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

As the operator of a surface water treatment plant treating 4.3 mgd, how many pounds of alum are required if the dosage is 12 mg/L?

1. 12910 lbs

2. 10000 lbs

3. 11500 lbs

4. 13000 lbs

The correct answer is: 12910 lbs

To determine the pounds of alum required for treating 4.3 million gallons per day (mgd) at a dosage of 12 mg/L, we need to follow a few calculation steps. First, convert mgd to gallons per day, knowing that 1 mg/L is equivalent to 1 part per million (ppm) in water, which implies that for every million gallons of water treated, the operations would use 12 mg of alum per liter of water utilized. To find the amount of alum required, we perform the following calculations: 1. **Convert mgd to gallons per day**: The flow rate of 4.3 mgd is already in gallons, so we have: \[ 4.3 \text{ mgd} = 4.3 \times 1,000,000 \text{ gallons} = 4,300,000 \text{ gallons per day} \] 2. **Convert gallons to liters**: Since 1 gallon is approximately 3.78541 liters, we can convert the volume: \[ 4,300,000 \text{ gallons} \times 3.78541 \text{ liters/gallon} =