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Aquifer agency looks to desalinization to stave off future drought

Tuesday, February 2, 2010 by John Davidson

Not many people are aware of it, but a massive portion of the Barton Springs segment of the Edwards Aquifer is a saline zone – a body of underground saltwater unsuitable for human consumption that runs parallel to the fresh water zone. According to Barton Springs Edwards Aquifer Conservation District Board Chair Bob Larsen, the saline zone is understudied and untapped, but he and his colleagues at the aquifer agency want to change that.


The aquifer district, along with Texas State University and Texas Disposal Systems, is seeking a state grant of up to $600,000 to build an experimental desalinization plant that would utilize new technologies to make the Aquifer Saline Zone water safe for drinking and other uses.


Part of the impetus for such a plant is that the freshwater portion of the Edwards aquifer is totally subscribed, according to Larsen, and could not be relied upon to produce more water in the event of a drought. “We’re looking for alternative sources of water, and the alternative source would be this huge Saline Edwards,” he said. “It’s this vast resource but in its current state we can’t use it, we don’t know that much about it, and we’ve never really evaluated it to any great extent.”


At its meeting last week, the BSEACD board approved spending up to $10,000 on a contract with engineering firm AECOM to help prepare the grant application. The application deadline is March 1.


If the aquifer agency and its partners get the state grant, they will use the money to build an experimental desalinization plant that would produce between 500,000 and 1 million gallons of fresh water per day. “By some standards, that’s small; by our standards it’s large,” Larsen said.


A larger, permanent facility could produce up to 10 million gallons per day – a huge boost to the region’s fresh water resources. Since putting treated water back into the Edwards aquifer is prohibited under current state law, the proposed desalinization plant could pump directly into existing infrastructure to distribute the treated water, according to Larsen.


But before that happens, geologists and other experts must carefully study the saline zone to ensure that drilling into it would not contaminate the freshwater portion of the aquifer. Because very little is known about the interaction between the saline and freshwater zones of the aquifer, Larsen believes that even a small test facility could be hugely beneficial.


“It will provide us with a lot of data that we do not have,” Larsen said. “We’d love to get some information on how usable this water is, what the chemistry is, in addition to the quality and the quantity.”


A test facility would also provide regional experts an opportunity to test new desalinization technologies designed to more efficiently dispose of the brine produced by the desalinization process. The most common desalinization process, called reverse osmosis, produces between 20 and 30 percent brine – water completely saturated with salt that is unusable. But Larsen says a new technology, which would be employed at the experimental plant, produces only about 4 percent brine.


The plant itself would be energy-intensive, requiring large amounts of water on a daily basis. In order to avoid tapping into Austin Energy’s power grid, which could be costly, the agency and its partners plan to use refuse-derived fuels and methane to power the facility. According to Larsen, Texas Disposal Systems already has enough methane recovered from the decomposition of organic materials in its landfill to power such a facility for 50 or 60 years.


If the scheme works, the agency and its partners would look for ways to expand the operation and replicate it elsewhere throughout the state.


“These are closed green systems. It’s using wastewater, using waste fuels to drive it, and coming out with good water that could be mixed with existing water distribution systems and really help us,” Larsen said. “When we went through the last drought, we had a large shortage of water. So we have to look at alternative sources; we can’t continue to use traditional freshwater sources.”

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