Enhanced anaerobic digestion of waste activated sludge using magnetite-modified sludge ceramsite: Performance and microbial dynamics

The effect of magnetite-modified sludge ceramsite on anaerobic digestion of sludge was systematically investigated in this study. The results revealed that the addition of magnetite significantly altered the properties of the ceramsite, while magnetite-modified ceramsite significantly altered the sludge anaerobic digestion process. Biochemical methane production potential experiments demonstrated that the cumulative methane production of the experimental group with moderate ceramsite addition was enhanced by 17.8% compared to the control group without ceramsite. This enhancement was attributed primarily to the favorable pore structure and biocompatibility of the modified ceramsite. The incorporation of magnetite facilitated the enrichment of microorganisms and the reduction of Fe(III), thereby promoting anaerobic digestion. Moreover, the ceramsite exhibited strong buffering capacity, contributing to the enhanced stability of the digestive system. Microbiological analyses revealed that the addition of ceramsite significantly altered the microbial community. Appropriate ceramsite addition resulted in the enrichment of bacteria associated with organic matter degradation and methanogenesis. Furthermore, potential iron-reducing bacteria ( Clostridium_sensu_stricto ) and bacteria capable of direct interspecies electron transfer ( Syntrophomonas ) were also enriched in the anaerobic system. This study demonstrates a viable approach for the efficient resource utilization of sludge.