Microbial community succession, species interactions and metabolic pathways of sulfur-based autotrophic denitrification system in organic-limited nitrate wastewater

Elemental sulfur (S⁰) introduction could achieve the co-existence of heterotrophic denitrification (HDN) and autotrophic denitrification (ADN) in practical organic-limited nitrate wastewater treatment. Until now, changes in key functional species, metabolic pathways and microbial products in the succession process of microbialcommunities based on different of pollutant concentration and trophic conditions are still unclear. In present study, high-efficiency of total nitrogen (TN) removal achieved in S⁰-based ADN bioreactor at influent nitrate of 30-240 mg/L. Content of proteins and polysaccharides in extracellular polymeric substances (EPS) declined with nitrate loads increased. The key functional heterotrophic denitrifiers (Hyphomicrobium, Trichococcus, Rivibacter) and autotrophic biotope (Thiobacillus, Thiomonas, Ferritrophicum, Flavobacterium, Stenotrophomonas, Cloacibacterium and Pseudoxanthomonas) jointly contributed to high nitrogen removal efficiency at different nitrate loads. Furthermore, network analysis verified that symbiotic relationships accounted for the major proportion (88.3%) of the microbial network. The enhanced of nitrogen and sulfur metabolism improved nitrogen removal and S⁰-based autotrophic denitrification capacity.