A December 22 Bay Journal article examined how bioreactors can help Eastern Shore farms reduce nitrogen and phosphorus runoff into the Chesapeake Bay and its tributaries. Former riverkeeper Drew Koslow has formed a company and secured funding to assist farmers in placing bioreactors on their lands. He has installed six bioreactors in the Choptank River wastershed. From the article:

In a bioreactor, pipes funnel water to a pit filled with buried wood chips. The wood chips are a substrate for bacteria that thrive in that environment and convert the nitrate from the fertilizer or manure into nitrogen gas, which dissipates into the atmosphere. By the time the water flows out the other side of the wood chips, the nitrogen content is about 50 percent lower, and in some cases, even lower.

Bioreactors help to mimic the natural process that would have occurred on land that is more suited to be a fallow wetland, but has been engineered for agriculture. The denitrification process at sewage treatment plants works much in the same way, though it tends to be more expensive. …

The technology is slowly making its way out of the laboratories and onto more farms in the Chesapeake Bay as well as in the Midwest. The Eastern Shore has 12 bioreactors, according to Jason Keppler, program manager for the watershed implementation program at the Maryland Department of Agriculture. The department helped to pay for them through a conservation innovation grant, but Keppler said he hopes the bioreactors and the filters that attach to them to reduce phosphorus will be part of the state cost-share assistance program by early 2016.

The article also discussed the maintenance and costs of bioreactors:

Richard Edwards let Koslow put a bioreactor on his 700-cow, Caroline County dairy farm two years ago. He gave up an acre of land for the practice and has to do very little to maintain it. Edwards said that he had good relationships with the soil district, Koslow and environmental groups, and wanted to do his part to improve water quality. …

The U.S. Department of Agriculture has helped fund six bioreactors in New York State in the Upper Susquehanna and Finger Lakes watersheds. In those, the bioreactors removed 57 percent of the nitrogen being discharged into the stream. The bioreactors cost $10,000–$30,000 to install, depending on location.