Earthquakes in Oklahoma

ENID, Okla. — In northwest Oklahoma, water is a hot commodity

Why is produced water from hydraulic fracturing put back into the ground?

Produced water has high salinity, comparable to the Dead Sea in Israel, so it’s not high quality and would be difficult and expensive to treat, said Todd Halihan, a professor at Oklahoma State University’s Boone Pickens School of Geology.

“The main problem is the salt,” he said. “You can’t do anything with it. It’s so salty you wouldn’t get much back out of it.”

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The Civil and Environ­mental Engineering Depart­ment at Colorado School of Mines is researching how to treat hydraulic fracturing wastewater for other uses.

Tzahi Cath, a professor with the department, said the technology exists to purify such water.

“We can take any water and turn it into any water that we want,” he said. “The bottom line is that even frack blowback water or produced water can be treated, depending on the cost, and reused for different purposes: putting it back in the river, irrigation, livestock water and even drinking water.”

Treating fracking and produced water can be difficult, he said.

“It’s complicated water,” he said. “The quality changes all the time: day to day, well to well, basin to basin. That’s the big challenge with treating this because you need a flexible system. But it’s possible.”

The biggest hurdle is desalinating the water, he said, but before removing the salt, the water has to be pretreated.

“You have to remove the organic matter, little particles in the water, hydrocarbons, gel systems they use in the fracking,” he said, adding this can be done with filters and a reverse osmosis or distillation system. “Once you condition the water and prepare it for desalination, it depends on the salinity of the water. The cost of treatment is going to increase exponentially for increasing salinity.”

Cost increases depend on the desired rate of return. An increase in rate of return increases the expense to pull the next clean gallon of water from the brine, he said, and would require economic analysis.

Startup costs would de­­pend on the size of the plant and what kind of water is being treated, he said.

“For a treatment plant that treats several thousands of gallons a day, it’s in the few millions of dollars,” he said. “I don’t think the cost is the problem. The problem is the rate of return. How quickly will the plant return the investment?”

But reusing wastewater is possible, he said, and fracking and produced water isn’t the hardest water to treat; water from paper plants is more difficult to treat because of tiny fibers.

“We have the technology,” he said. “There are companies that sell distillation systems for high-salinity water. There’s nothing special we need to invent today.”