A water system pumps 1.20 MGD and disinfects using 12.5% commercial sodium hypochlorite solution. If the desired chlorine dosage is 3.00 mg/L, how many pounds of the 12.5% hypochlorite solution are required per day?

Formula Used: Liquid Solution Feed (lbs/day) = [Flow (MGD) × Dose (mg/L) × 8.34] ÷ [Active Strength (% / 100)]

Step-by-Step Mathematical Derivation:

1. Calculate pure 100% active chlorine requirement: 1.20 MGD × 3.00 mg/L × 8.34 = 30.024 lbs pure Cl2/day.
2. Account for the 12.5% solution strength by dividing by 0.125: 30.024 lbs/day ÷ 0.125 = 240.19 lbs/day (~240.2 lbs/day).

⚠️ Common Exam Trap: Always divide by the decimal percentage (0.125) rather than multiplying. A diluted 12.5% liquid requires 8 times more gross product weight than pure gas.