Hydrodynamic behaviour and faecal coliform removal in a maturation pond

A tracer test was performed in a 3,000 m(3) and 1 m deep maturation pond lo cated in the south of France. A retention time distribution was determined on the basis of tracer study. Tracer distribution into the pond was also mo nitored. Physico-chemical parameters and faecal coliform contents were meas ured at pond inlet and outlet and at 4 points in the pond. During the same period, two 20 m(3) and 1 m deep pilot pools were sat dose to the pond and filled with inlet water. A die-off constant was calculated after the variat ions of feacal coliform contents observed in the pilot pools. The objective was to verify whether faecal coliform removal can be predicted from observ ed retention time distribution, assuming a first-order faecal coliform deca y with a die-off constant determined in pilot pools. A very good prediction was achieved despite some uncertainties in the experimental data mainly du e to pond operation and climatic conditions.