Granular activated carbon remediates antibiotic resistance propagation and methanogenic inhibition induced by polystyrene nanoplastics in sludge anaerobic digestion

Nano/microplastics (NPs/MPs) are prevalent in the sewage sludge in wastewater treatment plants and are inevitably introduced into anaerobic digesters, causing oxidative stress to the microbiome and acting as carriers for antibiotic resistance genes (ARGs). The use of granular activated carbon (GAC) has been shown to increase biomethane production via direct interspecies electron transfer (DIET); however, its impact on reducing oxidative stress and maintaining a stable microbial community in the presence of NPs/MPs is yet to be determined. This study explored the effect of GAC (5 and 15 g/L) on the anaerobic digestion of sludgecontaminated with PsNPs (150 ug/L). The results indicated that PsNPs reduced biomethane yield by 32.3%, but the GAC amendment reversed this impact, enhancing biomethane production by enriching DIET-active microbes and adsorbing PsNPs. Moreover, GAC reduced ARGs and reactive oxygen species (ROS) levels in the digesters, suggesting its ability to remediate NPs-induced methanogenic inhibition and ARGs spread.