A STOCHASTIC APPROACH TO MODELING SOLID TRANSPORT IN SETTLING TANKS

Dispersion and settling models for suspended solids (SS) in turbulent flow are in the majority of cases Eulerian and deterministic. They sim ulate SS transport using a convection-diffusion equation. When the dif fusion term is supposed not to be zero at the boundary of a settling t ank, we show that an alternative(or equivalent) description of the bas ic convection-diffusion equation for the concentration of suspended so lids consists in modelling the particles trajectories as a stochastic diffusion process. This paper has two aims, firstly to present the pro posed stochastic approach and secondly to apply this new method to the calculation of a settling tank's efficiency. (C) 1998 IAWQ. Published by Elsevier Science Ltd.