engleski

Photodegradation of natural organic matter in water with UV irradiation at 185 and 254 nm: importance of hydrodynamic conditions on the decomposition rate

The photodegradation of the natural organic matter (NOM) in water by means of UV irradiation was studied. Experiments were done with samples of natural lake water (Njivice, Island Krk, Croatia) rich in NOM with apparent humic character. Kinetic investigation of the photodegradation of NOM was conducted using two low-pressure mercury lamps of the same nominal power: a/ with suprasil quartz envelope emitting UV at both wavelengths - 254 nm and 185 nm (hereafter VUV), b/ with standard quartz envelope emitting only at  = 254 nm (hereafter UV), in same photochemical reactor under different experimental conditions. The main experimental finding that was made in the course of the work is determination of contribution of irradiation at  = 185 nm to the NOM degradation at different hydrodynamic conditions. In comparison to UV254nm irradiation solely, addition of 185 nm irradiation (by applying VUV lamp) increased overall degradation rate ten fold at lower and seventeen fold at higher Reynolds numbers, respectively. Photodegradation induced by UV irradiation was not dependent on intensity of flow in photochemical reactor at all. Hydrodynamic characteristics of the photoreactor are of crucial importance for total energy efficiency of an advanced oxidation process based on VUV irradiation.

Photodegradation; hydrodynamic conditions; degradation rate; Reynolds number; VUV; UV

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