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There were significant differences of the DOM fractions in the DMBR before and after AT addition. The peaks of I, II and III disappeared compared to the influent with AT addition. The peak V composed of microbial products and humic acid-like organics significantly increased compared to the influent and the reactor without AT addition. Meanwhile the peak V of the effluent in the sDMBR with AT addition was high, indicating that the microbial products accumulated in the reactor after AT addition. Moreover, the representative complex organics based on the characteristic peak are summarized in Table 4. The two dominating peaks could be divided among the detected contour lines. Shapes of sample spectra from the sDMBRs with and without AT addition were significantly different. A peak that could be attributed to a protein-like substance observed at Ex/Em = 270/320 nm dominated in the case of mixed liquid in the sDMBR, whereas peaks that could be attributed to humic acid-like substance at Ex/Em = 330/400 nm and Ex/Em = 270/450 nm became apparent in the case of mixed liquid in the sDMBR. However, relative dominance of the peak of protein-like substances differed in the descending order of sDMBR without AT addition < sDMBR with AT addition. The results also proved that the AT added sDMBR could obtain a steady performance with the fluorescent intensity reduced by 16 ∼ 35% compared to the sDMBR without AT addition. Moreover, the decreasing number of conjugated bonds in the protein-like structure was observed in DOM during the sDMBR treatment process, indicating a potential of EEM fluorescence spectra as an effective analytical tool for DOM (Duan et al. 2011c). The DOM removal efficiency clarified that the AT addition played an important role in the DOM removal.

Table 4

Characteristics of EEM fluorescent intensity (FI) for specific peaks in sDMBR with and without AT addition

Protein like-peak
Fulvic acid-like peak
Samplesλex/λemFIλex/λemFI
Influent 230/363 280/363 940.3 1,204.6 330/405 568.1 
Mixture liquid in sDMBR without AT addition 260/420 235.8 340/417 427.0 
Effluent in sDMBR without AT addition 260/425 211.5 340/410 413.2 
Mixture liquid in sDMBR with AT addition 260/423 80.21 340/419 146.96 
Effluent in sDMBR with AT addition 260/427 65.01 340/420 111.59 
Protein like-peak
Fulvic acid-like peak
Samplesλex/λemFIλex/λemFI
Influent 230/363 280/363 940.3 1,204.6 330/405 568.1 
Mixture liquid in sDMBR without AT addition 260/420 235.8 340/417 427.0 
Effluent in sDMBR without AT addition 260/425 211.5 340/410 413.2 
Mixture liquid in sDMBR with AT addition 260/423 80.21 340/419 146.96 
Effluent in sDMBR with AT addition 260/427 65.01 340/420 111.59 

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