Author(s): Andres Torres; Jean-Luc Bertrand-Krajewski
Linked Author(s): Jean-Luc Bertrand-Krajewski
Keywords: Measurements; Settling velocities; Stormwater; Suspended solids; Uncertainties
Abstract: Field experiments were carried out to contribute to the assessment of the VICAS protocol. Samples have been taken in the detention and settling tank Django Reinhardt in Chassieu, France, using sediment traps located on the tank bottom. The first kind of experiments consists on mass balance tests. Results indicate that the mass balance is good, with absolute errors below 5 % . In addition, tests of repeatability have also been carried out. Three 5 L sub-samples have been taken from an initial 25 L sample collected on site. The settling velocities have been measured simultaneously with three identical apparatus. Tests indicate that the repeatability is good if experiments are made by a trained operator. Uncertainties in the final distribution curves have been evaluated by using Monte Carlo simulations and the law of propagation of uncertainties. All calculations have been implemented in a MatLab code named UVICAS used for each experiment. This code allows analysing the main sources of uncertainties and their evolution during experiments. Uncertainties in the final distribution curves decrease with increasing values of settling velocities. In addition, the most contributing sources of uncertainty have been identified. Results obtained in this work confirm the interest and the applicability of the VICAS protocol: i) mass balance and repeatability are good if experiments are made by a trained operator, ii) uncertainties in the final distribution curves are low. The resulting values of settling velocities obtained with the VICAS protocol can be used to design settling tanks, to analyze their functioning, and also for modelling purposes.
Year: 2007