Influence of sewage discharge on the pollution of an estuary (Morlaix, France).

The purpose of this paper is to evaluate the pollution introduced into the Morlaix estuary by the city discharge of sewage and to determine its consequences on the microbiological quality of estuarine water and sediment. It has been shown that between 10(13) and 10(14) fecal coliforms and streptococci and between 10(6) and 10(7) enteroviruses are thus conveyed per day. The study of the downstream contamination indicates that the bacterial and viral density is much more significant in the sediment and that the bacterial concentration decreases gradually from upstream to downstream whereas the viral density only varies slightly in the water and shows very irregular fluctuation in the sediment.