Modelling of E. colidistribution in coastal areas subjected to combined sewer overflows

Rivers, lakes and the sea were the natural receivers of raw urban waste and storm waters for a longtime but the low sustainability of such practice, the increase of population and a renewedenvironmental sensibility increased researcher interest in the analysis and mitigation of the impact ofurban waters on receiving water bodies (RWB). In Europe, the integrated modelling of drainagesystems and RWB has been promoted as a promising approach for implementing the WaterFramework Directive. A particular interest is given to the fate of pathogens and especially ofEscherichia coli, in all the cases in which an interaction between population and the RWB is foreseen.The present paper aims to propose an integrated water quality model involving the analysis ofseveral sewer systems (SS) discharging their polluting overflows on the coast in a sensitive marineenvironment. From a modelling point of view, the proposed application integrated one-dimensionaldrainage system models with a complex three-dimensional model analysing the propagation in spaceand time of E. coli in the coastal marine area. The integrated approach was tested in a real case study(the Acicastello bay in Italy) where data were available both for SS model and for RWB propagationmodel calibration. The analysis shows a good agreement between the model and monitored data.The integrated model was demonstrated to be a valuable tool for investigating the pollutantpropagation and to highlight the most impacted areas.