Reducing Sediment Deposition on Deflector in Vortex Settling Basins

This paper presents a retrofit for vortex settling basins (VSBs) by perforating the deflector to reduce sediment deposition and thereby lowering VSB failure risks. Experiments were conducted for two retrofitted VSBs with the deflector perforated on the outside overflow area only and the other entirely perforated. The sediment deposition, sediment trapping efficiency, and water abstraction ratio of the retrofitted VSBs were measured and compared with an original VSB with an unperforated deflector. The VSB with a partially perforated deflector exhibited a similar sediment trapping efficiency and water abstraction ratio to the original VSB, with an average reduction over 40% in sediment deposition on the deflector. The VSB with an entirely perforated deflector had a lower sediment trapping efficiency and greater sediment deposition on the deflector.