Monitoring device

Abstract

Provided is a monitoring device capable of improving sensitivity in detection of particles to be monitored contained in treated water obtained by wastewater treatment. The monitoring device (4) is provided with: a branch pipe (402) that branches from a pipe (401) that guides treated water obtained by drainage treatment; a membrane sensor (45) having a filtration membrane that is provided in a direction intersecting the flow of the treated water flowing through the branch pipe (402) and that filters the treated water; and a pressure sensor (46) that measures a differential pressure between a first pressure of the treated water upstream of the membrane sensor (45) and a second pressure of the treated water downstream of the membrane sensor (45). The filtration membrane has a smaller pore diameter than particles to be monitored.

Description

Technical Field

[0001] The present invention relates to a monitoring device for detecting leakage of particles to be monitored in wastewater treatment. Background Art

[0002] Patent Documents 1 and 2 disclose devices for detecting the integrity of a filtration membrane.

[0003] The device disclosed in Patent Document 1 receives the permeate of the filter membrane and detects damage to the filter membrane based on the pressure on the supply side of the first sensor membrane, the pressure between the first sensor membrane and the second sensor membrane, and the pressure on the permeate side of the second sensor membrane. The first sensor membrane is arranged parallel to the flow of the permeate of the filter membrane. That is, in the device described in Patent Document 1, a cross-flow filtration method is adopted.

[0004] The device disclosed in Patent Document 2 receives the permeate of the filter membrane into the first chamber, and detects damage to the filter membrane based on the measured pressure of the pressure measuring device provided on the supply side of the sensor membrane and the measured pressure of the pressure measuring device provided on the permeate side of the sensor membrane. The sensor membrane provided between the first chamber and the second chamber is provided in parallel with the flow of the permeate of the filter membrane. That is, in the device described in Patent Document 2, a cross-flow filtration method is adopted.

[0005] In order to detect the particles of the monitored object contained in the treated water obtained by drainage treatment, a device using a cross-flow filtration method such as Patent Document 1 and Patent Document 2 has a sensor membrane with a membrane surface arranged in parallel with the flow of the treated water supplied to the sensor membrane, so that the accumulation of particles on the membrane surface of the sensor membrane can be suppressed by the flow. Therefore, the clogging of the sensor membrane can be suppressed, and thus there is an advantage that the replacement frequency of the sensor membrane can be reduced. However, since the total amount of particles of the monitored object contained in the treated water supplied to the sensor membrane is not filtered by the sensor membrane, only a part of the particles of the monitored object contained in the treated water supplied to the sensor membrane can be captured. Therefore, in the device using the cross-flow filtration method, it is difficult to improve the sensitivity in the detection of particles of the monitored object contained in the treated water obtained by drainage treatment. There is room for improvement.

[0006] In contrast, a device that adopts a dead-end filtration method has a sensor membrane with a membrane surface arranged crosswise with the flow of the treated water supplied to the sensor membrane, and filters the total amount of the treated water supplied to the sensor membrane. Therefore, it is possible to capture the total amount of particles of the monitored object contained in the treated water supplied to the sensor membrane, and thus has the advantage of being able to improve the sensitivity in detecting the particles of the monitored object contained in the treated water obtained by drainage treatment. However, compared with a device that adopts a cross-flow filtration method, more particles other than the monitored object are also captured. Therefore, in a device that adopts a dead-end filtration method, compared with a device that adopts a cross-flow filtration method, there is room for improvement in that the sensor membrane that captures the particles of the monitored object has a high frequency of replacement and that leakage of the particles of the monitored object may cause false detection.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: U.S. Patent No. 8135547

[0010] Patent Document 2: U.S. Patent No. 10159941 Summary of the invention

[0011] Problem that the invention aims to solve

[0012] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a monitoring device capable of improving the sensitivity in detecting particles to be monitored contained in treated water obtained by wastewater treatment.

[0013] Means used to solve problems

[0014] A first embodiment of the present invention is a monitoring device for detecting leakage of particles of a monitored object during drainage treatment, and is characterized in that it comprises: a branch pipe branching from a pipe that guides treated water obtained through the drainage treatment; a membrane sensor having a filter membrane, the filter membrane being arranged in a direction intersecting with the flow of the treated water flowing in the branch pipe and filtering the treated water; and a pressure sensor for measuring the differential pressure between a first pressure of the treated water on the upstream side of the membrane sensor and a second pressure of the treated water on the downstream side of the membrane sensor, the filter membrane having a pore size smaller than that of the particles of the monitored object.

[0015] According to the first embodiment of the present invention, the filter membrane for filtering the treated water flowing in the branch pipe is arranged in a direction intersecting with the flow of the treated water. In other words, the monitoring device adopts a dead-end filtering method. In addition, since the filter membrane has a smaller pore size than the particles of the monitored object, the particles of the monitored object can be captured more reliably. Therefore, the monitoring device can improve the sensitivity in detecting the particles of the monitored object.

[0016] A second aspect of the present invention is the monitoring device according to the first aspect of the present invention, wherein the filter membrane is a track-etched membrane.

[0017] According to the second aspect of the present invention, since the filter membrane is a track-etched membrane, the pore size distribution of the pores formed in the filter membrane is uniform. Therefore, the monitoring device can suppress erroneous detection of leakage of particles to be monitored and can improve the sensitivity in detecting particles to be monitored.

[0018] A third aspect of the present invention is the monitoring device according to the first or second aspect of the present invention, wherein the pore size is formed so as to allow proteins smaller than the particles to be monitored to pass therethrough.

[0019] According to the third aspect of the present invention, the filter membrane can allow proteins smaller than the particles of the monitoring object to pass through. That is, the particles captured by the filter membrane per unit time can be further reduced. Therefore, the monitoring device can further extend the time until the filter membrane is replaced, thereby suppressing the replacement frequency of the filter membrane and improving the sensitivity in detecting the particles of the monitoring object.

[0020] The fourth aspect of the present invention is a monitoring device according to any one of the first to third aspects of the present invention, characterized in that the protein adsorption rate of the filter membrane is lower than the protein adsorption rate of cellulose acetate (CA), polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) respectively.

[0021] According to the fourth aspect of the present invention, the protein adsorption rate of the filter membrane is less than a predetermined value. Therefore, it is possible to further suppress the situation where the protein is adsorbed on the filter membrane and causes clogging of the filter membrane. Therefore, the monitoring device can suppress the replacement frequency of the filter membrane and further improve the sensitivity in detecting the particles of the monitoring object.

[0022] The fifth aspect of the present invention is a monitoring device according to any one of the first to fourth aspects of the present invention, characterized in that the pressure sensor calculates the filtration resistance by dividing the differential pressure by the filtration flux, and detects the leakage based on the ratio of the time average value of the filtration resistance at a first moment to the time average value of the filtration resistance at a second moment after the first moment.

[0023] According to the fifth aspect of the present invention, the monitoring device can detect leakage of particles to be monitored with higher accuracy regardless of temporal changes in the flow rate of treated water flowing through the branch pipe.

[0024] A sixth aspect of the present invention is the monitoring device according to any one of the first to fourth aspects of the present invention, wherein the pressure sensor calculates a filtration resistance only from the differential pressure and detects the leakage based on the filtration resistance.

[0025] According to the sixth aspect of the present invention, the monitoring device can detect leakage of particles to be monitored with higher accuracy.

[0026] The seventh aspect of the present invention is a monitoring device according to any one of the first to sixth aspects of the present invention, characterized in that it also has an exhaust valve, which is arranged on the upstream side of the membrane sensor and discharges air mixed in the treated water flowing in the branch pipe toward the membrane sensor.

[0027] According to the seventh aspect of the present invention, the monitoring device can discharge air mixed in the treated water and suppress the deviation of the value of the monitoring index (such as filtration resistance). Thus, the monitoring device can detect the particles of the monitoring object with higher accuracy and can detect the leakage of the particles of the monitoring object with higher accuracy.

[0028] An eighth aspect of the present invention is the monitoring device according to any one of the first to seventh aspects of the present invention, further comprising a concentration equalizing mechanism, the concentration equalizing mechanism being disposed on the upstream side of the membrane sensor and making the concentration of the treated water equal.

[0029] According to the eighth aspect of the present invention, the concentration equalization mechanism can make the concentration of the entire treated water obtained by the drainage treatment uniform. Thus, the monitoring device can reduce the concentration polarization of solids in the entire treated water obtained by the drainage treatment. Therefore, even if the flow rate of the treated water flowing in the branch pipe is relatively small relative to the total flow rate of the treated water obtained by the drainage treatment, the leakage of the particles of the monitored object can be detected with higher accuracy.

[0030] Effects of the Invention

[0031] According to the present invention, it is possible to provide a monitoring device capable of improving the sensitivity in detecting particles to be monitored contained in treated water obtained by wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a block diagram showing a monitoring device according to an embodiment of the present invention.

[0033] Figure 2 This is a schematic cross-sectional view showing a filter membrane of the membrane sensor according to the present embodiment.

[0034] Figure 3 This is a schematic cross-sectional view showing a filter membrane of a membrane sensor according to a comparative example.

[0035] Figure 4 This is a diagram illustrating an example of the results of studies conducted by the present inventors. DETAILED DESCRIPTION

[0036] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0037] In addition, the embodiments described below are preferred specific examples of the present invention, and therefore various technically preferred limitations are added, but as long as there is no record of the meaning of the present invention being particularly limited in the following description, the scope of the present invention is not limited to these modes. In addition, in each of the accompanying drawings, the same reference numerals are marked on the same constituent elements and detailed descriptions are appropriately omitted.

[0038] Figure 1 It is a block diagram showing a monitoring device according to an embodiment of the present invention.

[0039] The monitoring device 4 involved in this embodiment detects leakage of particles of the monitoring object during drainage treatment. For example, drainage treatment includes biological treatment and membrane treatment. However, the drainage treatment of this embodiment does not necessarily need to include biological treatment and membrane treatment, and may include, for example, a total turbidity removal process using sand filtration, fiber filtration, and wound filter. In the description of this embodiment, the case where drainage treatment includes biological treatment and membrane treatment is cited as an example. In this case, Figure 1 As shown, the monitoring device 4 according to the present embodiment detects leakage of particles to be monitored due to damage of a membrane used in the membrane treatment 3 during wastewater treatment in which the biological treatment 2 and the membrane treatment 3 are performed.

[0040] Figure 1 The process of biological treatment 2 shown is a process of introducing treated water into a biological reactor tank for biological treatment to obtain biologically treated water. Biological treatment 2 is not particularly limited as long as it is a process for treating the treated water introduced into the biological reactor tank in the presence of microorganisms. In other words, biological treatment 2 can be an aerobic biological treatment or an anaerobic biological treatment. In other words, the microorganisms can be aerobic microorganisms or anaerobic microorganisms. As biological treatment 2, for example, activated sludge method (including membrane separation activated sludge method), carrier method, fixed bed biofilm method, etc. can be cited.

[0041] Through the biological treatment step 2, biologically treated water with reduced organic water pollutants contained in the water to be treated is obtained.

[0042] Figure 1 The membrane treatment 3 shown can be performed in the latter stage of the biological treatment 2, or can be performed in the same stage as the biological treatment 2. Specifically, the membrane separation device (not shown) used in the membrane treatment 3 can be arranged outside the biological reaction tank used in the biological treatment 2, or can be arranged inside the biological reaction tank. In the case where the membrane separation device is arranged outside the biological reaction tank, the membrane separation device performs solid-liquid separation on the biological treatment water obtained by the process of the biological treatment 2 to obtain membrane-treated water. On the other hand, in the case where the membrane separation device is arranged inside the biological reaction tank, the membrane separation device performs solid-liquid separation on the liquid in the biological reaction tank to obtain membrane-treated water. The membrane-treated water of this embodiment is an example of the "treated water" of the present invention.

[0043] The membrane used in the membrane treatment 3, i.e., the membrane provided in the membrane separation device, is not particularly limited as long as it is a membrane capable of performing solid-liquid separation on the biological treatment water and the liquid in the tank of the biological reaction tank. As the membrane used in the membrane treatment 3, for example, a precision filtration membrane (MF membrane), an ultrafiltration membrane (UF membrane), etc. can be cited. As the shape of the membrane used in the membrane treatment 3, for example, a hollow fiber membrane, a tubular membrane, a flat membrane, etc. can be cited. As the material of the membrane used in the membrane treatment 3, for example, organic membranes such as cellulose acetate, polyvinylidene fluoride, polyolefin, chlorinated polyethylene, polyamide, polyacrylonitrile, polytetrafluoroethylene, and inorganic membranes such as ceramics (such as mullite, alumina, zirconium oxide), etc. can be cited.

[0044] In addition, as described above, the wastewater treatment of this embodiment does not necessarily need to include membrane treatment. For example, biologically treated water can also be obtained by solid-liquid separation using a solid-liquid separation mechanism (e.g., a sedimentation tank) other than a membrane separation device. In this case, the biologically treated water of this embodiment becomes an example of "treated water" of the present invention.

[0045] Figure 1 The monitoring device 4 shown includes a pipe 401 , a branch pipe 402 , a water supply switching valve 42 , a membrane sensor 45 , a differential pressure sensor 46 , and a flow rate sensor 47 .

[0046] The pipe 401 guides the membrane treated water obtained by the membrane treatment 3. The branch pipe 402 branches from the pipe 401 and guides at least a part of the membrane treated water flowing in the pipe 401 to the membrane sensor 45. The water supply switching valve 42 is provided in the branch pipe 402, and switches between a state in which at least a part of the membrane treated water flowing in the pipe 401 flows to the membrane sensor 45 and a state in which the membrane treated water flowing in the pipe 401 is prevented from flowing to the membrane sensor 45. That is, when the water supply switching valve 42 is opened, at least a part of the membrane treated water flowing in the pipe 401 flows to the membrane sensor 45. On the other hand, when the water supply switching valve 42 is closed, the membrane treated water flowing in the pipe 401 does not flow to the membrane sensor 45, but is guided to the post-process of the monitoring device 4.

[0047] The membrane sensor 45 has a filter membrane, and uses the filter membrane to filter the membrane-treated water flowing in the branch pipe 402. The filter membrane of the membrane sensor 45 is set in a direction that intersects the flow of the membrane-treated water, and filters the total amount of the membrane-treated water flowing in the branch pipe 402 to capture the particles of the monitoring object. In other words, the membrane sensor 45 adopts a dead-end filtering method. The filter membrane of the membrane sensor 45 has a pore size smaller than the particles of the monitoring object.

[0048] Among them, in the present specification, the "dead-end filtration method" refers to a method in which a filter membrane for filtering treated water such as membrane treated water and biological treated water is arranged in a direction intersecting (specifically, orthogonal) with the flow of the treated water flowing in the branch pipe 402, and the total amount of the treated water flowing in the branch pipe 402 is filtered. On the other hand, in the present specification, the "cross-flow filtration method" refers to a method in which a filter membrane for filtering treated water such as membrane treated water and biological treated water is arranged in a direction parallel to the flow of the treated water flowing in the branch pipe 402, and a part of the treated water flowing in the branch pipe 402 is filtered.

[0049] The particles of the monitoring object captured by the filter membrane of the membrane sensor 45 are particles that are not included in the membrane treated water when the membrane used in the membrane treatment 3 is not damaged, and are particles with a diameter of, for example, about 3 μm or more. Examples of the particles of the monitoring object captured by the filter membrane of the membrane sensor 45 include Cryptosporidium and Giardia lamblia. On the other hand, the particles other than the monitoring object captured by the filter membrane of the membrane sensor 45 are particles that are included in the membrane treated water even if the membrane used in the membrane treatment 3 is not damaged, and are particles with a diameter of, for example, less than about 1 μm. Examples of the particles other than the monitoring object captured by the filter membrane of the membrane sensor 45 include proteins.

[0050] The filter membrane of the membrane sensor 45 will be described in detail later.

[0051] The differential pressure sensor 46 measures the differential pressure between the first pressure of the membrane treated water at the first position A1 on the upstream side (i.e., the primary side) of the membrane sensor 45 and the second pressure of the membrane treated water at the second position A2 on the downstream side (i.e., the secondary side) of the membrane sensor 45. The differential pressure sensor 46 of this embodiment is an example of the "pressure sensor" of the present invention. The first position A1 is an arbitrary position of the branch pipe 402 on the upstream side of the membrane sensor 45. The second position A2 is an arbitrary position of the branch pipe 402 on the downstream side of the membrane sensor 45.

[0052] The differential pressure sensor 46 calculates the filtration resistance as a monitoring index and detects the leakage of the particles to be monitored based on the filtration resistance. For example, the differential pressure sensor 46 calculates the filtration resistance by dividing the differential pressure between the first pressure and the second pressure by the filtration flux. In this application specification, "filtration flux" refers to the amount of water filtered by the membrane per unit membrane area per unit time (m 3 / (m 2 ·d) or m / d), for example, per membrane area (1m 2 ) per day (m 3 / d). Furthermore, the differential pressure sensor 46 detects the leakage of the particles of the monitoring object based on the ratio of the time average value of the filtration resistance at the first moment to the time average value of the filtration resistance at the second moment after the first moment. For example, the second moment is a time that is about 1 hour or more and 6 hours later than the first moment. Alternatively, when the flow rate of the membrane treated water flowing in the branch pipe 402 is stable, the differential pressure sensor 46 may calculate the filtration resistance only based on the differential pressure between the first pressure and the second pressure, and detect the leakage of the particles of the monitoring object based on the filtration resistance.

[0053] The filtration flux in the membrane sensor 45 of the present embodiment is, for example, about 5 m / d, which is higher than the filtration flux (about 1 m / d or less) in a general membrane separation activated sludge method.

[0054] In addition, a first pressure sensor for measuring the first pressure of the membrane treated water at the first position A1 and a second pressure sensor for measuring the second pressure of the membrane treated water at the second position A2 may be provided instead of the differential pressure sensor 46. In this case, the control unit (not shown) calculates the differential pressure between the first pressure and the second pressure based on the detection signal related to the first pressure received from the first pressure sensor and the detection signal related to the second pressure received from the second pressure sensor.

[0055] like Figure 1As shown, the flow sensor 47 measures the flow rate of the membrane treated water flowing in the branch pipe 402 on the downstream side (i.e., the secondary side) of the membrane sensor 45. However, in the monitoring device 4 involved in this embodiment, the dead-end filtering membrane sensor 45 is used, so the flow rate of the membrane treated water flowing in the branch pipe 402 is roughly the same everywhere. Therefore, the arrangement of the flow sensor 47 is not limited to the downstream side of the membrane sensor 45, and it can also be the upstream side of the membrane sensor 45.

[0056] like Figure 1 As shown, the monitoring device 4 may further include a concentration equalizing mechanism 41 , a water supply amount regulating valve 43 , a water supply pump 44 , and an exhaust valve 48 .

[0057] The concentration equalizing mechanism 41 is provided on the upstream side of the membrane sensor 45. Specifically, the concentration equalizing mechanism 41 is provided on the pipe 401 on the upstream side of the portion (i.e., the branch portion) where the branch pipe 402 is connected to the pipe 401. The concentration equalizing mechanism 41 can make the concentration of the membrane treated water uniform. Examples of the concentration equalizing mechanism 41 include a line mixer, a stirrer, and the like.

[0058] like Figure 1 As shown, the water supply amount regulating valve 43 is provided in the branch pipe 402 between the water supply switching valve 42 and the water supply pump 44 to adjust the flow rate of the membrane treated water flowing in the branch pipe 402. However, the water supply amount regulating valve 43 only needs to be able to adjust the flow rate of the membrane treated water flowing in the branch pipe 402, so it can also be arranged on the discharge side of the water supply pump 44. In addition, the water supply amount regulating valve 43 may not be provided, and the flow rate of the membrane treated water flowing in the branch pipe 402 may be adjusted by the water supply switching valve 42. In addition, in the case where a variable flow type fixed flow pump is used as the water supply pump 44, and in the case where a variable flow mechanism such as an inverter is provided in the water supply pump 44, the water supply amount regulating valve 43 can also be omitted.

[0059] like Figure 1 As shown, the water delivery pump 44 is provided in the branch pipe 402 between the water delivery amount adjustment valve 43 and the membrane sensor 45 , draws membrane treated water from the pipe 401 to the branch pipe 402 , and delivers the drawn membrane treated water to the membrane sensor 45 .

[0060] like Figure 1 As shown in FIG. 4 , the exhaust valve 48 is provided in the air exhaust pipe 403, and the air mixed in the membrane treated water flowing toward the membrane sensor 45 in the branch pipe 402 can be exhausted through the air exhaust pipe 403. The air exhaust pipe 403 is connected to the branch pipe 402 on the upstream side of the membrane sensor 45. By opening the exhaust valve 48, the air mixed in the membrane treated water can be exhausted through the air exhaust pipe 403.

[0061] The air mixed in the membrane treated water flowing toward the membrane sensor 45 in the branch pipe 402 is lighter than the membrane treated water as a liquid, and therefore tends to accumulate in the upper part of the vertical direction in the branch pipe 402. Therefore, the exhaust valve 48 is preferably provided at the uppermost position in the vertical direction in the branch pipe 402. Figure 1 In the case of the dead-end filtration method shown in the figure, compared with the cross-flow filtration method as in the above-mentioned Patent Documents 1 and 2, the piping ( Figure 1 The branch pipe 402 in the membrane sensor is likely to be long, so air is likely to be trapped inside the pipe that guides the membrane treated water to the membrane sensor. If air is trapped inside the pipe that guides the membrane treated water to the membrane sensor, measurement errors are likely to occur in the differential pressure sensor. In this embodiment, Figure 1 As shown, air accumulation in the branch pipe 402 can be eliminated by the exhaust valve 48, so that the measurement accuracy of the differential pressure sensor 46 can be improved. Therefore, the detection accuracy of the membrane sensor 45 can be improved.

[0062] Among them, as mentioned above, the membrane sensor 45 of this embodiment adopts a dead-end filtration method. Therefore, compared with the membrane sensor adopting the cross-flow filtration method, the filter membrane of the membrane sensor 45 can capture more particles of the monitored object. Therefore, the monitoring device 4 involved in this embodiment can improve the sensitivity in the detection of particles of the monitored object. However, the sensor membrane adopting the dead-end filtration method filters the total amount of treated water, so compared with the membrane sensor adopting the cross-flow filtration method, it will also capture more particles other than the monitored object. Therefore, compared with the membrane sensor adopting the cross-flow filtration method, the membrane sensor adopting the dead-end filtration method has a high frequency of replacement of the filter membrane that captures the particles of the monitored object and a situation in which the leakage of the particles of the monitored object is erroneously detected.

[0063] In this regard, in the monitoring device 4 involved in this embodiment, the filter membrane of the membrane sensor 45 has a pore size smaller than the particles of the monitoring object. In addition, the pore size distribution of the pores formed in the filter membrane of the membrane sensor 45 is narrower than the prescribed distribution. Since the dead-end filtration method is adopted, the pore size of the filter membrane of the membrane sensor 45 is more uniform, so the filter membrane of the membrane sensor 45 can allow particles other than the monitoring object (such as proteins smaller than the particles of the monitoring object) to pass through, and on the other hand, it can more reliably capture the particles of the monitoring object (such as Cryptosporidium, Giardia lamblia, etc.). Therefore, the monitoring device 4 involved in this embodiment can suppress the leakage of the particles of the monitoring object from being misdetected, and can improve the sensitivity in the detection of the particles of the monitoring object. In addition, the protein adsorption rate of the filter membrane of the membrane sensor 45 is less than the prescribed value. Therefore, it is possible to suppress the protein contained in the treated water as particles other than the monitoring object from being adsorbed on the filter membrane of the membrane sensor 45. As a result, the monitoring device 4 involved in this embodiment can suppress the replacement frequency of the filter membrane of the membrane sensor 45.

[0064] Hereinafter, the film sensor 45 of the present embodiment will be further described with reference to the drawings.

[0065] Figure 2 This is a schematic cross-sectional view showing a filter membrane of the membrane sensor according to the present embodiment.

[0066] Figure 3 This is a schematic cross-sectional view showing a filter membrane of a membrane sensor according to a comparative example.

[0067] also, Figure 2 (a) and Figure 3 (a) shows a state before the particle 52 to be monitored is captured by the filter membrane. Figure 2 (b) and Figure 3 (b) shows a state where the particle 52 to be monitored is captured by the filter membrane.

[0068] As an example of particles 51 other than the monitored object, the size of the aforementioned protein particles is smaller than the monitored object particles 52. In addition, it is known that proteins are adsorbed on the surfaces of materials such as plastics, glass, and metals in a water-soluble state. When the treated water is organic wastewater, the concentration of proteins is high not only in the treated water, but also in treated water such as biological treatment water and membrane treatment water, compared with the case where the treated water is inorganic wastewater.

[0069] Among them, first of all, refer to Figure 3 (a) and Figure 3(b) describes the filter membrane 451A of the membrane sensor 45A of the comparative example. The pore size distribution of the pores formed in the filter membrane 451A is relatively wide. In other words, the diameter of the pores formed in the filter membrane 451A is relatively uneven. Examples of the material of the filter membrane 451A of the comparative example include cellulose acetate (CA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and the like.

[0070] When the pore size distribution is relatively wide, that is, when the pore diameters are relatively non-uniform, as in the filter membrane 451A of the comparative example, many particles 51 other than the monitoring target, such as proteins, are captured by the filter membrane 451A. Figure 3 As shown in (a), even if the membrane used in the membrane treatment 3 is not damaged, many particles 51 other than the monitored object will be captured by the filter membrane 451A. Figure 1 The differential pressure between the first pressure and the second pressure may sometimes become the same as the case where the membrane used in the membrane treatment 3 is damaged. Thus, even if the membrane used in the membrane treatment 3 is not damaged, the differential pressure sensor 46 may sometimes erroneously detect that the membrane used in the membrane treatment 3 is damaged. In addition, even if the membrane used in the membrane treatment 3 is not damaged, many particles 51 other than the monitored object are captured by the filter membrane 451A. Figure 3 As shown in (b), when the membrane used in the membrane treatment 3 is damaged and the particle 52 to be monitored is captured by the filter membrane 451A, the differential pressure between the first pressure and the second pressure, in other words, the filtration resistance as a monitoring indicator, sometimes has difficulty in showing an inflection point. In addition, since the filter membrane 451A may be clogged with particles 51 other than the monitored object, the replacement frequency of the filter membrane 451A may become high.

[0071] In contrast, Figure 2 (a) and Figure 2As shown in (b), the filter membrane 451 of the membrane sensor 45 of the present embodiment has a hole 452 whose pore size is smaller than the particle 51 of the monitored object. The pore size distribution of the hole 452 formed in the filter membrane 451 is narrower than the prescribed distribution. In other words, the diameter of the hole 452 formed in the filter membrane 451 is relatively uniform. The pore size distribution of the hole 452 formed in the filter membrane 451 is narrower than the pore size distribution of cellulose acetate (CA), polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). As the filter membrane 451 of the present embodiment, track-etched membranes made of polycarbonate (PC), polyester (PEs) and the like can be cited. Among them, in the present application specification, "track-etched membrane" refers to a filter membrane manufactured using an etching process using an ion beam. Compared with polytetrafluoroethylene (PTFE) and the like, the track-etched membrane has the characteristics of narrow pore size distribution and thin membrane thickness. Specifically, examples of the material of the filter membrane 451 include Isopore (registered trademark) manufactured by Merck.

[0072] The pore size of the filter membrane 451 of the membrane sensor 45 of this embodiment is preferably a size capable of capturing particles such as Cryptosporidium and Giardia lamblia as monitored objects, and a size capable of allowing particles such as proteins other than monitored objects to pass through.

[0073] According to these technical features related to the filter membrane 451 of this embodiment, as Figure 2 As shown in (a), the filter membrane 451 of this embodiment can allow many particles 51 other than the monitored object, such as proteins, which are smaller in size than the monitored object particles 52, to pass through the holes 452. Figure 2 As shown in (b), the filter membrane 451 can more reliably capture the monitored particle 52. Therefore, the monitoring device 4 according to this embodiment can suppress the false detection of the leakage of the monitored particle 52 and improve the sensitivity in the detection of the monitored particle 52.

[0074] In addition, the protein adsorption rate of the filter membrane 451 is less than the specified value. The protein adsorption rate of the filter membrane 451 is less than the protein adsorption rate of cellulose acetate (CA), polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). The protein adsorption rate of Isopore manufactured by Merck is 3 μg / cm 2 , which is lower than the protein adsorption rate of Omnipore (registered trademark) made of hydrophilic polytetrafluoroethylene (PTFE) manufactured by Merck (4 μg / cm 2 ).

[0075] Thus, it is possible to suppress the adsorption of proteins contained in treated water such as biological treated water and membrane treated water as particles 51 other than the monitored object to the filter membrane 451. Therefore, it is possible to further suppress the adsorption of proteins to the filter membrane 451 and the clogging of the filter membrane 451. Thus, the monitoring device 4 according to the present embodiment can suppress the replacement frequency of the filter membrane 451 provided in the membrane sensor 45.

[0076] In addition, as regards Figure 1 As described above, the differential pressure sensor 46 calculates the filtration resistance by dividing the differential pressure between the first pressure and the second pressure by the filtration flux, and detects the leakage of the monitored particle 52 based on the ratio of the time average value of the filtration resistance at the first moment to the time average value of the filtration resistance at the second moment after the first moment. Thus, the monitoring device 4 according to the present embodiment can detect the leakage of the monitored particle 52 with higher accuracy regardless of the temporal change in the flow rate of the membrane treated water flowing in the branch pipe 402.

[0077] Or, as about Figure 1 As described above, when the flow rate of the membrane treated water flowing in the branch pipe 402 is stable, the differential pressure sensor 46 can also calculate the filtration resistance based on the differential pressure between the first pressure and the second pressure, and detect the leakage of the monitored particles 52 based on the filtration resistance. In this case, the monitoring device 4 involved in this embodiment can also detect the leakage of the monitored particles 52 with higher accuracy.

[0078] In addition, the exhaust valve 48 can be opened intermittently to discharge the air mixed in the membrane treated water flowing toward the membrane sensor 45 in the branch pipe 402 through the air exhaust pipe 403. For example, the exhaust valve 48 is opened about once a day for about 1 minute. Thus, the monitoring device 4 involved in this embodiment can discharge the air mixed in the membrane treated water and suppress the deviation of the value of the filtration resistance as a monitoring index. Thus, the monitoring device 4 can detect the particles 52 of the monitoring object with higher accuracy and can detect the leakage of the particles 52 of the monitoring object with higher accuracy.

[0079] In addition, the concentration equalization mechanism 41 is provided on the upstream side of the membrane sensor 45, and can make the concentration of the membrane treated water uniform. Thus, the monitoring device 4 according to the present embodiment can reduce the concentration polarization of solids in the entire membrane treated water. Therefore, even when the flow rate of the membrane treated water flowing in the branch pipe 402 is relatively small relative to the total flow rate of the membrane treated water flowing in the pipe 401, the leakage of the particles 52 to be monitored can be detected with higher accuracy.

[0080] Next, an example of the results of experiments performed by the present inventors will be described with reference to the drawings.

[0081] Figure 4 This is a diagram illustrating an example of the results of studies conducted by the present inventors.

[0082] Figure 4 The horizontal axis of the graph shown represents the filtration time (min). Figure 4 The vertical axis of the graph shown represents filtration resistance (kPa / (m / d)).

[0083] The inventors used Isopore (material: PC) manufactured by Merck and Omnipore (material: PTFE) manufactured by Merck to compare the changing tendency of filtration resistance during water flow. Isopore (material: PC) manufactured by Merck is a track-etched membrane. Hereinafter, for the sake of convenience, Isopore (material: PC) manufactured by Merck is referred to as "first material 455", and Omnipore (material: PTFE) manufactured by Merck is referred to as "second material 456".

[0084] The nominal pore size of the first material 455 is 1.2 μm, which is approximately the same as the nominal pore size (1.0 μm) of the second material 456. The protein adsorption rate of the first material 455 is lower than that of the second material 456, but is approximately the same. On the other hand, the pore size distribution of the first material 455 is narrower than that of the second material 456.

[0085] The experimental conditions are explained. The diameter of the filter membrane is The filtrate is tap water. The inventors added sludge to the tap water at a time when 60 to 90 minutes had passed since the start of filtration. The sludge was 10,790 mg / L MLSS. The sludge addition rate was 100 ppm. Before the sludge was added, the turbidity of the filtrate passed through the filter membrane of the first material 455 was 0.12 NTU. After the sludge was added, the turbidity of the filtrate passed through the filter membrane of the first material 455 was 0.44 NTU. Before the sludge was added, the turbidity of the filtrate passed through the filter membrane of the second material 456 was 0.10 NTU. After the sludge was added, the turbidity of the filtrate passed through the filter membrane of the second material 456 was 0.48 NTU.

[0086] The temperature of the filtered liquid passing through the filter membrane of the first material 455 was 21.2° C. The temperature of the filtered liquid passing through the filter membrane of the second material 456 was 22.5° C. The filtration flux was 40 m / d. The inventor used a portable turbidity meter 2100P manufactured by HACH as a turbidity meter. In addition, the inventor used a pressure sensor instead of a differential pressure sensor.

[0087] In addition, the present inventors calculated the filtration resistance R using the following formula.

[0088] R(kPa / (m / d))=((Pf1-Pf2)-(Ps1-Ps2)) / F

[0089] R: Filtration resistance

[0090] Pf1: Filtration primary side pressure during filtration [kPa]

[0091] Pf2: Filtration secondary side pressure during filtration [kPa]

[0092] Ps1: Filtration primary side pressure when filtration stops [kPa]

[0093] Ps2: Filtration secondary side pressure when filtration stops [kPa]

[0094] F: Filtration flux [m / d]

[0095] Primary filtration side: the filtered water side, i.e. the upstream side of the filtration membrane

[0096] Secondary filtration side: the water side of the membrane filtration, i.e. the downstream side of the filtration membrane

[0097] The experiment was carried out under the above conditions. As a result, the filtration resistance during water flow changes with time. Figure 4 That is, it was confirmed that when no sludge was mixed ( Figure 4 In the example before the addition of sludge shown in FIG. 4 , the increase in the filtration resistance of the first material 455 is smaller than the increase in the filtration resistance of the second material 456. In addition, regarding the presence or absence of an inflection point of the filtration resistance caused by the addition of sludge, it was confirmed that the inflection point of the first material 455 is easier to determine than the inflection point of the second material 456. In other words, the rate of change of the filtration resistance of the first material 455 caused by the addition of sludge is greater than the rate of change of the filtration resistance of the second material 456 caused by the addition of sludge.

[0098] according to Figure 4 As shown in the figure, the nominal pore size and protein adsorption rate of the first material 455 are approximately the same as the nominal pore size and protein adsorption rate of the second material 456, so it is believed that Figure 4 The difference in the temporal change of the filtration resistance shown is caused by the width or narrowness of the pore size distribution.

[0099] The second material 456 with a relatively wide pore size distribution can also easily capture substances with a smaller nominal pore size. Therefore, even if sludge is not mixed in, the filtration resistance will increase. When the capture of particles, that is, the clogging of the filter membrane progresses, even particles smaller than sludge (large particles) will accumulate on the membrane surface. Therefore, it is believed that even if sludge is mixed in, there will be no clear inflection point in the filtration resistance of the second material 456.

[0100] On the other hand, in the first material 455 having a relatively narrow pore size distribution, the capture rate of particles smaller than the pore size is lower than that in the second material 456. Therefore, the clogging of the filter membrane progresses more slowly than that of the second material 456. With regard to the mixing of sludge (large particles) and the accumulation on the membrane surface, the clogging mechanism of the filter membrane of the first material 455 is different from that of the filter membrane of the second material 456. Therefore, it is considered that a clear inflection point is generated in the filtration resistance of the first material 455.

[0101] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the scope of the claims. The structures of the above embodiments can be partially omitted or arbitrarily combined in a manner different from the above.

[0102] Description of Reference Numerals

[0103] 2: Biological treatment, 3: Membrane treatment, 4: Monitoring device, 41: Concentration equalization mechanism, 42: Water supply switching valve, 43: Water supply amount adjustment valve, 44: Water supply pump, 45: Membrane sensor, 45A: Membrane sensor, 46: Differential pressure sensor, 47: Flow sensor, 48: Exhaust valve, 51: Particles, 52: Particles, 401: Pipe, 402: Branch pipe, 403: Air exhaust pipe, 451: Filter membrane, 451A: Filter membrane, 452: Hole, 455: First material, 456: Second material, A1: First position, A2: Second position, R: Filtration resistance

Claims

1. A monitoring device for detecting leakage of particles of a monitoring object in wastewater treatment, characterized in that: have: A branch pipe branching from a pipe for guiding treated water obtained through the wastewater treatment; a membrane sensor having a filter membrane, the filter membrane being arranged in a direction intersecting with the flow of the treated water flowing in the branch pipe and filtering the treated water; as well as a pressure sensor for measuring a differential pressure between a first pressure of the treated water on the upstream side of the membrane sensor and a second pressure of the treated water on the downstream side of the membrane sensor, The filter membrane has a pore size smaller than that of the particles to be monitored.

2. The monitoring device according to claim 1, characterized in that The filter membrane is a track-etched membrane.

3. The monitoring device according to claim 1 or 2, characterized in that: The pore size is formed so as to allow proteins smaller than the particles to be monitored to pass therethrough.

4. The monitoring device according to any one of claims 1 to 3, characterized in that: The protein adsorption rate of the filtration membrane is lower than the protein adsorption rates of cellulose acetate (CA), polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

5. The monitoring device according to any one of claims 1 to 4, characterized in that: The pressure sensor calculates filtration resistance by dividing the differential pressure by filtration flux, and detects the leakage based on a ratio of a time average value of the filtration resistance at a first moment and the time average value of the filtration resistance at a second moment after the first moment.

6. The monitoring device according to any one of claims 1 to 4, characterized in that: The pressure sensor calculates a filtration resistance only from the differential pressure, and detects the leakage based on the filtration resistance.

7. The monitoring device according to any one of claims 1 to 6, characterized in that: The invention further includes an exhaust valve which is provided on the upstream side of the membrane sensor and discharges air mixed in the treated water flowing toward the membrane sensor through the branch pipe.

8. The monitoring device according to any one of claims 1 to 7, characterized in that: The device further includes a concentration equalizing mechanism which is provided on the upstream side of the membrane sensor and makes the concentration of the treated water uniform.

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