Simultaneous elimination of sulfide and nitrite from synthetic wastewaters was investigated using a bioreactor.The performance of two ASO reactors utilizing diverse electron acceptors was compared to evaluate the loading potential treating synthetic wastewaters. The data of ASO reactor were used in back propagation neural network system to predict its performance.The ASO reactor was operated to investigate the effects of various influent nitrites to sulfide molar ratios upon the sulfide and nitrite removal efficiencies from the synthetic wastewater. The effects of pH upon anoxic sulfide oxidation in ASO reactor were evaluated.Two bacterial strains QZ1 and QZ2 were isolated from sludge of anoxic sulfide oxidizing (ASO) reactor . Based on 16S rDNA sequence analysis and morphological characteristics, isolates QZ1 and QZ2 were identified as Pseudomonas stutzeri QZ1 and Ochrobactrum sp. QZ2, respectively. Both strains were facultative chemolithotrophs, using sulfide as electron donor and nitrite as electron acceptor. Both isolates produced either elemental sulfur or sulfate as the product of sulfide oxidation, depending on the initial sulfide and nitrite concentrations.