TY - JOUR
T1 - Aspect ratio and baffles impact hydraulic performance of full-size denitrifying bioreactors
AU - de Oliveira, Luciano Alves
AU - Dougherty, Hannah
AU - Cooke, Richard A C
AU - Maxwell, Bryan M.
AU - Helmers, Matthew J.
AU - Birgand, François
AU - Pittelkow, Cameron M
AU - Christianson, Reid D.
AU - Christianson, Laura E.
N1 - Primary funding for this analysis was provided by the: USDA NRCS ( NR185A12XXXXC004 CESU under the Great Rivers Umbrella Agreement 68-3A75-18-518 504); Illinois Nutrient Research and Education Council ( 2016-4-360276-980 ; 2017-4-360498-302 ); and University of Illinois College of Agricultural, Consumer, and Environmental Sciences Dudley Smith Initiative . Additional funding for specific study locations was provided by: USDA NCR-SARE FNC21-1279 ; USDA NIFA project No. NC09825 ; and the Illinois Farm Bureau Bioreactor Partnership (Illinois Farm Bureau, Illinois Land Improvement Contractors Association, Illinois NRCS). Co-authors LAO and HD's time was partially supported by USDA NIFA HATCH project No. ILLU-802-925 and a National Needs Graduate Fellowship Program 2015-38420-23707 (HD). The authors thank Fernando Zucher and Andrew Pattison for their efforts in the field and Daniel Hiatt and Michael Wallace for laboratory analysis. This study was made possible by the generosity of private farm owners who allowed this work to be performed. This product was developed with support from the Sustainable Agriculture Research and Education (SARE) program , which is funded by the USDA-NIFA . Any opinions, findings, conclusions, or recommendations expressed within do not necessarily reflect the view of the SARE program or the USDA. Mention of companies and manufacturers' names does not imply endorsement by the USDA. The USDA is an equal opportunity provider and employer.
PY - 2023/4
Y1 - 2023/4
N2 - Denitrifying woodchip bioreactors treating subsurface drainage in the US have high aspect ratios (i.e., length: width ratios; approximately 4:1) to encourage plug flow dynamics. Improved understanding of bioreactor hydraulics across aspect ratios would help assess possible increased flexibility for this practice to capture greater hydraulic loading or provide greater nitrate mass removal. The objective of this study was to assess the hydraulic impacts of aspect ratio and baffles using conservative tracer testing at full-scale denitrifying woodchip bioreactors. Fourteen tracer tests were performed at six bioreactors, spanning three design styles: (1) “conventional” bioreactors with high aspect ratios of ≥2.6:1; (2) a “wide” bioreactor with a low aspect ratio of 0.3:1; and (3) a relatively wide “advanced” bioreactor with baffles placed to route flow sinuously perpendicular (sideways) to the hydraulic gradient. The wide bioreactor had the most dispersion, the most short circuiting, and was the most well mixed based on the tanks-in-series model. The advanced design with baffles had higher volumetric efficiencies than the conventional and wide designs (2.9, 2.2, and 2.1, respectively) and trended toward the highest nitrate removals. The concept of baffles at relatively wide bioreactors merits additional field-scale assessment to increase hydraulic loading while maintaining hydraulic efficiency. The Morill Dispersion and Short Circuiting Indices were strongly and significantly correlated (Pearson's r: −0.88) across the fourteen tests as were the volumetric and hydraulic efficiency metrics (r: 0.87). While aspect ratio and baffles have been well studied in wetlands and other reactor types, this work is the first to establish these concepts using tracer testing at three woodchip bioreactor design styles.
AB - Denitrifying woodchip bioreactors treating subsurface drainage in the US have high aspect ratios (i.e., length: width ratios; approximately 4:1) to encourage plug flow dynamics. Improved understanding of bioreactor hydraulics across aspect ratios would help assess possible increased flexibility for this practice to capture greater hydraulic loading or provide greater nitrate mass removal. The objective of this study was to assess the hydraulic impacts of aspect ratio and baffles using conservative tracer testing at full-scale denitrifying woodchip bioreactors. Fourteen tracer tests were performed at six bioreactors, spanning three design styles: (1) “conventional” bioreactors with high aspect ratios of ≥2.6:1; (2) a “wide” bioreactor with a low aspect ratio of 0.3:1; and (3) a relatively wide “advanced” bioreactor with baffles placed to route flow sinuously perpendicular (sideways) to the hydraulic gradient. The wide bioreactor had the most dispersion, the most short circuiting, and was the most well mixed based on the tanks-in-series model. The advanced design with baffles had higher volumetric efficiencies than the conventional and wide designs (2.9, 2.2, and 2.1, respectively) and trended toward the highest nitrate removals. The concept of baffles at relatively wide bioreactors merits additional field-scale assessment to increase hydraulic loading while maintaining hydraulic efficiency. The Morill Dispersion and Short Circuiting Indices were strongly and significantly correlated (Pearson's r: −0.88) across the fourteen tests as were the volumetric and hydraulic efficiency metrics (r: 0.87). While aspect ratio and baffles have been well studied in wetlands and other reactor types, this work is the first to establish these concepts using tracer testing at three woodchip bioreactor design styles.
KW - Dispersion
KW - Hydraulic efficiency
KW - Hydraulic retention time
KW - Short circuiting
KW - Tracer test
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U2 - 10.1016/j.ecoleng.2023.106912
DO - 10.1016/j.ecoleng.2023.106912
M3 - Article
AN - SCOPUS:85147191437
SN - 0925-8574
VL - 189
JO - Ecological Engineering
JF - Ecological Engineering
M1 - 106912
ER -