Recently, Dwell had the opportunity to tour the San Francisco’s Public Utilities Commission headquarters, which seemed appropriate as we gear up for the special bathrooms and spas issue (hitting newsstands in early November). SFPUC recently revamped their building to be LEED Platinum and installed a wastewater management system called the "Living Machine."
Developed by Worrell Water Technologies in 1999, the Living Machine relies on biomimicry to convert black water to non-potable water, which can be reused to flush toilets and irrigate gardens. Unsurprisingly, black water comes from waste systems, like toilets, and must undergo a more rigorous cleansing system than mere graywater.
Although the Living Machine system isn’t cost-effective for a small home, it is a viable option for housing developments, schools, resorts, and offices, all of which produce high levels of black water. One has already been installed in housing development in Puget Sound, Washington for 25 houses. “What is unique about Living Machine Systems is that the system is built modularly and can expand as a subdivision or building’s needs expand,” explains William Kirksey, the Global Development Officer at Living Machine Systems and Senior Vice President of Worrell Water Technology.
Living Machine systems don’t provide an entirely closed loop system—water is lost through irrigation and drinking water must be pumped in – but it conserves approximately 60% of the water. At the Public Utility Commissions building I toured, this translates to over 750,000 gallons of water per year.
As this animation shows, the Living Machine System mimics the tidal estuary process. First, water is pumped into a tank where debris can settle and degrade. Then it is flowed into an equalization tank that determines the release of high and low “tides” into specially engineered gravel, sand, and plant boxes (wetland cells). The next two stages involve different tidal wave cells with different organisms that “eat” and purify the black water.
“Laboratory research allowed us to determine how to get maximum production out of the microbes, and unlike natural wetlands, we can pump water in and out about twelve to sixteen times a day,” says Kirksey. To remove any microscopic sediment that might have gone through, the water is screened one last time, treated with ultraviolet light and, in municipal buildings, lightly chlorinated to meet city standards.
As urban planners and architects continue to search for new ways to be environmentally sustainable, this is yet another option to ease off our dependence on fresh water. “It’s a natural model and is what we’ve reverted back to across different energy-saving platforms: lots of small components working together within a larger system,” says Kirksey.