Surface Overflow Rate & Solids Loading Rate
Check secondary clarifier hydraulic and solids loading — SOR in gpd/ft² and SLR in lb/day/ft² — against typical design ranges.
Formulas
Surface area: circular A = 0.785 × D² · rectangular A = L × W (ft²)
SOR (gpd/ft²) = flow (gpd) ÷ area (ft²)
SLR (lb/day/ft²) = (Q + Qr) (MGD) × MLSS (mg/L) × 8.34 ÷ area (ft²)
Typical secondary clarifier: SOR 400–800 gpd/ft² · SLR 20–30 lb/day/ft² (up to ~40 peak).
Surface area: circular A = 0.785 × D² · rectangular A = L × W (ft²)
SOR (gpd/ft²) = flow (gpd) ÷ area (ft²)
SLR (lb/day/ft²) = (Q + Qr) (MGD) × MLSS (mg/L) × 8.34 ÷ area (ft²)
Typical secondary clarifier: SOR 400–800 gpd/ft² · SLR 20–30 lb/day/ft² (up to ~40 peak).
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