Science Inventory

Characterizing Ohio River NOM Variability and Reconstituted-Lyophilized NOM as a Source Surrogate

Citation:

Rossman, P., D. Boccelli, AND J. Pressman. Characterizing Ohio River NOM Variability and Reconstituted-Lyophilized NOM as a Source Surrogate. JOURNAL OF THE AMERICAN WATER WORKS ASSOCIATION. American Water Works Association, Denver, CO, 109(1):E1-E9, (2017). https://doi.org/10.5942/jawwa.2017.109.0008

Impact/Purpose:

Disinfection byproducts (DBPs) can form when disinfectants react with water that contains natural organic matter (NOM). This research assessed seasonal variability in NOM by using samples collected from the Ohio River over 15 months and characterized NOM composition. The purpose of this project was to gain insights with respect to DBP formation and water treatment process adaptation. In addition, this project considered seasonal NOM changes that might be associated with climate change. The results of this study will be useful for all drinking water utilities, engineers, operators, regulators, and academicians that contend with disinfection byproducts caused by the combination of NOM and drinking water disinfectants.

Description:

Surface water contains natural organic matter (NOM) that reacts with disinfectants creating disinfection byproducts (DBPs), some of which are USEPA regulated contaminants. Characterizing NOM can provide insight with respect to DBP formation and water treatment process adaptation to climate change as the nature of NOM varies. In this study, NOM was collected from the Ohio River over 15 months (April 2010 to July 2011) in order to assess seasonal variability in NOM characteristics. In addition, NOM was concentrated, lyophilized (freeze-dried) to create a temporal NOM library, and reconstituted to demonstrate the dried NOM remained similar to the original source NOM from which it was processed. Using fluorescence spectroscopy and parallel factor analysis (PARAFAC), similar spectral components for both the ultrafiltered source water (UF1X) and reconstituted NOM were observed throughout the study, with overall average emission and excitation wavelengths of 418 nm and 270 nm, respectively, for component 1 and 482 nm and 370 nm, respectively, for component 2. Furthermore, high performance liquid chromatography – size exclusion chromatography (HPLC-SEC) resulted in similar molecular size distributions, with a peak between 2.3×10^5 Da and 1.3×10^5 Da. Component locations in fluorescence excitation-emission matrices, results from PARAFAC analysis, the fluorescence index and humification index values, HPLC-SEC data, and elemental analysis indicated that the NOM was humic-like throughout the study timeframe with only small seasonal changes in some parameters. Similarity between results for UF1X and reconstituted NOM provided additional evidence that any losses in NOM appear to affect the entire mixture, as opposed to specific fractions and validates the use of the lyophilized and reconstituted NOM as a surrogate for its source. This temporal library of humic-like, drinking water relevant NOM is the first of its kind in the drinking water industry.