We all play a role in agriculture because we all eat and we all need clean water. Simple technologies like woodchip bioreactors can help meet both goals by helping farmers maintain good drainage and providing cleaner water downstream says Laura Christianson, Research Assistant Professor of Crop Sciences,University of Illinois at Urbana-Champaign:
Researchers studying ways to improve agricultural water quality have shown that we can use a natural process called denitrification to treat subsurface drainage water on farms. It relies on bacteria found in soil around the world to convert nitrate – the form of nitrogen in farm drainage water – to nitrogen gas, which is environmentally benign and makes up more than three-fourths of the air we breathe.
These bacteria use carbon as a food source. In oxygen-free conditions, such as wetlands or soggy soils, they are fueled by carbon in the surrounding soil, and inhale nitrate while exhaling nitrogen gas. Bioreactors are engineered environments that take advantage of their work on a large scale.
Denitrifying bioreactors on farms are surprisingly simple. To make them we dig trenches between farm fields and the outlets where water flows from tile drains into ditches or streams. We fill them with wood chips, which are colonized by native bacteria from the surrounding soil, and then route water from farm drainage systems through the trenches. The bacteria “eat” the carbon in the wood chips, “inhale” the nitrate in the water, and “exhale” nitrogen gas. In the process, they reduce nitrogen pollution in water flowing off of the farm by anywhere from 15 percent to over 90 percent.