Operation method of raw water compartment and water treatment device

Abstract

This invention provides a raw water spacer that can form a membrane module that inhibits the adhesion of cationic substances to the surface of a membrane, and a method for operating a water treatment apparatus equipped with the membrane module. The raw water spacer includes a plurality of first linear bodies and a plurality of second linear bodies forming a mesh-like planar structure. The plurality of first linear bodies and the plurality of second linear bodies are composed of a composite material formed by incorporating carbon nanotubes into a substrate resin, wherein each 100 parts by weight of the composite material contains 1 to 7 parts by weight of carbon nanotubes. The surface roughness of the plurality of first linear bodies and the plurality of second linear bodies is configured such that the arithmetic mean height Sa, as specified in ISO 25178, reaches 0.2 μm to 0.5 μm.

Description

Technical Field

[0001] This invention relates to a raw water spacer and a method for operating a water treatment device. Prior Technology

[0002] In a multi-stage filtration water treatment system, a known water treatment device uses the filtered water from the previous stage of filtration as raw water and utilizes a reverse osmosis membrane (hereinafter referred to as RO membrane) to separate the components that could not be removed by the previous stage of filtration. Examples of the components to be separated include ions (Ion) and TOC (Total Organic Carbon). Such water treatment devices typically employ a spiral-type membrane module, with multiple membranes wound around a water pipe.

[0003] This type of water treatment device feeds raw water containing the target components and water into a membrane separation module, allowing it to pass through a membrane disposed within the module. The water is separated into permeate (water that has passed through the membrane) and concentrated water (water that has not passed through the membrane). The membrane is located inside the membrane separation module. A raw water spacer is also installed inside the membrane separation module to ensure the flow path of the raw water between the two membranes.

[0004] Patent Document 1 discloses a mesh-like raw water spacer, comprising polypropylene resin and carbon nanotubes, and is composed of a molded article separately formed from the separation membrane. In the technology described in Patent Document 1, the proportion of carbon nanotubes is specified as 5.3 to 18 parts by weight relative to 100 parts by weight of polypropylene resin.

[0005] Patent document 1 is Japanese Patent Application Publication No. 7072175. Summary of the Invention

[0006] In the RO membrane module, when separating raw water into permeate and concentrate, cationic substances contained in the raw water may adhere to and accumulate on the RO membrane surface. For example, when wastewater or polluted water is purified by biological treatment to decompose organic matter, even after pre-filtration, cationic proteins from microorganisms that could not be separated by the pre-filtration may still remain in the filtered water. When this filtered water is used as raw water, cationic proteins may adhere to and accumulate on the membrane surface, leading to a decline in membrane performance.

[0007] Furthermore, in operations such as cleaning electronic materials, the cleaning water used in these operations may contain cationic surfactants. When this cleaning water is used as the raw water, the cationic surfactants may adhere to and accumulate on the surface of the separation membrane, leading to a decline in the membrane's performance.

[0008] When such cationic substances adhere to and accumulate on the surface of the separation membrane, adding a cleaning step to remove these substances not only reduces the operating rate of the water treatment unit due to the time-consuming cleaning process, but also increases operating costs. Therefore, from the perspective of improving the operating rate of water treatment units, it is urgent to develop separation membrane modules that prevent cationic substances from adhering to the surface of the separation membrane.

[0009] Based on the above background, the inventors repeatedly studied separation membranes that are not prone to the adhesion of cationic substances. Through empirical research, it was found that if a raw water separator that meets specific conditions is used as the raw water separator disposed inside the separation membrane module, the adhesion of cationic substances to the separation membrane surface can be effectively inhibited, thus completing the invention of this technology.

[0010] One aspect of the present invention aims to provide a raw water spacer that can constitute a separation membrane module that inhibits the adhesion of cationic substances to the surface of the separation membrane, and a method of operating a water treatment device having the separation membrane module.

[0011] One embodiment of the present invention is a raw water spacer, which is disposed inside a separation membrane module in a water treatment device, ensuring the flow path of raw water between two separation membranes. The water treatment device passes raw water containing the target components and water to the separation membrane module, causing it to separate into permeate water that passes through the separation membrane and concentrated water that does not pass through the separation membrane. The separation membranes are disposed inside the separation membrane module. The raw water spacer includes a plurality of first linear bodies and a plurality of second linear bodies. The plurality of first linear bodies are arranged side-by-side. The plurality of second linear bodies are arranged side-by-side. The plurality of first linear bodies and the plurality of second linear bodies are arranged in intersecting directions, forming a mesh-like surface. The plurality of first linear bodies and the plurality of second linear bodies are configured such that, when the raw water spacer is positioned between two separation membranes, the plurality of first linear bodies contact one of the separation membranes, and the plurality of second linear bodies are interposed between the plurality of first linear bodies and the other separation membrane to ensure a gap for the formation of a raw water flow path; and the plurality of second linear bodies contact the other separation membrane, and the plurality of first linear bodies are interposed between the plurality of second linear bodies and one of the separation membranes to ensure a gap for the formation of a raw water flow path. Furthermore, the plurality of first linear bodies and the plurality of second linear bodies are composed of a composite material formed by incorporating carbon nanotubes into a base resin, wherein each 100 parts by mass of the composite material contains 1 to 7 parts by mass of carbon nanotubes. The surface roughness of the plurality of first linear bodies and the plurality of second linear bodies is configured such that the arithmetic mean height Sa, as specified in ISO 25178, reaches 0.2 μm to 0.5 μm.

[0012] In one embodiment of the present invention, the composite material can be the following: after adding a base resin to the composite material, the concentration of carbon nanotubes in the composite material is diluted to 100 times, and the diluted material is molded into a molded article with a thickness of 0.3 mm. In an image of the surface of the molded article, three 2 mm × 2 mm fields of view are randomly selected, and when observing each field of view, the average number of carbon nanotubes with a particle area of ​​25 μm² or more but less than 100 μm² observed in each field of view is less than 50 at the three locations, and the average number of carbon nanotubes with a particle area of ​​100 μm² or more but less than 20000 μm² observed in each field of view is less than 10 at the three locations.

[0013] In one embodiment of the present invention, the quadrilateral grid formed by the first and second linear bodies can be configured such that the distance between the diagonal directions of the quadrilaterals is 4.0 mm to 5.0 mm. The operation method of the water treatment device in one embodiment of the present invention involves passing raw water containing the target components and water to a separation membrane module, causing it to separate into permeate water that passes through the separation membrane and concentrated water that does not pass through the separation membrane. The separation membrane is disposed inside the separation membrane module, wherein a raw water spacer is disposed inside the separation membrane module to ensure the flow path of the raw water between the two separation membranes. The raw water spacer includes a plurality of first linear bodies and a plurality of second linear bodies. The plurality of first linear bodies are arranged side by side. The plurality of second linear bodies are arranged side by side. The plurality of first linear bodies and the plurality of second linear bodies are arranged in intersecting directions, forming a mesh-like surface. The plurality of first linear bodies and the plurality of second linear bodies are configured such that, when the raw water spacer is positioned between two separation membranes, the plurality of first linear bodies contact one of the separation membranes, and the plurality of second linear bodies are interposed between the plurality of first linear bodies and the other separation membrane to ensure a gap for the formation of a raw water flow path; and the plurality of second linear bodies contact the other separation membrane, and the plurality of first linear bodies are interposed between the plurality of second linear bodies and one of the separation membranes to ensure a gap for the formation of a raw water flow path. Furthermore, the plurality of first linear bodies and the plurality of second linear bodies are composed of a composite material formed by incorporating carbon nanotubes into a base resin, wherein each 100 parts by mass of the composite material contains 1 to 7 parts by mass of carbon nanotubes. The surface roughness of the plurality of first linear bodies and the plurality of second linear bodies is configured such that the arithmetic mean height Sa, as specified in ISO 25178, reaches 0.2 μm to 0.5 μm.

[0014] In one embodiment of the present invention, the mass transfer coefficient of the two separation membranes disposed on opposite sides of the control raw water spacer, when the solute in the raw water is NaCl, is 1.3 to 2.4 times that of the control raw water spacer at a linear velocity of 0.02 m / s to 0.14 m / s, compared to the control raw water spacer. The control raw water spacer uses a substrate resin without carbon nanotubes instead of a composite material, and otherwise has the same structure as the raw water spacer.

[0015] In one embodiment of the present invention, the raw water may contain a cationic substance selected from at least one of cationic proteins and cationic surfactants as the component to be separated. Simple Explanation of the Diagram

[0016] [Figures 1A and 1B] Figure 1A is a top view of the original water spacer; Figure 1B is an enlarged view of part IB shown in Figure 1A. [Figures 2A and 2B] Figure 2A is a partial top view of the raw water spacer, showing the flow path of the raw water; Figure 2B is a cross-sectional view showing the flow path of the raw water at the cross-section indicated by lines IIB to IIB in Figure 2A. [Figure 3] Figure 3 is a graph showing the measurement results of the arithmetic mean height of the surface of the raw water spacer in Examples 1 to 4 and Comparative Examples 1 to 2. [Figures 4A, 4B, 4C, 4D, 4E, 4F] Figures 4A, 4B, and 4C are photographs showing the dispersibility of the composite material of Example 1. Figures 4D, 4E, and 4F are photographs showing the dispersibility of the composite material of Comparative Example 1. [Figures 5A and 5B] Figure 5A is a graph showing the measurement results of the mass transfer coefficients of Examples 1 to 4 and Comparative Examples 1 to 2; Figure 5B is a graph showing the rate of change of the mass transfer coefficients of Examples 1 to 4 and Comparative Example 1 relative to Comparative Example 2. [Figures 6A and 6B] Figure 6A is a graph showing the measurement results of the mass transfer coefficients of Examples 1, 5, Comparative Example 2 and Comparative Example 3; Figure 6B is a graph showing the rate of change of the mass transfer coefficients of Examples 1, 5 and Comparative Example 3 relative to Comparative Example 2. [Figures 7A and 7B] Figure 7A is a graph showing the measurement results of the mass transfer coefficients of Example 6 and Comparative Example 4; Figure 7B is a graph showing the rate of change of the mass transfer coefficient of Example 6 relative to Comparative Example 4. [Figures 8A and 8B] Figure 8A shows the change in transmittance over time for Examples 1 to 4 and Comparative Example 2; Figure 8B shows the change in transmittance over time for Examples 1 to 4 and Comparative Example 2. [Figures 9A and 9B] Figure 9A is a schematic diagram showing the simulation results of the attachment state of lysozyme in the CNT / PP model; Figure 9B is a schematic diagram showing the simulation results of the attachment state of lysozyme in the PP model. [Figure 10] Figure 10 shows the relationship between the water flow velocity near the surface of the original water spacer and the distance from the surface of the original water spacer. Implementation

[0017] The following uses figures to illustrate the applicable embodiments of the present invention. Exemplary embodiments are described below for the operation method of the aforementioned raw water spacer and water treatment device. (1) Composition of the raw water spacer. As shown in Figures 1A and 1B, the raw water spacer 1 includes a plurality of first linear bodies 11A arranged side-by-side and a plurality of second linear bodies 11B arranged side-by-side. The plurality of first linear bodies 11A and the plurality of second linear bodies 11B are staggered at positions forming a quadrangular grid. When viewed from the direction shown in Figure 1B, the plurality of first linear bodies 11A are positioned closer to the observer than the plurality of second linear bodies 11B. The plurality of first linear bodies 11A and the plurality of second linear bodies 11B form a structure where they are fused together at their intersections.

[0018] Such a mesh structure can be manufactured by rotational extrusion molding. In this rotational extrusion molding process, the raw water spacer component material 1, in a molten state, is extruded downwards in a vertical direction through a die lip consisting of an annular outer die and an annular inner die fitted into the inner circumference of the outer die. A plurality of grooves are etched parallel to each other along the axial direction on the inner circumferential surface of the front end side of the outer die in the extrusion direction and the outer circumferential surface of the front end side of the inner die in the extrusion direction, with the groove spacing remaining constant in the circumferential direction.

[0019] When the outer and inner molds rotate in opposite directions, and the material constituting the water spacer 1 is extruded from the multiple grooves engraved on the outer and inner molds, the material is extruded in a linear form. At this time, the extruded linear body is extruded in a spiral shape along with the rotation of the outer and inner molds. However, the rotation directions of the outer and inner molds are opposite.

[0020] Therefore, the spiral twisting directions of the plurality of linear bodies extruded from the outer mold groove and the plurality of linear bodies extruded from the inner mold groove are mutually opposite. When the linear body extruded from either the outer or inner mold groove forms a left-handed spiral shape, the linear body extruded from the other groove forms a right-handed spiral shape.

[0021] Furthermore, the inner circumference of the outer mold and the outer circumference of the inner mold are in contact with each other. Therefore, multiple linear bodies extruded from the outer mold groove and multiple linear bodies extruded from the inner mold groove are extruded in a spiral shape at the contact points. As a result, linear bodies with left-handed spiral shapes and linear bodies with right-handed spiral shapes are formed into a cylindrical mesh in a mesh-like interlacing manner. At this time, at the intersection between the linear bodies with left-handed spiral shapes and the linear bodies with right-handed spiral shapes, the linear bodies in a high-temperature softened state fuse together.

[0022] The material is formed into a cylindrical mesh using this method and then pulled vertically downwards by a traction machine. During this process, the cylindrical mesh is first adjusted to the specified dimensions using a sizing die, and then sent to a cooling layer for cooling. After cooling, one circumferential section of the cylindrical mesh is cut axially, thereby forming a planar mesh. The planar mesh is then annealed in a tempering tank and wound by a winding machine.

[0023] In this embodiment, the diameters of the first linear body 11A and the second linear body 11B are each approximately 0.4 mm. Furthermore, at the intersection of the first linear body 11A and the second linear body 11B, they are fused together with one side embedded into the other side by approximately 0.1 mm. Therefore, the thickness of the original water spacer 1 is approximately 0.7 mm.

[0024] According to the raw water spacer 1 having the above-described structure, as shown in Figures 2A and 2B, when the raw water spacer 1 is positioned between two separation membranes 21 and 22, a plurality of first linear bodies 11A contact one of the separation membranes 21. Between the plurality of first linear bodies 11A and the other separation membrane 22, a plurality of second linear bodies 11B are interposed to ensure a gap 23. Simultaneously, the plurality of second linear bodies 11B contact the other separation membrane 22. Between the plurality of second linear bodies 11B and one of the separation membranes 21, a plurality of first linear bodies 11A are interposed to ensure a gap 24.

[0025] As described above, the thickness of the raw water spacer 1 is approximately 0.7 mm, and the diameters of the first linear body 11A and the second linear body 11B are approximately 0.4 mm. Therefore, the dimensions of the gaps 23 and 24 are approximately 0.3 mm. By ensuring these gaps 23 and 24, a flow path F is formed between the two separation membranes 21 and 22, as illustrated by the dashed arrows in Figures 2A and 2B.

[0026] The quadrilateral grid spacing formed by the first linear body 11A and the second linear body 11B is configured such that the distance between two opposite diagonals on one side is 4mm to 5mm, and the distance between two opposite diagonals on the other side is also 4mm to 5mm. When the distance between both opposite diagonals is 4mm or more, the grid area is not too small, which can sufficiently ensure the flow path width of the raw water when it flows through the grid. In addition, when the distance between both opposite diagonals is less than 5mm, the grid area is not too large, which can inhibit the separation membranes from contacting each other through the grid, thereby inhibiting the blockage of the raw water flow path caused by the contact points between the separation membranes.

[0027] As a constituent material for forming the raw water spacer 1, a composite material incorporating carbon nanotubes (hereinafter referred to as CNTs) in a base resin is used. In this embodiment, polypropylene (hereinafter referred to as PP) is used as the base resin. CNTs have a structure similar to graphene sheets rolled into a cylindrical shape, with a diameter of several nm to tens of nm and a length that is tens to thousands of times greater than the diameter. CNTs can be divided into single-layer CNTs, where the graphene sheet is essentially a single layer, and multi-layer CNTs with two or more layers. As long as the purpose of the present invention is not impaired, single-layer or multi-layer CNTs can be used.

[0028] The composite material contains 1 to 7 parts by mass of CNTs per 100 parts by mass. When the amount of CNTs in the composite material is 1 part by mass or more per 100 parts by mass, the mass transfer coefficient can be increased by more than 1.3 times compared to using a base resin without CNTs. Furthermore, when the amount of CNTs in the composite material is 7 parts by mass or less per 100 parts by mass, excessive increase in the viscosity of the composite material can be suppressed, thereby avoiding deterioration in processability. In addition, by controlling the amount of CNTs to 7 parts by mass or less, material costs can be effectively reduced, thereby lowering the selling price of the raw water spacer 1.

[0029] Furthermore, the surface roughness of the first linear body 11A and the second linear body 11B is configured such that the arithmetic mean height Sa reaches 0.2 μm to 0.5 μm as specified in ISO 25178. When the arithmetic mean height Sa is set to 0.2 μm to 0.5 μm, the mass transfer coefficient described later can be increased by 1.3 to 2.4 times compared to the case of using a substrate resin without CNTs.

[0030] Furthermore, the aforementioned composite material is preferably a material with excellent CNT dispersibility. That is, it is preferably a material in which CNTs are fully pulverized into fine particles and dispersed in the base resin. However, it is difficult to determine whether the CNTs are sufficiently dispersed by visual inspection of the aforementioned composite material. Therefore, the inventors used the following method to confirm the dispersibility of CNTs.

[0031] First, a base resin was added to the aforementioned composite material to dilute the concentration of CNTs in the composite material to 100 times, and this diluted material was molded into a 0.3 mm thick article. Three 2 mm × 2 mm fields of view were randomly selected from images of the surface of this article, and each field of view was observed. Furthermore, in this embodiment, a digital microscope (Keyence Corporation, model: VHX-7000) was used to photograph the surface of the article.

[0032] This method increases the spacing between CNT particles and eliminates overlap between multiple particles. This allows for observation of individual particle sizes, enabling the identification of particle sizes within the composite material. Furthermore, coarse, incompletely pulverized CNT particles are actually cable-like aggregates formed by the irregular entanglement of multiple CNTs. Therefore, even after the aforementioned dilution treatment, the entangled CNTs hardly unravel, maintaining their cable-like structure. Thus, after the dilution treatment, the CNT particle size remains unchanged, allowing for precise determination of the particle size and quantity within the composite material.

[0033] When conducting the above observations, the first condition was that the average number of CNT particles with a particle area of ​​25 μm² or more but less than 100 μm² observed in each field of view was less than 50 at three locations. The second condition was that the average number of CNC particles with a particle area of ​​100 μm² or more but less than 20,000 μm² observed in each field of view was less than 10 at three locations.

[0034] If a molded article that simultaneously satisfies conditions 1 and 2 above can be obtained, then the composite material can be considered to be a material in which CNTs are thoroughly pulverized into fine particles and dispersed in the base resin. When the number of CNT particles with a particle area of ​​25 μm² or more but less than 100 μm² is less than 50 at an average of three locations, the arithmetic mean height Sa specified in ISO 25178 can be controlled to be less than 0.5 μm. Furthermore, when CNC particles with a particle area of ​​100 μm² or more but less than 20000 μm² are considered coarse particles, but their number is less than 10 at an average of three locations, the influence caused by the presence of coarse particles can be suppressed to a negligible level.

[0035] (2) Performance evaluation. (2.01) Evaluation of the configuration of the separation membrane module. Prepare raw water spacers as shown in Examples 1 to 6 and Comparative Examples 1 to 4 below, and configure separation membrane modules in which the raw water spacers are assembled, and then evaluate their respective performance.

[0036] [Example 1] A water separator was manufactured using polypropylene (PP) as the base resin and a composite material containing CNTs in the base resin via rotational extrusion molding. In Example 1, a composite material containing 7 parts by weight of CNTs was used per 100 parts by weight of the composite material. In the pretreatment step, the CNTs and the base resin were stirred at high speed to thoroughly pulverize the CNTs. After this pretreatment step, the base resin was melted and kneaded. The diameter of the first and second linear bodies was approximately 0.4 mm, and the thickness of the water separator was approximately 0.7 mm. The spacing of the quadrangular grid formed by the first and second linear bodies was 4 mm between two opposite diagonals on one side and 4 mm between two opposite diagonals on the other side.

[0037] The aforementioned raw water separator is used to construct the separation membrane module. The RO membrane used is the RO membrane obtained by disassembling a commercially available separation membrane module (manufactured by Nitto Denko Corporation, model: ESPA2-4040). The effective area of ​​the separation membrane module is 1800 cm², the diameter is 5 cm, and the axial length is 30 cm. Furthermore, the aforementioned commercially available separation membrane module from which the RO membrane of Example 1 was disassembled possesses ultra-low pressure operation characteristics, making it suitable for various fields such as industrial wastewater recovery and sewage treatment.

[0038] [Comparative Example 1] The aforementioned pretreatment steps were omitted, and the remaining steps and conditions were the same as in Example 1, thereby manufacturing the raw water spacer and forming a separation membrane module.

[0039] [Example 2] A composite material containing 1 part by mass of CNT in every 100 parts by mass of the composite material was used, and the remaining steps and conditions were the same as in Example 1, thereby manufacturing a raw water spacer and forming a separation membrane module.

[0040] [Example 3] A composite material containing 3 parts by mass of CNTs was used for every 100 parts by mass of the composite material. The remaining steps and conditions were the same as in Example 1, thereby manufacturing a raw water spacer and forming a separation membrane module.

[0041] [Example 4] A composite material containing 5 parts by mass of CNTs was used for every 100 parts by mass of the composite material. The remaining steps and conditions were the same as in Example 1. The raw water spacer was then manufactured and configured as a separation membrane module.

[0042] [Comparative Example 2] A substrate resin without CNTs was used to replace the composite material. All other steps and conditions were the same as in Example 1, thereby manufacturing a raw water spacer and configuring it as a separation membrane module. In addition, the raw water spacer of Comparative Example 2 is equivalent to the control raw water spacer of the present invention.

[0043] [Comparative Example 3] Regarding the spacing of the quadrangular grid formed by the first linear body and the second linear body, the diagonal distance on one side is set to 3 mm, and the diagonal distance on the other side is set to 3 mm. The remaining steps and conditions are the same as in Example 1, thereby manufacturing the raw water spacer and forming a separation membrane module.

[0044] [Example 5] Regarding the spacing of the quadrangular grid formed by the first linear body and the second linear body, the diagonal distance on one side is set to 5mm, and the diagonal distance on the other side is set to 5mm. The remaining steps and conditions are the same as in Example 1, thereby manufacturing the raw water spacer and forming a separation membrane module.

[0045] [Example 6] A raw water spacer identical to that in Example 1 was manufactured, and a separation membrane module was constructed using this raw water spacer. However, the RO membrane used was a commercially available separation membrane module (manufactured by DuPont, product name: Filmtec BW30-4040) disassembled from the original membrane, which differs from Example 1. Furthermore, the aforementioned commercially available separation membrane module from which the RO membrane of Example 6 was removed is primarily intended for applications such as pure water production.

[0046] [Comparative Example 4] A raw water spacer identical to that of Comparative Example 2 (i.e., the control raw water spacer of the present invention) was manufactured, and a separation membrane module was constructed using the raw water spacer. However, the same RO membrane as in Example 6 was used as the RO membrane.

[0047] (2.02) Surface roughness measurement. For the raw water spacers described in Examples 1-4 and Comparative Examples 1-2, the arithmetic mean height Sa, as specified in ISO 25178, was measured as the surface roughness for each. The arithmetic mean height Sa was measured using a commercially available confocal laser microscope (product name: 3D Measurement Laser Microscope LEXT OLS4000, manufactured by Olympus Corporation, Japan). The measurement results are shown in Figure 3.

[0048] The arithmetic mean height Sa of the raw water spacers described in Examples 1 to 4 is in the range of 0.2 μm to 0.5 μm. On the other hand, the arithmetic mean height Sa of the raw water spacers described in Comparative Examples 1 to 2 exceeds 0.5 μm. It is presumed that in Examples 1 to 4, the CNTs in the extruded material are oriented along the extrusion direction, thus improving the surface smoothness of the molded product. On the other hand, in Comparative Example 1, although the amount of CNTs is similar to that in Example 1, the CNT particles contain more coarse particles. Therefore, it is presumed that the surface of the molded product in Comparative Example 1 is rougher, resulting in the arithmetic mean height Sa exceeding 0.5 μm. As for Comparative Example 2, it differs from Examples 1 to 4 in that it does not contain CNT particles. Therefore, it is presumed that the CNTs are not oriented in the extruded material, resulting in a rough surface of the molded product.

[0049] (2.03) Verification of dispersibility. For the raw water spacers described in Example 1 and Comparative Example 1, the dispersibility of CNT particles contained in the constituent materials of each raw water spacer was confirmed using the aforementioned method. Specifically, a base resin was first added to the constituent materials of each raw water spacer to dilute the CNT concentration in the composite material to 100 times, and then this diluted material was molded into a molded article with a thickness of 0.3 mm.

[0050] After capturing images of the surface of the molded article using a digital microscope, three 2mm × 2mm fields of view were randomly selected and observed. For the material corresponding to Example 1, the images of the three fields of view are shown in Figures 4A, 4B, and 4C, respectively. For the material corresponding to Comparative Example 1, the images of the three fields of view are shown in Figures 4D, 4E, and 4F, respectively.

[0051] In each field of view, the dark areas correspond to CNT particles. Based on this, the area of ​​each dark area was calculated using computer analysis, and the number of CNT particles with an area of ​​25 μm² or more but less than 100 μm², and the number of CNT particles with an area of ​​100 μm² or more but less than 20,000 μm² were counted. The counting results are shown in Table 1.

[0052] Table 1 Particle area Example 1 Comparative Example 2 Field of view 1 Vision 2 Field of view 3 Field of view 1 Vision 2 Field of view 3 25μm2 or more but less than 100μm2 twenty four 41 40 295 239 252 100μm2 or more but less than 20000μm2 2 5 7 114 109 90

[0053] Comparing Example 1 and Comparative Example 1, although both have 7 parts by mass of CNT in every 100 parts by mass of composite material, Comparative Example 1 clearly contains more coarse CNT particles and the CNTs are not uniformly dispersed.

[0054] (2.04) Relationship between surface roughness and mass transfer coefficient. The separation membrane modules described in Examples 1 to 4 and Comparative Examples 1 to 2 were assembled in a cross-flow device, and the mass transfer coefficient of the separation membrane surface was measured according to the following steps.

[0055] First, prepare pure water as the raw water (inlet water) and pass it through the membrane module. Set the inlet water flow rate to 1000 mL / min and the inlet water pressure to 0.35~0.50 MPa. Measure the water volume (permeate water, concentrate water), water temperature (raw water, permeate water, concentrate water), concentration (raw water, permeate water, concentrate water), pH value (raw water), and inlet water pressure every 30 minutes.

[0056] Next, prepare a 0.1% (1000 ppm) NaCl (sodium chloride) saline solution as the raw water. Adjust the pH of the solution to 7 (using 0.1 mol / L NaOH (sodium hydroxide) for adjustment) and measure the mass transfer coefficient. Set the influent flow rate to 250~2000 mL / min and the influent pressure to 0.35 MPa (adjustable as needed). Measure the water volume (permeate, concentrate), water temperature (raw water, permeate, concentrate), concentration (raw water, permeate, concentrate), pH value (raw water), and influent pressure every 30 minutes.

[0057] Based on the above measurement results, the mass transfer coefficient is calculated according to the following steps. First, the permeation flow of pure water is measured to obtain the permeation coefficient Lp [m / d / MPa]. The permeation coefficient Lp [m / d / MPa] can be calculated using the formula Lp = Jw / ΔP based on the pure water permeation rate Jw [m / d] and the inlet pressure difference ΔP [Pa]. Next, the permeation flow is measured with varying brine flow rates, and the permeation pressure Δπ [Pa] for each flow rate is obtained. The permeation pressure Δπ [Pa] can be calculated using the formula Δπ = ΔP - Jv / Lp based on the brine permeation rate Jv [m / d].

[0058] Next, the membrane surface concentration Cm [mg / L] is obtained from the permeation pressure Δπ. The slope coefficient f between the saline concentration and the permeation pressure is taken as "0.8479" based on literature values ​​and the van't Hoff equation. The membrane surface concentration Cm [mg / L] can be calculated using the formula Cm = Δπ / f. Then, the mass transfer coefficient k [m / d] is obtained from the membrane surface concentration Cm according to the concentration polarization formula. Based on the saline feed concentration Cb [mg / L], the mass transfer coefficient k can be calculated using the formula k = Jv / ln(Cm / Cb).

[0059] The measurement results of the mass transfer coefficient of the separation membrane modules of Examples 1 to 4 and Comparative Examples 1 to 2 are shown in Figures 5A and 5B. As shown in Figure 5A, the measurement results of the mass transfer coefficient of Examples 1 to 4, where the arithmetic mean height Sa of the surface of the raw water spacer is in the range of 0.2 μm to 0.5 μm, are better than those of Comparative Examples 1 to 2, where the arithmetic mean height Sa exceeds 0.5 μm.

[0060] Figure 5B is a graph showing the change factor (hereinafter referred to as the mass transfer coefficient change rate) of the mass transfer coefficients of Examples 1 to 4 and Comparative Example 1 compared to Comparative Example 2, with Comparative Example 2 corresponding to the control raw water spacer as the reference. In Examples 1 to 4, the mass transfer coefficient change rate at each linear velocity was more than 1.3 times.

[0061] On the other hand, in Comparative Example 1, the rate of change of the mass transfer coefficient gradually approached 1.0 times as the linear velocity increased. Although the CNT dosage was the same in Example 1 and Comparative Example 1, as mentioned above, the surface roughness of the raw water spacers differed between the two. Therefore, it is expected that by incorporating CNTs and adjusting the surface roughness of the raw water spacers to an arithmetic mean height Sa within the range of 0.2 μm to 0.5 μm, the rate of change of the mass transfer coefficient could be increased by more than 1.3 times compared to the control raw water spacer.

[0062] (2.05) Relationship between grid spacing and mass transfer coefficient. The separation membrane modules described in Example 5 and Comparative Example 3 were installed in a cross-flow device, and the mass transfer coefficient of the separation membrane surface was measured according to the steps described in section (2.04) above.

[0063] The measurement results of the mass transfer coefficients of the separation membrane modules of Examples 1, 5, Comparative Example 2, and Comparative Example 3 are shown in Figures 6A and 6B. As can be clearly seen from Figure 6A, the measurement results of the mass transfer coefficients of Examples 1, 5, and 3 are all better than the measurement results of Comparative Example 2 without CNTs.

[0064] Figure 6B, compared to Comparative Example 2, shows the ratio of the mass transfer coefficient of Examples 1, 5, and 3 to that of Comparative Example 2 (i.e., the rate of change of the mass transfer coefficient). In Examples 1 and 5, the rate of change of the mass transfer coefficient at each linear velocity was approximately 1.3 times or more. Therefore, it is expected that by using raw water spacers with a longitudinal and transverse spacing of 4 mm or more, the rate of change of the mass transfer coefficient can be increased to more than 1.3 times.

[0065] On the other hand, in Comparative Example 3, when the linear velocity was 0.02 m / s and 0.07 m / s, the rate of change of the mass transfer coefficient decreased to less than 1.3 times. This indicates that when the mesh spacing is less than 4 mm, the mass transfer coefficient decreases accordingly. The presumed reason is that when the mesh spacing is less than 4 mm, the raw water spacers impede the flow of raw water, leading to pressure loss and reducing the stirring efficiency of the membrane surface, ultimately causing a decrease in the mass transfer coefficient.

[0066] (2.06) Effect of membrane differences. The membrane modules described in Example 6 and Comparative Example 4 were installed in a cross-flow device, and the mass transfer coefficient of the membrane surface was measured according to the steps described in section (2.04) above.

[0067] The measurement results of the mass transfer coefficient of the separation membrane modules of Example 6 and Comparative Example 4 are shown in Figures 7A and 7B. Figure 7A clearly shows that the mass transfer coefficient measurement results of Example 6 are better than those of Comparative Example 4 without CNTs.

[0068] Figure 7B, compared to Comparative Example 4, shows the ratio of the mass transfer coefficient of Example 6 to that of Comparative Example 4 (i.e., the rate of change of the mass transfer coefficient). In Example 6, the rate of change of the mass transfer coefficient at each linear velocity was more than 1.7 times, reaching a maximum of 2.4 times. This indicates that even with different membrane performance, using a composite material incorporating CNTs to construct the raw water spacer can still improve the mass transfer coefficient compared to the control raw water spacer.

[0069] (2.07) Relationship between mass transfer coefficient and salt permeation. The larger the mass transfer coefficient, the less salt permeates through the separation membrane. Table 2 below shows the relationship between mass transfer coefficient and salt permeation.

[0070] Table 2 Mass transfer coefficient k (Jv / ln(Cm / Cb)) Membrane concentration Cm (Δπ / 0.8479) The concentration of saline solution in the influent, Cb Salt water permeation volume Jv Salt permeation Salt reduction rate [m / d] [wt%] [wt%] [m3 / (day·m2)] [wt%] 1.0 0.16 0.10 0.45 0.0016 - 1.3 0.14 0.10 0.45 0.0014 10% 2.4 0.12 0.10 0.45 0.0012 twenty three%

[0071] When the mass transfer coefficient increases from 1.0 [m / d] to 1.3 [m / d], the salt permeation of the separation membrane decreases by 10%. When the mass transfer coefficient increases from 1.0 [m / d] to 2.4 [m / d], the salt permeation of the separation membrane decreases by 23%. Therefore, increasing the mass transfer coefficient can improve the salt separation efficiency of the separation membrane module.

[0072] Generally, to improve the mass transfer coefficient (i.e., reduce the concentration polarization layer on the membrane surface), an excessive amount of feed water is often introduced in the horizontal direction relative to the separation membrane surface, forcing the concentrated components to diffuse backwards on the membrane surface and be expelled. However, this method increases the energy required for the feed water, necessitating the installation of large pumps and other countermeasures, thus increasing water production costs.

[0073] In contrast, using the aforementioned raw water spacer improves the mass transfer coefficient compared to using the control raw water spacer, thereby reducing water production costs. Furthermore, an increased mass transfer coefficient and a thinner concentration polarization layer help reduce solute precipitation on the separation membrane and effectively reduce protein concentration. Therefore, the durability of the separation membrane module is extended, thus increasing the continuous operating time of the water treatment unit.

[0074] (2.08) Fouling assessment using lysozyme. The separation membrane modules described in Examples 1 to 4 and Comparative Example 2 were assembled in a cross-flow device, and the permeation coefficient of the separation membrane was measured according to the following steps.

[0075] First, lysozyme, a cationic protein, was added to pure water to create a raw water solution with a fouling concentration of 1 mg / L. The pH of the solution was adjusted to 7 (using 0.1 mol / L NaOH), and scaling measurements were then performed. The inlet water flow rate was set to 1000 mL / min, and the inlet water pressure was set to 0.5 MPa. Measurements were taken at 0, 3, 21, 24, 27, 45, and 48 hours after the start of the measurements, focusing on water flow rate (permeate and concentrate), water temperature (raw water, permeate, and concentrate), pH (raw water), and inlet water pressure. Immediately after the measurements, the pH was adjusted to 7 (using 0.1 mol / L NaOH), and the pressure, inlet water flow rate, and water temperature were also adjusted.

[0076] After scaling measurements were completed, caustic soda (sodium hydroxide) with a pH of 11-12 was used as the cleaning solution. Alkaline cleaning was performed on the membrane module under the conditions of a cleaning time of 60 minutes, a flow rate of 2000 mL / min, and a water temperature of 25°C. Following alkaline cleaning, neutralization was performed with 3 mol / L HCl (hydrochloric acid), and the permeate flow rate after cleaning was confirmed under the conditions of an influent flow rate of 1000 mL / min and an influent pressure of 0.5 MPa.

[0077] The measurement results are shown in Figures 8A and 8B. As shown in Figure 8A, the permeability coefficient decreased over time for all examples, from Example 1 to Example 4, and for Comparative Example 2. However, compared to Comparative Example 2, Examples 1 to 4 maintained a higher permeability coefficient, indicating that their separation membranes were less prone to fouling than those of Comparative Example 2. Furthermore, compared to Comparative Example 2, Examples 1 to 4 exhibited superior cleanability after alkaline cleaning.

[0078] (2.09) Analysis of the adhesion state of lysozyme on the surface of the raw water spacer. Molecular dynamics simulation was used to analyze the adhesion state of lysozyme on the surface of the raw water spacer. The molecular dynamics simulation was performed using LAMMPS (Large-scale Atomic / Molecular Massively Parallel Simulator). Two models were prepared: the PP model equivalent to Comparative Example 2 and the CNT / PP model equivalent to Example 1.

[0079] The PP model has 100 PP molecular chains. To avoid spherical aggregation, spring-like constraint points were added to randomly selected PP atoms. The CNT / PP model consists of three graphene layers placed beneath the PP model. The atomic charges of each model were set using the charge balance method. The lysozyme molecular structure was obtained from the Protein Data Bank (PDB), and the single-chain structure was extracted after downloading the file.

[0080] To evaluate the interaction between each model and lysozyme, lysozyme was applied to the surface of each model for assessment. Figure 9A shows the simulation results for the CNT / PP model, and Figure 9B shows the simulation results for the PP model.

[0081] As shown in Figure 9A, in the CNT / PP model, lysozyme did not adhere to the surface of the original water spacer but detached immediately. Conversely, as shown in Figure 9B, in the PP model, lysozyme adhered to the PP surface. This difference in adhesion characteristics is presumably due to the interaction between the polar and nonpolar amino acid residues contained in lysozyme. When CNTs are added to the PP material, the surface polarity of this composite material will change, which is expected to enhance the repulsion properties against lysozyme. This effect is also expected to apply to cationic solutes other than lysozyme.

[0082] (2.10) Relationship between water flow velocity near the surface of the original water spacer and distance from the surface of the original water spacer. Using the PP model (equivalent to Comparative Example 2, hereinafter referred to as the PP spacer) and the CNT / PP model (equivalent to Example 1, hereinafter referred to as the CNT / PP spacer) as described in section (2.09) above, the relationship between water flow velocity near the surface of the original water spacer and distance from the surface of the original water spacer was analyzed. The analysis results are shown in Figure 10.

[0083] According to the analysis results shown in Figure 10, the water flow velocity within 5 angstroms below the surface of the original water spacer is approximately 0.1 m / s. Therefore, it can be inferred that an interfacial water layer of approximately 5 angstroms thickness will form near the surface of the original water spacer within the CNT / PP spacer.

[0084] On the other hand, for the PP spacer, even within a range of less than 5 angstroms from the surface of the original water spacer, the water flow velocity remained above approximately 0.22 m / s. This suggests that the PP spacer did not form the interfacial water layer observed with the CNC / PP spacer.

[0085] If we define the water flow velocity at a distance of 40 angstroms from the surface of the original water spacer as V40, and the water flow velocity at a distance of 5 angstroms from the surface of the original water spacer as V5, then the velocity difference D is D = V40 ~ V5. In the case of CNT / PP spacers, the water flow velocity V40 = 1.34 m / s, the water flow velocity V5 = 0.12 m / s, and the velocity difference D = 1.22 m / s. On the other hand, in the case of CNT / PP spacers, the water flow velocity V40 = 1.35 m / s, the water flow velocity V5 = 0.27 m / s, and the velocity difference D = 1.08 m / s.

[0086] In other words, the aforementioned velocity difference D is greater in CNT / PP spacers than in PP spacers. The larger this velocity difference D is, the stronger the agitation force of the water flow, which in turn agitates the surface of the separation membrane. Therefore, it can be inferred that when using CNT / PP spacers, the mass transfer coefficient of the separation membrane surface is higher than when using PP spacers.

[0087] (3) Effects of this embodiment. According to the above description of the raw water spacer, as described in Examples 1 to 4, its arithmetic mean height Sa, as specified in ISO 25178, is within the range of 0.2 μm to 0.5 μm. Therefore, compared to Comparative Example 2, where the arithmetic mean height Sa exceeds 0.5 μm, this embodiment can increase the mass transfer coefficient of the separation membrane surface by more than 1.3 times. Thus, the raw water spacer can promote mass transfer on the separation membrane surface and inhibit the adhesion of fouling substances to the separation membrane surface. Furthermore, since cationic substances such as lysozyme are not easily adhering to the surface of the raw water spacer, it can inhibit the fouling substances adhering to the raw water spacer from becoming focal points, thus preventing the diffusion and growth of a fouling membrane formed by cationic substances towards the separation membrane side.

[0088] Furthermore, in this embodiment, as described in Example 1, when observing CNT particles using the aforementioned method, the average number of CNT particles with a particle area of ​​25 μm² or more but less than 100 μm² at the three locations is 50 or less. Furthermore, the average number of CNT particles with a particle area of ​​100 μm² or more but less than 20,000 μm² at the three locations is 10 or less. Therefore, compared to Comparative Example 1, which contains coarse CNT particles, this embodiment can improve the smoothness of the raw water spacer surface. It is expected that when the surface of the raw water spacer becomes smoother, the raw water spacer will no longer obstruct the flow of raw water, thereby correspondingly improving the raw water stirring effect in the area near the separation membrane surface. Therefore, such factors can increase the mass transfer coefficient of the separation membrane surface.

[0089] (4) Other embodiments. The above description provides exemplary embodiments of the operation method of the raw water separator and water treatment device. However, the above embodiments are merely examples of one embodiment of the present invention. That is, the present invention is not limited to the aforementioned exemplary embodiments, and various embodiments can be adopted without departing from the technical concept of the present invention.

[0090] Furthermore, the multiple functions realized by one constituent element of the above-described embodiments can be realized by multiple constituent elements. The multiple functions realized by multiple constituent elements of the above-described embodiments can be realized by one constituent element. The single function realized by multiple constituent elements of the above-described embodiments can be realized by one constituent element. A portion of the composition of the above-described embodiments can be omitted. At least a portion of the composition of the above-described embodiments can be added to or replaced in the composition of other above-described embodiments.

[0091] (5) Technical concept disclosed in this specification. [Item 1] A raw water spacer is disposed inside a separation membrane module in a water treatment device and ensures the flow path of raw water between two separation membranes. The water treatment device passes the raw water containing the target components and water to the separation membrane module, separating it into permeate water that passes through the separation membrane and concentrated water that does not pass through the separation membrane. The separation membrane is disposed inside the separation membrane module. The raw water spacer includes: a plurality of first linear bodies arranged side by side; and a plurality of second linear bodies arranged side by side. The plurality of first linear bodies and the plurality of second linear bodies are arranged in a mutually intersecting direction and form a mesh-like surface. The plurality of first linear bodies and the plurality of second linear bodies are configured such that when the raw water spacer is disposed between two separation membranes... At the same time, the plurality of first linear bodies contact one of the separation membranes, and the plurality of second linear bodies are interposed between the plurality of first linear bodies and another separation membrane to ensure the gap forming the flow path of the raw water. Furthermore, the plurality of second linear bodies contact another separation membrane, and the plurality of first linear bodies are interposed between the plurality of second linear bodies and one of the separation membranes to ensure the gap forming the flow path of the raw water. In addition, the plurality of first linear bodies and the plurality of second linear bodies are composed of a composite material formed by incorporating carbon nanotubes into the substrate resin. Each 100 parts by mass of the composite material contains 1 to 7 parts by mass of carbon nanotubes. The surface roughness of the plurality of first linear bodies and the plurality of second linear bodies is configured such that the arithmetic mean height Sa, as specified in ISO 25178, reaches 0.2 μm to 0.5 μm.

[0092] [Project 2] As in Project 1, the raw water spacer, wherein the composite material is as follows: after the base resin is added to the composite material, the concentration of the carbon nanotubes in the composite material is diluted to 100 times, and the diluted material is molded into a molded product with a thickness of 0.3 mm. In the image of the surface of the molded product, three 2 mm × 2 mm fields of view are randomly selected, and when each field of view is observed, the number of carbon nanotubes with a particle area of ​​25 μm2 or more but less than 100 μm2 observed in each field of view is less than 50 on average at the three locations, and the number of carbon nanotubes with a particle area of ​​100 μm2 or more but less than 20000 μm2 observed in each field of view is less than 10 on average at the three locations.

[0093] [Item 3] The original water spacer of Item 1 or Item 2, wherein the quadrilateral grid formed by the first linear body and the second linear body is configured such that the distance between the diagonal directions of the quadrilateral is 4.0 mm to 5.0 mm.

[0094] [Project 4] The operation method of the water treatment device involves passing raw water containing the target components and water to a separation membrane module, causing it to separate into permeate water that passes through the separation membrane and concentrated water that does not pass through the separation membrane. The separation membrane is disposed inside the separation membrane module. The separation membrane module contains a raw water spacer for ensuring the flow path of the raw water between two separation membranes. The raw water spacer includes: a plurality of first linear bodies arranged side-by-side; and a plurality of second linear bodies arranged side-by-side. The plurality of first linear bodies and the plurality of second linear bodies are arranged in a mutually intersecting direction and form a mesh-like surface. The plurality of first linear bodies and the plurality of second linear bodies are configured such that when the raw water spacer is positioned between two separation membranes... The plurality of first linear bodies contact one of the separation membranes, and the plurality of second linear bodies are interposed between the plurality of first linear bodies and another separation membrane to ensure the gap forming the flow path of the raw water. Furthermore, the plurality of second linear bodies contact another separation membrane, and the plurality of second linear bodies are interposed between the plurality of first linear bodies and one of the separation membranes to ensure the gap forming the flow path of the raw water. The plurality of first linear bodies and the plurality of second linear bodies are a composite material formed by incorporating carbon nanotubes into the substrate resin. Each 100 parts by mass of the composite material contains 1 to 7 parts by mass of carbon nanotubes. The surface roughness of the plurality of first linear bodies and the plurality of second linear bodies is configured such that the arithmetic mean height Sa, as specified in ISO 25178, reaches 0.2 μm to 0.5 μm.

[0095] [Item 5] The operation method of the water treatment device as described in Item 4 is configured such that, compared to the control raw water spacer, when the solute in the raw water is NaCl, the mass transfer coefficient of the two separation membranes disposed on the surfaces of the two membranes separated by the raw water spacer or the control raw water spacer is 1.3 to 2.4 times that of the control raw water spacer at a linear velocity of 0.02 m / s to 0.14 m / s. The control raw water spacer uses the substrate resin without the carbon nanotube to replace the composite material, and otherwise has the same structure as the raw water spacer.

[0096] [Item 6] The operation method of the water treatment device as described in Item 4 or Item 5, wherein the raw water contains a cationic substance selected from at least one of cationic proteins and cationic surfactants as the separation target component.

[0097] 1: Raw water separator IB: Partial view of raw water compartment IIB: Cutting line 11A: First linear body 11B: Second linear body F: Flow path 21,22: Separation membrane 23, 24: Gap

Claims

1. A raw water spacer, disposed within a membrane separation module in a water treatment apparatus, ensuring a flow path for the raw water between two membrane separation membranes, wherein the water treatment apparatus supplies the raw water containing the target components and water to the membrane separation module, separating it into permeate water that passes through the membrane separation module and concentrated water that does not pass through the membrane separation module, wherein the membrane separation module is disposed within the membrane separation module, and the raw water spacer comprises: A plurality of first linear bodies arranged side by side; A plurality of second linear bodies arranged side-by-side, the plurality of first linear bodies and the plurality of second linear bodies being arranged in intersecting directions to form a mesh-like surface, wherein the plurality of first linear bodies and the plurality of second linear bodies are configured such that, when the raw water spacer is positioned between two separation membranes, the plurality of first linear bodies contact one of the separation membranes, and the plurality of second linear bodies are interposed between the plurality of first linear bodies and the other separation membrane to ensure the gaps forming the flow path of the raw water, and the A plurality of second linear bodies contact another separation membrane, with a plurality of first linear bodies interposed between the plurality of second linear bodies and one of the separation membranes to ensure the gap forming the flow path of the raw water. The plurality of first linear bodies and the plurality of second linear bodies are composed of a composite material formed by incorporating carbon nanotubes into the substrate resin. Each 100 parts by weight of the composite material contains 1 to 7 parts by weight of carbon nanotubes. The surface roughness of the plurality of first linear bodies and the plurality of second linear bodies is configured such that the arithmetic mean height Sa, as specified in ISO 25178, reaches 0.2 μm to 0.5 μm.

2. As in request item 1, the raw water spacer, wherein, The composite material is as follows: after the base resin is added to the composite material, the concentration of the carbon nanotubes in the composite material is diluted to 100 times, and the diluted material is molded into a molded article with a thickness of 0.3 mm. In the image of the surface of the molded article, three 2 mm × 2 mm fields of view are randomly selected, and when each field of view is observed, the number of carbon nanotubes with a particle area of ​​25 μm2 or more but less than 100 μm2 observed in each field of view is less than 50 on average at the three locations, and the number of carbon nanotubes with a particle area of ​​100 μm2 or more but less than 20000 μm2 observed in each field of view is less than 10 on average at the three locations.

3. As in request item 1 or 2, the raw water spacer, wherein, The quadrilateral grid formed by the first linear body and the second linear body is configured such that the distance between the diagonal directions of the quadrilateral is 4.0 mm to 5.0 mm.

4. A method for operating a water treatment apparatus, comprising passing raw water containing the target component and water to a separation membrane module, thereby separating the raw water into permeate water that passes through the separation membrane and concentrated water that does not pass through the separation membrane, wherein the separation membrane is disposed inside the separation membrane module, wherein... The membrane module internally includes a raw water spacer for ensuring the flow path of the raw water between two membranes. The raw water spacer includes a plurality of first linear bodies arranged side-by-side and a plurality of second linear bodies arranged side-by-side. The plurality of first and second linear bodies are arranged in a cross-shaped direction and form a mesh-like surface. The plurality of first and second linear bodies are configured such that, when the raw water spacer is positioned between the two membranes, the plurality of first linear bodies contact one of the membranes, and there is a gap between the plurality of first linear bodies and the other membrane. A plurality of second linear bodies are interposed therein to ensure the gap forming the flow path of the raw water, and the plurality of second linear bodies contact another separation membrane. A plurality of first linear bodies are interposed between the plurality of second linear bodies and one of the separation membranes to ensure the gap forming the flow path of the raw water. The plurality of first linear bodies and the plurality of second linear bodies are composed of a composite material formed by incorporating carbon nanotubes in the base resin. Each 100 parts by weight of the composite material contains 1 to 7 parts by weight of carbon nanotubes. The surface roughness of the plurality of first linear bodies and the plurality of second linear bodies is configured such that the arithmetic mean height Sa, as specified in ISO 25178, reaches 0.2 μm to 0.5 μm.

5. The method of operating the water treatment apparatus as claimed in claim 4, wherein, compared to the control raw water spacer, when the solute in the raw water is NaCl, the mass transfer coefficient of each of the two separation membranes disposed on opposite sides of the control raw water spacer, at a linear velocity of 0.02 m / s to 0.14 m / s, is 1.3 to 2.4 times that of the control raw water spacer. The control raw water spacer uses the substrate resin that is not fitted with the carbon nanotube to replace the composite material, and otherwise has the same structure as the raw water spacer.

6. The operation method of the water treatment device as requested in item 4 or 5, wherein, The raw water contains at least one cationic substance selected from cationic proteins and cationic surfactants, which is the component to be separated.

Images