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69th SWCS International Annual Conference “Making Waves in Conservation: Our Life on Land and Its Impact on Water” July 27-30, 2014 Lombard, IL
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Using Denitrifying Bioreactors to Treat Subsurface Drainage
DischargesLarry Geohring, Will Pluer, Todd Walter
Cornell UniversityBiological & Environmental Engineering
Denitrifying Bioreactors
• DNBRs treat excess nitrogen in field runoff
• Designed to provide ideal conditions for denitrifiers– Anaerobic– Carbon source– Excess NO3-
INTRODUCTION
• 3 Farm Sites– Freeville Veggie– Vance Dairy– Burns Dairy
• Susquehanna basin– Upstate NY
• Tile drain systems• Woodchip/biochar fills• Sealed/open designs• Field/control inflow
Field DBNRs
INTRODUCTION
Lab DNBRs
• 6 Lab reactors– 3 Woodchip– 3 Woodchip/biochar
• Control variables:– Inflow NO3-
– pH– Residence time– Temperature– Microbial community
INTRODUCTION
Continuous: NOx
FIELD RESULTS
Continuous: PO4
FIELD RESULTS
Continuous: DOC
FIELD RESULTS
Field Runs: N2O
FIELD RESULTS
Field Runs: CH4
FIELD RESULTS
Lab Runs: NOx
LAB RESULTS
Lab Runs: N2O
LAB RESULTS
Lab Runs: CH4
LAB RESULTS
General Efficacy
CONCLUSIONS
• Effectively remove NO3-
– 45-60% NOx-N reduction• Initial flush periods of P, DOC• No indication of P treatment
– Other media may target PO43- better
• Storm flows reduce treatment time– Missing highest loading period
Control Variables
CONCLUSIONS
• High variability among reactors• Low inflow NO3- results in low reduction and high methane
• High flow results in low reduction and high N2O
• High pH sensitivity• Biochar shifting microbe community?
Gas Emissions
CONCLUSIONS
• Emissions of N2O and CH4– N2O decrease with residence time
• Total GHG footprint could be significant
• No control discouraged N2O + CH4– New designs or controls
• Water quality probably outweighs trace gas emissions
Acknowledgements
PIs: Dr. Todd Walter & Larry Geohring& Dr. Tammo Steenhuis
Partner: Upper Susquehanna CoalitionHelp: Siobhan Powers, Shane DeGaetano,
Sarah Levine, Anne Elise CreamerFunds: USDA NIFA, NRCS-CIG, NSF IGERT
Any Questions?