INFLUENCE OF GEL LAYER RHEOLOGY ON ULTRAFILTRATION FLUX OF WHEAT-STARCH EFFLUENT

Ultrafiltration flux rates of wheat starch effluent in a tubular membrane system revealed unusual values of the exponents in the mass transfer model (Sh equals a Re**n Sc**m). For turbulent flow the values of the exponent n ranged from 0. 2 to 0. 9 and m from 0. 0 to 0. 35 depending on the relative amounts of protein, pentosans and suspended solids in the wheat starch effluent. Samples of the gel layer exhibited rheological behaviour ranging from pseudoplastic to Newtonian depending on the suspended solids content of the effluent. The thickness of the gel layer was evaluated for the different patterns of gel layer rheology and applied in a pressure-driven filtration model.