DESIGN OF SETTLING BASINS

Abstract

Settling basins are used to remove undesired sediment from irrigation and power channels. Irrespective of method of disposal of the settled material like intermittent mechanical dredging, continuous hydraulic flushing etc., the design of its dimensions remains the same. Based on the hydraulic principle of settling of sediment particles, various methods of design are available viz. Camp, USBR, Mosonyi, Garde et al. etc. All these methods enable determination of length of the basin for known width of basin and depth of flow. The channel approaching the settling basin is widened and its floor is deepened through an expansion transition to join the basin. It is done to reduce the flow velocity in the basin. This can be accomplished by various combinatS: , width and depth and hence length of the settling basin to achieve a desired efficiency of settling. Out of all these, the optimum size of the basin can be identified by cost criterion. Since neither internal volume of the basin nor its surface area of floor and walls can be individually representative of the cost, a volume equivalent to the internal volume and concrete volume is evolved and minimised. Design equations have been developed for the prediction of the dimensions corresponding to the minimised equivalent volume. The proposed method has been demonstrated through design example of settling basin provided at Maneri Bhali Stage II.