Unravelling the Resilience of Magnetite Assisted Granules to Starvation And Oxytetracycline Stress

Abstract

In anaerobic granular sludge (AnGS) process, starvation and antibiotics pollution are two frequently challenged issues. Supplying magnetite into anaerobic system has been proved efficient to accelerate microbial aggregates. Nevertheless, whether these magnetite-based granules are still superior over normal granules after a long-term starvation period remains unknown, the responsiveness of these granules to antibiotics stress is also ambiguous. In current study, we investigated the resilience of magnetite-based AnGS to starvation and oxytetracycline stress, by unravelling the variations of reactor performance, sludge properties, ARGs dissemination and microbial community. Compared with the AnGS formed without magnetite, the magnetite assisted AnGS appeared more robust defense to starvation and oxytetracycline (OTC) stress. With magnetite supplement, the average methane yield after starvation recovery and OTC stress was enhanced by 48.95%, 115.87% and 488.41%, respectively, accompanied with less VFAs accumulation, improved tetracycline removal rate (76.3-86.6% vs. 51.0-53.5%) and higher ARGs reduction. Meanwhile, magnetite supplement effectively ameliorated the potential sludge breakage by triggering more large granules formation. Trichococcus was considered an important impetus in maintaining the stability of magnetite-based AnGS process. By inducing more syntrophic methanogenesis partnerships, especially for hydrogenotrophic methanogenesis, magnetite ensured the improved reactor performance and stronger resilience at stress conditions.

Keywords: anaerobic granular sludge, magnetite, starvation, oxytetracycline, microbial community.