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Light-introduced partial nitrification in an algal-bacterial granular sludge bioreactor: Performance evolution and
Guangchao Si1, Bing Liu2, Yingrui Liu1
1School of Water Conservancy and Environment, University of Jinan, Jinan 250022, PR China.
Bioresource Technology
|April 27, 2022
Summary
Light significantly influences partial nitrification in algal-bacterial granular bioreactors. This study achieved stable partial nitrification, enhancing granular sludge properties and inhibiting nitrite-oxidizing bacteria under specific light conditions.
Area of Science:
- Environmental Science
- Biotechnology
- Wastewater Treatment
Background:
- Partial nitrification is crucial for efficient nitrogen removal in wastewater treatment.
- Algal-bacterial aerobic granular sludge (AB-AGS) offers advantages in wastewater treatment processes.
- Understanding the impact of environmental factors like light is essential for optimizing bioreactor performance.
Purpose of the Study:
- To investigate the effect of light intensity on achieving partial nitrification in an algal-bacterial granular bioreactor.
- To elucidate the nitrite accumulation mechanism under light influence.
- To analyze the changes in AB-AGS characteristics and microbial community structure.
Main Methods:
- Operation of a partial nitrification algal-bacterial granulation bioreactor for 150 days under controlled light conditions (200 μmol/(m²·s)).
- Monitoring of effluent nitrogen species (NH₄⁺-N, NO₂⁻-N, NO₃⁻-N) and N₂O emissions.
- Analysis of algal-bacterial aerobic granular sludge (AB-AGS) properties, including sphericity, diameter, and extracellular polymeric substances (EPS).
- Microbial community analysis to determine the abundance of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB).
Main Results:
- Stable partial nitrification was achieved at 200 μmol/(m²·s) illuminance, with effluent concentrations of 1.1 mg/L NH₄⁺-N, 61.7 mg/L NO₂⁻-N, and 8.0 mg/L NO₃⁻-N.
- AB-AGS exhibited improved characteristics, with average sphericity increasing from 82.7% to 91.1% and significant diameter growth.
- Extracellular protein content in LB-EPS and TB-EPS increased by 1.5 and 0.5 times, respectively.
- N₂O emission accounted for 2.4% of removed nitrogen.
- Nitrosomonas-related AOB predominated (0.2%–2.1%), while Nitrospira-related NOB were fully inhibited (<0.01%) under combined light and free ammonia inhibition.
Conclusions:
- Light plays a critical role in achieving and maintaining partial nitrification in algal-bacterial granular bioreactors.
- Optimized light conditions promote the formation of robust AB-AGS with enhanced properties.
- The study demonstrates effective inhibition of NOB, favoring AOB, leading to nitrite accumulation, crucial for subsequent denitrification processes.
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