Method for the biological treatment of nitrogen in effluents by nitritation

Patent metadata

Field	Value
Publication number	US-11447409-B2
Application number	US-201816652190-A
Country	US
Kind code	B2
Filing date	Oct 4, 2018
Priority date	Oct 4, 2017
Publication date	Sep 20, 2022
Grant date	Sep 20, 2022

Abstract

The invention relates to a method for the biological treatment of nitrogen in the form of ammonium in wastewater, by nitritation in a biological reactor, comprising: at least one step a of aerating the biological reactor containing the wastewater to be treated, at least one step b of eliminating at least part of the nitrites produced in step a, and a step c of extracting, from the reactor, a fraction of the sludge resulting from steps a and b. The invention also concerns a method for the biological treatment of nitrogen in wastewater, by nitritation/denitritation and/or deammonification, wherein the nitritation is implemented using the nitritation method according to the invention.

First claim

The invention claimed is:

1. A method for the biological treatment of nitrogen in the form of ammonium in wastewater, by nitritation in a biological reactor, comprising:
at least one step a of aerating the biological reactor containing the wastewater to be treated, wherein the aeration is controlled in order to maintain a concentration of dissolved oxygen in the reactor at an average value that is greater than or equal to 1 mg/L, so as to oxidize at least part of the ammonium into nitrites by the ammonia-oxidizing bacteria present in said reactor, characterized in that the method further comprises:
at least one step b of eliminating at least part of the nitrites produced in step a by:
a sampling b1 of water treated in step a outside the reactor, and/or by
an anoxic biological transformation b2, steps a and b being carried out successively and cyclically so that the nitrite concentration in the reactor at the start of step a is less than 2 mg of N-NO2/L or at least two times lower than the concentration of ammonium in the reactor, and

a step c of extracting, from the reactor, a fraction of the sludge resulting from steps a and b, per unit of time, calculated so that an effective age of aerated sludge of the reactor is obtained which is less than or equal to a theoretical minimum age of aerated sludge necessary for nitrification as defined by a decreasing exponential distribution as a function of the reactor temperature,
such that the production of nitrates is minimized in comparison to the production of nitrites in the reactor by suppressing the activity of nitrite-oxidizing bacteria by means of said aeration in step a, said elimination of nitrites in step b and said effective age of aerated sludge in step c; and
the steps a, b and c are repeated until the ratio of the concentration of nitrites to the sum of the concentrations of nitrites and nitrates at the end of the aeration step a is greater than 0.8.

2. The method according to claim 1 , wherein the biological reactor is an activated sludge reactor.

3. The method according to claim 1 , wherein the concentration of dissolved oxygen in step a is greater than or equal to 2 mg/L.

4. The method according to claim 1 , wherein the sampling b1 of water treated in step a, outside the reactor (first reactor), is carried out by draining b3 at least a fraction of the contents of the reactor resulting from step a and/or recirculating b4 at least a fraction of the contents of the reactor resulting from step a towards a second biological reactor which feeds the first reactor.

5. The method according to claim 1 , wherein the anoxic biological transformation b2 is implemented by heterotrophic denitritation in the presence of carbon and/or deammonification by Anammox.

6. The method according to claim 1 , wherein the elimination of at least part of the nitrites produced in step a is carried out by the anoxic biological transformation b2 and the sequence of steps a and b2 is repeated cyclically in said biological reactor.

7. The method according to claim 1 , wherein the elimination of at least part of the nitrites produced in step a is carried out by a recirculation b4 of at least a fraction of the contents of the reactor (first reactor) resulting from step a towards a second biological reactor which feeds the first reactor, and by the anoxic biological transformation b2 of said fraction in said second reactor.

8. The method according to claim 1 , wherein the elimination of at least part of the nitrites produced in step a is carried out by a draining b3 of at least a fraction of the contents of the reactor resulting from step a and the anoxic biological transformation b2 of the fraction eventually remaining in said biological reactor.

9. The method according to claim 1 , wherein the effective age of aerated sludge of said reactor is between 50% and 90% of the theoretical minimum age of aerated sludge.

10. The method according to claim 1 , wherein steps a, b and c are repeated until the ratio of the concentration of nitrites to the sum of the concentrations of nitrites and nitrates at the end of the aeration step a is greater than 0.9.

11. A method for the biological treatment of nitrogen in wastewater, by nitritation-denitritation and optionally deammonification, characterized in that the nitritation is implemented by the method according to claim 1 .

12. The method according to claim 1 , wherein the effective age of aerated sludge of said reactor is between 60% and 80% of the theoretical minimum age of aerated sludge.

Assignees

• Suez Groupe
• Suez Int

Inventors

• Caligaris Marc
• Saur Thibaut
• Mozo Irène

Classifications

• C02F3/305

  characterised by the denitrification · CPC title

• C02F2101/16

  Nitrogen compounds, e.g. ammonia · CPC title

• C02F3/301

  Aerobic and anaerobic treatment in the same reactor · CPC title

• Y02W10/10

  Biological treatment of water, waste water, or sewage · CPC title

• C02F3/303

  characterised by the nitrification · CPC title