Method for treating organic wastewater and organic wastewater treating system

Patent metadata

Field	Value
Publication number	US-10099952-B2
Application number	US-201615394196-A
Country	US
Kind code	B2
Filing date	Dec 29, 2016
Priority date	Aug 12, 2016
Publication date	Oct 16, 2018
Grant date	Oct 16, 2018

Abstract

A method for treating organic wastewater includes: proceeding with anaerobic fermentation on organic wastewater to obtain a fermentation liquid; nitrifying a portion of the fermentation liquid to obtain a first fermentation liquid containing nitrate nitrogen, and separating the remaining portion of the fermentation liquid to obtain a second fermentation liquid containing propionic acid; mixing the first and second fermentation liquids to obtain a mixture; and removing nitrogen and phosphorus from the mixture and then proceeding with sedimentation to obtain a sediment and a supernatant discharged as purified water. An organic wastewater treating system includes an anaerobic fermentation reactor, an aeration tank, a fermentation liquid separating equipment, a biological removal reactor for removing nitrogen and phosphorus, and a sedimentation tank. The mixing ratio of two fermentation liquids is controlled to achieve balance between carbon, nitrogen, and phosphorus during the nitrogen and phosphorus removal process, achieving highly efficient and simultaneous removal of carbon, nitrogen, and phosphorus without additional carbon source.

First claim

The invention claimed is:

1. A method for treating organic wastewater comprising:
proceeding with anaerobic fermentation on organic wastewater to obtain a fermentation liquid, wherein the organic wastewater is selected from a kind of wastewater containing protein, and the anaerobic fermentation is proceeded at a pH value of 9±0.5 for a period of time ranging from 1 hour to 24 days or a kind of wastewater containing carbohydrate, the anaerobic fermentation is proceeded at a pH value of 8±0.5 for a period of time ranging from 0.5 hour to 16 days;
nitrifying a portion of the fermentation liquid to obtain a fermentation liquid containing nitrate nitrogen, and separating a remaining portion of the fermentation liquid to remove residue, obtaining a fermentation liquid containing propionic acid;
mixing the fermentation liquid containing nitrate nitrogen and the fermentation liquid containing propionic acid to obtain a mixture; and
conducting a process for removing nitrogen and phosphorus from the mixture and then proceeding with sedimentation to obtain a supernatant and a sediment, and discharging the supernatant as purified water.

2. The method according to claim 1 , wherein the anaerobic fermentation is proceeded at a pH value of 9 for 12 days.

3. The method according to claim 1 , wherein sludge generated during discharge of dairy wastewater of a dairy processing plant is inoculated into the organic wastewater before anaerobic fermentation, and an amount of inoculation is 5±1% of a volume of the organic wastewater.

4. The method according to claim 1 , wherein the anaerobic fermentation is proceeded at a pH value of 8 for 8 days.

5. The method according to claim 1 , wherein sludge generated during discharge of alcohol wastewater of an alcohol manufacturing plant is inoculated into the organic wastewater before anaerobic fermentation, and an amount of inoculation is 3.8±1% of a volume of the organic wastewater.

6. The method according to claim 1 , wherein:
in step (1), the fermentation liquid includes at least 70 wt % of propionic acid; and/or
in step (2), the fermentation liquid containing nitrate nitrogen and the fermentation liquid containing propionic acid are mixed at a ratio to make a ratio of a sum of total nitrogen and total phosphorus of the mixture to a biological oxygen demand to be in a range of 1:8 to 1:15; and/or
in step (4), the process for removing nitrogen and phosphorus is conducted at a pH value of 7.5±0.5.

7. The method according to claim 6 , wherein:
in step (2), the fermentation liquid containing nitrate nitrogen and the fermentation liquid containing propionic acid are mixed at a ratio to make the ratio of the sum of total nitrogen and total phosphorus of the mixture to the biological oxygen demand to be 1:11; and/or
in step (4), the process for removing nitrogen and phosphorus is conducted at a pH value of 7.5.

8. The method according to claim 1 , further comprising:
mixing a portion of the sediment with organic wastewater to obtain a second mixture and proceeding with anaerobic fermentation on the second mixture to obtain a second fermentation liquid;
nitrifying a portion of the second fermentation liquid to obtain a third fermentation liquid containing nitrate nitrogen, and separating a remaining portion of the second fermentation liquid to remove residue, obtaining a fourth froth containing propionic acid;
mixing the third fermentation liquid containing nitrate nitrogen and the fourth fermentation liquid containing propionic acid to obtain a third mixture; and
mixing the third mixture with a remaining portion of the sediment to obtain a fourth mixture, conducting a process for removing nitrogen and phosphorus from the fourth mixture and proceeding with sedimentation to obtain a second supernatant and a second sediment, and discharging the second supernatant as purified water.

9. The method according to claim 8 , wherein the third mixture is mixed with 0.5-50 wt % of the sediment.

10. An organic wastewater treating system for carrying out the method for treating organic wastewater according to claim 1 , with the organic wastewater treating system comprising:
an anaerobic fermentation reactor for proceeding with anaerobic fermentation on organic wastewater to obtain the fermentation liquid;
an aeration tank for proceeding with nitrification of the portion of the fermentation liquid to obtain the fermentation liquid containing nitrate nitrogen;
a fermentation liquid separating equipment for separating the remaining portion of the fermentation liquid and removing the residue to obtain the fermentation liquid containing propionic acid;
a biological removal reactor for removing nitrogen and phosphorus, with the biological removal reactor mixing the fermentation liquid containing nitrate nitrogen and the fermentation liquid containing propionic acid to obtain the mixture for conducting the process for removing nitrogen and phosphorus from the mixture; and
a sedimentation tank for proceeding with sedimentation of an effluent of the biological removal reactor for removing nitrogen and phosphorus, obtaining the supernatant and the sediment.

11. The organic wastewater treating system according to claim 10 , further comprising a distributor, with the distributor adding a portion of the sediment into the biological removal reactor for removing nitrogen and phosphorus, thereby mixing the portion of the sediment with the mixture before the process for removing nitrogen and phosphorus, with the distributor also adding a remaining portion of the sediment into the anaerobic fermentation reactor to mix with the organic wastewater before anaerobic fermentation.

12. The organic wastewater treating system according to claim 11 , wherein the portion of the sediment is about 0.50-50 wt % of the sediment.

13. The organic wastewater treating system according to claim 10 , wherein the organic wastewater is wastewater containing protein, and the anaerobic fermentation is proceeded at a pH value of 9±0.5 for a period of time ranging from 1 hour to 24 days.

14. The organic wastewater treating system according to claim 13 , wherein the anaerobic fermentation is proceeded at a pH value for 12 days.

15. The organic wastewater treating system according to claim 10 , wherein the organic wastewater is wastewater containing carbohydrate, and the anaerobic fermentation is proceeded at a pH value of 8±0.5 for a period of time ranging from 0.5 hour to 16 days.

16. The organic wastewater treating system according to claim 15 , wherein the anaerobic fermentation is proceeded at a pH value of 8 for 8 days.

17. The organic wastewater treating system according to claim 10 , wherein:
the fermentation liquid includes at least 70 wt % of propionic acid; and/or
the fermentation liquid containing nitrate nitrogen and the fermentation liquid containing propionic acid are mixed at a ratio to make a ratio of a sum of total nitrogen and total phosphorus of the mixture to a biological oxygen demand to be in a range of 1:8 to 1:15; and/or
the process for removing nitrogen and phosphorus is conducted at a pH value of 7.5±0.5.

18. The organic wastewater treating system according to claim 17 , wherein:
the fermentation liquid containing nitrate nitrogen and the fermentation liquid containing propionic acid are mixed at a ratio to make the ratio of the sum of total nitrogen and total phosphorus of the mixture to the biological oxygen demand to be 1:11; and/or
the process for removing nitrogen and phosphorus is conducted at a pH value of 7.5.

Assignees

• Univ Tongji
• Nanjing University Of Technology

Inventors

• Chen Yinguang
• Ren Hongqiang
• Zheng Xiong
• Huang Haining
• Liu Hui

Classifications

• C02F2001/007

  Processes including a sedimentation step · CPC title

• C02F2103/327

  from processes relating to the production of dairy products · CPC title

• C02F2101/105

  Phosphorus compounds · CPC title

• C02F3/308

  Biological phosphorus removal · CPC title

• C02F3/303

  characterised by the nitrification · CPC title