Effect of Magnetite on Anaerobic Digester Biogas, Hydrogen Sulfide Gas, Digester Effluent, and Related Processes

AbstractSome wastewater treatment (WWT) facilities are using magnetite in their treatment process, through a technology called BioMag, and stabilizing their wasted sludge using anaerobic digestion (AD) after recovering most of the magnetite for reuse. This research investigated whether this magnetite would benefit the AD process to assess the possibility of magnetite recovery after AD, which could reduce the loading on the recovery equipment as well as operation and maintenance costs of magnetite recovery due to decreased sludge quantities. Because some conflicting results were found in previous studies, which could be due to particle size, or to particle stability, because some studies used synthesized magnetite particles that can be unstable, which may affect the properties and behavior of the magnetite, this study used the same magnetite supplied for the BioMag process. The effects of this magnetite on biogas production, biogas composition, hydrogen sulfide gas (H2S) reduction, and digester effluent were investigated. Results showed an increase in the effluent dissolved iron and a 49% reduction in H2S. No considerable effect was seen on the gas volume and composition.