A purification system can provide for efficient heating of liquid via film heating, which, rather than heating a large volume of liquid, can heat a thin layer of liquid thus reducing the amount of energy required to evaporate the liquid. Film heating can enable evaporation of liquids using less energy than other methods. In addition, when liquids (e.g., seawater) having dissolved solids (e.g., salts) are heated, both the liquid and the solids must be heated. As evaporation occurs, the concentration of solids increases and more energy must be supplied to the liquid in order to cause evaporation. Because purification system can heat only a layer of liquid, less energy is required to heat the solids, which can allow for higher energy efficiencies in purifying liquids. These efficiencies can lead to decreased cost of potable water. Related apparatus, systems, techniques, and articles are also described.