U team improves bioreactors to clean up fertilizer runoff

Researchers are using microbes to speed up the removal of excess nitrogen from runoff.

Keaton Schmitt

Long troughs of wood chips could soon clean runoff from fertilized farms because of the work of a University of Minnesota research team.
University researchers partnered with the U.S. Department of Agriculture to study bioreactors, which are large containers with microscopic organisms inside that enable chemical reactions, clearing nitrogen and other chemicals from waste water.
When water runoff moves through the bioreactor, microorganisms use up nitrogen compounds, releasing nitrogen safely into the air, said Gary Feyereisen, USDA engineer and University professor.
In some cases, the process can also remove sulfur compounds from the water.
However, current bioreactors only get rid of 30 percent of nitrogen from the runoff, and scientists don’t fully understand how to most effectively improve the technology, said Director of the University’s Biotechnology Institute Michael Sadowsky, who was also on the team.
“It sounds simple, but there [are] a lot of different things that have to happen for it to work right,” said Carl Rosen, a team member and University soil, water and climate professor.
And different conditions between reactors make running controlled experiments difficult, Sadowsky said.
“When people change stuff in the current reactors … [researchers] can’t do a true scientific study,” he said.
Last year, the team began work on a Wilmar, Minn., farm to divide a 360-foot bioreactor into smaller sub-sections to better control experiments, he said.
Feyereisen said now that the team has run initial tests after the build, they want to experiment with different microbe conditions.
“We’re really poised right now to start the experiments,” he said.
Rosen said possible changes include modifying the amount and flow of carbon needed to remove nitrogen or adding more and better microbes.
“We’re basically studying how to optimize the bioreactor,” he said.