This study concentrates on the control of the largest European wastewater treatment plant (WWTP), Seine-Aval (SAV). This WWTP can be viewed as the interconnection of multiple unit operations. We start by deriving the dynamical models of the wastewater treatment units on the basis of mass balances and inspired from the activated sludge model (ASM) of the IWA. The model is then used to design a centralized controller with the objective to meet the wastewater European directives constraints. The identification of the model parameters and the controller design are based on two years of data collected at SAV. The centralized controller has been tuned and evaluated with three scenarios that consider dry, rainy and stormy weathers. The results show that WWTP performance are improved by 50 percent in dry weather (10 percent in the rain) while observing new European water policies and reducing the need and costs in reactants. The model definition and problem formulation allow to account for more complex phenomena in the future.