Method for treating waste water comprising ammonia

Abstract

This invention provides a method for treating wastewater containing ammonia, comprising: generating an acidic aqueous solution in which ammonium ions are dissolved by supplying treated water containing gaseous free ammonia to a first region and supplying an acidic aqueous solution through one side of a second region, wherein the first region and the second region are separated by a first gas-liquid separation membrane, and the free ammonia in the treated water is transferred to the second region and dissolved in the acidic aqueous solution in the second region; obtaining at least a portion of the acidic aqueous solution in which the ammonium ions are dissolved from the second region through the other side of the second region; dissolving additional ammonium ions in the acidic aqueous solution in the second region by supplying at least a portion of the obtained acidic aqueous solution in which the ammonium ions are dissolved to the second region through one side of the second region, wherein the free ammonia in the first region is transferred to the second region; and obtaining at least a portion of the acidic aqueous solution in which the additional ammonium ions are dissolved from the second region through the other side of the second region; wherein the steps of dissolving additional ammonium ions and obtaining at least a portion of the acidic aqueous solution are repeated until the pH of the second region reaches a predetermined value.

Description

Technical Field

[0001] This invention relates to a method for treating wastewater containing ammonia. Prior Technology

[0002] Ammonia wastewater treatment methods are mainly divided into physiochemical methods and biological methods. Examples of physiochemical methods include ammonia stripping, discontinuous chlorination, selective ion exchange, and coagulation precipitation. Biological methods include nitrification, which aims to remove organic nitrogen and ammonia nitrogen, and denitrification, which aims to remove nitrite and nitrate.

[0003] Ammonia wastewater discharged from the electronics industry has several characteristics, often containing high concentrations of recalcitrant substances and trace amounts of toxic materials, which may cause process instability during biological treatment. In view of this problem, ammonia wastewater is typically treated using physicochemical methods with tower-type equipment. However, tower-type facilities are tall, inevitably requiring outdoor (rooftop) installation, which necessitates significant manpower and time for maintenance. Furthermore, the operation requires high temperatures and specific pH levels, necessitating high efficiency. Additionally, existing physicochemical methods may generate flocculated sludge or introduce compounds that could cause secondary environmental pollution, thus limiting their use and making them difficult to effectively treat ammonia wastewater. Existing technical documents Patent documents

[0004] Korean Patent Application No. 1747254 Summary of the Invention

[0005] The purpose of this invention is to provide a method for treating wastewater containing ammonia.

[0006] To achieve the above objectives, the present invention employs the following technical methods.

[0007] 1. A method for treating wastewater containing ammonia, comprising: supplying treated water containing gaseous free ammonia to a first region and supplying an acidic aqueous solution through one side of a second region to generate an acidic aqueous solution in which ammonium ions (NH4+) are dissolved, wherein the first region and the second region are separated by a first gas-liquid separation membrane, and the free ammonia in the treated water is transferred to the second region and dissolved in the acidic aqueous solution in the second region; passing through the other side of the second region to obtain at least a portion of the acidic aqueous solution in which the ammonium ions are dissolved from the second region; and by passing through the second region... The process involves resupplying at least a portion of the obtained ammonium ions dissolved in an acidic aqueous solution in one region to the second region to dissolve additional ammonium ions in the acidic aqueous solution in the second region, wherein free ammonia from the first region is transferred to the second region; and obtaining at least a portion of the additional ammonium ions dissolved in an acidic aqueous solution from the second region through the other side of the second region; wherein the steps of dissolving additional ammonium ions and obtaining at least a portion of the acidic aqueous solution are repeated until the pH of the second region reaches a predetermined value.

[0008] 2. The method for treating wastewater containing ammonia according to 1 above, wherein the acidic aqueous solution is a phosphoric acid aqueous solution, and the acidic aqueous solution contains less than 40 parts by weight of phosphoric acid based on a total of 100 parts by weight of the aqueous solution.

[0009] 3. The method for treating wastewater containing ammonia according to 2 above, wherein, based on a total of 100 parts by weight of aqueous solution, the phosphoric acid aqueous solution contains 5 to 10 parts by weight of phosphoric acid.

[0010] 4. The method for treating wastewater containing ammonia according to 1 above, wherein the predetermined value is increased by 3 to 4 compared to the pH value of the second region immediately after the supply of the acidic aqueous solution.

[0011] 5. The method for treating wastewater containing ammonia according to 1 above further includes: stopping the repeated steps of dissolving additional ammonium ions and obtaining at least a portion of the acidic aqueous solution when the pH value of the second region reaches the predetermined value, and further supplying the acidic aqueous solution through one side of the second region.

[0012] 6. The method for treating wastewater containing ammonia according to 1 above, wherein the treated water is supplied to the first region by generating a vortex.

[0013] 7. The method for treating wastewater containing ammonia according to 1 above, wherein at least a portion of the ammonium ions in the wastewater containing ammonia is converted into gaseous free ammonia by adding an alkaline substance ("alkali") to the wastewater to be treated.

[0014] 8. The method for treating wastewater containing ammonia according to 1 above further includes: generating a vortex phenomenon by transmitting the treated water containing free ammonia through a vortex generator before the step of supplying the treated water containing free ammonia to the first area.

[0015] 9. The method for treating wastewater containing ammonia according to 8 above further includes: prior to the step of generating eddy current phenomenon, treating the wastewater containing ammonia to obtain the treated water containing gaseous free ammonia by using an alkaline substance, and converting at least a portion of the ammonia contained in the wastewater to gaseous free ammonia.

[0016] 10. The method for treating wastewater containing ammonia according to 1 above, wherein the wastewater is wastewater from a semiconductor manufacturing process.

[0017] 11. The method for treating wastewater containing ammonia according to 1 above, wherein the treated water supplied to the first area is not circulated in the first area, but is discharged from the first area and moved to a subsequent treatment process.

[0018] 12. The method for treating wastewater containing ammonia according to 11 above, wherein when the ammonia concentration in the treated water in the first area reaches a predetermined value, it is discharged.

[0019] 13. The method for treating wastewater containing ammonia according to 11 above further includes: before the step of generating an acidic aqueous solution in which ammonium ions (NH4+) are dissolved, circulating the wastewater containing ammonia to a second gas-liquid separation membrane to obtain treated water containing gaseous free ammonia.

[0020] The method for treating wastewater containing ammonia according to the present invention can remove ammonia from wastewater at low cost and with high efficiency by supplying an acidic aqueous solution of optimal concentration to a first gas-liquid separation membrane.

[0021] Furthermore, according to the method for treating wastewater containing ammonia according to the present invention, the products generated in the treatment process can be used as fertilizers for use with acidic aqueous solutions, thereby gaining environmental advantages.

[0022] In the method for treating wastewater containing ammonia according to the present invention, a vortex phenomenon is generated in the treated water containing free ammonia and applied to a first gas-liquid separation membrane, thereby promoting the movement of free ammonia and exhibiting excellent effect in removing ammonia from wastewater.

[0023] The method for treating wastewater containing ammonia described in this invention can circulate the ammonia-containing wastewater through a second gas-liquid separation membrane to obtain treated water containing gaseous free ammonia, and supply the treated water containing gaseous free ammonia to a region of a first gas-liquid separation membrane and discharge it from the first gas-liquid separation membrane, thereby effectively removing ammonia from the wastewater with higher efficiency. Simple Explanation of the Diagram

[0024] The above and other objects, features and advantages of the present invention will become more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, wherein:

[0025] Figure 1 is a process flow diagram for removing ammonia from wastewater according to an embodiment of the present invention;

[0026] Figure 2 is a schematic diagram of the device for removing ammonia from wastewater according to an embodiment of the present invention;

[0027] Figure 3 is a schematic diagram of an apparatus for removing ammonia from wastewater according to another embodiment of the present invention;

[0028] Figure 4 shows the results of comparing ammonia removal efficiency based on the concentration of the phosphoric acid aqueous solution;

[0029] Figure 5 shows the salting-out degree based on the concentration of the phosphoric acid aqueous solution;

[0030] Figure 6 shows the results of comparing ammonia removal efficiency based on the supply areas of treated water and acidic aqueous solution;

[0031] Figure 7 shows the results of comparing ammonia removal efficiency based on the circulation direction of treated water and acidic aqueous solution;

[0032] Figure 8 shows the ammonia removal efficiency of the gas-liquid separation membrane zone, where the treated water system is provided according to pH value and the acidic aqueous solution is circulated.

[0033] Figure 9 illustrates the experimental setup used to compare the ammonia removal efficiency in cases where treated water is supplied by generating eddies and in cases where treated water is supplied without providing eddies; and

[0034] Figure 10 is a graph comparing the ammonia removal efficiency when the treated water is supplied by generating eddies versus when the treated water is supplied without providing eddies. Implementation

[0035] This invention provides a method for treating wastewater containing ammonia.

[0036] Wastewater can be selected from domestic wastewater, livestock wastewater, dairy wastewater, food wastewater, factory wastewater, and industrial wastewater.

[0037] Specifically, the wastewater can be wastewater generated during semiconductor manufacturing processes. The wastewater treatment method of the present invention can reduce ammonia in wastewater generated during semiconductor manufacturing processes and containing high concentrations of ammonia with excellent efficiency.

[0038] According to the present invention, when using a method for treating wastewater containing ammonia, even indoors, a small amount of energy can be used to effectively treat wastewater containing ammonia without generating waste such as sludge.

[0039] In the following, the wastewater treatment method containing ammonia according to an embodiment of the present invention will be described in detail with reference to FIG1.

[0040] This invention provides a method for treating wastewater containing ammonia, comprising:

[0041] An acidic aqueous solution containing dissolved ammonium ions is generated by supplying treated water containing gaseous free ammonia to the first zone and supplying an acidic aqueous solution through one side of the second zone.

[0042] The first region and the second region are separated by a first gas-liquid separation membrane. Free ammonia in the treated water is transferred to the second region and dissolved in the acidic aqueous solution of the second region (S1).

[0043] Through the other side of the second region, at least a portion of the acidic aqueous solution in which ammonium ions are dissolved is obtained from the second region (S2);

[0044] Additional ammonium ions are dissolved in the acidic aqueous solution in the second region by supplying at least a portion of the obtained ammonium ions dissolved therein to the second region from one side.

[0045] In this process, the free ammonia in the first region is transferred to the second region (S3); and

[0046] Through the other side of the second region, at least a portion of the acidic aqueous solution in which additional ammonium ions are dissolved is obtained from the second region (S4).

[0047] At this point, the steps of dissolving additional ammonium ions and obtaining at least a partially acidic aqueous solution can be repeated until the pH of the second region reaches a predetermined value.

[0048] Ammonia in wastewater can exist in the form of dissolved ammonium ions (NH4+) or gaseous free ammonia (NH3).

[0049] For example, wastewater containing ammonia can be wastewater in which only ammonium ions are dissolved, wastewater in which both ammonium ions and free ammonia coexist, or wastewater containing only free ammonia. Free ammonia can be ammonia gas.

[0050] Gas-liquid separation membranes are porous membranes that can only allow gases such as free ammonia contained in wastewater to pass through.

[0051] Gas-liquid separation membranes can be made from a variety of known materials and can be of various types.

[0052] The material of the gas-liquid separation membrane is not limited. For example, the gas-liquid separation membrane can be a hydrophobic membrane, a hydrophilic membrane, a porous membrane, a non-porous membrane, a homogeneous membrane, a heterogeneous membrane, an organic membrane, or an inorganic membrane. Specifically, it can be a hydrophobic porous membrane.

[0053] There are no restrictions on the type of gas-liquid separation membrane, as long as it allows free ammonia to pass through. For example, the gas-liquid separation membrane can be plate-shaped, tubular, spiral-shaped, or hollow fiber-shaped.

[0054] According to one embodiment, when the first gas-liquid separation membrane in the step (S1) of generating an acidic aqueous solution in which ammonium ions are dissolved has a cylindrical shape, treated water containing gaseous free ammonia can be supplied to the inner region based on the first gas-liquid separation membrane, while the acidic aqueous solution is supplied to the outer region.

[0055] According to another embodiment, when the first gas-liquid separation membrane in the step (S1) of generating an acidic aqueous solution in which ammonium ions are dissolved has a cylindrical shape, the acidic aqueous solution can be supplied to the inner region based on the first gas-liquid separation membrane, while the treated water containing gaseous free ammonia is supplied to the outer region.

[0056] The mechanism by which free ammonia dissolves through the first gas-liquid separation membrane and its concentration decreases in the acidic aqueous solution and the treated water during the step (S1) in which ammonium ions are generated and dissolved therein will be explained below.

[0057] If treated water containing free ammonia is supplied to a first region based on a first gas-liquid separation membrane, and an acidic aqueous solution with a very low concentration of free ammonia or containing a small amount of free ammonia is supplied to a second region, the free ammonia in the treated water can pass through the pores of the first gas-liquid separation membrane due to the concentration difference of free ammonia in the two regions divided by the membrane, and then move to the acidic aqueous solution with a relatively low concentration of free ammonia. Since the second region, where the acidic aqueous solution is present, has a low pH environment, the free ammonia that has passed through the first gas-liquid separation membrane can react with the acidic aqueous solution in the second region to dissolve the ammonium ions therein, thereby producing an acidic aqueous solution containing dissolved ammonium ions. Therefore, the concentration of free ammonia in the acidic aqueous solution in the second region can be maintained at a very low level, allowing the free ammonia contained in the treated water in the first region to continuously permeate into the pores of the first gas-liquid separation membrane and move to the acidic aqueous solution. That is, free ammonia in the treated water can pass through the first gas-liquid separation membrane to move to the region containing the acidic aqueous solution or the region containing the acidic aqueous solution containing dissolved ammonium ions. Furthermore, mobile free ammonia can dissolve in acidic aqueous solutions as ammonium ions, and the ammonium ions dissolved in the acidic aqueous solutions can be recovered. Through the series of processes described above, the concentration of free ammonia in the treated water can be reduced, and the reduction rate of ammonia in the wastewater can be increased.

[0058] In step (S1) of generating an acidic aqueous solution in which ammonium ions are dissolved, the wastewater pretreated and supplied to the first zone as treated water containing gaseous free ammonia can be obtained by adding an alkaline material ("alkali").

[0059] For example, by adding alkali to the water to be treated containing ammonia, treated water containing gaseous free ammonia can be obtained and supplied to the first area, such that at least some of the ammonium ions dissolved in the water to be treated are converted into gaseous free ammonia.

[0060] For example, by adding alkali to the water to be treated containing ammonia, the treated water containing gaseous free ammonia supplied to the first zone can have a pH adjusted to about 10 to 12.

[0061] The alkali can be selected from NaOH, slaked lime, quicklime, and soda ash.

[0062] In step (S1) of generating an acidic aqueous solution in which ammonium ions are dissolved, the treated water containing gaseous free ammonia supplied to the first region may be untreated wastewater.

[0063] In step (S1) of generating an acidic aqueous solution in which ammonium ions are dissolved, the acidic aqueous solution supplied through one side of the second region may be a water-soluble solution of an acidic material selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, citric acid and oxalic acid, but is not limited thereto.

[0064] Based on a total of 100 parts by weight of aqueous solution, an acidic aqueous solution may contain less than 40 parts by weight of acidic substances.

[0065] According to one embodiment, the acidic aqueous solution supplied through one side of the second region may be a phosphoric acid aqueous solution containing less than 40 parts by weight of phosphoric acid, based on a total of 100 parts by weight of the aqueous solution.

[0066] For example, an aqueous solution of phosphoric acid may contain less than 40 parts by weight, 35 parts by weight or less, or 30 parts by weight or less of phosphoric acid based on a total of 100 parts by weight of the aqueous solution.

[0067] Specifically, the content of the phosphoric acid aqueous solution can be 5 to 15 parts by weight. For some cases, it is 5 to 10 parts by weight.

[0068] When using a phosphoric acid aqueous solution containing 40 parts by weight or more of phosphoric acid based on a total of 100 parts by weight of aqueous solution, a large amount of ammonium phosphate will precipitate out and contaminate the first gas-liquid separation membrane, which may reduce the ammonia removal efficiency of the first gas-liquid separation membrane.

[0069] When using a phosphoric acid aqueous solution containing 5 to 15 parts by weight of phosphoric acid based on a total of 100 parts by weight of aqueous solution, even a small amount of phosphoric acid can effectively reduce ammonia, thus achieving excellent economic and environmental benefits.

[0070] Phosphoric acid has the advantage of enabling equipment to be used for a longer period of time because it corrodes equipment more slowly than other acidic substances such as sulfuric acid. Furthermore, when phosphoric acid is used, the resulting ammonium phosphate, which is discharged as waste, has greater value as fertilizer.

[0071] In step (S1) of generating an acidic aqueous solution in which ammonium ions are dissolved, the treated water can be supplied to the first region by generating a vortex phenomenon.

[0072] When treated water is supplied by generating a vortex, the free ammonia contained in the treated water can more effectively penetrate through the first gas-liquid separation membrane. Ultimately, the amount of ammonia contained in the treated water can be reduced more effectively.

[0073] In step (S2), obtaining at least a portion of the acidic aqueous solution in which ammonium ions are dissolved from the second region via the other side of the second region, the acidic aqueous solution in which ammonium ions are dissolved may mean: free ammonia transferred during penetration through the first gas-liquid separation membrane is dissolved in the acidic aqueous solution supplied in the second region in the form of ammonium ions.

[0074] In step (S2), which involves obtaining at least a portion of an acidic aqueous solution in which ammonium ions are dissolved from the second region via the other side of the second region, the portion referred to as the other side is different from the side of the second region in step (S1) where the acidic aqueous solution in which ammonium ions are dissolved is supplied.

[0075] In step (S2), when at least a portion of the acidic aqueous solution in which ammonium ions are dissolved is obtained from the second region via the other side of the second region, this portion can be supplied back to one side of the second region (see S3). That is, the obtained acidic aqueous solution in which ammonium ions are dissolved can be supplied back to one side of the second region for repeated circulation. As the acidic aqueous solution in which ammonium ions are dissolved circulates through the second region, the concentration of ammonium ions in the acidic aqueous solution can be increased.

[0076] In step (S2), when at least a portion of the acidic aqueous solution in which ammonium ions are dissolved is obtained from the other side of the second region, the ammonium ions in the obtained acidic solution can react with the acidic substance to form an ammonium salt, and the formed ammonium salt can be used as a compound fertilizer. Ammonium salts can also be obtained by heating the acidic aqueous solution in which ammonium ions are dissolved and then precipitating the heated solution. For example, when an aqueous solution of phosphoric acid is used as the acidic aqueous solution, ammonium phosphate can be obtained.

[0077] In step (S3) where additional ammonium ions are dissolved in the acidic aqueous solution in the second region, the acidic aqueous solution in which the obtained ammonium ions are dissolved can be supplied to one side of the second region.

[0078] In this process, free ammonia in the treated water of the first region can be transferred to the second region and dissolved again as ammonium ions in the acidic aqueous solution where ammonium ions are dissolved, thereby increasing the concentration of ammonium ions in the acidic aqueous solution. Through the above continuous process, the free ammonia and ammonia in the treated water can be effectively reduced.

[0079] In the step (S3) of dissolving additional ammonium ions in the acidic aqueous solution in the second region, this side may be the same as the side supplying the acidic aqueous solution in the step (S1) of generating the acidic aqueous solution in which ammonium ions are dissolved.

[0080] In step (S4), obtaining at least a portion of the acidic aqueous solution in which additional ammonium ions are dissolved, the acidic aqueous solution in which additional ammonium ions are dissolved can mean that free ammonia moving through the first gas-liquid separation membrane is dissolved in the form of ammonium ions in the acidic aqueous solution in which ammonium ions are dissolved and then resupplying to the second region. Free ammonia that has penetrated and moved through the first gas-liquid separation membrane is dissolved in the form of ammonium ions in the aqueous acidic solution containing the dissolved ammonium ions that is resupplying to the second region.

[0081] In step (S4) of obtaining at least a portion of the acidic aqueous solution in which additional ammonium ions are dissolved, the other side may be the same as the other side of obtaining the acidic aqueous solution from the second region in step (S2) of obtaining at least a portion of the acidic aqueous solution in which ammonium ions are dissolved through the other side of the second region.

[0082] The steps of dissolving additional ammonium ions in the acidic aqueous solution in the second region (S3) and obtaining at least a portion of the acidic aqueous solution in which the additional ammonium ions are dissolved (S4) can be repeated until the pH value of the second region reaches a predetermined value. If the predetermined value is exceeded, a large amount of ammonium ions may dissolve in the acidic aqueous solution and precipitate as ammonium salt, which may contaminate the first gas-liquid separation membrane, thereby reducing the efficiency of ammonia removal from wastewater.

[0083] The predetermined value can be an increase of 3 to 4 compared to the pH value of the second region measured immediately after the supply of the acidic aqueous solution.

[0084] According to one embodiment, when the pH value of the second region is measured to be 0.5 immediately after supplying the acidic aqueous solution in which ammonium ions are dissolved in the second region in step (S1), the steps of dissolving additional ammonium ions in the acidic aqueous solution in the second region (S3) and obtaining at least a portion of the acidic aqueous solution in which additional ammonium ions are dissolved (S4) can be repeated until the pH value of the second region becomes 3.5 to 4.5.

[0085] According to one embodiment, when an acidic aqueous solution is supplied and circulated, the pH value of the second area supplying the acidic aqueous solution can increase, and when the pH value increases to a predetermined range or higher, it can be confirmed that the ammonia wastewater treatment efficiency is significantly reduced. Therefore, when the pH value increases to a predetermined range or higher, by removing the circulated acidic aqueous solution and resupplying fresh acidic aqueous solution, ammonia wastewater can be treated with excellent efficiency in terms of cost and time.

[0086] The method for treating wastewater containing ammonia according to the present invention further includes:

[0087] When the pH value of the second region reaches a predetermined value, the steps of dissolving additional ammonium ions in the acidic aqueous solution of the second region (S3) and obtaining at least a portion of the acidic aqueous solution in which additional ammonium ions are dissolved (S4) are stopped, and the acidic aqueous solution is further supplied through one side of the second region (S5).

[0088] According to one embodiment, when the pH value of the second region is measured to be 0.5 immediately after the acidic aqueous solution in which ammonium ions are dissolved is supplied in step (S1) of generating the acidic aqueous solution, the acidic aqueous solution in which ammonium ions are dissolved can be circulated in the second region until the pH of the second region becomes 3. Simultaneously, if the pH exceeds 3, fresh acidic aqueous solution can be supplied again from one side of the second region to replace the acidic aqueous solution in which ammonium ions are dissolved.

[0089] When the acidic aqueous solution is supplied again in the step (S5) of further supplying the acidic aqueous solution through the second region, the free ammonia in the water to be treated in the first region can move to the second region and then dissolve in the resupplied phosphoric acid aqueous solution in the form of ammonium ions, thereby producing an acidic aqueous solution in which ammonium ions are dissolved.

[0090] An acidic aqueous solution (S2) in which the generated ammonium ions dissolve can be obtained through the other side of the second region, and the acidic aqueous solution in which the generated ammonium ions dissolve can be circulated through the second region.

[0091] In the method for treating wastewater containing ammonia according to the present invention, the treated water supplied to the first region can be discharged from the first region and transferred to a subsequent treatment process without being circulated in the first region. That is, unlike the acidic aqueous solution supplied to the second region, the treated water supplied to the first region is not circulated in the first region.

[0092] In the method for treating wastewater containing ammonia according to the present invention, when the residual ammonia concentration in the treated water of the first zone reaches a predetermined value, the treated water can be discharged from the first zone and transferred to a subsequent process. The predetermined value may be 50 mg / L. If wastewater with insufficient ammonia concentration is transferred to a subsequent treatment process, the toxicity of ammonia may adversely affect the subsequent treatment process.

[0093] After the treated water with reduced ammonia is discharged from the first region and transferred to subsequent processes, the treated water containing gaseous free ammonia can be resupplyed to the first region separated by the first gas-liquid separation membrane.

[0094] The method for treating wastewater containing ammonia according to the present invention may further include, prior to the step of supplying the treated water containing free ammonia to the first region, passing the treated water containing free ammonia through a vortex generator to generate a vortex phenomenon. As described above, when the treated water is supplied by generating a vortex phenomenon, the free ammonia contained in the treated water can more effectively penetrate through the first gas-liquid separation membrane, and the ammonia contained in the ultimately treated water can be reduced more efficiently.

[0095] The eddy current generator used here can be a known device, for example, a pipeline mixer.

[0096] The method for treating ammonia-containing wastewater according to the present invention further includes, prior to the step of generating eddy currents, adding an alkaline substance to treat the ammonia-containing wastewater and converting at least a portion of the ammonia in the wastewater into gaseous free ammonia, thereby obtaining treated water containing gaseous free ammonia. By treating it into gaseous free ammonia, treated water containing gaseous free ammonia is obtained. According to the step of obtaining treated water containing gaseous free ammonia, the concentration of free ammonia in the treated water supplied to the first gas-liquid separation membrane can be higher, thereby more effectively reducing ammonia in the wastewater.

[0097] In the method for treating wastewater containing ammonia described in this invention, treated water and acidic aqueous solution can be circulated into the first gas-liquid separation membrane in opposite or the same directions.

[0098] The treated water supplied to the first region based on the first gas-liquid separation membrane can be discharged from the first region and transferred to subsequent treatment processes. That is, the treated water supplied to the first region based on the first gas-liquid separation membrane can be directly discharged through the first gas-liquid separation membrane without being recycled and transferred to subsequent processes.

[0099] According to the method for treating wastewater containing ammonia described in this invention, even if the treated water supplied to the first region of the first gas-liquid separation membrane as described above is not circulated in the first gas-liquid separation membrane, ammonia in the wastewater can be removed with excellent efficiency. Therefore, it has the advantage that wastewater containing a large amount of ammonia can be treated simultaneously by directly transferring the treated water to subsequent processes without circulating it in the first gas-liquid separation membrane.

[0100] The method for treating wastewater containing ammonia according to the present invention may further include, prior to the step of generating an acidic aqueous solution in which ammonium ions (NH4+) are dissolved, circulating the water to be treated, containing ammonia, through a second gas-liquid separation membrane to obtain treated water containing gaseous free ammonia.

[0101] According to one embodiment, untreated water containing ammonia is circulated in a second gas-liquid separation membrane to produce treated water containing free ammonia, which is reduced compared to the untreated water. The treated water is then supplied to a first region of a first gas-liquid separation membrane to discharge the treated water from the first gas-liquid separation membrane, where the ammonia has been further reduced, and proceeds sequentially to the next process (see Figure 3).

[0102] When the method of the present invention further includes the step of circulating the water to be treated containing ammonia to a second gas-liquid separation membrane, the ammonia removal efficiency can be improved.

[0103] The method for treating wastewater containing ammonia according to the present invention may further include generating a vortex phenomenon by means of a vortex generator before supplying treated water containing free ammonia to a first zone.

[0104] The present invention also provides an apparatus for treating wastewater containing ammonia.

[0105] The apparatus for treating wastewater containing ammonia according to an embodiment of the present invention will be described in detail below with reference to Figures 2 and 3.

[0106] According to an embodiment of the present invention, an apparatus 1000 for treating wastewater containing ammonia may include an ammonia wastewater tank 100, an acidic aqueous solution tank 200, and a first gas-liquid separation membrane module 300.

[0107] The ammonia wastewater tank 100 may contain wastewater containing ammonia and may be connected to one side of the first region of the first gas-liquid separation membrane module 300 to supply the ammonia-containing wastewater to the first region.

[0108] The other side of the first region of the first gas-liquid separation membrane module 300 can be connected back to the ammonia wastewater tank 100. In this case, the wastewater discharged from the first gas-liquid separation membrane module 300, i.e., treated water with reduced ammonia content, can be supplied to the ammonia wastewater tank 100 and then re-supplied to the first gas-liquid separation membrane module 300 for circulation (see Figure 2). Thus, if the wastewater discharged from the first gas-liquid separation membrane module 300 is circulated through the first gas-liquid separation membrane module 300, the efficiency of ammonia removal from the circulating wastewater can be improved. However, once the wastewater is being supplied to the first gas-liquid separation membrane module 300 for circulation, other wastewater cannot be supplied to the first gas-liquid separation membrane module 300. Therefore, from the viewpoint of the entire wastewater treatment process, there is a disadvantage that the total amount of ammonia wastewater that can be treated per day is very small. Furthermore, another disadvantage is that additional equipment or costs are required to circulate the wastewater discharged from the first gas-liquid separation membrane module 300.

[0109] The apparatus of the present invention can be configured such that, once wastewater is supplied, it is not circulated through the first gas-liquid separation membrane module 300 but is directly transferred to a subsequent treatment process (see FIG. 3). Specifically, the other side of the first region of the first gas-liquid separation membrane module 300 can be directly connected to the area for subsequent treatment or the treated water tank 700, in which the wastewater discharged from the first gas-liquid separation membrane module 300 can be stored. The treated water tank 700 can be a space in which the wastewater discharged from the first gas-liquid separation membrane module 300 can be stored before being transported to the area for subsequent treatment.

[0110] In this configuration, the wastewater discharged from the first gas-liquid separation membrane module 300, i.e., the treated water with reduced ammonia content, can be moved to subsequent treatment processes instead of being supplied to the ammonia wastewater tank 100. Since the device 1000 of this invention ensures excellent ammonia removal efficiency, even if the wastewater discharged from the first gas-liquid separation membrane module 300 is moved directly to subsequent processes without being recycled in the first gas-liquid separation membrane module 300, this will not adversely affect the performance of the next process. In this configuration, large volumes of wastewater can be treated more efficiently throughout the entire wastewater treatment process.

[0111] A second gas-liquid separation membrane can be arranged in batches around the ammonia wastewater tank 100. As described above, with the device in this configuration, the wastewater moves directly to subsequent treatment processes without being recycled to the first gas-liquid separation membrane module 300, and the amount of ammonia can be reduced more effectively when the second gas-liquid separation membrane is installed.

[0112] Ammonia wastewater may contain no free ammonia at all, or it may contain free ammonia.

[0113] The acidic aqueous solution tank 200 may contain an acidic aqueous solution or an acidic aqueous solution in which ammonium ions are dissolved, and may be connected to a second region of the first gas-liquid separation membrane module 300 to supply the acidic aqueous solution in which ammonium ions are dissolved to the second region.

[0114] An acidic aqueous solution in which ammonium ions are dissolved can be obtained by allowing free ammonia to pass through a first region of a first gas-liquid separation membrane. The free ammonia is subsequently contained in an acidic aqueous solution present in a second region, or dissolved in an acidic aqueous solution in the form of ammonium ions.

[0115] The first gas-liquid separation membrane module 300 has a structure including a gas-liquid separation membrane and can act to reduce the amount of free ammonia present in the treated water.

[0116] The first gas-liquid separation membrane module 300 can adopt a structure known in the field of water treatment, and the specific structure is not limited.

[0117] The first gas-liquid separation membrane module 300 may include a gas-liquid separation membrane, and may be divided into a first region and a second region according to the gas-liquid separation membrane.

[0118] For example, the first gas-liquid separation membrane module 300 may include a cylindrical gas-liquid membrane and may be divided into an inner region and an outer region. In this case, the first region may be the inner region and the second region may be the outer region; otherwise, the first region may be the outer region and the second region may be the inner region.

[0119] According to one embodiment, the internal area of ​​the first gas-liquid separation membrane module 300 can be connected to the ammonia wastewater tank 100, while the external area can be connected to the acidic aqueous solution tank 200.

[0120] According to one implementation scheme, the outer area of ​​the first gas-liquid separation membrane module 300 can be connected to the ammonia wastewater tank 100, and the inner area can be connected to the acidic aqueous solution tank 200.

[0121] According to an embodiment of the present invention, an apparatus 1000 for treating wastewater containing ammonia may further include a first eddy current generator 400 located in a channel connecting an ammonia wastewater tank 100 and a first gas-liquid separation membrane module 300.

[0122] The first eddy current generator 400 can be installed on the channel connecting one area of ​​the ammonia wastewater tank 100 and the first gas-liquid separation membrane module 300.

[0123] When the first eddy current generator 400 is used, an eddy current phenomenon can occur when ammonia wastewater flows from the ammonia wastewater tank 100 to the first gas-liquid separation membrane module 300. The free ammonia contained in the ammonia wastewater can pass through the gas-liquid separation membrane more effectively, thereby ultimately reducing the ammonia content in the wastewater more effectively.

[0124] The form or type of the first eddy current generator 400 is not limited, as long as the generator can generate eddy currents in the ammonia wastewater moving from the ammonia wastewater tank 100 to the first gas-liquid separation membrane module 300.

[0125] The first eddy current generator 400 can be a known eddy current generator, and can be, for example, a line mixer.

[0126] According to an embodiment of the present invention, an apparatus 1000 for treating wastewater containing ammonia may include a second eddy current generator 600 located in a channel connecting an acidic aqueous solution tank 200 and a first gas-liquid separation membrane module 300.

[0127] The second eddy current generator 600 can be installed on the channel connecting the acidic aqueous solution tank 200 and a region of the first gas-liquid separation membrane module 300.

[0128] When the second eddy current generator 600 is used, eddy currents may occur in acidic aqueous solutions or in acidic aqueous solutions moving from the acidic aqueous solution tank 200 to the first gas-liquid separation membrane module 300, and the aqueous solution may be transferred to the first gas-liquid separation membrane module 300 more efficiently, thereby reducing the ammonia content in the wastewater more effectively.

[0129] The form or type of the second eddy current generator 600 is not limited, as long as the generator can generate eddy current phenomena in the acidic aqueous solution or when the acidic aqueous solution moves from the acidic aqueous solution tank 200 into the first gas-liquid separation membrane module 300.

[0130] The second eddy current generator 600 can be a well-known eddy current generator, and for example, it can be a linear mixer.

[0131] According to an embodiment of the present invention, an apparatus 1000 for treating wastewater containing ammonia may further include an alkaline substance ("alkali") addition unit 500 located in the channel of the connected ammonia wastewater tank 100 and the first gas-liquid separation membrane module 300.

[0132] Alkaline substances can be injected into the alkali addition unit 500. The alkaline substances can be selected from NaOH, KOH, slaked lime, quicklime, and soda ash.

[0133] When an alkaline substance is injected through the alkali addition unit 500, the ammonium ions present in the ammonia wastewater moving from the ammonia wastewater tank 100 to the first gas-liquid separation membrane module 300 can be converted into free ammonia, thereby more effectively reducing the amount of ammonia.

[0134] The alkali addition unit 500 can be located in the channel connecting the ammonia wastewater tank 100 and the first vortex generator 400.

[0135] When alkaline substances are injected into the alkali addition unit 500, which is located in the channel connecting the ammonia wastewater tank 100 and the first vortex generator 400, a larger amount of ammonium ions in the wastewater can be converted into free ammonia compared to when no alkaline substances are injected. Then, through the gas-liquid separation membrane, the ammonia content in the wastewater is effectively reduced.

[0136] The configuration and effects of the present invention will be described in more detail below with reference to embodiments. However, the following embodiments are provided for illustrative purposes only to aid in understanding the present invention, and the scope and boundaries of the present invention are not limited thereto.

[0137] [1. Ammonia removal efficiency depends on the concentration of the acidic aqueous solution]

[0138] In Examples 1 to 3 and Comparative Example 1, the differences in ammonia removal effects caused by the concentration of phosphoric acid aqueous solution were investigated.

[0139] [Example 1]

[0140] Treated water, obtained by treating raw water containing ammonia with NaOH, is supplied from one side to the inner region via a cylindrical gas-liquid separator (trade name: Liqui-cel, manufacturer: 3M) and discharged through a different side (see Figure 3). Additionally, an aqueous solution containing 2.6 wt.% ("wt.%) of phosphoric acid is supplied to the outer region based on the cylindrical gas-liquid separator and then circulated. The phosphoric acid solution circulates in a direction different from the treated water. When the pH of the outer region based on the cylindrical gas-liquid separator is approximately 3 to 4 higher than the initially supplied phosphoric acid solution, the circulated phosphoric acid solution is removed and replaced with a resupply of an aqueous solution containing 10 wt.% phosphoric acid based on the total weight of the initially supplied solution. The supply rates of the treated water and the phosphoric acid solution to the two regions based on the cylindrical gas-liquid separator are set to 0.118 m / s and 0.0031 m / s, respectively.

[0141] [Example 2]

[0142] The same procedure as in Example 1 was performed, except that a phosphoric acid aqueous solution containing 10 wt.% phosphoric acid based on the total weight of the aqueous solution was used as the phosphoric acid aqueous solution for supplying and resupplying to the external region based on the cylindrical gas-liquid separation membrane.

[0143] [Example 3]

[0144] The same procedure as in Example 1 was performed, except that a phosphoric acid aqueous solution containing 30 wt.% phosphoric acid based on the total weight of the aqueous solution was used as the phosphoric acid aqueous solution for supplying and resupplying to the external region based on the cylindrical gas-liquid separation membrane.

[0145] [Comparative Example 1]

[0146] The same procedure as in Example 1 was performed, except that a phosphoric acid aqueous solution containing 40 wt.% phosphoric acid based on the total weight of the aqueous solution was used as the phosphoric acid aqueous solution for supplying and resupplying to the external region based on the cylindrical gas-liquid separation membrane.

[0147] [Confirmation of ammonia removal effectiveness]

[0148] To confirm the ammonia removal efficiency in the wastewater of Examples 1 to 3 and Comparative Example 1, the ammonia concentration in the treated water was measured after a certain period of time in each process. The results, as shown in Table 1 and Figure 4, confirm that a concentration higher than the predetermined concentration of the phosphoric acid aqueous solution has no effect on the ammonia removal efficiency in the wastewater. In particular, it can be seen that when the concentration of the phosphoric acid aqueous solution is 40% or higher, the ammonia removal efficiency in the wastewater actually decreases by 10%.

[0149]

[0150] The results show that when a 40% phosphoric acid aqueous solution is used for treatment, a large amount of salt precipitates in the external region based on the gas-liquid separation membrane due to the reaction between the free ammonia passing through the membrane and the phosphoric acid aqueous solution, thus contaminating the membrane (see Figure 5). Therefore, it can be concluded that the free ammonia remaining in the treated water is difficult to pass through the gas-liquid separation membrane, reducing the ammonia removal rate in the treated water.

[0151] [2. Depends on the ammonia removal efficiency of the area supplying treated water and acidic aqueous solutions]

[0152] Based on Example 4 and Comparative Example 2, the differences in ammonia removal efficiency depending on the region supplying treated water and phosphoric acid aqueous solution were investigated.

[0153] [Example 4]

[0154] The treated water obtained by treating raw water containing ammonia with NaOH is supplied from one side to the inner region of a cylindrical gas-liquid separator membrane and then discharged from the other side. Further, an aqueous phosphoric acid solution containing 10 wt.% phosphoric acid is supplied to the outer region of the cylindrical gas-liquid separator membrane and circulated. The phosphoric acid solution circulates in a direction different from that of the treated water. The supply rates of the treated water and the phosphoric acid solution to the two regions based on the cylindrical gas-liquid separator membrane are set to 0.118 m / s and 0.0031 m / s, respectively.

[0155] [Comparative Example 2]

[0156] The same procedure as in Example 4 was performed, except that the treated water was supplied to the outer region based on the cylindrical gas-liquid separation membrane, and an aqueous phosphoric acid solution containing 10 wt.% phosphoric acid based on the total weight of the aqueous solution was supplied to the inner region and circulated.

[0157] [Confirmation of ammonia removal effectiveness]

[0158] To compare the ammonia removal efficiency in the wastewater of Example 4 and Comparative Example 2, the ammonia concentration in the treated water was measured after a specific time in each method.

[0159] As a result, as shown in Figure 6, compared with the external pressure method in which treated water is supplied to the outer region based on the cylindrical gas-liquid separation membrane (Comparative Example 2), the internal pressure method in which treated water is supplied to the inner region based on the cylindrical gas-liquid separation membrane (Example 4) showed a better ammonia removal effect.

[0160] [3. The ammonia removal effect depends on the circulation direction of the treated water and the acidic aqueous solution]

[0161] According to Examples 5 and 6, the differences in ammonia removal efficiency depended on the supply direction (circulation direction) of the treated water and the phosphoric acid aqueous solution.

[0162] [Example 5]

[0163] The treated water obtained by treating raw water containing ammonia with NaOH is supplied from one side to the inner region of a cylindrical gas-liquid separator membrane and then discharged from a different side. Further, an aqueous phosphoric acid solution containing 10 wt.% phosphoric acid is supplied to the outer region of the cylindrical gas-liquid separator membrane and circulated. The supply rates of the treated water and the phosphoric acid solution to the two regions of the cylindrical gas-liquid separator membrane are set to 0.118 m / s and 0.0031 m / s, respectively. The treated water and the phosphoric acid solution are circulated in different directions.

[0164] [Example 6]

[0165] The same procedure as in Example 5 was performed, except that the treated water and the phosphoric acid aqueous solution were circulated in the same direction.

[0166] [Confirmation of ammonia removal effectiveness]

[0167] To compare the ammonia removal efficiency in the wastewater of Examples 5 and 6, the ammonia concentration in the treated water was measured after a specific time in each method.

[0168] As shown in Figure 7, the methods of circulating treated water and phosphoric acid aqueous solution in different directions (Example 5) and circulating treated water and phosphoric acid aqueous solution in the same direction (Example 6) showed similar ammonia removal effects.

[0169] [4. Determine the optimal supply conditions for the acidic aqueous solution circulating in one region of the gas-liquid separation membrane.]

[0170] To determine the optimal supply conditions for the circulating phosphoric acid aqueous solution in a region of the gas-liquid separation membrane according to Example 7, the pH conditions and ammonia removal efficiency of the region of the gas-liquid separation membrane, wherein the phosphoric acid aqueous solution is circulated, the following studies were conducted.

[0171] [Example 7]

[0172] Treated water obtained by treating raw water containing ammonia with NaOH is supplied from one side to the inner region of a cylindrical gas-liquid separator membrane and then discharged from a different side. Further, an aqueous solution of phosphoric acid containing 10 wt.% phosphoric acid is supplied to the outer region of the cylindrical gas-liquid separator membrane and subsequently circulated continuously, separate from the treated water. The pH of the outer region of the cylindrical gas-liquid separator membrane was measured to be 1 when the phosphoric acid solution was initially supplied. The supply rates of the treated water and the phosphoric acid solution to the two regions of the cylindrical gas-liquid separator membrane were set to 0.118 m / s and 0.0031 m / s, respectively.

[0173] [Confirmation of ammonia removal effectiveness]

[0174] The pH value of a region containing phosphoric acid solution in the gas-liquid separation membrane and the ammonia removal efficiency of another region containing wastewater were measured at intervals of 20 to 30 minutes, starting from the time of the first treatment of the phosphoric acid solution. The results showed that compared to the initial pH value, the pH value of the region of the gas-liquid separation membrane containing circulating phosphoric acid solution increased by 2 to 4, and the ammonia removal efficiency decreased significantly (see Figure 8). This result indicates that if the circulating phosphoric acid solution in the region of the gas-liquid separation membrane containing the circulating phosphoric acid solution is removed, the pH value of the gas-liquid separation membrane containing the circulating phosphoric acid solution will increase by 2 to 4 compared to the initial pH value when the pH value in that region rises. Then, by further providing fresh phosphoric acid solution, the ammonia removal efficiency will be even higher, and excellent efficiency can be achieved even with small amounts of phosphoric acid.

[0175] [5. Ammonia removal effect when supplying treated water based on a region-generated eddy current phenomenon of gas-liquid separation membrane]

[0176] Based on Example 8 and Comparative Example 4, the differences in ammonia removal efficiency for different supply methods of treated water containing free ammonia were compared.

[0177] [Example 8]

[0178] The treated water obtained by treating raw water containing ammonia with NaOH is supplied from one side to the inner region of a cylindrical gas-liquid separator membrane and then discharged from the other side. During this process, the treated water is supplied while generating a vortex (see Figure 9). Further, a phosphoric acid aqueous solution containing 10 wt.% phosphoric acid is supplied to the outer region of the cylindrical gas-liquid separator membrane and then continuously circulated. The phosphoric acid aqueous solution circulates in a direction different from that of the treated water. Compared to the initial supply of the phosphoric acid aqueous solution, when the pH of the outer region of the gas-liquid separator membrane is increased by 3 to 4, the phosphoric acid aqueous solution circulating in the outer region is removed, and then a new phosphoric acid aqueous solution containing 10 wt.% phosphoric acid is supplied, with a total weight equal to the initially supplied aqueous solution. The supply rates of the treated water and the phosphoric acid aqueous solution to the two regions of the cylindrical gas-liquid separator membrane are set to 0.118 m / s and 0.0031 m / s, respectively.

[0179] [Comparative Example 4]

[0180] Perform the same procedure as in Example 8, except that treated water is supplied without generating eddies.

[0181] [Confirmation of ammonia removal effectiveness]

[0182] To compare the ammonia removal efficiency in the wastewater of Example 8 and Comparative Example 4, the ammonia removal rate of the treated water was measured after a specific time in each process. The results showed that Example 8, in which the eddy current phenomenon was generated, achieved an ammonia removal rate as high as approximately 5% (see Figure 10).

[0183]

[0184] S1: An acidic aqueous solution in which ammonium ions are produced and dissolved.

[0185] S2: Obtain at least a portion of the acidic aqueous solution in which ammonium ions are dissolved from the second region through the other side of the second region.

[0186] S3: Dissolve additional ammonium ions in an acidic aqueous solution located in the second region.

[0187] S4: Obtain at least a portion of the acidic aqueous solution in which additional ammonium ions are dissolved from the second region via the other side of the second region.

[0188] S5: Further supply of acidic aqueous solution through one side of the second region.

[0189] 1000: Apparatus for treating wastewater containing ammonia

[0190] 100: Ammonia wastewater tank

[0191] 200: Acidic aqueous solution tank

[0192] 300: First gas-liquid separation membrane module

[0193] 400: First eddy current generator

[0194] 500: Alkali Addition Unit

[0195] 600: Second eddy current generator

[0196] 700: Second gas-liquid separation membrane

Claims

1. A method for treating wastewater containing ammonia, comprising: An acidic aqueous solution containing ammonium ions (NH4+) dissolved therein is generated by supplying treated water containing gaseous free ammonia to a first region and supplying an acidic aqueous solution through one side of a second region. The first region and the second region are separated by a first gas-liquid separation membrane, and the free ammonia in the treated water is transferred to the second region and dissolved in the acidic aqueous solution therein. At least a portion of the acidic aqueous solution containing the ammonium ions dissolved therein is obtained from the other side of the second region. At least a portion of the obtained acidic aqueous solution containing the ammonium ions dissolved therein is supplied through one side of the second region. The wastewater is partially transferred to the second region to dissolve additional ammonium ions in the acidic aqueous solution of the second region, wherein free ammonia from the first region is transferred to the second region; and through the other side of the second region to obtain at least a portion of the acidic aqueous solution in which the additional ammonium ions are dissolved; wherein the steps of dissolving the additional ammonium ions and obtaining at least a portion of the acidic aqueous solution are repeated until the pH value of the second region increases by 3 to 4 compared to the pH value of the second region immediately after the supply of the acidic aqueous solution, and wherein the wastewater is wastewater from a semiconductor manufacturing process.

2. The method for treating wastewater containing ammonia as described in claim 1, wherein, The acidic aqueous solution is a phosphoric acid aqueous solution, and based on a total of 100 parts by weight of aqueous solution, the phosphoric acid aqueous solution contains less than 40 parts by weight of phosphoric acid.

3. The method for treating wastewater containing ammonia as described in claim 2, wherein, Based on a total of 100 parts by weight of the aqueous solution, the phosphoric acid aqueous solution contains 5 to 10 parts by weight of phosphoric acid.

4. The method for treating wastewater containing ammonia as described in claim 1 further includes: When the pH value of the second region reaches the predetermined value, the steps of dissolving additional ammonium ions and obtaining at least a portion of the acidic aqueous solution are stopped, and the acidic aqueous solution is further supplied through one side of the second region.

5. The method for treating wastewater containing ammonia as described in claim 1, wherein, By generating eddies, the treated water is supplied to the first area.

6. The method for treating wastewater containing ammonia as described in claim 1, wherein, The treated water containing free ammonia is obtained by adding an alkaline substance ("alkali") to water containing ammonia to convert at least a portion of the ammonium ions in the water into gaseous free ammonia.

7. The method for treating wastewater containing ammonia as described in claim 1 further includes: Prior to the step of supplying the treated water containing free ammonia to the first region, the treated water containing free ammonia is passed through a vortex generator to generate a vortex phenomenon.

8. The method for treating wastewater containing ammonia as described in claim 7 further includes: Prior to the step of generating the eddy phenomenon, the water to be treated, which contains ammonia, is treated with an alkaline substance and at least a portion of the ammonia contained in the water to be treated is converted into gaseous free ammonia to obtain the treated water containing gaseous free ammonia.

9. The method for treating wastewater containing ammonia as described in claim 1, wherein, The treated water supplied to the first area is not circulated within the first area, but is discharged from the first area and moved to subsequent treatment processes.

10. The method for treating wastewater containing ammonia as described in claim 9, wherein, When the ammonia concentration in the treated water of the first zone reaches a predetermined value, it is discharged, wherein the predetermined value is 50 mg / L.

11. The method for treating wastewater containing ammonia as described in claim 9, further comprising: Prior to the step of generating an acidic aqueous solution in which ammonium ions (NH4+) are dissolved, the water to be treated containing ammonia is circulated to a second gas-liquid separation membrane to obtain treated water containing gaseous free ammonia.

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