Fast, simultaneous simulation of the integrated urban wastewater system using mechanistic surrogate models

The urban wastewater system components (sewer, treatment plant, and river) are often modelled using complex mechanistic models. Mechanistic surrogate models are introduced here as simplified models that still contain some phy sical knowledge. Surrogate models are faster, but are less but still suffic iently accurate, and require more data to be calibrated. The possibilities of replacing actual field data by virtual data generated with a complex mec hanistic model for calibration of the surrogate model are examined. As an e xample, a series of tanks with variable volume is shown to approximate suff iciently well the flow propagation in the river Zwalm (Belgium) as predicte d by the "de Saint-Venant" equations. The three surrogate models can be implemented in the WEST(R) simulator. whi ch makes a simultaneous simulation of the system possible. In this work a c onnection is made between the ASM1 and the new IWA River Model No. 1 (RWQM 1) by using a translator between the models in such a way that both mass an d elemental balances remain closed for the overall system. This approach is illustrated with a case study on the river Lambro (Italy). The dispersion process in this river with steady flow could be modelled by using a tanks i n series model, while the water quality in the river was predicted to impro ve substantially with an increase in hydraulic capacity of the treatment pl ant. The simulation results with the upgraded plant still need to be checke d by field data.