Winery waste water could help battle drought

A groundbreaking study by researchers at UC Davis could pave the way for winery waste water to be used to irrigate vineyards, helping to overcome a lack of water in drought-stricken wine regions.

Water used in vineyards is typically fresh from the source, which in times of drought can be scarce. However a study by UC Davis has looked at the potential of using waste water, left over from cleaning equipment in the winery, to irrigate vines.

Titled “California Winery Wastewater Survey: Assessing the Salinity Challenge for Wastewater Reuse”, the study suggests that winery wastewater could be a viable water source, if it is treated correctly.

As part of their investigation, scientists at the University of California, Davis, assessed winery wastewater samples monthly over two years at 18 wineries in the Napa and Lodi regions of California, assessing its potential affect on the soil and resulting wine.

It concluded that under the right conditions waste water is a viable source to irrigate vineyards.

“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,’” said lead author and UC Davis researcher Maya Buelow.

“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.”

While many wineries already treat their wastewater, the biggest challenge to being able to use it to irrigate vines is its excess salinity, introduced into wastewater through cleaning agents. Salts are not removed by treatment systems and impact how water moved through soil.

Despite this obstacle the study found that, of the winery waste water samples tested, salinity levels were generally below the threshold of what would be considered hazardous to most wine grape rootstocks.

A solution, and trend already growing within the wine industry, would be to switch from sodium-based to potassium-based cleaners. This would most benefit soils dominated by montmorillonite, a clay mineral. However both types of cleaners would have a negative impact on soils dominated by vermiculite, a mineral. Neither type of cleaner reduced salinity infiltration rates in soils with kaolinite, also a clay mineral.

Speaking about the wider benefits of harnessing the potential of waste water, Buelow said: “This is very applicable to nearly every agricultural system out there. 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 winery wastewater survey was published in the American Journal of Enology and Viticulture.