Fouling-Resistant Ultrafiltration Membranes for Treatment of Oily Bilge Water

There is a recognized need for more effective and economical treatment processes for oily bilge waters. Direct filtration through currently available ultrafiltration (UF) membranes is a mechanically simple process that can provide excellent effluent quality. A limitation to more extensive use of this technology is the tendency of the hydrophilic membranes currently used to foul in the presence of oils, with a resultant drop in permeation capacity. Compact Membrane Systems, Inc. (CMS) has developed proprietary, inherently nonfouling UF membranes. In tests with simulated naval graywater, a CMS membrane delivered two to three times the steady-state permeate flow of a conventional hydrophilic UF membrane at process conditions typical of commercial installations. With the CMS membrane, the operating time between cleaning was more than three times longer. The goal of this project is to demonstrate that similar increases in permeate flux and operating time between cleanings can be achieved in the treatment of oily bilge waters. The low free surface energy of the CMS UF membrane should minimize adsorption of both oily substances and those bilge water constituents that foul hydrophilic membranes. During Phase I, CMS will vary water quality conditions by varying oil percentage and those additives (e.g., surfactants) that enhance fouling. By broadly evaluating performance, the range of applicability of the concept should be demonstrated. Rigorous analysis of various contact angles (e.g., oil/air/solid, water/air/solid, and water/oil/solid) will be used to explain results. This is a resubmittal of a previous request strengthened by revisions recommended by peer reviews.