JP2015134327A - Evaluation method of separation membrane surface, control method of water treatment system and water treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaluation method of a separation membrane surface capable of evaluating the proliferating amount of microorganisms on the separation membrane surface in an earlier stage than generation on the separation membrane surface, a control method of a water treatment system using the evaluation method and the water treatment system.SOLUTION: An evaluation method of a separation membrane surface evaluates the proliferating amount of microorganisms on the RO membrane surface of an RO membrane module from the mass of microorganisms being proliferated on a thin film equivalent to an RO membrane and locating at the measuring part of a measurement sensor 38a disposed at the upstream of the RO membrane module for separating substances to be separated from a raw water. The evaluation method of the separation membrane surface is provided with a microorganism proliferation accelerator mechanism. A control method of a water treatment system using the evaluation method of the separation membrane surface and the water treatment system are also provided.

Description

  The present invention relates to a separation membrane surface evaluation method in a water treatment system for purifying water, a control method for the water treatment system, and a water treatment system.

  In water treatment systems that purify seawater and wastewater, separation membranes are often used to remove substances to be separated from raw water. In such a separation membrane, microfiltration membranes or ultrafiltration membranes in which micropores (micropores) are formed to physically exclude particles larger than the micropores, Reverse osmosis membranes (RO membranes), nanofilter membranes (NF membranes), ion exchange membranes, etc. that remove substances to be separated using the difference between the diffusion rate and permeation rate of molecules and the affinity between separation membranes and molecules is there.

  However, fouling (clogging) occurs with any type of separation membrane. For example, in microfiltration membranes and ultrafiltration membranes, minute substances enter into the micropores and the micropores are clogged, resulting in clogging. Further, in RO membranes, NF membranes, ion exchange membranes, etc., fouling occurs due to the adsorption of molecules on the surface of the separation membrane or the growth of microorganisms using the molecules as a medium. When fouling occurs, the separation performance for separating the substance to be separated from the raw water decreases.

  Therefore, techniques disclosed in Patent Document 1 and Patent Document 2 are known as techniques for detecting fouling. Patent Document 1 uses a sensor having a material similar to a separation membrane material formed on the surface, and changes in the amount of adsorption of a substance to be separated on the sensor surface and changes in the concentration of organic matter before and after the sensor. A technique for evaluating the influence of water quality on fouling is disclosed. Patent Document 2 discloses a control method in which a biofilm forming substrate is disposed in a reverse osmosis membrane system, and the amount of biofilm is measured to control the operation of the system.

JP 2011-002397 A WO2008 / 038575

  There are roughly three modes of fouling of the separation membrane. Inorganic material deposition, organic material adsorption, and microbial growth. The FI method (Fouling Index), which is a JIS standard, is used as an evaluation method for physical blockage of micropores in separation membranes used in water treatment systems. This method is mainly used for microfiltration that separates particles around 1 μm. This is an evaluation method for a film, and is suitable for evaluating fouling caused by deposition of inorganic substances.

  Patent Document 1 discloses a method for measuring the amount of organic matter adsorbed on the surface of a sensor on which a material similar to a separation membrane material is formed, and a method for performing pretreatment of a water treatment system using the method. It is disclosed. This method is suitable for evaluating fouling due to adsorption of organic substances.

  The FI method and the method of Patent Document 1 are for analyzing raw water, and the possibility can be grasped before actual fouling occurs. On the other hand, fouling due to the growth of microorganisms cannot be evaluated only by analyzing raw water. The reason is as follows. First, it is mentioned that not all substances in the raw water are nutrients for microbial growth. In addition, the growth rate of microorganisms may be affected by slight changes in the environment in which the microorganisms are placed, and analysis of substances contained in raw water and measurement of temperature, pH, etc. at a certain point in time will only cause the growth of microorganisms. It is the reason that cannot be evaluated.

  Patent Document 2 discloses a technique in which the separation membrane itself is arranged in a system and appropriately cut out, and the amount of biofilm attached to the surface is evaluated by the amount of ATP (adenosine triphosphate) which is an energy substance possessed by living organisms. Yes. In this technique, a substance to be separated (a substance derived from a living organism) existing as a cell can be detected, and is suitable for evaluating fouling due to the growth of microorganisms. However, detection is performed after a phenomenon corresponding to fouling actually occurs, and fouling cannot be detected in advance and fed back to control of the system or the like. Moreover, since the biofilm-forming substrate is cut out from the system and analyzed, the water quality change in the system cannot be continuously monitored in-line.

  In view of such a situation, the problem to be solved by the present invention is a separation membrane that detects fouling (biofouling) generated by the propagation of microorganisms on the surface of the separation membrane earlier than the actual occurrence of fouling. A surface evaluation method, a control method of a water treatment system using the separation membrane surface evaluation method, and a water treatment system provided with the separation membrane surface evaluation method.

  The problem is that an acceleration mechanism for accelerating the growth of microorganisms in the upstream of the separation membrane that separates the substance to be separated from the raw water, the main flow toward the separation membrane in the flow of the raw water, and the other branch flow And a branch flow in which a measurement sensor having a thin film of the same quality as the separation membrane is arranged, a branching process that branches into the flow, and a change that occurs in the measurement unit of the measurement sensor due to microorganisms grown by the acceleration mechanism An evaluation step for evaluating a change occurring on the surface of the separation membrane surface, and a control method for controlling a water treatment system using the separation membrane surface evaluation method And by using a water treatment system.

  According to the present invention, a stable control method for a water treatment system can be provided.

It is a figure which shows the structural example of the seawater desalination system which concerns on this embodiment. It is a figure which shows the structural example of a measurement part. It is sectional drawing which shows the structure of a measurement sensor. It is a graph which shows the effect of the present invention. It is a figure which shows the structural example of a measurement part.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
Example 1
In this embodiment, a seawater desalination system that desalinates seawater using an RO membrane is used as an example of a water treatment system, but the present invention is a seawater desalination system that uses an NF membrane, an ion exchange membrane, etc. in addition to the RO membrane. Also, the present invention can be applied to a reuse water production system that purifies waste water to produce reuse water, a pure water / ultra pure water production system that produces pure water or ultra pure water, and the like.

  As shown in FIG. 1, the seawater desalination system 1 according to the present embodiment removes salt, organic matter, microorganisms, fungi, boron, solid suspended solids and the like contained in seawater as substances to be separated. In this order, the seawater intake unit 10, the pretreatment unit 20, and the desalination unit 30 are mainly included in this order from the upstream side. Hereinafter, microorganisms including fungi are referred to as microorganisms.

  The seawater intake unit 10 includes an intake pipe 11, an intake pump 12, and a raw water tank 13. The intake pipe 11 may be installed in the sea to absorb the seawater as raw water, or may be configured to extend to the offshore and absorb deep water as raw water, or after being buried in the seabed and filtered with seabed sand The structure which sucks up seawater (raw water) may be sufficient. The intake pump 12 may be configured to be installed in the sea as well as configured to be installed on land.

  In addition, in order to prevent microorganisms, algae, shellfish, etc. from growing in the intake pipe 11 and blocking the intake pipe 11, chemicals (such as bactericides) that prevent the growth of these organisms are injected into the intake pipe 11. It is good also as a structure to be made.

  The pretreatment unit 20 includes, for example, a sand filtration tank 21, an ultrafiltration membrane module 22, a water pump 22 a, and an RO membrane supply water tank 23, and is a pretreatment for sterilizing living microorganisms and removing other organic substances. Execute the process. Furthermore, the pretreatment unit 20 includes a chemical injection system 24 that injects a plurality of types of chemicals into raw water. The medicinal injection system 24 is configured according to the type of chemicals to be injected into the raw water. FIG. 1 shows a sterilizing agent injecting unit 24a for injecting a sterilizing agent for sterilizing microorganisms. PH adjusting agent injection unit 24b for injecting pH adjusting agent for the purpose, coagulant injecting unit 24c for injecting coagulant for efficiently removing suspended components (organic substances) that become separated substances in sand filtration tank 21, neutralization A neutralizing / reducing agent injection unit 24d for injecting the agent and the reducing agent is illustrated.

  Hypochlorous acid, chlorine, or the like is injected from the sterilizing agent injection unit 24a into the raw water as a sterilizing agent for sterilizing microorganisms. The killing rate and survival rate of microorganisms in the raw water vary depending on the interval and concentration of intermittent injection of the bactericide injected from the bactericide injection unit 24a.

  Hypochlorous acid and chlorine injected as a bactericidal agent reduce the membrane function of the RO membrane module 32 in the RO membrane module 32 of the desalting unit 30, so that the raw water is reduced before being sent to the RO membrane module 32. The configuration is preferred. For this reason, it is preferable to avoid excessive injection of the bactericidal agent, and the bactericidal agent injection portion 24a is provided with an adjustment valve VL1 for adjusting the injection amount of the bactericidal agent.

  Moreover, the structure by which a disinfectant is inject | poured into the intake pipe 11 from the disinfectant injection part 24a may be sufficient. In this case, it is preferable that the conduit for injecting the bactericide into the intake pipe 11 is provided with the adjustment valve VL8 for adjusting the injection amount.

  Moreover, in order to prevent generation | occurrence | production of the scale by a multivalent ion and to improve agglomeration efficiency, it is preferable that the raw | natural water processed with the seawater desalination system 1 is adjusted to acidity (pH 3-5). Therefore, a pH adjuster such as sulfuric acid is injected into the raw water from the pH adjuster injecting section 24b, and the pH is adjusted appropriately. Reference sign VL2 is an adjustment valve that adjusts the injection amount of the pH adjusting agent.

  Further, a coagulant such as polyaluminum chloride or ferric chloride is injected into the raw water from the coagulant injection part 24c. Since the flocs of suspended components (organic matter) contained in the raw water are promoted by the flocculant, the fine particles of 0.1 μm or more of the suspended components easily grow into flocs of 1 μm or more by injecting the flocculant. The efficiency of removing suspended components in the filtration tank 21 is improved. When the injection amount of the flocculant is too small, the floc does not grow properly, and the suspended component (organic matter) as the substance to be separated may pass through the sand filtration tank 21. Further, when the injection amount of the flocculant is excessive, the surplus that is not used for the growth of flocs applies a load to the RO membrane provided in the RO membrane module 32 of the desalting unit 30. Therefore, the coagulant injection part 24c is provided with an adjustment valve VL3 for adjusting the injection amount of the coagulant.

  From the neutralization reducing agent injection 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. Reference sign VL4 is an adjustment valve that adjusts the injection amount of the neutralizing agent and the reducing agent.

  As described above, in the pretreatment process in the pretreatment unit 20, a process of sterilizing microorganisms by injecting a bactericide, a process of injecting a flocculant to grow organic flocs, and removing organic substances in the sand filtration tank 21. And is executed.

  In addition, the apparatus which comprises the pre-processing part 20 is not limited to a present Example, For example, the sand filtration tank 21 may be abbreviate | omitted according to the water quality.

  The desalination unit 30 includes a main line LM configured to include a high-pressure pump 31, an RO membrane module 32 and a fresh water tank 33, and a sub-configuration configured to include an RO membrane module 32, an energy recovery device 34 and a concentrated water tank 35. A line LS. Further, the desalting unit 30 is provided with a waste water tank 36, a measuring unit 38, and a chemical injection system 39 for injecting a plurality of types of chemicals into the raw water.

  A semipermeable membrane is used on the surface of the RO membrane (RO membrane surface) provided in the RO membrane module 32. The semipermeable membrane is a membrane that allows only water molecules to permeate due to the difference in interaction between the water molecules and the substance to be separated and the membrane, and examples thereof include cellulose acetate type and aromatic polyamide type. Among these, aromatic polyamide RO membranes are widely used as industrial semipermeable membranes because of their high water molecule permeability and electrolyte removal performance. In the present embodiment, an aromatic polyamide RO membrane is used, but an RO membrane made of another material such as cellulose acetate may be used.

  The configuration of the RO membrane module 32 is not limited. For example, although not shown, an element obtained by folding a composite membrane (RO membrane) in which a polyamide membrane having a thickness of 0.1 μm or less is formed on a microporous support having a thickness of several hundreds of μm into a shape called a spiral, What is necessary is just to set it as the RO membrane module 32 comprised by the element which bundled the filamentous membrane. In this case, there are many cylindrical elements having a diameter of 4 inches (about 10 cm), 8 inches (about 20 cm), 16 inches (about 40 cm) and a length of about 1 m, and such elements are pressure vessels called vessels. RO membrane modules 32 arranged in series are used.

  For example, in an element with a composite membrane folded in a spiral shape, a polyethylene spacer is sandwiched between the membranes to prevent the membranes from sticking to each other, but the gap between the spacer and the composite membrane is reduced to about 0.5 μm. . In view of this, a safety filter that removes a substance to be separated of several μm may be attached upstream of the RO membrane module 32.

  Large substances to be separated having a size of 1 μm or more are removed by the pretreatment unit 20, but by the time the raw water reaches the RO membrane module 32, minute organic substances (substances to be separated) that have not been removed by the pretreatment unit 20 reaggregate. In some cases, an organic substance or the like to be separated from the pipe is peeled off and a separated substance of several μm is generated. The safety filter of the RO membrane module 32 is attached to prevent such a substance to be separated from flowing into the RO membrane module 32 and closing the flow path of the raw water in the element.

  The chemical injection system 39 is configured according to the type of chemical used for cleaning the RO membrane module 32. FIG. 1 shows the antimicrobial agent injection unit 39a for injecting an antimicrobial agent that suppresses the growth of microorganisms. An acid injection part 39b for removing and an alkali injection part 39c for mainly removing organic substances are shown.

  2,2-Dibromo-3-nitrilopropionamide (commonly known as DBNPA) or the like is injected into the raw water as an antibacterial agent that suppresses the growth of microorganisms from the antibacterial agent injection unit 39a. The killing rate and survival rate of microorganisms in the raw water vary depending on the interval and concentration of intermittent injection of the antibacterial agent injected from the antibacterial agent injection unit 39a.

  It should be noted that excessive injection of DBNPA or the like injected as a bactericide is preferably avoided, and the bactericide injection part 39a is provided with a control valve VL5 for adjusting the injection amount of the bactericide.

  Further, in order to periodically remove the generated scale, an acid such as sulfuric acid is injected into the RO membrane supply water from the acid injection unit 39b. Reference numeral VL6 is an adjustment valve for adjusting the amount of injected acid.

  Further, alkali such as caustic soda is injected into the RO supply water from the alkali injection part 39c. The alkali injection part 39c is provided with an adjustment valve VL7 for adjusting the injection amount of alkali.

  As described above, in the seawater desalination system 1 configured as shown in FIG. 1, seawater (raw water) taken from the sea through the intake pipe 11 by the intake pump 12 of the seawater intake unit 10 is temporarily stored in the raw water tank 13. Then, after a part of the material to be separated contained in the raw water is removed by precipitation, the water is sent to the pretreatment unit 20.

  In the pretreatment unit 20, the raw water subjected to the bactericide injection from the bactericide injection unit 24a, the pH adjustment agent injection from the pH adjustment agent injection unit 24b, and the flocculant injection from the flocculant injection unit 24c is sand. It flows into the filtration tank 21. In the sand filtration tank 21, flocs of substances to be separated (organic matter) grown to 1 μm or more mainly by the flocculant are filtered and removed, and the raw water that has passed through the sand filtration tank 21 is sent to the ultrafiltration membrane module 22 by the water pump 22a. Water is sent to. The ultrafiltration membrane module 22 separates and removes finer particles to be separated of 0.1 μm or more, polymers having a molecular weight of several thousand, bacteria, and the like from raw water. Microorganisms such as bacteria contained in the raw water are almost 100% removed by the ultrafiltration membrane module 22.

  The raw water is pressurized to about 0.1 to 0.5 MPa by a pressurizing means such as a water pump 22 a and is fed (pressure fed) to the ultrafiltration membrane module 22. The higher the pressure of the raw water sent to the ultrafiltration membrane module 22, the higher the speed of permeation through the ultrafiltration membrane module 22. However, the performance (separation performance) for separating the substance to be separated from the raw water decreases.

  The raw water that has passed through the ultrafiltration membrane module 22 is injected with the neutralizing agent and the reducing agent from the neutralizing / reducing agent injection part 24d, and the raw water adjusted to be acidic with the pH adjuster is neutralized and injected. The disinfectant is reduced. The raw water is stored in the RO membrane supply water tank 23.

  The raw water stored in the RO membrane supply water tank 23 is pressurized by the high-pressure pump 31 of the desalting unit 30, supplied (pressure-fed) to the RO membrane module 32, and filtered. The raw water from which the substance to be separated is removed by the RO membrane module 32 is stored in the fresh water tank 33 as fresh water. On the other hand, the raw water that does not pass through the RO membrane of the RO membrane module 32 becomes concentrated water containing the substance to be separated while being pressurized by the high-pressure pump 31, and is stored in the concentrated water tank 35.

  In some cases, a drainage system (not shown) for returning the concentrated water stored in the concentrated water tank 35 to the sea, for example, may be provided. In this case, the drainage system is configured to perform a process for reducing the salinity concentration and a process for extracting a substance that can be a raw material for the salinity and chemicals.

  The energy recovery device 34 provided in the desalting unit 30 is, for example, a turbine that rotates with energy when high-pressure water (high-pressure water) is drained, and a generator that generates electric power by the rotation of the turbine. Can be used as drive power for the high-pressure pump 31 and the like. As an example, the high pressure water (high pressure water) may be stored in the concentrated water tank 35.

  As described above, in the seawater desalination system 1 that desalinates seawater, which is raw water, the RO membrane module 32 includes an RO membrane as a separation membrane. The following two systems are known as filtration systems for filtering raw water with such a separation membrane.

  One of the filtration methods is a “total amount filtration method”, which is a method in which the entire amount of raw water is passed through a separation membrane. In this method, the substance to be separated that does not pass through the separation membrane is deposited on the membrane surface of the separation membrane. And since the micropore of a separation membrane is obstruct | occluded by deposition of a to-be-separated substance, the phenomenon (fouling) that permeated water amount falls with an operating time generate | occur | produces.

  Another one of the filtration methods is a “cross-flow filtration method”, in which raw water is allowed to flow along the membrane surface of the separation membrane, and a part thereof passes through the separation membrane. In the cross-flow filtration method, the substance to be separated that does not permeate the separation membrane is discharged together with the raw water and does not accumulate on the membrane surface or the like. Therefore, in the ideal cross flow filtration method, the amount of water that permeates the separation membrane is determined mainly by the flow rate of the raw water and the transmembrane pressure difference, and is almost stable regardless of the operation time.

  In a module using a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, or an RO membrane, a crossflow filtration method may be used.

  However, even in the cross-flow filtration method, the organic matter (substance to be separated) contained in the raw water is gradually adsorbed on the separation membrane due to long-time operation, the micropores are blocked, and the permeated water amount of the separation membrane gradually decreases (also this Called fouling).

  The substances adsorbed on the separation membrane of the cross-flow filtration method include inorganic scale that precipitates due to high electrolyte concentration near the membrane surface, bio-fouling caused by the growth of microorganisms contained in the raw water on the membrane surface, and raw water. There is an organic matter scale that adsorbs organic matter contained in.

  For example, for inorganic scales that precipitate when the electrolyte concentration increases, it is possible to adjust the conditions so that the inorganic scale does not easily precipitate even when the electrolyte concentration increases by injecting an inorganic scale inhibitor or pH adjuster, or to clean the membrane surface. This can be done by removing the water by flowing it.

  However, the organic matter scale cannot be completely removed by the shearing force and gradually accumulates over a long period of operation. For example, in the case of the seawater desalination system 1 shown in FIG. 1, there are variations depending on the configuration and performance of the pretreatment unit 20, the quality of seawater (raw water), the type of chemicals injected by the chemical injection system 24, etc. In terms of total organic carbon, an organic substance of about 0.1 to 10 mg / L is contained in the raw water sent to the desalting unit 30.

  Further, when the organic matter scale is adsorbed and accumulated on the separation membrane, microorganisms grow using the organic matter as a culture medium to form a biofilm, which causes biofouling.

  In the case of the seawater desalination system 1 shown in FIG. 1, microorganisms contained in seawater (raw water) are killed by the sterilizing agent injected from the sterilizing agent injecting section 24a. However, as described above, RO membranes (especially aromatic polyamides) are vulnerable to hypochlorous acid and chlorine, which are bactericides, so the raw water in a state where bactericides are reduced by the reducing agent and no bactericidal components are contained. Water is sent to the desalting unit 30.

  The members such as pipes constituting the desalination unit 30 are sufficiently cleaned after construction, and further regularly cleaned with chemicals after the start of use, but it is impossible to completely eliminate microorganisms from the members such as pipes. is there.

  In addition, microorganisms that cannot be sterilized by the sterilizing agent injected from the sterilizing agent injecting unit 24a may flow into the desalting unit 30 and enter the desalting unit 30 (more specifically, downstream of the RO membrane supply water tank 23). Microorganisms may be present. In this case, since the raw water sent to the desalting unit 30 does not contain a sterilizing component (bactericidal agent having sterilizing power), the microorganisms present in the desalting unit 30 cannot be removed. A biofilm is formed by the microorganisms present in the portion 30.

  Thus, when fouling due to organic matter scale (organic matter fouling) or biofouling due to biofilm occurs in the RO membrane module 32, the filtration capability of the raw water in the RO membrane is reduced, so that the RO membrane needs to be replaced. In the seawater desalination system 1 shown in FIG. 1, the elements of the RO membrane module 32 are cleaned and the RO membrane module 32 is replaced.

  When such elements are washed or replaced, the seawater desalination system 1 is stopped for a long time, so that the operating rate is lowered. Moreover, since the component cost of an element and the work cost of replacement | exchange are added to a running cost, the running cost of the seawater desalination system 1 rises.

  Seawater (raw water) desalinated by the seawater desalination system 1 contains many types of substances to be separated (organic matter and microorganisms), but the types of organic matter and microorganisms that cause organic fouling and biofouling are limited. It has been.

  For example, the degree of influence on the occurrence of fouling differs depending on the difference in affinity with the RO membrane for organic substances and the difference in growth power and biofilm characteristics (viscosity, molecular weight of metabolites, etc.) for microorganisms. Therefore, the correlation between the total organic carbon amount and the microbial amount (ATP (adenosine triphosphate) amount) of raw water and the occurrence of fouling in the RO membrane is not necessarily high. In other words, if the RO membrane replacement time is determined based on the total amount of organic carbon and the amount of microorganisms, the RO membrane may be replaced when it is not originally required to be replaced.

  Therefore, it is preferable to measure whether or not fouling actually occurs and determine the replacement timing of the RO membrane based on the measurement result. Therefore, as shown in FIG. 2, the desalination unit 30 of the seawater desalination system 1 (see FIG. 1) according to the present embodiment has a measuring unit configured to detect the adsorption amount of organic matter and the adsorption amount of microorganisms. 38 is provided.

  As shown in FIG. 2, the measurement unit 38 is disposed downstream of the high-pressure pump 31 (that is, on the RO membrane module 32 (see FIG. 1) side from the high-pressure pump 31), and includes a temperature adjustment unit 37. A branch pipe PB branched from the middle of the pipe PM connecting the high-pressure pump 31 and the RO membrane module 32 is provided. The temperature adjusting unit 37 further includes a heating / cooling element 37a, a heat insulating unit 37b, and a measurement sensor 38a. In this case, since the high-pressure pump 31 can be used in common, it is possible to operate without adding another device. Note that, as one modification of the present embodiment, the above-described measuring unit 38 may be arranged upstream of the high-pressure pump 31 because high pressure is applied. In the case of a modification, it is necessary to connect a liquid feed pump.

  The heating / cooling element 37a is a Peltier element in this embodiment. In the present embodiment, the heat insulating portion 37b is a titanium metal block surrounded by a polystyrene foam.

  In the present embodiment, the measurement sensor 38a is a weight measurement sensor that measures the mass of the adsorbate adsorbed on the measurement surface (measurement unit) of the sensor by a quartz crystal microbalance method. Hereinafter, a specific example of the configuration will be described by taking the measurement sensor 38a as an example.

  As shown in FIG. 3, in the quartz crystal microbalance method, for example, measurement using the principle that the resonance frequency of shear vibration generated in the AT cut quartz plate 250a of the measurement sensor 38a is proportional to the mass of the AT cut quartz plate 250a. This is a method for detecting a change in mass when an adsorbate adheres to the measurement surface F1 (surface on which SiO2 (250c) is formed) or a microorganism grows as a change in resonance frequency. In other words, the change in the resonance frequency becomes the change in the mass of the adsorbate or the propagation material.

  In the measurement sensor 38a, for example, a gold electrode 250b having a thickness of about 300 nm is formed on both surfaces of a quartz crystal resonator (AT cut crystal plate 250a) having a thin disk shape having a thickness of about 0.3 mm and a diameter of about 14 mm. The aromatic polyamide film 251 is formed on the measurement surface F1 of the sensor chip 250 (for example, a commercial product manufactured by Q-Sense) on which the SiO2 (250c) having a thickness of about 100 nm is formed by sputtering on the measurement surface F1. It is set as the film | membrane structure.

  The details of the structure of the measurement sensor 38a and the method of measuring the mass by the measurement sensor 38a are described in Patent Document 1 described above. In the present embodiment, the structure of the measurement sensor 38a and the method of measuring the mass are exemplified in Patent Document 1, but other structures and methods may be used as a matter of course.

  The film quality used for the measurement sensor 38a may be a thin film of the same quality as the RO membrane module 32. The same quality means that the same material, thin films produced in the same lot, the same product model number, etc., and not the limited meaning of using exactly the same material. Thus, by adopting a thin film of the same quality, it is possible to create a state in which the growth of microorganisms is close to the membrane surface of the measurement sensor 38a and the RO membrane module 32, and the progress of fouling is predicted or detected in advance. be able to. Therefore, it is clear that the homogeneous film quality is sufficient if the environment for the growth of the microorganisms is close.

  Further, the membrane used for the measurement sensor 38a may be a thin film in which microorganisms are more likely to grow than the RO membrane module 32. In this case, microorganisms grow more actively in the environment around the measurement sensor 38a than in the environment around the surface of the RO membrane module 32, and the progress of fouling on the surface of the RO membrane can be predicted or detected.

  A plurality of these measurement sensors 38a are prepared, and the prepared thin film may be combined with a thin film having the same quality as the thin film of the RO membrane module 32 and a thin film in which microorganisms are more likely to grow than the thin film of the RO module 32. In this case, the environment around the RO membrane module 32 and the environment in which fouling easily occurs can be measured and measured together. That is, it is possible to predict the actual environment and the environment that can occur in the future. The relation of the film quality of the above thin film can be adopted in Example 2 described later, and has the above effects.

  As shown in FIG. 2, the seawater desalination system 1 according to the present embodiment (see FIG. 1) includes a measurement unit 38 that includes a measurement sensor 38 a disposed in the temperature adjustment unit 37, and is based on the growth of microorganisms. The progress of fouling can be detected prior to the progress on the RO membrane surface.

  Raw water containing the same substance to be separated flows into the pipe PM and the branch pipe PB. Microorganisms and organic substances are adsorbed on the measurement surface F1 (see FIG. 3) of the measurement sensor 38a provided in the branch pipe PB. Further, since the aromatic polyamide film 251 (see FIG. 3) equivalent to the RO film provided in the RO membrane module 32 (see FIG. 1) is formed on the measurement surface F1 of the measurement sensor 38a, the measurement sensor 38a has Organic matter and microorganisms adsorbed on the measurement surface F 1 are substances to be separated adsorbed on the RO membrane module 32. That is, a substance that is a substance to be separated removed by the RO membrane module 32 is adsorbed on the measurement surface F1 of the measurement sensor 38a. At this time, the temperature of the temperature adjusting unit 37 (see FIG. 2) is preferably set to the growth of microorganisms from the pipe PM, for example, when the temperature of the pipe PM is 15 ° C. to 25 ° C. Set to 30 ° C. Fouling occurs in the RO membrane module 32 due to the growth of such microorganisms. Thereby, in the measurement surface F1 which measures the surface of the measurement sensor 38a, since the growth of microorganisms progresses more rapidly than the RO membrane surface of the RO membrane module 32, the mass change derived from the growth of microorganisms is observed from the actual fouling. It becomes possible to detect early.

  For example, as shown in FIG. 4, with respect to the mass change estimated value WR (broken line) corresponding to the growth of microorganisms on the RO membrane module 32, it corresponds to the growth of microorganisms on the measurement surface F1 of the surface of the measurement sensor 38a. The measured mass is as shown by WS (solid line). Then, the difference ΔT between the mass change measurement value WS of the measurement sensor 38a and the mass change estimation value WB on the RO membrane module 32 indicates the acceleration amount of the growth of microorganisms, and indicates that ΔT can be detected early.

  Further, the seawater desalination system 1 (FIG. 1) is used to efficiently desalinate seawater using the amount of fouling caused by the growth of microorganisms in the RO membrane of the RO membrane module 32 measured as described above. See). For example, the seawater desalination system 1 can be operated to efficiently desalinate seawater by the following three methods.

<Controlling the operation of the pretreatment unit 20>
As described above, the measurement value of the measurement sensor 38a indicates the amount of growth in which microorganisms that are not sterilized by the pretreatment unit 20 (see FIG. 1) grow on the RO membrane of the RO membrane module 32 (see FIG. 1). Therefore, the sterilization process in the pretreatment unit 20 is adjusted so as to suppress the growth of microorganisms.

  For example, the concentration of the bactericide in the pretreatment unit 20 and the interval of intermittent injection are adjusted so that the number of days Δt until the amount of growth of the microorganisms reaches a certain value Wx is 5 days or more, The concentration of the reducing agent and the injection amount are adjusted.

  That is, in the RO membrane of the RO membrane module 32, when the microorganisms grow beyond a predetermined growth rate Wx / Δt, the sterilization of the microorganisms in the pretreatment process in the pretreatment unit 20 is strengthened. .

  However, when the proliferation of microorganisms in the RO membrane module 32 increases, the proliferation cannot be suppressed even if the sterilization in the pretreatment unit 20 is strengthened. Therefore, for example, when the biofouling amount (microbe growth amount) exceeds a preset predetermined value Wy, the concentration of the bactericide and the interval of intermittent injection are maintained. This makes it possible to minimize the concentration of the bactericide in the raw water of the pretreatment unit 20.

<Cleaning the RO membrane>
The measurement value WA of the measurement sensor 38a (see FIG. 2) provided in the branch pipe PB indicates the fouling amount due to the growth of microorganisms on the elements of the RO membrane of the RO membrane module 32 after one day to several days. Therefore, for example, when the measurement value WA of the measurement sensor 38a exceeds a predetermined value, the RO membrane module 32 is washed with a cleaning agent. In the present embodiment, the desalting unit 30 includes a chemical injection system 39 including a bactericide injection unit 39a, an acid injection unit 39b, and an alkali injection unit 39c. By selecting an appropriate drug and injecting it into the RO membrane module 32, the biofouling layer (microbe growth layer) on the surface of the RO membrane element can be removed.

  At this time, the temperature of the temperature adjusting unit 37 is set to be the same as that of the main pipe PM, and a chemical is injected into the branch pipe PB in the same manner as the main pipe PM, and the change in the weight of the measurement sensor 38a is measured. Removal of the microbial growth layer by treatment can be measured in real time. Thereby, it is possible to adjust the concentration and flow rate of the medicine and to determine the cleaning end time.

As described above, the seawater desalination system 1 (see FIG. 1) according to the present embodiment is arranged upstream of the RO membrane module 32 (see FIG. 1), and is provided with a temperature control unit 37 (see FIG. 2). The growth of microorganisms on the RO membrane of the RO membrane module 32 (see FIG. 1) can be measured based on the measurement value of the measurement sensor 38a provided in the PB (see FIG. 2). That is, fouling derived from microorganisms can be detected in advance. The seawater desalination system 1 can be suitably operated according to the amount of growth of microorganisms on the RO membrane, and seawater can be desalinated efficiently.

Since the present embodiment can be configured with a simpler apparatus than the conventional apparatus configuration by adopting the above configuration, an inexpensive water treatment system can be provided.
(Example 2)
In this embodiment, the seawater desalination system 1 similar to Example 1 was used. However, the configuration of the measurement unit 38 is different from that of the first embodiment.

  As shown in FIG. 5, the measurement unit 38 in the present embodiment is disposed downstream from the high-pressure pump 31 (that is, the RO membrane module 32 (see FIG. 1) side from the high-pressure pump 31), and has a temperature adjustment unit 37. Therefore, it is provided in the branch pipe PB branched from the middle of the pipe PM connecting the high pressure pump 31 and the RO membrane module 32. The temperature adjusting unit 37 further includes a heating / cooling element 37a, a heat insulating unit 37b, and a measurement sensor 38a. Moreover, the chemical injection system 38b for inject | pouring a chemical | medical solution into the branch piping PB is provided. As in the first embodiment, as a modification of the present embodiment, the above-described measuring unit 38 may be arranged upstream of the high-pressure pump 31 because a high pressure is applied.

  In the seawater desalination system 1 according to the present embodiment, the reason why the measurement sensor 38a can detect the progress of fouling due to the growth of microorganisms ahead of the progress on the surface of the RO membrane is as follows.

  Raw water containing the same substance to be separated flows into the pipe PM and the branch pipe PB. Microorganisms and organic substances are adsorbed on the measurement surface F1 (see FIG. 3) of the measurement sensor 38a provided in the branch pipe PB. Further, since the aromatic polyamide film 251 (see FIG. 3) equivalent to the RO film provided in the RO membrane module 32 (see FIG. 1) is formed on the measurement surface F1 of the measurement sensor 38a, the measurement sensor 38a has Organic matter and microorganisms adsorbed on the measurement surface F 1 are substances to be separated adsorbed on the RO membrane module 32. That is, a substance that is a substance to be separated removed by the RO membrane module 32 is adsorbed on the measurement surface F1 of the measurement sensor 38a. At this time, by supplying continuously or intermittently a substance that is a nutrient for the growth of microorganisms, such as amino acids, from the medicinal injection system 38b earlier than the RO membrane element surface of the RO membrane module 32, It becomes possible to promote the growth of microorganisms.

  Note that the temperature of the temperature adjusting unit 37 (see FIG. 5) may be equal to the temperature of the pipe PM, but is more suitable for the growth of microorganisms, for example, when the temperature of the pipe PM is 15 ° C. to 25 ° C. The temperature of the section 37 may be set from 20 ° C. to 30 ° C. Fouling occurs in the RO membrane module 32 due to the growth of such microorganisms. On the surface of the measurement sensor 38a, since the growth of microorganisms proceeds more rapidly than the surface of the RO membrane of the RO membrane module 32, it is possible to detect a mass change derived from the growth of microorganisms earlier than the actual fouling. That is, fouling derived from microorganisms can be detected in advance. As a result, it is possible to control the operation of the pretreatment unit 20 and to properly clean the RO membrane module 32.

  Note that the design of the present invention can be changed as appropriate without departing from the spirit of the invention.

  For example, as shown in FIGS. 2 and 5, the measurement sensor 38a is provided in the branch pipe PB that bypasses the RO membrane module 32, but the branch pipe PB is joined to the pipe PM downstream of the measurement sensor 38a. There may be.

  Moreover, the structure provided with the water storage tank (not shown) which stores the raw | natural water which flowed through the branch piping PB may be sufficient.

  According to the present embodiment, by adopting the above configuration, it is possible to configure with a simpler apparatus as compared with the conventional apparatus configuration, and thus it is possible to provide an inexpensive water treatment system.

  Further, the method for measuring the amount of growth of microorganisms in the measurement sensor 38a (see FIGS. 2 and 5) is not limited to the quartz crystal microbalance method. Other measurement methods for the quartz crystal microbalance include a surface plasmon resonance method, a total reflection Fourier transform infrared absorption method, and an ellipsometry method. There is also a method of measuring the growth of microorganisms by forming a thin film equivalent to a separation membrane for evaluating fouling on the measurement surface of a measuring instrument that performs surface reflectance measurement.

1 Seawater desalination system (water treatment system)
DESCRIPTION OF SYMBOLS 10 Seawater intake part 20 Pretreatment part 30 Desalination part 38a Measurement sensor 32 RO membrane module (RO membrane, separation membrane)
250 AT-cut quartz plate (quartz crystal)
F1 measurement surface (measurement part)
PM main piping PB branch piping

Claims (13)

Acceleration mechanism for accelerating the growth of microorganisms in the upstream of the separation membrane for separating the substance to be separated from the raw water, and the main flow toward the separation membrane in the flow of the raw water and the branch flow that is the other of the main flows. And a branch flow in which a measurement sensor having a thin film of the same quality as the separation membrane is arranged,
An evaluation step for evaluating a change that occurs on the surface of the separation membrane, based on a change that occurs in the measurement part of the measurement sensor due to microorganisms that have grown by the acceleration mechanism,
A separation membrane surface evaluation method characterized by comprising: The separation membrane surface evaluation method according to claim 1,
The thin film of the same quality is a thin film different from the separation membrane, and is a thin film that is more prone to microbial growth than the separation membrane.
Separation membrane surface evaluation method characterized by the above. The separation membrane surface evaluation method according to claim 1,
The evaluation step has a temperature adjustment mechanism, and grows microorganisms by maintaining the temperature detected by the measurement sensor higher than the temperature of the separation membrane,
Separation membrane surface evaluation method characterized by the above. The separation membrane surface evaluation method according to claim 1,
In the evaluation step, the acceleration mechanism includes a step of performing a process of growing microorganisms by a chemical injection system that replenishes a substance that promotes the growth of microorganisms arranged upstream of the measurement sensor.
Separation membrane surface evaluation method characterized by the above. The separation membrane surface evaluation method according to claim 1,
In the branching step, upstream of the separation membrane that is a reverse osmosis membrane, branching into the main flow and the branch flow,
In the evaluation step, a change occurring on the surface of the separation membrane which is a reverse osmosis membrane is evaluated.
Separation membrane surface evaluation method characterized by the above. The separation membrane surface evaluation method according to claim 1,
In the evaluation step, the separation is performed using a weight change measured by a quartz crystal microbalance method using the measurement sensor including the measurement unit in which the thin film is formed on one surface of the crystal resonator. Evaluate changes that occur on the membrane surface,
Separation membrane surface evaluation method characterized by the above. A control method of a water treatment system for sterilizing microorganisms contained in the raw water in a pretreatment step upstream of a separation membrane for separating a substance to be separated from raw water,
In the evaluation step, growth of microorganisms on the separation membrane surface is evaluated by the separation membrane surface evaluation method according to any one of claims 1 to 6, and in the pretreatment step, If the growth of microorganisms exceeds a predetermined value, enhance the sterilization of the microorganisms,
A method for controlling a water treatment system. In a chemical injection process performed by a chemical injection system disposed upstream of a separation membrane that separates a substance to be separated from raw water, at least one of an acid, an alkali, an antibacterial agent for washing the separation membrane in the raw water, or A method for controlling a water treatment system for injecting a plurality of cleaning agents comprising:
In the evaluation step, the growth of microorganisms on the separation membrane surface is evaluated by the separation membrane surface evaluation method according to any one of claims 1 to 5, and in the drug injection step, the separation membrane surface is evaluated. When the growth of microorganisms exceeds a predetermined value, the separation membrane surface is washed by the chemical injection system.
A method for controlling a water treatment system. A separation membrane for separating the material to be separated from the raw water;
Upstream of the separation membrane, a main flow toward the separation membrane in the flow of the raw water, and a branch portion that branches into a branch flow that is the other different from the main flow,
An acceleration mechanism for accelerating the growth of microorganisms arranged in the branch flow;
A measurement sensor comprising a thin film of the same quality as the separation membrane disposed in the branch flow;
An evaluation unit that evaluates a change that occurs on the surface of the separation membrane surface, based on a change that occurs in the measurement unit of the measurement sensor due to microorganisms grown by the acceleration mechanism;
A water treatment system comprising: The water treatment system according to claim 9,
The thin film of the same quality is a thin film different from the separation membrane, and is a thin film that is more prone to microbial growth than the separation membrane.
A water treatment system characterized by that. The water treatment system according to claim 9,
The evaluation unit has a temperature adjustment mechanism, and grows microorganisms by maintaining the temperature detected by the measurement sensor higher than the temperature of the separation membrane,
A water treatment system characterized by that. The water treatment system according to claim 9,
In the evaluation unit, the acceleration mechanism causes microorganisms to grow by a chemical injection system that replenishes a substance that promotes the growth of microorganisms arranged upstream from the measurement sensor.
A water treatment system characterized by that. The water treatment system according to claim 9,
The branched flow is branched into the main flow and the branched flow upstream of the separation membrane that is a reverse osmosis membrane, and the evaluation unit evaluates a change that occurs on the surface of the separation membrane that is a reverse osmosis membrane. ,
A water treatment system characterized by that.

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