With hydraulic fracturing for oil and gas continuing to proliferate across the U.S., scientists and environmental activists are raising questions about whether millions of gallons of contaminated drilling fluids could be threatening water supplies and human health. An hour south of Pittsburgh, in Pennsylvania’s Washington County, millions of gallons of wastewater from hydraulic fracturing wells are stored in large impoundment ponds and so-called “closed container” tanks. The wastewater is then piped to treatment plants, where it is cleaned up and discharged into streams; trucked to Ohio and pumped deep down injection wells; or reused in other fracking operations. But tracking where the fracking wastewater from Washington County and sites across the United States ends up — and how much pollution it causes — is exceedingly difficult. In a study conducted last year , researchers from the environmental consulting firm, Downstream Strategies , attempted to trace fracking water — from […]