From Wastewater to Recycled Water

Interview with Chris Francis, Lab Manager at NapaSan by Craig Smith

Most people probably don’t think twice about what happens to water when it goes down the shower drain or when the toilet is flushed, and they don’t have to. For the past 75 years, that’s been the job of the Napa Sanitation District (NapaSan) and they’ve got it covered.

Prior to the formation of NapaSan in 1945, raw sewage flowed directly into the river. Low oxygen levels caused a massive fish kill, and the smell of decaying fish and sewage was too much to bear. Today, NapaSan treats 10M gallons of water daily. Over 700 million gallons of the water received is recycled every year, and from November through April, some treated water is discharged to the Napa River.

Chris performing river sampling (left), Tara McClinton in the lab conducting bioassay (center), biosolids being spread on NapaSan ranch land (right)

Chris performing river sampling (left), Tara McClinton in the lab conducting bioassay (center), biosolids being spread on NapaSan ranch land (right)

The safety of that water is assured in part by Chris Francis, who oversees NapaSan’s laboratory, pretreatment program, and all interaction with regulatory agencies. It’s his job to make sure that NapaSan’s treatment efforts are effective and that discharged water won’t harm the public or the environment. That includes working with local industries to ensure their wastewater doesn’t threaten NapaSan’s infrastructure, employees, or the Napa River.

Francis is Napa born and raised. At Vintage High, teachers influenced him to pursue science, and he majored in Applied Ecology at UC Irvine. His career direction was set by a class called “Conservation in the American West.” “We talked about how man and nature coexist, and how vitally important that relationship is,” said Francis. After graduation, he started working in the Water Division at Orange County Public Health. He enjoyed the work, but missed Napa.

“I moved back and taught science at Vintage for two years. It was a great experience, but I realized I’m not cut out for a career as a teacher.” Francis began working at Dey Labs, doing pharmaceutical quality control. The work was interesting, but he increasingly wanted to get back into water. “I never thought much about waste water,” he said of his current position at NapaSan, “but thirteen years later, here I am. And it’s great. There aren’t many areas where the relationship between man and the environment is more intimate than how we manage our waste.”

NapaSan is a state-of-the-art tertiary treatment facility that treats all of the wastewater for the City of Napa. The process begins when the water goes down the drain in your home. It feeds downward into a 270 mile pipe system. With the help of three pump stations, the wastewater eventually arrives at NapaSan’s treatment plant, the Soscol Water Recycling Facility. Once there the water is screened for solids and clarified before moving on to Aeration Basins for biological treatment. The wastewater is diffused with air bubbles to promote the growth of bacteria and other microorganisms. These microbes consume organic material and nutrients in the waste. The treated water is clarified once more, filtered, and disinfected through chlorination. From here it is distributed to Recycled Water users or de-chlorinated and discharged to the Napa River. The whole process takes under twenty-four hours.

The success of Napa’s program goes hand-in-hand with our large agriculture footprint. Vineyards use much of the reclaimed water. Most of the solid waste avoids landfill and is beneficially reused as fertilizer for animal feed crops such as sorghum and alfalfa on NapaSan’s ranches.

One of NapaSan’s goals is to maximize resource recovery. “We currently meet 50% of our energy needs with renewable energy produced on-site. Methane gas from our anaerobic digester is captured and converted to electricity that we use to power our operations along with the energy generated by our 1 Megawatt solar array,” Francis said. In addition to producing energy from the digester gas, NapaSan recycles as much water as possible every year to be used for irrigation of vineyards, golf courses, farmland, commercial landscaping, school yards, and cemeteries. Use of this water saves potable water from being used for irrigation and reduces demand on groundwater supply.

NapaSan is a forward thinking agency that takes its role as a steward of public health and the environment very seriously.

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It's That Time of Year Again

This month the Friends' annual fundraising letter goes out.  In these pandemic times, it seems more important than ever to continue our work.  For the past 25 years the Friends of the Napa River have advocated for a Living River and the restoration of historic marsh, riparian, and wetland habitat on your behalf. 

With your support, the Napa River escaped becoming a channel lined with endless concrete walls through the City of Napa and instead has wetlands, a new Oxbow Commons Park in the heart of downtown, and other features to handle floodwaters. Your support helped facilitate Napa Creek flood control; Rutherford-to-Oak Knoll river restoration; flood control and water projects in Yountville, St. Helena, Calistoga, and American Canyon; and on and on.

As the needs of our watershed and the Living River projects evolve, Friends of the Napa River remain focused on two key activities: advocacy and connecting youth and the community with our watersheds.

Donate today and become a Friend of the Napa River!

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Groundwater and the River, continued

We were talking last month about the California Sustainable Groundwater Management Act (SGMA), which was passed in 2014.  As you may recall, this has required Napa County to take a close look at the way we use groundwater.  Last summer the County began an intensive process to develop a Groundwater Sustainability Plan (GSP) for the Napa Valley subbasin of the Napa River, scheduled for completion in November 2021, exactly one year from now.  The process includes a public advisory committee; the Friends of the Napa River are represented on that committee.

I mentioned the distinction between gaining and losing streams.  These terms describe the relationship between flow in a surface channel like the Napa River and the underlying water table.  If the two are in hydraulic contact - if there is no intervening geological barrier - then either the channel is fed by groundwater or the reverse happens, depending on whether the water table slopes toward the stream (for a gaining stream) or away from it (for a losing stream).

The water table near a flowing stream is typically adjacent to it.  But sometimes the two are disconnected, as in the first diagram below.  In this picture, the ground all around the streambed is not saturated with groundwater, so you can see that water is going to soak into it at some rate. 

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More commonly, the relationship is more direct than that, and changes in the water table can clearly affect flow in the stream.  The next diagram illustrates the depletion of surface flow by groundwater pumping.  This stream might be a losing stream anyway, but the effect is intensified by pumping.  The wells shown in the diagram each create what is called a cone of depression, as the surface of the water table slopes more steeply downhill in the vicinity of the wells.  Depending on various factors, including how close the hydraulic connection between stream and well is, this situation could lead to undesirable depletions of surface water, one of the possible undesirable results the GSP aims to prevent.

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Napa County's GSP will include an expanded network of monitoring wells, and there will be new modeling and analytic tools as well.  It will be important to monitor surface water flow as well, to fine-tune our understanding of the interface between surface and ground water.  And there is also the issue of groundwater-dependent ecosystems, which must also be considered in the sustainability plan. 

There's a lot of work to do here. The Friends appreciate the efforts of County staff and their consultants, and of the many citizens contributing to the work of the public advisory committee. Thanks also to the Nature Conservancy, for the use of these excellent visuals.

Bob Zlomke

Link to Groundwater and the River, part one

What Happens after the Fires?

Everyone's yearned for the end of this year's fire season, which has once again offered painful proof of the changing climate. But what to do when this year's wildfires are finally behind us? Here are a couple of thoughts.

Very often, the best response is to rely on the landscape to heal itself. Nature's restoration work is flawless, in the end. However, we need to stay out of its way, because there can be unexpected dangers from flash floods, debris flows, and other unusual conditions, as well as damaged infrastructure.

After many wildfires, California state Watershed Emergency Recovery Teams (WERTs) are deployed to conduct post-fire assessments. When their reports are available, they offer the best information on threats to life and property after the fire. You can find out more on the Napa County website; the WERT report for the recent Hennessey fire is available here.

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