In this report, model predictive control (MPC) of large-scale sewage systems is addressed considering different modelling approaches that include several inherent continuous/discrete phenomena(overflows in sewers and tanks) and elements (weirs) in the system that result in distinctbehaviour depending on the dynamic state (flow/volume) of the network. These behaviourscan not be neglected nor can be modelled by a pure linear representation. In order the MPC controller takes into account these phenomena and elements, a modelling approach based on piece-wise linear functions is proposed and compared against a hybrid modelling approach previouslyreported by the authors. Control performance results and associated computation timesof the closed-loop scheme considering both modelling approaches are compared by using a real case study based on the Barcelona sewer network.