High-Density Microarray Analysis of Microbial Community Structures in Membrane Bioreactor at Short Sludge Retention...

Area of Science:

• Environmental microbiology
• Wastewater treatment technologies
• Bioreactor engineering

Background:

• Membrane bioreactors (MBR) are widely used for wastewater treatment due to high effluent quality and reduced sludge production.
• Sludge retention time (SRT) is a critical operational parameter influencing MBR microbial community structure and function.
• Understanding microbial community shifts under varying SRTs is essential for optimizing MBR performance.

Purpose of the Study:

• To investigate the impact of short sludge retention times (SRTs) on microbial community composition in membrane bioreactors (MBRs).
• To compare microbial communities in MBRs operated at different SRTs and operational modes (continuous vs. sequencing batch).

Main Methods:

• Microarray analysis was employed to profile microbial communities in three distinct MBR systems.
• MBRs were operated at short SRTs: 5 days (CS5), 3 days continuous (CS3), and 3 days sequencing batch (SS3).

Main Results:

• MBR at 5-day SRT (CS5) exhibited the highest operational taxonomic units (OTUs) richness but the lowest diversity and uniformity.
• Proteobacteria was the dominant phylum across all reactors; Bacteroidetes dominated continuous systems, while Actinobacteria dominated the sequencing batch system.
• Significant differences in bacterial community composition were observed, particularly at the class and order levels of Proteobacteria, distinguishing CS5 from CS3 and SS3.

Conclusions:

• Short SRTs, especially 5 days, significantly alter microbial community structure and diversity in MBRs.
• The operational mode (continuous vs. sequencing batch) also influences the microbial community composition.
• MBR performance and stability are closely linked to the microbial community structure, which is sensitive to SRT manipulation.