Membrane bio reactor system

Abstract

An MBR system is provided. An MBR system according to one embodiment of the present invention comprises a membrane filtration tank, a filtration unit including a filter element installed inside the membrane filtration tank, a filtered water storage tank, an air tank storing air supplied to the filtration unit, a flow path unit including a first flow path connecting the filtration unit and the filtered water storage tank and a second flow path connecting the filtration unit and the air tank, a valve unit including a first valve located on the first flow path and opening and closing the first flow path and a second valve located on the second flow path and opening and closing the second flow path, and a pressure reduction unit, wherein raw water is permeated from the outside to the inside of the filter element through a pressure difference between the outside and inside of the filter element formed by driving the pressure reduction unit to produce filtered water, and the produced filtered water is transferred to the filtered water storage tank through the first flow path, and air stored in the air tank is transferred to the filter element through the second flow path, and the transferred air is passed from the inside to the outside of the filter element to remove contaminants on the filter element contaminated by the first operation The second operation for removal constitutes a single cycle and is performed repeatedly. Accordingly, it is possible to operate the water treatment for a long time while minimizing functional degradation, such as an increase in differential pressure due to increased contamination of the flat membrane filter element during wastewater treatment, and to minimize or prevent the loss of filtered water that occurs when cleaning the filter element using the filtered water produced during the cleaning of the flat membrane.

Description

Technology Field

[0001] The present invention relates to an MBR system, and more specifically, to an MBR system using a flat membrane filter device. Background Technology

[0002] Due to rapid industrial development and the concentration of the population in cities, the volume of wastewater discharged from residential areas and industrial facilities is increasing. Accordingly, various wastewater treatment facilities are being developed to treat wastewater economically and efficiently.

[0003] Typically, wastewater treatment facilities are equipped with multiple filters containing filter elements for filtering wastewater, but pollutants filtered from the wastewater remain on the surface of the filter elements after filtering the wastewater.

[0004] However, if a filter element contaminated with pollutants is continuously operated, the differential pressure across the membrane increases significantly, leading to a substantial decrease in filtration efficiency; in severe cases, this can result in a situation where water treatment operation itself becomes impossible.

[0005] To address these issues, conventional methods have involved periodically cleaning filter elements by either injecting air onto the membrane surface to remove contaminants or using chemical cleaning methods, such as applying cleaning agents like citric acid to the filtration tank where the filter element is located. However, in the case of membrane cleaning using air, even with high air injection pressure, it is difficult to remove contaminants located inside the membrane rather than just on the surface; moreover, this method can lead to physical damage to the membrane surface.

[0006] In addition, chemical cleaning presents problems such as increased costs and water pollution due to the use of chemicals, as well as concerns regarding chemical damage to the membrane caused by the chemicals.

[0007] To address this problem, a cleaning method has been proposed that removes contaminants present not only on the membrane surface but also within the membrane to the outside by passing uncontaminated water in the opposite direction to the filtration direction of the raw water through the membrane. The water-based cleaning method has the advantage of not causing chemical damage to the membrane and ensuring no water pollution during the cleaning process. However, when using water for cleaning, filtered water is typically used, and since the water is passed in the opposite direction to the filtration direction at a pressure approximately 1.5 to 3 times higher than the filtration flow rate, the consumption of filtered water used for cleaning is high, leading to a problem of reduced filtered water production. In particular, if the cleaning cycle is set short to maintain membrane performance for an extended period, the decrease in filtered water production can be a critical issue for securing the flow rate.

[0008] Furthermore, conventional flat membranes often employ a multilayer structure in which multiple filter elements are stacked. However, if water is passed in the opposite direction to the filtration flow rate at a pressure higher than the filtration rate, a high pressure may be instantaneously applied to the contaminated flat membrane. This can cause interlayer separation in the multilayer flat membrane, raising concerns that the membrane's filtration function may be lost.

[0009] Accordingly, there is an urgent need to develop an MBR system that enables long-term water treatment operation while minimizing the functional degradation of flat membranes during the treatment of raw water such as sewage, wastewater, and sewage using filter modules employing flat membranes, and can minimize or prevent the loss of filtered water produced during the cleaning of the flat membranes. Prior art literature

[0010] Registered Patent Publication No. 10-1242080 The problem to be solved

[0011] The present invention has been devised in consideration of the above points, and aims to provide an MBR system that enables long-term water treatment operation while minimizing the functional degradation of the filter element during raw water treatment using the filter element, and can increase the efficiency of filtered water production by preventing or minimizing the use of produced filtered water during the cleaning of the filter element. means of solving the problem

[0012] To achieve the above objectives, the present invention comprises a membrane filtration tank for holding raw water having an activated sludge concentration of 3,000 to 15,000 mg / ℓ; a filtration unit including a filter element installed inside the membrane filtration tank to filter the raw water; a filtered water storage tank disposed outside the membrane filtration tank for storing filtered water produced from the filtration unit; an air tank storing air supplied to the filtration unit to remove contaminants on the surface of the filter element; a flow path unit including a first flow path connecting the filtration unit and the filtered water storage tank and a second flow path connecting the filtration unit and the air tank; a valve unit including a first valve located on the first flow path for opening and closing the first flow path and a second valve located on the second flow path for opening and closing the second flow path; and a pressure reducing unit located on the first flow path between the filtered water storage tank and the first valve, wherein the raw water from the outside of the filter element through the pressure difference between the outside and inside of the filter element formed by driving the pressure reducing unit The present invention provides an MBR system comprising a cycle in which a first operation is performed by permeating into the interior to produce filtered water and transferring the produced filtered water to a filtered water storage tank through a first flow path while a first valve is open and a second valve is closed, and a second operation is performed by closing the first valve and opening the second valve to transfer air stored in an air tank to a filter element through a second flow path, and passing the transferred air from the interior to the exterior of the filter element to remove contaminants on the filter element contaminated by the first operation, and said cycle is repeated.

[0013] According to one embodiment of the present invention, the valve section further includes a third valve connected to the outside air on a first flow path between the first valve and the filter section, and the cycle may further include a third operation in which, after the second operation ends, the second valve is closed and the third valve is opened to ventilate the air remaining in the filter section due to the second operation to the outside air.

[0014] In addition, the first operation can be performed such that the membrane filtration flow rate is 10 to 40 LMH.

[0015] In addition, the air pressure in the second operation above may exceed 100 kPa.

[0016] In addition, the side opposite to the side connected to the air tank is connected to a predetermined point on the first flow path between the first valve and the filter section, and is connected to the filter section via the first flow path, and during the second operation, the filtered water remaining on the first flow path between the first valve and the filter section and the second flow path between the second valve and the filter section passes from the inside to the outside of the filter member together with air to remove contaminants on the filter member. At this time, the pressure of the air may be 10 to 100 kPa.

[0017] In addition, the average pore size of the raw water side surface of the filter member may be 0.5㎛ or less.

[0018] In addition, the first operation may be performed for 5 to 15 minutes at a membrane filtration flow rate of 10 to 40 LMH, the second operation may be performed for 10 to 60 seconds with air at a pressure of 10 to 100 kPa, and the third operation may be performed for 10 to 120 seconds.

[0019] In addition, when operating for the first time at a membrane filtration flow rate of 20 LMH, the differential pressure of the filtration section may fluctuate to 10 kPa or less compared to the initial differential pressure after 100 days.

[0020] In addition, the filtration unit is a flat membrane type filter device comprising a filter assembly in which a plurality of flat membrane filter units are integrated via a connecting bar, and at least one common collection member for collecting filtered water discharged from the plurality of filter units. The filter unit comprises a flat membrane filter member having a filtration flow from the outer side to the inner side on both surfaces, and a support frame coupled to the edge side of the filter member to support the filter member, having a flow path through which filtered water produced through the filter member flows in and out, and a receiving port formed therein for discharging the filtered water. The common collection member can be connected to match one-to-one with the receiving port provided in each of the plurality of filter units.

[0021] In addition, the filter member may include a plate-shaped first support and a fiber web formed of nanofibers disposed on both sides of the first support.

[0022] In addition, the fiber web can be attached to one surface of the first support through heat fusion via a second support that is thinner than the first support.

[0023] In addition, the first support and the second support may be a sheath-core type composite fiber composed of a core portion which is polypropylene and a sheath portion which is polyethylene with a melting point of 60 to 180°C. Effects of the invention

[0024] According to the present invention, water treatment operation can be performed for a long time while minimizing functional degradation, such as increased differential pressure due to increased contamination of the filter element during raw water treatment, and filtered water production efficiency can be increased by minimizing or preventing the loss of filtered water that occurs when washing the filter element using the produced filtered water during washing. Brief explanation of the drawing

[0025] FIG. 1 is a schematic diagram showing a sewage treatment system according to one embodiment of the present invention, FIG. 2 is a schematic diagram of a flat membrane filter device according to an embodiment of the present invention used in the wastewater treatment system of FIG. 1, showing a state in which one of a plurality of filter modules is separated from the main frame. FIG. 3 is a drawing showing a filter module according to an embodiment of the present invention, FIG. 4 is an enlarged view showing the coupling relationship between the gap adjustment member and the fastening bar in FIG. 3. FIG. 5 is a drawing showing a different form of a receiving port in a filter module according to one embodiment of the present invention. FIG. 6 is a drawing showing a filter unit according to an embodiment of the present invention. FIG. 7 is a cross-sectional view of the frame applied to FIG. 6, FIG. 8 is a diagram showing the path of flow of filtered water into the receiving port side in a filter unit according to an embodiment of the present invention, and FIGS. 9 to 13 are graphs of wastewater treatment results operated through a wastewater treatment system according to various embodiments of the present invention and a wastewater treatment system according to various comparative examples. Specific details for implementing the invention

[0026] Hereinafter, embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein. In the drawings, parts unrelated to the explanation have been omitted to clearly explain the present invention, and the same reference numerals are assigned to identical or similar components throughout the specification.

[0028] Referring to FIG. 1, an MBR system (1000) according to one embodiment of the present invention comprises: a membrane filtration tank (410) for holding raw water; a filtration unit (300) installed inside the membrane filtration tank to filter the raw water; a filtered water storage tank (420) disposed outside the membrane filtration tank (410) and storing filtered water produced from the filtration unit (300); an air tank (430) storing air supplied to the filtration unit (300) to remove contaminants on the surface of a filter member inside the filtration unit (300); a flow path (720) including a first flow path (721) connecting the filtration unit (300) and the filtered water storage tank (420) and a second flow path (722) connecting the filtration unit (300) and the air tank (430); a first valve (610) located on the first flow path (721) and opening and closing the first flow path (721); and It includes a valve section comprising a second valve (620) located on the second flow path (722) and opening and closing the second flow path (722), and a pressure reduction section (520) located on the first flow path (721) between the filtered water storage tank (420) and the first valve (610). Additionally, it may further include a raw water supply flow path and a raw water supply pump (510) for introducing raw water into the membrane filtration tank (410). Additionally, it may further include a filtered material discharge flow path and a filtered material discharge pump (530) capable of transporting foreign substances remaining after the raw water is filtered through the filtration section (300) to the outside of the membrane filtration tank (410), and a discharge control valve (630) may be further provided on the filtered material discharge flow path so that the filtered material discharge flow path is opened only when the filtered material is discharged.

[0029] An MBR system (1000) according to one embodiment of the present invention can be operated in such a manner that a set is formed and the system is operated by repeatedly performing a first operation in which raw water is passed from the outside to the inside of a filter member through a pressure difference between the outside and inside of a filter member formed by driving the pressure reduction unit (520) to produce filtered water, and the produced filtered water is transferred to a filtered water storage tank (420) through a first flow path (721) while the first valve (610) is open and the second valve (620) is closed, and the air stored in the air tank (430) is transferred to the filter member through a second flow path by closing the first valve (610) and opening the second valve (620), and the transferred air is passed from the inside to the outside of the filter member to remove contaminants on the filter member contaminated by the first operation.

[0031] First, the raw water to be treated is sewage with an activated sludge concentration of 3,000 to 15,000 mg / ℓ, and, for example, sewage that has flowed into a conventional sewage treatment plant may be pretreated through an aeration tank employing an aeration pipe before flowing into the membrane filtration tank (410). In addition, the sewage may be rainwater, sewage, wastewater, or a mixture of two or more of these. The raw water may be supplied to the membrane filtration tank (410), for example, through a raw water supply pump (510).

[0032] In addition, the above membrane filter tank (410) has an internal space capable of accommodating incoming raw water and may be a membrane filter tank installed in a conventional sewage treatment plant.

[0033] In addition, a filter unit (300) for filtering the incoming raw water is disposed in the internal space of the membrane filtration tank (410). The filter unit (300) may be any known filter device used in an MBR system without limitation, but as an example, it may be a flat membrane type filter device employing a filter member that is a flat membrane as shown in FIGS. 2 to 8.

[0034] For example, a filtration unit (300) which is a flat membrane type filter device may be equipped with at least one filter module (200) as shown in FIG. 2, and the filter module (200) may include a filter assembly (210) in which a plurality of filter units (100) are integrated via a fastening bar as shown in FIG. 3 to 5, at least one common collecting member (230) for collecting filtered water discharged from the plurality of filter units (100), and a fixed frame (220).

[0035] Referring to FIGS. 6 to 8, the filter unit (100) may include a filter member (110) and a support frame (120) coupled to the edge side of the filter member (110), and may further include a spacing adjustment member (130, 130').

[0036] The above filter member (110) is a member for filtering foreign substances contained in sewage, and a known filter member may be used. However, the above filter member (110) may be designed to have a filtration flow from the outer side, which is the two surfaces, to the inner side, which is the inner part of the filter member (110). As an example of being designed to have such a filtration flow, the above filter member (110) may be in the form of a plate in which a fiber web (112) formed of nanofibers is arranged on both sides of a first support (111).

[0037] At this time, the fiber web (112) is intended to filter out foreign substances contained in the raw water as the raw water passes into the filter member (110) by the pressure reduction unit (520), and the first support body (111) can support the fiber web (112) and serve as a passageway for the filtered water produced by the fiber web (112).

[0038] At this time, the filter member (110) may be formed as a three-layer structure in which the fiber web (112) is directly attached to both sides of the first support (111), but as shown in FIG. 6, it may also be formed as a five-layer structure in which the fiber web (112) is attached to each side of the first support (111) via the second support (113).

[0039] Here, the thickness of the first support (111) is thicker than the thickness of the second support (113) and the fiber web (112), respectively. For example, the thickness of the first support (111) may account for more than 90% of the total thickness of the 3-layer or 5-layer structure filter member (110), and through this, it may be easy to provide a supporting force that prevents damage or deformation of the filter member (110) even when a large pressure is applied to the filter member (110) during the first operation, which is a filtration process, or the second operation, which is a washing process, described later.

[0040] Meanwhile, in a three-layer structure, the first support (111) can be attached to the fiber web (112) through heat fusion. However, if the first support (111) occupies most of the total thickness of the filter member (110), heat at a high temperature exceeding the heat capacity of the first support (111) must be applied for a long time while the fiber web (112) is placed on both sides of the first support (111) to partially melt the surface of the first support (111), which may cause unintended deformation or damage to the fiber web (112). However, in the case of a five-layer structure, the first support (111) and the fiber web (112) are attached through a second support (113) which is much thinner than the first support, thereby preventing the fiber web (112) from melting or deforming.

[0041] For example, the fiber web (112) can be attached to the first support (111) via the second support (113) through heat fusion, ultrasonic fusion, high-frequency fusion, etc. At this time, the second support (113) may be formed of a composite fiber consisting of a core portion which is a support fiber and a sheath portion which has a lower melting point than the support fiber and covers the outer surface of the support fiber, and can be easily and with better adhesion strength with the first support (111) and the fiber web (112) respectively by melting part or all of the sheath portion. For example, the above composite fiber may be a sheath-core type composite fiber composed of a core part made of polypropylene and a sheath part made of polyethylene with a melting point of 60 to 180°C. This has the advantage of minimizing interlayer separation or damage within the filter member (110) even with pressure changes during the first operation applied through the pressure reduction part (520) and high-pressure air applied during the second operation. In particular, in the case of a low-melting point composite fiber in which a polyester component with a different melting point is placed in the sheath part and the core part, respectively, even if attachment is possible under similar temperature conditions, attachment may not be easy due to the brittle characteristics of the material, or it may easily detach even if attached. In addition, there is a concern that interlayer separation may be accelerated by the pressure applied during the first and second operations.

[0042] In addition, the first support (111) may also be a member formed of a sheath-core type composite fiber composed of a core part made of polypropylene and a sheath part made of polyethylene with a melting point of 60 to 180°C, just like the second support (113). Through this, superior adhesion strength can be achieved by increasing compatibility between the first support (111) and the second support (113), and thus, interlayer separation can be further minimized during the first operation and the second operation.

[0043] The first support (111) and the second support (113) may be porous substrates capable of serving as passages through which filtered water produced by the fiber web (112) moves. For example, the first support (111) and / or the second support (113) may be any one of commonly used known fabrics, knits, or non-woven fabrics, and may be, for example, non-woven fabric.

[0044] Additionally, the thickness of the first support (111) may be, for example, 2 to 8 mm, more preferably 2 to 5 mm, and even more preferably 3 to 5 mm. If the thickness is less than 2 mm, it may not exhibit sufficient mechanical strength to withstand frequent washing. Additionally, if the thickness exceeds 8 mm, when the filter member is implemented as a filter unit described later and then assembled within a limited space to be implemented as a filter module, the density of the filter member per unit volume of the module may decrease.

[0045] Preferably, the first support (111) satisfies the thickness conditions described above, and at the same time, the basis weight may be 250 to 800 g / m², and more preferably 350 to 600 g / m². If the basis weight is 250 g / m², it may be difficult to achieve sufficient mechanical strength and there may be a problem of reduced adhesion with the second support, and if the basis weight exceeds 800 g / m², it may not form a sufficient flow path, resulting in reduced flow rate and a problem of difficulty in smooth cleaning due to increased differential pressure.

[0046] In addition, the second support (113) may be a nonwoven fabric, for example, and the fibers forming the second support (113) may have an average diameter of 5 to 30 μm. In addition, the thickness of the second support (113) may be 100 to 400 μm, more preferably 150 to 400 μm, even more preferably 150 to 250 μm, and for example, 200 μm.

[0047] Additionally, the second support (113) may have an average pore size of 20 to 100 μm and a porosity of 50 to 90%. However, it is not limited thereto.

[0048] In addition, the basis weight of the second support (113) may be 10 to 200 g / m², more preferably 35 to 200 g / m², and more preferably 35 to 80 g / m², and for example, 40 g / m². If the basis weight is less than 10 g / m², the amount of fibers forming the second support distributed at the interface formed with the fiber web described later may be small, and accordingly, the effective adhesive surface area of ​​the second support in contact with the fiber web may be reduced, making it impossible to achieve the desired level of bonding strength. In addition, it may not be possible to achieve sufficient mechanical strength to support the fiber web, and there may be a problem of reduced adhesion strength with the first support. In addition, if the basis weight exceeds 200 g / m², it may be difficult to secure the desired level of flow rate, and there may be a problem of difficulty in smooth backwashing due to increased differential pressure.

[0049] The fiber web (112) above is intended to filter out foreign substances contained in raw water and can be formed using nanofibers. For example, the nanofiber may include a fiber-forming component comprising polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF) and an emulsifying agent that improves the miscibility of the fiber-forming component. Here, the fiber-forming component may include polyacrylonitrile (PAN, hereinafter referred to as PAN) which has high hydrophilicity and polyvinylidene fluoride (PVDF, hereinafter referred to as PVDF) which has very high hydrophobicity. The mechanical strength and chemical resistance of the nanofiber can be ensured through PVDF, and the hydrophobicity of the nanofiber caused by PVDF can be prevented through PAN, and the hydrophilicity of the nanofiber can be improved, thereby enabling improved water permeability when the nanofiber is attached to a filter member.

[0050] Additionally, the nanofibers may have an average diameter of 0.05 to 1 μm and an aspect ratio of 1,000 to 100,000, but are not limited thereto. For example, the nanofibers provided in the fiber web (112) may include a first group of nanofibers with a diameter of 0.1 to 0.2 μm, a second group of nanofibers with a diameter of 0.2 to 0.3 μm, and a third group of nanofibers with a diameter of 0.3 to 0.4 μm, in amounts of 35 wt%, 53 wt%, and 12 wt%, respectively, with respect to the total weight of the fiber web (112).

[0051] In addition, the thickness of the fiber web (112) may be formed to be 0.5 to 200 μm, and for example, 20 μm. The porosity of the fiber web (112) may be 40 to 90%, and more preferably 60 to 90%. In addition, the average pore size may be 0.1 to 5 μm, and more preferably 0.1 to 3 μm, and for example, 0.25 μm. In addition, the basis weight of the fiber web (112) may be 0.05 to 20 g / m², and for example, 10 g / m², but is not limited thereto and may be appropriately changed considering the desired water permeability and filtration efficiency.

[0052] In addition, the fiber web (112) may be provided as a single layer or as multiple layers.

[0054] Meanwhile, the support frame (120) is positioned on the edge side of the filter member (110) described above and supports the edge side of the filter member (110), thereby allowing the filter member (110) to maintain a plate-like shape.

[0055] Such a support frame (120) may be made of a single member to support the edge side of the filter member (110) entirely or partially, but it may be implemented in a form in which a plurality of frames (120a, 120b) are combined to the edge side of the filter member (110).

[0056] For example, the plurality of frames (120a, 120b) may each be positioned on the edge side of the filter member (110) such that one end contacts the other end, and the end sides of two adjacent frames (120a, 120b) may be connected to each other through a spacing adjustment member (130, 130') positioned on the corner side of the filter member (110).

[0057] However, the shape of the support frame is not limited to this, and it may be changed to various shapes such as circular, arc-shaped, polygonal, and combinations thereof depending on the shape of the filter member (110), and it is noted that any shape is acceptable as long as it completely wraps around the edge of the filter member.

[0058] At this time, the support frame (120) performs the role of supporting the filter member (110) and also performs the role of a channel for moving the filtered water produced by the filter member (110) toward the receiving port (133) through the suction force provided from the pressure reduction unit (520).

[0059] To this end, each frame (120a, 120b) constituting the support frame (120) may be provided in a roughly 'C' shape with one side open, and a flow path (124) through which filtered water from the filter member (110) flows may be formed on the inside (see FIG. 7).

[0060] Specifically, the plurality of frames (120a, 120b) may include a plate-shaped first plate (121) and a pair of second plates (122, 123) extending in a vertical direction from each end of the first plate (121). Through this, the filter member (110) can be supported by the pair of second plates (122, 123) facing each other, by inserting the edge side into the space formed between the pair of second plates (122, 123). At this time, the edge side of the filter member (110) inserted into the space formed between the pair of second plates (122, 123) can be inserted at a certain distance from the first plate (121).

[0061] That is, a restraining member (125) for limiting the insertion depth of the filter member (110) may be provided on the opposing surfaces of a pair of second plates (122, 123) facing each other. Through this, during the process in which the edge side of the filter member (110) is fastened to each frame (120a, 120b), the insertion depth of the filter member (110) is limited through the restraining member (125), thereby allowing a predetermined space to be formed between the edge side end of the filter member (110) and the first plate (121).

[0062] Accordingly, when the filter member (110) and the frame (120a, 120b) are combined, the edge of the filter member (110) is always maintained separated from the first plate (121), thereby forming a flow path (124) through which filtered water produced through the first operation or air applied during the second operation can move.

[0063] In the present invention, the restraining member (125) may be formed on the opposing surfaces of a pair of second plates (122, 123) facing each other, but may also be formed only on the inner surface of one of the pair of second plates (122, 123). Additionally, the restraining member (125) may be provided entirely along the longitudinal direction of each frame or partially provided. Furthermore, when the restraining member (125) is formed on the opposing surfaces of a pair of second plates (122, 123) facing each other, each restraining member (125) is spaced apart with a predetermined gap so that filtered water can move toward the flow path (124) through the gap.

[0064] The above spacing adjustment member (130, 130') is coupled to the corner side of the support frame (120) to fasten two adjacent frames (120a, 120b) and simultaneously adjust the spacing between adjacent filter members (110).

[0065] Such spacing adjustment members (130, 130') may be provided in multiple numbers and may be coupled to the corner side of the support frame (120) to fix the ends of two adjacent frames (120a, 120b).

[0066] To this end, the spacing adjustment member (130, 130') may include a body (131) with one side open so that the end sides of adjacent frames (120a, 120b) can be inserted.

[0067] Accordingly, among the plurality of frames (120a, 120b) constituting the support frame (120), two frames (120a, 120b) adjacent to each other can be fixed by the body (131) by having their respective end portions inserted into the interior of the body (131).

[0068] For example, one end of one of two adjacent frames (120a, 120b) (120a) may be inserted into the first direction of the body (131), and the other end of the frame (120b) may be inserted into the second direction of the body (131) and positioned to come into contact with the end of the frame (120a) inserted into the first direction.

[0069] At this time, the flow path (124) formed in the frame (120a) inserted in the first direction and the flow path (124) formed in the frame (120b) inserted in the second direction are arranged to communicate with each other, so that all flow paths formed in each of the multiple frames (120a, 120b) can be communicated.

[0070] Here, the first direction and the second direction may be directions that are orthogonal to each other on the same plane, or directions that are inclined to have a predetermined angle with respect to a straight line on the same plane.

[0072] Meanwhile, the above-described filter unit (100) may be arranged in a plurality of parallels to each other, and a spacing adjustment member (132) may be provided so that each filter member (110) can be spaced apart.

[0073] The above-mentioned spacing adjustment member (132) may be provided in at least one of the plurality of frames (120a, 120b) constituting the support frame (120), but may also be provided in at least one of the spacing adjustment members (130, 130').

[0074] For example, the spacing adjustment member (132) may include an extension plate and a spacing member having a fastening hole (132b) formed therein, and may be formed on one side of the spacing adjustment member (130, 130') (see FIG. 8).

[0075] Specifically, the extension plate may extend outwardly from the body (131) of the spacing adjustment member (130, 130'), and a fastening hole (132b) through which the fastening bar (240) passes may be formed. Here, although the drawing shows the fastening hole (132b) being formed in a circular shape through the extension plate, it is not limited thereto and may have a shape corresponding to the cross-sectional shape of the fastening bar (240). For example, the fastening hole (132b) may be formed in a circular, arc-shaped, polygonal cross-section, or a combination thereof.

[0076] At this time, the spacing member may protrude a certain height from one side of the extension plate to have a predetermined thickness, and the spacing member may be provided to completely or partially surround the edge of the fastening hole (132b).

[0077] Here, the spacing member may be formed on each side of the extension plate (132a), may be formed only on one side of the extension plate (132a), or may be formed as a multi-stage structure having different heights from one side of the extension plate (132a).

[0078] Here, the spacing between multiple filter members (110) arranged parallel to each other can be arranged to have a spacing of 3 mm or more, but is not limited thereto, and can be arranged to have various spacings by appropriately changing the height or thickness of the spacing members.

[0079] Through this, when a plurality of filter units (100) according to the present invention are connected to each other via a connecting bar (240), even if each filter unit (100) is completely in close contact, the filter members (110) arranged parallel to each other can be spaced apart at a predetermined distance through the spacing member. As a result, the filter module (200) can produce filtered water by allowing raw water to exist on both sides of each filter member (110), thereby moving raw water from the outside of both sides of the filter member (110) to the inside of the filter member (110) by the suction force provided from the pressure reduction unit (520).

[0080] In addition, when a second operation is performed to remove foreign substances attached to the filter member (110) after the first operation, the foreign substances attached to the filter member (110) may fall into the space between adjacent filter members (110) after being separated from the filter member (110).

[0081] Meanwhile, at least one of the above spacing adjustment members (130, 130') may be provided with a receiving port (133) for discharging filtered water moved along a flow path (124) formed in each frame (120a, 120b) to the outside.

[0082] That is, among the plurality of spacing adjustment members (130, 130') coupled to the corners of the support frame (120), the spacing adjustment member (130') that does not have the receiving port (133) formed therein performs only the role of connecting a pair of adjacent frames, whereas the spacing adjustment member (130) that has the receiving port (133) formed therein can also perform the role of an outlet that discharges the filtered water produced through the receiving port (133) to the outside.

[0083] These receiving ports (133) can be connected to the common collecting member (230 in FIG. 3) to be described later.

[0084] Here, the receiving port (133) may be provided in only one of the multiple spacing adjustment members (130, 130'), but it is advantageous to provide equal suction pressure toward the filter member (110) by providing it in each of the two spacing adjustment members (130).

[0085] In addition, the receiving port (133) may be formed integrally with the body (131) of the gap adjustment member (130), but a coupling hole may be formed in the body and a receiving port having a predetermined length may be detachably coupled to the coupling hole. That is, the receiving port may be provided as a hollow type having a predetermined length and may be screw-coupled or snap-coupled to the coupling hole formed in the body. Accordingly, if it is necessary to change or replace the receiving port during operation, only the receiving port can be easily detached to replace or change it.

[0086] At this time, when the spacing adjustment member (130) having the receiving port (133) formed therein is combined with two adjacent frames (120a, 120b), a collection space (134) may be formed that communicates with the flow paths (124) formed in each of the two frames (120a, 120b), and the collection space (134) may be formed at a position that communicates with the receiving port (133).

[0087] For example, the collection space (134) may be formed at the end of the two frames (120a, 120b) inserted into the spacing adjustment member (130) when the spacing adjustment member (130) having the receiving port (133) formed therein is combined with the two frames (120a, 120b), and the collection space (134) may be formed by cutting the end of one of the two frames (120a, 120b) inserted into the spacing adjustment member (130) so that they do not fit together.

[0088] Accordingly, the filtered water that travels along the flow path (124) formed in one of the two frames (120a, 120b) and the filtered water that travels along the flow path (124) formed in the other frame (120b) meet each other in the collection space (134) and can be discharged to the outside through the receiving port (133) connected to the collection space (134).

[0089] As a result, the filtered water produced by moving from the outside to the inside of the filter member (110) by the suction force provided from the pressure reduction unit (520) during the first operation flows into each of the flow paths (124) formed in the plurality of frames (120a, 120b), moves along the flow path (124) toward the collection space (134), and can be discharged to the outside through the receiving port (133).

[0090] Meanwhile, during the second operation, air pressurized through the depressurization unit (520) can be supplied to each of the flow paths (124) formed in the plurality of frames (120a, 120b) after being introduced through the receiving port (133) and passing through the collection space (134).

[0091] Meanwhile, the above-described filter unit (100) can be configured into a single modular filter module (200) by having a plurality of them arranged parallel to each other and fixed to each other via a fastening bar (240).

[0092] For example, the filter module (200) may include a filter assembly (210), a fixed frame (220), and a common collection member (230) as shown in FIG. 3.

[0093] The filter assembly (210) described above may be in a form in which multiple filter units (100) are provided and arranged in parallel with each other, and integrated through a single fastening bar (240) having a predetermined length.

[0094] At this time, the filter assembly (210) can secure a predetermined space between the filter members (110) facing each other by spacing adjacent filter members (110) apart through a spacing member provided in each filter unit (100). In addition, if a fixing member (242), such as a nut, is fastened to both sides of the fastening bar (240), the gap formed between each filter unit (100) can be maintained uniformly.

[0095] The fixed frame (220) may be connected to both ends of the fastening bar (240) and integrated with the filter assembly (210). Such a fixed frame (220) may be made of a plate-shaped member, but may be provided as a frame structure so that raw water can flow into the filter assembly (210).

[0096] For example, the fixed frame (220) may include a front frame (221) and a rear frame (222) respectively positioned on the front and rear of the filter assembly (210), and both ends of the fastening bar (240) may be connected to the front frame (221) and the rear frame (222), respectively. Accordingly, the filter assembly (210) and the fixed frame (220) may be integrated through the fastening bar (240).

[0097] Here, the front frame (221) and the rear frame (222) may be provided with a fastening hole (not shown) into which the end of the fastening bar (240) is inserted, and may be inserted by a fitting method, or a through hole (not shown) penetrating the front frame (221) and the rear frame (222) may be provided so that both ends of the fastening bar (240) pass through and may be fixed through a separate fixing member.

[0098] At this time, a separate handle (223) may be provided on one side of the fixed frame (220) so that a user or worker can easily attach the modular flat filter module (200).

[0099] Additionally, each member constituting the front frame (221) and the rear frame (222) may be a plate-shaped bar having a predetermined width and length, an 'I' beam, an 'L' beam, or provided in the form of a square tube.

[0100] In this way, the flat membrane type filter module (200) according to the present invention may have a plurality of filter units (100) arranged parallel to each other, and the filter member (110) provided in each filter unit (100) may be arranged in a state spaced apart at a predetermined interval through a spacing member. Accordingly, suction force provided from the outside, for example, suction force provided from a pressure reduction unit (520), is transmitted to the plurality of filter units (100) through each receiving port (133), thereby enabling the production of filtered water individually from the plurality of filter units (100) in a single process.

[0101] As a result, filtered water can be produced in large quantities simultaneously through multiple filter units (100), and the production efficiency of the filtered water can be increased.

[0102] The above common collection member (230) is intended to transmit suction force to each filter unit (100) so that filtered water can be produced simultaneously in each filter unit (100) through a single suction process, and to integrate the filtered water produced in each filter into one.

[0103] That is, the common collection member (230) is connected to the receiving port (133) provided in each filter unit (100) so that suction force is simultaneously transmitted to each filter unit, and filtered water is individually produced in each filter unit (100) through the transmitted suction force, and the filtered water produced in each filter unit (100) can be integrated by flowing into the common collection member (230) via the collection space (134) and the receiving port (133) by the suction force.

[0104] In addition, the above common collection member (230) can perform the role of distributing high-pressure air to each filter unit (100) during the second operation.

[0105] Such a common collection member (230) may be provided as a single unit, but when multiple receiving ports (133) are provided in each filter unit, it may be provided to correspond to the number of receiving ports (133) and connected one-to-one with each receiving port (133).

[0106] For example, as illustrated in FIG. 3, when two receiving ports (133) are provided on the upper and lower sides of each filter unit (100), the common collecting member (230) may also be provided in two, and one of the two common collecting members (230) may be connected to the receiving port (133) located on the upper side and the other common collecting member (230) may be connected to the receiving port (133) located on the lower side.

[0107] A common collection member (230) such as this may include a main body (231) having a storage space (234) in which filtered water introduced from the receiving port (133) is temporarily collected, an inlet (232) for introducing filtered water discharged from the receiving port (133) into the storage space (234), and an outlet (233) for discharging the filtered water introduced into the storage space (234) to the outside (e.g., a filtered water storage tank (350)) or providing suction force provided from the outside to the receiving port (133).

[0108] Here, during the second operation to remove foreign substances attached to the filter member (110), the inlet (232) can function as an outlet that supplies high-pressure air to the filter unit (100), and the outlet (233) can function as an inlet that introduces high-pressure air provided from the outside to the common collection member (230).

[0109] At this time, the inlet port (232) may be provided in multiple numbers so as to be connected to each receiving port (133) provided in each filter unit (100), and the inlet port (232) and the receiving port (133) may be connected to each other in a one-to-one matching manner.

[0110] For example, the plurality of inlets (232) may be connected one-to-one with the receiving port (133) via a tube as shown in FIG. 3, or the receiving port (133) may be directly connected to the inlet (232') formed in the common collecting member (230') as shown in FIG. 5.

[0111] Here, when the receiving port (133) is directly connected to the inlet port (232') of the common collection member (230'), the inlet port (232') is formed in the shape of a hole on one side of the main body (231'), which has a storage space (234) where filtered water flowing in from the receiving port (133) is temporarily collected, so that the receiving port (133), which is formed to protrude to a predetermined length, can be directly inserted into the inlet port (232'). At this time, a sealing member (not shown) may be provided on the contact surface between the inlet port (232') and the receiving port (133) to prevent the filtered water from leaking to the outside.

[0112] Meanwhile, when the inlet port (232) and the receiving port (133) are connected via a tube, the common collecting member (230) may be positioned at the middle of the height of the fixed frame (220) so as to be spaced apart from the receiving port (133) at a predetermined distance.

[0113] This is because if the gap between the receiving port (133) and the inlet port (232) is too narrow, the tube may bend during the process of connecting the tubes, thereby hindering the smooth flow of filtered water.

[0114] In this way, the filter module (200) employed in the sewage treatment system according to the present invention allows filtered water to be produced simultaneously in each filter unit through a single suction process by connecting the common collection member (230) to the receiving port (133) provided in each filter unit (100), and also allows a second operation to remove foreign substances attached to each filter member (110) to be performed simultaneously. Furthermore, since a plurality of filter units (100) spaced apart at appropriate intervals through the spacing adjustment member (130, 130') are integrated and modularized, the installation work is not only simple, but the module unit can also be replaced, thus providing the advantage of easy maintenance.

[0116] Meanwhile, the filter module (200) may be provided as a single unit in the filtration unit (300), which is a flat membrane type filter device, but may also be provided as a plurality of units and supported through a main frame as shown in FIG. 2. The main frame is for supporting the filter module (200) and may be composed of a hollow frame structure having a main flow path (315) inside.

[0117] The main frame includes an upper main frame (311) positioned on the upper side of the filter module (200) to firmly support the filter module (200), and a lower main frame (312) positioned on the lower side of the filter module (200), and the upper main frame (311) and the lower main frame (312) can be interconnected via a plurality of support bars (313).

[0118] Through this, the mainframe can form a space for inserting and arranging at least one filter module (200).

[0119] At this time, a guide rail (314) may be provided on at least one side of the upper main frame (311) and the lower main frame (312) to support the corner side of the filter module (200) when the filter module (200) is inserted and to guide the sliding movement of the filter module (200).

[0120] For example, the guide rail (314) may be provided in the shape of an angle-type bar with an approximate 'L' shape and may be positioned in the same direction as the insertion direction of the filter module (200). Accordingly, when the filter module (200) is inserted, the corner side of the filter module (200) is supported, thereby allowing for smooth sliding movement.

[0121] Preferably, the guide rail (314) may be formed on the upper main frame (311) and the lower main frame (312), respectively, so that the upper corner and the lower corner of the filter module (200) can be supported simultaneously.

[0122] Meanwhile, a main channel (315) into which filtered water introduced from the filter module (200) is integrated may be formed inside at least one of the upper main frame (311) and the lower main frame (312).

[0123] For example, the main channel (315) may be formed inside any one of the multiple members constituting the lower main frame (312). Additionally, the lower main frame (312) may be provided with multiple fitting holes (316a, 316b) communicating with the main channel (315).

[0124] Here, the plurality of fittings (316a, 316b) serve as inlets and outlets for the inflow and outflow of filtered water, and some of the plurality of fittings (316a, 316b), such as 316a, may be interconnected with the discharge port (233) of the common collection member (230) via a connecting pipe (371). At this time, the connecting pipe (371) may be a rigid pipe member or a known tube made of a flexible rubber material.

[0125] And among the multiple fittings (316a, 316b), the remaining (316b) is connected to the filtered water storage tank (420) via the first Euro (721), so that the filtered water produced from each filter unit can be transferred to the filtered water storage tank (420) by the suction force provided through the pressure reduction unit (520) during the first operation.

[0126] Here, if the filter module (200) is provided as a single unit, the main frame (310) may be omitted, and in such a case, the outlet (233) of the common collection member (230) may be directly connected to the filtered water storage tank (420).

[0127] The above-mentioned pressure reduction unit (520) is located on the first flow path (721) and can provide suction power so that the filter unit (100) provided in each filter module (200) can produce filtered water. At this time, one side of the first flow path (721) may be connected to at least one of the fittings (316a, 316b) of the main frame (310), specifically to the fitting (316b).

[0128] That is, the suction force provided through the pressure reduction unit (520) in the first operation can be transmitted to the filter member (110) side through the main flow path (215), the common collection member (230), and the receiving port (133) via the flow path (124) formed in the plurality of frames (120a, 120b) constituting the support frame. Accordingly, raw water present around the filter unit (100) moves toward the filter member (110) by the suction force and is filtered through the fiber web (112). The filtered water that passes through the fiber web (112) and moves to the first support body (111) flows into the flow path (124) of the support frame by the suction force, moves toward the collection space (134), then moves toward the common collection member (230) through the receiving port (133) to be collected, and can be collected toward the filtered water storage tank (420) by passing through the main flow path (315) and the first flow path (721) of the main frame.

[0129] Accordingly, the sewage treatment system (1000) according to the present invention can produce a large amount of filtered water by having a plurality of filter units (100) operate simultaneously by means of the suction force provided through the pressure reduction unit (520) in the first operation.

[0131] In the sewage treatment system (1000) according to the present invention described above, the first operation is a filtration process using the filtration unit (300), which is the flat membrane type filter device described above. The filtration process is performed by making the pressure on the inner side, for example, near the first support body (111), lower than the pressure on the outer side, which is the two surfaces of the filter member (110), through the pressure reduction unit (520) described above, thereby forming the flow of raw water from the outer side to the inner side of the filter member (110). The produced filtered water can be transferred to a filtered water storage tank (420) through the first flow path (721) while the first valve (610) is open and the second valve (620) is closed.

[0132] At this time, the first operation can be performed such that the membrane filtration flow rate is 10 to 40 LMH, which has the advantage of increasing the production volume of filtered water and improving the efficiency of the subsequent second operation. If the flow rate is less than 10 LMH, the amount of filtered water obtained is small, and the efficiency of filtered water production may decrease. In addition, if the flow rate exceeds 40 LMH, the contamination of the filter element may worsen, and there is a concern that the efficiency of the second operation may decrease. More specifically, the first operation can be performed for 5 to 15 minutes such that the membrane filtration flow rate is 10 to 40 LMH; if it is performed for less than 5 minutes, the number and / or duration of the second operation increase during the set operation time, which may cause damage or deformation of the filter element and result in a smaller amount of filtered water obtained. In addition, if it is performed for more than 15 minutes, the number or duration of the second operation during the set operation time is reduced, making it difficult to achieve sufficient cleaning efficiency. Furthermore, there is a concern that the cleaning process may not be performed at the appropriate time, leading to contamination of the filter element with excessive foreign matter and making it more difficult to remove foreign matter from the filter element.

[0134] When the first operation described above is performed for a predetermined period of time, the first operation is stopped and the second operation is performed. The second operation is a cleaning process that removes contaminants within the filter member (110) by passing air from the inside to the outside of the filter member (110). Specifically, the first valve (610) is closed and the second valve (620) is opened to transfer air stored in the air tank (430) to the filter member (110) through the second flow path (722), and the transferred air is passed from the inside to the outside of the filter member (110) to remove contaminants on the filter member (110) contaminated by the first operation. The air stored in the air tank (430) may be supplied through an air supply unit (800), and the air supply unit (800) may be, for example, an air compressor.

[0135] According to one embodiment of the present invention, unlike that shown in FIG. 1, the second flow path (722) can be directly connected to the filtration unit (300), and a cleaning process can be performed by directly supplying air to the filter member (110) through the second flow path (722). At this time, the pressure of the air conveyed through the second flow path (722) may exceed 100 kPa. If the pressure is 100 kPa or less, foreign substances cannot be removed by air alone, and when using a filter member (110) with an average pore size of 0.8 μm or less, particularly an average pore size of 0.5 μm or less, the air pressure is low, making it difficult for the air to move from the inside of the filter member (110) to the outside surface, and as a result, the filter member may not be cleaned. Meanwhile, if the pressure exceeds 200 kPa, there is a risk that the filter member may be damaged or deformed by the air.

[0136] Meanwhile, according to a preferred embodiment of the present invention, when performing the second operation using only air, it is inevitably necessary to operate at a high pressure. In order to prevent damage or deformation of the filter member that may occur as a result and to more effectively remove foreign substances within the filter member (110), the filtered water remaining in the first flow path (721) between the first valve (610) and the filtration unit (300) that is closed after the first operation is completed can be passed through the filter member (110) along with air to perform a cleaning process. In this case, compared to the case where only air is used, there is an advantage that sufficient cleaning effect can be achieved even when low-pressure air is applied, while minimizing damage to the filter member (110). In other words, the second operation can be performed at a lower pressure compared to the case where the second operation is performed using only air. At this time, the pressure of the air may be 10 to 100 kPa, and more preferably 30 to 60 kPa. If air is supplied to the filter element along with the remaining filtered water, and the air pressure exceeds 100 kPa, there is a risk that the air passing through with the filtered water may cause damage or deformation to the filter element. In addition, if the pressure is less than 10 kPa, the air pressure is insufficient, and even if filtered water is used together, it may not produce a sufficient cleaning effect.

[0137] Meanwhile, in order for the filtered water remaining on the first flow path (721) to be supplied to the filter member (110) along with air, the second flow path (722) may be designed such that the side opposite to the one connected to the air tank (430) is connected to a predetermined point (P) on the first flow path (721) between the first valve (610) and the filter member (300), and thus the flow path (720) is connected to the filter member (300) via the first flow path (721). Through this, during the second operation, the filtered water remaining on the first flow path (721) between the first valve (610) and the filter member (300) and the second flow path (722) between the second valve (620) and the filter member (300) passes from the inside to the outside of the filter member (110) along with air, thereby effectively removing contaminants on the filter member at a lower air pressure.

[0139] The above second operation can be performed for 10 to 60 seconds, but if performed for less than 10 seconds, it is difficult to achieve a sufficient cleaning effect, and if performed for more than 60 seconds, it may cause damage or deformation of the filter member or the degree of improvement in cleaning effect may be minimal.

[0141] The first and second operations described above may be repeated continuously to form a cycle; preferably, the cycle may further include a third operation to ventilate the air remaining in the filtration section to the outside air due to the second operation. The third operation is a process to relieve the pressure applied to the inside of the filter member (110) due to the air filled in the second flow path (722) between the second valve (620) and the filtration section (300) due to the second operation. The third operation can be performed by appropriately employing a known method for relieving pressure within the second flow path (722), and for example, the pressure within the second flow path (722) can be relieved using a third valve installed within the second flow path (722). If the first operation is performed after the second operation without the third operation, the air remaining in the first flow path during the first operation may be sucked into the pressure-applying means, causing the pressure-applying means to fail to operate properly or extending the time required for operation, thereby reducing the efficiency of filtered water production. Meanwhile, as in the design of the flow path (720) shown in FIG. 1 according to a preferred embodiment of the present invention described above, if one side of the second flow path (722) is connected to the first flow path (721), the third operation can ventilate the air filled in the first flow path (721) between the first valve (610) and the filter section (300) together with the outside air. In addition, in this case, it may be more efficient to install the third valve (640) on the first flow path (721).

[0143] Meanwhile, an MBR system (1000) according to one embodiment of the present invention, which performs water treatment by repeatedly performing the first operation and the second operation, or the first to third operation described above, can improve the fluctuation of differential pressure occurring in the filter member (110) during water treatment operation due to contamination of the filter member (110). In order to further minimize or prevent the fluctuation of differential pressure, the average pore size of both sides of the filter member (110), for example, the fiber web (112), may be 0.5㎛ or less, and more preferably 0.3㎛ or less. If the average pore size exceeds 0.5㎛, membrane contamination occurs more easily and frequently, whereas it is difficult to remove foreign matter accumulated in the pores of the filter member (110), which lowers the efficiency of the second operation, and there is a concern that the range of differential pressure fluctuation may be large or the differential pressure fluctuation may not be stable.

[0145] According to one embodiment of the present invention, the MBR system (1000) effectively removes foreign matter within the filter element (110), thereby minimizing differential pressure fluctuations and ensuring stable fluctuations even when operation continues. For example, when operating for the first time at a membrane filtration flow rate of 20 LMH, after 100 days, the differential pressure of the filtration unit (300) can fluctuate to 10 kPa or less compared to the initial differential pressure, allowing for very stable treatment of large-scale sewage for a long time. In addition, washing is not performed using the produced filtered water, and even when it is used, only a small amount of filtered water remaining in the flow path is utilized, so the efficiency of filtered water production can be greatly improved compared to cases where washing is performed using filtered water.

[0147] <Preparation Example 1>

[0148] A flat membrane filter device as shown in FIG. 2 was implemented. Specifically, the filter member within the filter unit employed in the filter device was used in which a second support was placed on both sides of a first support, a fiber web formed of nanofibers was placed on the upper surface of each of the second supports, and each of these was attached by heat fusion, and specifically, a filter member manufactured by the following method was used. In addition, the effective membrane area of ​​the implemented filter device was prepared to be 2.5 m² and 16 m², respectively.

[0149] Specifically, to manufacture a fiber web, 12 g of polyvinylidene fluoride (Arkema, Kynar 761) as a fiber-forming component was dissolved in 88 g of a mixed solvent of dimethylacetamide and acetone in a weight ratio of 70:30 using a magnetic bar at a temperature of 80°C for 6 hours to prepare a spinning solution. The spinning solution was introduced into the solution tank of an electrospinning device and extruded at a speed of 15 µl / min / hole. At this time, the temperature of the spinning section was maintained at 30℃ and the humidity at 50%, the distance between the collector and the spinning nozzle tip was set to 20 cm, and a nonwoven fabric (Namyang Nonwoven Fabric Co., Ltd., CCP40) with a thickness of about 200 μm and a basis weight of 40 g / m² was placed on the upper part of the collector as a second support, formed from a low-melting point second composite fiber with an average diameter of 20 μm, having a polyethylene with a melting point of about 120°C as the sheath and a polypropylene as the core. Then, a voltage of 40 kV was applied to the spinning nozzle pack using a high-voltage generator, and at the same time, an air pressure of 0.03 MPa was applied per spinning pack nozzle to manufacture a laminate having a fiber web formed of PVDF nanofibers with an average diameter of 250 nm on one side of the second support. The manufactured fiber web was formed into nanofibers with an average diameter of 250 nm by including a first group of nanofibers with a diameter of 0.1 to 0.2 μm, a second group of nanofibers with a diameter of 0.2 to 0.3 μm, and a third group of nanofibers with a diameter of 0.3 to 0.4 μm in amounts of 35 wt%, 53 wt%, and 12 wt%, respectively, with a basis weight of 10 g / m², a thickness of 13 μm, an average pore size of 0.3 μm, and a porosity of about 75%.

[0150] Next, the solvent and moisture remaining in the fiber web of the laminate were dried, and a calendering process was performed by applying heat and pressure at a temperature of 140°C or higher and 1 kgf / ㎠ to heat-fuse the second support and the nanofiber web. As shown in Fig. 6, the second support and the nanofiber web of the manufactured laminate were heat-fused and bonded, and the nanofiber web was realized as a three-dimensional network structure.

[0151] Subsequently, the laminate was arranged so that the second support faced both sides of the first support in the manufactured laminate. At this time, the first support used a nonwoven fabric (Namyang Nonwoven Fabric, NP450) with a thickness of 5 mm, a basis weight of 450 g / m² formed from a low-melting point first composite fiber with a diameter of approximately 30 μm, having a polyethylene sheath with a melting point of approximately 120°C and a polypropylene core. Subsequently, a filter member was manufactured by applying heat of 140°C and a pressure of 1 kgf / cm².

[0153] <Preparation Example 2>

[0154] A flat membrane filter device with an effective filtration area of ​​2.5 m² was implemented by performing the same procedure as in Preparation Example 1. However, the fiber web used had a basis weight of 6 g / m², a thickness of 13 μm, an average pore size of 0.8 μm, and a porosity of approximately 70%.

[0156] <Example 1>

[0157] As shown in Fig. 1, an MBR system was configured, and specifically, a flat membrane filter device according to Preparation Example 2 was placed in the membrane filtration tank as a filtration unit, and raw water with a concentration of approximately 12,000 mg / ℓ was introduced into the membrane filtration tank. The raw water was treated for 5.8 days by performing the following first to third operations as a set. Specifically, the first operation was performed for 10 minutes through the pressure reduction unit so that the membrane filtration flow rate became 15 LMH. The filtered water obtained during the first operation was stored in the filtered water storage tank through the first flow path. Subsequently, the first operation was stopped, the first valve was closed, and the second valve was opened to transfer air from the air tank to the second flow path. Then, the second operation was performed for 20 seconds to allow the air to pass from the inside to the outside of the filter element via the first flow path along with the filtered water remaining in the flow path. At this time, the air pressure was set to 50 kPa. Afterwards, the second operation was stopped and the third valve was opened to perform the third operation, which involves releasing air remaining in the filter member, etc., for 120 seconds.

[0159] <Comparative Example 1>

[0160] The procedure was carried out in the same manner as Example 1, but the second and third operations were omitted. Specifically, the first operation was performed for 10 minutes, followed by a 140-second rest, and then the first operation was performed again.

[0162] <Experimental Example 1>

[0163] The membrane filtration flow rate and membrane differential pressure according to the water treatment operation in Example 1 and Comparative Example 1 were measured at the start, and the results are shown in Fig. 9 below.

[0165] As can be seen from Fig. 9, in Comparative Example 1, in which the second operation was not performed, it can be seen that after 5.8 days, the differential pressure fluctuated by more than 10 kPa compared to the initial filtration pressure. However, in Example 1, in which the second operation was performed using air, it can be seen that the differential pressure fluctuation remained stable at less than 5 kPa even after 5.8 days.

[0167] <Example 2>

[0168] As shown in Fig. 1, an MBR system was configured, and specifically, a flat membrane filter device with an effective filtration area of ​​2.5 m² according to Preparation Example 1 was placed in a membrane filtration tank, and raw water with a concentration of approximately 12,000 mg / ℓ was introduced into the membrane filtration tank. The raw water was treated for 8.8 days by performing the following first to third operations as a set. Specifically, the first operation was performed for 10 minutes through a pressure reduction unit so that the membrane filtration flow rate became 20 LMH. The filtered water obtained during the first operation was stored in a filtered water storage tank through the first flow path. Subsequently, the first operation was stopped, the first valve was closed, and the second valve was opened to transfer air from the air tank to the second flow path. Then, the second operation was performed for 10 seconds to allow the air to pass from the inside to the outside of the filter element via the first flow path along with the filtered water remaining in the flow path. At this time, the air pressure was set to 30 kPa. Afterwards, the second operation was stopped and the third valve was opened to perform the third operation, which involves releasing air remaining in the filter member, etc., for 110 seconds.

[0170] <Example 3>

[0171] Water treatment was performed in the same manner as in Example 2, but a flat membrane filter device according to Preparation Example 2 was used, and during the second operation, the air pressure was set to 50 kPa for 15 seconds, and the third operation was performed for 120 seconds.

[0173] <Experimental Example 2>

[0174] The membrane filtration flow rate and membrane differential pressure according to the water treatment operation in Examples 2 and 3 were measured at the start, and the results are shown in Figure 10 below.

[0176] As can be seen through Fig. 10, it can be confirmed that the flat membrane filter device of Example 2 shows a stable differential pressure change compared to Example 3 during water treatment, and in particular, the fact that it showed a lower differential pressure change even when the second operation was performed at a lower pressure indicates that it is more optimized for the water treatment operating conditions of the sewage treatment system of the present invention.

[0178] <Example 4>

[0179] A flat membrane filter device with an effective filtration area of ​​2.5 m² according to Preparation Example 1 was placed in a membrane filtration tank, and raw water with a concentration of approximately 12,000 mg / ℓ was introduced into the membrane filtration tank. The raw water was treated for 15.6 days by performing the following first to third operations as a set. Specifically, the first operation was performed for 9 minutes so that the membrane filtration flow rate became 25 LMH through a pressure application means. The filtered water obtained during the first operation was stored in a filtered water storage tank through the first flow path. Subsequently, the first operation was stopped, the first valve was closed, and the second valve was opened to transfer air from the air tank to the second flow path. Then, the second operation was performed for 12 seconds so that the air passed from the inside to the outside of the filter element via the first flow path along with the filtered water remaining in the flow path. At this time, the air pressure was set to 30 kPa. Afterwards, the second operation was stopped, and the third operation was performed to release the air remaining in the filter member, etc. for 48 seconds.

[0181] <Comparative Example 2>

[0182] Example 1 was performed in the same manner for water treatment, but without injecting air during the second operation, the filtered water stored in the filtered water storage tank was passed from the inside to the outside of the filter element at 48 LMH using a pressure pump separately installed on the first flow path, and the second operation was performed for 1 minute, and the first and second operations were repeated for 15.6 days without performing the third operation.

[0184] <Experimental Example 3>

[0185] The membrane filtration flow rate and membrane differential pressure according to the water treatment operation in Example 4 and Comparative Example 2 were measured at the start, and the results are shown in Fig. 11 below.

[0187] As can be seen through Fig. 11, it can be confirmed that Comparative Example 2 and Example 4, in which the second operation was performed using filtered water, showed similar differential pressure changes, and through this, it can be seen that there is a similar level of cleaning effect.

[0189] In addition, the results of the water treatment for Example 4 and Comparative Example 2 are as shown in Table 1 below.

[0190] item Example 4 Comparative Example 2 First process time (minutes) 9 9 Second process time (minutes) 0.2 1 3rd process time (minutes) 0.8 0 Total daily driving times 144.0 144.0 Total daily first driving time (minutes / day) 1296.0 1296.0 Total daily second driving time (minutes / day) 28.8 144.0 Total daily 3rd driving time (minutes / day) 115.2 0.0 Total daily driving time (minutes / day) 1440.0 1440.0 Unit area (m²) 2 Daily filtered water volume (m) per ) 3 / Day) 1.35 1.35 Unit area (m²) 2 Daily required amount of filtered water for the second operation per ) (m 3 / Day) 0.0 0.28 Unit area (m²) 2 Daily discharge volume per ) (m 3 / Day) 1.35 1.07 Membrane filtration operating rate (%) 90.00 90.00 Membrane filtration recovery rate (%) 100.0 79.6

[0191] As can be seen from Table 1

[0192] In the case of Comparative Example 2, it can be seen that the filtered water recovery rate is significantly reduced by about 20% compared to Example 4, and it can be seen that Example 4 shows a washing effect similar to Comparative Example 2 but is very excellent in terms of filtered water production efficiency.

[0194] <Example 5>

[0195] A pilot wastewater treatment system as shown in Fig. 1, capable of treating 12 m³ per day, was prepared within a public wastewater treatment plant located in Paju-si, Gyeonggi-do. A flat membrane filter device with an effective filtration area of ​​16 m² according to Preparation Example 1 was installed in a membrane filtration tank, and raw water was introduced. The raw water was treated for 103 days by performing the following first to third operations as a set. Specifically, the first operation was performed for 9 minutes with the membrane filtration flow rate reaching 25 LMH through a pressure reduction unit. The filtered water obtained during the first operation was stored in a filtered water storage tank via the first flow path. Subsequently, the first operation was stopped, the first valve was closed, and the second valve was opened to transfer air from the air tank to the second flow path. Then, the second operation was performed for 12 seconds, allowing the air to pass from the inside to the outside of the filter element via the first flow path along with the filtered water remaining in the flow path. At this time, the air pressure was set to 30 kPa. Afterward, the second operation was stopped, and the third operation was performed to release air remaining in the filter element, etc., for 48 seconds. As a result of the operation for 103 days, the activated sludge concentration in the raw water was maintained at 11,400 to 12,000 mg / L.

[0197] <Comparative Example 3>

[0198] The procedure was carried out in the same manner as Example 5, but the second and third operations were omitted, and specifically, the first operation was repeated by performing the first operation for 9 minutes, resting for 60 seconds, and then performing the first operation again.

[0200] <Experimental Example 3>

[0201] The membrane filtration flow rate and membrane differential pressure according to the water treatment operation in Example 5 and Comparative Example 3 were measured at the start, and the results are shown in Fig. 12 below.

[0203] As can be seen through Fig. 12, in the case of Comparative Example 3, which is labeled as the second series and did not perform a cleaning process of the filter element through the second operation, the filtration pressure rose to -60kPa after about 67 days of operation and the operation was stopped, and it can be confirmed that the operation can be restarted after performing a cleaning process of the filter element using chemicals.

[0204] Meanwhile, in the case of Example 5, which is labeled as Series 1, the change in membrane differential pressure was only -8 kPa when the filtration pressure was 2 kPa after 103 days of operation starting from an initial filtration pressure of 10 kPa, and it can be confirmed that the membrane differential pressure is maintained stably.

[0206] In addition, when checking the removal rate of E. coli and SS in the filtered water obtained after 30 days of sewage treatment operation according to Example 5, it was found that suspended solids (SS) and E. coli were not detected, indicating excellent filtration efficiency.

[0208] <Example 6>

[0209] In order to verify the allowable membrane filtration flow rate during the first operation, the same procedure as in Example 5 was performed, but the filtration flow rate during the first operation was changed to 35 LMH, and wastewater treatment was performed for about 15 days.

[0211] <Experimental Example 4>

[0212] The membrane filtration flow rate and membrane differential pressure according to Example 6 were measured at the start of the water treatment operation, and the results are shown in Fig. 13 below.

[0214] As can be seen through Fig. 13, in the case of Example 6, labeled as the second series, it can be confirmed that the membrane differential pressure is stably maintained even when the membrane filtration flow rate is changed from 25 LMH to 35 LMH.

[0216] <Examples 7 ~ 8>

[0217] Wastewater treatment was performed by repeating the first to third operations, with the same procedure as in Example 4, but including an additional process of adjusting the first flow path equipment so that no filtered water remains in the first flow path between the first and second operations, thereby transferring all the filtered water in the first flow path to the filtered water tank. In this case, the air pressure in Example 7 was the same as in Example 4, and the air pressure in Example 8 was adjusted to 60 kPa.

[0219] <Experimental Example 5>

[0220] The membrane filtration flow rate and membrane differential pressure according to the water treatment operation of Examples 4 and 7 were measured at the start, and the changes in membrane differential pressure after 5 days and 15 days are shown in Table 2 below.

[0221] Example 4 Example 7 Example 8 Membrane filtration flow rate (LMH) during first operation 25 25 25 Whether filtered water remains in the first euro after the first operation existence doesn't exist doesn't exist Air pressure (kPa) during second operation 30 30 60 Change in pressure difference (kPa) After 5 days Less than 5 Less than 5 Less than 5 After 15 days Less than 5 Up to 9.5 Up to 6.8

[0223] As a result of the evaluation, in the case of Example 1, the differential pressure fluctuation remained below 5 kPa until 15 days had passed, whereas in the case of Examples 7 and 8, the differential pressure change remained below 5 kPa for about 5 days, and then after 15 days, the differential pressure fluctuations reached 9.5 kPa and 6.8 kPa, respectively. This indicates that when performing the second operation by passing air without filtered water in the first flow path, a higher air pressure must be applied to reduce the change in membrane differential pressure. However, in the case of Example 4, even though the second operation was performed with an air pressure of 30 kPa, the change in membrane differential pressure was stably maintained below 5 kPa. This indicates that the efficiency of the second operation can be improved when passing a small amount of filtered water remaining in the first flow path and air together through the filter element.

[0225] Although an embodiment of the present invention has been described above, the concept of the present invention is not limited to the embodiments presented in this specification. Those skilled in the art who understand the concept of the present invention may easily propose other embodiments within the scope of the same concept by adding, changing, deleting, or adding components, and such embodiments shall also be considered to fall within the scope of the concept of the present invention. Explanation of the symbols

[0226] 100: Filter unit 110: Filter element 200,200': Filter module 300: Filtration section 1000: MBR system

Claims

Claim 1 A membrane filtration tank for holding raw water having an activated sludge concentration of 3,000 to 15,000 mg / ℓ; for filtering the raw water, the membrane filtration tank is installed inside the membrane filtration tank and comprises a plate-shaped first support and a fiber web formed of nanofibers disposed on both sides of the first support, wherein the average pore size of the fiber web on the raw water side surface is 0.A filtration unit comprising a filter element having a size of 5㎛ or less; a filtered water storage tank disposed outside the membrane filtration tank and storing filtered water produced from the filtration unit; an air tank storing air supplied to the filtration unit to remove contaminants on the surface of the filter element; a flow path unit comprising a first flow path connecting the filtration unit and the filtered water storage tank, and a second flow path connecting the filtration unit and the air tank, wherein the side opposite to the side connected to the air tank is in communication with a predetermined point on the first flow path between the first valve and the filtration unit and is connected to the filtration unit via the first flow path; a valve unit comprising a first valve located on the first flow path and opening and closing the first flow path, a second valve located on the second flow path and opening and closing the second flow path, and a third valve connected to the outside air on the first flow path between the first valve and the filtration unit. A pressure reducing unit located on a first flow path between the filtered water storage tank and a first valve; wherein raw water is permeated from the outside to the inside of a filter member through a pressure difference between the outside and inside of a filter member formed by driving the pressure reducing unit to produce filtered water, and the produced filtered water is transferred to the filtered water storage tank through the first flow path while the first valve is open and the second valve is closed; a second operation in which the first valve is closed and the second valve is opened to transfer air stored in an air tank to the filter member through the second flow path, and the transferred air passes from the inside to the outside of the filter member together with the filtered water remaining on the first flow path between the first valve and the filtering unit and the second flow path between the second valve and the filtering unit to remove contaminants on the filter member contaminated by the first operation; and after the second operation is completed, the second valve is closed and the third valve is opened to ventilate the air remaining in the filtering unit due to the second operation to the outside air. An MBR system in which a third operation constitutes a cycle and is performed repeatedly, wherein the first operation is performed at a membrane filtration flow rate of 10 to 40 LMH, and the air pressure in the second operation is 30 to 60 kPa. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 An MBR system according to claim 1, characterized in that the first operation is performed for 5 to 15 minutes, the second operation is performed for 10 to 60 seconds, and the third operation is performed for 10 to 120 seconds. Claim 9 An MBR system according to claim 1, characterized in that, during the first operation at a membrane filtration flow rate of 20 LMH, the differential pressure of the filtration section changes to 10 kPa or less compared to the initial differential pressure after 100 days. Claim 10 In claim 1, the filtration unit is a flat membrane type filter device comprising a filter assembly in which a plurality of filter units are integrated via a connecting bar and at least one common collecting member for collecting filtered water discharged from the plurality of filter units, wherein the filter unit comprises a flat membrane filter member having a filtration flow from the outer side to the inner side, a support frame coupled to the edge side of the filter member to support the filter member, a flow path through which filtered water produced through the filter member flows in and out, and a receiving port formed for discharging the filtered water, and wherein the common collecting member is connected to match one-to-one with the receiving port provided in each of the plurality of filter units. Claim 11 delete Claim 12 In claim 1, the fiber web is attached to one surface of the first support through heat fusion via a second support having a thinner thickness than the first support. Claim 13 An MBR system according to claim 12, characterized in that the first support and the second support are sheath-core type composite fibers composed of a core portion of polypropylene and a sheath portion of polyethylene having a melting point of 60 to 180°C.

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