Nitrate and nitrite utilization during denitrifying phosphorus removal: Electron acceptor preference and feasible
Ruimiao Zhang1, Junguo He2, Mengfei Wang1
1School of Environment, Harbin Institute of Technology, Harbin 150090, Heilongjiang, PR China; State Key Laboratory of Urban Water Resources and Environment, Harbin Institute of Technology, Harbin 150090, Heilongjiang, PR China.
Bioresource Technology
|July 8, 2024
Summary
Denitrifying phosphorus removal (DPR) sludge contains organisms that prefer nitrite over nitrate for denitrification. This study clarifies the denitrification capacity of denitrifying polyphosphate-accumulating organisms (DPAOs) in DPR systems.
Area of Science:
- Environmental microbiology
- Wastewater treatment technologies
- Biogeochemical cycles
Background:
- Denitrifying phosphorus removal (DPR) is crucial for removing nitrogen and phosphorus from wastewater.
- Denitrifying polyphosphate-accumulating organisms (DPAOs) dominate DPR, but their denitrification capacity is often obscured by coexisting denitrifying glycogen-accumulating organisms (DGAOs).
- Understanding DPAOs' specific denitrification capabilities is essential for optimizing DPR processes.
Purpose of the Study:
- To evaluate the denitrification capacity of DPAOs under different nitrogen conditions (nitrate vs. nitrite).
- To investigate the influence of DGAO abundance on DPAO denitrification in DPR sludge.
- To determine the preferred electron acceptor for DPAO denitrification.
Main Methods:
- Cultivation of nitrate-DPR and nitrite-DPR sludge in separate reactors.
- Manipulation of feeding strategies with nitrate and nitrite during the anoxic phase.
- Analysis of DGAO abundance and assessment of denitrification rates (nitrate and nitrite reduction).
Main Results:
- DPAOs demonstrated a significantly higher nitrite reduction rate (1.63 times) compared to nitrate reduction rate in nitrate-DPR sludge.
- In nitrite-DPR sludge, nitrite reduction rates were over three times higher than nitrate reduction rates, regardless of DGAO abundance.
- These results confirm DPAOs' preference for nitrite as an electron acceptor.
Conclusions:
- DPAOs exhibit a strong preference for utilizing nitrite over nitrate for denitrification.
- DPAOs are more efficient in reducing nitrite than nitrate, suggesting a role in nitrite supply within DPR systems.
- Optimizing DPR processes may involve managing nitrogen species to favor nitrite availability for enhanced DPAO activity.
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