Tracing the variation of dissolved organic matter in the two-stage anoxic/aerobic process treating swine wastewater using fluorescence excitation-emission matrix with parallel factor analysis.

Swine wastewater has become one of the main agricultural pollution sources. Quantitative characterization of dissolved organic matter (DOM) is often used in various water bodies, but there are few studies on DOM analysis of swine wastewater. In this study, swine wastewater was treated by a step-feed two-stage anoxic/aerobic (SF-A/O/A/O) process. By using parallel factor (PARAFAC) analysis of fluorescence excitation-emission matrix (EEM), the main components of swine wastewater were aromatic protein-like substances (C1), tryptophan-like substances (C2), fulvic acid-like/humic-like substances (C3) and humic-like substances (C4). Protein-like substances were degraded significantly, while humic-like substances were difficult to be utilized by microorganisms. Fluorescence spectral indexes showed that the characteristics of endogenous input and humus were enhanced. Moreover, several significant correlations between DOM components, fluorescence spectral indexes and water quality indexes were observed. These findings help to understand the biochemical role and the impact of DOM in water quality monitoring and control of swine wastewater.