Performance of electroactive anaerobic granular sludge under ammonia stress: Performance, microbe and morphology

Thermal hydrolysis pretreatment increases the organic loading rate by releasing organics into the liquid phase. However, high solid anaerobic digestion often faces ammonia stress, which inhibits methanogenic performance. This study explored the feasibility of direct interspecies electron transfer (DIET) in improving the performance of anaerobic granular sludge (AnGS) under ammonia stress. Furthermore, when incubated with ethanol, COD removal efficiency decreased from 95 ± 4 % under conventional ammonia nitrogen conditions to 75 ± 3 % under ammonia stress. Similarly, 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride-electron transport system activity declined by 16 % under ammonia stress. Microbial community analysis revealed a shift in DIET partners, from Geobacter - Methanothrix to unclassified genus from family Anaerolineaceae, order Bacteroidales, and family Clostridiaceae - Methanosarcina under ammonia stress. Methanothrix deficiency under ammonia stress altered the spatial structure of AnGS. Therefore, reconstructing spatial structure of AnGS by providing filamentous methanogens skeleton could improve DIET performance under ammonia stress.