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Underflow geometry in secondary sedimentation
Author(s) -
Samstag Randal W.,
Dittmar David F.,
Vitasovic Zdenko,
McCorquodale J. Alex
Publication year - 1992
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/wer.64.3.3
Subject(s) - arithmetic underflow , sedimentation , settling , mechanics , countercurrent exchange , stratified flow , flow (mathematics) , froude number , work (physics) , dispersion (optics) , geometry , reynolds number , geotechnical engineering , environmental science , geology , physics , mathematics , sediment , environmental engineering , turbulence , thermodynamics , geomorphology , optics , computer science , programming language
Previous work by the authors suggested that activated sludge sedimentation might be highly sensitive to underflow geometry. Field, physical model, and stratified flow numerical model tests were conducted to evaluate this hypothesis. Field work included solids settling velocity, dye dispersion, and flow pattern/solids distribution tests. Physical tests included operation of a pie‐shaped 1:12.5 scale model of a circular, center‐feed tank with sludge withdrawal simulating countercurrent, uniform, and cocurrent geometries. A stratified flow numerical model that simulated the effects of density currents was calibrated to the results of the full‐scale testing. The results failed to confirm the experimental hypothesis. Model performance was relatively insensitive to underflow geometry in a circular tank when density effects were simulated.