Denitrifying bioreactors for treatment of tile drainage

Much of the hypoxia in the Gulf of Mexico has been attributed to agricultural nonpoint pollution sources in the Midwestern states. There is, therefore, a critical need to develop practical and cost effective methods to reduce nitrate loadings from these areas. As the hypoxic zone is thought to be larger this year than ever before, the time is ripe for new technologies to reduce nutrient loads in the Mississippi River. Denitrifying drainage bioreactors can provide cost-effective treatment of tile water at the field scale while requiring minimal system maintenance. These bioreactors consist of a trench filled with an available carbon source (usually woodchips) that is readily colonized by bacteria and fungi capable of utilizing nitrate as an electron acceptor. A handful of such bioreactors have been installed in the US Midwest and have shown good nitrate removal. This poster describes the design, field installation, and cost estimates of full-scale denitrifying bioreactors.