nd b) power processes, e. g., reverse osmosis (RO), electrodialysis (ED), and freezing, whose main energy input is work (fluid pressure, really).
Distillation is a heating to form water vapor (leaving salt behind), followed by recondensation of the vapor to liquid water. Electrodialysis and RO are electrochemical and hydraulic pressure methods for driving water molecules through a membrane--again, leaving the salt molecules behind. Freezing is a process of crystallizing water (alone) and then isolating the pure-water crystals (from the salt molecules), with subsequent remelting of the water crystals.
Silver (6-14) has computed the energy for, and "performance ratios" of, each process-type as shown in the following table:
Relative Energy Requirements of Desalination Processes
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Desalting Energy Required: Output/Energy:
Process Heat Energy per H2O Output lb/1000 BTU
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