Changes in Microbial Biofilm Communities during Colonization of Sewer Systems

Area of Science:

• Environmental Microbiology
• Anaerobic Digestion
• Wastewater Engineering

Background:

• Sewer biofilms harbor sulfate-reducing bacteria (SRB) and methanogenic archaea (MA), producing problematic sulfide (H2S) and methane (CH4).
• Understanding the interplay between microbial community shifts and gas production is crucial for managing sewer impacts.

Purpose of the Study:

• To investigate the temporal dynamics of H2S and CH4 production and emission rates during biofilm development in a laboratory sewer system.
• To correlate these gas emission rates with changes in the sewer biofilm microbial community composition.

Main Methods:

• Utilized a laboratory sewer pilot plant simulating anaerobic rising sewers.
• Employed process data alongside molecular techniques: quantitative PCR (qPCR), denaturing gradient gel electrophoresis (DGGE), and 16S rRNA gene pyrotag sequencing.

Main Results:

• Early biofilm stages (2 weeks) showed high H2S emissions (290.7±72.3 mg S-H2S L⁻¹ day⁻¹) with gut-derived methanogens and low CH4 emissions (17.9±15.9 mg COD-CH4 L⁻¹ day⁻¹).
• After 1 year, CH4 emissions significantly increased (327.6±16.6 mg COD-CH4 L⁻¹ day⁻¹) as methanogens adapted to sewer conditions (e.g., Methanosaeta spp.) replaced initial colonizers.
• The laboratory system effectively mimicked full-scale sewer microbial and operational functions.

Conclusions:

• Biofilm development drives a shift in microbial communities, altering the balance of H2S and CH4 production in sewers.
• The study provides valuable insights into the complex microbial dynamics governing gas emissions in sewer systems.
• The experimental model's validity for studying sewer biogeochemistry was confirmed.