Treatment Efficiency and Microbial Community Diversity in a Magnetic Field Enhanced Sequencing Batch Reactor (SBR)

Abstract

The application of SBR reactors is becoming more common and in order to further improve the efficiency of their treatment it has been proposed to add a magnetic field to SBR systems. The effects of different magnetic fields on the degradation efficiency of conventional pollutants in an SBR was studied. MiSeq high-throughput sequencing techniques were used to analyze the diversity of microbial communities in activated sludge under magnetic field conditions. These results show that the addition of a magnetic field improves the performance of a SBR system to an extent and magnetic induction effects are most obvious at 7×10-2 T. This is identified through a significant effect on the removal efficiency of total nitrogen and an increase in the denitrification rate from 65.69% to 85.98%. It also significantly improves the activity of sludge dehydrogenase and has a positive effect on the removal of various pollutants. The diversity of microbial communities in activated sludge under different magnetic field intensities shows a greater microbial abundance and diversity in the active sludge. The bacterial domain in the experimental SBR includes 14 phyla, which are mainly Proteobacteria (25.3%-61.5%), Bacteroidetes (18.6%-46.2%), Actonobacteria (5.3%-47.2%), and Acidobacteria (0.4%-4.0%). Important denitrification bacteria such as Rhodoblastus, Paracoccus of α-Proteobacteria, Alicycliphilus, Comamonas, Xenophilus, Acidovorax, Dechloromonas, Thauera of β-Proteobacteria, Desulfovibrio of δ-Proteobacteria and Planctomycetes, etc. at a moderate magnetic induction of 7×10-2 T have a high abundance and there is an internal relationship between this and an increase in denitrification efficiency. Polyphosphate-accumulating organisms (PAOs) such as Acinetobacter, Pseudomonas, Propionicimonas, etc., are present at higher levels under these conditions and follow the same trends as for the phosphorus removal rates. There is a correlation between bacterial community structure changes and sewage treatment efficiency in activated sludge. Applied magnetic fields have a positive effect on sewage treatment by changing the microbial community structure.