Time-based succession existed in rural sewer biofilms: Bacterial communities, sulfate-reducing bacteria and methanogenic archaea, and sulfide and methane generation

Highlights: • Obvious succession of bacteria, SRB, and MA existed in rural sewer biofilms. • Biofilm thickness variation in rural sewers was different with municipal sewers. • SRB number was much higher than MA and MA were eliminated in rural sewer biofilms. • Rural sewers sulfide accumulation was the main problem rather than CH₄ accumulation. Rural sewers are applied widely to collect rural sewage and biofilm characteristics in rural sewers may be different with municipal sewers. The succession of bacteria communities, sulfate-reducing bacteria (SRB) and methanogenic archaea (MA) need to be studied since rural sewers have a potential risk of sulfide and methane accumulation. In this study, lab-scale rural sewer facilities were established to analyze the characteristics of sewer biofilm and the generation of sulfide and methane. The results indicate that the variation tendency of biofilm thickness in rural sewers was different with municipal sewers. Time-based bacterial succession existed in rural sewer biofilms and the predominant genus was changed from Acinetobacter (approximately 19.10%) to Pseudomonas (approximately 12.61%). SRB (mean 1.49 × 10⁶ dsrA copies/cm²) were abundant than MA (mean 2.57 × 10⁵ mcrA copies/cm²) while MA were eliminated gradually in rural sewer biofilms. The tendency of sulfide and methane generation was similar with the number variation of SRB and MA, indicating sulfide accumulation might be more serious trouble than methane accumulation in a long-run rural sewer. Overall, this study deeply analyzed the succession of rural sewer biofilms and found that MA and methane were automatically inhibited in rural sewers.