Seminole to Tap Salty Aquifer For Drinking Water

Q&A

Seminole, Texas, draws its drinking water from the depleting Ogallala Aquifer, so the city is exploring new sources, including the deeper Santa Rosa Aquifer. But there's a problem: The Santa Rosa is brackish - a mixture of seawater and fresh water. To treat the water, the state's Office of Rural Community Affairs, Texas Tech University and Seminole are partnering to build a first-of-its-kind system to desalinate inland ground water using wind power. We spoke to Texas Tech professor Ken Rainwater, director of the university's Water Resources Center, about the $1 million pilot program.

Is it difficult to meld desalination technologies with wind turbines?

We have existing technologies on both the land and water side; we're just bringing them together by using a [50-kilowatt wind turbine to power a reverse osmosis plant]. The target area that we're thinking about, typically the people have used shallow, fresh ground water with minimal treatment - just disinfection. So their main cost was pumping the water out of the ground and putting a little chlorine in it and putting it in the distribution system. What's happening now is for some of these places in our region, the drinking water standards have changed and some of them have issues with things like arsenic, for example - that's one of the things about a year and a half ago that a lot of places are in violation of when the standard dropped from 50 ppm [parts per million] to 10 ppm. The other thing is that some of the places with shallow ground water, the well fields they have are declining, and they are concerned about other supplies for the future. Reverse osmosis can handle stuff like that, so we're just trying to bring them together.

Will it cost Seminole more to treat brackish water?

The Santa Rosa [Aquifer] is deeper and less is known about it, but it hasn't been exploited as drinking water. It tends to be brackish in terms of water quality - sometimes even worse than that. If it's going to be used, you would have to reduce the dissolved solids there. So since these communities are going to have to address some additional treatment costs, and perhaps well and pumping costs, one of the things that was realized early on is that from about a third to one-half of the cost of desalination - essentially with reverse osmosis or something else - is energy. If you can make the local community the owner of its own renewable energy generation system through wind power, then they don't feel the cost the same way. Plus, they can perhaps sell excess energy back to the grid if that's viable in their location.

How does the cost compare to surface-level drinking water?

If you put together a system to provide 1 million gallons per day and you accounted for everything you've done in terms of amortizing out the wind turbines, the cost of energy, the cost of pumping in transmission for the water, and the cost of treatment for the water, you get on the order of $5 per thousand gallons.

For the small municipalities, it's just been pumping it from wells and disinfecting it [in the past]. Their cost would've probably been only $1.50 or less [per thousand gallons].

Are other Texas municipalities expressing interest in the system?

We've had a couple of workshops and people have shown up, but we haven't really had a real group step forward like Seminole again, yet. We did a survey a year and a half ago, and we found a number of communities that are in violation of one of the primary or secondary drinking water standards that is primarily ground water-dependent. They're going to have to