Bio-oxidation of sulfide under denitrifying conditions is a key process in the treatment of gas and liquids that are contaminated with sulfide and nitrite. A lab-scale continuous flow stirred tank reactor (CFSTR) was operated with nitrite as the electron acceptor for the evaluation of the effects of loading rates, hydraulic retention time (HRT) and substrate concentrations on the performance of the autotrophic denitrification process. The influent sulfide concentration was maintained at 0.16 kg/m(3) and the HRT was decreased from 8.4 to 2 h and for the entire study period, the sulfide removal efficiency was above 80% for the loading rates that ranged from 0.47 to 2.16 kg S-2/m(3)day. However, lower influent loading of NO2 (-)-N that correspond to the stoichiometric ratios was used and the nitrite removal efficiency was close to 100%. The stoichiometry of sulfide oxidation was calculated by assuming the different end-products based on thermodynamic approach. We compared the calculated values with experimental yield values.