Method for producing recycled water

Patent metadata

Field	Value
Publication number	US-2024182342-A1
Application number	US-202218553234-A
Country	US
Kind code	A1
Filing date	Feb 2, 2022
Priority date	Apr 9, 2021
Publication date	Jun 6, 2024
Grant date	—

Abstract

An object of the present invention is to provide a method for producing recycled water, according to which when recycled water is prepared from waste water, chemical cleaning of a membrane can be significantly reduced and fouling of the membrane can be eliminated by substantially only washing with water. The above object is achieved by providing a method for producing recycled water, the method including the following steps (A) to (D) of: (A) subjecting waste water to an anaerobic treatment and an aerobic treatment which are carried out by microorganisms, the waste water having been discharged during a production process of a PHA; (B) subjecting treated water obtained in step (A) to pretreatment filtration performed by a membrane bioreactor method; (C) subjecting the treated water obtained in step (B) to an alkali treatment; and (D) filtering, through an ion removal membrane, the treated water obtained in step (C).

First claim

1 . A method for producing recycled water, the method comprising:
subjecting waste water to an anaerobic treatment and an aerobic treatment which are carried out by microorganisms to obtain first treated water, the waste water having been discharged during a production process of a polyhydroxyalkanoate; subjecting the first treated water to pretreatment filtration by a membrane bioreactor method to obtain second treated water; subjecting the second treated water to an alkali treatment to obtain third treated water; and filtering the third treated water through an ion removal membrane.

2 . The method according to claim 1 , wherein in the alkali treatment, pH of the third treated water is adjusted to 7 to 11, turbidity of the third treated water is adjusted to not less than 0.1, and FI value of the third treated water is adjusted to not less than 4.5.

3 . The method according to claim 1 , wherein in the alkali treatment, FI value of the third treated water is adjusted to not less than 6.0.

4 . The method according to claim 1 , wherein the alkali treatment applies at least one selected from the group consisting of an aqueous solution of an alkali metal hydroxide, an aqueous solution of an alkali metal carbonate, an aqueous solution of an alkali metal hydrogen carbonate, an aqueous solution of organic acid alkali metal salts, an aqueous solution of an alkali metal borate, an aqueous solution of an alkali metal phosphate, an aqueous solution of an alkali earth metal hydroxide, and ammonia water.

5 . The method according to claim 1 , further comprising;
precipitating a solid containing a polyvalent ion in the third treated water before the filtering.

6 . The method according to claim 5 , wherein the polyvalent ion is at least one selected from the group consisting of Si2+, Ca2+, PO42-, SO42-, Mg2+, Mn2+, Zn2+, Fe2+, Fe3+, Sr2+, Cu2+, A13+, and Sn3+.

7 . The method according to claim 5 , further comprising: of
removing, by sedimentation, the solid that has been precipitated in the third treated water before the filtering.

8 . The method according to claim 1 , wherein, the ion removal membrane has an MgSO 4 blocking rate of 60% to 100% at the time when a pressure of 3000 kPa is applied at 20° C.

9 . The method according to claim 1 , the ion removal membrane has a transmembrane pressure difference of 0.4 MPa to 4.14 MPa.

10 . A method for producing a polyhydroxyalkanoate, comprising:
crushing or solubilizing microorganism cells that include a polyhydroxyalkanoate to obtain a composition; and separating the polyhydroxyalkanoate in the composition, wherein the crushing or solubilizing and the separating use recycled water produced by the method of claim 1 .

11 . The method according to claim 1 , wherein in the alkali treatment, pH of the third treated water is adjusted to 7 to 11.

12 . The method according to claim 1 , wherein in the alkali treatment, pH of the third treated water is adjusted to 7 to 11, and FI value of the third treated water is adjusted to not less than 4.5.

13 . The method according to claim 2 , wherein the alkali treatment is applies at least one selected from the group consisting of an aqueous solution of an alkali metal hydroxide, an aqueous solution of an alkali metal carbonate, an aqueous solution of an alkali metal hydrogen carbonate, an aqueous solution of organic acid alkali metal salts, an aqueous solution of an alkali metal borate, an aqueous solution of an alkali metal phosphate, an aqueous solution of an alkali earth metal hydroxide, and ammonia water.

14 . The method according to claim 3 , wherein the alkali treatment is applies at least one selected from the group consisting of an aqueous solution of an alkali metal hydroxide, an aqueous solution of an alkali metal carbonate, an aqueous solution of an alkali metal hydrogen carbonate, an aqueous solution of organic acid alkali metal salts, an aqueous solution of an alkali metal borate, an aqueous solution of an alkali metal phosphate, an aqueous solution of an alkali earth metal hydroxide, and ammonia water.

15 . The method according to claim 2 , further comprising:
precipitating a solid containing a polyvalent ion in the third treated water before the filtering.

16 . The method according to claim 15 , wherein the polyvalent ion is at least one selected from the group consisting of Si 2+ , Ca 2+ , PO 4 2− , SO 4 2− , Mg 2+ , Mn 2+ , Zn 2+ , Fe 2+ , Fe 2+ , Sr 2+ , Cu 2+ , Al 3+ , and Sn 3+ .

17 . The method according to claim 15 , further comprising:
removing, by sedimentation, the solid that has been precipitated in the third treated water before the filtering.

18 . The method according to claim 3 , further comprising:
precipitating a solid containing a polyvalent ion in the third treated water before the filtering.

19 . The method according to claim 18 , wherein the polyvalent ion is at least one selected from the group consisting of Si 2+ , Ca 2+ , PO 4 2− , SO 4 2− , Mg 2+ , Mn 2+ , Zn 2+ , Fe 2+ , Fe 2+ , Sr 2+ , Cu 2+ , Al 3+ , and Sn 3+ .

20 . The method according to claim 18 , further comprising:
removing, by sedimentation, the solid that has been precipitated in the third treated water before the filtering.

Assignees

• Kaneka Corp

Inventors

• Fukumoto Asuka
• Hirano Masaru

Classifications

• C02F3/1268

  Membrane bioreactor systems · CPC title

• C12F3/04

  Recovery of volatile fermentation products from carbon dioxide · CPC title

• C12F3/02

  of carbon dioxide · CPC title

• C12P5/023

  Methane · CPC title

• C12P7/04

  acyclic · CPC title