Characterization Of Wastewater Quality Using Fluorescence Excitation-emission Matrix

Dissolved organic matter (DOM) widely existed in various water bodies. The presence of DOM not only has a substantial effect on the health of ecosystem, but also presents challenges in water treatment processes. In this study, DOM was characterized using fluorescence excitation-emission matrix and parallel factor (EEM-PARAFAC) analysis. The correlation between EEM data of DOM and conventional water parameters, and the efficiency of sequential UV-based and biofilm process for the treatment of secondary effluent, as well as the fluorescence quenching effects of antibiotics on the main components of dissolved organic matter were all investigated. The following conclusions were obtained.(1) The correlation between EEM data of DOM and conventional water parameters COD and TOC was investigated. The results showed that three fluorescent components could be obtained when DOM was characterized using EEM-PARAFAC. The correlation between the scores of protein-like component and COD, TOC was strong. Thus, the prediction of COD and TOC of wastewater could be performed by the scores of protein-like component, and the accuracy of prediction could be enhanced by adding the scores of other two fluorescent components on the base of multiple regression analysis.(2) The efficiency of sequential UV-based and biofilm process for the treatment of secondary effluent was investigated. The results showed that UV254 and trace organic contaminants could be removed effectively by UV-based processes, but only low mineralization can be achieved. However, UV254 could be further removed by subsequent biofilm treatment processes, and more important, TOC could also be reduced during these processes. The results from EEM-PARAFAC and gel-permeating chromatography indicated that higher molecular weight DOM was decomposed into lower molecular weight DOM during UV-based processes, which was more biodegradable and was further degraded in the following biofilm process, causing the obvious mineralization of secondary effluent.(3) The fluorescence quenching effects of antibiotics on the main components of dissolved organic matter were investigated. The results showed that among these four antibiotics, roxarsone, sulfaquinoxaline sodium and oxytetracycline led to a stronger quenching effect than erythromycin. Moreover, from the side of DOM, tyrosine and tryptophan exhibited a similar quenching effect, but they were higher than humic acids at the same concentration of antibiotics. For humic acid, a significant quenching effect was observed only with the addition of roxarsone.