Performance study of an industrial RO plant for seawater desalination João Abel G.C.R. Pais, Licínio Manuel G.A. Ferreira* Department of Chemical Engineering, University of Coimbra, Pólo II, Pinhal de Marrocos, 3030–290 Coimbra, Portugal Tel. +351 (239) 798745; Fax: +351 (239) 798703; email: lferreira@eq.uc.pt Received 7 February 2006; Accepted 7 June 2006 Abstract In this work, an approach to study the long-term performance of an industrial water desalination plant is described. Operational data corresponding to the time period of 454 days were analysed and from the results obtained it was found that the normalized water permeability coefficient declined by about 7%. Due mainly to the temperature effects, the salt permeability coefficient exhibit significant changes only during the summer period. The equations used allowed a good description of the performance of the plant. Keywords: Reverse osmosis; Desalination; Permeability coefficient; Performance 1. Introduction Reverse osmosis (RO) is a separation process for water desalination which has some advantages in terms of saving energy, modularity, flexibility, ability to construct small size plants or even less installation space when compared to other tradi- tional techniques, which include namely thermal processes, such as the multi-stage flash (MSF) distillation [1,2]. In the RO process, a semi- permeable membrane is used for separation of *Corresponding author. particles sizes of 5×10 !3 –1×10 !4 µm, including single charge ions as such Na + and Cl ! [3]. The separation is driven under high pressures, not more than 7.0 MPa for most of commercially available RO membranes [1] in which the fluxes of water and salt through the membrane are considered viable economically, at industrial scale, if the operation is carried out at pressures 50 to 100% higher than the transmembrane osmotic pressure. In the desalination, variables such as the per- meate (purified water) quantity and quality Desalination 208 (2007) 269–276 0011-9164/07/$– See front matter © 2007 Published by Elsevier B.V. doi:10.1016/j.desal.2006.06.017