In this study, a mini pilot scale reverse osmosis (RO) system containing two spiral wound FilmTech BW30-2540 membranes was installed at a geothermal area in Izmir, Turkey. The desalination and boron removal performances of this system were investigated. The effect of such parameters as operating pressure and the number of membranes employed during the operation on desalination performance of the system was investigated. The system performance was evaluated at 12 and 15 bar of operating pressures as a function of the number of membranes used. Desalination performance of brackish water reverse osmosis (BWRO) system was determined by the quality and quantity analyses of the product water. When the operating pressure was increased, a high permeate recovery, permeate flux and salt rejection were obtained with both single and double membrane configurations. The maximum boron rejection was 47% at 12 bar of applied pressure while it increased to 49% at 15 bar of applied pressure using a single membrane mode of operation. The lowest average boron concentration in the product water was 4.7 mg/L at 15 bar of applied pressure for a single membrane configuration. (C) 2012 Elsevier B.V. All rights reserved.