The present invention relates to the use of a hydrophilic membrane to provide by the process of pervaporation through the membrane water suitable for agricultural irrigation, industrial use, hydrating or rehydrating of food or agricultural or pharmaceutical compositions. The present invention also relates to a water purification apparatus which includes the hydrophilic membrane, comprising one or more layers of hydrophilic polymers, to purify water which may contain suspended or dissolved impurities and solids, including but not limited to seawater, brackish water and other kinds of polluted water.