Early stages in biofilm development in methanogenic fluidized-bed reactors

Area of Science:

• Environmental microbiology
• Biotechnology
• Anaerobic digestion

Background:

• Fluidized-bed reactors (FBRs) are crucial for wastewater treatment.
• Understanding biofilm development is key to optimizing FBR performance.
• Sludge granules in methanogenic FBRs harbor complex microbial communities.

Purpose of the Study:

• To investigate the initial colonization and development of biofilms in methanogenic FBRs using sand as a carrier.
• To characterize the microorganisms involved in early biofilm formation and compare them to mature sludge granules.
• To determine the influence of start-up conditions on biofilm development.

Main Methods:

• Laboratory-scale study of biofilm development in methanogenic FBRs.
• Microbial characterization (morphology, elemental composition, adhesion) of biofilm layers and initial colonizers.
• Monitoring biofilm formation under varying wastewater compositions and inoculation times.
• Assessing the impact of substrate availability on attached biomass.

Main Results:

• Facultative anaerobic bacteria from outer biofilm layers of mature sludge granules were identified as primary sand colonizers.
• Methanothrix species and other methanogens were rarely found among primary colonizers.
• Biofilm formation proceeded similarly across different start-up conditions (wastewater, inoculation, anaerobicity).
• Absence of wastewater (substrate) led to rapid washout of attached biomass.

Conclusions:

• Facultative anaerobic bacteria play a dominant role in the initial stages of biofilm formation on sand in methanogenic FBRs.
• Substrate availability is critical for maintaining attached biomass in FBRs.
• The study provides insights into microbial succession during biofilm development in anaerobic wastewater treatment systems.