (not shown) provided on the inner surface of the cutter case 31, and are thereby arranged in parallel inside the cutter case 31.

[0037] The cutters 32 of the plurality of cutters 32 are provided in series below the membrane element 20. The longitudinal direction D7 of each cutter 32 is the same direction as the width direction D6 of the membrane element 20.

[0038] The air diffusion unit 40 has an air diffusion case 41, an air diffuser 42, and legs 44. The air diffuser 42 is supported by a support (not shown) provided inside the air diffusion case 41. The air diffuser 42 diffuses air to the membrane elements 20 from below. Specifically, the air diffuser 42 has a plurality of air vents 42b formed in a plurality of pipes. The air diffuser 42 diffuses air G supplied from the outside by releasing a large number of air bubbles from the air vents 42b into the wastewater. As a result of the air being diffused by the air diffuser 42, the microorganisms in the activated sludge enter an aerobic state, and the treatment of the wastewater progresses.

[0039] The drain line 12 has a plurality of drain pipes 13 and a collecting pipe 14. One end of each drain pipe 13 is connected to the upper end of the membrane element 20. The one end of the connected drain pipe 13 communicates with the water passage in the filter plate 21 described above. The other end of each drain pipe 13 is connected to the collecting pipe 14.

[0040] The membrane case 11 has a flange 11b, the cutter case 31 has an upper flange 31b and a lower flange 31c, and the aeration case 41 has a flange 41b. The flanges 31b, 31c of the cutter case 31 are configured to be connectable and detachable to the flange 11b of the membrane case 11 and the flange 41b of the aeration case 41, respectively, by bolts 9, nuts (not shown), etc. In other words, the cutter unit 30 is disposed below the membrane unit 10 and above the aeration unit 40 in a detachable manner.

[0041] Next, the membrane separation apparatus 100 will be further described with reference to Fig. 3 in addition to Fig. 2. Fig. 3 is a vertical cross-sectional view taken along line AA in Fig. 2. As shown in Fig. 3, the membrane separation apparatus 100, with the units 10, 30, and 40 connected, is used by being immersed in wastewater in the aerobic tank 61 (see Fig. 1).

[0042] When the units 10, 30, 40 are connected, a gap G5 is formed between the lower end 21b of the membrane element 20 of the membrane unit 10 (hereinafter referred to as the membrane element lower end 21b) and the upper surface 32c of the cutter 32 of the cutter unit 30. The gap G5 is set appropriately taking into consideration manufacturing variations of the membrane elements 20, the cutters 32, etc.

[0043] 3, multiple membrane elements 20 are arranged in parallel inside the membrane case 11 at a predetermined interval L1 in the thickness direction of the filter plate 21. The predetermined interval L1 is set as a design value taking into consideration the processing capacity, size, etc. of the membrane separation apparatus 100. Between the membrane elements 20, an inter-membrane element gap G2 is formed between the opposing separation membranes 22.

[0044] Each cutter 32 has a cross section shaped like an inverted isosceles triangle and has a sharp cutting edge 32b at its lower end. That is, the cutting edges 32b of the multiple cutters 32 face downward. The multiple cutters 32 are arranged in parallel in the thickness direction of the cutter 32 at intervals L2 corresponding to the predetermined intervals L1 between the multiple membrane elements 20. In the illustrated example, the predetermined intervals L1 between the membrane elements 20 and the corresponding intervals L2 between the cutters 32 are approximately the same or the same interval. The corresponding intervals L2 may be configured to be, for example, an integer multiple of the predetermined interval L1.

[0045] The cutters 32 are arranged in parallel, and an upper inter-cutter gap G3 is formed above the cutters 32, and a lower inter-cutter gap G4 is formed below the cutters 32. In the illustrated example, the cutters 32 have a vertical cross-sectional shape of an inverted isosceles triangle that is convex downward, so the lower inter-cutter gap G4 is larger than the upper inter-cutter gap G3. In the illustrated example, the thickness T2 of the upper side of each cutter 32 is approximately the same as or the same as the thickness T1 of the membrane element 20. Therefore, the upper inter-cutter gap G3 is approximately the same as or the same as the gap G2 between the membrane elements.

[0046] With the membrane separation device 100 immersed in the aerobic tank 61 (see FIG. 1), the membrane element 20 is aerated from below by the aeration device 42. This generates an upward flow F1 in the wastewater in the aerobic tank 61. The flow velocity of the upward flow F1 is non-uniform depending on the location, resulting in a random flow.

[0047] [About the action] Next, the operation of the membrane separation apparatus 100 described above will be described. As shown in Fig. 3, the upward flow F1 from below the aeration unit 40 causes the lumps of screened residue Sm in the wastewater to rise due to an upward acting force F. The rising lumps of screened residue Sm then reach the cutter unit 30, and the upper surface of the lumps of screened residue Sm then comes into contact with the cutting edge 32b of the cutter 32 at the contact site Sc. The lumps of screened residue Sm that has come into contact with the cutting edge 32b of the cutter 32 continues to be subjected to an upward acting force F by the upward flow F1, and as a reaction force, they receive an acting force F from the cutting edge 32b of the cutter 32 at the contact site Sc.

[0048] As explained above, the upward flow F1 is a random flow with uneven flow velocity depending on the location, and therefore the force F acting on the lumpy screened residue Sm acts randomly. As a result, the lumpy screened residue Sm is oscillated with its upper surface in contact with the cutting edge 32b of the cutter 32. As the lumpy screened residue Sm is oscillated while receiving the force F from the cutting edge 32b of the cutter 32, it is broken into multiple small pieces of screened residue S at the contact points Sc.

[0049] Note that the term "separation" in the above description may also be "cutting." Furthermore, "separation" includes releasing the entanglement of the screened residue S, even if it does not go as far as physically cutting. In other words, as explained above, clumped screened residue Sm often becomes an enlarged clump due to the "entanglement" of multiple fine screened residues S. Therefore, in order to prevent the clumped screened residue Sm from remaining at the lower end 21b of the membrane element, it may be sufficient to apply a certain force F to release the "entanglement" and separate the clumped residue Sm, even if it does not go as far as "physical cutting."

[0050] Since the distance between the contact areas Sc is equal to the distance between the cutters' lower gap G4, the lumpy residue Sm is divided based on the cutter's lower gap G4. Therefore, the lumpy residue Sm is divided into pieces with dimensions close to the cutter's lower gap G4.

[0051] Furthermore, the cutter 32 of the membrane separation apparatus 100 is disposed so that the longitudinal direction of the cutter 32 (arrow D7 in FIG. 2) is the same as the width direction of the membrane element 20 (arrow D6 in FIG. 2). That is, the membrane separation apparatus 100 is disposed so that the cutter 32 covers the lower end portions 21b of the membrane elements. As a result, the clumped screened residue Sm is cut by the cutter 32 before it gets caught on the lower end portions 21b of the membrane elements. Therefore, the membrane separation apparatus 100 prevents the clumped screened residue Sm from accumulating at the lower end portions 21b of the membrane elements.

[0052] As described above, the membrane separation apparatus 100 uses the cutting edges 32b of the multiple cutters 32 of the cutter unit 30 to cut and break down the lumpy screened residue Sm below the membrane elements 20. Therefore, the membrane separation apparatus 100 prevents the lumpy screened residue Sm from remaining at the lower ends 21b of the membrane elements, or prevents the remaining lumpy screened residue Sm from accumulating and contacting the membrane elements 20. Furthermore, the cutter unit 30 of the membrane separation apparatus 100 is configured to be detachable. Therefore, the membrane separation apparatus 100 can be constructed by simply modifying an existing apparatus by inserting and attaching the cutter unit 30 between the membrane elements 10 and the aeration unit 40. In other words, the membrane separation apparatus 100 can be constructed using an existing apparatus.

[0053] The separated screen residue S is then moved upward through the gaps G2 between the membrane elements by the upward flow F1, as shown, to above the membrane unit 10. The screen residue S then passes through the gaps G1 (see FIG. 2) in the drain pipe 13 and is discharged to the outside of the membrane separation apparatus 100. The screen residue S discharged to the outside of the membrane separation apparatus 100 is then lowered, together with the wastewater, into the aerobic tank 61 by the downward flow (not shown) outside the membrane separation apparatus 100. A portion of the screen residue S that has descended and settled is then returned, together with the wastewater, to the upstream side 72 of the filtration screen 71 in the pre-filtration tank 7 (see FIG. 1).

[0054] In the water treatment system 1 (see FIG. 1), the membrane separation device 100 suppresses the accumulation of clumped screened residue Sm at the lower end 21b of the membrane element, thereby improving the circulation of screened residue S in the treatment tank 6. Therefore, the water treatment system 1 can increase the amount of screened residue S returned to the pre-filtration tank 7 together with the wastewater. The screened residue S in the returned wastewater is captured by the filtration screen 71 in the pre-filtration tank 7. This reduces the amount of screened residue S in the treatment tank 6 (see FIG. 1), making it less likely that clumped screened residue Sm will be generated due to the enlargement of the screened residue S. Therefore, the water treatment system 1 can further suppress the accumulation of clumped screened residue Sm in the membrane separation device 100.

[0055] Furthermore, as explained above, the water treatment facility 1 can select whether to return the sludge in the treatment tank 6 together with the wastewater to the pre-filtration tank 7, or to discharge it outside the water treatment facility 1. Therefore, for example, when the amount of screen residue S contained in the wastewater is large, the water treatment facility 1 can select to return the wastewater to the pre-filtration tank 7. Furthermore, for example, when the amount of screen residue S contained in the wastewater is sufficiently small, the water treatment facility 1 can select to discharge the wastewater outside the water treatment facility 1 without returning it to the pre-filtration tank 7. Therefore, the water treatment facility 1 can efficiently suppress the retention of screen residue S in the membrane separation device 100.

[0056] As an effect of the above-mentioned operation, the membrane separation device 100 and the water treatment facility 1 can prevent damage to the membrane elements 20 by utilizing existing equipment.

[0057] <Embodiment 2, Embodiment 3, Embodiment 4, Embodiment 5> Next, membrane separation devices 200, 300, 400, and 500 according to second, third, fourth, and fifth embodiments of the present invention will be described with reference to FIGS. 4, 5, 6, 7A, and 7B.

[0058] First, with reference to FIG. 4, a membrane separation apparatus 200 according to a second embodiment of the present invention will be described. FIG. 4 is a longitudinal cross-sectional view of the membrane separation apparatus 200 according to the second embodiment of the present invention. As shown in FIG. 4, the membrane separation apparatus 200 has a plurality of cutters 232. The plurality of cutters 232 each have a substantially rectangular cross-sectional shape. Each of the plurality of cutters 232 has a cutting edge 232b at each of its two lower ends in the thickness direction. Because the cross-sectional shape is substantially rectangular, as shown in the figure, the inter-cutter gaps G23 between the plurality of cutters 232 are substantially the same regardless of the vertical position. In the example shown, the inter-cutter gaps G23 are substantially the same as or the same as the inter-membrane element gaps G2.

[0059] By providing the cutting edges 232b as described above, the number of contact areas Sc where the cutting edges 232b of the cutters 232 come into contact with the lumpy screened residue Sm is increased in the multiple cutters 232 in the membrane separation apparatus 200 compared to the membrane separation apparatus 100 of the first embodiment. Therefore, the membrane separation apparatus 200 can cut the lumpy screened residue Sm into smaller pieces compared to the membrane separation apparatus 100 of the first embodiment. Specifically, the membrane separation apparatus 100 of the first embodiment cuts the lumpy screened residue Sm based on the inter-cutter lower gap G4 (see FIG. 3), whereas the membrane separation apparatus 200 of the second embodiment cuts the lumpy screened residue S based on the inter-cutter gap G23. Because the inter-cutter gap G23 is smaller than the inter-cutter lower gap G4, the membrane separation apparatus 200 can reduce the dimensions of the cut screened residue S compared to the membrane separation apparatus 100 of the first embodiment. Therefore, the membrane separation apparatus 200 prevents the lumpy screened residue Sm from accumulating at the lower end 21b of the membrane element.

[0060] Next, a membrane separation apparatus 300 according to a third embodiment of the present invention will be described with reference to Fig. 5. Fig. 5 is a longitudinal sectional view of the membrane separation apparatus 300 according to the third embodiment of the present invention. As shown in Fig. 5, the membrane separation apparatus 300 has a plurality of cutters 332. The plurality of cutters 332 are configured so that a thickness T32 of the cutters 332 is thinner than a thickness T1 of the membrane element 20.

[0061] By configuring the cutter 332 as described above, the membrane separation apparatus 300 can reduce the width W2 of the gap G5 between the cutter 332 and the membrane element 20 compared to the membrane separation apparatus 100 of embodiment 1. Specifically, the width W2 of the gap G5 between the cutter 332 and the membrane element 20 shown in Fig. 5 can be made smaller than the width W1 of the gap G5 between the cutter 332 and the membrane element 20 shown in Fig. 3. Therefore, by reducing the width W2 of the gap G5, the membrane separation apparatus 300 prevents the screened residue S and clumped screened residue Sm from clogging and remaining in the gap G5.

[0062] Next, a membrane separation apparatus 400 according to a fourth embodiment of the present invention will be described with reference to Fig. 6. Fig. 6 is a longitudinal sectional view of the membrane separation apparatus 400 according to the fourth embodiment of the present invention. As shown in Fig. 6, the cutter unit 430 of the membrane separation apparatus 400 has a plurality of composite cutters 432. The composite cutter 432 has a resin cutter body 33 and a metal blade portion 34 provided on the cutter body 33. The blade portion 34 has a cutting edge 34b.

[0063] The resin cutter body 33 can be manufactured at low cost by a manufacturing method such as injection molding. The metal blade 34 can have a sharp and durable cutting edge 34b, making it easy to cut up the clumps of screened residue Sm. Therefore, the membrane separation device 400 can effectively and inexpensively prevent the clumps of screened residue Sm from remaining at the lower end 21b of the membrane element.

[0064] Next, a membrane separation apparatus 500 according to a fifth embodiment of the present invention will be described with reference to Figures 7A and 7B. Figure 7A is a perspective view of a cutter unit 530 of the membrane separation apparatus 500 according to the fifth embodiment of the present invention. Figure 7B is a longitudinal cross-sectional view taken along line BB in Figure 7A. As shown in Figures 7A and 7B, the cutter unit 530 of the membrane separation apparatus 500 has a plurality of cutters 532. The plurality of cutters 532 are configured so that their cutting edges 532b are inclined in the vertical direction. In the example shown in Figure 7B, the cutting edges 532b of the cutters 532 are inclined at an angle θ with respect to the horizontal direction.

[0065] With the above-described configuration, in the membrane separation apparatus 500, a force corresponding to the inclination of the cutting edge 532b is applied to the lumpy screened residue Sm in a direction along the cutting edge 532b. That is, the lumpy screened residue Sm that contacts the cutting edge 532b is subjected to a component force Fd of the acting force F of the upward flow F1, which is corresponding to the inclination of the cutting edge 532b. The lumpy screened residue Sm is subjected to the component force Fd in the longitudinal direction of the cutting edge 532b (arrow D7 in FIG. 2) at the contact site Sc. The lumpy screened residue Sm that has received the component force Fd moves diagonally upward in the longitudinal direction of the cutting edge 532b (arrow D8 in FIG. 7B) while receiving the acting force F from the cutting edge 532b, and is therefore more likely to be broken up. Therefore, the membrane separation apparatus 500 can effectively prevent the lumpy screened residue Sm from remaining at the lower end 21b of the membrane element.

[0066] The membrane separation devices 100, 200, 300, 400 according to the first, second, third, and fourth embodiments may be configured to have resin cutters 32, 232, 332, 432 among the plurality of cutters 32, 232, 332, 432. The resin cutters 32, 232, 332, 432 can be manufactured at low cost by a manufacturing method such as injection molding or additive manufacturing.

[0067] The multiple cutters 32, 232, 332, 432 may all be made of resin, or may be made of resin as an integral part of the cutter case 31. By making the cutter units 30, 230, 330, 430 out of resin as an integral part of the cutter case 31, the manufacturing costs of the cutter units 30, 230, 330, 430 can be further reduced. Therefore, the membrane separation devices 100, 200, 300, 400 can inexpensively prevent the clumped screen residue Sm from accumulating at the lower ends 21b of the membrane elements. Furthermore, the cross-sectional shape (inverted isosceles triangle) of the multiple cutters 32 described above is just one example, and the cross section may be, for example, an inverted right-angled triangle, as long as the cutting edges 32b are configured to face downward.

[0068] The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above embodiments and can be embodied in various forms without departing from the spirit and scope of the present invention. The drawings mainly show each component in a schematic manner for ease of understanding, and the thickness, length, number, spacing, etc. of each component shown in the drawings may differ from the actual ones due to the convenience of creating the drawings. Furthermore, the materials, shapes, dimensions, etc. of each component shown in the above embodiments are merely examples and are not particularly limited, and various modifications are possible within a scope that does not substantially deviate from the configuration of the present invention. [Explanation of symbols]

[0069] S sediment Sm lump residue F1 Upflow 1. Water treatment facilities 6 Treatment tank 7 Pre-filtration tank 10 membrane units 11 Membrane Case 12 Drainage line 20 Membrane element 21 Filter plate 22 Separation membrane 30 Cutter unit 31 Cutter Case 32 Cutter 32b cutting edge 40 Aeration unit 41 Aeration case 42 Air diffuser 61 Aerobic tank 62 Anaerobic tank 71 Filtration Screen 81 First Return Line 82 Second Return Line 83 Sewage transport line 100 Membrane separation equipment

Claims

1. a plurality of membrane elements for filtering the water to be treated; an air diffuser provided below the membrane element; a separating device that is detachably provided below the membrane element and above the air diffuser; Equipped with The membrane element comprises: A filter plate extending in the vertical and width directions; a separation membrane provided on the surface of the filter plate; and The plurality of membrane elements are arranged in parallel at predetermined intervals in the thickness direction of the membrane elements, The air diffuser diffuses air from below the plurality of membrane elements, The cutting device has a plurality of elongated cutters with cutting edges facing downward, The membrane separation device, wherein the plurality of cutters are arranged in parallel at intervals corresponding to the predetermined intervals in the thickness direction of the cutters, and the respective cutters are arranged in series below the membrane element.

2. The membrane separation apparatus according to claim 1 , wherein the longitudinal direction of the cutter is the same as the width direction of the membrane element.

3. The membrane separation device according to claim 2 , wherein the cutting edges of the plurality of cutters are provided at both lower ends in the thickness direction of the cutters.

4. The membrane separation apparatus according to claim 2 , wherein the plurality of cutters include a cutter having a thickness thinner than a thickness of the membrane element.

5. The membrane separation apparatus according to claim 2 , wherein the plurality of cutters include cutters made of resin.

6. the plurality of cutters include composite cutters; The composite cutter comprises: A resin cutter body, a metal blade portion provided on the cutter body and having the cutting edge; The membrane separation device according to claim 2 ,

7. The membrane separation device according to claim 2 , wherein the plurality of cutters include a cutter whose cutting edge is inclined in the vertical direction.

8. A treatment tank having one or more membrane separation devices according to any one of claims 2 to 6; a supply line that supplies the water to be treated to the treatment tank; a pre-filtration device provided in the supply line; a return line for returning the water to be treated in the treatment tank from the treatment tank to the pre-filtration device; Equipped with The pre-filtration device filters the water to be treated.

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