The photosensitized processes significantly enhance photolysis of various chemicals in the aqueous system with dissolved organic matter (DOM) as sensitizer. The excitation of chromophores on the DOM molecule further generates reactive species as triplet states DOM, singlet oxygen, hydroxyl radical, carbonate radical etc. We investigated the photosensitization properties of Beaufort Fulvic Acid, Suwannee River Fulvic Acid, South Platte River Fulvic Acid, and Jeddah wastewater treatment plant effluent organic matter with a sunlight simulator. DOM photochemical properties were characterized by observing their performances in 3DOM*, singlet oxygen, hydroxyl radical production with indirect probing protocols. Sensitized degradation of 0.1 μM and 0.02 μM 2, 4, 6- Trimethylphenol exhibited higher pseudo-first-order rate constant than that of 10 μM. Pre-irradiated DOMs were found to be depressed in photochemical properties. Photolysis of 5 different contaminants: ibuprofen, bisphenol A, acetaminophen, cimetidine, and caffeine were found to be enhanced in the presence of sensitizers. The possible reaction pathways were revealed. Long time irradiance induced change in contaminants degradation kinetics in some DOM solutions, which was proposed to be due to the irradiation initiated indirect transformation of DOMs. Key Words: Photolysis Dissolved Organic Matter, Triplet State DOM, Singlet Oxygen, Hydroxyl Radical, Contaminants Degradation.

Water from the Llobregat is used to supply a significant part of the city of Barcelona. At the same time, 60 wastewater treatment plants discharge into this basin. Two field campaigns conducted in the Llobregat Catchment detected more than 80 pharmaceu-ticals in the water. Therefore, it is clear that water quality in Llobregat is a potential concern. A GIS hydrology water quality model has been applied in order to predict the concentrations of one of the pharmaceuticals, diclofenac, in the catchment. Con-sumption, excretion, and degradation data has been studied to calibrate the model. This exercise proves that it is relatively straightforward to predict the concentrations of new and emerging contaminants at basin scale. Nonetheless, the limited and inac-curate available data was a relevant obstacle in this modelling process.