1. School of Environment and Resource，Southwest University of Science and Technology，Mianyang 621010，China
2. College of Resource and Environmental Engineering，Yibin University，Yibin 644007，China
3. National Research Center for Municipal Wastewater Treatment and Reuse，Southwest University of Science and Technology，Mianyang 621010，China
Abstract：The anaerobic-anoxic-oxic moving bed bio-film reactor(MBBR) process was used to treat campus sewage, and the removal efficiencies of main pollutants were studied in this paper. The composition and transformation of dissolved organic matter (DOM) in wastewater were analyzed with three-dimensional fluorescence spectra and ultraviolet spectroscopy. The results showed that the MBBR process had good purification effect on contaminants. The removal rate of COD, NH3-N, TN, TP and DOC had reached 83.0%, 70.9%, 52.4%, 59.2% and 62.2%, respectively. Moreover, there were three dominant peaks in the three-dimensional fluorescence spectrogram, and their central locations were near Ex/Em=230/325 nm(peak T), Ex/Em=280/350 nm(peak S) and Ex/Em=350/440 nm(peak R), respectively. The main fluorescent material in sewage included tryptophan (Trp), soluble microbial products (SMP) and humic acid (HA). The central position and fluorescence intensity of the peaks had changed along the MBBR process, indicating that the composition and concentration of DOM vary with the treatment process. The peaks of Trp and SMP almost disappeared after treatment, which revealed that MBBR process has remarkable effect on the removal of proteinoid. Meanwhile the fluorescence intensity of SMP in anaerobic tank, anoxic tank and oxic tank decreased to 37.1%, 20.3% and 13.1%, respectively, showing that the microorganism can well decompose SMP in each biochemical stage of the MBBR process. However, the fluorescence intensity of HA decreased slightly, and the process seemed to be ineffective on removing of humic acid. In addition, the vales of HIX, FI and BIX had gradually increased and the metabolism of microorganisms played an important role in the degradation of contaminants in the MBBR process. The humification and maturity of DOM had gradually enhanced with HIX during MBBR process. The FI values of wastewater from anoxic tank, oxic tank and effluent were about 1.9 (1.899, 1.881, 1.887, respectively), implying that the humus organic compounds in sewage were mainly derived from microbial metabolic activities. And the BIX values of DOM in anoxic pond, oxic pond and effluent were around 1.0 (0.985, 1.018, 0.979, respectively), indicating that other DOM in wastewater were also mainly caused by microbial metabolism. Besides, the value of E250/E365 had decreased gradually along the process but SUVA254 had risen continuously, which illuminated that the composition and content of DOM in sewage had changed significantly after being treated by the MBBR process. And the conjugate unsaturated double bonds of organic matter had increased, as well as the degree of polymerization, humification and molecular mass.
