Recovery of stillage soluble solids from hard and soft wheat by reverse osmosis and ultrafiltration
1987
Wu, Y.V.
Ultrafiltration (UF) combined with reverse osmosis (RO) was used to separate wheat stillage solubles into small volumes of concentrated solutions and large volumes of permeates suitable for reuse. The UF permeate at 680 kPa (100 psi) accounted for 10-25% of total nitrogen and 20-36% of total solids of the stillage solubles. The UF permeate was used as the feed solution of RO. The RO permeate obtained at 1,360 kPa (200 psi) accounted for 4-4.8% of total nitrogen, 5.8-8.1% of total solids, and 77-90% of total volume of the UF permeate from wheat stillage solubles. Increasing RO pressure to 5,440 kPa (800 psi) reduced total nitrogen and solids of the permeate by about 40 times. The percentage of nitrogen and solids from stillage solubles that can be economically recovered by combined UF and RO at 1,360 kPa (assuming only the amount of nitrogen and solids in the RO permeate is discarded) is 98.7-99.2% and 97.5-97.8%, respectively, whereas the corresponding value for combined UF and RO at 5,440 kPa is 100.0%. Conductivity of the RO permeate at 5,440 kPa was lower than that of tap water. The cost-effective UF and RO methods developed for wheat stillage solubles may encourage increased food use of wheat distillers' grains while reducing the total cost of the wheat alcohol process.
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