title: Metagenomic sequencing
design: Different doses of nano zero-valent iron (nZVI) and Fe3O4 nanoparticles (Fe3O4 NPs) were added to AD reactors respectively. After the mesophilic semi-continuous anaerobic digestion of sludge for 105 days, the sludge in the reactor was collected and the microorganisms in the sludge were sequenced.