Cal Poly students study how algae can cut wastewater treatment costs
In more than a dozen large tubs at the San Luis Obispo city wastewater treatment plant, Cal Poly students and scientists spend a lot of time studying green-tinted water.
The tubs are filled with wastewater, and algae is allowed to grow in an effort to remove contaminants from the water. The study aims to find out whether the algal-treated wastewater is a more efficient and effective way to recycle the dirty water than traditional methods.
And the study has two end products: clean, treated wastewater and algae that can be used for bioplastics, biofuels or fertilizers.
“I like being a part of something that is going to help make things more sustainable in the future,” said Carly Lesne, a graduate student who spends about 20 hours a week researching the algae-filled wastewater.
Lesne works alongside several other Cal Poly students on the project in the university’s Sustainability Utilities Research and Education program, which offers research opportunities to students of all experience levels.
The university has been studying the use of algae to treat wastewater since about 2007 and has been supported by grants from the California Energy Commission, U.S. Department of Energy and private companies over the years.
“The algae, just like any other plant, they’re just teeny tiny microscopic plants, they produce oxygen and they take in CO2 and take in sunlight,” Lesne said. “Combine that with bacteria, and they can help treat the wastewater.”
This method could prove to be less expensive and use less energy than the typical methods of treating wastewater — such as pumping it with air or adding harsh chemicals.
“I describe these things as kind of like biological solar panels that soak up the sunlight and do something good for us: generating oxygen; sucking up polluting nutrients out of the water,” said Tryg Lundquist, a Cal Poly professor and director of the Sustainability Utilities Research and Education program.
The Cal Poly team has also recently begun researching special types of filamentous algae and their effectiveness in removing specific minerals such as phosphorus from wastewater.
Then, the resulting biomass is sent to an outside company that creates bioplastics, which in turn sells it to other companies to make products such as shoes, Lundquist said.
Although the Cal Poly project receives wastewater from the city of San Luis Obispo, ratepayers are not impacted, and the algal-treated wastewater is then sent through the city’s treatment system.
That’s to ensure the wastewater goes through an approved treatment process before it’s sent out for irrigation or construction projects.
The Cal Poly algae project represents “an incredible partnership” between the city of San Luis Obispo and the university, said the city’s deputy director of wastewater, Chris Lehman.
“No other wastewater agency in California does this,” he said. “We benefit from Cal Poly’s data, the industry benefits from the research and the students benefit from gaining experience. It’s pretty cool stuff.”
Lehman added that the research conducted by Cal Poly helps the city work toward its climate action plan, as it has provided them with more innovative ways to efficiently and effectively treat wastewater. While the city is currently at the mercy of the chemicals and technology available to it for treating the wastewater at certain mandated standards, if the university’s algae research proves successful and scalable — the city could implement it, he said.
The latter is proving to be a particular hurdle for the city, which takes in about 3.4 million gallons of wastewater each day, while Cal Poly’s algae project treats roughly 20,000 gallons each day, Lehman said.
“The algae project is just one thing of many projects Cal Poly is doing at our facility,” Lehman noted. “We’re learning together how to do this more efficiently. The students have put forth some really innovative and out-of-the-box thinking that we’re excited about.”
