Alfredini, P.; Arasaki, E., and de Melo Bernardino, J.C., 2017. Santos sea outfall wastewater dispersion process: Physical modeling evaluation.To be environmentally sustainable, the ocean disposal of domestic sewage via a sea outfall must be carefully studied, such as previous modeling of waste-plume dispersion processes, for environmental impact assessments. A scale model, reproducing the Santos Bay and Estuary was calibrated at the Hydraulic Laboratory of Polytechnic School, University of São Paulo, Brazil. The complete modeling of this large estuarine system used numerical and scale models, which were all related to each other. Such an overall model, composed of individual hydraulic and numerical components, is called a hybrid model. It combines the advantages of both model components and adequate field survey measurements and is particularly important for simulating the plume dispersion process in Santos Bay. The goal hereby is to present a performance comparison of the outfall plume dispersion for improvement in the length of the Santos outfall. The study required preliminary numerical simulations in the near-field mixing processes to define the boundary conditions in the beginning of the far field. In addition, numerical simulations in the far field were required to reproduce the wind effect for calibrating the scale model of the air-tunnel hydro-aerodynamics. Scale model runs, using an advanced methodology for dye-plume monitoring, were calibrated with a numerical model of the plume dispersion and validated with independent runs of another numerical model of plume dispersion and comparison with satellite images of the plume. The conclusion was that an enlargement of 1 km of the outfall would reduce the risk of the plume returning.