DC Water's Blue Plains waste water treatment facility. CC image from erin m.
While perusing Twitter (hat tip to Jeff Wood), I came across this Guardian article about urban uses of natural processes to do the dirty work of urban pollution mitigation. The piece discusses all types of green infrastructure and the natural processes they emulate, such as bio-filtration. I’ve taken note of local examples before, but the phrasing of their summary of the concept caught my eye:
Gray infrastructure is the system of pipes and ditches that channel storm water. Green infrastructure is the harnessing of the natural processes of trees and other vegetation — so-called ecosystem services — to carry out the functions of the built systems. Green infrastructure often intercepts the water before it can run into streets and become polluted and stores the water for gradual release through percolation or evapotranspiration. Trees also clean dirty water through natural filtering functions.
While drawing the contrast between green and gray infrastructures, the idea of “harnessing… natural processes” sparked a memory of this extensive summary from Mammoth of DC’s Blue Plains wastewater treatment facility – gray infrastructure on a massive scale. In describing what goes on at Blue Plains, they note “the process of waste water treatment mimics — in an accelerated fashion — the natural cleaning processes of waterbodies.” The accompanying footnote:
Scott Huler explains this in his fascinating On the Grid, quoting a Raleigh wastewater treatment superintendent T.J. Lynch:
“All we’re doing is what a river would do… what happens in our plant is the exact same thing that happens in a stream. That’s exactly where the process came from. We’ve just concentrated it. It might take the river a couple hundred miles to accomplish what we’d do in a couple days.”
Figuring out where any given piece of green infrastructure might fall in the spectrum from a naturally occurring ecology to a engineered technology is an interesting mental exercise. Rhetoric about sustainability aside, the same physical process is occurring using mostly similar mechanisms.
