A consequence of intensive livestock production is the production of large quantities of manure. Manure management is a matter of serious concern these days for two reasons: the need for efficiency of operation to increase profitability and the need for environmental responsibility. The problems with manure production include emissions to air (e.g., ammonia, nitrous oxide and methane) and water pollution through the leaching of nitrates. There is some evidence of soil pollution too, especially where repeated heavy doses of manure are applied. Disease risks, both to the livestock and the general public, are now also of concern. Several alternatives for manure management and treatment are currently available. One such method is aeration. The objective of this overview is therefore to discuss some recent data on such liquid manure treatment systems, including (i) the theoretical approaches carried out at pilot scale in order to understand the mechanisms and processes involved, and (ii) the monitoring of farm size units, to provide updated information on the actual performances of such aerobic treatment plants with regard to nutrient (N, P) removal efficiency, fate of nitrogen forms, and separation performance. Laboratory experiments were performed to determine the major factors affecting nitrogen transformations and related nitrous oxide emissions from aerobically treated piggery slurry. Full oxidation of ammonium (95%) and high nitrogen removal (66%) could be obtained using simultaneous nitrification and denitrification promoted by a low aeration level and raw slurry with sufficient carbon content. The results obtained in this study also confirm the production of nitrous oxide during continuous aerobic treatment of pig slurry. Intensive biological processes for eliminating nitrogen and removing odour are being installed on individual farms in Brittany. About 400 farm waste treatment plants have been built and are currently in operation, and with potentially 600 to 700 additional units to be built in the near future. Aeration of the slurry induces nitrification and subsequent denitrification into the atmosphere as nitrogen gas. The remaining slurry is allowed to settle naturally and separate into an odourless liquid and sludge. The treated liquid, which is around 65% of the manure volume, contains only 2-7% of the original nitrogen, and only 10% of the phosphorus, and therefore can be recycled rapidly for irrigation with a reduced environmental risk.