Advances and Challenges in Membrane Desalination and Osmotic Power Generation

Membrane based water treatment and desalination technologies have been gaining momentum in potable water production from seawater and brackish groundwater, in municipal and industrial water reuse, as well as for management and reuse of agricultural drainage water. Considerable progress has been made since the early days of Reverse Osmosis (RO) and more recent development in Forward Osmosis (FO) with respect to water development of high performance fouling and chlorine resistant membranes, improvements of in feed pretreatment and reduction in RO energy consumption. Given the increased level of water scarcity in various regions of the world there has been growing efforts to expand the use of otherwise unutilized inland groundwater resources, lower the cost of seawater desalination and even produce energy from salinity gradients (i.e., pressure retarded osmosis (PRO). Here a fundamental description and evaluation of RO, FO and PRO will be provided with a focus on assessment of the merits of various process alternatives to common RO process configurations, the viability of PRO and challenges in FO. In particular, recent results from CFD analysis of FO and PRO and fundamental theoretical analysis of RO energy consumption (for different configurations) will be presented to clarify overoptimistic expectations and address the remaining major challenges.