The effects of WO3 nanoparticles(NPs)with various concentrations on nitrogen removal and extracellular polymeric substances(EPS)of activated sludge were investigated in sequencing batch reactors(SBR).The results showed that 10 mg/L WO3 NPs(WO10)in the SBR had no effect on nitrogen removal process,while 100 mg/L WO3 NPs(WO100)reduced the specific nitrate and nitrite reduction rates,leading to the accumulation of nitrite and nitrate in the effluent.WO10 had very limited effects on EPS content and composition,but WO100 significantly increased the amount of loosely bound EPS(LB-EPS)and polysaccharide content in EPS.The results of Fourier infrared spectroscopy(FTIR)indicated that WO10 only affected the functional groups of LB-EPS,while WO100 exhibited varying degrees of influence on the functional groups of both LB-EPS and tightly bound EPS(TB-EPS).Functional groups such as—OH,C=O and C—O—C were involved in the interactions between EPS and WO3 NPs.Further analysis revealed that WO3 NPs changed the secondary structure composition of proteins in EPS,which affected the flocculation capability of activated sludge.
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