Contribution of domestic effluents to hydrocarbon levels of dry weather flow in combined sewers

The importance of hydrocarbon contamination of the sewer network has been reported by many authors recently. Most of the studies are focused on the introduction of such pollutants into combined sewers by street and roof stormwater, but few evaluate the contribution of domestic inputs to hydrocarbon pollution. As a consequence, this work—carried out on the framework of the OPUR (Observatory of Urban Pollutants) research program—assesses the resolved aliphatic (AH), unresolved complex mixture (UCM) and polycyclic aromatic hydrocarbon (PAH) concentrations of domestic effluents (DE) and evaluates the role played by such effluents on the hydrocarbon levels of dry weather flow (DWF) in combined sewers. Results show hydrocarbon concentrations in the 200 – 300 μg · l−1, 300 – 1 000 μg · l−1 and 0.9 – 1.4 μg · l−1 ranges for AHs, UCM and the 16 PAHs of the US-EPA, respectively. The assessment of hydrocarbon fluxes conveyed by domestic effluents on the scale of the ‘Le Marais’ experimental urban catchment (42 ha, centre of Paris) reveals the predominant contribution of domestic inputs to the DWF pollution and highlights the unsuspected role of households.