Low-intensity magnetization pretreatment to enhance biomethane generation and the abundance of key microorganisms for anaerobic digestion of sewage sludge.

This work explores the impact of static magnetic field (SMF) intensity on biomethane production from anaerobic digestion (AD) of sewage sludge. Two different SMF intensities (20 mT and 1.5 T) were applied to magnetize the sludge destined to the AD process. The magnetic pretreatment at 20 mT was particularly effective, as it increased biomethane production by 12.7 % compared to the control test. On the contrary, exposing the sludge to 1.5 T adversely affected biomethane production, resulting in a 15.1 % decrease. The positive correlation observed between low-intensity SMF exposure and enhanced biomethane yield, in contrast to the inhibitory effect of high-intensity SMF, suggests the existence of an optimal intensity threshold within the lower range for maximizing methane production. The impact of magnetic pretreatment on the anaerobic microbial community was investigated through high-throughput sequencing analysis of magnetized sludge samples. This approach enabled the identification of specific shifts in microbial populations associated with SMF exposure, thereby elucidating the role of SMF in modulating key microbial communities for the AD process. The findings of this study provide insights into the potential mechanisms underlying these responses and underscore the potential of SMF application for improving the anaerobic valorization of sewage sludge.