Isolation and application of a mixotrophic sulfide-oxidizing Cohnella thermotolerans LYH-2 strain to sewage sludge composting for hydrogen sulfide odor control

To investigate the influences of sulfide oxidizing bacteria on H2S odor control in sewage sludge composting, a facultative chemolithotroph strain was isolated and identified as Cohnella thermotolerans LYH-2. Strain LYH-2 decreased the initially added sulfide by 94.6% when glucose and NH4Cl were used as the optimal energy substrates. The biotransformation of sulfide substrates followed first-order reaction kinetics, and the highest degradation rate constant (0.0537 h-1) and bacterial dry weight (0.745 g/L) were obtained at 300 mg/L of initial sulfide. The C. thermotolerans strain was inoculated as the bacterial agent into the sewage sludge and rice husk composting in forced ventilation composting reactors for 25 d; the bacterial inoculation prolonged the thermophilic period by 2 d, decreased 35.4% of H2S odor emission, and accelerated the composting process compared to the control group. The results demonstrated that C. thermotolerans inoculants effectively controlled H2S emission and promoted maturity in sewage sludge composting.