Evaluation of the pollutant interactions between different overlying water and sediment in simulated urban sewer system by excitation-emission matrix fluorescence spectroscopy.

The water quality in the sewer systems can be significantly influenced by the interaction between sediment and overlying water, which are still many doubts about the impact of pollutants transformation, degradation sequence, and reaction time. In this study, the exchanging processes between sewer sediment and four different overlying waters were evaluated in simulated urban sewer systems (dark and anaerobic environments). Dissolved organic matter (DOM) was used as an indicator to reflect the mitigation and exchange processes of pollutants. Excitation-emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC) as an effective method for deciphering DOM properties was applied. There are three findings: (1) Three main processes (biological degradation, desorption, and adsorption) happened in the simulated sewer systems, in which the predominant pathway in the interaction process is biological degradation though consuming amino acid components. (2) The characteristics of overlying water could induce significant changes in sediment signatures; the amino acid-like components are more susceptible to degradation, and the humic-like compositions are more readily absorbed by sediments. (3) The reaction time is another significant factor (14 days was the turning point of the processes). This study unravels the transformation processes in sediment and different overlying waters, which provides the theoretical foundation for urban sewer efficient management and operation.