Wastewater concentration device and concentration process

Abstract

This wastewater concentration device and method comprises: an osmotic-assisted reverse osmosis device having a primary chamber and a secondary chamber separated by an osmotic-assisted reverse osmosis membrane, and performing an osmotic-assisted reverse osmosis process; and a water supply device for supplying water to be treated into the primary chamber. The water supply device uses a cation exchange device or an anion exchange device to treat at least a portion of the water to be treated so that the pH of the water to be treated supplied to the osmotic-assisted reverse osmosis device is between a first predetermined pH value and a second predetermined pH value (where the first predetermined pH value is an alkaline pH value and the second predetermined pH value is an acidic pH value).

Description

Technical area

[0001] The present invention relates to a wastewater concentration device, and more particularly to a wastewater concentration device using an osmotic-assisted reverse osmosis process. Furthermore, the present invention relates to a wastewater concentration method using this concentration device. State of the art

[0002] Many attempts have been made to concentrate waste liquids to recover valuable materials or reduce the cost of industrial waste. Large quantities of isopropyl alcohol (IPA) are used in the electronics industry, and there is a movement to reclaim and reuse it for resource conservation and decarbonization purposes.

[0003] Conventionally, the evaporation process using an evaporator has generally been used as a method for concentrating wastewater. The challenge of this process is the high energy consumption due to the phase change of water. The use of an RO membrane is expected to reduce energy consumption because it does not involve phase change of water. However, due to the increasing osmotic pressure of the wastewater, high pressure must be applied, which requires high-pressure equipment. To concentrate an aqueous IPA solution with a concentration of 1 to 5 wt% to an IPA concentration of 15 wt% or more, a pressure of 10 MPa or more is required, which is impractical.

[0004] When concentrating an aqueous solution with high osmotic pressure using a reverse osmosis membrane (RO membrane), there is an osmotic-assisted reverse osmosis (OARO) method. In this method, an aqueous solution with a lower osmotic pressure than the feed water side is passed through the permeate water side to reduce the osmotic pressure difference and lower the driving pressure (Patent Literature 1, etc.). Since the OARO method also passes liquid through the permeate side, hollow-fiber RO membranes are structurally suitable. A commercially available hollow-fiber RO membrane is the BC (brine concentration) membrane from Toyobo Co., Ltd. Since the BC membrane is made of cellulose acetate, the pH value must be maintained between 3 and 8.

[0005] When using a BC membrane to concentrate wastewater, if the pH of the wastewater is lower than 3 or higher than 8, the pH must be adjusted. This requires the addition of alkali or acid for neutralization, which leads to problems such as increased osmotic pressure, increased salt concentration, and increased chemical costs. Citation listPatent literature

[0006] Patent Literature 1: Japanese Patent Publication No. 2019-504763. Summary of the inventionTechnical problem

[0007] When concentrating wastewater using the osmotic-assisted reverse osmosis process, there are cases where the pH of the wastewater is higher than 8 or lower than 3. To adjust the pH, the addition of acid or base is generally considered, but the salt generated by neutralization will further increase the osmotic pressure. Furthermore, if the purpose is to concentrate organic components, the generated salt would also be concentrated at the same time.

[0008] The present invention aims to provide a wastewater concentration apparatus and a concentration method that can perform stable wastewater concentration treatment by adjusting the pH value of the water supplied to the osmotic-assisted reverse osmosis apparatus. Solution to the problem

[0009] A wastewater concentrating apparatus according to one aspect of the present invention is a wastewater concentrating apparatus including an osmotic-assisted reverse osmosis apparatus that performs an osmotic-assisted reverse osmosis process and has a primary chamber and a secondary chamber separated by an osmotic-assisted reverse osmosis membrane, and a water supply device that supplies water to be treated to the primary chamber, in which the water supply device includes an ion exchange device.

[0010] In the wastewater concentration device according to one aspect of the present invention, a pH of the water to be treated is alkaline and the ion exchange device is a cation exchange device.

[0011] In the wastewater concentration device according to one aspect of the present invention, a pH of the water to be treated is acidic and the ion exchange device is an anion exchange device.

[0012] In the wastewater concentration device according to one aspect of the present invention, the water supply device is configured to mix treated water from the ion exchange device with water to be treated that has not undergone ion exchange treatment to adjust the pH of the water supplied to the osmotic-assisted reverse osmosis device to a range between a first predetermined pH value and a second predetermined pH value (wherein a first predetermined pH value is an alkaline pH value and a second predetermined pH value is an acidic pH value).

[0013] In the wastewater concentration device according to one aspect of the present invention, the water supply device is configured to be switchable between: a flow path selector that mixes treated water from the ion exchange device with water to be treated that has not undergone ion exchange treatment to adjust the pH of the water supplied to the osmotically assisted reverse osmosis device to a range between a first predetermined pH value and a second predetermined pH value (wherein a first predetermined pH value is an alkaline pH value and a second predetermined pH value is an acidic pH value); and a flow path selector that supplies treated water having a pH value between a first predetermined pH value and a second predetermined pH value from the ion exchange device to the osmotically assisted reverse osmosis device.

[0014] In the wastewater concentration device according to one aspect of the present invention, the water supply device is configured to be switchable between: a flow path selector that mixes treated water from the ion exchange device with water to be treated that has not undergone ion exchange treatment to adjust the pH of the water supplied to the osmotic-assisted reverse osmosis device to a range between a first predetermined pH value and a second predetermined pH value (wherein a first predetermined pH value is an alkaline pH value and a second predetermined pH value is an acidic pH value); a flow path selector that directs treated water having a pH between a first predetermined pH and a second predetermined pH from the ion exchange device to the osmotically assisted reverse osmosis device; and a flow path selection that directs the water to be treated as it is to the osmotically assisted reverse osmosis device when a pH value of the water to be treated is between a first predetermined pH value and a second predetermined pH value.

[0015] In the wastewater concentration device according to one aspect of the present invention, a material of the osmotically assisted reverse osmosis membrane is cellulose acetate.

[0016] A wastewater concentration method according to one aspect of the present invention is a wastewater concentration method that uses a wastewater concentration device including an osmotically assisted reverse osmosis device having a primary chamber and a secondary chamber separated by an osmotically assisted reverse osmosis membrane, and a water supply device including an ion exchange device that supplies water to be treated to the primary chamber. In the wastewater concentration method, a pH value of the water supplied to the osmotically assisted reverse osmosis device is adjusted by passing water through the ion exchange device.

[0017] In the wastewater concentration method according to one aspect of the present invention, a pH of the water supplied to the osmotic-assisted reverse osmosis device is adjusted to a range between a first predetermined pH and a second predetermined pH (wherein a first predetermined pH is an alkaline pH and a second predetermined pH is an acidic pH).

[0018] In the wastewater concentration method according to one aspect of the present invention, when a pH of the water to be treated is higher than a first predetermined pH, at least a part of the water to be treated is treated by a cation exchange device, and when a pH of the water to be treated is lower than a second predetermined pH, at least a part of the water to be treated is treated by an anion exchange device. Effects of the invention

[0019] According to one aspect of the present invention, when high-pH wastewater is concentrated using the osmotically assisted reverse osmosis process, the wastewater is pretreated with a cation exchange resin to remove cationic components contributing to the high pH, ​​while simultaneously lowering the pH of the wastewater by hydrogen ions released by ion exchange. Furthermore, when low-pH wastewater is concentrated using the osmotically assisted reverse osmosis process, the wastewater is pretreated with anion exchange resin to remove anionic components contributing to the low pH, while simultaneously raising the pH of the wastewater by hydroxide ions released by ion exchange.

[0020] It is noted that according to one aspect of the present invention, when wastewater having a high pH higher than 8 is treated with a cation exchange resin and the pH decreases to lower than 3, it is possible to adjust the pH to a range of 3 to 8 by mixing it with the original high pH wastewater. Similarly, when wastewater having a low pH lower than 3 is treated with an anion exchange resin and the pH increases to higher than 8, it is possible to adjust the pH to a range of 3 to 8 by mixing it with the original low pH wastewater. It is noted that pH 3 and 8 are exemplary and the values ​​are not limited to them.

[0021] In this way, for both high-pH and low-pH wastewater, ion exchange resin treatment can simultaneously reduce the salt concentration and adjust the pH. Note that according to the present invention, even in cases where the osmotically assisted reverse osmosis membrane material is not cellulose acetate and the pH range is not 3 to 8, it is possible to perform osmotically assisted reverse osmosis membrane treatment after ion exchange resin treatment to reduce acids, bases, and salts in the wastewater. Short description of the drawings [ Fig. 1] is a configuration diagram of an osmotic-assisted reverse osmosis device according to an embodiment. [ Fig. 2] is a configuration diagram of an osmotic-assisted reverse osmosis device according to an example. [ Fig. 3] is a graph showing experimental results. Description of the embodiments

[0022] An embodiment will be described below with reference to the drawings.

[0023] Fig. Figure 1 is a configuration diagram of an osmotic-assisted reverse osmosis device according to an embodiment of the present invention. Wastewater to be treated (raw wastewater) is introduced into a piped water tank 2 through a raw water pipe 1. The raw wastewater in the piped water tank 2 is pumped to a pipe 4 by a pump 3. A pH meter 5 is attached to the pipe 4. The pipe 4 branches into branch pipes 6, 7, and 8.

[0024] The branch line 6 is connected to the inlet side of a cation exchange resin tower 13 via a valve 10. The outlet side of the cation exchange resin tower 13 is connected to a mixing line 20 via a line 15.

[0025] The branch line 7 is connected to the mixing line 20 via a valve 11.

[0026] The branch line 8 is connected to the inlet side of an anion exchange resin tower 14 via a valve 12. The outlet side of the anion exchange resin tower 14 is connected to the mixing line 20 via a line 16.

[0027] pH meters 17, 18 and 22 are attached to lines 15 and 16 as well as to the mixing line 20.

[0028] A pump 21 is attached to the mixing line 20, and the outlet side of the pump 21 is connected to an inlet of a primary chamber 31 of an osmotic-assisted reverse osmosis (OARO) device 30. The interior of the OARO device 30 is divided into a primary chamber 31 and a secondary chamber 32 by an osmotic-assisted reverse osmosis membrane 33 consisting of a cellulose acetate membrane.

[0029] A concentrated water line 34 is connected to the outlet of the primary chamber 31. In this embodiment, line 35, which branches off from the concentrated water line 34, is connected to the inlet of the secondary chamber 32. A diluted water discharge line 36 is connected to the outlet of the secondary chamber 32.

[0030] Output signals from pH meters 5, 17, 18 and 22 are input to a control unit 23 and valves 10, 11 and 12 are controlled by signals from control unit 23.

[0031] The concentration of wastewater by this osmotically assisted reverse osmosis device is carried out according to one of the following flows (1) to (5). (1) Wastewater with a pH higher than 8 → treatment with cation exchange resin → Wastewater with a pH of 3 to 8 → treatment with osmotically assisted reverse osmosis membrane (2) Wastewater with a pH value higher than 8 → treatment with cation exchange resin → wastewater with a pH value lower than 3 → mixing with original wastewater → wastewater with a pH value of 3 to 8 → treatment with osmotic-assisted reverse osmosis membrane (3) Wastewater with a pH value lower than 3 → treatment with anion exchange resin → wastewater with a pH value of 3 to 8 → treatment with osmotically assisted reverse osmosis membrane (4) Wastewater with a pH value lower than 3 → treatment with anion exchange resin → wastewater with a pH value higher than 8 → mixing with original wastewater → wastewater with a pH value of 3 to 8 → treatment with osmotic-assisted reverse osmosis membrane (5) Wastewater with a pH value of 3 to 8 → Direct treatment with osmotically assisted reverse osmosis membrane River (1)

[0032] In the case of flow (1), valve 10 is opened, valves 11 and 12 are closed, and the wastewater is passed through the cation exchange resin tower 13. Since the pH value of the effluent from the cation exchange resin tower 13, detected by the pH meters 17 and 22, is between 3 and 8, it is, in this case, directly fed into the primary chamber 31 of the osmotic-assisted reverse osmosis device 30, and the concentrated water flows out from line 34. Part of the concentrated water is passed through line 35 into the secondary chamber 32. The primary chamber 31 is in a state where the water pressure is higher than in the secondary chamber 32 because the discharge pressure of the pump 21 is applied.As a result, H2O components from the wastewater in the primary chamber 31 penetrate through the osmotically assisted reverse osmosis membrane 32 into the secondary chamber 32, and the effluent from the primary chamber 31 becomes concentrated water, while the effluent from the secondary chamber 32 becomes diluted water. River (2)

[0033] In flow (2), valves 10 and 11 are opened, and valve 12 is closed. The pH of the effluent from the cation exchange resin tower 13, detected by the pH meter 17, is lower than 3, but by mixing with the original wastewater having a pH higher than 8 from line 7 in the mixing line 20, the pH in the mixing line 20 reaches a value of 3 to 8. Note that the opening degrees of valves 10 and 11 are controlled so that the pH value detected by the pH meter 22 is between 3 and 8. River (3)

[0034] In the case of flow (3), valve 12 is opened, valves 10 and 11 are closed, and the wastewater is passed through the anion exchange resin tower 14. Since the pH value of the effluent from the anion exchange resin tower 14, detected by the pH meters 18 and 22, is between 3 and 8, it is, in this case, directly fed into the primary chamber 31 of the osmotic-assisted reverse osmosis device 30, and the concentrated water flows out of the line 34. Part of the concentrated water is passed through the line 35 into the secondary chamber 32. The primary chamber 31 is in a state where the water pressure is higher than in the secondary chamber 32 because the discharge pressure of the pump 21 is applied.As a result, H2O components from the wastewater in the primary chamber 31 penetrate through the osmotically assisted reverse osmosis membrane 32 into the secondary chamber 32, and the effluent from the primary chamber 31 becomes concentrated water, while the effluent from the secondary chamber 32 becomes diluted water. River (4)

[0035] In flow (4), valves 11 and 12 are opened, and valve 10 is closed. The pH of the effluent from the anion exchange resin tower 14, detected by the pH meter 18, is higher than 8, but by mixing with the original wastewater having a pH lower than 3 from line 7 in the mixing line 20, the pH in the mixing line 20 reaches a value of 3 to 8. Note that the opening degrees of valves 11 and 12 are controlled so that the pH value detected by the pH meter 22 is between 3 and 8. River (5)

[0036] In the case of flow (5), valves 10 and 12 are closed and valve 11 is opened, the wastewater with a pH of 3 to 8 in the pipe water tank 2 is passed through line 7, the mixing line 20 and the pump 21 to the primary chamber 31 of the osmotic-assisted reverse osmosis device 30, concentrated water flows out of line 34 and diluted water flows out of line 36.

[0037] In this way, according to each of the flows (1) to (5), even if the osmotic-assisted reverse osmosis membrane 33 is a cellulose acetate membrane, since the pH value of the wastewater passed through the osmotic-assisted reverse osmosis device 30 is between 3 and 8, the concentration treatment can be stably carried out for a long period of time without deterioration.

[0038] It is noted that the osmotically assisted reverse osmosis membrane is not limited to a cellulose acetate membrane.

[0039] According to the embodiment described above, the outlet pressure of the pump 21 for conveying the water to be treated to the osmotically assisted reverse osmosis device 30 is preferably about 1 to 10 MPa, more preferably about 3 to 8 MPa.

[0040] According to the above-described embodiment, the first predetermined pH value is 8 and the second predetermined pH value is 3, but the present invention is not limited thereto. According to the present invention, the first predetermined pH value may be 6 to 8, particularly 7 to 8, and the second predetermined pH value may be 3 to 6, particularly approximately 3 to 5. Examples

[0041] As in Fig. As shown in Figure 2, wastewater with a pH of 11.2 was concentrated using an osmotically assisted reverse osmosis test system equipped with a cation exchange resin tower 47, in which osmotically assisted reverse osmosis devices 60 and 70 were installed in two stages in series, and the concentrated water from the osmotically assisted reverse osmosis device 60 was further concentrated by the osmotically assisted reverse osmosis device 70. The essential conditions were as follows: Wastewater: IPA wastewater from the electronics industry (pH 11.2, IPA concentration 1.1 wt%, Na ions 31 mg / L) Cation exchange resin tower: Filled with 125 mL of cation exchange resin (KR-UC1, manufactured by Kurita Water Industries Ltd.) Osmotic-assisted reverse osmosis device: HOLLOSEP Mini (registered trademark) BC membrane module (hollow fiber membrane module, membrane area 1.1 m 2, manufactured by Toyobo Co., Ltd.) Wastewater volume in raw water tank 41 (before water flow starts): 10 L Water supply volume of pump 43: 120 mL / min Outlet pressure of booster pump 52: 5.5 MPa Water discharge volume into secondary chambers 62 and 72: 20 mL / min [Example 1]

[0042] Valves 46 and 49 were opened, and wastewater was pumped to two pipes 44 and 45 via a pipe 42 and pump 43. The ratio [water supply volume to pipe 44] / [water supply volume to pipe 45] was set at 20 / 7.

[0043] The pH of the effluent from the cation exchange resin tower 47 to line 48 (detected by the pH meter 82) was 3.3, the Na concentration was 0.2 mg / L, and the IPA concentration was 1.1 wt% (the same as the IPA concentration of the raw water).

[0044] The pH of the mixed water in line 51 (detected by pH meter 83) was 4.0. This mixed water was pumped into the primary chamber 61 of the osmotic-assisted reverse osmosis device 60 by pump 52, and the concentrated water from the primary chamber 61 was pumped into the primary chamber 71 of the osmotic-assisted reverse osmosis device 70 by line 64.

[0045] A portion (20 mL / min) of the concentrated water flowing from the primary chamber 71 into line 74 was passed through the secondary chamber 72 via the branch line 76, and its effluent was passed through the secondary chamber 62 of the osmotic-assisted reverse osmosis device 60 via line 66. The diluted water flowing from the secondary chamber 62 into line 67 and the remaining portion of the concentrated water from line 74 were returned to the raw water tank 41 via line 78. <ergebnisse>

[0046] The process was carried out over 9 days, and the IPA concentration in the concentrated water from line 74 was 4.6 wt% on days 4 and 8. Furthermore, the acetic acid concentration in raw water tank 41, measured by ion chromatography (instrument: ICS900, column: IonPac ICE-AS1 (manufacturer: Thermo Fisher Scientific)), was consistently below the detection limit of 0.5 mg / L. [Comparison example 1]

[0047] A test was conducted under the same conditions as in Example 1, except that valve 46 was closed and valve 49 was opened and the entire raw water volume was passed directly through the osmotically assisted reverse osmosis devices 60 and 70.

[0048] The measurement results of the acetic acid concentration in the raw water tank 41 are shown in Fig. 3 shown.

[0049] As in Fig. As shown in Figure 3, the acetic acid concentration increased over time. This is believed to be due to the hydrolysis of cellulose acetate, the material of the BC membrane, which leads to the elution of acetic acid when conducted at a pH of 11.2. Note that the IPA concentration of the concentrated water in Comparative Example 1 was 3.6 wt% on day 4 and 3.2 wt% on day 8.

[0050] Based on the above results, it was recognized that stable concentration treatment can be carried out by performing ion exchange resin treatment before concentrating the wastewater with the BC membrane and adjusting the pH to 3 to 8.

[0051] The present invention has been described in detail with reference to specific embodiments, but it will be apparent to those skilled in the art that various changes are possible within the scope of achieving the effects of the invention.

[0052] This present application is based on Japanese Patent Application No. 2022-161068 filed on October 5, 2022, the entire contents of which are incorporated by reference into this application. List of reference symbols 2, 41 raw water tank 13, 47 Cation exchange resin tower 14 Anion exchange resin tower 30, 60, 70 Osmotically assisted reverse osmosis device 33, 63, 73 Osmotically assisted reverse osmosis membrane QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2019-504763

[0006] JP 2022-161068

[0052] < / ergebnisse>

Claims

[1] A wastewater concentration apparatus comprising an osmotically assisted reverse osmosis apparatus which performs an osmotically assisted reverse osmosis process and has a primary chamber and a secondary chamber separated by an osmotically assisted reverse osmosis membrane, and a water supply device which supplies water to be treated to the primary chamber, wherein the water supply device comprises an ion exchange device. [2] The wastewater concentrating device according to claim 1, wherein a pH of the water to be treated is alkaline and the ion exchange device is a cation exchange device. [3] The wastewater concentrating device according to claim 1, wherein a pH of the water to be treated is acidic and the ion exchange device is an anion exchange device. [4] The wastewater concentration device according to claim 1, wherein the water supply device is configured to mix treated water from the ion exchange device with water to be treated which has not been subjected to ion exchange treatment to adjust the pH of the water supplied to the osmotic-assisted reverse osmosis device to a range between a first predetermined pH value and a second predetermined pH value (wherein a first predetermined pH value is an alkaline pH value and a second predetermined pH value is an acidic pH value). [5] A wastewater concentration device according to claim 1, wherein the water supply means is configured to be switchable between: a flow path selector that mixes treated water from the ion exchange device with water to be treated that has not undergone ion exchange treatment to adjust the pH of the water supplied to the osmotically assisted reverse osmosis device to a range between a first predetermined pH value and a second predetermined pH value (wherein a first predetermined pH value is an alkaline pH value and a second predetermined pH value is an acidic pH value); and a flow path selector that directs treated water having a pH between a first predetermined pH and a second predetermined pH from the ion exchange device to the osmotically assisted reverse osmosis device. [6] A wastewater concentration device according to claim 1, wherein the water supply means is configured to be switchable between: a flow path selector that mixes treated water from the ion exchange device with water to be treated that has not undergone ion exchange treatment to adjust the pH of the water supplied to the osmotic-assisted reverse osmosis device to a range between a first predetermined pH value and a second predetermined pH value (wherein a first predetermined pH value is an alkaline pH value and a second predetermined pH value is an acidic pH value); a flow path selector that directs treated water having a pH between a first predetermined pH and a second predetermined pH from the ion exchange device to the osmotically assisted reverse osmosis device; and a flow path selection that directs the water to be treated as it is to the osmotically assisted reverse osmosis device when a pH value of the water to be treated is between a first predetermined pH value and a second predetermined pH value. [7] The wastewater concentrating device according to any one of claims 1 to 6, wherein a material of the osmotically assisted reverse osmosis membrane is cellulose acetate. [8] A wastewater concentration method using a wastewater concentration device comprising an osmotically assisted reverse osmosis device having a primary chamber and a secondary chamber separated by an osmotically assisted reverse osmosis membrane, and a water supply device having an ion exchange device that supplies water to be treated to the primary chamber, wherein the wastewater concentration method comprises: Adjusting a pH value of the water supplied to the osmotic-assisted reverse osmosis device by passing water through the ion exchange device. [9] The wastewater concentration method according to claim 8, wherein a pH of the water supplied to the osmotic-assisted reverse osmosis device is adjusted to a range between a first predetermined pH and a second predetermined pH (wherein a first predetermined pH is an alkaline pH and a second predetermined pH is an acidic pH). [10] The wastewater concentration method according to claim 9, wherein, when a pH of the water to be treated is higher than a first predetermined pH, at least a part of the water to be treated is treated by a cation exchange device, and when a pH of the water to be treated is lower than a second predetermined pH, at least a part of the water to be treated is treated by an anion exchange device.

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