Desalination a big part of Texas' water future
Published 6:35 pm, Monday, November 14, 2011
EL PASO - For El Paso and a growing number of Texas cities, the question isn't whether they have enough water, but what price people are willing to pay to make it drinkable.
Aquifers beneath the Chihuahua desert are filled with brackish groundwater, belying the seared landscape above. Salty water rushes down rivers. And the Gulf of Mexico offers a virtually unlimited supply.
For centuries, Texans had cheaper ways to quench their thirst. But population growth - up 20 percent over the past decade, to 25 million people, and predicted to almost double by 2060 - is driving up demand, just as the supply is shrinking. The latest draft of the state water plan predicts existing supplies will fall by 10 percent in the next 50 years.
But Texas has more than 2.7 billion acre-feet of brackish groundwater, enough to meet current demands for more than 176 years.
For many cities, the cost of desalination - up to four times that of other water treatments, sometimes even more for seawater desalination - is no longer a deal-breaker.
The state's first permanent seawater desalination plant will open on South Padre Island in 2014. Until then, all of the state's 44 desalination plants - most of them small, scattered across West Texas and the Rio Grande valley - treat brackish groundwater.
The El Paso plant is the state's largest, capable of producing 27.5 million gallons of water a day for city customers and those on the Fort Bliss Army post.
Most years, desalination is a small piece, as El Paso uses fresh groundwater and draws about half its water supply from the muddy Rio Grande, the international boundary running behind the 18-foot steel border fence dividing El Paso and Juarez, Mexico.
But not even a city that receives less than nine inches of rain a year is immune to the drought sweeping the rest of the state, and Balliew said the river is almost certain to produce less water next year.
Slow to catch on in U.S.
Seawater desalination has been slow to catch on in the United States, although it is common in the Middle East, the Caribbean and elsewhere.
There are a few plants in Florida and California, and many U.S. Navy ships have small desalination plants.
The state Water Development Board launched several demonstration proj- ects for seawater desalination over the past decade. Last spring voters in the Laguna Madre Water District, which serves South Padre Island, Port Isabel and the surrounding area, authorized a full-scale plant.
Other cities along the coast are considering similar ventures, although none have decided how to pay for them. And that's the catch, even as the seemingly inexhaustible supply of seawater washes ashore.
Gavino Sotelo, general manager of the Laguna Madre Water District, said building and operating a seawater plant will probably cost three times as much as a similar plant to treat surface water from the Rio Grande, which currently provides the district's main source of water.
"Voters here know what our situation is with the river," Sotelo said, noting that the Rio Grande peters out before reaching the Gulf during dry years. "They know we can't continue to rely on a river that everybody on both sides of the border uses at once."
The $13.2 million plant will be built on the bay to offer some protection from hurricanes, with water piped less than half a mile across the island.
Part of long-term plan
Other coastal communities are thinking about seawater desalination, too, although details are fuzzy.
A $255 million plant in Freeport is part of the Houston region's long-range plan, with a potential date of 2050. San Antonio has similar long-range plans, involving about 140 miles of pipeline to bring the water to the city.
For now, count San Antonio among the growing number of cities bullish on brackish water desalination.
A plant above the Wilcox Aquifer in south Bexar County will open in 2016, said Chuck Ahrens, vice president for water resources at the San Antonio Water System. It could be expanded as the city lessens its dependence on the Edwards Aquifer.
Edwards Aquifer water is cheap, plentiful and pure, but - unlike other Texas aquifers - is subject to federal regulations to protect endangered species in aquifer-dependent springs.
Water customers will cover the desalination plant's $145 million price tag through higher rates, Ahrens said.
Cost isn't the only factor. Before building a plant, operators must address environmental concerns, including how to dispose of the salty concentrate the process produces.
High start-up costs
El Paso has changed its relationship with water over the past few decades, both embracing its desert heritage - fewer green lawns and a year-round culture of conservation - and developing new water sources.
In addition to the Rio Grande, the city relies upon two aquifers, the Mesilla Bolson and the Hueco Bolson, both of which also dip into Mexico.
Both provide freshwater, but the Hueco has almost four times as much brackish water, said Christina Montoya, a spokeswoman for El Paso Water Utilities.
The utility and the Army independently began planning a desalination plant for the Hueco water in the early 2000s and worked together to build the Kay Bailey Hutchison Desalination Plant, which opened in 2007 on Fort Bliss.
The plant covers 18,000 square feet - about one-third the size of a football field - and is so mechanized it requires just 14 people to operate around the clock.
Start-up costs - building the plant, drilling the wells, buying the membranes through which the water is filtered - are high.
But Balliew said the operating costs in El Paso are manageable.
Freshwater from the two aquifers provides the city's cheapest source of drinking water, at about 45 cents for 1,000 gallons, he said.
Treating water from the muddy Rio Grande is more expensive, about $1.85 per 1,000 gallons. That compares to $2.10 for every 1,000 gallons of desalinated brackish water, Balliew said.
Unlike the river, however, the city's supply of brackish groundwater isn't expected to run dry anytime soon.