The treatment of metal working (MW) fluids using the high-shear rotary ultrafiltration (HSRUF) system has been reported by Viadero and Reed (1999) and Reed et al. (1997b). In the HSRUF system, membrane rotation induces hydraulic turbulence which minimizes the deleterious effects of concentration polarization as well as decreasing the potential for membrane fouling as feed solutions are concentrated. Under opeating conditions of low hydraulic turbulence and high feed concentration, permeate flux can become pressure independent. The pressure independent 'limiting' flux, J~*, has been described using the thin film model which predicts J~* will decrease semi-logarithmically with increasing feed concentration, however, Pritchard et al. (1995) has reported a two phase flux in a conventional UF module in which the rate of change in J~* with feed concentration decreased at high concentrations. The HSRUF system was effective at treating synthetic MW fluids at feed concentrations of 40
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