Theory of Water Filtration

by Thomas R. Camp,

Serial Information: Journal of the Sanitary Engineering Division, 1964, Vol. 90, Issue 4, Pg. 1-30

Document Type: Journal Paper


The Kozeny equation of laminar flow through granular materials is extended to the transition region by means of a chart of the friction factor versus the Reynolds number. A chart of the backwashing number versus the Reynolds number is developed for estimating wash rates required at impending suspension and during suspension of filter grains. The friction factor during backwash decreases greatly at porosities greater than approximately 0.6. Small floc particles deposit in a filter, as a sheath, around the sand grains. A chart for the easy computation of the deposit ratio from the sand size and hydraulic gradient is presented. The rate of removal for a given volumetric concentration of floc in the water at each depth is found to decrease greatly with depth. This decrease in effectiveness is related to the adhesiveness of the floc to the sand.

Subject Headings: Sandy soils | Water management | Filtration | Granular materials | Friction | Reynolds number | Backwashing | Laminar flow

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