Microbial Insight into a Pilot-Scale Enhanced Two-Stage High-Solid Anaerobic Digestion System Treating Waste...

Area of Science:

• Environmental Microbiology
• Biotechnology
• Waste Management

Background:

• High solid anaerobic digestion (HSAD) is an effective sludge treatment method, widely adopted in Europe and Asia.
• Enhanced HSAD with thermal pre-treatment (TPT) improves methane yield and volatile solids (VS) reduction.
• The microbial ecology of enhanced HSAD systems remains incompletely understood.

Purpose of the Study:

• To investigate the microbial community structure and function in an enhanced two-stage HSAD system.
• To elucidate the metabolic pathways supporting efficient waste activated sludge degradation under high solid conditions.

Main Methods:

• A pilot-scale enhanced two-stage HSAD system was operated with waste activated sludge at 9% solid content.
• The system incorporated thermal pre-treatment (TPT) at 70 °C, followed by thermophilic anaerobic digestion (TAD) and mesophilic anaerobic digestion (MAD).
• Microbial community analysis was performed to identify dominant microorganisms and their metabolic roles.

Main Results:

• Hydrogenotrophic methanogens, primarily *Methanothermobacter* spp., dominated the microbial community, reaching nearly 100% relative abundance in both TAD and MAD stages.
• Syntrophic acetate oxidation (SAO) bacteria were identified in the TAD stage, actively converting acetate to H₂ and CO₂.
• The observed microbial composition and metabolic pathways were linked to the high solid and protein content of the sludge and specific operational parameters.

Conclusions:

• The enhanced HSAD system effectively utilizes hydrogenotrophic methanogenesis and syntrophic acetate oxidation for sludge degradation.
• Understanding these microbial dynamics is crucial for optimizing enhanced HSAD processes for waste activated sludge treatment.
• This study provides valuable insights for both academic research and industrial applications in anaerobic digestion.