The invention relates to a method and a device for continuously or semi-continuously treating/dehydrating organic sludge (1, 41, 69}, wherein a three-phase emulsion of air, solid matter and water is produced by injecting air (6, 47, 68) into the sludge, introducing a flocculant (13, 50, F) into said emulsion in order to create a floc (14, 51) and then degassing said floc at atmospheric pressure. The floc is degassed by soft impact of the floc on itself or on an energy absorbing shutter (39, C), braking the floc, and the floc matured in this way is recovered in a filtration and/or decanting device (56, 74).