A secondary clarifier has a diameter of 75.0 feet with a peripheral effluent weir. If it processes a daily flow of 2.50 MGD, what is the Weir Overflow Rate (WOR) in gallons per day per linear foot of weir (gpd/ft)?

Formula Used: WOR (gpd/ft) = Daily Influent Flow (gpd) ÷ (π × Diameter in feet)

Step-by-Step Mathematical Derivation:

1. Calculate peripheral weir circumference: π × 75.0 ft = 3.14159 × 75.0 = 235.62 ft.
2. Convert daily flow to gallons per day: 2.50 MGD = 2,500,000 gpd.
3. Divide flow by weir length: 2,500,000 gpd ÷ 235.62 ft = 10,610 gpd/ft.

⚠️ Common Exam Trap: Do not confuse weir circumference (π × D) with surface area (0.7854 × D²). Weir overflow rate is per LINEAR foot of weir crest.