Removal of arsenic (V) from water using surfactant micelles and ultrafiltration membrane was investigated using simulated water and stirred cell ultrafiltration unit. The effects of membrane materials (regenerated cellulose and polyethersulfone), membrane nominal molecular weight cut-off (NMWCO, 5 and 10 kDa), feed water arsenic concentration (from 0 to 221 mug/L), and feed water pH (5.5 and 8) on the efficiency of arsenic (V) removal and the permeate flux were studied with and without the surfactant addition. Polyethersulfone (PES) membranes without the surfactant micelles were found to be ineffective for arsenic removal. Regenerated cellulose (RC) membranes provide better removal than PES membranes due to its negatively charged surface at the experimental conditions. However, the arsenic concentration in permeate water (product water) is not reduced to the new maximum contaminant level (MCL) of 10 mug/L. With the addition of 10 mM cationic surfactant cetylpyridinium chloride (CPC) to the feed water, both PES and RC membranes reduce the arsenic concentration in permeate water well below the MCL. The arsenic removal efficiency and absolute permeate flux were found to depend on the membrane materials, membrane NMWCO, and water pH. Highest arsenic removal, 100%, is achieved for the feed water arsenic concentrations of 22 and 43 mug/L using 5 kDa PES membranes at pH of 5.5 and 10 kDa RC at pH of 8. Regardless of the feed water arsenic concentration, 100% arsenic removal is obtained with 5 kDa PES membranes at pH of 8. (C) 2004 Elsevier B.V. All rights reserved.