Problem 1: Flow Conversion
Question:
Convert 500 gallons per minute (GPM) to MGD.
Formula:
Solution:
500 × 1440 = 720,000
720,000 ÷ 1,000,000 = 0.72 MGD
✅ Answer: 0.72 MGD
Problem 2: Pounds Formula
Question:
A plant treats 2 MGD with a BOD concentration of 180 mg/L.
How many pounds of BOD enter the plant daily?
Formula:
Solution:
2 × 180 × 8.34
= 3,002.4 lbs/day
✅ Answer: 3,002 lbs/day
Problem 3: Detention Time
Question:
A tank volume is 500,000 gallons. Flow is 0.5 MGD.
Formula:
Solution:
500,000 ÷ 500,000
= 1 day
✅ Answer: 1 day detention time
Problem 4: Chlorine Dosage
Question:
How many pounds of chlorine are needed for a 3 MGD plant dosing 2 mg/L?
Solution:
3 × 2 × 8.34
= 50.04 lbs/day
✅ Answer: 50 lbs/day
Problem 5: Surface Overflow Rate
Question:
A clarifier treats 1 MGD and has a surface area of 800 sq ft.
Formula:
Solution:
1,000,000 ÷ 800
= 1,250 gpd/sq ft
✅ Answer: 1,250 gpd/ft²