TW201730116A - Water treatment system and water treatment method using osmosis membrane - Google Patents

Abstract

The invention provides a water treatment system and water treatment method that can reduce the additive amount of fungicide in a water treatment using at least two stages of reverse osmosis membranes. In a water treatment system 1 using at least a first stage, namely, first reverse osmosis membrane device 12 and a second stage, namely, second reverse osmosis membrane device 14 that treats the permeate of the first reverse osmosis membrane device 12, for conducting at least two stages of reverse osmosis membrane treatments, the concentrated water of the second reverse osmosis membrane device 14 is circulated to the supplied water of the first reverse osmosis membrane device 12 for being used, and fungicide that forms a blocking rate over 70% at the reverse osmosis membrane is added to the supplied water of the second reverse osmosis membrane device 14.

Description

Water treatment system using reverse osmosis membrane and water treatment method

The present invention relates to a water treatment system and a water treatment method using a reverse osmosis membrane.

In the water treatment using a reverse osmosis membrane (RO membrane), the generation of mucus is often a problem, and it is currently treated with the addition of an organic bactericide or the addition of a chlorine-based bactericide and a bromine-based bactericide (for example, refer to a patent). Document 1, Patent Document 2). In order to improve the water quality of the reverse osmosis membrane, it is required that the bactericide is blocked by the reverse osmosis membrane.

Further, there is a case where the water treatment is carried out using a two-stage reverse osmosis membrane as in Patent Document 3. In the method of Patent Document 3, the reverse osmosis membrane of the first stage blocks most of the sterilizing agent, so in order to respond to the mucus of the reverse osmosis membrane of the second stage, it is necessary to add a sterilizing agent again, and the reverse osmosis membrane in the first stage. A chlorine-based bactericide is used, and an alkali bactericide is used for the reverse osmosis membrane of the second stage. However, there are two points of administration, and the amount of the sterilizing agent added tends to increase, so that the apparatus is complicated and the running cost is also increased. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] JP-A-2005-062889 (Patent Document 3) Japanese Patent No. 5050605

[Problems to be Solved by the Invention] An object of the present invention is to provide a water treatment system and a water treatment method which can reduce the amount of the sterilizing agent added in the water treatment using the reverse osmosis membrane of two or more stages. [Means for solving the problem]

The present invention relates to a water treatment system using a reverse osmosis membrane of two or more stages, comprising at least a reverse phase osmosis membrane device of the first stage and a second stage of reverse osmosis water of the reverse osmosis membrane apparatus of the first stage a permeable membrane device and a circulating member that circulates the concentrated water of the second-stage reverse osmosis membrane device in the feed water of the reverse osmosis membrane device of the first stage; and is added to the supply water of the reverse osmosis membrane of the second stage A bactericide having a barrier ratio of 70% or more to the reverse osmosis membrane.

In the above water treatment system, the above-mentioned sterilizing agent having a barrier ratio of 70% or more in the reverse osmosis membrane is preferably a hypobromous acid stabilizer composition, chloramine sulfonic acid, hypochlorous acid, hypobromous acid or thiazolone ( At least one of a compound of isothiazolone) and a halogenated cyanoacetamide compound.

In the water treatment system, it is preferable to provide a degassing membrane after the addition of the sterilizing agent having a barrier ratio of 70% or more to the reverse osmosis membrane to perform degassing of the supply water of the reverse osmosis membrane of the second stage.

In the water treatment system, the sterilizing agent having a barrier ratio of 70% or more in the reverse osmosis membrane is preferably an anionic sterilizing agent, and the reverse osmosis membrane device of the second stage is preferably provided with an anion charged membrane.

In the water treatment system described above, the reverse osmosis membrane device of the first stage is preferably provided with a neutral membrane.

Further, the present invention provides a water treatment method in which at least the reverse osmosis membrane of the first stage and the reverse osmosis membrane of the second stage of the reverse osmosis water of the reverse osmosis membrane of the first stage are used to carry out the reverse of two stages or more. a permeable membrane treatment which circulates the concentrated water of the reverse osmosis membrane of the second stage to the supply water of the reverse osmosis membrane of the first stage, and is added to the reverse osmosis membrane in the supply water of the reverse osmosis membrane of the second stage A bactericide with a rate of 70% or more.

In the water treatment method, the sterilizing agent having a blocking ratio of 70% or more in the reverse osmosis membrane is preferably a hypobromous acid stabilizer composition, chloramine sulfonic acid, hypochlorous acid, hypobromous acid or oxathiazolone compound. And at least one of the halogenated cyanoacetamide compounds.

In the water treatment method, after the addition of the sterilizing agent having a barrier ratio of the reverse osmosis membrane of 70% or more, it is preferable to use a degassing membrane to perform degassing of the supply water of the reverse osmosis membrane of the second stage.

In the water treatment method, the sterilizing agent having a barrier ratio of 70% or more to the reverse osmosis membrane is preferably an anionic sterilizing agent, and the reverse osmosis membrane of the second stage is preferably an anion charged membrane.

In the above water treatment method, the reverse osmosis membrane of the first stage is preferably a neutral membrane. [Effects of the Invention]

According to the present invention, it is possible to provide a water treatment system and a water treatment method which can reduce the amount of the sterilizing agent added in the water treatment using the reverse osmosis membrane of two or more stages.

The embodiments of the present invention will be described below. This embodiment is an example of the present invention, and the present invention is not limited to the embodiment.

<Water Treatment System and Water Treatment Method> A schematic configuration of an example of a water treatment system according to an embodiment of the present invention will be described with reference to Fig. 1 . The water treatment system 1 includes a first reverse osmosis membrane device 12 of the first stage and a second reverse osmosis membrane device 14 of the second stage. The water treatment system 1 may be provided with the raw water tank 10 in the front stage of the first reverse osmosis membrane device 12.

In the water treatment system 1 of Fig. 1, the pipe 16 is connected to the raw water inlet of the raw water tank 10, and the outlet of the raw water tank 10 is connected to the inlet of the first reverse osmosis membrane device 12 by a pipe 18. The reverse osmosis water outlet of the first reverse osmosis membrane device 12 is connected to the inlet of the second reverse osmosis membrane device 14 by a pipe 20, and the pipe 24 is connected to the reverse osmosis water outlet of the second reverse osmosis membrane device 14. The pipe 22 is connected to the concentrated water outlet of the first reverse osmosis membrane device 12, and the concentrated water outlet of the second reverse osmosis membrane device 14 and the concentrated water inlet of the raw water tank 10 are connected by a circulation pipe 26 as a circulation member. A pipe 28 to which a sterilizing agent is added as a sterilizing agent addition member is connected to the pipe 20.

The operation of the water treatment method and the water treatment system 1 of the present embodiment will be described.

The raw water to be treated is passed through the pipe 16 and stored in the raw water tank 10 as needed, and then transported to the first reverse osmosis membrane device 12 of the first stage through the pipe 18. The first reverse osmosis membrane treatment (first reverse osmosis membrane treatment step) is carried out in the first reverse osmosis membrane device 12. The first reverse osmosis water from the first reverse osmosis membrane device 12 is sent to the second reverse osmosis membrane device 14 of the second stage through the pipe 20, and the first concentrated water is discharged through the pipe 22.

In the second stage of the second reverse osmosis membrane device 14 of the second stage, for example, in the pipe 20, the pipe 28 to which the sterilizing agent is added is added to the reverse osmosis membrane in the supply water of the second reverse osmosis membrane device 14. A bactericide having a rate of 70% or more (biocide addition step). In the supply water of the first reverse osmosis membrane device 12 of the first stage, a sterilizing agent may be added or a sterilizing agent may not be added, but a sterilizing agent is preferably not added. The sterilizing agent is not added to the supply water of the first reverse osmosis membrane device 12 of the first stage, whereby the amount of the sterilizing agent added can be further reduced.

The second reverse osmosis membrane treatment (second reverse osmosis membrane treatment step) is carried out in the second reverse osmosis membrane device 14. The second reverse osmosis water from the second reverse osmosis membrane device 14 is discharged as treated water through the pipe 24, and the second concentrated water is circulated through the circulation pipe 26 to the supply water of the first reverse osmosis membrane device 12 of the first stage, for example Cycle to the original water tank 10 (cycle step). In the circulation step, the second concentrated water may be circulated to the pipe 16, the pipe 18, and the like.

The sterilizing agent added to the feed water in the second reverse osmosis membrane device 14 has a blocking ratio of 70% or more in the reverse osmosis membrane, so that most of the sterilizing agent is blocked by the second-stage reverse osmosis membrane and remains in the second Concentrated in water. The second concentrated water derived from the second reverse osmosis membrane device 14 is caused to circulate the second concentrated water of the second reverse osmosis membrane device 14 of the second stage in the water flow before the first reverse osmosis membrane device 12 of the first stage. The sterilizing agent is mixed in the supply water (raw water) of the first reverse osmosis membrane device 12. Thereby, in the water treatment using the reverse osmosis membrane of two or more stages, the addition amount of the bactericide can be reduced.

Further, although the two-stage reverse osmosis membrane is used in the example of Fig. 1, the present invention is not limited thereto, and the second stage is reversed by the water treatment method and the water treatment system using the reverse osmosis membrane of two or more stages. The concentrated water of the permeable membrane is circulated in the supply water of the reverse osmosis membrane of the first stage, and is added to the reverse osmosis membrane in the feed water of the second stage, and the sterilizing agent having a barrier ratio of 70% or more added to the reverse osmosis membrane can reduce sterilization. The amount of the agent added.

A typical organic bactericide, that is, an oxathiazolone compound, is passed through a reverse osmosis membrane, and the second concentrated water of the second reverse osmosis membrane device 14 is circulated before the first reverse osmosis membrane device 12 The amount of water flowing in the previous stage of the first reverse osmosis membrane device 12 is still small. Therefore, it is preferable to use more than 90% of the bactericide which is blocked by the reverse osmosis membrane, and it is more preferable that 99% or more of the sterilizing agent which is blocked by the reverse osmosis membrane.

In the second reverse osmosis membrane device 14 to which the sterilizing agent has just been added, since the sterilizing agent component is preferably circulated in a large amount, it is preferable to use an anion-based reverse osmosis membrane (anionic charged membrane) having a high sterilizing agent. On the other hand, in the first reverse osmosis membrane device 12 upstream of the sterilizing agent addition point, since the sterilizing agent component remains in the latter stage due to the neutral membrane having a low steric agent rejection rate, the sterilizing agent injection amount in the latter stage is further increased. cut back.

As shown in Fig. 2, between the first reverse osmosis membrane device 12 of the first stage and the second reverse osmosis membrane device 14 of the second stage, there is a unit operation of biological contamination (for example, for carbon dioxide, etc.) The degassing film 30) to be degassed can suppress the biological contamination of the operation of the unit by adding a sterilizing agent between the first reverse osmosis membrane device 12 and the degassing membrane 30 in the first stage. In other words, the degassing membrane 30 for degassing the supply water for performing the second reverse osmosis membrane device 14 of the second stage is provided with a biocide having a barrier ratio of 70% or more added to the reverse osmosis membrane. In the subsequent stage, biological contamination of the degassing film 30 or the like can be suppressed.

The reverse osmosis membrane used in the first reverse osmosis membrane device 12 and the second reverse osmosis membrane device 14 is used as a mainstream, and a neutral membrane, an anion charged membrane, and Cationic charged film. The neutral film means a range of -15 to 5 (mV) at a pH of 7.0, which is obtained by a zeta potential measurement method described in the examples below, and an anion charged film means at pH 7. The dynamic potential of .0 is less than -15 (mV). The reverse osmosis membrane of the first reverse osmosis membrane device 12 may be a cellulose acetate-based polymer membrane, and the reverse osmosis membrane of the second reverse osmosis membrane device 14 may be a polyamine-based polymer membrane. In this case, a sterilizing agent such as hypochlorous acid may be added to the supply water of the first reverse osmosis membrane device 12 of the first stage, and the barrier ratio of the reverse osmosis membrane may be added to the supply water of the second reverse osmosis membrane device 14 . More than 70% of fungicides.

Examples of the commercially available intermediate film include: OFR-625 (manufactured by Aojia Jinan Co., Ltd.), BW30XFR (manufactured by The Dow Chemical Co., Ltd.), LFC3 (manufactured by Nitto Denko Corporation), and TML20 (Dongli Co., Ltd.) Company system) and so on.

Examples of the commercially available anion charged film include ES15, ES20, CPA3 (above, manufactured by Nitto Denko Corporation), RE-8040BLN (manufactured by Woongjin Co., Ltd.), and the like.

In the water treatment method and the water treatment system according to the embodiment of the present invention, the first reverse osmosis membrane device 12 of the first stage includes a neutral membrane, and the second reverse osmosis membrane device 14 of the second stage has an anion charged membrane. When the sterilizing agent having a barrier ratio of 70% or more in the reverse osmosis membrane is an anionic bactericide, the anionic sterilizing agent is more likely to be blocked in the second reverse osmosis membrane device 14 (anionic charged membrane) in the second stage. Therefore, it is easy to circulate in the first reverse osmosis membrane device 12 (neutral membrane) of the first stage. Further, the anionic fungicide easily passes through the first reverse osmosis membrane device 12 of the first stage, and the sterilizing agent component remains in the supply water of the second reverse osmosis membrane device 14 of the second stage, thereby further reducing the sterilizing agent. The amount injected.

The water to be treated (raw water) may, for example, be an electronic industrial drain such as an alcohol-containing water containing an alcohol such as methanol, ethanol or isopropyl alcohol. Since the electronic industry drainage such as alcohol-containing water has a high risk of generating mucus, the water treatment method and the water treatment system according to the present embodiment can be suitably used in the desalination step of the electronic industry drainage.

Examples of the bactericidal agent having a barrier ratio of 70% or more to the reverse osmosis membrane include an anionic bactericide such as a hypobromous acid stabilized composition, chloramine sulfonic acid, hypochlorous acid, or hypobromous acid; and 5-chloro a thiazolone compound such as 2-methyl-4-isothiazolin-3-one or 2-methyl-4-isothiazolin-3-one; 2,2-dibromo-3-nitropropyl A neutral bactericide such as a halogenated cyanoacetamide compound such as guanamine or the like, preferably a hypobromous acid stabilized composition having a blocking ratio of 80% or more in a reverse osmosis membrane, chloramine sulfonic acid, thiazolone The compound or the halogenated cyanoacetamide compound has a blocking ratio of 90% or more, particularly 99% or more, of the hypobromous acid stability composition, chloramine sulfonic acid and halogenated cyanoacetamide compound in the reverse osmosis membrane. At least one of them is better. In addition, in the present specification, the blocking ratio of the reverse osmosis membrane means that an anion charged film "ES15" (an aromatic polyamine-based anion charged film, manufactured by Nitto Denko Corporation) is used as a reverse osmosis membrane as described later in the examples. Barrier rate.

The halocylidene compound is, for example, a compound represented by the following formula. 【化1】 In the above formula, X ₁ and X ₂ each independently represent a halogen atom or a hydrogen atom such as F, Cl, Br or I, and R ₁ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

<Hybromobromic acid stabilized composition> The hypobromous acid stabilized composition contains a "bromine oxidizing agent" and an "amine sulfonic acid compound", and may also contain a base.

Further, the hypobromous acid stabilized composition contains "a reaction product of a bromine-based oxidizing agent and an aminesulfonic acid compound", and may contain a base.

The ratio of the equivalent of the "amine sulfonic acid compound" to the equivalent of the "bromine oxidizing agent" is preferably 1 or more, and more preferably 1 or more and 2 or less. When the ratio of the equivalent of the "amine sulfonic acid compound" to the equivalent of the "bromine oxidizing agent" is less than 1, the reverse osmosis membrane may be deteriorated. If it exceeds 2, the production cost may increase.

Examples of the bromine-based oxidizing agent include bromine (liquid bromine), bromine chloride, bromic acid, bromate, and hypobromous acid. Further, the "bromine compound and a chlorine-based oxidizing agent" obtained by reacting a bromine compound with a chlorine-based oxidizing agent such as hypochlorite is also included in the "bromine-based oxidizing agent".

Among these, the preparation of "bromine and aminesulfonic acid compound (mixture of bromine and aminesulfonic acid compound)" or "reaction product of bromine and aminesulfonic acid compound" is compared with "hypochlorous acid and bromine compound". In the preparation of the "amine sulfonic acid" and the preparation of "bromine chloride and amine sulfonic acid", since the former has less chloride ions, the reverse osmosis membrane is not further deteriorated, and the possibility of corrosion of metal materials such as pipes is low. Therefore, it is better.

Examples of the bromine compound include sodium bromide, potassium bromide, lithium bromide, ammonium bromide, and hydrobromic acid. Among these, from the viewpoint of the cost of the preparation and the like, sodium bromide is preferred.

Examples of the chlorine-based oxidizing agent 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, and isocyanuric acid chloride or Salt and so on. Among these, examples of the salt form include alkali metal hypochlorites such as sodium hypochlorite and potassium hypochlorite; and alkali metal hypochlorites such as calcium hypochlorite and barium hypochlorite; sodium chlorite and sub An alkali metal chlorite such as potassium chlorate; an alkaline earth metal salt of chlorite such as bismuth chlorite; other metal chlorite such as nickel chlorite; chloric acid such as ammonium chlorate, sodium chlorate or potassium chlorate An alkali metal salt; an alkaline earth metal salt of chloric acid such as calcium chlorate or barium chlorate. These chlorine-based oxidizing agents may be used alone or in combination of two or more. As for the chlorine-based oxidizing agent, sodium hypochlorite is preferably used in view of operability and the like.

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

Examples of the amine sulfonic acid compound include, for example, an aminesulfonic acid (sulfonamide) in which both of the two R groups are hydrogen atoms, and N-methylaminesulfonic acid and N-ethyl are also exemplified. One of the two R groups of aminesulfonic acid, N-propylaminesulfonic acid, N-isopropylaminesulfonic acid, N-butylaminesulfonic acid, etc. is a hydrogen atom, and the other is a carbon number of 1-8. Alkyl amine sulfonic acid compound; N,N-dimethylamine sulfonic acid, N,N-diethylamine sulfonic acid, N,N-dipropylamine sulfonic acid, N,N-dibutylamine Two of the R groups such as sulfonic acid, N-methyl-N-ethylamine sulfonic acid, and N-methyl-N-propylamine sulfonic acid are amine sulfonic acids having an alkyl group of 1 to 8 carbon atoms. The compound; one of the two R groups of N-phenylamine sulfonic acid or the like is a hydrogen atom, and the other is an aminesulfonic acid compound having an aryl group having 6 to 10 carbon atoms, or the like. Examples of the amine sulfonate include an alkali metal salt such as a sodium salt or a potassium salt; an alkaline earth metal salt such as a calcium salt, a barium salt or a barium salt; a manganese salt, a copper salt, a zinc salt, an iron salt, a cobalt salt, and a nickel. Other metal salts such as salt; ammonium salts and barium salts. The amine sulfonic acid compound and the salt may be used singly or in combination of two or more kinds. As the amine sulfonic acid compound, an aminesulfonic acid (sulfonic acid) is preferably used from the viewpoint of environmental load and the like.

Examples of the base include a hydroxide base such as sodium hydroxide or potassium hydroxide. From the viewpoint of product stability at a low temperature, etc., it is also possible to use sodium hydroxide and potassium hydroxide in combination. Further, the base may be used in the form of an aqueous solution without using a solid.

In the case of the hypobromous acid stabilized composition, since the polyamine-based reverse osmosis membrane or the like is further deteriorated and the effective leakage of the halogen into the RO reverse osmosis water is less, it is preferable to contain bromine and an amine. a sulfonic acid compound (containing a mixture of bromine and amine sulfonic acid compounds), such as a mixture of a bromine and amine sulfonic acid compound with a base and water; or a reaction product containing a bromine and an amine sulfonic acid compound, such as bromine and amine sulfonic acid. A reaction product of the compound and a mixture of a base and water.

Although the hypobromous acid stabilized composition has a bactericidal effect, unlike the hypochlorous acid or the like, the film is deteriorated, and the hypobromous acid stabilized composition hardly causes the film to deteriorate. The effect on film degradation can be substantially ignored in general use concentrations. Therefore, it is most suitable as a bactericide.

Unlike the hypobromous acid stabilized composition and hypochlorous acid, the hypobromous acid stabilized composition hardly passes through the reverse osmosis membrane and the like, so that the treated water quality is hardly affected. Further, the concentration can be measured on site in the same manner as hypochlorous acid or the like, so that concentration management can be performed more accurately.

The pH of the hypobromous acid stabilized composition is, for example, more than 13.0, more preferably more than 13.2. When the pH of the composition is 13.0 or less, the effective halogen in the composition may become unstable.

The concentration of bromic acid in the stabilized composition of hypobromous acid is preferably less than 5 mg/kg. When the concentration of the bromic acid in the stabilized composition of the bromic acid is 5 mg/kg or more, the concentration of the bromate ion such as RO reverse osmosis water may increase.

<Method for Producing Hypobromide Stabilizing Composition> The hypobromous acid stabilized composition can be obtained by mixing a bromine-based oxidizing agent with an aminesulfonic acid compound, or a base can be mixed.

The method for producing a hypobromous acid stabilized composition containing a brominated or aminesulfonic acid compound or a reaction product containing a reaction product of bromine and an aminesulfonic acid compound preferably comprises the following steps: blunting the bromine It is added to a mixture containing water, a base and an aminesulfonic acid compound in a gaseous environment and reacted; or bromine is added to a mixed liquid containing water, a base and an aminesulfonic acid compound in a passive gas atmosphere. By adding and reacting in a passive gas atmosphere or adding it in a passive gas atmosphere, the concentration of bromate ions in the composition becomes low and the concentration of bromate ions in the reverse osmosis water or the like becomes low.

The passive gas to be used is not limited, and it is preferably at least one of nitrogen gas and argon gas in consideration of production and the like, and in particular, nitrogen gas is preferable in terms of production cost and the like.

When the bromine is added, the oxygen concentration in the reactor is preferably 6% or less, more preferably 4% or less, still more preferably 2% or less, and particularly preferably 1% or less. When the oxygen concentration in the reactor at the time of bromine reaction exceeds 6%, the amount of bromic acid generated in the reaction system may increase.

The addition ratio of bromine is preferably 25% by weight or less based on the total amount of the composition, and more preferably 1% by weight or more and 20% by weight or less. When the addition ratio of bromine exceeds 25% by weight based on the total amount of the composition, the amount of bromic acid generated in the reaction system may increase. If it is less than 1% by weight, the modification effect may be poor.

The reaction temperature at the time of adding bromine is preferably controlled within a range of from 0 ° C to 25 ° C, and it is more preferable to control the production cost in the range of from 0 ° C to 15 ° C. When the reaction temperature at the time of adding bromine exceeds 25 ° C, the amount of bromic acid generated in the reaction system may increase, or if it does not reach 0 ° C, it may be frozen. [Examples]

Hereinafter, the present invention will be described in more detail by way of examples and comparative examples, but the invention is not limited by the following examples.

<Example 1 and Comparative Examples 1 and 2> Example 1 was carried out by using the water treatment system of Fig. 1 and Comparative Example 1 using the conventional water treatment system of Fig. 3. In the conventional water treatment system 5 of FIG. 3, the pipe 32 to which the sterilizing agent is added to the supply water of the first reverse osmosis membrane device 12 of the first stage is connected to the pipe 18. In the case where the sterilizing agent is added (administered) at one point (dosing point 2) from the pipe 28 to which the sterilizing agent is added as shown in Fig. 1, and the pipe 32 from which the sterilizing agent is added and the pipe 28 to which the sterilizing agent is added, as shown in Fig. 3 When the addition (dosing) of the sterilizing agent was carried out at two points (each of the dispensing points 1 and 2), the types of the sterilizing agent were changed as shown in Table 1, and the amount of the sterilizing agent (agent) added was compared. The bactericide is set to be 3 mg/L or more in front of the reverse osmosis membrane. As the reverse osmosis membrane of the first stage and the second stage, a reverse osmosis membrane "ES15" manufactured by Nitto Denko Corporation is used as an anion charged film. The amount of supplied water Q was set to 200 L/h of pure water, the recovery rate of the reverse osmosis membrane of the first stage was set to 50%, and the recovery rate of the reverse osmosis membrane of the second stage was set to 90%.

[Measurement of the dynamic potential of the reverse osmosis membrane] The potential of the reverse osmosis membrane was determined by the ELSZseries, a dynamic potential-particle size measurement system manufactured by Otsuka Electronics Co., Ltd. The electrokinetic map of the reverse osmosis membrane is calculated from the following equations of Mori Okamoto and Smoluchowski.

(Mori Okamoto's formula) U _obs (z)=AU ₀ (z/b) ² +ΔU ₀ (z/b)+(1-A)U ₀ +U _p here, z: from the center of the test cell Position distance U _obs (z): apparent mobility at the z position in the test cell A: 1/[(2/3)-(0.420166/K)] K=a/b: 2a and 2b test slots The transverse and longitudinal lengths of the profile, a>b U _p : the true mobility of the particles U ₀ : the average mobility ΔU ₀ on the top and bottom of the test slot: the difference in mobility between the top and bottom of the test slot (Smoluchowski算=4πηU/ε Here, U: electrical mobility ε: dielectric constant of solvent η: viscosity of solvent

A 10 mM aqueous NaCl solution (pH about 5.4) was used as a measuring solution. Prepare 2 pairs of the aqueous solution and sample for each sample, adjust the pH of one of them to be acidic (pH 2, 3, 4, 5, 6, 7), and adjust the pH of the other to alkaline (pH 8, 9) ), measuring the potential at each pH. The physical property value of the solvent was the value of pure water at 25 ° C (refractive index: 1.3328, viscosity: 0.8878, dielectric constant: 78.3).

[Evaluation of Barrier Rate of Fungicide in Reverse Osmosis Membrane] With respect to each of the sterilizing agents having the blending compositions shown in Table 1, the flat membrane test apparatus was used to evaluate the barrier ratio of the sterilizing agent to the reverse osmosis membrane under the following conditions.

(Test conditions) Test apparatus: flat membrane test apparatus (refer to Fig. 4) Flat membrane tank: Membrane master C70-F flow type flat membrane test tank Flat membrane type: anion charged membrane "ES15" (aromatic polyamine-based anion charged Membrane, low pressure RO membrane, manufactured by Nitto Denko Co., Ltd.) Flat membrane diameter: 75 mm in diameter Test water: Ultrapure water test water pH: 7.0 (adjusted with hydrochloric acid and sodium hydroxide after adding each of the following fungicides) Test water volume: 50L test water temperature: 25°C±1°C Supply pressure: 0.75MPa Test water volume: 5L/min Evaluation fungicide: Refer to Table 1 Biocide concentration: 3mg/L

(Test method) Each sterilizing agent was added to the test water, pH adjustment was performed, and the mixture was circulated for 30 minutes. Thereafter, each reverse osmosis water was sufficiently blown, and then raw water and reverse osmosis water were sampled, and the concentration of the sterilizing agent was measured to calculate the barrier. rate. The bactericide was added directly to the water tank to make it 3 mg/L.

The barrier ratio of each bactericide to the reverse osmosis membrane was determined by the following formula. The barrier ratio (%) of the reverse osmosis membrane = (concentration of the sterilizing agent supplied to the water - the concentration of the sterilizing agent of the reverse osmosis water) / (the concentration of the sterilizing agent supplied to the water) × 100

[Preparation of hypobromous acid stability composition] Liquid bromine was mixed under a nitrogen atmosphere: 16.9 wt% (wt%), aminesulfonic acid: 10.7 wt%, sodium hydroxide: 12.9 wt%, potassium hydroxide: 3.94 wt% The remaining part is water, and a hypobromous acid stability composition is obtained. The pH of the hypobromous acid stabilized composition was 14, and the effective halogen concentration (concentration in terms of available chlorine) was 7.5% by weight. The detailed preparation method of the hypobromous acid stability composition is as follows.

In order to maintain the oxygen concentration in the reaction vessel at 1%, the flow rate of nitrogen gas was controlled by a mass flow controller, and 1436 g of water and 361 g of sodium hydroxide were added by continuous infusion. The sealed 2 L four-necked flask was mixed, and after adding 300 g of the amine sulfonic acid and mixing, and maintaining the temperature of the reaction liquid at 0 to 15 ° C, 473 g of liquid bromine was added, and then added. 230 g of 48% potassium hydroxide solution, based on the weight ratio of the total amount of the composition, the aminesulfonic acid was 10.7%, the bromine was 16.9%, and the equivalent ratio of the aminesulfonic acid to the equivalent of bromine was 1.04, and the purpose was obtained. Hypobromide stabilizes the composition. The pH of the resulting solution was measured by the glass electrode method and was 14 at this point. The bromine content of the resulting solution was measured by a method in which bromine was converted into iodine by potassium iodide and then subjected to redox titration using sodium thiosulfate. At this point, it was 16.9%, which was 100.0% of the theoretical content (16.9%). In addition, the oxygen concentration in the reaction vessel at the time of the bromine reaction was measured using "Oxygen monitor JKO-02 LJDII" manufactured by JICO Co., Ltd. In addition, the concentration of bromic acid did not reach 5 mg/kg.

【Table 1】

[Example 1-1 and Comparative Example 1-1] In Example 1-1 and Comparative Example 1-1, a hypobromous acid stabilized composition (anionic) was added as a bactericidal agent. At this time, the blocking ratio (RO blocking ratio) of the hypobromous acid stabilizer composition to the reverse osmosis membrane was measured, and the point system was 99.1% at this time.

In Comparative Example 1-1, a sterilizing agent was added from the dosing point 1 at a sterilizing agent concentration C1, and a sterilizing agent was added from the dosing point 2 at a sterilizing agent concentration C2, so that the sterilizing agent concentrations C1 and C2 were both 3 mg/L. The amount of the bactericide added is X1 + X2 = 21.5 g / d. Then, in Example 1-1, the sterilizing agent was added from the dosing point 2 so that the sterilizing agent concentration C1 in the supply water of the first reverse osmosis membrane device 12 was 3 mg/L. At this point, the sterilizing agent addition amount X2 was 14.5. g/d, bactericide concentration C2 was 6.1 mg / L (> 3 mg / L). The amount of the bactericide added in Example 1-1 was reduced by 7.0 g/d as compared with Comparative Example 1-1. The results are shown in Table 2.

[Example 1-2 and Comparative Example 1-2] In Example 1-2 and Comparative Example 1-2, oxathiazolone (neutral) was added as a bactericide. KATHON (registered trademark) WT (manufactured by The Dow Chemical Co., Ltd.) which is a bactericide containing an thiazolone compound in the preparation is used. At this time, the barrier ratio of the thiazolone to the reverse osmosis membrane was measured, and the point system was 81.8% at this time.

In Comparative Example 1-2, a sterilizing agent was added from the dosing point 1 at a sterilizing agent concentration C1, and a sterilizing agent was added from the dosing point 2 at a sterilizing agent concentration C2, so that the sterilizing agent concentrations C1 and C2 were both 3 mg/L. The amount of the bactericide added is X1 + X2 = 20.3 g / d. Then, in Example 1-2, the sterilizing agent was added from the dosing point 2 so that the sterilizing agent concentration C1 in the supply water of the first reverse osmosis membrane device 12 was 3 mg/L. At this point, the sterilizing agent addition amount X2 was 16.1. Mg/L, bactericide concentration C2 is 7.3 mg / L (> 3 mg / L). The amount of the bactericide added in Example 1-2 was reduced by 4.2 g/d as compared with Comparative Example 1-2. The results are shown in Table 2.

[Example 1-3 and Comparative Example 1-3] Examples 1-3 and Comparative Example 1-3 were added with hypochlorous acid (anionic) as a bactericide. At this time, the blocking ratio of hypochlorous acid to the reverse osmosis membrane was measured, and at this point, the system was 71.0%.

In Comparative Example 1-3, a sterilizing agent was added from the dosing point 1 at a sterilizing agent concentration C1, and a sterilizing agent was added from the dosing point 2 at a sterilizing agent concentration C2, so that the sterilizing agent concentrations C1 and C2 were both 3 mg/L. The amount of the bactericide added was X1 + X2 = 19.5 g / d. Then, in Example 1-3, the sterilizing agent was added from the dosing point 2 so that the sterilizing agent concentration C1 in the supply water of the first reverse osmosis membrane device 12 was 3 mg/L. At this point, the sterilizing agent addition amount X2 was 17.8. g/d, bactericide concentration C2 is 8.3 mg / L (> 3 mg / L). The amount of the bactericide added in Examples 1-3 was reduced by 1.7 g/d as compared with Comparative Example 1-3. The results are shown in Table 2.

[Examples 1-4 and Comparative Examples 1-4] Examples 1-4 and Comparative Examples 1-4 used a halogenated cyanoacetamide compound as a bactericide. At this time, the blocking ratio of the halocylidene compound to the reverse osmosis membrane was measured, and at this point, the system was 97.0%.

In Comparative Example 1-4, a sterilizing agent was added from the dosing point 1 at a sterilizing agent concentration C1, and a sterilizing agent was added from the dosing point 2 at a sterilizing agent concentration C2 so that the sterilizing agent concentrations C1 and C2 were both 3 mg/L. The amount of the bactericide added was X1 + X2 = 21.4 g / d. Then, in Example 1-4, the sterilizing agent was added from the dosing point 2, and the sterilizing agent concentration C1 in the supply water of the first reverse osmosis membrane device 12 was 3 mg/L. At this point, the sterilizing agent addition amount X2 was 14.6. g/d, bactericide concentration C2 is 6.2 mg / L (> 3 mg / L). The amount of the bactericide added in Examples 1-4 was reduced by 6.8 g/d as compared with Comparative Examples 1-4. The results are shown in Table 2.

[Comparative Example 2-1 and Comparative Example 2-2] Comparative Example 2-1 and Comparative Example 2-2 were added with chloramine (anionic) as a bactericidal agent. At this time, the blocking ratio of chloramine to the reverse osmosis membrane was measured, and the point system was 10.2% at this time.

In Comparative Example 2-2, a sterilizing agent was added from the dosing point 1 at a sterilizing agent concentration C1, and a sterilizing agent was added from the dosing point 2 at a sterilizing agent concentration C2, so that the sterilizing agent concentrations C1 and C2 were both 3 mg/L. The amount of the bactericide added was X1 + X2 = 15.1 g / d. Then, in Comparative Example 2-1, the sterilizing agent was added from the dosing point 2, and the sterilizing agent concentration C1 in the supply water of the first reverse osmosis membrane device 12 was 3 mg/L. At this point, the sterilizing agent addition amount X2 was 91.5. g/d, the bactericide concentration C2 was 40.8 mg/L (>3 mg/L). The amount of the bactericide added in Comparative Example 2-1 was increased by 76.4 g/d as compared with Comparative Example 2-2. The results are shown in Table 2.

【Table 2】

<Example 2 and Comparative Example 3> Example 2 uses the water treatment system of Fig. 1, and Comparative Example 3 uses the conventional water treatment system of Fig. 3, and uses chloramine sulfonic acid (anionic) as a bactericide. test.

[Example 2-1 and Comparative Example 3-1] In Example 2-1 and Comparative Example 3-1, the reverse osmosis membrane "ES20" manufactured by Nitto Denko Corporation was used as the first stage and the second stage. Reverse osmosis membrane at the stage. At this time, the blocking ratio of chloramine sulfonic acid to the reverse osmosis membrane was measured, and the point system was 99.6% at this time.

In Comparative Example 3-1, a sterilizing agent was added from the dosing point 1 at a sterilizing agent concentration C1, and a sterilizing agent was added from the dosing point 2 at a sterilizing agent concentration C2, so that the sterilizing agent concentrations C1 and C2 were both 3 mg/L. The amount of the bactericide added was X1 + X2 = 21.6 g / d. Then, in Example 2-1, the sterilizing agent was added from the dosing point 2 so that the sterilizing agent concentration C1 in the supply water of the first reverse osmosis membrane device 12 was 3 mg/L. At this point, the sterilizing agent addition amount X2 was 14.4. g/d, bactericide concentration C2 is 6.0 mg / L (> 3 mg / L). The amount of the bactericide added in Example 2-1 was reduced by 7.2 g/d as compared with Comparative Example 3-1. The results are shown in Table 3.

[Example 2-2 and Comparative Example 3-2] In Example 2-2 and Comparative Example 3-2, the reverse osmosis membrane "ES20" manufactured by Nitto Denko Corporation was used as the reverse osmosis of the first stage. As the membrane, a neutral membrane, "LFC3" manufactured by Nitto Denko Corporation, was used as the second-stage reverse osmosis membrane. At this time, the barrier ratio of chloramine sulfonic acid to the reverse osmosis membrane was measured, and the point system was 97.9% at this time.

In Comparative Example 3-2, a sterilizing agent was added from the dosing point 1 at a sterilizing agent concentration C1, and a sterilizing agent was added from the dosing point 2 at a sterilizing agent concentration C2, so that the sterilizing agent concentrations C1 and C2 were both 3 mg/L. The amount of the bactericide added was X1 + X2 = 21.4 g / d. Then, in Example 2-2, the sterilizing agent was added from the dosing point 2, and the sterilizing agent concentration C1 in the supply water of the first reverse osmosis membrane device 12 was 3 mg/L. At this point, the sterilizing agent addition amount X2 was 14.5. g/d, bactericide concentration C2 was 6.1 mg / L (> 3 mg / L). The amount of the bactericide added in Example 2-2 was reduced by 6.9 g/d as compared with Comparative Example 3-2, and the decrease was smaller than that of Comparative Example 3-1 and Example 2-1. The results are shown in Table 3.

【table 3】

According to the above test, the amount of reduction of the sterilizing agent of the examples was large as compared with the comparative example.

By using the water treatment system and the water treatment method of the embodiment as described above, the amount of the sterilizing agent can be reduced in the water treatment using the reverse osmosis membrane of two or more stages.

1, 3, 5 ‧ ‧ water treatment system
10‧‧‧ original sink
12‧‧‧1st reverse osmosis membrane device
14‧‧‧Second reverse osmosis membrane device
16, 18, 20, 22, 24‧‧‧ piping
26‧‧‧Recycling piping
28, 32‧‧‧ Adding fungicide piping
30‧‧‧Degassing membrane

Fig. 1 is a schematic block diagram showing an example of a water treatment system according to an embodiment of the present invention. Fig. 2 is a schematic block diagram showing another example of a water treatment system according to an embodiment of the present invention. Fig. 3 is a schematic block diagram showing a conventional water treatment system. Fig. 4 is a schematic structural view showing a flat membrane test apparatus used for evaluating the barrier ratio of a reverse osmosis membrane in the examples.

no

Claims (10)

A water treatment system using a reverse osmosis membrane of two or more stages, characterized in that it comprises at least: a reverse osmosis membrane device of the first stage; a reverse osmosis membrane device of the second stage, and a reverse osmosis membrane device of the first stage a reverse osmosis water; and a circulation member, wherein the concentrated water of the reverse osmosis membrane device of the second stage is circulated in the feed water of the reverse osmosis membrane device of the first stage; and is added to the supply water of the reverse osmosis membrane of the second stage A bactericide having a barrier ratio of 70% or more to the reverse osmosis membrane. The water treatment system of claim 1, wherein the sterilizing agent having a barrier ratio of 70% or more in the reverse osmosis membrane is a hypobromous acid stabilized composition, chloramine sulfonic acid, hypochlorous acid, hypobromous acid. At least one of an thiathiazolone compound and a halogenated cyanoacetamide compound. The water treatment system according to claim 1 or 2, wherein after the addition of the sterilizing agent having a barrier ratio of 70% or more to the reverse osmosis membrane, a degassing membrane is provided, and the reverse osmosis of the second stage is performed. Degassing of the feed water of the membrane. The water treatment system according to claim 1 or 2, wherein the sterilizing agent having a barrier ratio of 70% or more in the reverse osmosis membrane is an anionic bactericide, and the second-stage reverse osmosis membrane device is provided with an anion charging. membrane. The water treatment system of claim 4, wherein the first stage reverse osmosis membrane device comprises a neutral membrane. A water treatment method for performing a reverse osmosis membrane treatment of two or more stages by using at least a reverse osmosis membrane of a first stage and a reverse osmosis membrane of a second stage of reverse osmosis water of the reverse osmosis membrane of the first stage; Therefore, the concentrated water of the reverse osmosis membrane of the second stage is recycled to the feed water of the reverse osmosis membrane of the first stage, and the barrier ratio of the reverse osmosis membrane is 70 in the supply water of the reverse osmosis membrane of the second stage. More than % of fungicides. The water treatment method according to claim 6, wherein the sterilizing agent having a barrier ratio of 70% or more in the reverse osmosis membrane is a hypobromous acid stability composition, chloramine sulfonic acid, hypochlorous acid, hypobromous acid. At least one of the thiazolone compound and the halogenated cyanoacetamide compound. The water treatment method according to claim 6 or 7, wherein the second stage reverse osmosis membrane is carried out using a degassing membrane after adding the sterilizing agent having a barrier ratio of 70% or more to the reverse osmosis membrane. Supply water degassing. The water treatment method according to claim 6 or 7, wherein the sterilizing agent having a barrier ratio of 70% or more in the reverse osmosis membrane is an anionic bactericide, and the second-stage reverse osmosis membrane is an anion charged membrane. . The water treatment method according to claim 9, wherein the reverse osmosis membrane of the first stage is a neutral membrane.