JP5282864B2 - Membrane separation method and membrane separation apparatus - Google Patents

Description

  In the present invention, when water to be treated such as industrial water, city water, and well water is subjected to membrane separation treatment, adsorption of membrane contaminants contained in the water to be treated to the membrane surface is reduced, and deterioration of membrane separation performance is suppressed. The present invention relates to a membrane separation method and a membrane separation apparatus that can be used.

  As a method for treating treated water such as industrial water, city water, and well water to make pure water, for example, microfiltration membrane (MF membrane), ultrafiltration membrane (UF membrane), reverse osmosis membrane (RO membrane) There is a method of membrane separation treatment that allows water to pass through the membrane. Industrial water, city water, well water, etc. are usually membrane contaminants that contaminate membranes, such as humic acid and fulvic acid organic substances, biological metabolites such as sugar produced by algae, and synthetic chemicals such as surfactants. Therefore, when the membrane separation treatment is performed, there is a problem that these membrane contaminants are adsorbed on the membrane surface and the membrane separation performance deteriorates.

  Therefore, before the membrane separation treatment, an inorganic flocculant and an anionic polymer flocculant are added to the water to be treated to agglomerate to condense the membrane contaminants, and the liquid is solidified by precipitation or pressurized flotation. After the separation, a method of subjecting the supernatant, that is, the water to be treated from which membrane contaminants have been removed, to membrane separation treatment is performed. However, when the polymer flocculant is added, a new problem arises in that the polymer flocculant remaining in the water is adsorbed on the subsequent membrane to contaminate the membrane and deteriorate the separation performance of the membrane.

  As a method for solving such a problem, the present applicant added an inorganic flocculant and a polymer flocculant to the water to be treated, and after adding the inorganic flocculant again after the aggregation reaction and before solid-liquid separation. In addition, an application for a coagulation separation method for solid-liquid separation was filed earlier (see Patent Document 1).

  However, in the method of Patent Document 1, it is necessary to add an inorganic flocculant and a polymer flocculant to the water to be treated and then add the inorganic flocculant again. Therefore, a simpler method is required. Yes.

Japanese Patent Laid-Open No. 11-77062

  In view of the circumstances described above, the present invention is a membrane capable of reducing adsorption of membrane contaminants contained in the water to be treated to the membrane surface and reducing deterioration of the membrane separation performance when the water to be treated is subjected to membrane separation treatment. An object is to provide a separation method and a membrane separation apparatus.

  As a result of intensive investigations to achieve the above object, the present inventor has added, to the treated water, particles made of a cationic polymer that swells in water and does not substantially dissolve in water before the membrane separation treatment. It was found that the object was achieved, and the present invention was completed.

That is, the membrane separation method of the present invention is a copolymer of a cationic monomer having a functional group such as primary amine, secondary amine, tertiary amine and their acid salts, quaternary ammonium groups, and a crosslinking agent monomer. Particles made of a cationic polymer that is a reverse phase (W / O) emulsion polymer that swells to a particle size of 10 to 200 times in water and does not substantially dissolve in water relative to the particle size when present and not swollen Is added to the water to be treated and subjected to an adsorption treatment, and the water to be treated subjected to the adsorption treatment is subjected to a membrane separation treatment with a separation membrane.

  Here, it is preferable to add an inorganic flocculant to the water to be treated during the adsorption treatment.

  The membrane separation treatment may include a separation treatment using at least a microfiltration membrane or an ultrafiltration membrane, and the particles after the adsorption treatment may be removed from the water to be treated by the membrane separation treatment. .

  Furthermore, the membrane separation process may include a separation process using a reverse osmosis membrane of at least one stage.

  Then, after the adsorption treatment, pure water may be obtained by deionizing the water to be treated.

  Further, the separation membrane may be washed with a washing solution having a pH of 11 to 14 at an arbitrary frequency, and the washing with the washing solution may be backwashed.

Other aspects of the present invention include a reaction vessel, a treated water introduction means for introducing treated water into the reaction vessel, a primary amine, a secondary amine, a tertiary amine and their acid salts, a quaternary ammonium group, and the like. It is a copolymer of a cationic monomer having a functional group and a cross-linking agent monomer, and swells to a particle size 10 to 200 times in water with respect to the particle size when not swollen and does not substantially dissolve in water. A polymer particle introduction means for introducing particles made of a cationic polymer which is a reverse phase (W / O) emulsion polymer into the reaction vessel or the previous stage of the reaction vessel and adding the particles to the water to be treated; and A membrane separation apparatus comprising: a discharge unit that discharges the water to be treated that has been subjected to adsorption treatment; and a membrane separation processing unit that performs a membrane separation process on the water to be treated discharged from the discharge unit using a separation membrane.

  The membrane separation processing means may be a pure water production apparatus that has at least one or more reverse osmosis membranes and further includes a deionization processing means for deionizing the water to be treated downstream of the reaction tank. .

  Moreover, it is good also as a membrane separation apparatus which further has the washing | cleaning liquid introduction means which introduce | transduces the washing | cleaning liquid of pH 11-14 into the said membrane separation process means.

  By adding particles made of a cationic polymer that swells in water and does not substantially dissolve in water to the water to be treated, it is possible to adsorb membrane contaminants on the particles. Then, when the water to be treated in which membrane contaminants are adsorbed on particles made of a cationic polymer that swells in water and does not substantially dissolve in water, a conventional polymer flocculant or inorganic flocculant was used. Compared to the case, when the water to be treated is subjected to membrane separation treatment, adsorption of membrane contaminants contained in the water to be treated to the membrane surface can be reduced, and deterioration of membrane separation performance can be reduced. Further, in the system for membrane separation treatment of the water to be treated in which the membrane contaminant is adsorbed on the particles made of a cationic polymer that swells in water and does not substantially dissolve in water, the separation membrane is washed with a washing solution having a pH of 11 to 14. As a result, membrane contaminants adsorbed on the separation membrane can be removed, so that deterioration of membrane separation performance can be further reduced.

Hereinafter, the present invention will be described in detail based on embodiments.
The membrane separation method of the present invention involves subjecting the water to be treated to membrane separation after adding particles made of a cationic polymer that swells in water and does not substantially dissolve in water.

  As treated water, for example, humic acid and fulvic acid organic substances, biological metabolites such as sugar produced by algae, or synthetic chemicals such as surfactants contaminate the membrane used in the subsequent membrane separation treatment. Water containing the substance (membrane contaminant) to be used, specifically, industrial water, city water, well water, and the like, are not limited thereto.

  Cationic polymers that swell in water that constitutes the particles to be added to the water to be treated and do not substantially dissolve in water include, for example, primary amines, secondary amines, tertiary amines and their acid salts, quaternary ammonium groups, and the like. It is a copolymer of a cationic monomer having a functional group and a cross-linking agent monomer for substantially not dissolving in water. Specific examples of the cationic monomer include dimethylaminoethyl (meth) acrylate acid salt or its quaternary ammonium salt, dimethylaminopropyl (meth) acrylamide acid salt or its quaternary ammonium salt, diallyldimethylammonium chloride, and the like. It is done. Examples of the cross-linking agent monomer include divinyl monomers such as methylene bisacrylamide. Moreover, it is good also as a copolymer with the anionic or nonionic monomer copolymerizable with the said cationic monomer. Specific examples of the anionic monomer to be copolymerized include (meth) acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, and alkali metal salts thereof. It is necessary to use a small amount so as not to impair the properties as a conductive polymer. Nonionic monomers include (meth) acrylamide, N isopropylacrylamide, N methyl (NN dimethyl) acrylamide, acrylonitrile, styrene, methyl or ethyl (meth) acrylate. Each monomer may be one kind or plural kinds. The amount of the crosslinking agent monomer such as divinyl monomer is required to be 0.0001 to 0.1 mol% based on the total monomer, and this amount is composed of a cationic polymer that swells in water and does not substantially dissolve in water. The degree of particle swelling and the particle size in water can be adjusted. And as the particle | grains which consist of a cationic polymer which swells in water and does not melt | dissolve in water substantially, for example, Akogel C (made by Mitsui Cytec Co., Ltd.) is marketed. Alternatively, an anion exchange resin such as WA20 (manufactured by Mitsubishi Chemical Corporation) may be used as a cationic polymer that swells in water and does not substantially dissolve in water. Further, the average particle size of the particles made of a cationic polymer that swells in water and does not substantially dissolve in water is not particularly limited, but the average particle size in a reversed-phase emulsion liquid or a suspension-like dispersion liquid, that is, in water The average particle size in the unswelled state is preferably 100 μm or less, more preferably 0.1 to 10 μm. This is because the smaller the particles, the higher the effect of adsorbing the membrane contaminants contained in the water to be treated. However, if the particles are too small, solid-liquid separation becomes difficult.

  There is no particular limitation on the form of adding particles composed of a cationic polymer that swells in water and does not substantially dissolve in water to the water to be treated. For example, the particles may be used as they are, or dispersed in water, You may add in the form of an emulsion liquid or a suspension-like dispersion liquid. In any case, the water to be treated is adsorbed by adding particles made of a cationic polymer that swells in water and does not substantially dissolve in water, that is, the water to be treated swells in water. The membrane contaminants contained in the water to be treated may be adsorbed on the particles by contacting with particles made of a cationic polymer that is substantially insoluble in water.

  Moreover, you may add the particle | grains which consist of a cationic polymer which swells in 2 or more types of water, and does not melt | dissolve in water substantially to treated water. Since the cationic polymer constituting the above particles swells in water and does not substantially dissolve in water, particles made of a cationic polymer that swells in water and does not substantially dissolve in water are also classified as ordinary polymer flocculants. Unlike, it swells in water and does not substantially dissolve in water. “Substantially insoluble in water” means that the degree of water solubility is such that it can exist as particles composed of a cationic polymer in water. Specifically, for example, solubility in water at 30 ° C. Is about 0.1 g / L or less. The degree of swelling of these particles in water is about 10 to 200 times the particle size in water with respect to the particle size when not swollen with water.

  Here, although it demonstrates in detail below about the particle | grains which consist of a cationic polymer made into the form of a reverse phase emulsion liquid, it is not limited to this form. In addition, it is not a special thing but is a very general reverse phase (W / O) emulsion polymer.

  The inverse emulsion liquid contains the cationic polymer, water, a hydrocarbon liquid, and a surfactant. And mass ratio (%) of each component is cationic polymer: water: hydrocarbon liquid: surfactant = 20-40: 20-40: 20-40: 2-20, and the cationic polymer and water. The total mass is preferably 40 to 60% by mass with respect to the total mass of the cationic polymer, water, hydrocarbon liquid and surfactant.

  Examples of the hydrocarbon liquid include, but are not limited to, isoparaffins such as isohexane, and aliphatic hydrocarbon liquids such as n-hexane, kerosene, and mineral oil.

  Examples of the surfactant include polyoxyethylene ethers of higher aliphatic alcohols having 10 to 20 carbon atoms, or higher fatty acids having 10 to 22 carbon atoms, such as HLB (hydrophilic lipophilic balance) of 7 to 10. A polyoxyethylene ester is mentioned. Examples of the former include polyoxyethylene (EO addition mole number = 3 to 10) ethers such as lauryl alcohol, cetyl alcohol, stearyl alcohol, and oleyl alcohol. Examples of the latter include polyoxyethylene (EO addition mole number = 3 to 10) esters such as lauric acid, palmitic acid, stearic acid, and oleic acid.

  The reverse phase emulsion liquid is obtained by polymerizing a monomer (emulsion polymerization or suspension polymerization) by mixing a cationic monomer or a crosslinking agent monomer, which is a raw material of the cationic polymer, with water, a hydrocarbon liquid, and a surfactant. However, the present invention is not limited to this. For example, after various monomers are solution polymerized, they are pulverized with a homogenizer, and then added to a hydrocarbon liquid together with a dispersant such as a surfactant. It is done.

  When particles made of a cationic polymer that swells in water and does not substantially dissolve in water are added to the water to be treated, the surface area of the particles is preferably large. Therefore, it is preferable to add the particles in the form of the above-mentioned reversed phase emulsion liquid or suspension-like dispersion liquid to the water to be treated after adding the particles to the water under stirring to swell the particles.

  There is no particular limitation on the amount of particles composed of a cationic polymer that swells in water and does not substantially dissolve in water, but it is 1 to 50% by mass with respect to membrane contaminants contained in the water to be treated. It is preferable to set the degree. The pH of the water to be treated to which particles made of a cationic polymer that swells in water and does not substantially dissolve in water is not particularly limited, but may be a low pH, for example, about pH 5.0 to 7.5. preferable. This is because the cohesiveness is particularly good.

  Thus, after adding the particle | grains which consist of a cationic polymer which swells in water and does not melt | dissolve substantially in water, and carries out an adsorption process, the to-be-processed water is membrane-separated.

  Examples of the membrane separation treatment include a microfiltration membrane (MF membrane), an ultrafiltration membrane (UF membrane), a nanofiltration membrane (NF membrane), or a reverse osmosis membrane (RO membrane). These membranes may be used alone or in one or more stages. For example, membrane separation treatment that combines various membranes, such as membrane separation treatment with MF membrane or UF membrane, followed by membrane separation treatment with RO membrane. It is good.

  Here, industrial water, city water, well water, etc., which are treated water, include humic acid and fulvic acid organic substances, biological metabolites such as sugar produced by algae, synthetic chemical substances such as surfactants, etc. Therefore, when the membrane separation process is performed, there is a problem that the membrane contaminant is adsorbed on the membrane surface and the membrane separation performance is deteriorated. In the present invention, before the membrane separation treatment, particles made of a cationic polymer that swells in water and does not substantially dissolve in water are added. Therefore, the membrane separation treatment is performed after membrane contaminants are adsorbed and aggregated on the particles. Will do. Therefore, since water with a low dissolved organic matter concentration of membrane contaminants such as biological metabolites can be subjected to membrane separation treatment, adsorption of membrane contaminants to the membrane can be reduced, and deterioration of membrane separation performance can be suppressed.

  Further, an inorganic flocculant may be added to the water to be treated during the adsorption treatment. By adding an inorganic flocculant as a flocculant for the membrane contaminant, the membrane pollutant is agglomerated and the membrane pollutant removal effect is increased. The inorganic flocculant may be added before the membrane separation treatment, and may be before or after the addition of particles made of a cationic polymer that swells in water and does not substantially dissolve in water. Alternatively, it may be added simultaneously with the particles composed of a cationic polymer which swells in water and does not substantially dissolve in water. The inorganic flocculant is not particularly limited, and examples thereof include an aluminum salt such as a sulfuric acid band and polyaluminum chloride, and an iron salt such as ferric chloride and ferrous sulfate. Moreover, there is no limitation in particular also in the addition amount of an inorganic flocculant, What is necessary is just to adjust according to the property of the to-be-processed water to process, but about 0.5-10 mg / L in conversion of aluminum or iron with respect to to-be-processed water. It is. Depending on the nature of the water to be treated, when polyaluminum chloride (PAC) is used as an inorganic flocculant, particles made of a cationic polymer that swells in water and does not substantially dissolve in water and an inorganic flocculant are added. Aggregation is optimal when the pH of the treated water is about pH 5.0 to 7.0.

  Moreover, you may have further deionization processes, such as an ion exchange process. Thereby, pure water or ultrapure water can be obtained.

  Furthermore, before the membrane separation treatment, solid-liquid separation may be performed in which particles made of a cationic polymer containing a membrane contaminant generated by the adsorption treatment are removed from the water to be treated by precipitation treatment or pressure flotation treatment. Precipitation treatment and pressurized flotation treatment are carried out by adjusting the pH with caustic soda, slaked lime, sulfuric acid, etc. after adding particles or inorganic flocculant consisting of a cationic polymer that swells in water and does not substantially dissolve in water to the treated water. Finally, the suspension is flocked with an organic polymer flocculant. Moreover, an organic coagulant can also be used together as needed. There is no particular limitation on the organic coagulant, for example, polyethyleneimine, ethylenediamine epichlorohydrin polycondensate, polyalkylene polyamine, polymers having quaternary ammonium salts of diallyldimethylammonium chloride or dimethylaminoethyl (meth) acrylate as constituent monomers, etc. Examples include cationic organic polymers that are usually used in water treatment. Moreover, there is no limitation in particular also in the addition amount of an organic coagulant | flocculant, What is necessary is just to adjust according to the property of to-be-processed water, However It is 0.01-10 mg / L in solid content with respect to to-be-processed water. The organic polymer flocculant is not particularly limited, and a polymer flocculant usually used in water treatment can be used. For example, poly (meth) acrylic acid, copolymers of (meth) acrylic acid and (meth) acrylamide, and anionic organic polymer flocculants such as alkali metal salts thereof, poly (meth) acrylamide, etc. Nonionic organic polymer flocculants, homopolymers composed of cationic monomers such as dimethylaminoethyl (meth) acrylate or quaternary ammonium salt thereof, dimethylaminopropyl (meth) acrylamide or quaternary ammonium salt thereof, and the like Examples thereof include cationic organic polymer flocculants such as a copolymer of a cationic monomer and a nonionic monomer copolymerizable. Moreover, there is no limitation in particular also in the addition amount of an organic type polymer flocculant, and what is necessary is just to adjust according to the property of treated water, but it is 0.01-10 mg / L in solid content with respect to to-be-treated water in general. .

In addition, you may remove from the to-be-processed water the particle | grains which consist of a cationic polymer after a membrane | separation process. For example, particles made of a cationic polymer after the adsorption treatment may be removed from the water to be treated by a separation treatment using a microfiltration membrane or an ultrafiltration membrane.
And you may further perform the refinement | purification processes of to-be-processed water, such as a decarboxylation process and an activated carbon process.
Moreover, you may add a coagulant | flocculant, a disinfectant, a deodorant, an antifoamer, an anticorrosive, etc. as needed. Furthermore, you may use ultraviolet irradiation, ozone treatment, biological treatment, etc. together as needed.

  As described above, according to the membrane separation method of the present invention, when the water to be treated is subjected to the membrane separation treatment, the adsorption of membrane contaminants contained in the water to be treated to the membrane surface is reduced and the membrane separation performance is deteriorated. Can be suppressed. An example of a membrane separation apparatus using this membrane separation method is shown in the schematic system diagram of FIG.

  As shown in FIG. 1, the membrane separation apparatus 1 includes a reaction tank 10, treated water introduction means 11 such as a pump for introducing treated water (raw water), and a cation that swells in water and does not substantially dissolve in water. Chemical introduction means 13 (polymer particle introduction means) comprising a pump or the like for introducing chemicals from a chemical tank 12 in which chemicals such as particles made of a conductive polymer are held to the reaction tank 10, and water to be treated adsorbed in the reaction tank 10 Discharge means 14 for discharging the gas. Further, on the downstream side of the reaction tank 10, a membrane separation processing unit 15, a decarboxylation processing unit 16, an activated carbon processing unit 17, and a reverse osmosis membrane separation processing unit 18 are provided in this order.

  In such a membrane separation apparatus 1, firstly, water to be treated (raw water) such as industrial water, city water, and well water is introduced into the reaction tank 10. A chemical such as particles made of a cationic polymer that swells in water held in the chemical tank 12 and does not substantially dissolve in water is introduced into the reaction tank 10 by the chemical introduction means 13 and added to the water to be treated. And the to-be-processed water to which the chemical | medical agent was added is stirred with the stirrer 19, and is adsorption-treated. Next, the water to be treated that has been subjected to the adsorption treatment is discharged from the reaction tank 10 by the discharge means 14, sent to the membrane separation treatment means 15 having an MF membrane, subjected to membrane separation treatment, and particles made of a cationic polymer after the adsorption treatment. Is removed from the treated water. In the present invention, since membrane contaminants are adsorbed using particles made of a cationic polymer that swells in water and does not substantially dissolve in water, membrane separation treatment is performed by the membrane separation treatment means 15. Adsorption to the surface can be reduced and deterioration of membrane separation performance can be suppressed.

  Next, the water to be treated that has been subjected to membrane separation treatment is sent to the subsequent decarboxylation treatment means 16 and the activated carbon treatment means 17 filled with activated carbon, and is subjected to decarboxylation treatment and activated carbon treatment. Then, it is sent to the reverse osmosis membrane separation processing means 18 having the RO membrane, and membrane separation processing by the RO membrane is performed. The treated water that passes through the reverse osmosis membrane separation treatment means 18 is obtained by adsorbing membrane contaminants using particles made of a cationic polymer that swells in water and does not substantially dissolve in water, Since the water to be treated after being subjected to membrane separation treatment by the membrane separation treatment means 15 having an MF membrane, it is very clear and significantly suppresses the deterioration of the RO membrane that is greatly affected by membrane contaminants such as biological metabolites. be able to. If deionization treatment such as ion exchange is performed before or after membrane separation processing by the reverse osmosis membrane separation processing means 18, pure water or ultrapure water can be obtained, and the membrane separation apparatus 1 can produce pure water. Equipment and ultrapure water production equipment.

  In the membrane separation apparatus shown in FIG. 1, the chemical is introduced into the reaction tank 10. However, the chemical may be added to the water to be treated before being introduced into the reaction tank 10. Moreover, although the MF membrane is shown as the membrane separation processing means 15, a UF membrane, an RO membrane, an NF membrane, or the like may be used. Further, in the membrane separation apparatus 1 of FIG. 1 described above, the particles made of the cationic polymer after the adsorption treatment are removed by the membrane separation treatment means 15, but the particles are subjected to precipitation treatment or pressurized flotation in the reaction vessel 10. You may make it process and remove from to-be-processed water.

  Further, it is preferable to wash the separation membrane with a washing solution having a pH of about 11 to 14, preferably a pH of 12 to 13, at an arbitrary frequency. In the present invention, in order to subject the treated water in which the membrane contaminant is adsorbed to particles made of a cationic polymer that swells in water and does not substantially dissolve in water, the membrane contaminant contained in the treated water is removed. Adsorption on the membrane surface can be reduced, and deterioration of membrane separation performance can be reduced. However, when the membrane separation is continued, solid matter that is thought to be caused by particles composed of a cationic polymer that swells in water and does not substantially dissolve in water starts to adhere to the membrane surface. Furthermore, since the solid matter adsorbed on the separation membrane can be dissolved and removed by washing the separation membrane with a washing solution having a pH of about 11 to 14, deterioration of membrane separation performance can be reliably suppressed. In the present invention using particles made of a cationic polymer that swells in water and does not substantially dissolve in water, in a cleaning solution having a pH of about 3 to 8 that is usually used in backwashing (backwashing) or the like of the separation membrane, Although the removal of the solid matter becomes insufficient, the solid matter can be effectively removed by using a cleaning solution having a high pH of about 11 to 14 as described above. In the case of washing with a cleaning solution having a high pH, the separation membrane is preferably a membrane excellent in alkali resistance such as a PVDF (polyvinylidene fluoride) membrane.

  Examples of the cleaning solution having a pH of 11 to 14 include a solution obtained by mixing sodium hydroxide, sodium hypochlorite and the like with the water to be treated that has been subjected to membrane separation treatment. In the case of sodium hypochlorite, it is preferable to use the cleaning liquid mixed with the water to be treated so as to be about 10 to 12% by weight. Moreover, as a cleaning method, a method used for cleaning a normal separation membrane is applied, and specific examples include backwashing, flushing, and immersion cleaning.

  The frequency of washing is not particularly limited and may be set as appropriate depending on the properties of the water to be treated and the separation membrane. For example, the membrane separation treatment is interrupted when the membrane separation treatment is preferably performed for 5 minutes to 3 hours, particularly preferably for 10 to 60 minutes. Thereafter, washing such as back washing may be preferably performed for 10 to 120 seconds, particularly preferably 20 to 60 seconds, with a pH 11 to 14 cleaning solution. In addition, after washing the separation membrane with a cleaning solution having a pH of 11 to 14, the separation membrane is washed or rinsed with treated water or acid that has been subjected to membrane separation treatment as necessary, so that the treated water at the time of restarting operation can be obtained. It is preferable to prevent the pH from becoming too high.

  An example of a membrane separation apparatus using a membrane separation method including a step of washing the separation membrane with a washing solution having a pH of 11 to 14 is shown in a schematic system diagram of FIG. The same components as those in FIG. 1 are denoted by the same reference numerals, and a part of the overlapping description is omitted.

  As shown in FIG. 2, the membrane separation device 50 includes a reaction tank 10, a treated water introduction means 11 such as a pump for introducing treated water (raw water), and a cation that swells in water and does not substantially dissolve in water. Chemical introduction means 13 (polymer particle introduction means) comprising a pump or the like for introducing chemicals from a chemical tank 12 in which chemicals such as particles made of a conductive polymer are held to the reaction tank 10, and water to be treated adsorbed in the reaction tank 10 Discharge means 14 for discharging the gas. Further, on the downstream side of the reaction tank 10, a membrane separation processing unit 15 and a treated water tank 20 for storing the water to be treated that has been subjected to membrane separation processing by the membrane separation processing unit 15 are sequentially provided. Further, the cleaning liquid introducing means 22 for introducing the cleaning liquid obtained by mixing the alkaline liquid 21 into the water to be treated stored in the treating water tank 20 to the membrane separation processing means 15, and the alkaline liquid 21 in the water to be treated stored in the treating water tank 20. PH measuring means 23 for measuring the pH of the cleaning liquid mixed with

  In such a membrane separation apparatus 50, first, treated water (raw water) such as industrial water, city water, and well water is introduced into the reaction tank 10. Then, particles made of a cationic polymer that swells in water held in the chemical tank 12 and does not substantially dissolve in water, and chemicals such as an inorganic flocculant are introduced into the reaction tank 10 by the chemical introduction means 13 and treated water. To be added. And the to-be-processed water to which the chemical | medical agent was added is stirred with the stirrer 19, and is adsorption-treated. Next, the water to be treated that has been subjected to the adsorption treatment is discharged from the reaction tank 10 by the discharge means 14, sent to the membrane separation treatment means 15 having a PVDF MF membrane, subjected to membrane separation treatment, and the cationic polymer after the adsorption treatment. The particles consisting of are removed from the water to be treated. In the present invention, since membrane contaminants are adsorbed using particles made of a cationic polymer that swells in water and does not substantially dissolve in water, membrane separation treatment is performed by the membrane separation treatment means 15. Adsorption to the surface can be reduced and deterioration of membrane separation performance can be suppressed. Next, the water to be treated that has undergone membrane separation is stored in the treated water tank 20.

  Here, the separation membrane such as the MF membrane of the membrane separation treatment means 15 is a solid matter or other turbidity caused by particles made of a cationic polymer that gradually swells in water by the membrane separation treatment and does not substantially dissolve in water. Membrane separation performance deteriorates due to adhesion of contaminants. Therefore, if the membrane separation process is performed at an arbitrary frequency, for example, for about 14 minutes, the valve 30 provided between the reaction tank 10 and the membrane separation processing means 15 and the membrane separation processing means 15 and the treated water tank 20 are disposed. During the membrane separation process, the valve 31 opened is closed to interrupt the membrane separation process. Then, another valve 32 connecting the treated water tank 20 and the membrane separation processing means 15 is opened, and a washing liquid having a pH of 11 to 14 in which the alkaline liquid 21 is mixed with the treated water stored in the treated water tank 20 is introduced into the washing liquid such as a pump. The separation membrane is introduced into the membrane separation processing means 15 by means 22 and, for example, is allowed to pass through the separation membrane for about 1 minute, so that the separation membrane is back-washed with the cleaning liquid. The cleaning liquid is discharged as waste water from the membrane separation processing means 15 through the valve 33 to the outside of the membrane separation device 50.

  Then, after the cleaning of the separation membrane with the pH 11 to 14 cleaning liquid is completed, the valves 30 and 31 are opened again, the valves 32 and 33 are closed, and the membrane separation process is restarted. In this way, by washing the separation membrane, the membrane contaminants adsorbed on the separation membrane can be removed, so that deterioration of the membrane separation performance can be reliably suppressed.

  In the membrane separation apparatus shown in FIG. 2, backwashing is performed with a cleaning liquid. However, the present invention is not limited to this, and for example, deposits on the membrane surface are removed by flowing the cleaning liquid over the membrane surface of the separation membrane at a high flow rate. Flushing may be used. Further, although the MF membrane is shown as the membrane separation processing means 15, it may be a UF membrane, RO membrane, NF membrane or the like, and these membranes may be used in combination.

  EXAMPLES Hereinafter, although this invention is explained in full detail based on an Example and a comparative example, this invention is not limited at all by this Example.

Example 1
Particles made of a cationic polymer (Acogel C, manufactured by Mitsui Cytec Co., Ltd.) that swells in water and does not substantially dissolve in water in each aggregation jar containing 1000 mL of industrial water containing humic substances and biological metabolites as treated water. ) Was added as acogel C to 0.5, 1, 2, 4, 10 mg / L and stirred.

  Next, the water to be treated to which the particles were added was prepared using a Buchner funnel having an outer diameter of 40 mm and a height of 100 mm on the upper part of the eye plate, and a membrane filter (Millipore) having a diameter of 47 mm and a micropore of 0.45 μm. The filtration is performed in a state where the upper space is always filled with water, and the time T1 (second) until the filtration amount reaches 500 ml and the time T2 (second) until the filtration amount reaches 1,000 ml are measured. The MFF value at each concentration was determined from [Equation 1]. In addition, it shows that the to-be-processed water measured is clear, so that a MFF value is small. Moreover, the light absorbency (E260: organic substance density | concentration parameter | index) in wavelength 260nm was also measured about the to-be-processed water obtained by filtering and the MFF value showed the minimum value. Table 1 shows the minimum value of MFF and the value of E260 at the minimum value of MFF. In addition, the industrial water used as to-be-processed water was E260 = 0.298, and turbidity = 22 by the transmitted light measuring method using a kaolin standard solution.

(Example 2)
Instead of Akogel C, anion exchange resin (WA20 manufactured by Mitsubishi Chemical Corporation, particles made of a cationic polymer that swells in water and does not substantially dissolve in water) is used, and the anion exchange resin is 0.5, 1, 2, The same operation as in Example 1 was carried out except that it was added so as to be 4, 10, and 20 mg / L.

(Example 3)
The same operation as Example 1 was performed except that polyaluminum chloride (PAC) was added as an inorganic flocculant together with Akogel C. PAC (10% by weight as Al ₂ O ₃ ) polyaluminum chloride is added in order from 0.5 to 1.5 mg / L (as Al) in descending order of the concentration of acogel C. did.

(Comparative Example 1)
The same operation as in Example 1 was performed except that polyaluminum chloride was used instead of Akogel C.

(Comparative Example 2)
Instead of Akogel C, the same operation as in Example 1 was performed except that particles made of a nonionic polymer that swells in water and does not substantially dissolve in water (Akogel N, manufactured by Mitsui Cytec Co., Ltd.) were used.

  As a result, in each of Examples 1 to 3 and Comparative Examples 1 and 2, E260 and MFF decreased with an increase in the addition concentration, and each reached a substantially constant value when exceeding a certain concentration. Specifically, in Comparative Example 1 using only an inorganic flocculant, the minimum value of the MFF value is 1.31, whereas particles made of a cationic polymer that swells in water and does not substantially dissolve in water are used. In Example 1 and Example 2 in which the inorganic flocculant was added by the addition of particles composed of a cationic polymer that in turn was 1.22 and 1.26 and swelled in water and not substantially dissolved in water As a result, the water to be treated could be remarkably clarified. Therefore, if water to be treated is used for membrane separation treatment after adding particles made of a cationic polymer that swells in water and does not substantially dissolve in water, membrane contamination is suppressed because the water to be treated is clearer and membrane contamination is suppressed. It was found that the deterioration of can be prevented. In Example 3 to which particles made of a cationic polymer that swells in water and does not substantially dissolve in water and an inorganic flocculant were added, the MFF value was 1.06, and the effect was particularly remarkable. Further, in Comparative Example 2 using particles made of a nonionic polymer that swells in water and does not substantially dissolve in water, the MFF value was high, and clear water to be treated was not obtained.

Example 4
As the water to be treated, using the same industrial water as in Example 1 shown in FIG. 1, particles made of a cationic polymer that swells in water and does not substantially dissolve in water (Acogel C, manufactured by Mitsui Cytec) and poly Aluminum chloride (PAC) was sequentially added to 4 mg / L and 30 mg / L and stirred to form aggregates, and then the water to be treated to which the particles and the inorganic flocculant were added was 0.45 μm. Solid-liquid separation was performed with an MF membrane (manufactured by Cellulose Acetate) to remove agglomerates, and then membrane separation treatment was performed in which water to be treated was passed through a reverse osmosis membrane (RO membrane). At this time, the RO membrane differential pressure increase rate was measured. The results are shown in Table 2. The concentration of Akogel C (= 4 mg / L) is in Example 1, the concentration of polyaluminum chloride (PAC) (= 30 mg / L) is in Comparative Example 1, and the concentration when the MFF value shows the minimum value. did.

(Comparative Example 3)
The same operation as in Example 4 was performed except that the concentration of polyaluminum chloride was changed to 70 mg / L without using Akogel C.

  As a result, as compared with Comparative Example 3 using only the inorganic flocculant without using particles made of a cationic polymer that swells in water and does not substantially dissolve in water, the cation that swells in water and does not substantially dissolve in water In Example 4 using particles composed of a conductive polymer, the rate of increase in the RO membrane differential pressure can be significantly reduced, and it swells in the water to be treated before the membrane separation treatment with the RO membrane and does not substantially dissolve in water. It has been found that the addition of particles made of a cationic polymer can suppress the deterioration of the separation performance of the RO membrane.

(Example 5)
As the water to be treated, using the same industrial water as in Example 1 shown in FIG. 2, particles made of a cationic polymer that swells in water and does not substantially dissolve in water (Akogel C, manufactured by Mitsui Cytec) and poly Aluminum chloride (PAC) was added in order to 2 ppm and 30 ppm in order, and agglomerates were produced by stirring. Then, the water to be treated to which the particles and the inorganic flocculant were added was added to a 0.1 μm MF membrane (PVDF Product) for 14 minutes, and solid-liquid separation was performed to remove aggregates. Thereafter, the MF membrane was back-washed for 1 minute at a flow rate of 2 m / day using a cleaning solution in which hypochlorous acid was added to the water to be treated that had been subjected to membrane separation treatment with the MF membrane to a pH of 12. The membrane separation treatment and the backwashing step were continuously performed, and the MF transmembrane pressure difference at this time was measured.

As a result, the transmembrane pressure difference at the start of water flow was 27 kPa, but even after 480 hours had passed since the start of water flow, the transmembrane pressure difference was less than 50 kPa, and the flow rate did not decrease. The separation performance was not degraded. The FI value after 480 hours passed was 2.8, and it was confirmed that the MF membrane was not damaged. In addition, FI (Fouling Index) value is a value shown in JIS K 3802, and mainly quantifies a trace amount of turbidity in the feed water with respect to fouling of the reverse osmosis membrane module, that is, clarification of the shared water FI = [1−T ₀ / T ₁₅ ] × [100/15] (T ₀ : start when sample water is filtered under a pressure of 206 kPa with a membrane filter having a nominal pore diameter of 0.45 μm. Time required to filter 500 mL of sample (sec), T ₁₅ : Time required to filter 500 mL of sample water again after continuous filtration for 15 minutes (standard value) after T ₀ ).

(Example 6)
Instead of a cleaning solution in which hypochlorous acid is added to the water to be treated that has been subjected to membrane separation treatment with an MF membrane as a cleaning solution for backwashing, the pH is set to 12 to the water to be treated that has undergone membrane separation treatment with an MF membrane. The same operation as in Example 5 was performed, except that a cleaning solution in which chlorous acid was added to adjust the pH to 11 was used.

  As a result, the transmembrane pressure difference at the start of water flow was 20 kPa, and the transmembrane pressure difference was a value with no problem until about 200 hours after the start of water flow. However, the transmembrane pressure difference began to increase even after backwashing was performed 200 hours after the start of water flow, and reached 200 kPa after 420 hours of water flow.

1 is a schematic system diagram of a membrane separation apparatus according to an embodiment of the present invention. 1 is a schematic system diagram of a membrane separation apparatus according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 50 Membrane separation apparatus 10 Reaction tank 11 To-be-treated water introduction means 12 Chemical tank 13 Chemical introduction means 14 Discharge means 15 Membrane separation treatment means 16 Decarbonation treatment means 17 Activated carbon treatment means 18 Reverse osmosis membrane separation treatment means 19 Stirrer 20 Treatment Water tank 21 Alkaline liquid 22 Cleaning liquid introducing means 23 pH measuring means 30 to 33 Valve

Claims (10)

Particle size when it is a copolymer of a cationic monomer having a functional group such as primary amine, secondary amine, tertiary amine and their acid salts, quaternary ammonium groups, and a crosslinking agent monomer and is not swollen In contrast, particles made of a cationic polymer that is a reverse phase (W / O) emulsion polymer that swells to a particle size 10 to 200 times in water and does not substantially dissolve in water is added to the water to be treated and adsorbed. A membrane separation method comprising treating the treated water subjected to adsorption treatment with a separation membrane. The membrane separation method according to claim 1, wherein an inorganic flocculant is added to the water to be treated during the adsorption treatment. The membrane separation treatment includes a separation treatment using at least a microfiltration membrane or an ultrafiltration membrane, and the particles after the adsorption treatment are removed from the water to be treated by the membrane separation treatment. 3. The membrane separation method according to 1 or 2. The membrane separation method according to any one of claims 1 to 3, wherein the membrane separation treatment includes a separation treatment using at least one or more reverse osmosis membranes. The membrane separation method according to any one of claims 1 to 4, wherein pure water is obtained by deionizing the water to be treated after the adsorption treatment. The membrane separation method according to any one of claims 1 to 5, wherein the separation membrane is washed with a washing solution having a pH of 11 to 14 at an arbitrary frequency. The membrane separation method according to claim 6, wherein the washing with the washing liquid is back washing. A reaction tank, a treated water introduction means for introducing treated water into the reaction tank, and a cationic monomer having a functional group such as a primary amine, a secondary amine, a tertiary amine and their acid salts, and a quaternary ammonium group; A reverse phase (W / O) which is a copolymer with a crosslinking agent monomer and swells to a particle size of 10 to 200 times in water with respect to the particle size when not swollen and does not substantially dissolve in water Polymer particle introduction means for introducing particles made of a cationic polymer, which is an emulsion polymer, into the reaction tank or the previous stage of the reaction tank and adding the particles to the water to be treated, and discharging the water to be treated adsorbed in the reaction tank And a membrane separation processing means for subjecting the water to be treated discharged from the discharge means to a membrane separation treatment with a separation membrane. The membrane separation processing means has a reverse osmosis membrane of at least one stage and is a pure water production apparatus further comprising a deionization processing means for deionizing the water to be treated downstream of the reaction tank. The membrane separator according to claim 8. The membrane separation apparatus according to claim 8 or 9, further comprising a cleaning solution introduction unit that introduces a cleaning solution having a pH of 11 to 14 into the membrane separation processing unit.

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