Method and plant for the treatment of effluents containing nitrogen in a sequencing batch reactor

A method for the treatment of effluents containing nitrogen in the form of ammonium, using a sequencing batch reactor (1), according to which:

• a volume of effluent to be treated in a complete cycle is introduced into the batch reactor in successive volume fractions, each volume fraction being treated during a subcycle, the successive introduction of the volume fractions making it possible to exert a bacterial selection pressure favorable to the development and to the activity of nitriting bacteria by means of ammoniacal single-shots,
• each subcycle comprises a phase of feeding with a volume fraction and, in an alternating manner, two treatment stages, i.e.:
• an aerated first stage, during which complete or partial oxidation of the ammonium so as to give nitrites takes place,
• followed by a nonaerated second stage, under anoxic conditions, during which the nitrites produced and the ammonium are converted to nitrogen gas,
• wherein:
• during the aerated first stage, the dissolved oxygen concentration in the batch reactor is maintained between 0.1 mgO2/l and 0.6 mgO2/l,
• the N—NO2:N—NH4 ratio is adjusted so as to be between 0.9 and 1.5 at the beginning of the nonaerated stage,
• and the nonaerated stage is carried out by deammonification, without the provision of a carbon-based substrate.