In this study, the biokinetics of autotrophic denitrification with biogenic S-0 (ADBIOS) for the treatment of nitrogen pollution in wastewaters were investigated. The used biogenic S-0, a by-product of gas desulfurization, was an elemental microcrystalline orthorhombic sulfur with a median size of 4.69 mu m and a specific surface area of 3.38 m(2)/g, which made S-0 particularly reactive and bioavailable. During denitritation, the biomass enriched on nitrite (NO2-) was capable of degrading up to 240 mg/l NO2--N with a denitritation activity of 339.5 mg NO2--N/g VSS.d. The use of biogenic S-0 induced a low NO2--N accumulation, hindering the NO2--N negative impact on the denitrifying consortia and resulting in a specific denitrification activity of 223.0 mg NO3--N/g VSS.d. Besides Thiobacillus being the most abundant genus, Moheibacter and Thermomonas were predominantly selected for denitrification and denitritation, respectively.