Hydraulic fracturing, or fracking, has resulted in a boom in the oil and gas industry across the US. But the rapid growth of the industry has raised the issue of how to dispose of the billions of gallons of wastewater generated as a result of fracking operations.

A recent study has found that treating this wastewater before releasing it into the environment does not necessarily make it safe. The study, which was recently published in the American Chemistry Society's journal Environmental Science & Technology, has reported that release of treated fracking wastewater has led to a Pennsylvanian watershed becoming contaminated with radioactive material and hormone disrupting chemicals, both of which pose a human health risk.

According to the US Energy Information Administration, in 2015, more than 50% of all oil produced in the US, and 66% of gas produced was a result of the hydraulic fracturing method used to extract oil and gas from deep below the Earth's surface. This method of extraction is expected to expand even further in the future. Yet while fracking has led to a transition away from burning coal, which could effectively reduce atmospheric emissions, large volumes of wastewater are produced as a result, which contain a wide array of pollutants, including heavy metals, salts, hormone disrupting chemicals, polycyclic aromatic hydrocarbons and radioactive material, which could potentially pose both an environmental and human health risk.

A Pennsylvanian report estimated 1.7 billion gallons of wastewater was produced by 10,000 oil and gas wells at fracking sites in the Marcellus Shale in 2015. This wastewater is collected by wastewater treatment facilities that, after providing limited treatment, release the partially treated water into nearby surface waters. William Burgos together with a team of scientists from Penn State University, Colarado State University and Dartmouth College wanted to determine whether treating and releasing fracking wastewater in this manner might be having an impact on the environment.

In order to assess this, they analyzed porewater and sediment samples they had collected from a lake situated further downstream from two fracking wastewater treatment facilities in Pennsylvania. They found high levels of salts, alkaline earth metals, organic chemicals and radium all tended to occur within the same layer of the sediments collected. The organic chemical contaminants included both hormone disrupting nonylphenol ethoxylates and carcinogenic polycyclic aromatic hydrocarbons. Sediment layers that were deposited between 5-10 years ago — during a time when fracking wastewater disposal peaked — had the highest concentrations of contaminants. High concentrations of radium were found in samples collected 12 miles further downstream of the wastewater treatment plants. The authors conclude that while it is not yet clear what, if any, potential environmental and health risks this contamination may pose, they suggest that it would be prudent to impose more stringent regulations on fracking wastewater disposal in order to protect both environmental and human health.

Journal Reference:

William D. Burgos, Luis Castillo-Meza, Travis L. Tasker, Thomas J. Geeza, Patrick J. Drohan, Xiaofeng Liu, Joshua D. Landis, Jens Blotevogel, Molly McLaughlin, Thomas Borch, Nathaniel R. Warner. Watershed-Scale Impacts from Surface Water Disposal of Oil and Gas Wastewater in Western Pennsylvania. Environmental Science & Technology, 2017; DOI: 10.1021/acs.est.7b01696