Comparison of spiral wound UF membrane performance between turbulent and laminar flow regimes

A spiral wound ultrafiltration (UF) membrane module was used for clarification of synthetic fruit juice at two different operating conditions; namely, with and without permeate recycle for turbulent flow regime. Membrane performance at different transmembrane pressure (TMP) drops was studied in terms of volume reduction factor (VRF), transient flux decline and increments of total resistance for with and without permeate recycle. For turbulent flow regime, VRF values were slightly higher than in laminar case. Transient flux decline in laminar flow regime was higher compared to turbulent flow regime. For with and without permeate recycle, total membrane resistance was less in turbulent flow compared to laminar flow regime. With increase of turbulence, fouling layer on membrane surface was decreased, resulting in higher transient flux decline compared to laminar flow regime. Maximum membrane fouling was observed for without permeate recycle at low operating time. With increase of turbulence, pectin concentration was found to increase in permeate sample. On the basis of pectin particle in permeate, three diffusion models, such as, Brownian, shear induced and combined diffusion models were used to estimate the theoretical flux. At laminar flow regime, the Brownian diffusion model estimated flux data were best fitted with experimental flux data due to lower pectin particle size in permeate. In turbulent flow regime, due to clustering, pectin particle size was enhanced and shear induced diffusion model predicted permeate flux values were best fitted with experimental flux. Fouled UF membrane modules were cleaned with different cleaning agents, such as, deionised water, SDS and EDTA. Maximum cleaning efficiency was achieved with EDTA solution in terms of recovery of membrane permeability.