Several farmers in the Chesapeake Bay region are testing a new conservation practice that can reduce nitrogen coming off farm fields’ drainage systems.

The practice is called a bioreactor. Instead of surface water from the fields collecting in a drain or ditch and discharging to streams and rivers, the collected water flows through a pipe that takes it to a buried trench filled with wood chips. The wood chips are a substrate for bacteria that digest the nitrogen. Then, the denitrified water continues flowing out the other side of the wood chip “box.” Thus, what ultimately runs off the farm fields has much less nitrogen in it.

The technology is designed to mimic the natural processes found in a small stream where vegetation and small organisms take up nitrogen in the water and then send cleaner water downstream. It also mimics some of the denitrification technologies used at sewage treatment plants and at digesters on dairy farms.

Research on the practice in the Midwest showed that bioreactors reduce the nitrogen flowing into waterways 30–50 percent in an average rainfall year. With the Chesapeake Bay watershed states under pressure to reduce pollution loads from agriculture, officials said the bioreactor could become a standard practice.

“We’re really excited about it,” said John Rhoderick, the administrator of operations for resource conservation at the Maryland Department of Agriculture.

“It’s early, but I’m really hopeful that this will work out.”

Denitrifying bioreactors have been around since the 1990s, when scientists in Canada began looking at the technology to reduce nitrate from septic systems. Around the same time, New Zealand researchers began using sawdust to reduce nitrogen in groundwater.

Midwestern researchers began looking at the technology in 2001. By 2011, 30 bioreactors were in the ground from Minnesota to Illinois, according to Patrick H. Willey of the National Resources Conservation Service, the environmental arm of the USDA.

At Iowa State University, agricultural engineer Laura Christianson was studying the bioreactors and their efficiency. She was impressed by their ability to reduce the nitrogen flowing into them 30–50 percent. When the Conservation Fund offered her a position developing bioreactors at its Freshwater Institute in Shepherdstown, WV, she was thrilled to have a chance to help export the technology to the Chesapeake Bay watershed. The Freshwater Institute applies research, engineering and economic development expertise to solve water resource management problems. Christianson said she is working on developing six as demonstration projects.

“We now see a lot of potential for these treatments on The Shore,” she said. “And it doesn’t take land out of production, so the farmer can farm over the entire reactor.”

Virginia Tech researchers installed the first of the Delmarva Peninsula’s bioreactors in 2012 on a farm in Painter, VA. Rhoderick and Louise Lawrence, chief of research conservation at Maryland’s agriculture department, were following the progress there.

So was Drew Koslow, the Choptank Riverkeeper. Koslow has already helped some Shore farmers put in ditch water-management structures using environmental grant money. He wondered if he could get funds to put in bioreactors, then monitor them over several years to see how much they reduced nitrogen. If they worked, Koslow reasoned, the practice could become part of the cost-share program — meaning the state department of agriculture would help farmers put in bioreactors just as it does with cover crops and grass waterways.

Rhoderick and Lawrence wanted to see where the research would lead on Maryland soils, as Midwestern states have different hydrologies and typically allow greater nitrogen applications. Koslow received a $50,000 grant from the Maryland Department of Natural Resources to put in the practices at two farms.

His first candidate for the bioreactor was Richard Edwards, a Caroline County dairy farmer. Koslow was already monitoring the water near Edwards’ farm as part of a subwatershed study, and he noticed high levels of nitrate flowing into a creek near the farm that was a tributary of the Tuckahoe River.

Koslow asked Edwards if he would be interested in trying the bioreactor. Edwards agreed. Developing the bioreactor was a challenge, Koslow said. He’d never done one before, and he had to get parts from Iowa and Oregon. Christianson helped him with the plans, and he also consulted Virginia Tech researchers, but planning and design was more involved than he anticipated.

MDA officials said they don’t know how much nitrogen reduction will come from the bioreactor, as this project marks the first time one will we be monitored in Maryland, and the Midwest is too different for comparison. Tom Fisher of the University of Maryland Center for Environmental Science Horn Point Laboratory will monitor the nitrate levels over the next several years. But before the installation, Koslow measured Edwards’ discharges at about 30 milligrams per liter, which is about what sewage treatment plants discharged in the 1970s. Now, the gold standard in the Chesapeake Bay is 3 milligrams per liter.

Koslow said Edwards’ bioreactor cost $19,000 to design and install, and construction took two days.

“You put this in the ground and basically leave it for 15 years, and it’s going to do its thing,” Koslow said.

Koslow had enough money on his grant for another bioreactor project. He contacted Bill Mason, a crop farmer in Ruthsburg, a rural crossroads in Queen Anne’s County. Mason farms 600 acres, most of it organic, growing corn, soybeans, barley and wheat. Known as a conservation-minded farmer, Mason has worked with Fisher and scientists from Penn State University, who have installed different cover crop practices on his farm.

Mason wasn’t familiar with the practice, but said he was game to try it.

“We’re much in favor of water quality and try to do best management practices on our farm and try to do the best job we can do,” Mason said. “We didn’t have a whole lot of information about it. But with the info we did have, we thought we’d like to try it. We thought it might be good to be in the forefront. If it does work, it would perhaps help other farmers.”

Mason’s project was easier than Edwards’, because Koslow had done it once before, but December’s snow delayed installation by a few days. Koslow recently received a grant from the Chesapeake Bay Trust to install a third bioreactor.

It will take a few years of monitoring and more installations until state officials can be sure that the bioreactors deliver on their promise.

Koslow hopes the bioreactors will become part of Maryland’s agricultural cost-share program soon, but he also has bigger plans; he’d like to see bioreactors built across the watershed as well as acknowledged in the Total Maximum Daily Load’s pollution diet as a practice that reduces nitrogen. He sees many advantages: low cost, little required maintenance, long life, no land taken out of production and effectiveness in all-weather situations.

“Our goals are larger than working on just one farm. We think it can be really effective as part of this cleanup,” Koslow said. “It’s not like you have to rely on the weather to make it work.”

Editor’s note: Drew Koslow wishes to acknowledge the staff of Midshore Riverkeeper as well as the U.S. Fish and Wildlife’s Chesapeake Bay Field Office; the Caroline County and Queen Anne’s County Soil Conservation Districts; the USDA’s Natural Resources Conservation Service; Sweetbay Conservation and the Maryland Department of Agriculture for their support of this project.