Clarifier Surface, Weir, and Solids Loading
Surface overflow rate = flow/area (gpd/ft^2), weir overflow = flow/weir (gpd/ft), solids loading = flow x MLSS x 8.34 / area. 1 MGD, 40 ft dia (1257 ft^2), MLSS 2500 -> SOR 796, weir 7,958, solids 16.6; double the flow and SOR passes the ~1000 limit (floc carryover). The state design criteria govern.
Formula and source
SOR = flow x 1e6 / area (gpd/ft^2); weir = flow x 1e6 / weir_len (gpd/ft); solids = flow x MLSS x 8.34 / area (lb/ft^2/day).
Clarifier surface, weir, and solids loading rates, standard wastewater-operations practice (Ten States Standards / Metcalf & Eddy), by name.
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