Aging sewers leaking nitrogen into urban watersheds

Space Daily via SPX: Aging sewer systems are spilling a considerable amount of nitrogen into urban watersheds, diminishing both the quality of water and ecosystems' habitats. However, many studies documenting the impacts of nitrogen on urban environs have not properly estimated the contribution of leaky sewer systems-until now.

Using water samples from the Pittsburgh-based Nine Mile Run watershed, a Pitt research team reveals in the current issue of Environmental Science and Technology that an estimated 10 to 20 tons of reactive nitrogen from sewage flows into Pittsburgh's Monongahela River every year from the six-square-mile watershed.

That means that up to 12 percent of all sewage produced by residents living in the Nine Mile Run watershed area leaks from the sewers and is transferred to the stream, negatively affecting stream water quality.

"This is a very complicated problem," said Marion Divers, principal author of the paper and a Pitt PhD candidate who conducted the study under the supervision of Pitt assistant professors of geology and planetary science Emily Elliott and Daniel Bain, who were coauthors of the paper.

"You build a sewer system once, put it underground, and unless there's a catastrophic failure, you may not have a reason to dig it up and make sure it's not leaking. Now sewers across the United States and in Pittsburgh are aging, and as these systems grow older, more sewage is leaking into groundwater and streams."...

The Monongahela River and downtown Pittsburgh at night, shot by Joey Gannon, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license