In this paper, field performance of a small-scale seawater reverse osmosis unit installed in Urla Bay-lzmir, Turkey was analyzed and presented. The design of SWRO system in Urla consists of two types of FilmTec polyamide thin film composite spiral wound seawater reverse osmosis membranes (high rejection FILMTEC XUS SW30XHR-2540 RO membrane and FILMTEC SW30-2540 RO membrane) which could be operated in parallel. To make a comparative study between two types of membranes regarding their desalination performances and boron rejections, each membrane was operated individually for each set of experiments. This comparison was made via investigation of the effects of feed seawater temperature (10-16 degrees C), operating pressure (55, 60 and 62 bar), and pH adjustment on the feed side (pH 7.0-7.5). (C) 2010 Elsevier B.V. All rights reserved.