Effects of static magnetic field exposure on the biodegradation of volatile organic compounds with different hydrophilicities
The biodegradation of three model Volatile Organic Compounds (VOCs) was carried out in fed batch bioreactors in absence and presence of static magnetic fields (SMFs) of different intensities (20, 40, and 70 mT). The VOCs represented highly hydrophobic, moderately hydrophilic and hydrophilic pollutants encountered in gaseous industrial emissions (hexane, toluene, and methanol, respectively). SMFs did not have a strong influence on hexane consumption rates, associated CO2 production, and biomass growth. Contrarily, SMFs enhanced the treatment of VOCs with higher water solubility. Particularly, toluene maximum consumption rates increased by 38%, compared to the non-exposed control, in presence of a 70 mT SMF (0.43 mg h-1), associated with a higher CO2 production and biomass growth. The composition of the bacterial community was also affected, with a higher relative abundance of Pseudomonas (increasing from 3 to 11%). Similarly, methanol consumption was enhanced by 30% at any SMF applied. Such enhancement could be related to a higher enzymatic activity, as SMF 40 mT achieved higher methanol mineralization percentages compared to the non-exposed control (62 vs. 44%, respectively). A proper SMF can thus improve the treatment of vapors of hydrophilic or moderately hydrophilic VOCs, which is limited by biological consumption rates. SMFs seem to influence enzymatic activities, and, in some cases, the composition of microbial populations.