Volatile compounds are desorbed from an aqueous liquid containing ammonia, by means of a stripping column. The aqueous liquid is supplied to the upper part of the column and a gaseous mixture including free oxygen is blown into the lower part of the column. Sodium hydroxide and/or calcium hydroxide is supplied to an intermediate part of the column at a plurality of levels. A gaseous mixture including ammonia is withdrawn from the top of the column. The pH and the temperature of the aqueous liquid are measured at a plurality of levels in the column. The flow rate of the aqueous liquid and the flow rate and temperature of the gaseous mixture blown in and of the hydroxide are controlled so that the pH of the aqueous liquid, at least in a predetermined zone of the column, is at least 11.