Microbial community dynamics during aerobic granulation in a sequencing batch reactor (SBR)

Area of Science:

• Environmental microbiology
• Wastewater treatment technologies
• Bioreactor engineering

Background:

• Aerobic granules in sequencing batch reactors (SBRs) are crucial for removing wastewater contaminants like xenobiotics and dyes.
• Granule instability over time leads to reduced pollutant removal efficiency.
• Understanding granule formation and microbial dynamics is key to optimizing SBR performance.

Purpose of the Study:

• To investigate the microbial community structure during the formation and disintegration of aerobic granules in an SBR.
• To determine the factors contributing to aerobic granule instability and loss of function.

Main Methods:

• 16S rRNA gene and internal transcribed spacer (ITS) PCR amplicon sequencing were used to analyze microbial communities.
• Microbial relative abundance was tracked throughout the acclimation, granulation, and mature granule phases.
• Granule morphology and stability were monitored over the experimental period.

Main Results:

• The relative abundance of *Acinetobacter* reached 70.8% during the acclimation phase.
• *Agrobacterium* (35.9%) and *Dipodascus* (89.7%) dominated during the granulation and mature granule phases, respectively.
• Fluffy granules with filamentous overgrowth appeared on day 43, leading to lysis and biomass washout by day 46.

Conclusions:

• The reactor operation strategy successfully maintained stable aerobic granules for 46 days.
• Granule disintegration after day 46 was attributed to shifts in the microbial community structure, not changes in reactor operation.
• Further research into microbial dynamics is needed to enhance the long-term stability of aerobic granules for wastewater treatment.