06 Jul 2015
Nearly three-quarters of the Earth’s surface is covered by water, but according to the United Nations, more than 97 percent of it is saltwater unsuited for human consumption or agriculture.
The United Nations Population Fund reports that by 2025 two-thirds of the world’s projected population of 7.9 billion may live in areas where access to safe water is limited. “Every time we add a person, it’s not just the water that person consumes but also the additional water for agriculture and industry that you have to use,” says Earl Jones, director of water-scarcity solutions in General Electric Co.’s (GE) Water & Process Technologies unit.
The removal of salt from seawater is an increasingly cost effective answer to the earth’s growing clean-water needs. By 2025, two-thirds of the world’s population may live in areas where access to safe water is limited, reports the U.N.
The removal of salt from water is emerging as one of the best solutions to the world’s water problem, analysts say. According to GOLDMAN SACH S Group Inc. (GS), desalination is a $5 billion global market, with growth of 10 percent to 15 percent a year. Water Desalination Report, a trade journal, reports that more than 12,000 desalination plants are operating World-wide, with 53 percent of the world’s desalination capacity in the Middle East.
“Today, the global capacity is about 40 million cubic meters of desalinated water per day,” says Antoine Frérot, CEO of Veolia Water, the water division of Veolia Environnement (VE). “By 2015, it will be around 70 million cubic meters per day.” Improvements in two technologies are making desalination more cost-efficient, say the experts:
The thermal process, which couples a thermal desalination plant with a power plant to provide the energy, involves evaporating water to remove salt.
Reverse osmosis, the other process, uses semipermeable membranes. About 84 percent of the world’s thermal desalination capacity, which requires more energy than reverse-osmosis facilities, is located in the Middle East, according to Water Desalination Report.
“We have one huge advantage in the Gulf,” says Phil Cox, CEO of International Power PLC (IPR), which builds, owns and operates thermal desalination plants in that region. “The price of natural gas is extremely low here compared with the rest of the world,” he adds. Outside the Middle East, reverse osmosis is the less expensive alternative, says Jean-Louis Chaussade, CEO of Suez Environment, a unit of Suez SA (SZE). “At our biggest reverse osmosis plants, we operate at roughly 60 cents per cubic meter of use,” says Chaussade.
Aside from GE, International Power, Suez and Veolia, other companies that construct, own and/or operate desalination systems worldwide include The AE S Corp. (AES), Crane Co.’s (CR) Crane Environmental, Siemens AG’s (SI) Power Generation unit and ITT Corp. (ITT). ABB Ltd . (ABB) provides electrical systems for desalination plants, and Met-Pro Corp.’s (MPR) Fybroc division manufactures pumps used in reverse-osmosis plants.
The motivation is there to solve the world’s water needs, the companies say. “According to the U.N., the No. 1 cause of death and illness in developing nations is waterborne diseases,” says GE’s Jones. “We have the technology to fix these problems. It’s very easy to get motivated because of the great opportunity to do good.”
The Scale Effect
The world’s largest reverse-osmosis plant in terms of production is Veolia Water’s Ashkelon Seawater Desalination Plant (see illustration) south of Tel Aviv, which has a daily capacity of 320,000 cubic meters per day, according to the company. The plant produces enough water to meet the needs of 15 percent of Israeli households, Veolia reports. “There is a scale effect,” says Veolia Water CEO Antoine Frérot. “At a small desalination plant, the price of water is around $2 per cubic meter. In Ashkelon, the price is 55 cents per cubic meter.”
Other big projects are in the works: General Electric Co.’s (GE) Infrastructure, Water & Process Technologies reports that it plans to open Africa’s largest seawater desalination project in Algiers, Algeria. An international consortium led by Siemens’ Power Generation unit says it plans to build the world’s largest independent water and power project in Riyadh, Saudi Arabia. Uwe Rokossa, Siemens projects sales director for new plants and services in the Middle East predicts: “We will see a continuation of big power and desalination projects.”
Steam Power and Hybrids
Thermal desalination requires steam to boil seawater, GE explains. According to GE’s Earl Jones, the most widely used thermal process is called multistage flash, which heats seawater in a brine tank, immediately converting it to steam. The resulting salt-free steam is captured, cooled and condensed, creating desalinated water, Jones reports. Since only some of the seawater is converted to steam, the process is repeated multiple times in different receptacles, each time using lower atmospheric pressures. The hybrid approach, which combines thermal and reverse-osmosis processes, is an emerging technology, according to Suez Environment, which provides the reverse-osmosis part of the first-ever hybrid facility in the United Arab Emirates. Having both techniques in one plant allows for flexibility, the company says. Suez Environment reports that when demand for electricity from the thermal side’s power plant is low, priority can be given to the less-energy-intensive reverse-osmosis process.
Another form of the hybrid approach involves having a mixture of different membranes inside a reverse-osmosis pressure vessel, says Lance Johnson, senior sales and marketing manager for Dow Water Solutions. “As the water moves down the vessel, the salt concentration increases. At the tail end, where the salinity is highest, you’d have a lower-pressure membrane than at the front end to boost productivity.
Emerging “Nano-Materials” and Membranes
Mixing high and low pressure membranes in a pressure vessel can lower cost.” Applying nanotechnology to membrane science is another promising avenue, according to GE’s Jones, who notes that membranes made out of nanotubes can process water faster than older methods. “Imagine getting fire-hose volumes and velocities out of your garden hose. Nanotechnology could fundamentally change the economics of desalination.”