Particle Concentration Predictions in Settling Basins

Abstract

The equation governing the concentration field for a dilute suspension of particles is presented for flow in circular and rectangular primary settling basins. The formulation is valid for two‐dimensional, mean steady, isothermal, turbulent flow conditions. Basin flow velocities are obtained from a hydrodynamic model which determines the turbulent diffusion coefficients for mass transport as part of the overall solution. A numerical solution to the mathematical model is formulated by application of the Galerkin finite element method to the equation residuals. The resulting linear, algebraic equation set is solved by a standard elimination scheme. Results include contour plots of particle concentration fields for rectangular and circular basins and removal efficiencies for these tanks. The effect of partial resuspension at the bed (deposition retarded) is included in the analysis.