Influence of spacer thickness on permeate flux in spiral-wound seawater reverse osmosis systems Original Research Article

A primary reason for flux decline during the initial period of a membrane separation process is concentration polarization of the solute at the membrane surface. The objective of the present study was to analyze and model concentration polarization in spiral-wound seawater membrane elements. In particular, the influence of spacer thickness in the membrane units on permeate flow and its salinity was evaluated. Membrane parameters were also estimated using an analytical osmotic pressure model for high salinity applications. The effects of spacer thickness on permeate flux suggest that the observed flux decreases by up to 50% in going from a spacer thickness of 0.1168 to 0.0508 cm. The different geometry/configuration of the spacer may influence turbulence at the membrane surface that in turn affected concentration polarization. This suggests less turbulence with the smaller spacer thickness. The membrane module with an intermediate spacer thickness of 0.0711 cm was found to be the best economically since it gave the highest water production rate (L/h).