Stimulating volatile fatty acid production in anaerobic digestion: Bacterial community shifts induced by nano-zero valent iron and magnetite nanoparticles

Abstract

The production of volatile fatty acids (VFA) through anaerobic digestion has gained significant attention due to its potential benefits for renewable energy, biofuel production, waste valorization, bioproduct synthesis, and wastewater treatment. Nano-zero valent iron (nZVI) and magnetite nanoparticles (FeO-NPs) have been identified as effective nanomaterials for enhancing methane production, although their application in stimulating VFA production remains underexplored. This study aimed to increase VFA production by adding nZVI, Fe3O4-NPs, and nZVI/Fe3O4-NPs while investigating the associated changes in bacterial communities. AD of glucose was performed using municipal wastewater sludge over 25 days, with the sludge amended with 400mgL¹of nanoparticles. Total DNA samples were collected post-digestion to analyze bacterial community shifts. Results showed a significant enhancement of VFA production by both nZVI and FeO-NPs, with the highest output in the FeO-NPs treatment (811.7mg COD L¹), followed by nZVI (769.9mg COD L¹) and combined nZVI/FeO-NPs (455.7mg COD L¹). This significant enhancement highlights the potential of these nanoparticles in waste-to-energy anaerobic digestion systems. Propionic acid was predominant in nZVI, whereas acetic acid was most abundant in FeO-NPs. Microbial community analysis revealed Firmicutes as the most abundant phylum across treatments, with varying effects due to nZVI and FeO-NPs.