Water desalination doesn’t produce salt?

by David Safier

In an attempt to cure some of my ignorance, I did a google search on water desalination (desalinization, desalinisation) and found an Economist article from June, 2008. It has lots of excellent technical information.

The most important fact in terms of answering my question — Why isn't desalination coupled with the production of sea salt? — is that most processes only extract a certain amount of fresh water and spit out the rest of the liquid with a higher concentration of salts. I guess that's the most efficient way to do it.

Having at least partially answered that question, let me give you a few other bits of information, if you're interested:

As more parts of the world face prolonged droughts or water shortages, desalination is on the rise. In California alone some 20 seawater-desalination plants have been proposed, including a $300m facility near San Diego. Several Australian cities are planning or constructing huge desalination plants, with the biggest, near Melbourne, expected to cost about $2.9 billion. Even London is building one. According to projections from Global Water Intelligence, a market-research firm, worldwide desalination capacity will nearly double between now and 2015.

Not everyone is happy about this. Some environmental groups are concerned about the energy the plants will use, and the greenhouse gases they will spew out. A large desalination plant can suck up enough electricity in one year to power more than 30,000 homes.

The good news is that advances in technology and manufacturing have reduced the cost and energy requirements of desalination. And many new plants are being held to strict environmental standards. One recently built plant in Perth, Australia, runs on renewable energy from a nearby wind farm. In addition, its modern seawater-intake and waste-discharge systems minimise the impact on local marine life. Jason Antenucci, deputy director of the Centre for Water Research at the University of Western Australia in Perth, says the facility has “set a benchmark for other plants in Australia.”

[snip]

The energy-recovery devices in the 1980s were only about 75% efficient, but newer ones can recover about 96% of the energy from the waste stream. As a result, the energy use for reverse-osmosis seawater desalination has fallen. The Perth plant, which uses technology from Energy Recovery, a firm based in California, consumes only 3.7kWh to produce one cubic metre of drinking water, according to Gary Crisp, who helped to oversee the plant’s design for the Water Corporation, a local utility.

So, I guess if you can find a particularly windy stretch of ocean, put up some wind turbines and a desalination plant, you're good to go.

That's it. We will now return to our regularly scheduled blogging.

NOTE: Right after I put up this post, I found a comment from Ben Kalafut that basically explained to me what I found out myself. Ben concludes, "if someone was to be looking for startup capital for opening up a cogenerating nuclear power/desalination plant in the Tijuana area that would sell water and electricity to the Californians, I'd put in a thousand dollars!"

Ben,Sen. Al Melvin is your man. He advocates putting a nuclear power/desalination combo in Sonora somewhere. Write that check and get in on the ground floor!

0 responses to “Water desalination doesn’t produce salt?

  1. bigbearchaseme

    So Thane, because Senator Melvin advocates a desalination plant in Sonora, that means the US government, or the state of Arizona government would be the builders, and operators of said plant? I think the government of Mexico would object, don’t you? Most likely this would be a private initiative, and not government(well not US, maybe Mexico).

  2. I imagine Ben Kalafut should have been more specific in his offer. I imagine he really meant: If a businessman (or businesswoman) “was to be looking for startup capital…” not government legislators.

    As for Mr. Melvin’s position on nuclear energy it appears to be based on the following article (perhaps with a few changes to include desalination):

    http://www.hillsdale.edu/news/imprimis/archive/issue.asp?year=2008&month=02