It is desired to increase the protein concentration in whey by a factor of 10 by the use of membrane filtration to give an enriched fraction to produce a 50% protein whey powder. The whey initially contains 5% of total solids, 10% of these being protein. Pilot scale measurements on this whey show that a permeate flow of 40 kg m–2 h–1 can be expected, so that the plant is required to handle 40,000 kg in 8 h. Estimate the number of membrane sheets of 10 m2 area required.