Mathematical simulation of contaminant transport in water distribution systems

The paper describes a mathematical model, denominated QualSim_PFN, which aims at the simulation of space and time changes of the quality characteristics of water flowing in a Water Distribution System (WDS). The model is presented and step by step compared to the EPANET model, which so far considered, at present, the world standard in the field of the simulation of quality changes within water distribution networks. The procedures adopted to set up the QualSim_PFN model allows to take in consideration different phenomena, such as the turbulent dispersion and the molecular diffusion which, though usually considered of secondary importance, can assume, in some cases, great relevance (especially in the cases where the flow velocities are reduced). Through specific reaction equations, the model takes in consideration the interaction among different substances eventually present in the water, allowing, by precise choice for the time step used in the simulations, to minimize the percent error in the contaminant concentrations and early warning time computations. The QualSim_PFN model is finally applied to different study-cases, displaying its ability to overcome some of the limitations existing in other models.