Enhanced sludge thermophilic anaerobic digestion performance by single-chambered microbial electrolysis cells under ammonia inhibition

Abstract

Enrichment of the microbial mass is critical to enhance the performance of anaerobic digestion, especially under adverse conditions. In this study, microbial electrolysis cells combined with anaerobic digesters were used for anaerobic digestion of ammonia rich synthetic substrates and sludge. For the synthetic substrate, with the increasing of applied voltage, the methane yield presented earlier increase and later decrease trend. The methane yield was the highest at an applied voltage of 0.7 V. For the sludge, the amounts of ammonia nitrogen and free ammonia nitrogen at an applied voltage of 0.7 V were higher than that at 0 V, and the maximum methane yield at voltages of 0 V and 0.7 V were 52.6 and 97.8 mL g−1-VSSadded, respectively. Methanosarcina and Methanothermobacter were the predominant archaea. Archaea species at an applied voltage of 0.7 V were more diverse than those at an applied voltage of 0 V. The results indicated that microbial electrolysis cells could increase the number and mass of microbial species in the thermophilic anaerobic digesters under ammonia inhibition. This study might provide a feasible method to operate sludge thermophilic anaerobic digestion at higher organic loading rates.