Effect of magnetic fields on simultaneous nitrification and denitrification microbial systems

Abstract

Magnetic fields positively influence the nitrogen removal efficiency in activated sludge systems. However, the structural succession pattern of microorganisms by magnetic fields still remains further explored. In this paper, a magnetic simultaneous nitrification and denitrification (MSND) reactor was constructed, and the influence of optimized magnetic field intensity (0, 10, 20 and 30 mT) on the nitrogen removal efficiency was investigated at HRT 6 h, 28.0–30.0 °C, and pH 7.0–8.0. Molecular biology was used to investigate the succession process of the dominant microbial flora and the functional gene structure of MSND systems. The results showed that the denitrification effects of the MSND system were significantly enhanced, which contributed to the lower concentration of total nitrogen in the effluent of the magnetic reactor than that of the nonmagnetic group reactor. The magnetic fields induced the succession of microbial community structure and improved the stability of microbial communities, thereby the relative abundances of nitrifying and denitrifying bacteria, and the functional genes were improved. In particular, the abundance of functional genes related to gene proliferation and transmembrane transport was increased. Therefore, the efficient nitrogen removal was achieved, which gives inspiration in the enhanced wastewater treatment by magnetic fields. HIGHLIGHTS The influence of magnetic fields with different magnetic field strengths on SND systems was explored.; The succession process of microbial dominant flora and functional gene structure in the SND system was analyzed.; The biological mechanism of the better denitrification effect of SND under magnetic field conditions was clarified.;

Keywords

• functional gene prediction
• magnetic field
• microbial communities
• simultaneous nitrification and denitrification