The increasing demand for potable water is forcing municipalities around the world to utilize alternative water sources. One of the most promising alternatives is the reuse of municipal wastewater for potable purposes. However, the well-documented presence of persistent trace organic compounds (TOrCs) at concentrations that are physiologically active in this water resource provides environmental and human health challenges that must be addressed.<br/>It has been proven that some TOrCs are naturally attenuated via photo-degradation. In natural sunlight, effluent organic matter (EfOM) in treated wastewater acts as a sensitizer for the generation of reactive oxygen species (ROS) that contribute to the photo-transformation of trace organic contaminants. However, variability of: (i) chemical and physical properties of TOrCs, (ii) chemical and physical characteristics of the wastewater effluent, and (iii) environmental exposure, all play a significant role in TOrCs fate, which highlights the need to understand their transformation pathways and mechanisms. In a previous work, generation of singlet oxygen by EfOM exposed to sunlight was found to be the prevalent ROS in the degradation of phenolic compounds. However, uncertainties from that study include the effect of wavelength on the quantum yield for the production of singlet oxygen, as well as the nature of the EfOM sensitizers. Here, the degradation of two model chemical targets—p-cresol and furfuryl alcohol (FFA) – under UVA (300-400 nm), sunlight, and monochromatic light sources in the spectral range 250-600 nm was studied. A comprehensive mechanism and complementary kinetic model were developed to predict target photo-transformations involving singlet oxygen generated from methylene blue as a model sensitizer. The dependence of the quantum yield for the production of singlet oxygen by the sensitizer on the wavelength of irradiating light and other kinetic parameters were determined independently in experiments with monochromatic light and then used as predictive tools to quantify accurately the performance of target photo-transformation in UVA and sunlight.

Photodegradation of trace organic contaminants by singlet oxygen: a kinetic/transport model

2019 Spring National Meeting

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