Effective treatment of wastewaters is one of the key actions to reduce the nutrient load of surface waters, which is one of the goals in EU policies (Water Framework Directive). There is an urgent need to develop more sustainable wastewater treatment plants (WWTP) to reduce the energy consumption and corresponding carbon dioxide (CO2) emissions. One of the keystones for the development of energy-efficient wastewater treatments is the use of an autotrophic nitrogen removal. Recently, significant emission of nitrous oxide (N2O), a greenhouse gas (GHG) 300 times more potent than carbon dioxide, have been detected associated to the biological nitrogen removal (BNR) in the wastewater treatment. Therefore, the main research objectives of the proposed research project are two: (i) the minimization of N2O emissions during the autotrophic nitrogen removal; and (ii) the achievement of a fully integrated autotrophic nitrogen removal for main stream wastewater treatment. These two aspects will contribute to the development of a truly sustainable WWTP with low carbon footprint. To this end, a mathematical model able to predict the amount of N2O emissions and the performance of a nitritation-Anammox reactor for main stream wastewater treatment will be developed. Validation of the modeling results will be possible through monitoring of the N2O emissions in a pilot plant prototype. Ad hoc process control strategies will be inserted in the model and evaluated through specific simulations. Numerical optimization of setpoints will be carried out to minimize the N2O emissions whereas a high nitrogen removal is achieved. The best process control strategy will be implemented first in a laboratory-scale reactor and later in a pilot scale prototype reactor treating real wastewater to test the achieved improvements in terms of the efficiency of the nitrogen removal and the minimization of N2O emission.