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Showing 2 results for Sedimentation

H. Ghiassian, M. Jalili, I. Rahmani, Seyed M. M. Madani,
Volume 11, Issue 4 (12-2013)
Abstract

The concept of Geosynthetic Cellular Systems (GCS) has recently emerged as a new method in construction of breakwaters and coastal protective structures. The method potentially has significant advantages compared to conventional systems from the standpoint of constructability, cost effectiveness, and environmental considerations. This paper presents the results of physical model testing on the hydraulic responses of GCS structures under wave action. A series of model tests were carried out in a wave flume on GCS models with different shapes and soil types, subjected to various wave characteristics. Horizontal wave forces acting on the models were measured at different elevations. The maximum horizontal force in each test was calculated and compared with conventional formula of predicting wave pressure on breakwaters. The results show that Goda’s equation overestimates the hydrodynamic water pressure on these structures. This can be attributed to the influence of seeping water through the GCS models because of relative permeability of the GCS.
A. Fraji, Gh. Asadollahfardi, A. Shevidi,
Volume 11, Issue 4 (12-2013)
Abstract

Secondary clarifiers with large areas are widely applied in wastewater treatment plants. A pilot study was conducted to examine the possibility of applying one and two-stage inclined tube settlers instead of conventional secondary clarifiers. Tube diameter in the first stage of the two-stage settler was wide as the conventional ones, but in the second stage, it was narrow to improve the efficiency. The results indicated that in short detention times, the tube settler was more effective in shorter detention time than the conventional secondary sedimentation basin, and its effluent of TSS and turbidity was acceptable to discharge into the surface waters. The average removal of TSS, BOD5, and COD, in a 20-minute detention time in the tubes, in the one-stage tube settler pilot plants was 97.6%, 96.4%, and 96.36%, respectively, while in the conventional secondary sedimentation basin was 98.2%, 99%, and 98.6%, respectively. There was a good agreement between theoretical analyses and experimental results of the pilot plant. Two-stage tube settlers in the series could improve hydraulic condition and removal efficiency of TSS, in comparison with the one-stage tube settler. The average TSS removal, in shorter detention times than that the one-stage, was 97.8%.

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