Rapid characterization of the changes in dissolved organic matter polarity and size during water treatment

Characterization of dissolved organic matter (DOM) is extremely important for water utilities in order to minimize potential detrimental effects of disinfection by-products formation, fouling of membranes and biological re-growth and off-taste and odor occurring in the distribution system. Diverse analytical methods have been developed for the characterization of DOM, mostly relying on complex and lengthy procedures limiting real time information. In addition, most DOM characterization methods include preparation steps, such as changes in pH, which may change the DOM structure and conformation from its natural state. Rapid characterization of DOM and how it evolves throughout treatment processes is needed to be able to modify treatment parameters as needed to minimize the effects of DOM. PRAM (polarity rapid assessment method), fluorescence EEM (excitation emission matrix) and HPLC-SEC (size exclusion chromatography) offer great advantages for the continuous monitoring of DOM changes in treatment facilities with minimum sample preparation steps. These techniques offer the advantage of providing information in short periods of time. This paper assesses the changes in DOM polarity and size characteristics through the water treatment process at the River Mountains Water Treatment Facility in Henderson, Nevada indicating the value of the approach. Initial data shows temporal variation in DOM polarity as wells as differences in the effects of ozone pre-treatment as measured by the PRAM method. Size data indicates minimum differences in molecular weight distributions. A pre-concentration step, required prior to analysis of DOM size distribution, may be inhibiting the detection of differences in molecular weight distributions. Fluorescence data show a reduction in the intensity of the fulvic component between influent and finished waters.