Water treatment apparatus and method of operating a water treatment apparatus

Abstract

A water treatment apparatus and a method of operating the water treatment apparatus, including: a first membrane filtration device; a second membrane filtration device provided at a subsequent stage of the first membrane filtration device; a storage tank that stores a portion of permeated water that has permeated the first membrane filtration device; a circulation flow path provided between the first membrane filtration device and the storage tank, which enables the permeated water stored in the storage tank to circulate between the first membrane filtration device and the storage tank; a pump provided in the circulation flow path; and a control unit that, after completion of filtration membrane cleaning in conjunction with air introduction to the first membrane filtration device, controls the pump to circulate the permeated water stored in the storage tank between the first membrane filtration device and the storage tank via the circulation flow path.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2022-72081, filed on April 26, 2022, the contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to a water treatment device and a method for operating the water treatment device. Background Technology

[0003] For example, membrane filtration devices are widely used in pure water production and wastewater recycling as mechanisms for removing turbidity or organic matter. One example of a membrane filtration device is the apparatus described in Patent Document 1. Depending on the object being separated, microfiltration membranes (MF membranes) or ultrafiltration membranes (UF membranes) are used; typically, the former has pores of approximately 0.1 μm, while the latter has pores of 0.005 μm to 0.5 μm.

[0004] For example, water treatment equipment that includes a UF membrane device and a reverse osmosis (RO) membrane device is known as a filtration membrane device. The UF membrane device and the RO membrane device each include a UF membrane and an RO membrane, respectively. In such water treatment equipment, pure water is produced by removing turbidity components from the raw water using a UF membrane and then desalinating it using an RO membrane. Figure 7 An example of this type of water treatment equipment is shown in the figure.

[0005] exist Figure 7 The water treatment equipment 201 shown includes a raw water tank 202, a UF membrane device 203, an RO membrane device 204, and a permeate tank 205. Additionally, in Figure 7 In the water treatment equipment 201 shown, a relay tank 206 and a dirt removal filter 207 are provided between the UF membrane unit 203 and the RO membrane unit 204. The reasons for the installation of these devices will be described below. These devices are connected by flow paths L202-L204, L206, and L207, respectively. Furthermore, a supply path L209 is connected to the relay tank 206, which supplies cleaning water to the primary or secondary side of the UF membrane unit 203.

[0006] An air supply system 210 is connected to the UF membrane device 203 to supply air to the UF membrane device 203, and a cleaning water discharge system 211 is connected to discharge the cleaning water after cleaning.

[0007] Pumps P202, P206, P207, and P209 are respectively installed in flow paths L202, L206, L207, and L209. Pumps P206 and P207 are configured as booster pumps. Pumps P202 and P207 are respectively equipped with Variable Voltage and Variable Frequency (VVVF) inverter devices 216 and 217. Additionally, flow meters 226 and 227 are installed in flow paths L203 and L204. The flow measurement results obtained by flow meters 226 and 227 are output to VVVF inverter devices 216 and 217. VVVF inverter units 216 and 217 are configured to control pumps P202 and P207 based on flow measurement results.

[0008] exist Figure 7 In the water treatment equipment 201 shown, when cleaning the UF membrane of the UF membrane unit 203, air is used for cleaning, and air remains inside the UF membrane unit 203. Air-based cleaning is performed by supplying air to the UF membrane unit 203 from the air supply system 210. Alternatively, UF membrane treated water, used as cleaning water, may be supplied from the relay tank 206 simultaneously with the air supply.

[0009] When pure water production is restarted while air remains inside the UF membrane unit 203, the treated water (hereinafter referred to as UF membrane treated water) passing through the UF membrane contains air bubbles. If this UF membrane treated water containing air bubbles is supplied to pump P207, pump P207 will malfunction. Therefore, as described above, the existing water treatment equipment 201 is equipped with a relay tank 206 and a sludge filter 207. The relay tank 206 is an open-type tank.

[0010] Relay tank 206 stores the UF membrane-treated water after passing through UF membrane unit 203. Since relay tank 206 is designed to be open, air bubbles mixed into the UF membrane-treated water are degassed in relay tank 206. Additionally, relay tank 206 serves as a buffer for adjusting the amount of water supplied to RO membrane unit 204.

[0011] On the other hand, since the relay tank 206 is an open type, foreign matter can sometimes be mixed into the UF membrane treated water from the outside. Therefore, in order to prevent foreign matter from being mixed into the RO membrane unit 204, a dirt removal filter 207 is installed.

[0012] As explained above, in the existing water treatment equipment 201, a relay tank 206 and a dirt removal filter 207 must be installed between the UF membrane unit 203 and the RO membrane unit 204, which increases the number of machines and the installation space required for the water treatment equipment 201. This increased installation space becomes a significant problem, especially when a mobile water treatment equipment 201 is installed in a residential setting.

[0013] [Existing Technical Documents]

[0014] [Patent Literature]

[0015] Patent Document 1: International Publication No. 2020 / 194820 Summary of the Invention

[0016] [The problem the invention aims to solve]

[0017] The present invention was made in view of the above circumstances, and its object is to provide a water treatment device and a method of operating thereof that can reduce the installation space.

[0018] [Technical means to solve the problem]

[0019] To address the aforementioned issues, the present invention employs the following structure.

[0020] [1] A water treatment device, comprising: a first membrane filtration device;

[0021] The second membrane filtration device is installed after the first membrane filtration device;

[0022] A storage tank for storing a portion of the permeate water after passing through the first membrane filtration device;

[0023] A circulation path is provided between the first membrane filtration device and the storage tank, so that the permeate stored in the storage tank can circulate between the first membrane filtration device and the storage tank;

[0024] Pump, equipped in the circulation path; and

[0025] The control unit controls the pump after the filter membrane cleaning, which is accompanied by air introduction into the first membrane filter device, is completed, so that the permeate stored in the storage tank circulates between the first membrane filter device and the storage tank via the circulation path.

[0026] [2] According to the water treatment equipment described in [1], wherein the circulating flow path includes:

[0027] A first circulation path supplies the permeate water, after passing through the first membrane filtration device, to the storage tank; and

[0028] The second circulation path can supply the permeate stored in the storage tank to the primary side of the first membrane filtration device.

[0029] The pump is equipped in the second circulation path.

[0030] [3] The water treatment equipment according to [1] or [2], wherein the circulation flow path is a closed flow path and the storage tank is an open storage tank.

[0031] [4] According to the water treatment equipment described in [1] or [2], wherein the first membrane filtration device comprises a plurality of membrane filtration units connected in parallel with each other.

[0032] The circulating flow path can supply the permeate water to each membrane filtration unit.

[0033] The control unit causes the permeate stored in the storage tank to circulate between any of the membrane filtration units and the storage tank via the circulation path.

[0034] [5] A method of operating a water treatment device, the water treatment device comprising: a first membrane filtration device; a second membrane filtration device disposed after the first membrane filtration device; and a storage tank for storing a portion of the permeate water after passing through the first membrane filtration device, the method of operating the water treatment device comprising:

[0035] The water supply process involves supplying the permeate water filtered in the first membrane filtration device to the second membrane filtration device; and

[0036] In the cleaning process, midway through the water flow process, the filter membrane of the first membrane filter device is cleaned.

[0037] The cleaning process includes at least the following:

[0038] During the air cleaning stage, the filter membrane of the first membrane filter device is cleaned to remove the air used; and

[0039] In the degassing stage, after the air cleaning stage, the permeate water is allowed to pass through the primary side of the first membrane filter device, while the permeate water is circulated between the first membrane filter device and the storage tank through a circulation path.

[0040] [6] According to the operation method of the water treatment equipment described in [5], wherein the storage tank is configured as an open storage tank.

[0041] In the degassing process, the air discharged from the first membrane filtration device along with the permeate water is degassed in the storage tank.

[0042] [7] According to the operation method of the water treatment equipment described in [5] or [6], wherein the first membrane filtration device includes a plurality of membrane filtration units connected in parallel with each other.

[0043] The circulating flow path can supply the permeate water to each of the multiple membrane filtration units.

[0044] The cleaning process is performed on a portion of the multiple membrane filtration units, and the water flow process is performed on the remaining membrane filtration units.

[0045] [8] According to the operation method of the water treatment equipment described in [7], in the case of sequentially performing a cleaning process on the plurality of membrane filter units, a water flow process is performed on all membrane filter units between the preceding cleaning process for the membrane filter units and the subsequent cleaning process for the other membrane filter units.

[0046] [The effects of the invention]

[0047] The present invention provides a water treatment device and its operation method that can reduce the installation space. Attached Figure Description

[0048] Figure 1 This is a schematic diagram illustrating a water treatment device according to an embodiment of the present invention.

[0049] Figure 2 This is a schematic diagram illustrating the first membrane filtration device included in the water treatment apparatus according to an embodiment of the present invention.

[0050] Figure 3 This is a schematic diagram showing the main parts of the first membrane filtration device.

[0051] Figure 4A This is a schematic diagram illustrating the operation method of the water treatment equipment according to an embodiment of the present invention.

[0052] Figure 4B This is a schematic diagram illustrating the operation method of the water treatment equipment according to an embodiment of the present invention.

[0053] Figure 4C This is a schematic diagram illustrating the operation method of the water treatment equipment according to an embodiment of the present invention.

[0054] Figure 4D This is a schematic diagram illustrating the operation method of the water treatment equipment according to an embodiment of the present invention.

[0055] Figure 5A This is a schematic diagram illustrating the operation method of the water treatment equipment according to an embodiment of the present invention.

[0056] Figure 5BThis is a schematic diagram illustrating the operation method of the water treatment equipment according to an embodiment of the present invention.

[0057] Figure 5C This is a schematic diagram illustrating the operation method of the water treatment equipment according to an embodiment of the present invention.

[0058] Figure 5D This is a schematic diagram illustrating the operation method of the water treatment equipment according to an embodiment of the present invention.

[0059] Figure 6A This is a schematic diagram illustrating the operation method of the water treatment equipment according to an embodiment of the present invention.

[0060] Figure 6B This is a schematic diagram illustrating the operation method of the water treatment equipment according to an embodiment of the present invention.

[0061] Figure 7 This is a schematic diagram showing existing water treatment equipment.

[0062] [Explanation of Symbols]

[0063] 100: Water treatment equipment

[0064] 101: Original sink

[0065] 102: First membrane filtration device

[0066] 102A, 102B: Membrane filtration units

[0067] 103: Second membrane filtration device

[0068] 104: Water Treatment Tank

[0069] 105: Storage tank

[0070] L110: Circulating Flow Path

[0071] P3: Pump

[0072] 110: Control Department

[0073] L102, L104: First circulation path

[0074] L105: Second circulation path Detailed Implementation

[0075] The water treatment equipment and its operation method according to embodiments of the present invention will be described with reference to the accompanying drawings.

[0076] The water treatment apparatus 100 of this embodiment includes: a first membrane filtration device 102; a second membrane filtration device 103 disposed after the first membrane filtration device 102; a storage tank 105 for storing a portion of the permeate water after passing through the first membrane filtration device 102; a circulation path L110 disposed between the first membrane filtration device 102 and the storage tank 105; a pump P3 disposed in the circulation path L110; and a control unit 110. Furthermore, a raw water tank 101 is included before the first membrane filtration device 102. Furthermore, a treated water tank 104 is included after the second membrane filtration device 103. The water treatment apparatus 100 further includes: an air supply unit 107 for supplying air to the first membrane filtration device 102; and a cleaning water discharge unit 106 for discharging cleaning water from the first membrane filtration device 102.

[0077] In the water treatment apparatus 100 of this embodiment, raw water is filtered in the first membrane filtration device 102 to produce primary permeate water, and the primary permeate water is filtered in the second membrane filtration device 103 to produce secondary permeate water. A portion of the primary permeate water prepared by the first membrane filtration device 102 is temporarily stored in the storage tank 105. During the cleaning process of the first membrane filtration device 102, the primary permeate water is circulated between the first membrane filtration device 102 and the storage tank 105.

[0078] The various devices, flow paths, and auxiliary machines constituting the water treatment equipment 100 will be described in detail below.

[0079] exist Figure 1 The water treatment equipment 100 shown includes flow paths L101 to L107. These flow paths are designed to be closed. These flow paths connect the raw water tank 101, the first membrane filter 102, the second membrane filter 103, the treated water tank 104, the storage tank 105, the air supply unit 107, and the cleaning water discharge unit 106 to each other. In addition, valves V102 and V104 are provided in flow paths L102 and L104, respectively.

[0080] The circulation path L110 includes a first circulation path and a second circulation path. The first circulation path includes a portion of the flow path L102 and a flow path L104 branching from the flow path L102, supplying a portion of the primary permeate water prepared by the first membrane filtration device 102 to the storage tank 105. The second circulation path includes the flow path L105 and is capable of supplying the primary permeate water stored in the storage tank 105 to the primary side of the first membrane filtration device 102. Additionally, the circulation path L110 also includes the storage tank 105. A pump P3 is provided in the flow path L105 (second circulation path) for circulating the primary permeate water between the first membrane filtration device 102 and the storage tank 105. The circulation path L110 is configured as a closed-loop flow path.

[0081] Furthermore, as described later, the first membrane filtration device 102 includes a plurality of membrane filtration units 102A and 102B connected in parallel with each other. For this first membrane filtration device 102, the circulation path L110 can supply primary permeate water to the membrane filtration units 102A and 102B respectively.

[0082] Pumps P1 and P2 are respectively installed in flow paths L101 and L102. Pump P1 pressurizes the raw water and supplies it to the primary side of the first membrane filter 102. Pump P2 pressurizes the first-pass water and supplies it to the primary side of the second membrane filter 103. A VVVF inverter 113 is attached to pump P2. In addition, a flow meter 114 is installed in flow path L103. The flow rate measured by the flow meter 114 is output to the VVVF inverter 113. The VVVF inverter 113 is configured to control pump P2 based on the flow rate measurement result. Thus, the amount of water supplied to the second membrane filter 103 is controlled.

[0083] Storage tank 105 temporarily stores the primary permeate water prepared by the first membrane filtration device 102. Storage tank 105 forms part of the circulation path L110. Storage tank 105 is configured as an open type storage tank. Thus, in the operation method described later, when primary permeate water mixed with air bubbles is circulated, the air bubbles are degassed in storage tank 105.

[0084] like Figure 2 As shown, the first membrane filtration device 102 includes multiple membrane filtration units 102A and 102B connected in parallel with each other. Figure 2 The diagram shows two membrane filtration units 102A and 102B, but the number of membrane filtration units is not limited to two; it can also be three, four, or more than five.

[0085] Figure 3 An enlarged cross-sectional view of membrane filtration unit 102A is shown. Furthermore, the structure of membrane filtration unit 102B is the same as that of membrane filtration unit 102A. Figure 3 As shown, the membrane filtration unit 102A includes a container 1 arranged with the axis of the cylinder as the vertical direction (vertical direction in this embodiment). A plurality of hollow fiber membranes 2 are disposed inside the container 1.

[0086] The hollow fiber membrane 2 is fixed to the upper part of the container 1 by a synthetic resin potting section 3, which serves as a fixing part, but is not fixed to the lower part of the container 1. For example, epoxy resin can be used as the synthetic resin for the potting section 3. For instance, the hollow fiber membrane 2 is assembled into a U-shape, and both ends of the hollow fiber membrane 2 are fixed using the potting section 3. In this case, the middle part of the hollow fiber membrane 2 is located at the lower part of the container 1.

[0087] The hollow fiber membrane 2 is, for example, an ultrafiltration membrane (UF membrane). An example of a UF membrane is a membrane having pores of 0.005 μm to 0.5 μm. There are no particular limitations on the hollow fiber membrane 2; membranes with an inner diameter of 0.2 mm to 1.0 mm, an outer diameter of 0.5 mm to 2.0 mm, and an effective length of approximately 300 mm to 2500 mm can typically be used. There are also no particular limitations on the raw materials for the UF membrane; polyvinylidene fluoride (PVDF), polyethylene, polypropylene, etc., can be used. Furthermore, the UF membrane included in the first membrane filtration device 102 is not limited to a hollow fiber membrane; it can also be a spiral membrane, a tubular membrane, or a flat membrane.

[0088] A treated water chamber (permeable water chamber) 7 and a raw water chamber 10 are respectively formed on the upper and lower sides of the filling section 3. The upper end of the hollow fiber membrane 2 extends through the filling section 3, and its upper opening faces the treated water chamber 7. The interior of the hollow fiber membrane 2 is connected to the treated water chamber 7. When the hollow fiber membrane 2 is assembled into a U-shape, both ends of the hollow fiber membrane 2 extend through the filling section 3. In addition, the raw water chamber 10 is the primary side of the hollow fiber membrane 2, and the permeable water chamber 7 is the secondary side of the hollow fiber membrane 2.

[0089] The filling part 3 is, for example, disc-shaped, and its outer peripheral surface or outer peripheral edge contacts the inner surface of the container 1 in a watertight manner.

[0090] Inside container 1 (raw water chamber 10), a central tube 4 extends in a generally vertical direction (axial direction of container 1). The central tube 4 is arranged, for example, along the central axis of container 1. The central tube 4 is a circular tube closed at the front end (upper end), and on its side circumferential surface, a plurality of spray holes 4a are integrally provided, spanning vertically and spaced apart in the circumferential direction.

[0091] The height (length in the vertical direction) of the central tube 4 is not particularly limited, but it is preferable that the upper end of the central tube 4 is located near the lower surface of the potting section 3. Alternatively, the upper end of the central tube 4 may be embedded in the potting section 3.

[0092] The connection states of membrane filter unit 102A with flow paths L101, L102, L104 (first circulation flow path), L105 (second circulation flow path), L106 (L106a, L106b), and L107 (L107a, L107b) will be described below. The connection states of membrane filter unit 102B with each flow path are the same as those of membrane filter unit 102A.

[0093] The lower end of the central pipe 4 faces the opening 11 on the bottom surface of the container 1. A flow path L101 is connected to the opening 11, and a valve V101 is installed in the flow path L101. Flow paths L105 merge at a point on the container 1 side closer to the valve V101. Flow path L101 is connected to the raw water tank 101. During the water supply process, raw water is supplied from the raw water tank 101 to the interior of the container 1 (raw water chamber 10 (primary side)) through the flow path L101.

[0094] Flow path L105 (second circulation flow path) is connected to storage tank 105. During the cleaning process of the first membrane filtration device 102, primary permeate water (permeate water) is supplied from storage tank 105 to the interior of container 1 (raw water chamber 10 (primary side)) through flow path L105. The primary permeate water supplied to raw water chamber 10 is filtered by hollow fiber membrane 2 and sent to the outside of container 1 through permeate chamber 7.

[0095] By switching the opening and closing of valves V101 and V105, the supply of raw water / primary permeate water to container 1 can be switched. Raw water can be supplied from the lower part of the raw water chamber 10 by setting valve V101 to open and valve V105 to close, and by pumping raw water through flow path L101 using pump P1. Alternatively, primary permeate water can be supplied from the lower part of the raw water chamber 10 by setting valve V101 to close and valve V105 to open, and by pumping primary permeate water through flow path L105 using pump P3.

[0096] Additionally, a flow path L107a is connected to the opening 11, and a valve V107a is installed in the flow path L107a. Furthermore, a flow path L107b is connected to the lower part of the central pipe 4, and a valve V107b is installed in the flow path L107b. Flow paths L107a and L107b are branched from flow path L107. Flow path L107 is connected to the air supply unit 107. Thus, air is supplied from the air supply unit 107 to the interior of the container 1 (raw water chamber 10) via flow paths L107 and L107a. Additionally, air is supplied to the central pipe 4 via flow paths L107 and L107b.

[0097] By switching the opening and closing of valves V107a and V107b, the air supply path to container 1 can be switched. By setting valve V107a to open and valve V107b to close, air can be supplied from the lower side of the interior of container 1 (raw water chamber 10) via opening 11. Alternatively, by setting valve V107a to close and valve V107b to open, air can be supplied from the upper side of the interior of container 1 (raw water chamber 10) via central pipe 4. Furthermore, when the interior of container 1 (raw water chamber 10) is filled with water, air can be supplied via flow path L107a or flow path L107b, thereby also supplying air bubbles from opening 11 or central pipe 4 to perform foam cleaning of the hollow fiber membrane 2.

[0098] Furthermore, an upper outlet 8 is provided on the upper part of the side of container 1. The upper outlet 8 is located near the lower surface of the filling section 3. A flow path L106a is connected to the upper outlet 8, and a valve V106a is provided in the flow path L106a. In addition, a flow path L106b is connected to the opening 11, and a valve V106b is provided in the flow path L106b. Moreover, the flow paths L106a and L106b merge to form a flow path L106, which is connected to the drain trough 106a of the cleaning water discharge section 106. The cleaning water or air inside the container 1 (raw water chamber 10) is discharged through the flow paths L106a, L106b and L106.

[0099] By switching valves V106a and V106b on and off, the discharge path of either or both of the cleaning drainage or air from container 1 can be switched. By opening valve V106a and closing valve V106b, either or both of the cleaning drainage or air can be discharged from the upper side of container 1 via the upper discharge port 8. Alternatively, by closing valve V106a and opening valve V106b, either or both of the cleaning drainage or air can be discharged from the lower side of container 1 via opening 11. The cleaning drainage is conveyed to the drain tank 106a via flow path L106.

[0100] A primary permeate outlet 5 is provided at the top of container 1. A flow path L102 is connected to outlet 5. The primary permeate is taken out to the outside of container 1 via flow path L102 and is transported to the second membrane filter device 103. In addition, a flow path L107c branches off midway through flow path L102. A valve V107c is provided in flow path L107c. Flow path L107c is connected to air supply unit 107.

[0101] Furthermore, a branch flow path L104 branches off midway through flow path L102. A valve V102 is installed in flow path L102, which is located downstream of the branch point, and a valve V104 is installed in flow path L104. Flow path L104 is connected to storage tank 105.

[0102] With valve V107c closed, switching the opening and closing of valves V102 and V104 allows the primary permeate water to be supplied to either the second membrane filter 103 or the storage tank 105. During the water supply process, by opening valve V102 and closing valve V104, primary permeate water can be supplied to the second membrane filter 103. Conversely, during the cleaning process, by closing valve V102 and opening valve V104, primary permeate water can be supplied to the storage tank 105.

[0103] Furthermore, during the cleaning process, with valves V102 and V104 closed, valve V107c is opened, thereby supplying air into the interior of container 1 (through water chamber 7) via outlet 5. This allows for air backwashing of the hollow fiber membrane 2.

[0104] The flow path L102 needs to extend vertically to a certain length from the outlet 5 at the top of the container 1. Furthermore, the outlet 5 of the container 1 needs to be located at the very top of the container 1. In the operation method of this embodiment, during the degassing process, the air remaining in the container 1 needs to be discharged by circulating the primary permeate water. However, by extending the flow path L102 vertically to a certain length, its own buoyancy allows the air to be discharged from the container 1 towards the flow path L102 as early as possible.

[0105] then, Figure 1 The second membrane filtration device 103 shown produces secondary permeate by filtering primary permeate. The second membrane filtration device 103 includes a hollow fiber membrane 2. The hollow fiber membrane of the second membrane filtration device 103 may be, for example, a reverse osmosis membrane (RO membrane). There are no particular limitations on the raw materials for the RO membrane; cellulose acetate, aromatic polyamide, etc., can be used. Furthermore, the RO membrane included in the second membrane filtration device 103 is not limited to a hollow fiber membrane; it may also be a spiral membrane or a tubular membrane.

[0106] The treatment tank 104 stores the secondary permeate water prepared by the second membrane filtration device 103.

[0107] The cleaning water discharge unit 106 discharges the cleaning wastewater generated during the cleaning process of the first membrane filtration device 102. The first membrane filtration device 102 and the cleaning water discharge unit 106 are connected via a flow path L106. Figure 2 As shown, the cleaning water discharge section 106 includes a drain tank 106a for temporarily storing cleaning wastewater.

[0108] Air supply unit 107 supplies air to first membrane filter 102 during the cleaning process of first membrane filter 102. First membrane filter 102 and air supply unit 107 are connected via flow path L107.

[0109] After the filter membrane cleaning, which accompanies the air introduction into the first membrane filter unit 102, is completed, the control unit 110 controls the pump P3 to circulate the primary permeate water stored in the storage tank 105 between the first membrane filter unit 102 and the storage tank 105 via the circulation path L110. Additionally, the control unit 110 circulates the primary permeate water stored in the storage tank 105 between any one of the membrane filter units 102A, 102B and the storage tank 105 via the circulation path L110.

[0110] Next, the operation method of the water treatment equipment 100 of this embodiment will be described.

[0111] The operation method of the water treatment device 100 in this embodiment includes: a water supply process, in which primary permeate filtered in the first membrane filter 102 is supplied to the second membrane filter 103; and a cleaning process, in which the filter membrane of the first membrane filter 102 is cleaned during the water supply process. The cleaning process includes at least an air cleaning stage and a degassing stage. The air cleaning stage is to clean the filter membrane of the first membrane filter 102 with air. The degassing stage is to allow primary permeate to pass through the primary side of the first membrane filter 102 relative to the permeate membrane after the air cleaning stage, while circulating the primary permeate between the first membrane filter 102 and the storage tank 105.

[0112] The following is for reference Figures 1-3 The operation method of the water treatment equipment 100 will be explained in detail. Furthermore, the opening and closing of valves and the operation and stopping of pumps described below are all performed via commands from the control unit 110.

[0113] In the water supply process, Figure 1 Pumps P1 and P2 are activated, valve V102 is opened, and valve V104 is closed. This supplies raw water from the raw water tank 101 to the first membrane filtration unit 102 via flow path L101. The raw water is filtered by the UF membrane (hollow fiber membrane 2) included in the first membrane filtration unit 102 to become primary permeate water. The primary permeate water is then transported via flow path L102 to the second membrane filtration unit 103. At this time, the primary permeate water is pressurized by pump P2 located midway through flow path L102 and transported to the second membrane filtration unit 103. The primary permeate water is filtered by the RO membrane included in the second membrane filtration unit 103 to become secondary permeate water. The secondary permeate water is then transported via flow path L103 to the treated water tank 104.

[0114] Reference Figures 2 to 4D The operation of the first membrane filtration device 102 in the water supply process is described in detail.

[0115] In the water supply process, Figure 2 and Figure 3 In this configuration, valves V101 in flow path L101 and V102 in flow path L102 are set to open. Conversely, valves V105 in flow path L105 (second circulation flow path) and V104 in flow path L104 (first circulation flow path) are set to close. Furthermore, valves V107a to V107c in flow path L107 are set to close, and valves V106a and V106b in flow paths L106a and L106b are set to close.

[0116] Thus, raw water is supplied to both membrane filtration units 102A and 102B via flow path L101. The raw water is supplied to the raw water chamber 10 (primary side) of container 1 and filtered by hollow fiber membrane 2 to become primary permeate. The primary permeate is then extracted through hollow fiber membrane 2 and sent to the permeate chamber 7 (secondary side) of container 1. It is then conveyed to the second membrane filtration device 103 via flow path L102.

[0117] As the water flow process continues, turbidity, organic matter, and other contaminants (hereinafter referred to as turbidity) contained in the raw water gradually accumulate on the primary side of the hollow fiber membrane 2. Therefore, a cleaning process is performed to prevent clogging of the hollow fiber membrane 2.

[0118] A cleaning process is performed on any one of the multiple membrane filtration units 102A and 102B included in the first membrane filtration device 102, while a water-passing process is continuously performed on the other membrane filtration units. This allows the water-passing process to be performed continuously in parallel with the cleaning process, thus enabling uninterrupted preparation of primary permeate water. Even when there are three or more membrane filtration units, only one membrane filtration unit needs to be cleaned, while the remaining membrane filtration units continue to undergo water-passing processes. The following description focuses on the case where membrane filtration unit 102A is cleaned and membrane filtration unit 102B is continuously subjected to water-passing processes.

[0119] In the cleaning process of this embodiment, the air cleaning stage and the degassing stage are performed sequentially.

[0120] The air cleaning stage involves cleaning the hollow fiber membrane 2 (filter membrane) built into the first membrane filtration device 102 using working air. There are various types of air-based membrane cleaning. Examples include: air backwashing, which supplies air from the secondary side of the hollow fiber membrane 2; air cleaning, which supplies air to the primary side of the hollow fiber membrane 2 to clean it; and foam cleaning, which cleans the hollow fiber membrane 2 by blowing air into it while the primary side of the hollow fiber membrane 2 is filled with water. In the air cleaning stage of this embodiment, any one of air backwashing, air cleaning, and foam cleaning, or two or more, can be performed as air-based membrane cleaning. In addition to air-based membrane cleaning, water cleaning, which supplies cleaning water to the primary side of the hollow fiber membrane 2, can also be performed during the cleaning process.

[0121] The following is for reference Figures 2 to 5D An example of the air cleaning stage will be explained. In the example described below, the sequential air backwashing, water rinsing, and foam rinsing will be explained.

[0122] Figure 4AThe diagram shows the membrane filtration unit 102A in the process of continuous water flow. Raw water is supplied to the raw water chamber 10 (primary side) through the flow path L101, filtered through the hollow fiber membrane 2, and taken out as primary permeate to the permeate chamber 7 (secondary side), and discharged from the flow path L102. At this time, valves V101 and V102 are opened, and other valves are closed.

[0123] Furthermore, the valve in the other membrane filtration unit 102B is set to the same opening and closing state as that in membrane filtration unit 102A. The cleaning process for membrane filtration unit 102A will be described below, but the opening and closing state of the valve in membrane filtration unit 102B, during the continuous water flow process, remains unchanged.

[0124] The following describes the air cleaning stage of the cleaning process for membrane filter unit 102A. First, valve V101 of flow path L101 is closed to stop the supply of raw water, and valve V102 of flow path L102 is also closed. Additionally, valve V106b of flow path L106b is opened. Thus, as... Figure 4B As shown, the raw water filling the raw water chamber 10 (primary side) is discharged from the raw water chamber 10 through the flow path L106b. The discharged raw water is transported to the cleaning water discharge section 106.

[0125] Next, perform air backwashing on the hollow fiber membrane 2. Open valve V107c in flow path L107c. Set valve V106b in flow path L106b to remain open. Then proceed as follows... Figure 4C As shown, air is supplied from the air supply unit 107 to the permeate water chamber 7 (secondary side) via flow path L107c and flow path L102, allowing it to pass through the hollow fiber membrane 2, be taken out to the primary water chamber 10 (primary side), and discharged from the flow path L106b. This performs air backwashing of the hollow fiber membrane 2.

[0126] Next, the air supply from the air supply unit 107 is stopped. Thus, as... Figure 4D As shown, the air pressure in the permeable water chamber 7 and the original water chamber 10 is reduced to atmospheric pressure.

[0127] Next, primary permeate water is supplied to the primary side of the hollow fiber membrane 2 for water rinsing. Valve V107c in flow path L107c and valve V106b in flow path L106b are closed. Valve V105 in flow path L105 and valve V106a in flow path L106a are opened. Then, pump P3 is activated. Thus, as... Figure 5A As shown, primary permeate water is supplied from storage tank 105 to raw water chamber 10 (primary side) to clean the surface of the primary side of hollow fiber membrane 2. The cleaned primary permeate water is discharged as cleaning wastewater through gravity flow path L106a. By performing water cleaning, turbidity accumulated on the surface of the primary side of hollow fiber membrane 2 is removed.

[0128] Next, foam cleaning is performed on the primary side of the hollow fiber membrane 2. With the raw water chamber 10 filled with primary permeate water, valve V105 of flow path L105 is closed. Pump P3 is stopped. Valve V107b of flow path L107b is opened. Valve V106a of flow path L106a is set to remain open. Thus, as... Figure 5B As shown, air is supplied to the primary water chamber 10 (primary side) via gravity flow path L107b. The air is supplied to the central tube 4 via gravity flow path L107b and ejected into the primary water chamber 10 from the ejector hole 4a located in the central tube 4. Since the primary water chamber 10 remains filled with primary permeate water, the ejected air forms bubbles and contacts the surfaces of the hollow fiber membrane 2 facing the central tube 4, performing foam cleaning on the upper part of the hollow fiber membrane 2. The cleaning air, along with a portion of the cleaning wastewater, is discharged via gravity flow path L106a. The upper part of the hollow fiber membrane 2 is foam cleaned in this manner.

[0129] Next, foam cleaning continues on the primary side of the hollow fiber membrane 2. With the raw water chamber 10 filled with primary permeate water, valve V107b of flow path L107b is closed. Valve V107a of flow path L107a is opened. Valve V106a of flow path L106a is set to remain open. Thus, as... Figure 5C As shown, air is supplied to the primary water chamber 10 (primary side) via gravity flow path L107a. Air is supplied from the opening 11 at the bottom of the container 1. Since the primary water chamber 10 remains filled with primary permeate water, the supplied air forms bubbles and contacts the primary side surface of the hollow fiber membrane 2, performing foam cleaning on the lower part of the hollow fiber membrane 2. The cleaning air is discharged via gravity flow path L106a. Foam cleaning of the lower part of the hollow fiber membrane 2 is performed in this manner.

[0130] Next, valve V107a of flow path L107a is set to remain open, valve V106a of flow path L106a is closed, and valve V106b of flow path L106b is opened. Thus, as... Figure 5D As shown, the lower part of the hollow fiber membrane 2 is continuously foamed and cleaned, while the cleaning water in the raw water chamber 10 is discharged by gravity through the flow path L106b.

[0131] like Figures 5B to 5D As explained in the document, the entire hollow fiber membrane 2 can be foamed and cleaned by changing the air supply path.

[0132] Next, the degassing stage will be explained. Since air remains inside the membrane filter unit 102A of the first membrane filter 102 after the air cleaning stage, if the water flow process is restarted in this state, the primary permeate water containing air bubbles will be transported to the pump P2 and the second membrane filter 103 via the flow path L102. This could potentially cause malfunctions in the operation of the pump P2 and the second membrane filter 103 due to the air-filled primary permeate water. Therefore, in this embodiment, the degassing process completely removes air bubbles from inside the membrane filter unit 102A.

[0133] Specifically, first, valves V104 in flow path L104 (first circulation flow path) and V105 in flow path L105 (second circulation flow path) are set to open. Additionally, valve V106a in flow path L106a is also set to open. Valve V106b in flow path L106b is set to close, and valve V107a in flow path L107a is also set to close. Then, pump P3 is activated. Thus, as... Figure 6A As shown, primary permeate water is supplied from the storage tank 105 to the primary water chamber 10. A portion of the primary permeate water is discharged through the flow path L106b. The discharged primary permeate water is transported to the cleaning water discharge section 106. This allows the air remaining in the primary water chamber 10 to be discharged as early as possible, filling the primary water chamber 10 with primary permeate water.

[0134] Additionally, the remaining portion of the primary permeate water supplied to the raw water chamber 10 (primary side) permeates through the hollow fiber membrane 2 and is extracted from the permeate chamber 7 (secondary side). The extracted primary permeate water is returned to the storage tank 105 via the flow path L104. The returned primary permeate water is then transported again to the membrane filtration unit 102A via the flow path L105. In this manner, the circulation of primary permeate water using the circulating flow path is stabilized.

[0135] Next, valve V106a of flow path L106a is set to closed. Valve V104 of flow path L104 (first circulation flow path) and valve V105 of flow path L105 (second circulation flow path) are set to remain open, and pump P3 is also set to remain operational. Thus, as... Figure 6B As shown, the primary permeate stored in the storage tank 105 circulates between the storage tank 105 and the membrane filtration unit 102A through the circulation path L110.

[0136] Through the circulation of the primary permeate water, a primary permeate water flow is generated inside the container 1 of the membrane filtration unit 102A. Air bubbles remaining inside the container 1 are discharged through this water flow from the outlet 5 of the container 1 to the flow path L102. Here, the flow path L102 extends vertically to a certain length from the outlet 5 at the top of the container 1. Furthermore, since the outlet 5 of the container 1 is located at the very top of the container 1, the air bubbles remaining inside the container 1 can be discharged to the outside of the container 1 as early as possible by the buoyancy of the air itself.

[0137] The discharged air bubbles, along with the primary permeate water, are transported to the storage tank 105 via the flow path L104. Since the storage tank 105 is designed to be open, the air bubbles arriving at the storage tank 105 are immediately degassed.

[0138] In this manner, the air introduced into the interior of the membrane filter unit 102A during the air cleaning stage can be almost completely discharged through the degassing stage.

[0139] After the cleaning process is completed, the membrane filtration unit 102A can be quickly moved to the water circulation process.

[0140] Alternatively, multiple membrane filtration units can be cleaned sequentially. That is, the cleaning process for other membrane filtration units 102B can certainly begin after the cleaning process for membrane filtration unit 102A is completed. However, if the cleaning process for other membrane filtration units 102B begins immediately after the cleaning process for membrane filtration unit 102A is completed, the supply of primary permeate water will fluctuate significantly, disrupting the balance between the supply of primary permeate water and the production of secondary permeate water in the second membrane filtration device 103, which may cause the operation of the second membrane filtration device 103 to become unstable.

[0141] Therefore, when performing sequential cleaning processes on multiple membrane filter units, it is preferable to perform a water-passing process on all membrane filter units between the preceding cleaning process for one membrane filter unit and the subsequent cleaning process for other membrane filter units. That is, the cleaning process for membrane filter unit 102B can begin after the cleaning process for membrane filter unit 102A is completed and membrane filter unit 102A is moved to the water-passing process. While membrane filter unit 102A is being moved to the water-passing process, a water-passing process is also being performed in membrane filter unit 102B. In this way, the next cleaning process can be performed once all membrane filter units have been moved to the water-passing process.

[0142] As explained above, the water treatment apparatus 100 according to this embodiment includes a circulation path L110, a pump P3, and a control unit 110 that circulates primary permeate stored in a storage tank 105 between the first membrane filter 102 and the storage tank 105. Therefore, even when cleaning the filter membrane accompanied by air introduction into the first membrane filter 102 is performed, air bubbles remaining in the first membrane filter 102 can be removed as early as possible. In addition, compared with conventional water treatment apparatus, the number of machines can be significantly reduced, thus making the water treatment apparatus 100 more compact.

[0143] In addition, the circulation path L110 includes: a first circulation path that supplies primary permeate water to the storage tank 105; and a second circulation path that can supply primary permeate water stored in the storage tank 105 to the first membrane filtration device 102. Therefore, the circulation path of primary permeate water is shortened, making the water treatment equipment 100 more compact.

[0144] Furthermore, since the storage tank 105 is an open type, air bubbles contained in the primary permeate water can be released in the storage tank 105. In addition, since the circulation flow path L110 is a closed type, air bubbles can be prevented from mixing in from the outside.

[0145] In addition, the first membrane filtration device 102 includes multiple membrane filtration units 102A and 102B connected in parallel. Furthermore, the circulation path L110 can supply primary permeate water to membrane filtration units 102A and 102B respectively. Moreover, the control unit 110 causes the primary permeate water stored in the storage tank 105 to circulate between any membrane filtration unit and the storage tank 105 through the circulation path L110. Therefore, even if one membrane filtration unit is in the cleaning process, the water flow process can continue in other membrane filtration units, so the production of secondary permeate water will not be reduced.

[0146] The operation method of the water treatment equipment according to this embodiment includes a cleaning process, wherein the cleaning process is performed on the filter membrane of the first membrane filter device 102 during the water flow process. The cleaning process includes at least: an air cleaning stage, in which the filter membrane of the first membrane filter device 102 is cleaned with the air used; and a degassing stage, in which, after the air cleaning stage, primary permeate water is allowed to pass through the primary side of the first membrane filter device 102, and the primary permeate water is circulated between the first membrane filter device 102 and the storage tank 105. Therefore, even if air remains in the first membrane filter device 102 in the form of bubbles after the air cleaning stage, the residual bubbles can be removed as early as possible through the degassing stage.

[0147] In addition, since the storage tank 105 is an open type of storage tank, the air bubbles contained in the primary permeate water can be released in the storage tank 105.

[0148] In addition, the first membrane filtration device 102 includes multiple membrane filtration units 102A and 102B connected in parallel. The circulation path L110 can supply primary permeate water to the membrane filtration units 102A and 102B respectively, perform a cleaning process on some of the membrane filtration units 102A, and perform a water flow process on the remaining membrane filtration units 102B, so as not to reduce the production of secondary permeate water.

[0149] Furthermore, when multiple membrane filtration units are sequentially cleaned, a water-passing process is performed on all membrane filtration units 102A and 102B between the initial cleaning process for membrane filtration unit 102A and the subsequent cleaning process for membrane filtration unit 102B. Therefore, the balance between the supply of primary permeate water and the production of secondary permeate water in the second membrane filtration device 103 is maintained within an appropriate range, and the entire water treatment equipment 100 can be operated stably.

[0150] [Industry availability]

[0151] As described above, the present invention provides a water treatment device and its operation method that can reduce the installation space required.

Claims

1. A water treatment device, comprising: First membrane filtration device; The second membrane filtration device is installed after the first membrane filtration device; A storage tank for storing a portion of the permeate water after passing through the first membrane filtration device; A circulation path is provided between the first membrane filtration device and the storage tank, so that the permeate stored in the storage tank can circulate between the first membrane filtration device and the storage tank; Pump, equipped in the circulation path; and The control unit controls the pump after the filter membrane cleaning, which is accompanied by air introduced into the first membrane filter device, is completed, so that the permeate stored in the storage tank circulates between the first membrane filter device and the storage tank via the circulation path. The circulation path includes a first circulation path, which supplies the permeate water after passing through the first membrane filtration device to the storage tank. The first circulation path includes a portion of a path that transports the permeate after passing through the first membrane filtration device to the second membrane filtration device; And a flow path that branches off from the flow path that carries the permeated water after passing through the first membrane filtration device to the second membrane filtration device and then to the storage tank; The circulation path is a closed-loop flow path, and the storage tank is an open-loop storage tank. The air bubbles contained in the permeate water are released in the storage tank.

2. The water treatment equipment according to claim 1, wherein, The circulating flow path includes: The first circulation path supplies the permeate water after it has passed through the first membrane filtration device to the storage tank; and The second circulation path can supply the permeate stored in the storage tank to the primary side of the first membrane filtration device. The pump is equipped in the second circulation path.

3. The water treatment equipment according to claim 1 or 2, wherein, The first membrane filtration device includes multiple membrane filtration units connected in parallel with each other. The circulating flow path can supply the permeate water to each membrane filtration unit. The control unit causes the permeate stored in the storage tank to circulate between any of the membrane filtration units and the storage tank via the circulation path.

4. A method for operating a water treatment device, the water treatment device comprising: First membrane filtration device; The second membrane filtration device is installed after the first membrane filtration device; The water treatment equipment includes an open storage tank for storing a portion of the permeate after passing through the first membrane filtration device, and the operation method of the water treatment equipment includes: The water supply process involves supplying the permeate water filtered in the first membrane filtration device to the second membrane filtration device; and In the cleaning process, midway through the water flow process, the filter membrane of the first membrane filter device is cleaned. The cleaning process includes at least the following: During the air cleaning stage, the membrane filter of the first membrane filter device is cleaned to remove the filtered air; and In the degassing stage, after the air cleaning stage, the permeate water is allowed to pass through the primary side of the first membrane filter device, while the permeate water is circulated between the first membrane filter device and the storage tank through a circulation path. The circulation path includes a first circulation path, which supplies the permeate water after passing through the first membrane filtration device to the storage tank. The first circulation path includes: a portion of a path for conveying the permeate after passing through the first membrane filtration device to the second membrane filtration device; and a path branching off from the path for conveying the permeate after passing through the first membrane filtration device to the second membrane filtration device and conveying it to the storage tank. The degassing stage includes: supplying the permeate water after it has passed through the first membrane filter to the storage tank through the first circulation path; and degassing the air discharged from the first membrane filter together with the permeate water in the storage tank.

5. The method for operating the water treatment equipment according to claim 4, wherein, The first membrane filtration device includes multiple membrane filtration units connected in parallel with each other. The circulation path can supply the permeate water to each of the multiple membrane filtration units. The cleaning process is performed on a portion of the multiple membrane filtration units, and the water flow process is performed on the remaining membrane filtration units.

6. The method of operating the water treatment equipment according to claim 5, wherein, When the cleaning process is performed sequentially on the plurality of membrane filtration units, a water flow process is performed on all membrane filtration units between the preceding cleaning process for the membrane filtration units and the subsequent cleaning process for the other membrane filtration units.

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