A plant effluent of 3.5 million gallons per day (MGD) contains 200 mg/L BOD. How many pounds of BOD enter the plant per day?

To calculate the amount of BOD entering the plant per day, you need to use the following formula:

[ \text{Pounds of BOD} = \text{Flow (MGD)} \times \text{Concentration (mg/L)} \times \text{Conversion factor} ]

The flow of the plant effluent is 3.5 million gallons per day and the concentration of BOD is 200 mg/L. The conversion factor from mg/L to pounds per day is 8.34 (this accounts for the conversion of gallons to liters, and liters to milligrams).

Now, substituting the values into the formula:

1. Convert MGD to gallons:

Flow = 3.5 MGD = 3.5 million gallons = 3,500,000 gallons.

2. Convert mg/L concentration to pounds:

Pounds of BOD = 3,500,000 gallons/day × 200 mg/L × 8.34 lbs/mg.

Now, doing the multiplication:

[ 3,500,000 \text{ gallons} \times 200 \text{ mg/L} \times 8.34 \text{ lbs/mg} = 5,838,000