Denitrification bioreactors are one technology used to reduce nitrogen pollution in waterways across the country. A conventional bioreactor design consists of a long and narrow excavation filled with a carbon source such as woodchips. Nitrate-laden water is directed to flow through the system, which maintains an anoxic environment. In the absence of oxygen, naturally occurring bacteria in the system then use available nitrate as part of their respiration process, effectively converting nitrate into inert nitrogen gas.

Reducing the amount of environmentally available nitrogen prevents eutrophication or algal blooms which have led to “dead zone” in both the Gulf of Mexico and the Chesapeake Bay. At The Conservation Fund’s Freshwater Institute, we have conducted research on the engineering-based design of enhanced-denitrification bioreactors, or “woodchip bioreactors,” to reduce point and non-point sources of nitrate from agriculture and industry.

Four 1:10th ratio “pilot-scale” (experimental) reactors have allowed for research examining the effects of hydraulic retention time, nitrogen and solids loading, and phosphorus removal utilizing on-site aquaculture wastewater. Laboratory column studies have also assessed the potential of pairing nutrient reduction strategies. Our ongoing research aims to improve the lifespan of systems treating wastewater high in nitrate, suspended solids, and biochemical oxygen demand while also assessing additional water quality benefits that may be associated with these systems.

For more information about woodchip bioreactors, please visit our publications page, view our Bioreactors and RAS poster (downloadable pdf), or contact (Christine Lepine).