Operational issues arising from scaling and fouling of membranes are addressed by pre-treatment processes and alternative membrane or membrane secondary structures. In the present work the flow patterns associated with fluids within the membrane module are investigated using Computational Fluid Dynamics (CFD) tools. The effects on flow patterns through a spacer filled Reverse Osmosis (RO) membrane with the secondary structure of the membranes (feed spacer filaments) at various angles with the inlet flow are analyzed. The presence of the feed spacers in membrane module appears to generate secondary flow patterns enhancing the prospects for self induced backwashing increasing the allowable operational time and membrane efficiency. The flow visualization in the present study is useful in understanding the complex flow patterns generated in spacer filled RO membrane modules and could possibly lead to developing a new RO membrane which is more efficient, economical and appears to be a practically viable solution to reduce costs associated with the maintenance of RO membranes. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.