Texas joins global efforts to boost fresh water supply by desalinating sea water
Monday, July 2, 2007
The process is expensive mostly because of the energy required.
BROWNSVILLE, Texas -- On a one-acre site alongside a string of shrimp boats docked on the Brownsville ship channel stands a $2.2 million assembly of pipes, sheds and humming machinery -- Texas' entree into global efforts to make sea water suitable to drink.
Opening a small spigot at the end of a fat pipe, plant operator Joel del Rio fills a plastic glass with what he says will taste "like regular bottled water."
"Sea water," he said. "It's never gonna run out."
The plant is a pilot project for the state's $150 million, full-scale sea water desalination plant slated for construction in 2010.
Desalting sea water is expensive, mostly because of the energy required. Current cost estimates run at about $650 per acre foot (326,000 gallons), as opposed to $200 for purifying the same amount of fresh water.
However, it is a growing field around the world as governments and private investors ante up where drinkable water needs are crucial.
Expected to grow
Global output is still relatively minute -- less than 0.1 percent of all drinking water. But according to a recent report by Global Water Intelligence, the worldwide desalination industry is expected to grow 140 percent over the next decade, with $25 billion in capital investment by 2010, or $56 billion by 2015.
While the U.S. has hundreds of plants to purify brackish ground water, desalination of saltier sea water is just getting started.
Texas Gov. Rick Perry began pushing for Gulf of Mexico desalination in 2002, after a state water plan determined that hundreds of communities could face water shortages in the next 50 years.
The Brownsville venture got fast-tracked during a period of alarming drought and rapid population growth. From 1990 to 2000, the Brownsville area grew 43 percent to 372,000 people, and the population is expected to approach 500,000 by 2020.
Desalination is "part of the tools in the toolbox" of 4,500 water management strategies in the state's water plan, Texas Water Development Board spokeswoman Carla Daws said.
"We should never become complacent because of the history of our state having repeated droughts," she said.
The pilot plant was built along the busy ship channel because passing ships stir up the water, providing a challenge for the purification systems, said Genoveva Gomez, the Brownsville project's lead engineer.
Water pumped into the plant goes to three separate pretreatment units, designed by three separate companies hoping to win a contract for the full-scale plant. Chemicals and filtration remove bacteria, sediment and other impurities.
The cleaned but still salty water then goes to the reverse-osmosis equipment, where it is pumped at high pressure through a process that separates dissolved salt molecules from the water, producing one stream of purified water and a second of concentrated brine that is returned to the sea.
Tyson Broad of the Sierra Club in Austin said he was concerned the plant would be constructed on the shores of the Laguna Madre and send a salty discharge into the bay.
"If that increases the salinity in the bay system that's going to probably make the area less tolerable to fish and for any of the organisms that need to rely on the bay," he said.
Gomez said the waste discharge from the pilot plant is cleaner than the sea water that came in, and said even a full-scale plant would have minimal environmental impact.
She said the high cost of desalinated sea water will as more companies enter the market.
"If that's the only solution we have, you get water from the sea or you don't have any, then the cost wouldn't matter," she said, pointing out that people already pay a dollar or more for a quart of bottle water. "Water is the oil of the 1980s."