QUEST Community Science Blog

Unless our sewage happens to end up in the Bay and in the headlines, most of us probably never give a second thought to where our wastewater is headed each time we run the tap or flush the toilet.

To learn more about the travels of sewage, I took a tour of the Las Gallinas Valley Sanitary District treatment plant led by Plant Manager Matt Pierce. The plant has been in operation for about 50 years and serves over 30,000 residents in north San Rafael.

After leaving sinks and showers throughout the District, wastewater travels through a network of pipes and pump stations. Once the sewage arrives at Las Gallinas, it passes through an inlet screen and a grit chamber, which together remove much of the dense, inorganic material-”like diamond rings,” Matt jokes.

A lot of what happens at the plant is not that different from what happens in your compost pile: “It’s basically bacteria at work,” Matt points out. (The much bigger challenge for sanitation districts these days are all the unnatural things we’re putting down the drain: household chemicals, personal care products, pharmaceuticals.)

From the grit chamber the sewage heads into a series of clarifiers, where gravity causes the organic solids to settle out. The biosolids pass through a thickener and then an anaerobic digester-the most, ahem, aromatic stop on our tour. After further thickening in storage ponds, the sludge is injected into a disposal field.

Meanwhile, the liquid from the clarifiers travels through two biofilters, where rotating arms spray the water over rock beds. The organic matter in the wastewater is a feast for microbial slime living on the rocks. In the nitrification tower, more microorganisms break down the ammonia in the water. In the final stages of treatment, the wastewater is chlorinated to kill any remaining bacteria, then dechlorinated since the chlorine is toxic to many aquatic species. Finally, the treated water is sprayed onto District fields or discharged into Miller Creek where it flows to San Pablo Bay.

The District has done a lot to minimize the environmental impacts of its operations. The plant is powered by a field of solar panels. The methane released in the sludge treatment process is captured and used to generate power and heat the digester. Some of the treated wastewater supports acres of fresh and saltwater wetlands-in fact the District’s land is a favorite local gem for walkers and birders. And in a partnership with the Marin Municipal Water District, more than a million gallons of treated wastewater are recycled daily for landscape irrigation and other projects.

There are plans to make even fuller use of the reclaimed water. The Bay Institute-in partnership with the Sonoma County Water Agency, Las Gallinas, and three other North Bay sanitation agencies-has developed a plan to use recycled water for wetland and creek restoration and for agricultural irrigation. Legislation sponsored by Congressman Mike Thompson to establish the program passed the House late last year; Senator Dianne Feinstein has introduced similar legislation that we are hopeful will pass this year.

With California’s growing demands for water, such creative means to conserve and recycle are critical to helping prevent this precious resource from just going “down the drain.”


Ann Dickinson is Communications Manager for The Bay Institute (www.bay.org), a nonprofit research, education, and advocacy organization dedicated to protecting and restoring San Francisco Bay and its watershed, “from the Sierra to the sea.”

January and February are exciting months for movie buffs like me. And no, I’m not referring to Golden Globes, Oscar nominations, or Screen Actors Guild awards. I’m talking about two wonderful “green” film festivals, both right here in our own watershed: the recent Wild & Scenic Environmental Film Festival in Nevada City, and the San Francisco Ocean Film Festival.

For The Bay Institute, this year’s Wild & Scenic Film Festival was particularly exciting because it included the first public screening of “Taking Root,” a film-in-progress about our STRAW (Students and Teachers Restoring a Watershed) Project. I recently talked to David Donnenfield, who is co-producing the film with Kevin White (Kevin also has two films in this year’s Ocean Film Festival: Restoring Balance: Removing the Black Rat from Anacapa Island and Returning Home: Bringing the Common Murre back to Devil’s Slide Rock.) I asked David how the two came to be making a movie about kids working to save an endangered freshwater shrimp.

Taking Root is part of a larger project entitled How on Earth, which began with the goal to survey the spectrum of restoration work happening across the country. David and Kevin wanted to look at projects large and small, in different regions and involving different constituencies and different issues. They also were interested in documenting projects initiated by kids-one of the things that drew them to our STRAW Project, founded in 1992 by a class of fourth-graders.

David attended film school at UCLA (after he “got the bug” while starring in a high school film), but says he was always more interested in social issues than theatrical production. As to why he finds the topic of environmental restoration of particular interest, David points to the late environmentalist David Brower’s 3-part concept of “Global CPR”– Conservation, Preservation, and Restoration. While we’ve all heard about conservation and preservation, David notes, “We felt that very little of the story of restoration had been told.” That’s a critical oversight, since “in the face of worldwide environmental decline, there is less and less to preserve but more to restore.”

In talking about their process for making films, David explains that they do a lot of research up front to understand the issues, the players, and how the story fits into the “big picture.” But there is also that sense of “serendipity and discovery” when they actually get out into the field, and that’s a large part of what they bring back to the editing room.

And, in fact, editing is the next big challenge for Taking Root. Production on the full-length film (which will run about 1/2 hour) is nearly complete, but David and Kevin are still raising funds to complete the editing. Meanwhile, folks around our office are already looking forward to next year’s Wild & Scenic Film Festival, where we hope to be nibbling organic popcorn and cheering the completed film’s premiere.

Ann Dickinson is Communications Manager for The Bay Institute (www.bay.org), a nonprofit research, education, and advocacy organization dedicated to protecting and restoring San Francisco Bay and its watershed, “from the Sierra to the sea.”