Reverse osmosis hybrid membrane inter-stage design: A comparative performance assessment

A Hybrid membrane Inter-stage Design (HID) combines membranes of different nominal flux and salt rejection - i.e. different models -, in the same pressure vessel of seawater reverse osmosis racks. The HID experiences reported in the literature show there are no quantitative analysis published and very few seawater reverse osmosis plants have used it to date. The main objective of this paper is to present the results of a thorough computer assessment of this innovative design for conventional seawater reverse osmosis installations. Two types of analysis have been conducted for all representative models of membranes. Firstly, membrane replacement with a view to reduce the energy consumption due to lower working pressures while the plant capacity remains unchanged. Secondly, to increase plant capacity by reducing the specific energy consumption while maintaining the power consumption of the plant. A general HID design criterion has been defined for the three main membrane manufacturers - i.e. Filmtec, Hydranautics and Toray. Moreover, the quantitative results are useful for retrofitting plants thanks to membrane replacement. (C) 2011 Elsevier B.V. All rights reserved.