Scaling Laws for Sedimentation Process in Water Flow-Driven Sedimentation Tanks

Abstract

This paper addresses scaling laws on sedimentation tanks whose aim is to separate particles from particle-containing water. Sedimentation process was categorized for four typical cases: Case 1 through Case 4; then scaling laws for each case were developed using law approach method. Case 1: Relatively large diameter particles, Case 2: Relatively small diameter particles, Case 3: Small diameter particles with low specific mass density, and Case 4: large diameter particles with high specific mass density. Two scale model sedimentation tanks were designed for sedimentation experiments. These two tanks were geometrically similar. The large tank (prototype) is twice as larger than the small tank (model). Experiments were conducted for Case 3 and Case 4 using prototype and model. The flow rate of water and the feeding rate of particles for prototype and model were adjusted based on scaling laws derived for each case. Sedimentation ratio (dimensionless parameter), defined as the ratio of sedimentary particle weight of particular size to the original weight of the corresponding size of particles with known size distribution, was measured in the above experiments and used to validate scaling laws. As a result, the proposed scaling laws for Case 3 and Case 4 were successfully validated.