Bromide levels rose in the Monongahela River in 2010 and remain elevated, possibly because of discharges of wastewater from Marcellus Shale drilling or electric power plants, said Jeanne VanBriesen, a Carnegie Mellon University civil and environmental engineering professor who spoke Thursday at a university research symposium about the river.
Ms. VanBriesen, who is also director of CMU's Center for Water Quality in Urban Environmental Systems, said the river's bromide levels are much higher than what would be expected in similar inland waterways and should be reduced to ensure that public drinking water supplies remain safe.
Bromides are nontoxic salt compounds, but they react with disinfectants used by municipal water treatment plants to form brominated trihalomethanes, also known at THMs, which are volatile organic liquid compounds that become part of the drinking water. The more bromides in the river water, the more THMs in the finished water, and studies show a link between ingestion of THMs and several types of cancer and birth defects.
"THMs are carcinogenic for long-term exposures," Ms. VanBriesen said, "so you don't want to keep putting more bromide into the [Mon] river basin."
Eleven public water treatment intakes are on the Monongahela River, supplying approximately 350,000 customers. Ms. VanBriesen's two-year study sampled river water at eight locations near public drinking water intakes and focused on chloride and bromide, elements that are components of total dissolved solids.
"Bromide going into the river system started to increase in mid-2010, and, if you look deeper, the relative amount of bromide is increasing," Ms. VanBriesen said. "It's an indication that something is changing in the basin. Freshwater shouldn't have this much bromide."
This spring, the Ohio River Valley Water Sanitation Commission designated bromide as a "compound of concern" for water treatment plants.
Ms. VanBriesen said her research hasn't pinpointed a single source but said bromide is contained in water discharges from air pollution control devices at coal-fired power plants and in wastewater or "produced water" from Marcellus Shale drilling operations.
Controls on some discharges from likely bromide sources and a much wetter 2011 that diluted bromide concentrations, she said, produced more stable water quality in the river this year compared with 2010, which was drier, reducing river flow.
Don Hopey: firstname.lastname@example.org or 412-263-1983.