Opportunities to reach economic sustainability in forward osmosis–reverse osmosis hybrids for seawater desalination Gaetan Blandin a,b , Arne R.D. Verliefde b , Chuyang Y. Tang c , Pierre Le-Clech a, ⁎ a UNESCO Centre for Membrane Science and Technology, School of Chemical Engineering, The University of New South Wales, Australia b Ghent University, Faculty of Bioscience Engineering, Department of Applied Analytical and Physical Chemistry, Particle and Interfacial Technology Group (PaInT), Coupure Links 653, B-9000 Ghent, Belgium c Department of Civil Engineering, The University of Hong Kong, Hong Kong, China HIGHLIGHTS • A flux threshold of 30 L·m -2 ·h -1 was defined for FO economic viability. • Current membrane developments do not match the fixed minimum flux threshold. • Membranes with higher A (N 5 L·m - 2 ·h - 1 ·bar - 1 ) and lower S (b 100 μm) are required. • Pressure assisted osmosis could be an economically favourable alternative to FO. GRAPHICAL ABSTRACT abstract article info Article history: Received 3 October 2014 Received in revised form 10 December 2014 Accepted 10 December 2014 Available online xxxx Keywords: Forward osmosis Economics Permeation flux Pressure assisted osmosis Hydraulic pressure Despite being energetically attractive, the economic sustainability of forward osmosis (FO) - reverse osmosis (RO) hybrid process for seawater desalination has not yet been fully demonstrated. This study is the first to carry out an extensive economic evaluation of FO-RO hybrid, benchmarked against stand-alone RO system. This assessment clearly highlights that FO-RO hybrid can be beneficial, comparatively to RO, only for high energy costs and/or substantial operational costs savings. It is also demonstrated that improvement in water permeation flux, typically above 30 L·m -2 ·h -1 for classical water recoveries, is an absolute prerequisite to lower investment costs down to an economically acceptable level. Such fluxes are not achieved with current membrane developments when realistic feed and draw solutions are considered. In a second step, a sensitivity analysis was carried out to as- sess the effects of process parameters on flux in FO, compared to the above-mentioned benchmark. Results indicate that for novel FO membranes, typically a coupling of higher water permeability (A N 5 L·m -2 ·h -1 ·bar -1 ) and lower structural parameter (S b 100 μm) is required. This study also shows that the concept of pressure assisted osmosis (PAO) can help to reach higher fluxes with current commercial membranes, thereby demonstrating more favourable economics compared to state-of-the-art FO membranes. © 2014 Published by Elsevier B.V. Desalination xxx (2014) xxx–xxx ⁎ Corresponding author at: UNESCO Centre for Membrane Science & Technology, School of Chemical Engineering, Building F10, The University of New South Wales, Sydney, NSW 2052, Australia. E-mail address: p.le-clech@unsw.edu.au (P. Le-Clech). DES-12379; No of Pages 11 http://dx.doi.org/10.1016/j.desal.2014.12.011 0011-9164/© 2014 Published by Elsevier B.V. Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal Please cite this article as: G. Blandin, et al., Opportunities to reach economic sustainability in forward osmosis–reverse osmosis hybrids for sea- water desalination, Desalination (2014), http://dx.doi.org/10.1016/j.desal.2014.12.011