Pyrosequencing reveals microbial community dynamics in integrated simultaneous desulfurization and denitrification process at different influent nitrate concentrations

Integrated simultaneous desulfurization and denitrification (ISDD) process has proven to be feasible for the coremoval of sulfate, nitrate, and chemical oxygen demand (COD). In this study, we aimed to reveal the microbial community dynamics in the ISDD process with different influent nitrate (NO₃⁻) concentrations. For all tested scenarios, full denitrification was accomplished while sulfate removal efficiency decreased along with increased influent NO₃⁻concentrations. The proportion of S⁰to influent SO₄²⁻maintained a low level (5.6–17.0%) regardless of the increased influent NO₃⁻concentrations. Microbial community analysis results showed that higher influent NO₃⁻concentrations affected the microbial community structure greatly. Phyla Proteobacteria, Spirochaetae, Firmicutes, Synergistetes, and Chloroflexi dominated in all the community compositions, of which Proteobacteria exhibited a clear difference among eight microbial samples. Members of δ-Proteobacteria, with 16S rRNA gene sequences related to Desulfobulbus, were clearly decreased at influent NO₃⁻= 3000 and 3500 mg/L, suggesting an inhibitory effect of NO₃⁻on sulfate reduction. In contrast, as influent NO₃⁻concentration increased, microbial community was notably enriched in γ-Proteobacteria and ε-Proteobacteria, which revealed the enrichment of 16S rRNA gene sequences related to Pseudomonas (γ-Proteobacteria), and Arcobacteria and Sulfurospirillum (ε-Proteobacteria).