Fracking Wastewater's Radioactivity Reduced with Help From Acid Mine Drainage

Fracking wastewater's radioactivity is reduced when mixed with acid mine drainage, scientists found. 

Fracking, short for hydraulic fracturing, refers to a process in which millions of gallons of water containg chemicals and sand are pumped deep into the earth in order to crack open shale deposits and extract the natural gas within the rock. Proponents of fracking point to the fact that burning natural gas produces less nitrogen oxides or carbon dioxide than coal or oil, prompting the Environmental Protection Agency to call it "a key role in our nation's clean energy future."

However, the process is not without its drawbacks, one of them being the resulting wastewater. Besides all the chemicals added in the first place, which, according to a 2011 congressional report, include known carcinogens, the "flowback fluid" created in the process often contains high levels of salt, naturally occurring radioactive materials (NORM) like radium, and toxic metals, such as barium.

"Barium is a highly toxic metal," Adina Payton, a marine scientist from the University of California, Santa Cruz, said in a Royal Society of Chemistry podcast. "It's extremely poisonous - no one in their right mind would consider consuming it."

Published in the journal Environmental Science & Technology, a new study led by Duke University scientists discovered that when it comes to combating to such toxic waste, it may be best to fight fire with fire.

"Fracking wastewater and acid mine drainage each pose well-documented environmental and public health risks," said Avner Vengosh, a professor of geochemistry and water quality at Duke's Nicholas School of the Environment. "But in laboratory tests, we found that by blending them in the right proportions we can bind some of the fracking contaminants into solids that can be removed before the water is discharged back into streams and rivers."

Acid mine drainage leaks out of abandoned coal mines in the Appalachian Basin where it poses a risk to animal and plant life alike. Hundreds of waterways spread out across Pennsylvania and West Virginia have been affected by the drainage.

By mixing it with shale fracking wastewater, both of which were taken from sites in western Pennsylvania and provided by the industry, the scientists found significant improvements in just hours.

"Our analysis suggested that several ions, including sulfate, iron, barium and strontium, as well as between 60 and 100 percent of the radium, had precipitated within the first 10 hours into newly formed solids composed mainly of strontium barite," Vengosh said.

Such radioactive solids could be removed and deposited at hazardous waste facilities the researchers said. When asked if he was worried about potential buildup of such solids, Vengosh told Nature World News: "If carried out in a managed and controlled way, I do not think that will be a problem."

The scientist further notes that the salinity of the mixtures' (they made 26 in all) were also reduced as a result of the process, meaning the water could be reused as part of the fracking process.

"Scarcity of fresh water in dry regions or during periods of drought can severely limit shale gas development in many areas of the United States and in other regions of the world where fracking is about to begin," Vengosh said. "Using acid mine drainage or other sources of recycled or marginal water may help solve this problem and prevent freshwater depletion."

Bill Chameides, dean of Duke's Nicholas School of the Environment, sees potential drawbacks to the proposal.

"You still have hazardous waste to dispose of which poses its own challenges and risks," he told Nature World News in an email. "And you have to collect [acid mine drainage] water and transport it to the fracking site (or vice versa)."

True, he said, the process would "be an overall improvement over just sending the two waste streams into the surface water, but in a perfect world one would prefer to not have the polluted waste streams to begin with."

The next step, Vengosh says, is putting the process to the test out in the field.

"While our laboratory tests show that is it technically possible to generate recycled, treated water suitable for hydraulic fracturing, field-scale tests are still necessary to confirm its feasibility under operational conditions," he said.