Settling velocities of TSS and of particulate pollutants (COP, PDCO, PTKN, PCu, PPb, PZn, PPAH) measured on a wide range of wet weather flow (WWF) samples collected at different levels of the Parisian combined sewer system are reported. The recorded V30 (0.01 to 0.1 mm.s-1) and V50 (0.09 to 0.6 mm.s−1) values exceed by a factor 10 those of dry weather sewage and also exceed the values measured for pavement runoff. These values lie however often below the 0.28 mm.s−1 reference value considered in France for the design of WWF settling facilities. A decrease in settleability is observed between a small upstream catchment and larger scaled downstream catchments. The settling behaviour of particulate pollutants varies depending on the considered parameter and can differ significantly from the TSS behaviour, due to a non homogeneous distribution of micropolluants over the different classes of particles. PZn and PTKN appear far less settleable than TSS, whereas PPAH show higher settleability.
Settling velocity of particulate pollutants from combined sewer wet weather discharges
M. C. Gromaire, M. Kafi-Benyahia, J. Gasperi, M. Saad, R. Moilleron, G. Chebbo; Settling velocity of particulate pollutants from combined sewer wet weather discharges. Water Sci Technol 1 December 2008; 58 (12): 2453–2465. doi: https://doi.org/10.2166/wst.2008.835
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