Competition and Inhibition of Sulfate Reducers and Methane Producers in Anaerobic Treatment

Competition for substrate between sulfate reducing and methane producing bacteria, and the inhibitory effects of sulfide produced from microbial sulfate reduction were investigated in this study for the selection of a proper anaerobic treatment process using laboratory anaerobic contact units. Substrates used were both synthetic waste with various COD/SO42− ratios, and industrial wastes. Sulfate reducers and methane producers were very competitive at COD/SO42− ratio of 1.7 to 2.7. As the ratio increased/methane producers predominated, and sulfate reducers were predominating as the ratio decreased. Inhibitory concentrations were 2000 mg/l sulfate (160 to 200 mg/l sulfide) for sulfate reducers and 1200 mg/l sulfate (120 to 140 mg/l sulfide) for methane producers with synthetic substrate. But sulfide inhibitory concentrations were varied with hydraulic or organic loading rates and substrate used. As loading rates increased/the inhibitory effect was greater. A sulfide concentration of 240mg/l did not inhibit methane producers for sea-food waste treatment.