Reducing Sediment Deposition on Columned Vortex-Settling Basin Floor by Installing Vanes

Abstract

Vortex-settling basins (VSBs) have been constructed with support columns under the deflector to enhance the structural stability of the deflector. This paper presents a retrofit for such columned VSBs by installing vanes at the bottom of the support columns to reduce the sediment deposition on the basin floor. Experiments were conducted for VSBs both with and without vanes, where the thickness and mass of sediment deposition, sediment trapping efficiency, and water abstraction ratio of the VSBs were measured and compared. The VSB with vanes exhibited a similar sediment trapping efficiency and water abstraction ratio to the original columned VSB. When the inflow is equal to or greater than the design discharge, the vanes showed a significant effect on reducing the mass of sediment deposition by an average of 11.71% and 22.25%, respectively, and the formed sandwave on the basin floor was smaller. When the inflow is less than the design discharge, the effect of the vanes was limited, with the mass of sediment deposition slightly reduced by 5.25% on average.