JP2020058972A - Positive osmosis membrane treatment method, positive osmosis membrane treatment system, water treatment method, and water treatment system - Google Patents

Abstract

To provide a positive osmosis membrane treatment method and a positive osmosis membrane treatment system, which prevent a fungicide from penetrating the positive osmosis membrane and enable a reuse of dilute attracting solutions; and a water treatment method and water treatment system using the positive osmosis membrane treatment method and the positive osmosis membrane treatment system.SOLUTION: A positive osmotic membrane treatment method comprising a positive osmotic membrane treatment step with a positive osmotic membrane treatment device 10, in which a concentrated water and a dilute attractive solution are obtained by contacting a treated water with attractive solution having a higher concentration than the treated water through a positive osmotic membrane 12, and in which a disinfectant comprising a bromine oxidizer or a chlorine oxidizer and a sulfamic acid compound is present in the treated water.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a forward osmosis membrane treatment method, a forward osmosis membrane treatment system, a forward osmosis membrane treatment method thereof, a water treatment method using the forward osmosis membrane treatment system, and a water treatment system.

  In a forward osmosis (FO) membrane treatment system, a concentrated water and a dilute attractant solution are obtained by contacting treated water and an attractant solution having a higher concentration than the treated water through a forward osmosis membrane. Control is an important issue. As a sterilizing method of the forward osmosis membrane treatment system, a chlorine-based sterilizing agent such as hypochlorous acid and chloramine, an oxidizing agent such as hydrogen peroxide, or 5-chloro-2-methyl-4-isothiazolin-3-one or the like is used. Organic fungicides are used (see, for example, Patent Documents 1 and 2).

  However, these bactericides (chlorine-based bactericides, oxidizers, organic bactericides) permeate the normal osmosis membrane, so the bactericidal active ingredient of the bactericide does not reach the outlet side of the normal osmosis membrane treatment device sufficiently. Therefore, there is a problem that the forward osmosis membrane cannot be sterilized sufficiently. In particular, the organic bactericide may affect the living body and environment. Especially when the product water is separated from the diluted attractant solution by treatment such as heating and the product water contains an organic fungicide, it is suitable for industrial applications, food applications, drinking applications, etc. Significantly limited. Moreover, in order to discharge a part or all of the diluted attractant solution containing the bactericide that has permeated the forward osmosis membrane, it is necessary to remove them. Furthermore, since chlorine-based bactericides and oxidants may reduce the performance of reverse osmosis membranes, especially polyamide-based reverse osmosis membranes, when re-treating a part or all of the diluted attractant solution with a reverse osmosis membrane, these There is a concern that the bactericide may deteriorate the performance of the reverse osmosis membrane.

JP, 2005-188787, A JP, 2018-015684, A

  An object of the present invention is to suppress a sterilizing agent from permeating a normal osmosis membrane, and to reuse a dilute attractant solution, a normal osmosis membrane treatment method, a normal osmosis membrane treatment system, and a normal osmosis membrane treatment method thereof. A water treatment method and a water treatment system using the forward osmosis membrane treatment system.

  The present invention includes a normal osmosis membrane treatment step of obtaining a concentrated water and a dilute attractant solution by contacting treated water and an attractant solution having a concentration higher than that of the treated water through a normal osmosis membrane. A method for treating a normal osmosis membrane in which a bactericide containing a bromine-based oxidant or a chlorine-based oxidant and a sulfamic acid compound is present in the water to be treated.

  The present invention includes a normal osmosis membrane treatment step of obtaining a concentrated water and a dilute attractant solution by contacting treated water and an attractant solution having a concentration higher than that of the treated water through a normal osmosis membrane. A method for treating a normal osmosis membrane, wherein a bactericide containing a brominated oxidant and a sulfamic acid compound is present in the water to be treated.

  The present invention includes a normal osmosis membrane treatment step of obtaining a concentrated water and a dilute attractant solution by contacting treated water and an attractant solution having a concentration higher than that of the treated water through a normal osmosis membrane. A method for treating a normal osmosis membrane, wherein a bactericide containing bromine and a sulfamic acid compound is present in the water to be treated.

  The present invention includes the forward osmosis membrane treatment method, in the preceding stage of the forward osmosis membrane treatment step, including a pretreatment step and a reverse osmosis membrane treatment step, the diluted attractant solution obtained by the forward osmosis membrane treatment step, It is a water treatment method used in the pretreatment step.

  The present invention comprises a normal osmosis membrane treatment means for obtaining concentrated water and a dilute attractant solution by contacting treated water and an attractant solution having a higher concentration than the treated water through a normal osmosis membrane. A forward osmosis membrane treatment system in which a bactericide containing a bromine-based oxidant or a chlorine-based oxidant and a sulfamic acid compound is present in the water to be treated.

  The present invention comprises a normal osmosis membrane treatment means for obtaining concentrated water and a dilute attractant solution by contacting treated water and an attractant solution having a higher concentration than the treated water through a normal osmosis membrane. A osmotic membrane treatment system in which a bactericide containing a brominated oxidant and a sulfamic acid compound is present in the water to be treated.

  The present invention comprises a normal osmosis membrane treatment means for obtaining concentrated water and a dilute attractant solution by contacting treated water and an attractant solution having a higher concentration than the treated water through a normal osmosis membrane. A forward osmosis membrane treatment system in which a bactericide containing bromine and a sulfamic acid compound is present in the water to be treated.

  The present invention comprises the forward osmosis membrane treatment system, the pre-treatment means and the reverse osmosis membrane treatment means before the forward osmosis membrane treatment means, and the diluted attractant solution obtained by the forward osmosis membrane treatment means, A water treatment system used in the pretreatment means.

  According to the present invention, the sterilizing agent is suppressed from permeating the normal osmosis membrane, and the normal osmosis membrane treatment method, the normal osmosis membrane treatment system, and the normal osmosis membrane treatment method, in which the diluted attractant solution can be reused, A water treatment method and a water treatment system using the osmosis membrane treatment system can be provided.

It is a schematic structure figure showing an example of the forward osmosis membrane treatment system concerning the embodiment of the present invention. It is a schematic structure figure showing an example of a water treatment system concerning an embodiment of the present invention.

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

<Normal osmosis membrane treatment method and forward osmosis membrane treatment system>
An example of the forward osmosis membrane treatment system according to the embodiment of the present invention is schematically shown in FIG. 1, and its configuration will be described.

  The forward osmosis membrane treatment system 1 according to the present embodiment provides treated water (FO treated water) and an attractant solution having a higher concentration than the treated water (FO treated water) via the forward osmosis membrane 12. A normal osmosis membrane treatment apparatus 10 is provided as a normal osmosis membrane treatment means for obtaining concentrated water (FO concentrated water) and a diluted attractant solution by bringing them into contact with each other.

  In the normal osmosis membrane treatment system 1 of FIG. 1, the FO treated water pipe 14 is connected to the FO treated water inlet of the forward osmosis membrane treatment device 10, and the FO concentrated water pipe 16 is connected to the FO concentrated water outlet. Has been done. The attractant solution inlet of the forward osmosis membrane treatment apparatus 10 is connected to the attractant solution pipe 18, and the dilute attractant solution outlet is connected to the dilute attractant solution pipe 20. A sterilizing agent addition pipe 22 is connected to the FO treated water pipe 14 as a sterilizing agent adding means.

  The operation of the forward osmosis membrane treatment method and the forward osmosis membrane treatment system 1 according to the present embodiment will be described.

  The FO treated water is sent to the primary side of the forward osmosis membrane treatment apparatus 10 through the FO treated water pipe 14 and is subjected to the forward osmosis membrane treatment in the forward osmosis membrane treatment apparatus 10 (forward osmosis membrane treatment step). In the forward osmosis membrane treatment apparatus 10, the attractant solution is sent to the secondary side of the forward osmosis membrane through the attractant solution pipe 18, and the FO treated water and the attractant solution are allowed to exist through the forward osmosis membrane 12 so that the osmosis is permeated. Water is transferred under pressure to the attractant solution. The diluted attractant solution used in the forward osmosis membrane treatment step is discharged through the diluted attractant solution pipe 20. The FO concentrated water obtained in the forward osmosis membrane treatment step is discharged through the FO concentrated water pipe 16. At least one of the diluted attractant solution and the FO retentate may be recovered and reused.

  Here, a bactericide containing a bromine-based oxidant or chlorine-based oxidizer and a sulfamic acid compound (hereinafter, may be referred to as a “normal osmosis membrane bactericide”) is present in the FO treated water. For example, the normal osmosis membrane bactericide is added to the FO treated water in the FO treated water pipe 14 through the bactericide addition pipe 22. A FO treated water tank for storing the FO treated water may be separately provided in front of the forward osmosis membrane treatment apparatus 10, and the sterilizing agent for the forward osmosis membrane may be added to the FO treated water tank.

  As described above, in the forward osmosis membrane treatment method and the forward osmosis membrane treatment system 1 according to the present embodiment, when the treated water is subjected to the forward osmosis membrane treatment, bromine is added to the treated water of the forward osmosis membrane treatment (FO treated water). A sterilizing agent for a forward osmosis membrane containing a oxidant or chlorine oxidant and a sulfamic acid compound is present. The present inventors have found that a bactericide for a normal osmosis membrane containing a bromine-based oxidant or a chlorine-based oxidizer and a sulfamic acid compound hardly permeates the normal osmosis membrane. This normal osmosis membrane bactericide exhibits a sufficient bactericidal effect on the normal osmosis membrane as compared with conventional chlorine-based bactericides, oxidizing agents, and organic bactericides. In addition, since the germicide hardly leaks into the attractant solution, the diluted attractant solution can be reused.

  Since the bactericidal active ingredient hardly permeates the normal osmosis membrane, the bactericide for normal osmosis membrane is concentrated as it goes to the outlet (FO concentrated water outlet) of the normal osmosis membrane treatment apparatus 10. Therefore, the bactericidal active ingredient of the bactericide can be sufficiently spread to the outlet (FO concentrated water outlet) side of the forward osmosis membrane treatment apparatus 10, and can be sufficiently sterilized to the outlet side of the forward osmosis membrane.

  In the conventional method, when a bactericide such as hypochlorous acid, chloramine, hydrogen peroxide, and an organic bactericide is added to the FO treated water, a part of the FO treated water is attracted by the osmotic pressure difference from the attractant solution. While moving to the side, a part of the bactericide moves to the attractant solution side. On the other hand, in the forward osmosis membrane treatment method and the forward osmosis membrane treatment system 1 according to the present embodiment, the use of the forward osmosis membrane sterilizing agent suppresses the sterilizing agent from permeating the forward osmosis membrane, The diluted attractant solution can be reused.

  “A bactericide containing a bromine-based oxidant and a sulfamic acid compound” is a bactericide containing a stabilized hypobromite composition containing a mixture of a “bromine-based oxidizer” and a “sulfamic acid compound”. Alternatively, it may be a bactericide containing a stabilized hypobromite composition containing a "reaction product of a brominated oxidant and a sulfamic acid compound". The "bactericide containing a chlorine-based oxidizing agent and a sulfamic acid compound" is a fungicide containing a stabilized hypochlorous acid composition containing a mixture of a "chlorine-based oxidizing agent" and a "sulfamic acid compound". Alternatively, it may be a bactericide containing a stabilized hypochlorous acid composition containing a "reaction product of a chlorine-based oxidizing agent and a sulfamic acid compound".

  That is, the method for treating a normal osmosis membrane according to the embodiment of the present invention is a mixture of a “bromine-based oxidizing agent” and a “sulfamic acid compound” in the water to be treated (FO treated water), or a “chlorine-based oxidizing agent”. And a "sulfamic acid compound". It is considered that this produces a stabilized hypobromic acid composition or a stabilized hypochlorous acid composition in the water to be treated.

  Further, the method for treating a normal osmosis membrane according to the embodiment of the present invention is a stabilized hypobromite which is a “reaction product of a brominated oxidant and a sulfamic acid compound” in water to be treated (FO treated water). An acid composition or a stabilized hypochlorous acid composition which is a “reaction product of a chlorine-based oxidizing agent and a sulfamic acid compound” is present.

  Specifically, the forward osmosis membrane treatment method according to the embodiment of the present invention, in the water to be treated, "bromine", "bromine chloride", "hypobromous acid" or "sodium bromide and hypochlorous acid In this method, a mixture of "reactant" and "sulfamic acid compound" is present. Alternatively, it is a method in which a mixture of "hypochlorous acid" and "sulfamic acid compound" is present in the water to be treated.

  Further, the method for treating a normal osmosis membrane according to the embodiment of the present invention, in the water to be treated, for example, "reaction product of bromine and sulfamic acid compound", "reaction product of bromine chloride and sulfamic acid compound", Stabilized hypobromous acid which is a "reaction product of a hypobromous acid and a sulfamic acid compound" or "a reaction product of a reaction product of sodium bromide and a hypochlorous acid and a sulfamic acid compound" A method of causing the composition to be present. Alternatively, it is a method in which a stabilized hypochlorous acid composition which is a "reaction product of a hypochlorous acid and a sulfamic acid compound" is present in water to be treated.

  In the forward osmosis membrane treatment method according to the present embodiment, the stabilized hypobromous acid composition or the stabilized hypochlorous acid composition is equal to or more than a conventional bactericide such as a chlorine-based oxidizing agent such as hypochlorous acid. Despite exhibiting a bactericidal effect, compared to conventional bactericides such as chlorine-based oxidizers, the effect of deterioration on the forward osmosis membrane is low, so while suppressing fouling on the forward osmosis membrane, Oxidative deterioration of the can be suppressed. Therefore, the stabilized hypobromous acid composition or the stabilized hypochlorous acid composition used in the forward osmosis membrane treatment method according to the present embodiment is a bactericide used in the method of treating the water to be treated with the forward osmosis membrane. Is suitable as

  Among the methods for treating a normal osmosis membrane according to the present embodiment, in the case of “a bactericidal agent containing a bromine-based oxidizing agent and a sulfamic acid compound”, since there is no chlorine-based oxidizing agent, the deterioration effect on the forward osmosis membrane is lower. . When a chlorine-based oxidant is contained, the formation of chloric acid is a concern.

  In the method of treating a normal osmosis membrane according to the present embodiment, when the “bromine-based oxidizing agent” is bromine, the chlorine-based oxidizing agent does not exist, and therefore the deterioration effect on the normal osmosis membrane is extremely low.

  In the forward osmosis membrane treatment method according to the present embodiment, for example, “bromine-based oxidizing agent” or “chlorine-based oxidizing agent” and “sulfamic acid compound” may be injected into the water to be treated by a chemical injection pump or the like. . The "bromine-based oxidizing agent" or "chlorine-based oxidizing agent" and the "sulfamic acid compound" may be added to the water to be treated separately, or may be added to the water to be treated after mixing the undiluted solutions. Good.

  Further, for example, even if the "reaction product of a bromine-based oxidizing agent and a sulfamic acid compound" or "reaction product of a chlorine-based oxidizing agent and a sulfamic acid compound" is injected into the water to be treated by a chemical injection pump or the like. Good.

  In the forward osmosis membrane treatment method according to the present embodiment, the ratio of the equivalent of the "sulfamic acid compound" to the equivalent of the "bromine-based oxidizing agent" or the "chlorine-based oxidizing agent" is preferably 1 or more, and 1 or more 2 The following range is more preferable. If the ratio of the equivalent of the "sulfamic acid compound" to the equivalent of the "bromine-based oxidizing agent" or the "chlorine-based oxidizing agent" is less than 1, the film may be deteriorated, and if it exceeds 2, the production cost increases. There is a case.

  The total chlorine concentration in contact with the forward osmosis membrane is preferably 0.01 to 100 mg / L in terms of effective chlorine concentration. If it is less than 0.01 mg / L, a sufficient bactericidal effect may not be obtained in some cases, and if it is more than 100 mg / L, deterioration of the forward osmosis membrane and corrosion of piping etc. may occur.

  Examples of the bromine-based oxidizing agent include bromine (liquid bromine), bromine chloride, bromic acid, bromate and hypobromite. The hypobromous acid may be produced by reacting a bromide such as sodium bromide with a chlorine-based oxidizing agent such as hypochlorous acid.

  Among these, the formulation of "bromine and sulfamic acid compound (mixture of bromine and sulfamic acid compound)" or "reaction product of bromine and sulfamic acid compound" using bromine, "hypochlorous acid and bromine compound Compared with the formulation of "sulfamic acid" and the formulation of "bromine chloride and sulfamic acid", etc., the bromic acid is less by-produced and the normal osmosis membrane is not further deteriorated.

  That is, in the forward osmosis membrane treatment method according to the embodiment of the present invention, it is preferable that bromine and a sulfamic acid compound are present in the water to be treated (a mixture of the bromine and the sulfamic acid compound is present). Further, it is preferable that a reaction product of bromine and a sulfamic acid compound is present in the water to be treated.

  Examples of the bromine compound include sodium bromide, potassium bromide, lithium bromide, ammonium bromide and hydrobromic acid. Of these, sodium bromide is preferable from the viewpoint of formulation cost and the like.

  Examples of chlorine-based oxidizing agents include chlorine gas, chlorine dioxide, hypochlorous acid or a salt thereof, chlorous acid or a salt thereof, chloric acid or a salt thereof, perchloric acid or a salt thereof, chlorinated isocyanuric acid or a salt thereof. Etc. Among these, as salts, for example, sodium hypochlorite, alkali metal hypochlorite such as potassium hypochlorite, calcium hypochlorite, alkaline earth hypochlorite such as barium hypochlorite. Metal salts, alkali metal chlorites such as sodium chlorite, potassium chlorite, alkaline earth metal chlorites such as barium chlorite, and other metal chlorites such as nickel chlorite , Ammonium chlorate, sodium chlorate, potassium chlorate and other alkali metal chlorates, calcium chlorate, barium chlorate and other alkaline earth metal chlorates, and the like. These chlorine-based oxidizing agents may be used alone or in combination of two or more. It is preferable to use sodium hypochlorite as the chlorine-based oxidant from the viewpoint of handleability and the like.

The sulfamic acid compound is a compound represented by the following general formula (1).
R ₂ NSO ₃ H (1)
(In the formula, R is independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.)

  Examples of the sulfamic acid compound include N-methylsulfamic acid, N-ethylsulfamic acid, N-propylsulfamic acid and N-, in addition to sulfamic acid (amidosulfate) in which both two R groups are hydrogen atoms. A sulfamic acid compound in which one of two R groups such as isopropylsulfamic acid and N-butylsulfamic acid is a hydrogen atom and the other is an alkyl group having 1 to 8 carbon atoms, N, N-dimethylsulfamic acid, N, Of two R groups such as N-diethylsulfamic acid, N, N-dipropylsulfamic acid, N, N-dibutylsulfamic acid, N-methyl-N-ethylsulfamic acid, N-methyl-N-propylsulfamic acid One of two R groups such as a sulfamic acid compound and N-phenylsulfamic acid, both of which are alkyl groups having 1 to 8 carbon atoms, An atom, the other is sulfamic acid compound or a salt thereof, such as an aryl group having 6 to 10 carbon atoms. As the sulfamate, for example, alkali metal salts such as sodium salt, potassium salt, calcium salt, strontium salt, alkaline earth metal salts such as barium salt, manganese salt, copper salt, zinc salt, iron salt, cobalt salt, Other metal salts such as nickel salts, ammonium salts and guanidine salts may be mentioned. The sulfamic acid compounds and salts thereof may be used alone or in combination of two or more. As the sulfamic acid compound, it is preferable to use sulfamic acid (amidosulfuric acid) from the viewpoint of environmental load.

  In the forward osmosis membrane treatment method according to this embodiment, an alkali may be further present. Examples of the alkali include alkali hydroxides such as sodium hydroxide and potassium hydroxide. From the viewpoint of product stability at low temperatures, sodium hydroxide and potassium hydroxide may be used in combination. Further, the alkali may be used as an aqueous solution instead of a solid.

  The shape of the forward osmosis membrane used in the forward osmosis membrane treatment step is not particularly limited, but for example, a hollow fiber membrane, a spiral wound membrane, a tubular membrane, a plate-and-frame structured membrane, or the like can be used. Examples of the material of the forward osmosis membrane include aromatic polyamide type, cellulose acetate type and polyketone type. Further, it is also possible to use a membrane in which a functional protein, an inorganic material or the like is incorporated into the base material of the separation membrane to impart separation performance or water permeability. The normal osmosis membrane treatment method according to the present embodiment is an aromatic polyamide-based membrane as a normal osmosis membrane, and a functional protein, an inorganic material, or the like is incorporated into a base material of an amide-based membrane to impart separation performance or water permeability to a membrane. It can be applied suitably. It is known that these films are particularly susceptible to deterioration due to conventionally used chlorine-based oxidizing agents.

  Examples of the normal osmosis membrane include HP5230 (manufactured by Toyobo), HFFO2 (manufactured by Aquaporin), and OsmoF2O (manufactured by Fluid Technology Solutions). These forward osmosis membranes may be used in a single stage or may be used by connecting a plurality of stages in series. That is, the concentrated water obtained by the first forward osmosis membrane treatment may be further concentrated by the second forward osmosis membrane treatment.

  By the way, the forward osmosis membrane and the reverse osmosis membrane have different membrane structures and properties due to the difference in their operating methods. Since the reverse osmosis membrane applies a high pressure to the primary side of the membrane, it is necessary to increase the film thickness in order to maintain the mechanical strength capable of withstanding the pressure. On the other hand, the forward osmosis membrane does not need to have the mechanical strength of the reverse osmosis membrane because the pressure applied to the membrane is lower than that of the reverse osmosis membrane, and further it is necessary to suppress the concentration polarization inside the membrane. It is required to reduce the film thickness. As a result of optimizing the membrane to the required operating conditions, the reverse osmosis membrane and the normal osmosis membrane have different membrane structures, although the membrane materials are the same, but the permeation performance and the blocking performance are different. Therefore, if the reverse osmosis membrane used in the reverse osmosis membrane treatment is used for forward osmosis, sufficient performance cannot be obtained.

  Examples of the attractant solution used in the forward osmosis membrane treatment step include an aqueous solution of an inorganic salt such as an aqueous solution of ammonium carbonate, an aqueous solution of magnesium salt and an aqueous solution of sodium salt, an aqueous solution of an organic substance such as sucrose, glucose and an organic polymer, and an ionic liquid. The diluted attractant solution used in the forward osmosis membrane treatment step may be used as it is in another step, or the diluted attractant solution may be heated or subjected to membrane separation or the like to separate water from the diluted attractant solution to obtain a solution. The water and concentrated attractant solution may be reused. In the case of performing a plurality of steps of the forward osmosis membrane treatment in the forward osmosis membrane treatment step, the attracting solution may be used in combination.

  The treated water (FO treated water) is not particularly limited, but for example, industrial water, surface water, tap water, groundwater, seawater, seawater desalination treatment in which seawater is desalted by a reverse osmosis method, an evaporation method, or the like. Examples thereof include water and various wastewater, such as wastewater discharged in the semiconductor manufacturing process and the like.

  The pH of the water to be treated is, for example, in the range of 2 to 12, and preferably in the range of 4 to 11. If the pH of the water to be treated is less than 2 or more than 12, the forward osmosis membrane may deteriorate.

  In the forward osmosis membrane treatment apparatus, when scale is generated at pH 5.5 or higher of the water to be treated, a dispersant may be used in combination with the disinfectant in order to suppress scale. Examples of the dispersant include polyacrylic acid, polymaleic acid, phosphonic acid and the like. The amount of the dispersant added to the water to be treated is, for example, in the range of 0.1 to 1,000 mg / L as the concentration in the FO concentrated water.

  Further, in order to suppress the generation of scale without using a dispersant, for example, normal osmosis is performed so that the silica concentration in the FO concentrated water is less than or equal to the solubility and the Langereria index, which is an index of calcium scale, is less than or equal to 0. Adjustment of operating conditions such as the recovery rate of the membrane treatment device, water temperature, and pH may be mentioned.

  Examples of the application of the forward osmosis membrane treatment system include desalination of seawater, volume reduction of waste water, concentration of valuables, concentration of foods and beverages, and the like.

<Water treatment method, water treatment system>
Next, the above-mentioned normal osmosis membrane treatment method, water treatment method using the normal osmosis membrane treatment system, and water treatment system will be described.

  A water treatment method according to an embodiment of the present invention includes the above-mentioned forward osmosis membrane treatment method, and includes a pretreatment step and a reverse osmosis membrane treatment step before the forward osmosis membrane treatment step and is obtained by the forward osmosis membrane treatment step. It is a water treatment method in which the diluted attractant solution is used in the pretreatment step. Further, the water treatment system according to the embodiment of the present invention comprises the above-mentioned normal osmosis membrane treatment system, and comprises a pretreatment means and a reverse osmosis membrane treatment means before the forward osmosis membrane treatment means. The diluted attractant solution obtained is the water treatment system used in the pretreatment means.

  An outline of an example of the water treatment device according to the embodiment of the present invention is shown in FIG. 2, and its configuration will be described.

  The water treatment system 3 according to the present embodiment includes a pretreatment device 24 as pretreatment means for pretreatment of water to be treated, a reverse osmosis membrane treatment of pretreatment water obtained by the pretreatment, and RO concentrated water. Reverse osmosis membrane treatment device 28 as a reverse osmosis membrane treatment means for obtaining RO permeated water, and a forward osmosis membrane as a forward osmosis membrane treatment means for performing a forward osmosis membrane treatment of RO concentrated water obtained by the reverse osmosis membrane treatment. And a processing device 10. The water treatment system 3 may include a turbidity removal device 26 as a turbidity removal unit that performs a turbidity removal process of the pretreated water obtained by the pretreatment.

  In the water treatment system 3 of FIG. 2, the treated water pipe 30 is connected to the treated water inlet of the pretreatment device 24, and the outlet of the pretreatment device 24 and the inlet of the suspended matter removing device 26 are connected by the pipe 32. The outlet of the suspended matter removing device 26 and the inlet of the reverse osmosis membrane processing device 28 are connected by a pipe 34. The RO concentrated water outlet of the reverse osmosis membrane treatment device 28 and the FO treated water inlet of the forward osmosis membrane treatment device 10 are connected by the FO treated water pipe 14, and the RO permeated water outlet of the reverse osmosis membrane treatment device 28 is connected to the RO permeated water outlet. , RO permeated water pipe 36 is connected. The attractant solution pipe 18 is connected to the attractant solution inlet of the forward osmosis membrane treatment apparatus 10, and the dilute attractant solution outlet of the forward osmosis membrane treater 10 and the dilute attractant solution inlet of the pretreatment unit 24 are the dilute attractant solution pipes. FO concentrated water pipe 16 is connected to the FO concentrated water outlet of normal osmosis membrane treatment apparatus 10. A backwash drainage pipe 38 may be connected to the backwash drainage outlet of the suspended matter removing device 26.

  The operation of the water treatment method and the water treatment system 3 according to this embodiment will be described.

  The treated water is sent to the pretreatment device 24 through the treated water pipe 30. In the pretreatment device 24, for example, a treatment for removing soluble silica, hardness components, etc. contained in the water to be treated is performed (pretreatment step).

  When the water to be treated contains soluble silica, the pretreatment device 24 may, for example, add a magnesium salt to the water to be treated to cause a reaction, and to make the soluble silica insoluble, and the treated water after the reaction. It has an aggregating treatment means for adding an aggregating agent to agglomerate, and a solid-liquid separating means for separating an agglomerate from the aggregating treated water. In the pretreatment device 24, for example, magnesium salt is added to the water to be treated under alkaline conditions (for example, pH 10 to 12) to insolubilize the soluble silica (magnesium reaction step). After that, an aggregating agent is added if necessary, and an aggregating treatment is performed (aggregating treatment step), and an aggregate is subjected to solid-liquid separation (solid-liquid separation step). The solid-liquid separation treated water obtained by the solid-liquid separation is sent as pretreatment water to the turbidity removal device 26 through the pipe 32, and turbidity removal processing by a UF membrane or the like is performed to remove turbidity components and the like. After being treated (turbidity removing step), the solution is sent to the reverse osmosis membrane treatment device 28.

  When the water to be treated contains a hardness component and the hardness component is removed by the lime softening method, the pretreatment device 24 may, for example, add an alkaline agent to the water to be treated and cause the reaction to cause an insolubility of the hardness component. It has a reaction means, an aggregating treatment means for aggregating by adding an aggregating agent to the treated water after the reaction as necessary, and a solid-liquid separation means for separating an aggregate from the aggregating treated water. . In the pretreatment device 24, for example, an alkaline agent is added to the water to be treated to insolubilize the hardness component (alkali agent reaction step). After that, an aggregating agent is added if necessary, and an aggregating treatment is performed (aggregating treatment step), and an aggregate is subjected to solid-liquid separation (solid-liquid separation step). The solid-liquid separation treated water obtained by the solid-liquid separation is sent as pretreatment water to the turbidity removal device 26 through the pipe 32, and turbidity removal processing by a UF membrane or the like is performed to remove turbidity components and the like. After being treated (turbidity removing step), the solution is sent to the reverse osmosis membrane treatment device 28.

  When the water to be treated contains a hardness component and the hardness component is removed by the resin softening method, the pretreatment device 24 has, for example, an ion exchange treatment means for performing an ion exchange treatment using an ion exchange resin or the like. In the pretreatment device 24, for example, water to be treated is passed through an ion exchange column filled with an ion exchange resin as an ion exchange treatment means, and a hardness component is adsorbed and removed (ion exchange step). The pretreated water obtained by the ion exchange treatment is sent to the turbidity removal device 26 through the pipe 32 and subjected to turbidity removal processing using a UF membrane or the like to remove turbidity components and the like (turbidity (Removing step), and the solution is sent to the reverse osmosis membrane treatment device 28. When it becomes necessary to regenerate the ion exchange resin, the regenerant is passed to regenerate the ion exchange resin.

  Next, the pretreatment water subjected to the turbidity removal treatment is subjected to reverse osmosis membrane treatment in the reverse osmosis membrane treatment device 28 to obtain RO concentrated water and RO permeated water (reverse osmosis membrane treatment step). The RO concentrated water obtained by the reverse osmosis membrane treatment is sent to the primary side of the forward osmosis membrane treatment apparatus 10 as the FO treated water through the FO treated water pipe 14, and the RO permeated water is the RO permeated water pipe 36. Exhausted through. In the turbidity removing device 26, the membrane may be backwashed at predetermined intervals. For example, RO permeated water or the like is supplied as backwash water to the turbidity removal device 26, and the backwash drainage is discharged through the backwash drainage pipe 38.

  The RO concentrated water obtained by the reverse osmosis membrane treatment is subjected to a forward osmosis membrane treatment in the forward osmosis membrane treatment apparatus 10 (a forward osmosis membrane treatment step). In the forward osmosis membrane treatment apparatus 10, the attractant solution is sent to the secondary side of the forward osmosis membrane through the attractant solution pipe 18, and the RO concentrated water and the attractant solution are allowed to exist through the forward osmosis membrane, thereby increasing the osmotic pressure. Water is transferred to the attractant solution.

  Here, the osmotic agent for a normal osmosis membrane containing a brominated oxidant or a chlorine oxidant and a sulfamic acid compound is present in RO concentrated water (FO treated water). For example, the normal osmosis membrane sterilizer is added to the RO concentrated water (FO treated water) in the FO treated water pipe 14 through the sterilizing agent addition pipe 22. Before the forward osmosis membrane treatment apparatus 10, for example, between the reverse osmosis membrane treatment apparatus 28 and the forward osmosis membrane treatment apparatus 10, a FO treated water tank for storing RO concentrated water (FO treated water) is separately provided. A sterilizing agent for a forward osmosis membrane may be added in the treated water tank.

  This normal osmosis membrane bactericide exhibits a sufficient bactericidal effect on the normal osmosis membrane as compared with conventional chlorine-based bactericides, oxidizing agents, and organic bactericides. In the water treatment method according to the present embodiment, by using the sterilizing agent for the forward osmosis membrane, since the bactericidal active ingredient hardly penetrates the forward osmosis membrane, the diluted attractant solution diluted by the forward osmosis membrane treatment is used in the pretreatment. It is possible to reuse the diluted attractant solution. When the diluted attractant solution contains an organic germicide, the germicidal active ingredient is contained in the backwash drainage of the suspended matter removing device 26 and the RO permeate of the reverse osmosis membrane treatment device 28. When the dilute attractant solution contains a chlorine-based germicide or an oxidant, if the chlorine-based germicide or the oxidant flows into the turbidity removal device 26 or the reverse osmosis membrane treatment device 28, the membrane is deteriorated. When the sterilizing agent for a normal osmosis membrane is used, such a risk is suppressed because the bactericidal active ingredient hardly permeates the normal osmosis membrane.

  The diluted attractant solution used in the forward osmosis membrane treatment step is sent to the pretreatment device 24 through the diluted attractant solution pipe 20, and is used in the pretreatment device 24 in the pretreatment step. The FO concentrated water obtained in the forward osmosis membrane treatment step is discharged through the FO concentrated water pipe 16. The FO concentrated water may be collected and reused.

  When the pretreatment device 24 includes a device for removing soluble silica, for example, a magnesium salt aqueous solution is used as the attractant solution in the forward osmosis membrane treatment device 10, and the diluted attractant solution ( The diluted magnesium salt solution) may be used as the magnesium salt added in the pretreatment device 24.

  When the pretreatment device 24 includes a device that removes hardness components by the lime softening method, for example, an alkaline agent aqueous solution is used as the attracting solution in the forward osmosis membrane treatment device 10 and used in the forward osmosis membrane treatment device 10. The diluted attractant solution (alkaline agent diluted aqueous solution) may be used as the alkaline agent added in the pretreatment device 24.

  When the pretreatment device 24 includes a device for removing the hardness component by the resin softening method, for example, an acid aqueous solution or an aqueous sodium chloride solution is used as the attracting solution in the forward osmosis membrane treatment device 10, and The dilute attracting solution (dilute aqueous acid solution or dilute aqueous sodium chloride solution) used may be used as a regenerant for the ion exchange resin in the pretreatment device 24.

  With the water treatment method and the water treatment apparatus according to the present embodiment, for example, water to be treated containing at least one of soluble silica and hardness component can be treated at low cost.

  By using the diluted attractant solution diluted by the forward osmosis membrane treatment in the pretreatment step, the cost required for reusing the attractant solution, which was originally necessary, is reduced, and there is no need to provide a regeneration facility. . The diluted attractant solution is diluted with the one originally used in the pretreatment step, so that there is almost no additional cost.

  The water to be treated, which is a treatment target of the water treatment method and the water treatment apparatus according to the present embodiment, is not particularly limited, but is, for example, water containing at least one of soluble silica and a hardness component, such as industrial water. , Surface water, tap water, groundwater, seawater, seawater desalination treated water obtained by desalting seawater by the reverse osmosis method or the evaporation method, various kinds of wastewater, such as wastewater discharged in the semiconductor manufacturing process.

  When the water to be treated contains soluble silica, the concentration of the soluble silica is, for example, in the range of 5 to 400 mg / L. When the water to be treated contains a hardness component, the concentration of the calcium hardness component is in the range of 5 to 600 mg / L. The total evaporation residue (TDS: Total Dissolved Solid) in the water to be treated is, for example, in the range of 100 to 50,000 mg / L.

  In the water treatment method and the water treatment apparatus according to the present embodiment, when the water to be treated contains both the soluble silica and the hardness component, the pretreatment means (pretreatment step) is the soluble silica removal means (soluble silica Both the removing step) and the hardness component removing means (hardness component removing step) may be provided. The order of the soluble silica removing means (soluble silica removing step) and the hardness component removing means (hardness component removing step) is as follows: first, the soluble silica removing means (soluble silica removing step); and secondly, the hardness component removing means. It may be (hardness component removal step), firstly hardness component removal means (hardness component removal step), and secondly soluble silica removal means (soluble silica removal step).

  In this case, at least one of an aqueous magnesium salt solution, an aqueous alkaline agent solution, an aqueous acid solution and an aqueous sodium chloride solution is used as the attracting solution in the forward osmosis membrane treatment apparatus 10 (forward osmosis membrane treatment step). The dilute attracting solution used (at least one of dilute aqueous solution of magnesium salt, dilute aqueous solution of alkaline agent, dilute aqueous solution of acid and dilute aqueous solution of sodium chloride) is a soluble silica removing means (dissolving solution) of the pretreatment device 24 (pretreatment step). It may be used in the more suitable one of the step (removing silica) and the hardness component removing means (hardness component removing process).

  Examples of the suspended matter removing means include a sand filtration device, a membrane filtration device such as an ultrafiltration (UF) membrane, and a pressure flotation device. The installation position of the suspended matter removing unit is not particularly limited, and may be, for example, before the pretreatment device 24 (pretreatment process) or the pretreatment device 24 (pretreatment process) and the reverse osmosis membrane treatment device 28 (reverse osmosis membrane treatment). Process).

[Pretreatment step: Removal of soluble silica]
In the pretreatment step when the water to be treated contains soluble silica, for example, magnesium salt is added to the water to be treated under alkaline conditions to insolubilize the soluble silica (magnesium reaction step).

The magnesium salt used may be a magnesium salt such as magnesium chloride (MgCl ₂ ) or magnesium sulfate (MgSO ₄ ) or a hydrate thereof, and is not particularly limited, but a hardly soluble substance is generated by addition of a sulfate salt. From the viewpoint of suppressing, magnesium chloride is preferable.

  The pH in the magnesium reaction step is not particularly limited as long as it is an alkaline condition. For example, the pH is in the range of 10 to 12, preferably in the range of 10.5 to 11.5, and preferably in the range of 11 to 11.5. The range is more preferable. If the pH in the magnesium reaction step is less than 10 or more than 12, the silica removal rate may be low.

  As the pH adjuster, an alkali such as sodium hydroxide or calcium hydroxide may be used, and if necessary, an inorganic acid such as hydrochloric acid or sulfuric acid may be used.

  The temperature in the magnesium reaction step is not particularly limited as long as it is a temperature at which the insolubilization reaction of silica proceeds, but is, for example, in the range of 1 ° C to less than 50 ° C, and in the range of 10 ° C to less than 50 ° C. Is more preferable. If the temperature in the magnesium reaction step is lower than 1 ° C, the insolubilization reaction of silica may be insufficient, and if it is 50 ° C or higher, the treatment cost may be high.

  The reaction time in the magnesium reaction step is not particularly limited as long as the insolubilization reaction of silica can proceed, but is, for example, in the range of 1 minute to 60 minutes, and more preferably in the range of 5 minutes to 30 minutes. preferable. If the reaction time in the magnesium reaction step is less than 1 minute, the insolubilization reaction of silica may be insufficient, and if it exceeds 60 minutes, the reaction tank may be too large.

  The amount of magnesium salt added is preferably in the range of 0.1 to 10 times, and more preferably in the range of 0.5 to 5 times the magnesium concentration with respect to the weight concentration of silica in the water to be treated. More preferable. If the amount of magnesium salt added is less than 0.1 times the weight concentration of silica in the water to be treated, the insolubilization reaction of silica may be insufficient, and if it exceeds 10 times the amount of sludge generated. May become excessive.

  In addition to magnesium salts, aluminum salts such as polyaluminum chloride (PAC) and aluminum sulfate, iron salts such as ferric chloride and ferric sulfate, and the like may be used to insolubilize soluble silica. From the viewpoint of silica removal rate and the like, it is preferable to use a magnesium salt.

  In the aggregating treatment step, for example, in the aggregating tank, the inorganic aggregating agent is added to the water to be treated after the magnesium reaction to aggregate the insoluble matter (aggregating step). Then, in a floc forming tank, a polymer flocculant is added to form flocs (floc forming step).

  Examples of the inorganic flocculant used in the flocculation step include iron-based inorganic flocculants such as iron chloride and aluminum-based inorganic flocculants such as polyaluminum chloride (PAC). Iron-based inorganic flocculants are preferred.

  The addition amount of the inorganic coagulant is preferably in the range of 0.1 to 10 times by weight, and more preferably in the range of 1 to 5 times by weight of the added magnesium salt. If the amount of the inorganic coagulant added is less than 0.1 times by weight the amount of the added magnesium salt, coagulation may be insufficient, and if it exceeds 10 times, the amount of sludge generated may increase. It may be excessive.

  The pH in the aggregating step is, for example, in the range of 3-11. If the pH in the aggregating step is less than 3 or more than 11, poor aggregation may occur. Further, when the pH in the aggregating step is less than 9, silica may be dissolved out from the flocs, so it is desirable to perform the aggregating step in the pH range of 9 to 11.

  The temperature in the aggregation step is, for example, in the range of 1 ° C to 80 ° C. If the temperature in the aggregation step is lower than 1 ° C or higher than 80 ° C, poor aggregation may occur.

  Examples of the polymer flocculant used in the floc forming step include cationic polymer flocculants such as polyacrylamide-based and polyacrylic acid ester-based, anionic polymer flocculants, nonionic polymer flocculants, and the like. Anionic polymer flocculants are preferred from the standpoint of properties and the like.

  Examples of commercially available polymer flocculants include anionic polymer flocculants such as Orfloc OA-3H (manufactured by Organo Corporation).

  The addition amount of the polymer flocculant is preferably in the range of 0.1 to 10 mg / L, and more preferably in the range of 1 to 5 mg / L with respect to the amount of raw water. If the addition amount of the polymer flocculant is less than 0.1 mg / L with respect to the amount of raw water, floc formation may not be improved, and if it exceeds 10 mg / L, the polymer flocculant dissolved in the treated water may be dissolved. It may remain.

  The pH in the floc forming step is, for example, in the range of 3-11. If the pH in the floc formation step is less than 3 or more than 11, poor aggregation may occur. Further, when the pH in the floc process is less than 9, silica may be dissolved from the floc, so it is desirable to perform the floc forming process in the pH range of 9 to 11.

  The temperature in the floc forming step is, for example, in the range of 1 ° C to 80 ° C. If the temperature in the floc forming step is lower than 1 ° C or higher than 80 ° C, poor cohesion may occur.

  In the above-mentioned aggregating treatment, the inorganic aggregating agent and the polymer aggregating agent are used as the aggregating step and the floc forming step, but at least one of an inorganic aggregating agent, a polymer aggregating agent and the like may be used. It is preferable to use at least one of an aggregating agent and an anionic polymer aggregating agent. At the time of aggregating the insolubilized silica by reacting with the magnesium salt, by using at least one of the iron-based inorganic aggregating agent and the anionic polymer aggregating agent, the aggregating property and the solid-liquid separation property are improved.

  In the solid-liquid separation step, for example, floc-formed aggregates are solid-liquid separated in a settling tank (solid-liquid separation step). The pretreated water obtained by the solid-liquid separation is sent to the reverse osmosis membrane treatment device 28 or the reverse osmosis membrane treatment device 28 through the turbidity removal device 26. On the other hand, sludge is discharged through a sludge pipe. The sludge may be collected and reused.

  As the solid-liquid separation in the solid-liquid separation step, in addition to sedimentation separation by natural sedimentation, pressure floating treatment, membrane filtration treatment and the like can be mentioned, and sedimentation separation is preferable from the viewpoint of separability and the like.

[Pretreatment process: Hardening component removal by lime softening method]
When the water to be treated contains a hardness component, the hardness component may be removed by the lime softening method. Hardness components are classified into primary hardness and permanent hardness. The primary hardness is removed by an alkaline agent such as sodium hydroxide (NaOH), and the permanent hardness is removed by addition of a carbonate such as sodium carbonate (NaCO ₃ ). In the present specification, carbonate is also described as an alkaline agent for convenience. That is, in the pretreatment step, the alkaline agent is added to the water to be treated to insolubilize the hardness component (alkali agent reaction step).

Examples of the alkaline agent used include calcium hydroxide (Ca (OH) ₂ ), sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydrogen carbonate (Ca (HCO ₃ ) ₂ ), magnesium hydrogen carbonate ( Mg (HCO ₃ ) ₂ ), sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), and the like can be given, and one or more of these can be used. That is, it is possible to add sodium hydroxide and sodium carbonate, respectively, if necessary. Sodium carbonate is preferable from the viewpoint of insolubilization efficiency and the like.

  The pH in the alkaline agent reaction step is not particularly limited as long as it is an alkaline condition. For example, the pH is in the range of 9 to 13, and preferably 11 to 12. If the pH in the alkaline agent reaction step is less than 9, the hardness component removal rate may be low, and if it exceeds 13, the amount of the alkaline agent added may increase.

  The temperature in the alkaline agent reaction step may be a temperature at which the insolubilization reaction of the hardness component proceeds, and is not particularly limited, but is in the range of 1 ° C to 80 ° C, for example. If the temperature in the alkaline agent reaction step is less than 1 ° C, the insolubilization reaction of the hardness component may be insufficient, and if it exceeds 80 ° C, the heat resistant temperature of the equipment may become a problem.

  The reaction time in the alkaline agent reaction step is not particularly limited as long as the insolubilization reaction of the hardness component can proceed, and is, for example, 10 minutes to 30 minutes. If the reaction time in the alkaline agent reaction step is less than 10 minutes, the insolubilization reaction of the hardness component may be insufficient, and if it exceeds 30 minutes, the reaction tank may be large and the equipment cost may be high.

  The addition amount of the alkaline agent is preferably in the range of 1.0 to 2.0 times, and in the range of 1.0 to 1.2 times the molar concentration of the hardness component in the water to be treated. Is more preferable. If the addition amount of the alkaline agent is less than 1.0 times the molar concentration of the hardness component in the water to be treated, the insolubilization reaction of the hardness component may be insufficient, and if it exceeds 2.0 times the amount. However, the cost of medicine may increase.

  The subsequent aggregation treatment step and solid-liquid separation step are the same as the above-mentioned pretreatment step (silica removal by magnesium salt). The pretreated water obtained by the solid-liquid separation is sent to the reverse osmosis membrane treatment device 28 or the reverse osmosis membrane treatment device 28 through the turbidity removal device 26.

[Pretreatment process: Hardening component removal by resin softening method]
In the pretreatment process by the resin softening method when the water to be treated contains a hardness component, for example, the water to be treated is passed through an ion exchange column filled with an ion exchange resin to remove the hardness component by adsorption (ion exchange). Process). The pretreated water obtained by the ion exchange treatment is sent to the reverse osmosis membrane treatment device 28 or the reverse osmosis membrane treatment device 28 through the turbidity removal device 26.

  The ion exchange resin used in the ion exchange step is a cation exchange resin, and examples thereof include Amberrex 100Na and IRC-76 (manufactured by Organo Corporation).

  When it becomes necessary to regenerate the ion exchange resin, the regenerant is passed to regenerate the ion exchange resin.

  Examples of the regenerant to be used include aqueous acid solutions of hydrochloric acid, sulfuric acid, nitric acid and the like, aqueous sodium chloride solution, aqueous potassium chloride solution, and one or more of these can be used. That is, it is possible to regenerate with an aqueous acid solution and then regenerate with an aqueous solution of sodium chloride if necessary. From the viewpoint of reuse of the attractant solution, an aqueous acid solution and an aqueous sodium chloride solution are preferable. When regenerated with an aqueous acid solution, the ion exchange resin is in the H form, and when regenerated with an aqueous sodium chloride solution, the ion exchange resin is in the Na form.

[Reverse osmosis membrane treatment process]
As a reverse osmosis membrane used in a reverse osmosis membrane treatment step, it can be suitably applied to a polyamide-based polymer membrane which has been mainstream these days. The polyamide-based polymer film has a relatively low resistance to an oxidizing agent, and when free chlorine or the like is continuously brought into contact with the polyamide-based polymer film, the film performance is significantly deteriorated. However, in the water treatment method according to the present embodiment, by using the sterilizing agent for a normal osmosis membrane, since the bactericidal active ingredient hardly permeates the normal osmosis membrane, even in a polyamide polymer membrane, such a remarkable membrane performance Is almost never reduced.

  The reverse osmosis membrane treatment may use a plurality of reverse osmosis membrane treatments in series or in parallel. The concentrated water obtained by the first reverse osmosis membrane treatment may be further concentrated by the second and third reverse osmosis membrane treatments, and the permeated water obtained by the first reverse osmosis membrane treatment may be subjected to another reverse osmosis. By performing the membrane treatment, the water quality can be further improved.

  Reverse osmosis membranes used in reverse osmosis membrane treatment process include ultra-low pressure reverse osmosis membranes and low pressure reverse osmosis membranes used for pure water production and wastewater recovery, as well as seawater desalination. The medium-pressure reverse osmosis membrane, the high-pressure reverse osmosis membrane, etc. used are mentioned. Examples of the ultra low pressure reverse osmosis membrane and the low pressure reverse osmosis membrane include ES15 (manufactured by Nitto Denko), TM720D (manufactured by Toray), BW30HRLE (manufactured by Dow Chemical), and LFC3-LD (manufactured by Hydronautics). Examples of the high-pressure reverse osmosis membrane include SWC5-LD (manufactured by Hydronautics), TM820V (manufactured by Toray), and XUS180808 (manufactured by Dow Chemical). When the reverse osmosis membrane step is used in multiple stages, different types of membranes can be selected according to the conditions such as TDS, pH, and water temperature of the water to be treated in each stage.

  In the concentration treatment step, chemicals such as a pH adjuster, a scale dispersant that suppresses scaling of the inorganic salt in the system, and a bactericide that suppresses microbial generation in the system may be added.

<Fungicide for forward osmosis membrane>
The disinfectant for a forward osmosis membrane according to the present embodiment is a stabilized hypobromite composition or stabilized hypochlorous acid containing a mixture of a "bromine-based oxidizer or chlorine-based oxidizer" and a "sulfamic acid compound". It contains a composition and may further contain an alkali.

  Further, the sterilizing agent for a forward osmosis membrane according to the present embodiment is a stabilized hypobromite composition containing a "reaction product of a bromine-based oxidizing agent and a sulfamic acid compound", or "a chlorine-based oxidizing agent and a sulfamic acid. It contains a stabilized hypochlorous acid composition containing a "reaction product with a compound", and may further contain an alkali.

  The bromine-based oxidizing agent, bromine compound, chlorine-based oxidizing agent, and sulfamic acid compound are as described above.

  As a commercially available product of the stabilized hypochlorous acid composition containing a chlorine-based oxidizing agent and a sulfamic acid compound, for example, "Clivater IK-110" manufactured by Kurita Water Industries Ltd. may be mentioned.

  As the sterilizing agent for a forward osmosis membrane according to the present embodiment, in order not to further deteriorate the forward osmosis membrane, one containing bromine and a sulfamic acid compound (one containing a mixture of bromine and a sulfamic acid compound), for example, A mixture of bromine, a sulfamic acid compound, an alkali and water, or one containing a reaction product of a bromine and a sulfamic acid compound, for example, a reaction product of a bromine and a sulfamic acid compound, an alkali and water. Mixtures are preferred.

  Among the normal osmosis membrane bactericides according to the present embodiment, a bactericide containing a stabilized hypobromite composition containing a brominated oxidant and a sulfamic acid compound, particularly a stabilizer containing bromine and a sulfamic acid compound. The bactericide containing the hypobromous acid composition has a high oxidizing power, a slime suppressing power, and a remarkable slime peeling power as compared with a bactericide containing a chlorine-based oxidizer and a sulfamic acid compound (chlorosulfamic acid etc.). Despite its high price, it hardly causes significant film deterioration like hypochlorous acid, which also has a high oxidizing power. At normal use concentrations, the effect on film degradation can be substantially ignored. Therefore, it is optimal as a bactericide.

  Unlike the disinfectant such as hypochlorous acid, the disinfectant for a normal osmosis membrane according to the present embodiment hardly permeates the normal osmosis membrane, and therefore has almost no effect on the diluted attractant solution. Further, since the concentration can be measured on site like hypochlorous acid and the like, more accurate concentration control is possible.

  The pH of the germicide for forward osmosis membrane is, for example, more than 13.0, and more preferably more than 13.2. If the pH of the normal osmosis membrane bactericide is 13.0 or less, the effective halogen in the normal osmosis membrane bactericide may become unstable.

  The bromic acid concentration in the germicide for forward osmosis membrane is preferably less than 5 mg / kg. When the bromic acid concentration in the germicide for forward osmosis membrane is 5 mg / kg or more, the concentration of bromate ion in the diluted attractant solution may be high.

<Method for producing sterilizing agent for forward osmosis membrane>
The osmotic agent for a forward osmosis membrane according to the present embodiment is obtained by mixing a bromine-based oxidant or a chlorine-based oxidizer with a sulfamic acid compound, and may be further mixed with an alkali.

  As a method for producing a sterilizing agent for a forward osmosis membrane containing a stabilized hypobromite composition containing bromine and a sulfamic acid compound, bromine is mixed with an inert gas atmosphere in a mixed solution containing water, an alkali and a sulfamic acid compound. It is preferable to include a step of adding and reacting below, or a step of adding bromine to a mixed solution containing water, an alkali and a sulfamic acid compound under an inert gas atmosphere. By adding and reacting in an inert gas atmosphere, or by adding in an inert gas atmosphere, the bromate ion concentration in the normal osmosis membrane bactericide becomes low, and the bromate ion concentration in the diluted attractant solution becomes low. Will be lower.

  The inert gas to be used is not limited, but at least one of nitrogen and argon is preferable from the viewpoint of manufacturing, etc., and nitrogen is particularly preferable from the viewpoint of manufacturing cost.

  The oxygen concentration in the reactor upon addition of bromine is preferably 6% or less, more preferably 4% or less, further preferably 2% or less, particularly preferably 1% or less. If the oxygen concentration in the reactor during the bromine reaction exceeds 6%, the amount of bromic acid produced in the reaction system may increase.

  The addition rate of bromine is preferably 25% by weight or less, and more preferably 1% by weight or more and 20% by weight or less, based on the total amount of the sterilizing agent for normal osmosis membrane. When the addition rate of bromine exceeds 25% by weight with respect to the total amount of the sterilizing agent for normal osmosis membranes, the production amount of bromic acid in the reaction system may increase. If it is less than 1% by weight, the bactericidal activity may be poor.

  The reaction temperature at the time of bromine addition is preferably controlled in the range of 0 ° C. or higher and 25 ° C. or lower, but more preferably controlled in the range of 0 ° C. or higher and 15 ° C. or lower in terms of production cost and the like. If the reaction temperature at the time of bromine addition exceeds 25 ° C, the production amount of bromic acid in the reaction system may increase, and if it is less than 0 ° C, it may freeze.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Preparation of Stabilized Hypobromous Acid Composition (Composition 1)]
Under a nitrogen atmosphere, liquid bromine: 16.9 wt% (wt%), sulfamic acid: 10.7 wt%, sodium hydroxide: 12.9 wt%, potassium hydroxide: 3.94 wt%, water: balance The components were mixed to prepare a stabilized hypobromite composition (composition 1). The stabilized hypobromite composition had a pH of 14 and a total chlorine concentration of 7.5% by weight. The total chlorine concentration is a value (mg / LasCl ₂ ) measured by a total chlorine measuring method (DPD (diethyl-p-phenylenediamine) method) using a multi-item water quality analyzer DR / 4000 manufactured by HACH. The detailed preparation method of the stabilized hypobromite composition is as follows.

  1436 g of water and 361 g of sodium hydroxide were added to a 2 L four-necked flask sealed by continuous injection while controlling the flow rate of nitrogen gas with a mass flow controller so that the oxygen concentration in the reaction vessel was maintained at 1%. After mixing and then adding 300 g of sulfamic acid and mixing, 473 g of liquid bromine was added, and 230 g of 48% potassium hydroxide solution was further added while maintaining cooling so that the temperature of the reaction solution was 0 to 15 ° C. , 10.7% by weight of the total composition of sulfamic acid, 16.9% bromine, the equivalent ratio of sulfamic acid to the equivalent of bromine is 1.04, the objective stabilized hypobromous acid composition ( A composition 1) was obtained. The pH of the resulting solution was 14 as measured by the glass electrode method. The bromine content of the resulting solution was 16.9% as measured by a method of converting bromine to iodine with potassium iodide and then performing redox titration with sodium thiosulfate, which was a theoretical content (16.9%). ) Was 100.0%. The oxygen concentration in the reaction vessel during the bromine reaction was measured using "Oxygen Monitor JKO-02 LJDII" manufactured by Zicoh Co., Ltd. The bromic acid concentration was less than 5 mg / kg.

The pH was measured under the following conditions.
Electrode type: Glass electrode pH meter: Toa DKK Co., IOL-30 type Electrode calibration: Kanto Chemical Co., Ltd. neutral phosphate pH (6.86) standard solution (second type), company boric acid Two-point calibration of salt pH (9.18) standard solution (type 2) was performed Measurement temperature: 25 ° C
Measured value: The value after the electrode is immersed in the measuring solution and stabilized is taken as the measured value, and the average value of three measurements

[Preparation of Stabilized Hypochlorous Acid Composition (Composition 2)]
12% aqueous sodium hypochlorite solution: 50% by weight, sulfamic acid: 12% by weight, sodium hydroxide: 8% by weight, water: balance to prepare a stabilized hypochlorous acid composition (composition 2) Was prepared. Composition 2 had a pH of 13.7 and a total chlorine concentration of 6.2% by weight.

<Example 1>
As the FO water to be treated, industrial wastewater concentrated to 8% by weight of total evaporation residue (TDS) was used, and the attracting solution was a 30% by weight MgCl ₂ aqueous solution, and the forward osmosis membrane treatment was carried out. The flow rate of the attractant solution was adjusted so that the flow rate of the FO concentrated water outlet was 50% of that of the FO treated water inlet (concentration ratio: 2). As the forward osmosis membrane (FO membrane), a cellulose acetate FO membrane (HPC3205, manufactured by Toyobo) was used. A stabilized hypobromite composition (composition 1) was added as a sterilizing agent for a forward osmosis membrane to FO treated water so that the total chlorine concentration was 1 ppm Cl at the FO treated water inlet. This operation was continued for a total of 200 hours, and the pressure loss (water flow differential pressure) between the FO treated water inlet and the FO concentrated water outlet of the forward osmosis membrane treatment apparatus and the rejection rate of the bactericide were evaluated. The water pressure difference immediately after the start of operation was 0.02 MPa. The results are shown in Table 1.
Rejection rate of bactericide [%] = (1- (dilute attractant solution flow rate x dilute attractant solution total chlorine concentration / FO treated water flow rate x FO treated water total chlorine concentration))

<Example 2>
In the FO treated water, a stabilized hypochlorous acid composition (composition 2; chlorosulfamic acid) was replaced with FO as a germicide for a forward osmosis membrane, instead of the stabilized hypobromite composition (composition 1). A forward osmosis membrane treatment was carried out in the same manner as in Example 1 except that the total chlorine concentration was 1 ppm Cl at the treated water inlet. The results are shown in Table 1.

<Comparative Example 1>
Instead of the stabilized hypobromite composition (composition 1) as a sterilizing agent for forward osmosis membranes in FO treated water, sodium hypochlorite, which is a chlorine-based sterilizing agent, is released at the FO treated water inlet. A forward osmosis membrane treatment was carried out in the same manner as in Example 1 except that the chlorine concentration was 1 ppm Cl. The results are shown in Table 1.

<Comparative example 2>
Instead of the stabilized hypobromite composition (composition 1) as a sterilizing agent for a forward osmosis membrane in FO treated water, 5-chloro-2-methyl-4-isothiazoline-3-as an organic sterilizing agent is used. The forward osmosis membrane treatment was carried out in the same manner as in Example 1 except that ON was added so that the TOC was 10 ppm at the FO treated water inlet. The results are shown in Table 1.

[result]
In Example 1, it was possible to suppress an increase in the water flow differential pressure of the forward osmosis membrane. Over 99% of the germicide was also blocked. The same tendency was observed in Example 2, but the water differential pressure slightly increased. In Comparative Examples 1 and 2, the water flow differential pressure was> 0.2 MPa, which exceeded the permissible water flow differential pressure (0.2 MPa) of the membrane. The bactericidal agent inhibition rate was also 85% or less, and leakage of the bactericidal active ingredient into the diluted attractant solution was confirmed.

  Thus, by using a stabilized hypobromous acid composition or a stabilized hypochlorous acid composition as a bactericide, the bactericide is suppressed from permeating the forward osmosis membrane, and the diluted attractant solution is reused. It turns out that is possible.

  1 forward osmosis membrane treatment system, 3 water treatment system, 10 forward osmosis membrane treatment device, 12 forward osmosis membrane, 14 FO treated water piping, 16 FO concentrated water piping, 18 attractant solution piping, 20 dilute attractant solution piping, 22 sterilization Agent addition pipe, 24 pretreatment device, 26 turbidity removal device, 28 reverse osmosis membrane treatment device, 30 treated water pipe, 32, 34 pipe, 36 RO permeated water pipe, 38 backwash drainage pipe.

Claims (8)

Water to be treated and an attractant solution having a higher concentration than the to-be-treated water are brought into contact with each other through a normal osmosis membrane, and include a normal osmosis membrane treatment step of obtaining concentrated water and a diluted attractant solution,
A forward osmosis membrane treatment method, characterized in that a bactericide containing a bromine-based oxidant or a chlorine-based oxidant and a sulfamic acid compound is present in the water to be treated. Water to be treated and an attractant solution having a higher concentration than the to-be-treated water are brought into contact with each other through a normal osmosis membrane, and include a normal osmosis membrane treatment step of obtaining concentrated water and a diluted attractant solution,
A forward osmosis membrane treatment method, characterized in that a bactericide containing a brominated oxidant and a sulfamic acid compound is present in the water to be treated. Water to be treated and an attractant solution having a higher concentration than the to-be-treated water are brought into contact with each other through a normal osmosis membrane, and include a normal osmosis membrane treatment step of obtaining concentrated water and a diluted attractant solution,
A forward osmosis membrane treatment method, characterized in that a bactericide containing bromine and a sulfamic acid compound is present in the water to be treated. A method for treating a normal osmosis membrane according to any one of claims 1 to 3,
In the preceding stage of the forward osmosis membrane treatment step, a pretreatment step and a reverse osmosis membrane treatment step are included.
The water treatment method, wherein the diluted attractant solution obtained in the forward osmosis membrane treatment step is used in the pretreatment step. The water to be treated and the attractant solution having a higher concentration than the water to be treated are brought into contact with each other through a normal osmosis membrane, and a normal osmosis membrane treatment means for obtaining a concentrated water and a diluted attractant solution is provided,
A forward osmosis membrane treatment system, wherein a bactericide containing a bromine-based oxidant or a chlorine-based oxidant and a sulfamic acid compound is present in the water to be treated. The water to be treated and the attractant solution having a higher concentration than the water to be treated are brought into contact with each other through a normal osmosis membrane, and a normal osmosis membrane treatment means for obtaining a concentrated water and a diluted attractant solution is provided,
A forward osmosis membrane treatment system, wherein a disinfectant containing a brominated oxidant and a sulfamic acid compound is present in the water to be treated. The water to be treated and the attractant solution having a higher concentration than the water to be treated are brought into contact with each other through a normal osmosis membrane, and a normal osmosis membrane treatment means for obtaining a concentrated water and a diluted attractant solution is provided,
A forward osmosis membrane treatment system, wherein a disinfectant containing bromine and a sulfamic acid compound is present in the water to be treated. A forward osmosis membrane treatment system according to any one of claims 5 to 7,
A pretreatment unit and a reverse osmosis membrane treatment unit are provided in the preceding stage of the normal osmosis membrane treatment unit,
The water treatment system, wherein the diluted attractant solution obtained by the forward osmosis membrane treatment means is used in the pretreatment means.

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