Weak magnetic field affected microbial communities and function in the A/O/A sequencing batch reactors for enhanced aerobic granulation

Abstract The lab-scale systems loaded with weak magnetic field (0, 10, 20 and 40mT) were established to explore the effects of weak magnetic field strength on aerobic granulation. Results showed that weak magnetic field could promote the granulation of aerobic sludge obviously, especially when the magnetic field intensity was 10mT. Three-dimensional fluorescence scanning results revealed that magnetic field was beneficial to the enrichment of tryptophan and aromatic proteins. Besides, the magnetic field strength of 10mT could improve TN removal rate obviously, which reached 96.99%, while the other three reactors were less than 80%. Illumina MiSeq sequencing showed that the magnetic field changed the bacterial richness and diversity in this system. And genes Candidatus_Competibacter which contributed to aerobic granulation was identified and found in higher proportions when the magnetic field strength was 10mT. Therefore, this study helps revealing the mechanisms of accelerating sludge granulation through applying weak magnetic field.