KR102380597B1 - Seawater desalination system using capacitive deionization electrode - Google Patents

Abstract

The present invention provides a water intake step of taking seawater, a pretreatment step of removing impurities contained in the withdrawn seawater, a reverse osmosis step of treating the pretreated seawater with a reverse osmosis device, and the treated water generated through the reverse osmosis step It relates to a seawater desalination system comprising a pH control step of adjusting the pH and a CDI treatment step of treating the pH-adjusted treated water using a capacitive deionization (CDI) device equipped with an ion exchange membrane, wherein the By selectively removing monovalent ions by the ion exchange membrane, the concentration of salt contained in seawater is lowered while the concentration of divalent cations is maintained, so that it is possible to directly produce drinking water without a separate remineralization step. .

Description

Seawater desalination system using capacitive deionization electrode

The present invention relates to a seawater desalination system using a capacitive deionization (CDI), and more particularly, a seawater desalination system using a capacitive desalination electrode equipped with an ion exchange membrane that can selectively remove only monovalent cations. is about

Since the 2000s, the amount of water used for agricultural, urban, and industrial purposes has been increasing rapidly around the world. It is expected that 3 billion people will face water scarcity by 2025, especially in the Middle East and Africa.

Seawater accounts for about 97% of all water resources on the planet, and is an almost infinite water resource.

Seawater contains various substances such as sodium, magnesium, and chlorine ions in high concentrations, so it is not suitable for drinking water. In order to use seawater as drinking water, it is necessary to remove such salt, and evaporation and membrane separation are used as representative salt removal technologies. Among salt removal technologies, evaporation is a method that uses a phase change between liquid and gas, and is classified into multi-stage evaporation and multiple effect methods. It is a method to remove salt or impurities. The membrane separation method uses a semi-permeable membrane that passes water but does not pass salt, and a reverse osmosis (RO) process in which fresh water is obtained by applying a pressure higher than the osmotic pressure to the semi-permeable membrane is most widely used.

1 schematically shows a process diagram of a seawater desalination system using a reverse osmosis process, and a conventional seawater desalination system generally includes a pre-treatment step, a reverse osmosis step and a post-treatment step.

First, substances that cause turbidity, such as bacteria, colloids, clay, and suspended matter, present in the seawater taken in through the pretreatment step are removed, and then converted into fresh water through the reverse osmosis step.

The reverse osmosis step is typically performed in a two-stage reverse osmosis method including a sea water reverse osmosis (SWRO) reverse osmosis step, a pH control step, and a brackish water reverse osmosis (BWRO) reverse osmosis step to produce high-purity water, Through the same process, the salt component contained in the water is excessively removed, and since it has a hardness close to that of distilled water, it becomes difficult to use it as drinking water.

Accordingly, seawater is converted into fresh water usable as drinking water by supplementing the insufficient salt component through the post-treatment step.

However, this conventional seawater desalination system goes through two reverse osmosis steps, and requires a post-treatment step to additionally supplement the salt removed through reverse osmosis, so the water treatment efficiency is low and high power is consumed for system operation. Therefore, it is necessary to develop a seawater desalination system that can achieve high desalination efficiency with little power.

Registered Patent No. 10-2013255 (Registered on August 28, 2019)

An object of the present invention is to provide a seawater desalination system using a capacitive desalination electrode equipped with an ion exchange membrane capable of selectively removing only monovalent cations.

One embodiment of the present invention for achieving the object as described above, relates to a seawater desalination system using a capacitive desalination electrode, and more particularly, a water intake step of water intake; A pretreatment step of removing impurities contained in the withdrawn seawater; Reverse osmosis step of treating the pretreated seawater with a reverse osmosis device; a pH adjustment step of adjusting the pH of the treated water produced through the reverse osmosis step; and a CDI treatment step of treating the pH-controlled treated water using a capacitive deionization (CDI) device equipped with an ion exchange membrane, wherein the ion exchange membrane selectively removes monovalent ions It relates to a seawater desalination system using a capacitive desalination electrode, characterized in that.

The pretreatment step may be a step in which sulfuric acid is mixed with the seawater withdrawn.

In the pretreatment step, at least one or more of a scale inhibitor, a coagulant, and an oxidizing agent may be further mixed.

In the pretreatment step, at least any one or more processes of dissolved air flotation, single medium filtration, double medium filtration and ultrafiltration may be performed.

The reverse osmosis step may be a reverse osmosis step using a sea water reverse osmosis (SWRO) device.

The pH adjustment step may be a step of adjusting the pH of the treated water generated through the reverse osmosis step to 9-10.

The pH adjusting step may be a step of mixing the treated water produced through the reverse osmosis step and a pH adjusting agent, wherein the pH adjusting agent includes a divalent cation and shows basicity in an aqueous solution.

The pH adjusting agent may be at least one of calcium oxide, magnesium oxide, magnesium hydroxide, and calcium hydroxide.

In the pH adjustment step, an organic acid or a hydrate of the organic acid may be further mixed.

The organic acid may be at least one selected from the group consisting of acetic acid, butanoic acid, citric acid, and malic acid.

The pH adjusting agent and the organic acid or the hydrate of the organic acid may be mixed in a weight ratio of 1:1 to 2.

The ion exchange membrane may include a cation exchange membrane for selectively removing monovalent cations and an anion exchange membrane for selectively removing monovalent anions.

The capacitive desalination electrode device may be a capacitive desalination electrode including a pair of electrodes and an ion exchange membrane disposed between the pair of electrodes.

The capacitive desalination electrode device may include at least two capacitive desalination electrodes.

Another embodiment of the present invention is a pre-treatment device for removing impurities contained in the taken-in seawater, a reverse osmosis device for producing brackish water by reverse osmosis treatment of the pre-treated seawater in the SWRO method, and monovalent ions are selectively selected It relates to a seawater desalination system using a capacitive desalination electrode including a first capacitive desalination electrode device and a second capacitive desalination electrode device comprising an ion exchange membrane to be removed by a ion exchange membrane and alternately charging and discharging.

At this time, the brackish water is supplied separately to the first capacitive desalination electrode device and the second capacitive desalination electrode device, and when the first capacitive desalination electrode device is discharged, a part of the brackish water flowing into the first capacitive desalination electrode device is supplied to the pH control reactor, and the pH-controlled treated water discharged from the pH control reactor is supplied to the second capacitive desalination electrode device for charging, and when the second capacitive desalination electrode device is discharged, the second capacitive type A portion of brackish water flowing into the desalination electrode device may be supplied to the pH control reactor, and the pH-controlled treated water discharged from the pH control reactor may be supplied to the first capacitive desalination electrode device in which charging is performed.

Sulfuric acid may be mixed with the seawater taken in by the pretreatment device.

In the pH control reactor, a pH adjusting agent containing divalent cations and showing basicity in aqueous solution is added to brackish water to adjust the pH to 9-10.

In the pH control reactor, the pH control agent and the organic acid or the hydrate of the organic acid may be added together.

Since the seawater desalination system using the capacitive desalination electrode of the present invention produces treated water with a high concentration of divalent cations, the additional remineralization process accompanying the seawater desalination process can be omitted, thereby reducing power consumption. there is.

1 is a process diagram of a seawater desalination system using a conventional two-stage reverse osmosis process.
2 is a process diagram of a seawater desalination system using a capacitive desalination electrode of the present invention.
3 is a diagram schematically illustrating the principle of a selective monovalent ion exchange membrane.
4 is a cross-sectional view schematically illustrating a capacitive desalination electrode according to an embodiment of the present invention.
5 is a process diagram of a seawater desalination system using a capacitive desalination electrode according to an embodiment of the present invention.
6 is a photograph showing the results of the experimental example.

Before describing in detail through preferred embodiments of the present invention, terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and meanings consistent with the technical spirit of the present invention and should be interpreted as a concept.

Throughout this specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

Hereinafter, an embodiment of the present invention will be described. However, the scope of the present invention is not limited to the following preferred embodiments, and those skilled in the art can implement various modified forms of the contents described herein within the scope of the present invention.

2 is a seawater desalination system using a capacitive desalination electrode according to an embodiment of the present invention. A pretreatment step (S2) of removing impurities contained in the withdrawn seawater; Reverse osmosis step (S3) of treating the pretreated seawater with a reverse osmosis device; a pH adjustment step (S4) of adjusting the pH of the treated water generated through the reverse osmosis step; and a CDI treatment step (S5) of treating the pH-adjusted treated water using a capacitive deionization (CDI) device equipped with an ion exchange membrane.

At this time, the ion exchange membrane is a selective monovalent ion exchange membrane, which selectively removes monovalent ions to reduce the salinity of the finally produced water, and at the same time maintains the concentration of divalent cations such as magnesium or calcium, thereby separately recharging minerals. Since drinking water can be produced directly without steps, desalination efficiency can be improved and energy consumed for facility operation can be reduced.

First, the water intake step (S1) is a step of taking in seawater, which is raw water for desalination, and it is preferable to take in as clean seawater as possible in order to reduce the load of the pretreatment step (S2). In order to obtain good quality raw water, for example, deep seawater of 60 m or more can be taken in. The seawater taken in through the water intake step (S1) may be subjected to a pretreatment step (S2) after passing through devices such as a filter and a disk filter in order to remove sand and the like contained in the seawater.

The pretreatment step (S2) is a step of removing various impurities contained in the seawater taken in to prevent contamination or damage to the reverse osmosis membrane. Suspended substances such as colloids or particulate matter, organic pollutants including organic matter and microorganisms, and other inorganic compounds such as calcium carbonate and calcium sulfate can be removed through this step.

Specifically, in this step, these impurities are aggregated to form flocs, and then the flocs may be removed through precipitation, flotation or filtration. At least one of Dissolved air flotation (DAF), single media filtration (SMF), dual media filtration (DMF) and ultrafiltration (UF) in such a floc removal process The above process may be performed.

Sulfuric acid may be mixed with the seawater taken in this step. As the sulfuric acid is mixed, the pH of the seawater is lowered, the formation of scales such as carbonate or calcium sulfate is suppressed, the aggregation of impurities is promoted, and the organic matter removal efficiency is increased. Contamination or damage to the reverse osmosis membrane can be prevented.

In addition, at least one additive of a scale inhibitor, a coagulant, and an oxidizing agent may be further mixed, and a material that can be used as the additive is not particularly limited.

Next, a reverse osmosis step (S3) of treating the pretreated seawater with a reverse osmosis device may be performed. As a reverse osmosis device, there is a SWRO device using the SWRO (Sea water reverse osmosis) method and a BWRO device using the BWRO (Brackish water reverse osmosis) method. , BWRO equipment operates at low pressure and has a high salt rejection rate of 70-85%. In the present invention, a sea water reverse osmosis (SWRO) device is used as the reverse osmosis device.

In the prior art, the desalination efficiency was increased and the system operation cost was reduced by performing the first reverse osmosis using the SWRO device and then the second reverse osmosis using the BWRO device. In addition, by adopting such a two-stage reverse osmosis process, the boric acid component that is not removed through the SWRO device was removed through the BWRO device, thereby improving the quality of the produced water.

However, since the concentration of total dissolved solids (TDS) contained in the fresh water discharged from the BWRO device of the two-step reverse osmosis process is excessively low to 30 ppm or less, it has characteristics close to that of distilled water, so that it can be used as drinking water. Since there is no problem, after the two-step reverse osmosis process, a post-treatment step of re-mineralization must be accompanied.

Therefore, in the present invention, by treating brackish water, which is treated water obtained through the reverse osmosis step (S3) using a SWRO device, using a capacitive desalination electrode, boric acid is effectively removed, and produced water suitable for drinking water without re-mineralization want to create Accordingly, in the seawater desalination system using the capacitive desalination electrode of the present invention, the process steps involved in seawater desalination are reduced, the system operating cost is reduced, and the seawater desalination efficiency can be improved.

In order to obtain this effect, specifically, a pH control step (S4) of adjusting the pH of the treated water generated through the reverse osmosis step (S3) and a capacitive desalination electrode (capacitive) equipped with an ion exchange membrane for the pH-adjusted treated water A CDI processing step S5 of processing using a deionization, CDI device is performed.

The pH of the seawater that has been previously subjected to the pretreatment step (S2) is about 5 to 6, and this pH is maintained even after the reverse osmosis step (S3). In this low pH range, boron (B) exists in the form of boric acid (B(OH) ₃ ), but when the pH of the solution is basic at about 9 to 10, it is ionized and tetrahydroxyborate (B(OH) ₄ ^- ), and thus can be removed by being adsorbed to the capacitive desalination electrode in the subsequent CDI treatment step (S5).

In the case of using the capacitive desalination electrode as described above, the removal rate of boron-containing compounds can be improved by about 20% compared to the conventional seawater desalination system shown in FIG. .

A pH adjusting agent is added to the treated water generated through the reverse osmosis step (S3) in the pH adjusting step (S4), so that the pH of the treated water is adjusted to 9-10. In this case, as the pH adjusting agent, a component that contains divalent cations and shows basicity in aqueous solution may be used, and calcium oxide (CaO), magnesium oxide (MgO), magnesium hydroxide (Mg(OH) ₂ ) And at least one of calcium hydroxide (Ca(OH) ₂ ) may be used.

Calcium oxide, magnesium oxide, magnesium hydroxide, and calcium hydroxide contain divalent cations and have a property of being soluble in water, so that the concentration of divalent cations in treated water can be increased, and thus, it is inevitably removed in the subsequent CDI treatment step (S5). By supplementing some divalent cations, the fresh water finally produced through the CDI treatment step (S5) can be used as drinking water. In addition, it is possible to convert boric acid to tetrahydroxyborate by increasing the pH of the treated water, thereby contributing to the removal of boric acid contained in seawater.

On the other hand, the pH adjusting agent has a property of being soluble in water, but there is a problem in that it is not easy to adjust the pH due to low solubility. This problem can be solved by adding an organic acid or a hydrate of the organic acid together with the pH adjusting agent.

When a strong acid is added to increase the solubility of the pH adjuster, it may be difficult to achieve the original purpose of raising the pH through the pH adjusting step (S4) as well as safety issues. It is preferable to do

In this case, at least one selected from the group consisting of acetic acid, butanoic acid, citric acid and malic acid may be used as the organic acid, and citric acid may be preferably used.

In addition, the pH adjusting agent and the organic acid or hydrate of the organic acid may be mixed in a weight ratio of 1:1 to 2, preferably, in a weight ratio of 1:1.3 to 1.7, more preferably in a weight ratio of 1:1.4 to 1.6. can be If the weight ratio of the organic acid or the hydrate of the organic acid to the pH adjuster is low, the solubility of the pH adjuster does not sufficiently increase, so there is a problem in that the pH adjusting effect and the TDS of fresh water, which is the final product, are excessively lowered, and the organic acid or organic acid to the pH adjuster If the weight ratio of the hydrate is high, the effect of increasing the solubility is insignificant, so it is preferable that the two substances are mixed within the above-mentioned weight ratio.

The treated water whose pH has been adjusted through this step is converted into drinkable fresh water through the CDI treatment step (S5), which is treated using a capacitive deionization (CDI) device equipped with an ion exchange membrane.

In this case, the ion exchange membrane includes a cation exchange membrane for selectively removing monovalent cations such as sodium ions and an anion exchange membrane for selectively removing monovalent anions such as chlorine ions, and the treated water flowing into the capacitive desalination electrode device Only the monovalent cations and monovalent anions contained in the are selectively removed, and the divalent or higher ions are discharged into the effluent.

This selective monovalent ion exchange membrane removes only monovalent ions in the same principle as shown in FIG. 3 . Referring to the selective monovalent cation exchange membrane of FIG. 3 as an example, the selective monovalent cation exchange membrane has holes of a size that only monovalent cations can pass through, so that divalent cations having a larger ionic radius than monovalent cations do not pass through, By allowing only monovalent cations to pass through and adsorbing them to the electrode, monovalent cations from the influent can be removed and divalent cations can be discharged. According to the same principle, the selective divalent anion exchange membrane removes only monovalent anions.

At this time, if the electrical attraction is strong, some divalent cations also pass through the hole and are adsorbed and removed by the electrode, but the amount of divalent cations removed in this way is very small. Since the pH adjusting agent containing the valent cation is added, the decrease in TDS of the final effluent due to the loss of the divalent cation here is very insignificant.

Accordingly, only monovalent ions of the effluent are selectively removed, and fresh water rich in divalent cations such as magnesium ions and calcium ions is generated, which can be used directly as drinking water without an additional remineralization step.

The capacitive desalination electrode device used at this time includes a pair of electrodes 110a and 110b and an ion exchange membrane disposed between the pair of electrodes, as shown in FIG. 4 , and the ion exchange membrane is a cation exchange membrane 120b ) and an anion exchange membrane 120a may be an MCDI (membrane capacitive deionization) series capacitive desalination electrode.

In this case, the influent passes through the flow path between the two ion exchange membranes 120a and 120b, and ions in the influent are removed and discharged into fresh water, and the removed ions are discharged through the space between the electrode and the ion exchange membrane or are adsorbed to the electrode. can be removed.

In addition, the two ion exchange membranes 120a and 120b may include a polyolefin-based reinforcing material to have a high strength while having a thin film thickness when wet. The two ion exchange membranes 120a and 120b may have a membrane thickness of 160 μm or less, preferably 120 μm or less, and a Mullen burst strength of 0.1 MPa or more, preferably 1.8 MPa or more. In addition, the electrical resistance, which is an alternating current resistance value in an aqueous solution of NaCl at a temperature of 25° C. and 0.5 mol/L concentration, may be 2.0 Ω·cm ² or less, preferably 1.8 Ω·cm ² or less, in the case of a cation exchange membrane, and in the case of an anion exchange membrane to 2.5 Ω·cm ² or less, preferably 2.4 Ω·cm ² or less.

The capacitive desalination electrode device of the present invention may be used as a single electrode described with reference to FIG. 4, or two or more may be used in the form of a module connected in parallel or in series.

As an example of the seawater desalination system using the capacitive desalination electrode according to the embodiment of the present invention, the seawater desalination system using the two capacitive desalination electrodes shown in FIG. 5 may be used.

A seawater desalination system according to an embodiment of the present invention includes: a pre-treatment device 210 for removing impurities contained in the taken-in seawater; A reverse osmosis device 220 for producing brackish water by reverse osmosis treatment of the pretreated seawater in the SWRO method, and a first capacitive desalination electrode device 231 and a second capacitive desalination electrode that alternately charge and discharge a device 232 , wherein the radix is supplied separately into a first capacitive desalination electrode device 231 and a second capacitive desalination electrode device 232 .

In one example of the present invention, when the first capacitive desalination electrode device 231 is discharged, a portion of brackish water flowing into the first capacitive desalination electrode device 231 is supplied to the pH control reactor 240, and the pH is adjusted The pH-adjusted treated water discharged from the reactor 240 is supplied to the second capacitive desalination electrode device 232 for charging.

That is, the entire amount of brackish water is not supplied to the pH control reactor 240, but some of the brackish water supplied to the capacitive desalination electrode device for discharging is separated to adjust the pH, and then supplied to the capacitive desalination electrode device for charging the pH. Control efficiency can be improved, and since the pH-adjusted treated water is not supplied to the capacitive desalination electrode device that is discharged, the amount of chemicals used for pH control can be reduced.

In addition, the line through which brackish water is supplied to the pH control reactor 240 and the pH control reactor 240 without a flow controller for controlling the flow rate of the influent flowing into each capacitive desalination electrode device 231 and 232 during charging and discharging conversion ) to control the flow rate of the influent flowing into each capacitive desalination electrode device (231, 232) by a simple operation of controlling a 3-way valve or on-off valve installed in the line supplied to the capacitive desalination electrode device (231, 232) There are advantages that can be

Conversely, when the second capacitive desalination electrode device 232 is discharged, a portion of the influent flowing into the second capacitive desalination electrode device 232 is supplied to the pH control reactor 240 , and the pH control reactor 240 . The pH-adjusted treated water discharged from the is supplied to the first capacitive desalination electrode device 231 for charging.

The effluent discharged from the capacitive desalination electrode devices 231 and 232, which is finally charged, removes only monovalent ions and is converted into fresh water rich in divalent cations, so that it can be used as drinking water.

The pretreatment device 210 is a device in which the pretreatment step S2 described above is performed, and various impurities may be aggregated and removed in the form of flocs through the pretreatment device 210 . Sulfuric acid is mixed with seawater in the pretreatment device 210 to lower the pH of the seawater and increase the efficiency of removing impurities at the same time.

The reverse osmosis device 220 is a device in which the above-described reverse osmosis step (S2) is performed, and may be a SWRO-type reverse osmosis device, and includes a first capacitive desalination electrode device 231 and a second capacitive desalination electrode device. Reference numeral 232 denotes a CDI device in which the above-described CDI processing step S5 is performed.

The pH control reactor 240 is a device in which the pH control step (S4) of the present invention is performed, and receives at least a portion of brackish water having a low pH and mixes it with a pH control agent to adjust the pH to 9 to 10, inside the reactor A stirrer for mixing the brackish water and the pH adjusting agent may be provided, and a diaphragm may be provided as necessary.

At least one pH adjusting agent among calcium oxide (CaO), magnesium oxide (MgO) magnesium hydroxide (Mg(OH) ₂ ) and calcium hydroxide (Ca(OH) ₂ ) may be input to the pH control reactor 240 , In order to increase the solubility of such a pH adjusting agent, an organic acid or a hydrate of the organic acid may be preferably added together.

The seawater desalination system of the present invention uses a capacitive desalination electrode device equipped with an ion exchange membrane that selectively removes monovalent ions, increases monovalent ion removal efficiency, effectively removes boric acid, and magnesium ions or calcium ions It is possible to produce fresh water that can be used as drinking water due to the abundance of divalent cations such as .

Therefore, the CDI treatment process can replace both the conventional BWRO process and the remineralization process, so process efficiency can be improved, and there is an advantage that can be installed in a smaller area.

Hereinafter, specific actions and effects of the present invention will be described through an embodiment of the present invention. However, this is presented as a preferred example of the present invention, and the scope of the present invention is not limited according to the embodiments.

[ Experimental example ]

In order to check the solubility of the pH adjuster according to the addition of the organic acid in brackish water, the pH adjuster or the pH adjuster and the organic acid of the weight described in Table 1 were added together in 250 ml of 660 ppm sodium chloride solution, which is artificial brackish water at room temperature, and stirred. , was visually confirmed and the solubility was confirmed by measuring the pH.

Citric acid was used as the organic acid, the calcium hydroxide of Samjeon Soonyak was used as the pH adjusting agent of Example 1 and Comparative Example 1, and the calcium hydroxide of white light material was used as the pH adjusting agent of Examples 2 and 2, and after stirring, each solution was taken and shown in FIG. 6, and the measured pH is also described in Table 1.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Calcium hydroxide (g) 0.175 0.175 0.175 0.175 Citric acid (g) 0.15 0.15 unadded unadded final pH 11.8 11.8 5.6 5.6

Referring to the experimental results of Table 1 and FIG. 6 together, in the case of Examples, calcium hydroxide is completely dissolved in the photograph and the pH is also basic, but in the case of Comparative Examples, undissolved calcium hydroxide can be confirmed with the naked eye. In addition, it was confirmed that the pH was 5.6, indicating that calcium hydroxide was hardly dissolved.

Therefore, it can be confirmed from the experimental results that it is preferable to add citric acid together with calcium hydroxide in order to increase the solubility of calcium hydroxide in water.

The present invention is not limited to the specific embodiments and descriptions described above, and without departing from the gist of the present invention claimed in the claims, any person skilled in the art to which the invention pertains can implement various modifications and such modifications shall fall within the protection scope of the present invention.

100, 100': capacitive desalination electrode 110a, 110b, 110a', 110b': electrode
120a: anion exchange membrane 120b: cation exchange membrane
210: pretreatment unit 220: reverse osmosis unit
231: first capacitive desalination electrode device 232: second capacitive desalination electrode device
240: pH control reactor

Claims (18)

water intake step of water intake;
A pretreatment step of removing impurities contained in the withdrawn seawater;
Reverse osmosis step of treating the pretreated seawater with a reverse osmosis device;
a pH adjustment step of adjusting the pH of the treated water generated through the reverse osmosis step; and
A CDI treatment step of treating the pH-controlled treated water using a capacitive deionization (CDI) device equipped with an ion exchange membrane;
The ion exchange membrane is characterized in that it selectively removes monovalent ions,
Here, the pH adjusting step is a step of mixing the treated water produced through the reverse osmosis step and a pH adjusting agent, wherein the pH adjusting agent contains a divalent cation and is characterized in that it exhibits basicity in an aqueous solution,
In the pH adjustment step, the seawater desalination system using a capacitive desalination electrode, characterized in that the organic acid or the hydrate of the organic acid is further mixed. According to claim 1,
The pretreatment step is a seawater desalination system using a capacitive desalination electrode, characterized in that the sulfuric acid is mixed with the seawater withdrawn. 3. The method of claim 2,
Seawater desalination system using a capacitive desalination electrode, characterized in that at least one of a scale inhibitor, a coagulant, and an oxidizing agent is further mixed in the pretreatment step. According to claim 1,
Seawater desalination system using a capacitive desalination electrode, characterized in that at least one of dissolved air flotation, single medium filtration, double medium filtration and ultrafiltration is performed in the pretreatment step. According to claim 1,
The reverse osmosis step, sea water desalination system using a capacitive desalination electrode, characterized in that the reverse osmosis step using a SWRO (Sea water reverse osmosis) device. According to claim 1,
The pH adjustment step is a seawater desalination system using a capacitive desalination electrode, characterized in that it is a step of adjusting the pH of the treated water generated through the reverse osmosis step to 9 to 10. delete According to claim 1,
The pH adjusting agent is a seawater desalination system using a capacitive desalination electrode, characterized in that at least any one or more of calcium oxide, magnesium oxide, magnesium hydroxide and calcium hydroxide. delete According to claim 1,
The organic acid is at least one selected from the group consisting of acetic acid, butanoic acid, citric acid and malic acid, seawater desalination system using a capacitive desalination electrode. According to claim 1,
Seawater desalination system using a capacitive desalination electrode, characterized in that the pH adjusting agent and the organic acid or the hydrate of the organic acid are mixed in a weight ratio of 1:1 to 2. According to claim 1,
The ion exchange membrane, seawater desalination system using a capacitive desalination electrode, characterized in that it comprises a cation exchange membrane for selectively removing monovalent cations and an anion exchange membrane for selectively removing monovalent anions. According to claim 1,
The capacitive desalination electrode device is a seawater desalination system using a capacitive desalination electrode, characterized in that it is a capacitive desalination electrode comprising a pair of electrodes and an ion exchange membrane disposed between the pair of electrodes. 14. The method of claim 13,
The capacitive desalination electrode device, seawater desalination system using a capacitive desalination electrode, characterized in that it comprises at least two or more capacitive desalination electrodes. A pretreatment device that removes impurities contained in the withdrawn seawater,
Reverse osmosis device to produce brackish water by reverse osmosis treatment of pretreated seawater in SWRO method, and
A first capacitive desalination electrode device and a second capacitive desalination electrode device comprising an ion exchange membrane that selectively removes monovalent ions and alternately charging and discharging;
The brackish water is supplied separately into a first capacitive desalination electrode device and a second capacitive desalination electrode device,
When the first capacitive desalination electrode device is discharged, a portion of brackish water flowing into the first capacitive desalination electrode device is supplied to the pH control reactor, and the pH-controlled treated water discharged from the pH control reactor is charged with the second capacitive desalination electrode device. It is supplied as a capacitive desalination electrode device,
When the second capacitive desalination electrode device is discharged, a part of the brackish water flowing into the second capacitive desalination electrode device is supplied to the pH control reactor, and the pH-controlled treated water discharged from the pH control reactor is the first charged water. Seawater desalination system using a capacitive desalination electrode, characterized in that it is supplied to a capacitive desalination electrode device. 16. The method of claim 15,
Seawater desalination system using a capacitive desalination electrode, characterized in that sulfuric acid is mixed with the seawater taken in the pretreatment device. 16. The method of claim 15,
Seawater desalination system using a capacitive desalination electrode, characterized in that the pH is adjusted to 9-10 by adding a pH adjusting agent containing divalent cations to brackish water and showing basicity in aqueous solution in the pH control reactor. 18. The method of claim 17,
In the pH control reactor, the seawater desalination system using a capacitive desalination electrode, characterized in that the pH control agent and the organic acid or a hydrate of the organic acid are fed together.

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