Filter membrane cleaning device, water treatment device and filter membrane cleaning method

Abstract

The filter membrane cleaning device comprises: a circulation flow path (29) in which ozone gas supplied by an ozone gas supply unit (23) is dissolved in non-ozone water supplied from a non-ozone water supply flow path (21) to generate ozone water (28), and a circulation pump (30) for circulating the generated ozone water (28); and a control unit (37) for controlling the non-ozone water supply pump (19), the circulation pump (30) and the ozone water supply pump (33) to simultaneously supply non-ozone water to the circulation flow path (29), generate ozone water (28) in the circulation flow path (29), circulate the ozone water (28) in the circulation flow path (29), and supply ozone water (28) to the filter membrane (3). Thus, the water treatment device (100) of this embodiment can suppress the reduction of the cleaning effect of the filter membrane (3) without providing an ozone water generating tower.

Description

Technical Field

[0001] The present invention relates to a filter membrane cleaning device, a water treatment device and a filter membrane cleaning method. Background Art

[0002] As a method for separating and removing turbid substances from treated water such as sewage and factory wastewater, membrane filtration using a filtration membrane is known. If the membrane filtration is continued, turbid substances adhere to the surface and pores of the filtration membrane and cause clogging, so that the filtration performance gradually decreases. Therefore, in order to maintain the filtration performance, the filtration membrane is cleaned using ozone water.

[0003] For example, in the water treatment device of Patent Document 1, non-ozone water not containing ozone is sent to an ozone water generating tower, and ozone gas is supplied to the non-ozone water in the ozone water generating tower to generate ozone water, and the generated ozone water is used to clean the filter membrane.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2003-251160 Summary of the invention

[0007] Problems to be solved by the invention

[0008] However, in the water treatment device of Patent Document 1, it is necessary to set up an ozone water generating tower for generating and storing ozone water for cleaning the filter membrane. Therefore, in the water treatment device of Patent Document 1, ensuring the space for setting up the ozone water generating tower and the initial cost are issues. Therefore, as a method for generating ozone water without setting up an ozone water generating tower, a method of generating ozone water in a pipe by supplying ozone gas into the pipe so that the ozone gas is dissolved in the non-ozone water in the pipe is studied. When this method is adopted, when the distance from the ozone gas supply unit to the filter membrane is short, or when the supply speed of ozone water to the filter membrane is fast, the concentration of dissolved ozone in the ozone water may not rise to a preset value and be supplied to the filter membrane. Therefore, there is a problem of reducing the cleaning effect of the filter membrane.

[0009] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide a filtration membrane cleaning device capable of suppressing a decrease in the cleaning effect of a filtration membrane.

[0010] Solutions to Solve Problems

[0011] The filter membrane cleaning device involved in the present disclosure comprises: an ozone gas supply unit that supplies ozone gas; a non-ozone water supply flow path provided with a non-ozone water supply pump that supplies water that does not contain ozone, that is, non-ozone water; a circulation flow path in which ozone gas supplied by the ozone gas supply unit is dissolved in non-ozone water supplied from the non-ozone water supply flow path to generate ozone water, and provided with a circulation pump that circulates the generated ozone water, and the ozone gas supply unit and the non-ozone water supply flow path are connected to the circulation flow path; an ozone water supply flow path provided with an ozone water supply pump that supplies a part of the ozone water circulating in the circulation flow path to the filter membrane, and is connected to the circulation flow path; and a control unit that controls the non-ozone water supply pump, the circulation pump, and the ozone water supply pump to simultaneously supply non-ozone water to the circulation flow path, generate ozone water in the circulation flow path, circulate the ozone water in the circulation flow path, and supply ozone water to the filter membrane.

[0012] In addition, the water treatment device involved in the present disclosure comprises: a membrane separation tank having a filtration membrane for performing membrane filtration treatment on water to be treated; a membrane filtration water tank for storing membrane filtration water that has been subjected to membrane filtration treatment in the membrane separation tank; an ozone gas supply unit for supplying ozone gas; a non-ozone water supply flow path provided with a non-ozone water supply pump for supplying water that does not contain ozone, i.e., non-ozone water; a circulation flow path in which ozone gas supplied by the ozone gas supply unit is dissolved in non-ozone water supplied from the non-ozone water supply flow path to generate ozone water, and a circulation flow path provided with a pump for dissolving the ozone gas supplied by the ozone gas supply unit in the non-ozone water supplied from the non-ozone water supply flow path to generate ozone water a circulation pump for circulating the generated ozone water, wherein an ozone gas supply unit and a non-ozone water supply flow path are connected to the circulation flow path; the ozone water supply flow path is provided with an ozone water supply pump for supplying a part of the ozone water circulating in the circulation flow path to the filter membrane, and is connected to the circulation flow path; and a control unit controls the non-ozone water supply pump, the circulation pump and the ozone water supply pump to simultaneously supply non-ozone water to the circulation flow path, generate ozone water in the circulation flow path, circulate the ozone water in the circulation flow path and supply ozone water to the filter membrane.

[0013] In addition, the filter membrane cleaning method involved in the present disclosure is characterized in that it has: a step of supplying water that does not contain ozone, that is, non-ozone water, to a circulation flow path; a step of dissolving ozone gas in the non-ozone water in the circulation flow path to generate ozone water; a step of circulating the ozone water in the circulation flow path; and a step of supplying a part of the ozone water circulating in the circulation flow path to the filter membrane, and simultaneously performing the steps of supplying non-ozone water to the circulation flow path, generating ozone water in the circulation flow path, circulating the ozone water in the circulation flow path, and supplying ozone water to the filter membrane.

[0014] Effects of the Invention

[0015] According to the present disclosure, there is provided a filter membrane cleaning device for cleaning a filter membrane using ozone water generated by dissolving ozone gas in non-ozone water. The device can suppress reduction in the cleaning effect of the filter membrane by simultaneously supplying non-ozone water to a circulation path, generating ozone water in the circulation path, circulating ozone water in the circulation path, and supplying ozone water to the filter membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the water treatment device according to the first embodiment.

[0017] Figure 2 This is a schematic diagram showing an ozone water generating unit and an ozone gas supply unit according to the first embodiment.

[0018] Figure 3 This is a flowchart showing the filtration membrane treatment according to the first embodiment.

[0019] Figure 4 This is a flowchart showing the method for cleaning the filtration membrane according to the first embodiment.

[0020] Figure 5 This is a schematic diagram of a water treatment device according to a comparative example of Embodiment 1.

[0021] Figure 6 This is a schematic diagram of a water treatment device according to a second embodiment.

[0022] Figure 7 This is a flowchart showing a method for cleaning a filtration membrane according to the second embodiment.

[0023] Figure 8 This is a schematic diagram of a water treatment device according to a third embodiment. DETAILED DESCRIPTION

[0024] Implementation Method 1

[0025] use Figure 1 , a water treatment device 100 including the filtration membrane cleaning device of the first embodiment will be described. Figure 1 This is a schematic diagram of a water treatment device 100 according to Embodiment 1. The water treatment device 100 includes: a membrane separation tank 2 including a filtration membrane 3 for performing membrane filtration treatment on water to be treated 1; a membrane filtration water tank 16 storing membrane filtration water 17 that has been subjected to membrane filtration treatment in the membrane separation tank 2; a membrane filtration flow path 4; and a filtration membrane cleaning device.

[0026] In the membrane separation tank 2, for example, the treated water 1 treated by the activated sludge process is separated and the turbid substances are removed by using a filter membrane 3. The treated water 1, for example, is water from a water pipe, a sewer, secondary treated sewage, industrial wastewater, seawater, feces and urine, and flows into the membrane separation tank 2 via the treated water flow path 5. The membrane separation tank 2 may also be connected to a sludge extraction flow path 10. A sludge extraction pump 9 for extracting sludge is provided on the sludge extraction flow path 10. In addition, an air diffuser 8 may also be arranged at the bottom of the membrane separation tank 2. The membrane surface aeration blower 6 is connected to the air diffuser 8 via the air supply pipe 7.

[0027] The material of the filter membrane 3 is not limited, but preferably a fluorine resin compound with excellent resistance to ozone as a strong oxidant. In addition, polyolefins such as polyethylene, polypropylene, and polybutene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA), tetrafluoroethylene-hexafluoropropylene copolymers (FEP), tetrafluoroethylene-ethylene copolymers (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymers (ECTFE), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) and other fluorine resin compounds, cellulose such as cellulose acetate and ethyl cellulose, ceramics, etc. can also be used. In addition, two or more of the above materials can also be combined.

[0028] The type of the filtration membrane 3 is not limited. For example, various filtration membranes 3 known in the technical field such as a microfiltration (MF) membrane and an ultrafiltration (UF) membrane can be used.

[0029] The average pore size of the filter membrane 3 is not limited, but is preferably 0.001 μm or more and 1 μm or less, and more preferably 0.01 μm or more and 0.1 μm or less. By using the filter membrane 3 having an average pore size within this range, not only the contaminants attached to the surface of the filter membrane 3 in contact with the treated water 1 can be efficiently removed, but also the contaminants chemically attached to the surface of the filter membrane 3 in contact with the membrane filtered water 17 or in the pores of the filter membrane 3 can be efficiently removed.

[0030] The shape of the filtration membrane 3 is not limited. For example, it can be formed into a shape known in the technical field such as a cylinder or a flat membrane. In addition, an impregnated type, a shell type, a monolithic type, etc. can also be adopted.

[0031] There is no limitation on the water flow method of the filter membrane 3. For example, a full-flow filtration method or a cross-flow filtration method can be adopted. It can be an external pressure filtration method in which the treated water 1 flows through the outside of the filter membrane 3 and the membrane filtered water 17 flows through the inside, or it can be an internal pressure filtration method in which the treated water 1 flows through the inside of the filter membrane 3 and the membrane filtered water 17 flows through the outside.

[0032] The membrane filtration water tank 16 stores the membrane filtration water 17 that has been subjected to the membrane filtration treatment in the membrane separation tank 2 .

[0033] The membrane filtration flow path 4 is, for example, a pipe, and is a flow path that connects the filtration membrane 3 and the membrane filtration water tank 16, and sends the membrane filtration water 17 to the membrane filtration water tank 16. The membrane filtration flow path 4 is provided with a membrane filtration pump 12, a membrane filtration water flow rate measuring unit 13, and a pressure gauge 14. During the membrane filtration treatment, the membrane filtration water 17 separated in the membrane separation tank 2 by the membrane filtration pump 12 is sent to the membrane filtration water tank 16 via the membrane filtration water flow path 15. The membrane filtration water flow rate measuring unit 13 measures the flow rate of the membrane filtration water 17 flowing through the membrane filtration flow path 4.

[0034] Next, the filter membrane cleaning device is described. The filter membrane cleaning device dissolves ozone gas in non-ozone water, which is water not containing ozone, to generate ozone water 28, and uses the generated ozone water 28 to clean the filter membrane 3. The filter membrane cleaning device includes a non-ozone water supply flow path 21, a circulation flow path 29, an ozone gas supply unit 23, an ozone water supply flow path 35, and a control unit 37. The non-ozone water supply flow path 21, the circulation flow path 29, and the ozone water supply flow path 35 are formed by, for example, pipes.

[0035] The non-ozone water supply flow path 21 is a flow path that connects the membrane filtration water tank 16 and the circulation flow path 29, and supplies the membrane filtration water 17 stored in the membrane filtration water tank 16 to the circulation flow path 29. That is, in the present embodiment, the non-ozone water used to generate the ozone water 28 is the membrane filtration water 17 stored in the membrane filtration water tank 16. The non-ozone water supply flow path 21 includes a switching unit 18, a non-ozone water supply pump 19, and a non-ozone water supply flow rate measuring unit 20. The switching unit 18 opens and closes the non-ozone water supply flow path 21 according to an instruction from the control unit 37. The non-ozone water supply pump 19 supplies the membrane filtration water 17 as non-ozone water from the membrane filtration water tank 16 to the circulation flow path 29. The non-ozone water supply flow rate measuring unit 20 measures the flow rate of the non-ozone water flowing through the non-ozone water supply flow path 21.

[0036] The circulation flow path 29 is a flow path for generating ozone water 28 and circulating the generated ozone water 28. The circulation flow path 29 is connected to the ozone gas supply unit 23, the non-ozone water supply flow path 21, the ozone water supply flow path 35, the ozone gas removal unit 26, and the overflow water flow path 27. The ozone gas removal unit 26 is a pipe, for example, for discharging the ozone gas that is not dissolved in the ozone water 28 in the circulation flow path 29 from the circulation flow path 29. The overflow water flow path 27 is a flow path for removing the ozone water 28 from the circulation flow path 29 when the ozone water 28 exceeding a preset water volume circulates in the circulation flow path 29. In order to prevent the ozone water 28 from mixing into the ozone gas removal unit 26, the overflow water flow path 27 is set at a water level lower than that of the ozone gas removal unit 26 in the circulation flow path 29.

[0037] In addition, the circulation flow path 29 has a switching unit 36, a circulation pump 30, a circulation flow measurement unit 31, and a dissolved ozone concentration measurement unit 32. The switching unit 36 ​​is a three-way valve, for example, that connects the circulation flow path 29 and the ozone water supply flow path 35 and can switch the flow path of the ozone water 28 according to the instruction from the control unit 37. The circulation pump 30 circulates the ozone water 28 in the circulation flow path 29. The circulation flow measurement unit 31 measures the flow rate of the ozone water 28 flowing through the circulation flow path 29. The dissolved ozone concentration measurement unit 32 measures the dissolved ozone concentration of the ozone water 28 in the circulation flow path 29, and is, for example, an absorbance type ozone concentration meter or an electrode type ozone concentration meter. The dissolved ozone concentration measurement unit 32 can be arranged between the switching unit 36 ​​of the circulation flow path 29 and the portion connected to the ozone gas supply unit 23. Although not shown in the figure, a static mixer, for example, as a unit for uniformly mixing the ozone water 28 can also be provided in the circulation flow path 29.

[0038] The ozone gas supply unit 23 generates ozone gas and supplies the generated ozone gas to the circulation flow path 29. The ozone raw material supplied to the ozone gas supply unit 23 is not limited. For example, liquid oxygen, PSA (Pressure Swing Adsorption) or PVSA (Pressure Vacuum Swing Adsorption) generated oxygen can be used.

[0039] Figure 2 This is a schematic diagram showing the ozone water generating unit 22 and the ozone gas supply unit 23 according to the first embodiment. Figure 2 Yes means Figure 1 The ozone water generating section 22 is an enlarged view of the details of the portion indicated by the reference numeral 22 of the figure. The ozone water generating section 22 is a portion connected to the ozone gas supply section 23, the non-ozone water supply flow path 21, the ozone gas removal section 26, and the overflow water flow path 27 in the circulation flow path 29. The ozone gas supply section 23 is connected to the circulation flow path 29 to supply ozone gas into the circulation flow path 29. In more detail, the ozone water generating section 22 of the circulation flow path 29 is provided with a diffuser 25, and the ozone gas supply section 23 is connected to the diffuser 25 via an ozone gas supply pipe 24. Figure 2 In the figure, the case of using the diffuser 25 as a component for supplying ozone gas from the ozone gas supply section 23 to the circulation flow path 29 is illustrated, but any component can be used as long as it can dissolve ozone gas in non-ozone water in the circulation flow path 29 to generate ozone water 28. For example, a jet-type, mechanical stirring-type, and bottom-injection-type ozone gas supply component can also be used.

[0040] In the circulation flow path 29, ozone gas is dissolved in the non-ozone water supplied from the non-ozone water supply flow path 21, and the generated ozone water 28 is circulated by the circulation pump 30. More strictly speaking, the non-ozone water supplied from the non-ozone water supply flow path 21 to the circulation flow path 29 becomes the ozone water 28 diluted by mixing with the ozone water 28 circulating in the circulation flow path 29, and the ozone gas supplied by the ozone gas supply unit 23 is dissolved in the diluted ozone water 28.

[0041] As described above, the water treatment device 100 of this embodiment supplies ozone gas from the ozone gas supply unit 23 into the circulation flow path 29. Thus, the water treatment device 100 of this embodiment can generate ozone water 28 in the ozone water generation unit 22 of the circulation flow path 29, and therefore does not need to include an ozone water generation tower as in a conventional water treatment device.

[0042] The ozone water generating tower provided in the conventional water treatment device is a water tank designed to store the capacity of the ozone water 28 required for cleaning the filter membrane 3. The maximum capacity of the ozone water generating unit 22 of the present embodiment can be designed to be smaller than the capacity of the ozone water 28 required for cleaning the filter membrane 3. For example, the maximum capacity of the ozone water generating unit 22 is less than one quarter of the capacity of the ozone water 28 required for cleaning the filter membrane 3.

[0043] Furthermore, the ozone water generating unit 22 is a part of the circulation flow path 29, and the generated ozone water 28 is not stored in the ozone water generating unit 22 but circulates in the circulation flow path 29, which is also different from the ozone water generating tower provided in the conventional water treatment apparatus.

[0044] Furthermore, the overflow water flow path 27 is connected to the ozone water generating unit 22 , but the overflow water flow path 27 is generally not connected to the ozone water generating tower included in the conventional water treatment apparatus.

[0045] return Figure 1 The ozone water supply flow path 35 is a flow path that connects the circulation flow path 29 and the filtration membrane 3 and supplies a portion of the ozone water 28 circulating in the circulation flow path 29 to the filtration membrane 3. A portion of the ozone water supply flow path 35 may be shared with the membrane filtration flow path 4. Figure 1 The figure shows an example in which an ozone water supply flow path 35 and a membrane filtration flow path 4 are connected by a switching unit 11, and a flow path from the switching unit 11 to the filtration membrane 3 is shared. The switching unit 11 is, for example, a three-way valve that can switch the flow path of the membrane filtration water 17 or the ozone water 28 according to the instruction of the control unit 37. The ozone water supply flow path 35 is provided with an ozone water supply pump 33 and an ozone water supply flow rate measuring unit 34. The ozone water supply pump 33 delivers ozone water 28 from the circulation flow path 29 to the filtration membrane 3 via the ozone water supply flow path 35. The ozone water supply flow rate measuring unit 34 measures the flow rate of the ozone water 28 flowing in the ozone water supply flow path 35.

[0046] All pumps and switching parts are connected to the control part 37. And the control part 37 controls the operation of all pumps and switching parts. In addition, the measurement results of all flow measurement components and pressure gauges 14 are sent to the control part 37. In addition, the control part 37 controls the operation of the ozone gas supply part 23. The control method of the control part 37 will be described in the water treatment method described later.

[0047] Next, the water treatment method using the water treatment device 100 is described. The water treatment method is roughly divided into membrane filtration treatment and cleaning treatment of the filter membrane 3. After the membrane filtration treatment treats the treated water 1 by the activated sludge method, the filter membrane 3 is used to separate and remove the turbid substances. If the membrane filtration treatment is continued, there is a problem that the filtration performance is reduced. Specifically, with the continuous use of the filter membrane 3, the turbid substances are attached to the surface of the filter membrane 3 in contact with the treated water 1, the surface of the filter membrane 3 in contact with the filtered water, and the pores of the filter membrane 3, respectively, and blockage occurs, and the filtration performance gradually decreases. In particular, when the filter membrane 3 is blocked, the pressure required for the membrane filtration treatment increases. Therefore, the membrane filtration flux, the membrane filtration water volume per unit time and per unit membrane area are reduced. Therefore, in order to maintain the performance of the filter membrane 3, the water treatment device 100 regularly performs the cleaning treatment of the filter membrane 3. The operation of the pump and the switching unit described later is controlled by the control unit 37.

[0048] The switching between the membrane filtration process and the cleaning process of the filtration membrane 3 can be set according to the duration of the membrane filtration process, for example.

[0049] First, the membrane filtration process will be described. Figure 3 This is a flowchart showing the filtration membrane treatment according to the first embodiment.

[0050] The control unit 37 closes the circulation flow path 29 side of the switching unit 11, and opens the membrane separation tank 2 side and the membrane filtration water tank 16 side (step S1). Then, the control unit 37 starts the membrane filtration pump 12 (step S2). Thus, the treated water 1 is membrane filtered by the filtration membrane 3, and the membrane filtered water 17 filtered by the filtration membrane 3 is sent to the membrane filtration water tank 16 via the membrane filtration flow path 4. In addition, the control unit 37 keeps the membrane surface aeration blower 6 running during the membrane filtration process, and changes the operation time of the sludge extraction pump 9 according to the sludge concentration in the membrane separation tank 2, so as to extract the sludge in the membrane separation tank 2.

[0051] Next, the cleaning process of the filtration membrane 3 will be described. Figure 4 Flow chart showing the cleaning method of the filtration membrane of Embodiment 1. When the membrane filtration treatment is performed, the control unit 37 stops the membrane filtration pump 12 and ends the membrane filtration treatment (step S3). Then, the control unit 37 closes the membrane filtration tank 16 side of the switching unit 11 and opens the membrane separation tank 2 side and the circulation flow path 29 side (step S4).

[0052] Next, the control unit 37 performs pre-cleaning of the filter membrane 3 (step S5). Although pre-cleaning of the filter membrane 3 is not necessary, by performing pre-cleaning, it is possible to easily remove the contaminants attached to the surface of the filter membrane 3 in contact with the treated water 1. Specifically, the water treatment device 100 uses a pre-cleaning liquid that does not contain a chemical to pre-clean the filter membrane 3. For example, the control unit 37 turns on the switching unit 36 ​​and the switching unit 18, and starts the non-ozone water supply pump 19, the circulation pump 30, and the ozone water supply pump 33. Thus, the control unit 37 can deliver the membrane filtered water 17 to the filter membrane 3 to perform pre-cleaning. In addition, the water treatment device 100 can also easily remove the contaminants attached to the surface of the filter membrane 3 in contact with the treated water 1 by exposing the filter membrane 3 to the air for a certain period of time.

[0053] Next, the control unit 37 generates and circulates the ozone water 28. First, the control unit 37 closes the ozone water supply flow path 35 side of the switching unit 36, and opens the circulation flow path 29 side in a manner that the ozone water 28 circulates in the circulation flow path 29 (step S6). At this time, the ozone water 28 generated when the filter membrane 3 was cleaned last time remains in the circulation flow path 29. Since the ozone water 28 remaining in the circulation flow path 29 has been cleaned for a period of time since the last time the filter membrane 3 was cleaned, the ozone is decomposed, and the dissolved ozone concentration is lower than that in the last time the filter membrane 3 was cleaned. Therefore, the control unit 37 starts the circulation pump 30 and the ozone gas supply unit 23 (step S7). As a result, the control unit 37 dissolves the ozone gas in the ozone water 28 remaining in the circulation flow path 29, generates ozone water 28 with a higher concentration, and circulates the generated ozone water 28 in the circulation flow path 29. Then, the control unit 37 determines whether the value of the dissolved ozone concentration measuring unit 32 has risen to a preset value (step S8). If the control unit 37 determines that the value of the dissolved ozone concentration measuring unit 32 has not risen to the preset value, the control unit 37 supplies ozone gas from the ozone gas supply unit 23 and circulates the ozone water 28 until the value of the dissolved ozone concentration measuring unit 32 rises to the preset value.

[0054] Considering that ozone is decomposed before being supplied to the filter membrane 3 via the ozone water supply flow path 35, the dissolved ozone concentration of the ozone water 28 decreases, and the value preset in the dissolved ozone concentration measuring unit 32 may be set higher than the dissolved ozone concentration of the ozone water 28 to be achieved when supplying to the filter membrane 3. Since the extent to which ozone is decomposed before being supplied to the filter membrane 3 via the ozone water supply flow path 35 varies depending on the length of the ozone water supply flow path 35 and the supply flow rate, it can be verified through experiments.

[0055] The preset value in the dissolved ozone concentration measuring unit 32 is preferably 10 mg / L or more and 50 mg / L or less. When the dissolved ozone concentration of the ozone water 28 is less than 10 mg / L, it takes time to decompose the contaminants attached to the filter membrane 3, and the required amount of ozone water 28 increases, so the running cost associated with cleaning the filter membrane 3 increases. On the other hand, when the dissolved ozone concentration of the ozone water 28 is higher than 50 mg / L, the operation time of the ozone gas supply unit 23 becomes longer, so the running cost required to generate the ozone water 28 increases. In addition, the time for interrupting the membrane filtration of the treated water 1 also becomes longer, so the amount of membrane filtered water 17 decreases.

[0056] If no ozone water 28 remains in the circulation flow path 29 , the control unit 37 may control the switching unit 18 and the non-ozone water supply pump 19 to supply a preset amount of non-ozone water to the circulation flow path 29 .

[0057] The control unit 37 may also generate and circulate the ozone water 28 simultaneously with the membrane filtration process. Figure 3 and Figure 4 Thus, after the membrane filtration process is completed, the cleaning process of the filtration membrane 3 can be started quickly.

[0058] Next, the case where the ozone water 28 starts to be supplied to the filter membrane 3 and the filter membrane 3 is backwashed is described. The control unit 37 controls the non-ozone water supply pump 19, the circulation pump 30, and the ozone water supply pump 33 to simultaneously supply the non-ozone water to the circulation flow path 29, generate the ozone water 28 in the circulation flow path 29, circulate the ozone water 28 in the circulation flow path 29, and supply the ozone water 28 to the filter membrane 3 (step S9). The specific operation of the water treatment device 100 is described below.

[0059] First, the control unit 37 opens the switching unit 18, opens all directions of the switching unit 36, opens the circulation flow path 29 side and the membrane separation tank 2 side of the switching unit 11, and closes the membrane filtration water tank 16 side. Then, the control unit 37 starts the non-ozone water supply pump 19 and the ozone water supply pump 33. Thus, the supply of non-ozone water to the circulation flow path 29, the generation of ozone water 28 in the circulation flow path 29, the circulation of ozone water 28 in the circulation flow path 29, and the supply of ozone water 28 to the filtration membrane 3 are simultaneously performed, and the backwashing of the filtration membrane 3 is started. As described above, since the control unit 37 continues to generate and circulate ozone water 28, the control unit 37 drives the circulation pump 30 in addition to the non-ozone water supply pump 19 and the ozone water supply pump 33.

[0060] Here, the control method of the non-ozone water supply pump 19, the ozone water supply pump 33 and the circulation pump 30 by the control unit 37 is described. After driving all the non-ozone water supply pump 19, the ozone water supply pump 33 and the circulation pump 30, the control unit 37 controls each pump as follows.

[0061] First, at least one of the non-ozone water supply pump 19 and the ozone water supply pump 33 is controlled so that the flow rate of the non-ozone water supplied from the non-ozone water supply flow path 21 to the circulation flow path 29 is equal to the flow rate of the ozone water 28 supplied from the circulation flow path 29 to the ozone water supply flow path 35. That is, the control unit 37 controls at least one of the non-ozone water supply pump 19 and the ozone water supply pump 33 so that the value of the non-ozone water supply flow rate measuring device 20 is equal to the value of the ozone water supply flow rate measuring device 34. For example, when the value of the ozone water supply flow rate measuring device 34 becomes high, the control unit 37 controls to increase the output of the non-ozone water supply pump 19 so that the value of the non-ozone water supply flow rate measuring device 20 also becomes high. On the contrary, when the value of the ozone water supply flow rate measuring device 34 becomes low, the control unit 37 controls to reduce the output of the non-ozone water supply pump 19 so that the value of the non-ozone water supply flow rate measuring device 20 also becomes low.

[0062] Furthermore, the control unit 37 controls the circulation pump 30 so that the flow rate of the ozone water 28 in the circulation flow path 29 is higher than the flow rate of the ozone water 28 supplied from the circulation flow path 29 to the ozone water supply flow path 35. That is, the control unit 37 controls at least one of the circulation pump 30 and the ozone water supply pump 33 so that the value of the circulation flow rate measuring unit 31 is higher than the value of the ozone water supply flow rate measuring unit 34. For example, when the value of the ozone water supply flow rate measuring unit 34 is higher than the value of the circulation flow rate measuring unit 31, the control unit 37 controls to increase the output of the circulation pump 30.

[0063] When the ozone water 28 circulating in the circulation flow path 29 is diluted by supplying non-ozone water to the circulation flow path 29 and the value of the dissolved ozone concentration measured by the dissolved ozone concentration measuring unit 32 in the circulation flow path 29 is less than a preset threshold value, the control unit 37 performs control as follows. The control unit 37 stops the non-ozone water supply pump 19 and the ozone water supply pump 33, closes the ozone water supply flow path 35 side of the switching unit 36, and closes the switching unit 18. Then, the control unit 37 continues to start the circulation pump 30. Thus, when the value of the dissolved ozone concentration measured by the dissolved ozone concentration measuring unit 32 is less than a preset threshold value, the control unit 37 stops supplying non-ozone water to the circulation flow path 29 and supplying ozone water 28 to the filter membrane 3, and only performs the generation of ozone water 28 in the circulation flow path 29 and the circulation of ozone water 28 in the circulation flow path 29. As a result, the dissolved ozone concentration of the ozone water 28 circulating in the circulation flow path 29 gradually increases. After that, when the value of the dissolved ozone concentration measuring unit 32 becomes equal to or higher than a preset threshold value, the control unit 37 opens the ozone water supply flow path 35 side of the switching unit 36, opens the switching unit 18, and starts the non-ozone water supply pump 19 and the ozone water supply pump 33. That is, the control unit 37 simultaneously supplies the non-ozone water to the circulation flow path 29, generates the ozone water 28 in the circulation flow path 29, circulates the ozone water 28 in the circulation flow path 29, and supplies the ozone water 28 to the filter membrane 3, and restarts the backwashing of the filter membrane 3. In this way, the dissolved ozone concentration of the ozone water 28 can be kept equal to or higher than the preset threshold value.

[0064] The time for cleaning the filter membrane 3 using the ozone water 28 is not particularly limited, and can be appropriately set according to the amount of contaminants attached to the filter membrane 3. Generally, the cleaning time of the filter membrane 3 is preferably less than 60 minutes. It is preferred that the cleaning time is short. If the cleaning time is long, the operating time of the ozone gas supply unit 23 and the operating time of the pump become longer, thereby increasing the running cost. In addition, the time for interrupting the membrane treatment of the treated water 1 also becomes longer, so the amount of membrane filtered water 17 is reduced.

[0065] The membrane permeation flux, which is the amount of ozone water 28 supplied per unit filter membrane area, is not particularly limited as long as a flux that can be filled to the end of the filter membrane 3 can be ensured. Specifically, the membrane permeation flux of the ozone water 28 is preferably 1LMH (L / m2 / h) or more and 60LMH or less. When the membrane permeation flux of the ozone water 28 is higher than 60LMH, the supply speed of the ozone water 28 is faster than the decomposition speed of the contaminants attached to the filter membrane 3, so the ozone water 28 that does not react with the contaminants flows out to the outside of the filter membrane 3. As a result, the amount of ozone water 28 used increases more than necessary, which may increase the cost required for cleaning the filter membrane 3. When the membrane permeation flux of the ozone water 28 is lower than 1LMH, the ozone water 28 cannot be filled to the end of the filter membrane 3, the contaminants attached to the filter membrane 3 cannot be decomposed, or the concentration may decrease during transportation. The cleaning treatment of the filtration membrane 3 in the present embodiment can be performed by a cleaning method of passing ozone water 28 into the filtration membrane 3 and then retaining the ozone water 28 in the filtration membrane 3 or a cleaning method of immersing and retaining the filtration membrane 3 in ozone water 28.

[0066] The ozone water 28 discharged from the filtration membrane 3 after the cleaning treatment of the filtration membrane 3 is discharged into the membrane separation tank 2 and can be used as the treated water 1 for membrane filtration treatment. Alternatively, the ozone water 28 discharged from the filtration membrane 3 after the backflow cleaning can also be recovered and treated separately as the treated liquid.

[0067] When the cleaning process of the filter membrane 3 is finished, the control unit 37 stops the non-ozone water supply pump 19, the circulation pump 30, and the ozone water supply pump 33 (step S10). Then, the control unit 37 closes the circulation flow path 29 side of the switching unit 11 and closes the switching unit 18 (step S11). Thus, the supply and circulation of the ozone water 28 are stopped. Then, the control unit 37 implements Figure 3 In the steps S1 and S2 shown, the membrane filtration treatment of the water to be treated 1 is restarted. Thus, the membrane filtration treatment of the water to be treated 1 can be performed continuously and efficiently.

[0068] The effects of the water treatment device 100 according to the present embodiment will be described in comparison with a conventional water treatment device and a water treatment device of a comparative example. Figure 5 1 is a schematic diagram of a water treatment device of a comparative example of Embodiment 1. In conventional water treatment devices, it is necessary to provide an ozone water generating tower for generating and storing ozone water 28 for washing the filter membrane 3. Therefore, in conventional water treatment devices, ensuring space for providing the ozone water generating tower and initial cost are issues.

[0069] Figure 5The water treatment device of the comparative example shown connects a membrane filtration water tank 16 and a filtration membrane 3, connects an ozone gas supply unit 23 to a flow path for supplying membrane filtration water 17 from the membrane filtration water tank 16 to the filtration membrane 3, generates ozone water 28 in the flow path, and supplies the generated ozone water 28 to the filtration membrane 3. Since the water treatment device of the comparative example generates ozone water 28 in the flow path, it is not necessary to set an ozone water generating tower of a conventional water treatment device. However, in the water treatment device of the comparative example, for example, when the distance from the ozone gas supply unit 23 to the filtration membrane 3 is short, or when the supply flow rate of the ozone water 28 to the filtration membrane 3 is high, it is possible that the ozone gas supplied from the ozone gas supply unit 23 to the flow path is supplied to the filtration membrane 3 before the ozone gas is fully dissolved in the membrane filtration water 17, and the dissolved ozone concentration in the ozone water 28 does not rise to a preset value and is supplied to the filtration membrane 3. Therefore, the water treatment device of the comparative example has a problem of reducing the cleaning effect of the filtration membrane 3.

[0070] In contrast, the water treatment device 100 in this embodiment is as follows Figure 1 As shown, the water treatment device 100 of this embodiment is provided with a circulation flow path 29 and a control unit 37. The circulation flow path 29 is a flow path for dissolving ozone gas supplied by the ozone gas supply unit 23 in the non-ozone water supplied from the non-ozone water supply flow path 21 to generate ozone water 28. A circulation pump 30 is provided to circulate the generated ozone water 28. The control unit 37 controls the non-ozone water supply pump 19, the circulation pump 30, and the ozone water supply pump 33 to simultaneously supply non-ozone water to the circulation flow path 29, generate ozone water 28 in the circulation flow path 29, circulate the ozone water 28 in the circulation flow path 29, and supply ozone water 28 to the filter membrane 3. Therefore, the water treatment device 100 of this embodiment does not need to be provided with an ozone water generation tower provided in a conventional water treatment device. Moreover, in the water treatment device 100 of the present embodiment and the water treatment device of the comparative example, when the distance from the ozone gas supply unit 23 to the filter membrane 3 is equal and the supply flow rate of the ozone water 28 to the filter membrane 3 is equal, the water treatment device 100 of the present embodiment can easily maintain the dissolved ozone concentration of the ozone water 28 compared with the water treatment device of the comparative example. Therefore, the water treatment device 100 of the present embodiment can suppress the reduction of the cleaning effect of the filter membrane 3 compared with the water treatment device of the comparative example.

[0071] That is, the water treatment device 100 of the present embodiment dissolves ozone gas in non-ozone water in the circulation flow path 29 to generate ozone water 28. Furthermore, the water treatment device 100 of the present embodiment simultaneously supplies non-ozone water to the circulation flow path 29, generates ozone water 28 in the circulation flow path 29, circulates ozone water 28 in the circulation flow path 29, and supplies ozone water 28 to the filter membrane 3, thereby eliminating the need to store ozone water 28 in a volume required for cleaning the filter membrane 3. As a result, it is possible to eliminate the need to provide an ozone water generation tower required in conventional water treatment devices.

[0072] In addition, when the circulation of the ozone water 28 in the circulation flow path 29 and the supply of the ozone water 28 to the filter membrane 3 are not performed simultaneously as in the water treatment device of the above-mentioned comparative example, if the same amount of ozone gas is supplied to the flow path from the ozone gas supply unit 23, the ozone gas may not be sufficiently dissolved depending on the distance from the ozone gas supply unit 23 to the filter membrane 3 and the supply flow rate of the ozone water 28 to the filter membrane 3, and the dissolved ozone concentration in the ozone water 28 may not rise to a preset value and be supplied to the filter membrane 3. The water treatment device 100 of the present embodiment simultaneously supplies non-ozone water to the circulation flow path 29, generates ozone water 28 in the circulation flow path 29, circulates the ozone water 28 in the circulation flow path 29, and supplies the ozone water 28 to the filter membrane 3. That is, the entire amount of the ozone water 28 generated in the circulation flow path 29 is not supplied to the filter membrane 3, but a part of the ozone water 28 generated in the circulation flow path 29 is supplied to the filter membrane 3, and a part of it circulates in the circulation flow path 29. In this way, since part of the generated ozone water 28 circulates in the circulation flow path 29, the time until the ozone water 28 is supplied to the filter membrane 3 becomes longer, so it is easy to increase the dissolved ozone concentration in the ozone water 28 to a preset value. Therefore, the water treatment device 100 of the present embodiment can suppress the reduction of the cleaning effect of the filter membrane 3 compared with the water treatment device of the comparative example.

[0073] In addition, when the flow rate of the non-ozone water supplied from the non-ozone water supply flow path 21 to the circulation flow path 29 is greater than the flow rate of the ozone water 28 supplied from the circulation flow path 29 to the ozone water supply flow path 35, the dissolved ozone concentration of the ozone water 28 circulating in the circulation flow path 29 is difficult to increase. In addition, since the ozone water 28 discharged from the circulation flow path 29 through the overflow water flow path 27 increases, the ozone water 28 is consumed wastefully. On the contrary, when the flow rate of the ozone water 28 supplied from the circulation flow path 29 to the ozone water supply flow path 35 is greater than the flow rate of the non-ozone water supplied from the non-ozone water supply flow path 21 to the circulation flow path 29, the ozone water 28 circulating in the circulation flow path 29 is exhausted, and the circulation pump 30 may be operated idle. Therefore, the control unit 37 controls at least one of the non-ozone water supply pump 19 and the ozone water supply pump 33 so that the flow rate of the non-ozone water supplied from the non-ozone water supply flow path 21 to the circulation flow path 29 is equal to the flow rate of the ozone water 28 supplied from the circulation flow path 29 to the ozone water supply flow path 35. As a result, the flow rate of the non-ozone water flowing into the circulation flow path 29 is equal to the flow rate of the ozone water 28 flowing out of the circulation flow path 29, so that the volume of the ozone water 28 circulating in the circulation flow path 29 can be kept constant.

[0074] Furthermore, the control unit 37 controls at least one of the circulation pump 30 and the ozone water supply pump 33 so that the flow rate of the ozone water 28 in the circulation flow path 29 is higher than the flow rate of the ozone water 28 supplied from the circulation flow path 29 to the ozone water supply flow path 35. Here, the flow rate of the ozone water 28 in the circulation flow path 29 of the present embodiment is set to x, and the flow rate of the ozone water 28 supplied from the circulation flow path 29 to the ozone water supply flow path 35 is set to y. x>y.

[0075] Here, it is assumed that the control unit 37 controls the flow rate of the ozone water 28 in the circulation flow path 29 and the flow rate of the ozone water 28 supplied from the circulation flow path 29 to the ozone water supply flow path 35 to be x. In this case, since the flow rate of the ozone water 28 supplied to the ozone water supply flow path 35 is high, the reduction in the dissolved ozone concentration of the ozone water 28 can be suppressed, but the amount of ozone water 28 used increases. In contrast, the water treatment device 100 of this embodiment can reduce the amount of ozone water 28 used because the flow rate y of the ozone water 28 supplied to the ozone water supply flow path 35 is lower than the flow rate x of the ozone water 28 in the circulation flow path 29.

[0076] Next, it is assumed that the control unit 37 controls the flow rate of the ozone water 28 in the circulation flow path 29 and the flow rate of the ozone water 28 supplied from the circulation flow path 29 to the ozone water supply flow path 35 to y. In this case, since the flow rate of the ozone water 28 is low, the amount of ozone water 28 used can be reduced, but when the ozone water is supplied to the filter membrane 3, the dissolved ozone concentration of the ozone water 28 may decrease. In contrast, the water treatment device 100 of the present embodiment can suppress the decrease in the dissolved ozone concentration in the ozone water 28 because the flow rate x of the ozone water 28 in the circulation flow path 29 is higher than the flow rate y of the ozone water 28 supplied from the circulation flow path 29 to the ozone water supply flow path 35.

[0077] In addition, when the value of the dissolved ozone concentration measured by the dissolved ozone concentration measuring unit 32 is less than a preset threshold value, the control unit 37 stops supplying the non-ozone water to the circulation flow path 29 and the ozone water 28 to the filter membrane 3, and only performs the generation of the ozone water 28 in the circulation flow path 29 and the circulation of the ozone water 28 in the circulation flow path 29. Furthermore, when the value of the dissolved ozone concentration measured by the dissolved ozone concentration measuring unit 32 becomes equal to or higher than a preset threshold value, the control unit 37 restarts supplying the non-ozone water to the circulation flow path 29 and the ozone water 28 to the filter membrane 3. In this way, the dissolved ozone concentration of the ozone water 28 can be maintained at or higher than the preset threshold value.

[0078] In addition, when the pore size of the filter membrane 3 is small, the ozone gas that is not dissolved in the ozone water 28 does not pass through the pores of the filter membrane 3, so there is a possibility that the undissolved ozone gas does not pass through the filter membrane 3 and causes gas lock in the flow path. Therefore, the water treatment device 100 of the present embodiment is provided with an ozone gas exhaust unit 26 that is connected to the circulation flow path 29 and discharges the ozone gas that is not dissolved in the circulation flow path 29 from the circulation flow path 29. Thus, the ozone gas that is not dissolved in the ozone water 28 can be discharged from the circulation flow path 29, so that gas lock can be prevented.

[0079] In addition, when the water treatment device 100 supplies ozone water 28 to the filter membrane 3 and non-ozone water to the circulation flow path 29 at the same time, it is possible that the timing of starting the supply of ozone water 28 and non-ozone water may not be consistent. For example, consider the case where the supply of non-ozone water to the circulation flow path 29 starts earlier than the supply of ozone water 28 to the filter membrane 3. In this case, the amount of water in the circulation flow path 29 temporarily exceeds the maximum capacity of the circulation flow path 29, and a load is generated on the flow path, pump and switching part. Therefore, the water treatment device 100 is provided with an overflow water flow path 27, which is connected to the circulation flow path 29, and when ozone water 28 exceeding a preset amount of water circulates in the circulation flow path 29, ozone water 28 is discharged from the circulation flow path 29. Thus, when the amount of water in the circulation flow path 29 temporarily exceeds the maximum capacity of the circulation flow path 29, the ozone water 28 circulating in the circulation flow path 29 can be discharged from the circulation flow path 29. Furthermore, the overflow water flow path 27 is provided at a water level lower than the ozone gas removing unit 26 in the circulation flow path 29. Thus, when the ozone water 28 in the circulation flow path 29 increases, the ozone water 28 can be prevented from mixing into the ozone gas removing unit 26.

[0080] In addition, the water treatment device 100 of the present embodiment uses the membrane filtered water 17 as the non-ozone water. Therefore, it is not necessary to newly provide a water tank for storing the non-ozone water.

[0081] Implementation Method 2

[0082] use Figure 6 A water treatment device 100 including a filtration membrane cleaning device according to the second embodiment will be described. Figure 61 is a schematic diagram of a water treatment device 100 according to Embodiment 2. In Embodiment 1, an example in which the washing water for washing the filter membrane 3 is ozone water 28 is shown. In this embodiment, an example in which at least two kinds of chemicals, namely, ozone water 28 and washing water containing chemicals other than ozone, are used as washing water for washing the filter membrane 3 is described. The basic structure of the water treatment device 100 equipped with the filter membrane washing device of this embodiment is the same as that of the water treatment device 100 equipped with the filter membrane washing device of Embodiment 1, and therefore only the differences will be described. In addition, the same reference numerals are given to the same structures as those of the water treatment device 100 equipped with the filter membrane washing device of Embodiment 1.

[0083] Hereinafter, the ozone water 28 is referred to as first cleaning water 28, and the cleaning water containing a chemical other than ozone is referred to as second cleaning water 38. The type of chemical contained in the second cleaning water 38 is not limited to one.

[0084] The water treatment device 100 including the filtration membrane cleaning device of the present embodiment includes a cleaning flow path 43 and a cleaning water tank 39 storing the second cleaning water 38 .

[0085] The cleaning flow path 43 is a flow path connecting the filtration membrane 3 and the cleaning water tank 39 . Figure 6 The example of the flow path from the filtration membrane 3 to the switching unit 42 of the cleaning flow path 43 is shown in common with the membrane filtration flow path 4 and the ozone water supply flow path 35. The cleaning flow path 43 includes a cleaning pump 40 for supplying the second cleaning water 38 stored in the cleaning water tank 39 to the filtration membrane 3, and a cleaning flow rate measuring unit 41 for measuring the flow rate of the second cleaning water 38 flowing through the cleaning flow path 43.

[0086] The type of reagent of the second cleaning water 38 stored in the cleaning water tank 39 is not particularly limited as long as it is a substance that can decompose organic or inorganic substances other than ozone, and substances known in the technical field can be used. As examples of reagents that can decompose organic matter, sodium hypochlorite, hydrogen peroxide, sodium hydroxide, etc. can be cited. Among them, the type of reagent of the second cleaning water 38 is preferably sodium hypochlorite, which is cheap and easy to maintain in concentration. In addition, the type of reagent of the second cleaning water 38 can be single or in combination of two or more. In the case of combining two or more reagents that can decompose organic matter, for the first reagent, the standard oxidation-reduction potential (25°C) measured using a hydrogen electrode is preferably less than 2.0V, and for the second reagent, the standard oxidation-reduction potential (25°C) measured using a hydrogen electrode is preferably 2.0V or more. Specifically, as the first reagent, sodium hypochlorite is preferably used, and as the second reagent, cleaning water containing ozone is preferably used.

[0087] In addition, substances capable of decomposing inorganic substances are, for example, inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as oxalic acid and citric acid. They may also be used alone or in combination of two or more. It is also possible to use a combination of two or more substances capable of decomposing organic substances and substances capable of decomposing inorganic substances. In this case, it is not limited to which one is used as the first agent or the second agent. For example, when a substance capable of decomposing organic substances is used as the first agent, a substance capable of decomposing inorganic substances is used as the second agent. When a substance capable of decomposing inorganic substances is used as the first agent, a substance capable of decomposing organic substances is used as the second agent.

[0088] The concentration of the reagent in the second cleaning water 38 is not particularly limited. For example, when using a substance that can decompose organic matter, sodium hypochlorite (effective chlorine concentration) is preferably 1.0 g / L or more and 5.0 g / L or less, and sodium hydroxide is preferably 1.0 g / L or more and 4.0 g / L or less. When using a substance that can decompose inorganic matter, hydrochloric acid, sulfuric acid, and nitric acid are preferably 1.0 g / L or more and 10.0 g / L or less, oxalic acid is preferably 1.0 g / L or more and 2.0 g / L or less, and citric acid is preferably 1 g / L or more and 10 g / L or less. If the concentration of the reagent is lower than the above range, it takes time to decompose the turbid substances attached to the filter membrane 3, and as the amount of cleaning water 28 used increases, the capacity of the reagent tank also increases. On the other hand, if the concentration of the reagent is higher than the above range, the amount of reagent used increases, so the cost required for the reagent increases.

[0089] The cleaning time of the filtration membrane 3 using the second cleaning water 38 is not particularly limited, and can be appropriately set according to the amount of contaminants attached to the filtration membrane 3. Generally, when sodium hypochlorite is used, it is preferably 90 minutes or less, and when oxalic acid or citric acid is used, it is preferably 5 minutes or more and 7 minutes or less. It is preferred that the cleaning time of the filtration membrane 3 using the second cleaning water 38 is short. If the cleaning time is long, the time for interrupting the membrane treatment of the treated water 1 also becomes long, so the amount of membrane filtered water decreases.

[0090] The membrane surface permeation flux as the water supply amount per unit membrane area of ​​the second cleaning water 38 is not particularly limited. Usually, it is sufficient as long as the flux that can be filled to the end of the filter membrane 3 can be ensured. Specifically, when sodium hypochlorite is used, it is preferably 6LMH (L / m2 / h) or less. If the membrane surface permeation flux is too high, as the required amount of the second cleaning water 38 increases, the cost of the reagent increases or the capacity of the reagent box increases. If the membrane surface permeation flux is too low, the second cleaning water 38 will not be filled to the end of the filter membrane 3, and the dirty substances attached to the filter membrane 3 cannot be decomposed.

[0091] All pumps and switching units are connected to the control unit 37. In addition, the measurement results of all flow rate measuring devices and the pressure gauge 14 are sent to the control unit 37. The control unit 37 controls the operation of all pumps and switching units. In addition, the control unit 37 controls the operation of the ozone supply unit.

[0092] The cleaning method of the filtration membrane 3 of the present embodiment may include a cleaning method of passing the second cleaning water 38 into the filtration membrane 3 and then retaining the second cleaning water 38 in the filtration membrane 3 or a cleaning method of immersing and retaining the filtration membrane 3 in the second cleaning water 38 .

[0093] Next, a water treatment method using the water treatment device 100 of the present embodiment will be described. Here, first, an example in which the filtration membrane 3 is cleaned using the second cleaning water 38 and then the filtration membrane 3 is cleaned using the ozone water 28 as the first cleaning water 28 will be described. Since the membrane filtration process and the method of cleaning the filtration membrane 3 using the ozone water 28 as the first cleaning water 28 are the same as those in Embodiment 1, the method of cleaning the filtration membrane 3 using the second cleaning water 38 will be described. Figure 7 This is a flowchart showing the method for cleaning the filtration membrane 3 according to the second embodiment, and only the method for cleaning the filtration membrane 3 using the second cleaning water 38 is shown.

[0094] When the membrane filtration treatment is being performed, the control unit 37 stops the membrane filtration pump 12 (step S20). Next, the control unit 37 closes the membrane filtration water flow path 15 side of the switching unit 42 and opens the cleaning flow path 43 side (step S21). Then, the control unit 37 starts the cleaning pump 40 (step S22), supplies the second cleaning water 38 to the filtration membrane 3 via the cleaning flow path 43, and starts the cleaning treatment of the filtration membrane 3. When the cleaning treatment of the filtration membrane 3 using the second cleaning water 38 is completed, the control unit 37 stops the cleaning pump 40 (step S23), closes the cleaning flow path 43 side of the switching unit 42 (step S24), and stops the supply of the second cleaning water 38.

[0095] In addition, the control unit 37 may generate and circulate the ozone water 28 as the first cleaning water 28 while performing the cleaning process of the filter membrane 3 using the second cleaning water 38. Thus, after the cleaning process of the filter membrane 3 is performed using the second cleaning water 38, the cleaning process of the filter membrane 3 can be quickly started using the ozone water 28 as the first cleaning water 28. Then, the control unit 37 performs the cleaning process of the filter membrane 3 using the ozone water 28 described in the first embodiment.

[0096] Similar to Embodiment 1, the water treatment device 100 in this embodiment includes a circulation flow path 29 and a control unit 37. The circulation flow path 29 is a flow path for dissolving ozone gas supplied by the ozone gas supply unit 23 in non-ozone water supplied from the non-ozone water supply flow path 21 to generate ozone water 28. A circulation pump 30 for circulating the generated ozone water 28 is provided. The control unit 37 controls the non-ozone water supply pump 19, the circulation pump 30, and the ozone water supply pump 33 to simultaneously supply non-ozone water to the circulation flow path 29, generate ozone water 28 in the circulation flow path 29, circulate the ozone water 28 in the circulation flow path 29, and supply ozone water 28 to the filter membrane 3. Therefore, the water treatment device 100 in this embodiment does not need to be provided with an ozone water generating tower as in conventional water treatment devices. Moreover, in the water treatment device 100 and Figure 5 In the water treatment device of the comparative example shown in FIG. 1 , when the distance from the ozone gas supply unit 23 to the filter membrane 3 is equal and the supply flow rate of the ozone water 28 to the filter membrane 3 is equal, the water treatment device 100 of the present embodiment is the same as that of the comparative example. Figure 5 Compared with the water treatment device of the comparative example shown in FIG. 1 , the dissolved ozone concentration of the ozone water 28 can be easily maintained. Figure 5 Compared with the water treatment apparatus of the comparative example shown, it is possible to suppress a decrease in the cleaning effect of the filtration membrane 3.

[0097] In addition, the water treatment device 100 of the present embodiment further comprises: a cleaning water tank 39 storing second cleaning water 38 containing a chemical other than ozone; and a cleaning flow path 43 provided with a cleaning pump 40 for supplying the second cleaning water 38 stored in the cleaning water tank 39 to the filter membrane 3, and connecting the filter membrane 3 and the cleaning water tank 39. Thus, the first cleaning water 28 and the second cleaning water 38, which are ozone water 28, can be used together to perform cleaning treatment on the filter membrane 3.

[0098] In addition, the control unit 37 may also perform the cleaning process of the filtration membrane 3 while diluting the second cleaning water 38 with the membrane filtered water 17. Specifically, the control unit 37 closes the membrane filtered water flow path 15 side of the switching unit 11, and opens the filtration membrane 3 side and the circulation flow path 29 side. Then, the control unit 37 opens the cleaning flow path 43 side of the switching unit 42, and opens the switching unit 18 and the switching unit 36. Then, the control unit 37 starts the non-ozone water supply pump 19, the circulation pump 30, and the cleaning pump 40. Thus, the cleaning process of the filtration membrane 3 can be performed while diluting the second cleaning water 38 with the membrane filtered water 17. In addition, the control unit 37 can adjust the concentration and flow rate of the diluted second cleaning water 38 supplied to the filtration membrane 3 by adjusting at least one of the cleaning pump 40 and the non-ozone water supply flow rate measuring unit 20 according to the value of the cleaning flow rate measuring unit 41.

[0099] In addition, in this embodiment, an example is shown in which the first cleaning water 28 and the second cleaning water 38 are used together to clean the filter membrane 3, but the types of cleaning water are not limited to two. For example, ozone water 28 containing ozone, cleaning water containing a substance that can decompose organic matter, and cleaning water containing inorganic matter may be used together. In addition, when cleaning the filter membrane 3 using a plurality of cleaning waters, the order of the cleaning waters used to clean the filter membrane 3 is not particularly limited.

[0100] In addition, the flow path from the filtration membrane 3 to the switching unit 42 of the cleaning flow path 43 may include a member such as a static mixer for uniformly mixing the second cleaning water 38 and the membrane filtrated water 17 .

[0101] Implementation 3

[0102] use Figure 8 A water treatment device 100 including a filtration membrane cleaning device according to a third embodiment will be described. Figure 8 1 is a schematic diagram of a water treatment device 100 according to Embodiment 3. In Embodiments 1 and 2, an example of using membrane filtered water 17 as non-ozone water is described. In this embodiment, an example of using clarified water 45 other than membrane filtered water 17 as non-ozone water is described. The basic structure of the water treatment device 100 equipped with the filter membrane cleaning device of this embodiment is the same as that of the water treatment device 100 equipped with the filter membrane cleaning device of Embodiment 1 or Embodiment 2, so only the differences are described. In addition, the same reference numerals are attached to the same structures as those of the water treatment device 100 equipped with the filter membrane cleaning device of Embodiment 1 and Embodiment 2.

[0103] The water treatment device 100 of this embodiment includes a clear water tank 44 storing clear water 45 other than the membrane filtered water 17, and a non-ozone water supply flow path 21 connects the clear water tank 44 and the circulation flow path 29. The clear water 45 other than the membrane filtered water 17 may be any water of minimum quality when generating the ozone water 28, for example, at least one of tap water, industrial water, ion exchange water, pure water, and ultrapure water.

[0104] The cleaning process of the filtration membrane 3 of the present embodiment is the same method as that of the cleaning process of the filtration membrane 3 described in the first or second embodiment except that the clear water 45 is used as the non-ozone water.

[0105] Similar to Embodiment 1, the water treatment device 100 in this embodiment includes a circulation flow path 29 and a control unit 37. The circulation flow path 29 is a flow path for dissolving ozone gas supplied by the ozone gas supply unit 23 in non-ozone water supplied from the non-ozone water supply flow path 21 to generate ozone water 28. A circulation pump 30 for circulating the generated ozone water 28 is provided. The control unit 37 controls the non-ozone water supply pump 19, the circulation pump 30, and the ozone water supply pump 33 to simultaneously supply non-ozone water to the circulation flow path 29, generate ozone water 28 in the circulation flow path 29, circulate the ozone water 28 in the circulation flow path 29, and supply ozone water 28 to the filter membrane 3. Therefore, the water treatment device 100 in this embodiment does not need to be provided with an ozone water generating tower as in conventional water treatment devices. Moreover, in the water treatment device 100 and Figure 5 In the water treatment device of the comparative example shown in FIG. 1 , when the distance from the ozone gas supply unit 23 to the filter membrane 3 is equal and the supply flow rate of the ozone water 28 to the filter membrane 3 is equal, the water treatment device 100 of the present embodiment is the same as that of the comparative example. Figure 5 Compared with the water treatment device of the comparative example shown in FIG. 1 , the dissolved ozone concentration of the ozone water 28 can be easily maintained. Figure 5 Compared with the water treatment apparatus of the comparative example shown, it is possible to suppress a decrease in the cleaning effect of the filtration membrane 3.

[0106] In addition, the water quality of the membrane filtered water 17 may be affected by the water quality of the treated water 1. Therefore, when the membrane filtered water 17 is used as non-ozone water, the ozone gas blown into the membrane filtered water 17 reacts with the substances dissolved in the membrane filtered water 17, and the amount of ozone that can be dissolved in the membrane filtered water 17 may decrease. As a result, a large amount of ozone gas may be required to increase the dissolved ozone concentration of the ozone water 28, and it may take time to increase the dissolved ozone concentration to a preset concentration.

[0107] In the second embodiment, when the second cleaning water 38 is diluted with the membrane filtered water 17 , the chemical reacts with the substance dissolved in the membrane filtered water 17 , and the concentration of the chemical dissolved in the membrane filtered water 17 decreases, which may reduce the cleaning effect of the filtration membrane 3 .

[0108] Therefore, the water treatment device 100 of this embodiment uses the clarified water 45 other than the membrane filtered water 17 as the non-ozone water. Specifically, it is at least any one of tap water, industrial water, ion exchange water, pure water and ultrapure water. Thus, compared with the case where the membrane filtered water 17 is used as the non-ozone water, the ozone water 28 can be generated and the second washing water 38 can be diluted efficiently and stably.

[0109] In addition, the structure shown in the above-mentioned embodiment is only an example, and it can also be combined with other well-known technologies. In addition, it is also possible to combine the embodiments with each other, and it is also possible to omit or change a part of the structure within the scope of not departing from the gist.

[0110] Description of Reference Numerals

[0111] 1 treated water, 2 membrane separation tank, 3 filtration membrane, 4 membrane filtration flow path, 5 treated water flow path, 6 membrane surface aeration blower, 7 air supply piping, 8 air diffuser, 9 sludge extraction pump, 10 sludge extraction flow path, 11 switching unit, 12 membrane filtration pump, 13 membrane filtration water flow rate measuring unit, 14 pressure gauge, 15 membrane filtration water flow path, 16 membrane filtration water tank, 17 membrane filtration water, 18 switching unit, 19 non-ozone water supply pump, 20 non-ozone water supply flow rate measuring unit, 21 non-ozone water supply flow path, 22 ozone water generating unit, 23 ozone gas supply unit, 24 ozone gas 100 a water treatment device; 110 a cleaning water tank; 111 a cleaning pump; 112 a cleaning flow measuring component; 113 a dissolved ozone concentration measuring component; 114 a cleaning flow measuring component; 115 a cleaning flow measuring component; 116 a cleaning flow measuring component; 117 a cleaning flow measuring component; 118 a cleaning water treatment device; 119 a cleaning water tank; 120 a cleaning water tank; 121 a cleaning flow measuring component; 122 a cleaning water treatment device; 123 a cleaning water tank; 124 a cleaning flow measuring component; 125 a cleaning water treatment device; 126 a cleaning water tank; 127 a cleaning water tank; 128 a cleaning water supply pipe; 130 a diffusion device; 131 a ozone gas removal unit; 132 an overflow water flow path; 133 an ozone water (first cleaning water); 134 a circulation flow measuring component; 135 a dissolved ozone concentration measuring component; 136 a dissolved ozone concentration measuring component; 137 a ozone water supply pump; 138 an ozone water supply flow measuring component; 138 a second cleaning water; 139 a cleaning water tank; 140 a cleaning pump; 141 a cleaning flow measuring component; 142 a switching unit; 143 a cleaning flow path; 144 a clarified water tank; 145 clarified water; 144 a water treatment device; 145 a clarified water; 146 a water treatment device; 147 a water treatment device; 148 a water treatment device; 149 a water treatment device; 150 a water treatment device; 151

Claims

1. A filter membrane cleaning device, wherein: The filter membrane cleaning device comprises: An ozone gas supply unit for supplying ozone gas; The non-ozone water supply flow path is provided with a non-ozone water supply pump for supplying water that does not contain ozone, i.e., non-ozone water; a circulation flow path, which is a flow path in which the ozone gas supplied by the ozone gas supply unit dissolves in the non-ozone water supplied from the non-ozone water supply flow path to generate ozone water, and is provided with a circulation pump for circulating the generated ozone water, and the ozone gas supply unit and the non-ozone water supply flow path are connected to the circulation flow path; an ozone water supply flow path, provided with an ozone water supply pump for supplying a portion of the ozone water circulating in the circulation flow path to the filtration membrane, and connected to the circulation flow path; as well as The control unit controls the non-ozone water supply pump, the circulation pump and the ozone water supply pump to simultaneously supply the non-ozone water to the circulation flow path, generate the ozone water in the circulation flow path, circulate the ozone water in the circulation flow path and supply the ozone water to the filtration membrane.

2. The filter membrane cleaning device according to claim 1, characterized in that: The control unit controls at least one of the non-ozone water supply pump and the ozone water supply pump so that a flow rate of the non-ozone water supplied from the non-ozone water supply flow path to the circulation flow path is the same as a flow rate of the ozone water supplied from the circulation flow path to the ozone water supply flow path.

3. The filter membrane cleaning device according to claim 1 or 2, characterized in that: The control unit controls at least one of the circulation pump and the ozone water supply pump so that a flow rate of the ozone water in the circulation flow path is higher than a flow rate of the ozone water supplied from the circulation flow path to the ozone water supply flow path.

4. The filter membrane cleaning device according to claim 1 or 2, characterized in that: The circulation flow path further includes a dissolved ozone concentration measuring unit for measuring the dissolved ozone concentration of the ozone water in the circulation flow path. The control unit stops supplying the non-ozone water to the circulation flow path and the ozone water to the filter membrane when the dissolved ozone concentration is less than a preset threshold value, generates the ozone water in the circulation flow path and circulates the ozone water in the circulation flow path, and restarts supplying the non-ozone water to the circulation flow path and the ozone water to the filter membrane when the dissolved ozone concentration becomes higher than the preset threshold value.

5. The filter membrane cleaning device according to claim 1 or 2, characterized in that: The filter membrane cleaning device further includes an overflow water flow path connected to the circulation flow path and used to discharge the ozone water from the circulation flow path when the ozone water exceeding a preset water volume circulates in the circulation flow path.

6. The filter membrane cleaning device according to claim 1 or 2, characterized in that: The filter membrane cleaning device further includes an ozone gas exhaust unit connected to the circulation flow path and exhausting the ozone gas that is not dissolved in the circulation flow path from the circulation flow path.

7. The filter membrane cleaning device according to claim 1 or 2, characterized in that: The filter membrane cleaning device also has: a cleaning water tank storing cleaning water containing chemicals other than the ozone; and The cleaning flow path is provided with a cleaning pump for supplying the cleaning water stored in the cleaning water tank to the filtering membrane, and connects the filtering membrane and the cleaning water tank.

8. The filter membrane cleaning device according to claim 1 or 2, characterized in that: The non-ozone water is at least any one of membrane filtered water, tap water, industrial water, ion exchange water, pure water and ultrapure water.

9. A water treatment device, wherein: The water treatment device comprises: A membrane separation tank having a filter membrane for performing membrane filtration treatment on the treated water; A membrane filtration water tank for storing membrane filtered water subjected to membrane filtration treatment in the membrane separation tank; An ozone gas supply unit for supplying ozone gas; The non-ozone water supply flow path is provided with a non-ozone water supply pump for supplying water that does not contain ozone, i.e., non-ozone water; a circulation flow path, which is a flow path in which the ozone gas supplied by the ozone gas supply unit dissolves in the non-ozone water supplied from the non-ozone water supply flow path to generate ozone water, and is provided with a circulation pump for circulating the generated ozone water, and the ozone gas supply unit and the non-ozone water supply flow path are connected to the circulation flow path; an ozone water supply flow path, provided with an ozone water supply pump for supplying a portion of the ozone water circulating in the circulation flow path to the filtration membrane, and connected to the circulation flow path; as well as The control unit controls the non-ozone water supply pump, the circulation pump and the ozone water supply pump to simultaneously supply the non-ozone water to the circulation flow path, generate the ozone water in the circulation flow path, circulate the ozone water in the circulation flow path and supply the ozone water to the filtration membrane.

10. A filter membrane cleaning method, characterized in that: The filter membrane cleaning method comprises: The step of supplying water not containing ozone, i.e., non-ozone water, to the circulation flow path; A step of dissolving ozone gas in the non-ozone water in the circulation flow path to generate ozone water; A step of circulating the ozone water in the circulation flow path; as well as a step of supplying a portion of the ozone water circulating in the circulation flow path to a filtration membrane, The non-ozone water is supplied to the circulation flow path, the ozone water is generated in the circulation flow path, the ozone water in the circulation flow path is circulated, and the ozone water is supplied to the filtration membrane at the same time.

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