Effectiveness of Backwashing for Wastewater Filters

by John L. Cleasby, (M.ASCE), Prof.; Dept. of Civ. Engrg. and Engrg. Research Inst., Iowa State Univ., Ames, Iowa,
James C. Lorence, (A.M.ASCE), Project Engr.; Clark Dietz Assocs., Inc., Urbana, Ill.; formerly, Grad. Student in Sanitary Engrg., Iowa State Univ., Ames, Iowa,

Serial Information: Journal of the Environmental Engineering Division, 1978, Vol. 104, Issue 4, Pg. 749-765

Document Type: Journal Paper


The use of deep granular filters in waste treatment is of growing importance. The key to long-term operating success of such filters is proper bed design and adequate bed cleaning during backwashing. A number of questions related to adequate backwashing of granular filters are investigated which lead to the following conclusions. Auxiliary means of improving filter backwashing are essential for wastewater filters. Three auxiliary methods were compared in a wastewater pilot filtration study. The most effective backwash was provided by air scour and water backwash simultaneously at subfluidization velocities. The other two methods, surface and subsurface wash auxiliary on air scour prior to water fluidization wash, were about comparable in effectiveness. The performance of coarse sand, dual-, and triple-media filters is compared, and the backwashing routines appropriate for each media are considered.

Subject Headings: Backwashing | Wastewater management | Filters | Granular materials | Waste treatment | Scour | Water management | Recycling

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