The inhibitory effects of ammonium and sulfide on the methane production using acetate or propionate as a carbon source were investigated under different pH and temperature conditions. The methane production rate, duration of the lag phase, and inhibition threshold limit during methane production were estimated using the Gompertz equation and inhibitor mathematical model. The methane production rates at 53°C were 2.3-2.7 times higher than those at 35°C in the case of non-inhibitors. Increasing the NH4+ and/or S2- concentration decreased the methane production rate and increased the duration of the lag phase. For methane fermentation that was not acclimated to high NH4+ concentration, the critical NH4+ concentration beyond which methane fermentation would stop was 4000-5650mg/L, depending on the pH, temperature, and carbon source. When NH4+ and S2- were coexistent, the critical NH4+ concentration decreased to approximately 3800mg/L when propionate was used and to approximately 4450mg/L when acetate was used. However, no synergistic effect of NH4+ and S2- on the methane production rate was found at an NH4+ concentration of < 5000mg/L and S2- concentration of 50mg/L.
Copyright ？ 2018 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.