Control of the WWTP is not a trivial task sinos the unit is nonlinear, features large time constants and delays, and interaction between variables is important. Model Predictive Control algorithm is a good candidate for such demanding task. The paper presents the results for controlling the WWTP using MPC. The Benchmark Simulation Model No. 1-BSM1 has been used as a standard for performance assessment and evaluation of the control strategy. Control of the Dissolved Oxygen in the aerated reactors and nitrate level in the anoxic compartments has been performed using the MPC control strategy. Air flow rate in the aerated reactors and internal recycle flow have been chosen as manipulated variables. The obtained results show the incentives of MPC over classical PI control with respect to overshoot and time response. A combined feedback-feedforward MPC scheme is also proposed for disturbance rejection and its incentives are shown.