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Denitrification in Wood Chip Bioreactors at Different Water Flows
Author(s) -
Greenan Colin M.,
Moorman Thomas B.,
Parkin Timothy B.,
Kaspar Thomas C.,
Jaynes Dan B.
Publication year - 2009
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2008.0413
Subject(s) - denitrification , effluent , nitrate , bioreactor , nitrous oxide , chemistry , environmental chemistry , nitrogen , environmental engineering , environmental science , pulp and paper industry , organic chemistry , engineering
Subsurface drainage in agricultural watersheds exports a large quantity of nitrate‐nitrogen (NO 3 –N) and concentrations frequently exceed 10 mg L −1 A laboratory column study was conducted to investigate the ability of a wood chip bioreactor to promote denitrification under mean water flow rates of 2.9, 6.6, 8.7 and 13.6 cm d −1 which are representative of flows entering subsurface drainage tiles. Columns were packed with wood chips and inoculated with a small amount of oxidized till and incubated at 10°C. Silicone sampling cells at the effluent ports were used for N 2 O sampling. 15 Nitrate was added to dosing water at 50 mg L −1 and effluent was collected and analyzed for NO 3 –N, NH 4 –N, and dissolved organic carbon. Mean NO 3 –N concentrations in the effluent were 0.0, 18.5, 24.2, and 35.3 mg L −1 for the flow rates 2.9, 6.6, 8.7, and 13.6 cm d −1 , respectively, which correspond to 100, 64, 52, and 30% efficiency of removal. The NO 3 –N removal rates per gram of wood increased with increasing flow rates. Denitrification was found to be the dominant NO 3 –N removal mechanism as immobilization of 15 NO 3 –N was negligible compared with the quantity of 15 NO 3 –N removed. Nitrous oxide production from the columns ranged from 0.003 to 0.028% of the N denitrified, indicating that complete denitrification generally occurred. Based on these observations, wood chip bioreactors may be successful at removing significant quantities of NO 3 –N, and reducing NO 3 –N concentration from water moving to subsurface drainage at flow rates observed in central Iowa subsoil.