Remodeling a Sedimentation Basin Outlet Structure for Improving Performance

Abstract

This study was conducted to evaluate the effect of the launder type on settling performance and hydrodynamic behavior within the two certain full-scale sedimentation basins (flow rate per one basin; 10,000 m3/day); one has the transverse type launder (existing basin), and the other has the finger-type launder in combination with the longitudinal baffle (remodeled basin). Comparative experimental investigations have been carried out through residual turbidity and particle concentration measurements in each effluent from two basins with the transverse and the finger-type launders, respectively. From the experimental results, it could be observed that the turbidity removal rate in the finger-type launder basin (remodeled basin) is about 30% higher than that in the transverse-type launder basin (existing basin). Also, from the measurement of total particle concentration in each effluent, the removal efficiency was improved 27% within the remodeled basin compared to the existing basin. To explain the comparative experimental results and investigate the hydrodynamic behavior within each basin in more detail, the authors conducted computational fluid dynamics (CFD) simulation and verified simulation results with acoustic Doppler velocimetry (ADV) technique. From the CFD simulation results, it was investigated that extreme upward flow occurs underneath of the transverse launder. On the other hand, in the case of the remodeled basin, the upward flow, which occurred beneath the launder, was much less than that in the existing basins.