Effects of scale and Froude number on the hydraulics of waste stabilization ponds

This paper presents the findings from a series of computational fluid dynamics simulations to estimate the effect of scale and Froude number on hydraulic performance and effluent pollutant fraction of scaled waste stabilization ponds designed using Froude similarity. Prior to its application, the model was verified by comparing the computational and experimental results of a model scaled pond, showing good agreement and confirming that the model accurately reproduces the hydrodynamics and tracer transport processes. Our results showed that the scale and the interaction between scale and Froude number has an effect on the hydraulics of ponds. At 1:5 scale, the increase of scale increased short-circuiting and decreased mixing. Furthermore, at 1:10 scale, the increase of scale decreased the effluent pollutant fraction. Since the Reynolds effect cannot be ignored, a ratio of Reynolds and Froude numbers was suggested to predict the effluent pollutant fraction for flows with different Reynolds numbers.