Effect of hydrocarbon contaminants on the performance of RO membranes

This paper is related to potential problems associated with the desalination performance of reverse osmosis (RO) units in conditions when the feed may be contaminated with crude oil and fuel oil spillages. The work has involved the examination of the behaviour of polyamide seawater membranes and brackish water membranes with feedwater comprising NaCl/water solutions of 2000-35000 mg/l concentration. The effect of a range of contaminants on RO membrane performance was assessed by comparing the water flux and salt rejection of membrane samples before and after their exposure to the oil-based media which comprised crude oil, crude oil/water mixtures, diesel and diesel/water mixtures. Also included in the study were hexane and hexane/water mixtures. The results demonstrated serious degradation of desalination performance after exposure to some, but not all, of the contaminating fluids. The "pure" hydrocarbons, and also when they are in emulsion form with water, cause extremely severe reductions of RO membrane performance as opposed to the situation when they are in solution in the aqueous phase.