Mechanistic insights into the sludge biodrying process: the evolution of sludge structure and microbial community.

Abstract

This study deciphers sludge biodrying through a microbial-structural coevolution framework: Thermophilic consortia (Geobacillus/Bacillus; 63.27% abundance) drive bio-heat generation (>65°C), triggering particle fragmentation (decreased particle size by 63%), pore-network expansion (SEM-validated), and matrix loosening (decreased fractal dimension by 32%). This structural evolution enables phase-specific moisture redistribution - surface water (decreased from 68.52% to 19.82%) transforms into interstitial water (increased from 28.71% to 69.08%) and ultimately vapour flux, a process accelerated by capillary migration and enhanced airflow diffusion. The synergy of microbial succession (with dominance shifting from Firmicutes to Actinobacteria), structural reconfiguration, and moisture thermodynamics achieves deep dewatering (reducing moisture content from 80.62% to 41.62%), while mechanistic insights enable precision aeration phasing for energy reduction and cycle shortening via moisture-state-guided control.