Emerging technology: Denitrification bioreactors for nitrate reduction in agricultural waters

Excerpt

As a major contributor to the national water quality challenge of hypoxia in the Gulf of Mexico, nitrate demands innovative approaches for mass loading reductions. In the US Midwest, the high percentage of agricultural land use combined with the large extent of agricultural drainage leads to significant losses of this nutrient to surface and ground waters. Many Midwesterners are looking for new methods to help meet the call for a minimum of 45% reduction in total nitrogen loads from the EPA Science Advisory Board. Denitrification bioreactors for agricultural drainage are one of the newest potential technologies being investigated for providing practical, low cost, edge-of-field nitrate removal.

Harnessing the process of denitrification for nitrate removal is certainly not a new idea. Waste water treatment plants have been designed to maximize denitrification for many decades. More recently, denitrification treatments have been successfully reducing nitrate in groundwater and also in septic effluent. In an agricultural context, denitrification can be enhanced with the use of subsurface, carbon-filled excavations through which drainage is routed. This environment provides an enhanced setting for denitrification to occur at higher rates than are typical in the soil. Providing an ample supply of a readily available carbon source (wood chips),…