Using algae to treat wastewater could be an innovative way for small communities across the country to save energy and keep pollutants out of the environment, according to new research from Clemson University’s College of Engineering and Science.

Scientists have long known that algae can remove certain pollutants from water and be harvested to create biofuel, but the Clemson study was the first to find several other environmental benefits.

Muriel Steele works in the lab.

Muriel Steele works in the lab.
Image Credit: Clemson University

The Clemson team analyzed five wastewater treatment scenarios and the environmental impact of each. Ph.D. student Muriel Steele led the study under the advisement of David Ladner, an assistant professor of environmental engineering and Earth sciences.

Steele said what excited her most about the study is that it analyzed the tradeoffs of various treatment methods.

“A lot of people think of ‘environmentally friendly’ as meaning one thing,” she said. “But I like to look at tradeoffs. Treating your wastewater to this pristine effluent seems like the environmentally friendly thing to do, but if it takes a lot of energy, is it necessary? I like weighing options.”

Researchers found that using algae during the primary stage of the treatment process was most promising.

It would require the least amount of energy and reduce carbon dioxide emissions that are mainly responsible for global warming.  The method would contribute the least to ecotoxicity, which is what happens when chemicals harm the environment.

It was second best in preventing eutrophication, which occurs when excessive fertilizers run into lakes and rivers. The nutrients in those fertilizers can cause an explosion of plant growth that sucks the oxygen out of the water and can kill fish.

“Not only can the algae remove nutrients, but they can help decrease environmental impacts from other wastewater treatment unit processes,” according to a paper the team had published in Environmental Science: Processes & Impacts.

“This has not been articulated previously, so the work presented here represents a paradigm shift for the many investigators looking into growing algae by reclaiming nutrients from wastewater.”

Researchers did caution, though, that the treatment method they found most promising would require lots of land because the tanks that hold the wastewater would have to be much shallower than those at a traditional treatment plant.

The shallower tanks would allow the sunlight to penetrate the wastewater and sustain photosynthesis needed for the algae to grow.

One of the main reasons to explore algae use in small systems is they are often in rural areas, where land is more readily available than in urban areas, researchers found.

Another cautionary note from researchers was that the method would require treatment plants to put wastewater through “primary sedimentation” to remove solids. Many small plants do not have the needed equipment and instead use other processes to treat solids.

David Freedman, chairman of the Department of Environmental Engineering and Earth Sciences, congratulated the team on a job well done.

“This was a creative way to analyze wastewater treatment,” Freedman said. “The study broke new ground and could lead to more sustainable treatment methods. It’s terrific work.”

The Clemson team was the first to look at how algae could be worked into wastewater treatment and to also do a broader “lifecycle assessment” that considered how each scenario would affect ecotoxicity, energy consumption, eutrophication and global warming.

“We’re definitely the first to look at some of the details of the process engineering and connect that with life cycle assessment,” Ladner said.

To ground the study in a realistic scenario, researchers used the Cochran Road Wastewater Treatment Plant in the City of Clemson as a model. It serves a population of 6,680 customers and is typical for systems found in rural areas.

The team reported its findings last year in Environmental Science: Processes & Impacts. Authors were Steele, Ladner and Annick Anctil, who was an assistant professor at Clemson before taking a position at Michigan State University.

Researchers called for further lab and pilot-scale research to move the technology into the real world. Steele said she is now turning her attention to lagoon wastewater treatment systems in Utah.