The heat of an Alabama summer afternoon certainly wasn’t helping the aroma of several million gallons of raw and partially treated sewage. This field trip to the Auburn Wastewater Treatment Plant was always the worst one I led for my Intro to Environmental Engineering class. Fortunately, we were near the end of the process and far from the most fragrant part of the plant. At this point the wastewater had been treated by the sludge, which is a “fancy” name for the bacteria that eat the organics in the wastewater. The sludge had been separated out of the treated water, the bacteria had eaten each other, and the remainder had just been pressed to remove excess moisture.
We were standing next to a twelve-foot-tall pile of biosolids, the dewatered bacteria, when the tour guide pulled his usual stunt. He took an ungloved hand and stuck it into the pile, pulling out a handful of what appeared to be a dark, rich soil. The class reacted the way classes on these trip always react: with revulsion. That’s how people respond to things recovered from wastewater, completely unaware of how valuable they can be.
The Great Poop Train
Biosolids look like rich soil because they are rich in nitrogen and organics, which are beneficial for the growth of plants. But that doesn’t make them any more desirable to keep around, and cities often go to great lengths to dispose of them. By 1986, New York City completed its 14 wastewater treatment plants. The resulting wastewater system handled 1.3 billion gallons of wastewater produced every day, creating several thousand tons of biosolids. So the city set out to find somewhere to get rid of it. At first, it was dumped into the ocean. But in 1988, the Environmental Protection Agency told the city they had to stop dumping and find a good use for the biosolids to make amends for their previous polluting ways.