PITTSBURGH - Researchers at Carnegie Mellon University say a water quality problem in the Monongahela River that may have been linked to Marcellus Shale natural gas drilling is going away.
Jeanne VanBriesen said Thursday that preliminary data from tests this year showed that levels of salty bromides in the river have declined significantly when compared to 2010 and 2011. In many cases the bromides were at undetectable levels this year, and in general they returned to normal levels.
"These are very nice, low bromide levels, where we would like them to be," VanBriesen said of the 2012 test results, which were presented at a water quality conference in Pittsburgh.
VanBriesen said the decline appears to coincide with a voluntary ban on disposing gas drilling wastewater that took effect in the spring of 2011. The wastewater contains large amounts of naturally occurring, ultra-salty bromides, and drillers had been taking millions of barrels of it to conventional wastewater treatment plants that discharge into the Monongahela River.
But in early 2011, the state Department of Environmental Protection called on drillers to voluntarily stop using riverside plants to get rid of the wastewater, and major companies and industry groups agreed to the request.
The state's request was made after VanBriesen and other researchers presented evidence that the discharges were altering river chemistry in a way that had the potential to affect drinking water, and operators of municipal water supplies grew concerned.
Although not considered a pollutant by themselves, the bromides combine with the chlorine used in water treatment to produce compounds that can threaten public health, and levels had soared in 2009 and 2010. Bromide levels in the river declined somewhat in 2011, but not enough for researchers to say that the river had returned to normal levels.