Effect of high axial velocity on performance of cellulose acetate hyperfiltration membranes

Abstract

The effect of axial velocity on performance characteristics of a commercial cellulose acetate membrane was determined in a parallel plate test channel over a 270-fold velocity range, from 0.09 to 24 ft/sec and an applied pressure range of 200 to 1200 psig. Feed was demineralized water or untreated river water spiked with MgCl 2 to give solution concentrations of 0.04 to 0.08 M. At 800 psig system pressure and 24 ft/sec circulation velocity, intrinsic rejection was ∼ 97% and permeability was 0.6 gal/day · ft 2· atm with demineralized water feed spiked with MgCl 2. Substantially no flux decline was observed with demineralized water feed in a 93-hour run at 24 ft/sec. Even with untreated river water feed containing 10–100 ppm suspended solids, flux decline was relatively modest (a slope of -0.03 on a plot of log flux vs. log time) at a circulation velocity of 24 ft/sec. Reduction of circulation velocity to 1.64 ft/sec resulted in a marked decline in flux with time.