At The Conservation Fund Freshwater Institute, we have invested significant effort into research on the engineering-based design of enhanced-denitrification bioreactors, or “woodchip bioreactors”, to reduce point and non-point sources of nitrate from multiple types of agriculture and industry. On the research front, we aim to improve the nitrate-removal ability of woodchip bioreactors, and we work with a number of partners on bioreactor installation and monitoring to mitigate nitrate output across the country.

A conventional woodchip bioreactor design consists of an excavation, filled with an organic carbon source, through which nitrate-laden water is routed. The maintenance of saturation precipitates the anoxic (sans oxygen) conditions required by the denitrifying bacteria to convert nitrate in the water to nitrogen gas, thus cleaning the water.

Our bioreactor research of four “pilot-scale” (test) reactors allowed the comparison of a range of hydraulic retention times for treating aquaculture wastewater. This research demonstrated excellent nitrate and solids removal but limited total phosphorus removal, and quantified the potential for woodchip clogging when treating the effluent of recirculating aquaculture systems. The 1:10 ratio pilot-scale work is leading up to installation of full-sized woodchip bioreactors at the Freshwater Institute.

For more information about woodchip bioreactors, please visit our publications page or contact s.summerfelt@freshwaterinstitute.org (Steven Summerfelt).