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The rise of reverse osmosis means less stainless on tap

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The global desalination market is expected to keep companies supplying those systems extremely busy not just in the near term, but for the next 20, 30 or even 50 years as fresh water scarcity worsens while technological solutions to address the problem become better and more affordable.

Cedella Beazley, global marketing manager of Filmtec reverse osmosis membranes for Dow Water Solutions, Minneapolis, said there are currently 75 major desalination plants in various stages of development worldwide, including facilities for the treatment of not just saltwater but also brackish water and in some cases wastewater.

She estimated that desalination plant capacity, especially facilities using reverse osmosis technology, will continue to be quite strong, possibly exhibiting low double-digit percentage growth year on year, although the annual growth rate will bounce around a bit based on what big plants are installing one year vs. the next.

It also varies by the kind of water being treated, according to Randolph L. Truby, chief executive officer of Toray Membrane USA Inc., San Diego, who placed the annual growth of seawater desalination at as much as 20 percent while brackish water desalination grows at a "calmer" 3 to 5 percent a year and wastewater treatment at about 10 to 12 percent.

And these growth rates are likely to continue. "You hear about new projects all the time under development. We are seeing it especially in the Middle East, China, India, Australia and Singapore," Truby said. "It is truly global."

Beazley agrees, noting that one push has been coming from countries that are becoming more industrialized, such as China and India. But there also is increased demand from other countries that are already industrialized, such as Spain and Australia, which are experiencing droughts that have significantly reduced water availability.

Growing populations and rising demand are stretching water supplies worldwide, according to GE Water Process Technologies, Minnetonka, Minn. "Today, about one-third of the world's population lives in countries with moderate to high water stress," the company said. "If the present consumption patterns continue, two of every three people on Earth will live in water-stressed conditions by 2025."

The problem is that all the easy-to-reach water sources are drying up at the same time that the world's population is booming, said Chuck Martz, Dow Water Solutions' global marketing director. "Only about 3 percent of the world's fresh water is accessible. About 2 percent is tied up in the polar ice caps, so only about 1 percent of fresh water is truly accessible," he said.

While many other areas of the world are even more water stressed than the United States, some parts of the country are starting to suffer from water scarcity as well. Jorge Arroyo, engineer for water science and conservation at the Texas Water Development Board, said that in the next 50 years Texas' existing fresh water supply is expected to decline about 17 percent at the same time that the state's population is expected to double.

Texas already has about 80 million gallons per day of brackish water desalination capacity, Arroyo said, and a number of new facilities—both seawater and brackish water plants—will be built in the state in the next 50 years, including several smaller ones in the next 10 years.

While most desalination plants were traditionally based on thermal desalination, or distillation, in the past 10 years or so demand for reverse osmosis systems has been growing and is beginning to overtake thermal, Beazley said, largely because both the capital costs and operating costs of reverse osmosis have come down considerably. Reverse osmosis uses a lot less energy than thermal desalination, she said, and the fact that it uses less metal also provides a savings, especially given recent rising commodity prices.

"The reverse-osmosis module is almost all polymer-based and its pressure vessels are fiberglass," Martz said. "It is primarily the racks, the pumps and the pipe that are metal. Any parts that come into contact with the water are stainless steel. Others are not necessarily stainless."

Reverse-osmosis plants, however, do use pipes to transport the water, Truby said, adding that pipe, especially in seawater systems, needs to be made from high-grade stainless steels, as do certain valves and fittings.

By comparison, pretty much the whole thermal desalination unit is stainless steel or other corrosion-resistant alloys, Martz said.

"People are feeling the volatility of the price of stainless," Truby acknowledged. "It is something that contractors need to be aware of when bidding on projects. As the price goes up, so does the price of the plant."

That has not had much of a dampening effect, however. "If you need water, you have to build a desalination plant no matter what the commodity costs," Arroyo said.


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