Physico-chemical process for removal of nitrogen species from recirculated aquaculture systems

Patent metadata

Field	Value
Publication number	US-9560839-B2
Application number	US-201113988263-A
Country	US
Kind code	B2
Filing date	Nov 17, 2011
Priority date	Nov 17, 2010
Publication date	Feb 7, 2017
Grant date	Feb 7, 2017

Abstract

The present invention provides processes for removing nitrogen species from fresh water or high salinity water recirculated aquaculture systems. The processes are based on physico-chemical treatments which are performed at ambient temperatures and at low p H values thus keeping the total ammonia nitrogen concentrations below a value which is considered detrimental for the growth or survival rate of cultured fish/shrimp.

First claim

The invention claimed is:

1. A process for removing nitrogen species from a fresh water recirculated aquaculture system (RAS) while maintaining a total ammonia nitrogen (TAN) concentration in the water in said system between 15 and 50 mgN/L, the process comprising the steps of:
a. maintaining the pH of the water in the RAS below pH 7.5 by adding an acid;
b. extracting a portion of the water from the RAS;
c. passing the portion of the water from the RAS through an ion exchange resin so as to remove NH 4 + ions from the water;
d. regenerating the NH 4 + enriched ion-exchange resin obtained in step (c) using a solution comprising high concentrations of an exchange cation and chloride as a counter anion at concentrations higher than 50 g Cl/L so as to produce brine containing NH 4 + ions; and
e. converting NH 4 + ions accumulated in the brine obtained during step (d) to gaseous nitrogen (N 2 ) by electrochemically generating active chlorine species capable of ammonia-to-nitrogen gas oxidation.

2. The process of claim 1 further comprising a step of recycling at least some of the portion of the water obtained after step (c) back to the RAS.

3. The process of claim 2 , wherein the exchange cation in step (d) is Ca 2+ , and the process further comprises removing phosphorus species by precipitation with calcium ions released into the water after the ion exchange step (c) when recycling the water back to the RAS.

4. The process of claim 3 , wherein the calcium-phosphate salts are separated from the RAS using a solid filter or a separation unit.

5. The process of claim 1 , wherein the exchange cation in step (d) is selected from the group consisting of Ca 2+ , Mg 2+ , Na + , and K + .

6. The process of claim 5 , wherein the exchange cation in step (d) is Ca 2+ .

7. The process of claim 1 , wherein steps (a)-(e) are performed continuously.

8. The process of claim 1 , wherein steps (a)-(c) are performed continuously and steps (d-e) are performed during low cost electricity hours.

9. The process of claim 1 , wherein the ion exchange resin is selected from the group consisting of a zeolite and a polymeric cation exchange resin.

10. The process of claim 1 , wherein the acid is H 2 SO 4 .

11. The process of claim 1 , further comprising adding a base during the electrolysis step (e).

12. The process of claim 11 , wherein the base is selected from the group consisting of Ca(OH) 2 , CaO, NaOH and KOH.

13. The process of claim 1 , further comprising stripping of CO 2 wherein stripping of CO 2 comprises the addition of pure oxygen or aeration.

14. The process of claim 1 , further comprising repeating steps (a) to (e) in a continuous manner, as needed.

15. The process of claim 1 , wherein the exchange cation in step (d) is Ca 2+ , and the process further comprises removing phosphorus species by precipitation with calcium ions added to the RAS to induce precipitation of calcium-phosphate salts.

16. The process of claim 15 , wherein the calcium-phosphate salts are separated from the RAS using a solid filter or a separation unit.

17. The process of claim 1 , wherein the recirculated aquaculture system (RAS) has a total ammonia nitrogen concentration at 15 or 30 mgN/L.

18. The process of claim 1 , further comprising a step of adding CaO or Ca(OH) 2 during step (e).

Assignees

• Lahav Ori
• Gendel Youri
• Mozes Noam
• Benet Perlberg Ayana
• Hanin Yuri
• Technion Res & Dev Foundation

Inventors

• Lahav Ori
• Gendel Youri
• Mozes Noam
• Benet Perlberg Ayana
• Hanin Yuri

Classifications

• C02F1/586

  by removing ammoniacal nitrogen (for biological methods C02F3/00) · CPC title

• C02F1/4674

  with halogen or compound of halogens, e.g. chlorine, bromine · CPC title

• C02F1/66

  by neutralisation; pH adjustment (for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58) · CPC title

• C02F2209/06

  pH · CPC title

• A01K63/04 Primary

  Arrangements for treating water specially adapted to receptacles for live fish · CPC title