nZVI-Mediated Cell Membrane Repair and Respiratory Chain Reconstruction Enhance Biological Denitrification Mechanisms under Chlorfenapyr Stress

This study addresses the decline in biological denitrification performance caused by the respiratory chain inhibition of the arylpyrrole insecticide chlorfenapyr. A nanoscale zero-valent iron (nZVI) enhanced biological aerated filter (BAF) system was constructed to investigate the enhancement efficiency of nZVI and its regulatory mechanisms on the metabolism of denitrifying microorganisms. The results showed that nZVI significantly improved the system's shock load resistance and recovery resilience. Under chlorfenapyr stress, the system maintained a maximum NH4+-N removal rate of 83.86% and TN removal rate of 80.88%. Multi-omics analysis indicated that nZVI promoted the expression of extracellular polymeric substances (EPS) related genes to ensure their secretion and structural stability. This process effectively reduced reactive oxygen species (ROS) levels and achieved 81% biodegradation of chlorfenapyr. nZVI alleviated the impact of chlorfenapyr stress on the dominant phylum Pseudomonadota and simultaneously induced the directional enrichment of Luteimonas and Truepera with tolerance and degradation potential. Analysis of the respiratory chain and nitrogen metabolism pathways revealed that nZVI up-regulated the expression of genes encoding respiratory chain core complexes including Complex I through Complex V. nZVI also mitigated the 10% inhibition of denitrification (NAR) genes caused by chlorfenapyr and promoted the dissimilatory nitrate reduction to ammonium (DNRA) pathway. Metabolic correlation analysis further demonstrated that nZVI induced the directional enrichment of the key functional genus Luteimonas and driven its secretion of Lpc (18:1) and Lpc (19:1-Sn1) to strengthen biofilm repair. This work provides theoretical support for the efficient and stable operation of high-toxicity and high NH4+-N wastewater treatment.