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 P-31 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. (C) 2016 Elsevier Ltd. All rights reserved.