JP6251148B2 - Water treatment system - Google Patents

Description

  The present invention relates to a water treatment system.

  As background arts in this technical field, there are JP-A-8-126882 (Patent Document 1) and International Patent Publication WO 08/038575 (Patent Document 2).

  Japanese Patent Laid-Open No. 8-126882 (Patent Document 1) states that “based on the supply water pressure, the supply water side membrane surface osmotic pressure of the reverse osmosis membrane module and the osmotic water flow rate, A water production plant in which a permeation coefficient is obtained, and when the value obtained by subtracting the initial value from the water permeation coefficient is less than or equal to the first reference value, the membrane is diagnosed as soiled, and when the value is greater than or equal to the second reference value, the membrane is diagnosed The operation control device (see claim 1) "is described.

  International Patent Publication No. WO 08/038575 (Patent Document 2) states that “a biofilm amount on a biofilm-forming substrate is evaluated at a frequency of once a day to 6 months, and based on the evaluation results, The operation method of a reverse osmosis membrane filtration plant for controlling the operation method (see summary) is described.

JP-A-8-126882 International Patent Publication WO 08/038575

  When the adhering matter adhering to the membrane surface of the separation membrane is removed by washing and the separation performance is restored, excessive washing may cause deterioration of the separation membrane. When the separation performance of the separation membrane deteriorates from the preset performance, the unit provided with the separation membrane must be replaced, and the operation of the water treatment system needs to be stopped for a long time when replacing the unit. Therefore, the water treatment cost of the water treatment system increases due to the consumables for the separation membrane and the reduction in the operation rate of the water treatment system.

  Therefore, the present invention provides a water treatment system with a low replacement frequency of the separation membrane by suppressing deterioration of the separation membrane due to the cleaning treatment.

  In order to solve the above problems, in the water treatment system according to the present invention, a branch pipe is connected to a main pipe between an inlet through which a cleaning liquid is injected from a membrane cleaning liquid injection section and a unit including a separation membrane. A monitor unit having a sensor is connected to this. While the raw water is being filtered in the unit, the raw water is passed through the sensor to deposit fouling-causing substances on the sensor surface, and the cleaning liquid is passed through the unit to clean the separation membrane provided in the unit. In the meantime, the cleaning liquid is passed through the sensor and the sensor surface is exposed to the cleaning liquid in the same state as the separation membrane provided in the unit. After confirming that the fouling-causing substance is removed from the sensor surface and the sensor surface returns to the initial state, the end point of cleaning of the separation membrane provided in the unit is determined.

  ADVANTAGE OF THE INVENTION According to this invention, the water treatment system with a low replacement frequency of a separation membrane can be provided by suppressing degradation of the separation membrane by a washing process.

It is the schematic which shows an example of a structure of the seawater desalination system by a present Example. It is sectional drawing which shows an example of a structure of the sensor by a present Example. It is process drawing explaining an example of the process of forming an aromatic polyamide film in the measurement surface of the sensor chip by a present Example. It is sectional drawing which shows an example of the attachment structure of the sensor by a present Example. It is a perspective view which shows an example of the attachment structure of the sensor by a present Example. It is an operation | movement flowchart of the seawater desalination system by a present Example.

  In the following embodiments, when necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other, and one is the other. There are some or all of the modifications, details, supplementary explanations, and the like.

  Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and may be more or less than the specific number.

  Further, in the following embodiments, the constituent elements (including element steps) are not necessarily indispensable unless otherwise specified and clearly considered essential in principle. Needless to say.

  In addition, when referring to “consisting of A”, “consisting of A”, “having A”, and “including A”, other elements are excluded unless specifically indicated that only that element is included. It goes without saying that it is not what you do. Similarly, in the following embodiments, when referring to the shapes, positional relationships, etc. of the components, etc., the shapes are substantially the same unless otherwise specified, or otherwise apparent in principle. And the like are included. The same applies to the above numerical values and ranges.

  In all the drawings for explaining the following embodiments, components having the same function are denoted by the same reference numerals in principle, and repeated description thereof is omitted. Hereinafter, the present embodiment will be described in detail with reference to the drawings.

  First, since it seems that the water treatment system by this Embodiment becomes clearer, the subject in the water treatment system which the present inventors performed comparative examination is demonstrated in detail.

  In a water treatment system that purifies raw water such as seawater or wastewater, prevention of fouling (clogging) of the separation membrane and proper cleaning of the separation membrane when fouling occurs are important operational issues.

  Fouling is detected as a phenomenon in which the operating pressure increases during operation of the water treatment system. There are two types of pressure increase, and one pressure increase indicates an increase in transmembrane pressure due to clogging of the separation membrane or deposits on the membrane surface. On the other hand, a water treatment system employs a hollow element or spiral configuration because it requires a large number of separation membranes to be housed in an element with a small volume, and the flow path between the separation membrane and the separation membrane becomes narrow. ing. For this reason, another increase in pressure is that the flow resistance is increased due to the adhering matter or the like adhering to the membrane surface of the separation membrane, thereby increasing the water flow resistance. Here, an embodiment corresponding to the deposit on the membrane surface of the separation membrane that causes an increase in the transmembrane pressure difference will be described.

  Among the separation membranes, in the nanofilter membrane and reverse osmosis membrane having the smallest pore diameter, only water molecules permeate the membrane. These membranes are used to separate ionic components. When fouling occurs, the amount of permeated water decreases and the transmembrane pressure difference increases. In that case, the membrane is cleaned with chemicals to restore performance, but chemical cleaning leads to deterioration of the membrane, shortening the useful life of the membrane and reducing the quality of the permeated water. Keeping the volume to a minimum is a challenge for stable operation of the water treatment system.

  The desalination plant described in Patent Document 1 describes a control method for diagnosing the deterioration state of a reverse osmosis membrane from changes in pressure and flow rate and automatically instructing the timing of washing. However, it is necessary to combine multiple measuring devices and sensors, and for calculating the timing of washing, the correlation between the reverse osmosis membrane pressure change, flow rate change, and deterioration state is determined in advance using a demonstration plant or the like. It takes time to develop. In addition, changes in pressure and flow rate can only be detected after fouling of the reverse osmosis membrane has progressed, and may not be recovered by washing the reverse osmosis membrane.

  In the reverse osmosis membrane filtration plant described in Patent Document 2, the cleaning timing of the reverse osmosis membrane can be appropriately determined by a monitor device provided upstream of the reverse osmosis membrane. However, the recovery status of the reverse osmosis membrane during cleaning cannot be observed on the spot, and another mechanism is required for controlling the chemical solution until the end of cleaning.

  Hereinafter, a water treatment system according to the present invention will be described in detail with reference to the accompanying drawings.

  In a water treatment system, a substance to be separated is removed from raw water or pretreated water, and a separation membrane is often used to remove the substance to be separated. In water treatment systems that use separation membranes, microfiltration membranes (Ultrafiltration Membrane), reverse osmosis membranes (hereinafter referred to as RO membranes), nanofilter membranes are used as separation membranes. (Nanofiltration Membrane: hereinafter referred to as NF membrane) and ion exchange membrane (Ion Exchange Membrane) are used. Among these, RO membranes are suitable for seawater desalination and are frequently used. Therefore, a seawater desalination system using an RO membrane having an element structure will be described below as an example.

  Note that the separation membrane described in detail below may be cleaned with chemicals, and the separation membrane is not limited to the RO membrane. That is, an NF membrane or an ion exchange membrane may be used as the separation membrane. Water treatment systems are not limited to seawater desalination systems, but also reused water production systems that purify wastewater and produce reused water, and pure water and ultrapure water production systems that produce pure water or ultrapure water, etc. It may be.

<Configuration of seawater desalination system>
FIG. 1 is a schematic diagram illustrating an example of a configuration of a seawater desalination system 1 according to the present embodiment.

  As shown in FIG. 1, the seawater desalination system 1 removes salt, organic matter, microorganisms (including fungi), boron, and solid suspended solids that become suspended substances from seawater as separated substances. Turn into. Therefore, it arrange | positions from the upstream side in order of the seawater intake part 10, the pre-processing part 20, and the desalination part 30 as a main part.

  The seawater intake section 10 located on the most upstream side of the seawater desalination system 1 includes a water intake pipe 11 that takes seawater into the seawater desalination system 1, a water intake pump 12 that pumps seawater, and a raw water tank 13 that stores the pumped seawater. And have.

  Here, the intake pipe 11 may have a structure in which the tip portion is introduced into the sea to take in seawater as raw water, or a structure in which deep water is taken as raw water by extending to the offshore. Moreover, the structure which takes in the seawater used as raw water after being embed | buried under the seabed and filtered with seabed sand may be sufficient. In order to prevent microorganisms, algae, shellfish and the like from growing in the intake pipe 11 and blocking the intake pipe 11, a chemical (for example, a disinfectant) that prevents the growth of these organisms is injected into the intake pipe 11. Also good. The intake pump 12 may be installed on land or in the sea.

  The pretreatment unit 20 that processes the seawater taken by the seawater intake unit 10 includes a sand filtration tank 21, a water pump 22 a, an ultrafiltration membrane unit 22, and a supply water tank 23. The sand filtration tank 21 contains a predetermined amount of sand inside the tank, and separates suspended components (non-soluble inorganic components and organic components) to be separated. The ultrafiltration membrane unit 22 has an ultrafiltration membrane that separates submicron particles (polymer, microorganisms, etc.). The water supply pump 22 a supplies filtrate from the sand filtration tank 21 to the ultrafiltration membrane unit 22. The supply water tank 23 temporarily stores raw water supplied to the RO membrane unit 32 included in the desalination unit 30 on the downstream side.

  The pretreatment unit 20 executes a pretreatment process for sterilizing living microorganisms and removing other organic substances. Therefore, the pretreatment unit 20 includes a chemical injection system 24 that injects a plurality of types of chemicals into raw water. The chemical injection system 24 is provided for each type of chemical injected into the raw water, and each has a chemical storage tank and a liquid feed pump. In the example of the seawater desalination system 1 shown in FIG. 1, the chemical injection system 24 includes a bactericidal agent injecting unit 24a, a pH adjusting agent injecting unit 24b, a flocculant injecting unit 24c, and a neutralizing / reducing agent injecting unit 24d. have.

  The sterilizing agent injecting section 24a includes a sterilizing agent storage tank 24a1 and a liquid feed pump 24a2. Inject upstream. In the middle of the pipes 24a3 and 24a4, control valves VL11 and VL12 are provided, respectively. The pipe 24a3 for injecting the bactericide into the raw water intake pipe 11 can be omitted depending on the degree of contamination of seawater.

  From the sterilizing agent injecting section 24a, hypochlorous acid or chlorine is injected into the raw water as a sterilizing agent for sterilizing microorganisms. A bactericidal agent is intermittently injected from the bactericidal agent injecting section 24a, and the killing rate or survival rate of microorganisms in the raw water changes depending on the injection interval and concentration of the bactericidal agent. Therefore, the injection amount and injection interval of the bactericide are controlled using the adjustment valves VL11 and VL12.

  Note that hypochlorous acid or chlorine injected as a bactericidal agent lowers the membrane function of the RO membrane provided in the RO membrane unit 32 of the desalting unit 30. Therefore, as will be described later, the raw water is reduced before being fed to the RO membrane unit 32, and excessive injection of the bactericide is avoided.

  The pH adjuster injecting section 24b has a pH adjuster storage tank 24b1 and a liquid feed pump 24b2. In order to prevent scales due to multivalent ions and improve the efficiency of aggregation, the pH adjuster injecting section 24b is provided via a pipe 24b3. Is injected into the upstream side of the sand filtration tank 21. An adjustment valve VL2 is provided in the middle of the pipe 24b3.

  In order to prevent the generation of scale due to multivalent ions and improve the aggregation efficiency, the raw water treated in the seawater desalination system 1 is preferably adjusted from acidic to neutral (for example, pH 5 to 7). Therefore, a pH adjusting agent such as sulfuric acid is injected into the raw water from the pH adjusting agent injection unit 24b to adjust to a suitable pH. The injection amount of the pH adjusting agent is controlled by the adjustment valve VL2.

  The flocculant injecting section 24c has a flocculant storage tank 24c1 and a liquid feed pump 24c2, and in order to efficiently remove suspended components that are substances to be separated in the sand filtration tank 21, via a pipe 24c3, The flocculant is injected into the upstream side of the sand filtration tank 21. An adjustment valve VL3 is provided in the middle of the pipe 24c3.

  From the flocculant injection part 24c, polyaluminum chloride or ferric chloride is injected into the raw water as the flocculant. The growth of the flocs of the suspended components contained in the raw water is promoted by the flocculant. When the flocculant is injected, the fine particles of 0.1 μm or more of the suspended component easily grow into flocs of 1 μm or more, and the removal efficiency of the suspended component in the sand filtration tank 21 is improved.

  When the amount of the flocculant injected is too small, flocs grow insufficiently and the suspended components may pass through the sand filtration tank 21. On the contrary, when the injection amount of the flocculant is excessive, surplus flocculant that is not used for floc growth becomes a load on the RO membrane provided in the RO membrane unit 32 of the desalting unit 30. Therefore, the injection amount of the flocculant is controlled using the adjustment valve VL3.

  The neutralizing / reducing agent injection unit 24d includes a neutralizing / reducing agent storage tank 24d1 and a liquid feed pump 24d2, and the neutralizing agent and the reducing agent are disposed downstream of the ultrafiltration membrane unit 22 via the pipe 24d3. Then, it is injected into the upstream side of the supply water tank 23. An adjustment valve VL4 is provided in the middle of the pipe 24d3. In the neutralization reducing agent injection | pouring part 24d, the neutralizing agent for neutralizing the raw | natural water adjusted to the acidity of pH 3-5 and the reducing agent for mainly reducing a disinfectant are inject | poured into raw | natural water. The injection amounts of the neutralizing agent and the reducing agent are controlled using the adjustment valve VL4.

  The raw water that has passed through the pretreatment unit 20 flows to the desalting unit 30 by the supply pump 25. The desalting unit 30 includes a main line LM having a high-pressure pump 31, an RO membrane unit 32, and a fresh water tank 33, and a sub-line LS having an RO membrane unit 32 and a concentrated water tank 35. The high-pressure pump 31 obtains a pressure required to flow the raw water by overcoming the flow path resistance in the RO membrane unit 32.

  The RO membrane unit 32 includes an RO membrane, and a semipermeable membrane is used on the surface of the RO membrane. A semipermeable membrane is a membrane that allows only water molecules to permeate due to the difference between the interaction between the semipermeable membrane and water molecules and the interaction between the semipermeable membrane and the substance to be separated. Some are polyamide-based. Among these, RO membranes using aromatic polyamide-based semipermeable membranes are used as industrial semipermeable membranes because of their high water molecule permeability and electrolyte removal performance.

  An RO film formed by winding a plurality of layers around the central axis as an element is called a spiral element. Commercial spiral type elements are standardized by various companies, and are formed into a cylindrical shape having a diameter of 4 inches (about 10 cm), 8 inches (about 20 cm) or 16 inches (about 40 cm) and a length of about 1 m. Yes. A plurality of, for example, 6 elements are arranged in series in a pressure vessel called a vessel, and a plurality of, for example, 20 vessels are assembled in a matrix to form the RO membrane unit 32.

  The fresh water tank 33 stores the raw water from which the material to be separated has been removed by the RO membrane unit 32 as fresh water. The concentrated water tank 35 is a tank for storing concentrated water that is raw water that has not permeated the RO membrane provided in the RO membrane unit 32.

  The desalting unit 30 further includes a membrane cleaning liquid injection unit 34. The membrane cleaning liquid injection unit 34 includes a cleaning liquid tank 341 and a liquid feed pump 342, and injects the cleaning liquid upstream of the RO membrane unit 32. In the middle of the pipe 343, an adjustment valve VL5 is provided. A cleaning solution for removing fouling or scaling of inorganic components generated in the RO membrane provided in the RO membrane unit 32 is injected from the membrane cleaning solution injection unit 34. The amount of the cleaning liquid injected is controlled using the adjustment valve VL5. In addition, the flow rate of the cleaning liquid is measured using the branch pipe flow meter 344 and the main pipe flow meter 345, and is recorded so that the attached amount of the RO membrane 32 and the sensor 36a can be converted.

  In this embodiment, the cleaning liquid injected from the membrane cleaning liquid injection section 34 is injected upstream of the RO membrane unit 32. However, in order to obtain a physical cleaning effect, the cleaning liquid is injected downstream of the RO membrane unit 32. May be. Also in this case, from the upstream side of the cleaning liquid flow at the time of cleaning, the membrane cleaning liquid injection section 34, the branch pipe PB of the monitor section, and the RO membrane unit 32 are arranged in this order. Since the flow direction is opposite to that when raw water is treated, a branch pipe for draining the cleaning liquid is required on the high-pressure pump 31 side of the RO membrane unit 32.

  Here, a feature of the present invention is that a branch pipe PB is connected to the main pipe PM between the supply water tank 23 and the RO membrane unit 32, and raw water flows through the RO membrane unit 32 through the branch pipe PB. A monitor unit 36 is provided for monitoring fouling that occurs at the time.

  That is, the raw water that has passed through the pretreatment unit 20 and has flowed to the desalination unit 30 by the supply pump 25 flows separately to the main pipe PM and the branch pipe PB. Most of the raw water flows into the main pipe PM and is pumped to the RO membrane unit 32 by the high-pressure pump 31. The remaining raw water is sent to a sensor 36a in the monitor 36 after the flow rate is adjusted by an adjustment valve VL36 provided in the branch pipe PB. The sensor 36a is a sensor that measures the mass of a fouling-causing substance adhering to the sensor surface that is a measurement surface, and is connected to a device that can perform in-situ measurement. The raw water that has passed through the sensor 36 a is sent to the concentrated water tank 35.

<Water treatment method in seawater desalination system>
The operation of the seawater desalination system 1 configured as described above will be described in detail below.

  In the seawater desalination system 1, a water intake pump 12 of a seawater intake unit 10 takes in raw seawater from the sea through a water intake pipe 11. The taken raw water is temporarily stored in the raw water tank 13, and a part of the substance to be separated contained in the raw water is precipitated and removed in the raw water tank 13 and sent to the pretreatment unit 20.

  In the pretreatment unit 20, the bactericide is injected into the raw water from the bactericide injection unit 24a, the pH adjuster is injected into the raw water from the pH adjuster injection unit 24b, and the flocculant is injected into the raw water from the flocculant injection unit 24c. The raw water into which these chemicals are injected is guided to the sand filtration tank 21. The flocs of substances to be separated (mainly organic substances) in the raw water which have grown to 1 μm or more mainly by the flocculant are filtered and removed by the sand filtration tank 21. The raw water that has passed through the sand filtration tank 21 is sent to the ultrafiltration membrane unit 22 by the water pump 22a.

  In the ultrafiltration membrane unit 22, particulate matter to be separated having a particle size of 0.05 μm or more, polymer having a molecular weight of several thousands, bacteria, and the like, which are finer than the matter to be separated filtered by the sand filtration tank 21, are obtained from raw water. Separated and removed. Microorganisms such as bacteria contained in the raw water are almost 100% removed by the ultrafiltration membrane unit 22.

  At that time, the raw water is pressurized to about 0.1 to 0.5 MPa by the water feed pump 22 a and fed to the ultrafiltration membrane unit 22. The raw water sent to the ultrafiltration membrane unit 22 has a higher rate of permeation through the ultrafiltration membrane unit 22 as the pressure increases. However, the higher the pressure of the raw water, the lower the performance (separation performance) for separating the substance to be separated from the raw water.

  A neutralizing agent and a reducing agent are injected into the raw water that has passed through the ultrafiltration membrane unit 22 from the neutralizing / reducing agent injection unit 24d. The raw water adjusted to be acidic with a pH adjuster is neutralized with a neutralizer. At the same time, the injected germicide is reduced. The raw water neutralized and reduced in this way is stored in the supply water tank 23.

  The raw water stored in the supply water tank 23 is pumped to the RO membrane unit 32 by the high pressure pump 31 and filtered by the RO membrane unit 32. The raw water from which the substance to be separated has been removed by the RO membrane unit 32 is stored in a fresh water tank 33. On the other hand, the raw water that does not pass through the RO membrane provided in the RO membrane unit 32 becomes concentrated water containing the substance to be separated and is stored in the concentrated water tank 35.

  In addition, you may make it provide the drainage system which returns the concentrated water stored by the concentrated water tank 35 to the sea, for example. In that case, the drainage system may execute a process of reducing the salinity concentration or a process of separating a substance that can be a raw material of the salt and chemicals.

<Sensor structure>
By the way, the RO membrane provided in the RO membrane unit 32 is a semipermeable membrane, and acts as a separation membrane that allows only water molecules to pass through. When fouling occurs in this separation membrane, the separation performance and processing capacity for separating the substance to be separated from the raw water is lowered. Specifically, when the fouling occurs in the operation of the RO membrane unit 32 configured by accommodating a plurality of elements in a cylindrical container (vessel) and assembling the plurality of containers in a matrix shape, the amount of permeated water is constant. In operation, the pressure increases, and in the operation where the pressure is constant, the amount of permeated water decreases.

  In order to avoid this problem, the water treatment system including the seawater desalination system 1 incorporates a pretreatment process for removing in advance a substance to be separated that can be a fouling-causing substance. In the unlikely event that fouling occurs, the cleaning method is changed according to the pore size and strength of the RO membrane, the fouling-causing substance is discharged from the element, and the RO membrane unit 32 is maintained.

  Therefore, in this embodiment, a branch pipe PB is connected to the main pipe PM between the supply water tank 23 and the RO membrane unit 32, and a monitor unit 36 is provided in the branch pipe PB. And while performing normal filtration operation in the RO membrane unit 32 located in the main pipe PM, the raw water is supplied to the sensor 36a through the branch pipe PB, and the sensor surface is exposed to the raw water in the same state as the RO membrane, Accumulate fouling-causing substances on the sensor surface. When cleaning the RO membrane unit 32, the cleaning liquid is supplied to the sensor 36a through the branch pipe PB, and the sensor surface is exposed to the cleaning liquid in the same state as the RO membrane. After confirming that the fouling-causing substances are removed from the sensor surface, the sensor surface state returns to the initial state, and determining the end point of cleaning, the sensor surface is cleaned at a strength corresponding to the fouling state of the sensor surface at that time. I do. The surface of the sensor used here is coated with the same material as the RO membrane, and selectively captures fouling-causing substances. In this example, an aromatic polyamide was used as the material equivalent to the RO membrane.

  Details of the monitor unit 36 will be described below. In the present embodiment, the sensor 36a is a weight measuring sensor that measures the mass of an adhering substance adhering to the sensor surface by the quartz crystal microbalance method. However, the method is not limited as long as the surface of the sensor is made of the same material as the RO membrane and is captured on the sensor but can measure the amount of the fouling-causing substance. For example, there are infrared spectroscopy, infrared reflectance measurement, and surface plasmon resonance.

  FIG. 2 is a cross-sectional view showing an example of the configuration of the sensor 36a according to the present embodiment.

As shown in FIG. 2, the sensor 36a includes a sensor chip 360 (for example, a commercially available product manufactured by Q-Sense) and an aromatic polyamide film 361 formed on the measurement surface F1 of the sensor chip 360. In the sensor chip 360, for example, a gold electrode 360b having a thickness of about 300 nm is formed on both surfaces of a quartz crystal resonator (AT-cut crystal plate 360a) having a thin disk shape having a thickness of about 0.3 mm and a diameter of about 14 mm. A SiO ₂ film 360c having a thickness of about 100 nm is formed on the measurement surface F1 by sputtering through a gold electrode 360b.

Next, an example of a process for forming the aromatic polyamide film 361 on the measurement surface F1 of the sensor chip 360 will be described with reference to FIGS. FIG. 3 is a process diagram illustrating an example of a process of forming the aromatic polyamide film 361 on the measurement surface F1 of the sensor chip 360 according to the present embodiment. The surface opposite to the measurement surface F1 on which the SiO ₂ film 360c is formed by sputtering is referred to as a back surface F2. Here, the material to be deposited on the sensor 36a is aromatic polyamide, which is a representative material of the RO membrane, but is not limited to this, and is applied to other separation membranes that perform chemical cleaning. In this case, the material to be formed on the sensor 36a is selected in accordance with the material of the separation membrane, and the film is formed on the measurement surface F1 of the sensor chip 360. Examples of the material used for the separation membrane include polyethylene, tetrafluoroethylene, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, polyethersulfone, and polycarbonate.

  Step S1 (back surface protection): A masking film or the like is attached to the back surface F2, and the back surface F2 is covered and protected.

  Step S2 (dry cleaning): Excimer UV (wavelength 192 nm) is irradiated on the measurement surface F1, thereby making the measurement surface F1 hydrophilic and removing oils and fats.

  Step S3 (Silane coupling treatment): After immersing the sensor chip 360 in a 1% aqueous solution of a silane coupling agent (3-aminopropyltrimethoxysilane) for 2 minutes, the sensor chip 360 taken out is rinsed with running water and then blown with nitrogen. Drain the liquid.

  Step S4 (heating): The sensor chip 360 is heated at 80 ° C. for 10 minutes to cause a coupling reaction.

  Step S5 (immersion in diamine aqueous solution): The sensor chip 360 is put into a container such as a petri dish with the measurement surface F1 facing upward, and the entire sensor chip 360 is immersed in a 0.04 wt% m-phenylenediamine aqueous solution. Pour in.

  Step S6 (dicarboxylic acid hexane solution dripping): A hexane solution of 0.04 wt% terephthalic acid chloride is poured onto the surface of the m-phenylenediamine aqueous solution so as to be laminated with a thickness of about 1 mm.

  Step S7 (formation of polyamide thin film): Leave for 20 to 30 seconds to form a polyamide thin film at the interface.

  Step S8 (transfer): The sensor chip 360 is pulled up obliquely, and the polyamide thin film formed at the interface is transferred to the measurement surface F1 of the sensor chip 360.

  Step S9 (heating): The sensor chip 360 is heated on a hot plate at 80 ° C. for 5 minutes to evaporate the aqueous solution remaining on the sensor chip 360.

  Step S10 (Washing): The sensor chip 360 is washed with pure water to remove excess m-phenylenediamine aqueous solution and drained by nitrogen blowing.

  Step S11 (removal of protective material): The masking film attached to the back surface F2 is peeled off.

As described above, the aromatic polyamide film 361 having a uniform film thickness (for example, about 50 nm) is formed on the measurement surface F1 (the surface on which the SiO ₂ film 360c is formed) of the sensor chip 360 by the steps S1 to S11. The

  In this example, an aromatic polyamide monomer was interfacially polymerized to form a polymer film at the interface, and then this film was transferred to the measurement surface F1 of the sensor chip 360. At this time, the monomer is not limited to the combination described above, and a combination of an aromatic dicarboxylic acid chloride or aromatic tricarboxylic acid chloride and an aromatic diamine or aromatic triamine can also be used.

  In this embodiment, the silane coupling agent is used to improve the adhesion between the aromatic polyamide film 361 and the measurement surface F1 of the sensor chip 360. However, the present invention is not limited to this. As a method for improving adhesion, for example, a monomer having a silicone structure can be added, or other adhesion improvers can be used.

  As another method for forming an aromatic polyamide film, a solvent-soluble aromatic polyamide, for example, 4,4′-oxydianiline and isophthalic acid chloride are polymerized to synthesize polyamide, and then precipitated to form a solid. Then, a method of dissolving in a good solvent (for example, N-methylpyrrolidone) and drying the solvent after spin coating may be used.

  Next, an example of the mounting structure of the sensor 36a will be described with reference to FIGS. FIG. 4 is a cross-sectional view showing an example of a mounting structure of the sensor 36a according to the present embodiment. FIG. 5 is a perspective view showing an example of a mounting structure of the sensor 36a according to the present embodiment.

The crystal resonator microbalance method is a measurement method using a principle that the resonance frequency of shear vibration generated in the AT cut crystal plate 360a (see FIG. 2) of the sensor 36a is proportional to the mass of the AT cut crystal plate 360a, for example. Yes, a change in mass when a fouling-causing substance in the substance to be separated adheres to the measurement surface F1 (surface on which the SiO ₂ film 360c is formed) is detected as a change in resonance frequency. That is, the change in the resonance frequency becomes the change in the mass of the fouling-causing substance. According to the study by the present inventors, even if the fouling-causing substance adheres to the measurement surface F1, the pressure does not increase immediately, and the amount of adhesion that does not cause the pressure increase is the resonance frequency in the quartz crystal microbalance method. It was revealed that the change in the change is less than 1/500, preferably less than 1 / 1,000 of the initial frequency.

  As shown in FIG. 1 and FIG. 2, for example, the fouling causing substance in the separated material contained in the raw water flowing through the branch pipe PB of the monitor unit 36 is attached to the measurement surface F1, and the attached fouling. In order to measure the change in the mass of the causative substance with the sensor 36a, a configuration is required in which the measurement surface F1 is in contact with the raw water in the branch pipe PB and the back surface F2 is not in contact with the raw water. In addition, since the resonance frequency of the sensor chip 360 is greatly changed by a change in ambient temperature, it is preferable that the temperature change around the sensor 36a is suppressed to 0.02 ° C. or less.

  Therefore, as shown in FIGS. 4 and 5, the inside of the bottomed cylindrical outer ring 370 that is screwed into a screw hole that penetrates the pipe wall surface PMf of the main pipe PM and is fixed in a state of passing through the pipe wall surface PMf. It is set as the attachment structure in which the substantially cylindrical insert 371 fits.

  The bottomed outer ring 370 is attached to the main pipe PM such that the bottom 370a is on the inside of the main pipe PM, that is, on the raw water side, and a through hole 370b is opened at the center of the bottom 370a, for example. Is preferred.

  Further, an O-ring 372a made of, for example, an elastic member is formed in an annular shape on the upper surface 371a of the insert 371 fitted inside the outer ring 370 and facing the lower side of the bottom portion 370a of the outer ring 370. An O-ring 372b made of an elastic member is formed in an annular shape on the side of the bottom 370a facing the upper surface 371a of the insert 371 so as to face the O-ring 372a of the insert 371.

  The sensor 36a is sandwiched between the O-ring 372b of the outer ring 370 and the O-ring 372a of the insert 371. Accordingly, the diameters of the annular O-rings 372a and 372b are preferably equal to the diameter (for example, about 14 mm) of the sensor chip 360 (see FIG. 2) constituting the sensor 36a.

  The sensor 36a is configured to be sandwiched so that the measurement surface F1 is on the bottom 370a side of the outer ring 370. According to this configuration, the measurement surface F1 of the sensor 36a comes into contact with the raw water flowing through the main pipe PM through the through hole 370b opened in the bottom 370a. In addition, a configuration in which the sensor 36a is sandwiched with a suitable pressing force capable of maintaining a liquid-tight state between the O-rings 372a and 372b and the sensor 36a is preferable. With this configuration, it is possible to prevent the back surface F2 of the sensor 36a from coming into contact with the raw water flowing through the main pipe PM.

  The insert 371 is a solid cylinder formed of, for example, resin or metal, and has a Peltier element 374 as a temperature adjusting element near the surface on the upper surface 371a side and a temperature for measuring the temperature in the vicinity of the Peltier element 374. A configuration in which the sensor 374a is embedded is preferable. The Peltier element 374 is controlled by a control device (not shown) so that the temperature measured by the temperature sensor 374a is maintained at a preset temperature (for example, the preset temperature is maintained within an error range of 0.1 ° C.). The configuration is preferred.

  With this configuration, the ambient temperature of the sensor 36a can be kept constant, and the temperature change of the resonance frequency of the sensor chip 360 (see FIG. 2) can be suppressed.

  The temperature sensor 374a is not limited to a configuration embedded in the insert 371. For example, it is good also as a structure arrange | positioned in the vicinity of the sensor 36a and measuring the temperature of the vicinity of the sensor 36a.

  Further, the O-ring 372a formed on the upper surface 371a of the insert 371 has an annular contact 372a1 with a gold electrode 360b (see FIG. 2) formed on the sensor chip 360 (see FIG. 2) of the sensor 36a. It is provided so as to cover a part of the O-ring 372a. The contact 372a1 is electrically connected to, for example, a conductive wire 373 wired in the insert 371, and is configured to apply a predetermined voltage to the sensor chip 360 (see FIG. 2). Further, the resonance frequency of the sensor 36a is measured through the contact 372a1 and the conducting wire 373.

  The insert 371 may be configured to be fitted inside the outer ring 370 and to be prevented from coming off by a retaining plate 375a fixed to the outer ring 370 by a screw member 375b from the outside of the main pipe PM. Alternatively, the insert 371 may be pressed into the outer ring 370 with a predetermined pressing force.

  The seawater desalination system 1 according to the present embodiment includes a monitor unit 36 including a sensor 36a capable of measuring a weight, and determines the amount of substances to be separated (organic matter, microorganisms, etc.) that cause fouling on the RO membrane. Can be evaluated. At this time, in order to realize the same state as that of the RO membrane unit 32, the linear velocity of the raw water and the cleaning liquid is adjusted by the RO membrane unit 32 and the sensor 36a. The average linear flow velocity in the RO membrane unit 32 is 0.1 to 0.2 m / s, but reaches 0.5 to 0.7 m / s on the inlet side of the RO membrane unit 32. Since fouling is likely to occur on the inlet side of the RO membrane unit 32, the linear flow rate of the sensor 36a is adjusted to the flow rate on the inlet side. However, since this flow rate differs for each seawater desalination system 1 or RO membrane, it is not necessarily within this range. Further, when it is desired to determine the end point of cleaning at the average soiled portion of the RO membrane, the sensor 36a may be flowed at an average linear flow velocity.

<Operation example of seawater desalination system 1>
Next, an operation example of the seawater desalination system 1 including the monitor unit 36 will be described with reference to FIGS. 1 and 6. FIG. 6 is an operation flowchart of the seawater desalination system 1 according to this embodiment.

  Step S100: First, the initial frequency of the sensor 36a is measured to determine the end point of cleaning. Since the measurement at this time is affected by ions, pH and temperature in the surrounding solvent, the cleaning liquid used for cleaning is passed through the sensor 36a, and the measurement is performed at a temperature within ± 3 ° C. of the temperature setting at the time of cleaning. Do. The measurement at this time is performed at least twice when the flow rate of the cleaning liquid is zero and when the flow rate is the linear flow rate at the time of cleaning. This is because the measured value may shift due to a change in the water pressure applied to the sensor 36a depending on the flow rate. The frequency when the flow rate is zero is the initial value M00 of the film on which the fouling-causing substance is not attached, and the frequency when the flow rate is the linear flow velocity v (m / s) at the time of cleaning is the fouling-causing substance attached. Record as the initial value M01 of no film.

  Step S110: The filtration operation of the desalting unit 30 is started.

  Step S120: A part of the raw water is branched from the main pipe PM to the branch pipe PB, and the sensor 36a is exposed to the raw water by adjusting the linear flow rate to be the same value as in the RO membrane unit 32. When the linear flow rate is the same, the amount of fouling substance in contact with the membrane surface is the same, and the RO membrane unit 32 and the sensor 36a are in the same fouling state.

  While the fouling causing substance is accumulated in synchronization with the RO membrane provided in the RO membrane unit 32, the accumulated amount of the fouling causing substance can be monitored by measuring the weight of the sensor 36a. However, temperature control is difficult, and when the amount of adhesion increases, the measurement weight upper limit may be exceeded, so it is not always necessary to perform weight measurement.

  Step S130: Once the RO membrane cleaning time is determined by the change in the weight of the sensor 36a, the change in the RO membrane pressure, the change in other water quality indicators, etc., the operation of the desalting unit 30 is once stopped.

  Step S140: Thereafter, the flow path of the piping is switched so that the cleaning liquid is drained from the membrane cleaning liquid injection part 34 through the RO membrane unit 32.

  Step S150: Next, the cleaning liquid is flowed to the RO membrane unit 32 through the main pipe PM and to the monitor unit 36 through the branch pipe PB. At this time, the linear flow velocity of the cleaning liquid supplied to the sensor 36 a is set to the same value as that of the RO membrane unit 32.

  Step S160: After starting the flow of the cleaning liquid, the crystal resonator of the sensor 36a is oscillated and the measurement of the frequency is started. The frequency measurement in step S160 is performed in a state where the cleaning liquid is passed, and the measurement value is M11 (t).

  Step S161: The first evaluation of the end point of cleaning (coarse end point determination) is performed. In the first evaluation of the end point of cleaning (coarse end point determination), the measured value M11 (t) measured in step S160 is compared with the initial value M01 measured in step S100, and the measured value M11 (t) and the initial value M01 are compared. When the frequency difference becomes 1/1000 or less of the initial value M00. The frequency measurement is performed with the cleaning liquid flowing until the frequency difference between the measured value M11 (t) and the initial value M01 becomes 1/1000 or less of the initial value M00. Here, the determination value is set to 1/1000 or less, but the allowable range is obtained to be 1/500 or less, and can be set as appropriate in each operating plant.

  Step S162: In Step S161, when the frequency difference between the measured value M11 (t) and the initial value M01 is equal to or less than 1/1000 of the initial value M00, the cleaning of the RO membrane unit 32 is continued and the sensor 36a The flow rate of the cleaning liquid is zero, and the frequency (measured value M10) of the sensor 36a is measured.

  Step S163: The second evaluation of the end point of cleaning (precise end point determination) is performed. In the second evaluation (precise end point determination) of the end point of cleaning, the measured value M10 measured in step S162 is compared with the initial value M00 measured in step S100, and the frequency difference between the measured value M10 and the initial value M00 is the initial value. Suppose that it is less than 1/1000 of M00.

  Step S170: In step S163, when the frequency difference between the measured value M10 and the initial value M00 becomes 1/1000 or less of the initial value M00, it is determined that the cleaning is finished, and the cleaning of the RO membrane unit 32 is stopped. .

  Step S171: If the frequency difference between the measured value M10 and the initial value M00 is not less than 1/1000 of the initial value M00 in Step S163, the supply of the cleaning liquid to the sensor 36a is resumed for a certain time (for example, about 5 Min) Perform additional washing with washing solution. Thereafter, the frequency measurement in step S162 and the determination in step S163 are repeated, and when the frequency difference between the measured value M10 and the initial value M00 is less than 1/1000 of the initial value M00, the process proceeds to step S170 and the RO membrane unit Stop washing 32. Next, when the seawater desalination system 1 is operated and the RO membrane unit 32 is cleaned, the initial value M00 may be replaced with the initial value M01 after cleaning to determine the end point.

  By determining the end point of the cleaning in this way, a layer of the fouling cause substance that does not greatly affect the permeation performance is provided on the element on the inlet side of the RO membrane unit 32 having the largest amount of fouling cause substance adhesion. Can leave. That is, the cleaning can be completed in a state where the membrane surface of the RO membrane provided in the RO membrane unit 32 is not exposed to the cleaning liquid. Thereby, it is possible to prevent deterioration of the RO membrane provided in the RO membrane unit 32 and to restore the permeation performance.

  Here, an example of the separation membrane cleaning method and replacement method will be described.

  The operation when the end point of the RO membrane cleaning is detected by the seawater desalination system described above will be described.

  The cleaning of the RO membrane tends to take time from the start of cleaning to the end point as the number of cleaning increases. In this case, the cleaning time gradually increases.

  For example, when the end point is not reached, the washing is not finished and the seawater desalination system cannot be operated. On the other hand, the seawater desalination system can be operated because the RO membrane is washed without reaching the end point. Therefore, when it is determined that the cleaning is completed by detecting only the end point, the efficiency of the seawater desalination system is reduced as described above.

  In such a case, it is preferable to measure the cleaning time together with the state of the dirt at the time of cleaning, that is, the degree of cleaning, instead of simply determining the end of cleaning based on the end point. In this case, from the relationship between the cleaning degree and the cleaning time, it may be determined that the cleaning is completed even if the cleaning degree does not reach the end point by a certain cleaning time. Even if the end point is not reached, the RO membrane can be washed in a certain amount, so that the seawater desalination system can be operated.

  If the cleaning end point is not reached even after cleaning, that is, if the RO membrane performance does not recover to a predetermined value, the user of the seawater desalination system or the system administrator is notified by e-mail, management terminal, etc. It is good to inform using. By notifying that the end point has not been reached, the RO membrane replacement time can be estimated. It can also contribute to the planning of maintenance plans for replacement. Further, it may be notified to the manufacturer handling the RO membrane. In this case, since the manufacturer can know in advance that the replacement time is near, it is possible to know that the time to replace the RO membrane is approaching without waiting for an order from the user, system administrator or maintenance company. Therefore, it is possible to prepare a replacement RO membrane in advance and perform the replacement work. Therefore, since the replacement time can be estimated in advance, maintenance of the seawater desalination system and replacement of the RO membrane can be easily performed.

  The cleaning time of the RO membrane may be specified using the past cleaning time and the state of seawater, and the cleaning time may be changed according to the number of times of cleaning. In this case, it is possible to set a cleaning time more suitable for the state of the RO membrane, so that the cleaning efficiency can be increased.

  Although the invention made by the present inventors has been specifically described based on the embodiment, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

DESCRIPTION OF SYMBOLS 1 Seawater desalination system 10 Seawater intake part 11 Intake pipe 12 Intake pump 13 Raw water tank 20 Pretreatment part 21 Sand filtration tank 22 Ultrafiltration membrane unit 22a Water feed pump 23 Supply water tank 24 Chemical injection system 24a Sterilizer injection part 24a1 Storage Tank 24a2 Liquid feed pump 24a3, 24a4 Pipe 24b pH adjuster injection part 24b1 Storage tank 24b2 Liquid feed pump 24b3 Pipe 24c Coagulant injection part 24c1 Storage tank 24c2 Liquid feed pump 24c3 Pipe 24d Neutralizing reductant injection part 24d1 Storage tank 24d2 Liquid pump 24d3 Pipe 25 Supply pump 30 Desalination part 31 High pressure pump 32 RO membrane unit 33 Fresh water tank 34 Membrane cleaning liquid injection part 341 Cleaning liquid tank 342 Liquid feed pump 343 Pipe 344 Branch pipe flow meter 345 Main pipe flow meter 35 Concentrated water tank 36 Mo Nita 36a Sensor 360 Sensor chip 360a AT cut crystal plate 360b Gold electrode 360c SiO ₂ film 361 Aromatic polyamide film 370 External ring 370a Bottom 370b Through hole 371 Insert 371a Top surface 372a O-ring 372a1 Contact 372b O-ring 373 Conductor 374 Peltier element 374a Temperature sensor 375a Retaining plate 375b Screw member F1 Measuring surface F2 Rear surface LM Main line LS Subline PB Branch piping PM Main piping PMf Piping wall surface VL11, VL12, VL2, VL3, VL4, VL5, VL36 Control valve

Claims (11)

A desalting unit;
A pretreatment section for pretreating the raw water supplied to the desalting section;
A water treatment system comprising:
The desalting part is
Main piping,
A unit comprising a separation membrane, and separating the substance to be separated from the raw water using the separation membrane;
A monitor unit having a sensor having a fouling forming material on the surface simulating the separation membrane;
A cleaning liquid injection section for supplying a cleaning liquid for cleaning the separation membrane to the main pipe;
With
An inlet through which the cleaning liquid is injected from the cleaning liquid injection section and the unit are connected to the main pipe,
The monitor unit is connected to a branch pipe branched from the main pipe between the inlet and the unit,
The cleaning liquid is allowed to flow from the cleaning liquid injection unit to the unit and the monitor unit, and the end point of cleaning of the separation membrane provided in the unit is determined from a change in the amount of deposits attached to the surface of the fouling forming material of the sensor. Identify ,
The end point of the cleaning is a water treatment system specified by a change in the amount of the deposit and a preset cleaning time. The water treatment system according to claim 1 ,
A water treatment system in which a change in the amount of the adhering substance does not reach the end point, and the end point of the cleaning is determined when a preset cleaning time is reached. The water treatment system according to claim 1 ,
Having a display,
The water treatment system which displays the replacement time of the unit on the display unit when the change in the amount of the deposit does not reach the end point. The water treatment system according to claim 3 ,
A water treatment system in which the unit is replaced based on the replacement time displayed on the display unit. The water treatment system according to claim 1,
The amount of the adhering matter is a water treatment system which is measured by a quartz resonator microbalance method, an infrared spectroscopy method, an infrared reflectance measurement method, or a surface plasmon resonance method. A desalting unit;
A pretreatment section for pretreating the raw water supplied to the desalting section;
A water treatment system comprising:
The desalting part is
Main piping,
A unit comprising a separation membrane, and separating the substance to be separated from the raw water using the separation membrane;
A monitor unit having a sensor having a fouling forming material on the surface simulating the separation membrane;
A cleaning liquid injection section for supplying a cleaning liquid for cleaning the separation membrane to the main pipe;
With
An inlet through which the cleaning liquid is injected from the cleaning liquid injection section and the unit are connected to the main pipe,
The monitor unit is connected to a branch pipe branched from the main pipe between the inlet and the unit,
The cleaning liquid is allowed to flow from the cleaning liquid injection unit to the unit and the monitor unit, and the end point of cleaning of the separation membrane provided in the unit is determined from a change in the amount of deposits attached to the surface of the fouling forming material of the sensor. Identify ,
(A) Before flowing the raw water to the main pipe and the branch pipe, a first frequency when the cleaning liquid does not flow to the branch pipe, and a flow of the cleaning liquid to the branch pipe at a first linear flow velocity Measuring a second frequency with the sensor;
(B) After the step (a), the step of flowing the raw water into the main pipe and the branch pipe;
(C) a step of stopping the flow of the raw water after the step (b);
(D) After the step (c), the cleaning liquid is flowed to the main pipe and the branch pipe, and the third frequency when the cleaning liquid is flowed to the branch pipe at the first line flow velocity is measured by the sensor. The process of
(E) After the step (d), when the difference between the third frequency and the second frequency reaches 1/500 or less of the first frequency, the separation membrane included in the unit is washed. Determining the end point,
Water treatment system that performs water treatment including A desalting unit;
A pretreatment section for pretreating the raw water supplied to the desalting section;
A water treatment system comprising:
The desalting part is
Main piping,
A unit comprising a separation membrane, and separating the substance to be separated from the raw water using the separation membrane;
A monitor unit having a sensor having a fouling forming material on the surface simulating the separation membrane;
A cleaning liquid injection section for supplying a cleaning liquid for cleaning the separation membrane to the main pipe;
With
An inlet through which the cleaning liquid is injected from the cleaning liquid injection section and the unit are connected to the main pipe,
The monitor unit is connected to a branch pipe branched from the main pipe between the inlet and the unit,
The cleaning liquid is allowed to flow from the cleaning liquid injection unit to the unit and the monitor unit, and the end point of cleaning of the separation membrane provided in the unit is determined from a change in the amount of deposits attached to the surface of the fouling forming material of the sensor. Identify ,
(A) Before flowing the raw water to the main pipe and the branch pipe, a first frequency when the cleaning liquid does not flow to the branch pipe, and a flow of the cleaning liquid to the branch pipe at a first linear flow velocity Measuring a second frequency with the sensor;
(B) After the step (a), the step of flowing the raw water into the main pipe and the branch pipe;
(C) a step of stopping the flow of the raw water after the step (b);
(D) After the step (c), the cleaning liquid is flowed to the main pipe and the branch pipe, and the third frequency when the cleaning liquid is flowed to the branch pipe at the first line flow velocity is measured by the sensor. The process of
(E) After the step (d), when the difference between the third frequency and the second frequency reaches 1/500 or less of the first frequency, the separation membrane included in the unit is washed. Determining the first end point of
(F) After the step (e), measuring the fourth frequency when the cleaning liquid is not flowed to the branch pipe with the sensor,
(G) After the step (f), when the difference between the fourth frequency and the first frequency reaches 1/500 or less of the first frequency, the separation membrane included in the unit is washed. Determining the second end point of
Water treatment system that performs water treatment including The water treatment system according to claim 1,
A water treatment system in which the unit is replaced when it is determined that the decomposition performance of the separation membrane is deteriorated from a preset performance. In the water treatment system of any one of Claims 1-8 ,
The water treatment system, wherein the separation membrane is a reverse osmosis membrane. In the water treatment system of any one of Claims 1-8 ,
The water treatment system, wherein the fouling forming material is an aromatic polyamide membrane. In the water treatment system of any one of Claims 1-8 ,
A water treatment system that purifies seawater or wastewater.

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