Characterization of Setting Tanks by Eddy Diffusion

The mathematical formulation of tracer dispersion curves of settling tanks has been investigated. As a result, the coefficient of eddy diffusion characterizing the settling zone can be obtained either analytically or by the graphical solution of the formulation. The available relations in the literature describing the effect of eddy diffusion on the settling properties of suspended particles can then be used to predict the corresponding particle removal. A similarity rule for modeling sedimentation tanks is deduced from the verified relations. It calls for preserving two ratios proposed as Hazen and Camp numbers in both the model and the prototype systems. The proposed similarity rule approaches Reynolds' law as the coefficient of eddy diffusion decreases, approaching the kinematic viscosity of the fluid.