Rethinking Winery Wastewater

The sustainability movement has taken hold in California wine country, where environmentally friendly winegrowing practices are slowly becoming the rule rather than the exception. There’s even a green certification system. But in one area — wastewater — there’s plenty of work to be done. On average, wineries create 6 gallons of wastewater for every gallon of wine, a fact that explodes the notion carried by the common bumper sticker “Conserve Water, Drink Wine.”

A recent article in SF Gate offers a thorough look at the wastewater challenges faced by California wineries — and the potential solutions available to deal with them.

It’s not hard to imagine a solution. Wineries all own vineyards or buy from them. Vineyards need water.

Problem solved, right?

Not quite. Microbes can break down the grape juice and plant matter flushed into the water, but they need oxygen to do it. That’s not the problem. The problem is how much oxygen those microbes need, a measurement called biochemical oxygen demand (BOD). In winery waste, there’s not nearly enough supply for that demand.

“Winery wastewater obviously has lots of suspended solids,” [Sheldon Sapoznik, Napa County’s land use development supervisor] says, “and that means there’s a lot of BOD. We require that BOD be down to less than 50 before irrigation.”

To put it in perspective, wine wastewater has an average BOD of 2,500 to 10,000. Human sewage has a BOD of only 150 to 300. 

The most common treatment method is a pond. Pump the wastewater into the pond, aerate it with motors, and in 60 to 90 days you have clean water. The problem? The ponds are ugly, noisy and smelly.

Another option is a leach field (an underground septic system) but it only works for certain soil types, and the treated water isn’t available for irrigation. Also available are hydrate systems — tanks with filters that remove big solids and oxygen pumps that let microbes break down the rest — which take up relatively little space and pass Napa’s notoriously tough agricultural rules. But hydrate systems are expensive and they require maintenance.

Maybe the most promising solution lies in rethinking the pond. Rather than digging a rectangular hole and dumping water in it, the Parducci winery in Mendocino built a full-on wetlands zone, which has become a magnet for wildlife and a popular attraction for tourists. Inspired by the amazing natural filtering abilities of the Everglades, the Parducci wetlands system uses native grasses to pull out metals and residual grape sugars. Over 22 species of animals now call the wetlands home. 

(via SF Gate)

Photos: Greywater recycling at Parducci winery in Mendocino, California. (via Treehugger)

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