The Effect of Static Magnetic Field on Methanogenesis in the Anaerobic Digestion of Municipal Sewage Sludge

The present study aimed to determine the effect of a 17.6 mT static magnetic field (SMF) on the efficiency of anaerobic digestion (AD) of municipal sewage sludge (MSS). The SMF had a significant impact on methane (CH4) production efficiency, the levels of fermentation rate (eta FMSS) vs. removal rate (eta VS), and the structure of the anaerobic bacteria consortium, but it did not affect cumulative biogas production. The highest CH4 yield (431 +/- 22 dm(CH4)(3)/kgVS) and the highest methane content in the biogas (66.1% +/- 1.9%) were found in the variant in which the SMF exposure time was 144 min/day. This variant also produced the highest eta FMSS and eta VS values, reaching 73.8% +/- 2.3% and eta VS 36.9% +/- 1.6%, respectively. Longer anaerobic sludge retention time in the SMF area significantly decreased AD efficiency and caused a significant reduction in the number of methanogens in the anaerobic bacteria community. The lowest values were observed for SMF exposure time of 432 min/day, which produced only 54.8 +/- 1.9% CH4 in the biogas. A pronounced reduction was recorded in the Archaea (ARC915) and Methanosaeta (MX825) populations in the anaerobic sludge, i.e., to 20% +/- 11% and 6% +/- 2%, respectively.

Automated summary

The study investigated the effect of a 17.6 mT static magnetic field on the efficiency of anaerobic digestion of municipal sewage sludge. Results showed significant impact on methane production efficiency, fermentation rate, and bacterial community structure, but no effect on cumulative biogas production. Longer exposure time to the magnetic field led to decreased efficiency and reduced populations of methanogens in the anaerobic sludge.