Denitrifying bioreactors are a simple technology for removing nitrate from wastewater and agricultural drainage waters, such as from tile drains. Simply, these are structures containing a slowly degrading carbon source, such as woodchips, through which water containing nitrate is passed. The woodchips support denitrifying microbes that convert nitrate to nitrogen gas, which is released to the atmosphere.
Louis describes some of his early work on denitrifying bioreactors here. A recent overview of the science of denitrifying bioreactors at the annual conference of the Soil Science Society of America can be found here. Also a talk given at the Treatment forum, hosted by the Department of Environment and Heritage Protection (EHP), Brisbane (2016) is here.
We are collaborating with a team led by Rupert Craggs and Chris Tanner from NIWA to identify approaches to enhance the removal rates of nitrate and phosphorus in woodchip bioreactors. We are focusing on dosing with soluble carbon, short-term nitrate binding, redox control, and phosphorus binding.
Previously we collaborated with Art Gold and Kelly Addy (University of Rhode Island), Mark David (University of Illinois), Brian Needelman (University of Maryland), Francois Birgand (North Carolina State University) and Laura Christianson (University of Illinois) in the US. Laura Christianson summarises a meta-analysis of bioreactor performance that was led by Kelly here. In Australia, we are collaborating with Rhianna Robinson and Ian Layden (Department of Agriculture and Fisheries, Brisbane).
These systems are now starting to be used in many parts of the world including New Zealand, Australia, Iowa, Illinois, Rhode Island, Florida. Louis would be interested in hearing from anyone who has built a denitrifying bioreactor.
Below is a photo of 6-year-old wood chips below the water table from the denitrifying bioreactor based in Karaka
Louis was guest editor for a special issue of Ecological Engineering, which included an overview of denitrifying bioreactors that can be found in Schipper, L.A.; Robertson, W.D.; Gold A.J.; Jaynes, D.B.; Cameron, S.G. (2010) Denitrifying bioreactors – an approach for reducing nitrate loads to receiving waters. Ecological Engineering. 36 (11): 1532-1543.