Denitrifying bioreactors and dissolved phosphorus: Net source or sink?
A P Sanchez-Bustamante Bailon1, A Margenot1, R A C Cooke2
1Department of Crop Sciences, University of Illinois, Urbana-Champaign, Illinois, USA.
Journal of Environmental Quality
|May 6, 2024
Summary
Woodchip bioreactors can remove nitrate pollution but may release dissolved reactive phosphorus (DRP). This study found bioreactors removed DRP in most cases, though results varied, highlighting a potential tradeoff in water quality management.
Area of Science:
- Environmental Science
- Water Quality Management
- Agricultural Engineering
Background:
- Nitrate pollution is a major concern in tile-drained US Midwest agriculture.
- Denitrifying woodchip bioreactors effectively reduce nitrate, but phosphorus release is a potential issue.
- Understanding nutrient tradeoffs is crucial for effective water quality strategies.
Purpose of the Study:
- To assess if denitrifying woodchip bioreactors act as a net source or sink for dissolved reactive phosphorus (DRP).
- To identify flow-related factors influencing DRP removal or release.
- To evaluate the DRP benefits and tradeoffs of bioreactors in agricultural drainage.
Main Methods:
- Analysis of 23 site-years of data from full-scale bioreactors in Illinois.
- Monitoring of 1904 sample events across 10 bioreactors.
- Calculation of DRP removal efficiency and rate, correlated with flow and loading conditions.
Main Results:
- DRP was removed in 15 out of 23 site-years.
- Median annual DRP removal efficiency was 12%, with a median rate of 7.1 mg DRP/m³ per day.
- Highest DRP removal rates occurred with high inflow concentrations and low hydraulic retention times.
Conclusions:
- Woodchip bioreactors demonstrated DRP removal in most assessed cases, but with significant variability.
- Bioreactor performance regarding DRP is influenced by loading conditions and hydraulic retention time.
- These findings contribute to understanding the strategic tradeoffs of using bioreactors for agricultural water quality improvement.
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