Attention, Eco-Hipsters: The Next Big Thing Is Artisanal Wastewater

A new study says keeping the waste in wastewater can conserve water and lower carbon emissions.

(Photo: Justin Sullivan/Getty Images)

Jul 24, 2014· 1 MIN READ
Katharine Gammon has written for Nature, Wired, Discover, and Popular Science. A new mom, she lives in Santa Monica.

When the subject of recycled water—the stuff that comes out of your toilet—is raised, care is taken to stress to the squeamish that this “gray water” is fully treated before it’s sprayed on lawns and landscaping.

Now researchers have found that less is more when it comes to treating wastewater for use in irrigation. Instead of spending money and energy to remove nitrates from wastewater, leaving in a small amount is a two-fer: You can irrigate and fertilize—“fertigate”—at the same time to keep lawns green and growing. No trips to the garden store needed to buy fertilizer.

That’s important, given that the Western United States is suffering severe drought and as much as 70 percent of household water consumption goes to flora, not fauna.

The trick is adjusting the amount of nitrates left in wastewater to match seasons and growing conditions. Such customized water can help cities cut their carbon footprint, according to Bernd Leinauer, a turf grass expert at New Mexico State University and coauthor of the study, which was published in the journal Crop Science.

Pumping water to treatment plants consumes a large amount of energy, as does making fertilizer. “Since this is something already in the water, if we leave it in, we save a lot of energy,” said Leinauer of nitrates.

Drip irrigation systems would send the wastewater directly to plant roots, which also would save water and help eliminate the yuck factor for home owners.

Maintaining lawns in the arid Southwest may seem counterintuitive, but Leinauer said that grass bestows environmental benefits in desert climates. For instance, New Mexico State University is planting more grass to prevent erosion and dust storms. Grass can also create recreational opportunities.

“The economic return per acre-foot of water spent on golf courses is larger than for growing alfalfa,” said Leinauer.

At a test facility, Leinauer has found that turf plots drip-irrigated with customized wastewater are just as green and healthy as those receiving potable water and mineral fertilizers. While the results are promising, questions remain about how a system would work in rainier places, where excess nutrients could leach out of grass, creating pollution problems in downstream watersheds.

Lawns and turf grass cover more areas in the U.S. than any other plant, making them the most ubiquitous irrigated crop. Creative approaches to growing grass—especially in the Southwest—will only become more important in a warming world.

“We need to ask ourselves if population growth and urban sprawl in the desert in general is justifiable,” said Leinauer. “As long as people move to desert cities, having green spaces and irrigated spaces are absolutely important.”