Desalination… In Brief

How it Works:

Distillation -- the traditional technology. Water is heated to produce steam. The steam is condensed into water that has very little salt.

Reverse Osmosis -- the modern approach. Water under pressure is forced through semi-permeable membranes. Water molecules pass through the membranes; salt does not.

Where the Water Comes From:

Seawater is the primary source of water to be used for desalination. But even in areas far from the coast, such as the Midwest, there are large supplies of underground water, called brackish groundwater, which readily and effectively can be treated through desalination.

The Extent of Desalination Today:

Today, 11,000 facilities operate in 120 countries around the world, with a global capacity of 4 billion gallons daily. Most of the capacity is located in the Middle East. Among the 1,200 plants in the U.S., a new plant in Tampa processes 25 million gallons per day. There are five projects in Southern California in early stages of development; others are under review in Texas and Florida.

How Desalinated Water Tastes:

Blind taste tests indicate that taste is not an issue. Desalinated water tastes like … water.

What it Costs:

Advancements in reverse osmosis technology have brought desalination costs closer to the alternatives (importation, dams, wells). In 1992, the cost to desalinate an acre-foot* of water was about $2,000. Today, that cost is less than $800 per acre-foot, while the cost of importing water has risen to about $500. Experts anticipate that at some point these costs will intersect.

Environmental Impact:

Some believe we should focus water-related policies on improving conservation methods. Others question the effects of returning the by-product of desalination - "brine" - on marine life. State, municipal and federal agencies are working together to manage the potential impact.

* Acre-foot. The term used to measure large volumes of water. An acre-foot of water is the amount of water it takes to cover an acre to a depth of one foot. One acre-foot equals 325,851 gallons.


"In the thirsty, growing cities...simple conservation simply won't do the trick."

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The New Water Supply Coalition. 1750 H Street, NW, Suite 600, Washington DC 20006. Ph: 202.737.0700 Fax: 202.737.0455