Demand for reclaimed water will grow as will need to protect public health.

The answer to the question, “How do you use reclaimed water in a green building?” sounds the same as the punch line to an old joke: “Verycarefully.” What’s different is that the health consequences of using reclaimed water improperly can be anything but funny.

Sources for graywater such as showerheads, faucets and sink drains can provide a fertile breeding ground for waterborne pathogens. Roof-collected rainwater systems can become a suitable reservoir for the survival and proliferation of Legionella bacteria and may have led to cases of Legionnaires’ disease.

The need to recycle water in sustainable construction for non-potable – and perhaps even potable – purposes only will grow as the world’s consumption of water increases. A U.S. government report from March estimates global water demand likely will outstrip current sustainable supplies by 40% by 2030.

Last month, I told you about some of the actual and potential water savings revealed during the International Emerging Technology Symposium, held May 1-2 in Bethesda, Md. You can view the presentations by visiting

There you’ll notice a few speakers, such asDr. Janet StoutandTim Keane, address health concerns associated with some plumbing systems and products. Stout, a microbiologist and director of the Special Pathogens Laboratory at the University of Pittsburgh, says we could replace 7% of the world’s drinking water production by collecting and reusing graywater, rainwater and wastewater to flush our toilets, irrigate our lawns and wash our clothes.

She goes on to point out, however, that water from these sources can carry pathogens such as e. coli and Legionella. These sources include rainwater, collected directly from the sky or off a roof, and graywater drained from showers, sinks, bathtubs and washing machines.

Complicating the situation is that in the United States, Stout says, no federal standards control the quality of reclaimed water. It’s regulated by the states, not the EPA.

“Drinking water standards were developed for treated water and natural groundwater,” Stout says. “They may not be adequate for identifying potential pathogens in reclaimed water.”

Research has demonstrated that some methods of treating reclaimed water work better than others. Stout cites a British study that found ultra-filtration and reverse osmosis removed 99% of coliforms found in graywater, groundwater and roof-collected rainwater being reclaimed to flush toilets.

Treatment plays an important role in using reclaimed water. As an overall approach, though, Stout suggests these components:

  • Design the reclaimed water system properly;

  • Use appropriate materials to make the system;

  • Treat the water properly with disinfection materials and procedures;

  • Use the water appropriately;

  • Test water quality periodically;

  • Educate users about regulatory issues for the use of reclaimed water systems; and

  • Maintain and operate the system and the processes that treat the water in a consistent manner.

    Despite the health risks, avoiding the use of reclaimed water will not be a viable option as global water demand continues to escalate. As engineers, you must make sure the plumbing systems you design for green buildings incorporate safeguards to protect the public health as they use water more efficiently.

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