[caption id="attachment_16651" align="alignright" width="288" caption="Napa sanitation looks at options for winery wastewater"][/caption]
NAPA – A new study of existing and planned winery process wastewater disposal in the industrial areas around Napa County Airport recommends Napa Sanitation District keep better tabs on the winery waste stream reaching the Soscol treatment plant and offer a lower-cost, local option for disposal of high-strength production effluent.
An engineering consultant suggested these two "management concepts" to help the district better manage projected increases in volume and strength of sewage over the next two decades and to help south Napa Valley wine operations avoid the cost of trucking waste to the large East Bay Municipal Utility District plant in Oakland.
"Once the current wineries are regulated and their discharges characterized, the logical second step is to address trucked waste currently off-hauled to out-of-county treatment facilities," wrote Monica Oakley of Oakley Water Strategies in the 28-page technical memorandum presented to the district board Nov. 4.
"If sufficient treatment capacity is available, direct injection of high-strength wastes into the anaerobic digester would benefit local wineries, increase NSD's energy production through increased methane production and provide an additional revenue stream to NSD that is currently lost to out-of-county facilities."
A number of airport-area wineries have all their process wastewater, or the strongest elements, trucked to Oakland because of the potentially steep cost of funneling it into the local sewer directly or treating the waste before discharging it there.
Wineries are charged based on waste volume content, which can be very high around harvest and potentially shut down biological treatment processes at the plant. So a number of south Napa wineries balance sewer fees with other costs and decide how much to treat waste on site before sending it to the sewer or having it trucked to Oakland, according to Napa-based civil engineers who develop such analyses and design treatment system.
Of the 43 wine-related businesses in the district's service area identified in the study, 33 are wineries varying in size from small-scale operations to commercial production, seven are tasting rooms or storage facilities for tanks and barrels, and three are casegoods warehouses.
Those facilities are estimated to produce nearly 80 million gallons of process waste water annually. Ten more facilities that are planned or finished recently account for about another 48 million gallons annually.
"It took us by surprise how many came in and how many there are to come," said General Manager Michael Abramson.
The consultant identified these two treatment options – status quo pretreatment and trucking strong waste directly to the digester – as being middle of the road in terms of cost to the district and wineries. They and the other six treatment alternatives will be analyzed as part of an 18-month effort to craft district master plans for treatment, recycling, automation and other operations through 2030.
By March 2010 the district plans to have a list of treatment-system alternatives and by July, capital-project recommendations as well as clarity on whether a second biodigester would be needed at the plant, according to Mr. Abramson. The plans are set to be completed in September.