.Algae Action

Prof teams up with Santa Rosa to scrub our water clean with . . . green


Nestled within the dry and brittle grasses of my yard, there is a green patch of earth, unexpectedly lush with a thick swath of large, leafed comfrey, towering borage and leggy peppermint. I don’t water this part of my yard; it just is this way. Lately, however, it’s been extra lush, suspiciously so for late summer, and so last week I bent down to feel the soil with my fingers. It was wet to the touch. There is no longer any mystery regarding where my wastewater goes. Shower water, bath water, dish water, washing-machine water, toilet water–it must all be right here, under a mini NorCal jungle.

I live outside city limits, but what about everyone else? Where does their wastewater go? Naturally, when I heard through the green vine that a Sonoma State University professor, a local green builder and the director for project development for the city of Santa Rosa have teamed up to install an experimental algae wastewater scrubber at Santa Rosa’s Laguna Treatment Plant, I simply had to go there.

Through a triad of interviews, I learned that there is a lot that happens to water once it goes to the Laguna Treatment Plant. It is filtered and treated, oxygenated, treated again and practically annihilated until it becomes, for all practical purposes, comparably innocuous. Next up, the water sits nestled in a 40-acre lake, where it oxygenates some more. Then it gets portioned off to farmers who irrigate their fields and wineries with it, or is piped to the Geysers–around 11 million gallons of it per day–where it is eventually converted into 85 megawatts of electricity per year. Oh, and sometimes, when the rains come, just a little bit of it, a sip, is let off into a couple of local waterways. No more then 5 percent. But still.

Though nearly half of the world’s population would find the finished product that comes out of the city’s Laguna Treatment Plant drinkable, the North Coast Regional Water Quality Control Board thinks this is not good enough. The treated wastewater, and we’re talking about up to 21 million gallons per day, still contains excess nutrients, nitrogen and phosphorous, predominately, that promote unwanted growth of plants in waterways, not to mention the entry of heavy metals into our ecosystems.

To help solve this problem, Dr. Michael Cohen, professor of biology at SSU, along with the help of graduate student Catherine Hare, have been studying the ability of algae to remove pollutants from treated wastewater. Dell Tredinnick, director of project developments for the city of Santa Rosa, looks specifically for green projects that can make, or at least save, money for the city. This is his job, and he’s obviously good at it, because when Dr. Cohen’s proposal crossed his desk, he approved the funding to build an experimental algae scrubber at the treatment plant.

Cohen had already been working for some time on a trial system at SSU, but in order for the project to grow, he needed a larger facility and ready access to treated wastewater. Contractor Bob Duckworth, a graduate of SSU’s green building program who specializes in energy-efficient building and design, was also fascinated by the possibilities of this project, and eager to team up with Cohen in order to make the algae scrubber a viable reality.

I met Duckworth at the treatment plant after work, ready to take on the visual challenge of witnessing millions of gallons of Santa Rosa’s finest. The sight of a lovely little brown duck, floating on the surface of one of the treatment pools, was indeed memorable, but not as memorable as what Duckworth showed me next. Contrary to the large processing reservoirs I first observed, the six shallow, algae-filled ponds are surprisingly full of life, and not in a creepy way like with the duck.

Duckworth explained how the treated wastewater flowing into the ponds is first dechlorinated through an oxygenation process and then fed, via a diagonal pattern, from pond to pond, all the while being scrubbed of toxins by algae and duckweed. Small fish dart just below the surface, and a couple of dragonflies dipped and swerved. I’ve probably swum in worse.

Over the next year, Cohen and his colleagues will study the system, test the water and vary the plant life in order to establish whether or not this could be the next best thing since the flushing toilet. As an added incentive, the harvested algae could be converted into biofuel, for the city’s fleet of work trucks, and into methane to fuel the treatment plant.

Ever the enthusiast, I asked Bob if I might be able to put a small-scale algae scrubber in my yard. The system would be an improvement over what I have going on now, and there’s something strangely soothing about the algae scrubbers–all of this revolting wastewater being transformed into something with fishes in it. It feels a little Zen. But Duckworth shook his head. This is not a science experiment meant to help a single person with a foundering leach field; it’s an experiment designed to help save the world.

Want to see it for yourself? Thirty-minute tours of Santa Rosa’s Laguna Wastewater Treatment Plant are available by appointment. 4300 Llano Road, Santa Rosa. Phone 707.543.3350


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