It is known as desalination. The simplest method is thermal:boil the saline water, capture the steam and condense it back intowater, leaving the salt behind. Another method is electrical: passan electric current through the saline water. The current drivesions across a selectively permeable membrane, carrying thedissociated salt ions with it. Another method is reverse osmosisusing pressure: Pressure is used to drive water through a membrane,leaving the salt behind.