During secondary filtration, air bubbles are blown up through the water to help bacteria turn toxic ammonia into nitrates. Credit: By Darrow Montgomery

Pondering the unlikely beauty of D.C.’s wastewater treatment plant.

Pity the poor rube who falls into the nitrification tanks!
Put the biosolids on Solids Road.
Bacteria hard at work making nitrogen out of nitrates.
Aeration pumps run on more than 4,000 volts and 2,000 horsepower each.