Reusing wastewater at vineyards won’t spoil wine

"This is a good baseline data set to look at and say, 'Now we know what's in our wastewater and what we can do to deal with it before we put it on the grapes,'" says Maya Buelow. (Credit: iStockphoto)

Making wine requires water beyond what it takes to grow grapes. There are bottles to wash, barrels to scrub, and floors to clean. But what if winemakers treated the water left over from all that cleaning and reused it to irrigate vineyards?

Researchers thought the idea had potential, but wondered if the wastewater might be harmful to the vines, the soil, or even the wine.

To find out, they assessed winery wastewater samples monthly over two years at 18 wineries in the Napa and Lodi regions of California. The conclusion of two studies suggests that under the right conditions, winery wastewater is indeed a viable water source to irrigate vineyards.

The first study, published in the American Journal of Enology and Viticulture, provides the first data to support the California wine industry’s reuse of treated winery wastewater, and describes recommended conditions for the practice, with a key focus on salinity issues.

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“This is a good baseline data set to look at and say, ‘Now we know what’s in our wastewater and what we can do to deal with it before we put it on the grapes,'” says Maya Buelow, a researcher at the University of California, Davis. “Vines are a high cash crop, and growers need to proceed with caution and gather site-specific soil and wastewater data, but there are wineries successfully doing this.”

Most wineries in the study were already doing a good job of treating their wastewater through a series of retention ponds and other treatment systems, the researchers say.

Salt concetrations, which affect how water moves through the soil, remain a challenge, however. Salts are usually introduced into the wastewater by cleaning agents and aren’t removed by treatment systems. But findings in the second study, published in Agriculture Water Management, show levels of salts at the wineries are usually below thresholds for most wine grape rootstocks and soil salinity hazards.

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There’s also a trend within the wine industry to switch from sodium-based to potassium-based cleaners. The study examined the risks and benefits of such a shift for specific soil types. The scientists emphasize that further research is needed to develop best management guidelines, but their results indicate that:

  • Soils dominated by montmorillonite, a clay mineral, could benefit from shifting to potassium-based cleaners.
  • Both types of cleaners may negatively affect soils dominated by vermiculite.
  • Neither type of cleaner reduced infiltration rates in soils with kaolinite, also a clay mineral.

“This is very applicable to nearly every agricultural system out there,” Buelow says. “Many other segments of the food industry produce significant amounts of wastewater, such as dairy, pig, poultry, and food processing operations. There are opportunities for them to reuse wastewater, as well.”

The Kearney Foundation of Soil Science funded the studies.

Source: UC Davis