De l'utilisation pertinente des modèles de calcul des flux polluants en réseaux d'assainissement urbains

Models aiming to evaluate storm weather pollutant loads are useful tools for the design and the management of urban sewer systems. Nevertheless, their use requires precaution and rigour because of their sensitivity to experimental data and their basic assumptions. This sensitivity has been analysed for three modelling approaches : 1) site mean concentration (CM), 2) event mean concentration (CME) and 3) detailed modelling of pollutants production and transfer (MPT), in a case study dealing with the design of a storage tank based on data series of rainfall intensity, water depth, flow velocity and TSS concentrations collected in the Marais catchment. Simulation results show that, with a large number of events used for calibration, the CM and CME models converge towards similar values. On the contrary, for any number of events used for calibration, the MPT model gives storage tank volumes which are higher than those given by the CME or CM models.