Texas Commission on Environmental Quality (TCEQ). Class C Water License Exam

If a dosage of 4.0 mg/l is added to 750,000 gallons of water, how many pounds of chlorine are needed?

1. 20 pounds

2. 25 pounds

3. 30 pounds

4. 35 pounds

The correct answer is: 25 pounds

To calculate the amount of chlorine in pounds required for a dosage of 4.0 mg/l in 750,000 gallons of water, you can follow these steps: 1. **Convert gallons to liters**: There are approximately 3.785 liters in a gallon, so first convert 750,000 gallons to liters: \[ 750,000 \text{ gallons} \times 3.785 \text{ liters/gallon} = 2,839,125 \text{ liters} \] 2. **Calculate the amount of chlorine in milligrams**: Since the dosage is in mg/l, we multiply the concentration of chlorine by the total volume in liters to find the total amount in milligrams: \[ 4.0 \text{ mg/l} \times 2,839,125 \text{ liters} = 11,356,500 \text{ mg} \] 3. **Convert milligrams to pounds**: There are 453,592 milligrams in a pound, so convert the total milligrams to pounds: \[ \frac{11,356,500 \text{ mg}}{453,592 \text{ mg/pound}}