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.”

In Silicon Valley, a battle between neighbors has turned into a different kind of face off: solar energy versus trees. It turns out that growing redwood trees can actually be a crime in California, if they block solar panels… as one couple in Sunnyvale found out the hard way. David Gorn reports on a new kind of legal battle — the struggle over who has the right… to sunlight.

You may listen to the “The Right to Sunlight: Solar vs. Redwood Trees” Radio report online, as well as find additional links and resources.

Andrea Kissack is Senior Editor for QUEST at KQED Public Radio.

It would be easy to think that the 2007 Energy Bill, signed by President Bush at the end of last year, was all about automotive fuel economy. The legislation that requires fleet-wide average fuel economy for cars and light trucks to reach 35 miles per gallon by 2020 has generated a lot of buzz. On the negative side, the lack of strong support for renewable fuels such as wind and solar has generated some buzz as well. I cannot find anything in the Bill about renewing solar and conservation tax credits for homes, and that is a big, big omission.But there is a lot in the bill that is positive for residential buildings–not enough to tackle problems like our addiction to fossil fuel and the specter of climate change, but certainly a step in the right direction.

Here are some home energy highlights, thanks to a summary of the bill by the Alliance to Save Energy, a nonprofit coalition of business, government, environmental, and consumer leaders:

Appliance energy efficiency: The bill establishes new external power supply efficiency standards, based on the standards of California and other states; updates and creates new appliance efficiency standards and test procedures and provides for a regular review of those procedures; updates boiler efficiency standards and creates an electricity use standard for furnace fans; creates regional, climate-specific standards for furnaces, air conditioners, and heat pumps; requires DOE to include consideration of energy consumed while in standby mode for appliances already addressed by efficiency standards in their active mode; and directs the Federal Trade Commission to require energy labels for televisions, personal computer monitors, cable and set top boxes, and digital video recorders.

Building efficiency: The 2007 Energy Bill directs DOE to set standards for manufactured housing that are at least as stringent as the International Energy Conservation Code (IECC) national model code. There are also lots of provisions to increase the energy and water efficiency of government buildings and to create green building demonstration projects. The latter’s effect on housing? The government’s purchasing power moves whole industries–in this case it moves the building industry in the right direction.

Lighting: The Energy Bill directs DOE to set performance standards for general-service light bulbs to achieve a 25%–­30% savings compared to incandescent bulbs by 2012–14. The bill also directs DOE to establish Bright Tomorrow Lighting prizes for the development of solid-state lighting.

Green jobs: The Energy Bill authorizes a Department of Labor energy efficiency and renewable energy worker training program, and establishes within the Office of Solar Energy Technologies a grant program to create and strengthen solar-industry workforce training and internship programs for installation, operation, and maintenance of solar-energy devices.

The bill also supports the recommendations offered by a group from Lawrence Berkeley National Laboratory, including that of Home Energy Magazine Technical Editor Steve Greenberg, for greening the capitol complex, a set of buildings in Washington, D.C., including the Capitol, office buildings, and the capitol complex power plant. No mention is made of hot air energy recovery efforts from the chambers where Congress does its business.

Jim Gunshinan is Managing Editor of Home Energy Magazine. He holds an M.S. in Bioengineering from Pennsylvania State University, State College, Pennsylvania, and a Master of Divinity (MDiv) degree from University of Notre Dame.

latitude: 37.6871, longitude: -121.697

If investment is any guide, California’s renewable energy companies are leaping into the new year. Investors poured billions of dollars into clean tech in 2007 to catapult green technologies to market. In the first three quarters of 2007, U.S. venture capital firms invested $2.6 billion in clean tech companies. That’s compared with $1.8 billion for all of 2006.

Over the past year, a few types of renewable energy have seen a lot of attention. One is solar thermal power - a form of energy that hasn’t been built in decades. In the 1980’s, several large solar thermal plants were built in the Mojave Desert. The technology sounds pretty simple: Mirrors are used to reflect sunlight onto on a liquid or substance, usually water. The water is super-heated by the sun and bingo - becomes steam. The steam is then used to turn large turbines. California utilities are starting to look these plants again, and companies like Ausra in Palo Alto and BrightSource Energy in Oakland are benefiting.

Thin-film solar is another area that has gotten a lot of buzz. Only a few companies are currently selling thin-film. While today’s panels aren’t quite as efficient as silicon solar cells (the kind you see on rooftops), many are hoping they’ll be cheaper and stronger. That makes it easier for companies to manufacture Building Integrated Photovoltaics - building materials like roof tiles with solar built-in.

Energy efficiency is another area companies are getting into, and in this case, it’s energy management. Several companies are working on devices would manage energy use in your home. They could feed power from a solar system back to the grid and turn on your appliances late at night, when power is cheapest. PG&E is taking a step forward by installing Smart Meters in homes now - new digital electric meters that provide real-time data to customers and utilities. After that comes real-time electricity pricing for those who want it, meaning it’s not just how much you use, it’s when you use it.

You may listen to the “The New Clean Tech” radio report online, as well as find additional links and resources.

Lauren Sommer is an Associate Media Producer for QUEST.

latitude: 37.2647, longitude: -121.79