What is the backwash rate of a rapid sand filter measuring 10 feet by 10 feet with a flow rate of 12 gpm/sq ft?

To calculate the backwash rate of a rapid sand filter, you need to consider the area of the filter and the flow rate. In this case, the filter has dimensions of 10 feet by 10 feet, creating a total surface area of 100 square feet (10 ft x 10 ft = 100 sq ft).

The flow rate provided is 12 gallons per minute per square foot. To find the total backwash flow rate, you multiply the surface area by the flow rate per square foot:

Total Backwash Rate = Surface Area x Flow Rate per Square Foot Total Backwash Rate = 100 sq ft x 12 gpm/sq ft = 1,200 gpm

This calculation gives us the correct backwash rate of 1,200 gallons per minute, making it the right answer. Understanding how to apply the flow rate to the surface area is crucial in calculating backwash rates for filters in water treatment processes.