TW202225101A - System and method of treating waste water - Google Patents

Abstract

Provided are a system and a method of treating waste water. The system includes a forward osmosis (FO) liquid concentration apparatus and an electrodialysis (ED) apparatus. The FO liquid concentration apparatus increases the concentration of salts in wastewater to between 7% to 14%. The ED apparatus is disposed downstream of the FO liquid concentration apparatus and coupled to the FO liquid concentration apparatus to receive the wastewater introduced from the FO liquid concentration apparatus, and make the salts in the wastewater into acid solution and basic solution.

Description

Wastewater Treatment System and Method

The present disclosure relates to a wastewater treatment system and method.

In recent years, circular economy and low-environmental impact technologies have attracted much attention, and the demand for zero liquid discharge (ZLD) and water resource recovery technologies has also increased accordingly. In the current zero-discharge technologies, most of the wastewater is subjected to pre-treatment, reverse osmosis treatment, separation of salts in wastewater, evaporation, crystallization and drying in sequence. However, the above-mentioned wastewater treatment technology is expensive, and the resulting salts can only be discarded and buried, thus causing pollution to the environment and ecology.

The present disclosure provides a wastewater treatment system, which includes a forward osmosis liquid concentration device and an electrodialysis device.

The present disclosure provides a wastewater treatment method, which uses a forward osmosis liquid concentration device to increase the concentration of salts in the wastewater to between 7% and 14%, and uses an electrodialysis device to convert the salts in the wastewater into an acid solution with lye.

The wastewater treatment system of the present disclosure includes a forward osmosis liquid concentration device and an electrodialysis device. The forward osmosis liquid concentrator increases the concentration of salts in the wastewater to between 7% and 14%. The electrodialysis device is arranged downstream of the forward osmosis liquid concentration device, and is coupled with the forward osmosis liquid concentration device to receive the waste water discharged from the forward osmosis liquid concentration device, and make the salts in the waste water into acid solution and alkali solution.

The wastewater treatment method of the present disclosure includes the following steps. The wastewater is supplied to a forward osmosis liquid concentrator to increase the concentration of salts in the wastewater to between 7% and 14%. Through the forward osmosis liquid concentration device, the wastewater is introduced into the electrodialysis device to make the salts in the wastewater into acid solution and alkali solution.

In order to make the above-mentioned features and advantages of the present disclosure more obvious and easy to understand, the following embodiments are given and described in detail with reference to the accompanying drawings as follows.

The following examples are described in detail with the accompanying drawings, but the provided examples are not intended to limit the scope of the present disclosure.

The terms "including", "including", "having", etc. mentioned in this article are all open-ended terms, that is, "including but not limited to".

Also, herein, a range represented by "one value to another value" is a general representation that avoids listing all the values in the range in the specification. Thus, the recitation of a particular numerical range includes any number within that numerical range as well as any smaller numerical range bounded by any number within that numerical range.

In an embodiment of the present disclosure, the wastewater treatment system includes a forward osmosis liquid concentration device and an electrodialysis device. Through the forward osmosis liquid concentration device, the salt concentration in the wastewater can be concentrated to between 7% and 14%. In this way, the electrodialysis device can have higher efficiency when the salts in the wastewater are subsequently made into acid solution and alkali solution. In addition, after the salts in the wastewater are made into acid solution and alkali solution, the remaining aqueous solution can be mixed with untreated wastewater and supplied to the forward osmosis liquid concentration device and the electrodialysis device, and the above steps are repeated to achieve wastewater. The goal of zero emissions. The wastewater treatment system and method of the embodiments of the present disclosure will be described in detail below.

FIG. 1 is a schematic block diagram of a wastewater treatment system according to an embodiment of the disclosure. Referring to FIG. 1 , a wastewater treatment system 10 according to an embodiment of the present disclosure includes a forward osmosis liquid concentration device 100 and an electrodialysis device 102 . In addition, the wastewater treatment system 10 may further include a pretreatment device 104 according to actual needs. The wastewater treatment system 10 is used to treat wastewater containing salts. The salts are, for example, sodium chloride, sodium sulfate, lithium chloride, lithium sulfate, or a combination thereof. In the case where the wastewater treatment system 10 includes the pretreatment device 104 , the wastewater may first be supplied to the pretreatment device 104 for pretreatment, and the forward osmosis liquid concentration device 100 is disposed downstream of the pretreatment device 104 and coupled to the pretreatment device 104 Then, the electrodialysis device 102 is disposed downstream of the forward osmosis liquid concentration device 100 and is coupled to the forward osmosis liquid concentration device 100 .

The pretreatment device 104 may pretreat the wastewater containing salts to concentrate the concentration of the salts in the wastewater to above 4%, but less than 7%. The pretreatment device 104 is, for example, a well-known reverse osmosis device, which can concentrate the concentration of salts in the wastewater up to about 4%. Concentrating and increasing the concentration of the salts in the waste water can facilitate the subsequent efficiency of the salts into the acid solution and the lye solution. In addition, in one embodiment, the pretreatment device 104 can include a pretreatment device and a reverse osmosis device, wherein the pretreatment device can first concentrate the concentration of salts in the wastewater to about 1%, and the reverse osmosis device can concentrate the salts in the wastewater. The concentration increased to about 2% to 4%.

The forward osmosis liquid concentration device 100 is disposed downstream of the pretreatment device 104 and is coupled to the pretreatment device 104 to receive wastewater from the pretreatment device 104 . After the wastewater in which the salt concentration is preliminarily increased enters the forward osmosis liquid concentration device 100, the forward osmosis liquid concentration device 100 concentrates the salts in the wastewater again. In this embodiment, the forward osmosis liquid concentration device 100 increases the concentration of salts in the wastewater to between 7% and 14%. In this way, the efficiency of subsequent salt formation into acid solution and lye solution can be greatly improved.

In this embodiment, the forward osmosis liquid concentration device 100 includes a forward osmosis liquid concentration unit 100a and an extraction solution recovery unit 100b, wherein the forward osmosis liquid concentration unit 100a is coupled with the pretreatment device 104, and the extraction solution recovery unit 100b is connected with the forward osmosis solution The liquid concentration unit 100a is coupled. The forward osmosis liquid concentration unit 100a has a membrane, and by using the osmotic pressure difference between the two ends of the membrane as a driving force, the water at the inlet end (high salt concentration, low osmotic pressure) is attracted to the extraction liquid end (salt concentration). higher, high osmolality). At this time, the concentration of salts in the waste water increases, while the concentration of the extract at the extract end is reduced by dilution with water. In addition, the diluted extract is discharged to the extract recovery unit 100b, and the extract recovery unit 100b concentrates the diluted extract and then supplies it to the extract end of the forward osmosis liquid concentration unit 100a, so that the forward osmosis liquid concentration unit 100a The salts in the wastewater can be continuously concentrated. However, the forward osmosis liquid concentrating device used in the present disclosure is not limited to the above structure.

The electrodialysis device 102 is disposed downstream of the forward osmosis liquid concentration device 100 and is coupled to the forward osmosis liquid concentration device 100 . In one embodiment, the electrodialysis device 102 may be as shown in FIG. 3 . 3, the electrodialysis device 102 includes a waste water chamber 300, a positive electrode chamber P, a negative electrode chamber N, an acid solution chamber A, an alkaline solution chamber B, a first buffer chamber B1 and a second buffer chamber B2. The waste water chamber 300 is used for receiving waste water containing salts. The positive electrode chamber P and the negative electrode chamber N are respectively disposed on opposite sides of the waste water chamber 300 . The positive electrode chamber P has an electrode PE therein, and is used to receive the electrode chamber liquid (eg, sodium sulfate solution). The negative electrode chamber N has an electrode NE, and is used to receive the electrode chamber liquid (eg, sodium sulfate solution). When a voltage is applied to the electrode PE and the electrode NE, the anions of the salts in the wastewater can be moved toward the positive electrode, and the cations of the salts in the wastewater can be moved toward the negative electrode. In this way, the concentration of salts in the wastewater can be reduced to achieve the purpose of wastewater treatment. During wastewater treatment, the current density is, for example, between 10 mA/cm ² and 100 mA/cm ² .

The acid solution chamber A is provided between the waste water chamber 300 and the positive electrode chamber P, and is connected to the positive electrode chamber P. The acid chamber A is used to receive an aqueous solution (eg pure water) and anions from the first buffer chamber B1 (which will be described later). In this embodiment, the interface between the acid solution chamber A and the positive electrode chamber P is the bipolar membrane PM1. The hydroxide ions in the bipolar membrane PM1 move toward the positive electrode to the positive electrode chamber P, and the hydrogen ions and the anions from the first buffer chamber B1 form an acid solution. The acid concentration in the acid chamber A increases with increasing wastewater treatment time until the desired acid concentration (referred to herein as the target concentration of anions in the acid) is reached. At this time, the acid solution can be received from the acid solution chamber A to achieve the purpose of reuse of waste water.

The alkaline solution chamber B is provided between the waste water chamber 300 and the negative electrode chamber N, and is connected to the negative electrode chamber N. The lye chamber B is used to receive an aqueous solution (eg pure water) and cations from the second buffer chamber B2 (which will be described later). In this embodiment, the interface between the lye chamber B and the negative electrode chamber N is the bipolar film PM2. The hydrogen ions in the bipolar membrane PM2 move to the negative end to the negative chamber N, while the hydroxide ions form lye with the cations from the second buffer chamber B2. The lye concentration in the lye chamber B increases with the time of wastewater treatment until the desired lye concentration (referred to herein as the target concentration of cations in the lye) is reached. At this time, the prepared lye solution can be received from the lye solution chamber B to achieve the purpose of reusing the waste water.

The first buffer chamber B1 is provided between the acid solution chamber A and the waste water chamber 300 , and is connected to the acid solution chamber A and the waste water chamber 300 . The first buffer chamber B1 is used to receive the first buffer solution containing the same anions as the anions in the acid solution to be produced (ie, the anions to be recovered and reused in the wastewater). In this embodiment, the interface between the first buffer chamber B1 and the waste water chamber 300 is an anion exchange membrane M1, and the interface between the first buffer chamber B1 and the acid solution chamber A is also an anion exchange membrane M2. That is, the interface between the first buffer chamber B1 and the waste water chamber 300 and the interface between the first buffer chamber B1 and the acid solution chamber A have the same electrical properties. In this way, in the process of wastewater treatment, the anions of the salts in the wastewater move toward the positive electrode and enter the first buffer chamber B1, and the anions in the first buffer chamber B1 are the same as the anions in the acid solution to be prepared. Anions enter the acid chamber A to form acid with hydrogen ions from the bipolar membrane PM1.

In addition, in this embodiment, the concentration of anions in the first buffer solution is not lower than the target concentration of the same anions in the waste water chamber 300 and not higher than the target concentration of the same anions in the acid solution chamber A. Since the anion concentration in the first buffer solution is between the target concentration in the wastewater chamber 300 and the target concentration in the acid chamber A, when the ion concentration in the wastewater chamber 300 decreases as the wastewater treatment time increases, It can slow down the water in the waste water chamber 300 from entering the acid liquid chamber A due to the excessive osmotic pressure difference between the acid liquid chamber A and the waste water chamber 300, so as to avoid the reduction of the recovery concentration of the acid liquid. In addition, with the arrangement of the first buffer chamber B1, the ions in the acid solution chamber A can be prevented from returning to the waste water chamber 300 due to the excessive ion concentration difference, so as to avoid the reduction of the efficiency of waste water treatment and acid solution recovery. In addition, since the anions in the first buffer solution are the same as the anions in the acid solution to be prepared, that is, when the wastewater contains a variety of anions, these anions will only enter the first buffer chamber B1, and the first buffer The anions in the solution will enter the acid solution chamber A, thereby improving the purity of the acid solution prepared.

The second buffer chamber B2 is provided between the alkali solution chamber B and the waste water chamber 300 , and is connected to the alkali solution chamber B and the waste water chamber 300 . The second buffer chamber B2 is used to receive the second buffer solution containing the same cations as the cations in the alkali solution to be prepared (ie, the cations to be recovered and reused in the wastewater). In this embodiment, the interface between the second buffer chamber B2 and the waste water chamber 300 is the cation exchange membrane M3, and the interface between the second buffer chamber B2 and the lye chamber B is also the cation exchange membrane M4. That is, the interface between the second buffer chamber B2 and the waste water chamber 300 and the interface between the second buffer chamber B1 and the lye chamber B have the same electrical properties. In this way, in the process of wastewater treatment, the cations of the salts in the wastewater move toward the negative electrode and enter the second buffer chamber B2, and the cations in the second buffer chamber B2 are the same as the cations in the lye to be prepared. The cations then enter the lye chamber B to form lye with the hydroxide ions from the bipolar membrane PM2.

In addition, in this embodiment, the concentration of cations in the second buffer solution is not lower than the target concentration of the same cations in the waste water chamber 300, and not higher than the target concentration of the same cations in the lye chamber B. Since the cation concentration in the second buffer solution is between the target concentration in the wastewater chamber 300 and the target concentration in the lye chamber B, when the ion concentration in the wastewater chamber 300 decreases as the wastewater treatment time increases, It can slow down the water in the waste water chamber 300 from entering the lye chamber B due to the excessive osmotic pressure difference between the lye chamber B and the waste water chamber 300, so as to avoid the reduction of the recovery concentration of the lye solution. In addition, the arrangement of the second buffer chamber B2 can prevent the ions in the lye chamber B from returning to the waste water chamber 300 due to the excessive ion concentration difference, so as to avoid the reduction of the efficiency of waste water treatment and lye recovery. In addition, since the cations in the second buffer solution are the same as the cations in the alkali solution to be prepared, that is, when the wastewater contains multiple cations, these cations will only enter the second buffer chamber B2, while the second buffer The cations in the solution will enter into the lye chamber B, thereby improving the purity of the lye solution prepared.

In this embodiment, the first buffer chamber B1 is arranged between the acid solution chamber A and the waste water chamber 300 , and the second buffer chamber B2 is arranged between the alkali solution chamber B and the waste water chamber 300 . Therefore, the first buffer chamber B1 and the second buffer chamber B2 can reduce the concentration difference between the waste water chamber 300 and the acid solution chamber A and the alkali solution chamber B respectively and form a concentration gradient, so that the acid solution chamber A or the alkali solution chamber B The ions do not permeate back into the waste water chamber 300 and reduce the osmotic pressure difference. In other words, if the first buffer chamber B1 is not arranged between the acid solution chamber A and the waste water chamber 300 and/or the second buffer chamber B2 is not arranged between the alkali solution chamber B and the waste water chamber 300, the The concentration difference between the liquid chamber A and/or the alkali liquid chamber B and the waste water chamber 300 is too large, resulting in the problem that the recovery efficiency of the acid liquid and/or the alkali liquid is reduced.

In addition, in this embodiment, the first buffer chamber B1 and the second buffer chamber B2 are separate chambers, and the first buffer chamber B1 and the second buffer chamber B2 communicate with each other. Therefore, the first buffer solution is the same as the second buffer solution, and both contain both the anions required to produce acid and the cations required to produce alkali. In another embodiment, the first buffer chamber B1 may not communicate with the second buffer chamber B2. In this case, the first buffer solution is different from the second buffer solution.

In other embodiments, the electrodialysis device 102 may have a structure similar to that shown in FIG. 3 , but the first buffer chamber B1 and the second buffer chamber B2 may be omitted. It should be noted that, in other embodiments, the present disclosure can also be implemented in the case where the buffer chamber is not provided in the electrodialysis device 102 .

In this embodiment, the waste water chamber 300 of the electrodialysis device 102 is coupled to the forward osmosis liquid concentration unit 100a, and the waste water (salt concentration has been increased to 7% to 14%), and the salts in the wastewater are made into acid and lye. Since the electrodialysis device 102 has a charged dialysis membrane, ions can be separated in an aqueous solution by using the potential difference as a driving force. Through the above procedure, the electrodialysis device 102 can separate the anions and cations of salts in the wastewater, and split the water through the bipolar membrane to generate hydrogen ions and hydroxide ions, which are respectively made into acid solutions (such as sulfuric acid, sulfuric acid, etc.). Hydrochloric acid, etc.) and lye (such as sodium hydroxide, lithium hydroxide, etc.), and the acid and lye can be used in various industries. In addition, the remaining aqueous solution after the acid solution and alkali solution are made can also be used, or can be mixed with untreated wastewater and supplied to the pretreatment device 104 or the forward osmosis liquid concentration device 100 for continuous wastewater treatment.

As can be seen from the above, through the wastewater treatment system 10 of the embodiment of the present disclosure, the wastewater can be processed into acid solution and alkali solution, and the remaining aqueous solution after the acid solution and alkali solution are prepared can be used or can be mixed with untreated water. Wastewater is mixed and treated. In this way, the problem of environmental and ecological pollution caused by waste and burial of salt can be effectively solved, and at the same time, the goal of zero discharge of waste water can be achieved.

In addition, the wastewater treatment system 10 of the embodiment of the present disclosure includes the forward osmosis liquid concentrating device 100 and the electrodialysis device 102 , instead of increasing the salt concentration by the thermal evaporation device, it can effectively reduce energy consumption and cost.

The wastewater treatment method of the embodiment of the present disclosure will be described below.

FIG. 2 is a flowchart of a method for treating wastewater according to an embodiment of the disclosure. Please refer to FIG. 1 and FIG. 2 at the same time. First, in step S200, wastewater containing salts (such as sodium chloride, sodium sulfate, lithium chloride, lithium sulfate or a combination thereof) is provided to the pretreatment device 104 to preprocessing. In this step, the concentration of salts in the wastewater can be concentrated to more than 4%, but less than 7%. In other embodiments, step S200 may be omitted depending on actual requirements.

Next, in step S202, the pretreated wastewater is supplied to the forward osmosis liquid concentration device 100, and the concentration of salts in the wastewater is concentrated for the second time, so as to increase the concentration of salts to 7% to 14% between.

Then, in step S204, the secondary concentrated waste water is supplied to the electrodialysis device 102 which is simultaneously equipped with an anion exchange membrane, a cation exchange membrane and a bipolar membrane, so as to make the waste water into acid solution and alkali solution.

After that, in step S206, the acid solution and the alkali solution are recovered from the acid solution chamber and the alkali solution chamber of the electrodialysis device. In addition, the remaining aqueous solution in the waste water chamber of the electrodialysis device may also be recovered, or may be mixed with untreated waste water and steps S200 to S206 may be repeated. In this way, the waste water can be made into acid solution and alkali solution for recycling, and at the same time, the goal of zero discharge of waste water can be achieved.

The wastewater treatment system and method of the present disclosure will be described below with experimental examples and comparative examples, and the treatment results are shown in Table 1.

Forward osmosis liquid concentration device: use Na ₂ SO ₄ extraction solution, the sweep velocity is 25 cm/s, and the effective operating area of the permeable membrane is 1 m ² .

Electrodialysis device: as shown in Figure 3.

Experimental example 1

Under the condition that the concentration of the Na ₂ SO ₄ extract of the forward osmosis liquid concentration device is 30% and the osmotic pressure is 89 atm, the wastewater containing NaCl is supplied to the forward osmosis liquid concentration device, and concentrated for 4 hours to reduce the concentration of NaCl The concentration was concentrated from 3.5% to 7.5%. After that, the concentrated waste water is drawn out and supplied to an electrodialysis device to make the waste water into HCl and NaOH.

Experimental example 2

Under the condition that the concentration of the Na ₂ SO ₄ extract of the forward osmosis liquid concentration device is 30% and the osmotic pressure is 89 atm, the wastewater containing NaCl was supplied to the forward osmosis liquid concentration device, and concentrated for 4.5 hours to reduce the concentration of NaCl After the concentration was concentrated from 3.5 to 8%, the concentrated wastewater was exported and supplied to an electrodialysis unit to make the wastewater into HCl and NaOH.

Experimental example 3

Under the condition that the concentration of Na ₂ SO ₄ extraction solution of the forward osmosis liquid concentration device is 40% and the osmotic pressure is 117 atm, the wastewater containing NaCl is supplied to the forward osmosis liquid concentration device to concentrate the concentration of NaCl to 12.6% . After that, the concentrated wastewater was supplied to an electrodialysis device to convert the wastewater into HCl and NaOH.

Comparative example

The wastewater containing 4% NaCl was directly supplied to the electrodialysis device, and the concentration of NaCl was increased to between 7% and 14% without going through the forward osmosis liquid concentration device, so as to make the wastewater into HCl and NaOH.

Table 1 Comparative example Experimental example 1 Experimental example 2 Experimental example 3 Acid/lye produced after electrodialysis HCl NaOH HCl NaOH HCl NaOH HCl NaOH Concentration of HCl/NaOH(%) 2.1 2.6 4.6 4.5 5.3 5.2 8.3 7.1 Energy consumption (kWh/kg) 9 7 9 8 9 9 10 9 Current efficiency (%) 57 25 74 48 77 51 88 79

It can be clearly seen from Table 1 that, compared with the comparative example (the concentration of salts in the wastewater is not increased to between 7% and 14% through the forward osmosis liquid concentration device), in the wastewater treatment system of the embodiment of the present disclosure , through the forward osmosis liquid concentration device, the concentration of salts in the wastewater is first increased to between 7% and 14%, which can effectively increase the concentration of the acid solution and alkali solution made, and can effectively improve the recovery of acid and alkali. rate and current efficiency.

Although the present disclosure has been disclosed above with examples, it is not intended to limit the present disclosure. Anyone with ordinary knowledge in the technical field may make some changes and modifications without departing from the spirit and scope of the present disclosure. The scope of protection of the present disclosure shall be determined by the scope of the appended patent application.

10: Wastewater treatment system 100: Forward osmosis liquid concentration device 100a: Forward osmosis liquid concentration unit 100b: Extraction recovery unit 102: Electrodialysis device 104: Pretreatment device 300: Wastewater Room A: Acid chamber B: lye chamber B1: The first buffer chamber B2: Second buffer chamber M1, M2: anion exchange membrane M3, M4: cation exchange membrane N: Negative Electrode Chamber NE, PE: electrode P: positive compartment PM1, PM2: bipolar membrane S200, S202, S204, S206: Steps

FIG. 1 is a schematic block diagram of a wastewater treatment system according to an embodiment of the disclosure. FIG. 2 is a flowchart of a method for treating wastewater according to an embodiment of the disclosure. FIG. 3 is a schematic diagram of an electrodialysis device according to an embodiment of the disclosure.

10: Wastewater treatment system

100: Forward osmosis liquid concentration device

100a: Forward osmosis liquid concentration unit

100b: Extraction recovery unit

102: Electrodialysis device

104: Pretreatment device

Claims (10)

A wastewater treatment system comprising: Forward osmosis liquid concentrators to increase the concentration of salts in wastewater to between 7% and 14%; and The electrodialysis device is arranged downstream of the forward osmosis liquid concentration device, and is coupled to the forward osmosis liquid concentration device, receives the waste water introduced by the forward osmosis liquid concentration device, and removes all the waste water from the waste water. The salts are made into acid and lye. The wastewater treatment system according to claim 1, further comprising a pretreatment device disposed upstream of the forward osmosis liquid concentrating device, and coupled to the forward osmosis liquid concentrating device, to adjust the concentration of salts in the wastewater Increase to above 4% and below 7%. The wastewater treatment system of claim 1, wherein the forward osmosis liquid concentration device comprises a forward osmosis liquid concentration unit and an extract liquid recovery unit coupled to the forward osmosis liquid concentration unit, the extract liquid recovery unit receiving The forward osmosis liquid concentrating unit dilutes the extract and provides the extract having an osmotic pressure between 70 atm and 200 atm to the forward osmosis liquid concentrating unit. The wastewater treatment system according to claim 1, wherein the dialysis membrane in the electrodialysis device comprises a bipolar membrane, an anion selective membrane and a cation selective membrane. The wastewater treatment system of claim 4, wherein the electrodialysis device comprises: a waste water chamber to receive the waste water containing the first ions; The positive electrode chamber and the negative electrode chamber are respectively arranged on opposite sides of the waste water chamber; an acid liquid chamber, arranged between the waste water chamber and the positive electrode chamber; an lye chamber, disposed between the waste water chamber and the negative electrode chamber; and a first buffer chamber, disposed between one of the acid solution chamber and the alkali solution chamber and the waste water chamber, receiving a first buffer solution containing the first ions, The interface between the waste water chamber and the first buffer chamber is a first ion exchange membrane, and the interface between the one of the acid chamber and the alkali chamber and the first buffer chamber The interface is the second ion exchange membrane, and the first ion exchange membrane and the second ion exchange membrane have the same electrical properties. The wastewater treatment system of claim 1, wherein the salts in the wastewater include sodium chloride, sodium sulfate, lithium chloride, lithium sulfate, or a combination thereof. A wastewater treatment method, comprising: providing wastewater to a forward osmosis liquid concentrator to increase the concentration of salts in the wastewater to between 7% and 14%; and Through the forward osmosis liquid concentration device, the waste water is introduced into an electrodialysis device, so that the salts in the waste water can be made into acid solution and alkali solution. The wastewater treatment method according to claim 7, wherein before providing the wastewater to a forward osmosis liquid concentration device, it further comprises providing the wastewater to a pretreatment device, and removing the salts in the wastewater concentration increased to above 4% and below 7%. The wastewater treatment method according to claim 7, further comprising providing the diluted extract in the forward osmosis liquid concentration device to an extract recovery unit, and the extract recovery unit has an osmotic pressure ranging from 70 atm to 200 atm The extracted liquid between them is supplied to the forward osmosis liquid concentration unit. The wastewater treatment method according to claim 7, wherein the salts in the wastewater include sodium chloride, sodium sulfate, lithium chloride, lithium sulfate or a combination thereof.

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