Tag Archives: concrete sewers

Our Poop Problem

Anyone else feel like we missed a huge opportunity when we didn't use the economic crisis as a reason to put people back to work by engaging them in massive public works projects? Seeing reports about our aging and crumbling infrastructure you can't help but think, "Why didn't we take some of those billions (trillions?) of dollars we spent bailing out various industries and dedicate them to upgrading our roads, bridges and sewers?" Wait…sewers? Yep. Apparently our concrete sewers aren't being eaten by the very stuff they transport:

“The veins of our cities are in serious trouble, and they’re in serious trouble because of corrosion, and this corrosion has been unanticipated and it’s accelerating,” said Mark Hernandez at a symposium on the microbiology of the built environment in Washington DC yesterday. Hernandez is a civil engineer, but he’s meeting with microbiologists because this problem is bacterial. Essentially, it’s an infection of the nation’s sewage system.

Here’s what’s going on. One set of microbes emits hydrogen sulfide, the gas that is also responsible for raw sewage’s unpleasant smell. This gas fills the empty space between the top of the pipe and the water flow. Another set of microbes living in this headspace turns hydrogen sulfide to sulfuric acid, which eats away at concrete, leaving behind gypsum, the powdery stuff you find in drywall.

“Essentially what we’re ending up with is wet drywall,” said Hernandez. This is one reason the American Society of Civil Engineers has gave our wastewater infrastructure a D grade.