What should the setting be on a chlorinator in pounds per day if the dosage desired is 3.25 mg/L and the pumping rate from the well is 735 gpm?

• A. 20.1 lb/d
• B. 28.7 lb/d
• C. 8.83 lb/d
• D. 239.4 lb/d

Answer: (B)

Calculating the daily chlorinator setting comes down to turning a mg/L dosage into a pounds-per-day feed based on the amount of water treated each day. First figure the total water volume processed per day: 735 gallons per minute multiplied by 60 minutes per hour and 24 hours per day gives gallons per day, and then convert to liters. So: 735 × 60 × 24 = 1,058,400 gallons/day, which is 1,058,400 × 3.78541 ≈ 4,006,469 liters/day. Multiply by the target dosage: 3.25 mg/L × 4,006,469 L/day ≈ 13,021,000 mg/day. Convert to pounds by dividing by 453,592 mg per pound, giving about 28.7 pounds per day. Therefore the chlorinator setting should be about 28.7 lb/d.