Long-Term Impact of Nano Zero-Valent Iron on Methanogenesis in Anaerobic Sludge System: Evaluating Methanogenic Activity, Microbial Community Structure, and Transcription Activity

Abstract

NZVI is commonly used in industrial wastewater treatment. However, its long-term inhibition mechanisms of metabolization in anaerobic sludge systems are not well understood. This study investigated the long-term effects of NZVI on methanogenic activity, microbial community, and transcription activity. The results demonstrated that only 5000 mg/L NZVI led to a significant reduction in cumulative methane production (14.4% of control) within 30 days. NZVI adversely affected cell viability, ATP production, and extracellular polymer (EPS), particularly at higher concentrations. Cell membranes played a crucial role in resisting chronic NZVI toxicity. Moreover, high NZVI levels hindered the transcription of key enzymes CoM and mcrA, while low NZVI levels down-regulated the transcription of cdh and hdr, respectively. Besides, amino-utilizing bacteria was reduced under the high NZVI concentration, while low NZVI changed dominant genus with potential protein hydrolysis function from Candidatus Cloacamonas to Sedimentibacter. The similar change was observed in the archaeal community

Keywords: Nano zero-valent iron, Methanogenesis, microbial community, Metatranscriptomics, Long-term