The use of covalently attached organo-selenium to inhibit S. aureus and E. coli biofilms on RO membranes and feed spacers

A surface treatment of organo-selenium compounds covalently attached to reverse osmosis membranes and feed spacers was analyzed for biofouling inhibition. The organo-selenium compounds were tested for their ability to inhibit biomass formation and reduce biofilm thickness at the membrane surface. The surface treated 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 consisted of a synthetic wastewater media, selected as a high nutrient source to model a primary wastewater. The bacterial strains used were chosen to represent Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) types. Inhibition levels of total biomass concentration averaged 2.2 and 3.7 logs, and reduction of biofilm thickness averaged 2.8 and 3.8 logs for each respective strain; and when the feed spacer also received the surface treatment total biomass inhibition reached between 5.7 and 5.9 logs, and biofilm thickness was reduced between 6.8 and 7.1 logs. Prior to receiving the surface treatment, RO membranes averaged a flux loss of 55% due to biofouling; however, when receiving the surface treatment, the flux loss was reduced to 15%, and when the combination of membrane and spacer was coated, biofouling averaged 8%.