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

Abstract

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 (ηFMSS) vs. removal rate (ηVS), and the structure of the anaerobic bacteria consortium, but it did not affect cumulative biogas production. The highest CH4 yield (431 ± 22 dm3CH4/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 ηFMSS and ηVS values, reaching 73.8% ± 2.3% and ηVS 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.

Wastewater Treatment and Biogas Production: Innovative Technologies, Research and Development Directions

“…As demonstrated in other studies, the SMF also influences the growth and metabolism of bacteria. The SMF had a significant impact on methane production efficiency, the fermentation rate level, removal rate and the structure of the anaerobic bacteria consortium, but it did not affect cumulative biogas production [6]. The highest CH 4 yield (431 ± 22 dm 3 CH4 /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.…”

“…Zieli ński et al [6] determined the effect of a 17.6 mT static magnetic field (SMF) on the efficiency of anaerobic digestion (AD) of municipal sewage sludge (MSS). Only a few reports can be found on the use of the static magnetic field (SMF) to improve the anaerobic digestion of MSS.…”

“…The highest CH 4 yield (431 ± 22 dm 3 CH4 /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. A 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 [6].…”

Synergistic Effect of Magnetite and Bioelectrochemical Systems on Anaerobic Digestion

“…Of late, a new concept that uses the application of a constant magnetic field coupled with anaerobic digestion has revealed microbial activity improvement and high methane generation [ 7 , 8 ]. A much more promising constant magnetic field system is an anaerobic bioelectrochemical system (BES), which is an electrochemical digester wherein electrochemically active bacteria, otherwise known as exoelectrogens, improve the redox reactions at the surface of an electrode.…”

“…The results revealed a high increase in accumulated methane production of up to 21.5% over the control when using the digester with an electromagnetic strength of 7.5 mT, whereas carbon oxygen demand (COD) removal increased by 15%. A study was done by Zielinski et al [ 8 ] on the impact of a 17.6 mT constant magnetic field on the anaerobic digestion process of sewage sludge. The static magnetic field had a substantial effect on the generation of methane, rate of fermentation versus rate of removal, and the morphology of the anaerobic microbial population.…”