Extended Plain Sedimentation

by Kuan M. Yao, (M.ASCE), World Health Organization Prof. of San. Engrg.; Univ. of Engrg. and Tech., Lahore, Pakistan,

Serial Information: Journal of the Environmental Engineering Division, 1975, Vol. 101, Issue 3, Pg. 413-423

Document Type: Journal Paper


Extended plain sedimentation could be a possible alternative for pretreatment of surface waters in water purification. It does not add pollution to the environment and its sludge is less objectionable for disposal. Theoretical investigation shows that gravitational effect dominates settling down to the particle size of 1 μ. Experimental results indicate that extended plain sedimentation is technically feasible to remove a substantial amount of turbidity with residual turbidity down to less than 10 FTU. An 88% turbidity removal could be achieved in a settling tank of 7.5-day detention. Suspended solids concentration appears to be more appropriate as an indicator of the performance of settling of natural waters. From the viewpoint of functioning of settling tanks, extended plain sedimentation should mean extension towards a lower design overflow rate rather than towards longer detention periods.

Subject Headings: Turbidity | Sedimentation tanks | Sediment | Surface water | Water treatment | Water tanks | Water surface | Pollution

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