AWWA MTC64605

This project tests the capability of a two-stage reverse osmosis (RO)/electrodialysis (ED) process to achieve high recovery (95 percent) for membrane desalination of Colorado River water. In order to overcome the high-energy consumption of ED membranes at elevated salinity levels, Lawrence Livermore National Laboratory has recently developed low-resistivity nanoporous ED membranes. The nanoporous ED membranes have pore sizes ranging from 6 to 16 nm, resulting in ion "double-layer overlap" inside the ED pores. The double-layer overlap allows for preferential rejection of targeted solutes by modifying the ED membrane pore size for a given ionic strength. This paper discusses how nanoporous ED membranes can be used to recover concentrate that is supersaturated with respect to various salts from a primary RO unit. Includes 5 references, figures.