The University of Massachusetts Amherst
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NSF CAREER Program Funds Butler’s Pioneering Research Using Algae and Bacteria for Wastewater Treatment

Caitlyn Butler

The influential National Science Foundation Faculty Early Career Development (CAREER) Program has awarded Assistant Professor Caitlyn Butler of the Civil and Environmental Engineering (CEE) Department at the University of Massachusetts Amherst $500,000 to pursue her pioneering research on special “Algal-Sludge Granules,” which can produce their own oxygen during wastewater treatment, thus cutting electricity consumption in half, while also cleansing wastewater.

Butler’s CAREER project, which will study the relationship between algae and bacteria in Algal-Sludge Granules, dovetails with additional research she is conducting with CEE Associate Professor Chul Park. Their collaborative research promises a three-way fix for wastewater treatment. Their proposed process could provide a groundbreaking new way to eliminate harmful organic compounds and nitrogen from wastewater, slash the huge energy bill for wastewater treatment, and even make green biofuels as a byproduct.

As Butler explains, “The potential benefits of our proposed process are, number one, there would be this huge energy savings, because the algae would provide the oxygen needed to drive the secondary treatment process [the phase when bacteria and nitrogen, among other things, are removed from wastewater]. The second benefit is that, out of this process, algal biomass could potentially be harvested from the secondary treatment and used as biofuel feedstock.”

One ongoing problem addressed by the cooperative research of Butler and Park is that a whopping two percent of the country’s electricity is used to generate the abundant oxygen needed in wastewater treatment plants. What’s more, wastewater treatment is becoming increasingly energy-intensive as treatment requirements become more stringent.

For her CAREER project, Butler is specifically studying how bacteria and algae work together in these energy saving Algal-Sludge Granules.

Technically speaking, an Algal-Sludge Granule treatment process employs aggregate biofilms of eukaryotic microalgae and prokaryotic bacteria to achieve organics and nitrogen removal from wastewater. The Algal-Sludge Granules are oxygenic, thus eliminating the requirements for aeration. They are large aggregates (0.5-1 cm in diameter) that settle easily. The proposed process would occupy a smaller treatment footprint than many algae-based wastewater treatment systems.

In that context, Butler’s NSF CAREER project seeks to understand the fundamental relationships between the algae and bacteria in the Algal-Sludge Granules, further enhance treatment efficiency, and demonstrate the resilience of the process.

Butler’s NSF research will demonstrate the mechanisms by which the algae and bacteria aggregate to form the granule and the structural integrity of different granule morphologies and how physical characteristics relate to performance and microbial ecology.

As Butler explains, “One thing we are doing is studying how these granules function under conditions of stress. For example, in wastewater treatment facilities, there are seasonal fluctuations in the wastewater stream. Will these fluctuations change the ecology of the granules? Will the granules behave the way we would like them to? So we want to find out how these granules function under different forms of potential stress.”

Butler’s hypothesis is that the granules are very adaptable, so that even though the content of wastewater is very different at various times of the year, she believes they can adjust to those changes.

“So we’re going to try and mimic those conditions in the lab and see what happens,” says Butler. “We will use a simple kinetic model and recreate those wastewater conditions in the lab and use micro-sensors to measure the oxygen concentration and other characteristics in the granules and thereby measure the gradient of change.”

In parallel with her research, Butler will work with a teacher from the Clarke Schools for Hearing and Speech to build technical literacy in hearing-impaired students, using the highly visual components of algal granules to teach concepts of mass-balance, environmental contamination, and water and wastewater treatment. (March 2015)