If a 100-mgd flow of wastewater is dosed at a rate of 12 mg/L, the chlorine feed should be closest to what daily rate (lb/d)?

If a 100-mgd flow of wastewater is dosed at a rate of 12 mg/L, the chlorine feed should be closest to what daily rate (lb/d)?

• A. 10,000
• B. 2,000
• C. 5,000
• D. 20,000

Answer: (A)

When dosing a disinfectant, you convert the amount added from mg per liter to pounds per day for the plant’s flow. The daily chlorine feed in pounds per day equals the flow in million gallons per day times the dose in mg/L times a conversion factor of about 8.34. That 8.34 comes from how many pounds are in a million gallons of water at a concentration of 1 mg/L. So for 100 million gallons per day and a dose of 12 mg/L, the calculation is: 100 × 12 × 8.34 ≈ 10,008 lb/d, which is about 10,000 lb per day. That’s why the closest daily rate is approximately 10,000 lb/d. The other numbers would require much lower or higher dose values than 12 mg/L for the 100 mgd flow, so they don’t fit with the given situation.

When dosing a disinfectant, you convert the amount added from mg per liter to pounds per day for the plant’s flow. The daily chlorine feed in pounds per day equals the flow in million gallons per day times the dose in mg/L times a conversion factor of about 8.34. That 8.34 comes from how many pounds are in a million gallons of water at a concentration of 1 mg/L.

So for 100 million gallons per day and a dose of 12 mg/L, the calculation is:

100 × 12 × 8.34 ≈ 10,008 lb/d, which is about 10,000 lb per day.

That’s why the closest daily rate is approximately 10,000 lb/d.

The other numbers would require much lower or higher dose values than 12 mg/L for the 100 mgd flow, so they don’t fit with the given situation.