Nature's way: "Living machine" recycles nonpotable water

April 01, 2001 |

The Adam Joseph Lewis Center at Oberlin (Ohio) College incorporates a wastewater-treatment system-deemed a "living machine"-designed to recycle up to 2,000 gallons of the building's wastewater daily by mimicking nature. The system will also serve as a teaching tool.

The system consists of five components:

  • Anaerobic digester. Waste from the restrooms enters the anaerobic digester, where solids and fats are settled out. Anaerobic bacteria-microbes that "breathe" in the absence of oxygen-convert wastes into ammonia, methane and organic acids. Water then flows into a closed aerobic reactor.

  • Closed aerobic reactor. Here, aquarium pumps and diffusers aerate the wastewater, reducing the amount of organic material remaining by 90 percent.

  • Open aerobic tanks. Located in the solarium, these tanks hold plants-such as papyrus, calla lilies and willows root-that provide a habitat for protozoan and microinvertebrates that graze on bacteria and pathogens in the wastewater.

  • Clarifier. Here, wastewater entering through a baffle separates into clear water on top and a layer of sludge formed by bacteria. The sludge is returned to the closed aerobic tanks while a spillway sends the water to the wetland.

  • Wetland. The floor of the solarium is an artificial wetland, stocked with plants similar to those found in the open aerobic tanks. Here, protozoan and microinvertebrates further purify the water, which seeps from the east end of the solarium to the west end, where it is piped into a holding tank. An ultraviolet disinfection unit then eliminates any remaining pathogens and the water is collected into a pressurized holding tank where it is sent back through to the building's toilets and urinals.

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