Gayathri Vaidyanathan, E&E reporter
CHARLOTTE, N.C. -- Treatment facilities in Pennsylvania that process oil and gas wastewater are discharging radioactive elements and salts into streams and rivers, according to preliminary research from Duke University.
The trace metals and radioactive elements have settled and built up in the sediment beds over time, with significant implications for the environment, said Avner Vengosh, a researcher at Duke University who has previously published on water contamination by shale gas development in the United States. He was presenting at a meeting of the Geological Society of America here from ongoing, unpublished research.
The contamination is ongoing and was not fixed when Pennsylvania updated its regulations in 2010 to set stringent discharge limits for wastewater treatment plants that accept oil and gas wastes.
That's because the contamination documented by the Duke researchers is not from wastewater generated by hydraulic fracturing in the Marcellus Shale. Instead, the contaminants are probably linked to wastewater generated from conventionally drilled gas and oil wells.
"I think the distinction between shale gas and the conventional oil and gas and their impact on the environment should not be made; I think it's all the same package deal and the effect is very similar," he said.
The issue of water contamination has received great attention with the increased use of hydraulic fracturing, in which companies blast pressurized water, sand and chemicals at shale rock to release trapped oil and gas. The process uses about 4 million gallons of water, and a fraction returns to the surface containing salts, radioactive ions and other toxic chemicals.
The wastewater, called "produced water" or brine, is typically disposed of through injection deep underground, but Pennsylvania's geology does not allow for this. Companies have adapted by treating the wastewater to remove contaminants, and Pennsylvania updated its rules in 2010 to tighten regulation of the practice (EnergyWire
, May 10).
Meanwhile, conventional wells have not received as much attention, even though the brine generated after drilling them has high levels of radioactivity and salt content comparable to the Marcellus, Vengosh said. These wells could be a significant source of contaminants to surface waters, he added.
The researchers studied one treatment facility in western Pennsylvania that discharges into a stream. The stream has a salt content of 100 milligrams per liter of water. The treatment facility was adding water to the stream containing about 200,000 mg of salt per liter as well as metals and radioactive elements. In comparison, seawater has about 35,000 mg of salt per liter.
The vast excess of salt has created a dead zone stretching 500 meters downstream, Vengosh said.
In addition, the sediments at the bed of the stream had absorbed the metals, causing a buildup of contaminants and radioactivity, he said. The discharges have continued even after the 2010 update of Pennsylvania's laws, he said.
Further analysis of the chemicals showed the originating brine is not from the Marcellus Shale, he said. Rather, the brine is from conventional wells drilled into other formations.
And the contaminants may have been accumulating in the sediments from before the advent of the Marcellus Shale drilling, he said.
The treatment facility "is supposed to prevent contamination of the environment, and I don't think it does."