The Living Machine: A Flush Worth Following

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Living Machine 045_2
Greenhouse plants are used to help filter wastewater from toilets at an Oberlin College building.

On the small liberal arts campus of Oberlin College in Northeast Ohio, you would expect to see some funky hairdos, a smattering of fixed-gear bikes, and certainly some people strolling barefoot to class. But you might not expect to find their bathroom stalls peppered with “Poop Haikus.”

At the Adam Joseph Lewis Center for Environmental Studies, musings on human excrement dominate the toilet landscape.Living Machine 033

One student writes:

"Normally I hate
Pooping in a public place
Here I feel proud"

Why the sense of pride?  Because the building is a Living Machine.  Literally.


It’s an in-house wastewater treatment and reuse system that mimics the processes of natural wetlands. Student (and faculty) poop fuels the machine, and the water used to flush it down is recycled over and over, after passing through an elaborate cleaning system.

An electronic dashboard displays the amount of recycled vs. city water used at any given moment in the building.

I toured "the machine" with biologist John Peterson and building manager Sean Hayes.  We set out to follow the flush.

The first stop is an underground tank, full of—you guessed it—poop.“I think I just saw something coming in!” exclaimed Peterson after lifting the lid of the tank, and Hayes crouched down to confirm the turd sighting.  This first tank is where the anaerobic action happens—microbes that don’t dig oxygen live here and start breaking down and converting the organic waste.

Then the sludge travels to another underground tank, this one with a bubbler that aerates the system.  A different set of bacteria hang out here and greedily munch on the carbs and proteins, further breaking down the mess.  They’re also helping convert a key element, nitrogen, into a plant-friendly form.

Biologist John Peterson describes how the tropical plants suck up nitrogen and house beneficial bacteria in their roots.
Biologist John Peterson describes how the tropical plants suck up nitrogen and house beneficial bacteria in their roots.

After this, the mixture heads indoors, into a series of open tanks in a greenhouse.  You can watch the greenhouse live on a webcam (though I can’t say it’s compelling television).  Big tropical plants sprout from the tanks; Calla Lilies are in bloom during my visit.  The plants suck up nitrogen and their roots house more beneficial bacteria.  In addition to burning up organic matter and removing pathogens, it’s important for wastewater treatment schemes to remove nutrients like nitrogen and phosphorous, which if released into the environment, contribute to harmful algal blooms.

Next stop is a gurgle through the clarifier basin—where the sludge settles and is sent back to the underground tanks to keep the microbe levels high—and then the clear water is piped underneath the gravel bed of the greenhouse.  This is referred to as the “marsh.”  Here, more anaerobic microbes finish the cleaning job.

When a toilet needs refilling—or the landscaping needs watering—the clean, treated water is passed through an ultraviolet light to kill any lingering pathogens, and then it’s put into action.

The water in the building’s toilets is slightly brown, but Peterson says it’s cleaner than much of the world’s drinking water.

The Living Machine technology was invented by biologist John Todd in the late nineties (hear him talk about it), and versions of it are now in place in several buildings across the country.

The usefulness of the technology here in Oberlin, where water isn’t scarce, is less about its practical benefits and more about the educational ones. Local schools organize field trips to see the machine at work, and college students organize campaigns to promote on-campus pooping. Even internet gazers get involved with interactive tools and webcams.

It introduces the concept of internal recycling and systems-thinking, says Peterson. "It challenges people to think: what’s waste vs. what’s resource?"

Peterson says coming to this building is an experience—an experience that starts with a trip to the bathroom.  As a friend of mine who had visited the campus proudly told me, “Yep, I made a contribution.”


Explore a waterless way to deal with human excrement:  the composting toilet