듀크 대학교 과학자들이 실행한 새 연구가 펜실베니아와 버지니아 서부에 위치한 원유 및 가스 작업장에서 발생해 강이나 하천으로 배출되는 폐수에 포함된 두 개의 고수준 잠재적 위험 오염물을 밝혀냈다. 통상적인 원유 및 가스정에서 발생하는 폐수의 오염물질 수준은 수압파쇄 셰일가스정에서 나오는 것만큼 많은 것으로 밝혀졌다.

 

 

 

New research conducted by Duke University scientists has revealed high levels of two potentially hazardous contaminants -- ammonium and iodide -- in wastewater being discharged into streams and rivers from oil and gas operations in the states of Pennsylvania and West Virginia. Contamination levels were found to be as high in wastewater from conventional oil and gas wells as those from hydraulically fractured shale gas wells.

 

"This discovery raises new concerns about the environmental and human health impacts of oil and gas wastewater in areas where it is discharged or leaked directly into the environment," said Avner Vengosh, professor of geochemistry and water quality at Duke's Nicholas School of the Environment. "Our data clearly show that the current brine treatment practice in Pennsylvania is not sufficient to remove these contaminants."

 

The peer-reviewed study is the first to document the presence of high levels of ammonium and iodide in oil and gas wastewater. Public concern for water contamination has focused on the impact of hydraulic fracturing fluids from shale gas exploration, but the study shows that wastewater from conventional oil and gas exploration contains levels of ammonium and iodide that are just as high. Previous studies have shown that fracking fluids contain high levels of salts, barium and radioactive elements, in addition to man-made chemicals.

 

"By measuring naturally occurring ammonium and iodide in numerous samples from different geological formations in the Appalachian Basin, including flowback waters from shale gas wells in the Marcellus and Fayetteville shale formations, we show that fracking fluids are not much different from conventional oil and gas wastes," said Jennifer S. Harkness, lead author of the study and a PhD student at Duke's Nicholas School of the Environment.

 

When dissolved in water, ammonium can convert into ammonia, which is highly toxic to aquatic life. The scientists detected ammonium levels of up to 100 milligrams per liter in oil and gas effluents they collected at the wastewater discharge sites. Those levels are more than 50 times higher than EPA's water-quality threshold for protecting freshwater organisms. Elevated iodide in surface water can promote the formation of highly toxic byproducts in drinking water when mixed with the chlorine used to disinfect the water at municipal treatment plants located downstream from oil and gas operations. Such disinfection byproducts are not monitored by state or federal agencies.

 

To conduct the new study, the researchers collected and analyzed 44 samples of waters produced from conventional oil and gas wells in New York and Pennsylvania and 31 samples of flowback waters from hydraulically fractured shale gas wells in Pennsylvania and Arkansas. They also collected and analyzed oil and gas effluents that were being directly discharged into streams, rivers and surface waters at three disposal sites in Pennsylvania and a spill site in West Virginia.

 

"Wastewater from both conventional and unconventional oil and gas operations is exempted from the Clean Water Act, which allows their disposal to the environment," Vengosh said. "This practice is clearly damaging the environment and increases the health risks of people living in these areas, and thus should be stopped."

 

[출처 = Water World / 2015년 1월 14일]