Denitrifying Bioreactors Resist Disturbance from Fluctuating Water Levels
Open Access
- 28 June 2017
- journal article
- research article
- Published by Frontiers Media SA in Frontiers in Environmental Science
Abstract
Nitrate can be removed from wastewater streams, including subsurface agricultural drainage systems, using woodchip bioreactors to promote microbial denitrification. However, the variations in water flow in these systems could make reliable performance from this microbially-mediated process a challenge. In the current work, the effects of fluctuating water levels on nitrate removal, denitrifying activity, and microbial community composition in laboratory-scale bioreactors were investigated. The performance was sensitive to changing water level. An average of 31% nitrate was removed at high water level and 59% at low water level, despite flow adjustments to maintain a constant theoretical hydraulic retention time. The potential activity, as assessed through denitrifying enzyme assays, averaged 0.0008 mg N2O-N/h/dry g woodchip and did not show statistically significant differences between reactors, sampling depths, or operational conditions. In the denitrifying enzyme assays, nitrate removal consistently exceeded nitrous oxide production. The denitrifying bacterial communities were not significantly different from each other, regardless of water level, meaning that the denitrifying bacterial community did not change in response to disturbance. The overall bacterial communities, however, became more distinct between the two reactors when one reactor was operated with periodic disturbances of changing water height, and showed a stronger effect at the most severely disturbed location. The communities were not distinguishable, though, when comparing the same location under high and low water levels, indicating that the communities in the disturbed reactor were adapted to fluctuating conditions rather than to high or low water level. Overall, these results describe a biological treatment process and microbial community that is resistant to disturbance via water level fluctuations.Keywords
Funding Information
- National Science Foundation (CBET-0853820)
This publication has 30 references indexed in Scilit:
- Denitrifying Bioreactors for Nitrate Removal: A Meta-AnalysisJournal of Environmental Quality, 2016
- Spatial Variation in the Bacterial and Denitrifying Bacterial Community in a Biofilter Treating Subsurface Agricultural DrainageMicrobial Ecology, 2013
- Pilot-Scale Evaluation of Denitrification Drainage Bioreactors: Reactor Geometry and PerformanceJournal of Environmental Engineering, 2011
- Nitrate removal and hydraulic performance of organic carbon for use in denitrification bedsEcological Engineering, 2010
- Sources of Nitrate Yields in the Mississippi River BasinJournal of Environmental Quality, 2010
- Denitrification in Wood Chip Bioreactors at Different Water FlowsJournal of Environmental Quality, 2009
- Selection of organic substrates as potential reactive materials for use in a denitrification permeable reactive barrier (PRB)Bioresource Technology, 2008
- Comparing Denitrification Estimates for a Texas Estuary by Using Acetylene Inhibition and Membrane Inlet Mass SpectrometryApplied and Environmental Microbiology, 2003
- Removal of agricultural nitrate from tile-drainage effluent water using in-line bioreactorsJournal of Contaminant Hydrology, 1994
- Statistical design and analysis for a 'biological effects' studyMarine Ecology Progress Series, 1988