JP2012192366A - Membrane filtration system and method for detecting filter membrane damage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane filtration system which performs filtration treatment of water to be treated and monitors damage to a filter membrane, and to provide a method for detecting filter membrane damage.SOLUTION: The membrane filtration system 1 includes: a membrane filtration apparatus 10, which is partitioned into a first side region 10b and a second side region 10c by the filter membrane 10a arranged inside and in which a material to be separated in the water to be treated supplied from the first side region 10b is filtered by the filter membrane 10a; a circulating water line 32 in which magnetic material particulates are added to the water to be treated and the water to be treated, to which the magnetic material particulates are added, is circulated in the first side region 10b; and a particulate meter 14 which measures the number of particulates in treated water penetrating from the first side region 10b to the second side region 10c through the filter membrane 10a.

Description

  The present invention relates to a technique for detecting damage to a filtration membrane constituting a membrane filtration system.

  The water used for cleaning precision instrument parts such as semiconductors and for sterilization cleaning in the food and pharmaceutical fields is preferably filtered water from which fine particles and bacteria are highly removed. Conventionally, microfiltration membrane devices, ultrafiltration membrane devices and the like are known as membrane filtration devices for obtaining such high-purity filtered water. When the filtration membranes constituting these membrane filtration devices are subjected to physical or chemical damage, fine particles and the like leak from the damaged portions, so that the filtration performance is lowered and the water quality is deteriorated. As a method for continuously monitoring the decrease in filtration performance, for example, a method of continuously measuring treated water (filtered water) that has passed through a filtration membrane with a laser-type precision fine particle meter is known. In addition, although it cannot be said that it is a method for continuously monitoring the decline in filtration performance, for example, air leakage is detected by supplying pressurized air to the filtration membrane and detecting the amount of air passing through the filtration membrane to detect damage to the filtration membrane. Damage to the filtration membrane by checking (bubble point measurement) or passing filtered water through the turbidity membrane for damage confirmation to detect sudden pressure rise or drop in filtration flow rate of the turbidity membrane for damage confirmation There is a method of monitoring a decrease in filtration performance using a method for detecting the above (see, for example, Patent Documents 1 to 3).

  Currently, the lower limit of quantification of the fine particle meter used in the method for continuously monitoring the decrease in filtration performance is 1 / ml for 0.05 μm fine particles (for example, particle sensor KS-18F in liquid, manufactured by Rion). .

  Here, for example, when considering a process for obtaining highly clean water from river water, normally, sand filtration is first performed, turbidity is removed, and ion exchange or reverse osmosis filtration is performed. Is called. By such treatment, pure water from which fine particles have been removed is obtained. In the above-described microfiltration membrane device and ultrafiltration membrane device, fine particles remaining slightly in the pure water thus obtained are targeted for removal. Generally, the number of fine particles contained in pure water obtained by reverse osmosis filtration is around 200 / ml for fine particles of 0.1 μm and 1,000 to 3,000 / ml for fine particles of 0.05 μm. Degree. The number of fine particles contained in the treated water obtained by ultrafiltration of the pure water is as small as 0.05 μm or less of 0.05 μm fine particles. When ultrafiltration of pure water is performed using, for example, a hollow fiber membrane, even if one of tens of thousands of membranes is damaged and fine particles contained in the pure water leak out, it is treated with another healthy membrane. Since it is diluted tens of thousands of times with treated water containing almost no fine particles, it is extremely difficult to detect the leakage of fine particles even if a fine particle meter is used.

  On the other hand, in the case of air leak check (bubble point measurement) and the method of passing filtered water through a turbidity removal membrane for damage confirmation, treatment of raw water and detection of membrane damage are performed separately, resulting in membrane damage. There is a risk that the treated water obtained from the time it is detected until it reaches the use point.

JP 2005-13992 A JP-A-1-307409 JP-A-6-15271

  Accordingly, an object of the present invention is to provide a membrane filtration system and a filtration membrane damage detection method for monitoring damage to a filtration membrane that is difficult to detect even by monitoring with a precision microparticle meter, in addition to advanced filtration treatment of water to be treated. is there.

  The membrane filtration system of the present invention is divided into a primary side region and a secondary side region by a filtration membrane arranged inside, and the separation target substance in the water to be treated supplied from the primary side region is filtered by the filtration membrane. A membrane filtration device, an adding means for adding magnetic fine particles to the treated water, and a number of fine particles for measuring the number of fine particles in the treated water permeated from the primary side region to the secondary side region through the filtration membrane Measuring means.

  Further, the membrane filtration system preferably includes a circulation unit that circulates the water to be treated to which the magnetic fine particles have been added by the addition unit in the primary side region.

  In the membrane filtration system, it is preferable that the circulating means includes a magnetic body recovery device that recovers magnetic fine particles in the circulating water to be treated using magnetic force.

  The membrane filtration system preferably includes backwashing means for backwashing the filtration membrane of the membrane filtration device after collecting the magnetic fine particles by the magnetic material collection device.

  The membrane filtration system further includes backwash drainage circulation means for circulating backwash wastewater discharged by backwashing the filtration membrane through the magnetic substance collection device, The magnetic fine particles are preferably recovered from the circulating backwash waste water.

  The membrane filtration system preferably includes an ultrasonic vibration device that applies ultrasonic vibration to the magnetic material recovery device, and the magnetic fine particles are detached from the magnetic material recovery device by the ultrasonic vibration.

  In the membrane filtration system, it is preferable that the circulation unit includes a unit for measuring the turbidity or the number of fine particles of the water to be treated that circulates in the primary region.

Further, in the membrane filtration system, the particle diameter of the magnetic fine particles is in the range of 50 nm to 100 nm, the addition amount of the water to be treated is preferably in the range of ¹⁰ 5 ^{to 10 10} cells / ml.

  Further, in the membrane filtration system, a filtration step of filtering the separation target substance in the for-treatment water supplied from the primary side region of the filtration membrane disposed inside the membrane filtration device through the filtration membrane, and in the for-treatment water An addition step of adding magnetic fine particles, and a fine particle number measurement step of measuring the number of fine particles in the treated water permeated from the primary region of the filtration membrane through the filtration membrane to the secondary region of the filtration membrane (this book The filtration membrane damage detection method of the invention).

  The filtration membrane damage detection method preferably includes a circulation step of circulating the water to be treated to which the magnetic fine particles have been added in the addition step in a primary region of the filtration membrane.

  ADVANTAGE OF THE INVENTION According to this invention, the damage of a filtration membrane can be monitored with the filtration process of the to-be-processed water by a filtration membrane.

It is a mimetic diagram showing an example of the composition of the membrane filtration system concerning this embodiment. It is an operation | movement flowchart at the time of the filtration and circulation process in a membrane filtration system. It is an operation | movement flowchart of the collection process of the magnetic fine particle in a membrane filtration system. It is an operation | movement flowchart of the backwashing process in a membrane filtration system. It is an operation | movement flowchart of the magnetic fine particle peeling process in a membrane filtration system. It is a schematic diagram which shows an example of the other structure of the membrane filtration system which concerns on this embodiment. It is a figure which shows the result of the particle number measured with the fine particle meter in Example 1. FIG. It is a figure which shows the result of the turbidity measured with the turbidimeter in Example 1. It is a figure which shows the result of the particle number measured with the fine particle meter in Example 2. FIG. It is a figure which shows the result of the turbidity measured with the turbidimeter in Example 2.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  FIG. 1 is a schematic diagram illustrating an example of a configuration of a membrane filtration system according to the present embodiment. A membrane filtration system 1 shown in FIG. 1 includes a membrane filtration device 10, an electromagnetic collection device 12a as a magnetic material collection device, an ultrasonic generator 12b, a particle meter 14, a turbidimeter 16, a raw water tank 18, a treated water tank 20, The raw water pump 22, the backwash pump 24, the flow meters 26a, 26b, and 26c, and each piping line are provided. A filtration membrane 10a is arranged inside the membrane filtration device 10, and the inside of the membrane filtration device 10 is divided into a primary side region 10b and a secondary side region 10c.

  The electromagnet type recovery device 12a includes a main body portion 12c through which water to be treated flows, and an electromagnet 12d disposed on the outer periphery of the main body portion. The ultrasonic generator 12b is also arranged on the outer periphery of the main body. The main body 12c of the present embodiment is a cylindrical body made of a magnetic material such as stainless steel, and a magnetic current is generated by passing a direct current through the electromagnet 12d, so that a magnetic field space is formed inside the main body 12c. The

  A raw water inflow line 28 is connected between the raw water tank 18 and a primary side supply port (not shown) of the membrane filtration device 10, and a secondary discharge port (not shown) of the membrane filtration device 10 and the treated water tank 20. A treated water discharge line 30a is connected to the inlet of the water. A treated water discharge line 30 b is connected to the outlet of the treated water tank 20. The raw water inflow line 28 is provided with a raw water pump 22, a flow meter 26a, and a first valve V1, and the treated water discharge line 30a is provided with a fine particle meter 14 and a second valve V2. A circulating water line 32a is connected between the primary outlet (not shown) of the membrane filtration device 10 and the inlet (not shown) of the main body 12c of the electromagnetic recovery device 12a, and the main body of the electromagnetic recovery device 12a. A circulating water line 32 b is connected between the outlet 12 c (not shown) and the raw water inflow line 28 upstream of the raw water pump 22. A third valve V3 and a flow meter 26b are installed in the circulating water line 32a. A backwash water line 34a is connected between the discharge port (not shown) of the treated water tank 20 and the treated water discharge line 30a on the upstream side of the second valve V2, and the raw water flows downstream from the first valve V1. A backwash water line 34 b is connected to the line 28. The backwash water line 34a is provided with the backwash pump 24, the fifth valve V5 and the flow meter 26c, and the backwash water line 34b is provided with the fourth valve V4. A magnetic fine particle addition line 38 is connected to the circulating water line 32a.

  As a general membrane filtration method, there are a total amount filtration method for filtering all treated water and a circulating filtration method for returning a part of the treated water to raw water while filtering the treated water. Although the membrane filtration system of the present invention can be applied to both a total filtration method and a circulation filtration method, it uses magnetic fine particles to detect membrane damage, so it can be applied to a circulation filtration method in which the concentration of fine particles can be kept constant on the primary side. It is preferable to do.

  The operation of the membrane filtration system of this embodiment will be described.

  FIG. 2 is an operation flow diagram during the circulation filtration step in the membrane filtration system. The arrows in the figure represent the flow of water during operation, and the white display valve represents an open state and the black display valve represents a closed state.

  In the raw water tank 18, treated water containing separation target substances such as fine particles and microorganisms is stored. In the present embodiment, even when pure water containing almost no fine particles is filtered as a processing target, damage to the filtration membrane used for the filtering process can be found. As the water to be treated water, treated water obtained by further performing ion exchange treatment, reverse osmosis filtration membrane and the like after sand filtration treatment and the like is suitable.

  First, the first valve V1 of the raw water inflow line 28, the second valve V2 of the treated water discharge line 30a, and the third valve V3 of the circulating water line 32a are opened, and the raw water pump 22 is operated. The treated water containing the separation target substance in the raw water tank 18 flows from the raw water inflow line 28 into the primary side region 10 b of the membrane filtration device 10. A portion of the water to be treated permeates through the filtration membrane 10a to the secondary side region 10c of the membrane filtration device 10, and the separation target substance in the water to be treated is removed by the filtration membrane 10a. The treated water that has not permeated the secondary region 10c of the membrane filtration device 10 passes through the circulation line 32a and returns to the raw water inflow line 28 for circulation. The treated water that has permeated into the secondary region 10 c passes through the treated water discharge line 30 a and is stored in the treated water tank 20. Further, when a predetermined amount of treated water is stored in the treated water tank 20, the treated water is extracted from the treated water discharge line 30b and discharged out of the system. Thus, the filtration process which removes the isolation | separation target substance in to-be-processed water with the filtration membrane 10a is performed. When the filtration membrane 10a is damaged during the filtration process, the separation target substance leaks from the damaged portion. For example, the water to be treated is pure water containing a small amount of the separation target substance. In addition, since the substance to be separated that leaks is a very small amount, it is usually impossible to detect with a fine particle meter, and there is a possibility that discovery of damage to the filtration membrane may be delayed.

  However, in the present embodiment, damage to the filtration membrane 10a can be detected during the circulation filtration step by the method described below. During the above-described circulation filtration step, magnetic fine particles are introduced into the magnetic fine particle addition line 38. Here, in a normal state in which no damage or the like occurs in the filtration membrane 10a, a part of the magnetic fine particles may be collected by the filtration membrane 10a, but most of the magnetic fine particles are passed through the circulating water lines 32a and 32b. It circulates through the primary side area | region 10b with treated water. In an abnormal state in which damage or the like has occurred in the filtration membrane 10a, the magnetic fine particles and the separation target substance pass from the damaged portion and leak to the secondary side region 10c of the membrane filtration device 10. When the magnetic fine particles pass through the treated water discharge line 30a together with the treated water, the number of fine particles in the treated water is measured by the fine particle meter 14 installed in the treated water discharge line 30a (particulate number measuring step). With such a configuration, if the filtration membrane 10a has been damaged, the amount of magnetic fine particles that can be measured by the particle meter passes through the treated water discharge line 30a, so whether or not the filtration membrane 10a has been damaged. It becomes possible to monitor continuously.

  In the present embodiment, for example, a threshold value is set in advance for the number of fine particles measured by the fine particle meter 14, and when the threshold value is exceeded, it is determined that the filtration membrane 10a is damaged, and the operator uses raw water. The operation of the pump 22 is stopped. Alternatively, the fine particle meter 14 and the raw water pump 22 may be electrically linked so that the raw water pump 22 is automatically stopped when a preset threshold value is exceeded. Further, a buzzer or the like may be installed in the fine particle meter 14 and when the threshold value is exceeded, a warning sound may be emitted from the buzzer to prompt the operator to stop the operation of the raw water pump 22.

  Moreover, in addition to the measurement by the fine particle meter 14, the turbidimeter 16 installed in the circulating water line 32a may be used together for the damage of the filtration membrane 10a. That is, if the magnetic fine particles pass through the filtration membrane 10a, the magnetic fine particles passing through the circulating water line 32a are also reduced by that amount, so that the turbidity of the water to be treated passing through the circulating water line 32a is lowered. Therefore, by measuring the turbidity of the water to be treated by the turbidimeter 16 in addition to the measurement of the number of fine particles by the fine particle meter 14, it is possible to more reliably monitor the damage of the filtration membrane 10a. In the present embodiment, for example, a threshold value is set in advance for the numerical values measured by the particle meter 14 and the turbidimeter 16, and the particles in the treated water passing through the treated water discharge line 30a exceed the threshold value and pass through the circulating water line 32a. When the turbidity of to-be-processed water falls the threshold value, the structure which judges that the filtration membrane 10a is damaged and stops operation | movement of the raw | natural water pump 22 may be sufficient.

  When the circulation of the water to be treated is continued in the primary region 10b of the membrane filtration device 10, the magnetic fine particles are collected in the filtration membrane 10a of the membrane filtration device 10 and the amount of circulating magnetic fine particles decreases. There is a case to do. If the amount of circulating magnetic fine particles is reduced in this way, even if the filtration membrane 10a is damaged, the amount of magnetic fine particles leaking from the damaged portion may be reduced. Then, even if the filtration membrane 10a is damaged, the amount of the magnetic fine particles leaking from the damaged portion becomes a very small amount, so that the number of fine particles cannot be measured by the fine particle meter 14, and the filtration membrane 10a is damaged. May not be confirmed. Therefore, in this embodiment, it is desirable to monitor the amount of magnetic fine particles flowing through the circulating water line 32a by detecting the turbidity of the water to be treated passing through the circulating water line 32a by the turbidimeter 16. For example, when a threshold value is set in advance to the numerical value measured by the turbidimeter 16 and the turbidity of the water to be treated passing through the circulating water line 32a decreases the threshold value, the membrane 10a of the membrane filtration device 10 is damaged. It is preferable that a predetermined amount of the magnetic fine particles is introduced from the magnetic fine particle addition line 38 when it is determined that an amount of the magnetic fine particles that can be confirmed is not circulating.

  FIG. 3 is an operation flow chart of the magnetic particle recovery process in the membrane filtration system.

  When the filtration step and the circulation step described above are continued, the magnetic fine particles and the substances to be separated in the water to be treated are collected in the filtration membrane 10a in the filtration membrane 10a of the membrane filtration device 10. In such a state, not only damage of the filtration membrane 10a cannot be confirmed due to a decrease in circulating magnetic fine particles, but also the filtration rate is reduced due to clogging of the filtration membrane 10a. Therefore, it is necessary to periodically stop the filtration process and the circulation process and perform the backwashing of the membrane filtration device 10. Prior to the backwashing step, it is preferable to collect the magnetic fine particles from the viewpoint of effective utilization of the magnetic fine particles. Below, the collection | recovery process is demonstrated using FIG.

  In the recovery process, the first valve V1 of the raw water inflow line 28 and the third valve V3 of the circulating water line 32 are opened, the second valve V2 of the treated water discharge line 30a opened in the filtration process is closed, and the raw water pump 22 is operated. . Further, the power supply of the electromagnet type recovery device 12a is turned on, a current is passed through the electromagnet 12d to generate a magnetic force, and a magnetic field space is formed in the main body portion 12c. The treated water passes through the circulating water line 32a and flows into the main body 12c from the inlet of the main body 12c of the electromagnet recovery device 12a. Then, the magnetic fine particles in the water to be treated adhere to the wall surface in the main body 12c due to the magnetic field space formed in the main body 12c. The treated water is discharged from the outlet of the main body 12c, passes through the circulating water line 32b, the raw water inflow line 28, and the primary side region 10b of the membrane filtration device 10 and flows again to the circulating water line 32a. By circulating in this way, the magnetic fine particles added to the water to be treated can be recovered by the electromagnet recovery device 12a.

  FIG. 4 is an operation flowchart of the backwashing process in the membrane filtration system. As described above, in order to prevent clogging of the filtration membrane 10a and the like, it is preferable that the filtration membrane 10a of the membrane filtration device 10 is regularly backwashed (after backwashing) (after collecting the magnetic fine particles). In the backwash process, the fourth valve V4 of the backwash water line 34b is opened (the valve V5 of the backwash water line 34a is also opened), the first valve V1 of the raw water inflow line 28 and the third valve of the circulating water line 32a described above. Close V3. Moreover, the raw | natural water pump 22 is stopped and the backwash pump 24 is operated. During the backwash process, it is desirable to turn on the electromagnet recovery device 12a to generate a magnetic field, and to adhere magnetic fine particles to the inner wall of the main body 12c of the electromagnet recovery device 12a. . The treated water in the treated water tank 20 flows through the backwash water line 34 a and the treated water discharge line 30 a and flows into the secondary region 10 c of the membrane filtration device 10. The treated water permeates to the primary region 10b of the membrane filtration device 10 through the filtration membrane 10a, and the filtration membrane 10a is backwashed. The treated water that has passed through the filtration membrane 10a passes through the backwash water line 34b as backwash wastewater and is discharged out of the system. Thereby, clogging of the filtration membrane 10a etc. can be prevented and the filtration performance of the membrane filtration apparatus 10 can be recovered.

  FIG. 6 is a schematic diagram illustrating an example of another configuration of the membrane filtration system according to the present embodiment. In the membrane filtration system 2 shown in FIG. 6, the same components as those of the membrane filtration system 1 shown in FIG. The membrane filtration system 2 shown in FIG. 6 includes a drain tank 36, a magnetic fine particle addition line 38, and backwash water circulation lines 40a and 40b in addition to the configuration of the membrane filtration system 1 shown in FIG. A backwash water line 34 b is connected to a backwash water inlet (not shown) of the drain tank 36. Further, a backwash water circulation line 40a is connected between a circulation water outlet (not shown) of the drainage tank 36 and the circulation water line 32a, and a reverse flow is provided between the circulation water inlet of the drainage tank 36 and the circulation water line 32b. A washing water circulation line 40b is connected. A magnetic fine particle addition line 38 is installed in the backwash water circulation line 40a.

  By adopting the apparatus configuration of the membrane filtration system 2 shown in FIG. 6, it is possible to recover the magnetic fine particles from the backwash waste water passing through the backwash water line 34b. After the backwash drainage passing through the backwash water line 34b is stored in the drain tank 36, the magnetic fine particle addition line 38 circulates between the drain tank 36 and the electromagnetic recovery device 12a via the backwash water circulation lines 40a and 40b. Let Then, in a state where the separation of the magnetic fine particles and the contaminating fine particles has sufficiently progressed, water may be drained, and the primary side of the membrane filtration device 10 may be filled again with water to peel off the magnetic fine particles described later.

  FIG. 5 is an operation flow diagram of the magnetic fine particle peeling step in the membrane filtration system. After backwashing the filtration membrane 10a of the membrane filtration device 10, in order to reuse the magnetic particles collected by the electromagnet recovery device 12a, the magnetic particles can be peeled from the electromagnet recovery device 12a (peeling step). preferable. In the stripping step, the first valve V1 of the raw water inflow line 28, the second valve V2 of the treated water discharge line 30a, the third valve V3 of the circulating water line 32a are opened, and the above-described fourth valve V4 of the backwash water line 34b is opened. close. Moreover, the backwash pump 24 is stopped and the raw water pump 22 is operated. Further, the electromagnetic recovery device 12a is turned off to stop the generation of magnetic force, and the ultrasonic generation device 12b is turned on to apply ultrasonic vibration to the main body 12c of the electromagnetic recovery device 12a. The magnetic fine particles adhering to the wall surface in the electromagnet type recovery device 12a are peeled off from the wall surface by the vibration of the ultrasonic wave, and circulated together with the treated water flowing into the electromagnet type recovery device 12a from the circulating water line 32a. The water passes through the water line 32b, the raw water inflow line 28, and the primary side region 10b of the membrane filtration device 10 and flows again to the circulating water line 32a. In this way, the magnetic fine particles adhering to the wall surface in the main body 12c of the electromagnet recovery device 12a are removed while circulating the water to be treated in the primary region of the membrane filtration device 10 to newly The above-described circulation filtration step or the like can be performed without adding magnetic fine particles to the substrate or by reducing the amount of magnetic fine particles to be added.

  By repeating each of the above steps as one cycle, it is possible to accurately monitor the filtration membrane for a long period of time.

  Moreover, the treated water obtained by this embodiment is used as washing water etc. of a food processing factory, a chemical factory, a semiconductor factory, a machine factory, etc. In addition, since the membrane filtration system of this embodiment can accurately detect damage to the filtration membrane, it becomes possible to continuously and easily manage the removal performance of the membrane filtration device for sterilization purposes, It can be used as an alternative method of heat treatment for the purpose of sterilization. As a result, heat energy necessary for sterilization is unnecessary, so that water to be treated that requires removal of microorganisms can be treated at low cost.

  Next, the configuration of each part will be described.

The magnetic fine particles used in the present embodiment are added to the water to be treated in order to confirm that the separation target substance is leaked due to damage to the filtration membrane 10a. Must have a particle size of This depends on the type of substance to be separated, but the particle diameter of the magnetic fine particles is preferably in the range of 50 nm to 100 nm, for example. Examples of the magnetic fine particles of the present embodiment include nickel (Ni), permalloy (Ni-Fe), iron (Fe), iron (Fe) -silicon (Si) based alloy, iron (Fe) -nitrogen (N). Alloy, iron (Fe) -carbon (C) alloy, iron (Fe) -boron (B) alloy, iron (Fe) -phosphorus (P) alloy, iron (Fe) -aluminum (Al) alloy , Iron (Fe) -aluminum (Al) -silicon (Si) alloy, goethite (FeOOH), hematite (Fe ₂ O ₃ ), magnetite (Fe ₃ O ₄ ), manganese (Mn) -zinc (Zn) ferrite , Nickel (Ni) -zinc (Zn) ferrite, cobalt (Co) ferrite, manganese (Mn) ferrite, nickel (Ni) ferrite, copper (Cu) ferrite, zinc (Zn) ferrite, magnesium (Mg) Ferrite, lithium (Li) ferrite, manganese (Mn) - magnesium (Mg) ferrite, copper (Cu) - Zinc (Zn) ferrite, manganese (Mn) - Zinc (Zn) ferrite, and the like.

  The method for producing the magnetic fine particles is not particularly limited. For example, as described in JP 2010-111519 A, an aqueous solution of an inorganic metal salt and an aliphatic hydroxy polycarboxylic acid are mixed. Then, an alkali solution is added thereto to adjust the pH to 5 to 7, and the obtained raw material sol is ultrasonically sprayed into an oxygen-containing carrier gas supplied into a heating furnace and thermally decomposed. Can be mentioned.

The addition amount of the magnetic fine particles may be set as appropriate so that damage to the filtration membrane 10a can be confirmed. For example, it is preferably in the range of 10 ⁵ to ¹⁰ 10 particles / ml in the water to be treated. . The addition amount of the magnetic particles is less than 10 ⁵ / ml, less the amount of magnetic particles leaking from the damaged portion of the filtration membrane 10a, measuring particle number by particle meter 14 installed in the treated water discharge line 30a In some cases, confirmation of damage to the filtration membrane 10a may be delayed. Further, if the amount of magnetic fine particles added is more than 10 ¹⁰ particles / ml, the amount collected on the filtration membrane 10a of the membrane filtration device 10 during the filtration step increases, and the filtration membrane 10a is frequently clogged. May occur.

  In the present embodiment, the water to be treated in the primary region 10b of the membrane filtration device 10 is circulated by connecting the circulating water line 32b to the raw water inflow line 28, but is not necessarily limited to this configuration. Instead, for example, one end of the circulating water line 32b is connected to the primary outlet of the membrane filtration device 10, and the other end is connected to the outlet of the main body 12c of the electromagnet recovery device 12a. A configuration in which a circulation pump is installed in the water line 32a) may be used.

  The membrane filtration device 10 used in the present embodiment may be appropriately selected according to the use of treated water, water quality, the particle size and amount of fine particles (including magnetic fine particles) in treated water, For the purpose of water production, for example, a reverse osmosis filtration device, etc., and for the purpose of removing fine particles in pure water, for example, an ultrafiltration membrane device, a microfiltration membrane device, etc. Is mentioned. The module format of the filtration membrane 10a installed in the membrane filtration device 10 may be any type such as a hollow fiber shape, a spiral shape, a tubular shape, and a flat membrane shape. In addition, there are two types of filtration methods for membrane modules: the whole-volume filtration method and the cross-flow filtration method. Either filtration method may be used, but as mentioned above, magnetic particles are used to detect membrane damage. A cross-flow filtration method that can control the fine particle concentration at a constant level is preferable. In addition, there are two types of water flow methods for membrane filtration, external pressure type and internal pressure type.

  In the present embodiment, a current is passed through the electromagnet 12d to generate a magnetic force, the magnetic fine particles are collected, the current to the electromagnet 12d is stopped, the magnetic force disappears (and by ultrasonic vibration), and the magnetic fine particles are peeled off. Although the electromagnet type recovery device 12a has been described as an example, it is not limited thereto. For example, it may be a permanent magnet type recovery device in which a permanent magnet is arranged on the outer periphery of a cylindrical main body 12c such as stainless steel. However, when a permanent magnet is employed, for example, an air cylinder or the like as a magnet moving means is installed on the permanent magnet, and the permanent magnet is moved closer to or away from the main body portion 12c. Need to control. That is, a magnetic field space is formed in the main body portion 12c by bringing the permanent magnet close to the main body portion 12c by the air cylinder, and the magnetic fine particles are attached and recovered in the main body portion 12c. Further, by separating the permanent magnet from the main body portion 12c by the air cylinder, the magnetic field space in the main body portion 12c is eliminated, and the magnetic fine particles are separated from the main body portion 12c.

  The electromagnet 12d used in the present embodiment may be a normal conducting magnet or a superconducting magnet. However, it is preferable to use a superconducting magnet when forming a strong magnetic field. It is preferable to use a conductive magnet. Moreover, in this embodiment, although the electromagnet 12d is installed in the outer periphery of the main-body part 12c, the inside of the main-body part 12c may be sufficient. As a result, the magnetic fine particles directly adhere to the electromagnet 12d, so that the main body 12c does not have to be a magnetic material. The shape of the main body 12c is not limited to a cylindrical shape as long as the water to be treated can flow, and may be a hopper shape, for example.

Although the ultrasonic generation conditions by the ultrasonic generator 12b are not particularly limited, for example, a frequency range of 10 to 200 kHz and an output range of 0.1 to 10 w / cm ² are desirable. The output time of the ultrasonic generator 12b (the magnetic particle peeling process time) is preferably in the range of 1 to 100 seconds, and more preferably in the range of 10 to 100 seconds.

  Adjustment of the flow rate of the treated water passing through the raw water inflow line 28, the flow rate of treated water passing through the circulating water line 32, the flow rate of treated water passing through the backwash water line 34a, and the like is performed by a flow meter 26a installed in each line. 26b, 26c, and appropriately performed by adjusting the output of the raw water pump 22 and the backwash pump 24. For example, the flow rate of the raw water pump: the flow rate of the backwash pump is in the range of 1: 2 to 1: 5. It is desirable to be set to.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail more concretely, this invention is not limited to a following example.

Example 1
Using the membrane filtration system 1 shown in FIG. 1, the circulation filtration step (including the fine particle measurement step), the recovery step, the backwashing step, and the magnetic fine particle peeling step described above are set as one cycle for a total of 20 times (10 days). went. Table 1 summarizes the open / close state of the valve, the operating state of the pump, and the operation time of each step in each step. The output time of the ultrasonic generator 12b was set to 1, 5 or 10 seconds.

The treated water used in Example 1 was pure water discharged from a pure water production apparatus. In this pure water, 2000 particles / ml of 0.05 to 1.0 μm were present. The amount of treated pure water used in the membrane filtration system 1 was about 500 m ³ / d.

As the membrane filtration device 10 of Example 1, an ultrafiltration membrane device was used. The details of the ultrafiltration membrane device are as follows.
Dimensions: Outer diameter 300mm x Height 1500mm
Filtration area (membrane area): 50 m ²
Filtration membrane: hollow fiber type / number of membranes 22,000 / module, manufactured by polyethersulfone, nominal molecular weight cut off 150,000 Da (fractionated particle size 8.3 nm)
Filtration method: Cross flow Filtration flux: 5.0 m / d
Treatment flow rate: 10.4 m ³ / h
Circulating water volume: 10.4 m ³ / h
Backwashing: conducted twice a day

Details of the electromagnet recovery device 12a of the first embodiment are as follows.
Dimensions of the main body: width 35.5cm x depth 2cm x height 27cm
Electromagnet area: 958.5 cm ²

The ultrasonic generation conditions by the ultrasonic generator 12b of the first embodiment are as follows.
Frequency: 170kHz
Output: 300 w (0.31 w / cm ² )

As magnetic fine particles of Example 1, ferrite fine particles having a particle diameter of 0.05 to 0.075 μm were used, and 5.0 × 10 ¹¹ particles / ml × 100 ml were used. The turbidity of the water to be treated in the circulation system immediately after the addition of the ferrite fine particles was 0.002 degrees.

  As the turbidimeter 16 installed in the circulating water line 32a, a high-sensitivity turbidimeter with an AN455C particle measuring function manufactured by Hitachi High-Tech Control Systems, Inc. was used. The turbidity of the to-be-treated water passing through the circulating water line 32 was measured by the turbidimeter 16 every minute.

  For the particle counter 14 installed in the treated water discharge line 30a, an in-liquid particle sensor KS-18F (measurement range 0.05 to 0.2 μm) manufactured by Rion Co. was used. The fine particle meter 14 measured fine particles in the treated water passing through the treated water discharge line 30a every minute.

  In Example 1, although no particular control is performed, in the operation of the actual apparatus, for example, when the number of fine particles in the treated water measured by the fine particle meter 14 becomes 10 particles / ml or more with a particle size of 0.05 μm or more, It is judged that the filter membrane 10a has been damaged, and the operation of the apparatus is stopped. When the turbidity of the water to be treated measured by the turbidimeter 16 becomes 0.015 degrees or less, the magnetic fine particles are replenished. It may be defined as follows.

  FIG. 7 shows the result of the number of particles measured by the micrometer in Example 1, and FIG. 8 shows the result of the turbidity measured by the turbidimeter in Example 1. The result (each plot) of FIG. 7 is the maximum value of the number of fine particles in the circulation filtration step in one cycle. The results (each plot) in FIG. 8 are the minimum values of turbidity in the circulation filtration process in one cycle.

  As shown in FIG. 7, the fine particles in the treated water passing through the treated water discharge line 30a always changed at 10 particles / ml or less. That is, it was confirmed that the filtration membrane 10a was not damaged. As a precaution, as a result of performing an air leak check on the filtration membrane 10a of the membrane filtration device 10 after the operation was completed, the filtration membrane 10a was not damaged.

  As shown in FIG. 8, the turbidity of the water to be treated passing through the circulating water line 32a begins to gradually decrease from the first cycle when the output time of the ultrasonic generator 12b is 1 second, and reaches 0. It was 015 degrees. This is considered to be because the magnetic fine particles captured by the electromagnet recovery device 12a were not completely separated from the main body portion 12c. On the other hand, when the output time of the ultrasonic generator 12b is 5 seconds or 10 seconds, the turbidity of the water to be treated passing through the circulating water line 32a is not less than 0.015 degrees even at the 20th cycle. In this example, it can be said that it is desirable to set the output time of the ultrasonic generator 12b to 5 seconds or more.

  The results in FIG. 8 indicate that the recovery rate of magnetic fine particles depends on the efficiency of ultrasonic peeling. That is, it can be seen that the circulation and collection step of the magnetic fine particles functions well, and the magnetic fine particles lost by backwashing are minimal.

(Example 2)
Using a membrane module obtained by cutting one of 22,000 filtration membranes of the ultrafiltration membrane device (membrane filtration device 10 in FIG. 1), the filtration and circulation steps ( The operation was performed under the same conditions as in Example 1 except that the particle number measurement step) was continuously performed. The operation time was 300 minutes.

  FIG. 9 shows the result of the number of particles measured by the fine particle meter 14 in Example 2, and FIG. 10 shows the result of the turbidity measured by the turbidimeter in Example 2.

  As shown in FIG. 9, the fine particles in the treated water passing through the treated water discharge line 30a varied between 24 and 91 particles / ml. The average number of fine particles in the treated water was 50 particles / ml. On the other hand, the turbidity of the water to be treated passing through the circulating water line 32a gradually decreased with the lapse of the operation time, and became 0.015 degrees after the operation time of 90 minutes, and decreased thereafter. When the time-dependent changes in the number of fine particles by the fine particle meter 14 and the turbidity by the turbidimeter 16 are observed, the magnetic fine particles in the water to be treated leak from the cut portion of the filtration membrane 10a with the passage of water passage time and enter the treated water. It can be judged that it leaked. In actual operation, the operation can be stopped when the number of fine particles in the treated water becomes 10 particles / ml or more. Thereafter, the presence or absence of damage to the membrane is confirmed by an air leak check or the like, and if it is confirmed by the air leak check or the like that it is definitely damaged, it is desirable to replace the membrane module.

  1, 2 Membrane filtration system, 10 Membrane filtration device, 10a Filtration membrane, 10b Primary region, 10c Secondary region, 12a Electromagnetic recovery device, 12b Ultrasonic generator, 12c Main body, 12d Electromagnet, 14 Particle meter , 16 Turbidimeter, 18 Raw water tank, 20 Treated water tank, 22 Raw water pump, 24 Backwash pump, 26a, 26b, 26c Flow meter, 28 Raw water inflow line, 30a, 30b Treated water discharge line, 32a, 32b Circulating water line , 34a, 34b Backwash water line, 36 Drain tank, 38 Magnetic fine particle addition line, 40a, 40b Backwash water circulation line.

Claims (10)

A membrane filtration device that is divided into a primary side region and a secondary side region by a filtration membrane disposed inside, and that filters the substance to be separated in the for-treatment water supplied from the primary side region through the filtration membrane;
An adding means for adding magnetic fine particles to the treated water;
A membrane filtration system, comprising: a fine particle number measuring unit that measures the number of fine particles in the treated water that has permeated from the primary region to the secondary region through the filtration membrane.   The membrane filtration system according to claim 1, further comprising a circulation unit that circulates the water to be treated to which the magnetic fine particles have been added by the addition unit in the primary side region.   3. The membrane filtration system according to claim 2, wherein the circulating means includes a magnetic body recovery device that recovers magnetic fine particles in the circulating water to be treated using magnetic force.   4. The membrane filtration system according to claim 3, further comprising backwashing means for backwashing the filtration membrane of the membrane filtration device after collecting the magnetic fine particles by the magnetic material collection device.   Backwash wastewater circulating means for circulating backwash wastewater discharged by backwashing the filtration membrane through the magnetic material recovery device is provided, and the magnetic material recovery device is configured to circulate from the circulating backwash wastewater. The membrane filtration system according to claim 4, wherein the magnetic fine particles are collected. An ultrasonic vibration device for applying ultrasonic vibration to the magnetic substance recovery device;
The membrane filtration system according to any one of claims 3 to 5, wherein the magnetic fine particles are detached from the magnetic substance recovery device by the ultrasonic vibration.   The membrane filtration system according to claim 2, wherein the circulation unit includes a turbidity measurement unit that measures the turbidity of the water to be treated that circulates in the primary region. The particle diameter of the magnetic fine particles is in the range of 50 nm to 100 nm, and the amount added to the water to be treated is in the range of 10 ⁵ to ¹⁰ 10 particles / ml. The membrane filtration system according to Item. A filtration step of filtering the substance to be separated in the for-treatment water supplied from the primary side region of the filtration membrane disposed inside the membrane filtration device with the filtration membrane;
An addition step of adding magnetic fine particles to the treated water;
A filtration membrane damage detection method comprising: a fine particle number measurement step of measuring the number of fine particles in the treated water that have permeated from the primary region of the filtration membrane to the secondary region of the filtration membrane through the filtration membrane.   The filtration membrane damage detection method according to claim 9, further comprising a circulation step of circulating the treated water to which the magnetic fine particles are added in the addition step in a primary side region of the filtration membrane.

Images