Reverse osmosis (RO) membrane processes are the workhorse of the desalination industry.  The largest RO plants in the world found in the Middle East have capacities on the order of 62 million m3 per year or about 50 million gallons of fresh water per day.  RO plants can purify seawater or brackish water, however the equipment configuration, membranes, and pressured used vary depending on the source and quality of the saline water.  The process units in RO are typically spiral wound polyamide-based membranes that operate at approximately 200 to 400 psi.  The high pressures are needed to overcome the osmotic pressure of the saline water and produce a reasonable flux of clean product water (see picture at right).  In addition to the high pressures which requires a lot of energy, fouling of the membranes and their decomposition by chlorine are current problems of polyamide membranes.

Sandia’s research in reverse osmosis membranes entails the design, synthesis, and testing of new polymer and polymer composite membranes that could be applied to RO processes.  We seek to increase the flux of pure product water while decreasing the required pressure.  The materials we investigate are more stable to chlorine treatments and in some cases may be foul resistant.  Our experimental work on new materials is supported by modeling studies in order to better understand how to create membranes with high flux and high salt rejection. 

Banks of reverse osmosis modules

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