A filter with dimensions 20 ft × 30 ft and plant flow of 4 MGD evenly split between 4 filters has a loading rate of how many gpm/ft^2?

A filter with dimensions 20 ft × 30 ft and plant flow of 4 MGD evenly split between 4 filters has a loading rate of how many gpm/ft^2?

• A. 1.0 gpm/ft^2
• B. 2.3 gpm/ft^2
• C. 3.4 gpm/ft^2
• D. 4.6 gpm/ft^2

Answer: (B)

Loading rate is the flow per unit area of the filter. To find it, divide the plant flow among the filters, convert that flow to gallons per minute, and then divide by the filter’s surface area. The plant flow is 4 MGD and it’s evenly split among four filters, so each filter handles 1 MGD. Convert to gpm: 1 MGD = 1,000,000 gallons per day = 1,000,000 ÷ 1440 ≈ 694.4 gpm. The filter area is 20 ft × 30 ft = 600 ft². So the loading rate per filter is 694.4 ÷ 600 ≈ 1.16 gpm/ft². Rounded, that’s about 1.2 gpm/ft², closest to 1.0 gpm/ft² among typical choices. The result you get follows the basic principle: flow per unit area. If another answer like 2.3 gpm/ft² shows up, it would come from a different distribution of flow or a different filter count, not from these exact numbers.

Loading rate is the flow per unit area of the filter. To find it, divide the plant flow among the filters, convert that flow to gallons per minute, and then divide by the filter’s surface area.

The plant flow is 4 MGD and it’s evenly split among four filters, so each filter handles 1 MGD. Convert to gpm: 1 MGD = 1,000,000 gallons per day = 1,000,000 ÷ 1440 ≈ 694.4 gpm. The filter area is 20 ft × 30 ft = 600 ft². So the loading rate per filter is 694.4 ÷ 600 ≈ 1.16 gpm/ft².

Rounded, that’s about 1.2 gpm/ft², closest to 1.0 gpm/ft² among typical choices. The result you get follows the basic principle: flow per unit area. If another answer like 2.3 gpm/ft² shows up, it would come from a different distribution of flow or a different filter count, not from these exact numbers.