Pennsylvania has had a seriously bad problem with acid mine drainage for years–water that washes through old/abandoned coal mines that comes back out heavily laden with minerals that make it acidic and a danger to the environment. More recently, with the shale revolution, PA has also found itself with an abundance of shale wastewater–most of it “produced” water that comes from deep in the earth (not surface drinking water), also laden with all sorts of minerals. Both acid mine water and shale wastewater are not easy to treat. Some sharp kids and their professors at the University of Pittsburgh got the bright idea to combine the two together, and treat them together, at the same time. Why? Because they have opposite amounts of barium and sulfates. Combine the two and you can more easily remove the nasty stuff via “precipitation.” How cool is that?