Abstract EN:

At present, wet weather pollution discharged by sewer systems in natural environments is becoming a major environmental concem. This pollution appears during rainfall events and its impact is more important with increased rain intensity. Many studies show that extreme emissions of pollution by sewer systems are the result of heavy storms, with a low frequency of occurrence. However, these extreme emissions have a detrimental, sometimes even disastrous effect on water quality. In wet weather flow pollution, suspended solids are a major vector of pollution absorbed to organic and minerai particles carried by stormwater. The generation and transport of pollution in systems during a storm event is the result of a complex interaction of processes occurring in different space and time scales. A typology of existing models shows that this complexity has often been included into these models, which consider each water cycle and water quality phenomena. However, such complex models increase the difficulty in applying them because of insufficient knowledge concerning the processes involved, the uncertainties of data which is rarely available and the difficulty in calibration. Studies in various locations show that suspended solid characteristics are similar for the same kind of sewer systems and rain conditions; usually it has been observed that the sewer system acts like a filter and reduces the variability and the heterogeneity of the output variables. Rainfall is the most important input for many hydrological and hydraulic design calculations. Long historical rainfall series should be used and a statistical analysis should be performed on the hydraulic results. These subsequent results can be used as input into pollution loads models. The present study requires the verification of the kind of simplifications that may be made with respect to rainfall input to rainfall-runoff models. The level of simplification can be different according to the purpose of the study and its application. [. . . ]