Stormwater treatment by dissolved air flotation: first results from a pilot project

A stormwater treatment plant using dissolved air flotation was operated in 1993, at the outlet of the Chelles River catchment area (Seine-et-Marne, France). The process was divided into two different stages. Firstly, a coagulation/flocculation stage, secondly a flotation stage in a flotation tank. The flow rate was set at 13 m³/h. Stormwater was the main part of the effluent but with some urban wastewater as the network is not strictly separate. The process efficiency was tested for suspended solids, chemical oxygen demand and hydrocarbons. A total hydrocarbon removal was observed. Finally, constant output concentrations were observed in spite of important input roughwater concentration variations.