Basic Desalination of Saltwater

For centuries, man has heated water until it evaporates, then recollected it free of impurities. This process, called distillation, is the basic form of desalination. Desalination converts seawater into water that for safe safe use.

History

• Desalination dates back to ancient times, and distillation is still the prime treatment process today. The first paper on the topic was published in the eighth century by an Arab chemist. Distillation historically has been used on ships to convert saltwater to freshwater.

Types

• Water desalinates by going through the hydrologic cycle -- evaporation, condensation and precipitation. Heating and cooling drive the cycle, either in nature or through man-made means. The three main forms of distillation powered by latent heat are multi-stage flash distillation (MSF), multiple-effect distillation (MED) and vapor compression distillation (VC). In MSF, flashes of water meet vapor multiple times. Tubes heat the water in the MED process, and compressed vapor added to water stimulates evaporation during the VC process.

Significance

• Today, desalination plants perform the same process used naturally centuries ago. Although the simplest method of desalination, distillation still is considered the most effective in desalinating water. It costs $800 to $1,400 on average to desalinate one acre-foot of saltwater, according to American Chemical Society.