Saline Brine Separation:\nThermodynamic and Techno-Economic\nComparison of Counterflow Reverse Osmosis with Electrodialysis

Separation into a more concentrated and a diluted stream\nis an\nenergy-efficient alternative to thermal distillation for saline brine\nmanagement. Here, we compare counterflow reverse osmosis (CFRO) with\nelectrodialysis (ED) for brine separation in terms of energy consumption\nand overall treatment cost. Conditions for energy-optimal thermodynamically\nequipartitioned operation are derived for both technologies. The brine-reflux\nCFRO configuration requires more energy/module area than does the\nsplit-feed design but can be operated at practical pressure levels\nfor high-salinity applications. After identification of the cost-optimal\nvoltage in ED and pressure in CFRO, realistic single-stage systems,\nincluding losses, are compared. CFRO consumes significantly lower\nenergy and is less expensive than ED for intermediate-salinity brine\nseparation, such as textile dyeing effluent recycling. Therefore,\nthis is an ideal beachhead application for CFRO compared to seawater\nbrine concentration up to near saturation, where its cost is comparable\nto that of ED.