Enhancement of the denitrification performance of an activated sludge using an electromagnetic field in batch mode

The influence of electromagnetic fields on bacterial denitrification has been tested on synthetic media with sludges from wastewater treatment stations, in batch mode. The effects of the intensity of the magnetic induction ratio B (mT), reaction volume and initial biomass concentration on the kinetics of the denitrification process were studied. Magnetic field had both an optimal stimulating effect on the activity of the denitrifying flora for B (mT)/mgx values of the order of 0.212, and an inhibitory effect for the values beyond the latter.Sludges underwent multiple exposure cycles to magnetic fields. It was shown that, after three exposure cycles, denitrification kinetics went from 6.5 to 12.7 mg N-NO^-₃.L^-1.h^-1 which corresponds to a 2.7 fold improvement. The improved performance persists even after the cessation of the magnetic field. Observation of the sludge by the environmentalelectron microscope shows that the microbial population forming the starting sludge; changed following exposure to the magnetic field. The action of the; electromagnetic field on the microbial populations in denitrification resulted in the modification of the diversity of the flora that is initially present, favoring the development of Proteo bacteria, particularly the Betaproteo bacteria subclass, which results in improved denitrification.