Fresh water is becoming a valuable commodity. The amount of fresh water worldwide is declining at the same time that the population is exploding—on track to reach 9.39 billion by 2050 from 6.68 billion currently, according to U.S. Census Bureau estimates.
One way to ensure that there is enough potable water to accommodate population growth, as well as to meet industrial and agricultural demand for clean water, is through water reuse and desalination technologies.
"There is the same amount of water on this planet as there was at the beginning of time. All water is reused, but through technology we can speed up Mother Nature's process," said Zachary Dorsey, a spokesman for the Alexandria, Va.-based WateReuse Association.
Houston-based water consultant Tom Pankratz, whose clients includes the International Desalination Association (IDA) and Global Water Intelligence, said that demand for such technologies has been growing steadily at about 8 to 10 percent a year globally, "really spiking" in the past few years.
The installed capacity of desalination plants, which are used not just to purify saltwater but also brackish water and wastewater, totaled around 46 million cubic meters (12.15 billion gallons) a day last year, up 8 percent from 42.6 million cubic meters (11.25 billion gallons) in 2006 and 15.3 percent ahead of 39.9 million cubic meters (10.54 billion gallons) in 2005, Pankratz said. That is expected to increase 12 percent to 51.5 million cubic meters (13.6 billion gallons) a day this year and another 13 percent to 58.1 million cubic meters (15.35 billion gallons) in 2009. By 2015, that figure is expected to reach 97.5 million cubic meters (25.76 billion gallons) a day.
The increase is being driven by the fact that traditional sources of water—rivers and even aquifers—are drying up or being used up, Pankratz said. In addition, there is an increasing amount of pollutants in both river water and groundwater from pharmaceuticals and personal care products—everything from caffeine, steroids, aspirin and estrogen to a whole gamut of chemicals. "Desalination has become a solution for that," he said.
And the cost of desalination has come down considerably through technological improvements, including more-efficient energy-recovery techniques. Pankratz said that the typical operating cost is now between $2.25 and $3.75 per thousand gallons of water, less than half the cost in the mid-1990s.
Even with rising commodity prices (desalination plants contain either high-end stainless, titanium, copper-based or polyvinyl chloride piping or tubing), the cost of building desalination plants has come down significantly, according to Renee Chu, program manager of environmental technologies at international consultant Frost & Sullivan, which she attributes to offshore manufacturing of facilities. "Many of the plants and their components are made in China," she said.
Currently there are about 12,500 desalination facilities of varying sizes in 120 different countries, about 60 percent of them in the Middle East, where desalination accounts for about 70 percent of water supplies, Dorsey said.
The expected growth of desalination varies widely, region by region, according to James D. Birkett, consultant and principal of West Neck Strategies, Nobleboro, Maine. He said that while much of the United States is dragging its feet, "international demand is growing like gangbusters, especially in the Middle East, Southeast Asia and some areas of Europe."
The strongest growth has been in Australia. Already the driest inhabited continent, Australia has been suffering from extreme drought conditions, Pankratz said. The first desalination facility was built there in 2007 and there are five other plants in varying stages of development. "It has very little to no alternatives to desalination," he said.
The reason that desalination hasn't taken off in a big way in the United States is that people aren't feeling the same sense of desperation as those elsewhere in the world, Birkett said. "We are blessed with a large amount of fresh water. In our case, demand isn't outstripping water supply, or at least it hadn't done so until recently. Also, the environmental requirements to build a facility here are very stringent. It took Tampa Bay (Fla.) about four years to get through a permit for a plant there."
That isn't to say there haven't been inroads made in the United States. Dorsey said that about eight states have been making major pushes in the water-reuse arena, the leaders of which are clearly Florida, Texas and California. "The southwest United States is dealing with an acute water shortage, so a number of municipalities are looking at multiple ways of dealing with this water shortage, including desalination," he said.
In Long Beach, Calif., a new desalination technology being looked at is an offshoot of the increasingly popular reverse-osmosis desalination process, Chu said. It is expected to be even more energy efficient than reverse osmosis, which is seen as the most energy efficient and cost effective of the two major desalination processes in use today.
With reverse osmosis, Pankratz said, the water is pumped through a semi-permeable membrane that is made of a plastic film that lets water, but no other materials, through. Piping is usually made from highly corrosion-resistant, high-performance austenitic stainless steels or super duplex stainless steels, given that the desalination environment used to transport the water is highly aggressive (about twice as corrosive as saltwater). Most new desalination facilities, other than those in the Middle East or the Caribbean, where energy is cheaper, use the reverse-osmosis technology, largely because it is much more energy efficient than the other major process, thermal desalination, or distillation.
With thermal desalination, the water to be treated is boiled until it produces vapors. When the vapors are cooled, it produces purer water, although Pankratz noted that often the water needs to go through the process five or six times to reach the purity desired. Tubing made of super duplex stainless, titanium, copper-nickel, aluminum-bronze or aluminum-nickel is used.
The Long Beach process is a nano filtration process, also using a membrane, although the membrane has pores that are larger than typical reverse-osmosis membranes. While the water needs to go through such a membrane a few times, Dorsey said the process is expected to use less energy than typical reverse osmosis.
"I think the growth of desalination will continue," especially given that many municipalities are coming to the realization that they have no choice in ensuring a pure water supply, Pankratz said. In the past, progress was held back by the fact that people were afraid of desalination. But now, with the cost coming down and most of the risks having been identified and mitigated, people are more open to the technology.