Abstract:Three-dimensional emission and excitation matrixs (EEMs) was used to characterize the soluble micro-products (SMP), loosely-bound extracellular polymeric substances (LB-EPS) and tightly-bound extracellular polymeric substances (TB-EPS) extracted from activated sludge in five municipal wastewater treatment plants in Xiamen (WWTP). Three fluorescence peaks were identified in EEMs of SMP, LB-EPS and TB-EPS, in which Peak A (Ex/Em=225~230/335~ 350nm) and Peak B (Ex/Em=275~280/330~350nm) were attributed to the protein-like fluorophores, and Peak C (Ex/Em=320~350/420~445nm) was characterized as humic-like fluorophores. Results of the peak intensity showed that the major components of LB-EPS and TB-EPS were significant correlated with TOC concentration in some degree. Fluorescence regional integration (FRI) analysis showed that microbial by-products existed in TB-EPS much more than that in LB-EPS and SMP. The sum FRI of I, II and IV regions presented linear relationship with TOC concentration in LB-EPS and TB-EPS.