Making seawater fit to drink

Cynthia Lopez of Mexico City had a question about seawater and drinking water.

Cynthia Lopez: As public water supplies become more scarce, what is the newest science for making saltwater more available?

EarthSky spoke to Tom Pankratz, independent consultant and a director of the International Desalination Association. Desalination is the process that makes saltwater fit to drink.

Tom Pankratz: As our traditional sources of water become less available, it’s necessary to turn to an alternative supply. And the only drought-proof supply, or the unlimited supply, is the sea. The problem is that removing the salt is a very expensive process.

In the past, desalination relied on boiling the water. But today’s newer techniques use a semi-permeable membrane.

Tom Pankratz: It’s a very thin plastic that allows only water molecules to pass through when it’s pumped to sufficient pressures. As the water passes through the membrane, the salt particles are left behind and then returned to the sea. The membrane is already effective, but the task now is to have the entire system operate at lower pressures and lower energy costs.

Pankratz said this technique is being used now mostly in the Middle East and Caribbean, as well as in the U.S. But Cynthia – in your hometown of Mexico City – this same technology could also be used to remove pollutants from city water supplies.

Our thanks to the Monsanto Fund, bridging the gap between people and their resources.

Our thanks to:
Tom Pankratz
International Desalination Association
Houston, TX