Impact of static magnetic field on electron transport and microbial community shifts in the nitritation sequencing batch reactor

To reveal the influence mechanisms of static magnetic field on the nitritation process from new perspectives of electron transport and microbial community shift, a static magnetic field-enhanced nitritation SBR process was employed, and the pollutant removals, the hydroxylamine oxidoreductase activity, the cytochrome c content, as well as the electron transport system activity of the activated sludge, were determined while the static magnetic field intensity was reduced from 40 mT to 0 mT via 20 mT and 10 mT. Meanwhile, the microbial community structure was examined. When the static magnetic field intensity was 10 mT, and the concentrations of COD and ammonium nitrogen in influent were 196.42 ± 5.19 mg/L and 96.99 ± 0.53 mg/L respectively, the nitrite accumulation rate was 93.56 ± 1.19%, meanwhile, the highest hydroxylamine oxidoreductase activity, cytochrome c content, and electron transport system activity which were 15.879 ± 0.055 U/mg MLVSS, 0.086 ± 0.001 mg/g MLVSS and 0.288 ± 0.005 μg O2/g·min respectively were obtained. Moreover, the abundance of Nitrosomonas sp. was much higher than those while the intensities were 40 mT, 20 mT and 0 mT. Static magnetic field can accelerate the start-up of the nitritation process, moreover, improve the performance of the process by changing the microbial community structure and improving the HAO activity, the Cyt c content, ETSA, as well as the energy generation of microorganisms. [Display omitted] •10 mT static magnetic field is the optimum for the nitritation process.•10 mT static magnetic field improves the relative abundance of Nitrosomonas sp. in activated sludge.•Static magnetic field can accelerate the start-up of the nitritation process.•Static magnetic field can enhance the electron transport of the nitritation process.