(8) Rapid Filtration with Backwashing a. A filter has the following dimensions: Length =48 inches, Width =28 inches, and Depth of filter media =18 inches. Assuming a backwash rate of 11 gallons per square foot per minute (gal2/ft2/min) is recommended, and an 8 -minute backwash is required, calculate the amount of water, in gallons, required for each backwash. b. A filter that is 1.2m by 2m has a backwash rate of 2m3/min. What is the backwash rate, in m3/min/m2 ? c. For a backwash flow rate of 2.5m3/min and a total backwash time of 10min, how many m3 of water will be required for backwashing? d. A filter is 10ft long and 5ft wide. If the desired backwash rate is 40gal/min/ft2, what backwash pumping rate will be required, in gal/min ? e. During a filter run, 20MG water were filtered. If 80,000 gallons of this water were used for backwashing, what percent of the product water was used for backwashing