A Review of Vortex Grit Basin Design

Due to the challenges associated with sampling, and the low priority often bestowed on grit removal, good data on grit removal in vortex grit basins is surprisingly rare. A review of experimental and full scale plant results, mathematical models and CFD model results were undertaken with the goal of identifying a common separating mechanism in vortex grit basins. Finding such a mechanism would lead to a mathematical model or equation that can be used for the design of vortex grit basins. Analysis of grit basins show that centrifugal forces are negligible and intricate flow patterns do not exist. Sedimentation under the influence of gravity is the main mechanism for grit removal in vortex grit basins. CFD modeling and the available data support this conclusion. Due to the high tangential velocity introduced by the influent flow, some allowance must be made to accommodate the resulting turbulence. Some mathematical models include such allowance, but the allowance has not been fully quantified. This is a key requirement for future research. CFD modeling is a tool that would allow for optimization of grit basin design, particularly for those parameters, such as outlet configuration, that cannot be easily included in a mathematical analysis. Suggestions are provided for other parameters that form part of vortex grit basin design.