Ghawi, H.

CFD Modelling of Sludge Sedimentation in Secondary Clarifiers

Abstract eng:
We present a Computational Fluid Dynamics (CFD) model that predicts the sedimentation of activated sludge in a full-scale circular secondary clarifier that is equipped with a suction-lift sludge removal system. The axisymmetric single-phase model is developed using the generalpurpose CFD solver FLUENT 6, which uses the finite-volume method. A convection-diffusion equation, which is extended to incorporate the sedimentation of sludge flocs in the field of gravity, governs the mass transfer in the clarifier. The standard k- ε turbulence model is used to compute the turbulent motion, and our CFD model accounts for buoyancy flow and nonNewtonian flow behaviour of the mixed liquor. The sludge settling velocity was measured as a function of the concentration, and we have used the double-exponential settling velocity function to describe its dependence on the concentration.

Contributors:

Kriš, J.

Publisher:

Slovak University of Technology in Bratislava, Faculty of Civil Engineering, 2008

Conference Title:

70 Years of FCE STU - Proceedings of the International Scientific Conference

Conference Title:

International Scientific Conference 70 Years of FCE STU

Conference Venue:

Bratislava (SK)

Conference Dates:

2008-12-04 / 2008-12-05