The invention relates to a method for processing nitrogen-concentrated effluents by ammonia oxidation into nitrites followed by nitrite denitritation in a gaseous nitrogen in a sequential biological reactor (1) consisting in pouring a processable effluent volume in to the reactor by successive volume fractions, in dividing the entire processing cycle into successive sub cycles, wherein each sub-cycle comprises a feeding phase, an aeration phase for nitrification and an anoxia phase along which a carbon-containing source is introduced into the reactor for converting nitrites into nitrogen. The inventive method also consists in evaluating a nitrogenous volume charge in the effluent to be processed, mainly by measuring the effluent conductivity (X) and the flow rate (Q) and in determining the number of feeding phases of the entire cycle according to nitrogenous charge and to a minimum volume of liquid in the reactor in such a way that an injected nitrogen concentration is diluted in the liquid volume, wherein the volume phase nitrogenous charge is however sufficient for producing a single shot or peak of the ammonia charge favourable for a nitrating biomass formation in the reactor.