A Practice-oriented Review of Woodchip Bioreactors for Subsurface Agricultural Drainage

Woodchip or denitrification bioreactors are an innovative, engineering-based technology to reduce the amount of nitrate in agricultural drainage. Increased interest in improving water quality in areas impacted by agricultural drainage has given bioreactors a boost of publicity over the past several years. While bioreactors continue to be an area of active research and are not a silver bullet to address drainage water quality concerns, the growing number of bioreactor installations by practitioners not involved in research demonstrates a need for a practice-oriented review of important aspects of these systems. This article provides context for enhanced-denitrification treatment of agricultural drainage, discusses the design and installation of bioreactors, and presents factors affecting their nitrate removal performance. Additionally, this review offers ideas for management and monitoring of agricultural drainage bioreactors. Bioreactors are a promising technology for improving drainage water quality, but much work remains to understand and optimize their performance. With additional evaluation and improved monitoring of bioreactors, a more complete picture of the potential contribution of these systems will be developed.