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Published on: December 25, 2015
Nitrite-oxidizing bacteria guild ecology associated with nitrification failure in a continuous-flow reactor
Charles W Knapp1, David W Graham
1School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, UK.
FEMS Microbiology Ecology
|September 18, 2007
Summary
Nitrification stability in wastewater treatment is threatened by disruptions to nitrite-oxidizing bacteria (NOB). High flow rates destabilized NOB guilds, leading to incomplete ammonia oxidation and eventual nitrification failure.
Area of Science:
- Environmental microbiology
- Wastewater treatment engineering
- Nitrogen cycle processes
Background:
- Nitrification is crucial for removing nitrogen in wastewater treatment plants.
- Ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) are essential for nitrification.
- Nitrification performance is often unpredictable due to sensitivity to operating conditions.
Purpose of the Study:
- To investigate the dynamics of the nitrite-oxidizing bacteria (NOB) guild under varying conditions.
- To understand how different dilution rates impact NOB guild stability and nitrification performance.
- To identify causes of nitrification failure in wastewater treatment systems.
Main Methods:
- Two parallel chemostats were operated at low (0.10 day⁻¹) and high (0.83 day⁻¹) dilution rates.
- Ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) guild abundances were monitored.
- Nitrogen-oxidation efficiency was measured throughout the experiment.
- Disturbance episodes and their impact on microbial communities were analyzed.
Main Results:
- At a low dilution rate (0.10 day⁻¹), NOB and AOB abundances and nitrification efficiency remained stable.
- At a high dilution rate (0.83 day⁻¹), two disturbance episodes destabilized the NOB guild, causing nitrification failure.
- The first disturbance led to the extinction of Nitrospira spp., resulting in nitrite accumulation.
- The second disturbance, possibly due to metal toxicity, caused complete loss of nitrification.
Conclusions:
- Nitrite-oxidizing bacteria (NOB) guild dynamics are critical for stable nitrification.
- High dilution rates can lead to NOB guild destabilization and nitrification failure.
- Extinction of key NOB species, like Nitrospira, severely impairs nitrogen removal processes.
- Understanding NOB guild behavior is essential for optimizing wastewater treatment plant performance at higher loading rates.
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