A feed spacer polymerized with organo-selenium was analyzed for biofouling inhibition to reverse osmosis membranes and feed spacers. The spacers polymerized with organo-selenium were tested for their ability to inhibit biomass formation and reduce biofilm thickness on the surface of RO membranes that the spacers were in contact with. The spacers and RO membranes were tested in a flow-cell system that exposed the sample membranes to normal operating conditions for RO membranes over a period of 24 h. This system utilized a synthetic wastewater, selected as a high nutrient source to model a primary wastewater, and bacterial test strains were chosen to represent Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. Initial tests with spacers containing 0.55% organo-selenium in the spacer material showed inhibition levels of 2.0 logs for total biomass, and 2.7 logs for average biofilm thickness against S. aureus only. At a spacer concentration of 1% organo-selenium, inhibition levels of total specific biomass concentration averaged 2.9 logs for each bacterial strain, and averaged a reduction of biofilm thickness of 2.9 and 3.9 logs for S. aureus and E. coil. (C) 2013 Elsevier B.V. All rights reserved.