Short CommunicationEffects of cerium oxide nanoparticles on the species and distribution of phosphorus in enhanced phosphorus removal sequencing batch biofilm reactor

•20 mg/L CeO2 NPs posed adverse effects on the process of P removal in biofilm.•The transformation of P in EPS was influenced during anaerobic period.•The formation of polyP in cells and EPS declined after aerobic exposure.•The characterizations and roles of EPS in P removal were impacted.

The short term (8 h) influences of cerium oxide nanoparticles (CeO2 NPs) on the process of phosphorus removal in biofilm were investigated. At concentration of 0.1 mg/L, CeO2 NPs posed no impacts on total phosphorus (TP) removal. While at 20 mg/L, TP removal efficiency reduced from 85.16% to 59.62%. Results of P distribution analysis and 31P nuclear magnetic resonance spectroscopy implied that the anaerobic degradation of polyphosphate (polyP) and the release of orthophosphate in extracellular polymeric substances (EPS) were inhibited. After aerobic exposure, the average chain length of polyP in microbial cells and EPS was shorter than control, and monoester and diester phosphates in cells were observed to release into EPS. Moreover, the EPS production and its contribution to P removal increased, while the capacity of EPS in P storage declined. X-ray diffraction analysis and saturation index calculation revealed that the formation of inorganic P precipitation in biofilm was inhibited.

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