Fluorescence Spectroscopy As a Tool for the Characterization of Natural Organic Matter and the Control and Optimization of Drinking Water Treatment Processes

Natural Organic Matter (NOM) present in source waters is a complex and not fully characterized mixture of humic, fulvic and protein like compounds which determine its characteristics and chemical properties. The unique character of the NOM in each water source is determined by biological, geographical and seasonal factors which cause dynamic behavior. Water treatment processes are highly influenced by the nature and concentration of NOM in the water under treatment. Coagulation efficiency and the extent of the Disinfection by-Products (DBP) formation are greatly determined by the specific character of the Natural Organic Matter in the source water. Fluorescence spectroscopy represents a tool for characterizing the nature of the NOM and assessing its dynamics, transformations and interactions under treatment. The analysis of the Excitation-Emission Matrices (EEM) requires the application of mathematical techniques that allow extracting the important amount of information present in these matrices. Parallel Factor Analysis (PARAFAC) has emerged as an integral approach for the analysis of the fluorescence matrices and its use has been widely reported in diverse environmental analyses. In this work, water samples from different water sources serving four different water treatment plants located in Ohio were collected during periods of over one year.  Samples of raw water and water after coagulation were obtained three times a week.  The continuous monitoring of the NOM levels represented as Total Organic Carbon (TOC) concentrations and the measurement of the fluorescence levels in the waters were carried out. The application of the PARAFAC technique allowed obtaining the distinctive fluorescence components in each water before and after treatment, offering insight not only about the particularities of each water source but also about  the efficiency of the specific coagulation process applied in each facility. Results indicate that fluorescence analysis coupled with PARAFAC application may represent a practical tool to be used in the control and optimization of the water treatment operations increasing the efficiency of the processes and assuring the desired quality characteristics in the drinking water being supplied.