This paper deals with dynamic simulation and optimization of wastewater treatment plants. Moreover, the benchmark plant (www.benchmarkWWTP.org) was considered and its corresponding model was used. Simulations were carried out using gProms software for dry, rain and storm weather data files. The optimization consisted in the determination of continuous aeration and internal recycle profiles which minimize the aeration energy under effluent constraints. The results obtained showed that we were able to save up to 30% of energy compared to the usual aeration policy and the effluent constraints are satisfied.