The anammox-based technologies are generally inhibitedby refractorydissolved organic matter (rDOM), which is ubiquitous in real wastewater.In this study, a novel cost-effective approach, namely, zero-valentiron (ZVI) treatment, was presented to alleviate such inhibitory effects.The results showed that ZVI mitigated the inhibition of fulvic acids(FA) to anammox. Due to the 2 g/L ZVI addition, the nitrogen removalefficiency (NRE) increased from 83.53 to 90.06% when the FA concentrationincreased from 0 to 160 mg/L in wastewater. Additionally, the co-occurrencenetwork linking Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS) and 16S rRNA sequencing results revealed the mechanismof ZVI mitigating inhibition by promoting the reduction of nitro andnitroso groups of FA and reshaping the metabolic division of functionalbacteria. Hydrolytic acidifying bacteria (e.g., Anaerolineaceae and Ignavibacterium) were enriched for FA degradation,which was ultimately beneficial for denitrifying bacteria and anaerobicammonium oxidation bacteria (AnAOB). Furthermore, metagenomics revealedthat ZVI stimulated multiple nitrogen removal formed by anammox, denitrification,and DNRA by accelerating extracellular electron transfer resortingto FA serving as an electron shuttle and upregulating functional genesencoding electron generation, transport, and consumption processes.
