Nitrogen losses to up to 70% of the original nitrogen content can occur during aerobic treatments. If nitrification does not occur, for example for treatment of less than 3 days, the nitrogen losses will be one under the form of ammonia emissions. The nitrifying activity is encouraged by long aeration treatments of more than 3 days. Up to 70 % of the nitrogen present originally in the slurry can be nitrified (as nitrite and nitrate). However if the ventilation conditions are not maintained, denitrification process will occur and N losses can be over 10% of the original nitrogen present in the slurry.