Impact of Combined Sewer Overflows (CSO) on the microbiological quality of the Seine River in Paris area.

CSO2Thanks to major improvements realized during the last ten years in the wastewater treatment plants of the Parisian area, combined sewer overflows (CSO), occurring during rain and storm events, have now become, at the annual level, the predominant source of microbial contaminants released in the Seine river in Paris area. In these conditions, it is important to improve our knowledge on the flow of microbial contaminants released by CSO’s and the impact of CSO’s on the microbiological quality of the Seine river.


To achieve these goals, field studies are conducted in order to evaluate the temporal fluctuations of the microbiological quality (concentration of fecal indicator bacteria, FIB) in both the CSO’s and in the Seine river downstream from CSO’s. Our final objective is to build a model able to predict the microbiological quality in the Seine river when CSO occur.


ESA-ULB (Servais, P.), UMR Sisyphe – Université Pierre et Marie Curie (Mouchel, J.M.), LEESU – Université Paris Val de Marne (Lucas, F.), SIAAP – Syndicat Interdépartemental d’Assainissement de l’Agglomération Parisienne (Rocher, V., Goncalves, A.), Mines Paris-Tech (Poulin, M., Flipo, N.)

ESA members participating to this study

Servais, P., Passerat, J., Ouattara, K.

Period of the study

January 2007- December 2014.

Financial support

PIREN Seine Program (


Passerat, J. Ouattara, K., Mouchel, J.M., Rocher, V. and Servais , P. 2011. Impact of an intense combined sewer overflow event on the microbiological water quality of the Seine River. Water Research. 45 : 893-903.

Lucas, F., Goncalves, A., Servais, P., Rocher, V., Masnada, S., Thérial, C. Lesage, L., Mouchel, J.M. 2012. Variabilité de la qualité microbiologique des eaux usées brutes dans une grande agglomération. Techniques, Sciences, Méthodes. 2012. 4: 44-55.

Lucas, F. Thérial, C., Goncalves, A., Servais, P., Rocher, V. & Mouchel, J.M. 2014. Variation of raw wastewater microbiological quality in dry and wet weather conditions. Environmental Science and Pollution Research. 21:5318–5328.