Citation:

Rossman, P. AND J. Pressman. Characterizing Variability In Ohio River Natural Organic Matter. In Proceedings, American Water Works Association Water Quality Technology Conference, Long Beach, CA, November 03 - 06, 2013. American Water Works Association, Denver, CO, ,, (2013).

Impact/Purpose:

The research conducted in this project will help utilities and researchers understand the changing nature of natural organic matter over time.

Description:

Surface water contains natural organic matter (NOM) which reacts with disinfectants creating disinfection byproducts (DBPs), some of which are USEPA regulated contaminants. Characterizing NOM can provide important insight on DBP formation and water treatment process adaptation to climate change as the nature of NOM varies over time. This study collected NOM from the Ohio River over a 15 month period (April 2010 to July 2011) in order to address seasonal variations in NOM with further implications for a long-term climate change study. The NOM was characterized using fluorescence spectroscopy, UV254, TOC, size-exclusion chromatography – organic carbon detection (SEC-OCD), and elemental analysis. Additionally, NOM was concentrated, freeze-dried (lyophilized), and validated in comparison to the source NOM creating a standardized freeze-dried NOM which may be used in water treatment process evaluations investigating utility adaptation to climate change. Raw Ohio River water was processed to concentrate NOM in the following order: ultrafiltration (UF); cation ion exchange; reverse osmosis (RO); sulfate removal; and lyophilization. Lyophilization allows for long-term storage of the NOM while having the ability to reconstitute at various NOM concentrations compared to liquid material with a short shelf-life. The lyophilized NOM was used for elemental analysis while the UF effluent, RO concentrate, and reconstituted lyophilized NOM were employed for all other analyses. Parallel factor analysis (PARAFAC) was used to determine the locations of principle components within three dimensional excitation-emission matrices (EEMs). TOC and UV254 results demonstrated seasonal variation of the NOM concentration. However, PARAFAC analysis determined the nature of the NOM components were primarily humic and remained constant during the study. The humic characterization was further supported by the humification index (HIX) (0.79-0.90) determined from fluorescence. In addition, elemental analysis revealed low hydrogen to carbon (H/C) (0.074-0.106) and mid-range oxygen to carbon (O/C) (0.62-0.84) ratios, also indicative of humic NOM. Humic substances are composed of naturally occurring, biologically decayed plant material that can affect the alkalinity, pH, and other treatment characteristics of surface water. However, since the humic nature of the NOM was relatively similar over the study, the primary difference was the NOM concentration. The reconstituted lyophilized NOM was validated against the source NOM, allowing its use as a standardized NOM material in treatment process studies that evaluate the effects of changing NOM character and concentration. This temporal library of well-characterized, drinking water relevant NOM is the first of its kind in the drinking water industry and will be a valuable research tool available to the drinking water community while allowing for the continued study of climate change effects on treatment technologies.

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