METHOD AND DEVICE FOR PREPARING FRESH WATER

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Provided are a method and device for obtaining fresh water from a liquid to be processed, e.g. seawater, using a forward osmosis membrane, wherein the solution obtained after separating the water from a diluted draw solution that was diluted by the inflow of water from the liquid to be processed can be stably regenerated an re-used as the draw solution. The method and device for preparing fresh water involve : an osmosis process in which a solution having water as a solvent and a draw solution obtained by dissolving a prescribed amount of a volatile substance in water are brought into contact across a semi-permeable membrane, and the water in the solution flows to the draw solution across the semi-permeable membrane; a distillation process in which the diluted draw solution diluted by the water in the osmosis process is set to a prescribed temperature and is supplied to a distillation column, and a gas comprising the volatile substance and water vapor is obtained from the top of the distillation column, while fresh water is obtained from the bottom of the distillation column; and a cooling/regeneration process in which the gas is cooled to regenerate the draw solution.