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Regulating Secretion of Extracellular Polymeric Substances through Dosing Magnetite and Zerovalent Iron Nanoparticles To Affect Anaerobic Digestion Mode

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journal contribution
posted on 23.04.2019, 00:00 by Shiyang Li, Yi Cao, Zhiqiang Zhao, Yaobin Zhang
Anaerobic digestion technology is a promising method to reduce the usage of fossil fuels by transforming organic waste into biogas. Nano zerovalent iron (nZVI) and nano iron oxide have been reported to affect metabolism modes of anaerobic digestion, i.e., interspecies hydrogen transfer (IHT) and direct interspecies electron transfer (DIET). However, the effects of the nanoparticles on extracellular polymeric substance (EPS) potentially capable of participating in the mass transfer or electron transfer of these two metabolism modes remains unclear. In this study, the addition of nanomagnetite (nFe3O4) significantly enhanced the performance of anaerobic treatment, while adding nZVI led to a decline of the performance. nFe3O4 stimulated the secretion of proteins and humic substances in EPS, which were confirmed electroactive to serve as electron shuttles to enhance the DIET pathway of anaerobic digestion. In contrast, the addition of nZVI increased EPS especially polysaccharide to resist cell disruption caused by nZVI, which resulted in an inefficient mass transfer to decrease IHT. These results were in agreement with the microbial community analysis and the functional gene prediction.