Water Desalination

Desalination Expands as Technology Becomes More Affordable

Desalination Plant
A New Zealand army officer tests water quality at an army mobile desalination and purification station supplying free water to residents in the suburb of New Brighton on February 26, 2011 in Christchurch, New Zealand. Cameron Spencer/Getty Images

Desalination (also spelled desalinization) is the process of creating fresh water by removing saline (salt) from bodies of salt water. There are varying degrees of salinity in water, which affects the difficulty and expense of treatment, and the level of saline is typically measured in parts per million (ppm). The U.S. Geological Survey provides an outline of what constitutes saline water: 1,000 ppm – 3,000 ppm is low salinity, 3,000 ppm – 10,000 ppm is moderate salinity, and 10,000 ppm – 35,000 ppm is high salinity.

Water that contains saline levels less than 1,000 ppm is generally considered fresh water, and is safe to drink and use for household and agricultural purposes. For a reference point, typical ocean water contains about 35,000 ppm, the Great Salt Lake contains variations of 50,000 – 270,000 ppm, and the Caspian Sea contains an average of about 12,000 ppm. The more concentrated saline is in a body of water, the more energy and effort it takes to desalinize it.

Desalination Processes

Reverse Osmosis

There are several setbacks of reverse osmosis. The membranes are currently prone to gather too much bacteria and “clog up,” although they have improved since they were first used. The membranes deteriorate when chlorine is used to treat the bacteria. Other setbacks are the arguable water quality that reverse osmosis produces, along with the considerable pre-treatment that the salt water requires.

Forward Osmosis

The main setback to forward osmosis is that it has great potential, but is still fairly new to large-scale desalination and therefore needs funding and research to explore the possibilities that could improve it and reduce energy costs.

Electrodialysis

Thermal Desalination

Multistage Flash Distillation

Multiple-Effect Distillation

Negatives of Desalination

Geography of Desalination

Saudi Arabia is currently the world’s number one producer of desalinated water. They use multi-flash distillation in several large plants, providing water for many large cities, including the largest city, Riyadh, situated hundreds of miles from the coast.

In the United States, the largest desalination plant is located in Tampa Bay, Florida, though it has a very small output compared to most facilities in the Middle East. Other states that are developing plans for large desalination plants include California and Texas. The United States need for desalination plants is not as severe as many other countries, but as the population continues to explode in dry, coastal areas, the need increases.

Future Options of Desalination

Desalination is process primarily done in developed countries with enough money and resources. If technology continues to produce new methods and better solutions to the issues that exist today, there would be a whole new water resource for more and more countries that are facing drought, competition for water, and overpopulation. Though there are concerns in the scientific world about replacing our current overuse of water with complete reliance on sea water, it would undoubtedly be at least an option for many people struggling to survive or maintain their standard of living.