In this presentation, we will discuss our ongoing work to characterize the photochemical behavior of dissolved organic matter (DOM) of wastewater treated in constructed wetlands. We have used a suite of spectroscopic and chromatographic techniques to characterize the DOM and quantify the potential production of reactive oxygenated species (ROS) in regional and laboratory scale constructed wetlands. DOM was fractionated based on its hydrophobicity and both the natural water isolates and fractionated DOM were characterized using SUVA254, spectral slope ratios, excitation emission matrix fluorescence spectroscopy (EEMs) and proton nuclear magnetic resonance (1H NMR). Wetland DOM photoreactivity was also assessed by measuring the formation rate and steady state concentrations of hydroxyl radical (●OH), singlet oxygen (1O2), and the triplet-excited state (3DOM*). The effluent was observed to transition from a microbially sourced protein-like DOM to a higher molecular weight terrestrial DOM with higher aromaticity. A negative correlation between the percent fluorescence of Peak T and Peaks A, C and M of the excitation emission spectra confirmed the transition from the spectrum of pure wastewater with a primarily protein-like signature to a spectrum characteristic of terrestrially derived DOM. This transition coincided with enhanced formation rates and steady state concentrations of singlet oxygen and excited triplet states of DOM. Size exclusion chromatography demonstrated that the influent wastewater had a lower molecular weight as compared to downstream wetland locations. Fractionation of DOM based on hydrophobicity followed by 1H NMR analysis indicated an increase in the complexity and composition of wetland effluent DOM. To better understand how engineered wetlands design relates to DOM production and quality we will also present preliminary results characterizing the DOM quantity, quality, and photoreactivity from lab scale wetland microcosms. These experiments assess the influence of key wetland features on the DOM photoreactivity and assist in understanding the engineering design of these natural treatment alternatives.

Dissolved organic matter (DOM) characterization and enhanced photoreactivity in constructed wetlands for wastewater treatment

255th National Meeting (2018)

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