Elemental sulfur-based autotrophic denitrification and denitritation: microbially catalyzed sulfur hydrolysis and...

The hydrolysis of elemental sulfur (S⁰) coupled to S⁰-based denitrification and denitritation was investigated in batch bioassays by microbiological and modeling approaches. In the denitrification experiments, the highest obtained NO₃^--N removal rate was 20.9 mg/l·d. In the experiments with the biomass enriched on NO₂^-, a NO₂^--N removal rate of 10.7 mg/l·d was achieved even at a NO₂^--N concentration as high as 240 mg/l. The Helicobacteraceae family was only observed in the biofilm attached onto the chemically-synthesized S⁰ particles with a relative abundance up to 37.1%, suggesting it was the hydrolytic biomass capable of S⁰ solubilization in the novel surface-based model. S⁰-driven denitrification was modeled as a two-step process in order to explicitly account for the sequential reduction of NO₃^- to NO₂^- and then to N₂ by denitrifying bacteria.