Environ. Sci. Technol. 2005, 39, 6453-6460
Impact of Reclaimed Water on Select Organic Matter Properties of a Receiving StreamsFluorescence and Perylene Sorption Behavior† R . D A V I D H O L B R O O K , * ,‡ JENNIFER BREIDENICH,§ AND PAUL C. DEROSE| Surface and Microanalysis Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, Department of Chemistry, Smith College, Northampton, Massachusetts 01063, and Analytical Chemistry Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899
Surface water samples obtained from the Bull Run tributary upstream and downstream of the Upper Occoquan Sewage Authority (UOSA) advanced wastewater reclamation facility (WRF) were characterized by fluorescence excitation-emission matrix (EEM) spectroscopy, and sorption coefficients (Kmoc) of macromolecular organic carbon isolates were quantified by fluorescence quenching. The EEM data revealed a signature fluorescence distribution in the downstream samples that was attributed to the presence of proteinlike material. The Kmoc values for upstream samples were consistently and significantly higher than those of corresponding downstream samples. There was a moderate correlation (R 2 ) 0.67) between log Kmoc and the molar extinction coefficient at 280 nm (280) and a strong correlation (R 2 ) 0.96) between Kmoc and the proteinlike fluorescence region for macromolecular isolates with negligible quantum yields. This study demonstrates that organic matter downstream of the UOSAWRF has unique fluorescence and perylene sorption characteristics compared to those of upstream organic matter during summer baseflow conditions. This implies that wastewater treatment facilities, including those advanced facilities designed to reclaim wastewater for indirect potable reuse, can influence the composition and behavior of organic matter in a receiving stream.
Introduction
Indirect potable reuse is a practice where highly treated wastewater effluent (reclaimed water) is used to supplement potable water supplies (e.g., surface water and aquifers) (1, 2). Ideally, receiving systems should not be detrimentally impacted by the presence of treated effluent. In practice, however, slight changes to the natural environment are to be expected. For example, surface water must typically undergo some type of treatment before being distributed to the public to remove natural organic material (NOM), the †
This paper is part of the Charles O’Melia tribute issue. * Corresponding author phone: (301)975-5202; fax: (301)417-1321; e-mail:
[email protected]. ‡ Surface and Microanalysis Science Division, National Institute of Standards and Technology. § Department of Chemistry, Smith College. | Analytical Chemistry Division, National Institute of Standards and Technology. 10.1021/es047971p Not subject to U.S. Copyright. Publ. 2005 Am. Chem. Soc. Published on Web 06/30/2005
majority of which is of terrestrial (allochthonous) origin (3, 4). Reclaimed water contains organic material that is derived from microbial (autochthonous) sources (5-7). Therefore, some fraction of the terrestrial organic matter in receiving streams is supplanted by microbial material as water is first removed and treated for drinking water and then returned as reclaimed water. Previous investigations by Drewes and Fox (8-10) have demonstrated that effluent organic matter influences the organic carbon concentrations of reclaimed water following soil-aquifer treatment, indicating a general persistence of microbial-derived material in the natural environment. Organic matter composition and behavior in aqueous environments is a critical factor in determining the productivity of natural systems (11, 12), the fate of contaminants (13), the mobility of trace metals (14), and the efficiency of drinking water treatment processes (15). In particular, macromolecular organic carbon (MOC), operationally defined in this study as organic carbon between 1 kDa and 0.45 µm in size, can facilitate sorption and govern the bioavailability of hydrophobic contaminants (16) and trace metals (17). By contrast, dissolved organic carbon (DOC), defined in this study as any organic carbon able to pass through a defined molecular weight cutoff ultrafilter (
