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

The kinetic investigation of photodegradation of the natural organic matter (NOM) in natural lake water was conducted using two low-pressure mercury lamps of the same nominal power: a/ with suprasil quartz envelope emitting at both wavelengths - 254 nm and 185 nm (hereafter VUV), b/ with standard quartz envelope emitting only at 254 nm (hereafter UV). In comparison to UV process, addition of 185 nm irradiation (VUV process) increased overall degradation rate ten fold at lower and seventeen fold at higher Reynolds numbers, respectively. Hydrodynamic characteristics of the photoreactor are of crucial importance for total energy efficiency for VUV processes.