A recent study at Clarkson University has found that wastewater treatment lagoons have the potential to serve as a local energy source.
Stefanie Kring, an environmental science and engineering Ph.D. student, discovered potential biofuel content in microbes that live in local wastewater treatment lagoons. She regularly visited the Canton aerated wastewater treatment lagoons during a summer research project.
Kring found the sunlit 8.5 acre lagoons full of planktonic (free-floating) organisms.
“These were the same types of organisms that we would normally see in any lake, river or pond nearby, except that here the biomass was much, much higher,” said Biology Professor Michael Twiss, who served as Kring's doctoral thesis supervisor.
Although the biofuel amount from these aerated wastewater lagoons is relatively small, these systems are found across the landscape in New York and elsewhere in the nation.
“At present, these lagoons are designed solely for wastewater treatment, but if the design could be modified to also serve the purpose of greater biofuel production then we may have found a productive path to satisfying some local needs for useful energy such as biodiesel,” said Professor Susan Powers, the Spence professor in sustainable environmental systems at Clarkson and co-investigator on the project.
Kring's analysis showed that the amount of algae was far lower than would be expected based on the high level of nutrients that were present. “How could this be and where were the algae going?” she wondered.
The answer lay in the numbers of zooplankton living in the lagoons. Zooplankton are shrimp-like crustaceans that feed primarily on algae in the water.
Normally, they are the middle step in an aquatic food chain that goes from algae to zooplankton to fish. “The lagoons contain some bottom-feeding fish, but they do not seem to be impacting the zooplankton population,” said Kring. This lack of predation allows zooplankton to proliferate, and exist in higher than average concentrations.
One of the biggest difficulties in using algae to make biofuels, like biodiesel, is getting the oil out of the algae, but the zooplankton can help.
“These zooplankton grow fast, they select algae from among all of the other particles present in the water, they break apart the algae in their digestive tracts and they preferentially accumulate the oil in their structures and eggs. Collecting zooplankton from water is much easier than collecting microscopic algae, due to their larger size," said Kring.
"Therefore, it will be less energy intensive to remove larger zooplankton from the water column, rather than microscopic algae.”
The results of her research were recently published in the journal “Environmental Technology.”