NON-STEADY-STATE MODELLING OF FAECAL COLIFORM REMOVAL IN DEEP TERTIARY LAGOONS

In Noirmoutier, a French island of the Atlantic coast, secondary effluents flow into a series of four lagoons and are reused for agricultural irrigation. The aim of this study was to provide a model capable of predicting the microbial quality of the water pumped for irrigation or discharged to the sea. The main bacterial removal mechanism was shown to be solar radiation. Faecal coliform numbers in the different lagoons were predicted with reasonnable accuracy in spite of high variation in inlet water quality.