When the new 13-story building for the San Francisco Public Utilities Commission (SFPUC) is completed in mid-2012, it will feature attractive exterior landscaping, just like any other large public building would. The key difference, however, is that the plantings will be part of an energy-efficient Living Machine system that will treat all the building’s graywater and blackwater for reuse on site, saving a projected 750,000 gallons of water per year, in addition to 500,000 gallons saved for irrigation.
Owned by Charlottesville, Va.–based Worrell Water Technologies, Living Machines mimic the processes of tidal wetlands to naturally treat wastewater in an easy-to-operate, self-contained system. The systems are small enough to be located entirely on site in most applications and do not produce the by-products associated with traditional wastewater treatment such as biosolids. “Our goal was to create a wastewater treatment system that was energy- and space-efficient,” says Eric Lohan, general manager of Living Machine Systems.
Most water-treatment systems use a process of pumping oxygen into large vats of wastewater, which produces significant sludge and is not energy-efficient, according to Lohan. Natural-treatment wetlands have been around for over 40 years, he explains, but on a larger scale—a scale that generally has not been appropriate for most suburban and urban applications. Other on-site treatment technologies, such as membrane bioreactors, may fit in a building basement, Lohan says, but they use a high degree of energy relative to their size.
“We were trying to find that middle ground so that our systems were small enough to use in suburban and certain urban sites,” he says, “but were much more energy-efficient than a membrane bioreactor.”
Living Machine Systems use a primary settlement tank and planted wetland cells lined with a gravel medium. Sequential wetland cells are filled and drained with wastewater about 12 times a day, mimicking tidal ebbs and flows. The process creates a biological interplay in which bacteria growing on the gravel medium and plant roots consume and remove the nutrients in the wastewater. When the water drains out, the basin is oxygenated, which promotes the rapid metabolism of more nutrients and solids. When the water completes the process (which might include a disinfection step in a separate tank, depending on the final use), it can then be repurposed on site for toilet flushing, irrigation, washing equipment, landscape water features, and other uses.
“Tidal wetlands tend to be the most productive ecosystems, promoting more biomass per square meter than a tropical rainforest,” Lohan says. “One of the reasons is because of the daily cycle. As the tides come in, nutrients come in, and as the tide goes out, oxygen comes in and provides a substrate for the bacteria.”
Living Machines were initially designed by a company called Living Technologies, which Worrell acquired in 1999. The first-generation machines were hydroponic systems that supported only tropical greenhouse plants and still used significant energy. After the acquisition, the company had enough capital for a new research and development effort that resulted in more-efficient next-generation Living Machines. Although it varies, the typical scale of the system is about 150 square feet for every thousand gallons of wastewater, Lohan says, with extra capacity built into the process. He notes that wastewater comes in many different concentrations, with lower-flow fixtures resulting in more concentrated wastewater. The systems can pump more cycles throughout the day if necessary, he says, and controls are Web-enabled so that operators can check levels using remote computers. Because there is no surfacing wastewater, Lohan adds, the potential for contact with human waste is eliminated. Fans are used to vent out most odors.
Hundreds of plants can be used in Living Machines, including a variety of native plants. The SFPUC building, for example, is located in an urban “canyon” with relatively little light. The team chose 12 plant species for that project, with the understanding that some of the species will do better than others and that only, say, eight of the 12 might ultimately thrive, Lohan says. “The good plants will take over,” he explains. “As we get more and more experience, it will become something of a self-designing process.”
To date, the company has installed over 30 Living Machines, including 15 of the next-generation model either operating or under construction. Projects range from the Port of Portland office building in Oregon and the Marine Corps Recruit Depot in San Diego to a demonstration project at Furman University in South Carolina and another in Ghana, Africa.
Lack of familiarity with the system during construction and occupancy is perhaps the biggest challenge for owners, says Laura Lesniewski, AIA, a principal with Kansas City, Mo.–based BNIM, which incorporated a Living Machine system into the Anita B. Gorman Conservation Discovery Center in Kansas City. (For more on this project, see eco-structure’s May/June 2010 Flashback column, “Natural Centerpiece,” at http://www.eco-structure.com/education-projects/natural-centerpiece.aspx) “Commitment by the owner to maintain the system—to treat it as a living system—is critical,” she says.
The benefits, Lesniewski says, include education, beauty, and biophilia within the building. Lohan adds that installing a Living Machine can contribute to several points under the LEED system, by reducing potable and irrigation water demand and by treating wastewater on site. “The Living Machine,” Lesniewski says, “showed that we do not need to treat our waste by sending it away, but instead could turn it into a beautiful and life-giving component of the design.”
Kim A. O’Connell writes frequently about historic preservation and sustainable design from Arlington, Va.