Design flow and nitrate removal evaluation of a wide denitrifying bioreactor with baffles

A relatively wide denitrifying woodchip bioreactor (LWD: 16.8 × 10.7 × 0.91 m) was installed with two flow-routing baffles in Illinois, USA with the design objectives of minimizing inflow manifold-related flow restrictions while maintaining both a relatively consistent footprint and nitrate-removal performance compared to conventional designs. This wide design did not improve the percentage of flow from the field that was treated (generally about 40% of flow treated) compared to other sites. However, the Richards-Baker flashiness index (0.74 to 0.91) and probability of exceedance evaluations indicated site drainage was flashy which might have accounted for the lower than expected performance. Nitrate removal was consistent with other bioreactors despite the new design ideas (22–24% edge of field N loss reduction; 0.72 to 1.3 g N removed m⁻³ d⁻¹). Within the context of the need for accelerated conservation drainage practice adoption across the US Midwest, trying to account for flow uncertainties like flashiness with site-specific designs could be a bottleneck for bioreactor design and implementation. It may be worthwhile to explore possible benefits of a simpler design approach (e.g. standardized plug-and-play designs) since there are many factors at play in bioreactor performance.