Difference and interplay of microbial communities, metabolic functions, trophic modes and influence factors between sludge and bulking agent in a composting matrix

The difference and interplay of microbial communities, metabolic functions and influence factors between sewage sludge and bulking agent were evaluated in 60 days composting. Results showed that fungal communities were mainly affected by pH (42.4%) and ORP (35.9%) of sludge but by VS (41.1%) and temperature (34.7%) of sawdust in a composting system. Bacterial communities were primarily affected by VS (43.5%) and C/N (34.8%) of sludge but by ORP (44.5%) and temperature (31.0%) of sawdust. Tepidimicrobium dominated in the sludge at thermophilic period, while Alcaligenes prevailed in the sawdust. Bacterial carbon metabolism was significantly higher in the sludge than that in the sawdust except carbohydrate metabolism. Saprophytic fungi were the main trophic mode both in the sludge and sawdust. Water transfer facilitated Aspergillus and Trichosporon moving from sludge to sawdust to decompose lignocellulose. Ammonia transfer promoted the migration of Alcaligenes and Pseudomonas from sludge to sawdust and facilitated ammonia assimilating.