US-20260125292-A1 - WASTEWATER CONCENTRATION DEVICE AND CONCENTRATION METHOD

US20260125292A1US 20260125292 A1US20260125292 A1US 20260125292A1US-20260125292-A1

Abstract

A wastewater concentration device and a wastewater concentration method are provided, including an osmotically assisted reverse osmosis device that performs an osmotically assisted reverse osmosis method having a primary chamber and a secondary chamber separated by an osmotically assisted reverse osmosis membrane, and a water supply means for supplying water to be treated to the primary chamber. The water supply means treats at least a portion of the water to be treated with a cation exchange device or an anion exchange device to adjust a pH of water supplied to the osmotically assisted reverse osmosis device to a range between a first prescribed pH and a second prescribed pH (where the first prescribed pH is an alkaline pH and the second prescribed pH is an acidic pH).

Inventors

Takahiro Kawakatsu
Kazuo Kumagai
Hideto Matsuyama

Assignees

KURITA WATER INDUSTRIES LTD.
NATIONAL UNIVERSITY CORPORATION KOBE UNIVERSITY

Dates

Publication Date: 20260507
Application Date: 20230921
Priority Date: 20221005

Claims (10)

1 . A wastewater concentration device comprising an osmotically assisted reverse osmosis device that performs an osmotically assisted reverse osmosis method having a primary chamber and a secondary chamber separated by an osmotically assisted reverse osmosis membrane, and a water supply means that supplies water to be treated to the primary chamber, wherein the water supply means comprises an ion exchange device.
2 . The wastewater concentration 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 concentration 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 means is configured to be capable of mixing treated water from the ion exchange device with water to be treated that has not undergone ion exchange treatment to adjust a pH of water supplied to the osmotically assisted reverse osmosis device to a range between a first prescribed pH and a second prescribed pH, where a first prescribed pH is an alkaline pH and a second prescribed pH is an acidic pH.
5 . The wastewater concentration device according to claim 1 , wherein the water supply means is configured to be switchable between: a flow path selection that mixes treated water from the ion exchange device with water to be treated that has not undergone ion exchange treatment to adjust a pH of water supplied to the osmotically assisted reverse osmosis device to a range between a first prescribed pH and a second prescribed pH, where a first prescribed pH is an alkaline pH and a second prescribed pH is an acidic pH; and a flow path selection that supplies treated water with a pH between a first prescribed pH and a second prescribed pH from the ion exchange device to the osmotically assisted reverse osmosis device.
6 . The wastewater concentration device according to claim 1 , wherein the water supply means is configured to be switchable between: a flow path selection that mixes treated water from the ion exchange device with water to be treated that has not undergone ion exchange treatment to adjust a pH of water supplied to the osmotically assisted reverse osmosis device to a range between a first prescribed pH and a second prescribed pH, where a first prescribed pH is an alkaline pH and a second prescribed pH is an acidic pH; a flow path selection that supplies treated water with a pH between a first prescribed pH and a second prescribed pH from the ion exchange device to the osmotically assisted reverse osmosis device; and a flow path selection that supplies the water to be treated as is to the osmotically assisted reverse osmosis device when a pH of the water to be treated is between a first prescribed pH and a second prescribed pH.
7 . The wastewater concentration device according to claim 1 , 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 means having an ion exchange device that supplies water to be treated to the primary chamber, wherein the wastewater concentration method comprises: adjusting a pH of water supplied to the osmotically 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 water supplied to the osmotically assisted reverse osmosis device is adjusted to a range between a first prescribed pH and a second prescribed pH, where a first prescribed pH is an alkaline pH and a second prescribed 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 prescribed pH, at least a portion of the water to be treated is treated by a cation exchange device, and when a pH of water to be treated is lower than a second prescribed pH, at least a portion of water to be treated is treated by an anion exchange device.

Description

TECHNICAL FIELD The present invention relates to a wastewater concentration device, and particularly to a wastewater concentration device using an osmotically assisted reverse osmosis method. Further, the present invention relates to a wastewater concentration method using this concentration device. RELATED ART There have been many attempts to concentrate waste liquid to recover valuable materials or reduce industrial waste costs. In the electronics industry, large amounts of isopropyl alcohol (IPA) are used, and there is a movement to recover and reuse it from the perspective of resource conservation and decarbonization. Conventionally, the evaporation method using an evaporator has been generally employed as a method for concentrating wastewater. In this method, the challenge is the high energy consumption due to the phase change of water. By using an RO membrane, energy consumption reduction is expected as it does not involve water phase change. However, as the osmotic pressure of the wastewater increases, high pressure must be applied, requiring high-pressure specification equipment. To concentrate an IPA aqueous solution with a concentration of 1 to 5 wt % to an IPA concentration of 15 wt % or higher, a pressure of 10 MPa or more is necessary, which is not practical. When concentrating a high osmotic pressure aqueous solution using a reverse osmosis (RO) membrane, there is an osmotically assisted reverse osmosis method (OARO method) in which 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.). In the OARO method, since liquid is also passed through the permeate side, hollow fiber RO membranes are structurally suitable. As a commercially available hollow fiber RO membrane, the BC (brine concentration) membrane from Toyobo Co., Ltd. is known. Since the material of the BC membrane is cellulose acetate, it is necessary to maintain the pH between 3 and 8. When using a BC membrane for concentrating wastewater, if the pH of the wastewater is lower than 3 or higher than 8, pH adjustment is necessary. This requires the addition of alkali or acid for neutralization, which leads to problems such as increased osmotic pressure, increased concentration of salts, and increased cost of chemicals. CITATION LIST Patent Literature Patent Literature 1: Japanese Patent Publication No. 2019-504763. SUMMARY OF INVENTION Technical Problem When concentrating wastewater using the osmotically assisted reverse osmosis method, 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 alkali is generally considered, but the salt generated by neutralization further increases the osmotic pressure. Further, in the case where the purpose was to concentrate organic components, the generated salt would also be concentrated simultaneously. The present invention aims to provide a wastewater concentration device and concentration method that may stably perform wastewater concentration treatment by adjusting the pH of the water supplied to the osmotically assisted reverse osmosis device. Solution to Problem A wastewater concentration device according to one aspect of the present invention is a wastewater concentration device that includes an osmotically assisted reverse osmosis device that performs an osmotically assisted reverse osmosis method having a primary chamber and a secondary chamber separated by an osmotically assisted reverse osmosis membrane, and a water supply means that supplies water to be treated to the primary chamber, in which the water supply means includes an ion exchange device. 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. 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. In the wastewater concentration device according to one aspect of the present invention, the water supply means is configured to be capable of mixing treated water from the ion exchange device with water to be treated that has not undergone ion exchange treatment to adjust a pH of water supplied to the osmotically assisted reverse osmosis device to a range between a first prescribed pH and a second prescribed pH (where a first prescribed pH is an alkaline pH and a second prescribed pH is an acidic pH). In the wastewater concentration device according to one aspect of the present invention, the water supply means is configured to be switchable between: a flow path selection that mixes treated water from the ion exchange device with water to be treated that has not undergone ion exchange treatment to adjust a pH of water supplied to the osmotically