Abstract
The fine sediment removal efficiency of a seepage settling basin built to control outflow sediment was investigated on-site. The target sediments were suspended sediment and microscopic load from upland fields.
In the seepage settling basin work desingned by this study, bed load is controlled by a vortex tube sand trap in the inlet canal and suspended load by underdrain filter material and improved gravity precipitation in the settling basin. The hydraulic design concept, structural components and construction of the settling basin are described.
It was found that suspended load is proportional to surface outflow rate from the upland field in terms of magnitude and rain. The sediment removal efficiency of the vortex tube sand trap for the period was 57%-100%.
The outflow of fine sediment is proportional to the second power of the runoff flow rate from the upland. This characteristic corresponds to the findings on wash load by river engineering. The effect of an underdrain was also studied through analysis of experimental data. The density of the underdrain correlates with the inflow density.
