By Kyle Ferrar –
When energy companies extract natural gas trapped deep underground, they’re left with water containing high levels of pollutants, including benzene and barium. Sometimes the gas producers dispose of this contaminated water by sending it to wastewater treatment plants that deal with sewage and water from other industrial sources. A new study suggests that the plants can’t handle this water’s high levels of contaminants: Water flowing out of the plants into the environment still has elevated levels of the chemicals from natural gas production, according to a study published in the journal Environmental Science and Technology.
Federal officials are planning to hold a “public meeting” on the development and processing of oil and gas on Alabama’s national forest lands in Montgomery on April 25. According to our previous reports on this subject, a spokesperson for the Bureau of Land Management indicated that hydraulic fracturing, or “fracking,” is now the primary method for developing these resources and is the main impetus for corporate interest in leasing national forest land for development these days.
According to a study published in Chemical Engineering News, about 23 percent of U.S. natural gas production involves “fracking,” where workers inject high volumes of water and chemicals at high pressures into the ground to break shale rock formations and to release trapped natural gas. Up to 80 percent of that injected water returns to the surface, where it’s collected as wastewater.
Companies tend to deal with this leftover water by reusing it, injecting it into deep storage wells, or sending it through sewage treatment plants.
In May 2011, however, the Pennsylvania Department of Environmental Protection asked that the state’s treatment plants voluntarily stop processing fracking wastewater. The request came in response to public concern over elevated bromide levels in the Pennsylvania Monongahela River watershed—an area with facilities that treat water from natural gas production. Scientists hadn’t definitively pinpointed fracking waste as the source of this pollution. Researchers haven’t studied how fracking wastewater affects the quality of water leaving sewage plants.
To learn more, Kyle J. Ferrar, a graduate student at the University of Pittsburgh, and his colleagues analyzed water from treatment facilities that initially processed fracking water and then later complied with the state’s recommendation. They took water samples from one private and two public facilities in Pennsylvania that treated water from the nearby Marcellus Shale region, the largest shale basin in the U.S. They collected samples both before and after the department’s request.
Using a variety of spectroscopic techniques, the team measured levels of chemicals found in gas production waste but aren’t typically present in other industrial wastewaters. Although levels of these chemicals varied widely among the three treatment plants, concentrations dropped significantly after the plants stopped taking the fracking waste, Ferrar says.
At a municipal plant in Greene County, for example, average barium concentrations fell from 5.99 to 0.14 milligrams per liter.
When the plants still handled the waste, levels of several of the chemicals exceeded drinking water standards set by the U.S. Environmental Protection Agency.
At the Greene County plant, the levels of barium and strontium, two toxic metals found in fracking wastewater, were on average 5.99 and 48.3 milligrams per liter, respectively.
EPA drinking water standards for these metals are 2 and 4 milligrams per liter, respectively.
Carl Kirby, a professor of geology at Bucknell University who studies the environmental impact of Marcellus Shale gas production, says the human health impact of elevated contaminant levels from processed fracking water is unclear, because the water the team sampled is not used directly as drinking water. He pointed out, however, that fracking contaminants eventually could reach larger water systems used for drinking water, albeit at significantly diluted levels.
Ferrar agrees that there is no immediate public health concern over the pollutant levels. But he does worry about how the elevated levels affect aquatic ecosystems receiving water from treatment plants. He hopes researchers will study further the impact of disposing of produced waters via wastewater treatment plants.
Adapted from a story published in the Chemical and Engineering News.
© 2013, Glynn Wilson. All rights reserved.