Hydrodynamic of circular primary clarifiers

Abstract

The strip integral method has been applied to a typical restricted inlet circular primary clarifier, in order to simulate the flow pattern and dispersion characteristics of the flow. This method assumes a dominant flow direction and with the use of velocity shape functions reduces the equations of motion and continuity to a set of simultaneous ordinary equations. Three shapes were chosen, corresponding to the boundary layer, the potential core, and the free mixing and recirculation zone. A Runge–Kutta method was used to integrate the set of ordinary differential equations. A standard finite element method was used in the withdrawal zone. The numerical predictions compared favorably with experimental velocity distributions obtained in a physical model of circular sedimentation tanks. The model is restricted to circular primary clarifiers of discrete suspension with low concentration operating at neutral density environment.The model was used to predict the velocity and dispersion characteristics of the circular tanks used at the West Windsor Pollution Control Plant, Windsor, Ontario.