Microbial community in granules from a high-rate EGSB reactor

Area of Science:

• Environmental Microbiology
• Biotechnology
• Anaerobic Digestion

Background:

• Anaerobic granular sludge is crucial for wastewater treatment.
• Understanding microbial community structure is key to optimizing reactor performance.
• Organic loading rates significantly impact microbial populations.

Purpose of the Study:

• To investigate the spatial distribution, quantity, and diversity of microorganisms in anaerobic granular sludge.
• To correlate microbial community changes with varying organic loading rates in an expanded granular sludge bed (EGSB) reactor.
• To identify dominant Archaea species under different operational conditions.

Main Methods:

• Fluorescent in situ hybridization (FISH) for spatial distribution.
• Real-time quantitative-polymerase chain reaction (RTQ-PCR) for microbial quantity.
• Denaturing gradient gel electrophoresis (DGGE) for community diversity.
• DNA sequencing of DGGE bands for species identification.

Main Results:

• Eubacteria predominantly occupied the outer granule layers, while Archaea (methanogens) were found in the inner layers.
• Archaea quantity was lower than Eubacteria but increased with higher organic loading rates.
• Archaea community structure and diversity changed significantly with increased organic loading and elapsed operating time.
• Dominant Archaea species identified included Methanocorpusculum, Methanobacterium, and Methanosaeta.

Conclusions:

• Microbial community structure in anaerobic granular sludge is sensitive to organic loading rates.
• Archaea populations adapt and increase with rising organic loads, indicating their role in methanogenesis.
• Specific Archaea genera dominate under high organic loading conditions, influencing reactor efficiency.