Characterization of Dissolved Organic Matter Removal during Biological Treatment of Commingled Chemical Industrial Wastewater: Relationship with Fluorescent Dissolved Organic Matter Transformation

In this study, the transformation characteristics of fluorescent dissolved organic matter (FDOM) were investigated to characterize the removal of dissolved organic matter (DOM) during biological treatment of commingled chemical industrial wastewater. The results of fluorescence excitation and emission spectroscopy and parallel factor analysis revealed three components (C1, C2, and C3) of FDOM, which were related not only to surface and sewage sources but also chemical industrial wastewater sources. Resin fractionation results showed that the removal of DOM was affected not only by substrate biodegradability but also by DOM generation, such as intermediates, end products, and soluble microbial products, during biological treatment. However, the same variation tendency between DOM and FDOM, based on molecular weight (MW) distribution, was observed during MW fractionation. The changes in DOM in MW>10 kDa fraction apparently corresponded with C2 variation; the tendency of DOM removal in MW of 0.5-10 kDa fraction was possibly related to the evolutions of all three components; and lastly, the removal of DOM in MW<0.5 kDa fraction was found in accordance with C1 and C3 transformations. The removal and transformation of DOM and FDOM were investigated using gas chromatography-mass spectrometer and Fourier transform infrared spectroscopy.