In this work, a global sensitivity analysis (GSA) is performed on a kinetic-dynamic model for a stabilization pond system, consisting of two aerobic ponds in series followed by a facultative one, to determine the most influential parameters of the model, as well as parameter ranking. GSA is implemented using Sobol's method, a variance-based technique which allows factor prioritization and factor fixing considering the whole range of parameter variation. The technique is implemented within the gPROMS platform, a differential algebraic equation oriented environment where stochastic simulations are performed. Time profiles for first order, total order, and interactional sensitivity indices are obtained for 72 differential state variables considering 20 parameters as uncertain. Numerical results provide useful information about the complex relationships between the variables of the wastewater treatment processes.