DESIGN OF SETTLING BASINS

Abstract

Settling basin is a device used for the removal of excess sediment load from canals and other water conductor systems. It is placed in the canal just downstream of head-works. The settling basin consists of an oversized section of the canal in which the velocity is low enough to permit the suspended particles to settle out. The sediment will then be removed from the settling basin by sluicing or mechanical means. Existing methods of design of settling basins are not satisfactory, therefore, the present study is taken up to collect additional data on efficiency by conducting a series of experiments which have been carried out in Hydraulics Laboratory using 0.30 m wide channel expanding to 0.75 m settling basin of various lengths. Two different sizes of sand of 0.106 mm and 0.082 mm are used as sediment load along with three different lengths of settling basin. Expe-rments have been carried out using three different slopes and different sediment concentrations. The analysis of the data including the data collected by Singh(12) has led to a relationship for prediction of efficiency of settling basin which can be expressed as follows: - (1 _e-kL/D} Here is the efficiency of settling basin , the parameters and k are functions of w/U* , where w is the particle fall velocity , U is the shear velocity, L is the length of settling basin and D is the depth of water in the basin.