Bench-scale testing of surfactant-modified reverse osmosis/nanofiltration membranes

An homologous series of polyethylene-oxide surfactants, with either octylphenol or polypropylene oxide 'head' groups, were applied to commercial cellulose acetate blend (CA) and polyamide (PA) reverse osmosis (RO) and nanofiltration (NF) membranes. The pressure-normalized permeate flow (NPF) and salt rejection were evaluated before and after fouling with a vegetable protein broth. Surface changes were characterized using atomic force microscopy and electro-kinetic analysis. The transport results from both the swatch and element testing were used in a simple economic model to assess operating costs. Results indicate that cost savings are possible based on the changes in NPF and salt rejection.