Decryption for nitrogen removal in Anammox-based coupled systems: Nitrite-induced mechanisms
Yitong Liang1, Zemin Li1, Bin Zhang2
1School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China.
Bioresource Technology
|June 8, 2023
Summary
Nitrite (NO2-) enhances Anammox and sulfur-oxidizing bacteria synergy for nitrogen removal up to 75 mg-N/L. Higher concentrations decouple cooperation, but optimal levels improve system reliability and gene expression.
Area of Science:
- Environmental Microbiology
- Biotechnology
- Wastewater Treatment
Background:
- Anammox bacteria (AnAOB) and sulfur-oxidizing bacteria (SOB) are crucial for autotrophic denitrification-Anammox systems.
- Understanding synergistic interactions is key to optimizing nitrogen removal processes.
- Nitrite (NO2-) is a key intermediate in nitrogen cycling, but its effects on AnAOB-SOB synergy are not fully understood.
Purpose of the Study:
- To investigate the impact of varying nitrite (NO2-) concentrations on the synergistic interactions between Anammox bacteria (AnAOB) and sulfur-oxidizing bacteria (SOB).
- To elucidate the underlying mechanisms of NO2- induced synergy and inhibition in autotrophic denitrification-Anammox systems.
- To provide theoretical guidance for the engineering application of coupled Anammox systems.
Main Methods:
- Experimental setup using an autotrophic denitrification-Anammox system with controlled NO2- concentrations (0-100+ mg-N/L).
- Monitoring of ammonium (NH4+) and nitrate (NO3-) conversion rates.
- Long-term reactor operation to assess system reliability and nitrogen removal performance.
- Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) to analyze hydrazine synthase gene transcription levels.
Main Results:
- NO2- at concentrations of 0-75 mg-N/L significantly enhanced NH4+ and NO3- conversion rates, intensifying AnAOB-SOB synergy.
- NO2- concentrations exceeding 100 mg-N/L led to decreased conversion rates and decoupled cooperation due to inhibition.
- Long-term operation with NO2- demonstrated improved system reliability and nitrogen removal.
- RT-qPCR analysis revealed a 5.00-fold increase in hydrazine synthase gene transcription in the presence of NO2- compared to its absence.
Conclusions:
- NO2- plays a critical role in modulating the synergy between AnAOB and SOB, with an optimal range for enhanced nitrogen removal.
- High NO2- concentrations can inhibit the synergistic relationship, leading to decreased efficiency.
- The study provides mechanistic insights into NO2- induced interactions, supporting the optimization of Anammox-based coupled systems for wastewater treatment.
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