Unraveling the Resistance Mechanism of Anammox Granular Sludge to Iron Nanoparticles

Abstract

Iron nanoparticles (FeNPs) generated from industrial activities could end up into the sewer system, and potentially affect wastewater treatment processes. The impact of FeNPs on anammox process is getting increasing attention. However, the resistance mechanism of anammox granular sludge (AnGS) to FeNPs has not been fully elucidated. The current study investigated the metabolic and morphological response of AnGS to acute and chronic FeNPs exposure. Results showed that nitrogen removal efficiencies were elevated under FeNPs exposure. Extracellular polymeric substances (EPS) of AnGS were stimulated by FeNPs, which largely contributed to the adsorption of FeNPs on AnGS surface. Highly absorbed particles appeared inside the bacterial cells, soft X-ray imaging illustrated that anammox bacteria maintained intact cellular and anammoxosome structures under FeNPs exposure. Anammox bacterial abundance increased under FeNPs exposure. and anammoxosome membrane ensured anammox bacterial metabolism under FeNPs exposure. This study extended fundamental understanding of AnGS resistance mechanisms to FeNPs.

Keywords: Iron nanoparticles (FeNPs), Anaerobic ammonia oxidation (anammox), Extracellular polymeric substances (EPS), Micromorphology