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California North Coast wineries have been deftly employing the microscopic world to make world-class wine for four decades, but harnessing microbes to devour process wastewater has proved elusive for more than a decade. Now, Napa Valley’s Rombauer Vineyards is bringing in digester technology already successful at local craft breweries to turn waste into water and energy but with refinements that can overcome past challenges for the wine business.

Rombauer has inked a deal with Cambridge, Mass.-based Cambrian Innovation to install an EcoVolt two-stage system to clean wastewater to potentially reusable levels, and in the process producing biogas and generating electricity. Cambrian has similar systems currently running at Lagunitas Brewing in Petaluma, Bear Republic Brewing in Cloverdale and Seismic Brewing in Santa Rosa. A system is going into Russian River Brewing’s new Windsor facility, set to open next year.

Lagunitas also hired Cambrian to operate its wastewater processing under a 20-year contract.

“Very large wineries have settling ponds to let water settle out to eliminate some of the waste,” said Bob Knebel, Rombauer chief operating officer. “We do not have that space or capacity.”

Rombauer has been using the traditional winery wastewater treatment process of filtration with diatomaceous earth. But any planned increase in winery production also increases the need for storage of process wastewater to treat, he said.

And the vintner’s efforts to reduce water use for each gallon of wine to a proprietary level “notably below industry averages” has resulted in increasing the strength of the process wastewater to levels difficult to treat with traditional methods, Knebel said.

One metric for measuring the concentration of wastewater is biochemical oxygen demand. Typical household wastewater BOD is 110–350 milligrams per liter (parts per million), but high sugar content in winery wastewater pushes BOD from 5,000–20,000.

Using two units packed into ocean-going shipping containers, Rombauer’s EcoVolt system is being designed to first use an anaerobic digester, with specially selected bacteria to break down 80 percent to 90 percent of the organic material, producing biogas that can be used to fire boilers or generators as well as directly generating electricity, according to Baji Gobburi, vice president of sales for Cambrian. The second “polishing” unit removes organic trace compounds and produces water with BOD of 10–20 milligrams per liter.

Projected energy generation is 30 kilowatts.

Rombauer could opt to fully reuse the outflow by attaching a reverse-osmosis treatment system, Knebel said.

Around the dawn of the 21st century, Clos Du Bois in Alexander Valley was the first in the wine business to install an anaerobic digester. But the vintner eventually went back to a traditional system with ponds.

A big problem often cited against use of such digesters in the wine business is big ebbs and flows of wastewater throughout the year, forcing plant operators to bring in sewage sludge, also called biosolids, from businesses such as dairies to give the bacteria enough food to stay alive. And the “crash” of the bacteria colony may not be seen for days afterward, when the tested outflow water quality plummets.

Cambrian Innovation started in 2006 and went back to Clos Du Bois in 2012 for a 15-month trial of its system, treating 10 percent of the winery wastewater. Brian Hemphill, the winery’s director of operations during the testing, joined Cambrian as senior director of operations late last year.

The difference Cambrian is bringing to the wine business this time are the types of bacteria and how they’re monitored. Dissimilatory metal-reducing bacteria that can transfer electrons to metal oxides were discovered in the late 1980s and have been researched for microbial fuel cells and bacterial batteries.

Cambrian’s system uses these electrical emissions from bacterial digestion of waste to adjust the food supply during periods of winery inactivity, Gobburi said.

“Now we don’t have to babysit the bacteria and we hook them up to an EKG machine of sorts,” he said. “We don’t have to wait until the patient flatlines. We know our system’s health, because our bacteria constantly gives us information and data.”

The system uses a fixed-film bioreactor to grow bacteria most compatible with the waste involved from inoculations, rather than imported sludge.

Rombauer has engineering and planning underway to prepare the winery for installation of the EcoVolt system, likely to come after harvest this fall, Knebel said.

“It’s quite an extensive project, and we can’t risk the possibility of being down in wastewater processing during that time,” he said.

Cambrian Innovation is in talks with dairies and other food producers about trials and installations of EcoVolt systems.

Jeff Quackenbush (707-521-4256, jquackenbush@busjrnl.com) covers wine, construction and commercial real estate.