In this study, the critical level of NH 4 + and Fe was estimated as a minimum concentration below which the activity of the hydrogenotrophic methanogenesis starts getting affected. For NH 4 + and Fe, the critical levels were estimated as 0.3 g/L and 1.5 mg/L, respectively. Dupnock and Deshusses, (2019) used artificial nutrient media in their study for BTF and reported similar values, where NH 4 + and Fe concentrations higher than 1 g/L and 2 mg/L, respectively were reported as optimal. They reported a 41% increase in PC after the NH 4 + and Fe concentrations in the nutrient media were optimized. For wastewater treatment by an anaerobic digester, a minimum requirement of Fe was estimated as 1.9 mg/L .